Musculoskeletal institute, Department of Orthopaedic Surgery and Traumatology, Rangueil Teaching Hospital Center, 1, avenue Jean-Poulhès, TSA 50032, 31059 Toulouse cedex 9, France.
Orthop Traumatol Surg Res. 2011 May;97(3):229-40. doi: 10.1016/j.otsr.2011.01.011. Epub 2011 Apr 1.
Significant femoral neck narrowing following hip resurfacing arthroplasty has been observed. Several factors contributing to the physiopathology of femoral neck narrowing have been suggested. The aim of this study was to evaluate the femoral neck radiographic changes observed after hip resurfacing at a minimum follow-up period of 5 years and to determine their causes.
We conducted a prospective study of 57 hip resurfacing arthroplasties performed in 53 patients (30 men, 23 women) of mean age 49.2 years (32-65) at surgery. These patients were clinically reviewed (inguinal pain during walking, WOMAC and UCLA scores) at 2 years and radiographically examined at 1, 2 and 5 postoperative years. The accuracy of our computer-aided measurement method was 1mm. Measurement of femoral neck to implant ratio was performed to assess the amount of neck thinning at the femoral neck-implant junction (N/H) and midway between the implant and the inter-trochanteric line (N(1/2)H) on an AP radiograph. Neck-thinning greater than 10% was considered as significant. Any other radiographic morphologic change in the femoral neck was investigated. Metallic ion concentration in blood was measured. A uni- and multivariate analysis was performed to determine the correlation with radiographic changes.
In one third of the patients, femoral neck narrowing was greater than 1mm at 2 and 5 postoperative years. Such result corresponds to a mean decrease in neck to implant ratio (N/H) of 5.9% (range, 2.3 to 9.4) at 2 years and 8.3% (range, 2.5 to 23.8) at 5 years. At 5 postoperative years, an overall neck thinning greater than 10% was reported in 3 patients (with a 10- to 17-% increase in femoral neck narrowing between the 2nd and the 5th postoperative year). In one case, neck thinning was associated with fracture of the femoral stem managed with revision surgery during which femoral neck necrosis was confirmed. Neck thinning was, in these cases, circumferential to the neck-implant junction. There was no significant negative impact on clinical scores and no relationship could be established between neck thinning and factors such as BMI or patient activity. Moreover, neck thinning greater than 10% was reported in two cases after 2 postoperative years through the appearance of a localized femoral neck notching which was absent in the postoperative period, secondary to a femoroacetabular impingement.
DISCUSSION-CONCLUSION: Femoral neck narrowing used to be a common phenomenon after HR when polyethylene acetabular bearings were implanted thus inducing osteolysis secondary to PE wear debris. The incidence of such phenomenon has decreased but still occurs after HR when using a metal-on-metal bearing surface. It has an early occurence but stabilizes after 2 postoperative years. Changes in mechanical stress distribution in the neck region after hip resurfacing have been hypothesized to be a cause of neck thinning. Other aetiologies may be suggested. An overall evolutive femoral neck narrowing after 2 postoperative years should raise the suspicion of necrosis leading to a risk of loosening, fracture or implant failure. Therefore, radiographic monitoring should be conducted. The presence of femoral neck notching secondary to femoroacetabular impingement represents a differential diagnosis which conservative treatment is advocated in the absence of any associated symptoms.
髋关节表面置换术后出现明显的股骨颈狭窄已被观察到。已经提出了几种导致股骨颈狭窄病理生理学的因素。本研究的目的是评估髋关节表面置换术后至少 5 年的股骨颈影像学变化，并确定其原因。
我们对 53 名患者（30 名男性，23 名女性）的 57 例髋关节表面置换术进行了前瞻性研究，平均年龄为 49.2 岁（32-65 岁）。这些患者在术后 2 年进行了临床评估（行走时腹股沟疼痛、WOMAC 和 UCLA 评分），并在术后 1、2 和 5 年进行了影像学检查。我们的计算机辅助测量方法的准确性为 1mm。通过测量股骨颈与植入物的比值（N/H）来评估股骨颈-植入物交界处（N/H）和植入物与转子间线之间中点（N(1/2)H）的颈缩程度。颈缩超过 10%被认为是显著的。还研究了股骨颈的任何其他影像学形态变化。测量了血液中的金属离子浓度。进行了单变量和多变量分析，以确定与影像学变化的相关性。
三分之一的患者在术后 2 年和 5 年时股骨颈狭窄大于 1mm。这种结果相当于在术后 2 年时颈植入物比值（N/H）平均下降 5.9%（范围 2.3-9.4），在术后 5 年时下降 8.3%（范围 2.5-23.8）。在术后 5 年时，有 3 名患者报告了总体颈缩大于 10%（在第 2 年和第 5 年之间，股骨颈狭窄增加了 10-17%）。在 1 例患者中，颈缩与股骨柄骨折有关，在 revision 手术中处理了骨折，在 revision 手术中证实了股骨颈坏死。在这些病例中，颈缩是围绕颈-植入物交界处的。临床评分没有显著的负面影响，也无法确定颈缩与 BMI 或患者活动等因素之间的关系。此外，在术后 2 年，由于出现局部股骨颈切迹，有 2 例患者报告了大于 10%的颈缩，在术后期间，由于股骨髋臼撞击，这种切迹不存在。
讨论-结论：当使用聚乙烯髋臼轴承时，髋关节表面置换术后股骨颈狭窄是一种常见现象，从而导致由于 PE 磨损碎片引起的骨溶解。当使用金属对金属轴承表面时，这种现象的发生率虽有所降低，但仍会发生。它发生较早，但在术后 2 年稳定。髋关节表面置换术后颈区机械应力分布的变化被假设为颈缩的原因。其他病因可能被提出。在术后 2 年出现总体上的股骨颈变窄应引起对导致松动、骨折或植入物失败风险的坏死的怀疑。因此，应进行影像学监测。由于股骨髋臼撞击导致的股骨颈切迹的存在代表了一种鉴别诊断，在没有任何相关症状的情况下，建议进行保守治疗。
