Summary
The KA technique resulted in a significantly shorter operation time and better overall functional outcome than the MA technique, even though the femoral component was placed slightly more valgus and the tibial component slightly more varus relative to the mechanical axis with the KA technique.
Abstract
Background
Although many studies have reported the clinical and radiographic outcomes of patients who underwent primary total knee arthroplasty (TKA) with one of the two techniques, few comparative studies exist, and no systematic reviews or meta-analyses have been published.
Questions/purposes: This meta-analysis compared clinical and radiographic outcomes and complications of kinematic alignment (KA) and mechanical alignment (MA) techniques in primary TKA.
Methods
All studies comparing the operation time, change in hemoglobin, length of hospital stay, postoperative complications, and clinical and radiographic outcomes as assessed with various measurement tools, from direct interview to imaging methods, in patients who underwent primary TKA through the KA or MA technique were included.
Results
Six studies were included in the meta-analysis. The proportion of patients who developed postoperative complications (OR 1.10, 95% CI: 0.49 to 2.46; P=0.69) did not differ significantly between the KA and MA techniques. The two groups were also similar in terms of change in hemoglobin (95% CI: -0.38 to 0.34; P=0.91), length of hospital stay (95% CI: -0.04 to 0.55; P=0.10), hip-knee-ankle angle (95% CI: -1.76 to 0.75; P=0.43), joint line orientation angle (95% CI: -4.27 to 4.23; P=0.99), tibial component slope (95% CI: -0.53 to 3.56; P=0.15), and femoral component flexion (95% CI: -2.61 to 7.57; P=0.34). In contrast, operation time (95% CI: -27.16 to -3.71; P=0.01), overall functional outcome (95% CI: 6.59 to 11.51; P<0.0001), knee anatomical axis (95% CI: -1.38 to -0.01; P=0.05), femoral component relative to the mechanical axis (95% CI: -2.47 to -1.40; P<0.0001), and tibial component relative to the mechanical axis (95% CI: 1.56 to 2.95; P<0.0001) were significantly different between the two groups.
Conclusion
There were no significant differences in postoperative complications, change in hemoglobin, length of hospital stay, hip-knee-ankle angle, joint line orientation angle, tibial component slope, or femoral component flexion between the KA and MA techniques for primary TKA. However, the KA technique resulted in a significantly shorter operation time and better overall functional outcome than the MA technique, even though the femoral component was placed slightly more valgus and the tibial component slightly more varus relative to the mechanical axis with the KA technique.