Survival analysis of an asymmetric primary total knee replacement: a European multicenter prospective study.

Purpose Of The Study: This multicenter prospective study objective is to provide midterm results and 10-year survival analysis of the original Natural Knee-I System™ as experienced by a group of surgeons performing, within various settings, primary total knee replacement (TKR) in the general population.

Hypothesis: The midterm experience with this TKR system in the hands of independent surgical teams can duplicate the satisfaction level that was already published by the designer's group itself.

Material And Method: Two hundred and sixty-three primary TKR were performed by seven surgical teams (37 surgeons) and prospectively evaluated in four European countries. Mean age of the 263 patients (sex ratio, 2.7 females/1 male) was 69 years (range, 35-92) and diagnosis was primary osteoarthritis in 85%. For the 247 TKR with complete operative data, the approach was subvastus in 59%, posterior cruciate ligament was spared in 78%, patella was resurfaced in 56%, and 79% of reconstructions were totally cement-free. Fixation mode was only depending on the surgeon's choice.

Results: At 76 months average follow-up (range 24-190 months), modified Hospital for Special Surgery knee mean score improved from 48 points preoperatively to 83 points. Four reoperations and five revision procedures were required for eight knees. Over the 14-year survey period, the overall revision rate burden was 2% and revision rate per 100 observed component/year, 0.32. At 10 years, survivorship (with revision for aseptic loosening as its end-point [two fully cementless knees]) was 98.6%.

Discussion: Both this multicenter study and data drawn from national registers provided outcomes with equivalent level of satisfaction at equivalent follow-up to those reported by the NK-I prosthesis designer. There was no significant difference between revision rates of cemented, hybrid or cementless reconstructions.

Conclusion: In non-designer orthopaedists' hands, the Natural Knee-I System™, either with cemented or cementless fixation, provided satisfying midterm results as normally expected in primary TKR with such a modern modular prosthesis.

Level Of Evidence: Level IV. Prospective study.