Lateral Unicompartmental Knee Arthroplasty Relieves Pain and Improves Function in Posttraumatic Osteoarthritis

Background Posttraumatic arthritis secondary to lateral tibial plateau fracture malunion causes pain and limited function for patients. It is sometimes technically challenging to correct malalignment in these patients with advanced arthritis using osteotomies. Lateral unicompartmental knee arthroplasty (UKA) may be an option to treat such patients. Questions/purposes We asked whether UKA for lateral posttraumatic osteoarthritis (1) reliably alleviates pain and improve function, (2) restores lower limb alignment, and (3) is as durable as UKA for primary lateral osteoarthritis. Patients and Methods We retrospectively reviewed 13 patients with lateral cemented UKA (mean age at surgery, 50.1 years) treated at two institutions between 1985 and 2007. We obtained Knee Society scores and evaluated radiographs for evidence of implant loosening or progression of arthritis in the medial compartment. Minimum followup was 3 years (mean, 10.2 years; range, 3-22.1 years). Results Mean Knee Society knee score improved from 51 points (range, 29-75 points) preoperatively to 88 points (range, 65-100 points) at last followup, suggesting the procedure relieved pain. Mean function score improved from 51 points (range, 10-89 points) preoperatively to 87 points (range, 35-100 points) at last followup. The mean hip-knee-ankle angle was 188A degrees preoperatively (range, 184A degrees-193A(0)) and 185A degrees (range, 183A degrees-188A degrees) at last followup. Prosthesis survivorship was 100% at 5 and 10 years and 80% at 15 years. Conclusions Despite the limited number of indications and technical considerations, our observations suggest lateral UKA is a reasonable option for treating lateral arthritis secondary to malunited fractures. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.