VALIDATION OF A NEW CLINICAL SIGN OF LUMBAR FACET SYNDROME

ABSTRACT Background Facet joints are true synovial joints, which derive their nerve supply from the sinuvertebral or recurrent nerve of Luschka as well as the posterior primary division of the corresponding spinal nerve. Diagnosis of low-back pain originating in facet joints is difficult and has traditionally relied upon invasive tests. To aid in the clinical diagnosis of this condition, the senior author described a new clinical sign. The following research project was designed to test the sign´s utility in the diagnosis of lumbar facet joint pain. Methods We conducted a prospective evaluation of patients suspected of having low back pain secondary to facet joint involvement (Lumbar Facet joint Pain Syndrome – LFPS) during a twelve month observation period; candidate patients were evaluated clinically using the new diagnostic sign which was then compared to findings on radionuclide bone scans and diagnostic medial branch blocks. Contingency table analysis was performed to calculate the sensitivity, specificity, positive and negative predictive values and accuracy of the new clinical sign. Results Contingency table analysis showed the following operating characteristics for the new diagnostic sign: Sensitivity: 70.37%, Specificity: 50%, Positive predictive value: 90.47%, Negative predictive value: 20% and accuracy 67.7%. Conclusions Although the new clinical sign failed to show the same operating characteristics as the ones originally described, it has a high sensitivity coupled with a good positive predictive value. We consider that although the sign by itself isn´t diagnostic of lumbar facet joint pain, its presence should alert the clinician of the diagnosis and the possibility of requiring additional testing.