Graft Impingement: Understanding Causes, Symptoms, Diagnosis, and Treatment

What is a Graft Impingement?

Graft impingement refers to a condition where surgically implanted graft tissue, or the surrounding scar tissue, becomes mechanically compressed or entrapped within a joint, leading to pain, restricted movement, and functional limitations. This complication is most commonly observed following reconstructive surgeries, particularly those involving the anterior cruciate ligament (ACL) in the knee or rotator cuff tendons in the shoulder.

Understanding Graft Impingement

A graft is a piece of tissue transplanted from one site to another, often used to replace damaged ligaments or tendons. In reconstructive surgery, this graft is meticulously placed and secured to restore joint stability and function. Impingement occurs when this graft, or the scar tissue that forms around it during healing, mechanically obstructs normal joint movement by rubbing against bone, other soft tissues, or even surgical hardware. This persistent friction can cause inflammation, pain, and damage to the graft or surrounding structures.

The mechanism often involves:

• Mechanical obstruction: The physical presence of the graft or scar tissue blocks the full range of motion.
• Inflammation: Constant rubbing irritates tissues, leading to swelling and pain.
• Fibrous tissue formation: The body's healing response can sometimes lead to excessive scar tissue (arthrofibrosis), which contributes to the impingement.

Common Locations and Types

Graft impingement can occur in various joints, but it is most frequently encountered in the knee and shoulder.

Anterior Cruciate Ligament (ACL) Reconstruction

Following ACL reconstruction, graft impingement is a significant concern that can hinder rehabilitation and functional recovery.

• Cyclops Lesion: This is a specific type of anterior impingement where a nodule of fibrous tissue, often resembling an eye (hence "cyclops"), forms on the anterior aspect of the ACL graft. This lesion can become entrapped between the femur and tibia, particularly during knee extension, leading to a loss of full extension.
• Bone Tunnel Impingement: The graft can impinge within or at the exit of the bone tunnels created for its passage. If the tunnels are misplaced or angled incorrectly, the graft may rub against the bony edges, causing irritation and potential graft wear.
• Patellar Impingement: In some cases, scar tissue or even the graft itself can impinge on the patella (kneecap) or the patellar tendon, especially if a patellar tendon autograft was used.

Rotator Cuff Repair

While less distinctly termed "graft impingement," issues related to tissue entrapment can occur post-rotator cuff repair.

• Subacromial Impingement: Although often associated with primary rotator cuff disease, post-surgical inflammation, scar tissue, or even prominence of repair hardware can contribute to impingement within the subacromial space, where the repaired tendons pass beneath the acromion.
• Internal Impingement: Less common but possible, particularly in overhead athletes, where the repaired tendon may impinge against the posterior-superior glenoid labrum during specific arm movements.

Causes and Risk Factors

Several factors can contribute to the development of graft impingement:

• Surgical Factors:
  • Improper Graft Placement: Suboptimal positioning of the graft tunnels or the graft itself can lead to it occupying space where it shouldn't.
  • Tunnel Malpositioning: Incorrect angles or sizes of bone tunnels can create sharp edges or narrow passages that impinge the graft.
  • Hardware Prominence: Screws or buttons used to secure the graft can sometimes protrude and cause impingement.
• Biological Factors:
  • Arthrofibrosis: Excessive scar tissue formation within the joint can envelop the graft and restrict its movement.
  • Inflammatory Response: An exaggerated inflammatory reaction post-surgery can lead to swelling and thickening of tissues, predisposing to impingement.
• Rehabilitation Factors:
  • Insufficient Range of Motion (ROM): Failure to regain full joint mobility, particularly extension (in the knee), can allow impingement to develop or worsen.
  • Early Aggressive Activity: Overloading the healing graft or joint too soon can exacerbate inflammation and scar tissue formation.
  • Inadequate Strengthening: Weak surrounding muscles may fail to stabilize the joint, contributing to abnormal mechanics.
• Anatomical Factors:
  • Pre-existing Bone Spurs (Osteophytes): These can narrow joint spaces and increase the risk of impingement.
  • Narrow Joint Spaces: Some individuals naturally have smaller joint spaces, making them more susceptible.

Signs and Symptoms

The symptoms of graft impingement typically emerge gradually post-surgery, often after an initial period of improvement, and can significantly impede rehabilitation progress.

• Persistent Pain: Localized pain, often described as a deep ache or sharp sensation, which worsens with specific joint movements or activities.
• Limited Range of Motion (ROM): A hallmark symptom, particularly a loss of full extension in the knee (e.g., inability to fully straighten the leg after ACL surgery) or restricted flexion/rotation in the shoulder.
• Clicking, Catching, or Locking Sensations: These mechanical symptoms indicate that the graft or scar tissue is physically obstructing joint movement.
• Swelling: Persistent or recurrent joint effusion (swelling) can be a sign of ongoing inflammation due to impingement.
• Weakness or Instability: Secondary to pain or mechanical blockage, individuals may experience perceived weakness or a feeling of instability in the affected joint.
• Failure to Progress in Rehabilitation: Despite consistent effort, the patient may plateau or regress in their recovery, failing to achieve expected milestones.

Diagnosis

Diagnosing graft impingement requires a thorough evaluation, often combining clinical assessment with imaging studies.

• Clinical Examination:
  • History Taking: Detailed questioning about symptoms, their onset, and impact on function.
  • Physical Examination: Assessment of joint range of motion (active and passive), palpation for tenderness, and specific orthopedic tests to identify mechanical blocks or pain provocation.
• Imaging Studies:
  • X-rays: Primarily used to assess bone tunnels, identify any prominent surgical hardware, or detect osteophytes.
  • Magnetic Resonance Imaging (MRI): The most valuable imaging modality for soft tissues. MRI can visualize the graft integrity, identify scar tissue formation (e.g., cyclops lesion), assess inflammation, and rule out other pathologies.
  • Computed Tomography (CT) Scan: Offers detailed bony anatomy assessment, particularly useful for evaluating tunnel placement and morphology.
• Diagnostic Arthroscopy: Considered the gold standard for definitive diagnosis. This minimally invasive surgical procedure allows the surgeon to directly visualize the inside of the joint, identify the impingement source, and often address it simultaneously.

Treatment Strategies

Treatment for graft impingement ranges from conservative management to surgical intervention, depending on the severity of symptoms, the degree of functional limitation, and the specific cause.

Conservative Management

This approach is typically attempted first, especially for milder cases or when symptoms are not severely debilitating.

• Physical Therapy: A cornerstone of treatment. Focuses on restoring full range of motion (critical for ACL impingement), strengthening surrounding musculature, manual therapy techniques to break down scar tissue, and neuromuscular re-education.
• Anti-inflammatory Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) can help reduce pain and inflammation associated with impingement.
• Corticosteroid Injections: Injections into the affected joint or around the impingement site can provide temporary relief from inflammation and pain, facilitating physical therapy.

Surgical Intervention

If conservative measures fail to alleviate symptoms or if there is a clear mechanical block significantly impeding function, surgery may be necessary.

• Arthroscopic Debridement: This is the most common surgical approach. Using an arthroscope, the surgeon can remove impinging scar tissue (e.g., cyclops lesionectomy), trim prominent soft tissue, or smooth bony edges causing friction.
• Hardware Removal: If prominent surgical hardware is identified as the cause of impingement, it may be surgically removed.
• Revision Surgery: In rare cases, if graft position is severely compromised or initial surgical technique is deemed the primary cause, revision surgery to reposition or replace the graft may be considered, though this is a more complex procedure.

Prevention and Rehabilitation Considerations

Preventing graft impingement begins with optimal surgical technique and continues through a diligent rehabilitation process.

• Optimal Surgical Technique: Precise bone tunnel placement, appropriate graft tensioning, and meticulous removal of meniscal remnants or soft tissue during the initial surgery are crucial to minimize impingement risk.
• Early and Progressive Rehabilitation: A structured rehabilitation program emphasizing immediate and sustained efforts to regain full joint range of motion, particularly full knee extension after ACL surgery, is paramount.
• Scar Tissue Management: Physical therapists employ manual therapy techniques, stretching, and mobilization exercises to prevent excessive scar tissue formation and maintain tissue pliability.
• Patient Education: Patients must be thoroughly educated on the signs and symptoms of impingement, the importance of adherence to rehabilitation protocols, and the need to communicate any new or worsening symptoms.
• Gradual Return to Activity: A carefully phased return to sport or high-impact activities helps prevent overloading the healing graft and joint, reducing the risk of inflammatory responses that can contribute to impingement.

Conclusion

Graft impingement is a recognized complication following reconstructive surgeries that can significantly impact recovery and long-term joint function. Understanding its causes, recognizing its symptoms, and pursuing timely and appropriate diagnosis and treatment are essential for successful outcomes. A collaborative approach involving the patient, orthopedic surgeon, and physical therapist is key to preventing, identifying, and effectively managing graft impingement, ultimately facilitating a return to optimal activity levels.