The authors start by highlighting that to date only meniscal allografts and the collagen meniscal implant have been shown to replace lost or damaged meniscal tissue successfully in patients. In a meniscal allograft the transplant generally replaces the entire meniscus and does not need a meniscal rim for attachment. A collagen meniscal implant may be used to fill a meniscal defect or to replace a meniscus, but it does need a meniscal rim to be sewn onto.
In this trial the collagen implant was used for damage to the medial meniscus. All patients entering the trial had either an irreparable injury to one medial meniscus or had already had a partial meniscectomy of one medial meniscus, with the rim of the meniscus still intact and the alignment of the long bones within normal limits (no bow legs or knock knees). Anyone with Grade-IV joint surface damage were excluded from the trial, as well as patients with posterior cruciate ligament damage or damage of the lateral meniscus that required repair or excision of more than 25%. A concurrent injury to the anterior cruciate ligament was not an exclusion factor.
311 patients were entered into the study from 16 sites and involved the participation of 26 surgeon-investigators. The patients were randomly divided into two groups - the one group had an arthroscopic partial meniscectomy and joint debridement ('cleaning out') (if indicated) and the other had the same PLUS a collagen meniscus implant. The study was not 'double-blind' as the rehabilitation protocol of the two groups needed to be different, and also the collagen group were required by the protocol to sign up for a 'second-look' arthroscopy. At the time of surgery the extent of the missing meniscus was measured as well as the grade of joint surface damage. The collagen implant group had the implant sutured to the remaining meniscus or meniscal rim. The control group then went onto a standard rehab protocol, while the collagen group had a knee brace applied and locked in full extension and remained non-weight-bearing on crutches for the first two weeks. They were allowed to bear weight if standing. The brace was worn for 6 weeks, although the patient removed it 3-4 times a day in order to do passive range-of-motion exercises, initially restricted to 0-60 degrees and increasing to 90 degrees in weeks 5 and 6. Crutches were continued for this time, but by 6 weeks they were allowed to bear full weight but continued the crutches until the 8th week. Then the rehab continued relatively normally until full unresticted activities by 6 months. At follow up visits both groups completed activity scores and patient-satisfaction scores and any complaints were documented.
After a year the collagen implant group underwent a second-look arthroscopy that included a biopsy of the implant area. Any residual meniscus defect was measured and recorded. Both groups were then followed up over a period of five years.
[Ed: Although the trial was funded by the manufacturers of the collagen implant, ReGen Biologics, the multicentre nature of the research and the reputation of the authors endorses the results.]
