ACL Reconstruction with Quadriceps Tendon Autograft

Indication. Symptomatic ACL insufficiency with documented instability on pivot-shift or Lachman testing — acute or chronic, having failed non-operative management with recurrent giving-way during pivoting or cutting, or with a concomitant repairable meniscal tear or chondral injury that needs a stable knee to succeed. High-demand athletes and occupational groups needing rotational stability (military, police, firefighter) are also offered reconstruction. Absolute indications

• Acute or chronic ACL insufficiency with documented instability on pivot-shift or Lachman testing
• Failed non-operative management with recurrent giving-way during pivoting or cutting activities
• Concomitant repairable meniscal tear or chondral injury requiring stabilisation for a successful outcome
• High-demand athlete or occupational requirement for rotational stability Relative indications
• Revision ACL reconstruction when hamstring or patellar tendon grafts were previously used or are unavailable
• Skeletally immature patients with significant growth remaining (quadriceps tendon avoids the physeal violation concerns associated with bone blocks)
• Patients with patellar tendinopathy, previous patellar tendon harvest, or anterior knee pain that bone-patellar-tendon-bone would exacerbate
• Large patients (greater than 100 kg) or those with a wide intercondylar notch requiring a robust graft cross-section The graft-choice decision. The quadriceps tendon is preferred in revision, skeletally immature and patellar-tendon-pathology settings, and in high-demand athletes who kneel — the graft chosen shapes donor morbidity far more than it shapes long-term stability.

Contraindications. Absolute: active knee infection or septic arthritis; severe osteoarthritis with joint-space narrowing greater than 50 percent or Kellgren-Lawrence grade 4 changes; fixed varus or valgus malalignment greater than 10 degrees requiring osteotomy first. Relative: poor quadriceps strength or neuromuscular control (optimise with prehabilitation); inability to comply with the rehabilitation protocol; a low-demand patient with minimal functional instability manageable with bracing and activity modification. Consent specifically for anterior knee discomfort, harvest-site quadriceps weakness (5-10 percent still present at 6 months), patellar fracture if a bone block is taken (0.5-1.5 percent), residual laxity or graft failure (2-6 percent primary), stiffness and cyclops lesion, infection (less than 1 percent), and the 9-12 month return-to-sport timeline with criteria-based clearance. Setup. Supine on a radiolucent table with 0-130 degrees of knee flexion achievable; a lateral post or leg holder allows valgus stress for the medial compartment. General or spinal anaesthesia with a single-shot adductor canal block (preferred over a femoral block to preserve quadriceps motor function for early mobilisation). Examine under anaesthesia — confirm Lachman and pivot-shift grade, side-to-side difference with KT-1000 or Rolimeter, and any meniscal or collateral pathology, comparing with the contralateral knee. Equipment: 30-degree and 70-degree arthroscopes, an ACL guide system with offset femoral aimer, 4.5 mm and 7-10 mm cannulated reamers, a suspensory fixation device (Endobutton, TightRope or similar), interference screws (7-9 mm), and an oscillating saw or osteotome for the bone block.

The goal is an anatomic single-bundle reconstruction: harvest a robust central quadriceps tendon graft, recreate the femoral and tibial footprints through independent anatomic tunnels, tension and fix the graft without impingement, and restore rotational stability. The exposure is the graft-harvest incision above the patella and the standard arthroscopy portals — both are laid out as the opening steps below.

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Rehabilitation | Phase | Timing | Immobilisation & weight-bearing | Therapy focus & goal | |-------|--------|--------------------------------|----------------------| | 1 | 0-2 weeks | Brace locked in extension 2-3 weeks (longer if bone block harvested); weight-bearing as tolerated with crutches | Quadriceps sets, straight-leg raises, ankle pumps, patellar mobilisation, cryotherapy. Goal: full extension, 90 degrees flexion, independent straight-leg raise | | 2 | 3-8 weeks | Brace progressively unlocked; transition to functional brace at 4-6 weeks | Progressive open- and closed-chain strengthening; stationary bike, elliptical, swimming once healed; NMES if activation poor. Goal: greater than 80 percent quadriceps symmetry, full painless ROM | | 3 | 9-16 weeks | Brace weaned | Single-leg strengthening, perturbation and balance training; plyometrics from 12-16 weeks. Goal: greater than 85 percent quadriceps symmetry, hop test greater than 85 percent | | 4 | 5-9+ months | None | Sport-specific agility, cutting and pivoting drills; ACL-RSI assessment. Goal: greater than 90 percent quadriceps and hop symmetry; return to pivoting sport at 9-12 months | Return-to-sport criteria (evidence-based)

• Quadriceps strength symmetry greater than 90 percent (isokinetic testing at 60 and 180 degrees per second)
• Single-leg hop test symmetry greater than 90 percent (single, triple, crossover, timed)
• Y-balance or star excursion balance test within 4 cm of the contralateral limb
• ACL Return to Sport after Injury (ACL-RSI) score greater than 65
• Completion of sport-specific training without apprehension
• Surgeon and physical therapist clearance Complications

Graft properties and biomechanics. The quadriceps tendon is a trilaminar structure (superficial rectus femoris, middle vastus lateralis and medialis, deep vastus intermedius) whose central third can be harvested without compromising the extensor mechanism when closed properly. Its cross-sectional area averages 90-110 mm2 versus 35-50 mm2 for four-strand hamstring and 45-60 mm2 for bone-patellar-tendon-bone, and its ultimate tensile strength exceeds 2000 N — comparable to the native ACL and superior to doubled hamstring in most cadaveric studies. Donor-site morbidity is lower than bone-patellar-tendon-bone: anterior knee pain at two years is reported in 5-15 percent versus 20-40 percent for patellar tendon, and harvest-site quadriceps weakness is transient, with isokinetic testing returning to greater than 90 percent symmetry by 6-9 months with structured rehabilitation. Comparative outcomes. Systematic reviews demonstrate equivalent or superior patient-reported outcomes (IKDC, Lysholm, KOOS) compared with hamstring and patellar tendon autografts at 2-5 year follow-up. Graft failure rates in primary reconstruction range from 2-6 percent at two years — comparable to other autografts — with lower revision rates in some high-risk series. Return-to-sport rates exceed 80 percent at 9-12 months when objective criteria (strength symmetry, hop testing, psychological readiness) rather than time alone guide clearance. Surgical anatomy (reference). The ACL femoral footprint lies on the medial wall of the lateral femoral condyle; the lateral intercondylar ridge (resident's ridge) defines the posterior limit of the footprint and the bifurcate ridge separates the anteromedial and posterolateral bundle footprints. The anatomic centre sits approximately 6-8 mm anterior to the posterior wall and 2-3 mm proximal to the inferior articular margin — placement posterior to the ridge risks posterior wall blowout, and anterior placement causes rotational instability. The tibial footprint lies in the centre of the intercondylar eminence just anterior and medial to the PCL insertion; the anterior horn of the lateral meniscus is the key landmark, the centre lying 1-2 mm posterior to it and the anterior edge approximately 7-10 mm anterior to the PCL. A tibial tunnel placed too anterior impinges in extension and one too posterior causes rotational laxity. A notch width index less than 0.2 is associated with increased ACL injury risk; notchplasty of 2-4 mm from the roof and lateral wall is performed when the intercondylar notch is stenotic (less than 12 mm) or osteophytes are present.