CHAPTER 25 Biologic Augmentation Devices
Chronic massive rotator cuff tears remain a difficult problem to treat for orthopedic surgeons. Rotator cuff atrophy, tendon retraction and scarring, and potentially glenohumeral arthritis are some of the aggravating factors. These patients may have failed previous open or arthroscopic procedures, adding the variables of deltoid deficiency, multiple empty anchors, and failed suture material. Achieving excellent results in this unfavorable biologic environment is usually impossible. Good results, including pain relief and improved function, can be achieved if the joint is stabilized with functional rotator cuff attachment to the humeral head.
Arthroscopic repairs for chronic massive rotator cuff deficiency require a keen understanding of the rotator cuff anatomy and the personality of the specific tear. Advanced arthroscopic techniques are often used, including releases of the adherent cuff, side to side repairs, bone marrow venting, and judicious placement of anchors. Even if the rotator cuff is secured to bone there is still much to do; there are many accounts of poor outcomes in this patient population after good-quality repair by a skilled surgeon. Often, a poor biologic environment leads to recurrent tears prior to healing. Until recently, there has been little available to improve the unhealthy biology.
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.
HISTORY AND PHYSICAL EXAMINATION
Chronic massive tears usually occur in patients older than 45 years and are less common in the younger patient population. The symptoms include chronic aching and weakness in the shoulder that worsens with abduction and external rotation. Catching, locking, and crepitation may also be present. Symptoms increase noticeably at night and sleep is frequently interrupted. In the most severe cases, shoulder elevation and external rotation are weak or impossible.
A comprehensive examination of the shoulder is necessary for all patients, complete with specific tests for the rotator cuff, starting with inspection and comparison to the unaffected side to evaluate for atrophy of the rotator cuff musculature. Humeral head subluxation and deltoid incompetence are easily assessed on many patients with inspection and palpation. Active and active-assisted range of motion are also tested. Active elevation may be severely limited but passive motion is often preserved.
Muscle testing starts with the arm at the side to test the infraspinatus and subscapularis muscles with internal and external rotation. The subscapularis can also be isolated with the belly press or lift-off test. The supraspinatus is tested with the arm in 60 degrees of abduction and 45 degrees of forward flexion, and the shoulder held in maximum internal rotation. The patient attempts to elevate as the examiner places progressive downward pressure. Impingement and acromioclavicular arthritis often coincide with rotator cuff pathology, so patients undergo specific tests for those entities as part of the complete examination.
Four standard views of the shoulder are obtained in all patients with rotator cuff problems:
The gold standard for imaging of the soft tissues around the shoulder, including the rotator cuff, is magnetic resonance imaging (MRI). This study provides the most information when a powerful 1.5-T magnet is used, with specialized shoulder coils and current software. Standard three-plane sequences should be obtained for T1- and T2-weighted images. Large full-thickness tears are easily visualized on the T2 coronal oblique images. The T1 sagittal oblique images are useful for visualizing the muscle bellies of the rotator cuff to determine the degree of atrophy. The axial oblique images are useful to evaluate the subscapularis and biceps tendons, because they are often involved in large and massive tears and are best visualized on this sequence.
Often, the treatment of a large or massive rotator cuff tear may follow failed open or arthroscopic surgery. In this case, it is best to obtain MRI images after intra-articular injection of dilute gadolinium-saline solution (1:100). This enhances visualization of intra-articular structures as well as the rotator cuff, biceps tendon, and old anchors in a revision setting. The MRI scan provides the most information to help determine the possibility of a primary repair; however, the decision to repair primarily, augment, or bridge is always made at the time of arthroscopy.
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 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
Patients with large rotator cuff tears, preserved function, and minimal discomfort can be treated conservatively in the short term. Corticosteroid injections combined with physical therapy offer symptomatic relief only. Unfortunately, the natural history predicts that the tear will enlarge and the joint may progress to rotator cuff arthropathy if the tendon is not surgically reattached to the tuberosity. At this point, the best option for most patients is an attempt at repair with an augmentation if necessary.
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
Glenohumeral Diagnostic Arthroscopy and Tendon Mobilization.
For all arthroscopic cases, the patient is positioned lateral decubitus on a beanbag. Bony prominences are padded and an axillary roll is placed. The standard position includes 70 degrees of abduction for glenohumeral work, 15 degrees abduction for bursal work, and 45 degrees abduction as the midposition to access the lateral aspect of the tuberosity. After creation of a standard posterior portal and an anterior interval portal, a complete diagnostic examination of the glenohumeral joint is performed, viewing from both portals. The rotator cuff tear is evaluated and débrided with an arthroscopic shaver; the tuberosity may be prepared from within the joint, usually by viewing from the anterior portal and working from the posterior portal. Intra-articular releases are performed to mobilize the tendon, if needed, using the shaver, arthroscopic liberator tool, or radiofrequency wand from the glenohumeral or bursal approach.