EARLY POSTOPERATIVE PERIPROSTHETIC FEMUR FRACTURE IN THE PRESENCE OF A NON-CEMENTED TAPERED WEDGE FEMORAL STEM

Abstract

Non-cemented tapered wedge femoral stems have gained popularity given their excellent long-term clinical success rates. However, there is sparse literature reporting the incidence of early postoperative periprosthetic femur fractures in patients with this stem design. The aim of this study is to report this incidence and to identify factors which may increase the risk of such fractures.

The charts of all patients who were implanted with a single design of a tapered wedge femoral stem at a single institution were retrospectively reviewed to identify any early periprosthetic femur fractures, defined as occurring within the first year of surgery. Demographic, operative, and radiographic details were analyzed for potential risk factors that may predispose to periprosthetic fractures, and compared to a cohort of patients with the same implant that was matched for age, sex, and pre-operative diagnosis and did not have a periprosthetic fracture.

Six fractures were identified in 2220 stems implanted over a five year period, for an incidence of 0.3%. The average time to fracture was nine weeks post-operatively. Five fractures were Vancouver Type B2, and the other was Vancouver Type A. Three stems were radiographically undersized, and two failed to achieve a proximal wedge fit because of distal fixation. When compared to the matched cohort, there was no statistical significance with regard to body-mass index, morphological cortical index, or canal-bone ratio. However the fracture cohort did have a statistically lower canal-calcar ratio (p < 0.05) and statistically higher canal-flare index (p < 0.05).

Early postoperative periprosthetic femur fracture around a tapered wedge stem is a rare but potentially devastating complication. Risk factors which may predispose to fracture are a proximal-distal mismatch in femoral geometry and an undersized implant.