Issue: August 2014
August 01, 2014
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MECI techniques showed superior imaging results over microfracture

Issue: August 2014

Patients who underwent matrix encapsulated autologous chondrocyte implantation and those who underwent microfracture for articular cartilage lesions in the knee experienced similar clinical improvements at 2-year follow-up, but patients who underwent the chondrocyte implantation procedure had better morphological and macroscopic results measured by T2 mapping and second-look evaluation, according to data presented at a recent meeting.

Clemente Ibarra, MD, of the Orthopedic Sports Medicine and Arthroscopy Division and Tissue Engineering, Cell Therapy and Regenerative Medicine Unit at the National Institute of Rehabilitation in Mexico City, and his colleagues conducted a prospective, randomized controlled trial to compare 2-year follow-up clinical outcomes, T2 mapping values and second-look evaluation of consecutive patients with symptomatic articular cartilage lesions in the knee. The lesions ranged in size from 1 cm2 to 4 cm2 and were classified as grade III to grade IV according to the International Cartilage Repair Society (ICRS) classification. The researchers randomly assigned 23 patients to matrix encapsulated autologous chondrocyte implantation (MECI) and 21 patients to microfracture.

"When patients were randomized to microfracture, the procedure was performed during the index procedure, and when they were randomized for cartilage implantation, we obtained 4 mm biopsy osteochondral specimens during the initial procedure," Ibarra said during his presentation.

Level 1 study

Surgeons harvested two osteochondral biopsies in the first surgery. Isolated chondrocytes were expanded in a monolayer culture. After 4 weeks, surgeons formed a construct with a collagen III scaffold enveloped in chondrocyte monolayers and incubated in DMEM-F12 and autologous human serum for 4 days. Surgeons debrided the lesion and fixed the construct with a bioabsorbable mini-anchor for condylar lesions or with a suture-passing technique for patellar lesions.

"During implantation, we evaluated chondrocytes, measured and repaired the defects and created a 2-mm drill hole in the center of the defect and inserted a mini-anchor to which the implant was inserted in an arthroscopic cannula," Ibarra said.

Blinded reviewers performed clinical and T2 mapping evaluations prospectively at baseline and 3 months, 6 months, 12 months, 18 months and 24 months. They analyzed six regions of interest during T2 mapping, including healthy native cartilage for basal tissue, superficial tissue and global native tissue as well as basal repaired tissue, superficial repaired tissue and global repaired tissue. Reviewers performed the second arthroscopic look at 12 months using the ICRS Macroscopic Evaluation Score.

Promising early results

Patients in both groups had similar demographic characteristics and comorbid conditions. At 2-year follow-up, researchers found no statistically significant differences between the two groups in Lysholm, Knee Injury and Osteoarthritis Outcome Score, Tegner and IKDC scores.

Researchers observed significant differences in T2 mapping of basal repaired tissue and global repaired tissue favoring the MECI technique. The second-look evaluation score was also significantly higher for patients who underwent MECI compared with those who underwent microfracture. The researchers also reported two failures in the microfracture group and none in the MECI group.

"We have presented a simple and reproducible technique for trained arthroscopic surgeons, predictable results up to 24 months, similar outcomes to those reported in the literature and a statistically significant difference by T2 mapping and second-look arthroscopy," Ibarra said. "However, we understand that second-look follow-up and a larger number of patients are needed for conclusions to be drawn." – by Tina DiMarcantonio

Reference:
Ibarra C. Paper #455. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 11-15, 2014; New Orleans.
For more information:
Clemente Ibarra, MD, can be reached at Av-Mexico Xochimilco 289, Mexico City, Mexico 14289; email: clementeibarra@yahoo.com.
Disclosure: Ibarra has no relevant financial disclosures.