Abstract
Introduction
Unicompartmental knee arthroplasty(UKA) has become a popular treatment alternative when one compartment of the knee is affected. Excellent intermediate results have been reported in association with the Miller-Galante unicompartmental implant. These excellent results are based on the development of the implants and the stringent patients selection. The functional cruciate ligaments has been a prerequisite for patients undergoing UKA. However, UKA can be one of the procedures in elderly patiants with deficient anterior cruciate ligaments(ACL) but with no symptoms of instability. The purpose of this report is to determine the clinical results after UKA in patients with ACL-deficient knees and compared those after UKA in ACL-intact knees.
Patients and Methods
We identified 332 cases operated from May 2000 to April 2013 whose ACL were evaluated before the operation by MRI., and classified into ACL-deficient group and ACL-intact group. Fixed-bearing Miller-Galante Unicompartmental Knee System or Zimmer Unicompartmental High-Flex Knee Sytem was implanted in all patients. ACL-deficient group included 17 men and 68 women who had an average age of 79 years(range, 70–91 years) at the time of the operation. The underlying diagnosis was osteoarthritis for 77 knees and osteonecrosis for 8 knees. ACL-intact group included 49 men and 198 women who had an average age of 77 years(range, 60–88 years) at the time of the operation. The underlying diagnosis was osteoarthritis for 176 knees and osteonecrosis for 71 knees. Followup for ACL-deficient group was 3.5 years(1–8.8years), and 3.6years (1–13.2years) for ACL-intact group.
Results
Japanese Orthopaedic Association score improved from 46.7points preoperatively to 76.5 points at the time of the latest followup in ACL deficient group, and 49.6 points to 81.5 points in ACL-intact group. 7 knees(8.2%) had a partial radiolucent line around the tibial component in ACL-deficient group, and 30 knees(12.6%) had a partial radiolucent line around the tibial component(30knees) or femoral component(one knee) in ACL-intact group, all of these radiolucent lines were <2mm in thickness and remained stable over time. Two knees(2.3%) in ACL-deficient group and five knees(2.0%) in ACL-intact group were revised because of progression of arthritis in the lateral tibiofemoral or patellofemoral components. All of the components in revised knees were well fixed and no polyethylene wear was seen at the time of revision. All of these results between two groups were not significantly different.
Conclusion
Controversy exists about whether a functional ACL is necessary to achieve success with UKA. In classical indication, UKA should not be done in patients with symptoms of ACL instability. In elderly active patient with deficient ACL, we should prefer total knee arthroplasty. But UKA should judiciously be done in eldery patients with deficient ACL whose activity is low but with no symptoms of instability.
