Dynamic Computed Tomography Evaluation of Patellar Tracking Following Unrestricted Kinematic Versus Mechanical Alignment in Primary Total Knee Arthroplasty: A Prospective Comparative Study.

INTRODUCTION

Restoration of physiological knee kinematics has become an important objective in total knee arthroplasty (TKA). Unrestricted kinematic alignment (KA) has been proposed as an alternative to conventional mechanical alignment (MA) to better reproduce native knee anatomy and improve patellofemoral biomechanics. This study compared post-operative patellar tracking and clinical outcomes between unrestricted KA and standard MA using dynamic computed tomography (CT).

MATERIALS AND

METHODS

A prospective comparative study was conducted among 50 patients with primary end-stage knee osteoarthritis undergoing primary TKA at a tertiary care teaching hospital. Patients were equally allocated into unrestricted KA (n = 25) and MA (n = 25) groups. Dynamic CT was performed postoperatively to assess patellar tracking, patellar tilt, and patellar translation. Functional outcomes were evaluated using Knee Society Score (KSS), functional KSS, post-operative range of motion (ROM), anterior knee pain, and complications. Statistical analysis was performed using the Statistical Package for the Social Sciences version 26.0, with P < 0.05 considered statistically significant.

RESULTS

Baseline demographic and clinical characteristics were comparable between the groups (P > 0.05). Normal patellar tracking was significantly more frequent in the KA group than the MA group (92.0% vs. 72.0%; P = 0.043). Mean patellar tilt (5.1 ± 2.0° vs. 8.4 ± 2.8°; P < 0.001) and patellar translation (2.8 ± 1.1 mm vs. 4.5 ± 1.6 mm; P < 0.001) were significantly lower following KA. Patients undergoing KA achieved significantly higher post-operative KSS (90.6 ± 5.4 vs. 84.8 ± 6.3; P = 0.001), functional KSS (88.7 ± 6.1 vs. 82.9 ± 6.8; P = 0.002), and ROM (122.6 ± 8.5° vs. 115.3 ± 9.6°; P = 0.007). Anterior knee pain was significantly less frequent in the KA group (24.0% vs. 52.0%; P = 0.038), whereas post-operative complications were comparable between groups (P = 0.293).

CONCLUSION

Unrestricted KA provides superior patellofemoral biomechanics, improved functional outcomes, and reduced anterior knee pain compared with standard MA without increasing post-operative complications. Dynamic CT is a valuable modality for objectively assessing post-operative patellar kinematics following TKA.