髋关节置换后假体脱位的症状

由于表面置换采用的假体直径较大，一般在36mm以上，而通常的全髋关节置换术所用的股骨头假体直径为28mm，所以表面置换术后假体的脱位、半脱位的发生率要比普通的全髋置换发生率低。在近几年的临床随访报道中，术后脱位的发生率为0.75%。比利时De Smet曾报道两次脱位都发生在同一患者身上，每次都是因为醉酒后外伤引起，两次都在无麻醉的情况下手法复位成功。Amstutze等报道一例术后50个月由于反复撞击半脱位的患者，最后该患者行翻修全髋置换。表面置换术后脱位的发生主要有两个原因：一是髋臼假体安放位置不良，这也是全髋置换导致脱位的主要原因；二是偏矩过小，这种情况往往发生在股骨头坏死较严重或髋臼发育不良的患者。

偏距的恢复在手术中尤为重要，与人工全髋关节置换不同的是，表面置换缺乏不同规格的头颈尺寸，以满足偏距调节的需求。因此在股骨头顶截骨时，一定要注意股骨头截骨导向器的安放，以恰好覆盖颈部锉骨面为宜，避免安放过深。股骨头顶部过度截骨可以引起偏距短缩，如合并旋转中心内移会引起外展肌松弛，可能导致髋关节不稳定甚至脱位。因此手术中应始终注意软组织的张力。

其他并发症如深静脉血栓、肺栓塞、异位骨化和术中神经血管损伤等与传统全髋置换术相似。

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