Clinical and Radiological Outcomes of Revision Anterior Cruciate Ligament Reconstruction Using a Quadriceps Tendon Autograft with a Bone Block: A Single-Center Case Series

<i>Background and Objectives:</i> Revision anterior cruciate ligament reconstruction (ACLR) is demanding and yields inferior outcomes compared with primary procedures. The quadriceps tendon (QT) autograft with bone block has biomechanical and biological advantages though clinical evidence in revision remains limited. This study evaluated the clinical and radiological outcomes of revision ACLR using bone-block QT autograft in young, active patients. <i>Materials and Methods:</i> A case series with a level of evidence of 4. Thirty-four patients (28 men, 6 women; mean age, 27.2 ± 5.8 years) who underwent revision ACLR with a bone-block QT autograft between 2021 and 2023 were retrospectively reviewed. The mean follow-up was 37.4 ± 3.2 months. Clinical assessments included the Lysholm, International Knee Documentation Committee (IKDC) subjective, and Tegner activity scores, along with isokinetic strength testing. Objective stability was evaluated using pivot shift grading and Telos stress radiography. Radiological analyses included 3D computed tomography for tunnel positioning and magnetic resonance imaging for tunnel widening. Perioperative and postoperative complications were recorded. <i>Results</i>: All clinical outcomes improved significantly from baseline to 2-year follow-up: Lysholm (62.7 ± 9.6 to 87.1 ± 10.3), IKDC (59.0 ± 10.8 to 79.5 ± 11.1), and Tegner (3.5 ± 1.2 to 5.6 ± 1.3; all <i>p</i> < 0.001). However, the Tegner score remained lower than the pre-injury level (6.1 ± 1.4; <i>p</i> = 0.035). At the final follow-up, 91.2% of the patients had returned to sports, with 59% resuming sports at their pre-injury level or higher. Side-to-side anterior laxity decreased from 8.5 ± 1.7 mm to 1.4 ± 1.1 mm on Telos stress radiography (<i>p</i> < 0.001). Preoperatively, 82% of patients demonstrated high grade pivot shift (≥grade 2), which improved to 91% graded as negative or grade 1 at final follow-up (<i>p</i> < 0.001). Isokinetic evaluation showed improvements in quadriceps (28.7% ± 12.5% to 12.4% ± 8.1%) and hamstring (18.3% ± 9.7% to 8.9% ± 6.5%) deficit (both <i>p</i> < 0.001). MRI demonstrated minimal tunnel widening (tibia, +1.3 ± 0.9 mm, <i>p</i> = 0.012; femur, +0.3 ± 0.6 mm, <i>p</i> = 0.148). Three complications (8.8%) were observed: one cyclops lesion, one transient extension deficit, and one graft rupture. No patellar fractures, septic arthritis, or revision procedures occurred during the follow-up period. <i>Conclusions</i>: Bone-block QT autografts provide a reliable option for revision ACLR, yielding functional improvement, restored stability, and minimal donor-site morbidity, with low complications. These findings support their consideration as the preferred graft choice for young active patients needing revision reconstruction.