Reduction of geometric misfit in straight antegrade humeral nailing by evaluating the effect of entry point angulation using a three-dimensional computational analysis.

BACKGROUND: Straight antegrade intramedullary nails are generally inserted utilising the apex as the surgical entry point in accordance with the mechanical axis of the bone. Our objective is to optimise the bone-nail fit in intramedullary nailing by subjecting the surgical entry point to varying angulations in both the mediolateral and anterior-posterior directions via a quantitative fit assessment in each configuration to identify the optimal angulation, defined as the angulation with the lowest occurrence of thin-out to improve nail fitting within the humerus. METHODS: Computed tomography (CT) scans from 10 cadaveric humeri models were used to generate three-dimensional bone models. The centreline profile of each humerus model was determined by dividing the humerus into multiple slices and identifying its respective centroid. The guidewire and nail models were then established and inserted into the humerus using the apex as the standard entry point. The bone-nail fit was measured utilising three fit quantification parameters: thin-out distance, nail protrusion volume into the cortical shell and deviation distance (top, middle, bottom) between the nail's longitudinal axis and medullary cavity centroid. FINDINGS: Results revealed a statistically significant association between angulation and occurrence of thin-out (p < .001) and showed that the optimally angulated entry point resulted in decreased cortical breach across the nail insertion depth compared to the standard entry point. INTERPRETATION: Our findings suggested that the current straight nail design may require further modifications to optimise the nail trajectory within the medullary canal by decreasing the bone-nail geometric mismatch to potentially maximise its working length.

Effect of implant length variations on stress shielding in proximal humeral replacement after tumor excision under torsion: Finite element study.

The proximal humerus is the most common site of occurrence of primary bone tumors in the upper limb. Endoprosthetic replacement is deemed as the preferred reconstructive option following primary resection of bone tumors. However, it has been also associated with complications such as stress shielding and aseptic loosening compromising prosthetic survival. Our objective was to conduct a finite element (FE) study to investigate the effect of varying endoprosthesis length on bone stresses as well as to quantify the extent of stress shielding across the bone length (BL) in a humerus-prosthesis assembly for proximal humeral replacement after tumor excision thereby allowing us to identify the optimal implant length with best biomechanical performance. FE models of the intact humerus and humerus-prosthesis assemblies were established where they were loaded at the elbow joint under torsion with the glenohumeral joint fixed to represent twisting. After dividing the bone into individual slices consisting of 5% BL, the maximum cortical and cancellous principal, von Mises and shear bone stresses were calculated. To measure the level of stress shielding, the percentage stress change from the intact state was evaluated across each slice. Similar stress patterns were observed between the intact state and shorter endoprosthesis compared to the longer endoprostheses. Our findings illustrated the possibility of stress shielding occurring under torsional forces with its effect increasing with implant lengthening. To conclude, we believe that using a shorter prosthesis may substantially diminish the risk of potential implant failure due to stress shielding.

Serum albumin level predicts survival after surgical treatment of metastatic femur fractures: a retrospective study.

BACKGROUND: Surgical treatment for metastatic pathological femur fractures is associated with high mortality. Correct estimation of prognosis helps in determining the palliative value of surgical treatment and informs surgical decision. This study evaluates the risk factors for mortality in these patients who were surgically treated. METHODS: This is a retrospective study of 112 patients with surgical treatment of metastatic pathological femur fractures. Risk factors evaluated included age, ASA status, Charlson comorbidity index, preoperative serum albumin and haemoglobin, primary tumour site, presence of visceral metastases, presence of spinal metastases, time from diagnosis of cancer to occurrence of pathological fracture, type of surgical procedure performed, lesion and whether treatment was received for an actual or impending fracture. A Cox regression model was used to determine if these factors were independent significant factors for survival. RESULTS: Mortality at 2 years after surgical treatment of metastatic femoral fractures was 86%. Cox regression analysis of risk factors revealed that preoperative serum albumin and type primary tumour were independent risk factors for mortality. Presence of visceral metastases was strongly correlated to serum albumin levels. CONCLUSION: Preoperative serum albumin level and primary tumour site are independent risk factors of survival in patients treated for pathological femur fractures. Serum albumin level may be used as a prognostic tool to guide treatment in this cohort of patients with high mortality rates.

Prophylactic fixation or surveillance: predicting subsequent displacement of lateral condyle of humeral fractures based on soft tissue swelling.

BACKGROUND: Nondisplaced or minimally displaced fractures (≤2 mm) of the lateral condyle of the humerus (LCH) could undergo subsequent displacement (>2 mm), which would be a potential surgical indication. We describe a new method to quantify soft tissue swelling in LCH fractures and to identify a threshold value to predict subsequent displacement of LCH fractures. We hypothesized that the larger the soft tissue swelling, the more likely a subsequent displacement would occur. METHODS: Elbow x-ray images (anteroposterior view) at initial presentation in 87 patients with subsequent displacement and in 87 patients with no subsequent displacement were compared. All fractures were initially nondisplaced or minimally displaced. The lateral elbow swelling-to-humeral shaft diameter (LES-H) ratio was measured. A threshold value for diagnosing a subsequent displacement was identified from the receiver operating characteristic curve analysis. RESULTS: Both groups had similar age (subsequent displacement: 5.1 ± 2.3 years vs. no subsequent displacement: 5.7 ± 3.2 years; P = .459). The LES-H ratio was significantly larger in the subsequent displacement group (1.8 ± 0.4 vs. 1.4 ± 0.4, P < .001). The area under the receiver operating characteristic curve was 0.728, which was moderately accurate in predicting subsequent displacement. A threshold LES-H ratio of 1.90 had a sensitivity of 41.4% and specificity of 90.8% in diagnosing subsequent displacement. The odds ratio of having subsequent displacement with LES-H ratio of ≥1.90 was 6.1 (95% confidence interval, 2.7-13.8; P < .001). CONCLUSION: The LES-H ratio could be used to objectively quantify soft tissue swelling in LCH fractures. An LES-H ratio of ≥1.90 was used as threshold value to predict subsequent displacement.

What Are the Preoperative Outcome Measures That Predispose to Periprosthetic Fractures After Primary Total Knee Arthroplasty?

BACKGROUND: There is little known in the literature about whether preoperative patient-reported outcome measures (PROMs) would affect the risk of periprosthetic fractures (PPFs) after primary total knee arthroplasty (TKA). Our study aims to evaluate the predictive values of PROMs on PPF after primary TKA. We hypothesize that poorer PROMs are associated with a higher risk of PPF after primary TKA. METHODS: We reviewed prospectively collected data in our hospital arthroplasty registry. Patients who sustained PPF after primary TKA between 2000 and 2015 were identified. Forty-two patients were identified and matched for gender, age, and body mass index to a control group of 84 patients who had primary TKA without PPF in a 2:1 ratio. Preoperative demographics, Short Form-36 (SF-36) scores, Oxford Knee score and Knee Society Score were evaluated. Variables of PROMs were entered into a multivariate logistic regression model. A variable was considered to be a significant predictor if its odds ratio was significant at P < .05. RESULTS: After multivariate regression analysis, SF-36 subdomains of physical functioning (PF) and vitality (VT) were identified as significant predictors for PPFs after primary TKA. A lower SF-36 PF and VT scores were associated with higher risks of sustaining a PPF after primary TKA. CONCLUSION: From our study, low preoperative SF-36 PF and VT scores are associated with a higher risk of PPFs after primary TKA. These results can allow the preoperative identification of patients at higher risk of PPF, and appropriate preoperative counseling, optimization, and close follow-up can be instituted for this at-risk group.

Minimal Clinically Important Differences for American Orthopaedic Foot & Ankle Society Score in Hallux Valgus Surgery.

BACKGROUND: The American Orthopaedic Foot & Ankle Society (AOFAS) score is one of the most common and adapted outcome scales in hallux valgus surgery. However, AOFAS is predominantly physician based and not patient based. Although it may be straightforward to derive statistical significance, it may not equate to the true subjective benefit of the patient's experience. There is a paucity of literature defining MCID for AOFAS in hallux valgus surgery although it could have a great impact on the accuracy of analyzing surgical outcomes. Hence, the primary aim of this study was to define the Minimal Clinically Important Difference (MCID) for the AOFAS score in these patients, and the secondary aim was to correlate patients' demographics to the MCID. METHODS: We conducted a retrospective cross-sectional study. A total of 446 patients were reviewed preoperatively and followed up for 2 years. An anchor question was asked 2 years postoperation: "How would you rate the overall results of your treatment for your foot and ankle condition?" (excellent, very good, good, fair, poor, terrible). The MCID was derived using 4 methods, 3 from an anchor-based approach and 1 from a distribution-based approach. Anchor-based approaches were (1) mean difference in 2-year AOFAS scores of patients who answered "good" versus "fair" based on the anchor question; (2) mean change of AOFAS score preoperatively and at 2-year follow-up in patients who answered good; (3) receiver operating characteristic (ROC) curves method, where the area under the curve (AUC) represented the likelihood that the scoring system would accurately discriminate these 2 groups of patients. The distribution-based approach used to calculate MCID was the effect size method. There were 405 (90.8%) females and 41 (9.2%) males. Mean age was 51.2 (standard deviation [SD] = 13) years, mean preoperative BMI was 24.2 (SD = 4.1). RESULTS: Mean preoperative AOFAS score was 55.6 (SD = 16.8), with significant improvement to 85.7 (SD = 14.4) in 2 years ( P value < .001). There were no statistical differences between demographics or preoperative AOFAS scores of patients with good versus fair satisfaction levels. At 2 years, patients who had good satisfaction had higher AOFAS scores than fair satisfaction (83.9 vs 78.1, P < .001) and higher mean change (30.2 vs 22.3, P = .015). Mean change in AOFAS score in patients with good satisfaction was 30.2 (SD = 19.8). Mean difference in good versus fair satisfaction was 7.9. Using ROC analysis, the cut-off point is 29.0, with an area under the curve (AUC) of 0.62. Effect size method derived an MCID of 8.4 with a moderate effect size of 0.5. Multiple linear regression demonstrated increasing age (ß = -0.129, CI = -0.245, -0.013, P = .030) and higher preoperative AOFAS score (ß = -0.874, CI = -0.644, -0.081, P < .001) to significantly decrease the amount of change in the AOFAS score. CONCLUSION: The MCID of AOFAS score in hallux valgus surgery was 7.9 to 30.2. The MCID can ensure clinical improvement from a patient's perspective and also aid in interpreting results from clinical trials and other studies. LEVEL OF EVIDENCE: Level III, retrospective comparative series.