Aims: Periprosthetic fractures (PPFs) around the knee are challenging injuries. This study aims to describe the characteristics of knee PPFs and the impact of patient demographics, fracture types, and management modalities on in-hospital mortality.Methods: Using a multicentre study design, independent of registry data, we included adult patients sustaining a PPF around a knee arthroplasty between 1 January 2010 and 31 December 2019. Univariate, then multivariable, logistic regression analyses were performed to study the impact of patient, fracture, and treatment on mortality.Results: Out of a total of 1,667 patients in the PPF study database, 420 patients were included. The in-hospital mortality rate was 6.4%. Multivariable analyses suggested that American Society of Anesthesiologists (ASA) grade, history of peripheral vascular disease (PVD), history of rheumatic disease, fracture around a loose implant, and cerebrovascular accident (CVA) during hospital stay were each independently associated with mortality. Each point increase in ASA grade independently correlated with a four-fold greater mortality risk (odds ratio (OR) 4.1 (95% confidence interval (CI) 1.19 to 14.06); p = 0.026). Patients with PVD have a nine-fold increase in mortality risk (OR 9.1 (95% CI 1.25 to 66.47); p = 0.030) and patients with rheumatic disease have a 6.8-fold increase in mortality risk (OR 6.8 (95% CI 1.32 to 34.68); p = 0.022). Patients with a fracture around a loose implant (Unified Classification System (UCS) B2) have a 20-fold increase in mortality, compared to UCS A1 (OR 20.9 (95% CI 1.61 to 271.38); p = 0.020). Mode of management was not a significant predictor of mortality. Patients managed with revision arthroplasty had a significantly longer length of stay (median 16 days; p = 0.029) and higher rates of return to theatre, compared to patients treated nonoperatively or with fixation.Conclusion: The mortality rate in PPFs around the knee is similar to that for native distal femur and neck of femur fragility fractures. Patients with certain modifiable risk factors should be optimized. A national PPF database and standardized management guidelines are currently required to understand these complex injuries and to improve patient outcomes.Cite this article: Bone Joint J 2024;106-B(2):158–165.

Introduction: The incidence of femoral periprosthetic fractures (PPFs) in the UK is on the rise. This rising incidence presents a clinical and an economic burden on the national health care services. There is also uncertainty about the most effective treatment modality for femoral PPFs, as well as a lack of evidence for a standardized management approach. We aimed to identify the true incidence and any variation in the management of femoral PPFs nationally. Methods and analysis: This multicentre national collaborative study has been designed by a trainee led research network in collaboration with a well-established university research organization. Data will be collected from participating centres over a period of 10 years (2010–2019). All adults presenting with a femoral PPF will be identified, and the mode of treatment for each fracture subtype will be recorded. Other measures will evaluate patient and treatment variables, objective and subjective outcome measures. Univariate and multivariate regression analyses will be used, as well as the coefficient of determination (R) in an attempt to measure the degree to which the models could explain the variation in management. Ethics and dissemination: This multicentre national project was approved by the local clinical governance department at each participating hospital site. The results of this study will be submitted to international peer reviewed journals and appropriate national and international conferences.