Woodgate Ian G, Rooney John, Mulford Johnathan S, Gillies R Mark
Department of Orthopaedic, St. Vincent's Clinic Darlinghurst, Sydney, Australia.
Department of Orthopaedic, Murray Maxwell Biomechanics Laboratory, Kolling Institute of Medical Research, Royal North Shore Hospital, St Leonards, NSW 2065, Australia.
J Orthop Case Rep. 2016 Jan-Mar;6(1):40-3. doi: 10.13107/jocr.2250-0685.373.
This is a report of a mechanical failure of an S-ROM revision total knee prosthesis. The prosthesis was used as a revision implant following deep peri-prosthetic infection in a morbidly obese male. The prosthesis failed on both the femoral and tibial sides at the modular metaphyseal stem junctions and required a further revision using the same type of implant after infection was excluded.
A 57 year old male had previously undergone a left total knee arthroplasty in 1999 for osteoarthritis. He acquired a late deep peri-prosthetic infection with a multi-resistant Staphylococcus epidermidis. The organism was sensitive to vancomycin and rifampicin. A two stage revision was undertaken after clinical signs of infection had resolved and blood parameters had normalized. Intra-operative gram stain was negative for micro-organisms and frozen section of deep tissue was less than five polymorphs per high power field. A cemented S-ROM prosthesis was implanted using a coronal tibial osteotomy and a lateral release for exposure. After three years of the second stage of revision, the patient again presented to the orthopaedic department after reportedly falling on a wet floor six weeks ago.
Radiographically, there was a broken tibial wire, osteolysis and pedestal formation around both the femoral and distal tibial stem extensions. The prosthesis was bent at the proximal tibial sleeve and stem junction. The prosthesis was considered loose with mechanical failure. At implant removal, it was noted that the femoral and tibial components at the modular metaphyseal sleeve-stem junction were fractured. Surgeons should be cautious in the use of these implants in morbidly obese patients where the stresses generated maybe above the yield stress of the material and the frictional forces that may overcome the modular taper junction's locking mechanism.
本文报告一例S-ROM翻修全膝关节假体的机械故障。该假体用于一名病态肥胖男性患者，在发生深部假体周围感染后作为翻修植入物。假体在股骨和胫骨侧的模块化干骺端柄交界处均出现故障，在排除感染后，需要使用同一类型的植入物进行进一步翻修。
一名57岁男性曾于1999年因骨关节炎接受左全膝关节置换术。他发生了晚期深部假体周围感染，感染菌为多重耐药的表皮葡萄球菌。该菌对万古霉素和利福平敏感。在感染的临床症状消退且血液参数恢复正常后，进行了两阶段翻修。术中革兰氏染色未发现微生物，深部组织冰冻切片每高倍视野多形核白细胞少于5个。采用冠状胫骨截骨术和外侧松解术暴露后，植入了骨水泥固定的S-ROM假体。在第二阶段翻修三年后，据报道患者六周前在湿滑地面摔倒，之后再次到骨科就诊。
影像学检查显示，胫骨钢丝断裂，股骨和胫骨远端柄延伸处周围出现骨溶解和骨桥形成。假体在胫骨近端套筒和柄交界处弯曲。假体被认为因机械故障而松动。取出植入物时，发现模块化干骺端套筒-柄交界处的股骨和胫骨部件骨折。对于病态肥胖患者使用这些植入物时，外科医生应谨慎，因为产生的应力可能超过材料的屈服应力，且摩擦力可能会克服模块化锥形交界处的锁定机制。
