The Influence of Global Femoral-offset Changes After Total Hip Arthroplasty on Function, Quality of Life and Abductor Muscle Strength: a Prospective Cohort Study

The results of total hip arthroplasty (THA) have shown great improvement during the last decades in terms of function, quality of life and prosthetic survival. Beside pain relief, surgeons aim to position the stem and cup in a correct manner to restore the biomechanical forces and range of motion of the operated hip. The femoral-offset (FO) is one of the important perioperative parameters in THA. A prospective cohort study was conducted between September 2010 and December 2013. All patients with unilateral primary osteoarthritis (OA) treated with THA were considered for inclusion. Patients with secondary OA, previous spinal, pelvic, or lower limb injuries or fractures were excluded. Global FO was measured in each patient within 3 months before the THA and at the second postoperative day using a standardized protocol. According to the postoperative measurement, patients were divided into three groups: 1) the decreased FO group, where the FO of operated side was reduced more than 5mm compared with the contralateral side, 2) the restored FO group, where the FO of operated side was within 5mm restored compared with the contralateral side, and 3) the increased FO group, where the FO of operated side was increased more than 5mm compared with the contralateral side.

Patients were followed-up at 12 - 15 months postoperatively with self-administered WOMAC and EQ-5D questionnaires in addition to a clinical assessment. Patients completed an additional questionnaire enquiring about any residual problems with the use of walking aid and residual pain around the operated hip. During the clinical assessment, palpation of the operated hip and measurement of the abductor muscle strength were undertaken.