What are the benefits and complications of Mosaicplasty (osteochondral autograft transplantation) for the knee?

Mosaicplasty for Knee: Benefits and Complications

Mosaicplasty (osteochondral autograft transplantation) is an effective single-stage procedure for treating focal, full-thickness cartilage defects <3 cm² in patients under 45 years old without osteoarthritis, achieving good-to-excellent results in 92% of femoral condyle cases, with the primary advantage being immediate hyaline cartilage restoration and weight-bearing capability. 1, 2

Key Benefits

Structural and Functional Advantages

• Single-stage procedure: Eliminates need for second surgery (unlike autologous chondrocyte implantation) 1
• Superior cartilage quality: Provides hyaline cartilage with mechanical properties superior to fibrocartilage repair 1
• Immediate weight-bearing: Allows near-immediate or immediate postoperative weight-bearing 1
• Direct structural reconstruction: Provides both cartilage and subchondral bone support in one procedure 3

Clinical Outcomes

The evidence demonstrates consistently favorable results across multiple studies:

• 92% good-to-excellent results for femoral condyle lesions in a large 10-year study of 831 patients 2
• Lysholm scores improved from 51.9 to 85.5 points in patellofemoral cases 4
• Return to sports: Patients successfully returned to baseline activity levels 1, 3
• Long-term graft survival: Arthroscopic follow-up showed congruent gliding surfaces and histological evidence of transplanted hyaline cartilage survival in 83% of cases 2

Ideal Patient Selection

Critical inclusion criteria based on guideline evidence 1:

• Age <45 years
• No signs of osteoarthritis
• Focal, full-thickness lesion that is contained
• Defect size <3 cm²
• Stable subchondral bone

Complications and Limitations

Common Complications

The complication profile is relatively favorable but includes:

• Hemarthrosis: Most common complication (13/39 in open procedures, 1/14 in arthroscopic) 5
  • Usually mild and painful
  • Typically managed conservatively with rest, ice, compression, elevation
  • Rarely requires aspiration 4
• Deep infections: 4 cases in 831 patients (0.5%) 2
• Donor-site morbidity: 3% long-term disturbance rate 2
  • Grafts harvested from lateral trochlea or non-weight-bearing areas
  • Alternative donor sites (upper tibiofibular joint) can minimize this risk 6

Technical Considerations

• Defect location matters: Arthroscopic approach restricted to medial and lateral femoral condyles, while open approach can address patella and trochlea 5
• Size limitations: Arthroscopic technique limited to smaller defects (mean 0.97 cm²) versus open approach (mean 2.96 cm²) 5
• Meticulous technique required: Must restore native articular surface and joint congruity to avoid complications 4

Practical Algorithm

For focal knee cartilage defects:

1. Confirm eligibility: Age <45, no OA, defect <3 cm², contained lesion
2. Defect location assessment:
   • Medial/lateral femoral condyle: Arthroscopic or open approach
   • Patella/trochlea: Open approach required
3. Defect size consideration:
   • <1 cm²: Arthroscopic preferred
   • 1-3 cm²: Either approach acceptable

   • 3 cm²: Consider osteochondral allograft instead 1

Critical Pitfalls to Avoid

• Do not use in patients with established osteoarthritis 1
• Do not use for defects >3 cm² (consider allograft for 2.5-6 cm² lesions) 1
• Avoid in patients >45 years old (consider alternative treatments) 1
• Ensure adequate subchondral bone bridge between drill holes to maintain structural integrity 1
• Monitor for postoperative hemarthrosis, particularly in first few weeks

Comparative Context

While the evidence shows mosaicplasty produces favorable outcomes, it's worth noting that for smaller defects, microfracture may be considered first-line 1. However, in skeletally immature patients with unsalvageable fragments, osteochondral autograft transplantation demonstrated statistically significant superior ICRS scores and fewer failures compared to microfracture 7, suggesting mosaicplasty's superiority in specific populations.

The procedure's main advantage over other cartilage repair techniques is the immediate provision of mature hyaline cartilage with intact subchondral bone support, avoiding the prolonged rehabilitation and uncertain cartilage quality associated with cell-based therapies.