Correlation between tibial tubercle-trochlear groove and 3D shiftactive extension in patellar dislocation: An active extension analysis based on three-dimensional measurements.

PURPOSE: To investigate the correlation between 3D shiftactive extension (lateral patellar shift in active extension position based on newly established 3D measurement method) and static tibial tubercle-trochlear groove (TT-TG) distance in full knee extension with muscle relaxation.

METHODS

42 knees of 24 patients with recurrent patellar dislocation were included in the study group and 38 knees of 30 subjects were included in the control group. TT-TG distance, bisect offset indexmuscle relaxation, bisect offset indexactive extension and 3D shiftactive extension were measured to investigate the correlation between patellar lateral shift measurements and TT-TG distance.

RESULTS

In the recurrent patellar dislocation group, the correlation between TT-TG distance and 3D shiftactive extension (r = 0.76 [95 % CI, 0.61 to 0.86]) was significantly higher than correlation between TT-TG distance and bisect offset indexactive extension (r = 0.61 [95 % CI, 0.32 to 0.79]) and correlation between TT-TG distance and bisect offset indexmuscle relaxation (r = 0.6 [95 % CI, 0.32 to 0.80]), with p = 0.01 and p = 0.03, respectively.

CONCLUSION

Significantly stronger correlation between TT-TG distance and 3D shiftactive extension in patients with patellar dislocation was observed in this study. 3D shiftactive extension could be considered as a preoperative evaluation for tibial tubercle osteotomy to both characterize the patellar lateral shift and estimate tibial tubercle lateralization to simplify the preoperative assessment procedures. The 3D shiftactive extension obtained under muscle contraction conditions both simulated the functional state of the patellofemoral joint and improved the limitations of the 2D measurements, helping to improve surgical decision-making for functional rehabilitation.

LEVEL OF EVIDENCE: Level III.