The posterior tibial slope does not influence the flexion angle in posterior-stabilized mobile-bearing total knee arthroplasty

No significant clinical differences between native or reduced posterior tibial slope in kinematically aligned total knee replacement with posterior cruciate-retaining

Aims & objectives

Total knee arthroplasty (TKA) is a common surgical procedure for end-stage knee osteoarthritis. However, conventional alignment techniques may lead to postoperative dissatisfaction in up to 20% of cases. Kinematic alignment (KA) has emerged as a new philosophy to restore the native joint line and achieve more natural kinematics. Preserving the posterior tibial slope (PTS) and posterior cruciate ligament (PCL) is crucial to maintaining the pre-arthritic joint line and improving knee kinematics. This study aimed to assess the prevalence of postoperative PTS changes and their impact on functional outcomes and range of motion.

Materials & methods

A retrospective single-center study was conducted on patients who underwent KA-TKA with PCL preservation. The preoperative and postoperative PTS were measured on lateral knee radiographs using the tibial proximal anatomic axis method. Patient-reported outcome measures (PROMs) were collected pre- and postoperatively up to a two-year follow-up.

Results

Of the 95 included patients, 62.1% achieved an anatomically similar PTS (within 3° from the preoperative value), while 37.9% experienced noticeable PTS changes. However, no significant associations existed between PTS changes and compromised PROMs (WOMAC, 22.2 and 23.1; FJS, 66.6 and 67.3), ROM (118.5° and 119.4°), or patient satisfaction. No postoperative complications requiring reoperation or component revisions were observed.

Conclusion

Preserving or modifying the native PTS during KA-TKA could be confidently undertaken without compromising functional outcomes or patient satisfaction.

Similar Midterm Outcomes of Total Knee Arthroplasties with Anterior and Posterior Tibial Slopes Performed on Paired Knees at a Minimum Follow-up of 5 Years

A small posterior tibial slope (PTS) is generally recommended in posterior stabilized (PS) total knee arthroplasty (TKA). An unwanted anterior tibial slope (ATS), which can affect postoperative results, may be created in PS TKA because of the inaccuracy of surgical instruments and techniques, as well as high interpatient variability. We compared midterm clinical and radiographic results of PS TKAs with ATS and PTS performed on paired knees using the same prosthesis. One-hundred-twenty-four patients who underwent TKAs with ATS and PTS on paired knees using ATTUNE posterior-stabilized prostheses were retrospectively reviewed after a minimum follow-up period of 5 years. The mean follow-up period was 5.4 years. The Knee Society Knee and Function scores, Western Ontario and McMaster Universities Osteoarthritis Index, Feller and Kujalar scores, and range of motion (ROM) were evaluated. The preferred TKA out of ATS and PTS was also investigated. The hip-knee-ankle angle, component positions, tibial slope, posterior femoral offset, Insall-Salvati ratio, and knee sagittal angle were measured by radiography. There were no significant differences in the clinical results, including ROM, between TKAs with ATS and PTS preoperatively and at the last follow-up. Regarding patient preference, 58 patients (46.8%) were satisfied with bilateral knees, 30 (24.2%) preferred knees with ATS, and 36 (29%) preferred knees with PTS. There was no significant difference in the rate of preference between TKAs with ATS and PTS (p = 0.539). Except for the postoperative tibial slope (-1.8 vs. 2.5 degrees, p < 0.001), there were also no significant differences in the radiographic results, including the knee sagittal angle, preoperatively and at the last follow-up. The midterm outcomes were similar between PS TKAs with ATS and PTS performed on paired knees at a minimum of 5 years of follow-up. Nonsevere ATS did not affect midterm outcomes in PS TKA with proper soft tissue balancing and the current prosthesis of improved design. However, a long-term follow-up study is required to confirm the safety of nonsevere ATS in PS TKA. LEVEL OF EVIDENCE::  III.