Introduction and Objective. Platelet-Rich-plasma (PRP) has been used in combination with stem cells, from different sources, with encouraging results both in vitro and in vivo in osteochondral defects management. Adipose-derived Stem Cells (ADSCs) represents an ideal resource for their ease of isolation, abundance, proliferation and differentiation properties into different cell lineages. Furthermore, Stem Cells in the adipose tissue are more numerous than from other sources. Aim of this study was to evaluate the potential of ADSCs in enhancing the effect of arthroscopic mesenchymal stimulation combined with infiltration of PRP. Materials and Methods. The study includes 82 patients. 41 patients were treated with knee arthroscopy, Steadman microfractures technique and intraoperative PRP infiltration, Group A. In the Group B, 41 patients were treated knee arthroscopy, Steadman microfractures and intraoperative infiltration of PRP and ADSCs (Group B). Group A was used as a control group. Inclusion criteria were: Age between 40 and 65 years, Outerbridge grade III-IV chondral lesions, Kellegren-Lawrence Grade I-II. Patient-reported outcome measures (PROMs) evaluated with KOOS, IKDC, VAS, SF-12 were assessed pre-operatively and at 3 weeks, 6 months, 1-year post-operative. 2 patients of Group A and 3 patients of Group B, with indication of Puddu plate removal after high tibial osteotomy (HTO), underwent an arthroscopic second look, after specific informed consent obtained. On this occasion, a bioptic sample was taken from the repair tissue of the chondral lesion previously treated with Steadman microfractures. Results. PROMs showed statistically significant improvement (p <0.05) with comparable results in both groups. The histological examination of the bioptic samples in Group B showed a repair tissue similar to hyaline cartilage, according to the International Cartilage Repair Society (ICRS) Visual Histological Assessment Scale. In Group A, the repair tissue was fibrocartilaginous. Conclusions. According to the PROMs and the histological results, showing repair tissue after Steadman microfractures qualitatively similar to hyaline cartilage, the combination of ADSCs and PRP could represent an excellent support to the arthroscopic treatment of focal chondral lesions and mild to moderate osteoarthritis

In Displaced Intracapsular Hip Fractures (ICHF) in young active patients, preservation of the femoral head and its blood supply are of high importance and urgent surgical treatment with anatomic reduction and internal fixation is the preferred intervention. Due to the strong varus displacement shear forces exerted across the hip, there are relatively high complication rates after fixation. There is no consensus regarding the optimal fixation device or technique. This retrospective study compared closed reduction internal fixation method using cannulated cancellous screw (CCS) with the Targon Femoral Neck (TFN) hip fixed angle screw. Data regarding, gender, operational data, duration of surgery, complications, NAS (Numerical Analogue Scale) pain score, Modified Harris Hip Score (MHHS) and SF-12 scores were retrieved for patients younger than 65 with displaced ICHF. Eighty-two patients were included in the study, 30 patients treated with CCS were compared to 52 patients treated with TFN. Fracture configuration (Garden and Pauwel classifications), mean time to surgery and complication rate did not differ significantly. Operative time did differ significantly between groups (CCS 56 minutes, TFN 92 minutes, p<0.001). At final follow-up the CCS group reported less pain (NAS 2.3 vs 3.5, p< 0.049) and better Mental Health Composite score of SF-12 (p=0.017) compared to the TFN group. Complication rates for the treatment of displaced ICHF with TFN and CCS showed no significant differences; however, the functional outcomes, as presented by the NAS and Mental Health Composite score of SF-12, showed superiority for CCS treatment. As this fixation method is related to reduce costs, we suggest CCS for the treatment of displaced ICHF in the young population

Femoroacetabular impingement (FAI) is the result of abnormal contact/impingement of the femoral head-neck junction and acetabulum during motion. This can be corrected by surgical dislocation (using Ganz's trochanteric osteotomy) and femoral osteochondroplasty +/− acetabular rim resection. Our study aimed to assess the improvement in hip scores following open osteochondroplasty to predict outcomes based on patient characteristics. This was a retrospective case note analysis of a single surgeon case series over a 4 year period. Inclusion criteria were open osteochondroplasty, complete pre- and post-op hip scores available), Tonnis osteoarthritis grade 0 or 1, with 1 year followup. Data was extracted from electronic and paper case notes for pre- and post-op Modified Harris Hip Scores (MHHS), Non-arthritis Hip Scores (NAHS) and SF-12 general satisfaction scores, as well as baseline patient demographics. Two independent observers used the PACS radiology system to examine x-rays and MRI. SPSS version 19 was used for statistical analysis. 42 patients met the inclusion criteria. There was an overall improvement in hip scores after the procedure. Mean pre-op scores were MHHS 52.5, NAHS 44.0, SF-12 32.1. Mean post-op scores were MHHS 66.1, NAHS 58.7, SF-12 36.4. Therefore mean improvements were seen in MHHS (13.6), NAHS (14.7) and SF-12 (4.3), all significant at p<0.005 when paired t-test was used for analysis. Pearson correlation for subgroup analysis showed no significant correlation of scores with age, centre-edge angle or alpha angles. Furthermore, no significant difference was seen between males and females (independent t test). Open osteochondroplasty improves symptoms and function based on patient reported outcome measures. Although the mean scores improved, some patients’ scores deteriorated. We have not identified any statistically significant predictors of outcome, and therefore patient selection remains unclear

A retrospective analysis was carried out to determine the influence of pre-existing spinal pathology on the outcome of Total Knee Replacement surgery. Data was collected from 345 patients who had undergone Total Knee Replacement, at four centres in the UK, between 2000 and 2007. Oxford Knee Scores (OKS), American Knee Society Scores (AKSS) and SF-12 questionnaires were recorded prospectively. Data was collected pre-operatively and then post-operatively at 3 months, 1 year and 2 years. Patients were divided into those with (n=40) and without a history of low back pain (n=305). In addition to determining the influence of low back pain on outcome after Total Knee Replacement we also examined the influence of concomitant hip and ankle pathology in the same cohort of patients. OKS scores were significantly worse for patients with symptomatic low back pain at 3 (p=0.05), 12 (p=0.009) and 24 months (p=0.039) following surgery. SF-12 physical scores followed a comparable pattern with significance demonstrated at 3 (p=0.038), 12 (p=0.0002) and 24 months (p=0.016). AKSS followed a similar pattern, but significance was only reached at 1 year (p=0.013). The mental component of the SF-12 measure demonstrated a significant improvement in patients' mental health post-operatively for patients with no history of low back pain. In contrast patients with low back pain showed no improvement in mental health scores post-operatively. In contrast to low back pain, hip and ankle pathology had no statistically significant detrimental effect on the outcome of Total Knee Replacement surgery. This study demonstrates that low back pain significantly affects the functional outcome after Total Knee Replacement surgery and that patients with low back pain show no improvement in mental health post-operatively

When performing total knee replacement (TKR), surgeons must select a size of tibial component tray that most closely matches the anatomy of the proximal tibia. As implants are available in a limited range of sizes, it may be necessary to slightly under or oversize the component. There are concerns overhang could lead to pain from irritation of soft tissues, and underhang could lead to subsidence and failure. 154 TKRs at 1- or 5-year follow up were reviewed prospectively. Oxford Knee Score (OKS), WOMAC and SF-12 was recorded along with pain scores. Scaled radiographs were reviewed and grouped into perfect sizing (78 TKRs, 50.6%), underhang in isolation (48 TKRs, 31.1%), minor overhang 1–3 mm (10 TKRs, 6.49%) or major overhang >3 mm (18 TKRs, 11.7%). There was no significant difference in the SF-12 (p=0.356), post-operative OKS (p=0.401) or WOMAC (p=0.466) score. For the OKS, there was no difference for the scores collected at 1 year (p=0.176) or at 5 years (p=0.883). Pre-operative OKS was well matched between the groups (p=0.152). There was no significant difference in the improvement in OKS from pre-operative scores (p=0.662). There was no significant difference in either the OKS or WOMAC pain scores (p=0.237 and 0.542 respectively). There was no significant association of medial overhang with?medial knee pain (p=1.000) or lateral overhang with lateral knee pain (p=0.569) when compared to the group of patients with a well sized tibial component. Our results suggest that tibial component overhang or underhang has no detrimental affect on outcome or pain scores. Surgeons should continue to select the tibial component that most closely fits the rim of the proximal tibia while accepting slight overhang if necessary due to the potential longer-term complications of subsidence and premature failure with an undersized tibial tray

Summary. Pyogenic spondylodiscitis is an uncommon but severe spinal infection. In majority of cases treatment is based on intravenous antibiotics and rigid brace immobilization. Posterior percutaneous spinal instrumentation is a safe alternative procedure in relieving pain, preventing deformity and neurological compromise. Introduction. Pyogenic spondylodiscitis (PS) is an uncommon but severe spinal infection. Patients affected by a non-complicated PS and treatment is based on intravenous antibiotics and rigid brace immobilization with a thoracolumbosacral orthosis (TLSO) suffices in most cases in relieving pain, preventing deformity and neurological compromise. Since January 2010 we started offering patients percutaneous posterior screw-rod instrumentation as alternative approach to TLSO immobilization. The aim of this study was to evaluate safety and effectiveness of posterior percutaneous spinal instrumentation for single level lower thoracic (T9-T12) or lumbar pyogenic spondylodiscitis. Materials and Methods. Retrospective cohort analysis on 27 patients diagnosed with PS who were offered to choose between 24/7 TLSO rigid bracing for 3 to 4 months and posterior percutaneous screw-rod instrumentation bridging the infection level followed by soft bracing for 4 weeks after surgery. All patients underwent antibiotic therapy. Fifteen patients chose conservative treatment, 12 patients chose surgical treatment. Patients were seen at 1, 3, 6, 9 months after diagnosis. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and complete blood count were measured at each follow-up visit. Segmental kyphosis was measured at diagnosis and at 9 months. VAS, SF-12, and EQ-5D questionnaires were recorded at each follow-up visit. Baseline groups’ demographic characteristics were assessed using independent sample t-tests for continuous variables and χ2 tests for frequency variables. Results. Complete healing was achieved in all patients, no difference was observed in healing time between the two groups (77.3±7.2 days vs 80.2±4.4). Instrumentation failure and screw loosening was not observed in any patient. In both group CRP and ESR decreased accordingly with response to antibiotic therapy. Surgically treated patients had significantly lower VAS scores at 1 month (3.05±0.57 in surgery group vs 5.20±1.21 in TLSO group) and 3 months (2.31±0.54 in surgery group vs 2.85±0.55 in TLSO group) post-diagnosis. Both groups had similar trends toward fast recovery in both mental (MCS) and physical components (PCS) of SF-12 questionnaire, surgically treated patients showed steeper and statistically significative improvement at 1 month (37.83±4.57 MCS in surgery group vs 24.52±3.03 MCS in TLSO group and 35.46±4.43 PCS in surgery group vs 27.07±4.45 PCS in TLSO group, p<0.001), 3 months (52.94±3.82 MCS in surgery group vs 39.45±4.92 MCS in TLSO group and 44.93±3.73 PCS in surgery group vs 35.33±6.44 PCS in TLSO group, p<0.001), and 6 months (54.93±3.56 MCS in surgery group vs 49.99±5.82 MCS in TLSO group) post-diagnosis, no statistically significant differences were detected at the other time points (9 months post-diagnosis). EQ-5D index was significantly higher in surgery patients at 1 month (0.764±0.043 in surgery group vs 0.458±0.197 in TLSO group) and 3 months (0.890±0.116 in surgery group vs 0.688±0.142 in TLSO group); no statistically significant changes were observed in segmental kyphosis between the two groups. Conclusion. Posterior percutaneous spinal instrumentation is a safe, feasible, and effective procedure in relieving pain, preventing deformity and neurological compromise. Surgical stabilization was associated with faster recovery, lower pain scores, and improved quality of life compared with TLSO conservative treatment at 1 and 3 months after diagnosis

Background. Acetabular fractures occur as a result of high-velocity trauma and are often associated with other life threatening injuries. Approximately one-third of these fractures are associated with dislocation of the femoral head but there are only few studies documenting the long term outcomes of this group of acetabular fracture. Methods. This was undertaken at the Royal Infirmary of Edinburgh which provides the definitive orthopaedic treatment for all major trauma including all acetabular fractures for the South East of Scotland. We retrospectively reviewed patients who sustained an acetabular fracture associated with a posterior hip dislocation from a prospectively gathered trauma database between 1990 to 2010. Patient characteristics, complications and the requirement for further surgery were recorded. Patient outcomes were measured using the Oxford Hip score and Short Form SF-12 health survey. Results. A total of 99 patients were treated over a 24 year period. The mean age was 41.3 years. The majority were male (75%). Road traffic accidents were the most common mechanism of injury (47%). The most common Letournal & Judet classification was a posterior wall fracture. Complications such as Sciatic Nerve Palsy was 12.1%, DVT 3%, Infection 5%, Heterotopic ossification 6.1%, Avascular necrosis at 11.1% and 19.2% went on to have a total hip replacement. The mean Oxford Score for Native hip was 34.7 and 31.8 for those who converted to hip replacement. SF12 Physical score was was 40.3 and 39 for the native hips and converted hips respectively. And the SF12 Mental score was 45.5 and 44.9 for the native hips and converted hips respectively. Conclusions. This is the first study to present the long term outcomes following an acetabular fracture dislocation. Our study suggests there is considerable disability in this group of patients and the requirement for subsequent THR has inferior patient reported outcomes. Level of Evidence. Cohort study, Level 2B

Obese patients undergoing total knee arthroplasty (TKA) face increased risks of complications such as joint infection and early revision. However, the influence of obesity on measures of patient function following TKA is poorly defined. Knee arthroplasty outcome data for procedures carried out over an eight month period was extracted from a regional database in the UK. We analysed the impact of weight categories (BMI<30, BMI=30–34.9, and BMI≥35) on the Forgotten Joint Score – 12 (FJS-12) and Oxford Knee Score (OKS). Data was available preoperatively and 12 months postoperatively. Physical and mental health was assessed with the SF-12 one year after surgery. Data from 256 patients were available. 49.6% had a BMI<30, 27.4% had a BMI 30–34.9 and 23.1% had a BMI≥35. Mean FJS-12 results at 1-year were 48.7 points for patients with a BMI<30, 40.7 points for patients with a BMI=30–34.9 and 34.0 points for patients with a BMI≥35. Effect sizes for change from baseline to 12-month post-op were 3.0 (Cohen's d) in patients with BMI<30 and d=2.2 in patients with BMI≥35. Mean OKS results at 1 year were 36.9 (BMI<30), 33.7 (BMI=30–34.9) and 32.0 (BMI≥35) respectively. Effect sizes for change from baseline to 12-month was d=2.1 (BMI<30) and d=1.9 (BMI≥35). Differences between BMI groups with regard to post-operative change were statistically significant for the FJS-12 (p=0.038) but not for the OKS (p=0.229). This study highlights that outcome scores may differ in their ability to capture the impact of obesity on patient function following TKA. The FJS-12 showed significant differences in outcome based on patient obesity category, whereas the OKS did not detect between group differences

The CCI mobile bearing ankle implant used at our orthopedic department 2010–2013, was abandoned due to failures and findings of bone loss at revision. The aim of this study was to a) Determine our true revision rate, b) Investigate accuracy of measuring prevalence, size and location of periprosthetic bone cysts through X-ray and CT and c) Relate these findings to implant alignment and patient reported outcome measurements (PROMs). 51 primary surgeries were performed, prior to this study 8 had been revised. Out of 43 un-revised patients, 36 were enrolled and underwent evaluation with metal artefact reduction CT-scans and conventional X-ray. They filled out 3 PROMs; SEFAS, SF-12, EQ-5D. Cyst volume larger than 0.1 ml was measured using VITREA volume tools for CT-scans and calculation of spherical volume for X-rays; using AP- and lateral projections. Location of lesions was recorded, according to their position relative to the implant. Medial-/lateral- and anterior-/posterior tilt of the implant parts was measured using IMPAX built in measuring tools, applied to AP- and lateral X-ray projection. The relation between lesions location and alignment of components was analyzed by logistic regression. Bias and ICC estimation between CT and X-ray was analyzed by mixed effect model. Log transformation was used to fit the normal distribution assumption. PROMs association to osteolytic volume was analyzed by linear- and logistic regression. P-values of 0.05 were considered statistically significant. Finding large osteolytic lesions caused 4 additional patients to undergo revision and 7 are being monitored due to high risk of failure. Of the original 51 implants 14 have been revised. 8 cases because of osteolytic lesions and aseptic loosening (true revisions w. exchange of components or bone transplants), 3 periprosthetic fractures (2 non-traumatic fractures) and 3 cases of exostosis. The 3- and 5 year revision rate was 14% and 16% for true revisions and 17% and 27% overall. Cystic lesions were found in 81% of participants. Total cyst-volume was on average 13% larger on X-ray, however this difference was not significant (p = 0.55), with intraclass correlation being 0.66. Total cystic volume was not significantly related to PROM-scores (P 0.16–0.5). Location of cysts showed association with alignment of components (P 0.02–0.08). Mean tibia component anterior tilt was 89 degrees (SD 4). Mean medial tilt was 91 degrees (SD 3) for the tibial and 90 degrees (SD 4) for the talar component. The implant investigated performs below standard, compared to public registries. 1, 2. that report overall 5 year revision rates at 5 – 6.5%. We obtained larger measurements from X-rays than CT, unlike previous studies comparing these modalities. Cysts were common and large. Correlation between lesion location and alignment of implant, with valgus and anterior tilt of components causing more lesions in adjacent zones, may suggest a link between implant failure and alignment of components

Knee osteoarthritis is common, disabling and can be effectively treated by total knee arthroplasty (TKA). In North America, consideration has been given to the varying outcomes amongst racial groups. However, scant attention has been paid to the outcomes of surgery in different racial groups found in the United Kingdom (UK). We investigated the results of surgery in one of the principal ethnic minorities in the UK; that of a south Asian population. We retrospectively analysed our prospectively collected database at the Southern General Hospital, Glasgow. We identified 39 Asian patients who had TKA. They were age and sex matched to a Caucasian group. Mean follow up was 40.3 months. Mean pre-operative oxford knee scores were poorer than in the Caucasian group (8.5 vs. 14.7, p=0.001.) Post operative oxford knee scores were similarly poorer in the Asian group (29.9 vs. 36.1, p=0.07.) Interestingly, the change in oxford knee scores was similar in both groups. SF-12 and WOMAC scores demonstrated poorer pre and post operative scores in the Asian group. Knee flexion was greater in the Asian group, however (107.5° vs. 106.2°, p=0.742.). We conclude that while patients of Asian origin have poorer post operative pain and function following TKA, they have a similar gain from surgery as do a Caucasian group and therefore surgery is effective intervention in this group. An important topic for further work is to identify why Asians present later in their arthritic disease process to healthcare professionals than do their Caucasian counterparts

The purpose of this study was to evaluate the effect of body mass index (BMI) on patients undergoing primary total knee arthroplasty for osteoarthritis. Data was collected on 664 patients at 4 centres all of whom received a Depuy PFC Sigma prosthesis. Data collected included patient demographics, Oxford Knee Score (OKS), American Knee Society Score, SF-12, complications of surgery and the need for revision. 14% of patients had a BMI<25, 35% were overweight (BMI-25–30), 32% suffered from Grade 1 obesity (BMI-30–35) and 19% had grade 2 obesity (BMI>35). Obese patients were more likely to be female, have a higher ASA grade, present at a younger age and do sedentary work or no work at all. Pre-operative Oxford knee score was significantly worse in the BMI>35 group (p<0.001). After surgery there was a significant improvement in functional outcome measures at 5 years post-operatively with all BMI groups improved by an average of 18 or 19 points in the OKS. However because those patients with high BMI have poorer pre-operative Oxford scores their post-operative scores were lower compared to patients with a normal BMI. Similar findings were noted with range of motion of the knee joint. Overall complication rates were found to be significantly higher in obese patients and both revision surgery and deep infection rates increased stepwise with increasing BMI levels. Deep Infection rates were as follows: BMI<25 0%, BMI-25–30 1.3%, BMI-30–35 1.4%, BMI-35–40 3.2% and BMI>40 6.1%. Revision rates were as follows: BMI<25 0%, BMI-25–30 0.9%, BMI-30–35 0.9%, BMI-35–40 3.2% and BMI>40 6.1%. Although obese patients with knee osteoarthritis do benefit from joint arthroplasty, they suffer from an increased rate of complications and need for revision surgery

Summary Statement. Service industry metrics (the net promoter score) are being introduced as a measure of UK healthcare satisfaction. Lower limb arthroplasty, as a ‘service’, scores comparably with the most successful commercial organisations. Background. Satisfaction with care is important to both the patient and the payer. The Net Promoter Score, widely used in the service industry, has been recently introduced to the UK National Health Service as an overarching metric of patient satisfaction and to monitor performance. This questionnaire asks ‘customers’ if they would recommend a service or products to others. Scores range from −100 (everyone is a detractor) to +100 (everyone is a promoter). In industry, a positive score is well regarded, with those over 50 regarded as excellent. Our aims were to assess net promoter scores for joint arthroplasty, to compare these scores with direct measures of patient satisfaction, and to evaluate which factors contributed to net promoter response. Methods. 6912 individuals undergoing primary lower limb joint replacement over a five year period (Jan 2007 – Dec 2011) took part in a prospective cohort study at a single NHS University hospital. Net promoter score, clinical outcomes as measured by PROMS (Oxford Hip or Knee Score and SF-12 score), multi-faceted patient satisfaction questionnaire, demographic data and length of hospital stay were recorded. Data was collected preoperatively and at 1 year post-surgery. Multivariate regression was performed to determine which factors could predict an outcome of ‘promoter’ and ‘detractor’ at 1 year post-surgery. Significance was accepted at p = 0.1 to accommodate the confounding effect of other variables. Results. Net promoter scores for knee and hip replacements were 49 and 71 respectively. Strong correlation was seen between overall satisfaction and whether the patient would recommend the operation to another (r = 0.637), though regression of these factors was modest (R. 2. = 0.406). Only 4 factors were relevant to the net promoter response: pain relief (OR 2.13, CI 1.83 – 2.49), meeting expectations (OR 2.57, CI 2.24 – 2.97), hospital experience (OR 2.33, CI 2.03 – 2.68) and arthroplasty type (OR 2.31, CI 1.68 – 3.17). These factors drove a model able to explain 95% of the variation in net promoter score. Conclusions. This is the first analysis of net promoter score for joint arthroplasty, and demonstrates values that compare favourably with the services provided by the most successful commercial organizations. The UK Department of Health describes this score as a measure of patient satisfaction. This is perhaps not completely accurate, as only a third of the variation in one response can be explained by the other, suggesting that although clearly related, these concepts are not the same. Pain relief, meeting of expectations of surgery, the hospital experience and whether the hip or knee joint is replaced are the only relevant factors in determining the net promoter response. Factors thought to influence clinical outcome such as depression, number of comorbidities, age and gender carry no influence with this metric

Summary Statement. In young, active patients cementless THR demonstrates excellent prosthetic stability by RSA and outstanding clinical outcomes at 5 years using a tapered titanium femoral stem, crosslinked polyethylene liners and either titanium or tantalum shells. Introduction. Early femoral implant stability is essential to long-term success in total hip replacement. Radiostereometric analysis (RSA) provides precise measurements of micromotion of the stem relative to the femur that are otherwise not detectable by routine radiographs. This study characterised micromotion of a tapered, cementless femoral stem and tantalum porous-coated vs. titanium acetabular shells in combination with highly cross-linked UHMWPE or conventional polyethylene liners using radiostereometric analysis (RSA) for 5 years following THR. Patients and Methods. This IRB-approved, prospective, double randomised, blinded study, involved 46 patients receiving a primary THR by a single surgeon. Each patient was randomised to receive a titanium (23) (Trilogy, Zimmer) or tantalum (23) (Modular Tantalum shell, Zimmer) uncemented hemispheric shell and either a highly-crosslinked or conventional polyethylene liner. Tantalum RSA markers were implanted in each patient. All patients had a Dorr A or B femoral canal and received a cementless, porous-coated titanium tapered stem (M/L Taper, Zimmer). All final femoral broaches were stable to rotational and longitudinal stress. RSA examinations, Harris Hip, UCLA, WOMAC, SF-12 scores were obtained at 10 days, 6 months, and annually through 5 years. Results. All patients demonstrated statistically significant improvement in Harris Hip, WOMAC, and SF-12 PCS scores post-operatively. Evaluation of polyethylene wear demonstrated that median penetration measurements were significantly greater in the conventional compared to the HXPLE liner cohorts at 1 year through 5 years follow-up (p<0.003). At 5 years, conventional liners showed 0.38 ± 0.05mm vertical wear whereas HXLPE liners showed 0.08 ± 0.02mm (p<0.003). Evaluation of the femoral stems demonstrated that the rate of subsidence was highest in the first 6 months (0.09mm/yr), with no other detectable motion through 5 years. Two outlying patients had significantly higher stem subsidence values at 6 months (0.7 mm and 1.0mm). One stem stabilised without further subsidence after 6 months (0.7mm), and the other stem stabilised at 1 year (1.5mm). Neither patient has clinical evidence of loosening. Evaluation of acetabular shells demonstrated less median vertical translation in tantalum than titanium shells at each time-point except at 3-years follow-up, however due to large standard errors, there was no significant difference between the two designs (p>0.05). These large standard errors were predominantly caused by two outliers, neither of which had clinical evidence of loosening. Discussion/Conclusion. In this RSA study of young THR patients, cementless tapered femoral stems, highly crosslinked polyethylene liners, and tantalum or titanium acetabular shells all demonstrated excellent performance through 5 years follow-up. Highly crosslinked polyethylene liners demonstrated significantly less wear than conventional liners. The femoral stem showed excellent stability through 5 years, with no clinical or radiologic episodes of failure. The small amount of micromotion seen is less than that previously reported for similar tapered, cementless stems and approaches the accuracy of RSA (0.05mm). Both acetabular shells demonstrated excellent stability with minimal micromotion at 5 years without significant differences in migration. All patients demonstrated significant clinical improvement in pain and function and additional RSA evaluation of these patients is planned

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.