Debridement of lesion and trimming of chondral flaps
Bone Marrow Stimulation (Micro-fracture)
Osteochondral Grafting:
Autograft (Mosaicoplasty)
Allograft
Chondrocyte Implantation:
ACI
MACI
Osteotomy/Arthroplasty
Factors Affecting Treatment Outcome
Worse outcomes if:
Age >40 years
Multiple lesions
Multi-compartment disease
Limb deformity
Inflammatory disease
Debridement of Lesion and Trimming of Chondral Flaps
Some studies show significant improvement in many patients; however, these improvements have not been sustained over time as it does not address the underlying problem.
Bone Marrow Stimulation (Micro-fracture)
Perforation of the subchondral plate to recruit mesenchymal stem cells from the bone marrow into the lesion.
Forms fibrocartilage, which is second-best to hyaline cartilage (contains less type 2 collagen).
Key Technical Points:
Form a stable confined clot within the lesion.
Create a stable cartilage shoulder around the lesion.
Remove the calcified base of the lesion with a curette.
Perforate the subchondral bone until fat droplets are seen.
Use CPM; restrict WB and ROM depending on location of lesion.
Advantages: Cheap, easy, single surgery, short recovery.
Disadvantages: Not hyaline cartilage; less useful >40 years due to lower marrow concentration of stem cells.
Outcomes:
Good results in many papers. RCTs show it to be better than ACI, although others have shown the opposite.
Results may deteriorate over time.
Remains a safe, easy first-line option with reasonable results, good to excellent results in around 2/3 of patients.
Use of multiple osteochondral plugs harvested from non-articular parts of the same knee to fill the defect. Produces a congruent, viable, and durable option.
Key Technical Points:
Pack cylinders closely to avoid large gaps.
Use cylinders of the same depth as the holes to prevent loosening/subsidence.
Create a congruent surface.
Advantages: Autologous, hyaline cartilage, single operation, low recovery time.
Disadvantages: Technical challenge, graft site morbidity, limited volume available.
Outcomes:
Good: 80% good or excellent at 36 months.
Two RCTs show better improvement than ACI, although all improved, and even some with debridement alone improved.
Osteochondral Grafting - Allograft
Use of fresh (frozen denatured chondrocytes) allograft to fill defects.
The graft is harvested fresh and stored in Hartmans or culture fluid in the fridge (4 degrees). The allograft bone is necrotic and is replaced by creeping substitution, providing a scaffold for cartilage incorporation.
The cartilage itself, being fairly avascular, resists immune reactions.
Advantages: No graft site morbidity, very good for large lesions, excellent congruency, hyaline cartilage.
Disadvantages: Poor availability of allograft, expensive, technically demanding, immune/infection risk.
Outcomes: Long-term graft survival has been shown with good results in case series, but no good evidence that this is better than other modalities.
Other types of allograft, such as fresh frozen and cryopreserved, are inferior in quality due to the denaturing of the chondrocytes and are not recommended.
Harvesting of host chondrocytes, growth in vivo, and re-implantation into defect. Potentially the best option as host hyaline cartilage is formed.
Advantages: Hyaline cartilage formed with potential for best longevity.
Disadvantages: Two operations needed, not available everywhere, long process, technically demanding.
Outcomes:
RCTs have shown mixed results, but several show superiority over microfracture and mosaicplasty. However, these treatments also gave good results in the same trials.
Chondrocytes are incorporated into a porcine collagen membrane, which gives a more even cell distribution and makes placement of the cells easier.
Shown good results, some better than ACI, although disadvantages are similar.
Conclusion
Conflicting evidence for more advanced techniques with benefits from ‘lesser’ methods. Therefore, first-line treatment should be microfracture/mosaicplasty for standard lesions and situations.