THE DIAGNOSIS OF ACUTE COMPLETE TEARS OF THE ANTERIOR CRUCIATE LIGAMENT - COMPARISON OF MRI, ARTHROMETRY AND CLINICAL EXAMINATION

We reviewed 38 patients with arthroscopically-proven complete ACL tear s operated on less than three weeks after injury. Their average age wa s 26 years (16 to 43), with 127 males and 11 females. All patients had had MRI preoperatively.The same examiner performed the Lachman, anter ior-drawer, and pivot-shift tests without anaesthesia, recording the d ifferences between the injured and the normal knees. The patients then had KT-1000 arthrometry by the same examiner at 15 lb (6.8 kg) and 20 lb (9 kg), with active displacement, and with maximum manual displace ment. All scored positive for differences greater than 3 mm. The resul ts of physical examination, KT-1000 tests and MRI were analysed using McNemar's test for matched data with continuity correction and a 95% c onfidence interval for each test. The sensitivity of the KT-1000 manua l maximum test was 97% for 3 mm and 100% for 2 mm; this was the most u seful arthrometric result. The Lachman test gave 95% sensitivity, prov iding the best simple clinical assessment. MRI was 97% sensitive for t he detection of all ACL injuries, but this fell to 82% with respect to complete rupture. We found no significant differences between the res ults of the Lachman test and the KT-1000 manual maximum test, but thes e were significantly better than all other tests. In an era of cost-co ntainment, we have shown that inexpensive tests in the clinic can allo w treatment to proceed rapidly and in the most economical manner witho ut the routine use of MRI.