Cheung Emilie V, O'Driscoll Shawn W
Mayo Clinic, Rochester, Minnesota 55905, USA.
J Bone Joint Surg Am. 2007 Jun;89(6):1269-74. doi: 10.2106/JBJS.F.00376.
Linked semiconstrained total elbow prostheses have been used successfully but may be at higher risk for implant loosening than unlinked implants are. The purpose of the present report was to describe a previously unreported and potentially preventable cause of mechanical loosening of the ulnar component of a linked total elbow prosthesis.
A series of ten patients who had painful pistoning of the polymethylmethacrylate-coated ulnar component of a Coonrad-Morrey linked total elbow prosthesis were evaluated clinically and radiographically.
All ten patients complained of elbow pain, and eight had a distinct sensation of the ulnar component moving within the ulna. Six patients either complained of squeaking within the elbow or could demonstrate squeaking on examination. Four patients had a complete radiolucent line around the ulnar component or the cement mantle, and six had an incomplete line around the ulnar component. Six patients had a radiolucent gap between the cement and the tip of the ulnar prosthesis. Two patients had proximal migration of the ulnar component within the cement mantle on lateral flexion radiographs. Three patients had anterior impingement, such as between the anterior flange of the humeral implant and a prominent coronoid process, on lateral flexion radiographs. At the time of revision arthroplasty, all ten patients were found to have a loose ulnar component, which was successfully revised with or without impaction grafting. At the time of the most recent follow-up, nine of the ten ulnar components were intact and stable. Three patients required an additional reoperation: one required triceps repair, one required revision of a loose humeral component, and one required a revision total elbow arthroplasty.
Pistoning of the ulnar component in the cement mantle leading to failure by means of a pullout mechanism can occur in association with the Coonrad-Morrey total elbow prosthesis with a polymethylmethacrylate-precoated ulnar component. To prevent this problem following any total elbow arthroplasty, the surgeon should check for anterior impingement intraoperatively by ensuring that there is no contact between the anterior flange and a prominent coronoid process or the cement and that no distraction of the trial ulnar component from the ulna occurs with passive elbow flexion. This condition also can be avoided by ensuring that the ulnar component is not inserted too far distally. This mechanism of failure should be considered when future total elbow arthroplasty implants are designed.
Therapeutic Level IV.
半限制型全肘关节假体已成功应用，但与非限制型假体相比，其植入物松动风险可能更高。本报告的目的是描述一种此前未报道的、可能可预防的半限制型全肘关节假体尺骨部件机械性松动的原因。
对10例使用Coonrad-Morrey半限制型全肘关节假体、聚甲基丙烯酸甲酯涂层尺骨部件出现疼痛性活塞样运动的患者进行了临床和影像学评估。
所有10例患者均主诉肘部疼痛，8例患者能明显感觉到尺骨部件在尺骨内移动。6例患者主诉肘部有摩擦声或检查时可发现摩擦声。4例患者尺骨部件或骨水泥套周围有完整的透亮线，6例患者尺骨部件周围有不完整的透亮线。6例患者骨水泥与尺骨假体尖端之间有透亮间隙。2例患者在侧屈位X线片上尺骨部件在骨水泥套内近端移位。3例患者在侧屈位X线片上有前方撞击，如肱骨植入物的前凸缘与突出的冠状突之间。在翻修关节成形术时，发现所有10例患者的尺骨部件均松动，采用或不采用打压植骨均成功进行了翻修。在最近一次随访时，10个尺骨部件中有9个完整且稳定。3例患者需要再次手术：1例需要修复肱三头肌，1例需要翻修松动的肱骨部件，1例需要翻修全肘关节置换术。
采用聚甲基丙烯酸甲酯预涂层尺骨部件的Coonrad-Morrey全肘关节假体可能会出现尺骨部件在骨水泥套内的活塞样运动，导致拔出机制失效。为防止全肘关节置换术后出现此问题，外科医生应在术中检查是否存在前方撞击，确保前凸缘与突出的冠状突或骨水泥之间无接触，并且被动屈肘时试验性尺骨部件不会从尺骨上分离。确保尺骨部件向远端插入不过深也可避免这种情况。在设计未来的全肘关节置换植入物时应考虑这种失效机制。
治疗性IV级。
