Poster 294: Patellar Tendon Insertion is Not Distalized following Tibial Tubercle Osteotomy with Distalization

Abstract

Objectives: Patella alta is a common anatomic risk factor in patients with patellofemoral instability and/or patellofemoral cartilage lesions, occurring in nearly 25% of these patients. Distalization tibial tubercle osteotomy (TTO) is effective in patients with patella alta in association with patellofemoral instability and cartilage lesions. Prior studies have suggested that increased patellar tendon length itself is a risk factor for recurrent patellofemoral instability, and have proposed the addition of a patellar tendon tenodesis via placement of a suture anchor proximal to the distalization TTO. However, concerns regarding increased patellofemoral cartilage stresses with addition of patellar tendon tenodesis have limited its adoption. The purpose of this study was to evaluate patellar tendon length and alignment parameters on preoperative and postoperative MRI and to evaluate patient reported outcomes (PROs) following distalization tibial tubercle osteotomy (TTO) without patellar tendon tenodesis in patients with patella alta. Methods: We conducted a retrospective review of 20 adult patients who underwent distalization TTO for patellar alta at our institution (December 2014-August 2021). All patients underwent preoperative and postoperative magnetic resonance (MR) imaging of the affected knee. Distalization TTO utilized a wedge-shaped osteotomy measuring ˜5cm in length and was fixed with two 4.5mm bicortical fully threaded screws following TT transfer. Caton-Deschamps (CDI), axial and sagittal TT-TG indices1, patellar tendon length and distances from tibial plateau to patellar tendon insertion and tibial tubercle were assessed (Figure 1). PROs included IKDC Subjective Knee Evaluation, KOOS Quality of Life Form, Kujala Anterior Knee Pain From, and Veterans RAND 12 Item Mental (VR12-MH) and Physical Health (VR12-PH) Surveys. Clinical data, including demographics, complication and perioperative data, was obtained from preoperative and postoperative charts in our electronic medical record. Results: Average age at time of surgery was 27.4 years (range: 14 – 42 years) and all patients were female. Average BMI was 24.9 +/- 4.4 kg/m2. Eleven patients (55%) were diagnosed with isolated patellofemoral cartilage lesions, four patients (20%) were diagnosed with patellofemoral instability without associated cartilage lesions and five patients (25%) were diagnosed with both instability and cartilage lesions. At the time of TTO distalization, eleven patients (55%) underwent matrix-induced autologous chondrocyte implantation (MACI), nine patients (45%) underwent MPFL reconstruction, four patients (20%) underwent lateral release/lengthening, and three patients (15%) underwent osteochondral allograft (OCA) implantation. Fourteen patients (70%) underwent anteromedialization of the tibial tubercle in addition to distalization. Radiographic parameters demonstrated improved patellar height (CDI decreased from 1.36 to 1.11 (p < 0.001), improved rotational alignment (axial TT-TG decreased from 14.3mm to 11.1mm (p = 0.018)) and anteriorization of the TT (sagittal TT-TG increased from -4.3mm to -1.4mm (p = 0.037)) following distalization TTO. Distance from the tibial plateau to the PT insertion decreased from 20.1mm preoperatively to 17.9mm postoperatively (p< 0.020) and patellar tendon length decreased from 53.4mm preoperatively to 50.0mm postoperative (p < 0.001). Average distalization was 6.4mm. IKDC scores increased from 37.1 to 60.5 (p = 0.011), KOOS QOL scores increased from 19.5 to 42.1 (p < 0.001), Kujala scores increased from 50.9 to 70.6 (p = 0.018), VR12-MH scores increased from 52.7 to 59.2 (p = 0.024) and VR12-PH scores increased from 35.1 to 41.7 (p = 0.009). Of the patients with preoperative patellofemoral instability, there were no cases of recurrent instability postoperatively. Ten patients (50%) underwent elective removal of hardware of TTO screws at an average of 10.7 months. There were four (20%) complications in this cohort, with two cases (10%) of postoperative arthrofibrosis requiring manipulation under anesthesia, one case (5%) of postoperative MRSA infection of the MPFL graft and one case (5%) of tibial tubercle delayed union requiring bone grafting and revision fixation. Conclusions: Distalization TTO without patellar tendon tenodesis is an effective surgical technique for improving patellar height in patients with patella alta and patellofemoral instability and/or patellofemoral cartilage lesions, with improvements in radiographic parameters and PROs postoperatively. There were no cases of recurrent instability in this cohort. The patellar tendon insertion does not appear to be significantly distalized following distalization TTO, likely related to scarring of the patellar tendon just proximal to the osteotomy site postoperatively. Given the complexity of risk factors associated with patellofemoral instability and patellofemoral cartilage lesions, distalization TTO provides an additional tool for patient-specific surgical management, without the need for patellar tendon tenodesis.