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First-, second-generation cartilage repair techniques have good short-term results
However, MRI results in literature show a variable defect fill rate of 18% to 95%, investigator notes.
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As researchers develop new technologies for articular cartilage repair, Kai Mithoefer, MD, took a look back at the indications, advantages and limitations of first- and second-generation techniques at the American Academy of Orthopaedic Surgeons annual meeting.
“Since the development of the first- and second-generation cartilage repair techniques there has been quite an evolution in articular cartilage restoration,” he said. “By increasing the amount of new cartilage repair volume, as well as quality, these technologies have been increasingly effective in producing a reliable, short-term clinical improvement. However, how the results look in the long run still needs to be evaluated.”
Marrow stimulation
Marrow stimulation techniques, such as abrasion chondroplasty and subchondral drilling, have shown clinical improvement in up to 60% of cases, but these procedures have limited durability and produce unpredictable amounts of repair tissue, Mithoefer said.
Microfracture is the most commonly used marrow stimulation technique, he said. The indications for the procedure include defects less than 4 cm², incidental cartilage lesion and primary treatment. Contraindications include patients with a body mass index greater than 30 kg/m², generalized degenerative joint changes, uncontained lesions, malalignment or joint instability.
“Some recently published studies have shown that removing the calcified cartilage layer improves the repair cartilage integration as well as provides better overall repair cartilage volume after microfracture,” Mithoefer said.
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Two images showing MRI of a cartilage defect before (a) and 6 months after treatment with microfracture (b) showing good repair cartilage fill and decreased subchondral edema. Arrows indicate the defect before and after microfracture chondroplasty showing complete fill of the defect. Images: Mithoefer K |
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In an evidence-based review of 28 studies with more than 3,000 patients, Mithoefer and colleagues found significant clinical improvement and a success rate of up to 100% for the first 2 years after microfracture. However, they discovered less predictable results after 2 years with decrease of the initial improvement in some patients. In addition, MRI results in the literature have shown a variable defect fill rate of 18% to 95%, and subchondral bone overgrowth in 25% to 40% of cases.
“It is felt that subchondral bone overgrowth might have a significant impact because it leads to a relative thinning of the overlying repair cartilage and might be a factor in the limited duration of the functional improvement after microfracture in some patients,” Mithoefer said. He cited low cost, short rehabilitation and excellent short-term results as advantages of the procedure and the predominance of fibrocartilage repair tissue and limited durability among its limitations.
ACI
Autologous chondrocyte implantation (ACI) can be used for small and large defects, chronic and acute lesions, and for defects in the femur and patellofemoral joint. Prospective histologic studies have shown hyaline-like cartilage in up to 72% of ACI cases, and clinical research has demonstrated functional improvement in 67% to 95%. MRI studies have shown good peripheral integration and fill grade, Mithoefer said.
He cited high cost, longer rehabilitation, technical difficulty, increased postoperative morbidity and a high rate of periosteal hypertrophy as limitations of ACI.
Mithoefer routinely performs collagen-membrane covered ACI. The procedure is less invasive, has a shorter operative time, reduces morbidity, and has minimized the risk of tissue hypertrophy. He noted that matrix-induced ACI has similar advantages, and that implantation can be performed arthroscopically in some cases.
For more information:
- Kai Mithoefer, MD, can be reached at Harvard Vanguard Medical Associates Orthopedics and Sports Medicine; 291 Independence Drive, Chestnut Hill, MA 02467; 617-541-6611; e-mail: kmithoefer@partners.org. He has no direct financial interest in any products or companies mentioned in this article.
References:
- Mithoefer, K. First and second generation cartilage repair: Debridement to cloned cell implantation. Symposium I: Hyaline cartilage biological joint repair, restoration and resurfacing. Presented at the American Academy of Orthopaedic Surgeons 76th Annual Meeting. Feb. 25-28, 2009. Las Vegas.
- Mithoefer K, McAdams T, Williams RJ, et al. Clinical Efficacy of the Microfracture Technique for Articular Cartilage Repair in the Knee: An Evidence-Based Systematic Analysis. Am J Sports Med. 2009; Feb 26. [Epub ahead of print].