Engineered pig tissue implants are helping the healing process of surgically repaired tendons.
Maybe the lowly pig will finally beat its bad rap as the barnyard's mess-maker-at least among people who suffer from bad shoulders, damaged elbows and other problematic joints.
USC orthopaedic surgeons are now using tissues from pigs-with a high-tech twist-to help their patients back to health.
The surgeons implant specially engineered tissues made from pigs' small intestines to improve healing of surgically repaired tendons. The patches are meant to scaffold or support tendons while they heal.
Across the country, medical researchers are exploring a variety of uses for implants made from pig intestines, from treating faulty heart valves to stopping urinary incontinence. USC orthopaedic surgeons are among the leaders in exploring clinical uses for the product in healing ligament, tendon and muscular problems, according to researchers who created the implants. They are the only orthopaedists in Southern California using the patch.
The U.S. Food and Drug Administration approved the patch, commercially known as the Restore Orthobiologic Soft Tissue Implant, for soft tissue surgery in October 1998.
"I use it in surgery if I'm working on a patient with a tear, and the tissue doesn't look good," said John M. Itamura, M.D., USC assistant professor of orthopaedic surgery. In other words, if the damaged tendon looks tenuous, or appears at risk of rupturing again, he explained.
Itamura has been using the patches since late 2000, with more than 30 patients so far receiving them for rotator cuff or elbow problems. Many others have called to ask about the procedure.
Although it is too early to assess results from the patch, Itamura has not yet seen any drawbacks. C. Thomas Vangsness, Jr., M.D., USC associate professor of orthopaedic surgery, and James E. Tibone, M.D., USC professor of orthopaedic surgery, also have used them with patients. Tibone also is conducting a study in animal models to examine more extensive use of the patch for rotator cuff problems.
But why pig intestine? For some reason, it appears to have reviving properties.
The companies using porcine tissue raise the pigs under tight controls to keep them free from disease. The manufacturers remove tissues called small intestinal submucosa (dubbed SIS by scientists) from the middle layers of the intestinal wall. These SIS layers are disinfected and processed into sheets or strips. DePuy OrthoTech, a Johnson & Johnson subsidiary, makes the Restore patch in Indiana. (Another company, Cook Biotech, sells sheets and strips of similar material to heal wounds and patch organs).
The material is a mixture of naturally occurring collagen and other proteins. Healthy skin, ligaments, tendons, blood vessels and cartilage all contain collagen.
Biomedical engineers at Purdue University in Indiana came up with the tissue technology, in development since 1987, according to Steve Badylak, senior research scientist in Purdue's biomedical engineering department and physician for the university's athletic teams.
The USC orthopaedic team is interested in a broad range of uses for the tissue, incorporating it into dependable surgical procedures for the benefit of patients, says Badylak, who has visited with the USC surgeons several times to cooperate on projects and discuss the latest research.
"These surgeons are taking the time to understand a different way to practice orthopaedic surgery," Badylak says. "That sets them apart, as a group."
Badylak recently spoke with Edward McPherson, M.D., USC associate professor of orthopaedic surgery, about the implants' potential in the realm of orthopaedic infections. McPherson has used them on soft tissue in several knee surgeries, in areas where the tissue was difficult to join and close.
"The data is still early, but so far we've had no problems and they've worked out very well," McPherson says.
Orthopaedic specialists have used the tissue to repair the rotator cuff, Achilles tendon, patellar tendon (a kneecap tendon) and tensor fasciae lata (a tendon running down the front side of the hip), with successful results, the company has reported.
In the case of a rotator cuff problem, Itamura explains, the surgeon first looks at the extent of an injury using an arthroscope. Then, under general anesthesia, the patient undergoes open surgery to repair the tear.
If Itamura sees the tendon needs support to heal, he sutures a six-centimeter-wide patch into place over it. Then he completes the surgery and closes the incision. Over time, the body creates new tissue in the area that matches surrounding tissue. The body also absorbs the implanted patch in two to four months.
Traditionally, surgeons have had to graft patients' own tissue or donated tissue to reinforce lost or damaged tendons or ligaments. The new patches allow for reinforcing tendons without invasive removal of other tendons or ligaments.
In the future, the technology is likely to spread to more complex procedures in a variety of disciplines.
Lawrence R. Menendez, M.D., USC professor and chief of orthopaedics at USC/Norris Cancer Hospital, has been exploring the material's potential use to help cancer patients. Menendez and Badylak are jointly testing an idea that someday might help those with tumors in bone and soft tissue.
When a patient has a soft tissue cancer such as a sarcoma, surgeons often have no choice but to remove important portions of tendon and bone in an arm or leg as they remove the tumor. But the researchers, using animal models, are studying whether they can recreate part of the knee joint lost to cancer. They are placing a roughened metal device on the end of the tibia (the long bone of the lower leg), then attaching the engineered porcine tissue to the patellar tendon under the knee-with the hope that the tendon will grow into and attach to the metal device.
"This is an entirely different approach to healing wounds and recreating tissue," says Badylak, "and the possibilities for applications just keep growing."