Radiographic Measurement of Anteriorization After Tibial Tubercle Osteotomy.

Abstract

Background: There is growing interest in sagittal plane malalignment as a risk factor for patellofemoral chondral wear and, correspondingly, as an important measure to correct when performing certain tibial tubercle osteotomy (TTO) procedures. However, a radiographic method to measure anteriorization after TTO has not been described.

Purpose: To develop and validate a radiographic method of measuring anteriorization after TTO.

Study design: Cross-sectional study (diagnosis); Level of evidence, 3.

Methods: Patients treated by 2 high-volume sports medicine surgeons at a single institution who underwent a TTO from 2015 to 2023 with available pre- and postoperative radiographic and magnetic resonance imaging (MRI) scans were identified. Approximately 10 mm and 0 mm of operative anteriorization were targeted for the anteromedializing and straight distalizing TTOs, respectively. Two methods to assess anteriorization after TTO on lateral knee radiographs were developed, using the preoperative to postoperative difference in distance between the anterior-most aspect of the tibial tubercle and either the center of the tibial shaft or the anterior tibial plateau. To validate the radiographic techniques, intraclass correlation coefficients (ICCs) were calculated between each method of radiographic measurement and the gold standard MRI measurement (preoperative to postoperative difference in sagittal tibial tubercle-trochlear groove distance).

Results: There were 70 patients (52 [74%] women) with a mean age of 31.5 ± 9.2 years. The mean anteriorization amount among the 57 anteriorizing TTOs was 4.9 ± 2.5 mm on the x-ray (XR) shaft technique, 4.6 ± 2.6 mm on the XR plateau technique, and 5.3 ± 2.7 mm on MRI (P = .35). The mean anteriorization amount among the 13 straight distalizing TTOs was 0.1 ± 2.5 mm on the XR shaft technique, -0.3 ± 2.2 mm on the XR plateau technique, and 0.6 ± 2.6 mm on MRI (P = .66). There was excellent agreement with MRI for both the XR shaft (ICC, 0.89) and XR plateau (ICC, 0.82) techniques. Interrater reliability was excellent for both techniques (ICC, 0.94-0.95).

Conclusion: Anteriorization after TTO can be measured using routine pre- and postoperative radiographs. Additionally, the amount of anteriorization achieved with modern anteromedializing TTO techniques was less than that traditionally targeted. Moving forward, surgeons can assess the amount of anteriorization achieved during TTO on standard radiographs, while researchers may investigate the potential role of anteriorization on postoperative outcomes.