Computerized virtual surgery demonstrates where acetabular rim osteophytes most reduce range of motion following total hip arthroplasty.

Abstract

Acetabular osteophytes are common findings during total hip arthroplasty (THA). This study was designed to determine the extent to which osteophytes may limit range of motion (ROM) and in which locations impingement is likely to occur if osteophytes are not removed during surgery. Computer-aided design was used to compare ROM of a modern hip implant in four cadaver models with and without 10-mm acetabular rim osteophytes added. A clock face, with 12 o'clock at the superior pole of the right acetabulum, was used to map impingement. The osteophyte model limited ROM in flexion (101° v. 113°, p = 0.03), 90° of flexion with internal rotation (16.7° v. 31.6°, p = 0.01), and external rotation (30.4° v. 49.5°, p = 0.01). Impingement occurred between 7 and 8 o'clock in external rotation and 1 and 2 o'clock in the other two motions. Osteophytes in these positions have the greatest impact on ROM and should be removed during THA.