Hip abductor muscle activity in persons with a hip prosthesis while carrying loads in one hand.

Abstract

Carrying loads in one hand may result in the hip abductor (HA) muscles needing to generate large forces. For a person with a prosthetic hip, these forces may contribute to loosening of the implant. In this study, surface electromyography (EMG) was used to estimate the relative demands placed on the HA muscles as persons with a prosthetic hip carried loads in one hand. Twenty-five active subjects (9 female, 16 male) with a prosthetic hip participated. Subjects were aged 40 to 86 years (mean = 63.7, SD = 10.7). Surface EMG data from the HA muscles (primarily the gluteus medius) were analyzed during mid-stance as subjects carried loads weighing 5%, 10%, and 15% of their body weight. Loads were carried in the hand opposite the side of the prosthetic hip (contralaterally held loads) or in the hand on the same side as the prosthetic hip (ipsilaterally held loads). Results showed that the contralaterally held loads produced greater HA muscle EMG activity levels than no-load walking. The ipsilaterally held loads produced lower HA muscle EMG activity levels than no-load walking. These EMG data, in addition to calculations using a simple biomechanical model, suggest that persons should use caution or avoid carrying loads in the hand on the side contralateral to their prosthetic hip.