Hombro y codo

Estructuras de tejido biológico en la cirugía de hombro. (Inglés)

Nina Silberstein

Implant surgery for previously inoperable rotator-cuff tears

Figure 1. Intraoperative view of a massive rotator cuff tear before repair with the cadaver allograft.1 The edge of the cuff is retracted to the level of the glenoid and spine of the scapula. Image courtesy of Stephen J. Snyder, MD, Southern California Orthopedic Institute, Van Nuys, Calif. A major development in shoulder surgery, the arthroscopic delivery of biologic scaffolds for rotator-cuff repair, is now a reality. For patients with inoperable rotator-cuff tears, the implants and techniques involved appear promising, based on clinical experience gained over the past 2 to 3 years. Two orthopedists have been among the first to perfect arthroscopic rotator-cuff repair using tissue scaffolds.

Stephen J. Snyder, MD, specializes in arthroscopic surgery and reconstructive procedures of the shoulder joint at the Southern California Orthopedic Institute, Van Nuys, Calif. His technique employs an allograft1 derived from cadaver skin that has been processed (using patented methods) to remove the epidermis and the dermal cells, but to retain the intact collagen matrix with preserved vascular channels. Richard Seldes, MD, is director, department of orthopedics, Forest Hills Hospital, Queens, NY. He uses a xenograft2 made of fetal bovine dermis that has undergone a patented production process that transforms it into a scaffold of acellular, nondenatured collagen.

ROTATOR-CUFF REPAIR Rotator-cuff tears, common in people more than 40 years old, are associated with participation in sports, with work-related overhead repetitive motion, and with acute trauma (including shoulder fractures and dislocations). Typical symptoms of rotator-cuff injury are pain at the front of the shoulder that radiates down the side of the arm, pain when lifting the arm to (or lowering it from) a fully raised position, stiffness, loss of motion, and a snapping sensation. Following a physician's examination, the diagnosis of rotator-cuff injury is made using strength testing and an MRI study.

Surgery to repair the rotator cuff is often advised when a rotator-cuff tear causes severe shoulder weakness or, in less severe cases, when there has been no improvement following nonsurgical treatment (typically consisting of some combination of resting, taking anti-inflammatory medication, limiting overhead activity, using a sling, having steroid injections, using strengthening exercises, and undergoing physical therapy).

Traditional (open) surgery to debride and repair a torn rotator cuff can require an incision at the top of the shoulder, and this may be 10 to 15 cm long. The deltoid muscle must be removed from its insertion point and reattached at the close of the procedure, and this can be traumatic. A second open procedure, the mini-open technique, splits the deltoid to provide surgical access to the rotator cuff. Because the incision is smaller, healing is likely to be more rapid than it is following the traditional repair.

Because arthroscopic repair is minimally invasive, involving only the small incisions needed to insert the arthroscope and the necessary miniaturized surgical instruments, trauma is minimized and healing is generally superior.

All techniques for rotator-cuff repair, however, have been unsuitable for patients with inadequate soft-tissue mobility (short tendons) or poor tissue quality. In these cases, previously considered inoperable, and for patients whose prior rotator-cuff repairs have failed, the use of the cadaver allograft or bovine xenograft may make the restoration of shoulder function possible for the first time.


Figure 2. View in surgery of Graft Jacket installed to fill defect in rotator cuff. Image courtesy of Stephen J. Snyder, MD, Southern California Orthopedic Institute, Van Nuys, Calif. The bovine xenograft, 2 a collagen membrane that is used to repair deficits and reinforce soft tissues, is indicated for repair of the rotator cuff. This implant, placed arthroscopically, is designed to serve as a scaffold for cellular remodeling over time and will have become host tissue by the time that healing is completed. Native fibroblasts will occupy the collagen fibers of the xenograft, and angiogenesis will be encouraged. "The ideal patient would be someone with a large tear (greater than 2 to 3 cm) or an older patient with a chronic tear," Seldes explains.

Snyder founded the International Shoulder Arthroscopy Study Group and sits on the board of directors of the Arthroscopy Association of North America. The allograft1 that he uses (Figures 2, 3) retains the native elastin, proteoglycans, basement membrane, and vascular channels. The extracellular framework, being intact, supports rapid cellular repopulation and revascularization (through a mechanism known as inosculation). The allograft is indicated for the repair of rotator-cuff tears and diabetic foot ulcers, as well as to reinforce primary soft-tissue repairs of the anterior shoulder capsule, Achilles tendon, and quadriceps tendon.

Figure 3. Postop MRI at 1 year showing good healed cuff and muscles. Image courtesy of Stephen J. Snyder, MD, Southern California Orthopedic Institute, Van Nuys, Calif. According to Snyder, the graft must have the necessary strength and ability to attract and house the stem cells that will then be transformed into fibroblasts; it must also have channels for blood vessels and a covering that will continually refresh the tissue and build a new rotator cuff. "It also has to have enough elasticity to prevent suture pullout, and an ability to encourage ingrowth of blood vessels," he says. The allograft is still in the preliminary stages of evaluation, but histology supports that it promotes rapid revascularization and carries a low risk of rejection.

TECHNIQUES Snyder has pioneered the technique for placing the allograft arthroscopically for the treatment of irreparable rotator-cuff tears. He describes arthroscopic implantation as "such a revolutionary approach to an otherwise unsolvable problem. It is good for irreparable tears on an otherwise good shoulder, without arthritis," he says. "The problem, for whatever reason, is that the rotator cuff has failed and cannot be repaired by standard methods. It is indicated for patients in good health who are nonsmokers, without infection or diabetes."

During the 2.5-hour surgery that Snyder performs, the defect is measured arthroscopically and the allograft is cut to the size needed. Special stitches are run outside and inside the body, and suture anchors are affixed to the bone. The sutures are run out through the allograft and pulled in to position it. Some additional stitches are made around the allograft's edge.

Figure 4. Arthroscopic repair of rotator cuff, using bovine xenograft,2 in progress. The method employed by Seldes also involves inserting a collagen patch (in this case, a bovine xenograft) that combines with a patient's own tissue and enhances healing through minimally invasive surgery. "We do not have to remove the muscle," Seldes says. "There is less pain, less stiffness, and earlier recovery." The procedure takes about 2 hours, and the patient can go home the same day.

RESULTS To date, Seldes has performed about 15 similar surgeries over the course of a year. Recovery time following repair using the xenograft can require from 4 to 6 weeks in an immobilizer, followed by an additional 3 to 6 months of physical therapy. Patients undergoing this procedure have regained 75% to 90% of their preinjury levels of use of the shoulder, depending on other factors such as age and extent of damage. "Any time you do surgery, there are risks," Seldes notes. "Any time you make a skin incision, there is a chance of bleeding, infection, or nerve damage, and sometimes the shoulder can get stiff."

For the xenograft itself, Seldes says that he has not seen any specific complications, although patients are being followed closely. "The success rate looks good," he sa
ys. "Certainly, these patients who were miserable before are starting to function. It looks pretty promising." Figure 5. Bovine xenograft2 in place. Snyder has performed 21 arthroscopic rotator-cuff repairs using the cadaver allograft over a 2-year period and believes in the technology. The beauty of the procedure, he reports, is that, with the new allograft, patients heal much more rapidly and can enter rehabilitation sooner. Snyder has a rigorous postoperative protocol that includes MRI examination 3 months after the procedure to confirm graft incorporation.

CONCLUSION Seldes is optimistic about the bovine xenograft and sees it as an integral part of the equipment and methods used to treat difficult cases. "This scaffold has great potential in light of the increased emphasis on using gene therapy and growth factors to heal rotator-cuff tears," he says. "In the future, it might be a good carrier for those types of therapies."

Orthopedic technology review. Vol 7 No 7. November/December 2005.

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