The influence of tibial tubercle–sparing slope-reducing osteotomy on patellar height in patients undergoing revision acl reconstruction

Background: A posterior tibial slope (PTS) >12° is an independent risk factor for anterior cruciate ligament (ACL) graft rupture, and a high tibial osteotomy (HTO) for slope correction can help avoid it. Management of patellar height is of major concern when performing HTO. Purpose: To evaluate the effect of tibial tubercle–sparing anterior closing-wedge osteotomy on patellar height in revision ACL reconstruction (ACLR). Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent arthroscopic revision ACLR combined with retro–tibial tubercle anterior closing-wedge HTO (ACW-HTO) between January 1, 2016, and March 31, 2021, were assessed for eligibility. Patellar height was measured on full weightbearing lateral radiographs according to the Insall-Salvati index (ISI) and Caton-Deschamps index (CDI) or frontal radiographs using the femoral patellar height index. The PTS was evaluated using the proximal anatomic axis of the tibia on standard short lateral radiographs. The delta (postoperative – preoperative) and the ratio (preoperative/postoperative) of the 3 patellar height indices and PTS were calculated. Preoperative and postoperative patellar heights were compared using independent t tests for each index. Also investigated was whether patients changed patellar height category (baja, normal, or alta) after slope osteotomy. Results: Among 475 revision ACLRs, 47 tibial tubercle–sparing ACW-HTOs were retained for analysis. No significant difference in patellar height was found between pre- and postoperative radiographs regardless of the index (preoperative – postoperative) (ISI: 1.0 ± 0.2 – 0.9 ± 0.2, P =.1729; CDI: 1.0 ± 0.2 – 1.0 ± 0.2, P =.4034; femoral patellar height index: 1.5 ± 0.2 – 1.5 ± 0.2; P =.5130). Fifteen patients (31.9%) exhibited a postoperative change in their patellar height category when measured by the ISI (6 moved up a category, 9 moved down one), and 18 patients (38.3%) changed category according to the CDI (10 moved up a category, 8 moved down one). No significant difference was found between pre- and postoperative patellar height among these patients (ISI: P =.2418; CDI: P =.3005). Conclusion: Changes in patellar height ratio are common after tibial tubercle–sparing ACW-HTO in patients undergoing revision ACLR. The clinical effect of these changes is unknown, and further study is needed to investigate whether they may result in patellofemoral symptoms.