ACL Surgery: Types, Graft Options, Repair Techniques, and Recovery

How Many Types of ACL Surgery Are There?

While there isn't a single, straightforward number of "types" due to variations in technique and graft sources, ACL surgery primarily falls into two main categories: ACL reconstruction (the most common) and the emerging field of ACL repair. The most significant distinctions often relate to the type of tissue used to replace or fix the torn ligament.

Understanding ACL Injury and Surgical Rationale

The anterior cruciate ligament (ACL) is one of the four major ligaments in the knee, crucial for stabilizing the joint and preventing excessive forward movement of the tibia (shin bone) relative to the femur (thigh bone), as well as controlling rotational stability. ACL tears are common, particularly in athletes involved in sports requiring sudden stops, changes in direction, jumping, and landing.

When the ACL is completely torn, it typically does not heal on its own. For individuals who wish to return to high-demand activities, or those experiencing significant knee instability in daily life, surgical intervention is often recommended. The primary goal of ACL surgery is to restore knee stability, prevent further damage to other knee structures (like menisci and articular cartilage), and enable a safe return to activity.

The Primary Surgical Approach: ACL Reconstruction

By far the most common surgical procedure for a torn ACL is ACL reconstruction. This involves removing the damaged ligament and replacing it with a new piece of tissue, known as a graft. The graft is then anchored into tunnels drilled into the femur and tibia, where it eventually heals and integrates with the surrounding bone, forming a new ACL. This procedure is typically performed arthroscopically, using small incisions and a camera to guide the surgeon.

Types of Grafts Used in ACL Reconstruction

The choice of graft material is a critical decision in ACL reconstruction, influencing surgical outcomes, recovery time, and potential donor site morbidity. Grafts are primarily categorized by their source:

Autografts (Tissue from the Patient's Own Body)

Autografts are widely considered the gold standard due to their biological compatibility, lower risk of disease transmission, and excellent integration with the host bone.

• Patellar Tendon Autograft (Bone-Patellar Tendon-Bone or BTB):

  • This graft involves taking the central third of the patellar tendon, along with small bone blocks from the patella (kneecap) and tibia.
  • Pros: Historically strong and stiff, with bone-to-bone healing that can lead to quicker initial fixation. Often favored for high-performance athletes.
  • Cons: Higher incidence of anterior knee pain (pain at the front of the knee, especially with kneeling), potential for patellar fracture, and donor site weakness.

• Hamstring Tendon Autograft (Semitendinosus and Gracilis):

  • This involves harvesting one or two of the hamstring tendons (semitendinosus and sometimes gracilis) from the inner thigh. These are then folded over to create a multi-stranded graft.
  • Pros: Less anterior knee pain and kneeling pain compared to BTB, smaller incisions, and less donor site morbidity.
  • Cons: Potential for hamstring weakness, slower bone-to-tendon healing compared to BTB's bone-to-bone, and some studies suggest a slightly higher risk of graft re-rupture in certain populations.

• Quadriceps Tendon Autograft:

  • A portion of the quadriceps tendon, sometimes with a bone block from the patella, is harvested from above the kneecap.
  • Pros: Excellent graft strength and volume, lower incidence of anterior knee pain compared to BTB, and a versatile option.
  • Cons: Potential for anterior knee pain or quadriceps weakness, and the harvest site can be more painful initially than hamstring.

Allografts (Tissue from a Deceased Donor)

Allografts are tissues obtained from deceased human donors and are processed and sterilized before use.

• Common Allograft Sources: Patellar tendon, Achilles tendon, tibialis anterior, and semitendinosus.
  • Pros: Avoids donor site morbidity (no additional pain or weakness from harvesting tissue from the patient), shorter surgical time, and smaller incisions.
  • Cons: Higher cost, small but present risk of disease transmission (despite rigorous screening and processing), slower graft incorporation, and some studies suggest a higher re-rupture rate in younger, active individuals compared to autografts. Often preferred for older, less active individuals or revision surgeries.

Synthetic Grafts

Synthetic grafts, made from artificial materials, have been explored historically (e.g., Dacron, Gore-Tex). However, due to high rates of failure, synovitis (inflammation of the joint lining), and other complications, they are rarely used in primary ACL reconstruction today, except in very specific, limited circumstances.

Emerging Surgical Techniques: ACL Repair

While reconstruction has been the standard for decades, recent advancements have reignited interest in ACL repair. This approach aims to preserve the patient's native ACL rather than replacing it. It is only suitable for a select group of patients, typically those with specific types of proximal (femoral-side) ACL tears where the ligament has pulled away from the bone, leaving enough healthy tissue to reattach.

• ACL Primary Repair: Involves reattaching the torn ends of the ACL, often using sutures or specialized implants.
• Internal Bracing: Sometimes used in conjunction with primary repair, this technique uses a strong, non-resorbable suture or tape placed alongside the repaired ACL to provide immediate stability and protect the repair during the initial healing phase.
• Bridge-Enhanced ACL Repair (BEAR® Implant): This is a newer, FDA-approved technique that uses a collagen-based implant to bridge the gap between the torn ends of the ACL. The implant is saturated with the patient's own blood, which acts as a scaffold to facilitate healing and regeneration of the native ligament. It is indicated for complete ACL tears where the femoral attachment site is intact and the tear occurred within a certain timeframe.

Pros of ACL Repair: Potential for preserving native knee anatomy and proprioception (the sense of joint position), potentially faster recovery, and avoidance of donor site morbidity. Cons of ACL Repair: Currently suitable for a limited subset of ACL tears, long-term outcomes are still being studied, and the re-rupture rates compared to reconstruction are still under investigation.

Factors Influencing Surgical Choice

The decision regarding which type of ACL surgery or graft to use is highly individualized and made in consultation with an orthopedic surgeon. Key factors include:

• Patient Age and Activity Level: Younger, highly active individuals often opt for autografts due to their proven durability.
• Concomitant Injuries: Other injuries in the knee (e.g., meniscus tears, other ligament damage) can influence graft choice and surgical approach.
• Surgeon Preference and Experience: Surgeons often have preferred techniques and graft choices based on their training and experience.
• Patient Preferences: Concerns about donor site pain, recovery speed, or desire to avoid allograft tissue can play a role.
• Previous Surgeries: Revision ACL surgeries often involve different considerations for graft selection.

The Rehabilitation Journey

Regardless of the specific surgical technique or graft type, a comprehensive and structured rehabilitation program is paramount for successful ACL recovery. This typically involves:

• Initial Phase: Focus on pain control, swelling reduction, restoring full knee extension, and gentle weight-bearing.
• Intermediate Phase: Progressing to strengthening exercises for the quadriceps, hamstrings, and glutes, along with balance and proprioception drills.
• Advanced Phase: Incorporating sport-specific drills, agility training, plyometrics, and gradual return to high-impact activities.

The entire rehabilitation process can take 6-12 months, or even longer, before a full return to sport is considered safe.

Conclusion

While the question "how many types of ACL surgery are there?" might seem simple, the answer reveals a nuanced field. The vast majority of ACL surgeries are reconstructions, differing primarily in the type of graft used (autograft vs. allograft, with specific autograft choices like patellar, hamstring, or quadriceps). More recently, ACL repair techniques, such as the BEAR implant, represent an exciting and growing, though still specialized, alternative for certain tear patterns. Each approach has its unique advantages and considerations, all aimed at restoring knee function and stability to enable a return to a healthy, active lifestyle.