Femoral neck shortening in adult patients under the age of 55 years is associated with worse functional outcomes: Analysis of the prospective multi-center study of hip fracture outcomes in China (SHOC).

INTRODUCTION: Young femoral neck fracture patients require surgical fixation to preserve the native hip joint and accommodate increased functional demands. Recent reports have identified a high incidence of fracture shortening and this may have negative functional consequences. We sought to determine if fracture shortening is associated with poor functional outcome in young femoral neck fracture patients.

PATIENTS AND METHODS: One hundred and forty-two patients with femoral neck fractures age 18-55 were recruited in this prospective cohort study across three Level 1 trauma hospitals in Mainland China. Patient-reported and objective functional outcomes were measured with the Harris Hip Score (HHS), Timed Up and Go (TUG), and SF-36 Physical Component Summary (SF-36 PCS) at 12 months. Radiographic fracture shortening was measured along the long axis of the femoral neck and corrected for magnification. Severe shortening was defined as ≥10mm. The primary analysis measured associations between severe radiographic shortening and HHS at one-year post-fixation.

RESULTS: One hundred and two patients had complete radiographic and functional outcomes available for analysis at one year. The mean age of participants was 43.7±10.8years and 53% were male. Fifty-five percent of fractures were displaced and 37% were vertically orientated (Pauwels Type 3). The mean functional outcome scores were: HHS 90.0±10.8, TUG 12.0±5.1s, and PCS 48.5±8.6. Severe shortening occurred in 13% of patients and was associated with worse functional outcome scores: HHS mean difference 9.9 (p=0.025), TUG mean difference 3.2s (p=0.082), and PCS mean difference 5.4 (p=0.055).

CONCLUSIONS: Severe shortening is associated with clinically important decreases in functional outcome as measured by HHS following fixation of young femoral neck fractures, occurring in 13% of patients in this population. The principle of fracture site compression utilized by modern constructs may promote healing; however, excessive shortening is associated with worse patient-reported outcomes and objective functional measures.