Total knee arthroplasty with retention of both cruciate ligaments. A nine to eleven-year follow-up study.

BACKGROUND: Although many early designs of total knee arthroplasty allowed the retention of both cruciate ligaments, in most current designs of knee replacement systems, either both cruciate ligaments are removed or the posterior cruciate ligament alone is retained. This report is a review of a series of total knee arthroplasties in which both cruciate ligaments were retained.

METHODS: The results of 163 total knee arthroplasties (130 patients) in which both cruciate ligaments were retained were assessed prospectively. One hundred and seven knees (eighty-nine patients) were followed for an average of ten years. There were thirty-four men and ninety-six women, and the average age at the time of the index arthroplasty was sixty-seven years (range, forty-two to eighty-four years). The diagnosis was osteoarthritis in 122 (75 percent) of the knees and rheumatoid arthritis in forty-one (25 percent). Twenty-six knees had a valgus deformity, 109 had a varus deformity, and twenty-eight had a normal alignment of 5 to 10 degrees of valgus. The anterior cruciate ligament was relatively normal in ninety-six knees and was partly degenerated in sixty-seven knees. With use of the rating system of the Knee Society, all 163 knees were prospectively evaluated at yearly intervals; fifty-six of these knees (in forty-one patients) were followed in this manner until the patient died or was lost to follow-up.

RESULTS: One hundred and four (97 percent) of the 107 knees available for study at an average of ten years had an excellent or good result. At the time of the latest follow-up, pain was adequately relieved in ninety-seven knees (91 percent) and the average range of flexion was 107+/-12.6 degrees (range, 65 to 135 degrees). Ninety-five knees (89 percent) had normal anteroposterior stability (less than five millimeters of movement in this plane), and twelve knees (11 percent) had five to ten millimeters of movement as demonstrated by the drawer sign. Ninety-six knees (90 percent) had normal mediolateral stability, and eleven (10 percent) had 5 to 10 degrees of laxity. Ninety-four knees (88 percent) had valgus alignment of 5 to 10 degrees. The average knee score was 91+/-8.4 points (range, 54 to 100 points), and the average functional score was 82+/-21 (range, 10 to 100 points). The survival rate at ten years, with revision as the end point, was 95+/-2.0 percent. Seven (4 percent) of the 163 knees in this series were revised. There were no revisions for patellar problems or aseptic loosening of the tibial component.

CONCLUSIONS: The good anteroposterior stability in this series after an average follow-up period of ten years indicates that both the anterior and the posterior cruciate ligaments, even when partly degenerated, remain functional when they are preserved in a total knee arthroplasty.