Using Collagen Implants to Activate Tendon Growth?
Christopher Chalk, D.C., M.P.H. • Mon, October 17th, 2016
A recent study published in Arthroscopy: The Journal of Arthroscopic and Related Surgery found that biopsies taken from patients who had a collagen implant placed over their rotator cuff repair, had new, dense, regularly oriented connective tissue growth over the rotator cuff tear.
In short, the collagen implant appeared to have activated tendon growth.
If confirmed with subsequent studies, this would represent a significant discovery.
The Birth of the Collagen Implant
“The design of the Rotation Medical Collagen Implant (RMCI) is based on the fundamental concept of improving the biomechanical environment of a partially torn rotator cuff tendon in the hopes of limiting further tear production which is known to occur in a high percentage of these injuries, ” Dr. Arnoczky, lead author of the study told OTW.
Steven Arnoczky, DVM is the Wade O. Brinker Endowed Professor of Surgery in the College of Veterinary Medicine at Michigan State University, working out of the Laboratory for Comparative Orthopedics Research. He was inducted into the American Orthopaedic Society for Sports Medicine's Hall of Fame (AOSSM) in 2014. He also receives support from Rotation Medical Inc.
A systematic review of rotator cuff tears by Strauss et al. (Arthroscopy 2011;27(4):568-80) found that up to 34.6% of partial thickness tears progress to full-thickness tears.
According to Dr. Arnoczky, a model developed by researchers at the Mayo Clinic showed that if 2 mm of new host tissue were formed over the supraspinatus tendon, that peak strain decreased 40% to 47% for partial thickness bursal or articular surface tears.
“Using the Mayo findings, we designed a collagen implant which allowed for rapid host tissue ingrowth and functional remodeling. We then examined the natural history of the implant in an animal model and were able to confirm both its safety and ability to rapidly induce the formation of new tendinous tissue, ” Dr. Arnoczky said. This was from a 2013 study entitled, “Tissue-engineered augmentation of a rotator cuff tendon using a reconstituted collagen scaffold: A histological evaluation in sheep”.
And yes the sheep did well.
The authors concluded, “The use of a reconstituted collagen scaffold consistently increased the thickness of a rotator cuff tendon by inducing the formation of a well-integrated and mature tendon-like tissue.”
“The positive findings of the pre-clinical animal study led to the ‘first in man’ studies to determine if the RMCI could rapidly induce new tissue formation over the bursal surface of unrepaired partial thickness lesions (bursal, intra-substance, and articular) as well as repaired full-thickness lesions. We also wanted to see if the RMCI could limit tear progression in the partial thickness patients and prevent re-tears in the full-thickness patients, ” Dr. Arnoczky explained.
The first study he is referring to is a 2015 study entitled, “Healing of full-thickness rotator cuff tears following arthroscopic augmentation with a collagen implant: 2-year Follow-up”.
This was followed by the 2016 study, “Healing of partial-thickness rotator cuff tears following arthroscopic augmentation with a collagen implant: A 2 year MRI follow-up”.
“The two-year MRI studies confirmed that the RMCI rapidly induced new tissue ingrowth and that all partial thickness lesions either healed completely or decreased in size, ” he said.
Yes but did any partial thickness lesions increase in size?
Dr. Arnoczky replied with an emphatic NO!
What about the full-thickness group?
“We did not see re-tears at two years using the MRI. In fact, the MRI images suggested that the new tissue generated by the implant, as well as the tissue which filled-in the partial thickness lesions, was not scar tissue but rather took on the MRI appearance of tendon.”
The New Study
This leads up to the current study which would definitively determine if the character of this new tissue is histologically tendon by doing a biopsy. As the authors point out, an MRI can only infer that the tissue is a tendon.
Seven patients who previously had arthroscopic rotator cuff repair (supraspinatus) with the addition of the bovine collagen implant had to have a second arthroscopic procedure. The most common reason for performing the second procedure was trauma. The time of the biopsies were one at five weeks, two at two months, three at three months and one at six months.
Dr. Arnoczky discussed the importance of the study design. “Because none of the second-look arthroscopic procedures which provided the biopsies were related to any clinical issues with the implant, we were able to look at the natural history of the implant in humans over a six-month period without any confounding variables.”
And you probably guessed the findings…
“Our findings were remarkably similar to what we saw in the preclinical animal study. The implant rapidly induced new tissue formation and allowed for the functional remodeling of the tissue into dense regularly-oriented connective tissue, which is the histological definition of a tendon. Also, we were able to confirm that the RMCI is removed by the host by six months without any evidence of an inflammatory or foreign body reaction.”
More Docs Using the Implant
Dr. Kevin A. Klean , DO and Shariff K. Bishai, DO, MS, FAOAO published a paper entitled” Clinical Experience with the Rotation Medical Bioinductive Implant for Rotator Cuff Repair with Biological Augmentation”. They report that the implant decreased rehabilitation time, sling use and had excellent outcomes with regard to function and pain. For the orthopedist, another advantage was a quicker surgical time than traditional repair.
Rotator Cuff Augmentation Patches
I asked Dr. Arnoczky about patches that have been used in the past for rotator cuff repair.
“The basic premise of which most of the rotator cuff ‘patches’ (porcine small intestine, fetal bovine skin, human dermal allografts, etc.) were based was the perceived need to immediately augment the strength of a full-thickness rotator cuff repair by adding foreign tissue. The reasons for the suboptimal results seen with some of the rotator cuff augmentation patches are likely multi-factorial. The behavior of these materials has been shown to be quite variable. They were not specifically designed to optimize new, functional tissue formation by the host, and some may even end up acting like a prosthesis.”
Prosthesis? I think I’ll opt for the natural remodeling process.
Dr. Arnoczky concluded by discussing future studies. He told OTW that a five-year MRI follow-up study on the 2015 and 2016 studies mentioned previously to confirm the durability of the partial-thickness and full-thickness repair results is planned. There is also a larger multi-center study currently underway to evaluate outcomes on both partial and full-thickness rotator cuff tears.