Unicompartmental Knee Replacement: The Never-Ending Debate

    Dr. Bassam Masri addresses issues related to the appropriateness of UKR for patients with knee osteoarthritis.

    Bassam A. Masri, MD, FRCSC, from the University of British Columbia in Vancouver, Canada, became interested in unicompartmental knee replacement (UKR) in the late 1990s and early 2000s because of the rapid recovery and short length of stay compared with total knee replacement (TKR).

    As they did then, he noted surgeons are still debating whether UKR is an appropriate option for patients with uncompartmental knee osteoarthritis.

    In a presentation at the ICJR Egypt meeting in Cairo earlier this year, Dr. Masri addressed some of the issues that are often debated.

    UKR versus TKR. Dr. Masri reviewed the current indications for performing a medial UKR and noted that at 1 surgical center nearly 60% of knee arthroplasties were unis. It is also notable that obesity and non-symptomatic patellofemoral arthritis are not considered contraindications to UKR.

    Mobile-bearing versus fixed-bearing UKR. A well-designed and well-implanted fixed-bearing UKR functions as well and lasts as long as a mobile-bearing UKR, Dr. Masri said. The indications for either still need further refinement, as there are differences between the 2 designs with regard to the role of the anterior cruciate ligament (ACL), surgical technique, survivorship, and volume effect.

    Role of the ACL. It has been stated that an ACL-deficient knee without instability may not be a contraindication for a fixed-bearing UKR, but Dr. Masri said there’s no reason to take a chance. In his practice, he will not perform a UKR on an ACL-deficient knee. Due to the motion of the bearing, a mobile-bearing UKR requires an intact and structurally sound ACL, as studies have shown a 16.2% early failure rate if the ACL is deficient.

    Survivorship. Dr. Masri compared survivorship data for TKR versus UKR and noted that the relative risk for revision is higher for UKR. This is mainly due to disease progression and lower threshold for revision of UKR. There is variability in revision risk data between different UKR designs, with “designer” UKR series showing excellent survivorship versus registry data showing lower survivorship rates. Revision rates for UKR also seem to depend on the age of the patient: Data from the 2014 Australian Registry show that as patient age increases, revision rates for UKR decrease. The relative revision risk, as compared with TKR, decreases as well.

    Outcomes. Compared with TKR, the 5-year survivorship of UKR is significantly lower. However, knee scores are the same for TKR and UKR, and range of motion is better for UKR, Dr. Masri said.

    Cost-effectiveness. Recent studies show that UKR and TKR are very cost-effective, but according to Dr. Masri, UKR becomes more cost-effective than TKR as patients get older.

    Surgeon experience. Dr. Masri said that in his opinion, surgeon must perform a minimum number of UKRs annually to maintain competency with the procedure. British studies quote a number of 20 cases per year, but 77% of surgeons perform only 10 or fewer UKRs per year.

    Click the image below to watch Dr. Masri’s presentation.