RANGE OF MOTION AFTER TOTAL HIP RESURFACING AND TOTAL HIP ARTHROPLASTY: A SINGLE-BLIND RANDOMISED CLINICAL STUDY

Abstract

The purpose of this study was to compare the post operative ROM of patients randomised between SRA and 28mm THA.

Restoration of normal ROM has been proposed as an advantage of hip resurfacing (SRA) over THA and is due to the use of larger diameter femoral heads. However, the head-neck diameter ratio, which is an important factor governing ROM, would in theory allow more ROM with THA (28mm head/14mm neck = ratio 2:1) versus SRA (approximate ratio 1.3–2.0:1).

Patients were randomised between SRA and THA. Osseous landmarks were identified with a marker pen. Both ASIS served as the reference line for the pelvis position. Digital photographs of hip motion were taken and a blinded rater (with respect to the side and type of surgery) performed range of motion testing on the operated and normal side. Pre-study validation of ROM measurement method with a software program revealed high intra and inter observer reliability.

Sixty SRA and sixty-two THA were evaluated at minimum follow-up of twelve months. Preoperative ROM and demographic data were similar for both groups. No significant differences (p> 0.05) were found in the total arc of motion (SRA=204.2°, THA=196.5°), arc of rotation (SRA=47.7°, THA=44.3°), flexion-extension arc (SRA=118.1, THA=120.1), abduction-adduction arc (SRA=43.1°, THA=42.9°).

In theory, ROM should have been greater in THA. Fear of instability may have limited ROM recovery potential in THA. Since pre operative soft tissue contracture is an important factor influencing post operative ROM, the complete capsular release performed during SRA may have been an advantage of this technique.