Page 20 - 2020 ISAKOS Newsletter Volume I

CURRENT CONCEPTS
Collagen Meniscus Implant (CMI):
Features, Techniques, and Clinical Outcomes
Associated Procedure
Meniscal tears are frequently associated with ACL injuries. In particular, irreparable damage to the posterior horn of the medial meniscus has been observed in association with up to one-third of ACL lesions. It is known that the menisci represent a secondary stabilizer of the knee, and the loss of meniscus has been identified as possible secondary cause of graft failure after ACL reconstruction. Therefore, the combined reconstruction of both structures is recommended. Bulgheroni et al. provided a comparative analysis of patients with combined ACL reconstruction and medial meniscal surgery reporting lesser degree of VAS pain and better control of the anterior tibial displacement at 9.6 year follow up in average in medial CMI group compared with meniscectomy group. These findings demonstrated that the collagen scaffold is a valid option when used in association with ACL reconstruction in patients with a chronic meniscal lesion associated with an ACL injury.
Coronal plane malalignment of the involved knee on preoperative long-leg weight-bearing radiographs should be corrected before or concurrently with CMI implantation. Linke et al., in a study in which the clinical results of combined CMI and HTO were compared with those of HTO alone, reported no significant differences between the two groups at 1 and 2 years of follow-up. These findings call into question the efficacy of CMI in patients with medial compartment overloading due to varus malalignment.
Complications
Relatively low rates of complications (7%) and reoperation (6.8%) have been reported. Although such rates may appear high for meniscal surgery, higher percentages of reoperations have been reported both for meniscal screws and arrows (33% to 68%) and for all-inside suture techniques (13% to 29%). The most frequent complications, especially in long term, have been knee swelling and residual compartmental pain. Other reported complications with a prevalence of <10% have included infection, nerve injuries, deep venous thrombosis, and implant failure. It also should be noted that a high rate of concomitant procedures (48.8%) could partially explain a reasonable number of the complications and reoperations that have occurred. Complications and failures directly related to the scaffold itself and the implantation procedure have been rare, confirming the safety of CMI implantation as reported in each individual study.
MRI Evaluation
MRI represents a non-invasive and well-tolerated method that has been used in large number of studies to evaluate the status of the CMI and the intra-articular behavior of the implant. Genovese et al. introduced a score to allow for the objective evaluation of the size and the signal intensity of the meniscal scaffold in relation to the surrounding native meniscus. The Genovese score considers morphology, size, and signal intensity and includes three grades: type 1 reflects a resorbed CMI with marked hyperintense signal, type 2 represents a small CMI with slightly hyperintense signal, and type 3 represents a CMI that is identical in size and signal intensity to the normal meniscus. However, the Genovese grading scale does not address meniscal extrusion and volume, both of which may influence the onset and progression of OA. Published investigations have shown that the CMI varied in signal and size at different follow-up times. In particular, the CMI appeared hypertrophic in the first year after surgery, with an abnormal, hyperintense, and inhomogeneous signal. These 1-year findings were seen in patients with good clinical results; therefore, it remains unclear what imaging findings should be considered as normal for the CMI. At long-term follow-up, evaluation of the CMI showed higher rates of scaffold with reduced size and with an MRI signal intensity more similar to normal meniscus.
Conclusions
CMI implantation has been shown to be safe for the knee joint. Good clinical results have been reported from 6 months through 10 years of follow-up when all associated pathologies have been adequately addressed. In particular, satisfactory results in terms of knee function and pain have been described in symptomatic patients with a previous meniscectomy. Additional studies are needed to gain more insight into the long-term clinical outcomes and to prove the long-term CMI behavior in terms of reducing degenerative changes.
References
1. Hinarejos P, Erggelet C, Monllau JC. Collagen Meniscus Implant: Basic Science, Technique and Results. In Hulet C, Pereira H, Peretti G, et al. Surgery of the Meniscus. Springer. 2016; 509-18. 2. Grassi A, Zaffagnini S, Marcheggiani Muccioli GM, et al. Clinical outcomes and complications of a collagen meniscus implant: a systematic review. Int Orthop 2014;38:1945-53. 3. Houck AD, Kraeutler MJ, Belk JW, et al. Similar clinical outcomes following collagen or polyurethane meniscal scaffold implantation: a systematic review. Knee Surg Sports Traumatol Arthrosc Off J ESSKA 2018;26:2259-69. 4. Zaffagnini S, Grassi A, Marcheggiani Muccioli GM, et al. MRI evaluation of a collagen meniscus implant: a systematic review. Knee Surg Sports Traumatol Arthrosc Off J ESSKA 2015;23:3228-37. 5. Kovacs BK, Huegli R, Harder D, et al. MRI variability of collagen meniscal implant remodelling in patients with good clinical outcome. Knee Surg Sports Traumatol Arthrosc Off J ESSKA 2019;https://doi.org/10.1007/s00167-019-05715-9.
18 ISAKOS NEWSLETTER 2020: VOLUME I