Sports Medicine: ACL Reconstruction - Trends and Controversies

The Anterior Cruciate Ligament (ACL) is the most studied structure in orthopaedics. With over 200,000 reconstructions performed annually in the US alone, one might assume the debate is settled. Far from it. The field is evolving rapidly, with shifts in graft choice, the resurgence of extra-articular augmentation, and a new focus on biology.

This article reviews the current "State of the Art" in ACL reconstruction, focusing on the high-yield topics for the FRACS exam and clinical practice.

Visual Element: 3D anatomy render showing the two-bundle anatomy of the ACL (Anteromedial and Posterolateral) and their footprints.

1. Anatomy and Biomechanics: The Foundation

The Two Bundles

• Anteromedial (AM) Bundle: Tight in Flexion. Controls Anterior Translation.
• Posterolateral (PL) Bundle: Tight in Extension. Controls Rotation.
• Clinical Pearl: The Lachman test (20° flexion) primarily tests the PL bundle. The Anterior Drawer (90° flexion) tests the AM bundle.

Isometry vs. Anatomy

Historically, we aimed for "Isometric" placement (high in the notch) to prevent graft stretching. We now know this fails to control rotation. Modern "Anatomic" placement puts the femoral tunnel lower (lateral wall) and deeper, restoring the native footprint and rotational stability.

2. Graft Selection: The Great Debate

There is no "perfect" graft. The choice must be tailored to the patient.

Bone-Patellar Tendon-Bone (BPTB)

• The Gold Standard: Still the benchmark for high-performance athletes.
• Pros: Bone-to-bone healing (fastest integration, ~6 weeks). Lowest failure rate in young pivoting athletes.
• Cons: Anterior knee pain (kneeling pain). Risk of patellar fracture.
• Best For: Footballers, high-demand athletes.

Hamstring (Quadrupled Semitendinosus/Gracilis)

• The Workhorse: Most common graft globally.
• Pros: Small incision, low morbidity, no kneeling pain.
• Cons: Soft tissue-to-bone healing (slower, ~12 weeks). "Bungee cord" effect (more elastic). Permanent hamstring weakness (flexion/internal rotation).
• Risk: Higher failure rate in females and hyperlax patients compared to BPTB.

Quadriceps Tendon (QT)

• The Rising Star: Gaining rapid popularity.
• Pros: Massive collagen volume (thicker than PT). Less anterior knee pain than BPTB. Can be harvested with or without a bone block.
• Cons: Learning curve for harvest. Aesthetics (suprapatellar scar).

Allograft

• The "Easy" Way:
• Pros: No donor site morbidity. Fast surgery.
• Cons: Higher failure rate in young active patients (irradiation weakens the graft). Slower biological incorporation (creeping substitution).
• Best For: Revision surgery, older patients (>40), multi-ligament injuries.

Visual Element: A decision matrix flowchart for Graft Selection based on Age, Activity Level, and Gender.

3. Surgical Technique: Anatomic Reconstruction

Tunnel Position

• Femur: Low on the lateral wall (2 o'clock left knee, 10 o'clock right knee). "High and Deep" is wrong; "Low and Deep" controls rotation.
• Tibia: In the footprint. The center is approx 15mm anterior to the PCL and in line with the posterior edge of the anterior horn of the lateral meniscus.

Fixation

• Suspensory: (e.g., Endobutton, Tightrope). Strong. Allows "cortical blowing" if tunnel is too short.
• Aperture: (e.g., Interference Screw). Joint line fixation. Stiffer construct.

4. The Comeback of Extra-Articular Tenodesis (LET/ALL)

In the 80s, we did open lateral procedures. We stopped. Now, they are back. Why? Rotational Control. The intra-articular ACL reconstruction is great for AP stability but sometimes fails to control the "pivot shift."

The Evidence (STABILITY Trial)

The STABILITY trial demonstrated that adding a Lateral Extra-articular Tenodesis (LET) to a Hamstring ACL reconstruction significantly reduced the re-rupture rate in high-risk patients.

Who gets a LET? (The High-Risk Profile)

1. Young patients (<20 years).
2. High-grade pivot shift (Grade 3).
3. Hyperlaxity / Genu Recurvatum.
4. Pivoting sports (Soccer, Rugby).
5. Revision cases.

5. Paediatric ACL: Saving the Physis

ACL injuries in skeletally immature patients are a nightmare.

• Drilling across the physis risks growth arrest and deformity (Valgus/Recurvatum).
• Conservative management is a disaster (meniscal tears occur rapidly).

Techniques

1. Physeal Sparing (All-Epiphyseal): Tunnels stay entirely within the epiphysis. Technically hard.
2. Trans-Physeal: Standard tunnels but small diameter (<8mm), central placement, and no fixation across the physis. Safe in pre-pubescent teens nearing maturity.
3. Iliotibial Band (Micheli/Kocher): Over-the-top, non-anatomic but safe.

6. Biological Augmentation

The future is biology.

• The BEAR Implant: Bridge-Enhanced ACL Repair. A sponge scaffold soaked in the patient's blood is sutured between the torn stump ends. FDA approved. Allows "healing" of the native ACL rather than reconstruction. Early results are promising for mid-substance tears.
• Remnant Preservation: Keeping the stump. It contains mechanoreceptors (proprioception) and vascular channels.

7. Rehabilitation and Return to Sport (RTS)

Surgery is only 50% of the cure.

• Time: Biology cannot be rushed. Ligamentization takes time. RTS before 9 months increases re-rupture rate by 50% for every month early.
• Criteria-Based Progression:
  • Full ROM.
  • No effusion.
  • Quad strength >90% of contralateral side.
  • Hop tests >90% symmetry.
  • Psychological readiness (ACL-RSI scale).

Evidence Corner: The "FIFA 11+" warm-up program has been proven to reduce ACL injury rates by up to 50% in soccer players. Prevention is better than cure.

Conclusion

ACL reconstruction has matured from "put a graft in the hole" to a bespoke surgery.

• Individualize the graft: Don't just use hamstrings because it's easy.
• Respect rotation: Consider LET for high-risk knees.
• Respect biology: Don't let them play before 9 months.

The goal is not just a stable knee, but a knee that prevents osteoarthritis for the next 40 years.