• THE USE OF BIORESORBABLE CAGES FOR ANTERIOR CERVICAL FUSION IN THE GOAT

    INTRODUCTION: The ideal device for the facilitation of bony fusion in the spine would provide structural support and stability for the interval during which bony growth transpires and then disappears once its presence was no longer needed. Such a device would necessarily have to withstand whatever loads were applied to it until replaced with bone; to resorb over an interval long enough to assure fusion but short enough not to prevent it; to resorb without producing an inflammatory response sufficient to impair fusion; and to produce no local chemical or pH changes sufficient to impair bone growth. Bioresorbable sutures made from various polylactide/polyglycolide polymers have been in clinical use for more than 30 years. Variations in the amino acid ratios of such polymers correspond to known variations in strength and in resorption rate.
  • COMPLICATIONS OF THE ANTERIOR RETROPHARYNGEAL APPROACH IN CERVICAL SPINE SURGERY

    INTRODUCTION: Anterior surgery of the upper cervical spine is a relatively rare occurrence since the majority of cervical spine disorders affect the lower cervical spine. Also, many upper cervical disorders can be effectively managed with a posterior approach. One of the classic anterior approaches to the upper cervical spine entails transoral access and provides direct exposure for anterior decompression of the distal brain stem and upper spinal cord. Prior to this, posterior fusion was the standard technique although this procedure was limited in that cord decompression required the removal of the posterior arch of the atlas without reducing the deformity. The anterior approach allowed for cord decompression and fusion to be performed simultaneously. The transoral approach has been associated with numerous complications including high infection rate, hemorrhage, progressive laryngeal stridor and asphyxiation.
  • C2 PEDICLE VS. PARS SCREWS: AN IMAGE-GUIDED ANATOMICAL ASSESSMENT

    INTRODUCTION: Numerous authors have used the term “C2 pedicle screw” to describe what is anatomically a C2 pars screw. With recent interest in transpedicular fixation of the cervical spine, this discrepancy in the literature warrants clarification. The purpose of this study was to investigate the pertinent surgical anatomy for the placement of C2 pedicular vs. pars screws. MATERIALS AND METHODS: The CT scans (1 mm cuts) of 14 patients with a variety of cervical disorders were assessed using the workstation of the StealthStation Image-Guided Surgery System (Sofamor Danek, Memphis, TN). Bilateral “virtual” 3.5 mm screws were placed in the C2 pedicles and pars. Optimal screw position was determined by the bony anatomy, neurovascular anatomy, and maximal screw length obtainable.
  • ENHANCEMENT OF METHYLPREDNISOLONE WITH 7.5% HYPERTONIC SALINE IN AN EXPERIMENTAL SPINAL CORD INJURY MODEL

    We have previously demonstrated, with a chronic model of spinal cord injury, that i.v. infusion of 7.5% hypertonic saline 5ml/kg significantly improves spinal cord blood flow. Our present investigation tested the hypothesis that hypertonic saline (HS) would enhance the delivery of methylprednisolone (MP) to the injured site and improve neurologic function. Rat spinal cords were compressed for 10 minutes to produce the injury and then neurologic function was assessed using BBB locomotor rating scale for ten days. The control group (n=4) received an i.v. injection of isotonic saline (5ml/kg) after injury. Group 1 (n=3) received an i.v. injection of 7.5% NaCl (5ml/kg). Group 2 (n=4) received an i.v. injection of MP (30mg/kg and isotonic saline (5ml/kg). Group 3 (n=9) received an i.v. injection of MP (30mg/kg) and 7.5% hypertonic saline (5ml/kg).
  • SWALLOWING DYSFUNCTION FOLLOWING ANTERIOR CERVICAL DISCECTOMY AND FUSION

    INTRODUCTION: Many complications following anterior cervical decompression and fusion have been noted. One such complication is postoperative swallowing dysfunction, the mechanism of which is not fully understood. Frempong-Boadu et al, reported at the Cervical Spine Research Society meeting in 1997 on 23 patients who underwent anterior cervical decompression and fusion who also underwent preoperative, one week and one month postoperative modified barium swallows. They concluded that almost half of all patients studied had preoperative swallowing abnormalities which were clinically silent. However, the existence of preoperative swallowing abnormalities did not correlate with postoperative abnormalities. The level and duration of cervical spine surgery, age, diabetes, hypertension and duration of preoperative neurologic symptoms were not risk factors for postoperative swallowing abnormalities.
  • MRI EVALUATION OF ACUTE CERVICAL INJURIES

    INTRODUCTION: The evaluation of acute cervical injuries typically consists of radiographs to determine the presence of a fracture or dislocation. Flexion/extension radiographs can demonstrate ligamentous injuries in certain cases, however, there is considerable controversy regarding their reliability and safety. Magnetic Resonance Imaging (MRI) has the ability to define the ligaments, discs, and soft tissues in the cervical area without manipulation of the neck and can be used in comatose or unresponsive patients. The purpose of this study was to determine the clinical utility of MRI studies in the evaluation of acute cervical injuries. METHODS: Eighty-seven patients initially seen in the emergency department at a level one trauma center who had possible cervical injuries and inconclusive radiographs were evaluated with MRI and included into the study.
  • RELATIONSHIP BETWEEN SPINAL-CORD DEFORMATION AND NEUROLOGICAL DEFICIT IN POST-REDUCTION CERVICAL-SPINE INJURIES

    INTRODUCTION: The mechanisms leading to the deleterious effects of severe spinal-cord injury are complex and multifactorial. Neurological deficit may stem from the initial insult to the cord or from secondary effects such as ischemia, hemorrhage, and/or edema. Our study examined the relationship between the severity of neurological deficit in cervical-spine injuries and the degree of post-reduction spinal-cord deformation. METHODS: We reviewed MRI scans and medical charts of patients with cervical spine injuries admitted to Harborview Medical Center between January 1995 and February 1997.
  • ARTHRODESIS FROM SYNERGISTIC COMBINATIONS OF BONE SUBSTITUTES AND INTERBODY FUSION CAGES

    INTRODUCTION: The integration of two technologies, interbody fusion cages and osteopromotive bone substitutes, has lead to a synergistic method of promoting arthrodesis after anterior cervical discectomy. Traditionally, bone grafts have been harvested from the iliac crest but the possibility of donor site morbidity or insufficient quantities have been among the key factors in the research and development of osteopromotive bone substitutes. At the forefront of this technology is rhBMP-2. In addition, the osteopromotive properties of a 15 sequence amino acid peptide, P15, has recently been shown to illicit promising osteopromotive behavior when coupled with hydroxyapatite granules. The Alpine cervical goat model has proven to be an aggressive animal model for examining the healing of fusions using bone grafts, instrumentation, or bone substitutes.