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Volume 105-B, Issue SUPP_3 February 2023 The New Zealand Orthopaedic Association and the Australian Orthopaedic Association (NZOA AOA) Combined Annual Scientific Meeting, Christchurch, New Zealand, 31 October – 3 November 2022. Part 2 of 2.

S.L. Chong M. Khademi K.M. Reddy G.H. Anderson

Treatment of posterior malleolar (PM) ankle fractures remain controversial. Despite increasing recommendation for small PM fragment fixation, high quality evidence demonstrating improved clinical outcomes over the unfixated PM is limited. We describe the medium-to-long term clinical and radiographical outcomes in younger adult patients with PM ankle fractures managed without PM fragment fixation.

A retrospective cohort study of patients aged 18-55 years old admitted under our orthopaedic unit between 1st of April 2009 and 31st of October 2013 with PM ankle fractures was performed. Inclusion criteria were that all patients must mobilise independently pre-trauma, have no pre-existing ankle pathologies, and had satisfactory bimalleolar and syndesmotic stabilisation. Open fractures, talar fractures, calcaneal fractures, pilon fractures, subsequent re-injury and major complications were excluded. All PM fragments were unfixated. Clinical outcomes were evaluated using Foot and Ankle Ability Measure (FAAM) with activities of daily living (ADL) and sports subscale, visual analogue scale (VAS) and patient satisfaction ratings. Osteoarthrosis was assessed using modified Kellgren-Lawrence scale on updated weightbearing ankle radiographs.

61 participants were included. Mean follow-up was 10.26 years. Average PM size was 16.19±7.39%. All participants were evaluated for clinical outcomes, demonstrating good functional outcomes (FAAM-ADL 95.48±7.13; FAAM-Sports 86.39±15.52) and patient satisfaction (86.16±14.42%), with minimal pain (VAS 1.13±1.65). Radiographical outcomes were evaluated in 52 participants, showing no-to-minimal osteoarthrosis in 36/52 (69.23%), mild osteoarthrosis in 14/52 (26.92%) and moderate osteoarthrosis in 2/52 (3.85%). Clinical outcomes were not associated with PM fragment size, post-reduction step-off, dislocation, malleoli fractured or syndesmotic injury. PM step-off and dislocation were associated with worse radiographical osteoarthrosis. Other published medium-to-long term studies reported overall good outcomes, with no differences after small fragment fixation.

The unfixated smaller posterior malleolus fragment demonstrated overall satisfactory clinical and radiographical outcomes at 10-year follow-up and may be considered a valid treatment strategy.

L. Roffe R. Peterson G. Smith R. Penumarthy N. Atkinson M. Ross L. Singelton C. Bodian S. Timoko-Barnes

Trauma and elective orthopaedic demands in New Zealand are increasing. In this study, prospective and retrospective data has been collected at Nelson Hospital and across New Zealand to identify the percentage of elective theatre time lost due to cancellation for acute patient care. Data has been collected from theatre management systems, hospital data systems and logged against secretarial case bookings, to calculate a percentage of elective theatre time lost to acute operating or insufficient bed capacity.

Data was collected over a five-month period at Nelson Hospital, with a total of 215 elective and 226 acute orthopaedic procedures completed. A total of 95 primary hip or knee arthroplasties were completed during this trial while 53 were cancelled. The total number of elective operative sessions (one session is the equivalent of a half day operating theatre time) lost to acute workload was 47.9. Thirty-three percent of allocated elective theatre time was cancelled - an equivalent of approximately one-full day elective operating per week.

Over a five-week period data was collected across all provincial hospitals in New Zealand, with an average of 18% of elective operating time per week lost due to acute workload. Elective cancellations were due to acute operating 40% of the time and bed shortages 60% of the time. The worst effected centre was Palmerston North which had an average of 33% of elective operating cancelled per week to accommodate acute surgery or due to bed shortages.

New Zealand's provincial orthopaedic surgeons are under immense pressure from acute operating that impedes provision of elective surgery. The New Zealand government definition of an ‘acute case’ does not reflect the nature of today's orthopaedic burden. Increasing and aging populations along with staff and infrastructure shortages have financial and societal impacts beyond medicine and require better definitions, further research, and funding from governance.

L.A. Holzer M. Finsterwald S. Sobhi P.J. Yates

This study aimed to analyze the effect of two different techniques of cement application: cement on bone surface (CoB) versus cement on bone surface and implant surface (CoBaI) on the short-term effect of radiolucent lines (RLL) in primary fully cemented total knee arthroplasties (TKA) with patella resurfacing.

379 fully cemented TKAs (318 patients) were included in this monocentric study. Preoperative and postoperative at week 4 and 12 month after surgery all patients had a clinical and radiological examination and were administered the Oxford Knee Score (OKS). Cement was applied in two different ways among the two study groups: cement on bone surface (CoB group) or cement on bone surface and implant surface (CoBaI group). The evaluation of the presence of RLL or osteolysis was done as previously described using the updated Knee Society Radiographic Evaluation System.

The mean OKS and range of motion improved significantly in both groups at the 4-week and 12-month follow-up, with no significant difference between the groups (CoB vs. CoBaI). RLL were present in 4.7% in the whole study population and were significantly higher in the CoBaI group (10.5%) at the 4-week follow-up. At the 12-month follow-up RLL were seen in 29.8% of the TKAs in the CoBaI group, whereas the incidence was lower in the CoB group (24.0% (n.s.)). There were two revisions in each group. None of these due to aseptic loosening.

Our study indicated that the application of bone cement on bone surface only might be more beneficial than onto the bone surface and onto the implant surface as well in respect to the short-term presence of RLL in fully cemented primary TKA.

The long-term results will be of interest, especially in respect to aseptic loosening and might guide future directions of bone cement applications in TKA.

M. Zhu R. Rahardja J.S. Davis L. Manning S. Metcalf S.W. Young

The optimum indications for debridement, antibiotics and implant retention (DAIR) are unclear. Previous studies have demonstrated higher success rate of DAIR within one year of the primary arthroplasty. This study aimed to compare the success rate of DAIR vs revision in “early” and “late” infections to provide guidance for clinical decision making.

The Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) cohort prospectively recorded PJIs between July 2014 and December 2017 in 27 hospitals. This study included PIANO patients with first time PJIs occurring after primary TKA. Treatment success was defined as the patient being alive, free from further revision and without clinical or microbiological evidence of reinfection at two years follow-up.

“Early” and “late” infections were analyzed separately. Univariate analysis compared demographic and disease specific factors between the DAIR and Revision groups. Multivariate binary logistic regression identified whether treatment strategy and other risk factors were associated with treatment success in “early” and “late” infections.

In 117 “early” (<1 year) infections, treatment success rate was 56% in the DAIR group and 54% in the revision group (p=0.878). No independent risk factors were associated with treatment outcome on multivariate analysis.

In 134 “late” (>1 year) infections, treatment success rate was 34.4% in the DAIR group and 60.5% in the revision group (OR 3.07 p=0.006). On multivariate analysis, revision was associated with 2.47x higher odds of success (p=0.041) when compared to DAIR, patients with at least one significant co-morbidity (OR 2.27, p=0.045) or with Staphylococcus aureus PJIs (OR 2.5, p=0.042) had higher odds of failure.

In “late” PJIs occurring >1 year following primary TKA, treatment strategy with revision rather than DAIR was associated with greater success. Patients with significant comorbidities and Staphylococcus aureus PJIs were at higher risk of failure regardless of treatment strategy.

M. Coia Jadresic J. Baker

Numerous prediction tools are available for estimating postoperative risk following spine surgery. External validation studies have shown mixed results. We present the development, validation, and comparative evaluation of novel tool (NZSpine) for modelling risk of complications within 30 days of spine surgery.

Data was gathered retrospectively from medical records of patients who underwent spine surgery at Waikato Hospital between January 2019 and December 2020 (n = 488). Variables were selected a priori based on previous evidence and clinical judgement. Postoperative adverse events were classified objectively using the Comprehensive Complication Index. Models were constructed for the occurrence of any complication and significant complications (based on CCI >26). Performance and clinical utility of the novel model was compared against SpineSage (https://depts.washington.edu/spinersk/), an extant online tool which we have shown in unpublished work to be valid in our local population.

Overall complication rate was 34%. In the multivariate model, higher age, increased surgical invasiveness and the presence of preoperative anemia were most strongly predictive of any postoperative complication (OR = 1.03, 1.09, 2.1 respectively, p <0.001), whereas the occurrence of a major postoperative complication (CCI >26) was most strongly associated with the presence of respiratory disease (OR = 2.82, p <0.001).

Internal validation using the bootstrapped models showed the model was robust, with an AUC of 0.73. Using sensitivity analysis, 80% of the model's predictions were correct. By comparison SpineSage had an AUC of 0.71, and in decision curve analysis the novel model showed greater expected benefit at all thresholds of risk.

NZSpine is a novel risk assessment tool for patients undergoing acute and elective spine surgery and may help inform clinicians and patients of their prognosis. Use of an objective tool may help to provide uniformity between DHBs when completing the “clinician assessment of risk” section of the national prioritization tool.

W. Chen N.J. Lightfoot M.J. Boyle

Higher levels of socioeconomic deprivation have been associated with worse health outcomes. The influence of socioeconomic deprivation on patients undergoing periacetabular osteotomy (PAO) has not previously been investigated.

A total of 217 patients (171 female, 46 male; median age 23.4 years) who underwent PAO by a single surgeon were identified. Patients were categorised into three groups according to their New Zealand Deprivation (NZDep) Index: minimal deprivation (NZDep Index 1–3, n=89), moderate deprivation (NZDep Index 4-6, n=94), and maximal deprivation (NZDep Index 7-10, n=34). The three groups were compared with respect to baseline variables, surgical details, complications, and pre-operative and two-year post-operative functional scores (including International Hip Outcome Tool (iHOT-12), EQ-5D quality of life score, and University of California Los Angeles (UCLA) activity score). Multivariate regression was undertaken to assess for the effect of NZDep Index on patient outcomes.

Patients in the maximal deprivation group were more likely to be Māori (p<0.001) and have surgery in a public rather than a private hospital (p=0.004), while the minimal deprivation group demonstrated a lower BMI (p=0.005). There were otherwise no other significant differences in baseline variables, surgical details, complications, nor pre-operative or two-year post-operative functional scores between the three groups (all p>0.05). Multivariate analysis identified a higher NZDep Index to be independently predictive of a lower pre-operative UCLA activity score (p=0.014) and a higher two-year iHOT-12 score (p<0.001).

Our results demonstrate an inequality in access to PAO, with patients exposed to higher levels of socioeconomic deprivation under-represented in our study population. When provided access to PAO, these vulnerable patients achieve significant functional improvement at least as great as patients with less socioeconomic deprivation. Initiatives to improve access to hip preservation care in socioeconomically deprived populations appear warranted.

Y.E. Koo N.J. Lightfoot M.J. Boyle

The influence of patient age on functional outcomes after periacetabular osteotomy (PAO) for acetabular dysplasia remains unclear, with previous studies utilising scores developed for older, arthritic patients. The purpose of this study is to assess the influence of patient age on International Hip Outcome Tool (iHOT-12) scores, two years after PAO.

Eighty-six patients (72 female, 14 male; mean age 26.9 years) who underwent PAO by a single surgeon and had completed a minimum of two years follow up were identified. Patients were categorised into three groups according to age at the time of surgery: adolescent (11-20 years; n=29), young adult (21–30 years; n=29), and mature (≥31 years; n=28). The three groups were compared with respect to baseline variables and functional outcomes (iHOT-12, EQ-5D quality of life score, University of California Los Angeles (UCLA) activity score, pain visual analogue score (VAS)). Multivariate regression was undertaken to assess for independent predictors of two-year iHOT-12 score.

The adolescent group demonstrated a lower BMI (p=0.004) while the mature group had a greater American Society of Anaesthesiology (ASA) score (p=0.049). There were otherwise no significant differences in baseline variables between the three groups (all p>0.05).

The three groups demonstrated significant post-operative improvements across all functional outcome measures. There were no significant differences in two-year iHOT-12, EQ-5D, UCLA score or pain VAS between the three groups (all p>0.05). Regression modelling found that patient age at the time of surgery did not have an independent effect on two-year iHOT-12 score (p=0.878).

We found that patient age at the time of surgery did not influence functional outcomes two years after PAO. Our results suggest that patient age should not be considered in isolation as an indication or contraindication for PAO.

M. Damiani

Autologous tendon cell injection (ATI) is a promising non-surgical treatment for tendinopathies and tendon tear that address its underlying pathology. The procedure involves harvesting autologous tendon tissue, the isolation of the tendon cells, expansion under quality assured GMP cell laboratory and the injection of the tendon cells via U/S into the degenerative tendon tissue. In clinical practice, the patella (PT) and palmaris longus (PL) tendons are common sites used for tendon tissue biopsy. The objective of this study is to compare the tendon cell quality, identity, purity, doubling time and yield of cells between PT and PL tendons for ATI.

Tendon tissue biopsies were harvested from PT via U/S using a 14-gauge needle or resected surgically from the PL tendon. The biopsies were transported to a GMP cell laboratory, where tendon cells were isolated, cultured and expanded for 4 to 6 weeks, and analysed for viability, cell doubling time, cellular characteristics including cell purity, potency and identity (PPI).

Tendon samples from 149 patients were analysed (63 PT). Average biopsy weight was 62mg for PT and 119mg for PI (p<0.001). Average cell doubling time (83.9 vs 82.7 hours), cellular yield (16.2 vs 15.2×106), viability (98.7 vs 99.0%) and passage number (3 vs 3) were not significantly different between tendons. Additionally, ddPCR analyses showed no differences of PPI including tendon cell markers of collagen type I, scleraxis and tenomodulin. No post-biopsy complications or contamination were reported for either group. Assessing tendon tissue from palmaris tendon is relatively easier.

Tendon tissue biopsy tissue for autologous tendon cell therapy can be obtained from either the PT or PL tendons. Tendon cells isolated from PT and PL were equal in growth characteristics and PPI. There are no differences in the quality of tendon cells isolated from the PT or PL.

M. Hardwick-Morris J. Twiggs B. Miles E. Jones W. J. M. Bruce W. L. Walter

In 2021, Vigdorchik et al. published a large multicentre study validating their simple Hip-Spine Classification for determining patient-specific acetabular component positioning in total hip arthroplasty (THA). The purpose of our study was to apply this Hip-Spine Classification to a sample of Australian patients undergoing THA surgery to determine the local acetabular component positioning requirements. Additionally, we propose a modified algorithm for adjusting cup anteversion requirements.

790 patients who underwent THA surgery between January 2021 and June 2022 were assessed for anterior pelvic plane tilt (APPt) and sacral slope (SS) in standing and relaxed seated positions and categorized according to their spinal stiffness and flatback deformity. Spinal stiffness was measured using pelvic mobility (PM); the ΔSS between standing and relaxed seated. Flatback deformity was defined by APPt <−13° in standing. As in Vigdorchik et al., PM of <10° was considered a stiff spine. For our algorithm, PM of <20° indicated the need for increased cup anteversion. Using this approach, patient-specific cup anteversion is increased by 1° for every degree the patient's PM is <20°.

According to the Vigdorchik simple Hip-Spine classification groups, we found: 73% Group 1A, 19% Group 1B, 5% Group 2A, and 3% Group 2B. Therefore, under this classification, 27% of Australian THA patients would have an elevated risk of dislocation due to spinal deformity and/or stiffness. Under our modified definition, 52% patients would require increased cup anteversion to address spinal stiffness.

The Hip-Spine Classification is a simple algorithm that has been shown to indicate to surgeons when adjustments to acetabular cup anteversion are required to account for spinal stiffness or flatback deformity. We investigated this algorithm in an Australian population of patients undergoing THA and propose a modified approach: increasing cup anteversion by 1° for every degree the patient's PM is <20°.

M. Hardwick-Morris J. Twiggs B. Miles E. Jones W. J. M. Bruce W. L. Walter

Dislocation is one of the most common complications in total hip arthroplasty (THA) and is primarily driven by bony or prosthetic impingement. The aim of this study was two-fold. First, to develop a simulation that incorporates the functional position of the femur and pelvis and instantaneously determines range of motion (ROM) limits. Second, to assess the number of patients for whom their functional bony alignment escalates impingement risk.

468 patients underwent a preoperative THA planning protocol that included functional x-rays and a lower limb CT scan. The CT scan was segmented and landmarked, and the x-rays were measured for pelvic tilt, femoral rotation, and preoperative leg length discrepancy (LLD). All patients received 3D templating with the same implant combination (Depuy; Corail/Pinnacle). Implants were positioned according to standardised criteria.

Each patient was simulated in a novel ROM simulation that instantaneously calculates bony and prosthetic impingement limits in functional movements. Simulated motions included flexion and standing-external rotation (ER). Each patient's ROM was simulated with their bones oriented in both functional and neutral positions.

13% patients suffered a ROM impingement for functional but not neutral extension-ER. As a result, 48% patients who failed the functional-ER simulation would not be detected without consideration of the functional bony alignment. 16% patients suffered a ROM impingement for functional but not neutral flexion. As a result, 65% patients who failed the flexion simulation would not be detected without consideration of the functional bony alignment.

We have developed a ROM simulation for use with preoperative planning for THA surgery that can solve bony and prosthetic impingement limits instantaneously. The advantage of our ROM simulation over previous simulations is instantaneous impingement detection, not requiring implant geometries to be analysed prior to use, and addressing the functional position of both the femur and pelvis.

M. Hardwick-Morris J. Twiggs B. Miles W. L. Walter

Iliopsoas tendonitis occurs in up to 30% of patients after hip resurfacing arthroplasty (HRA) and is a common reason for revision. The primary purpose of this study was to validate our novel computational model for quantifying iliopsoas impingement in HRA patients using a case-controlled investigation. Secondary purpose was to compare these results with previously measured THA patients.

We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitis, confirmed via the active hip flexion test in supine, and control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. The CT scans were segmented, landmarked, and used to simulate the iliopsoas impingement in supine and standing pelvic positions. Three discrete impingement values were output for each pelvic position, and the mean and maximum of these values were reported. Cup prominence was measured using a novel, nearest-neighbour algorithm.

The mean cup prominence for the symptomatic cohort was 10.7mm and 5.1mm for the asymptomatic cohort (p << 0.01). The average standing mean impingement for the symptomatic cohort was 0.1mm and 0.0mm for the asymptomatic cohort (p << 0.01). The average standing maximum impingement for the symptomatic cohort was 0.2mm and 0.0mm for the asymptomatic cohort (p << 0.01). Impingement significantly predicted the probability of pain in logistic regression models and the simulation had a sensitivity of 92%, specificity of 91%, and an AUC ROC curve of 0.95.

Using a case-controlled investigation, we demonstrated that our novel simulation could detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts. Interestingly, the HRA patients demonstrated less impingement than the THA patients, despite greater cup prominence. In conclusion, this tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.

M. Hardwick-Morris J. Twiggs B. Miles J. Balakumar W. L. Walter

Iliopsoas impingement occurs in between 5-30% of patients after hip arthroplasty and has been thought to only be caused by an oversized cup, cup malpositioning, or the depth of the psoas valley. However, no study has associated the relationship between preoperative measurements with the risk of impingement. This study sought to assess impingement between the iliopsoas and acetabular cup using a novel validated model to determine the risk factors for iliopsoas impingement.

413 patients received lower limb CT scans and lateral x-rays that were segmented, landmarked, and measured using a validated preoperative planning protocol. Implants were positioned according to the preference of ten experienced surgeons. The segmented bones were transformed to the standing reference frame and simulated with a novel computational model that detects impingement between the iliopsoas and acetabular cup. Definitions of patients at-risk and not at-risk of impingement were defined from a previous validation study of the simulation. At-risk patients were propensity score matched to not at-risk patients.

21% of patients were assessed as being at-risk of iliopsoas impingement. Significant differences between at-risk patients and not at-risk patients were observed in standing pelvic tilt (p << 0.01), standing femoral internal rotation (p << 0.01), medio-lateral centre-of-rotation (COR) change (p << 0.01), supine cup anteversion (p << 0.01), pre- to postoperative cup offset change (p << 0.001), postoperative gross offset (p = 0.009), and supero-inferior COR change (p = 0.02).

Impingement between the iliopsoas and acetabular cup is under-studied and may be more common than is published in the literature. Previously it has been thought to only be related to cup size or positioning. However, we have observed significant differences between at-risk and not at-risk patients in additional measurements. This indicates that its occurrence is more complex than simply being related to cup position.

M.L. Tay A.P. Monk C.M. Frampton G.J. Hooper S.W. Young

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand

The Oxford Knee Score (OKS) is a 12-item questionnaire used to track knee arthroplasty outcomes. Validation of such patient reported outcome measures is typically anchored to a single question based on patient ‘satisfaction’, however risk of subsequent revision surgery is also an important outcome measure. The OKS can predict subsequent revision risk within two years, however it is not known which item(s) are the strongest predictors. Our aim was to identify which questions were most relevant in the prediction of subsequent knee arthroplasty revision risk.

All primary TKAs (n=27,708) and UKAs (n=8,415) captured by the New Zealand Joint Registry between 1999 and 2019 with at least one OKS response at six months, five years or ten years post-surgery were included. Logistic regression and receiver operating characteristics (ROC) curves were used to assess prediction models at six months, five years and ten years.

Q1 ‘overall pain’ was the strongest predictor of revision within two years (TKA: 6 months, odds ratio (OR) 1.37; 5 years, OR 1.80; 10 years, OR 1.43; UKA: 6 months, OR 1.32; 5 years, OR 2.88; 10 years, OR 1.85; all p<0.05). A reduced model with just three questions (Q1, Q6 ‘limping when walking’, Q10 ‘knee giving way’) showed comparable or better diagnostic ability with the full OKS (area under the curve (AUC): TKA: 6 months, 0.77 vs. 0.76; 5 years, 0.78 vs. 0.75; 10 years, 0.76 vs. 0.73; UKA: 6 months, 0.80 vs. 0.78; 5 years: 0.81 vs. 0.77; 10 years, 0.80 vs. 0.77).

The three questions on overall knee pain, limping when walking, and knee ‘giving way’ were the strongest predictors of subsequent revision within two years. Attention to the responses for these three key questions during follow-up may allow for prompt identification of patients most at risk of revision.

M.L. Tay A.P. Monk C.M. Frampton G.J. Hooper S.W. Young

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand

Patient reported outcome measures (PROMs) are predictors of knee arthroplasty revision. Unicompartmental knee arthroplasty (UKA) is effective for patients with the correct indications, however has higher revision rates than total knee arthroplasty (TKA). Different revision thresholds for the procedures have been postulated. Our aims were to investigate: 1) if PROMs could predict knee arthroplasty revision within two years of the score at six months, five years and ten years follow-up, and 2) if revision ‘thresholds’ differed between TKA and UKA.

All TKAs and UKAs captured by the New Zealand Joint Registry between 1999 and 2019 with at least one OKS response at six months (TKA n=27,708, UKA n=8,415), five years (TKA n=11,519, UKA n=3,365) or ten years (TKA n=6,311, UKA n=1,744) were included. were propensity-score matched 2:1 with UKAs for comparison of revision thresholds.

Logistic regression indicated that for every one-unit decrease in OKS, the odds of TKA and UKA revision decreased by 10% and 11% at six months, 10% and 12% at five years and 9% and 5% at ten years. Fewer TKA patients with ‘poor’ outcomes (≤25) subsequently underwent revision compared with UKA at six months (5.1% vs. 19.6%, p<0.001), five years (4.3% vs. 12.5%, p<0.001) and ten years (6.4%vs. 15.0%, p=0.02). Compared with TKA, UKA patients were 2.5 times more likely to undergo revision for ‘unknown’ reasons, bearing dislocations and disease progression.

The OKS is a strong predictor of subsequent knee arthroplasty revision within two years of the score from early to late term. A lower revision threshold was found with UKA when compared with a matched TKA cohort. Higher revision rates of UKA are associated with both lower clinical thresholds for revision and additional modes of UKA failure.

M.L. Tay M. Carter S.M. Bolam N. Zeng S.W. Young

Source of the study: University of Auckland, Auckland, New Zealand

Unicompartmental knee arthroplasty (UKA) has benefits for patients with appropriate indications. However, UKA has a higher risk of revision, particularly for low-usage surgeons. The introduction of robotic-arm assisted systems may allow for improved outcomes but is also associated with a learning curve. We aimed to characterise the learning curve of a robotic-arm assisted system (MAKO) for UKA in terms of operative time, limb alignment, component sizing, and patient outcomes.

Operative times, pre- and post-surgical limb alignments, and component sizing were prospectively recorded for consecutive cases of primary medial UKA between 2017 and 2021 (n=152, 5 surgeons). Patient outcomes were captured with the Oxford Knee Score (OKS), EuroQol-5D (EQ-5D), Forgotten Joint Score (FJS-12) and re-operation events up to two years post-UKA. A Cumulative Summation (CUSUM) method was used to estimate learning curves and to distinguish between learning and proficiency phases.

Introduction of the system had a learning curve of 11 cases. There was increased operative time of 13 minutes between learning and proficiency phases (learning 98 mins vs. proficiency 85 mins; p<0.001), associated with navigation registration and bone preparation/cutting. A learning curve was also found with polyethylene insert sizing (p=0.03). No difference in patient outcomes between the two phases were detected for patient-reported outcome measures, implant survival (both phases 98%; NS) or re-operation (learning 100% vs. proficiency: 96%; NS). Implant survival and re-operation rates did not differ between low and high usage surgeons (cut-off of 12 UKAs per year).

Introduction of the robotic-arm assisted system for UKA led to increased operative times for navigation registration and bone preparation, but no differences were detected in terms of component placement or patient outcomes regardless of usage. The short learning curve regardless of UKA usage indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons.

M.L. Tay S.M. Bolam B Coleman J.T. Munro A.P. Monk G.J. Hooper S.W. Young

Source of the study: University of Auckland, Auckland, New Zealand

Unicompartmental knee arthroplasty (UKA) is effective for patients with isolated compartment osteoarthritis, however the procedure has higher revision rates. Long-term survivorship and accurate characterisation of revision reasons are limited by a lack of long-term data and standardised revision definitions. We aimed to identify survivorship, risk factors and revision reasons in a large UKA cohort with up to 20 years follow-up.

Patient, implant and revision details were recorded through clinical and radiological review for 2,137 consecutive patients undergoing primary medial UKA across Auckland, Canterbury, Counties Manukau and Waitematā DHB between 2000 and 2017. Revision reasons were determined from review of clinical, laboratory, and radiological records for each patient using a standardised protocol. To ensure complete follow-up data was cross-referenced with the New Zealand Joint Registry to identify patients undergoing subsequent revision outside the hospitals. Implant survival, revision risk and revision reasons were analysed using Cox proportional-hazards and competing risk analyses.

Implant survivorship at 15 years was comparable for cemented fixed-bearing (cemFB; 91%) and uncemented mobile-bearing (uncemMB; 91%), but lower for cemented mobile-bearing (cemMB; 80%) implants. There was higher incidence of aseptic loosening with cemented implants (3-4% vs. 0.4% uncemented, p<0.01), osteoarthritis (OA) progression with cemMB implants (9% vs. 3% cemFB/uncemMB; p<0.05) and bearing dislocations with uncemMB implants (3% vs. 2% cemMB, p=0.02). Compared with the oldest patients (≥75 years), there was a nearly two-fold increase in risk for those aged 55-64 (hazard ratio 1.9; confidence interval 1.1–3.3, p=0.03). No association was found with gender, BMI or ASA.

Cemented mobile-bearing implants and younger age were linked to lower implant survivorship. These were associated with disease progression and bearing dislocations. The use of cemented fixed-bearing and uncemented mobile-bearing designs have superior comparable long-term survivorship.

M.L. Tay B. Stone M. Nugent C.M. Frampton G.J. Hooper S.W. Young

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand

Outcomes following knee arthroplasty are typically defined as implant survivorship at defined timepoints, or revision incidence over time. These estimates are difficult to conceptualise, and lack context for younger patients with more remaining years of life. We therefore aimed to determine a ‘lifetime’ risk of revision as a more useful metric for total (TKA) and unicompartmental knee arthroplasty (UKA).

The New Zealand Joint Registry was used to identify 96,497 primary TKAs and 13,481 primary UKAs performed between 1999 and 2019. Patient mortality and revision incidence were also extracted. Estimates of lifetime risk were calculated using an actuarial lifetable method. The estimates were stratified by age and gender. Reasons for revision were categorised using previously published standardised definitions.

The lifetime risk of UKA revision was two-fold higher than TKA across all age groups (range 3.7-40.4% UKA, 1.6-22.4% TKA). Revision risk was higher for males with TKA (range 3.4%-25.2% males, 1.1%-20% females), but higher for females with UKA (range 4.3%-43.4% vs. 2.9%-37.4% for males). Revision due to infections were higher for TKA (1.5% males, 0.7% females) compared with UKA (0.4% males, 0.1% females). The increased risk in younger UKA patients was associated with higher incidence of aseptic loosening (UKA 2%, TKA 1%) and ‘unexplained pain’ (UKA 2%, TKA 0.2%).

The risk for UKA was two-fold higher than TKA, and this was partially explained by a higher proportion of revisions due to ‘unexplained pain’. For TKA, males had higher risk of revision, in contrast to UKA where females had higher risk; this gender difference was associated with higher incidence of infections with TKA. Younger age, gender and higher ASA status were also associated with increased lifetime risk of UKA revision. Lifetime risk of revision can provide a meaningful measure of arthroplasty outcomes to aid patient counselling.

M.J. Sandow Z.X. Cheng

This paper presents an ongoing review of the use of a wedge-shaped porous metal augments in the shoulder to address glenoid retroversion as part of anatomical total shoulder arthroplasty (aTSA).

Seventy-five shoulders in 66 patients (23 women and 43 men, aged 42 to 85 years) with Walch grade B2 or C glenoids underwent porous metal glenoid augment (PMGA) insertion as part of aTSA. Patients received either a 15º or 30º PMGA wedge (secured by screws to the native glenoid) to correct excessive glenoid retroversion before a standard glenoid component was implanted using bone cement. Neither patient-specific guides nor navigation were used. Patients were prospectively assessed using shoulder functional assessments (Oxford Shoulder Score [OSS], American Shoulder and Elbow Standardized Shoulder Assessment Form [ASES], visual analogue scale [VAS] pain scores and forward elevation [FE]) preoperatively, at three, six, and 12 months, and yearly thereafter, with similar radiological surveillance.

Forty-nine consecutive series shoulders had a follow-up of greater than 24 months, with a median follow-up of 48 months (range: 24–87 months). Median outcome scores improved for OSS (21 to 44), ASES (24 to 92), VAS (7 to 0), and FE (90º to 140º). Four patients died, but no others were lost to follow-up. Apart from one infection at 18 months postoperatively and one minor peg perforation, there were no complications, hardware failures, implant displacements, significant lucency or posterior re-subluxations. Radiographs showed good incorporation of the wedge augment with correction of glenoid retroversion from median 22º (13º to 46º) to 4º. All but four glenoids were corrected to within the target range (less than 10º retroversion).

The porous metal wedge-shaped augments effectively addressed posterior glenoid deficiency as part of aTSA for rotator cuff intact osteoarthritis, producing satisfactory clinical outcomes with no signs of impending future failure.

MJ Sandow C Howard ZX Cheng

Using a reverse engineering capability to quantify the factors that control the rigid body mechanics of the wrist, a mathematical forward animation capability and model of wrist motion that allows the carpus to move under its own rules is being developed. This characterises the isometric connections, from which was developed the Stable Central Column Theory of Carpal Mechanics - which incorporates the Law of Rules Based Motion.

This work has now advanced to the ability to reapply the extracted rules to allow rules-based rigid body reanimation of an individual wrist. As each wrist is unique, there is a given reality that each reanimation must be based on an individual wrist's unique rules, and the aspiration to create a standard or normal wrist is unrealistic.

Using True Life Anatomy (Adelaide, Aust) analysis software, the specific rules (morphology / connectivity / interaction / loading) of individual wrists have been characterised, and then reapplied in a rigid body reanimation environment using Adams (MSC Software, U.S.) software.

In the preliminary application of this biomechanics environment, by using the reverse engineering / forward reanimation process, wrist motion can be recreated - based purely on the unique rules, extracted from individual wrists. Instability of the proximal scaphoid was evident in several of the animations, and there was confirmation that the spatial attachment points of the isometric constraints are very exacting. The actual attachment and specific morphology of the carpal bones varied between individual wrists.

Using a reverse engineering and then forward reanimation process, we have been able to recreate wrist motion using the rigid body mechanics based on the Law of Rules Based Motion. Further work is required, but the potential to apply “what if” virtual surgery options to an individual injured wrist and more precisely characterise and test solutions to wrist dysfunction are becoming realised.

M.J. Sandow R. Page A. Hatton Y. Peng

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder.

Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed.

For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency.

Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision.

MJ Sandow ZX Cheng

Arthroscopic electrosurgical tools for ablative, desiccating or coagulative effect are delivered as monopolar or bipolar probes. Monopolar electrosurgery delivers various profiles of heat energy directly to the tissue within a non-conductive irrigant (such as water or glycine) whereas bipolar electrosurgery creates an energy source by producing an electrical arc between the bipolar electrodes on the instrument head within an electro-conductive irrigation solution (saline) - and the heat generated is then transferred to the target tissues. This study investigated the heat generation within the simulated in-vitro test model to review the level of local heat production and potential local tissue heat.

In a simulated In-vitro testing environment the local heat generation using bipolar or monopolar electrosurgical probes at standard power setting in either saline or water was tested, both touching and not touching a simulated tissue target, and for variable on-times.

Monopolar generated relatively little heat when used in water and not touching the tissue. By contrast the bipolar wand generated potentially damaging local tissue temperature rises when used in saline and not touching the tissue. Both probes generated high local tissue heat when touching the tissue in their recommended irrigation solution.

Monopolar electrosurgery delivered high localized temperature to the simulated tissue surface, but produced relatively little heat when not touching the tissue in a water solution. Bipolar however created high local temperature within the fluid adjacent to the probe irrespective if it was touching the tissue or not. Activation of the bipolar probe away from the tissue in saline irrigation may create a potential harmful temperature within the fluid medium without delivering therapeutic thermal effect to the target tissues. Monopolar electrosurgery appears to deliver a more controlled thermal effect, and only when in contact with the target tissues – potentially creating a reduced collateral thermal footprint.

M. Gunn

Escalating health care expenditure worldwide is driving the need for effective resource decision-making, with medical practitioners increasingly making complex resource decisions within the context of patient care. Despite raising serious legal and ethical issues in practice, this has attracted little attention in Australia, or internationally. In particular, it is unknown how orthopaedic surgeons perceive their obligations to the individual patient, and the wider community, when rationing care, and how they reconcile competing obligations. This research explores legal and ethical considerations, and resource allocation by Australian orthopaedic surgeons, as a means of achieving public health cost containment driven by macro-level policy and funding decisions.

This research found that Australian orthopaedic surgeon's perceptions, and resource allocation decision making, can be explained by understanding how principles of distributive justice challenge, and shift, the traditional medical paradigm. It found that distributive justice, and challenges of macro level health policy and funding decisions, have given rise to two new medical paradigms. Each which try to balance the best interests of individual patients with demands in respect of the sustainability of the health system, in a situation where resources may be constrained. This research shows that while bedside rationing has positioned the medical profession as the gate keepers of resources, it may have left them straddling an increasingly irreconcilable void between the interests of the individual patient and the wider community, with the sustainability of the health system hanging in the balance.

M. Marinova E. Houghton H. Seymour C. W. Jones

Ankle fractures in the elderly are common and have a mortality rate of 12% within the first year. Treatment is challenging due to osteoporotic bone and patient co-morbidities. Many patients struggle with non-weight-bearing (NWB) and presently there is no consensus in the literature regarding optimum management of these injuries.

We hypothesised that early weight-bearing in frail patients, Clinical Frailty scale (CFS) score of 4 or more will reduce morbidity and allow patients to return to their usual place of residence faster without jeopardising clinical outcome.

We conducted a retrospective analysis of 80 patients aged over 65 years managed at Fiona Stanley Hospital for ankle fractures between January 2016 and 2018. Patients were divided into two cohorts: 40 patients managed NWB and 40 who were permitted to weight-bear as tolerated (WBAT). Patients were stratified as fit (CFS 1–3) or frail (CFS 4+). Primary outcomes were one-year mortality, return to primary residence at six weeks and complications. Secondary outcomes included length of acute hospital stay and rehab stay.

For frail patients, those managed NWB stayed in rehab for 19 days longer (p=0.03) and had 28% more complications (p=0.03). By 6 weeks, fewer patients returned to full weight-bearing (p=0.03) and fewer patients had returned home (p=0.01). For fit patients, there were no significant differences in primary outcomes between NWB and WBAT.

Our novel study categorising patients by CSF demonstrates that early mobilisation in frail patients results in improved outcomes. Currently there is no formal treatment protocol for the management of ankle fractures in the elderly, and we hope that our proposed algorithm will assist surgeons at our institution and elsewhere.

Our study suggests that WBAT may benefit frail patients. We propose a protocol to assist in the management of geriatric ankle fracture patients based on clinical frailty scores.

M. Marinova A. Sundaram K. Holtham J. Ebert D. Wysocki D. Meyerkort R. Radic

Cryocompression therapy is a non-invasive and non-pharmacological modality used in managing acute post-operative inflammation and pain. A prospective, randomised controlled trial (RCT) was undertaken to evaluate the effectiveness of a post-operative cryocompression protocol using the Game ReadyTM (GR) device versus usual care on recovery following total knee arthroplasty (TKA).

A single centre RCT was conducted with 70 TKAs (68 patients) randomised to a 2-week intervention period consisting of treatment with GR cryocompression (n=33, 33.3% males) or a usual care protocol of ice with static compression using tubigrip (n=35, 54.3% males). Knee range of movement (ROM) (flexion and extension), a visual analogue pain score (VAS) and limb circumference were documented at day 1, 2 and 14, as well as 6 and 12 weeks post-surgery. ROM was also recorded at day 90, while medication use and length of hospital stay were documented. Patient reported outcome measures (PROMs) including the KOOS and patient satisfaction questionnaire were employed.

The GR group demonstrated 2.3° more (p=0.05) knee extension ROM overall, as well as 2. 8° more at day 1 (p=0.048), 3.8° at day 14 (p=0.007) and 5.4° at 3 months (p=0.017). There were no group differences (p>0.05) observed in pain (VAS), flexion ROM, limb circumference, opioid use or other PROMs. Across the full cohort, higher pain levels resulted in increased opioid intake (p=0.002), older patients used significantly less opioids (p<0.001) and males reported significantly less pain (VAS) than females (p=0.048).

Using GR following TKA is a safe, non-invasive tool that can be used to aid in the post-operative recovery period.

Patients using the GR cryocompression device gained significantly more extension ROM compared to the conventional ice with compression group, despite no other group differences.

J. St George M. Norquay O. Birke P. Gibbons D. Little

The risk of AVN is high in Unstable Slipped Capital Femoral Epiphysis (SCFE) and the optimal surgical treatment remains controversial. Our AVN rates in severe, unstable SCFE remained unchanged following the introduction of the Modified Dunn Procedure (MDP) and as a result, our practice evolved towards performing an Anterior Open Reduction and Decompression (AOR) in an attempt to potentially reduce the “second hit” phenomenon that may contribute. The aim of this study was to determine the early surgical outcomes in Unstable SCFE following AOR compared to the MDP.

All moderate to severe, Loder unstable SCFEs between 2008 and 2022 undergoing either an AOR or MDP were included. AVN was defined as a non-viable post-operative SPECT-CT scan.

Eighteen patients who underwent AOR and 100 who underwent MPD were included. There was no significant difference in severity (mean PSA 64 vs 66 degrees, p = 0.641), or delay to surgery (p = 0.973) between each group. There was no significant difference in the AVN rate at 27.8% compared to 24% in the AOR and MDP groups respectively (p = 0.732). The mean operative time in the AOR group was 24 minutes less, however this was not statistically significant (p = 0.084). The post-reduction PSA was 26 degrees (range, 13-39) in the AOR group and 9 degrees (range, −7 to 29) in the MDP group (p<0.001). Intra-operative femoral head monitoring had a lower positive predictive value in the AOR group (71% compared to 90%).

Preliminary results suggest the AVN rate is not significantly different following AOR. There is less of an associated learning curve with the AOR, but as anticipated, a less anatomical reduction was achieved in this group. We still feel that there is a role for the MDP in unstable slips with a larger remodelling component.

M. Hassanein A. Hassanein M. Hassanein M. Khaled N. Abol Oyoun

This study was performed at Assiut University, Assiut, Egypt.

Anterior distal femoral hemiepiphysiodesis (ADFH) using intra-articular plates for the correction of paediatric fixed knee flexion deformities (FKFD) has two main documented complications: postoperative knee pain and implant loosening. This study describes a biomechanical analysis and a preliminary report of a novel extra-articular technique for ADFH.

Sixteen femoral sawbones were osteotomized at the level of the distal femoral physis and fixed by rail frames to allow linear distraction simulating longitudinal growth. Each sawbone was tested twice: first using the conventional technique with medial and lateral parapatellar eight plates (group A) and then with the plates inserted in the proposed novel location at the most anterior part of the medial and lateral surfaces of the femoral condyles with screws in the coronal plane (group B). Gradual distraction was performed, and the resulting angular correction was measured. Strain gauges were attached to the plates, and the amount of strain (and equivalent stress) over the plates was recorded. This technique was then applied to 9 paediatric FKFDs of different aetiologies. The preoperative FKFD and the amount of subsequent angular correction were measured.

The amount of angular correction was higher in group B at 5, 10-, and 15-mm of distraction (p<0.001). The maximum and overall stresses measured throughout the distraction process were higher in group A (p<0.001). The mean FKFD improved from 24 ± 9° preoperatively to 9 ± 7° after 10 ± 3° months (p<0.001). The correction rate was 1.81 ± 0.65° per month.

During ADFH, the fixation of the eight plates in the coronal plane at the anterior part of the femoral condyles may produce greater correction and lower stresses over the implants as compared to the conventional technique. Preliminary results from our initial series seem to support the effectiveness of this technique with respect to the degree of angular correction achieved.

A.M. Boudali Y. Chai J. Farey J. Vigdorchik W.L. Walter

The spinopelvic alignment is often assessed via the Pelvic Incidence-Lumbar Lordosis (PI-LL) mismatch. Here we describe and validate a simplified method to evaluating the spinopelvic alignment through the L1-Pelvis angle (L1P). This method is set to reduce the operator error and make the on-film measurement more practicable.

126 standing lateral radiographs of patients presenting for Total Hip Arthroplasty were examined. Three operators were recruited to label 6 landmarks. One operator repeated the landmark selection for intra-operator analysis. We compare PI-LL mismatch obtained via the conventional method, and our simplified method where we estimate this mismatch using PI-LL = L1P - 90°. We also assess the method's reliability and repeatability.

We found no significant difference (p > 0.05) between the PI-LL mismatch from the conventional method (mean 0.22° ± 13.6) compared to L1P method (mean 0.0° ± 13.1). The overall average normalised root mean square error (NRMSE) for PI-LL mismatch across all operators is 7.53% (mean −3.3° ± 6.0) and 6.5% (mean −2.9° ± 4.9) for the conventional and L1P method, respectively. In relation to intra-operator repeatability, the correlation coefficients are 0.87 for PI, 0.94 for LL, and 0.96 for L1P. NRMSE between the two measurement sets are PI: 9.96%, LL: 5.97%, and L1P: 4.41%. A similar trend is observed in the absolute error between the two sets of measurements.

Results indicate an equivalence in PI-LL measurement between the methods. Reproducibility of the measurements and reliability between operators were improved. Using the L1P angle, the classification of the sagittal spinal deformity found in the literature translates to: normal L1P<100°, mild 100°<L1P<110°, and severe L1P>110°. Surgeons adopting our method should expect a small improvement in reliability and repeatability of their measurements, and a significant improvement of the assessment of the mismatch through the visualisation of the angle L1P.

N. Mohammed Abdul P. Yates T. Bernard

Total Knee Arthroplasty (TKA) is an effective surgery performed for knee osteoarthritis. Despite this success up to 20% of patients are less than fully satisfied. Rotating platform (RP) bearings have demonstrated significant reduction in rates of wear in laboratory studies but thus far have failed to demonstrate a clinical difference compared to fixed bearing (FB) arthroplasty in patients. This may be due to studies limited by small sample size and single centre design. Additionally, no studies have utilised modern patient-reported outcome measures (PROMs) such as PKIP to investigate differences between these bearings.

A non-randomised, prospective, multi-centre study was conducted across centres in Australia, United Kingdom and the United States from November 2012 to May 2015. Knee prosthesis included were the RP and FB models of the PFC Sigma Knee (Depuy, Synthes) and the ATTUNE Knee (Depuy, Synthes). Data was collected on pre-arthroplasty interventions, demographics and PROMs. PROMs included were the KOOS, OKS, EQ53DL and PKIP. Participants were followed-up for 2 years.

A total of 1,718 patients were recruited across 27 centres. 959 participants underwent a FB TKA, 759 participants underwent a RP TKA. No significant difference was found between RP and FB in change from baseline at 2 years across any parameter in all PROMs investigated at 2 years. Body Mass Index pre-operatively was the biggest indicator of change from baseline at 2 years.

Our data demonstrates similar improvements in the short-term in both RP and TKA across all PROMs. Patients reported similar scores in satisfaction, confidence, mobility and stability in the PKIP PROM for both RP and FB groups. We have not found any evidence to suggest that RP TKA is disadvantageous at 2 years, and this is reassuring for any surgeon looking to utilise this bearing type in practice.

Our data does not demonstrate a clinical advantage in RP TKA over FB TKA at 2 years in any PROM.

N. Mohammed Abdul A. Raymond M. Finsterwald S. Malik R. Aujla H. Wilson S. Dalgleish P. Truter U. Giwenewer A. Simpson A. Mattin S. Gohil B. Ricciardo L. Lam P. D'Alessandro

Traditionally, sports Injuries have been sub-optimally managed through Emergency Departments (ED) in the public health system due to a lack of adequate referral processes. Fractures are ruled out through plain radiographs followed by a reactive process involving patient initiated further follow up and investigation. Consequently, significant soft tissue and chondral injuries can go undiagnosed during periods in which early intervention can significantly affect natural progression. The purpose of this quality improvement project was to assess the efficacy of an innovative Sports Injury Pathway introduced to detect and treat significant soft tissue injuries.

A Sports Injury Pathway was introduced at Fiona Stanley Hospital (WA, Australia) in April 2019 as a collaboration between the ED, Physiotherapy and Orthopaedic Departments. ED practitioners were advised to have a low threshold for referral, especially in the presence of a history of a twisting knee injury, shoulder dislocation or any suggestion of a hip tendon injury. All referrals were triaged by the Perth Sports Surgery Fellow with early follow-up in our Sports Trauma Clinics with additional investigations if required. A detailed database of all referrals was maintained, and relevant data was extracted for analysis over the first 3 years of this pathway.

570 patients were included in the final analysis. 54% of injuries occurred while playing sport, with AFL injuries constituting the most common contact-sports injury (13%). Advanced Scope Physiotherapists were the largest source of referrals (60%). A total of 460 MRI scans were eventually ordered comprising 81% of total referrals. Regarding Knee MRIs, 86% identified a significant structural injury with ACL injuries being the most common (33%) followed by isolated meniscal tears (16%) and multi-ligament knee injuries (11%). 95% of Shoulder MRI scans showed significant pathology. 39% of patients required surgical management, and of these 50% were performed within 3 months from injury.

The Fiona Stanley Hospital Sports Injury Pathway has demonstrated its clear value in successfully diagnosing and treating an important cohort of patients who present to our Emergency Department. This low threshold/streamlined referral pathway has found that the vast majority of these patients suffer significant structural injuries that may have been otherwise missed, while providing referring practitioners and patients access to prompt imaging and high-quality Orthopaedic sports trauma services. We recommend the implementation of a similar Sports Injury Pathway at all secondary and tertiary Orthopaedic Centres.

N. Hong C. Jones T. Hong

Ideberg-Goss type VI/AO F2(4) glenoid fossa fractures are a rare and complex injury. Although some advocate non-operative management, grossly displaced glenoid fossa fractures in the young patient may warrant fixation. Current approaches still describe difficulty with access of the entirety of the glenoid, particularly the postero-superior quadrant.

We present 2 cases of Ideberg-Goss type VI/AO F2(4) glenoid fossa fractures treated with fixation through a novel “Deltoid Takedown” approach, which allows safe access to the whole glenoid with satisfactory clinical results at 5 and 7 years respectively.

N Green G Barlow D Erbulut M Stubican F Vindenes V Glatt K Tetsworth

This study investigated concurrent talar dome injuries associated with tibial pilon fractures, mapping their distribution across the proximal talar dome articular surface. It compared the two main mechanisms of injury (MOI), falling from a height and motor vehicle accident (MVA), and whether the fractures were open or closed.

From a previously compiled database of acute distal tibial pilon fractures (AO/OTA 43B/C) in adults of 105 cases, 53 cases were identified with a concurrent injury to the talar dome with a known mechanism of injury and in 44 it was known if the fracture was open or closed. Case specific 2D injury maps were created using a 1×1mm grid, which were overlayed in an Excel document to allow for comparative analyses. A two-way ANOVA was conducted that examined the effect of both MOI and if the fracture was open or closed on what percentage of the talar dome surface was injured.

There was a statistically-significant difference between the average percentage of injured squares on the talar dome by both whether the fracture was open or closed (f(1)=5.27, p= .027) and the mechanism of injury (f(1)=8.08, p= .007), though the interaction between these was not significant (p= .156). Open injuries and injuries that occurred during an MVA were more likely to increase the surface area of the talar dome injuries.

We have identified both MOI and if the fracture was either open or closed impacts the size of the injury present on the talar dome. Future research will investigate the aetiology of the differences noted, highlighting the clinical implications.

Surgeons treating tibial pilon fractures caused by either a MVA or an open fracture, should be aware of an increased risk of large injuries to the surface of the talar dome.

N. Paltoglou R. Page S. Gill

In Australia nearly two-thirds of arthroplasty procedures are performed in the private setting, which is disproportionate to the dimensioning 43.5% of the population with private health cover. The rapid growth of shoulder arthroplasty surgery will be absorbed by both private and public sectors. This study aimed to assess the influence of healthcare setting on elective shoulder arthroplasty outcomes, defined by revision rate, and functional measures.

Data was collected on all primary procedures performed from 2004 – 2019 within a regional area of Victoria, Australia. Patients were categorised into private or public settings. Trauma cases for acute proximal humerus fractures were excluded. The primary outcome of revision surgery was recorded as a cumulative percentage, and survival analysis conducted to calculate a hazard ratio (HR). Functional outcomes were measured through range-of-motion (ROM) and multiple validated patient-reported-outcome-measures (PROMs).

458 patients were identified in the study: 290 private and 168 public. There was no difference in the revision rate (3.8% private, 4.8% public), with an adjusted HR of 1.25 (p=0.66) for public compared to private. Baseline and post-operative functional measures were significantly greater in the private setting for ROMs and PROMs analysis, in particular post-operative QuickDASH (15.9±14.7 to 32.7±23.5; p<0.001) and Oxford Shoulder Score (42.6±6.3 to 35.7±11.2; p<0.001). However, there was no significant difference for any of the functional measures in the amount of change from baseline to 12-months between settings.

Although healthcare setting does not appear to influence revision rate for shoulder arthroplasty, clear differences were demonstrated for functional measures both pre and post operatively. This may be attributed to factors such as access to perioperative rehabilitation and should be an area to target future investigations.

I. Seth G. Bulloch N. Seth A. Siu S. Clayton K. Lower S. Roshan N. Nara

Complex regional pain syndrome type 1 (CRPS-I) is a devastating complication that can occur after limb extremity injuries. The effectiveness of vitamin C in preventing CRPS-I incidence is debatable. Therefore, we conducted a systematic review and meta-analysis to assess the role of vitamin C in CRPS-I prevention and its effect on pain score, functional outcomes and complications rate after wrist, ankle, and foot fractures.

We searched Medline, Embase, the Cochrane Library, Clinicaltrial.gov, and Google Scholar from infinity to May 2021 for relevant studies comparing the incidence of CRPS-I with administration of perioperative vitamin C versus placebo after wrist, ankle, and foot fractures. Continuous data such as functional outcomes and pain scores were pooled as mean differences (MD), whist dichotomous variables such as the incidence of CRPS-I and complications were pooled as odds ratios (OR), with 95% confidence interval (CI). Data analyses was done using R software (meta package, version 4.9-0) for Windows.

Eight studies, including two quasi-experimental studies, were included. The timeframe for vitamin C administration ranged from 42 to 50 days post-injury and/or surgical fixation and the dosage was either 500 mg or 1000 mg. The results showed that vitamin C was associated with a lower rate of CRPS-I relative to a placebo (OR 0.33, 95% CI [0.17, 0.63]). No significant difference was found between vitamin C and placebo in terms of complications (OR 1.90, 95% CI [0.99, 3.65]), functional outcomes (MD 6.37, 95% CI [-1.40, 14.15]), and pain scores (MD −0.14, 95% CI [-1.07, 0.79]).

The findings demonstrate that when compared to placebo, at least 42 days of vitamin C prophylaxis is associated with prevention of CRPS-I following wrist, ankle, and foot fractures, irrespective of vitamin C dosage or fracture type. No significant differences were found with secondary outcomes.

N. Flaaten G. Dyke

First rib fractures (FRFs) have historically been a marker for severe trauma and poor outcomes. The aim of this study was to assess whether an association still exists between a fractured first rib and global trauma scores suffered by the patient, examine mortality rate and identify other commonly associated injuries.

This study examined patients who presented to the Rockhampton Hospital with a traumatic FRF between the dates of July 2015 to June 2020. Patient demographics, mortality rate and additional injuries sustained by the patients were collected. The Injury Severity Score (ISS) was utilised and calculated for each patient. Analysis was conducted to determine associations between trauma scores and FRFs, mortality rate and other injuries sustained at the time of rib fracture.

In total, 545 patients had a rib fracture with 48 patients identified as having an FRF. Median age was 50 years. Thirty-seven (77%) were male. The most common mechanism of FRF was motor vehicle/motorbike accidents (71%). Fifty percent of patients with an observed FRF had the highest global ISS of very severe, with 13% severe, 22% moderate and 15% mild. No patients died from their injuries. Of those with an FRF, 79% experienced fractures other than ribs, 75% had other rib fractures and 52% had chest injuries.

A larger than expected proportion of FRFs were not associated with severe trauma scores or high mortality. These findings suggest that patients with an FRF may have a greater chance of surviving their traumatic FRF than previously reported. Clinicians should be aware of the potential for severity and other associated injuries, such as chest wall fractures and thoracic injuries, when treating a patient with a fracture of their first rib.

N. Ma S. Gogos A. Moaveni

Surgical site infections following orthopaedic surgery are a serious complication associated with increased morbidity and mortality. Intra-wound antibiotic powder may be able to provide infection prophylaxis locally with less systemic adverse effects, and promising results have been reported in systematic reviews of its use in spine surgery. This study aims to analyse the efficacy and adverse effect profile of intra-wound antibiotics in reducing surgical site infections in orthopaedic surgery for traumatic pelvic and lower limb fractures.

A systematic review was conducted for studies reporting on the incidence of surgical site infections following administration of intra-wound antibiotic powder in pelvic and lower limb trauma surgery. Randomised controlled trials, cohort and case-control studies were included. A meta-analysis was conducted for deep surgical site infections.

Seven studies were included in the systematic review including six retrospective case-control studies and one randomised controlled trial. Results of the meta-analysis suggest a potential 23% reduction in the odds of developing a deep surgical site infection in patients treated with intra-operative antibiotic powder compared with those managed with intravenous antibiotics alone (OR 0.77, 95% CI 0.52 – 1.13), although the results did not reach statistical significance.

Notable selective bias against intra-wound antibiotics and suboptimal study design were found in the retrospective studies, however the randomised controlled trial reported a significant reduction in deep surgical site infections with intra-wound vancomycin powder. There were no reports of systemic adverse outcomes and minimal risk of wound complications with the use of intra-wound antibiotics.

This review suggests the use of intra-wound antibiotic powder in pelvic and lower limb trauma surgery may reduce the incidence of deep surgical site infections. Further powered studies including randomised controlled trials are required to confirm the results highlighted in this study.

N. van der Gaast J.M. Huitema L. Brouwers M.J.R. Edwards E. Hermans J.N. Doornberg R.L. Jaarsma

Classification systems for tibial plateau fractures suffer from poor interobserver agreement, and their value in preoperative assessment to guide surgical fixation strategies is limited. For tibial plateau fractures four major characteristics are identified: lateral split fragment, posteromedial fragment, anterior tubercle fragment, and central zone of comminution. These fracture characteristics support preoperative assessment of fractures and guide surgical decision-making as each specific component requires a respective fixation strategy. We aimed to evaluate the additional value of 3D-printed models for the identification of tibial plateau fracture characteristics in terms of the interobserver agreement on different fracture characteristics.

Preoperative images of 40 patients were randomly selected. Nine trauma surgeons, eight senior and eight junior registrars indicated the presence or absence of four fracture characteristics with and without 3D-printed models. The Fleiss kappa was used to determine interobserver agreement for fracture classification and for interpretation, the Landis and Koch criteria were used.

3D-printed models lead to a categorical improvement in interobserver agreement for three of four fracture characteristics: lateral split (Kconv = 0.445 versus K3Dprint = 0.620; P < 0.001), anterior tubercle fragment (Kconv = 0.288 versus K3Dprint = 0.449; P < 0.001) and zone of comminution (Kconv = 0.535 versus K3Dprint = 0.652; P < 0.001).

The overall interobserver agreement improved for three of four fracture characteristics after the addition of 3D printed models. For two fracture characteristics, lateral split and zone of comminution, a substantial interobserver agreement was achieved.

Fracture characteristics seem to be a more reliable way to assess tibial plateau fractures and one should consider including these in the preoperative assessment of tibial plateau fractures compared to the commonly used classification systems.

L. Ernstbrunner M. Almond H. Rupasinghe O.I. Jo R.M. Zbeda D.C. Ackland E.T. Ek

The extracortical single-button (SB) inlay repair is one of the most preferred distal biceps tendon repair techniques. However, specific complications such as neurovascular injury and non-anatomic repairs have led to the development of techniques that utilize intracortical double-button (DB) fixation.

To compare the biomechanical stability of the extracortical SB repair with the anatomical DB repair technique.

Controlled laboratory study.

The distal biceps tendon was transected in 18 cadaveric elbows from 9 donors. One elbow of each donor was randomly assigned to the extracortical SBor anatomical DB group. Both groups were cyclically loaded with 60N over 1000 cycles between 90° of flexion and full extension. The elbow was then fixed in 90° of flexion and the repair construct loaded to failure. Gap-formation and construct stiffness during cyclic loading, and ultimate load to failure was analysed.

After 1000 cycles, the anatomical DB technique compared with the extracortical SB technique showed significantly less gap-formation (mean difference 1.2 mm; p=0.017) and significantly more construct stiffness (mean difference 31 N/mm; p=0.023). Ultimate load to failure was not significantly different comparing both groups (SB, 277 N ±92 vs. DB, 285 N ±135; p=0.859). The failure mode in the anatomical DB group was significantly different compared with the extracortical SB technique (p=0.002) and was due to fracture avulsion of the BicepsButton in 7 out of 9 specimens (vs. none in SB group).

Our study shows that the intracortical DB technique produces equivalent or superior biomechanical performance to the SB technique. The DB repair technique reduces the risk of nerve injury and better restores the anatomical footprint of biceps tendon. The DB technique may offer a clinically viable alternative to the SB repair technique.

O. Jo M. Almond H. Rupasinghe O.I. Jo D.C. Ackland L. Ernstbrunner E.T. Ek

Neer Type-IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. A novel plating technique using a superior lateral locking plate with antero-posterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment has been designed to enhance stability. The purpose of this study was to biomechanically compare three different clavicle plating constructs.

24 fresh-frozen cadaveric shoulders were randomised into three groups (n=8 specimens). Group 1: lateral locking plate only (Medartis Aptus Superior Lateral Plate); Group 2: lateral locking plate with CC stabilisation (Nr. 2 FiberWire); and Group 3: lateral locking plate with two AP locking screws stabilising the lateral fragment. Data was analysed for gap formation after cyclic loading, construct stiffness and ultimate load to failure, defined by a marked decrease in the load displacement curve.

After 500 cycles, there was no statistically significant difference between the three groups in gap-formation (p = 0.179). Ultimate load to failure was significantly higher in Group 3 compared to Group 1 (286N vs. 167N; p = 0.022), but not to Group 2 (286N vs. 246N; p = 0.604). There were no statistically significant differences in stiffness (Group 1: 504N/mm; Group 2: 564N/mm; Group 3: 512N/mm; p = 0.712). Peri-implant fracture was the primary mode of failure for all three groups, with Group 3 demonstrating the lowest rate of peri-implant fractures (Group 1: 6/8; Group 2: 7/8, Group 3: 4/8; p = 0.243).

The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications.

O.C. Critchley C. Guest S. Warby G. Hoy R.S. Page

Glenoid bone grafting in reverse total shoulder arthroplasty (RTSA) has emerged as an effective method of restoring bone stock in the presence of complex glenoid bone loss, yet there is limited published evidence on efficacy. The aim of this study was to conduct an analysis of clinical and radiographic outcomes associated with glenoid bone grafting in primary RTSA.

Patients who underwent a primary RTSA with glenoid bone grafting were retrospectively identified from the databases of two senior shoulder surgeons. Inclusion criteria included minimum of 12 months clinical and/or radiographical follow up. Patients underwent preoperative clinical and radiographic assessment. Graft characteristics (source, type, preparation), range of movement (ROM), patient-reported outcome measures (Oxford Shoulder Scores [OSS]), and complications were recorded. Radiographic imaging was used to analyse implant stability, graft incorporation, and notching by two independent reviewers.

Between 2013 and 2021, a total of 53 primary RTSA procedures (48 patients) with glenoid bone grafting were identified. Humeral head autograft was used in 51 (96%) of cases. Femoral head allograft was utilised in two cases. Depending on the morphology of glenoid bone loss, a combination of structural (corticocancellous) and non-structural (cancellous) grafts were used to restore glenoid bone stock and the joint line. All grafts were incorporated at review. The mean post-operative OSS was significantly higher than the pre-operative OSS (40 vs. 22, p < 0.001). ROM was significantly improved post-operatively. One patient is being investigated for residual activity-related shoulder pain. This patient also experienced scapular notching resulting in the fracturing of the inferior screw. One patient experienced recurrent dislocations but was not revised.

Overall, at short term follow up, glenoid bone grafting was effective in addressing glenoid bone loss with excellent functional and clinical outcomes when used for complex bone loss in primary RTSA. The graft incorporation rate was high, with an associated low complication rate.

P. Bekhit M. Saffi N. Hong T. Hong

Acromial morphology has been implicated as a risk factor for unidirectional posterior shoulder instability. Studies utilising plain film radiographic landmarks have identified an increased risk of posterior shoulder dislocation in patients with higher acromion positioning. The aims of this study were to develop a reproducible method of measuring this relationship on cross sectional imaging and to evaluate acromial morphology in patients with and without unidirectional posterior shoulder instability.

We analysed 24 patients with unidirectional posterior instability. These were sex and age matched with 61 patients with unidirectional anterior instability, as well as a control group of 76 patients with no instability. Sagittal T1 weighted MRI sequences were used to measure posterior acromial height relative to the scapular body axis (SBA) and long head of triceps insertion axis (LTI). Two observers measured each method for inter-observer reliability, and the intraclass correlation coefficient (ICC) calculated.

LTI method showed good inter-observer reliability with an ICC of 0.79. The SBA method was not reproducible due suboptimal MRI sequences. Mean posterior acromial height was significantly greater in the posterior instability group (14.2mm) compared to the anterior instability group (7.7mm, p=0.0002) as well when compared with the control group (7.0mm, p<0.0001). A threshold of 7.5mm demonstrated a significant increase in the incidence of posterior shoulder instability (RR = 9.4).

We conclude that increased posterior acromial height is significantly associated with posterior shoulder instability. This suggests that the acromion has a role as an osseous restraint to posterior shoulder instability.

P. Bekhit C. Ou J. Baker

Sarcopenia has been observed to be a predictor of mortality in international studies of patients with metastatic disease of the spine. This study aimed to validate sarcopenia as a prognostic tool in a New Zealand setting. A secondary aim of this study was to assess the intra-observer reliability of measurements of psoas and vertebral body cross sectional areas on computed tomography imaging.

A cohort of patients who had presented to Waikato Hospital with secondary neoplasia in the spinal column from 2014 to 2018 was selected. Cross sectional psoas and vertebral body areas were measured at the mid-pedicle L3 level, followed by calculation of the psoas to vertebral body cross sectional area ratio. Psoas to vertebral body cross sectional area ratio was compared with survivorship. The strength of the correlation between sarcopenia and survivorship was compared with the correlation between serum albumin and survivorship, as well as the correlation between the Metastatic Spine Risk Index (MSRI) and survivorship.

A total of 110 patients who received operative (34) and non-operative (76) were included. The results demonstrate that psoas to vertebral body cross sectional area ratio is not statistically significantly correlated with survivorship (p=0.53). Serum albumin is significantly correlated with survivorship (p<0.0001), as was the MSRI. There is good intra-observer and inter-observer reliability for measurements of psoas to vertebral body cross sectional area.

This study failed to demonstrate the utility for the psoas to vertebral body cross sectional area ratio that other studies have demonstrated in estimating survivorship. Serum albumin levels remain a useful prognostic indicator in patients with secondary tumours in the vertebral column.

P. Bekhit M. Coia J. Baker

Several different algorithms attempt to estimate life expectancy for patients with metastatic spine disease. The Skeletal Oncology Research Group (SORG) has recently developed a nomogram to estimate survival of patients with metastatic spine disease. Whilst the use of the SORG nomogram has been validated in the international context, there has been no study to date that validates the use of the SORG nomogram in New Zealand. This study aimed to validate the use of the SORG nomogram in Aotearoa New Zealand.

We collected data on 100 patients who presented to Waikato Hospital with a diagnosis of spinal metastatic disease. The SORG nomogram gave survival probabilities for each patient at each time point. Receiver Operating Characteristic (ROC) Area Under Curve (AUC) analysis was performed to assess the predictive accuracy of the SORG score. A calibration curve was also performed, and Brier scores calculated. A multivariate Cox regression analysis was performed.

The SORG score was correlated with 30 day (AUC = 0.72) and 90-day mortality (AUC = 0.71). The correlation between the SORG score and 90-day mortality was weaker (AUC = 0.69). Using this method, the nomogram was correct for 79 (79%) patients at 30-days, 59 patients (59%) at 90-days, and 42 patients (42%) at 365-days. Calibration curves demonstrated poor forecasting of the SORG nomogram at 30 (Brier score = 0.65) and 365 days (Brier score = 0.33). The calibration curve demonstrated borderline forecasting of the SORG nomogram at 90 days (Brier score = 0.28). Several components of the SORG nomogram were not found to be correlated with mortality.

In this New Zealand cohort the SORG nomogram demonstrated only acceptable discrimination at best in predicting life 30-, 90- or 356-day mortality in patients with metastatic spinal disease.

P. Kruger S. Lynskey A. Sutherland

The attitudes of orthopaedic surgeons regarding radiology reporting is not well-described in the literature. We surveyed Orthopaedic Surgeons in Australia and New Zealand to assess if they routinely review formal radiology reports.

An anonymized, 14 question online survey was distributed to consultant surgeons of the Australian and New Zealand Orthopaedic Associations (AOA, NZOA). Two hundred respondents completed the survey (Total number of Fellows: 283 NZOA, 1185 AOA). 18.5% of respondents always reviewed the formal Radiology report, 44.5% most of the time, 35% sometimes and 2% never. By imaging modality, MRI reports were the most frequently reviewed (92%), followed by ultrasound (74%) and nuclear medicine (63%). Only 10% of surgeons consulted formal reports for plain radiography. 55% of surgeons were still likely to disagree with the MRI report, followed by 46% for plain radiography. In cases of disagreement, only 21% of surgeons would always contact the reporting radiologist. The majority of Surgeons (85.5%) think there should be more collaboration between the disciplines, although only 50.5% had regular attendance of a Radiologist at their departmental audit.

This survey reveals that the majority of orthopaedic surgeons are not routinely reading radiology reports. This points towards a need for further interdisciplinary collaboration. To our knowledge, this is the first survey directly assessing attitudes of orthopaedic surgeons towards radiology reports.

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P.M. Walker

This technique is a novel superior based muscle sparing approach. Acetabular reaming in all hip approaches requires femoral retraction. This technique is performed through a hole in the lateral femoral cortex without the need to retract the femur.

A 5 mm hole is drilled in the lateral femur using a jig attached to the broach handle, similar to a femoral nail. Specialised instruments have been developed, including a broach with a hole going through it at the angle of the neck of the prosthesis, to allow the rotation of the reaming rod whilst protecting the femur. A special C-arm is used to push on the reaming basket. The angle of the acetabulum is directly related to the position of the broach inside the femoral canal and the position of the leg. A specialised instrument allows changing of offset and length without dislocating the hip during trialling.

Some instrumentation has been used in surgery but ongoing cadaver work is being performed for proof of concept. The ability to ream through the femur has been proven during surgery. The potential risk to the bone has been assessed using finite analysis as minimal. The stress levels for any diameter maintained within a safety factor >4 compared to the ultimate tensile strength of cortical bone.

The described technique allows for transfemoral acetabular reaming without retraction of the femur. It is minimally invasive and simple, requiring minimal assistance. We are incorporating use with a universal robot system as well as developing an electromagnetic navigation system. Assessment of the accuracy of these significantly cheaper systems is ongoing but promising.

This approach is as minimally invasive as is possible, safe, requires minimal assistance and has a number of other potential advantages with addition of other new navigation and simple robotic attachments.

H.V. Morris C. Cameron T.C. Vanderboor A.T.V. Nguyen M. Londahl Y.H. Chong P. Navarre

Fractures of the neck of femur are common in the older adult with significant morbidity and mortality rates. This patient cohort is associated with frailty and multiple complex medical and social needs requiring a multidisciplinary team to provide optimal care. The aim of this study was to assess the outcomes at 5 years following implementation of a collaborative service between the Orthopaedic and Geriatric departments of Southland Hospital in 2012.

Retrospective data was collected for patients aged 65 years and older who were admitted with a fragility hip fracture. Data was collated for 2011 (pre-implementation) and 2017 (post-implementation). Demographics and ASA scores were recorded. We assessed 30-day and 1-year mortality, surgical data, length of stay and complications.

There were 74 patient admissions in 2011 and 107 in 2017. Mean age at surgery was 84.2 years in 2011 and 82.6 years in 2017 (p>0.05). Between the 2011 and 2017 groups there has been a non-significant reduction in length of stay on the orthopaedic ward (9.8 days vs 7.5 days, p=0.138) but a significant reduction in length of stay on the rehabilitation ward (19.9 vs 9 days, p<0.001). There was a significant decrease in frequency of patients with a complication (71.6% vs 57%, p=0.045) and a marginal reduction in number of complications (p=0.057). Through logistic regression controlling for age, sex and ASA score, there was a reduction in the odds of having a complication by 12% between 2011 and 2017 (p<0.001). There was no difference in mortality between the groups.

The orthogeriatric model of care at Southland Hospital appears to have reduced both the frequency of complications and length of stay on the rehabilitation ward 5 years after its implementation. This is the first study in New Zealand demonstrating medium-term post-implementation follow-up of what is currently a nationally accepted standard model of care.

N.M. Abdul Z. Haywood S.J. Edmondston P.J. Yates

Patient reported outcome measures (PROMs) after total knee arthroplasty (TKA) are typically used to assess longitudinal change in pain and function after total knee arthroplasty (TKA). The Patient's Knee Implant Performance (PKIP) score was developed to evaluate outcomes more broadly including function, stability, confidence, and satisfaction. Although validated in patients having a primary TKA, the PKIP has not been evaluated as an outcome measure for patients having revision TKA. This study examined patient outcomes at one year following primary and revision TKA measured using the PKIP, compared to Oxford Knee Scores.

A retrospective analysis of pre-operative and one-year post-operative outcomes was completed for 39 patients (21 female) who had primary (n=27) or revision (n=12) TKA with a single surgeon between 2017 and 2020. The mean age was 69.2±7.4 years, and mean weight 87.4± 5.1kg. The change over time and correlation between the self-reported outcome measures was evaluated.

There was a significant improvement in the PKIP overall score at the 12-month follow-up (32± 13 v 69± 15, p= <0.001), with no significant difference between groups (3.3 points, p=0.50). Among the PKIP sub-scores, there was a significant improvement in knee confidence (3.5±2 vs 7.7±2; p<0.001), stability (3.4±2 vs 7.4±3; p<0.001) and satisfaction (2.5±1.7 vs 6.6±3, p<0.001). Between group differences in PKIP sub-scores one year after surgery were small and non-significant. For all patients, the OKS and PKIP scores were moderately correlated before surgery (r=0.64, p=<0.05), and at 1 year after surgery (r=0.61, p= <0.001).

Significant improvements in knee confidence, stability, and satisfaction one year after TKA were identified from the PKIP responses, with no significant difference between primary and revision surgery. The moderate correlation with the OKS suggests these questionnaires measure difference constructs and may provide complementary outcome information in this patient cohort.

R. Patel R. Elliott

Regional anaesthesia is integral to best practice analgesia for patients with neck of femur fractures (NOFFs). These patients are generally frail and are vulnerable to side effects of opioid analgesia. Femoral nerve block (FNB) or fascia-iliaca block (FIB) can reduce opioid requirement. Literature supports good efficacy for extra-capsular NOFFs however it is acknowledged to be suboptimal for intracapsular fractures.

We present a novel technique, using point of care ultrasound guidance to perform hip ultrasound guided haematoma (HUSH) aspiration, and injection of local anaesthetic (block) for intracapsular NOFFs.

This a case control series. A consecutive series of cognitively intact patients, with an isolated intra-capsular NOFF, received a HUSH block using 10mls of 0.75% Ropivicaine. Haematoma was aspirated and volume recorded. This was performed in addition to standard NOFF pathway analgesia that includes a FIB and multimodal analgesia including opioids. Visual Analogue Scale (VAS)pain scores at rest and on movement were recorded pre and post procedure as well as combined morphine equivalent units administered post HUSH block. The control arm was a retrospective group of similar patients who followed the routine care pathway including a FIB. VAS pain scores from observation charts and usage of morphine equivalent units were calculated.

Ten patients consented to receive HUSH blocks and we included thirty-eight patients in our control series. The HUSH block group showed mean VAS pain score of 4.2/10 at rest and 8.6 on movement prior to block. In the time after the block, VAS pain scores reduced to 1.5 at rest (p=0.007) and 3.1 on movement (p=0.0001) with a mean total morphine equivalent use of 8.75mg. This is significantly different from the control group's mean VAS pain at rest score 6.9 (p=0.0001) and 24.1mg total morphine equivalent (p=0.07).

HUSH Block in addition to fascia iliaca block appears to significantly better pain relief in intracapsular neck of femur fracture patients when compared to fascia iliaca block alone. We believe it is relatively easy to perform with readily available ultrasound scanners in emergency departments.

R. Sorial S. Coffey S. Callary

Roentgen Stereophotogrammetric Analysis (RSA) is the gold standard for measuring implant micromotion thereby predicting implant loosening. Early migration has been associated with the risk of long-term clinical failure. We used RSA to assess the stability of the Australian designed cementless hip stem (Paragon TM) and now report our 5-year results.

Fifty-three patients were prospectively and consecutively enrolled to receive a Paragon hip replacement. Tantalum beads were inserted into the bone as per RSA protocol and in the implant. RSA x-rays were taken at baseline 1–4 days post-surgery, at 6 weeks, 6 months, 12 months, 2 years, and 5 years. RSA was completed by an experienced, independent assessor.

We reported the 2-year results on 46 hips (ANZJS 91 (3) March 2021 p398) and now present the 5-year results on 27 hips. From the 2-year cohort 5 patients had died, 8 patients were uncontactable, 1 patient was too unwell to attend, 5 patients had relocated too far away and declined. At 5 years the mean axial subsidence of the stem was 0.66mm (0.05 to 2.96); the mean rotation into retroversion was 0.49˚ (−0.78˚ to 2.09˚), rotation of the stem into valgus was −0.23˚ (−0.627˚ to 1.56˚). There was no detectable increase in subsidence or rotation between 6 weeks and 5 years. We compared our data to that published for the Corail cementless stem and a similar pattern of migration was noted, however greater rotational stability was achieved with the Paragon stem over a comparable follow-up period.

The RSA results confirm that any minor motion of the Paragon cementless stem occurs in the first 6 weeks after which there is sustained stability for the next 5 years. The combination of a bi-planar wedge and transverse rectangular geometry provide excellent implant stability that is comparable to or better than other leading cementless stems.

R. Philippot

Instability and aseptic loosening are the two main complications after revision total hip arthroplasty (rTHA). Dual-mobility (DM) cups were shown to counteract implant instability during rTHA. To our knowledge, no study evaluated the 10-year outcomes of rTHA using DM cups, cemented into a metal reinforcement ring, in cases of severe acetabular bone loss. We hypothesized that using a DM cup cemented into a metal ring is a reliable technique for rTHA at 10 years, with few revisions for acetabular loosening and/or instability.

This is a retrospective study of 77 rTHA cases with severe acetabular bone loss (Paprosky ≥ 2C) treated exclusively with a DM cup (NOVAE STICK; SERF, DÉCINES-CHARPIEU, FRANCE) cemented into a cage (Kerboull cross, Burch-Schneider, or ARM rings). Clinical scores and radiological assessments were performed preoperatively and at the last follow-up. The main endpoints were revision surgery for aseptic loosening or recurring dislocation.

With a mean follow-up of 10.7 years [2.1-16.2], 3 patients were reoperated because of aseptic acetabular loosening (3.9%) at 9.6 years [7–12]. Seven patients (9.45%) dislocated their hip implant, only 1 suffered from chronic instability (1.3%). Cup survivorship was 96.1% at 10 years. No sign of progressive radiolucent lines were found and bone graft integration was satisfactory for 91% of the patients.

The use of a DM cup cemented into a metal ring during rTHA with complex acetabular bone loss was associated with low revision rates for either acetabular loosening or chronic instability at 10 years. That's why we also recommend DM cup for all high risk of dislocation situations.

R. Philippot

Dual mobility is a French concept that appeared in the 1970s and was initially intended to reduce dislocation rates.

In recent years, this concept has evolved with new HA titanium spray coatings, new external macrostructures, and better-quality polyethylene. This has allowed to extend the indications to younger and therefore active populations.

The objective of our work is to analyze at least 10 years a homogeneous and continuous series of 170 primary total hip replacements associating a latest generation Novae Sunfit® dual mobility cup with a straight femoral stem. Only primary arthroplasties for osteoarthritis or necrosis were included. Total hip arthroplasty was always performed through a posterolateral approach. All patients had regular clinical and radiological follow-up. The average follow-up in our series was 11.5 years. The average age of the population is 71 years.

At the last follow-up, there were 17 deaths, 6 losses to follow up and 9 adverse events, including 1 cup change for psoas impingement and 1 dislocation. The low rate of dislocation at 11 years confirms the high stability of the dual mobility, which should be recommended for primary procedure for patients at high risk of postoperative instability. The lack of intraprosthetic dislocation due to wear at 11 years of follow-up highlights the good quality of the latest generation of polyethylene, and the need to combine high-polished surfaces and a refined femoral neck with a dual mobility cup. Finally, the lack of aseptic loosening confirms the quality of the secondary fixation of these implants and justifies their wider use in all patients.

R. Philippot

THA in patients with acetabular bone defects is associated with a high risk of dislocation. Dual mobility (DM) cups are known to prevent and treat chronic instability. The aim of this study was to evaluate the dislocation rate and survival of jumbo DM cups.

This was a retrospective, continuous, multicenter study of all the cases of jumbo DM cup implantation between 2010 and 2017 in patients with acetabular bone loss (Paprosky 2A: 46%, 2B: 32%, 2C: 15% and 3A: 6%). The indications for implantation were revisions for aseptic loosening of the cup (n=45), aseptic loosening of the femoral stem (n=3), bipolar loosening (n=11), septic loosening (n=10), periprosthetic fracture (n=5), chronic dislocation (n=4), intraprosthetic dislocation (n=2), cup impingement (n=1), primary posttraumatic arthroplasty (n=8), and acetabular dysplasia (n=4). The jumbo cups used were COPTOS TH (SERF), which combines press-fit fixation with supplemental fixation (acetabular hook, two superior flanges with one to four screws, two acetabular pegs). A bone graft was added in 74 cases (80%). The clinical assessment consisted of the Harris hip score. The primary endpoint was surgical revision for aseptic acetabular loosening or the occurrence of a dislocation episode.

In all, 93 patients were reviewed at a mean follow-up of 5.3 ± 2.3 years [0, 10]. As of the last follow-up, the acetabular cup had been changed in five cases: three due to aseptic loosening (3.2%) and two due to infection (2.1%). The survivorship free of aseptic loosening was 96.8%. Three patients (3%) suffered a dislocation. At the last follow-up visit, the mean HSS scores were 72.15, (p < 0.05).

Use of a jumbo DM cup in cases of acetabular bone defects leads to satisfactory medium-term results with low dislocation and loosening rates.

R.H. Gregor G.J. Hooper C.M.A Frampton

Due to shorter hospital stays and faster patient rehabilitation Unicompartmental Knee Replacements (UKR) are now considered more cost effective than Total Knee Joint Replacements (TKJR). Obesity however, has long been thought of as a relative contraindication to UKR due to an unproven theoretical concern of early loosening.

This study is a retrospective review of patient reported outcome scores and revision rates of all UKR with recorded BMI performed by the Canterbury District Health Board (CDHB) from January 2011 and September 2021. Patient reported outcome scores were taken preoperatively, at 6 months, 1 year, 5 years and 10 years post operatively. These included WOMAC, Oxford, HAAS, UCLA, WHOQOL, normality, pain and patient satisfaction. 873 patients had functional scores recorded at 5 years and 164 patients had scores recorded at 10 years. Further sub-group analysis was performed based on patient BMI of <25, 25-30, 30-35 and >35. Revision data was available for 2377 UKRs performed in Christchurch during this period.

Both obese (BMI >30) and non-obese (BMI <30) patients had significantly improved post-operative scores compared to preoperative. Pre-operatively obese patients had significantly lower functional scores except for pain and UCLA. All functional scores were lower in obese patients at 5 years but this did not meet minimum clinical difference. At 10 years, there was significantly lower HAAS, satisfaction and WOMAC scores for obese patients but no difference in Oxford, normality, WHOQOL, UCLA and pain scores. There was no significant difference in the improvement from pre-operative scores between obese and non-obese patients. All cause revision rate for obese patients at 10 years was 0.69 per 100 observed component years compared to 0.76 in non-obese. This was not statistically significant.

Our study proves that UKR is an excellent option in obese patients with post-operative improvement in functional scores and 10 year survivorship equivalent to non-obese patients.

R. Boyle P. Stalley D. Franks M. Guzman A. Maher C. Scholes

We present the indications and outcomes of a series of custom 3D printed titanium acetabular implants used over a 9 year period at our institution (Sydney, Australia), in the setting of revision total hip arthroplasty.

Individualised image-based case planning with additive manufacturing of pelvic components was combined with screw fixation and off-the-shelf femoral components to treat patients presenting with failed hip arthroplasty involving acetabular bone loss. Retrospective chart review was performed on the practices of three contributing surgeons, with an initial search by item number of the Medicare Benefits Scheme linked to a case list maintained by the manufacturer. An analysis of indications, patient demographics and clinical outcome was performed.

The cohort comprised 65.2% female with a median age of 70 years (interquartile range 61–77) and a median follow up of 32.9 months (IQR 13.1 - 49.7). The indications for surgery were infection (12.5%); aseptic loosening (78.1%) and fracture (9.4%), with 65.7% of cases undergoing previous revision hip arthroplasty. A tumour prosthesis was implanted into the proximal femur in 21.9% of cases. Complications were observed in 31.3% of cases, with four cases requiring revision procedures and no deaths reported in this series. Kaplan-Meier analysis of all-cause revision revealed an overall procedure survival of 88.7% at two years (95%confidence interval 69 - 96.2) and 83.8% (95%CI 62 - 93.7) at five years, with pelvic implant-specific survival of 98% (95%CI 86.6 - 99.7) at two and five year follow up.

We conclude that an individualised planning approach for custom 3D printed titanium acetabular implants can provide high overall and implant-specific survival at up to five years follow up in complex cases of failed hip arthroplasty and acetabular bone loss.

R. Boyle R. Kim A. Maher P. Stalley V. Bhadri

PVNS or TGCT (Pigmented Villonodular Synovitis, or Tenosynovial Giant Cell tumour) is a benign tumour affecting the synovial lining of joints and tendon sheaths, historically treated with surgical excision or debridement. We have shown previously this management is fraught with high recurrence rates, especially in its diffuse form. We present the encouraging early results of medical management for this condition with use of a CSF1 inhibitor, in comparison to a cohort of 137 cases previously treated at our institution.

R. Rahardja H. Love M.G. Clatworthy S.W. Young

Arthrofibrosis is a less common complication following anterior cruciate ligament (ACL) reconstruction and there are concerns that undergoing early surgery may be associated with arthrofibrosis. The aim of this study was to identify the patient and surgical risk factors for arthrofibrosis following primary ACL reconstruction.

Primary ACL reconstructions prospectively recorded in the New Zealand ACL Registry between April 2014 and December 2019 were analyzed. The Accident Compensation Corporation (ACC) database was used to identify patients who underwent a subsequent reoperation with review of operation notes to identify those who had a reoperation for “arthrofibrosis” or “stiffness”. Univariate Chi-Square test and multivariate Cox regression analysis was performed. Hazard ratios (HR) with 95% confidence intervals (CI) were computed to identify the risk factors for arthrofibrosis.

9617 primary ACL reconstructions were analyzed, of which 215 patients underwent a subsequent reoperation for arthrofibrosis (2.2%). A higher risk of arthrofibrosis was observed in female patients (adjusted HR = 1.67, 95% CI 1.22 – 2.27, p = 0.001), patients with a history of previous knee surgery (adjusted HR = 1.97, 95% CI 1.11 – 3.50, p = 0.021) and when a transtibial femoral tunnel drilling technique was used (adjusted HR = 1.55, 95% CI 1.06 – 2.28, p = 0.024). Patients who underwent early ACL reconstruction within 6 weeks of their injury did not have a higher risk of arthrofibrosis when compared to patients who underwent surgery more than 6 weeks after their injury (3.5% versus 2.1%, adjusted HR = 1.56, 95% CI 0.97 – 2.50, p = 0.07). Age, graft type and concomitant meniscal injury did not influence the rate of arthrofibrosis.

Female sex, a history of previous knee surgery and a transtibial femoral tunnel drilling technique are risk factors for arthrofibrosis following primary ACL reconstruction.

R. Rahardja M. Zhu J.S. Davis L. Manning S. Metcalf S.W. Young

This study aimed to identify the success rate of debridement, antibiotics and implant retention (DAIR) for prosthetic joint infection (PJI) in a large prospective cohort of patients undergoing total knee arthroplasty (TKA). The ability for different PJI classification systems to predict DAIR success was assessed.

A prospective, multicenter study of PJIs occurring between July 2014 and December 2017 in 27 hospitals across Australia and New Zealand was performed. First time PJIs following primary TKA that were managed with DAIR were analyzed. DAIR success was defined as the patient being alive with documented absence of clinical or microbiological evidence of infection and no ongoing antibiotics for the index joint at 2-year follow-up. Multivariate analysis was performed for multiple PJI classification systems to assess their ability to predict DAIR success using their respective definitions of “early” PJI (Coventry ≤1 month, International Consensus Meeting ≤90 days or Auckland <1 year), or as hematogenous versus chronic PJI (Tsukayama).

189 PJIs were managed with DAIR, with an overall success rate of 45% (85/189). Early PJIs had a higher rate of DAIR success when analyzed according to the Coventry system (adjusted odds ratio = 3.85, p = 0.008), the ICM system (adjusted odds ratio = 3.08, p = 0.005) and the Auckland system (adjusted odds ratio = 2.60, p = 0.01). DAIR success was lower in both hematogenous (adjusted odds ratio = 0.36, p = 0.034) and chronic PJIs (adjusted odds ratio = 0.14, p = 0.003) occurring more than one year since the primary TKA.

DAIR success is highest when performed in infections occurring within one year of the primary TKA. Late infections had a high DAIR failure rate irrespective of their classification as hematogenous or chronic. Time since primary is a useful predictor of DAIR success.

R. Rahardja H. Love M.G. Clatworthy S.W. Young

The optimal method of tibial fixation when using a hamstring tendon autograft in anterior cruciate ligament (ACL) reconstruction is unclear. This study aimed to compare the risk of revision ACL reconstruction between suspensory and interference devices on the tibial side.

Prospective data on primary ACL reconstructions recorded in the New Zealand ACL Registry between April 2014 and December 2019 were analyzed. Only patients with a hamstring tendon autograft fixed with a suspensory device on the femoral side were included. The rate of revision ACL reconstruction was compared between suspensory and interference devices on the tibial side. Univariate Chi-Square test and multivariate Cox regression was performed to compute hazard ratios (HR) and 95% confidence intervals (CI) with adjustment for age, gender, time-to-surgery, activity at the time of injury, number of graft strands and graft diameter.

6145 cases were analyzed, of which 59.6% were fixed with a suspensory device on the tibial side (n = 3662), 17.6% fixed with an interference screw with a sheath (n = 1079) and 22.8% fixed with an interference screw without a sheath (n = 1404). When compared to suspensory devices (revision rate = 3.4%), a higher risk of revision was observed when using an interference screw with a sheath (revision rate = 6.2%, adjusted HR = 2.05, 95% CI 1.20 – 3.52, p = 0.009) and without a sheath (revision rate = 4.6%, adjusted HR = 1.81, 95% CI 1.02 – 3.23, p = 0.044). The number of graft strands and a graft diameter of ≥8 mm did not influence the risk of revision.

When reconstructing the ACL with a hamstring tendon autograft, the use of an interference screw, with or without a sheath, on the tibial side has a higher risk of revision when compared to a suspensory device.

R. Rahardja A. Mehmood B. Coleman J.T. Munro S.W. Young

The optimal timing of when to perform manipulation under anesthesia (MUA) for stiffness following total knee arthroplasty (TKA) is unclear. This study aimed to identify the risk factors for MUA following primary TKA and whether performing an “early” MUA within 3 months results in a greater improvement in range of motion.

Primary TKAs performed between January 2013 and December 2018 at three tertiary New Zealand hospitals were reviewed. International Classification of Diseases discharge coding was used to identify patients who underwent an MUA. Multivariate Cox regression was performed to identify patient and surgical risk factors for MUA. Pre- and post-MUA knee flexion angles were identified through manual review of operation notes. Multivariate linear regression was performed to compare the mean flexion angles pre- and post-MUA, as well as the mean gain in flexion, between patients undergoing “early” (<3 months) versus “late” MUA (>3 months).

7386 primary TKAs were analyzed in which 131 underwent subsequent MUA (1.8%). Patients aged <65 years were two times more likely to undergo MUA compared to patients aged ≥65 years (2.5% versus 1.3%, adjusted hazard ratio = 2.1, p<0.001). Gender, body mass index, patient comorbidities or a history of cancer were not associated with the risk of MUA. There was no difference in the final post-MUA flexion angle between patients who underwent early versus late MUA (104.7 versus 104.1 degrees, p = 0.819). However, patients who underwent early MUA had poorer pre-MUA flexion (72.3 versus 79.6 degrees, p = 0.012), and subsequently had a greater overall gain in flexion compared to patients who underwent late MUA (mean gain 33.1 versus 24.3 degrees, p<0.001).

Younger age was the only patient risk factor for MUA. A greater overall gain in flexion was achieved in patients who underwent early MUA within 3 months.

R. Rahardja H. Love M.G. Clatworthy S.W. Young

Meniscal repairs are commonly performed during anterior cruciate ligament (ACL) reconstruction. This study aimed to identify the risk factors for meniscal repair failure following concurrent primary ACL reconstruction.

Primary ACL reconstructions with a concurrent repair of a meniscal tear recorded in the New Zealand ACL Registry between April 2014 and December 2018 were analyzed. Meniscal repair failure was defined as a patient who underwent subsequent meniscectomy, and was identified after cross-referencing data from the ACL Registry with the national database of the Accident Compensation Corporation (ACC). Multivariate Cox regression was performed to produce hazard ratios (HR) with 95% confidence intervals (CI) to identify the patient and surgical risk factors for meniscal repair failure.

2041 meniscal repairs were analyzed (medial = 1235 and lateral = 806). The overall failure rate was 9.4% (n = 192). Failure occurred in 11.1% of medial (137/1235) and 6.8% of lateral (55/806) meniscal repairs. The risk of medial failure was higher with hamstring tendon autografts (adjusted HR = 2.00, 95% CI 1.23 – 3.26, p = 0.006) and in patients with cartilage injury in the medial compartment (adjusted HR = 1.56, 95% CI 1.09 – 2.23, p = 0.015). The risk of lateral failure was higher when the procedure was performed by a surgeon with an annual case volume of less than 30 ACL reconstructions (adjusted HR = 1.92, 95% CI 1.10 – 3.33, p = 0.021). Age, gender, time from injury-to-surgery and femoral tunnel drilling technique did not influence the risk of meniscal repair failure.

When repairing a meniscal tear during ACL reconstruction, the use of a hamstring tendon autograft or the presence of cartilage injury in the medial compartment increases the risk of medial meniscal repair failure. Lower surgeon case volume increases the risk of lateral meniscal repair failure.

R. Rahardja H. Love M.G. Clatworthy S.W. Young

The bone-patellar tendon-bone (BTB) autograft is associated with difficulty kneeling following anterior cruciate ligament (ACL) reconstruction, however it is unclear whether it results in a more painful or symptomatic knee when compared to the hamstring tendon autograft. This study aimed to identify the rate of significant knee pain and difficulty kneeling following primary ACL reconstruction and clarify whether graft type influences the risk of these complications.

Primary ACL reconstructions prospectively recorded in the New Zealand ACL Registry between April 2014 and November 2019 were analyzed. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was analyzed to identify patients who reported significant knee pain, defined as a KOOS Pain subscale score of ≤72 points, and kneeling difficulty, defined as a patient who reported “severe” or “extreme” difficulty when they kneel. The rate of knee pain and kneeling difficulty was compared between graft types via univariate Chi-square test and multivariate binary logistic regression with adjustment for patient demographics.

4492 primary ACL reconstructions were analyzed. At 2-year follow-up, 9.3% of patients reported significant knee pain (420/4492) and 12.0% reported difficulty with kneeling (537/4492). Patients with a BTB autograft reported a higher rate of kneeling difficulty compared to patients with a hamstring tendon autograft (21.3% versus 9.4%, adjusted odds ratio = 3.12, p<0.001). There was no difference between graft types in the rate of significant knee pain (9.9% versus 9.2%, p = 0.49) or when comparing absolute values of the KOOS Pain (mean score for BTB = 88.7 versus 89.0, p = 0.37) and KOOS Symptoms subscales (mean score for BTB = 82.5 versus 82.1, p = 0.49).

The BTB autograft is a risk factor for post-operative kneeling difficulty, but it does not result in a more painful or symptomatic knee when compared to the hamstring tendon autograft.

R. Rahardja H. Love M.G. Clatworthy S.W. Young

The bone-patellar tendon-bone (BTB) autograft has a lower rate of graft failure but a higher rate of contralateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction. Subsequent contralateral injury may be a marker of success of the BTB graft, but it is unclear whether the type of graft influences the rate of return to sport. This study aimed to compare the rates of return to weekly sport and return to preinjury activity levels between the BTB and hamstring tendon autografts following primary ACL reconstruction.

Prospective data on primary ACL reconstructions recorded in the New Zealand ACL Registry between April 2014-November 2019 were analyzed. The primary outcome was return to weekly sport, defined as a Marx activity score of 8, at 2-year follow-up. The secondary outcome was return to preinjury activity level, defined as a post-operative Marx activity score that was equal or greater to the patient's preinjury Marx score. Return to sport was compared between the BTB and hamstring tendon autografts via multivariate binary logistic regression with adjustment for patient demographics.

4259 patients were analyzed, of which 50.3% were playing weekly sport (n = 2144) and 28.4% had returned to their preinjury activity level (n = 1211) at 2-year follow-up. A higher rate of return to weekly sport was observed with the BTB autograft compared to the hamstring tendon autograft (58.7% versus 47.9%, adjusted odds ratio = 1.23, p = 0.009). Furthermore, the BTB autograft had a higher rate of return to preinjury activity levels (31.5% versus 27.5%, adjusted odds ratio = 1.21, p = 0.025).

The BTB autograft is associated with a higher return to sport and may explain the higher rate of contralateral ACL injury following primary ACL reconstruction.

R. Tan M. Jadresic J. Baker

Māori consistently have poorer health outcomes compared to non-Māori within Aotearoa. Numerous worldwide studies demonstrate that ethnic minorities receive less analgesia for acute pain management. We aimed to compare analgesic management of a common orthopaedic injury, tibial shaft fracture, between Māori and non-Māori.

A retrospective cohort study from January 1st, 2015, to December 31st 2020 inclusive. Eligible patients were 16-65 years old and had isolated closed tibial shaft fractures. 104 patients were included in the study, 48 Māori and 56 Non-Māori. Baseline demographics were similar between the 2 cohorts. The primary outcome measure was type of analgesia charted on the ward. Secondary outcome measures were pre-hospital medications given, pain scores on arrival to the emergency department (ED) and the ward, time to analgesia in ED and type of analgesia given in ED. Statistics were calculated using Fisher's exact test, Pearson's chi-squared test or Wilcoxson's rank sum test as appropriate

No statistically significant differences were found in opiates or synthetics charted to Māori vs Non-Māori (83% vs 89% and 77% vs 88% respectively), opiates given in ED, time to analgesia in ED or ED and ward arrival pain scores. Of statistical significance is that Māori were less likely to receive pre-hospital medication compared to Non-Māori (54% vs 80% respectively, p=0.004)

Māori were significantly less likely to receive pre-hospital pain medication compared to Non-Māori. However no other statistically significant findings were found when comparing pain scores, time to analgesia or type of pain relief charted for Māori vs non-Māori.

The reasons for Māori receiving significantly less prehospital medication were not explored in this study and further investigation is required to reduce the bias that exists in this area.

R. Faruque

Tendon injuries after distal radius fractures Introduction: Tendon injuries after distal radius fractures are a well-documented complication that can occur in fractures managed both operatively and non-operatively. The extensor tendons, in particular the extensor pollicis longus (EPL) tendon, can be damaged and present late after initial management in a cast, or by long prominent screws that penetrate the dorsal cortex and cause attrition. Similarly, a prominent or distally placed volar plate can damage the flexor pollicis longus tendon (FPL). The aim of our study was to evaluate the incidence of tendon injuries associated with distal radius fractures.

We conducted a single centre prospective observational study. Patients aged 18-99 who presented with a distal radius fracture between May 2018 to April 2020 were enrolled and followed-up for 24 months. Tendon injuries in the group were prospectively evaluated. Results: 199 patients with distal radius fractures were enrolled. 119 fractures (59.8%) had fixation and 80 (40.2%) were managed incast. In the non-operative group, 2 (2.5%) had EPL ruptures at approximately 4 weeks post injury. There were no extensor tendon ruptures in the operative group. In the operative group, there were 6 (5%) patients that required removal of metalware for FPL irritation. At the time of operation, there were no tendon ruptures noted. Within the operative group we evaluated plate prominence using a previously described classification (Soong et al.). 5 of the 6 patients (83%) with FPL irritation had Grade 3 prominence.

The incidence of both flexor and extensor tendon injury in our cohort was 4%, extensor tendon rupture was 1% and flexor tendon rupture was avoided by early metalware removal. This study demonstrates tendon injuries are not uncommon after distal radius fractures, and close examination and follow-up are necessary to prevent eventual rupture. Plate prominence at the time of fixation should be minimised to reduce the risk of rupture.

R.S. Ting R. Rosenthal Y. Shin M. Shenouda H.S. Al-Housni P.H. Lam G.A. Murrell

It is undetermined which factors predict return to work following arthroscopic rotator cuff repair. We aimed to identify which factors predicted return to work at any level, and return to pre-injury levels of work 6 months post-arthroscopic rotator cuff repair.

Multiple logistic regression analysis of prospectively collected demographic, pre-injury, preoperative, and intraoperative data from 1502 consecutive primary arthroscopic rotator cuff repairs, performed by a single surgeon, was performed to identify independent predictors of return to work, and return to pre-injury levels of work respectively, 6 months post-surgery.

Six months post-rotator cuff repair, 76% of patients returned to work (RTW), and 40% returned to pre-injury levels of work (Full-RTW). RTW at 6 months was likely if patients were still working after their injuries, but prior to surgery (Wald statistic [W]=55, p<0.0001), were stronger in internal rotation preoperatively (W=8, p=0.004), had full-thickness tears (W=9, p=0.002), and were female (W=5, p=0.030). Patients who achieved Full-RTW were likely to have worked less strenuously pre-injury (W=173, p<0.0001), worked more strenuously post-injury but pre-surgery (W=22, p<0.0001), had greater behind-the-back lift-off strength preoperatively (W=8, p=0.004), and had less passive external rotation range of motion preoperatively (W=5, p=0.034). Patients who were still working post-injury, but pre-surgery were 1.6-times more likely to RTW than patients who were not (p<0.0001). Patients who nominated their pre-injury level of work as “light” were 11-times more likely to achieve Full-RTW than those who nominated “strenuous” (p<0.0001).

Six months post-rotator cuff repair, a higher patient-rated post-injury, but pre-surgery level of work was the strongest predictor of RTW. A lower patient-rated pre-injury level of work was the strongest predictor of Full-RTW. Greater preoperative subscapularis strength independently predicted both RTW, and Full-RTW.

S.S. Jhingran D.C. Morris

Current recommendations advocate for surgery within 48 hours from time of injury as a keystone in care for elderly patients with hip fractures. A spare population density within regional Australia provides physical challenges to meet time critical care parameters. This study aims to review the impact of delays to timely surgery for elderly hip fracture patients within a regional Australian population.

A retrospective, comparative analysis was undertaken of 140 consecutive hip fracture patients managed at a single rural referral hospital, from June 2020 until June 2021. Factors such as age, time to transfer, time to surgery, 30-day complication and 6-month complication rates were collected. Statistical analysis was performed where applicable.

Mean time to surgery was 33.9 hours. A greater proportion of patients whom directly presented underwent surgery within the recommended 48 hours (91.5% vs 75.3%). The statistically significant delay in time to surgery was found to be 6.4 hours. Lower 180-day morbidity and mortality rates were observed in patients undergoing surgery within 48 hours (13.8% vs 36%), This is in comparison to the overall mortality rate of 19.2%.

Delay to surgery for elderly hip fracture patients was associated with an increase 30-day and 180-day morbidity and mortality rate. A greater proportion of patients transferred from peripheral hospitals experienced a delay in surgery. Early transfer and prioritization of such patients is recommended to achieve comparative outcomes for rural and remote Australians.

S.R. Abbot S. Proudman B. Ravichandran N. Williams

Minimally displaced paediatric proximal humerus fractures (PHFs) can be reliably managed non-operatively, however there is considerable debate regarding the appropriate management of severely displaced PHFs, particularly in older children and adolescents with limited remodelling potential. The purpose of this study was to perform a systematic review to answer the questions: “What are the functional and quality-of-life outcomes of paediatric PHFs?” and “What factors have been associated with a poorer outcome?”

A review of Medline and EMBASE was performed on 4th July 2021 using search terms relevant to PHFs, surgery, non-operative management, paediatrics and outcomes. Studies including ≥10 paediatric patients with PHFs, which assessed clinical outcomes by use of an established outcome measure, were selected. The following clinical information was collected: participant characteristics, treatment, complications, and outcomes.

Twelve articles were selected, including four prospective cohort studies and eight retrospective cohort studies. Favourable outcome scores were found for patients with minimally displaced fractures, and for children aged less than ten years, irrespective of treatment methodology or grade of fracture displacement. Older age at injury and higher grade of fracture displacement were reported as risk factors for a poorer patient-reported outcome score.

An excellent functional outcome can be expected following non-operative management for minimally displaced paediatric PHFs. Prospective trials are required to establish a guideline for the management of severely displaced PHFs in children and adolescents according to fracture displacement and the degree of skeletal maturity.

S.J. Lynskey M. Ziemann N. Jamnick S.D. Gill S.L. McGee L. Sominsky R.S. Page

Osteoarthritis (OA) is a disease of the synovial joint with synovial inflammation, capsular contracture, articular cartilage degradation, subchondral sclerosis and osteophyte formation contributing to pain and disability. Transcriptomic datasets have identified genetic loci in hip and knee OA demonstrating joint specificity. A limited number of studies have directly investigated transcriptional changes in shoulder OA. Further, gene expression patterns of periarticular tissues in OA have not been thoroughly investigated. This prospective case control series details transcriptomic expression of shoulder OA by analysing periarticular tissues in patients undergoing shoulder replacement for OA as correlated with a validated patient reported outcome measure of shoulder function, an increasing (clinically worsening) QuickDASH score. We then compared transcriptomic expression profiles in capsular tissue biopsies from the OA group (N=6) as compared to patients undergoing shoulder stabilisation for recurrent instability (the control group, N=26). Results indicated that top ranked genes associated with increasing QuickDASH score across all tissues involved inflammation and response to stress, namely interleukins, chemokines, complement components, nuclear response factors and immediate early response genes. Some of these genes were upregulated, and some downregulated, suggestive of a state of flux between inflammatory and anti-inflammatory signalling pathways. We have also described gene expression pathways in shoulder OA not previously identified in hip and knee OA, as well as novel genes involved in shoulder OA.

S.D.J. Morgan C.J. Wall R.N. de Steiger S.E. Graves R.S. Page M.F. Lorimer

The aim of this study was to examine the incidence of obesity in patients undergoing primary total shoulder replacement (TSR) (stemmed and reverse) for osteoarthritis (OA) in Australia compared to the incidence of obesity in the general population.

A 2017-18 cohort of 2,621 patients from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) who underwent TSR, were compared with matched controls from the Australian Bureau of Statistics (ABS) National Health Survey from the same period. The two groups were analysed according to BMI category, sex and age.

According to the 2017-18 National Health Survey, 35.6% of Australian adults are overweight and 31.3% are obese. Of the primary TSR cases performed, 34.2% were overweight and 28.6% were obese. The relative risk of requiring TSR for OA increased with increasing BMI category. Class-3 obese females, aged 55-64, were 8.9 times more likely to require TSR compared to normal weight counterparts. Males in the same age and BMI category were 2.5 times more likely. Class-3 obese patients underwent TSR 4 years (female) and 7 years (male) sooner than their normal weight counterparts.

Our findings suggest that the obese population is at risk for early and more frequent TSR for OA. Previous studies demonstrate that obese patients undergoing TSR also exhibit increased risks of longer operative times, higher superficial infection rates, higher periprosthetic fracture rates, significantly reduced post-operative forward flexion range and greater revision rates.

Obesity significantly increases the risk of requiring TSR. To our knowledge this is the first study to publish data pertaining to age and BMI stratification of TSR Societal efforts are vital to diminish the prevalence and burden of obesity related TSR.

There may well be reversible pathophysiology in the obese population to address prior to surgery (adipokines, leptin, NMDA receptor upregulation). Surgery occurs due to recalcitrant or increased pain despite non-op Mx.

S. Gupta G.H. Smith E.A. Wakelin T. Van Der Veen C. Plaskos J.W. Pierrepont

Evaluation of patient specific spinopelvic mobility requires the detection of bony landmarks in lateral functional radiographs. Current manual landmarking methods are inefficient, and subjective. This study proposes a deep learning model to automate landmark detection and derivation of spinopelvic measurements (SPM).

A deep learning model was developed using an international multicenter imaging database of 26,109 landmarked preoperative, and postoperative, lateral functional radiographs (HREC: Bellberry: 2020-08-764-A-2). Three functional positions were analysed: 1) standing, 2) contralateral step-up and 3) flexed seated. Landmarks were manually captured and independently verified by qualified engineers during pre-operative planning with additional assistance of 3D computed tomography derived landmarks. Pelvic tilt (PT), sacral slope (SS), and lumbar lordotic angle (LLA) were derived from the predicted landmark coordinates. Interobserver variability was explored in a pilot study, consisting of 9 qualified engineers, annotating three functional images, while blinded to additional 3D information. The dataset was subdivided into 70:20:10 for training, validation, and testing.

The model produced a mean absolute error (MAE), for PT, SS, and LLA of 1.7°±3.1°, 3.4°±3.8°, 4.9°±4.5°, respectively. PT MAE values were dependent on functional position: standing 1.2°±1.3°, step 1.7°±4.0°, and seated 2.4°±3.3°, p< 0.001. The mean model prediction time was 0.7 seconds per image. The interobserver 95% confidence interval (CI) for engineer measured PT, SS and LLA (1.9°, 1.9°, 3.1°, respectively) was comparable to the MAE values generated by the model.

The model MAE reported comparable performance to the gold standard when blinded to additional 3D information. LLA prediction produced the lowest SPM accuracy potentially due to error propagation from the SS and L1 landmarks. Reduced PT accuracy in step and seated functional positions may be attributed to an increased occlusion of the pubic-symphysis landmark. Our model shows excellent performance when compared against the current gold standard manual annotation process.

S. Gupta E. Wakelin S. Putman C. Plaskos

The Coronal Plane Alignment of the Knee (CPAK) is a recent method for classifying knees using the hip-knee-ankle angle and joint line obliquity to assist surgeons in selection of an optimal alignment philosophy in total knee arthroplasty (TKA)1. It is unclear, however, how CPAK classification impacts pre-operative joint balance. Our objective was to characterise joint balance differences between CPAK categories.

A retrospective review of TKA's using the OMNIBotics platform and BalanceBot (Corin, UK) using a tibia first workflow was performed. Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were landmarked intra-operatively and corrected for wear. Joint gaps were measured under a load of 70–90N after the tibial resection. Resection thicknesses were validated to recreate the pre-tibial resection joint balance.

Knees were subdivided into 9 categories as described by MacDessi et al.1 Differences in balance at 10°, 40° and 90° were determined using a one-way 2-tailed ANOVA test with a critical p-value of 0.05.

1124 knees satisfied inclusion criteria. The highest proportion of knees (60.7%) are CPAK I with a varus aHKA and Distal Apex JLO, 79.8% report a Distal Apex JLO and 69.3% report a varus aHKA. Greater medial gaps are observed in varus (I, IV, VII) compared to neutral (II, V, VIII) and valgus knees (III, VI, IX) (p<0.05 in all cases) as well as in the Distal Apex (I, II, III) compared to Neutral groups (IV, V, VI) (p<0.05 in all cases). Comparisons could not be made with the Proximal Apex groups due to low frequency (≤2.5%).

Significant differences in joint balance were observed between and within CPAK groups. Although both hip-knee-ankle angle and joint line orientation are associated with joint balance, boney anatomy alone is not sufficient to fully characterize the knee.

S.H. Ellis H. Heaton A. Watson J.T. Lynch P.N. Smith

Prosthetic joint infections (PJI) are one of the most devastating complications of joint replacement surgery. They are associated with significant patient morbidity and carry a significant economic cost to treat. The management of PJI varies from antibiotic suppression, debridement, antibiotics, and implant retention (DAIR) procedures through to single/multiple stage revision procedures. Concerns have been raised recently in relation to the rising number of revision arthroplasty procedures that are being undertaken in relation to infection. This database aims to collect data on all PJIs that have been managed in the Australian Capital Territory (ACT) region. This will allow us to investigate the microbial trends, outcomes of surgical intervention and patient outcomes within our local population.

This database will incorporate diagnostic, demographic, microbiological and treatment information in relation to local PJI cases. The data will be collated from the local infectious diseases database, hospital medical records, and where available the Australian Orthopaedic Association National Joint Replacement Registry Data.

The first 100 cases of PJI were assessed. 76% were defined as being acute. 56% of the patients received antibiotics prior to their diagnosis however only 3% were culture negative. 89% were monomicrobial and 11% polymicrobial. The intended management strategy was a DAIR in 38% of patients and a 2-stage revision in 12% of cases. The intended management strategy was successful in 46% of the patients.

The ACT is uniquely placed to analyze and create a local PJI database. This will allow us to guide further treatment and local guidelines in terms of management of these complex patients.

S. Hunter J. Baker

Acute Haematogenous Osteomyelitis (AHO) remains a cause of severe illness among children. Contemporary research aims to identify predictors of acute and chronic complications. Trends in C-reactive protein (CRP) following treatment initiation may predict disease course. We have sought to identify factors associated with acute and chronic complications in the New Zealand population.

A retrospective review of all patients <16 years with presumed AHO presenting to a tertiary referral centre between 2008-2018 was performed. Multivariate was analysis used to identify factors associated with an acute or chronic complication. An “acute” complication was defined as need for two or more surgical procedures, hospital stay longer than 14-days, or recurrence despite IV antibiotics. A “chronic” complication was defined as growth or limb length discrepancy, avascular necrosis, chronic osteomyelitis, pathological fracture, frozen joint or dislocation. 151 cases met inclusion criteria. The median age was 8 years (69.5% male). Within this cohort, 53 (34%) experienced an acute complication and 18 (12%) a chronic complication.

Regression analysis showed that contiguous disease, delayed presentation, and failure to reduce CRP by 50% at day 4/5 predicted an acutely complicated disease course. Chronic complication was predicted by need for surgical management and failed CRP reduction by 50% at day 4/5. We conclude that CRP trends over 96 hours following commencement of treatment differentiate patients with AHO likely to experience severe disease.

S. Hunter J. Baker

Acute Haematogenous Osteomyelitis (AHO) remains a cause of severe illness among children with the possibility of long-term consequences for growth and development. Previous research on sequelae from AHO rarely considers outcomes more than two years following treatment. This study aims to establish the quality of life of patients diagnosed with AHO in childhood up to 13 years after diagnosis, evaluating the impact on social, emotional, physical, and school function.

Children treated for AHO between 2008-2018 at a tertiary referral centre in New Zealand were identified. PedsQL™ questionnaires were conducted via phone with either the child or primary caregiver and responses analysed.

40 patients met inclusion criteria, were contactable by phone, and consented to participate. The mean age was 7 years (range 0-15) and most were female (60%). Health related quality of life (HRQOL) was scored as a percentage with most participants scoring >80% (n=27). Those who do experience reduced quality of life following treatment for AHO were likely to complain of pain, stiffness, or anxiety. The impact of significant childhood illness on mental health was not adequately captured by the PedsQL™ but was highlighted in qualitative feedback.

We conclude that the majority of children treated for AHO reported excellent health-related quality of life up to 13 years following treatment although an negative impact on mental health was reported using qualitative analysis. A refined scoring system is needed to assess the long-term impact of musculoskeletal infection.

S.C. Lau S. Kanavathy I. Rhee A. Oppy

The Lisfranc fracture dislocation of the tarsometatarsal joint (TMTJ) is a complex injury with a reported incidence of 9.2 to 14/100,000 person-years. Lisfranc fixation involves dorsal bridge plating, transarticular screws, combination or primary arthrodesis. We aimed to identify predictors of poor patient reported outcome measures at long term follow up after operative intervention.

127 patients underwent Lisfranc fixation at our Level One Trauma Centre between November 2007 and July 2013. At mean follow-up of 10.7 years (8.0-13.9), 85 patients (66.92%) were successfully contacted. Epidemiological data including age, gender and mechanism of injury and fracture characteristics such as number of columns injured, direction of subluxation/dislocation and classification based on those proposed by Hardcastle and Lau were recorded. Descriptive analysis was performed to compare our primary outcomes (AOFAS and FFI scores). Univariate analysis and multivariate regression analysis was done adjusted for age and sex to compare the entirety of our data set. p<0.05 was considered significant. The primary outcomes were the American Orthopaedic Foot and Ankle Society (AOFAS) Midfoot Score and the Foot Function Index (FFI).

The number of columns involved in the injury best predicts functional outcomes (FFI, P <0.05, AOFAS, p<0.05) with more columns involved resulting in poorer outcomes. Functional outcomes were not significantly associated with any of the fixation groups (FFI, P = 0.21, AOFAS, P = 0.14). Injury type by Myerson classification systems (FFI, P = 0.17, AOFAS, P = 0.58) or open versus closed status (FFI, P = 0.29, AOFAS, P = 0.20) was also not significantly associated with any fixation group.

We concluded that 10 years post-surgery, patients generally had a good functional outcome with minimal complications. Prognosis of functional outcomes is based on number of columns involved and injured. Sagittal plane disruption, mechanism and fracture type does not seem to make a difference in outcomes.

S. Kanavathy S.C. Lau B. Gabbe H. Bedi A. Oppy

Lisfranc injuries account for 0.2% of all fractures and have been linked to poorer functional outcomes, in particular resulting in post-traumatic arthritis, midfoot collapse and chronic pain. This study assesses the longitudinal functional outcomes in patients with low and high energy Lisfranc injuries treated both operatively and non-operatively.

Patients above 16 years with Lisfranc injuries from January 2008 and December 2017 were identified through the Victorian Orthopaedic Trauma Outcomes (VOTOR) registry. Follow-up performed at 6, 12 and 24 months through telephone interviews with response rate of 86.1%, 84.2% and 76.2% respectively. Longitudinal functional outcome data using Global Outcome Assessment, EQ-5D-5L, numerical pain scale, Short-Form 12, the WHO Disability Assessment Schedule and return to work status were collected. Univariate analysis was performed and variables showing a significant difference between groups (p < 0.25) were analysed with multivariable mixed effects regression model.

745 patients included in this retrospective cohort study. At 24 months, both the operative and non-operative groups demonstrated similar functional outcomes trending towards an improvement. Mixed effect regression models for the EQ items for mobility (OR 1.80, CI 0.91 – 3.57), self-care (OR 1.95, 95% CI 1.09-3.49), usual activities (OR 1.10, 95% CI 0.99-1.03), pain (OR 1.07, 95% CI 0.61-1.89), anxiety (OR 1.29, 95% CI 0.72-2.34) and pain scale (OR 1.07, 95% CI 0.51 – 2.22) and return to work (OR 1.28, 95% CI 0.56-2.91) between groups were very similar and not statistically significantly different.

We concluded that there was no statistically significant difference between operative and non-operative patients with low and high energy Lisfranc injuries. Current clinical practices in Lisfranc injury management are appropriate and not inadvertently causing any further harm to patients. Future research comparing fracture patterns, fixation types and corresponding functional outcomes can help determine gold standard Lisfranc injury management.

S.M. Bolam S. Konar G. Gamble S.J. Paine N. Dalbeth A.P. Monk B. Coleman J. Cornish J.T. Munro D.S. Musson

Traumatic rotator cuff injuries can be a leading cause of prolonged shoulder pain and disability, and contribute to significant morbidity and healthcare costs. Previous studies have shown evidence of socio-demographic disparities with these injuries. The purpose of this nationwide study was to better understand these disparities based on ethnicity, sex, and socio-economic status, in order to inform future healthcare strategies.

Accident Compensation Corporation (ACC) is a no-fault comprehensive compensation scheme encompassing all of Aotearoa/New Zealand (population in 2018, 4.7 million). Using the ACC database, traumatic rotator cuff injuries were identified between January 2010 and December 2018. Injuries were categorized by sex, ethnicity, age and socioeconomic deprivation index of the claimant.

During the 9-year study period, there were 351,554 claims accepted for traumatic rotator cuff injury, which totalled over $960 million New Zealand Dollars. The greatest proportion of costs was spent on vocational support (49.8%), then surgery (26.3%), rehabilitation (13.1%), radiology (8.1%), general practitioner (1.6%) and “Other” (1.1%). Asian, Māori (Indigenous New Zealanders), and Pacific peoples were under-represented in the age-standardized proportion of total claims and had lower rates of surgery than Europeans. Māori had higher proportion of costs spent on vocational support and lower proportions spent on radiology, rehabilitation and surgery than Europeans. Males had higher number and costs of claims and were more likely to have surgery than females. There were considerably fewer claims from areas of high socio-economic deprivation.

This large nation-wide study demonstrates the important and growing economic burden of rotator cuff injuries. Indirect costs, such as vocational supports, are a major contributor to the cost suggesting improving treatment and rehabilitation protocols would have the greatest economic impact. This study has also identified socio-demographic disparities which need to be addressed in order to achieve equity in health outcomes.

S.M. Bolam M.L Tay F Zaidi R.P. Sidaginamale M Hanlon J.T. Munro A.P. Monk

The introduction of robotics for total knee arthroplasty (TKA) into the operating theatre is often associated with a learning curve and is potentially associated with additional complications. The purpose of this study was to determine the learning curve of robotic-assisted (RA) TKA within a multi-surgeon team.

This prospective cohort study included 83 consecutive conventional jig-based TKAs compared with 53 RA TKAs using the Robotic Surgical Assistant (ROSA) system (Zimmer Biomet, Warsaw, Indiana, USA) for knee osteoarthritis performed by three high-volume (> 100 TKA per year) orthopaedic surgeons. Baseline characteristics including age, BMI, sex and pre-operative Kellgren-Lawrence grade were well-matched between the conventional and RA TKA groups. Cumulative summation (CUSUM) analysis was used to assess learning curves for operative times for each surgeon. Peri-operative and delayed complications were reviewed.

The CUSUM analysis for operative time demonstrated an inflexion point after 5, 6 and 15 cases for each of the three surgeons, or 8.7 cases on average. There were no significant differences (p = 0.53) in operative times between the RA TKA learning (before inflexion point) and proficiency (after inflexion point) phases. Similarly, the operative times of the RA TKA group did not differ significantly (p = 0.92) from the conventional TKA group. There was no discernible learning curve for the accuracy of component planning using the RA TKA system. The average length of post-operative follow-up was 21.3 ± 9.0 months. There was no significant difference (p > 0.99) in post-operative complication rates between the groups.

The introduction of the RA TKA system was associated with a learning curve for operative time of 8.7 cases. Operative times between the RA TKA and conventional TKA group were similar. The short learning curve implies this RA TKA system can be adopted relatively quickly into a surgical team with minimal risks to patients.

S.M. Bolam B. Arnold N.A. Sandiford

Prosthetic joint infection (PJI) remains one of the most challenging complications to manage following total joint arthroplasty (TJA). There is a paucity of published data on the management of PJI in smaller, rural hospital settings. In this study, we investigate [1] the success rate of surgical management for PJI following TJA and [2] the microbiology of infecting organisms in this unique geographical environment.

We performed a retrospective single-centre study at a rural hospital (Southland Hospital, Invercargill, New Zealand) over a 3-year period (2019 to 2022). All patients presenting with a first episode of PJI fulfilling Musculoskeletal Infection Society criteria after hip or knee arthroplasty were included. All patients had a minimum follow up of 6 months. Treatment success was defined eradication of infection.

Twenty-one cases (14 hips and 7 knees) were identified. These were managed with Debridement, antibiotics, and implant retention (DAIR) procedure (n=14, 67%), single-stage revision (n=6, 29%), or long-term suppressive antibiotics (n=1, 4%). Of the DAIR patients, infection recurred in 50% and underwent subsequent revision. Of the single-stage revision patients, 17% failed and underwent subsequent revision. The overall success rate was 90%. Methicillin-sensitive Staphylococcus aureus (MSSA) was the most isolated pathogen (57%,) with no methicillin-resistance Staphylococcus aureus (MRSA) identified. Overall, 90% of infecting organisms were cefazolin sensitive.

These results suggest that management of PJI is a safe and viable treatment option when performed in a rural hospital setting, with comparable treatment success rates to urban centres. The incidence of MRSA is low in this setting. Rates of antibiotic resistance were relatively low and most organisms were sensitive to cefazolin, the routine antibiotic used in prophylaxis.

S.M. Bolam Y.E. Park S. Konar K. Callon J. Workman A.P. Monk B. Coleman J.C. Cornish M. Vickers J.T. Munro D.S. Musson

We hypothesised that diet-induced obesity (DIO) would result in inferior enthesis healing in a rat model of rotator cuff (RC) repair and that dietary intervention in the peri-operative period would improve enthesis healing.

A total of 78 male Sprague-Dawley rats were divided into three weight-matched groups from weaning and fed either: control diet (CD), high-fat diet (HFD), or HFD until surgery, then CD thereafter (HF-CD). After 12 weeks, the left supraspinatus tendon was detached, followed by immediate surgical repair. At 2 and 12 weeks post-surgery, animals were culled, and RCs harvested for biomechanical and histological evaluation. Body composition and metabolic markers were assessed via DEXA and plasma analyses, respectively.

DIO was established in the HFD and HF-CD groups before surgery and subsequently reversed in the HF-CD group after surgery. Histologically, the appearance of the repaired entheses was poorer in both the HFD and HF-CD groups compared with the CD group at 12 weeks after surgery, with semiquantitative scores of 6.2 (p<0.01), 4.98 (p<0.01), and 8.7 of 15, respectively. The repaired entheses in the HF-CD group had a significantly lower load to failure (P=0.03) at 12 weeks after surgery compared with the CD group, while the load to failure in the HFD group was low but not significantly different (P=0.10). Plasma leptin were negatively correlated with histology scores and load to failure at 12 weeks after surgery.

DIO impaired enthesis healing in this rat RC repair model, with inferior biomechanical and histological outcomes. Restoring normal weight with dietary change after surgery did not improve healing outcomes. Circulating levels of leptin significantly correlated with poor healing outcomes. This pre-clinical rodent model demonstrates that obesity is a potentially modifiable factor that impairs RC healing and increases the risk of failure after RC surgery.

S.M. Bolam L. Munro M. Wright

The purpose of this study was (1) to evaluate the adequacy of informed consent documentation in the trauma setting for distal radius fracture surgery compared with the elective setting for total knee arthroplasty (TKA) at a large public hospital and (2) to explore the relevant guidelines in New Zealand relating to consent documentation.

Consecutive adult patients (≥16 years) undergoing operations for distal radius fractures and elective TKA over a 12-month period in a single-centre were retrospectively identified. All medical records were reviewed for the risks and complications recorded. The consent form was analysed using the Flesch Reading Ease Score (FRES) and the Simple Measure of Gobbledygook (SMOG) index readability scores.

A total of 133 patients undergoing 134 operations for 135 distal radius fractures and 239 patients undergoing 247 TKA were included. Specific risks of surgery were recorded significantly less frequently for distal radius fractures than TKA (43.3% versus 78.5%, P < 0.001). Significantly fewer risks were recorded in the trauma setting compared to the elective (2.35 ± 2.98 versus 4.95 ± 3.33, P < 0.001). The readability of the consent form was 40.5 using the FRES and 10.9 using the SMOG index, indicating a university undergraduate level of reading.

This study has shown poor compliance in documenting risks of surgery during the informed consent process in an acute trauma setting compared to elective arthroplasty. Institutions must prioritise improving documentation of informed consent for orthopaedic trauma patients to ensure a patient-centred approach to healthcare.

S. Le Rossignol P. Boekel M. Rikard-Bell A. Grant B. Brandon K. Doma W.B. O'Callaghan M. Wilkinson L. Morse

Glenoid baseplate positioning for reverse total shoulder replacements (rTSR) is key for stability and longevity. 3D planning and image-derived instrumentation (IDI) are techniques for improving implant placement accuracy. This is a single-blinded randomised controlled trial comparing 3D planning with IDI jigs versus 3D planning with conventional instrumentation.

Eligible patients were enrolled and had 3D pre-operative planning. They were randomised to either IDI or conventional instrumentation; then underwent their rTSR. 6 weeks post operatively, a CT scan was performed and blinded assessors measured the accuracy of glenoid baseplate position relative to the pre-operative plan.

47 patients were included: 24 with IDI and 23 with conventional instrumentation. The IDI group were more likely to have a guidewire placement within 2mm of the preoperative plan in the superior/inferior plane when compared to the conventional group (p=0.01). The IDI group had a smaller degree of error when the native glenoid retroversion was >10° (p=0.047) when compared to the conventional group. All other parameters (inclination, anterior/posterior plane, glenoids with retroversion <10°) showed no significant difference between the two groups.

Both IDI and conventional methods for rTSA placement are very accurate. However, IDI is more accurate for complex glenoid morphology and placement in the superior-inferior plane. Clinically, these two parameters are important and may prevent long term complications of scapular notching or glenoid baseplate loosening.

Image-derived instrumentation (IDI) is significantly more accurate in glenoid component placement in the superior/inferior plane compared to conventional instrumentation when using 3D pre-operative planning. Additionally, in complex glenoid morphologies where the native retroversion is >10°, IDI has improved accuracy in glenoid placement compared to conventional instrumentation. IDI is an accurate method for glenoid guidewire and component placement in rTSA.

S. Le Rossignol P. Boekel A. Grant K. Doma L. Morse

Currently, the consensus regarding subscapularis tendon repair during a reverse total shoulder arthroplasty (rTSA) is to do so if it is possible. Repair is thought to decrease the risk of dislocation and improve internal rotation but may also increase stiffness and improvement in internal rotation may be of subclinical benefit. Aim is to retrospectively evaluate the outcomes of rTSA, with or without a subscapularis tendon repair.

We completed a retrospective review of 51 participants (25 without and 26 with subscapularis repair) who received rTSR by a single-surgeon using a single-implant. Three patient reported outcome measures (PROM) were assessed pre-operatively and post-operative at twelve months, as well as range of movement (ROM) and plain radiographs. Statistical analysis utilized unpaired t tests for parametric variables and Mann-Whitney U test for nonparametric variables.

External Rotation ROM pre-operatively was the only variable with a significance difference (p=0.02) with the subscapularis tendon repaired group having a greater range. Pre- and post-operative abduction (p=0.72 & 0.58), forward flexion (p=0.67 & 0.34), ASES (p=0.0.06 & 0.78), Oxford (p=0.0.27 & 0.73) and post-operative external rotation (p=0.17)

Greater external rotation ROM pre-operatively may be indicative of the ability to repair the subscapularis tendon intra-operatively. However, repair does not seem to improve clinical outcome at 12 months.

There was no difference of the PROMs and AROMs between the subscapularis repaired and not repaired groups for any of the variables at the pre-operative or 12 month post operative with the exception of the external rotation ROM pre-operatively. We can conclude that from PROM or AROM perspective there is no difference if the tendon is repaired or not in a rTSR and indeed the patients without the repair may have improved outcomes at 12 months.

S. Le Rossingol P. Boekel A. Grant K. Doma L. Morse

The reverse total shoulder replacement (rTSR) has excellent clinical outcomes and prosthesis longevity, and thus, the indications have expanded to a younger age group. The use of a stemless humeral implant has been established in the anatomic TSR; and it is postulated to be safe to use in rTSR, whilst saving humeral bone stock for younger patients. The Lima stemless rTSR is a relatively new implant, with only one paper published on its outcomes.

This is a single-surgeon retrospective matched case control study to assess short term outcomes of primary stemless Lima SMR rTSR with 3D planning and Image Derived Instrumentation (IDI), in comparison to a matched case group with a primary stemmed Lima SMR rTSR with 3D planning and IDI.

Outcomes assessed: ROM, satisfaction score, PROMs, pain scores; and plain radiographs for loosening, loss of position, notching. Complications will be collated. Patients with at least 1 year of follow-up will be assessed.

With comparing the early radiographic and clinical outcomes of the stemless rTSR to a similar patient the standard rTSR, we can assess emerging trends or complications of this new device.

41 pairs of stemless and standard rTSRs have been matched, with 1- and 2-year follow up data. Data is currently being collated. Our hypothesis is that there is no clinical or radiographical difference between the Lima stemless rTSR and the traditional Lima stemmed rTSR.

S. Flynn M. Lemoine F. Boland F. O'Brien J.M. O'Byrne

Restoration a joint's articular surface following degenerative or traumatic pathology to the osteochondral unit pose a significant challenge. Recent advances have shown the utility of collagen-based scaffolds in the regeneration of osteochondral tissue. To provide these collagen scaffolds with the appropriate superstructure novel techniques in 3D printing have been investigated. This study investigates the use of polyɛ-caprolactone (PCL) collagen scaffolds in a porcine cadaveric model to establish the stability of the biomaterial once implanted.

This study was performed in a porcine cadaveric knee model. 8mm defects were created in the medial femoral trochlea and repaired with a PCL collagen scaffold. Scaffolds were secured by one of three designs; Press Fit (PF), Press Fit with Rings (PFR), Press Fit with Fibrin Glue (PFFG). Mobilisation was simulated by mounting the pig legs on a continuous passive motion (CPM) machine for either 50 or 500 cycles. Biomechanical tensile testing was performed to examine the force required to displace the scaffold.

18 legs were used (6 PF, 6 PFR, 6 PFFG). Fixation remained intact in 17 of the cohort (94%). None of the PF or PFFG scaffolds displaced after CPM cycling. Mean peak forces required to displace the scaffold were highest in the PFFG group (3.173 Newtons, Standard deviation = 1.392N). The lowest peak forces were observed in the PFR group (0.871N, SD = 0.412N), while mean peak force observed in the PF group was 2.436N (SD = 0.768). There was a significant difference between PFFG and PFR (p = 0.005). There was no statistical significance in the relationship between the other groups.

PCL reinforcement of collagen scaffolds provide an innovative solution for improving stiffness of the construct, allowing easier handling for the surgeon. Increasing the stiffness of the scaffold also allows press fit solutions for reliable fixation. Press fit PCL collagen scaffolds with and without fibrin glue provide dependable stability. Tensile testing provides an objective analysis of scaffold fixation. Further investigation of PCL collagen scaffolds in a live animal model to establish quality of osteochondral tissue regeneration are required.

S. Rele C. Shadbolt Y. Elsiwy E. Naufal D.J. Gould A. Bazargan Y.S.P. Lorenzo P.F.M. Choong M.M. Dowsey J.M. Stevens

Use of anticoagulants for thromboembolic prophylaxis is strongly supported by evidence. However, the use of these medications beyond the prophylactic period is poorly understood.

We identified anticoagulant naïve patients that underwent hip or knee replacement between 2012 and 2019 from an arthroplasty registry and probabilistically linked 3,018 surgeries with nationwide pharmaceutical claims data. Rates of anticoagulation use were examined during the early (<= 60 days post-discharge), mid-term (61–180 days post-discharge) and long-term (181–360 days post-discharge) periods. Multivariable logistic regression analysis was performed to identify patient- and surgery-related factors associated with long-term anticoagulant use.

Anticoagulants were supplied to 20% of arthroplasties within 60 days of discharge, 7% between 61-180 days, and 10% between 181–360 days. Older age, obesity, increased comorbidity burden, a longer length of stay, occurrence of a complication necessitating anticoagulation and dispensation of an anticoagulant within 60 days of discharge were all risk factors for long-term anticoagulant use.

Given the risks associated with unnecessary use of these medications, certain patients who are prescribed anticoagulants beyond prophylactic period may benefit from specialist medication review in the months following surgery.

A.D. Orsi E.A. Wakelin C. Plaskos S. McMahon S. Coffey

Inverse Kinematic Alignment (iKA) and Gap Balancing (GB) aim to achieve a balanced TKA via component alignment. However, iKA aims to recreate the native joint line versus resecting the tibia perpendicular to the mechanical axis. This study aims to compare how two alignment methods impact 1) gap balance and laxity throughout flexion and 2) the coronal plane alignment of the knee (CPAK).

Two surgeons performed 75 robotic assisted iKA TKA's using a cruciate retaining implant. An anatomic tibial resection restored the native joint line. A digital joint tensioner measured laxity throughout flexion prior to femoral resection. Femoral component position was adjusted using predictive planning to optimize balance. After femoral resection, final joint laxity was collected. Planned GB (pGB) was simulated for all cases posthoc using a neutral tibial resection and adjusting femoral position to optimize balance. Differences in ML balance, laxity, and CPAK were compared between planned iKA (piKA) and pGB. ML balance and laxity were also compared between piKA and final (fiKA).

piKA and pGB had similar ML balance and laxity, with mean differences <0.4mm. piKA more closely replicated native MPTA (Native=86.9±2.8°, piKA=87.8±1.8°, pGB=90±0°) and native LDFA (Native=87.5±2.7°, piKA=88.9±3°, pGB=90.8±3.5°). piKA planned for a more native CPAK distribution, with the most common types being II (22.7%), I (20%), III (18.7%), IV (18.7%) and V (18.7%). Most pGB knees were type V (28.4%), VII (37.8%), and III (16.2). fiKA and piKA had similar ML balance and laxity, however fiKA was more variable in midflexion and flexion (p<0.01).

Although ML balance and laxity were similar between piKA and pGB, piKA better restored native joint line and CPAK type. The bulk of pGB knees were moved into types V, VII, and III due to the neutral tibial cut. Surgeons should be cognizant of how these differing alignment strategies affect knee phenotype.

J. Petterwood S. McMahon S. Coffey E. Slotkin C. Ponder E.A. Wakelin A.D. Orsi C. Plaskos

Smartphone-based apps that measure step-count and patient reported outcomes (PROMs) are being increasingly used to quantify recovery in total hip arthroplasty (THA). However, optimum patient-specific activity level before and during THA early-recovery is not well characterised. This study investigated 1) correlations between step-count and PROMs and 2) how patient demographics impact step-count preoperatively and during early postoperative recovery.

Smartphone step-count and PROM data from 554 THA patients was retrospectively reviewed. Mean age was 64±10yr, BMI was 29±13kg/m2, 56% were female. Mean daily step count was calculated over three time-windows: 60 days prior to surgery (preop), 5-6 weeks postop (6wk), and 11-12 weeks postop (12wk).

Linear correlations between step-count and HOOS12 Function and UCLA activity scores were performed. Patients were separated into three step-count levels: low (<2500steps/day), medium (2500-5500steps/day), and high (>5500steps/day). Age >65years, BMI >30, and sex were used for demographic comparisons.

Student's t-tests determined significant differences in mean step-counts between demographic groups and in mean PROMs between step-count groups.

UCLA correlated with step-count at all time-windows (p<0.01). HOOS12 Function correlated with step-count preoperatively and at 6wk (p<0.01). High vs low step count individuals had improved UCLA scores preoperatively (∆1.8,p<0.001), at 6wk (∆1.1,p<0.05), and 12wk (∆1.6,p<0.01), and improved HOOS12 Function scores preoperatively (∆8.4,p<0.05) and at 6wk (∆8.8,p<0.001).

Younger patients had greater step-count preoperatively (4.1±3.0k vs 3.0±2.5k, p<0.01) and at 12wk (5.1±3.3k vs 3.6±2.9k, p<0.01). Males had greater step-count preoperatively (4.1±3.0k vs. 3.0±2.7k, p<0.001), at 6wk (4.5±3.2k vs 2.6±2.5k, p<0.001), and at 12wk (5.2±3.6k vs. 3.4±2.5k, p<0.001). Low BMI patients had greater step-count at 6wk (4.3±3.3k vs. 2.6±2.7k, p<0.01) and 12wk (5.0±3.6k vs. 3.6±2.6k, p<0.05).

Daily step-count is significantly impacted by patient demographics and correlates with PROMs, where patients with high step count exhibit improved PROMs. Generic recovery profiles may therefore not be appropriate for benchmarking across diverse populations.

S. Marasco T. Gieroba C. Di Bella S. Babazadeh D. Van Bavel

Identifying and restoring alignment is a primary aim of total knee arthroplasty (TKA). In the coronal plane, the pre-pathological hip knee angle can be predicted using an arithmetic method (aHKA) by measuring the medial proximal tibial angle (MPTA) and lateral distal femoral angle (aHKA=MPTA - LDFA). The aHKA is shown to be predictive of coronal alignment prior to the onset of osteoarthritis; a useful guide when considering a non-mechanically aligned TKA. The aim of this study is to investigate the intra- and inter-observer accuracy of aHKA measurements on long leg standing radiographs (LLR) and preoperative Mako CT planning scans (CTs).

Sixty-eight patients who underwent TKA from 2020-2021 with pre-operative LLR and CTs were included. Three observers (Surgeon, Fellow, Registrar) measured the LDFA and MPTA on LLR and CT independently on three separate occasions, to determine aHKA. Statistical analysis was undertaken with Bland-Altman test and coefficient of repeatability.

An average intra-observer measurement error of 3.5° on LLR and 1.73° on CTs for MPTA was detected. Inter-observer errors were 2.74° on LLR and 1.28° on CTs. For LDFA, average intra-observer measurement error was 2.93° on LLR and 2.3° on CTs, with inter-observer errors of 2.31° on LLR and 1.92° on CTs. Average aHKA intra-observer error was 4.8° on LLR and 2.82° on CTs. Inter-observer error of 3.56° for LLR and 2.0° on CTs was measured.

The aHKA is reproducible on both LLR and CT. CT measurements are more reproducible both between and within observers. The difference between measurements using LLR and CT is small and hence these two can be considered interchangeable. CT may obviate the need for LLRs and may overcome difficulties associated with positioning, rotation, body habitus and flexion contractures when assessing coronal alignment.

S.D. Gill J. Stella N. Lowry K. Kloot T. Reade T. Baker G. Hayden M. Ryan H. Seward R. S. Page

Australian Football (AF) is a popular sport in Australia, with females now representing one-third of participants. Despite this, the injury profiles of females versus males in largely unknown. The current study investigated fractures, dislocations and tendon ruptures in females versus males presenting to emergency departments (ED) with an AF injury.

All patients, regardless of age, presenting to one of 10 EDs in Victoria, Australia, with an AF injury were included. Data were prospectively collected over a 10-month period, coinciding with a complete AF season. Data were extracted from patient medical records regarding injury-type, body-part injured and treatments required. Female and male data were compared with chi-squared tests.

Of the 1635 patients presenting with an AF injury, 595 (36.0%) had a fracture, dislocation or tendon rupture, of whom 85 (14.3%) were female and the average age was 20.5 years (SD 8.0). Fractures accounted for most injuries (n=478, 80.3% of patients had a fracture), followed by dislocations (n=118, 19.8%) and tendon ruptures (n=14, 2.4%). Upper limb fractures were more common than lower limb fractures (71.1% v 11.5% of fractures). Females were more likely to fracture their hands or fingers than males (45.7% v 34.3%). Males were more likely to fracture ribs (5.4% v 0%). Most fractures (91.2%) were managed in the ED, with the remainder being admitted for surgery (GAMP/ORIF). Males were more likely to be admitted for surgery than females (11.2% v 5.9%). Regarding dislocations (n=118), females were more likely to dislocate the patella (36.8% v 8.1% of dislocations). Only males sustained a tendon rupture (n=14): finger extensor or flexor (57.1%), achilles tendon (28.6%) and patella tendon (14.3%).

Orthopaedic AF injuries are common presentations to EDs in Victoria, though few require specialist orthopaedic intervention. Injury profiles differed between genders suggesting that gender specific injury prevention and management might be required.

S. Cecchi R. Aujla P. Edwards J. Ebert P. Annear B. Ricciardo P. D'Alessandro

Avulsion of the proximal hamstring tendon from the ischial tuberosity is an uncommon but significant injury. Recent literature has highlighted that functional results are superior with surgical repair over non-surgical treatment. Limited data exists regarding the optimal rehabilitation regime in post-operative patients. The aim of this study was to investigate the early interim patient outcomes following repair of proximal hamstring tendon avulsions between a traditionally conservative versus an accelerated rehabilitation regimen.

In this prospective randomised controlled trial (RCT) 50 patients underwent proximal hamstring tendon avulsion repair, and were randomised to either a braced, partial weight-bearing (PWB) rehabilitation regime (CR = 25) or an accelerated, unbraced, immediate full weight-bearing (FWB) regime (AR group; n = 25). Patients were evaluated preoperatively and at 3 months after surgery, using the Lower Extremity Functional Scale (LEFS), Perth Hamstring Assessment Tool (PHAT), visual analog pain scale (VASP), Tegner score, and 12-item Short Survey Form (SF-12). Patients also filled in a diary questioning postoperative pain at rest from Day 2, until week 6 after surgery. Primary analysis was by per protocol and based on linear mixed models.

Both groups, with respect to patient and characteristics were matched at baseline. Over three months, five complications were reported (AR = 3, CR = 2). At 3 months post-surgery, significant improvements (p<0.001) were observed in both groups for all outcomes except the SF-12 MCS (P = 0.623) and the Tegner (P = 0.119). There were no significant between-group differences from baseline to 3 months for any outcomes, except for the SF-12 PCS, which showed significant effects favouring the AR regime (effect size [ES], 0.76; 95% CI, 1.2-13.2; P = .02).

Early outcomes in an accelerated rehabilitation regimen following surgical repair of proximal hamstring tendon avulsions, was comparable to a traditionally conservative rehabilitation pathway, and resulted in better physical health-related quality of life scores at 3 months post-surgery. Further long term follow up and functional assessment planned as part of this study.

S.L.K. Lee J.L. Lin J. Lynch P. Smith

Dysmorphic pelves are a known risk factor for malpositioned iliosacral screws. Improved understanding of pelvic morphology will minimise the risk of screw misplacement, neurovascular injuries and failed fixation. Existing classifications for sacral anatomy are complex and impractical for clinical use. We propose a CT-based classification using variations in pelvic anatomy to predict the availability of transosseous corridors across the sacrum. The classification aims to refine surgical planning which may reduce the risk of surgical complications.

The authors postulated 4 types of pelves. The “superior most point of the sacroiliac joint” (sSIJ) typically corresponds with the mid-lower half of the L5 vertebral body. Hence, “the anterior cortex of L5” (L5a) was divided to reference 3 distinct pelvic groups. A 4th group is required to represent pelves with a lumbosacral transitional vertebra. The proposed classification:

A – sSIJ is above the midpoint of L5a

B – sSIJ is between the midpoint and the lowest point of L5a

C – sSIJ is below the lowest point of L5a

D – pelves with a lumbosacral transitional vertebra

Specific measures such as the width of the S1 and S2 axial and coronal corridors and the S1 lateral mass angles were used to differentiate between pelvic types.

Three-hundred pelvic CT scans were classified into their respective types. Analysis of the specific measures mentioned above illustrated the significant difference between each pelvic type. Changes in the size of S1 and S2 axial corridors formed a pattern that was unique for each pelvic type. The intra- and inter-observer ratings were 0.97 and 0.95 respectively.

Distinct relationships between the sizes of S1 and S2 axial corridors informed our recommendations on trans-sacral or iliosacral fixation, number and orientation of screws for each pelvic type. This classification utilises variations in the posterior pelvic ring to offer a planning guide for the insertion of iliosacral screws.

T. Thai

Conventional fracture courses utilise prefabricated sawbones that are not realistic or patient specific. The aim of this study is to determine the feasibility of creating 3D fracture models and utilising them in fracture courses to teach surgical technique.

We selected an AO type 2R3C2 fracture that underwent open reduction internal fixation. De-identified CT scan images were converted to a stereolithography (STL) format. This was then processed using Computer Aided Design (CAD) to create a virtual 3D model. The model was 3D printed using a combination of standard thermoplastic polymer (STP) and a porous filler to create a realistic cortical and cancellous bone. A case-based sawbone workshop was organised for residents, unaccredited registrars, and orthopaedic trainees comparing the fracture model with a prefabricated T-split distal radius fracture. Pre-operative images aided discussion of fixation, and post-operative x-rays allowed comparison between the participants fixation. Participants were provided with identical reduction tools. We created a questionnaire for participants to rate their satisfaction and experience using a Likert scale.

The 3D printed fracture model aided understanding and appreciation of the fracture pattern and key fragments amongst residents and unaccredited trainees. Real case-based models provided a superior learning experience and environment to aid teaching. The generic sawbone provided easier drilling and inserting of screws. Preliminary results show that the cost of 3D printing can be comparable to generic sawbones.

It is feasible to create a fracture model with a real bone feel. Further research and development is required to determine the optimum material to use for a more realistic feel.

The use of 3D printed fracture models is feasible and provides an alternative to generic sawbone fracture models in providing surgical training to residents.

T.M. Grupp R.A. Schierjott A. Pfaff G. Tozzi J. Schwiesau A. Giurea

Total knee arthroplasty with a rotating hinge knee with carbon-fibre-reinforced (CFR)-PEEK as an alternative bushing material with enhanced creep, wear and fatigue behaviour has been clinically established [1–4]. The objective of our study was to compare results from in vitro biotribological characterisation to ex vivo findings on a retrievals.

A modified in vitro wear simulation based on ISO 14243-1 was performed for 5 million cycles on rotating hinge knee (RHK) designs (EnduRo®) out of cobalt-chromium and ZrN-multilayer ceramic coating. The rotational & flexion axles-bushings and the flanges are made of CFR-PEEK with 30% polyacrylonitrile fibre content.

Analysis of 12 retrieved EnduRo® RHK systems in cobalt-chromium and ZrN-multilayer in regard to loosening torques, microscopic surface analysis, distinction between different wear modes and classification with a modified HOOD-score has been performed.

For the RHK design with the polyethylene gliding surface and bushings and flanges made out of CFR-PEEK, a cumulative volumetric wear was measured to be 12.9±3.95 mm3 in articulation to cobalt-chromium and 1.3±0.21 mm3 to ZrN-multilayer coating - a significant 9.9-fold decrease (p=0.0072).

For the CFR-PEEK flexion bushing and flanges the volumetric wear rates were 2.3±0.48 mm3/million cycles (cobalt-chromium) and 0.21±0.02 mm3/million cycles (ZrN-multilayer) (p=0.0016). The 5 million cycles of in vitro wear testing reflect a mean in vivo service life of 2.9 years, which is in accordance to the time in vivo of 12-60 months of the retrieved RHK components [5]. The main wear modes were comparable between retrievals and in vitro specimens, whereby the size of affected area on the retrieved components showed a higher variation.

For the EnduRo® RHK design the findings on retrieved implants demonstrate the high suitability of CFR-PEEK as a biomaterial for highly loaded bearings, such as RHK bushings and flanges in articulation to cobalt-chromium and to a ZrN-multilayer coating.

T.M. Grupp A.L. Puente Reyna U. Bader A. Pfaff W.M. Mihalko B. Fink

ZrN-multilayer coating is clinically well established in total knee arthroplasty [1–3] and has demonstrated significant reduction in polyethylene wear and metal ion release [4,5].

The goal of our study was to analyze the biotribological behaviour of the ZrN-multilayer coating on a polished cobalt-chromium cemented hip stem.

CoCr28Mo6 alloy hip stems with ZrN-multilayer coating (CoreHip®AS) were tested versus an un-coated version. In a worst-case-scenario the stems with ceramic heads have been tested in bovine serum in a severe cement interface debonding condition under a cyclic load of 3,875 N for 15 million cycles. After 1, 3, 5, 10 & 15 million cycles the surface texture was analysed by scanning-electron-microscopy (SEM) and energy-dispersive x-ray (EDX). Metal ion concentration of Co,Cr,Mo was measured by inductively coupled plasma mass spectroscopy (ICP-MS) after each test interval.

Based on SEM/EDX analysis, it has been demonstrated that the ZrN-multilayer coating keeps his integrity over 15 million cycles of severe stem cemented interface debonding without any exposure of the CoCr28Mo6 substrate.

The ZrN-multilayer coated polished cobalt-chromium cemented hip stem has shown a reduction of Co & Cr metal ion release by two orders of a magnitude, even under severe stem debonding and high interface micro-motion conditions.

ZrN-multilayer coating on polished cobalt-chromium cemented hip stems might be a suitable option for further minimisation of Co & Cr metal ion release in total hip arthroplasty. Clinical evidence has to be proven during the next years.

T.G. O'Donnell T. Chung R. Bingham

Long femoral nails for neck of femur fractures and prophylactic fixation have a risk of anterior cortex perforation. Previous studies have demonstrated the radius of curvature (ROC) of a femoral nail influencing the finishing point of a nail and the risk of anterior cortex perforation. This study aims to calculate a patients femoral ROC using preoperative XR and CT and therefore nail finishing position.

We conducted a retrospective study review of patients with long femoral cephalomedullary nailing for proximal femur fractures (OTA/AO 31(A) and OTA/AO 32) or impending pathological fractures at a level 1 trauma centre between January 1, 2015 and December 31, 2020 with both full length lateral X-ray and CT imaging. Femoral ROC was calculated on both imaging modalities. Outcomes measured including nail finishing position, anterior cortex encroachment and impingement. The mean femoral ROC was 1026mm on CT and 1244mm on XR. CT femoral ROC strongly correlated with nail finishing point with a spearmans coefficient of 0.77. Additionally, femurs with a ROC <1000mm were associated with a higher risk of anterior encroachment (OR 6.12) and femurs with a ROC <900mm were associated with a higher risk of anterior cortex impingement (OR 6.47).

To our knowledge this is the first study to compare a measured femoral ROC to nail finishing position. The use of CT to measure femoral ROC and to a lesser extent XR was able to predict both nail finishing position and risk of anterior cortex encroachment. Preoperative XRs and CTs were able to identify patients with a small femoral ROC. This predicted patients at risk of anterior cortex impingement, anterior cortex encroachment and nail finishing position. We may be able to select femoral nails that resemble the native femoral ROC and mitigate the risk of anterior cortex perforation.

T. Peterson R. Green

A method is proposed to assess risk parameters of anterior cruciate ligament (ACL) injury using human pose estimation (HPE) and a single stereo depth camera. Detectron2 is used to identify key points of a subject performing a single leg jump test. This allows dynamic pivot of the knee to be assessed during landing using four risk parameters: knee valgus, knee translation in the coronal plane, pelvic tilt, and head-ankle alignment (body sway).

Results show the model has an accuracy of 7° in angular measurements and 38 mm in linear measurements. Compared to previous studies, which only consider front-on analysis, this method has partially reduced accuracy in linear measurements and half the accuracy in angular measurements. Despite this, coupling information from multiple risk parameters reduces the accuracy required on any one parameter and the use of a single depth camera enables reliable analysis at a subject orientation of ±45° relative to the camera.

These factors create a novel solution, proposing the ability for broad evaluation of ACL risk parameters in environments outside a testing laboratory, which has not been done before.

T. Woodfield J. Shum S Tredinnick B. Gadomski J. Fernandez K. McGilvray H. Seim B. Nelson C. Puttlitz J. Easley G.J. Hooper

Introduction: The mechanobiology and response of bone formation to strain under physiological loading is well established, however investigation into exceedingly soft scaffolds relative to cancellous bone is limited. In this study we designed and 3D printed mechanically-optimised low-stiffness implants, targeting specific strain ranges inducing bone formation and assessed their biological performance in a pre-clinical in vivo load-bearing tibial tuberosity advancement (TTA) model. The TTA model provides an attractive pre-clinical framework to investigate implant osseointegration within an uneven loading environment due to the dominating patellar tendon force.

A knee finite element model from ovine CT data was developed to determine physiological target strains from simulated TTA surgery. We 3D printed low-stiffness Ti wedge osteotomy implants with homogeneous stiffness of 0.8 GPa (Ti1), 0.6 GPa (Ti2) and a locally-optimised design with a 0.3 GPa cortex and soft 0.1 GPa core (Ti3), for implantation in a 12-week ovine tibial advancement osteotomy (9mm). We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate.

Optimised Ti3 implants exhibited evenly high strains throughout, despite uneven wedge osteotomy loading. We demonstrated that higher strains above 3.75%, led to greater bone formation. Histomorphometry showed uniform bone ingrowthin optimised Ti3 compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1.

Results from our study indicate lower stiffness and higher strain ranges than normally achieved in Ti scaffolds stimulate early bone formation. By accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. Design and 3D printing of exceedingly soft titanium orthopaedic implants enhance strain induced bone formation and have significant importance in future implant design for knee, hip arthroplasty and treatment of large load-bearing bone defects.

T. Woodfield J. Shum W. Linkhorn B. Gadomski C. Puttlitz K. McGilvray H. Seim B. Nelson J. Easley G.J. Hooper

Polyetheretherketone (PEEK) interbody fusion cages combined with autologous bone graft is the current clinical gold standard treatment for spinal fusion, however, bone graft harvest increases surgical time, risk of infection and chronic pain. We describe novel low-stiffness 3D Printed titanium interbody cages without autologous bone graft and assessed their biological performance in a pre-clinical in vivo interbody fusion model in comparison to the gold standard, PEEK with graft.

Titanium interbody spacers were 3D Printed with a microporous (Ti1: <1000μm) and macroporous (Ti2: >1000μm) design. Both Ti1 and Ti2 had an identical elastic modulus (stiffness), and were similar to the elastic modulus of PEEK. Interbody fusion was performed on L2-L3 and L4-L5 vertebral levels in 24 skeletally mature sheep using Ti1 or Ti2 spacers, or a PEEK spacer filled with iliac crest autograft, and assessed at 8 and 16 weeks. We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate. Functional spinal units were biomechanically tested to analyse range of motion, neutral zone, and stiffness. Results: Bone formation in macroporous Ti2 was significantly greater than microporous Ti1 treatments (p=.006). Fusion scores for Ti2 and PEEK demonstrated greater rates of bone formation from 8 to 16 weeks, with bridging rates of 100% for Ti2 at 16 weeks compared to just 88% for PEEK and 50% for Ti1. Biomechanical outcomes significantly improved at 16 versus 8 weeks, with no significant differences between Ti and PEEK with graft.

This study demonstrated that macroporous 3D Printed Ti spacers are able to achieve fixation and arthrodesis with complete bone fusion by 16 weeks without the need for bone graft. These significant data indicate that low-modulus 3D Printed titanium interbody cages have similar performance to autograft-filled PEEK, and could be reliably used in spinal fusion avoiding the complications of bone graft harvesting.

T. Tran B. Driessen V. Yap D.J. Ng O. Khorshid S. Wall P. Yates G. Prosser M. Wilkinson K. Hazratwala

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator.

A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 74 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prosthesis over the study period. A p-value <0.05 was considered statistically significant.

Demographics, Dorr types and blood serum markers were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/− 2.3mm for the morphometric stem and 2.4mm +/− 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years.

When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking.

T. D. Lamberton S. L. Whitehouse A. J. Timperley

We report the outcome of 320 primary Total Hip Arthroplasties (THA) with minimum 10-year follow-up (range 10-17 years, mean 12.6 years), performed by a single surgeon in Tauranga New Zealand, with the Exeter Contemporary Flanged all-polyethylene cup and Exeter femoral stem via a posterior approach. The aim of the study is to compare the results with the published results from the design centre and create a baseline cohort for further outcomes research in this centre.

All patients were prospectively followed at 6 weeks, 1 year, 5 years, 10 years, (and 15 years when available). Of 333 cases that matched the inclusion criteria, 13 procedures in 12 patents were excluded because of concomitant bone grafting and/or supplementary cage fixation, leaving 320 primary THA procedures in 280 patients, including 26 bilateral procedures in 13 patients.

Mean follow-up of the surviving cases was 12.6 (range 5.0-17.1) years. There were 12 revisions – 2 for fracture, 5 for instability, 1 for impingement pain and 4 for infection. There were no revisions for aseptic cup loosening. Kaplan-Meier survivorship with revision for aseptic loosening as the endpoint was 100% at 15.0 years (with minimum 40 cases remaining at risk). All-cause acetabular revision in 12 cases result in a Kaplan-Meier survival of 95.9% (95% CI: 93.5 to 98.3%).

Cemented THA with the Exeter Contemporary Flanged cup and the Exeter stem is a durable combination with results that can be replicated outside of the design centre. The Exeter Contemporary Flanged cup has excellent survivorship at 15 years when used with the Exeter stem. Cemented THA with well-proven components should be considered the benchmark against which newer designs and materials should be compared.

T Campbell L Hill H Wong D Dow O Stevenson M.L. Tay J T Munro S Young A P Monk

Contemporary indications for unicompartmental knee replacement (UKR) include bone on bone radiographic changes in the medial compartment with relatively preserved lateral and patellofemoral compartments. The role of MRI in identifying candidates for UKR is commonplace. The aim of this study was to assess the relationship between radiographic and MRI pre-operative grade and outcome following UKR.

A retrospective analysis of medial UKR patients from 2017 to 2021. Inclusion criteria were medial UKR for osteoarthritis with pre-operative and post-operative Oxford Knee Scores (OKS), pre-operative radiographs and MRI.

89 patients were included. Whilst all patients had grade 4 ICRS scores on MRI, 36/89 patients had grade 3 KL radiographic scores in the medial compartment, 50/89 had grade 4 KL scores on the medial compartment. Grade 3 KL with grade 4 IRCS medial compartment patients had a mean OKS change of 17.22 (Sd 9.190) meanwhile Grade 4 KL had a mean change of 17.54 (SD 9.001), with no statistical difference in the OKS change score following UKR between these two groups (p=0.873). Medial bone oedema was present in all but one patient. Whilst lateral compartment MRI ICRS scores ranged from 1 to 4 there was no association with MRI score of the lateral compartment and subsequent change in oxford score (P value 0.458). Patellofemoral Compartment (PFC) MRI ICRS ranged from 0 to 4. There was no association between PFC ICRS score and subsequent change in oxford knee score (P value .276)

Radiographs may under report severity of some medial sided knee osteoarthritis. We conclude that in patients with grade 3 KL score that would normally not be considered for UKR, pre-operative MRI might identify grade 4 ICRS scores and this subset of patients have equivalent outcomes to patients with radiographic Grade 4 KL medial compartment osteoarthritis.

V.K. Gupta M. Van Niekerk M. Hirner

Scapular notching is a common problem following reverse shoulder arthroplasty (RSA). This is due to impingement between the humeral polyethylene cup and scapular neck in adduction and external rotation. Various glenoid component strategies have been described to combat scapular notching and enhance impingement-free range of motion (ROM). There is limited data available detailing optimal glenosphere position in RSA with an onlay configuration. The purpose of this study was to determine which glenosphere configurations would maximise impingement free ROM using an onlay RSA prosthesis.

A three-dimensional (3D) computed tomography (CT) scan of a shoulder with Walch A1, Favard E0 glenoid morphology was segmented using validated software. An onlay RSA prosthesis was implanted and a computer model simulated external rotation and adduction motion of the virtual RSA prosthesis. Four glenosphere parameters were tested; diameter (36mm, 41mm), lateralization (0mm, 3mm, 6mm), inferior tilt (neutral, 5 degrees, 10 degrees), and inferior eccentric positioning (0.5mm, 1.5mm. 2.5mm, 3.5mm, 4.5mm). Eighty-four combinations were simulated. For each simulation, the humeral neck-shaft angle was 147 degrees and retroversion was 30 degrees.

The largest increase in impingement-free range of motion resulted from increasing inferior eccentric positioning, gaining 15.0 degrees for external rotation and 18.8 degrees for adduction. Glenosphere lateralization increased external rotation motion by 13. 6 degrees and adduction by 4.3 degrees. Implanting larger diameter glenospheres increased external rotation and adduction by 9.4 and 10.1 degrees respectively. Glenosphere tilt had a negligible effect on impingement-free ROM.

Maximizing inferior glenosphere eccentricity, lateralizing the glenosphere, and implanting larger glenosphere diameters improves impingement-free range of motion, in particular external rotation, of an onlay RSA prosthesis. Surgeons’ awareness of these trends can help optimize glenoid component position to maximise impingement-free ROM for RSA. Further studies are required to validate these findings in the context of scapulothoracic motion and soft tissue constraints.

V.K. Gupta Y. Zhou J.F. Manson J.P. Watt

Surgical site infections (SSIs) after spinal fusion surgery increase healthcare costs, morbidity and mortality. Routine measures of obesity fail to consider site specific fat distribution. We aimed to assess the association between the spine adipose index and deep surgical site infection and determine a threshold value for spine adipose index that can assist in preoperative risk stratification in patients undergoing posterior instrumented lumbar fusion (PILF).

A multicentre retrospective case-control study was completed. We reviewed patients who underwent PILF from January 1, 2010 to December 31, 2018. All patients developing a deep primary incisional or organ-space SSI within 90 days of surgery as per US Centre for Disease Control and Prevention criteria were identified. We gathered potential pre-operative and intra-operative deep infection risk factors for each patient. Spine adipose index was measured on pre-operative mid-sagittal cuts of T2 weighted MRI scans. Each measurement was repeated twice by three authors in a blinded fashion, with each series of measurement separated by a period of at least six weeks.

Forty-two patients were included in final analysis, with twenty-one cases and twenty-one matched controls. The spine adipose index was significantly greater in patients developing deep SSI (p =0.029), and this relationship was maintained after adjusting for confounders (p=0.046). Risk of developing deep SSI following PILF surgery was increased 2.0-fold when the spine adipose index was ≥0.51. The spine adipose index had excellent (ICC >0.9; p <0.001) inter- and intra-observer reliabilities.

The spine adipose index is a novel radiographic measure and an independent risk factor for developing deep SSI, with 0.51 being the ideal threshold value for pre-operative risk stratification in patients undergoing PILF surgery.

W. He R. Masters J. Baker

The minimisation of errors incurred during the learning process is thought to enhance motor learning and improve performance under pressure or in multitasking situations. If this is proven in surgical skills learning, it has the potential to enhance the delivery of surgical education. We aimed to compare errorless and errorful learning using the high-speed burr.

Medical students (n=30) were recruited and allocated randomly to an errorless or errorful group. The errorless learning group progressively learnt tasks from easy to difficult on cedar boards simulating bone. The errorful learning group also progressed through the same tasks but not in order of difficulty.

Transfer tasks assessed students’ performance of cervical laminoplasty on saw bone models to assess their level of learning from previous stages. During transfer task 2, students completed the procedure under time pressure and in the presence of distractors, in order to simulate real-life stressors in theatre. Accuracy, precision and safety of the procedure were scored by expert opinions from spine surgeons blinded to the grouping of the participants.

Both errorless and errorful learners demonstrated improvements in performance with increasing amounts of practice (demonstrated by the decreased time taken for the task as well as improvement in accuracy of the cuts (depth, width and smoothness). The performance of both groups was not impaired by the incorporation of a secondary task which required participants to multitask. No statistically significant difference in performance was noted between the two groups.

In contrast to previous research, there was no significant difference between errorless or errorful learning to develop skills with a high-speed, side-cutting burr. In both groups, practical learning during the session has led to improvement in overall performance with the burr relevant to cervical laminoplasty.

W.J. Caughey F. Zaidi C.J. Shepherd C.R. Rodriguez R.P. Pitto

Malnutrition is considered a risk factor for postoperative complications in total hip and knee arthroplasty, though prospective studies investigating this assumption are lacking. The aim of this study was to prospectively analyse the 90-day postoperative complications, postoperative length of stay (LOS) and readmission rates of patients undergoing primary total hip and total kneearthroplasty using albumin, total lymphocyte count (TLC) and transferrin as serum markers of potential malnutrition.

603 primary hip and 823 primary knee arthroplasties over a 3-year period from a single centre wereprospectively analysed. BMI, demographic and comorbidity data were recorded. Complications werecategorised as surgical site infection, venous thromboembolism (deep vein thrombosis andpulmonary embolus), implant related (such as dislocation), and non-implant related (such aspneumonia). Outcomes were compared between groups, with malnutrition defined as serumalbumin <3.5g/dL, transferrin <200 mg/dL, or TLC <1,500 cells/mm³.

Potential malnutrition was present in 9.3% of the study population. This group experienced a longeraverage LOS at 6.5 days compared to the normal albumin group at 5.0 days (p=0.003). Surgical siteinfection rate was higher in the malnourished group (12.5 vs 7.8%, p=0.02). There was no differencebetween the two groups in implant related complications (0.8 vs 1.0%, p=0.95) medicalcomplications (7.8 vs 13.3%, p=0.17), rate of venous thromboembolism (2.3 vs 2.7%) or 90-dayreadmission rate (14.1 vs 17.0%, p=0.56). TLC and transferrin were not predictive of any of theprimary outcomes measured (p<0.05). Pacific Island (p<0.001), Indian (p=0.02) and Asian (p=0.02) patients had lower albumin than NZ European.

This study demonstrates an association between low albumin levels and increased postoperativeLOS and surgical site infection in total joint arthroplasty, providing rationale for consideration ofpreoperative nutritional screening and optimisation.

W.C. Lee W.W. Kiang Y.D. Chen C.S.N. Yeoh W.W.T. Teo Z.H. Tang

The Femoral Neck System (FNS) was introduced as an alternative device for the fixation of neck of femur fractures (NOFFs). The purported advantages include superior angular and rotatory stability compared to multiple cancellous screws, via a minimally invasive instrumentation that is simpler than conventional fixed angle devices. There were limited clinical studies regarding the utility of this device. We aimed to study the outcomes of NOFFs fixed with the FNS.

This was a single-institution, retrospective review of all undisplaced elderly (≥60 years old) undisplaced young, and displaced young NOFFs fixed with the FNS. Demographics, surgical parameters, radiographic parameters, and clinical outcomes including complications were reviewed.

Thirty-six subjects with a median age of 75 [44,89] years old, had NOFF fixation using the FNS. Thirty-one (86.1%) had undisplaced fractures. There were 6 (16.7%), 26 (72.2%), and 4 (11.1%) subjects with Pauwels types 1, 2, and 3 respectively. Thirty-two (88.9%) had posterior tilt of <20º. The mean duration of surgery was 71±18 minutes. Excluding 4 patients whom required revision surgery, 2 patients whom demised, and 10 patients whom defaulted reviews, the mean follow-up duration was 55±13 weeks. Four complications were recorded, namely implant cut out at the femoral head at week 8, breaking of the locking screw at the run-off region at week 22, avascular necrosis at week 25, and a refracture following near fall, causing the fracture to fail in varus at week 7 postoperation.

While reasonably fast to instrument, failures still occur and it is likely multifactorial. However, the rate of reoperation is lower than what has been reported for NOFFs fixed with the a fixed-angle device or 3 cancellous screws. In conclusion, the FNS is a reasonably safe instrument to use. Surgeons’ discretion is still needed in patient selection, keeping in mind the need for satisfactory radiological parameters.

W.C. Lee C.M.B. Foong R. Kunnasegaran

Most studies comparing medial pivot to the posterior stabilised (PS) systems sacrifice the PCL. It is unknown whether retaining the PCL in the Medial Congruent (MC) system may provide further benefit compared to the more commonly used PS system.

A retrospective review of a single-surgeon's registry data comparing 44 PS and 25 MC with PCL retained (MC-PCLR) TKAs was performed.

Both groups had similar baseline demographics in terms of age, gender, body mass index, and American Society for Anaesthesiology score. There was no significant difference in their preoperative range of motion (ROM) (104º±20º vs. 102º±20º,p=0.80), Oxford Knee Score (OKS) (27±6 vs. 26±7,p=0.72), and Knee Society Scoring System (KS) Function Score (KS-FS) (52±24 vs. 56±24,p=0.62). The preoperative KS Knee Score (KS-KS) was significantly lower in the PS group (44±14 vs. 54 ± 18,p<0.05). At 3-months postoperation, the PS group had significantly better OKS (38±6 vs. 36±6,p=0.02) but similar ROM (111º±14º vs. 108º±12º,p=0.25), KS-FS (73±20 vs. 68±23, p=0.32) and KS-KS (87±10 vs. 86±9,p=0.26). At 12-months postoperation, both groups had similar ROM (115º±13º vs. 115º±11º,p=0.99), OKS (41±5 vs. 40±5,p=0.45), KS-FS (74±22vs.78±17,p=0.80), and KS-KS (89±10vs.89±11,p=0.75). There was statistically significant improvement in all parameters at 1-year postoperation (p<0.05). The PS group had significant improvement in all parameters from preoperation to 3-month postoperation (p<0.05), but not from 3-month to 1-year postoperation (p≥0.05). The MC-PCLR group continued to have significant improvement from 3-month to 1-year postoperation (p<0.05).

The MC provides stability in the medial compartment while allowing a degree of freedom in the lateral compartment. Preserving the PCL when using MC may paradoxically cause an undesired additional restrain that slows the recovery process of the patients after TKA.

In conclusion, compared to MC-PCLR, a PS TKA may expect significantly faster improvement at 3 months post operation, although they will achieve similar outcomes at 1-year post operation.

E. Naufal C. Shadbolt Y. Elsiwy S. Thuraisingam Y.S.P Lorenzo J. Darby S. Babazadeh P.F.M Choong M.M Dowsey J.M. Stevens

This study aimed to evaluate the month-to-month prevalence of antibiotic dispensation in the 12 months before and after total knee arthroplasty (TKA) and total hip arthroplasty (THA) and to identify factors associated with antibiotic dispensation in the month immediately following the surgical procedure.

In total, 4,115 THAs and TKAs performed between April 2013 and June 2019 from a state-wide arthroplasty referral centre were analysed. A cross-sectional study used data from an institutional arthroplasty registry, which was linked probabilistically to administrative dispensing data from the Australian Pharmaceutical Benefits Scheme. Multivariable logistic regression was carried out to identify patient and surgical risk factors for oral antibiotic dispensation.

Oral antibiotics were dispensed in 18.3% of patients following primary TKA and 12.0% of patients following THA in the 30 days following discharge. During the year after discharge, 66.7% of TKA patients and 58.2% of THA patients were dispensed an antibiotic at some point. Patients with poor preoperative health status were more likely to have antibiotics dispensed in the month following THA or TKA. Older age, undergoing TKA rather than THA, obesity, inflammatory arthritis, and experiencing an in-hospital wound-related or other infectious complications were associated with increased antibiotic dispensation in the 30 days following discharge.

A high rate of antibiotic dispensation in the 30 days following THA and TKA has been observed. Although resource constraints may limit routine wound review for all patients by a surgeon, a select cohort may benefit from timely specialist review postoperatively. Several risk factors identified in this study may aid in identifying appropriate candidates for such changes to follow-up care.

S.L. Francis B.PDS. Murphy Y. Elsiwy S. Babazadeh N.D. Clement J.D. Stoney J.M. Stevens

This study aims to implement and assess the inter and intra-reliability of a modernised radiolucency assessment system; the Radiolucency In cemented Stemmed Knee (RISK) arthroplasty classification. Furthermore, we assessed the distribution of regions affected by radiolucency in patients undergoing stemmed cemented knee arthroplasty.

Stemmed knee arthroplasty cases over 7-year period at a single institution were retrospectively identified and reviewed. The RISK classification system identifies five zones in the femur and five zones in the tibia in both the anteroposterior (AP) and lateral planes. Post-operative and follow-up radiographs were scored for radiolucency by four blinded reviewers at two distinct time points four weeks apart. Reliability was assessed using the kappa statistic. A heat map was generated to demonstrate the reported regions of radiolucency.

29 cases (63 radiographs) of stemmed knee arthroplasty were examined radiographically using the RISK system. Intra-reliability (0.83) and Inter-reliability (0.80) scores were both consistent with a strong level of agreement using the kappa scoring system. Radiolucency was more commonly associated with the tibial component (76.6%) compared to the femoral component (23.3%), and the tibial anterior-posterior (AP) region 1 (medial plateau) was the most affected (14.9%).

The RISK classification system is a reliable assessment tool for evaluating radiolucency around stemmed knee arthroplasty using defined zones on both AP and lateral radiographs. Zones of radiolucency identified in this study may be relevant to implant survival and corresponded well with zones of fixation, which may help inform future research.

J.M. Stevens J.D. Eldridge D. Tortonese M.R. Whitehouse H. Krishnan Y. Elsiwy D. Clark

In the unstable patellofemoral joint (PFJ), the patella will articulate in an abnormal manner, producing an uneven distribution of forces. It is hypothesised that incongruency of the PFJ, even without clinical instability, may lead to degenerative changes. The aim of this study was to record the change in joint contact area of the PFJ after stabilisation surgery using an established and validated MRI mapping technique.

A prospective MRI imaging study of patients with a history of PFJ instability was performed. The patellofemoral joints were imaged with the use of an MRI scan during active movement from 0° through to 40° of flexion. The congruency through measurement of the contact surface area was mapped in 5-mm intervals on axial slices. Post-stabilisation surgery contact area was compared to the pre-surgery contact area.

In all, 26 patients were studied. The cohort included 12 male and 14 female patients with a mean age of 26 (15-43). The greatest mean differences in congruency between pre- and post-stabilised PFJs were observed at 0-10 degrees of flexion (0.54 cm2 versus 1.18 cm2, p = 0.04) and between 11° and 20° flexion (1.80 cm2 versus 3.45 cm2; p = 0.01).

PFJ stabilisation procedures increase joint congruency. If a single axial series is to be obtained on MRI scan to compare the pre- and post-surgery joint congruity, the authors recommend 11° to 20° of tibiofemoral flexion as this was shown to have the greatest difference in contact surface area between pre- and post-operative congruency.

Y. Fang I.N. Ackerman I. Harris R. Page K. Cashman M. Lorimer E. Heath S. Graves S-E. Soh

While clinically important improvements in Oxford Shoulder Scores have been defined for patients with general shoulder problems or those undergoing subacromial decompression, no threshold has been reported for classifying improvement after shoulder replacement surgery. This study aimed to establish the minimal clinically important change (MCIC) for the Oxford Shoulder Score in patients undergoing primary total shoulder replacement (TSR).

Patient-reported outcomes data were sourced from the Australian Orthopaedic Association National Joint Replacement Registry Patient-Reported Outcome Measures Program. These included pre- and 6-month post-operative Oxford Shoulder Scores and a rating of patient-perceived change after surgery (5-point scale ranging from ‘much worse’ to ‘much better’). Two anchor-based methods (using patient-perceived improvement as the anchor) were used to calculate the MCIC: 1) mean change method; and 2) predictive modelling, with and without adjustment for the proportion of improved patients.

The analysis included 612 patients undergoing primary TSR who provided pre- and post-operative data (58% female; mean (SD) age 70 (8) years). Most patients (93%) reported improvement after surgery. The MCIC derived from the mean change method was 6.8 points (95%CI 4.7 to 8.9). Predictive modelling produced an MCIC estimate of 11.6 points (95%CI 8.9 to 15.6), which reduced to 8.7 points (95%CI 6.0 to 12.7) after adjustment for the proportion of improved patients.

For patient-reported outcome measures to provide valuable information that can support clinical care, we need to understand the magnitude of change that matters to patients. Using contemporary psychometric methods, this analysis has generated MCIC estimates for the Oxford Shoulder Score. These estimates can be used by clinicians and researchers to interpret important changes in pain and function after TSR from the patient's perspective. We conclude that an increase in Oxford Shoulder Scores of at least 9 points can be considered a meaningful improvement in shoulder-related pain and function after TSR.

Y. Chai A.M. Boudali J. Farey W.L. Walter

Human error is usually evaluated using statistical descriptions during radiographic annotation. The technological advances popularized the “non-human” landmarking techniques, such as deep learning, in which the error is presented in a confidence format that is not comparable to that of the human method. The region-based landmark definition makes an arbitrary “ground truth” point impossible. The differences in patients’ anatomies, radiograph qualities, and scales make the horizontal comparison difficult. There is a demand to quantify the manual landmarking error in a probability format.

Taking the measurement of pelvic tilt (PT) as an example, this study recruited 115 sagittal pelvic radiographs for the measurement of two PTs. We proposed a method to unify the scale of images that allows horizontal comparisons of landmarks and calculated the maximum possible error using a density vector. Traditional descriptive statistics were also applied.

All measurements showed excellent reliabilities (intraclass correlation coefficients > 0.9). Eighty-four measurements (6.09%) were qualified as wrong landmarks that failed to label the correct locations. Directional bias (systematic error) was identified due to cognitive differences between observers. By removing wrong labels and rotated pelves, the analysis quantified the error density as a “good doctor” performance and found 6.77°-11.76° maximum PT disagreement with 95% data points.

The landmarks with excellent reliability still have a chance (at least 6.09% in our case) of making wrong landmark decisions. Identifying skeletal contours is at least 24.64% more accurate than estimating landmark locations. The landmark at a clear skeletal contour is more likely to generate systematic errors. Due to landmark ambiguity, a very careful surgeon measuring PT could make a maximum 11.76° random difference in 95% of cases, serving as a “good doctor benchmark” to qualify good landmarking techniques.

Y. Chai A.M. Boudali J. Farey W.L. Walter

Pelvic tilt (PT) is always described as the pelvic orientation along the transverse axis, yet four PT definitions were established based on different radiographic landmarks: anterior pelvic plane (PTa), the centres of femoral heads and sacral plate (PTm), pelvic outlet (PTh), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking. Some studies referred to the words “pelvic tilt” for horizontal comparisons, but their PT definitions might differ. There is a demand for understanding their correlations and differences for education and research purposes.

This study recruited 105 sagittal pelvic radiographs (68 males and 37 females) from a single clinic awaiting their hip surgeries. Hip hardware and spine pathologies were examined for sub-group analysis. Two observers annotated four PTs in a gender-dependent manner and repeated it after six months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% significance interval.

The SS showed significant gender differences and the lowest correlations to the other parameters in the male group (−0.3< r <0.2). The correlations of SS in scoliosis (n = 7) and hip implant (female, n = 18) groups were statistically different, yet the sample sizes were too small. PTm demonstrated very strong correlation to PTh (r > 0.9) under the linear model PTm = 0.951 × PTh - 68.284.

The PTm and PTh are interchangeable under a simple linear regression model, which enables study comparisons between them. In the male group, SS is more of a personalised spinal landmark independent of the pelvic anatomy. Female patients with hip implant may have more static spinopelvic relationships following a certain pattern, yet a deeper study using a larger dataset is required. The understanding of different PTs improves anatomical education.

Y. Chai S. Khadra A.M. Boudali I. Darwish W.L. Walter

Accurate measurement of pelvic tilt (PT) is critical in diagnosing hip and spine pathologies. Yet a sagittal pelvic radiograph with good quality is not always available. Studies explored the correlation between PT and sacro-femoral-pubic (SFP) angle from anteroposterior (AP) radiographs yet demonstrated conflicting conclusions about its feasibilities. This study aims to perform a cohort-controlled meta-analysis to examine the correlation between the SFP angle and PT and proposes an application range of the method.

This study searched PubMed, Embase, Cochrane, and Web of Science databases for studies that evaluated the correlation between SFP angle and PT. The Pearson's correlation coefficient r from studies were tabulated and compared. Pooled r for overall and gender/age (teenage or adult) controlled subgroup were reported using Fisher's Z transformation. Heterogeneity and publication bias were evaluated using Egger's regression test for the funnel plot asymmetry.

Eleven studies were recruited, with nine reported r (totalling 1,247 patients). The overall pooled r was 0.61 with high inter-study heterogeneity (I2 = 75.95%). Subgroup analysis showed that the adult group had a higher r than the teenage group (0.70 versus 0.56, p < 0.001). Although statistically insignificant (p = 0.062), the female group showed a higher r than the male group (0.72 versus 0.65).

The SFP method must be used with caution and should not be used in the male teenage group. The current studies did not demonstrate that the SFP method was superior to other AP landmarks correlating to PT. Identical heterogeneity was observed among studies, indicating that more ethnicity-segregated and gender-specific subgroup studies might be necessary. More data input analysing the errors will be useful.

Y Zhou C Shadbolt S Rele T Spelman M Dowsey P Choong C Schilling

Utility score is a preference-based measure of general health state – where 0 is equal to death, and 1 is equal to perfect health. To understand a patient's smallest perceptible change in utility score, the minimal clinically important difference (MCID) can be calculated. However, there are multiple methods to calculate MCID with no consensus about which method is most appropriate. The aim of this study is to calculate MCID values for the Veterans-RAND 12 (VR12) utility score using varying methods. Our hypothesis is that different methods will yield different MCID values.

A tertiary institutional registry (SMART) was used as the study cohort. Patients who underwent unilateral TKA for osteoarthritis from January 2012 to January 2020 were included. Utility score was calculated from VR12 responses using the standardised Brazier's method. Distribution and anchor methods were used for the MCID calculation. For distribution methods, 0.5 standard deviations of the baseline and change scores were used. For anchor methods, the physical and emotional anchor questions in the VR12 survey were used to benchmark utility score outcomes. Anchor methods included mean difference in change score, mean difference in 12 month score, and receiver operating characteristics (ROC) analysis with the Youden index.

Complete case analysis of 1735 out of 1809 eligible patients was performed. Significant variation in the MCID estimates for VR12 utility score were reported dependent on the calculation method used. The MCID estimate from 0.5 standard deviations of the change score was 0.083. The MCID estimate from the ROC analysis method using physical or emotional anchor question improvement was 0.115 (CI95 0.08-0.14; AUC 0.656).

Different MCID calculation methods yielded different MCID values. Our results suggest that MCID is not an umbrella concept but rather many distinct concepts. A general consensus is required to standardise how MCID is defined, calculated, and applied in clinical practice.

Y Zhou M Dowsey T Spelman P Choong C Schilling

Approximately 20% of patients feel unsatisfied 12 months after primary total knee arthroplasty (TKA). Current predictive tools for TKA focus on the clinician as the intended user rather than the patient. The aim of this study is to develop a tool that can be used by patients without clinician assistance, to predict health-related quality of life (HRQoL) outcomes 12 months after total knee arthroplasty (TKA).

All patients with primary TKAs for osteoarthritis between 2012 and 2019 at a tertiary institutional registry were analysed. The predictive outcome was improvement in Veterans-RAND 12 utility score at 12 months after surgery. Potential predictors included patient demographics, co-morbidities, and patient reported outcome scores at baseline. Logistic regression and three machine learning algorithms were used. Models were evaluated using both discrimination and calibration metrics. Predictive outcomes were categorised into deciles from 1 being the least likely to improve to 10 being the most likely to improve.

3703 eligible patients were included in the analysis. The logistic regression model performed the best in out-of-sample evaluation for both discrimination (AUC = 0.712) and calibration (gradient = 1.176, intercept = −0.116, Brier score = 0.201) metrics. Machine learning algorithms were not superior to logistic regression in any performance metric. Patients in the lowest decile (1) had a 29% probability for improvement and patients in the highest decile (10) had an 86% probability for improvement.

Logistic regression outperformed machine learning algorithms in this study. The final model performed well enough with calibration metrics to accurately predict improvement after TKA using deciles. An ongoing randomised controlled trial (ACTRN12622000072718) is evaluating the effect of this tool on patient willingness for surgery. Full results of this trial are expected to be available by April 2023.

A free-to-use online version of the tool is available at smartchoice.org.au.

Y Zhou C Frampton M Hirner

Most previous studies investigating autograft options (quadriceps, hamstring, bone-patella-tendon-bone) in primary anterior cruciate ligament (ACL) reconstruction are confounded by concomitant knee injuries. This study aims to investigate the differences in patient reported outcome measures and revision rates for quadriceps tendon in comparison with hamstring tendon and bone-patella-tendon-bone autografts. We use a cohort of patients who have had primary ACL reconstruction without concomitant knee injuries.

All patients from the New Zealand ACL Registry who underwent a primary arthroscopic ACL reconstruction with minimum 2 year follow-up were considered for the study. Patients who had associated ipsilateral knee injuries, previous knee surgery, or open procedures were excluded. The primary outcome was Knee Injury and Osteoarthritis Outcome Score (KOOS) and MARX scores at 2 years post-surgery. Secondary outcomes were all-cause revision and time to revision with a total follow-up period of 8 years (time since inception of the registry).

2581 patients were included in the study; 1917 hamstring tendon, 557 bone-patella-tendon-bone, and 107 quadriceps tendon. At 2 years, no significant difference in MARX scores were found between the three groups (2y mean score; 7.36 hamstring, 7.85 bone-patella-tendon-bone, 8.05 quadriceps, P = 0.195). Further, no significant difference in KOOS scores were found between the three groups; with the exception of hamstring performing better than bone-patella-tendon-bone in the KOOS sports and recreation sub-score (2y mean score; 79.2 hamstring, 73.9 bone-patella-tendon-bone, P < 0.001). Similar revision rates were reported between all autograft groups (mean revision rate per 100 component years; 1.05 hamstring, 0.80 bone-patella-tendon-bone, 1.68 quadriceps, P = 0.083). Autograft revision rates were independent of age and gender variables.

Quadriceps tendon is a comparable autograft choice to the status quo for primary ACL reconstruction without concomitant knee injury. Further research is required to quantify the long-term outcomes for quadriceps tendon use.