Hinge prostheses in the revision of unicompartmental knee replacement: a descriptive analysis of data from the national joint registry for England, Wales and Northern Ireland

IntroductionUnicompartmental knee replacement (UKR) is an effective surgical strategy in patients with isolated medial or lateral compartment osteoarthritis. Study aims were to (1) describe the epidemiology of patients undergoing revision of UKR to a hinge knee replacement (HKR); (2) identify factors influencing time to revision; (3) evaluate HKR survival.Materials and methodsAn analysis of National Joint Registry data was undertaken, exploring revision of UKR to HKR between 2007 and April 2021. Descriptive analysis of eligible patients and Cox Regression to identify key determinants of time to revision were performed. Failure of HKR post-revision was assessed using survival analysis.Results111 patients underwent revision of UKR to HKR. Median age at revision was 70 years and most common indications were instability (n = 42) and infection (n = 22). The most common implant was a rotating HKR. Significant independent factors associated with earlier revision were periprosthetic fracture (p = 0.03) and malalignment (p = 0.03). Progressive osteoarthritis (p = 0.01) and higher ASA grades (3: p = 0.01, 4: p < 0.01) delayed time to revision; patient sex and age were not significant factors. Ten patients required subsequent re-revision; median age at re-revision was 61 years. HKR revised from UKR had an 89.3% revision-free risk at 5 years. Male sex (p < 0.01) and younger age (p < 0.01) were associated with re-revision.ConclusionsFactors associated with time to revision may be used to counsel patients prior to UKR. The survivorship of the HKR of 89.3% at 5 years is concerning and careful consideration should be given when using this level of constraint when revising UKR in younger or male patients.

Automated summary

This study analyzed data of patients who underwent revision from UKR to HKR, describing their epidemiology, factors influencing time to revision, and the survival rate of HKR. The most common indications for revision were instability and infection. Factors associated with earlier revision included periprosthetic fracture and malalignment, while progressive osteoarthritis and higher ASA grades delayed time to revision. Ten patients required subsequent re-revision, with male sex and younger age associated with re-revision.