Conversion of a fused or ankylosed knee to a total-knee arthroplasty

Purpose of review: Recent reports have revisited the issue of conversion of an ankylosed knee to total-knee arthroplasty (TKA). Here, recent studies are reviewed and placed within the context of previous reports. Recent findings: An ankylosed or formally fused knee has been considered a contraindication for TKA by many and therefore conversion to TKA has been infrequently performed. From a position of ankylosis in flexion, conversion to a TKA achieved a high degree of patient acceptance and improvement in ambulation, but was complicated by a high wound complication rate. While the majority of conversions had most often been performed with a condylar constrained implant, a posterior stabilized implant without condylar constraint achieved equivalent results in the largest series to date (36 patients) without complications due to instability. An extensile approach with a V-Y quadricepsplasty or tibial tubercle osteotomy is recommended with an anticipated mild postoperative extensor lag and prolonged rehabilitation period required. The postoperative flexion arc ranged from 73° to 91°. Wound healing problems occur in up to 50% of cases and careful preoperative assessment of the soft-tissue envelope is imperative. Preoperative soft-tissue expansion has been suggested as one possible solution to this problem, but has not yet been reported upon. Summary: Conversion of a bony ankylosis or fusion to TKA can yield acceptable results; there is, however, a high complication rate and long-term outcomes are lacking. Patients must be carefully advised about expected outcomes and complications with specific attention to potential wound complications.