In valgus knees, ligament balance remain difficult when implanting a total knee arthroplasty (TKA), this leads some authors to systematically propose the use of constrained devices. Others prefer reserving higher constraints to cases where it is not possible to obtain final satisfactory balance: less than 5 of residual frontal laxity in extension in each compartment, and a tibiofemoral gap difference not in excess to 3mm between flexion and extension. The goal of the study was to assess if is possible to establish preoperative criteria that can predict a constrained design prosthetic implantation at surgery. A consecutive series of 93 total knee prostheses, implanted to treat a valgus deformity of more than 5 was retrospectively analysed. Preoperatively, full weight bearing long axis AP views A-P were performed: hip knee angle (HKA) averaged 195 (186 to 226), 36 knees had more than 15 of valgus, and 19 others more than 20 of valgus. Laxity was measured by stress radiographies with a TelosTM system at 100 N. Fifty-two knees had preoperative laxity in the coronal plane of more than 10. Fourteen knees had more than 5 laxity on the convex (medial) side, 21 knees had more than 10 laxity on the concave (lateral) side. Statistical assessment, using univariate analysis, identified the factors that led, at surgery, to an elevated constraint selection level; these factors of independence were tested by multivariate analysis. Logistical regression permitted the classification of the said factors by their odds ratios (OR).Introduction
Materials and Methods
