Vancouver B and C periprosthetic fractures around the cemented Exeter Stem: sex is associate with fracture pattern.

ABSTRACT

INTRODUCTION: The aim of this study was to identify factors associated with the level of periprosthetic fracture involving a cemented polished tapered stem Vancouver B or Vancouver C. METHODS: A retrospective cohort study of 181 unilateral periprosthetic fractures involving Exeter stems was assessed by three observers (mean age 78.5, range 39-103; mean BMI 27.1, 17-39; 97 (54%) male). Patient demographics, deprivation scores, BMI and time since primary prosthesis were recorded. Femoral diameter, femoral cortical thickness, Dorr classification and distal cement mantle length were measured from calibrated radiographs. Interobserver reliability was calculated using intraclass correlation coefficients (ICCs). Univariate and multivariate analysis was performed to identify associations with Vancouver B or C fractures. RESULTS: 160/181 (88%) Vancouver B and 21/181 (12%) Vancouver C-level fractures occurred at a mean of 5.9 ± 5.4 years (0.2-26.5) following primary surgery. Radiographic measurements demonstrated excellent agreement (ICC > 0.8, p < 0.001). Mortality was significantly higher following Vancouver C compared to B fractures 90 day 14/160 Vs 5/21 (p = 0.05); 1 year 29/160 Vs 8/21 (p = 0.03). Univariate analysis demonstrated that Vancouver C fractures were associated with female sex, bisphosphonate use, cortical bone thickness, and distal cement mantle length (p < 0.05). On multivariate analysis, only female sex was an independent predictor of Vancouver C-level fractures (R2 =0.354, p = 0.005). CONCLUSION: Most PFFs involving the Exeter stem design are Vancouver B-type fractures and appear to be independent of osteoporosis. In contrast, Vancouver C periprosthetic fractures display typical fragility fracture characteristics and are associated with female sex, thinner femoral cortices, longer distal cement mantles and high mortality.