THE EFFECT OF SURGICAL APPROACH IN NARROWING OF THE FEMORAL NECK IN UNCEMENTED HIP RESURFACING ARTHROPLASTY: GANZ VERSUS THE POSTERIOR APPROACH

Abstract

Narrowing of the femoral neck after resurfacing arthroplasty of the hip has been described previously in both cemented and uncemented hip resurfacing. Traditionally hip resurfacing has been performed via a posterior approach though other surgical approaches including the Ganz and the anterolateral approach have been well described. In addition it is known that the blood supply of the femoral neck arises largely from posterior structures and it has been postulated that neck narrowing is a consequence of poor post-operative femoral neck vascularity. Our null hypothesis in this study was that the choice of surgical approach does not influence postoperative femoral neck narrowing. We retrospectively measured the diameter of the femoral neck in a series of 135 consecutive patients who underwent uncemented cormet hip resurfacing, with follow up from one to 3 years. Our sample included 50 females and 85 men with an average age of 56.4 years (standard deviation of 9.47). Seventy six patients had a Ganz approach, 5 had an anterolateral approach and 55 had a posterior approach. There were no failures due to femoral neck fracture and no revisions to total hip arthroplasty. Eleven patients required subsequent surgery all of which were due to complications following trochanteric osteotomy. Seven patients needed removal of metalwork and 4 patients had non-union of their osteotomy requiring revision. At one year the posterior approach group had an average of 5.2% neck narrowing versus 2.7% neck narrowing in the Ganz approach group (p value 0.06). At three years the average neck narrowing amongst all patients was 6.8% (standard deviation 3.1%) but the number of patients who had had a Ganz approach was too small to meaningfully apply inference statistics. Our study shows early results which show a statistically significant reduction in the rate of femoral neck narrowing in patients who have had a Ganz approach as compared to a posterior approach for unce-mented hip resurfacing arthroplasty. It also shows a high rate of complications inherent with the Ganz approach which in our patient group are entirely related to the trochanteric osteotomy.