The INDUS knee prosthesis – Prospective multicentric trial of a posteriorly stabilized high-flex design: 2 years follow-up

BACKGROUND: The anatomical and morphological differences and high-flexion daily activities in the Asian population have since ever prompted for development of customized knee replacement systems. INDUS knee system has advantages both of high-flex designs and is developed by keeping the anatomical variations of the native population in mind. The purpose of this study is to analyze the 2-year follow-up results using the INDUS prosthesis. MATERIALS AND METHODS: Two hundred and ninety-seven knees in 276 patients were prospectively analyzed. There were 65 men (72 knees) and 211 (225 knees) women with a mean age of 64.56 years. Two hundred and forty-five knees had primary osteoarthritis, 48 knees had rheumatoid arthritis, and four knees had post-traumatic arthritis. Clinical parameters, including the Knee Society scores (knee score and function score), range of motion, post-operative anterior knee pain, and complications were recorded. Pre- and post-operative serial radiographs were analyzed for limb alignment, component positioning, and evidence of loosening. RESULTS: The patients were followed-up for an average of 2.59 years (range, 2–3.3 years). The mean knee score and the mean function score were significantly improved from a pre-operative value of 39.4 points and 46.7 points to a post-operative value of 87 points and 86 points, respectively (P value <0.05). Two hundred and thirty four knees had no anterior knee pain while 63 knees had mild to moderate pain, but none of the patients requested any intervention for the same. Of the 276 patients (297 knees), 79 knees had flexion above 140°, 167 had a flexion range of 130–140°, 27 had a flexion range of 100–130°, and 24 knees had a flexion < 100°, with the mean range of movement being 132.9°. Improvements in the range of movement were retained over time and a total of 205 patients (224 knees, 75.7%) could squat or sit cross-legged at the final follow-up. The mean tibiofemoral angle was 8.5°±6.9° of varus pre-operatively and 5.4°±2.2° of valgus (3–7° of valgus) at the final follow-up, with no loss of alignment noted in any case. One knee underwent revision for late infection while another knee had periprosthetic supracondylar fracture treated with plate fixation. CONCLUSIONS: Use of the INDUS knee prosthesis has a favorable short-term outcome, with a mean range of 135° flexion and excellent knee scores.