Wedge effect following intramedullary hip screw fixation of intertrochanteric proximal femur fracture

The aim of the current study was to determine whether application of an intramedullary hip screw for definitive management of intertrochanteric fracture was associated with post-operative deformity. Specifically this study investigated whether nail insertion would cause a “wedge effect” of the intertrochanteric fracture manifesting as lateralization of the femoral shaft and varus malalignment.

The trauma database at the University of Pittsburgh Medical Center was investigated to identify all intertrochanteric fractures (AO/OTA 31A) over the past 3 years treated with an IMHS. Fractures eligible for inclusion were performed under the supervision of a fellowship trained orthopedic trauma surgeon. All fractures were reduced in optimal alignment using percutaneous or mini-open strategies during the reaming process and nail insertion. The entry portal was over-reamed by at least 1.5 mm. Cases selected for review of the “wedge effect” had optimal post-operative imaging allowing for assessment of discrepancy between the operative and normal hip.

Forty six patients with an average age of 77 years were included for study. Fifty percent were classified as unstable patterns. Shaft lateralization following IMHS fixation of the fractured hip was found to be an average of 7 mm greater than the contralateral intact hip (p < 0.001) (range 0–30 mm). The neck-shaft angle of the operative hips was 129° as compared to 133° on the intact side (p = 0.009). The stability of the fracture pattern was not predictive for post-operative lateralization of the femoral shaft or varus angulation (p > 0.05) (Table 2). There was no difference in post-operative deformity among techniques used for maintenance of reduction during reaming and nail insertion (p > 0.05). Despite deformity, all cases demonstrated radiographic radiographic fracture union.

Despite attention to detail, the application of an intramedullary hip screw for intertrochanteric fracture has the tendency to lateralize the shaft relative to the head/neck segment (The “wedge effect”).