Intradural disc herniation at the L2/3 level: a case report and literature review.

BACKGROUND: Intradural lumbar disc herniation (ILDH) is special type of lumbar disc herniation in which the lumbar nucleus pulposus prolapses and enters the dura mater. ILDHs comprise 0.04-0.33% of all herniated discs. In most cases, the diagnosis could not be confirmed preoperatively by identifying the typical features of ILDH in radiological evaluation. In the current report, we present a case of ILDH at lumbar 2/3 level and discuss the clinical presentations, typical imaging features, treatments, and outcomes. CASE DESCRIPTION: We describe a rare case of ILDH. The patient was a 65-year-old man with pain in waist and back, and with bilateral radiating pain of lower extremities and fatigue for more than 2 weeks. Magnetic resonance imaging (MRI) revealed a large round, low-density mass at lumbar 2/3, which was easily mimicked as an intradural spinal tumor lesion. While enhanced MRI showed the typical rim enhancement sign and "Hawk beak" sign. Due to progressive decrease in muscle strength in both lower limbs, posterior microscopically assisted laminectomy, dural incision of the lumbar 2/3 was performed. Pathological examination revealed degenerated fibrous connective tissue and cartilage tissue. The patient's lower back pain and radiating pain and numbness of both legs improved remarkably postoperatively, and he became asymptomatic at 3 months and 1-year postoperatively. CONCLUSIONS: ILDH is a rare intervertebral disc herniation in clinical practice. The pathogenesis of ILDH may be related to aseptic inflammatory edema, closely fixing of ventral dura and the posterior longitudinal ligament, repeated mechanical action and chemical corrosion. Typical rim enhancement sign, "Hawk beak" sign and "Y" sign are important features of MRI in diagnosing ILDH, and intraspinal gas is also helpful in computed tomography (CT) diagnosis of ILDH. Prompt microscopically assisted laminectomy, dura mater incision to remove the intradural disc, pedicle screw fixation regardless of fusion, surgical results are usually favorable. We also reviewed the literature and discussed the epidemiology, potential pathogenesis, diagnosis, treatment and poor prognostic factors of ILDH.

Pullout strength of reinserted pedicle screws using the previous entry point and trajectory.

PURPOSE: This study compared the biomechanics of reinserted pedicle screws using the previous entry point and trajectory with those of correctly inserted pedicle screws. METHODS: The study used 18 lumbar vertebrae (L1-6) from three fresh calf spines to insert 6.5 × 40-mm pedicle screws. A control screw was inserted correctly along the axis of one pedicle, while an experimental screw was reinserted completely using the previous entry point and trajectory in the other pedicle. The experimental screw was removed after being completely inserted in group A and after 80% of the total trajectory inserted in group B. And the experimental screw was removed after 60% of the total trajectory was reached in group C. The biomechanical values of the pedicle screws were measured. RESULTS: There were no significant differences in pedicle screw axial pullout strength between reinserted screws and correct screws in the 3 groups (PA = 0.463, PB = 0.753, PC = 0.753). Stiffness measurement increased for the reinserted screw compared with that of the control screw. Fracturing was observed between the vertebral body and pedicle. CONCLUSION: Theoretically, a surgeon can remove the pedicle screw when necessary, inspect the trajectory, and reinsert the screw using the previous entry point and trajectory.