Mao Yifan V, Dipane Matthew V, Zeegen Erik N, McPherson Edward J
UCLA David Geffen School of Medicine, Los Angeles, CA, USA.
Department of Orthopaedic Surgery, UCLA Health, Santa Monica, CA, USA.
Arthroplast Today. 2024 Jul 4;28:101448. doi: 10.1016/j.artd.2024.101448. eCollection 2024 Aug.
Patellar failure in total knee arthroplasty is a major source of complications postoperatively. Previous patellar failure reports commonly cited dissociations of modular and metal-backed patellar implants. However, mechanical breakage of monoblock all-polyethylene patellar implants is very rare. We present a case of an early shear failure of a 3-peg modified dome all-polyethylene patellar implant at 16 months. The patient underwent a revision procedure and at 1-year follow-up, the patient's patella and knee remained stable with no reported issues. Shear failure of polyethylene pegs requires excess cyclic shear stress imparted at the prosthetic-bone interface. Patellar implants with a cone design are more constrained and, if misaligned relative to the metallic trochlea, may impart excess shear force to the patella during flexion.
全膝关节置换术中髌骨失效是术后并发症的主要来源。既往关于髌骨失效的报道通常提及模块化和金属背衬髌骨植入物的分离。然而，整体式全聚乙烯髌骨植入物的机械性断裂非常罕见。我们报告一例3钉改良穹顶全聚乙烯髌骨植入物在16个月时发生早期剪切失效的病例。该患者接受了翻修手术，在1年的随访中，患者的髌骨和膝关节保持稳定，未报告任何问题。聚乙烯钉的剪切失效需要在假体-骨界面施加过量的循环剪切应力。锥形设计的髌骨植入物限制更大，如果相对于金属滑车未对齐，可能在屈曲过程中给髌骨施加过大的剪切力。
