Objective: Achieving optimal mechanical alignment and precise component positioning is critical for the success of total knee arthroplasty (TKA). It is also essential to consider the orientation of the joint line, particularly in relation to the ground, in the postoperative period. This study aimed to evaluate the postoperative knee joint line orientation in patients with severe preoperative varus deformities compared to those with mild to moderate deformities.
Materials and Methods: This retrospective study included 60 knees from 59 patients, divided into two groups: 30 knees with mild to moderate varus deformities (mechanical axis deviations <20°, Group 1) and 30 knees with severe varus deformities (mechanical axis deviations ≥20°, Group 2). A comparison was made between the preoperative and postoperative radiographs to analyze the mechanical axes, femoral and tibial component positioning, and joint line orientation in relation to the ground.
Results: The preoperative mean mechanical axis deviations were 11.13°±4.07° in Group 1 and 22.60°±2.24° in Group 2. While femoral and tibial component positioning did not significantly differ between the groups, joint line orientation relative to the floor showed significant differences. The mean tibial component inclination was 4.73°±2.58° in Group 2, compared to 3.07°±1.77° in Group 1 (p=0.005). Similarly, the mean femoral component inclination was 5.24°±2.36° in Group 2 and 3.69°±1.87° in Group 1 (p=0.007). In knees with severe varus deformities, joint line obliquity was significantly greater postoperatively.
Conclusion: Routine instrumentation for TKA is less reliable in severely deformed knees due to soft tissue contractures and the need for extensive release procedures. Severe varus deformities result in the inclination of components being more lateral and an increased obliquity of the joint line following mechanically aligned TKA. Further research is necessary to determine the long-term impact of this lateral inclination on prosthesis survival and clinical outcomes.