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Isolated patella defects treated with ACI led to long-term functional improvement
MRI demonstrated a correlation between fill grade, surface and integrity of the repair tissue with clinical scores.
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Patients with isolated patella defects who underwent autologous chondrocyte implantation experienced significant functional improvement that remained durable at the 15-year follow-up, according to study findings.
“[Autologous chondrocyte implantation] ACI works well on the patella for a problem that there is no other good solution for in a young patient,” Tom Minas, MD, director of the Cartilage Repair Center at the Brigham and Women’s Hospital and professor of orthopedics at Harvard Medical School, told Orthopedics Today. “You can monitor the clinical results with MRI scan and if you get a good repair tissue fill, [the patient does] well. If you get a poor repair tissue fill, then the chances are they are not going to do well,” he said.
Functional, MRI outcomes
Minas and his colleagues studied 30 patients with lesions of the patella who underwent ACI. They collected validated patient-reported outcomes, which included the SF-36, WOMAC score, Modified Cincinnati activity score, Knee Society score and a patient satisfaction survey. The investigators also objectively evaluated the patients’ MRIs.
To correct lateral maltracking and to obtain soft tissue balancing, the follow-up results showed 19 patients underwent tibial tubercle osteotomy. The average defect size was about 4.7 cm2. There were three type II defects, nine type III defects and 18 type IV defects based on the Pidoriano/Fulkerson classification.
Overall, 83% of patients reported good or excellent results and 13% of patients reported fair knee function at the 2-year to 14-year follow-up. All patients had significantly improved functional scores at 24 months and 80% of patients described their knees as being in a better condition postoperatively than preoperatively.
Workers’ compensation
Results showed three failures occurred among workers’ compensation patients. They tended to be older than the non-workers’ compensation patients, researchers noted.
A reoperation was performed for 60% of patients.
“This was mostly done arthroscopically for periosteal overgrowth in this ACI generation-one study,” Minas said, noting membrane-related overgrowth is rarely seen today because the periosteum was replaced with a collagen membrane in second generation ACI.
Postoperatively, 75% of the 24 patients who underwent MRI had complete fill of the defect at 24 months, minimum. Knee Society score and mental health positively correlated with fill grade on MRI, according to the researchers who noted this indicated there was an association between lower fill grade and lower scores.
“There is no good treatment for large cartilage defects of the knee cap,” Minas said. “People have tried using cadaveric allograft tissue, morselized cartilage tissue, microfracture, mosaicplasty. All of those techniques do not work well on the patella. They have a high failure rate, whereas ACI in the patella has an outstanding success rate and it is probably the gold standard for treatment of articular cartilage injuries to the patella.”
Increased recovery time
Although results were positive in these patients whose isolated patella defects were treated with ACI, recovery is slow for patients, Minas noted. The time to recovery may be reduced by using tissue-engineered cartilage, a procedure in which the tissue is developed and grown before it is implanted in the knee after about 6 weeks, he said.
The cartilage then integrates and matures once it is placed in the knee, Minas noted.
“That will probably decrease the recovery by half, at least, ... so instead of it taking 14 [months] to 18 months for patients to return to sports, they will probably be back to sports within 6 months, which will make a huge difference to patients,” Minas said. – by Casey Tingle
- Reference:
- Von Keudell A, et al. Cartilage. 2017;doi:10.1177/1947603516654944.
- For more information:
- Tom Minas, MD, can be reached at The Cartilage Repair Center, 850 Boylston St., Chestnut Hill, MA 02467; email: tminas@partners.org.
Disclosure: Minas reports he is a consultant for Vericel Corporation.