Correlation of Tibial Torsion With Lower Limb Alignment and Femoral Anteversion in Patients With Patellar Instability

BACKGROUND: Alignment and rotation of the lower extremities have been suggested to be predisposing pathologic factors for patellar instability. PURPOSE: To elucidate the relationship between the lower limb alignment and lower extremity rotation in patients with patellar instability. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Included were 83 patients with patellar instability. Computed tomography scans and standing full-leg radiographs were used to measure the tibial tuberosity–trochlear groove (TT-TG) distance, mechanical femorotibial angle (mFTA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), femoral torsion, and tibial torsion of the different segments. The relationships between femoral torsion, tibial torsion of the different segments, and the mFTA, mLDFA, and mMPTA were evaluated. The levels of tibial torsion and femoral torsion in patients with varus, normal, or valgus alignment were compared with 1-way analysis of variance and chi-square test. RESULTS: The total tibial torsion was significantly associated with total femoral anteversion (r = 0.329; P = .002) and mFTA (r = –0.304; P = .005). There were no significant correlations between mFTA and TT-TG distance or femoral anteversion. Compared with patients with valgus malalignment, patients with varus malalignment tended to have higher tibial torsion. CONCLUSION: Tibial torsion was associated with leg axis alignment and femoral anteversion in patients with patellar instability. Patients with patellar instability, especially those with concurrent leg axis deformities, should undergo further radiological imaging so that tibial torsion can be assessed and a diagnosis of torsion deformity made early in the treatment pathway and the proper surgical plan formulated.