Associated patellofemoral osteoarthritis is not a contraindication for unicompartmental knee replacement. Report of one hundred ten prostheses with an average 6-year follow-up.

INTRODUCTION: Associated patellofemoral joint osteoarthritis (APFJ-OA) has typically been considered a contraindication for unicompartmental knee arthroplasty (UKA) in the treatment of femorotibial joint osteoarthritis. However, this contraindication is being challenged. The aim of this study was to assess clinical and functional outcomes, complications, and implant survival in medial or lateral UKA, regardless of clinical symptoms or radiographic signs of APFJ-OA. METHODS: This retrospective, comparative study included patients treated with medial or lateral UKA regardless of preoperative symptoms or signs of APFJ-OA, with a minimum 2-year follow-up. Intraoperatively, knees were subdivided based on APFJ-OA grade, according to the Outerbridge classification. Clinical and functional outcomes were analyzed using the 2011 Knee Society Score (KSS) at the last follow-up control. APFJ-OA was treated systematically, in a tailored, stepwise fashion according to its severity. Complications and implant survival rates were evaluated. Two-sided paired T-test, ANOVA, and Kruskal-Wallis tests were used with a significance level of 5%. RESULTS: Finally, 110 UKAs were assessed 81 (73.6%) medial and 29 (26.4%) laterals. The average follow-up was 6 years (2-19.5). According to Outerbridge, 22 knees (20%) were in grade 2, 59 (53.6%) were in grade 3, and 29 (26.4%) were in grade 4. All three groups showed a statistically significant increase in KSS scores and range of motion. There were no significant differences in clinical KSS improvement and flexion contracture between Outerbridge groups (average 35.7 and -4.9, respectively). Group 3 showed statistically significant improvement in functional KSS when compared to group 2 (68.8 vs 61.2). In maximum flexion, groups 3 and 4 did significantly better than group 2 (20° vs 15°). Three prostheses (2.7%) needed revision after 7, 8.6, and 12 years due to aseptic tibial loosening. Implant survival was 100% at 5 (64 of 64), 97% at 7 (30 of 31), 93% at 9 (14 of 15), and 89% at 12 years, respectively (8 of 9). CONCLUSION: Clinical and functional results, complications, and survival of medial or lateral UKA were not negatively affected by APFJ-OA assessed intraoperatively using the Outerbridge classification after an average follow-up of 6 years. We consider that APFJ-OA is not a contraindication for UKA when treated systematically according to its severity. LEVEL OF EVIDENCE: IV.

Reemplazo unicompartimental bilateral de rodilla en un tiempo quirúrgico. Resultados a mediano plazo de 86 prótesis con un seguimiento promedio de 6.2 años / Bilateral simultaneous unicompartmental knee arthroplasty. Medium-term outcomes in 86 arthroplasties with an average follow-up of 6.2 years

Objetivo: Evaluar los resultados funcionales, las complicaciones y la supervivencia a mediano plazo de la prótesis unicompartimental bilateral medial o lateral de rodilla en un tiempo quirúrgico. Materiales y Métodos: Estudio retrospectivo de pacientes con prótesis unicompartimental bilateral medial o lateral de rodilla colocada en un tiempo quirúrgico por gonartrosis entre abril de 2004 y abril de 2020, seguimiento mínimo 1 año. Se evaluaron los resultados clínico-funcionales con el KSS 2011. Se determinaron los tiempos quirúrgico total y de internación, y el requerimiento de transfusiones. Se analizaron las complicaciones a corto y mediano plazo, y las tasas de revisión y de supervivencia de la prótesis. Resultados: Se evaluaron 86 prótesis unicompartimentales en 43 pacientes (seguimiento promedio 6.1 años). El KSS clínico y funcional aumentó de 46,1 ± 10,2 a 80,9 ± 15,9 y de 22,8 ± 11,9 a 89,8 ± 18,9, respectivamente. La flexión máxima mejoró de 106,3° ± 5,2° a 125,1° ± 4,2° y la contractura en flexión, de 7,5° ± 2,2° a 2,3° ± 1,6°. La cirugía duró 178.6 min y la internación, 39.8 h. Dos pacientes requirieron transfusión. La tasa de complicaciones fue del 6,9%, todas menores. Tres rodillas tuvieron un aflojamiento mecánico aséptico y requirieron revisión a prótesis total de rodilla o nueva prótesis unicompartimental tras 12, 8.6 y 7 años. La supervivencia de la prótesis fue del 96,5%. Conclusión: La prótesis unicompartimental bilateral medial o lateral en un tiempo quirúrgico para la gonartrosis unicompartimental de rodilla proporciona excelentes resultados clínico-funcionales, con bajas tasas de complicaciones. Nivel de Evidencia: IV

Objective: The purpose of this article is to examine the functional outcomes, complications, and medium-term survivorship of medial or lateral bilateral simultaneous unicompartmental knee arthroplasty (bUKA) for the treatment of bilateral knee osteoarthritis. Materials and Methods: Retrospective report of patients who underwent a medial or lateral bUKA for treatment of bilateral knee osteoarthritis between April 2004 and April 2020, with a minimum follow-up of 1 year. The KSS 2011 was used for the clinical-functional evaluation of each patient. The duration of surgery, length of hospital stay, and transfusion requirements were determined. The short-term and medium-term complications were analyzed, as well as the revision rate and the prosthesis survivorship. Results: We evaluated 86 bUKAs in 43 patients with a mean follow-up of 6.1 years. The clinical and functional KSS improved from 46.1 ± 10.2 to 80.9 ± 15.9 and 22.8 ± 11.9 to 89.8 ± 18.9 respectively. Postoperative maximal flexion improved from 106.3º ± 5.2º to 125.1º ± 4.2º and flexion contracture improved from 7.5º ± 2.2º to 2.3º ± 1.6º. The mean surgical time was 178.6 minutes and the hospital stay was 39.8 hours. Two patients required transfusions. The complication rate was 6.9%. Three knees (3.5%) required revision surgery for aseptic loosening after 7, 8.6 and 12 years. The survivorship rate was 96.5%. Conclusion: Simultaneous medial or lateral bUKA provides excellent clinical-functional outcomes with a low rate of complications in patients with bilateral knee osteoarthritis. Level of Evidence: IV