CHAPTER 25 Biologic Augmentation Devices
Augmentation for rotator cuff surgery has been at the forefront of research and development in recent years, yielding several products, most of which have not acquired widespread popularity. Xenograft materials are available, including porcine small intestine submucosa (SIS) (Restore Orthobiologic Soft Tissue Implant, DePuy Orthopaedics, Warsaw, Ind), fetal bovine dermis (TissueMend Soft Tissue Repair Matrix, Stryker Orthopaedics, Mahwah, NJ), porcine dermal collagen—Zimmer Collagen Repair Patch (Zimmer, Warsaw, Ind) and Permacol (Tissue Science Laboratories, Aldershot, UK), equine pericardium (OrthADAPT Bioimplant, Pegasus Biologics, Irvine, Calif). Some reported problems with these grafts include foreign body reactions mimicking infection, suture pull-out, loss of range of motion, and clinical failure.1–8 Synthetic materials are also available for augmentation, including polyurethane urea bands (Artelon, Artimplant, Lansdale, Pa), knitted polyester, polyethylene terephthalate, fiber mesh (Mersilene mesh, Ethicon, Somerville, NJ) and the expanded polytetrafluoroethylene patch (Gore-Tex Expanded PTFE Patch, W.L. Gore & Associates, Flagstaff, Ariz). There are limited reports with these synthetic materials in rotator cuff surgery and the failures have stemmed from foreign body reaction, bone resorption, and retears at the graft tendon junction.9–13
As early as 1978, human allograft tissue was used for augmentation of rotator cuff defects. These initial attempts with freeze-dried allograft tissue had mixed results. Acute rejection, infection, and clinical failure have limited its use.14,15 Presently, the allograft of choice is acellular human dermal matrix, GJA (GRAFTJACKET Matrix, Wright Medical Technology, Arlington, Tenn). This material is an aseptically handled, acellular human dermal tissue that is processed to maintain an intact collagen structure while avoiding cross linking. The GRAFTJACKET has proven to be a good matrix for in situ tissue engineering in tenocyte models and has demonstrated superior biomechanical properties in cadaveric studies.16,17 Histiologic and biomechanical data have been very promising in rat, canine and, most recently, primate models.18–20 Postoperative biopsy at 3 months of one patient demonstrated cellular and blood vessel infiltration, lack of inflammatory response, and neotendon formation.21 This material has demonstrated promising initial clinical results at several centers and is our preferred augmentation device.22–26
ANATOMY AND PATHOANATOMY
Basic rotator cuff anatomy is covered elsewhere in this text. Here we will focus on the anatomic changes relevant to large tears. Massive retracted tears pose unique anatomic constraints. They are associated with muscle atrophy and eventually fatty infiltration, which progresses with increasing size and duration of the tear. Even with successful repairs, only a portion of the atrophy is reversed and fatty infiltration remains constant. The tendons themselves can become degenerative and fibrotic. Superior migration of the humeral head can occur, making a primary repair even more difficult. Many massive rotator cuff tears can be repaired primarily using interval scar releases and margin convergence. In some cases, the final construct may have significant tension, with poor-quality tissue and even a residual defect. In these cases, it might be beneficial to add a patch augmentation to supplement the repair because the risk for retear is high. When primary repair is impossible, it is important to have the ability to bridge the gap with a biologic augmentation device. Currently, there are no tissue replacement devices approved by the U.S. Food and Drug Administration (FDA) for bridging gaps larger than 1 cm.
DIAGNOSTIC IMAGING
Four standard views of the shoulder are obtained in all patients with rotator cuff problems:
INDICATIONS AND CONTRAINDICATIONS
The indications and contraindications for bridging and augmentation of rotator cuff defects are still being defined. For bridging, the best demographic factor is motivated patients younger than 60 years with massive irreparable tears who have severe disabling pain and well-maintained active motion. An intact biceps tendon is helpful because it facilitates sewing the graft in anteriorly. Fatty infiltration of the rotator cuff musculature and superior migration of the humeral head are acceptable variables. Augmentation is typically used for tears that are at risk for failure with primary repair. These include rotator cuffs with repairs under tension, chronic large tears, fatty degeneration, poor tendon quality, or a small residual defect following a large repair. Age is a confounding variable because older patients are more at risk for retear but are also less likely to incorporate the graft successfully, likely because of the senescence of mesenchymal stem cells.26
Relative contraindications for both procedures include moderate glenohumeral osteoarthritis or rotator cuff arthropathy, immunocompromised state, and heavy smoking. Patients older than 60 years are potential candidates but outcomes may not be equivalent to those in the younger age group.26 Older patients with cuff tears, osteoarthritis, restricted motion, and little pain are not candidates for this procedure. These patients are best served with a reverse total shoulder arthroplasty.
TREATMENT OPTIONS
Treatment options for massive rotator cuff tears are limited in the very young population. Primary repair, either arthroscopically or with a miniopen repair, is possible. Repairing massive tears with compromised tissues dramatically increases the risk of failure with either technique. In this situation, it is best to augment with a biologic scaffold to reinforce the tenuous repair. In our opinion, alternatives to repair, such as reverse total shoulder arthroplasty, latissimus dorsi transfer, glenohumeral joint fusion, and arthroscopic débridement with partial repair, are second attempts, or salvage may be considered if the allograft fails. In addition to other shortcomings, these are all nonanatomic solutions. Latissimus dorsi transfers have demonstrated good results in certain patient populations but the postoperative immobilization is likely tolerated only by the most compliant of patients.27,28 Reverse total shoulder arthroplasty appears to be a good option for patients older than 70 years with limited function.29 In the younger population, arthroplasty plays a small role because of the possibility of multiple revision surgeries over the long term. Glenohumeral joint arthrodesis sometimes offers excellent pain relief but function is limited when compared with other techniques that preserve the glenohumeral joint.30 For the very young patient, the best option is probably patch augmentation with acellular human dermal matrix (GJA; Wright Medical Technology). There is a burgeoning interest in nonstructural biologic options, including bone morphogenic proteins and growth factors. In the future, these could be added to primary repairs or grafts to improve rotator cuff healing rates.31
Arthroscopic Techniques
Patch Augmentation of Rotator Cuff Tears
The technique described here is for augmentation of primarily repaired rotator cuff tears that appear to be at risk for failure. At-risk repairs include those with residual defects, poor-quality tissue, size larger than 3 cm, and previous failed repair attempts. The technique for biologic rotator cuff replacement has been described.23
