Can a new cartilage implant, such as the one being done in Germany, be used as an alternative to knee replacement for patients with cartilage damage or osteoarthritis?

Cartilage Implants for Knee Osteoarthritis: An Alternative to Knee Replacement?

Based on current evidence, cartilage implant procedures cannot be recommended as a reliable alternative to knee replacement for most patients with established osteoarthritis, though they may have limited application in specific cases of focal cartilage defects. 1

Current Status of Cartilage Repair Techniques

Available Techniques

Several cartilage repair techniques have been developed that may be used in specific clinical scenarios:

• Microfracture: Creates small holes in the subchondral bone to allow bone marrow stem cells to form fibrocartilage

  • Limited evidence shows 93% fill rate in small defects (average 1.54 cm²) 1
  • Better short-term outcomes compared to simple chondroplasty for isolated defects 1

• Autologous Chondrocyte Implantation (ACI): Two-stage procedure involving harvesting, cultivation, and reimplantation of chondrocytes

  • Matrix-assisted ACI (MACI) showed better outcomes than simple debridement in one study (HHS 87.4 vs 56.3) 1
  • Requires specialized facilities and multiple procedures

• Osteochondral Transplantation: Using autograft or allograft to replace damaged cartilage and underlying bone

  • Some evidence suggests better outcomes with osteochondral autologous transplantation (OAT) than microfracture in younger patients 1

Limitations of Current Evidence

The evidence supporting cartilage repair techniques has significant limitations:

• American Academy of Orthopaedic Surgeons (AAOS) guidelines state they are "unable to recommend for or against a specific cartilage repair technique" due to inconclusive evidence 1
• Studies on cartilage repair generally have low methodological quality (average score 43.5/100) 2
• Large variations in reported outcomes within each treatment modality 2
• Most studies focus on focal cartilage defects rather than diffuse osteoarthritis 1

Appropriate Patient Selection

Cartilage implant procedures may be considered in very specific circumstances:

• Most Appropriate Candidates:

  • Younger patients with focal cartilage defects (not diffuse OA) 1
  • Lesions smaller than 2-3 cm² 1
  • Patients with intact subchondral bone and healthy surrounding cartilage 1
  • Patients without significant malalignment or other joint pathology 1

• Poor Candidates:

  • Patients with diffuse osteoarthritis 1
  • Older patients with degenerative changes 1
  • Those with bone quality issues (osteoporosis, osteopenia) 3
  • Patients with significant joint space narrowing 1

Comparison to Knee Replacement

For patients with established osteoarthritis:

• Total Knee Replacement (TKR) remains the gold standard for advanced osteoarthritis with:

  • Good or excellent outcomes in 89% of patients up to five years after surgery 1
  • Well-established improvement in quality of life, pain reduction, and functional improvement 1
  • Clear indications: severe daily pain and radiographic evidence of joint space narrowing 1

• Cartilage Implant Limitations:

  • Not designed for diffuse osteoarthritis 1
  • Limited durability of repair tissue 4
  • Inconsistent outcomes across studies 2, 4
  • High cost with uncertain cost-benefit ratio 4

Risk Factors for Progression to Osteoarthritis

Understanding risk factors for osteoarthritis progression is important when considering joint preservation techniques:

• Previous cartilage injury increases OA odds 2.31 times 1
• Previous meniscectomy increases OA odds 1.87-3.14 times 1
• Trochlear dysplasia may increase OA odds up to 3.6 times 1

Clinical Recommendations

For patients asking about cartilage implants as an alternative to knee replacement:

1. For established osteoarthritis with significant joint space narrowing and daily pain:

   • Total knee replacement remains the most reliable option 1
   • Cartilage implant techniques are not recommended 1

2. For younger patients with focal cartilage defects:

   • Consider cartilage repair techniques if:
     • Defect is well-circumscribed and <3 cm² 1
     • Surrounding cartilage is healthy 1
     • Patient understands the limitations and uncertain long-term outcomes 2, 4

3. For patients seeking to delay knee replacement:

   • Consider more established non-surgical and joint preservation techniques first:
     • Weight management, physical therapy, and appropriate medications 1
     • High tibial osteotomy for unicompartmental OA (limited evidence) 1
   • Avoid arthroscopy with lavage/debridement as it is not recommended for primary knee OA 1

Important Caveats

• Pain relief from cartilage procedures may take 3+ months to manifest 3
• Long-term durability of cartilage repair tissue remains uncertain 4
• The cost-effectiveness of these procedures compared to traditional treatments is unresolved 4
• Most cartilage repair studies have methodological limitations, making firm recommendations difficult 2

While there is ongoing research in Germany and other countries on cartilage implant technologies, current evidence does not support their widespread use as an alternative to knee replacement for established osteoarthritis. These techniques may have a role in specific cases of focal cartilage damage in appropriately selected patients.