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Long-term data on meniscal allograft transplants remain inconclusive
Condyle flattening may predict outcomes best.
Meniscal allograft transplantation relieves pain and improves function, but with many long-term outcomes no better than “fair,” plus the potential for long-term failures, some orthopedic surgeons are showing concern.
Scott Rodeo, MD, who practices at the Hospital for Special Surgery in New York, said meniscal allograft transplantation offers “predictable” symptom relief. In one study of 40 transplants, 80% of the patients reported pain before surgery, but only 11% reported similar pain after surgery.
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Rodeo studied 42 freshly frozen, nonirradiated transplants at a minimum two-year follow-up. He used MRIs to objectively evaluate meniscal tissue signals, morphology, healing, size and position.
Of the 42 menisci, 29 (70%) had good or fair results with, MRI demonstrating an intact, well functioning meniscus. Thirteen (30%) showed some improvement on the standardized knee outcome scales but direct evaluation of the graft using MRI showed graft degeneration and failure, said Rodeo, who presented his results at the 6th Symposium of the International Cartilage Repair Society (ICRS). Other authors, such as Brian Cole, MD, of Chicago, reported similar outcomes, Rodeo noted.
Typical indications include pain and swelling from compartment overload after meniscectomy. Some patients presented with medial meniscus deficiency, abnormal axial alignment and previous anterior cruciate ligament reconstruction.
Contrainditions include malalignment and architectural changes such as condyle flattening, which Rodeo called “the strongest predictor of outcome.”
“There has been a worse outcome for meniscus transplantation in knees with more advanced arthrosis,” he added.
Predicting meniscal degeneration and failure is also challenging.
“We found that MRI usually demonstrates some abnormality in the intrameniscal signal,” he said. “We don’t know if this simply represents the normal remodeling process or, more likely, degenerative changes in the meniscal tissue. Potential failure of the transplanted meniscus may occur. The long-term protection [benefit] remains unknown.”
“I would advise, and we counsel patients, that meniscus transplantation may only be an interval approach to joint preservation,” he said.
Rodeo cited the MRI/arthroscopic study by Frank Noyes, MD, showing normal allograft characteristics in 43% of transplants and altered/failed characteristics in almost 60%.
“They concluded that the short-term outcome was good for pain relief, but the long-term function and joint protection are unknown,” Rodeo said.
He added that his study, as well as Noyes’s, showed abnormalities in meniscal signal and morphology in meniscal transplants.
Load sharing between the medial meniscus transplant and the ACL raises more questions.
“We have important questions about the long-term survival and function of the transplanted meniscus,” Rodeo said. “We have to learn more things about load sharing and interdependence biomechanically between the ACL and the medial meniscus.”
Many medial meniscus transplants fail in ACL-deficient knees. Conversely, ACL grafts bear higher loads in knees with deficient medial menisci, Rodeo said.
“Anterior cruciate ligament deficiency and resultant increased anterior tibial translation can excessively load the medial meniscus,” he said. “The forces on the ACL grafts are much higher when the medial meniscus is absent in contrast to an intact medial meniscus.”
Greater laxity
Other studies showed greater laxity after ACL reconstruction, Rodeo said. Researchers found that patients who had ACL reconstruction with concomitant medial meniscus transplants had better stability than those who had ACLs reconstructions with persistent medial meniscus deficiency.
In Europe, H.H. de Boer studied 63 medial meniscus transplants and found a “negative correlation” between ACL rupture and the results of meniscus implantation.
Other techniques play key roles in transplant success, Rodeo said. For example, using attached bone plugs improved meniscal horn fixation and improved the anatomical relationship between the horns, Rodeo said. He cited Stephen Howell’s cadaveric study showing that contact mechanics of the meniscus transplant placed using bone plugs were closer to normal. Also, meniscal horn fixation with sutures alone did not restore normal contact mechanics, Rodeo said.
Combined meniscus transplant and cartilage resurfacing procedures show some promise despite scarce outcome data. Rodeo advised surgeons to consider the combined approach in complex cases in which meniscus deficiency is not the only issue.
“I think we should consider meniscus replacement in the setting of cartilage resurfacing if the meniscus is absent,” Rodeo said. “The rationale, of course, is to protect the cartilage graft.”
Many hurdles remain. For example, the suitable compartment for combined transplantation and resurfacing is unknown. Also, osteotomy is not likely to make a compartment suitable for transplantation if there is condyle flattening, Rodeo said.
“In advanced knees have gone to osteotomy, you have that flattening of the condyle, and in that setting, we have seen less predictable results and higher failure rates,” he added.
Prophylactic transplantion
Rodeo does not recommend prophylactic transplantation for an asymptomatic patient with normal articular cartilage. However, he does recommended the procedure to be considered for an asymptomatic patient with early articular cartilage degeneration.
“The challenge at this time is to detect early cartilage degeneration before advanced changes occur,” he said. “We currently use MRI to detect early degeneration, and clinically you can use effusion as an early marker for the knee that is starting to degenerate.”
Advanced imaging (such as MRI T2 mapping techniques) should help physicians better diagnose cartilage degeneration, Rodeo said.
“Meniscal transplants do provide predictable relief of symptoms related to early compartment degeneration,” he concluded. “We’ve had some relatively high failure rates in knees with advanced degenerative changes. Long-term results remain unknown.
“I think this is a viable option as part of complex joint reconstruction or joint preservation. Certainly, ongoing studies are required,” he said.
For more information:
- Rodeo S. Meniscal allograft transplantation: long-term clinical results in the United States. Presented at the 6th Symposium of the International Cartilage Repair Society. Jan. 8-11, 2006. San Diego.