Distal femoral replacement for the treatment of periprosthetic distal femoral fractures around a total knee arthroplasty: a meta-analysis.

Background: Periprosthetic fracture is a rare complication of arthroplasty but can have devastating consequences for the patient and presents a complex surgical challenge. Locking compression plate and retrograde intramedullary nail are both widely accepted surgical fixation techniques for distal femoral periprosthetic fractures around a total knee arthroplasty. Although there is still a need for further high-quality research into both techniques, there is even less literature concerning the use of distal femoral replacement to treat distal femoral periprosthetic fractures. Interest has been piqued in distal femoral replacements for the treatment of distal femoral periprosthetic fractures due to the theoretical advantages of immediate post-operative weight-bearing and lack of dependence on fracture union, but there are still understandably reservations about performing such an extensive and invasive procedure when an accepted alternative is available. This meta-analysis aims to evaluate the current literature to compare the complication rates and return to pre-operative ambulatory status of distal femoral replacement and locking compression plate. Method: A literature search was performed to identify articles related to the management of distal femoral periprosthetic fractures around a total knee arthroplasty in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. Methodological quality was assessed using the methodological index for non-randomized studies (MINORS) criteria. Articles were reviewed, and data extracted for analysis. Results: Five articles met the inclusion criteria, reporting on 345 periprosthetic fractures. The overall rates of complications for distal femoral replacement and locking compression plate were: re-operation (6.1% vs 12.1%), infection (3.0% vs 5.3%), mortality (19.7% vs 19.3%), and return to pre-operative ambulatory status (60.9% vs 71.8%) (respectively). Conclusion: This meta-analysis shows no statistically significant difference in the rates of re-operation, infection, mortality or return to pre-operative ambulatory status when comparing distal femoral replacement to locking compression plate.

Antimicrobial prophylaxis with teicoplanin plus gentamicin in primary total joint arthroplasty.

Objectives: To compare prosthetic joint infection (PJI) and acute kidney injury (AKI) rates among cohorts before and after changing our hospital's antimicrobial prophylactic regimen from cefuroxime to teicoplanin plus gentamicin. Methods: We retrospectively studied all patients undergoing primary total joint arthroplasty at our hospital 18 months pre- and post-implementation of the change in practice. All deep infections identified during follow-up were assessed against the European Bone and Joint Infection Society (EBJIS) definitions for PJI. Survival analysis using Cox regression was employed to adjust for differences in baseline characteristics and compare the risk of PJI between the groups. AKIs were identified using pathology records and categorized according to the KDIGO (Kidney Disease - Improving Global Outcomes) criteria. AKI rates were calculated for the pre- and post-intervention periods. Results: Of 1994 evaluable patients, 1114 (55.9 %) received cefuroxime only (pre-intervention group) and 880 (44.1 %) patients received teicoplanin plus gentamicin (post-intervention group). The overall rate of PJI in our study was 1.50 % (30 of 1994), with a lower PJI rate in the post-intervention group (0.57 %; 5 of 880) compared with the pre-intervention group (2.24 %; 25 of 1114). A corresponding risk reduction for PJI of 75.2 % (95 % CI of 35.2-90.5; p=0.004) was seen in the post-intervention group, which was most pronounced for early-onset and delayed infections due to coagulase-negative staphylococci (CoNS) and cefuroxime-resistant Enterobacteriaceae. Significantly higher AKI rates were seen in the post-intervention group; however, 84 % of cases (32 of 38) were stage 1, and there were no differences in the rate of stage-2 or -3 AKI. Conclusions: Teicoplanin plus gentamicin was associated with a significant reduction in PJI rates compared with cefuroxime. Increases in stage-1 AKI were seen with teicoplanin plus gentamicin.

UK robotic arthroplasty clinical and cost effectiveness randomised controlled trial for hips (RACER-Hip): a study protocol.

INTRODUCTION: The number of robotic-assisted hip replacement procedures has expanded globally with the intended aim of improving outcomes. Intraoperative robotic-arm systems add additional costs to total hip replacement (THR) surgery but may improve surgical precision and could contribute to diminished pain and improved function. Additionally, these systems may reduce the need for expensive revision surgery. Surgery with conventional instruments may be just as successful, quick and affordable. There is timely demand for a robust evaluation of this technology. METHODS AND ANALYSIS: The Robotic Arthroplasty Clinical and cost Effectiveness Randomised controlled trial for Hips (RACER-Hip) is a multicentre (minimum of six UK sites), participant-assessor blinded, randomised controlled trial. 378 participants with hip osteoarthritis requiring THR will be randomised (1:1) to receive robotic-assisted THR, or THR using conventional surgical instruments. The primary outcome is the Forgotten Joint Score at 12 months post-randomisation; a patient-reported outcome measure assessing participants' awareness of their joint when undertaking daily activities. Secondary outcomes will be collected post-operatively (pain, blood loss and opioid usage) and at 3, 6, 12, 24 months, then 5 and 10 years postrandomisation (including function, pain, health-related quality of life, reoperations and satisfaction). Allocation concealment will be accomplished using a computer-based randomisation procedure on the day of surgery. Blinding methods include the use of sham incisions for marker clusters and blinded operation notes. The primary analysis will adhere to the intention-to-treat principle. Results will adhere to Consolidated Standards of Reporting Trials statements. ETHICS AND DISSEMINATION: The trial was approved by an ethics committee (Solihull Research Ethics Committee, 30 June 2021, IRAS: 295831). Participants will provide informed consent before agreeing to participate. Results will be disseminated using peer-reviewed journal publications, presentations at international conferences and through the use of social media. We will develop plans to disseminate to patients and public with our patient partners. TRIAL REGISTRATION NUMBER: ISRCTN13374625.

Hip Resurfacing Arthroplasty: Past, Present and Future.

The history of hip resurfacing arthroplasty (HRA) has faced numerous challenges and undergone decades of evolution in materials and methods. These innovations have been translated to the successes of current prostheses and represent a surgical and mechanical achievement. Modern HRAs now have long term outcomes with excellent results in specific patient groups as demonstrated in national joint registries. This article reviews the key moments in the history of HRAs with specific emphasis on the lessons learnt, current outcomes and future prospects.

Robotic Arthroplasty Clinical and cost Effectiveness Randomised controlled trial (RACER-knee): a study protocol.

INTRODUCTION: Robotic-assisted knee replacement systems have been introduced to healthcare services worldwide in an effort to improve clinical outcomes for people, although high-quality evidence that they are clinically, or cost-effective remains sparse. Robotic-arm systems may improve surgical accuracy and could contribute to reduced pain, improved function and lower overall cost of total knee replacement (TKR) surgery. However, TKR with conventional instruments may be just as effective and may be quicker and cheaper. There is a need for a robust evaluation of this technology, including cost-effectiveness analyses using both within-trial and modelling approaches. This trial will compare robotic-assisted against conventional TKR to provide high-quality evidence on whether robotic-assisted knee replacement is beneficial to patients and cost-effective for healthcare systems. METHODS AND ANALYSIS: The Robotic Arthroplasty Clinical and cost Effectiveness Randomised controlled trial-Knee is a multicentre, participant-assessor blinded, randomised controlled trial to evaluate the clinical and cost-effectiveness of robotic-assisted TKR compared with TKR using conventional instruments. A total of 332 participants will be randomised (1:1) to provide 90% power for a 12-point difference in the primary outcome measure; the Forgotten Joint Score at 12 months postrandomisation. Allocation concealment will be achieved using computer-based randomisation performed on the day of surgery and methods for blinding will include sham incisions for marker clusters and blinded operation notes. The primary analysis will adhere to the intention-to-treat principle. Results will be reported in line with the Consolidated Standards of Reporting Trials statement. A parallel study will collect data on the learning effects associated with robotic-arm systems. ETHICS AND DISSEMINATION: The trial has been approved by an ethics committee for patient participation (East Midlands-Nottingham 2 Research Ethics Committee, 29 July 2020. NRES number: 20/EM/0159). All results from the study will be disseminated using peer-reviewed publications, presentations at international conferences, lay summaries and social media as appropriate. TRIAL REGISTRATION NUMBER: ISRCTN27624068.

Camouflage uncovered: what should happen next?

Recent publications have drawn attention to the fact that some brands of joint replacement may contain variants which perform significantly worse (or better) than their 'siblings'. As a result, the National Joint Registry has performed much more detailed analysis on the larger families of knee arthroplasties in order to identify exactly where these differences may be present and may hitherto have remained hidden. The analysis of the Nexgen knee arthroplasty brand identified that some posterior-stabilized combinations have particularly high revision rates for aseptic loosening of the tibia, and consequently a medical device recall has been issued for the Nexgen 'option' tibial component which was implicated. More elaborate signal detection is required in order to identify such variation in results in a routine fashion if patients are to be protected from such variation in outcomes between closely related implant types.

Metal-on-metal total hip arthroplasty: does increasing modularity affect clinical outcome?

BACKGROUND: Modularity of metal-on-metal (MoM) implants has come under scrutiny due to concerns regarding additional sources of metal debris. This study is a retrieval analysis of implants from the same manufacturer with the same MoM bearing surface. The difference between the implants was presence or absence of modular junctions. METHODS: This is a retrospective study of 31 retrieved implants from 31 patients who received a Conserve Wright Medical MoM hip prosthesis. The 31 implants consisted of 16 resurfacings and 15 implants with modular junctions; 4 conventional THAs and 11 modular-neck THAs. RESULTS: 43% of pre-revision MRI scans performed on resurfacing implants and 91% performed on the modular implants illustrated evidence of an adverse local tissue reaction. There was no difference in pre-revision blood metal ion levels or bearing surface wear between the resurfacings and modular implants. The neck-head tapers of the modular group showed low levels of material loss. However, the neck-stem tapers showed increased severity of corrosion and material loss. CONCLUSIONS: The modular implants had an increased incidence of adverse local tissue reaction. This could be related to the presence of modular junctions, particular the neck-stem junction which showed increased susceptibly to corrosion.

Adventitial cystic disease of the common femoral vein: an unusual cause of lower extremity swelling and review of the literature.

We report the case of a 61-year-old man who had presented with acute unilateral limb swelling. Computed tomography venography and duplex ultrasound demonstrated compression of the right common femoral vein by a common femoral vein adventitial cyst. Before intervention, the patient had developed an acute deep vein thrombosis of the right common femoral vein and great saphenous vein. Preoperative magnetic resonance imaging demonstrated concern for synovial connection. After 6 months of anticoagulation therapy, the patient underwent adventitial cyst excision with ligation of the hip joint articular connection. At 4 months postoperatively, the patient was symptom free without cyst recurrence. The findings from the present case support the synovial theory for adventitial cystic disease.

BNT162b2 vaccine uptake and effectiveness in UK healthcare workers - a single centre cohort study.

In this single centre cohort study we assessed BNT162B2 vaccine uptake and effectiveness among UK healthcare workers (HCWs) during a time of high community COVID-19 prevalence. Early uptake among HCWs was 62.3% (1409/2260), however there were significant differences in uptake between age groups, ethnic origins, and job roles. Uptake increased to 72.9% after a vaccine hesitancy working group implemented specific measures. In the 42 days after vaccination, 49 new cases of COVID-19 were identified, of which 7 (14.3%) occurred in HCWs who were beyond 10 days of vaccination. Kaplan-Meier curves for partially vaccinated and unvaccinated groups were congruent until day 14 and continued to diverge up to 42 days. Cox regression analysis showed a 70.0% (95%CI 6.0-91.0; p=0.04) risk reduction for COVID-19 infection in partially vaccinated HCWs. Here we report early vaccination rates among HCWs are generally high although uptake is lower in certain groups. It is possible to improve vaccine uptake and efforts should focus on this, however, significant resource is required. The BNT162B2 vaccine is effective from 14 days post-vaccination in a frontline clinical setting and protection continues beyond 21 days post 1st dose without a 2nd dose, being given.

Reconstruction with a Custom made Prosthetic Wrist Arthrodesis after Bone Tumor Resections of the Distal Radius. Single Centre Experience.

Objective The present study aimed at analyzing the clinical, radiological and functional results of the reconstruction of the distal radius after tumor resection with a custom-made metal arthrodesis implant and compare them with other types of distal radius reconstruction, as presented in the literature. To our best knowledge, this is the first article describing this particular type of implant and patient functionality. Methods Functional outcomes of reconstruction of the distal radius were assessed in a series of 4 patients. Three of the patients having had resection of giant cell tumors (GCTs), one patient having had resection of osteosarcoma. Results There were no major implant-related complications like infection, nonunion or loosening. Two patients had to undergo further surgery for protruding metalwork. Overall function was good according to the Musculoskeletal Tumor Society MSTS and Disabilities of the Arm, Shoulder, and Hand (DASH) scores. Conclusion The present study shows that custom-made metal arthrodesis implant benefits from the fact that it can be used as a salvage option when other treatments have failed, or it can be used as a primary option in cases in which there is limited bone stock after distal radius tumor resection.

Reconstruction with a Custom made Prosthetic Wrist Arthrodesis after Bone Tumor Resections of the Distal Radius. Single Centre Experience / Reconstrução com implante metálico personalizado de artrodese após ressecções de tumor ósseo do rádio distal. Experiência em um único centro

Abstract Objective The present study aimed at analyzing the clinical, radiological and functional results of the reconstruction of the distal radius after tumor resection with a custom-made metal arthrodesis implant and compare them with other types of distal radius reconstruction, as presented in the literature. To our best knowledge, this is the first article describing this particular type of implant and patient functionality. Methods Functional outcomes of reconstruction of the distal radius were assessed in a series of 4 patients. Three of the patients having had resection of giant cell tumors (GCTs), one patient having had resection of osteosarcoma. Results There were no major implant-related complications like infection, nonunion or loosening. Two patients had to undergo further surgery for protruding metalwork. Overall function was good according to the Musculoskeletal Tumor Society MSTS and Disabilities of the Arm, Shoulder, and Hand (DASH) scores. Conclusion The present study shows that custom-made metal arthrodesis implant benefits from the fact that it can be used as a salvage option when other treatments have failed, or it can be used as a primary option in cases in which there is limited bone stock after distal radius tumor resection.

Resumo Objetivo O presente estudo teve como objetivo analisar os resultados clínicos, radiológicos e funcionais da reconstrução do rádio distal após a ressecção do tumor com implante metálico personalizado de artrodese e compará-los com outros tipos de reconstrução do rádio distal, conforme apresentado na literatura. Pelo que conhecemos, este é o primeiro artigo descrevendo esse tipo particular de implante e funcionalidade no paciente. Métodos Os desfechos funcionais de reconstrução do rádio distal foram avaliados em uma série de 4 pacientes. Três dos pacientes tiveram ressecção de tumores de células gigantes (TCGs), sendo um paciente com ressecção de osteossarcoma. Resultados Não houve complicações relacionadas ao implante, como infecção, não sindicalidade ou afrouxamento. Dois pacientes tiveram que passar por uma nova cirurgia para a protusão da prótese metálica. A função geral foi boa de acordo com as pontuações da Musculoskeletal Tumor Society (MSTS) e Disabilities of the Arm, Shoulder, and Hand (DASH). Conclusão O estudo mostra que o implante metálico personalizado de artrodese se beneficia do fato de que pode ser usado como opção de salvamento quando outros tratamentos falharam, ou pode ser usado como opção primária nos casos em que há estoque ósseo limitado após a ressecção do tumor do rádio distal.

Preoperative sonographic ulnar nerve mapping in the postoperative elbow.

OBJECTIVE: To describe the technique of sonographic ulnar nerve mapping in the postoperative elbow for surgical planning. MATERIALS AND METHODS: A retrospective review of a surgical databank identified 24 patients, all aged 18 years and older with a history of orthopedic elbow surgery, who were referred for preoperative sonographic mapping of the ulnar nerve prior to subsequent surgery. All cases were reviewed for patient demographics, clinical presentation, prior surgical interventions, and ultrasound technique. Charts were reviewed for intraoperative and postoperative outcomes, including nerve injury. RESULTS: The cohort included 12 males and 12 females with a mean age of 51 years (range 22-68 years) and a mean BMI of 29 (range 20-48). Preoperative sonographic ulnar nerve mapping occurred following various elbow surgeries including ulnar nerve transposition to assess nerve location prior to subsequent elbow surgery. Of the 24 patients with preoperative sonographic ulnar nerve mapping, subsequent surgery was performed arthroscopically in 14 and open in 10 cases. In 11 of the 24 cases, there was specific mention of a modified approach to joint access which was guided by the ulnar nerve map. There were no perioperative ulnar nerve-related complications, such as nerve transection. CONCLUSION: Preoperative mapping can facilitate planning of surgical access and ulnar nerve dissection. Sonographic mapping of the ulnar nerve reduces the potential uncertainty of nerve palpation in a complex postoperative elbow following ulnar nerve transposition. This technique may mitigate the risk of ulnar nerve injury.

Managing NON-DIAGNOSTIC biopsies in musculoskeletal tumours in a specialist centre: Deciding on the algorithm.

INTRODUCTION: Core needle biopsy is an effective method of obtaining tissue diagnosis. However, a diagnostic dilemma arises when lesional tissue is non-diagnostic which obviates considering radiological guided re-biopsy (RB) or an open surgical biopsy but the question raised is which serves as a better diagnostic tool. PATIENT AND METHODS: We retrospectively reviewed data from a prospectively collected database of 4516 core needle biopsies performed in our specialist musculoskeletal tumour centre over a 6-year period. Our aim was to evaluate the management of non-diagnostic biopsies (NDB) and establish a safe and accurate diagnostic strategy in the presence of a NDB. RESULTS: Two hundred fifteen (4.8%) NDB cases with complete follow-up were identified. Of these 157 (73%) were treated definitively on the basis of imaging and 58 (27%) had a RB, 48 (83%) of which led to a positive histological diagnosis. The remaining 10 were again non-diagnostic giving a total of 167 patients being treated definitively without a tissue diagnosis. The sensitivity and specificity for multidisciplinary team (MDT) assessment as a diagnostic tool was 0.75 and 0.88 respectively while that for RB was 0.91 and 0.9. CONCLUSION: Re-biopsy after first non-diagnostic core needle biopsy offers high sensitivity and specificity, especially in the presence of malignancy. In the absence of tissue diagnosis, however, MDT assessment is also highly accurate and a safe strategy in managing this complex group of patients. LEVEL OF EVIDENCE: Diagnostic Level III.

Does modularity of metal-on-metal hip implants increase cobalt: chromium ratio?

BACKGROUND: Blood metal ion levels are used in the surveillance of metal-on-metal (MoM) hip implants. Modular implants contain an extra source of metal debris that may affect the ratio of metal ions in the blood. METHODS: This was a retrospective study of 503 patients with hip replacements made by a single manufacturer (Smith & Nephew, Warwick, UK) with the same bearing surface. There were 54 total hip arthroplasties, 35 Birmingham Mid-Head Resections and 414 hip resurfacings. Whole blood metal ion levels and their ratios were analysed to investigate the effect of a modular junction. RESULTS: The cobalt:chromium ratios were greater in the total hip arthroplasty group (mean 2.3:1) when compared to the resurfacings group (mean 1.3:1, p = <0.05) and Birmingham Mid-Head Resection group (mean 1.1:1, p = 0.11). CONCLUSIONS: This study demonstrated a trend for a higher cobalt:chromium ratio in patients with MoM total hip replacement that may be due to metal debris from the modular stem-head junction. Further work is required to correlate clinical data with retrieval analysis to confirm the effect of taper material loss on the cobalt:chromium ratio.

Impact of comorbidities on the safety and effectiveness of hip and knee arthroplasty surgery.

AIMS: Access to joint replacement is being restricted for patients with comorbidities in a number of high-income countries. However, there is little evidence on the impact of comorbidities on outcomes. The purpose of this study was to determine the safety and effectiveness of hip and knee arthroplasty in patients with and without comorbidities. METHODS: In total, 312,079 hip arthroplasty and 328,753 knee arthroplasty patients were included. A total of 11 common comorbidities were identified in administrative hospital records. Safety risks were measured by assessing length of hospital stay (LOS) and 30-day emergency readmissions and mortality. Effectiveness outcomes were changes in Oxford Hip or Knee Scores (OHS/OKS) (scale from 0 (worst) to 48 (best)) and in health-related quality of life (EQ-5D) (scale from 0 (death) to 1 (full health)) from immediately before, to six months after, surgery. Regression analysis was used to estimate adjusted mean differences (LOS, change in OHS/OKS/EQ-5D) and risk differences (readmissions and mortality). RESULTS: Patients with comorbidities had a longer LOS and higher readmission and mortality rates than patients without. In hip arthroplasty patients with heart disease, for example, LOS was 1.20 days (95% confidence interval (CI) 1.15 to 1.25) longer and readmission rate was 1.52% (95% CI 1.34% to 1.71%) and mortality 0.19% (95% CI 0.15% to 0.23%) higher. Similar patterns were observed for knee arthroplasty patients. Patients without comorbidities reported large improvements in function (mean improvement OHS 21.3 (SD 9.91) and OKS 15.9 (SD 10.0)). Patients with comorbidities reported only slightly smaller improvements. In patients with heart disease, mean improvement in OHS was 0.39 (95% CI 0.27 to 0.51) and in OKS 0.56 (95% CI 0.45 to 0.67) less than in patients without comorbidities. There were no significant differences in EQ-5D improvement. CONCLUSION: Comorbidities were associated with small increases in adverse safety risks but they have little impact on pain or function in patients undergoing hip or knee arthroplasty. These results do not support restricting access to hip and knee arthroplasty for patients with common comorbidities. Cite this article: Bone Joint J 2021;103-B(1):56-64.

Non-invasive massive growing prostheses reduce infection in paediatric cancer patients.

PURPOSE: In this study, we asked the question of whether non-invasive (NI) extendible bone tumour implants are as reliable and reduce infection when compared with patients who received a minimally invasive (MI) extendible implant. METHODS: Forty-two NI extendible bone tumour implants were investigated at a mean follow-up of 22 months (range, 1-87 months) and 63 MI implants at a mean follow-up of 49 months (range, 1-156 months). RESULTS: Kaplan-Meier analysis showed that the probability of MI implant survival was 58.8% compared with 78.6% in NI patients. No significant difference between these two patient groups was found. Infection was the main reason for failure in the MI implant group where nine (35%) implants were revised. However, only one (11%) NI implant was revised for infection ( p = 0.042). None of the NI implants failed due to aseptic loosening; however, six (23%) MI implants were revised for aseptic loosening of the intramedullary stem. Four (15%) of the failed MI implants were revised due to full extension and five (56%) of failed NI implants were replaced as the implant had been fully extended where the patient still required growth. CONCLUSION: Where possible, an NI massive prosthesis should be used in this patient group. Our results suggest that MI prostheses should be infrequently used due to the high incidence of infection. Lengthening of NI prostheses is painless, can be carried out in the clinic and is more cost-effective. However, further work is required to increase the amount of growth potential available in these implants.

Retrieval Findings of Recalled Dual-Taper Hips.

BACKGROUND: The recent high-profile recalls of several dual-taper hip designs pose questions regarding why those designs perform poorly. We aimed to characterize taper damage in 1 recalled design to understand failure mechanisms to inform surgeons on which patients should be considered at risk of revision and when to revise. METHODS: High-precision measurement equipment was used to characterize the metal loss from the neck-stem interface of 116 retrieved Rejuvenate femoral stems (Stryker Howmedica Osteonics) revised because of an adverse reaction to metal debris. Head-neck taper surfaces were also investigated, and clinical and laboratory data were examined. RESULTS: The neck-stem junction of each implant was moderately to severely corroded and showed a characteristic wear pattern on both male and female taper surfaces. The severity of taper damage was positively correlated with time to revision (coefficient, 0.040 [95% confidence interval (CI), 0.028 to 0.051]; p < 0.0001) and with serum cobalt concentration (coefficient, 0.02 [95% CI, 0.01 to 0.02]; p < 0.0001) and serum chromium concentration (coefficient, 0.04 [95% CI, 0.009 to 0.070]; p = 0.0142). CONCLUSIONS: A forensic examination of the retrieved components that failed secondary to an adverse reaction to metal debris showed, in all cases, visible corrosion. Of the implant and patient factors investigated, we did not identify any predictors of corrosion. The severity of damage was found to increase with time; cobalt was significantly elevated over chromium. CLINICAL RELEVANCE: Surgeons should scrupulously follow and consider revision for patients with this implant design to avoid extensive tissue excision. Blood metal ion tests may aid in identifying the mechanisms of taper corrosion.

Factors associated with proximal femur fracture determined in a large cadaveric cohort.

Many researchers have used cadaveric fracture tests to determine the relationship between proximal femur (hip) fracture strength and a multitude of possible explanatory variables, typically considered one or two at a time. These variables include subject-specific proximal femur variables such as femoral neck areal bone mineral density (aBMD), sex, age, and geometry, as well as physiological hip fracture event variables such as fall speed and angle of impact. However, to our knowledge, no study has included all of these variables simultaneously in the same experimental dataset. To address this gap, the present study simultaneously included all of these subject-specific and fracture event variables in multivariate models to understand their contributions to femoral strength and fracture type. The primary aim of this study was to determine not only whether each of these variables contributed to the prediction of femoral strength, but also to determine the relative importance of each variable in strength prediction. A secondary aim was to similarly characterize the importance of these variables for the prediction of fracture type. To accomplish these aims, we characterized 197 proximal femurs (covering a wide range of subject-specific variables) with DXA and CT scans, and then tested the femurs to fracture in a sideways fall on the hip configuration. Each femur was tested using one of three fall speed conditions and one of four angles of impact (bone orientations). During each test, we acquired measurements of relevant force and displacement data. We then reduced the test data to determine femoral strength, and we used post-fracture CT scans to classify the fracture type (e.g., trochanteric, cervical). Using these results, the explanatory variables were analyzed with mixed statistical models to explain variations in hip fracture strength and fracture type, respectively. Five explanatory variables were statistically significant in explaining the variability in femoral strength: aBMD, sex, age, fall speed, and neck-shaft angle (P ≤ 0.0135). These five variables, including significant interactions, explained 80% of the variability in hip fracture strength. Additionally, when only aBMD, sex, and age (P < 0.0001) were considered in the model, again including significant interactions, these three variables alone explained 79% of the variability in hip fracture strength. So while fall speed (P = 0.0135) and neck-shaft angle (P = 0.0041) were statistically significant, the inclusion of these variables did not appreciably improve the prediction of hip fracture strength compared to the model that considered only aBMD, sex and age. For the variables we included in this study, in the ranges we considered, our findings indicate that the clinically-available information of patient age, sex and aBMD are sufficient for femoral strength assessment. These findings also suggest that there is little value in the extra effort required to characterize the effect of femoral geometry on strength, or to account for the probabilistic nature of fall-related factors such as fall speed and angle of impact. For fracture type, the only explanatory variable found to be significant was aBMD (P ≤ 0.0099). We found that the odds of having intertrochanteric fractures increased by 47% when aBMD decreased by one standard deviation (0.2 g/cm2).