Change of the cross-sectional area of vastus medialis oblique in patients with recurrent patellar dislocation treated by tibial tubercle transfer combined with medial patellofemoral ligament reconstruction on axial CT

PURPOSE: To investigate the change of the cross-sectional area (CSA) of vastus medialis oblique (VMO) in patients with recurrent patellar dislocation (RPD) treated by tibial tubercle transfer combined with medial patellofemoral ligament (MPFL) reconstruction by imaging methods, and to guide clinical treatment and rehabilitation. METHODS: From October 2015 to March 2022, 23 patients with RPD who underwent tibial tubercle transfer combined with MPFL reconstruction were retrospectively enrolled. All patients were assessed by CT in the supine position with the knee fully extended and the quadriceps relaxed. The CSA of VMO and the ratio of CSA of VMO to body weight (CSA/BW) were measured at the upper pole of the patella, 5 mm above the upper pole of the patella and 5 mm below the upper pole of patella. The differences of measured parameters were compared before surgery and at follow-up, including CSA of VMO and CSA/BW. Test level α = 0.05. RESULTS: The tibial tubercle-trochlear groove (TT-TG) distance was significantly reduced at follow-up compared with that before surgery (27.91 ± 1.95 mm vs 12.33 ± 1.07 mm, P < 0.001). The CSA of VMO was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (473.06 ± 106.32 mm(2) vs 562.97 ± 157.90 mm(2), P < 0.001), at the upper pole of the patella (641.23 ± 188.45 mm(2) vs 700.23 ± 177.55 mm(2), P = 0.029), and at 5 mm above the upper pole of the patella (788.25 ± 238.62 mm(2) vs 849.79 ± 180.84 mm(2), P = 0.018). The CSA/BW was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (7.83 ± 2.52 mm(2)/kg vs 9.22 ± 3.54 mm(2)/kg, P < 0.001), at the upper pole of the patella (10.48 ± 3.62 mm(2)/kg vs 11.42 ± 4.14 mm(2)/kg, P = 0.020), and at 5 mm above the upper pole of the patella (12.86 ± 4.65 mm(2)/kg vs 13.68 ± 3.86 mm(2)/kg, P = 0.017). CONCLUSION: After tibial tubercle transfer combined with MPFL reconstruction, CSA of VMO increased in patients with RPD, which will help to enhance patellar stability and reduce recurrence.