The effect of distal tibial tuberosity high tibial osteotomy on postoperative patellar height and patellofemoral joint degeneration

Background Distal tibial tuberosity high tibial osteotomy (DTT-HTO) can prevent distalization of the tibial tuberosity and thus patellar infera. However, no studies on the clinical and radiological effects of DTT-HTO on the patellofemoral joint have been conducted. The purpose of the study was to evaluate the effect of DTT-HTO on patella height and patellofemoral joint congruity based on the severity of patellofemoral joint OA. Methods Twenty-nine patients (33 knees) who underwent DTT-HTO and second-look arthroscopy when implant was removed between January 2018 and May 2020 were eligible for the study. Among them, 6 were males, and 23 were females, with ages from 51 to 78 years old. The Caton-Deschamps index (CDI), congruence angle (CA), and lateral patellar tilt (LPT) were measured to evaluate the effect of surgery on patellar height and patellofemoral joint congruity. The weight-bearing line ratio (WBLR) was measured to assess lower limb alignment. The cartilage lesion in the patellofemoral joint was assessed arthroscopically during surgery and implant removal by the International Cartilage Repair Society (ICRS) grading system at 18-24 months after surgery. The Hospital for Special Surgery (HSS) scale was used to evaluate knee joint function. Results Twenty-nine patients were followed up for 18-28 months. The preoperative CDI, CA, and LPT changed from 0.92 +/- 0.16 to 0.89 +/- 0.14, from 5.52 +/- 2.19 to 5.44 +/- 2.27, and from 6.95 +/- 2.88 to 6.54 +/- 2.42, respectively, and the differences were not statistically significant (p> 0.05). The preoperative WBLR significantly increased from 16.72 +/- 6.77 to 58.77 +/- 7.69% (p< 0.001). The cartilage lesions in the patella and femoral trochlea did not progress significantly from the first- to the second-look arthroscopy, according to the ICRS grades (p> 0.05). The HSS score significantly improved from 50.64 +/- 19.18 preoperatively to 67.33 +/- 14.72, 81.63 +/- 11.92, and 82.73 +/- 8.05 at the 3-month, 12-month, and last follow-up after surgery (p< 0.001). Conclusion DTT-HTO can effectively prevent patellar infera, and its effects on postoperative patellofemoral joint congruity and patellofemoral joint OA progression are inconspicuous. It can be recommended as a treatment of varus knee combined with patellar infera or patellofemoral joint OA.