An Assessment of Factors That Influence Outcome Following Fixation of Periprosthetic Distal Femur Fractures Associated with Total Knee Arthroplasty.

Background: Periprosthetic distal femur fractures following total knee arthroplasty (PDFFTKA) are increasingly common [1], mainly in elderly patients with significant co-morbidities [2]. Surgical management usually requires balancing prompt fixation for early mobilization with the need to consider the least physiologically demanding option [3].The aim of this study was to assess predictors of clinical and radiological outcome in patients with PDFFTKA treated with open reduction and internal fixation (ORIF).

Materials and methods: A retrospective cohort study of patients managed for PDFFTKA over the last 21 years in the Trauma & Orthopaedics Department of the Royal Shrewsbury Hospital (RSH) was carried out. Radiological images, pre- and post-operatively, were assessed for fracture related parameters. Last known functional status was evaluated using the most recent outpatient review letters. After assessment of normality of data, evaluation of predictors of clinical and radiological outcome was made using correlation analyses.

Results: There was no statistically significant correlation between age, primary TKA to fracture interval, and length of intact medial cortex vs clinical outcome for the parametric variables evaluated. For non-parametric variables assessed, there was a statistically significant correlation between clinical outcome and evidence of callus formation (Spearman rho value -0.476; p=0.022). In stratifying the patients with poor and good outcome, there was no difference noted in primary TKA to fracture interval, or length of intact medial cortex (mm) between both groups. In terms of the number of comminuted fragments and anterior flange to fracture distance (mm), there was also no difference noted between the poor and good functional groups.

Conclusions: 1. There was no observed correlation in pre-operative patient and fracture related variables with outcome in this population of patients with PDFFTKA. 2. Post-operative evidence of callus formation appears to be directly related to better clinical outcomes.