The use of biologic grafts in rotator cuff repair and reconstruction is an area of burgeoning interest and focused research. The main problem is that rotator cuff repair is a challenging task. Our understanding of the problems involved, surgical tools available, and techniques has changed radically since Dr. Codman’s first description of a repair in 1911. Despite these advances, we have come to learn that actually getting a complete repair in all cases remains a lofty goal. A recent multicenter study reported on the results of 576 arthroscopic repairs and noted a 25% rate of retear by MR or CT arthrogram. Functional results improved across the board although having an intact tendon was associated with even greater gains in activity level, motion, and especially strength. Pain, although significantly improved, was not statistically different in both healed and retear groups. Larger and more chronic tears were at greater risk of structural failure (1
). Other studies have corroborated their finding that patients who are able to obtain a complete repair do better than those who do not.
For those cases where a repair is impossible, options are limited, especially for younger and more active patients. Where are we failing? Biologically! Technically, we now recognize tear patterns better and are able to mobilize the tissues as needed. The anchors and the sutures available have amazing strength and holding ability. Almost any tear is now repairable. There is just not enough healing ability within the time constraints of the rehabilitative process. Metaphorically, it is a race. The race begins once the brace is applied in the operating room. Will the cuff heal before the forces applied to it in rehabilitation pull it apart?
Several factors contribute to a bad biologic environment, which creates poor healing ability. Numerous studies describe the poor blood flow at the insertion of diseased rotator cuff tendons and the various forces applied there during activity. The surgeon must first deal with the possibility of tendon loss in addition to tissue stiffness in larger more chronic tears. Although surgeons try to avoid doing so, the tendon is often placed under tension. The greater tuberosity with chronic tears also goes through degenerative changes resulting in osteopenia and cyst formation. The osteoblasts in the tuberosity show diminished ability to respond to mechanical stress, implying that they may not respond well to a repair process. Patient age and tear chronicity also play large roles with high recurrence rates reported in those older than 70 years who have significant fatty infiltration. Medications such as NSAIDs and other immune-modifying agents can also contribute to a surgical failure and should be stopped if possible. Surgeons are therefore often left trying to fix bad tissue to bad bone in a person with limited ability to heal: a daunting prospect.
Conceptually, grafting the rotator cuff would improve the strength of the primary fixation and add collagen at the repair site. Neviaser reported the use of grafts for massive tears. He used freeze-dried allograft rotator cuff tissue and reported good or excellent result in 14 of 16 patients (2
). Ten years later, Nasca used a similar graft but reported functional improvement in only 2 of 7 patients, although all had pain relief (3
). Almost 20 years later, Moore described his experience with allograft reconstruction. All of the patients who were imaged failed structurally, and outcomes were essentially the same as debridement(4
). Despite the relatively poor early outcomes, grafting remains an area of significant interest and study today, thanks to the development of several novel grafts.
The “modern” era of rotator cuff grafts began in 1999 with the introduction of the Restore (DePuy) xenograft. Since then, there has been a veritable explosion of graft development. There are properties inherent to each graft, which must be considered during selection. The source material, tissue preparation techniques, thickness, pliability, elasticity, and suture retention strength are all factors that can affect graft performance. Graft sources include allograft human cadaveric skin or tendon, xenograft skin
or pericardium, porcine small intestine submucosa, and synthetic grafts made of polyurethane urea or poly-L-lactide/glycolide polymer. The tissue grafts are acellular and sterilized using various proprietary techniques. Some companies then choose to cross-link the collagen in order to limit or slow the natural process of enzymatic degradation after implantation. Controversy exists over whether or not cross-linking is beneficial or detrimental (5
Ideally, any graft is slowly replaced with host tissue at such a pace that the structural integrity of the cuff repair is supported long enough to facilitate healing of the native cuff. This healing process may be on the order of months. In contrast, if the collagen fibers are too resistant to the enzymes, encapsulation and scar formation may occur around the graft. In addition, if the material elicits a large immunologic response, local soft tissue swelling and other signs of possible infection can occur. From a practical standpoint, trying to determine which patient is or is not infected could add unnecessary cost and delay recovery.
Grafts that are thinner tend to have less suture retention ability (6
). Tissue pliability is also important in considering grafts for arthroscopic applications. Typically, a graft applied arthroscopically is passed through a cannula. Therefore, the graft must be able to fold and resist tearing while being pushed and/or pulled through the cannula. Cross-linked grafts tend to have more stiffness. Currently, there are no randomized trials comparing graft materials in humans. Perhaps there is no best choice. At the time of this writing, the GraftJacket material has the most published data, demonstrating its effectiveness and safety. The landscape in this area of orthopedics is constantly shifting, and the individual surgeon is wise to review the most current literature and decide for themselves which graft to choose. Currently, marketed grafts and their various properties are listed in Table 12.1
As always, start with a good history and physical examination. The questions and exam maneuvers are those typically employed in evaluating someone with shoulder pain, although there are areas of specific focus. The chronicity of the tear is an important factor as well as the ability of the cuff to heal and regain function. Technically, an acute traumatic tear, even a large one, is easier to repair and more likely to heal than a chronic one. The tendons and muscle fibers are usually not so degenerative, although acute-onchronic tears can create an acute large tear with relatively poor tissue. Visual inspection can reveal significant atrophy of the supraspinatus and infraspinatus in chronic cases.
Both passive and active range of motion are important to measure. A shoulder that has become mechanically stiff associated with a chronic cuff tear will need either a capsular release or an alternative treatment considered before any significant functional gains will be realized with a repair. The function of the cuff muscles must also be assessed to identify which are dysfunctional. The supraspinatus can be tested at 90° of forward flexion, or in scaption with the thumb up to avoid inadvertent pain from impingement that can occur with the thumb down. The infraspinatus is tested with the shoulder in 30° of abduction. The subscapularis can be tested with the belly press test, although care should be taken to keep the forearm parallel to the abdomen. The bear hug test is another option for testing subscapularis tendon integrity.
Imaging is of significant help in determining whether or not a graft may be beneficial. Plain X-rays can reveal elevation of the humeral head and acetabularization of the acromion found in chronic severe cases of cuff arthropathy. An MRI gives an understanding of the size and pattern of the tear. Early changes of glenohumeral arthritis can also be seen. Fatty infiltration of the muscle bellies can be identified and quantified.
Once the diagnosis of a rotator cuff tear has been established, a treatment plan must be created. A full thickness tear is a surgical problem if cuff repair is the ultimate goal. The natural history of full thickness tears is that they persist and most likely get larger over time. Steroid injections can offer pain relief, but this must be tempered with the possibility of further tissue degradation. Patients can maintain a high level of shoulder function as long as the shoulder maintains a balance with the anterior and posterior muscle forces equalized. The decision to surgically intervene is based upon the patient’s goals and their health status.