VARUS AND VALGUS STRESS BEFORE AND AFTER TOTAL KNEE ARTHROPLASTY

Abstract

Purpose of the study: Achieving correct ligament balance for total knee arthroplasty remains a serious challenge, even for the experienced surgeon. Computer-assisted surgery allows real time assessment of the knee joint behavior and gives continuous measures of HKA under stress.

Material and methods: Between January 2003 and November 2004, 25 patients with osteoarthritis of the knee joint underwent computer-assisted surgery for implantation of posterior stabilized total knee prosthesis. The series included 13 right knees and 12 left knees in 8 men and 17 women, mean age 73.6±8.1 years, age range 44–84 years. Body mass index was 29±5.5 (range 21.6–42.7). The IKS function score was 35.8±17 (range 5–70) and the IKS knee score was 51.2±8.5 (range 30–73). Measurements were made for varus and valgus stress of 0–30°. Extensive lateral or medial release was also performed for six knees. The medial parapatellar approach with removal of osteophytes was used for all procedures.

Results: Preoperatively, four patients presented valgus (185.6±4.7, range 182–191°), one correct alignment and 20 presented varus (174±3.45, range 166–178°). Pre-operatively the mean varus stress angle was 5.13±3.44 (range 0–11°), the mean valgus stress angle was 1.5±1.53, range −4 to 4°). At the end of the procedure, the varus stress angle 1.78±1.59 (0–5°) and the valgus stress angle 1.79±1.6 (0–4°). At 45 days, mean flexion was 115±10° (range 60–126°). There was mobilization in two patients, one with a 5° extension deficit and the other with an extension deficit less than 10°.

Discussion: This study demonstrates the usefulness of navigation systems to assess the effect of peripheral release and to limit the extent of release procedures (six of 25 patients). Materializing step by step release of the peripheral structures is helpful in achieving correct release.

Conclusion: This work confirms that extensive release is not always necessary. This type of technique should allow better control and fine tuning of ligament balance and tension.

This work was supported by work on cadaver specimens measuring the step by step effect of ligament release.