Outcomes of lateral unicompartmental knee arthroplasty in post-traumatic osteoarthritis, a retrospective comparative study

Purpose: We asked whether the clinical and radiographic outcomes and survivorship after unicompartmental knee arthroplasty (UKA) for osteoarthritis (OA) consequent to lateral tibial plateau fracture were comparable with those obtained after lateral UKA for primary OA. Methods: A total of 13 patients receiving lateral UKA for OA secondary to tibial plateau fracture (post-traumatic UKA, P-UKA) were compared with 13 patients who underwent lateral UKA for primary OA (OA-UKA). Patients were matched for age at surgery, gender, body mass index, and follow-up length. Pre- and post-operative clinical and radiographic assessments included clinical (KSS-c) and functional (KSS-f) Knee Society Score, Hip-Knee-Ankle (HKA) angle, and signs of osteolysis. Results: Mean follow-up was similar in both groups: 9.9 ± 4.6 years for P-UKA and 9.3 ± 2.4 years for OA-UKA. The two way ANOVA procedure followed by the Bonferroni multiple comparisons test highlighted a baseline difference in KSS-c with P-UKA having greater scores than OA-UKA (+ 12; p < 0.05) and both groups showed large improvements in KSS-c (p < 0.001), KSS-f (p < 0.001), and HKA angle (p < 0.001) at follow-up. The nine year prosthesis survival rate, tested by the Kaplan-Meier methods, was 92% in both groups. Conclusion: Lateral UKA for OA secondary to tibial plateau fracture was efficient in restoring joint function, improving clinical results, and correcting lower limb alignment. Clinical outcomes and nine year survivorship did not differ from lateral UKA for primary OA. Consequently, lateral UKA should be considered a valid option in treating lateral posttraumatic OA in carefully selected patients. Trial registration number: (clinicaltrials.gov) NCT04198389.