Evaluation of a Femoral Stem with Reduced Stiffness: A Randomized Study with Use of Radiostereometry and Bone Densitometry

J. Kärrholm, Christian Anderber, F. Snorrason, J. Thanner, N. Langeland, H. Malchau, P. Herberts
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引用次数: 118

Abstract

Background: Femoral stems with reduced stiffness were introduced in total hip arthroplasty to facilitate proximal load transfer and thereby reduce periprosthetic bone loss. Poor fixation and unacceptably high revision rates turned out to be a major problem with these prostheses. The purpose of the present study was to evaluate the early performance of a low-modulus stem (one that is less stiff) with the potential to address the problem of fixation by the use of a surface coating. The coating consisted of a titanium porous mesh proximally covered with a mixture of hydroxyapatite and tricalcium phosphate.Methods: Thirty-nine men and twenty-six women (sixty-eight hips) with noninflammatory arthritis were studied. The patients were randomized to receive either a porous-coated composite stem with reduced stiffness (Epoch) or a stiff stem with a porous coating (Anatomic). Both stems were inserted without cement, had a ceramic coating on the proximal two-thirds, and were supplied with tantalum beads. At the time of the operation, tantalum markers were also placed into the proximal part of the femur. The patients were followed for up to two years after the operation and were evaluated with use of repeated radiostereometric measurements, measurements of bone-mineral density, conventional radiography, and Harris hip scores.Results: Both stems showed optimum fixation with median subsidence and stem rotations that were close to zero. Repeated measurements of bone-mineral density revealed early loss of bone mineral in all Gruen regions in both treatment groups. The loss of bone mineral around the Epoch stems was significantly reduced at two years in Gruen regions 1, 2, 6, and 7 (p < 0.0005 to 0.04). Measurements on postoperative radiographs showed no difference in stem positioning or fill, but the Epoch stems had significantly more endocortical contact on both the anteroposterior (p < 0.0005) and the lateral radiograph (p = 0.02).At two years postoperatively, the Epoch stems had fewer sclerotic lines surrounding the stem (p £ 0.002) and less sclerosis at the tip of the prosthesis (p = 0.001) compared with the Anatomic stems. The clinical results in terms of the Harris hip score, which was determined in all hips, and pain or discomfort, which was evaluated in thirty-seven hips treated at the same hospital, were not found to be different, with the numbers available.Conclusions: Contrary to previous studies of other designs with reduced stiffness, the Epoch stem achieved excellent primary fixation. Despite this rigid fixation, the proximal loss of bone-mineral density was less than that associated with the stem with a stiffer design. These results should encourage additional long-term studies with a larger patient population.
评估股骨干降低刚度:使用放射立体测量和骨密度测量的随机研究
背景:在全髋关节置换术中引入刚度降低的股骨柄,以促进近端负荷转移,从而减少假体周围的骨丢失。固定不良和不可接受的高翻修率是这些假体的主要问题。本研究的目的是评估低模量(硬度较低)的早期性能,通过使用表面涂层来解决固定问题的潜力。涂层由钛多孔网组成,近端覆盖有羟基磷灰石和磷酸三钙的混合物。方法:对39名男性和26名女性(68髋)非炎性关节炎患者进行研究。患者被随机分为两组,一组接受多孔涂层复合支架(Epoch),另一组接受多孔涂层硬支架(Anatomic)。两根茎均不加水泥,近三分之二处有陶瓷涂层,并提供钽珠。在手术时,钽标记物也被放置在股骨近端。术后随访患者长达两年,并通过重复放射立体测量、骨矿物质密度测量、常规x线摄影和Harris髋关节评分进行评估。结果:两根茎均表现出最佳固定,中间沉降和茎旋转接近于零。骨矿物质密度的反复测量显示,在两个治疗组中,所有Gruen区域的骨矿物质早期丢失。在Gruen区1、2、6和7,Epoch茎周围骨矿物质的损失在两年后显著减少(p < 0.0005至0.04)。术后x线片测量显示椎体的定位和填充没有差异,但Epoch椎体在正位片(p < 0.0005)和侧位片(p = 0.02)上明显有更多的皮质内接触。术后2年,Epoch假体与Anatomic假体相比,假体周围的硬化线较少(p = 0.002),假体尖端的硬化线较少(p = 0.001)。哈里斯髋关节评分是在所有髋关节中确定的,而疼痛或不适是在同一家医院治疗的37个髋关节中评估的,根据现有的数据,没有发现有什么不同。结论:与先前研究的其他降低刚度设计相反,Epoch柄获得了良好的初始固定。尽管采用了这种刚性固定,但近端骨矿物质密度的损失小于采用刚性固定的椎体。这些结果应该鼓励在更大的患者群体中进行更多的长期研究。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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