ACL Reconstruction with Quadriceps Tendon Autograft

Surgical Indications

Absolute Indications

• Acute or chronic ACL insufficiency with documented instability on pivot-shift or Lachman testing
• Failed non-operative management with recurrent giving-way episodes during pivoting or cutting activities
• Concomitant repairable meniscal tear or chondral injury requiring stabilisation for successful outcome
• High-demand athlete or occupational requirement for rotational stability (military, police, firefighter)

Relative Indications

• Revision ACL reconstruction when hamstring or patellar tendon grafts previously used or unavailable
• Skeletally immature patients with significant growth remaining (quadriceps tendon avoids physeal violation concerns associated with bone blocks)
• Patients with patellar tendinopathy, previous patellar tendon harvest, or anterior knee pain that would be exacerbated by bone-patellar-tendon-bone graft
• Large patients (greater than 100 kg) or those with wide intercondylar notch requiring a robust graft cross-section

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 preoperatively (optimise with prehabilitation)
• Inability to comply with postoperative rehabilitation protocol
• Low-demand patient with minimal functional instability who can be managed with bracing and activity modification

Evidence for Quadriceps Tendon Graft

Graft Properties and Biomechanics

• Quadriceps tendon cross-sectional area averages 90-110 mm2 versus 35-50 mm2 for four-strand hamstring and 45-60 mm2 for bone-patellar-tendon-bone
• Ultimate tensile strength exceeds 2000 N, comparable to native ACL and superior to doubled hamstring in most cadaveric studies
• Lower donor-site morbidity than bone-patellar-tendon-bone: anterior knee pain at 2 years reported in 5-15 percent versus 20-40 percent for patellar tendon
• Harvest-site quadriceps weakness is transient in most patients; isokinetic testing shows return 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 2 years, comparable to other autografts; revision rates are lower in some series when used in high-risk populations
• Return-to-sport rates exceed 80 percent at 9-12 months when objective criteria (strength symmetry, hop testing, psychological readiness) are used rather than time-based clearance

Quadriceps Tendon Anatomy Relevant to Harvest

Layers and Composition

The quadriceps tendon is a trilaminar structure formed by the convergence of the rectus femoris, vastus intermedius, vastus lateralis and vastus medialis aponeuroses. The superficial layer is rectus femoris, the middle layer is vastus lateralis and medialis, and the deep layer is vastus intermedius. A central 8-10 mm strip can be harvested without compromising extensor mechanism integrity when closed properly.

Safe Harvest Dimensions

• Width: 8-10 mm (central third) preserves adequate tendon on medial and lateral sides
• Length: 60-80 mm from superior patellar pole proximally provides sufficient intra-articular and tunnel length
• Thickness: full-thickness harvest of the central third is safe; partial-thickness harvest is an alternative but provides less robust graft
• Bone block option: 15-20 mm long by 8-10 mm wide by 8 mm deep trapezoidal block from the superior patella provides excellent tibial aperture fixation

Structures at Risk During Harvest

• Suprapatellar pouch: lies immediately deep to the tendon; inadvertent penetration allows fluid extravasation and potential infection risk
• Articular cartilage of the patella: protect during bone block harvest by using an oscillating saw with depth stop or osteotome under direct vision
• Medial and lateral vastus expansions: maintain at least 5 mm of tendon on each side of the harvest site

Knee Arthroscopic Anatomy for ACL Reconstruction

Femoral Footprint

• The ACL femoral footprint is located on the medial wall of the lateral femoral condyle
• Lateral intercondylar ridge (resident's ridge) is the key osseous landmark defining the posterior limit of the footprint
• Bifurcate ridge separates the anteromedial and posterolateral bundle footprints
• Anatomic centre is approximately 6-8 mm anterior to the posterior wall and 2-3 mm proximal to the inferior articular margin
• Tunnel placement posterior to the ridge risks posterior wall blowout; placement anterior to the ridge causes rotational instability

Tibial Footprint

• The ACL tibial footprint is located in the centre of the intercondylar eminence, just anterior and medial to the PCL insertion
• The anterior horn of the lateral meniscus provides a reliable landmark; the centre of the footprint lies 1-2 mm posterior to this structure
• The medial tibial spine and the PCL are posterior boundaries; the anterior edge of the footprint is approximately 7-10 mm anterior to the PCL
• A tibial tunnel placed too anterior causes impingement in extension; too posterior causes rotational laxity

Intercondylar Notch

• Notch width index (NWI) less than 0.2 is associated with increased ACL injury risk and may require notchplasty
• Roof angle and lateral wall osteophytes must be addressed to prevent graft impingement
• Notchplasty of 2-4 mm from the roof and lateral wall is performed when the notch is stenotic or when osteophytes are present

Positioning and Preparation

Patient position: Supine on radiolucent table with knee flexion of 0-130 degrees achievable. A lateral post or leg holder is used to allow valgus stress for medial compartment visualisation. The foot is placed in a well-padded holder or the leg is allowed to hang free. A tourniquet is applied to the proximal thigh but inflated only if needed for visualisation.

Anaesthesia: General or spinal anaesthesia with regional block (adductor canal or femoral nerve block) for postoperative analgesia. Preoperative single-shot adductor canal block is preferred to preserve quadriceps motor function for early mobilisation.

Examination under anaesthesia: Confirm Lachman grade, pivot-shift grade, side-to-side difference with KT-1000 or Rolimeter, and assess for concomitant meniscal or collateral ligament pathology. Compare with contralateral knee.

Equipment: 30-degree and 70-degree arthroscopes, ACL guide system with offset femoral aimer, tibial guide, 4.5 mm and 7-10 mm cannulated reamers, suspensory fixation device (Endobutton, TightRope, or similar), interference screws (bioabsorbable or titanium, 7-9 mm diameter), oscillating saw or osteotome for bone block harvest, tendon stripper or scalpel for soft-tissue harvest.

Quadriceps Tendon Graft Harvest

Step 1: Incision and Exposure

Make a 3-4 cm longitudinal midline incision centred 2-3 cm proximal to the superior pole of the patella. Incise skin and subcutaneous tissue. Identify and split the paratenon longitudinally. Expose the rectus femoris fascia and incise it in the midline to expose the quadriceps tendon.

Step 2: Tendon Harvest

Mark a central 8-10 mm wide strip of tendon. Using a number 15 blade or tendon stripper, harvest a full-thickness central third graft measuring 60-80 mm in length. If a bone block is desired, use an oscillating saw to create a 15-20 mm long by 8-10 mm wide by 8 mm deep trapezoidal osteotomy of the superior patella, ensuring the cut remains within the central 15 mm to avoid fracture. Elevate the graft from the vastus intermedius and deliver it.

Step 3: Graft Preparation

Whip-stitch both ends of the soft-tissue portion with non-absorbable suture (FiberWire or similar). If a bone block is present, prepare it for interference screw fixation by removing soft tissue and ensuring the block is 8-10 mm in diameter. Measure graft diameter at both ends and prepare suspensory button or interference screw accordingly. Store the graft in saline-soaked gauze until ready for passage.

Arthroscopic ACL Reconstruction

Step 4: Diagnostic Arthroscopy and Notch Preparation

Perform standard anterolateral and anteromedial portals. Perform a complete diagnostic arthroscopy, addressing meniscal and chondral pathology first. Debride residual ACL tissue from the tibial footprint. Perform notchplasty if the intercondylar notch width is less than 12 mm or if osteophytes are present — remove 2-4 mm from the roof and lateral wall using an arthroscopic burr.

Step 5: Femoral Tunnel Placement

Use the anteromedial portal with the knee flexed 120-130 degrees. Identify the lateral intercondylar ridge on the medial wall of the lateral femoral condyle. Place a guide pin at the centre of the anatomic footprint (6-8 mm anterior to the posterior wall, immediately distal to the ridge). Ream a 4.5 mm pilot tunnel, then over-ream with a cannulated reamer matched to graft diameter plus 0.5 mm. Aim for greater than 20 mm intraosseous tunnel length. If the tunnel is short, plan suspensory fixation.

Step 6: Tibial Tunnel Placement

Place the tibial guide through the anteromedial portal with the knee at 90 degrees. Position the guide tip at the centre of the tibial footprint (7-10 mm anterior to the PCL, 1-2 mm posterior to the anterior horn of the lateral meniscus). Drill a guide pin and confirm position fluoroscopically or arthroscopically. Over-ream with a cannulated reamer matched to graft diameter. Chamfer the tunnel aperture to prevent graft abrasion.

Step 7: Graft Passage and Fixation

Pass the graft through the tibial tunnel into the femoral tunnel using a passing suture or button. For suspensory femoral fixation, flip the button on the lateral cortex and confirm with fluoroscopy. For tibial fixation, use an interference screw (7-9 mm) with the knee at 20-30 degrees flexion and 80-100 N tension. Cycle the knee 20 times through full range of motion before final tibial screw insertion. Confirm no notch impingement in full extension and no PCL impingement in flexion.

Step 8: Closure and Dressing

Close all portals with absorbable suture. Close the quadriceps harvest incision in layers (rectus fascia, subcutaneous, skin). Apply sterile dressing and a hinged knee brace locked in extension. No drain is required.

Postoperative Protocol

Phase 1: Protection and Activation (Week 0-2)

• Brace locked in extension for first 2-3 weeks (longer if bone block harvest performed)
• Weight-bearing as tolerated with crutches; wean as quadriceps control returns
• Immediate quadriceps sets, straight-leg raises, ankle pumps
• Patellar mobilisation and effusion control (cryotherapy, elevation)
• Goal: full extension, 90 degrees flexion, independent straight-leg raise

Phase 2: Strength and Motion (Week 3-8)

• Unlock brace progressively; transition to functional brace at 4-6 weeks
• Progressive quadriceps strengthening (open and closed chain)
• Stationary bike, elliptical, swimming when incision healed
• Neuromuscular electrical stimulation if quadriceps activation poor
• Goal: greater than 80 percent quadriceps strength symmetry, full painless ROM

Phase 3: Advanced Strengthening and Proprioception (Week 9-16)

• Single-leg strengthening, perturbation training, balance board
• Plyometrics initiation at 12-16 weeks when strength criteria met
• Sport-specific drills without contact
• Goal: greater than 85 percent quadriceps symmetry, hop test greater than 85 percent

Phase 4: Return to Sport (Month 5-9+)

• Sport-specific agility, cutting, pivoting drills
• Psychological readiness assessment (ACL-RSI scale)
• Objective criteria: greater than 90 percent quadriceps strength symmetry, hop test greater than 90 percent, no effusion, full confidence
• Return to pivoting sports typically 9-12 months; earlier clearance only if all criteria met

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 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