Summary

By painstakingly recording every intervention, Mayo Clinic has developed the most comprehensive database on joint replacements in the world, and simultaneously advanced research, patient care and medical technology.

Whether it's a hip replacement, a new artificial knee or another prosthetic joint that a patient is receiving, their treatment by a Mayo Clinic orthopedic surgeon includes an advantage no other medical organization can claim - the most comprehensive database on joint replacements in the world. While that may sound like an interesting academic sidelight, it means far more. It may help explain why one woman experiences little problem with her new hip once she is through the initial adjustment period, and another of the same age needs to undergo successive surgeries to improve or regain function. Because the Mayo Clinic Joint Replacement Database contains virtually every fact on every knee, hip, shoulder, wrist, ankle, finger and elbow replacement performed at the Clinic since 1969, comparisons of surgical technique, implant types and patient demographics, conditions, and outcomes are not only encouraged, but readily available.

When surgeons can compare their upcoming hip replacement procedure with any of the 35,000 such operations performed at Mayo since its inception, the database becomes a key instrument for ensuring the best decisions and the best possible care. The database is the brainchild of orthopedic surgeon Mark Coventry, M.D. In 1969 at Mayo, Dr. Coventry performed the first Food and Drug Administration-approved hip arthroplasty or replacement.

Mark Coventry, M.D.

Dr. Coventry recognized the value of compiling detailed information about joint replacement surgeries that could be used for long-term studies comparing the effectiveness of different surgical techniques and implants. In the case of total hip arthroplasty, the surgery involves making one or more incisions to expose the joint, removing the damaged bone and cartilage, and replacing the ball of the thigh bone and the socket of the pelvic bone with an artificial joint made of some combination of metal, plastic or ceramic components. However, many variables can influence the long-term outcome of the surgery.

"A diversity of surgical philosophies exists even within the Mayo system," says Daniel Berry, M.D., Chair of the Department of Orthopedics and current administrator of the Joint Replacement Database. Variations of surgical technique can include the number and size of incisions, the model of implant used, and the method of adhering the implant to the bone. By following the functioning of artificial hips in patients over long periods of time, Mayo doctors can determine which surgical practices and implant models are the most effective.

Just the Facts, Please—But all of them

The Database includes information gathered from patients before, during, and after their surgeries. Prior to surgery, patients are asked to describe their levels of pain and joint function. Clinical exam findings, diagnoses, and previous surgeries are also included. During the surgery, the approach, implant model and design, and fixation method are carefully recorded. Post-operatively, patients are evaluated after one, two, and five years, and then at five-year intervals. Along with serving as a valuable research tool for orthopedic surgeons, the database benefits individual patients by reminding them when they are due for follow-up appointments. At each time interval, the patient is encouraged to return to Mayo for clinical and radiographic evaluation. Patients who are unable or unwilling to travel may complete a questionnaire, have their examination done close to home, and have their clinical findings and x-rays sent to Mayo. Patients who don't respond to follow-up requests are contacted by telephone and asked to complete a telephone interview. Mayo orthopedic consultants review this material and correspond directly with the patient regarding the status of the replacement. This multi-pronged approach for obtaining patient information for the database is remarkably efficient, with a 95 percent response rate at each phase. As a result, the Mayo Joint Replacement Database is the largest and most comprehensive of its kind in the country.

The most common complications that can arise in the months and years following hip arthroplasty are infection, blood clots, joint dislocation, fracture of the bone around the implant and implant wearing, loosening or breakage. These problems, while uncommon, are carefully documented in the Joint Replacement Database. In fact, the overall success rate of hip arthroplasty at 10 years is greater than 90 percent, with an 80 percent chance of the implant lasting for 20 years. Still, researchers are seeking ways to further improve the long-term success rate to reduce revision surgeries, which are often more difficult to perform and less promising in outcome than the patient's original arthroplasty.

Resulting Innovations

Investigators are researching improved methods of adhering the implant to the patient's bone.

Bernard Morrey, M.D.

In traditional hip arthroplasties, much of the patient's thigh bone must be prepared to allow fixation of the metal implant with or without the acrylic cement also used in dentistry. Bernard Morrey, M.D., orthopedic surgeon and former Chair of Orthopedics, invented in the early 1980s a type of implant that preserves more of the patient's bone. Designated the "Mayo Conservative Hip," this metal implant has a porous surface that allows bone "ingrowth" in a smaller portion of the thigh bone so that less bone must be removed to allow implant fixation. Less bone removal shortens the time required for surgery and recovery and reduces blood loss. Other areas of current research include improving the bearing surface to create less wear, and finding new implant materials and designs to increase flexibility and durability. As new technologies and surgical practices evolve, Mayo doctors can use the Joint Replacement Database to track improvements that enhance a patient's quality of life in the years following surgery.

Registry vs. Database

Following Mayo's lead, other medical centers worldwide are beginning to compile patient data in the form of joint replacement registries. The Swedish National Hip Arthroplasty Register is a well-known data repository that culls information from multiple medical institutes within the country of Sweden. Plans for nationwide arthroplasty registries in the United States have also been proposed. However, Dr. Morrey, who during his tenure as Department Chair made it his goal to transition from a registry to a more comprehensive database, emphasizes the difference between the two. "A registry, which is what most other institutions employ, is basically 'name, rank, and serial number'--basic facts regarding the patient, implant, and date of surgery. The comprehensiveness, duration, and volume of data are what make Mayo's Joint Replacement Database unique. "We can document not only that an implant failed, but why it failed and hence allow a direction to a possible solution," Dr. Morrey explained.

The Power of Information

Daniel Berry, M.D.

The true power of the database lies in the detailed information doctors can obtain through very specific queries. For example, an orthopedic surgeon can request information on all patients over 75 who received a certain type of implant and experienced joint dislocation. If more information is needed than is present in the database, the doctor can consult patient charts and x-rays, which are indefinitely retained in the Mayo Clinic's records. Information gleaned from the database in this manner can then be communicated worldwide to the orthopedic community through research publications.

"There are probably dozens of examples of surgical practices that have changed in response to information gained from the database, for example, how implants are fixed to the bone, and the dimensions of the optimal bearing surface," explains Dr. Morrey. "The Joint Replacement Database is an evolving resource. It began through the vision of Dr. Coventry, is upgraded according to the needs of the profession, and is consulted to write research papers, which in turn impact decisions on patient care." Thanks to this unique research tool, not only can the technology of joint replacement be advanced, but physicians can - in a sense - consult with their colleagues over the expanse of decades, making every effort possible to achieve the best care for every patient.

Related Research

Robin Patel, M.D., studies protective layers, called microbial biofilms, which are often involved when hip replacements get infected. Dr. Patel is developing new ways to diagnose prosthetic joint infection and new methods of treating biofilm-mediated infections. Read about her research with ultrasound technology.