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Unicondular Knee Arthroplasty: An Outpatient Alternative to Total Knees?
For younger patients with unicompartmental knee osteoarthritis, this controversial procedure may offer less morbidity and a four- to six-hour stay.
Dianne Taylor
Publish Date: June 9, 2008   |  Tags:   Orthopedics
Outpatient facilities wishing to capture a portion of the total knee market may be able to offer some patients with symptomatic knee osteoarthritis (OA) a less invasive alternative. During the past several years, advances in technique and technology have stirred new interest in unicondylar knee arthroplasty. Although it's still controversial, a growing number of orthopedic facilities are now offering this procedure.

The Unicondylar Concept
The unicondylar prosthesis allows the surgeon to ?retread' the joint surfaces in one of the three weight-bearing compartments of the knee. Typically, in patients with unicondylar disease, the medial compartment is affected. The device works only for patients whose other two compartments (lateral, patellofemoral) remain relatively healthy. John A. Repicci, DDS, MD, developer of the Repicci Unicondylar Program and a former dentist, says this concept of replacing only the affected tissue while leaving healthy tissue intact represents a transfer of technology and ideas from dentistry. "No good dentist would even consider giving a 62-year-old man with two missing teeth a full set of dentures," he explains. "Dentures are not nearly as efficient" as natural teeth.

Indeed, the primary advantage of the minimally invasive unicondylar approach over a total knee replacement (TKR) is substantially less morbidity. Reported advantages of the technique include:
  • Smaller incision. The surgeon can implant the components through a three-inch incision. TKRs typically require an eight-inch incision.
  • Less blood loss. According to Dr. Repicci, the Repicci II technique generally eliminates the need for blood transfusion.
  • Less joint disruption. There is no need to disrupt the knee cap as there is with TKR-an important factor that Dr. Repicci says reduces postop pain, lessens the need for physical therapy, and cuts healing time.
  • Less bone loss. No intramedullary drilling is required, and the surgeon removes about one-quarter inch of bone to fit the components. Bone preservation is critical because total knees have a limited life span, and numerous revisions are often impractical or impossible due to the significant bone loss that accompanies each revision. In TKR, all knee surfaces may lose up to one-half inch of bone in all three compartments.

According to Dr. Repicci, the unicondylar technique is a same-day procedure in 80 percent of cases, with the main determinant of length of stay being patient age. Candidates must be at least 50 years old, he says, and younger patients tend to recover faster because of their ability to care for themselves and tolerate pain and pain medications. These younger patients typically ambulate two to three hours after surgery with a knee immobilizer and leave the facility in approximately five to six hours. Full function typically returns by the sixth week, according to Dr. Repicci.

Unanswered Questions
The biggest uncertainty about the unicondylar approach is the clinical utility of the concept. Orthopedic surgeons already have a widely accepted surgical option for young patients with knee OA who remain symptomatic after conventional therapy: High tibial osteotomy (HTO). With HTO, surgeons remove a wedge of the tibia just below the knee to correct joint malalignment caused by the unicompartmental cartilage degeneration; this decompresses the affected compartment and relieves pain. Both HTO and unicondylar knee arthroplasty are bone-sparing techniques that can delay the need for TKR by approximately ten years. Perhaps the greatest difference between these two approaches is that, while HTO is reserved for the youngest of patients who are clearly not yet TKR candidates, unicondylar knee arthroplasty is an option for the older, middle-aged patient who desires a quick recovery and whose only other option may be a TKR. "Using an artificial knee before its time has tremendous disadvantages," says Dr. Repicci. The Swedish Knee Arthroplasty Register, a register of over 30,000 primary knee arthroplasties, showed that the total knee revision rate is exponentially higher in younger patients. In this study, as the age group dropped from 75 to 64 years, the total knee revision rate increased 300 percent-from approximately 5 percent in 75-year-olds to approximately 17 percent in 64-year-olds at ten years.

Nevertheless, critics argue that the unicondylar approach is highly technique-dependent, and the Swedish Knee Arthroplasty Register tends to bear this out. The register showed more early failures of the unicondylar systems, as compared with TKRs, due to instability, loosening, wear, and contralateral joint degeneration. Studies of the Repicci system indicate that it has a 90 percent survivability rate at ten years, but Dr. Repicci admits that survivability of all unicondylar systems is variable. For this reason, physician expertise, proper patient selection, and patient education are imperative. Dr. Repicci stresses the delivery system as key to the success of any outpatient unicondylar program because of the unique challenges inherent in treating older patients on an outpatient basis.

At the Joint Reconstruction Orthopedic Center at Buffalo, NY, Dr. Repicci and the nursing team promote the idea of ambulatory care to patients in groups of ten, starting with a class one week before the surgery. "In a group circumstance, patients can exchange ideas and gain comfort with the concept" of ambulatory care, he says. The same nurses provide both education and patient care, and this allows patients to develop a trust and bond with the nurses that Dr. Repicci says motivates their recovery.

For outpatient facilities, reimbursement presents yet another big variable. One Philadelphia-area outpatient facility has performed three Repicci procedures with good clinical success, but has only been able to offer it to patients covered by workers' compensation plans. According to Dr. Repicci, it is indeed difficult to obtain sufficient reimbursement right now, but he is hopeful that the increasing recognition by the orthopedic community will cause insurers to act. According to the makers of the Repicci II system, the estimated total fee for the procedure is typically less than half that of a typical TKR: $7,500 vs $16,000 for a TKR. Nevertheless, in today's environment, significant negotiation is par for the course. To improve the chances for success with insurers, Dr. Repicci recommends against coding for arthroscopy even though the procedure calls for an initial arthroscopic exploration of the joint to ensure that disease is limited to one compartment. Rather, Dr. Repicci codes for hemiarthroplasty plus patelloplasty, which is needed to achieve visualization, and he now uses a standard Medicare code for his Buffalo practice after much negotiation.

Outpatient facilities considering the procedure should also be sure to have good back-up systems in case of the need for an overnight stay. Because of the age group, good patient screening is also essential to minimize this possibility.

What the Future Holds
It is not clear what the future holds for this procedure, but some outpatient facilities are already aggressively marketing the technique. Dr. Repicci, who has performed approximately 2,000 such procedures, estimates that surgeons perform 10,000 unicondylar procedures each year, but that the market potential is upwards of 100,000 annually. For outpatient facilities that already offer orthopedic procedures, it may pay to be on the leading edge of this market.