title: 180° rotatory dislocation of the rotating platform of a posterior-stabilized mobile-bearing knee prosthesis; possible complication after closed reduction of a posterior dislocation--a case report.
abstract: Dislocation of the rotating platform is a significant early complication of mobile-bearing total knee arthroplasty. The authors report an unusual case of acute 180° rotatory dislocation of the rotating platform after closed reduction of a posterior dislocation of a posterior-stabilized mobile-bearing total knee prosthesis. A 71-year-old male with knee osteoarthritis underwent TKRA using a posterior-stabilized mobile-bearing prosthesis. Posterior dislocation of the prosthesis occurred at 5 weeks postoperatively, and closed reduction of the posterior dislocation resulted in complete 180° rotatory dislocation of the rotating platform. The patient was treated by open exploration and polyethylene exchange for a larger component. This case illustrates that dislocation of a posterior-stabilized mobile-bearing total knee prosthesis can occur given valgus laxity and causes a 90° spin-out of the polyethylene insert, and that closed reduction attempts may contribute to complete 180° rotatory dislocation of the rotating platform. Special attention should be given to both AP and lateral views to ensure that the platform is truly reduced and not rotated by 180°. Plain digital radiography, which enhances the density of polyethylene, or arthrography is helpful for diagnosing this complication.
authors.affiliation: Department of Orthopaedic Surgery, College of Medicine, Dongguk University, Gyeongju, Republic of Korea.
authors.forename: Ho Min
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, College of Medicine, Dongguk University, Gyeongju, Republic of Korea.
authors.forename: Young Sung
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, College of Medicine, Dongguk University, Gyeongju, Republic of Korea. Electronic address: kjpil@dongguk.ac.kr.
authors.forename: Jong Pil
authors.initials: JP
authors.lastname: Kim
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D006801:Humans; D031221:Knee Dislocation / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy*; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008349:Manipulation, Orthopedic / Q000009:adverse effects*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D012086:Reoperation
keywords: Dislocation; Mobile-bearing; Posterior-stabilized; Rotating platform; Spin-out; Total knee arthroplasty