[Objective measures of gait following revision hip arthroplasty. First medium-term results 2.6 years after surgery]

The purpose of the study was to identify the functional impairments after revision arthroplasty by gait analysis.

This retrospective study compared 33 patients (mean age 58.5 years) who have undergone revision of an acetabular component (mean follow-up 2.6 years) with a group of normal control subjects. Gait analysis including recording of the three dimensional kinetics and kinematics was performed in all patients. Surface electromyography of seven leg and trunk muscles were registered bilaterally. The vertical ground reaction forces were determined by two force plates. These data were correlated with the Harris Hip Score, the d'Aubigné Score and the radiographic analysis (centre of rotation).

The analysis revealed a decreased hip range of motion during gait (p < 0.0001). In the sagittal plane there was a significant decrease in the hip extension at the end of the stance phase (p < 0.0001). The control group reached a mean extension of - 7.6 degrees, the operated patients were limited by the extension deficit (+ 9.1) in step length (p < 0.0016) and velocity (p < 0.0001). Kinetic parameters indicated a reduced hip abductor moment (p < 0.0001). Compensation of gait instability was observed in an extended stance phase (p = 0.0389). The hip muscle activity was increased to stabilize the impaired hip. The changed kinematic parameters are observed with secondary impairments in knee extension and reduced dorsiflexion in ankle motion (p < 0.0001). Neither the Harris Hip score (77.8 points) nor the d'Aubigné score (14.9 points) were associated with the motion analysis (p > 0.05). Deterioration in kinematics are indicated by cranialisation of the centre of rotation (p = 0.18). However, medial movement of the centre of rotation does not influence the kinematic data (p > 0.05).

Despite sufficient satisfactory clinical data the gait analysis confirmed objective impairments of the operated hip and neighboring joints. Gait instability is revealed in a decreased hip extension and deficient hip abduction.