Abstract
The primary objective of implanting a total knee prosthesis is to release the patient from pain and to improve the joint mobility at the same time. This leads to an increased quality of life that is optimally kept for the patient's residual lifespan. Joint mobility and stability requires an intra-operative soft-tissue balancing. To reach the goal of a correct implant positioning and well-balanced ligaments two different operative procedures can be used: the so-called “Femur-first”-technique and the “Tibia-first” technique. Since now more than ten years the CT-free navigation is established as a routine procedure in TKA. Studies investigating this innovative technique have shown to lead to a higher precision regarding implant positioning and leg alignment. The present study compares navigated “Femur-first”-technique and “ Tibia-first”-technique. We hypothesised that, due to its better soft-tissue balance, the tibia first technique (T) would allow a flexion improvement of 10° compared to the femur first technique (F).
Between February 21, 2008, and October 10, 2009, 116 consecutive patients were implanted a Columbus® non-constrained total knee replacement (Aesculap®, Tuttlingen, Germany) using navigation; they were examined before the operation and 1 year after. The TKAs were performed by 3 surgeons experienced in knee replacement surgery. We used the femur first technique (F) in 63 patients, the tibia first technique (T) in 53 patients. We performed the final flexion measurement one year after the operation using a Goniometer and evaluated standing full-length radiographs. In addition, we took standard varus and valgus stress radiographs to evaluate the stability of the collateral ligaments and determine the relative position of the implants to one another. Finally, to compare the two patient groups, we used the following pain and function scores: Knee Society Score (KSS), Oxford Score, Knee Injury and Osteoarthritic Outcome Score (KOOS), Short Form 36 (SF 36), Tegner Lysholm Score.
Concerning maximal flexion as the main parameter, we did not find any significant difference between the F and T groups (maximal flexion in group F: 113.4± 9,8° and in group T: 113.5± 8.4°; p = 0.963); thus we could not confirm our hypothesis. Radiological evaluation of the stability of the collateral ligaments did not reveal any significant difference between the two groups both in the medial and lateral joint cavity (lateral collateral ligament in group F: 3.4± 1.4°, and in group T: 3.9± 1.7°; p = 0.850, and medial collateral ligament in group F: 4.0± 1.4°, and in group T: 4.1± 1.7°; p = 0.086). Concerning the mechanical axis on the standing full-length radiograph as part of the 1-year results, no significant difference was found between the two groups (p = 0.089). Likewise, the pain and function scores did not show any difference between the two groups.
Concerning operating time (OP time) and outliers exceeding 3° of varus/valgus deviation from the ideal mechanical axis, trends were identifiable. The number of outliers tended to be higher in the F group, the OP time in group T seemed longer.
As a conclusion, we can say that both the tibia first and the femur first techniques yield good clinical and radiological results in combination with navigation. In terms of function and patient satisfaction, we did not find any significant difference.
