A prospective functional outcome and motion analysis evaluation of the hip abductors after femur fracture and antegrade nailing

OBJECTIVE: To determine if dynamic hip abductor weakness during gait, evaluated through component measures of hip kinematics and hip kinetics, demonstrate longitudinal improvement after antegrade intramedullary nailing of femoral shaft fractures and if these improvements correlate with patient reported functional outcomes. DESIGN: Prospective patient protocol. SETTING: University-based, level I trauma center. PATIENTS: Eight nonconsecutive, isolated femur fracture patients. INTERVENTION: Antegrade intramedullary nailing of isolated femoral shaft fractures. MAIN OUTCOME MEASURE: Hip kinematics (hip abduction angle and ipsilateral lateral trunk lean), hip kinetics (hip abductor moment), and patient-reported functional outcome measures (Short Form - Musculoskeletal Function Assessment Survey) were assessed at 2 time points [Time1 = independent ambulation without ambulatory aide, 2.0 (±0.6) months; Time2 = approximately 6 months after injury with clinical and radiographic fracture healing, 7.2 (±1.5) months]. RESULTS: After surgical fixation of a femoral shaft fracture, subjects demonstrated significant time-dependent, negative effects on gait secondary to dynamic hip abductor weakness measured in terms of hip kinematics [hip abduction angle (P = 0.012) and lateral trunk lean (P = 0.046)] and hip kinetics [hip abductor moment (P = 0.029 at loading response; P = 0.022 at terminal stance)]. A significant improvement in the dysfunction index was found between the early and late assessments (21.3 ± 15.0, 6.5 ± 8.9, P = 0.008). At late assessment of functional outcome (22.5 ± 3.7 months), a significant correlation was observed between the dysfunction index and hip kinematics (ipsilateral trunk lean) at both Time1 (R = -0.811, P = 0.015) and Time2 (R = -0.713, P = 0.047). CONCLUSIONS: After isolated femur fracture, patients treated with antegrade intramedullary nailing demonstrated a significant negative effect on hip kinematics and kinetics, and this effect was time-dependent. Early postsurgical ipsilateral trunk lean correlated with long-term functional outcome scores; therefore, excessive frontal plane movement during gait in the early postoperative stages may be indicative of a poorer self-reported longer-term functional outcome.