Is distal screw entry point associated with subtrochanteric fracture after intracapsular hip fracture fixation?

BACKGROUND: Subtrochanteric fracture is a recognized complication following cannulated screw fixation of intracapsular hip fracture. We investigated the incidence of subtrochanteric fracture in a consecutive series of 304 patients and its association with screw entry point in the lateral femoral cortex.

METHODS: A retrospective consecutive case series of patients treated with internal fixation for intracapsular hip fracture by our unit between January 2003 and January 2010 were included. Two authors reviewed radiographs independently to determine distal screw entry point in the lateral femoral cortex. Hickey zone 1 was an entry point above the level of the upper border of the lesser trochanter. Hickey zone 2 was defined as an entry point between the upper and lower borders of the lesser trochanter. Hickey zone 3 was an entry point below the lower border of the lesser trochanter. Clinical notes were reviewed for subsequent subtrochanteric fracture. Association between subtrochanteric fracture and distal screw entry point in the lateral femoral cortex in relation to the upper border of the lesser trochanter was determined.

RESULTS: Two hundred and fifty-six post-operative radiographs were available for analysis. Mean patient age was 73 years (30–98), 75% were women. There were 24 patients with screw entry point in Hickey zone 1, 225 in Hickey zone 2, and 7 in Hickey zone 3. Two patients sustained subtrochanteric fracture. No subtrochanteric fractures occurred in patients with Hickey zone two-screw entry.

CONCLUSION: Subtrochanteric fracture is rare following cannulated screw fixation of intracapsular neck of femur fracture (0.78%). In this retrospective consecutive case series, no subtrochanteric fractures occurred when the entry point of the lowest screw in the lateral femoral cortex is between the levels of the upper and lower borders of the lesser trochanter.