Posterior retroextramarginal disc hernia (PREMDH): definition, diagnosis, and treatment

BACKGROUND: Detachment of the posterior part of the lumbar vertebral ring apophysis has been reported by many authors, associated or not with disc prolapse, and has been ascribed to various mechanisms, although the relationship between the two pathologies remains unclear. METHODS: We studied 26 patients (17 males and 9 females; mean age, 34.3 years) suffering from a lumbar disc herniation with nontraumatic detachment of the ring apophysis. Investigations included standard X ray, computed tomography (CT), tridimensional CT, and magnetic resonance imaging. Nineteen patients were operated on by microsurgical discectomy and removal of bone fragments. RESULTS: Clinical and neuroradiologic features of herniated disc associated with detachment of the ring apophysis have been recognized and have led to the definition of posterior retroextramarginal disc herniations. A further classification is suggested, considering two morphological types that imply clinically distinctive features and a different surgical approach. In all operated cases, removal of the bone fragments was necessary and the results were good. CONCLUSIONS: Our observations led us to postulate a common mechanism in the pathogenesis of disc herniation with nontraumatic detachment of the ring apophysis. They should be distinguished from other calcifications of the disc because a proper surgical technique, including removal of apophyseal fragments, is required.