Background: Varus malalignment after total knee replacement is mentioned to be a major risk factor for postoperative pain and functional impairments. This wide spread opinion is based on the historical data derived from implantations performed in the late 1970s and early 1980s. We tested the hypothesis whether significant varus malalignment leads to minor functional results and early loosening using modern implants and operating techniques.
Methods: Two hundred and eighteen knee joints (184 patients) having been replaced with a PFC Sigma or Natural Knee II with a minimum follow-up of 5 years were included in this case control study. From the 30 most varus malaligned knees (30 patients) 25 patients were available for clinical and radiographical examination (group A) and were compared with a control group without significant varus malalignment that was matched for sex, age and implant (group B). The Knee Society Score (KSS), the WOMAC and the SF36 were determined.
Results: No implant showed radiological signs of loosening or had been revised. The deviation from the mechanical axis was 6.3° [3.9°-10.7° varus] in group A and 0° [2.6° valgus to 2.1° varus] in group B (P < 0.001). The KSS was 158 [99-199] points in group A and 142 [78-198] points in group B (n.s.). The WOMAC did not reveal any significant differences between the groups either (group A 22 ± 27 points, group B 21 ± 21 points). Likewise in the SF36, neither in the sum nor in the individual scores was a significant difference found between groups A (56 ± 24 [8-90] points) and B (56 ± 18 [26-86] points).
Conclusions: The present data do not support the assumption that there is a correlation between varus malalignment and a bad medium-term radiological and clinical outcome after total knee arthroplasty. This questions the indication for revision of painful and varus malaligned prostheses, since an improvement of the clinical outcome is not to be expected.