Prothèses unicompartimentales — Conclusions de la Table Ronde Réponses aux questions posées

Unicompartmental knee arthroplasty (UKA) is an excellent operation provided the technique is properly applied and the indication is well established. Obesity (weight > 100 kg, or BMI > 32) is a contraindication. The shape of the femoral prosthetic condyle is a cause of loosening in the medium and long term. There is an important difference between medial UKA and lateral UKA. Indications are different and they correspond to different types of patients. UKA is not an alternative to osteotomy; it is in competition with both osteotomy and total knee prostheses and has its own indications. UKA without cement is possible provided sufficient primary stability is achieved. This appears difficult to achieve at the femoral level. The patella poses no problems provided the unicompartmental prosthesis is fitted correctly. The absence of anterior cruciate ligament, together with clinical or radiological anteroposterior laxity, is a contraindication to UKA. The average lifetime of a unicompartmental prosthesis is 8–10 years; lateral prostheses have a longer lifetime. Failure of UKA implies reoperation with conversion to the total knee prosthesis. Hypercorrection by lateral UKA is undesirable. In contrast, there is no objection to hypercorrection of less than 5° by medial UKA. After medial UKA, the recurrence of a varus deformity is possible only if lateral laxity has not been controlled or if one of the prosthetic components is displaced. UKA is not indicated if patellar surgery is required. Hypocorrection by lateral UKA is desirable. Medially, the residual varus should not exceed 5°. In medium and long-term failures, most complications affect the tibia (loosening, polyethylene wear).