Comparison of the Collagen Meniscus Implant with Partial Meniscectomy. A prospective randomized trial.

Rodkey WG, DeHaven KE, Montgomery WH, Baker CL, Beck CL, Hormel SE, Steadman, JR, Cole BJ and Briggs KK. J Bone Joint Surg. 2008;90-A:1413-1426.

This is the editor's interpretation of a paper published in the orthopaedic literature in 2008 - our attempt to make relevant medical articles accessible to lay readers. If you wish to read the original it is easy to ask your librarian to obtain a reprint for you from any medical library.

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.


The results of the collagen implant were good. The second-look arthroscopy showed that the implant had resulted in a significant increase in total tissue surface area. Any residual defect was due to rim fraying or partial resorption of the implant. The new tissue was stable in location, and maintained the shape of the original implant. No shrinkage was noted. There was no tearing away of the implant from the original meniscus.

In terms of symptoms, the results were compared across two groups - not only were the patients in the collagen/non collagen group compared, but also the researches compared an acute/chronic group. That is, the patients had originally been recorded as being in the 'acute' group if they had never had surgery to this meniscus before, and in the 'chronic' group if they had. What the researchers found was that the scores were pretty much the same for the implant group and the non-implant group with the exception of the score for activity. When looking at the activity scores they found that in the acute group, regardless of whether or not the patient had received a collagen implant, they regained an average of 41% of their lost activity. In the chronic group - those who had had a previous operation on the meniscus - the collagen implant group also regained this amount of lost activity, but the ones without the implant did not. They only regained 29%.

There was no significant different in complications between the groups.

And had the implant really turned into proper meniscal tissue? Not exactly. The biopsy showed that there was infiltration of cells into the scaffold. These cells seemed to be maturing into fibrocartilage cells but they were not fully true meniscus cells. The scaffolds were resorbing. The interface between original meniscus and scaffold tissue was supplied with blood vessels. Rarely some synovitis was present but no aggressive inflammation.

The authors concluded that the collagen implant offered benefits to patients who had a chronic meniscal defect, that is they had already had previous surgery on the meniscus, but that it offered no benefits in acute cases, that is when this was the first surgery on the torn meniscus.

[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.]