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Associations between TT-TG distance and rotational and coronal alignment in recurrent patellar dislocation
Liang Ma1, Qingyu Li1, Jiacheng Wei1
1Department of Orthopaedic Surgery, Hebei Medical University Third Hospital, Shijiazhuang, Hebei, 050051, China.
Purpose:
To evaluate the relationship between TT-TG distance and lower-limb anatomical parameters in recurrent patellar dislocation.
Methods:
Weight-bearing long-leg radiographs and knee CT scans of 99 patients with recurrent patellar dislocation were reviewed. Trochlear dysplasia was classified according to the Dejour version 2 classification. Tibial tubercle-trochlear groove (TT-TG) distance was measured together with coronal alignment (mFTA and related angles) and rotational alignment (tibiofemoral rotation and tibial torsion). Patients were stratified by TT-TG distance and mFTA-based alignment. Pearson correlations examined associations among anatomical parameters. In the TT-TG ≥ 20 mm group, multivariable regression explored factors potentially associated with TT-TG distance.
Results:
Most patients had trochlear dysplasia, and a high proportion were classified as Dejour type C or D (71/99, 71.7%). Overall, TT-TG distance was significantly positively correlated with TFR (r = 0.504, P < 0.001). TFR was significantly higher in the TT-TG ≥ 20 mm group than in the TT-TG < 20 mm group (11.05° ± 4.06° vs. 6.68° ± 4.85°, P < 0.001). In the TT-TG < 20 mm group, TT-TG distance was positively correlated with TFR (r = 0.422, P = 0.003) and tibial torsion (TT) (r = 0.320, P = 0.027). In contrast, in the TT-TG ≥ 20 mm group, TT-TG showed no significant correlations with the assessed anatomical parameters; however, TFR was negatively correlated with TGM (r = - 0.328, P = 0.019). Stratified analysis showed significant correlations between TFR and TT-TG distance in valgus (r = 0.676, P = 0.003) and neutral (r = 0.441, P < 0.001) alignment groups, but not in the varus group.
Conclusion:
In patients with recurrent patellar dislocation, TT-TG distance was positively associated with tibiofemoral rotation but not with coronal lower-limb alignment. This association was more evident in patients with TT-TG < 20 mm and was attenuated in those with TT-TG ≥ 20 mm. These findings suggest that TT-TG distance should be interpreted together with rotational alignment and trochlear morphology when planning individualized treatment.
