Background: Total knee arthroplasty in joints with valgus or varus deformity is technically demanding. Careful soft tissue balance as well as restitution of anatomical knee axis has a profound effect on postoperative function of the joint, however little is known about differences in subjective stability following surgery between preoperative valgus and varus knees.
Material and methods: Studied group consisted of 60 patients who underwent total condylar knee arthroplasty with one type of implant (Stryker Triathlon). Mean follow-up was 2,9 years (1-6 years). The group included 25 patients with valgus and 35 patients with varus preoperative deformity. All patients filled Knee Injury and Osteoarthritis Outcome Score (KOOS) forms. Detailed clinical and radiological assessment was performed.
Results: Mean KOOS score was slightly higher in patients with varus deformity, as compared to cases with valgus deformity. At physical examination higher LCL deficiency rate was observed in varus knees. Subjective instability was reported by eight patients (5 valgus and 3 varus). In all cases instability coexisted with decreased MCL tightness and implant position was correct in those patients. No subjective instability was reported by patients with clinical LCL deficiency. Furthermore KOOS scores in these patients were higher (85,8) as compared to cases with decreased MCL tension (79,1).
Conclusions: 1. In patients with proper implant alignment subjective instability is related to postoperative MCL deficiency, regardless preoperative deformity in coronal plane. 2. The post-op LCL laxity does not compromise subjective stability, nor influence subjective outcome, as demonstrated with KOOS scores.