古松 毅之

The authors analyzed the 5-year and 9-year survival in 134 of 165 patients who underwent total knee arthroplasties from 1989 to 1996 in our department. Patients were followed until December 31, 1998, or until the time of death. Diagnoses were rheumatoid arthritis in 81 patients (132 knees) and osteoarthritis in 53 patients (79 knees). The survival of the patients was compared to that of the age- and sex-adjusted general population. Kaplan-Meier survival curves were constructed. Twenty-two patients in the study died before the end of the follow-up. The cumulative 5-year patient survival was 88.7%, and 9-year patient survival was 64.4% for total knee arthroplasty patients. The standardized mortality ratio was 0.11 (95% confidence interval: 0.02-0.40) for the patients with osteoarthritis, and 0.81 (95% confidence interval: 0.52-1.25) for the patients with rheumatoid arthritis. The Cox proportional hazards model showed that the factors of male sex and rheumatoid arthritis were related to a higher mortality rate in the total knee arthroplasty group.

Instability of the knee after the medial collateral ligament (MCL) injury is usually assessed with the manual valgus stress test, even though, in recent years, it has become possible to apply magnetic resonance imaging (MRI) to the assessment of the damage of the ligament. The valgus instability of 24 patients (12 isolated injuries and 12 multiple ligament injuries) who suffered MCL injury between 1993 and 1998 was evaluated with the Hughston and Eilers classification, which involves radiographic assessment under manual valgus stress to the injured knees. We developed a novel system for classifying the degree of injury to the MCL by calculating the percentage of injured area based on MRI and investigated the relationship between this novel MRI classification and the magnitude of valgus instability by the Hughston and Eilers classification. There was a significant correlation between the 2 classifications (p=0.0006). On the other hand, the results using other MRI based classification systems, such as the Mink and Deutsch classificaiton and the Petermann classification, were not correlated with the findings by the Hughston and Eilers classification in these cases (p0.05). Since MRI is capable of assessing the injured ligament in clinical practice, this novel classification system would be useful for evaluating the stability of the knee and choosing an appropriate treatment following MCL injury.