Abstract
Dear Editor:
We read with interest the article by Cole et al, “Prospective Evaluation of Allograft Meniscus Transplantation: A Minimum 2-Year Follow-up” (June 2006, pp 919–927). This study presented the subjective and functional early (2- to 4.8-year) follow-up results of 44 meniscus allografts. The authors excluded patients with severe arthritic degeneration but included those who had concomitant procedures for chondral defects, which represented 47.5% of the study group. The results led the authors to conclude that “symptomatic patients with appropriate indications should expect to do well with respect to pain relief and an ability to increase activity levels after transplantation.”
In the Discussion section, the authors cited many other meniscus allograft investigations of short follow-up duration, all with high success rates in terms of subjective and functional criteria. However, the authors failed to cite many other studies that demonstrated different findings, especially when magnetic resonance imaging (MRI) was used to provide a more objective analysis of allograft size and position in the joint.1,2,4,6,7 The concern we have is that the authors presented 1 potentially biased view of this operation, without balancing the favorable short-term results to those raised by other investigators with respect to MRI findings and survivorship rates.
For instance, Stollsteimer et al 4 reported on 23 patients who received meniscal allografts and were followed from 13 to 69 months postoperatively. Eight patients (35%) required a second operation for meniscal symptoms. Although good pain relief was obtained in 18 knees, MRI data from 12 knees showed that shrinkage of the transplants had occurred, as the allografts were reported to be an average of 63% the size of the contralateral normal menisci.
Rath et al 3 followed 22 meniscal allografts 2 to 8 years postoperatively. Even though all patients except 1 had significant improvements in SF-36 scores, 8 menisci (36%) failed and were removed an average of 2.5 years postimplantation.
Van Arkel et al 6 reported on 19 cryopreserved meniscus allografts followed 14 to 55 months postoperatively with MRI, arthroscopy, and clinical examination. Based on clinical findings alone, 16 allografts were successful and 3 failed. However, MRI identified 8 of the 19 cases as failures because 7 allografts had severe or moderate shrinkage. None of the allografts were in a normal position; 11 showed subextrusion, 6 demonstrated extrusion, and 2 had bucket handle–like appearances.
Van Arkel and de Boer 5 presented a survival analysis of 63 consecutive meniscal allografts followed 4 to 126 months postoperatively. Persistent pain or mechanical damage (detached or torn allograft) was used to document allograft failure. The cumulative survival rates of lateral, medial, and combined allografts in the same knee were 76%, 50%, and 67%, respectively.
We recently reported the results of 40 consecutive meniscus allografts followed 2 to 5.7 years postoperatively. 1 Patients with advanced knee joint arthrosis were excluded from the procedure. Meniscus allograft characteristics were determined by a critical rating system that combined subjective, clinical, and MRI factors. An osteochondral autograft transfer was also done in 16 knees. The subjective and functional results appeared reasonable because 34 of the 38 patients (89%) rated their knee condition as improved. Before surgery, 30 patients (79%) had pain with daily activities, but at follow-up, only 4 (11%) had such pain. However, when MRI data were added to the rating, the meniscus allograft characteristics were found to be normal in 17 (42.5%), altered in 12 (30%), and failed in 11 (27.5%).
Potter et al 2 followed 29 fresh meniscal allografts with MRI and clinical examination 3 to 41 months postoperatively. Increased signal intensity was detected in the posterior horn in 15 knees, and peripheral displacement at the body was noted in 11 knees; all of these knees had moderate or severe chondral degeneration. Knees with mild degeneration had no abnormalities noted in the meniscus allografts and had superior clinical results compared with those with severe degeneration. These results were quite similar to those we previously reported in a group of 96 fresh-frozen irradiated allografts, which Cole et al cited in their article. In that investigation, the meniscus transplant failure rate ranged from 6% (1 of 18 knees) in knees with normal or only mild arthrosis on MRI to 80% (12 of 15 knees) in knees with advanced arthrosis. We believe that neither the irradiation of the graft nor fixation caused the failures in this study. The investigations cited above all used allografts that either had been cryopreserved, had been frozen, or were fresh at the time of implantation. The high failure rates show a lack of correlation or strong evidence that the irradiation process alone was the cause of the failures in our study. In addition, the knee joint remodeling that occurred in the knees with advanced arthrosis (narrowing of the joint space, flattening of the femoral condyle, increased concavity of the tibial plateau, and development of marginal osteophytes) had the potential to exert undue contact pressure on the meniscus allograft. We noted that Cole et al excluded patients with these advanced degenerative changes from their study, and we wondered if this decision was because of the data cited above from multiple centers demonstrating the potential high failure rates of meniscus allografts in knees with advanced arthrosis.
We also wondered in the authors' series how many patients did not have pain relief with daily activities or on tibiofemoral compression testing at follow-up. Because the subjective and functional scaled data were only presented as mean values, one cannot determine how many knees were clinically improved by the operation. For instance, in the Noyes symptom rating, we wondered what the distribution was of patients in the various categories for pain before and after surgery (moderate–severe with activities of daily living, none with activities of daily living, none with light sports activities, none with moderate sports activities, none with strenuous sports activities). If the authors calculated this factor by summing the scores for pain, swelling, partial giving-way, and full giving-way, we wonder if the mean value could have been inflated given that only 6 knees required a ligament reconstruction and most would therefore have scored highly on the 2 giving-way scales.
Second, the mean IKDC score was 64.1 ± 20 points at follow-up. Although this represented a statistically significant improvement over the preoperative score, it still indicates that many knees had problems, which needs clarification, because the IKDC maximum score is 100 points. Third, the overall condition of the knee would be another factor in which further data would be helpful, such as the distribution of patients in the various categories and how many patients improved by at least 2 points on the 0- to 10-point scale. Fourth, the Noyes sports activity data should be presented in distribution form, allowing an indication of exactly what types of athletics patients returned to at follow-up and whether any patients were participating with symptoms.
We hope that, in the future, MRI will become mandatory in studies that report the clinical assessment of meniscus allografts. We respect and agree with the authors' conclusion that longer term studies are required to determine the ability of these transplants to provide a chondroprotective effect to the meniscectomized tibiofemoral compartment. In our opinion, the long-term prognosis for this operation remains guarded and inconclusive and is most indicated in young symptomatic patients postmeniscectomy in whom there are no other options available.