Shoulder and elbow tendon injuries are some of the most challenging problems to treat surgically. Tendon repairs in the upper extremity can be complicated by poor tendon quality and, often times, poor healing. Extracellular matrices, such as human dermal allografts, have been used to augment tendon repairs in shoulder and elbow surgery. The indications and surgical techniques regarding the use of human dermal allograft continue to evolve. This article reviews the basic science, rationale for use, and surgical applications of human dermal allograft in shoulder and elbow tendon injuries.
Key points
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Allograft augmentation for tissue repair should be biologic, sterile, non-inflammatory, and have good suture pullout strength.
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Human dermal allograft is an extracellular collagen matrix that acts as a collagen scaffold for host cell repopulation and integration.
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Surgical applications for human dermal allografts are evolving.
Introduction
Tendon injuries to the upper extremity can be challenging to treat. Injuries to the shoulder and elbow (ie, rotator cuff tears, distal biceps ruptures, pectoralis major ruptures) are due to abnormal or degenerated tendons. Surgical repair of tendon injuries in the upper extremity can be complicated by early failure due to inadequate repair (mostly attributed to inadequate suture-tendon interface strength) or late failure (mostly attributable to inadequate tendon to bone healing). Massive rotator cuff tears can have failure rates greater than 90%. Failure of surgical repair of any tendon in the upper extremity can be related to many factors, namely tendon quality and the patient’s own biology.
Augmentation of tendons with xenograft collagen matrices has been reported in the literature with poor outcomes. Ianotti reported unfavorable outcomes with the use of a porcine submucosal patch in rotator cuff repairs. Walton and colleagues reported severe inflammatory reactions to the porcine patch, which resulted in the total abandonment of grafts in rotator cuff repair augmentation. Ultimately, the ideal augmentation graft should be biologic, sterile, noninflammatory, and have excellent suture pullout strength.
The use of extracellular matrices for augmentation of soft tissue repairs in orthopedic surgery has gained recent interest in an attempt to improve healing and surgical outcomes. There are many commercially available dermal allografts and xenografts for use in orthopedic surgery. These soft tissue grafts include human dermis, porcine dermis, porcine intestinal submucosa, and synthetic materials. While, there is a paucity of evidence available in the literature regarding the long-term outcomes with the use of these products, the small amount of literature currently available shows that the early results are promising. Many of the applications for the use of these soft tissue collagen matrices, particularly human dermal allograft, also referred to as acellular dermal matrix (ADM), continue to evolve. Human dermal allograft is an extracellular collagen matrix that has been shown to have tissue integration properties, in vivo revascularization, cellular incorporation, and excellent biomechanical properties that make it an attractive option for soft tissue augmentation procedures in orthopedics. Surgeons who wish to use these products in their practice should be versed with the available products on the market, their potential uses, preparation, safety, and surgical techniques. There are other collagen matrices currently available on the market, such as xenograft small intestinal submucosa (SIS) and synthetic collagen matrices that are beyond the scope of this article. This review focuses on the properties, uses, and surgical applications for the use of human dermal allografts in shoulder and elbow surgery.
Introduction
Tendon injuries to the upper extremity can be challenging to treat. Injuries to the shoulder and elbow (ie, rotator cuff tears, distal biceps ruptures, pectoralis major ruptures) are due to abnormal or degenerated tendons. Surgical repair of tendon injuries in the upper extremity can be complicated by early failure due to inadequate repair (mostly attributed to inadequate suture-tendon interface strength) or late failure (mostly attributable to inadequate tendon to bone healing). Massive rotator cuff tears can have failure rates greater than 90%. Failure of surgical repair of any tendon in the upper extremity can be related to many factors, namely tendon quality and the patient’s own biology.
Augmentation of tendons with xenograft collagen matrices has been reported in the literature with poor outcomes. Ianotti reported unfavorable outcomes with the use of a porcine submucosal patch in rotator cuff repairs. Walton and colleagues reported severe inflammatory reactions to the porcine patch, which resulted in the total abandonment of grafts in rotator cuff repair augmentation. Ultimately, the ideal augmentation graft should be biologic, sterile, noninflammatory, and have excellent suture pullout strength.
The use of extracellular matrices for augmentation of soft tissue repairs in orthopedic surgery has gained recent interest in an attempt to improve healing and surgical outcomes. There are many commercially available dermal allografts and xenografts for use in orthopedic surgery. These soft tissue grafts include human dermis, porcine dermis, porcine intestinal submucosa, and synthetic materials. While, there is a paucity of evidence available in the literature regarding the long-term outcomes with the use of these products, the small amount of literature currently available shows that the early results are promising. Many of the applications for the use of these soft tissue collagen matrices, particularly human dermal allograft, also referred to as acellular dermal matrix (ADM), continue to evolve. Human dermal allograft is an extracellular collagen matrix that has been shown to have tissue integration properties, in vivo revascularization, cellular incorporation, and excellent biomechanical properties that make it an attractive option for soft tissue augmentation procedures in orthopedics. Surgeons who wish to use these products in their practice should be versed with the available products on the market, their potential uses, preparation, safety, and surgical techniques. There are other collagen matrices currently available on the market, such as xenograft small intestinal submucosa (SIS) and synthetic collagen matrices that are beyond the scope of this article. This review focuses on the properties, uses, and surgical applications for the use of human dermal allografts in shoulder and elbow surgery.
The basics of dermal allograft
Human dermal allograft is a decellularized piece of human dermis that is processed and sterilized using various techniques to allow for human use. The dermal allograft is an extracellular collagen matrix, which is designed to be a collagen scaffold for tissue integration from the host. The allograft was intended for use as an “onlay” on top of a repair or as a bridge between tissues. The allograft also can be “incorporated into the repair” and can serve to strengthen the suture-tendon interface. For the allograft to be successful, it needs to have the ability to allow the host cells to migrate into it and incorporate themselves into the graft. The decellularization of human dermis is intended to remove the donor cells from the tissue, which may allow for the recipient cells to repopulate the graft faster and thus potentially allow for faster incorporation and revascularization, all while minimizing the risk of rejection and/or an inflammatory response. In theory, it provides a clean and cell-free scaffold. This decellularization process, however, may affect the biomechanical strength of the graft. Many available allografts have different levels of decellularization, although the ideal percentage of residual donor cells in the graft is unknown.
Dermal allografts, much like other extracellular collagen matrix scaffolds, elicit a histologic and a cytologic response to the tissues. Because it is an implantable product, the sterility of each product must be considered. Sterilization techniques for dermal allograft typically involve varying doses of radiation before packaging. Some available allografts are not sterilized. The clinical significance is currently unknown, but most implantable devices in orthopedics are sterilized before use. The biomechanical properties of each allograft may vary due to sterilization, preparation, storage, hydration, and methods of decellularization. These processes may affect the ability of the allograft to remodel and incorporate into the repair. The time frames of remodeling, incorporation, and degradation are currently not well understood for most dermal allograft products on the market at this time. Dermal allograft is an attractive option for tendon augmentation because it was shown to have superior suture pullout strength when used to augment rotator cuff repairs.
Options for Acellular Dermal Matrices
When selecting the proper allograft to use in practice, some important factors regarding ADM should be considered ( Table 1 ). Clinically applicable ADM products should be biocompatible, available in a range of sizes and thicknesses, have excellent suture retention properties, easy preparation, easy surgical handling, moderate costs, and ideally have some evidence-based support in the literature. Although clinical studies are currently lacking, there are some data to support the use of ADM in rotator cuff repairs.
| Product | Material | Processing | Sterilization | Donor DNA Removal | Storage | Storage Solution | Preparation Time | Strengths | Weaknesses |
|---|---|---|---|---|---|---|---|---|---|
| ArthroFlex (LifeNet Health) | Human dermis | Matracel | Low temp Low dose Irradiation | >97% | Room temperature | Saline | <1 min | Room temperature storage, sterile, fast preparation time | Relatively new product |
| Graft Jacket (Wright Medical) | Human dermis | Proprietary | None/Aseptic | N/A | Refrigerator | Dehydrated | >15 min | Numerous published studies | Refrigerator storage, >15 min preparation time, not sterile |
| AlloPatch HD (MTF) | Human dermis | Aseptic | None/Aseptic | N/A | Room temperature | 70% Ethanol | <5 min | Room temperature storage, hydrated | Ethanol storage, not sterile, low suture pullout strength |
| Matrix HD (RTI biologics) | Human dermis | Tutoplast | Irradiation | N/A | Room temperature | Dehydrated | >10 min | Room temperature storage, 5-y shelf life | >10 min preparation time, Tutoplast processing, irradiated |
There are 4 major ADMs available on the market at this time: ArthroFlex (LifeNet Health, Virginia Beach, VA), Graft Jacket (Wright Medical Technology, Memphis, TN), AlloPatch HD (MTF, Edison, NJ), and Matrix HD (RTI Surgical, Alachua, FL).
ArthroFlex is a human dermal allograft that is considered a sterile product. A patented decellularization process called “Matracell” is used to remove more than 97% of the DNA from the graft. This specialized process has no adverse effect on the biomechanical properties. ArthroFlex is stored at room temperature, is hydrated in the packaging, and has a quick preparation time ( Fig. 1 ). It is available off the shelf in multiple sizes and thicknesses.
GRAFTJACKET uses a proprietary decellularization process that renders the graft acellular. This product is processed with aseptic techniques and must be stored in a refrigerator. Because it is dehydrated, it requires a 15-minute rehydration and preparation time before implantation. This particular ADM product is available in multiple sizes and thicknesses off the shelf ( Fig. 2 ).
AlloPatch HD is an ADM that has a quick preparation time and is also stored at room temperature. This product is processed with aseptic techniques and is stored in 70% ethanol.
Matrix HD is another ADM that is stored at room temperature and has a 5-year shelf life ( Fig. 3 ). This product needs to be rehydrated and has an approximately 10-minute preparation time. This product undergoes a sterilization technique named “Tutoplast,” which is a specialized chemical sterilization process that removes bacteria and pathogens from the graft without affecting the collagen structure. In addition, there is a low dose of gamma irradiation at the end of the process for final sterilization and packaging.
Safety of Human Dermal Allograft
The implantation of allograft tissues poses a risk of disease transmission, as well as rejection of the graft by the recipient. Initial use of extracellular matrix (ECM) products began with porcine SIS graft that was associated with poor results, including a 30% rate of severe inflammatory response. ADM products, however, have been shown to be safe in a several of clinical studies.
The senior author (RM) has had personal experience with the use of ADM in more than 100 patients in the past 4 years. He has used ADM for augmentation of rotator cuff repair, distal biceps repairs, triceps repairs, pectoralis major repairs, elbow and knee capsule reconstructions, and acromioclavicular (AC) joint reconstruction, as well as patellar and quadriceps tendon ruptures. There have been no failures due to rejection, inflammatory reaction, or infection. Although this evidence is anecdotal, ADM appears to be safe for clinical use and long-term studies are currently in process at our institutions.
Applications in the shoulder
Rotator Cuff Tears
Rotator cuff repairs in older patients can have a poor outcome due to failure of the tendon repair or inability to heal to bone. Retear rates have been shown in the literature to be higher than 90% for large and massive tear. Multiple factors have been implicated as a role in rotator cuff repair failures, including smoking, age older than 63, massive tears, and fatty infiltration. Suture pullout through the tendon is thought to be the most common method of failure.
These problems sparked interest among surgeons to “augment” rotator cuff repairs. The use of extracellular collagen matrix for rotator cuff repairs is aimed at strengthening the repair by augmenting the suture-tendon interface, increasing the repair strength, and, thus, improving healing rates. Allografts have been shown to add to suture retention strength when used to augment a rotator cuff repair. In addition, ADM grafts were stronger when compared with SIS grafts. There have been multiple reports using ADM as a “bridging technique” in the repair of massive, retracted, irreparable rotator cuff tears by suturing the ADM graft to the rim of the retracted cuff tendon and repairing the ADM to the greater tuberosity. They demonstrated an arthroscopic technique with good clinical and radiographic (MRI) results. Burkhead and colleagues reported on a series of 17 patients with a massive or recurrent tear. ADM was used in an open rotator cuff repair as an “onlay.” This study showed improved shoulder outcome scores and pain scores with no complications. Later studies introduced the use of ADM in an arthroscopic rotator cuff repair and showed good results with no adverse events related to the graft reported.
There are currently 2 methods of using ADM for augmenting a rotator cuff repair: as an “onlay” on top of the repair to augment the repair and as a “bridge” to replace a deficient rotator cuff tendon. The indications for tendon augmentation with ADM as an “onlay” are advanced age, poor tendon quality, and for revision repairs. The rotator cuff surgery is performed arthroscopically. An anchor-based rotator cuff repair is performed using a standard posterior, posterolateral viewing, anterolateral working, and anterior portals. We prefer to use a SpeedBridge Repair (Arthrex, Naples, FL). The medial row anchors are placed first. One suture from each anchor is used to tie down the rotator cuff to the bone. The distance between the anchors is measured and the ADM is cut to a desired width and length. The fiber tape sutures are brought out through a cannula, placed through the ADM with a trochar/cutting needle, and the ADM is shuttled into the shoulder. A knotless lateral row anchor is then used to finish the cuff repair with the ADM on top of the tendon. The final construct is a double-row transosseous equivalent repair with an ADM “onlay.” The ADM can increase the strength of the repair at the suture-tendon interface ( Fig. 4 ).
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