What are the outcomes of autograft (autologous graft) versus allograft (homologous graft) in pediatric knee osteochondral defects?

Outcomes of Autograft versus Allograft in Pediatric Knee Osteochondral Defects

Both autograft and allograft transplantation demonstrate favorable outcomes for pediatric knee osteochondral defects, with selection primarily determined by defect size: autografts for smaller lesions (<3 cm²) and allografts for larger lesions (>2.5 cm²). 1

Autograft (Mosaicplasty) Outcomes

• Provides excellent clinical outcomes with immediate restoration of hyaline cartilage in a single procedure for pediatric patients with small to medium-sized defects 1
• Indicated for patients under 45 years with focal, full-thickness lesions <3 cm² in size without signs of osteoarthritis 1, 2
• Advantages include:
  • Elimination of need for second surgical procedure 1
  • Superior mechanical properties due to hyaline cartilage replacement 1, 2
  • Immediate or near-immediate weight bearing after surgery 1
  • No risk of disease transmission 1
  • Better outcomes in younger patients with isolated lesions between 1-4 cm² 2
• Limitations include:
  • Donor site morbidity 1
  • Technical challenges in graft harvest and placement 2
  • Limited by available donor tissue for larger defects 1

Allograft Outcomes

• Demonstrates excellent clinical results for larger osteochondral defects in pediatric patients 1, 3
• Indicated for patients ≤50 years with defects >2.5 cm² or with substantial subchondral bone loss 1, 4
• In pediatric and adolescent patients specifically:
  • 90% graft survivorship at 10 years 3
  • 88% good/excellent results in knees with grafts in situ at latest follow-up 3
  • Significant improvement in knee function scores 3
  • 89% of patients reported being "extremely satisfied" or "satisfied" 3
• Advantages include:
  • Eliminates donor site morbidity 1
  • Provides immediate mechanically functional joint surface 1
  • Suitable for larger lesions that are difficult to manage with other techniques 1, 4
  • High salvage rate (80%) of clinical failures with additional allograft 3
• Limitations include:
  • Risk of disease transmission 1
  • Relative paucity of donor tissue 1
  • Complex graft handling and procurement procedures 1
  • Reduced graft viability after 28 days of storage 1

Comparative Outcomes

• Recent meta-analysis (2023) comparing autograft vs. allograft in knee cartilage lesions found: 5
  • Similar survival rates: 88.2% for autografts vs. 87.2% for allografts at approximately 5 years
  • No significant difference in patient-reported outcome percentage change between techniques
  • No significant differences in graft failure risk between techniques
  • Neither age, sex, lesion size, number of plugs/grafts used, nor treatment location significantly affected outcomes between the two approaches

Decision Algorithm for Pediatric Knee Osteochondral Defects

1. For lesions <2 cm²:

   • First-line: Autograft (mosaicplasty) 1
   • Second-line: Microfracture or osteochondral allograft (single plug) 1

2. For lesions 2-6 cm²:

   • First-line: Osteochondral allograft 1
   • Second-line: Osteochondral autograft (for lesions closer to 2 cm²) 1, 5

3. For lesions >6 cm²:

   • Osteochondral allograft is preferred due to donor site limitations with autograft 1, 4

Clinical Pearls and Pitfalls

• Proper patient selection is paramount to success and long-term graft viability regardless of technique chosen 5
• For autografts, minimize donor site morbidity by careful harvest technique and limiting the number of plugs taken 2
• For allografts, ensure fresh grafts are used within 28 days to maintain chondrocyte viability 1
• Both techniques provide hyaline cartilage, which has superior mechanical properties compared to fibrocartilage resulting from microfracture techniques 1
• In pediatric patients with failed initial treatment, osteochondral allografts show high salvage success rates (80%) 3