Session V - Pelvis
Fri., 10/8/04 Spine & Pelvis, Paper #28, 4:48 pm
Muscle Strength Recovery and Functional Outcome after Acetabular Fracture
Purpose: Operative management of displaced acetabular fractures involves disruption of the large muscles about the hip, which are important for posture, function, and ambulation. Recovery of muscle strength after surgery is thought to be important for a desirable functional outcome. However, each of the factors that influence muscle-strength recovery has not been fully delineated. The purpose of this investigation was to assess muscle-strength recovery after operative treatment of an acetabular fracture and to relate muscle strength to functional recovery. Secondarily, we sought to further delineate the factors such as surgical approach, fracture type, length of follow-up, sex, and age that may affect muscle-strength recovery and outcome.
Methods: Between August 1996 and June 2002, 260 patients were treated for a displaced acetabular fracture at our institution. For inclusion, the patients had to have a displaced acetabular fracture as an isolated lower-extremity injury, absence of neurologic injury, and to have been treated with either a Kocher-Langenbeck or ilioinguinal approach. Forty-four patients met the inclusion criteria and 31 were willing to participate. Twenty-one of the patients were male, 10 were female, and the average age was 42 years (range, 18 to 68). Seventeen patients had an elementarytype fracture, and 14 had an associated-type fracture. Fifteen of the fractures were approached through an ilioinguinal approach and 16 through a Kocher-Langenbeck approach. At the time of the most recent follow-up, each patient completed a Musculoskeletal Function Assessment questionnaire (MFA), underwent a physical examination, radiographic assessment, and muscle strength determination with a KinCom dynamometer.
Results: The average time to follow-up was 33 months (range, 12 to 48). The average MFA score for the group was 21 (range, 0 to 57), including 14 patients who scored 12 or less. Patients had the worst scores in the "mobility" and "coping" categories and reported fewest problems with the "hand and fine-motor" and "thinking" categories. The average MFA score for those patients treated via a Kocher-Langenbeck approach was 24 (range, 0 to 57), whereas those patients treated via an ilioinguinal approach had an average MFA score of 17 (range, 0 to 47) (>0.05).
Work (J/Kg) and maximum strength (Nm/Kg) were measured for hip extension, flexion, adduction, and abduction at two different rates, including 30°/s and 10°/s. Strength values for the affected side were compared with the unaffected side by use of a paired t-test (SAS Institute, Cary, North Carolina). Statistically significant differences in muscle strength were only found between the affected and unaffected side with regard to hip abduction work (30°/s and 10°/s) and hip abductor max (30°/s; P <0.05). Statistical analysis was performed to determine how muscle strength recovery may be related to functional outcome. When the whole group was assessed, statistically significant correlations were found between hip extension, flexion and adduction strength, and MFA scores. In these patients, residual affected-side weakness correlated with worsening MFA scores (all P values <0.05). A stepwise linear regression analysis was performed to explore the possibility that this association was influenced by other factors. Each regression model contained MFA score as the dependent variable, and the independent variables were surgical approach, fracture type, length of follow-up, sex and age, and the strength measure. For all models, none of these variables, including approach and fracture type, were selected for inclusion in the model, meaning that these variables did not assist in the prediction of MFA score.
Conclusions/Significance: Long-term alterations in function and comfort are the likely outcome for those who have sustained a displaced acetabular fracture. These alterations have obvious consequences causing patients to change jobs and alter their leisure activities. Therefore, identifying and treating the factors that have a negative impact on recovery could ultimately improve functional outcome. In this study, we objectively evaluated the recovery of muscle strength after acetabular fracture surgery and correlated it with function. Although complete muscle-strength recovery was possible after acetabular fracture surgery, residual muscle weakness was found to correlate with poorer functional recovery. A similar relationship was not found between the surgical approach and the fracture-type pattern. On the basis of these data, increased functional recovery after open reduction internal fixation of a displaced acetabular fracture may be possible if residual muscle weaknesses are addressed with muscle-specific rehabilitation.