Effectiveness of proximal tibial tubercle transfer in patients with patella baja after total knee arthroplasty

Purpose Patella baja after total knee arthroplasty (TKA) is a common problem that is usually treated via proximal transfer of the tibial tubercle. As the long-term outcomes of this procedure are unclarified, this study aimed to investigate the changes in clinical function and radiographic patellar height during five years of follow-up. Methods Sixty patients with patella baja after TKA who underwent proximalisation of the tibial tubercle were followed up for a mean of 71 months (range 21-153 months). The pre- and postoperative range of motion (ROM) and clinical scores (Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)) were compared. The radiographic patellar height was measured with the Caton-Deschamps index (CDI), Blackburne-Peel ratio (BP), and modified Insall-Salvati index (MIS). Results Proximalisation of the tibial tubercle resulted in a significant improvement in the ROM from 80 degrees to 88 degrees. The KSS and WOMAC did not improve or even worsened after the intervention. The radiographic patellar height immediately after tibial tubercle transfer was not better than prior to the intervention (CDI 0.72 vs. 0.63, p = 0.72; BP 0.66 vs. 0.61, p = 0.72; MIS 1.59 vs. 1.55, p = 1.00) and further decreased significantly so that the mean final values were worse than the values in the native joint (CDI 0.59 vs. 0.78, p = 0.001; BP 0.58 vs. 0.74, p = 0.001; MIS 1.39 vs. 1.81, p < 0.001). Conclusion Proximalisation of the tibial tubercle in patients with patella baja after TKA does neither lead to significant improvements in the clinical outcome nor in the radiographic patellar height during long-term follow-up.