New techniques for exposure of posterior cervical spine through intermuscular planes and their surgical application.

STUDY DESIGN: Retrospective study of new muscle-preserving exposure techniques and their application to posterior cervical spine surgery. OBJECTIVE: To describe muscle-preserving techniques for exposure of the posterior cervical spine, and to demonstrate how their application to a variety of posterior cervical spine surgeries for varying pathologies allows preservation of cervical mobility and stability. SUMMARY OF BACKGROUND DATA: Although surgical approaches through intermuscular planes have been applied to the extremities and anterior spinal column, to our knowledge, they have yet to be applied to the posterior cervical spine. METHODS: We have used our new exposure techniques since 2000, applying them to selective mono laminoplasty (73 patients) for cervical myelopathy, muscle-preserving intervertebral foraminotomy (30 patients) for radiculopathy, posterior atlantoaxial instrumentation with muscle preservation (6 patients) for upper cervical instability, and muscle-reserving unilateral posterior arch recapping technique (11 patients) for cervical spinal cord tumors. A total of 120 patients were enrolled in this study. To evaluate surgical outcomes, we reviewed all their clinical records and pre- and postoperative images. RESULTS: In selective mono laminoplasty, recovery rate according to Japanese Orthopaedic Association (JOA) scores averaged 60.7%. In muscle-preserving intervertebral foraminotomy, the averaged visual analogue scale for radicular pain decreased from 2.53 preoperatively to 0.47 postoperatively. Of 120 patients, 119 showed neither loss of curvature nor neck motion according to a comparison of pre- and postoperative plain x-rays, with only 1 patient who underwent unilateral posterior arch recapping technique for intramedullary ependymoma showing both. No trace of damage to the deep muscles was observed in any of the 17 patients who underwent posterior atlantoaxial instrumentation with muscle preservation or unilateral posterior arch recapping technique on postoperative magnetic resonance imaging. CONCLUSION: The muscle-preserving exposure techniques described here can be applied to a variety of posterior cervical spine surgeries for varying pathologies, with no adverse effect on cervical mobility or stability.

Human hepatocyte growth factor promotes functional recovery in primates after spinal cord injury.

Many therapeutic interventions for spinal cord injury (SCI) using neurotrophic factors have focused on reducing the area damaged by secondary, post-injury degeneration, to promote functional recovery. Hepatocyte growth factor (HGF), which is a potent mitogen for mature hepatocytes and a mediator of the inflammatory responses to tissue injury, was recently highlighted as a potent neurotrophic factor in the central nervous system. We previously reported that introducing exogenous HGF into the injured rodent spinal cord using a herpes simplex virus-1 vector significantly reduces the area of damaged tissue and promotes functional recovery. However, that study did not examine the therapeutic effects of administering HGF after injury, which is the most critical issue for clinical application. To translate this strategy to human treatment, we induced a contusive cervical SCI in the common marmoset, a primate, and then administered recombinant human HGF (rhHGF) intrathecally. Motor function was assessed using an original open field scoring system focusing on manual function, including reach-and-grasp performance and hand placement in walking. The intrathecal rhHGF preserved the corticospinal fibers and myelinated areas, thereby promoting functional recovery. In vivo magnetic resonance imaging showed significant preservation of the intact spinal cord parenchyma. rhHGF-treatment did not give rise to an abnormal outgrowth of calcitonin gene related peptide positive fibers compared to the control group, indicating that this treatment did not induce or exacerbate allodynia. This is the first study to report the efficacy of rhHGF for treating SCI in non-human primates. In addition, this is the first presentation of a novel scale for assessing neurological motor performance in non-human primates after contusive cervical SCI.