Spontaneous relocation of a posterior dislocation of mobile bearing in a medial unicompartmental knee replacement

A structured evaluation of the symptomatic medial Oxford unicompartmental knee arthroplasty (UKA)

Unicompartmental knee arthroplasty (UKA) has several advantages over total knee arthroplasty; however, in many reports, the risk of revision remains higher after UKA.Many reasons for failure of UKA exist.Successful treatment starts with accurate assessment of the symptomatic UKA as a specific mode of failure requires a specific solution.A structured and comprehensive evaluation aids assessment of the symptomatic UKA.This review provides an overview of the causes for a symptomatic medial UKA, its risk factors, diagnostic modalities that can be used, and briefly discusses treatment options. Cite this article: EFORT Open Rev 2021;6:850-860. DOI: 10.1302/2058-5241.6.200105.

Successful revision of polyethylene only, after delayed presentation of a dislocated bearing in an Oxford unicompartmental knee replacement

We present the case of a 79-year-old man who dislocated the mobile bearing of a well-functioning Oxford unicompartmental knee replacement in a fall. The diagnosis was delayed by 14 days during which time the patient remained fully mobile. At the time of arthrotomy, there was some visible burnishing of the femoral articular surface where it had been rubbing on the tibial component. Both components were soundly fixed and had been functioning well for 7 years. The decision was made to leave the components in situ and simply replace the mobile meniscal bearing. The patient returned to full normal activity and has been followed-up for 3.5 years. Serial X-rays reveal no evidence of polyethylene wear and the knee remains pain free and fully functional. We conclude that it is safe to retain the components of an Oxford unicompartmental knee replacement despite some evidence of surface damage. Replacing just the mobile meniscus gave a good result in our patient.