The process of femoral impaction grafting requires vigorous impaction to obtain adequate stability but the force of impaction has not been determined. This process has been reported to result in femoral fractures with rates reaching 16%. The aims of this study were to determine the threshold force required for femoral impaction grafting, to determine the affect cortical thickness, canal diameter and bone mineral density (BMD) have on this threshold force and to measure subsidence of an Exeter prosthesis following impaction at the threshold force. Adult sow femurs were prepared and placed through a DEXA scanner and the BMD and canal diameter measured. Thirty five femurs were impacted with morsellised bone chips and an increasing force of 0.5kN was applied until the femur fractured. Using callipers the cortical thickness of the bone was measured along the fracture line. Once the threshold force was determined 5 femurs were impacted to this threshold force and an Exeter stem was cemented into the neomedullary canal and a 28mm Exeter head attached. Axial cyclic loading was performed between 440N (swing phase of gait) and 1320N (stance phase of gait) for 150,000 cycles at a frequency of 3Hz. The position sensor of the hydraulic testing machine measured the subsidence. 29 tests were successfully completed. The threshold force was found to be 4kN. There was no significant correlation between the load at fracture and the cortex: canal ratio or the bone mineral density. Following impaction with the maximum force of 4kN the average subsidence for the 5 femurs was 0.276mm (range 0.235 – 0.325mm). In this animal study the threshold force was 4kN. Minimal axial subsidence of the implant occurred when impacting the graft with this threshold force. We therefore achieved a stable construct without fracture which is the ultimate goal for the revision hip surgeon

The threshold for decompression in acute compartment syndrome is quoted as a pressure difference between the compartment and diastolic blood pressure of less than 30mmHg. This study reports the findings of continuous compartment pressure monitoring in children who underwent tibial osteotomies. In this prospective observational study, twenty seven children who underwent tibial osteotomies had anterior compartment pressures monitored using a transducer-tipped probe for a minimum of 72 hours following surgery. Pressure data were collected hourly together with evidence of clinical signs, symptoms and patterns of analgesic use. Patients were also reviewed for late sequelae of compartment syndrome. One case of compartment syndrome were encountered. Pressure differences (diastolic BP - compartment pressure) were found to vary widely, with many children exceeding the threshold for decompression but without manifesting other signs of compartment syndrome. Fasciotomies were not performed in view of the conflicting evidence and subsequent review confirmed the absence of late sequelae. In these children, low diastolic blood pressures were a common but normal feature. The prevalence of compartment syndrome was 3.7% (1/27). The positive predictive value of using the adult threshold was 7.1%; the negative predictive value was 100%. We conclude that the threshold for decompression as applied to adults is unsuitable for use in children inasmuch as a positive result would lead to a correct diagnosis in only 7.1% of children. A negative test is more useful in correctly excluding compartment syndrome in 100% of the children studied

Although wait-times for hip fracture surgery have been linked to mortality and are being used as quality-of-care indicators worldwide, controversy exists about the duration of the wait that leads to complications. Our objective was to use new population-based wait-time data to emprically derive an optimal time window in which to conduct hip fracture surgery before the risk of complications increases. We used health administrative data from Ontario, Canada to identify hip fracture patients between 2009 and 2014. The main exposure was the time from hospital arrival to surgery (in hours). The primary outcome was mortality within 30 days. Secondary outcomes included a composite of mortality or other medical complications (MI, DVT, PE, and pneumonia) also within 30 days. Risk-adjusted cubic splines modeled the probability of each complication according to wait-time. The inflection point (in hours) when complications began to increase was used to define ‘early’ and ‘delayed’ surgery. To evaluate the robustness of this definition, outcomes amongst propensity-score matched early and delayed patients were compared using percent absolute risk differences (% ARDs, with 95% confidence intervals [CIs]). There were 42,230 patients who met entry criteria. Their mean age was 80.1 (±10.7) and the majority were female (70.5%). The risk of complications modeled by cubic splines consistently increased when wait-times were greater than 24 hours, irrespective of the complication considered. Compared to 13,731 propensity-score matched patients who received surgery earlier, 13,731 patients receiving surgery after 24 hours had a significantly higher risk of 30-day mortality (N=898 versus N=790, % ARD 0.79 [95% CI 0.23 to 1.35], p = .006) and the composite outcome (N=1,680 versus N=1,383, % ARD 2.16 [95% CI 1.43 to 2.89], p < .001). Overall, there were 14,174 patients (33.6%) who received surgery within 24 hours and 28,056 patients (66.4%) who received surgery after 24 hours. Increased wait-time was associated with a greater risk for 30-day mortality and other complications. The finding that a wait-time of 24 hours represents a threshold defining higher risk may inform existing hip fracture guidelines. Since two-thirds of patients did not receive surgery within this timeframe, performance improvement efforts that reduce wait-times are warranted

Summary

A laboratory based study investigating fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting.

Background and purpose

The two most common complications of femoral impaction bone grafting are femoral fracture and massive implant subsidence. We investigated fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting. The study consisted of two arms, the first examining the force at which femoral fracture occurs in the embalmed human femur, and the second examining whether significant graft implant/subsidence occurs following impaction at a set force at two different impaction frequencies.

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

Aim. Swedish guidelines on antibiotic prophylaxis in arthroplasty surgery recommend cloxacillin in fixed doses that pay little attention to the patient's renal function and weight. Nevertheless, there are no studies on whether the resulting free prophylactic cloxacillin in vivo concentrations are optimal. We aimed to evaluate whether the current recommended prophylactic dosage of cloxacillin is adequate. Method. We performed a prospective two-centre study, measuring the free (active) cloxacillin concentrations in plasma throughout surgery, in patients subject to primary hip and knee prosthetic joint replacements, aiming at 100 patients per centre. To account for plasma-bone exposure differences, concentrations were considered adequate if twice the epidemiological cut-off value for cloxacillin concerning wild type Staphylococcus aureus whereas two-three times were labelled threshold values. The two enrolling hospitals are acute care hospitals in central Sweden, also performing 600 - 1200 primary hip and knee joint arthroplasties annually. All patients scheduled for elective primary hip or knee replacements from January 2022 to April 2024 were eligible for participation. Exclusion criteria were allergy towards penicillins, cognitive disorders leading to inability to sign informed consent, and an absence of interpreter in case of a patient not speaking Swedish or English. Results. We present results from the first 49 patients included. Four patients had free cloxacillin concentrations below cut-off (8.2%). These four cases had prolonged surgeries of 77-100 minutes. An additional 5/49 (10.2%) had threshold values. Conversely 5/49 (10.2%) cases had concentrations exceeding 15 times the needed. No cases with threshold or low cloxacillin concentrations were attributable to a lack of concerning timing and dosing of cloxacillin. All concentrations were above or equal to our cut-off at the start of surgery. Eighteen percent of patients were of normal of weight (BMI 18.5- 25). Of the rest 4% were morbidly obese (BMI >40), 41% obese (BMI 30-40) and 37% overweight (BMI 25-30). Twenty seven percent (43/159) had diabetes and 45% suffered cardiac disease. Conclusions. Some patients in our cohort had insufficient active cloxacillin levels at the end of prosthetic joint surgery. Previous studies indicate that insufficient prophylactic antibiotic concentrations might lead to an enhanced risk of prosthetic joint infections. Other patients were massively overdosed, leading to unnecessary ecological effects and potentially adverse reactions. As inadequate cloxacillin concentrations were not associated with a lack of compliance to current guidelines a change in practise might be needed. Our final results may help to determine how dosing should be adjusted

While pre-soaking grafts in vancomycin has demonstrated to be effective in observational studies for anterior cruciate ligament reconstruction (ACLR) infection prevention, the economic benefit of the technique is uncertain. The primary aim of this study was to determine the cost-effectiveness of vancomycin pre-soaking during primary ACLR to prevent post-operative joint infections. The secondary aims of the study were to establish the breakeven cost-effectiveness threshold of the technique. A Markov model was used to determine cost effectiveness and the incremental cost effectiveness ratio of additional vancomycin pre-soaking compared to intravenous antibiotic prophylaxis alone. A repeated meta-analysis of nine cohort studies (Level III evidence) was completed to determine the odds ratio of infection with vancomycin pre-soaking compared to intravenous antibiotics alone. Estimated costs and transitional probabilities for further surgery were obtained from the literature. Breakeven threshold analysis was performed. The vancomycin soaking technique provides an expected cost saving of $600AUD per patient. There was an improvement in the quality-adjusted life years of 0.007 compared to intravenous antibiotic prophylaxis alone (4.297 versus 4.290). If the infection rate is below 0.023% with intravenous antibiotics alone or the additional intervention cost more than $1000AUD, the vancomycin wrap would no longer be cost-effective. For $30AUD, the vancomycin soaking technique provides a $600AUD cost saving by both reducing the risk of ACLR related infection and economic burden of infection. Treating septic arthritis represents a mean cost per patient of 6 times compared to that of the primary surgery. There has been no previous cost-effectiveness study of the vancomycin wrap technique. The vancomycin pre-soaking technique is a highly cost-effective method to prevent post-operative septic arthritis following primary ACLR

Aim. Despite several synovial fluid biomarkers for diagnosis of periprosthetic joint infection (PJI) have being investigated, point-of-care (POC) tests using these biomarkers are not widely available. Synovial calprotectin has recently been reported to effectively exclude diagnosis of PJI and a novel lateral flow POC test using it has shown potential to be effective. Thus, the aims of this study were to 1) validate calprotectin POC with enzyme linked immunosorbet assay (ELISA) 2) at 2 separate thresholds for PJI diagnosis in total knee arthroplasty (TKA) patients using the 2013 Musculoskeletal Infection Society (MSIS) PJI diagnosis criteria as the gold standard. Method. Intraoperative synovial fluid samples were prospectively collected from 123 patients who underwent revision TKAs (rTKA) at two academic hospitals within the same healthcare system from October 2018 to January 2020. The study was conducted under IRB approval. Included patients followed the hospital standard for their PJI diagnostic work-up. Data collection included demographic, clinical, and laboratory data in compliance with MSIS criteria. Synovial fluid samples were analysed by calprotectin POC and ELISA tests in accordance with manufacturer's instructions. Patients were categorized as septic or aseptic using MSIS criteria by two independent reviewers blinded to calprotectin assay results. The calprotectin POC and ELISA test performance characteristics were calculated with sensitivities, specificities, positive, and negative predicted values (PPV and NPV, respectively) and areas under the curve (AUC) for 2 different PJI diagnosis scenarios: (1) a threshold of >50 mg/L and (2) a threshold of >14 mg/L. Results. According to MSIS criteria, 53 rTKAs were septic while 70 rTKA were aseptic. In the (1) >50 mg/mL threshold scenario, the calprotectin POC and ELISA performance showed 100% agreement with sensitivity, specificity, PPV, NPV, and AUC, respectively, of 98.1%, 95.7%, 94.5%, 98.5%, and 0.969. In the (2) >14 mg/mL threshold scenario, the POC slightly outperformed the ELISA with sensitivity, specificity, PPV, NPV and AUC of 98.1%, 87.1%, 85.2%, 98.4%, and 0.926, respectively (ELISA values were 98.1%, 82.9%, 81.3%, 98.3%, and 0.905, respectively). Conclusions. The calprotectin POC test performed as well as the ELISA at the >50mg/L threshold and was slightly better at the >14 mg/L threshold. The >50 mg/L threshold had a better specificity while maintaining the same sensitivity as the >14 mg/L threshold. This test could be effectively implemented as a rule out test. However, further investigations with larger cohorts are necessary to validate these results

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

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

Primary hip and knee joint replacements in Canada have been estimated to cost over $1.4 billion dollars annually, with revision surgery costing $177 million. The most common cause of revision arthroplasty surgery in Canada is infection. Periprosthetic joint infections (PJIs) are a devastating though preventable complication following arthroplasty. Though variably used, antibiotic laden bone cement (ALBC) has been demonstrated to decrease PJIs following primary total knee arthroplasty (TKA). Unfortunately, ALBC is costlier than regular bone cement (RBC). Therefore, the aim of this study was to determine if the routine use of ALBC in primary TKA surgery is a cost-effective practice from the perspective of the Canadian healthcare system. A decision tree was constructed using a decision analysis software (TreeAge Software, Williamstown, Massachusetts) to a two-year time horizon comparing primary TKA with either ALBC or RBC from the perspective of a single-payer healthcare system. All costs were in 2020 Canadian dollars. Health utilities were in the form of quality adjusted life years (QALYs). Model inputs for cost were derived from regional and national databases. Health utilities and probability parameters were derived from the latest literature. One-way deterministic sensitivity analysis was performed on all model parameters. The primary outcome of this analysis was an incremental cost-effectiveness ratio (ICER) with a willingness-to-pay (WTP) threshold of $50,000 per QALY. Primary TKA with ALBC (TKA-ALBC) was found to be more cost-effective compared to primary TKA with RBC (TKA-RBC). More specifically, TKA-ALBC dominated TKA-RBC as it was less costly on the long term ($11,160 vs. $11,118), while providing the same QALY (1.66). The ICER of this cost-utility analysis (CUA) was $-11,049.72 per QALY, much less than the WTP threshold of $50,000 per QALY. The model was sensitive to costs of ALBC-TKA as well as the probability of PJI following ALBC-TKA and RBC-TKA. ALBC ceased to be cost effective once the cost of ALBC was greater than $223.08 CAD per bag of cement. The routine use of ALBC in primary TKA is a cost-effective practice in the context of the Canadian healthcare system as long as the cost of ALBC is maintained at a reasonable price and the published studies to-date keep supporting the efficacy of ALBC in decreasing PJI following primary TKA. Further, this analysis is very conservative, and ALBC is likely much more cost-effective than presented. This is due to this model's revision surgery cost parameter being based on the average cost of all revision TKA surgery in Canada, regardless of etiology. Considering many PJIs require two-stage revisions, the cost parameter used in this analysis for revision surgery is an underestimate of true cost. Ultimately, this is the first cost-effectiveness study evaluating this topic from the perspective of the Canadian healthcare system and can inform future national guidelines on the subject matter

Acute Compartment Syndrome (ACS) is an orthopaedic emergency that can develop after a wide array of etiologies. In this pilot study the MY01 device was used to assess its ease of use and its ability to continuously reflect the intracompartmental pressure (ICP) and transmit this data to a mobile device in real time. This preliminary data is from the lead site which is presently expanding data collection to five other sites as part of a multi-center study. Patients with long bone trauma of the lower or upper extremity posing a possibility of developing compartment syndrome were enrolled in the study. Informed consent was obtained from the patients. A Health Canada licensed continuous compartmental pressure monitor (MY01) was used to measure ICP. The device was inserted in the compartment that was deemed most likely to develop ACS and ICP was continuously measured for up to 18 hours. Fractures were classified according to the AO/OTA classification. Patient clinical signs and pain levels were recorded by healthcare staff during routine in-patient monitoring and were compared to the ICP from the device. Important treatment information was pulled from the patient's chart to help correlate all of the patient's data and symptoms. The study period was conducted from November 2020 through December 2021. Twenty-six patients were enrolled. There were 17 males, and nine females. The mean age was 38 years (range, 17–76). Seventeen patients received the device post-operatively and nine received it pre-operatively. Preliminary results show that post-operative ICPs tend to be significantly higher than pre-operative ICPs but tend to trend downwards very quickly. The trend in this measurement appears to be more significant than absolute numbers which is a real change from the previous literature. One patient pre-operatively illustrated a steep trend upwards with minimal clinical symptoms but required compartment release at the time of surgery that exhibited no muscle necrosis. The trend in this patient was very steep and, as predicted, predated the clinical findings of compartment syndrome. This trend allows an early warning signal of the absolute pressure, to come, in the compartment that is being assessed by the device. Preliminary results suggest that this device is reliable and relatively easy to use within our institutions. In addition it suggests that intracompartmental pressures can be higher immediately post-op but lower rapidly when the patient does not develop ACS. These results are in line with current literature of the difference between pre and post-operative baselines and thresholds of ICP, but are much more striking, as continuous measurements have not been part of the data set in most of past studies. Further elucidation of the pressure thresholds and profiles are currently being studied in the ongoing larger multicenter study and will add to our understanding of the critical values. This data, plus the added value of continuous trends in the pressure, upwards or downwards, will aid in preventing muscle necrosis during our management of these difficult long bone fractures

This study used model-based radiostereometric analysis (MBRSA) to compare migration of a recently introduced cementless hip stem to an established hip stem of similar design. Novel design features of the newer hip stem included a greater thickness of hydroxyapatite coating and a blended compaction extraction femoral broach. Fifty-seven patients requiring primary total hip arthroplasty (THA) were enrolled at a single centre. Patients were randomized to receive either an Avenir collarless stem and Trilogy IT cup (ZimmerBiomet) or a Corail collarless stem and Pinnacle cup (DePuy Synthes) via a posterior or lateral approach. Both stems are broach-only femoral bone preparation. RSA beads (Halifax Biomedical) were inserted into the proximal femur during surgery. Patients underwent supine RSA imaging a 6 weeks (baseline), 6, 12, and 24 months following surgery. The primary study outcome was total subsidence of the hip stem from baseline to 24 months as well as progression of subsidence between 12 and 24 months. These values were compared against published migration thresholds for well-performing hip stems (0.5mm). The detection limit, or precision, of MBRSA was calculated based on duplicate examinations taken at baseline. Patient reported outcome measures were collected throughout the study and included the Oxford-12 Hip Score (OHS), EuroQoL EQ-5D-5L, Hip Osteoarthritis Score (HOOS) as well as visual analogue scales (VAS) for thigh pain and satisfaction. Analysis comprised of paired and unpaired t-tests with significance set at p≤0.05. Forty-eight patients (30 males) were included for analysis; 7 patients received a non-study hip stem intra-operatively, 1 patient suffered a traumatic dislocation within three weeks of surgery, and 1 patient died within 12 months post-surgery. RSA data was obtained for 45 patients as three patients did not receive RSA beads intra-operatively. Our patient cohort had a mean age of 65.9 years (±;7.2) at the time of surgery and body mass index of 30.5 kg/m2 (±;5.2). No statistical difference in total stem migration was found between the Avenir and Corail stems at 12 months (p=0.045, 95%CI: −0.046 to 0.088) and 24 months (p=0.936, 95% CI: −0.098 to 0.090). Progression of subsidence from 12-24 months was 0.011mm and 0.034mm for the Avenir and Corail groups which were not statistically different (p=0.163, 95%CI: −0.100 to 0.008) between groups and significantly less than the 0.5mm threshold (pNo statistically significant differences existed between study groups for any pre-operative function scores (p>0.05). All patients showed significant functional improvement from pre- to post-surgery and no outcome measures were different between study groups with exception of EQ-5D-5L health visual analogue scale at 12 months which showed marginally superior (p=0.036) scores in the Avenir group. This study was not powered to detect differences in clinical outcomes. This study has demonstrated no statistical difference in subsidence or patient-reported outcomes between the Corail hip stem and the more recently introduced Avenir hip stem. This result is predictable as both stems are of a triple-tapered design, are coated with hydroxyapatite, and utilize a broach-only bone preparation technique. Both stem designs demonstrate migration below 0.5mm suggesting both are low-risk for aseptic loosening in the long-term

Aim. D-dimer is a widely available serum test that detects fibrinolytic activities that occur during infection. Prior studies have explored its utility for diagnosis of chronic periprosthetic joint infections (PJI), but not explored its prognostic value for prediction of subsequent treatment failure. The purpose of this study was to: (1) assess the ability of serum D-dimer and other standard-of-care serum biomarkers to predict failure following reimplantation, and (2) establish a new cutoff value for serum D-dimer for prognostic use prior to reimplantation. Method. This prospective study enrolled 92 patients undergoing reimplantation between April 2015 and March 2019 who had previously undergone total hip/knee resection arthroplasty with placement of an antibiotic spacer for treatment of chronic PJI. Serum D-dimer level, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels were measured preoperatively for all patients. Failure following implantation was defined per the Delphi consensus criteria. Optimal cutoffs for D-dimer, ESR, and CRP were calculated based on ROC curves and compared in their association with failure following reimplantation criteria at minimum 1-year follow-up. Results. 15/92(16.3%) patients failed reimplantation surgery at mean follow up of 2.9 years (range 1.0–4.8). Optimal thresholds for D-Dimer, ESR and CRP were determined to be 1300ng/mL, 30mm/hr, and 1mg/L, respectively. The failure rate in patient with positive D-dimer was significantly higher at 32.0% (8/25) compared to those with negative D-dimer 10.6% (7/66); p=0.024. In comparison, 17.8% (8/45) of patients with ESR above threshold failed, compared to 13.89% (5/41) below (p=0.555) and 16.0% (4/25) of patients with CRP above threshold failed, compared to 16.1% (10/62) below (p=1.000). Conclusions. Patients with elevated D-Dimer appear to be at higher risk of failure after reimplantation surgery. This serum marker may be used to generate an additional data point in patients undergoing reimplantation surgery, especially in circumstances when optimal timing of reimplantation cannot be determined based on clinical circumstances

Objectives. Articular cartilage damage is a primary outcome of pre-clinical and clinical studies evaluating meniscal and cartilage repair or replacement techniques. Recent studies have quantitatively characterized India Ink stained cartilage damage through light reflectance and the application of local or global thresholds. We develop a method for the quantitative characterisation of inked cartilage damage with improved generalisation capability, and compare its performance to the threshold-based baseline approach against gold standard labels. Methods. The Trainable WEKA Segmentation (TWS) tool (Arganda-Carreras et al., 2017) available in Fiji (Rueden et al., 2017) was used to train two separate Random Forest classifiers to automatically segment cartilage damage on ink stained cadaveric ovine stifle joints. Gold standard labels were manually annotated for the training, validation and test datasets for each of the femoral and tibial classifiers. Each dataset included a sample of medial and lateral femoral condyles and tibial plateaus from various stifle joints, selected to ensure no overlap across datasets according to ovine identifier. Training was performed on the training data with the TWS tool using edge, texture and noise reduction filters selected for their suitability and performance. The two trained classifiers were then applied to the validation data to output damage probability maps, on which a threshold value was calibrated. Model predictions on the unseen test set were evaluated against the gold standard labels using the Dice Similarity Coefficient (DSC) – an overlap-based metric, and compared with results for the baseline global threshold approach applied in Fiji as shown in Figures 1 and 2. Results. Test set results for the global threshold approach against gold standard labels were 45.0% DSC for the femoral condyle and 32.0% DSC for the tibial plateau. Results for the developed TWS classifiers on the same unseen test data were 79.0% and 72.7% DSC, showing absolute gains of 34.0% and 40.7% DSC over the global threshold baseline for the femoral and tibial classifiers. The trained TWS classifiers were then applied to an external set of unlabelled images of ink stained femoral condyles and tibial plateaus. Model results on sample images shown in Figure 3 further highlight the generalisation capability of the developed models. The most prominent classification features were Hessian filters (32.9%), Entropy (19.4%), Gaussian blur (10.1%), Gabor filters (6.3%) and Sobel filters (6.0%), with all other features contributing less than 6%. Conclusions. Our findings show that the developed segmentation method more accurately quantifies cartilage damage and provides improved generalisation capability over a range of input variations such as inconsistent orientation and lighting conditions. The developed model enables the use of articular cartilage damage as a reliable and quantitative outcome measure in studies involving large datasets, with reduced requirements for complex pre-processing and specialised equipment. For any figures or tables, please contact the authors directly

Background. The purpose of this study was to determine if thresholds regarding the percentage of maximal improvement in the Simple Shoulder Test (SST) and American Shoulder and Elbow Surgery (ASES) score exist that predict “excellent” patient s­atisfaction (PS) following reverse total shoulder arthroplasty (RSA). Methods. Patients undergoing RSA using a single implant system were evaluated pre-operatively and at a minimum 2-year follow-up. Receiver-operating-characteristic (ROC) curve analysis determined thresholds to predict “excellent” PS by evaluating the percentage of maximal improvement for SST and ASES. Pre-operative factors were analyzed as independent predictors for achieving SST and ASES thresholds. Results. 198 (SST) and 196 (ASES) patients met inclusion criteria. For SST and ASES, ROC analysis identified 61.3% (p<.001) and 68.2% (p<.001) maximal improvement as the threshold for maximal predictability of “excellent” satisfaction respectively. Significant positive correlation between the percentage of maximum score achieved and “excellent” PS for both groups were found (r=.440, p<.001 for SST score; r=0.417, p<.001 for ASES score). Surgery on the dominant hand, greater baseline VAS Pain, and cuff arthropathy were independent predictors for achieving the SST and ASES threshold. Conclusion. Achievement of 61.3% of maximal SST score improvement and 68.3% of maximal ASES score improvement represent thresholds for the achievement of “excellent” satisfaction following RSA. Independent predictors of achieving these thresholds were dominant sided surgery and higher baseline pain VAS scores for SST, and rotator cuff arthropathy for ASES. Keywords. Percentage of maximal improvement; Predictors; American Shoulder and Elbow Surgery Score; Simply Shoulder Test; Reverse shoulder Arthroplasty; Satisfaction. Level of Evidence. Level III

Venous thromboembolism (VTE) is the second most common complication and pulmonary embolism (PE) is the fourth most common cause of death after a hip fracture. Despite thromboprophylaxis, deep vein thrombosis (DVT) is detected in up to 45% of hip fracture patients. Thrombelastography (TEG) is a whole-blood, point of care test capable of providing clinicians with a global assessment of the clotting process, from fibrin formation to clot lysis. Maximal amplitude (mA) from TEG analysis is a measure of clot strength. Elevated admission mA values of >65mm and >72mm have been determined to be independent predictors of in-hospital PE. The coagulation index (CI) is calculated based on TEG parameters and defines hypercoagulable state as CI >3. This study aimed to use serial TEG analysis to determine the duration of hypercoagulable state after hip fracture. A prospective cohort of hip fracture patients >50 years of age amenable to surgical treatment (AO 31A1–A3 & 31B1–B3) were enrolled at a Level I trauma centre. Serial TEG analysis (TEG 6S) was performed every 24-hours from admission until 5-days post-operatively and at 2- and 6-week follow-up visits. All patients received a minimum of 28 days of thromboprophylaxis. Descriptive statistics and single sample t-tests were used for comparison of mA to the 65mm threshold. Thirty-five patients (26 female) with a median age of 83 (range = 71–86) years were included. On admission, 31.4% and 82.9% of patients were hypercoagulable based on mA >65mm and CI, respectively. At 2 weeks, all patients remained hypercoagulable, however, mA >72mm showed that 16 patients (47.1%) were at even higher risk for VTE. At 6-weeks, 65.7% and 97.1% of patients were hypercoagulable based on mA >65mm and CI, respectively. When compared with the mA >65mm threshold, patients were hypocoagulable at the time of admission (mA = 62.2 (±6.3), p = 0.011), but became significantly more hypercoagulable at 2-weeks (mA = 71.6 (±2.6), p < 0 .001), followed by continued hypercoagulability at 6-weeks, however not significantly elevated above the 65mm threshold (mA = 66.2 (±3.8), p = 0.058). One patient developed a symptomatic DVT at 2-weeks and had a mA = 72.9 and a CI of 5.9. This is the first study to demonstrate that >50% of hip fracture patients remain hypercoagulable 6 weeks post fracture despite thromboprophylaxis, and there are individual hypercoagulable responses. This is critical, as guidelines only recommend 28 to 35 days of thromboprophylaxis in this high-risk population. Previously determined mA thresholds may be a more sensitive test for risk-stratifying patients' VTE risk than the CI threshold. Additionally, assessing ΔmA using serial TEG may better predict VTE risk

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

Functional outcomes are commonly reported in studies of musculoskeletal oncology patients undergoing limb salvage surgery; however, interpretation requires knowledge of the smallest amount of improvement that is important to patients – the minimally important difference (MID). We established the MIDs for the Musculoskeletal Tumor Society Rating Scale (MSTS) and Toronto Extremity Salvage Score (TESS) in patients with bone tumors undergoing lower limb salvage surgery. This study was a secondary analysis of the recently completed PARITY (Prophylactic Antibiotic Regimens in Tumor Surgery) study. This data was used to calculate: (1) the anchor-based MIDs using an overall function scale and a receiver operating curve analysis, and (2) the distribution-based MIDs based on one-half of the standard deviation of the change scores from baseline to 12-month follow-up, for both the MSTS and TESS. There were 591 patients available for analysis. The Pearson correlation coefficients for the association between changes in MSTS and TESS scores and changes in the external anchor scores were 0.71 and 0.57, indicating “high” and “moderate” correlation. Anchor-based MIDs were 12 points and 11 points for the MSTS and TESS, respectively. Distribution-based calculations yielded MIDs of 16-17 points for the MSTS and 14 points for the TESS. The current study proposes MID scores for both the MSTS and TESS outcome measures based on 591 patients with bone tumors undergoing lower extremity endoprosthetic reconstruction. These thresholds will optimize interpretation of the magnitude of treatment effects, which will enable shared decision-making with patients in trading off desirable and undesirable outcomes of alternative management strategies. We recommend anchor-based MIDs as they are grounded in changes in functional status that are meaningful to patients