Is acute locked back a form of discogenic pain?

Abstract

Acute locked back is characterized by the sudden onset, of severe incapacitating low back pain without radicular pain or neurological deficit in the lower extremities.We classified acute locked back as discogenic if it was relieved by an intradiscal injection of local anesthetics into the disc selected on MR imaging.Using these criteria,acute locked back was diagnosed in sixteen patients (70%) out of 23patients (mean age 36 years), and evaluated in terms of the clinical features and pathogenesis. Pain generally occurred upon casual motion of the lumbar spine during normal daily activities. Tenderness of paravertebral muscles was observed in 5 patients (31%). The painful region in 8 patients (50%) was observed at the central and bilateral portions of the low back. Severe narrowness of the disc on plain radiogram was not observed in any patients. Radiating tears on discogram, indicating intradiscal tears as far as the posterior annulus, were observed in all patients. Disc degeneration on T2-weighted image was observed in all patients and classified into grade 3 (Gibson’s classification) in 15 patients (94%). An enhanced lesion in the posterior annulus on enhanced MR images, indicating repair of the torn posterior annulus, was observed in 10 patients (63%). The pathogenesis of discogenic acute locked back is considered to be a re-rupture in the torn and repaired posterior annulus of a moderately degenerated disc.