Loss of Knee Extension Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Autograft.

Background: Primary anterior cruciate ligament reconstruction (ACLR) using quadriceps tendon (QT) autograft may increase the risk for postoperative loss of extension, although it is unclear if this is due to QT autograft diameter. Purpose: To document the rate of >5° loss of knee extension after QT autograft ACLR and determine associations between loss of extension, QT autograft diameter, and notch volume. Study Design: Case-control study; Level of evidence, 3. Methods: A retrospective review of a consecutive series of patients undergoing primary ACLR with QT autograft between January 2014 and December 2021 by 7 fellowship-trained orthopaedic surgeons at a single health care institution was performed. Patients with revision ACLR, multiligamentous knee surgery, concomitant cartilage procedures, <14 years of age, unavailable preoperative magnetic resonance imaging (MRI), or <6 months of follow-up were excluded. Loss of extension was defined using the International Knee Documentation Committee criteria for abnormal knee extension (>5° loss of extension compared with the contralateral knee) 3 to 12 months after ACLR, or any subsequent surgery for loss of extension. Patients who were unable to achieve terminal knee extension (defined as 0° of extension irrespective of the contralateral knee) were also identified and analyzed. Notch volume was measured by 2 observers using preoperative MRI scans, and a ratio of QT autograft diameter to notch volume was calculated. Univariate and multivariate analyses were performed to assess factors associated with postoperative loss of extension. Results: A total of 500 patients were identified, of whom 333 (67%) were included (mean age, 22.8 ± 7.7 years; 151 [45%] female). The mean follow-up was 1.6 ± 1.3 years (range, 0.5-9.5 years). The rate of postoperative loss of extension was 11% (n = 37), and 70% (26/37) of those with loss of extension underwent a subsequent surgery to restore extension (mean, 1.1 ± 1.2 years postoperatively). There was no difference in QT autograft diameter (9.5 mm vs 9.6 mm; Conclusion: Eleven percent of patients undergoing QT autograft ACLR experienced a loss of >5° knee extension compared with the contralateral knee or required additional surgery to restore extension. QT autograft diameter and notch volume were not associated with postoperative loss of extension among patients who underwent primary QT autograft ACLR. The inability to achieve terminal extension (0°) at the initial preoperative presentation increased the risk of postoperative loss of extension by 2.23-fold. Surgeons may consider the lack of terminal extension preoperatively as a risk factor for postoperative loss of extension following QT autograft ACLR rather than increased QT autograft diameter or decreased notch volume.