Abstract
Introduction:
Recent studies have concluded that gender influences hip morphology at the time of surgery as well as dysplastic development of the hip. This may lead to a particular choice of implant including stem design and/or neck modularity. In this study we hypothesized that not only gender but also morphotype and etiology (primary osteoarthritis versus aseptic osteonecrosis) may be a significant factor to predict the anatomy of the hip at the time of total hip arthroplasty (THA).
Methods:
We reviewed 690 patients undergoing THA for primary arthritis (OA) or avascular osteonecrosis (AVN) between April 2000 and June 2005 and stratified each into three groups based on their anatomic constitution: endomorph (EN), ectomorph (ECT), or mesomorph (ME) (determined by the ratio: pelvic width/total leg length measured on full-length X-rays). Two independent observers measured twice four parameters on preoperative CT scan: neck-shaft-angle angle (NSA), femoral offset value (FO), helitorsion (Ht) value and femoral neck anteversion (Av).
Results:
No significant difference were observed between men and women for the four parameters with respectively: NSA (129.29° ± 5.6 versus 129.3° ± 5.7), Av (20.3° ± 8.6 versus 20.27° ± 8.6), FO (19.7 mm ± 3.98 versus 19.74 mm ± 3.98) and Ht (19.97° ± 12.2 for men and 19.94° ± 12.3).
Significant difference were found for NSA: 130.1° ± 5.8 for ECT, 129.55° ± 6 for MES and 128.2° ± 5,1 for EN with p < 0.01. For Av, the values were: 18.9° ± 8.7 for ECT, 20.74° ± 8.1 for MES and 21.2° ± 8.95 for EN (p < 0.01). For FO the values were 19.1 mm ± 3.9 for ECT, 19.7 ± 4 for MES and and 20.44 mm ± 3.93 for EN (p < 0.01). No difference was found for Ht between the 3 groups.
A significant difference was found between patients suffering from OA and AVN: mean NSA was 130.36° ± 8.79 for OA patients versus 127.35° ± 8.38 for those who had an AVN (p < 0.01). A value was 17.06° ± 8.1 for OA and 23.7 ± 7.89 for AVN (p < 0.01). FO value was 18.72 mm ± 3.71 for OA versus 20.75 mm ± 4.15 for AVN (p <0.01). And Ht was 18.94° ± 9.64 for OA and 21.05° ± 14.5 for AVN patients (p < 0.01).
Discussion and conclusion:
Patients with short and wide morphotype (endomorph) had, irrespective of gender, lower values of NSA with greater anterversion and offset values, whereas patients with long and narrow morphotype (ectomorph) had higher values of NSA and smaller Av and FO (figure 1). In the same time patients suffering from AVN have lower NSA angle, lower Av, smaller FO and Ht (figure 2). Femoral stem design should allow the consideration of these differences to optimize the reconstruction of the hip at the time of THA including pre-operative and intra-operative modularity.
