Clinical Assessment of Atlantoaxial Instability by Sharp-Purser Test in Rheumatoid Arthritis

ABSTRACT

OBJECTIVE: To evaluate the validity of Sharp-Purser test in the assessment of anterior atlantoaxial subluxation in rheumatoid arthritis patients. METHOD: We assessed the validity of the Sharp-Purser test in 38 rheumatoid arthritis patients who were subjected to stabilization surgery. All patients were evaluated using manual laxity test and re-evaluated radiologically. RESULTS: In 31 out of 38 patients (81.6%) Sharp-Purser test was positive in spite of anterior displacement of C1 over C2 on radiograms, while the tests were negative in 7. Among those 7 patients with negative test, 4 (10.5%) were acute cases and 3 (7.9%) were chronic cases with high grade hypomobile slip. Among the 31 patients with positive Sharp-Purser test, ADI (atlantodental interval) was 4 mm in 4 patients, 5 mm in 9, and greater than 5 mm in 18 patients. Among the 7 patients with negative Sharp-Purser test, ADI was 4 mm in 4 patients and greater than 5 mm in 3 patients. CONCLUSION: Our results show that the Sharp-Purser test is a useful clinical examination to diagnose atlantoaxial instability.