ACL Reconstruction: Surgical Steps and Knee Anatomy

Part I: Anatomy of the Knee Relevant to ACL Reconstruction

• Femoral attachment: Semicircular area on the posteromedial aspect of the lateral femoral condyle, divided by the bifurcate ridge and bordered by the intercondylar ridge
• Tibial insertion: Broad, irregular, oval area just medial to the anterior horn of the lateral meniscus, posterior to the tubercle of the anterior horn of the medial meniscus
• Vascular supply: Middle geniculate artery (branch of popliteal artery); synovial plexus around the ligament
• Length: ~38 mm; diameter 10-12 mm (compared to PCL at 38 mm length, 13 mm diameter)
• Clinical test: Lachman test tests the AMB (anterior restraint); Pivot shift test tests the PLB (rotatory restraint)

Part II: ACL Reconstruction - Surgical Steps

• Young, active patients with functionally unstable ACL-deficient knee
• Athletes wishing to return to pivoting/cutting sports
• Concomitant meniscal tears requiring repair (instability must be corrected)
• Failure of conservative management with persistent instability

• Supine with a lateral post and a foot holder to hold the knee at ~90° of flexion
• Tourniquet applied to the proximal thigh
• Examination under anesthesia (EUA) to confirm laxity pattern before draping

• For hamstring graft: 3-4 cm oblique incision at the anteromedial proximal tibia, over the pes anserinus. Harvest semitendinosus ± gracilis tendons using a closed tendon stripper. Double or quadruple the tendon strands and size the graft (typically 8-10 mm).
• For BTB graft: Longitudinal incision over the patellar tendon; harvest a central 10 mm bone-tendon-bone strip (~25 mm patellar plug, 20-25 mm tibial plug).
• Prepare graft on the back table: trim to length, whipstitch the ends with #2 non-absorbable suture, measure and record graft diameter.

• Standard anteromedial and anterolateral portals established (inferolateral for scope, inferomedial for instruments), knee at 90° of flexion
• Systematic arthroscopic survey: suprapatellar pouch, patellofemoral joint, medial and lateral compartments including menisci, intercondylar notch, ACL and PCL
• Address concomitant injuries (meniscal repair/debridement, chondral lesions)
• ACL stump debridement: remove torn fibers from the tibial footprint using a shaver and electrocautery to visualize landmarks clearly
• Notchplasty if needed: a lateral notchplasty opens the roof of the intercondylar notch with a burr to prevent roof impingement of the graft; aim for ~1 cm clearance at full extension

• A tibial ACL drill guide (typically set at 55°) is placed with the guide tip at the center of the native ACL tibial footprint: approximately 7 mm anterior to the PCL, just anterior to the posterior slope of the medial tibial spine, medial to the lateral tibial spine
• A guide pin is passed from the anteromedial tibia (through the pes anserinus area) through the tibial footprint
• The pin exits arthroscopically into the joint at the correct position
• Ream the tibial tunnel over the pin to the measured graft diameter (typically 8-10 mm), angled at ~55° to the tibial plateau to ensure a proper intraarticular angle

• The femoral tunnel is the most critical step; anatomic femoral placement is paramount
• Two approaches exist:
  • Transtibial: Guide pin passed through the tibial tunnel upward to the femoral footprint; limited ability to achieve anatomic placement
  • Anteromedial (AM) portal technique: Preferred for anatomic reconstruction; a separate accessory anteromedial portal at 10 o'clock (right knee) allows direct access to the femoral footprint at the center of the native ACL attachment (posterior wall of the lateral femoral condyle, 1-2 mm anterior to the over-the-top position)
• Knee flexed to 110-120° for AM portal drilling to avoid posterior wall blowout
• Guide pin placed, tunnel reamed to graft diameter; tunnel length typically 25-30 mm

• A passing suture or looped wire is used to pull the graft through the tibial tunnel and into the femoral tunnel
• For hamstring/soft-tissue graft: A looped suspensory device (e.g., Endobutton or adjustable cortical button) is threaded through the femoral tunnel and deployed on the lateral femoral cortex
• For BTB graft: The patellar bone plug is impacted into the femoral tunnel
• Graft is seated firmly with the femoral fixation deployed first

• With the knee at 20-30° of flexion, gentle tension is applied to the graft while cycling the knee through full range of motion 10-20 times to pre-tension the graft
• Anterior drawer is checked and laxity corrected before fixation
• Tibial fixation at the tibial tunnel exit:
  • Soft-tissue graft: Interference screw (bioabsorbable or metal) driven beside the graft or a staple/suture post
  • BTB graft: Interference screw alongside the tibial bone plug
  • Backup fixation (staple, post) may be added

• Arthroscopic inspection confirms graft tension, absence of roof impingement at full extension, and that the graft lies in the anatomic position
• Gentle posterior drawer and Lachman maneuver confirm restored stability

• Irrigate joint thoroughly, close portals and harvest sites in layers
• Drain is not routinely required
• Perioperative cryotherapy and compressive dressing applied

1. Harvest gracilis tendon autograft; whipstitch the end
2. Femoral fixation: guide pin placed 8 mm proximal and 4.3 mm posterior to the lateral epicondyle
3. Tibial fixation: 22 mm posterior to Gerdy's tubercle, 10 mm distal to the joint line
4. Test isometry through range of motion before final fixation

• Malpositioned tunnels (most common cause): femoral tunnel too vertical/anterior
• Graft impingement on the notch roof at full extension
• Failure to address concomitant posterolateral corner (PLC) injury (occurs in ~10% of ACL tears)
• Use of allograft in young/high-demand athletes (2.1x higher revision rate vs. BTB)
• Premature return to sport before biologic graft incorporation (typically 9-12 months)

• 0-2 weeks: Crutches, full weight bearing tolerated, quad sets, straight leg raises
• 2-6 weeks: Range of motion 0-120°, closed-chain exercises
• 6-12 weeks: Progressive resistance, stationary bike, swimming
• 3-6 months: Running, agility training if quadriceps strength >70% of contralateral
• 9-12 months: Return to full sport; criteria-based clearance (strength symmetry, hop tests)

• Campbell's Operative Orthopaedics 15th Ed 2026, pp. 2784-2710 (ACL anatomy, reconstruction techniques, anterolateral ligament)
• Miller's Review of Orthopaedics 9th Edition, pp. 333-349 (knee anatomy, ACL/PCL bundles, arthroscopic portals, ACL pathology)
• AOSSM 2024: Evolving Concepts in ACL Surgery - graft selection, lateral augmentation
• PMC Comprehensive Review - Graft Choices & Surgical Techniques (2024) - single vs. double bundle outcomes, anatomic tunnel placement