RESURFACING ARTHROPLASTY VS STANDARD THR: COMPARISON OF POSTOPERATIVE FUNCTION

Abstract

Background: Resurfacing is becoming increasingly popular as an option for primary hip arthroplasty. However, there is minimal documentation of objective post-operative outcomes which support the perceived benefits of resurfacing over traditional stemmed THR. Most comparative studies have reported differences in X-ray findings, such as component alignment and femoral offset, which only allow speculation of their relative effects on patient function. Studies have also reported general clinical outcomes following resurfacing, and although resurfacing shows promising medium term results, these studies have been largely subjective and have lacked a direct same study comparison with standard THR.

Potential benefits of resurfacing include improved abductor muscle function, resulting from preservation of the femoral neck offset, and greater range of hip motion, resulting from the larger diameter bearings. Mont et al (2007) compared biomechanical outcomes during gait for individuals with unilateral resurfacing and standard arthroplasty and concluded that hip resurfacing yielded superior function, as defined by faster walking speeds. However, comprehensive data of 3-dimensional moments and hip kinematics was not presented and functional assessment was limited to gait analysis only.

Methods: Kinematic and kinetic outcomes were evaluated for 28 individuals (age 40–60) with unilateral resurfacing (Durom, Zimmer) or standard stemmed THR (ceramic-on-ceramic Trident, Stryker) at 3 and 12 months following surgery. Data was collected using an 8 camera Vicon 612 motion analysis system and two Kistler force plates while subjects completed level walking and stair ascent and descent activities using a 4-step stair case, instrumented with a force plate on the second step. A lower limb marker set was used with pointer trial calibration of anatomical landmarks. 3-dimensional hip moments, angles and temporospatial parameters were compared and preferred motion patterns analysed.

Results: Peak hip moments showed no statistically significant group difference during the ambulatory activities although slightly greater peak hip angles were achieved by those with standard THR. Stair negotiation highlighted greater differences in biomechanical outcomes between the groups than level gait analysis. Those with hip resurfacing exhibited less protective motion patterns and performed walking and stair negotiation at a faster pace.

Conclusions: The greater diameter bearings of the resurfacing prosthesis do not appear to yield a greater functional range of motion post-operatively. Preserving the femoral offset with a hip resurfacing does not appear to benefit abductor muscle function. Statistically, both arthroplasty types demonstrate equivalent functional outcomes.