Is Matrix-induced Autologous Chondrocyte Implantation (MACI) suitable for osteoarthritis of the knee?

MACI for Osteoarthritis of the Knee

Matrix-induced Autologous Chondrocyte Implantation (MACI) is not recommended for the routine treatment of knee osteoarthritis according to current clinical practice guidelines. 1

Current Guideline Recommendations for Knee OA

The American Academy of Orthopaedic Surgeons (AAOS) clinical practice guidelines for management of knee osteoarthritis do not include MACI as a recommended treatment option. Instead, they provide specific recommendations for various treatment modalities:

First-line Treatments

• Oral acetaminophen (strong recommendation) 1
• Weight loss and exercise programs (particularly quadriceps strengthening) 1
• Self-management educational programs 1

Other Treatment Options

• Transcutaneous electrical nerve stimulation (limited recommendation) 1
• Percutaneous electrical nerve stimulation (limited recommendation) 1
• Pulsed electromagnetic field therapy (limited recommendation) 1
• Extracorporeal shockwave therapy (limited recommendation) 1
• Platelet-rich plasma (limited recommendation) 1
• High tibial osteotomy for unicompartmental knee OA (limited recommendation) 1
• Denervation therapy (limited recommendation) 1

Not Recommended Treatments

• Oral narcotics (strong recommendation against) 1
• Hyaluronic acid injections (moderate recommendation against) 1
• Arthroscopic lavage and debridement (strong recommendation against) 1

Understanding MACI

MACI is a cartilage repair technique that involves:

1. Harvesting chondrocytes from the patient's healthy cartilage
2. Cultivating these cells in a laboratory
3. Seeding them onto a biodegradable collagen scaffold
4. Implanting this scaffold into the cartilage defect 1

While MACI has shown promising results for specific cartilage defects, particularly in younger patients, it has important limitations for osteoarthritis:

Evidence for MACI in Specific Conditions

• MACI has demonstrated effectiveness in treating isolated cartilage defects of the knee with good outcomes at 5-10 years 2, 3
• In a 10-year follow-up study, 92% of patients were satisfied with MACI for knee pain relief, though only 76% were satisfied with sports participation ability 2
• The procedure has a failure rate of approximately 9-11% over 10 years 2

Why MACI is Not Suitable for Most OA Cases

1. Disease Pathology: Osteoarthritis is a whole-joint disease affecting multiple tissues (cartilage, bone, synovium), while MACI addresses only focal cartilage defects 1

2. Patient Selection: MACI is typically indicated for:

   • Younger patients (typically under 50)
   • Focal cartilage defects (not diffuse degeneration)
   • Minimal to no joint space narrowing
   • Stable knee with proper alignment 4

3. Technical Challenges:

   • Requires two surgical procedures
   • Expensive and resource-intensive
   • Requires specialized facilities for cell cultivation 1

4. Limited Evidence: There is insufficient evidence supporting MACI for general osteoarthritis treatment in current clinical practice guidelines 1

Special Considerations

In very specific circumstances, MACI might be considered for younger patients with early, unicompartmental osteoarthritis with varus malalignment when combined with high tibial osteotomy. A small case series showed:

• Significant clinical improvement at 5 years in younger patients (mean age 47) with medial knee OA and varus alignment who underwent combined neutralizing HTO and MACI
• However, overall graft survival and cartilage infill were poor at 5 years 4

Clinical Decision Algorithm

For patients with knee osteoarthritis:

1. Assess disease severity and pattern:

   • Radiographic evaluation (joint space narrowing, osteophytes)
   • MRI assessment of cartilage integrity and other structures
   • Age and activity level of patient

2. For typical OA patients (older, diffuse disease):

   • Follow standard AAOS guidelines starting with conservative measures
   • Consider appropriate surgical options like osteotomy or arthroplasty when indicated

3. For younger patients (<50) with focal cartilage defects and minimal OA:

   • Consider referral to cartilage repair specialist to evaluate for potential cartilage restoration procedures
   • MACI might be considered only in highly selected cases with focal defects, not as a treatment for generalized OA

Conclusion

Based on current guidelines and evidence, MACI should not be used as a routine treatment for knee osteoarthritis. Standard treatment algorithms as outlined by the AAOS should be followed, with appropriate progression from conservative to surgical management based on disease severity and patient factors.