Three-dimensional lateral tilt can be a good assessment of lateral patellar maltracking.

PURPOSE: To investigate the correlation between patellar tilt and shift based on 4D-CT scans, and compare the value of 2D and 3D parameters in evaluating lateral patellar maltracking in patients with patella dislocation.

METHODS

Bisect offse index, lateral patellar tilt, 3D shift and 3D tilt were evaluated in 42 knees of patella dislocation patients and 42 knees of controls. 3D shift was defined as shift of the center of gravity of the patella relative to the origin in the X-axis direction. 3D tilt was defined as the spatial angle between the horizontal axis of the patella and the X0Z plane.

RESULTS

The trends of 3D shift, 3D tilt, bisect offse index, and lateral patellar tilt with knee flexion angle were different between the two groups (all p < 0.001). When the knee was fully extended and flexed at 30°, 45°, and 60°, the 3D tilt and lateral patellar tilt in the patella dislocation group was significantly higher than that in the control group (All p < 0.001 for 3D tilt/ p < 0.001, p = 0.002, p = 0.005, and p < 0.001 for lateral patellar tilt, respectively).3D shift was strong correlated with 3D tilt (r = 0.722, p < 0.001); bisect offse index was moderately correlated with lateral patellar tilt (r = 0.697, p < 0.001). The AUC values for 3D shift and 3D tilt at all different flexion angles were 0.931 and 0.955, respectively. The AUC values of bisect offse index and lateral patellar tilt at all different flexion angles were 0.964 and 0.971, respectively.

CONCLUSION

When assessing the axial alignment of the patellofemoral joint, it may not be necessary to use both 3D shift and 3D tilt of the patella simultaneously. This could allow surgeons to describe patellar alignment more simply and streamline the preoperative evaluation process. Clinicians should focus on patellar tilt and shift in the full extension during dynamic examination.

LEVEL OF EVIDENCE: Level III.