Raj D. Rao

Neck pain, cervical radiculopathy, and cervical myelopathy: pathophysiology, natural history, and clinical evaluation.

Degenerative cervical disk disease is a ubiquitous condition that is, for the most part, asymptomatic. When symptoms do arise as a result of these degenerative changes, they can be easily grouped into axial pain, radiculopathy and myelopathy. While the pathophysiology of radiculopathy and myelopathy is better understood, the source of neck pain remains somewhat controversial. A discussion of the mechanisms of neck and suboccipital pain, and the chemical and mechanical factors responsible for neurologic symptoms is warranted. Examination of the patient with these symptoms will reveal variations in the clinical presentation. A thorough understanding of the natural history of these conditions will allow appropriate treatment to be carried out. The natural history of these conditions suggests that for the most part patients with axial symptoms are best treated without surgery, while some patients with radiculopathy will continue to be disabled by their pain, and may be candidates for surgery. Myelopathic patients are unlikely to show significant improvement, and in most cases will show stepwise deterioration. Surgical decompression and stabilization should be considered in these patients.

Painful osteoporotic vertebral fracture. Pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management.

• Osteoporotic vertebral fractures may be a sentinel sign of failing health in elderly patients and are likely to become an increasing health-care concern as the population continues to age. • A reduction in the number, thickness, and interconnectivity of vertebral trabeculae in combination with altered load transmission across the degenerated disc predisposes a vertebral body to fracture from minor trauma. • The clinical course of these fractures is variable; some patients are asymptomatic, many respond to medications and activity modification, and a small subset have debilitating symptoms. • Good short-term results have been reported following both vertebroplasty and kyphoplasty for the treatment of osteoporotic and metastatic vertebral fractures. The long-term consequences of polymethylmethacrylate injection into the vertebral body are unclear, and discretion must be exercised in the use of these procedures. • Vertebral body height can be partially restored in some of these fractures by extension positioning of the patient on the table or by inflation of the vertebral body with a bone balloon. Osteoporotic vertebral compression fractures are a frequently encountered clinical problem, and they are becoming more important as the median age of the population continues to increase. Notwithstanding the potentially devastating consequences, many of these fractures are initially asymptomatic and appear to cause little morbidity other than decreased height and a more forward stooped posture. Only 23% 1 to 33% 2 of these fractures become clinically evident. When such a fracture does cause pain, the patient usually can be managed successfully with a combination of medications, activity modification, and occasionally bracing. Managing a patient who does not respond to this initial treatment regimen is challenging. The risks of anesthesia and the poor quality of bone in this elderly group make operative intervention such as fusion and application of instrumentation less attractive. Internal splinting of the vertebral …

Operative Treatment of Cervical Spondylotic Myelopathy

Cervical spondylotic myelopathy is a leading cause of spinal cord dysfunction in the adult population. Affected patients represent a large subset of individuals who undergo operative treatment of degenerative cervical conditions. In a study of 450 patients undergoing anterior neck surgery for the treatment of degenerative disc disease, 61% presented with radicular symptoms, 16% had pure myelopathic symptoms, and the remaining 23% had a combination of myelopathy and radiculopathy1. The subtle clinical findings of early cervical spondylotic myelopathy make diagnosis difficult, and true natural history studies are unavailable. The patients or their relatives notice increasing awkwardness with gait and balance that they attribute to old age or arthritis of the lower extremity joints. Patients may report an insidious onset of clumsiness or diffuse numbness in the hands, resulting in worsening of handwriting or …

Degenerative Cervical Spondylosis: Clinical Syndromes, Pathogenesis, and Management

Degenerative changes in the cervical spinal column are ubiquitous in the adult population, but infrequently symptomatic. The evaluation of patients with symptoms is facilitated by classifying the resulting clinical syndromes into axial neck pain, cervical radiculopathy, cervical myelopathy, or a combination of these conditions. Although most patients with axial neck pain, cervical radiculopathy, or mild cervical myelopathy respond well to initial nonsurgical treatment, those who continue to have symptoms or patients with clinically evident myelopathy are candidates for surgical intervention.

Whiplash injury determination with conventional spine imaging and cryomicrotomy

Study Design. Soft tissue–related injuries to the cervical spine structures were produced by use of intact entire human cadavers undergoing rear-end impacts. Radiography, computed tomography, and cryomicrotomy techniques were used to evaluate the injury. Objectives. To replicate soft tissue injuries resulting from single input of whiplash acceleration to whole human cadavers simulating vehicular rear impacts, and to assess the ability of different modes of imaging to visualize soft tissue cervical lesions. Summary of Background Data. Whiplash-associated disorders such as headache and neck pain are implicated with soft tissue abnormalities to structures of the cervical spine. To the authors’ best knowledge, no previous studies have been conducted to determine whether single cycle whiplash acceleration input to intact entire human cadavers can result in these soft tissue alterations. There is also a scarcity of data on the efficacy of radiography and computed tomography in assessing these injuries. Methods. Four intact entire human cadavers underwent single whiplash acceleration (3.3 g or 4.5 g) loading by use of a whole-body sled. Pretest and posttest radiographs, computed tomography images, and sequential anatomic sections using a cryomicrotome were obtained to determine the extent of trauma to the cervical spine structures. Results. Routine radiography identified the least number of lesions (one lesion in two specimens). Although computed tomography was more effective (three lesions in two specimens), trauma was not readily apparent to all soft tissues of the cervical spine. Cryomicrotome sections identified structural alterations in all four specimens to lower cervical spine components that included stretch and tear of the ligamentum flavum, anulus disruption, anterior longitudinal ligament rupture, and zygopophysial joint compromise with tear of the capsular ligaments. Conclusions. These results clearly indicate that a single application of whiplash acceleration pulse can induce soft tissue–related and ligament-related alterations to cervical spine structures. The pathologic changes identified in this study support previous observations from human volunteers observations with regard to the location of whiplash injury and may assist in the explanation of pain arising from this injury. Although computed tomography is a better imaging modality than radiography, subtle but clinically relevant injuries may be left undiagnosed with this technique. The cryomicrotome technique offers a unique procedure to understand and compare soft tissue–related injuries to the cervical anatomy caused by whiplash loading. Recognition of these injuries may advance the general knowledge of the whiplash disorder.

Biomechanical changes at adjacent segments following anterior lumbar interbody fusion using tapered cages.

Study Design. A biomechanical evaluation of anterior cages in a calf lumbar spine model. Objectives. To determine changes in spinal motion and intradiscal pressures at immediately adjacent lumbar motion segments following anterior insertion of tapered cages. Summary of Background Data. Stand-alone anterior lumbar interbody fusion (ALIF) is an effective approach in the treatment of discogenic low back pain. A tapered lumbar (LT) cage design attempts to restore physiologic lordosis and sagittal balance. We are not aware of any previous biomechanical evaluation of the effects of LT cages on adjacent motion segments. Methods. Nine fresh calf spines (L2–L5) were procured for the study. Pure moments (up to 8.5 Nm) in flexion, extension, and lateral bending were applied to the L2 vertebra in five steps through a nonconstrained loading system. With each step of loading, three-dimensional rotation at three intervertebral disc levels was obtained through a three-camera motion analysis system, and intradiscal pressures within the nucleus pulposus of the two nonoperated discs were measured with miniature transducers. The spines were tested initially intact and following paired anterior LT cage insertion. Results. Following ALIF, small to moderate increase in motion was found at both adjacent segments in flexion (superior: 12.5%, P < 0.05; inferior: 11.3%, P < 0.02) and lateral bending (superior: 7.8%, P < 0.02; inferior: 6.6%, P < 0.02). An increase in intradiscal pressure was noted at the superior adjacent segment under flexion (21%, P < 0.01) and lateral bending (16%, P < 0.03). Intradiscal pressure changes at the inferior adjacent level were not significant. Conclusions. Statistically significant changes in intradiscal pressures and motion were found at the adjacent levels following a single-level stand-alone ALIF procedure using paired LT cages.

Quantitative anatomy of subaxial cervical lateral mass: an analysis of safe screw lengths for Roy-Camille and magerl techniques.

Study Design. Determination of lateral mass screw lengths with Roy-Camille and Magerl techniques of screw insertion using computerized tomography in 98 young, asymptomatic North American volunteers. Objective. To provide reliable and normative data on safe screw lengths using the Roy-Camille and Magerl techniques of lateral mass fixation in the subaxial cervical spine. Summary of Background Data. Lateral mass screw lengths have been studied in the past using differing subject and measurement characteristics and small sample sizes. Results demonstrated considerable variation in screw length and influencing factors. Inappropriate screw lengths can result in neurovascular injury during screw insertion, facet joint damage, or inadequate fixation. Methods. Bicortical screw lengths were bilaterally measured at each spinal level from C3–C7 in 98 young volunteers using computed tomography reconstructions through the lateral masses obtained in the plane of the screw in Roy-Camille and Magerl techniques. Results. With both techniques, trajectories were longest at C4–C6, shorter at C3, and shortest at C7. Screw lengths were greater in males when compared with females at all levels. Average Magerl screw lengths were approximately 2.6 mm longer at C3–C6 levels, and approximately 1.3 mm longer at the C7 level when compared with Roy-Camille technique. There was minimal correlation between screw lengths and anthropometric measurements including stature, body weight, and neck length. Conclusion. Significant variations exist at each subaxial level with either technique. We recommend the surgeon determine screw lengths for fixation at each level using preoperative sagittal oblique computed tomography scans, which provide the most accurate technique of preoperative templating for screw length.

Does anterior plating of the cervical spine predispose to adjacent segment changes

Study Design. In a human cadaveric model, the effects of plate supplementation on the mechanical behaviors of adjacent segments were investigated. Objectives. The objective was to determine the effects of anterior cervical fusion and plating on the adjacent segments. Summary of Background Data. Increases in intradiscal pressure and intervertebral motion at adjacent segments have been reported in the lumbar spine following an instrumented fusion. It is unclear if the same phenomenon presents in the cervical spine. Methods. Seven human cadaveric cervical spines (C2–T1) were used, and fusion of the C5–C6 segment was chosen for the purpose of this study. Two miniature pressure transducers were implanted within each adjacent disc. Flexion, extension, lateral bending, and torsion loads up to 2.5 Nm were applied to the intact spine, and following each of the two procedures, anterior discectomy and grafted fusion, and anterior plating of the C5–C6 motion segment. Results. At the surgical level, a significant increase in segmental stiffness was observed after plating in all directions. Following the grafted fusion, there were no statistically significant changes at the superior adjacent segment, and there was a 13.7% increase in axial rotation in the inferior adjacent segment. Once anterior plating was applied, slight increase (<12%) over the intact spines was noted in lateral bending in both adjacent segments. However, there was no significant difference between the grafted fusion and anterior plated fusion at either adjacent segment. At both adjacent disc levels, the differences in intradiscal pressures between grafted fusion and plated fusion were less than 30% in all directions, and none of these differences was statistically significant. Conclusions. Intradiscal pressures and intervertebral motion at the adjacent levels are not significantly affected by the instrumented anterior fusion. The clinically observed degenerative change at adjacent segments in the cervical spine is more likely to be attributed to natural progression of the spondylotic process as opposed to biomechanical effect of the instrumentation or fusion.

Intradiscal pressure and kinematic behavior of lumbar spine after bilateral laminotomy and laminectomy

BACKGROUND CONTEXT Bilateral laminotomy has been proposed as an alternative to laminectomy for decompression of lumbar spinal stenosis. Preservation of the posterior midline ligaments with laminotomy is presumed to maintain spinal segment stability. There have been no previous studies that directly compare the amount of destabilization and increase in disc pressures between the two procedures. PURPOSE To quantify spinal segmental instability caused by bilateral laminotomy and laminectomy, and to compare the central and peripheral intradiscal pressures after the two procedures. STUDY DESIGN/SETTING Mechanical testing of the lumbar motion segments of calf spines. METHODS Nine fresh calf spines were tested under flexion, extension, lateral bending and axial rotation, intact first, then after laminotomy and laminectomy at the level of L4-L5. Four miniature pressure transducers were implanted in the central and peripheral disc at L4-L5 to measure intradiscal pressures. Three-dimensional motion was measured with motion analysis system. RESULTS Comparing with bilateral laminotomy, laminectomy showed significant increase in segmental motion at the surgical level in flexion (16%, p<.05), extension (14%, p<.04) and right axial rotation (23%, p<.03). In flexion, the stress at the anterior annulus increased a nonsignificant 20% after laminotomy, but significant 130% after laminectomy (p<.02). In the intact spine, the posterolateral annulus experienced the highest stress with lateral bending to the same side when compared with other loading directions. This stress remained unchanged after laminotomy but increased 9% after laminectomy (p<.06). In rotation, axial intradiscal stresses were evenly distributed and unchanged after each procedure. CONCLUSIONS Laminectomy causes more destabilization of a spinal motion segment than laminotomy and significantly increases disc stress in the anterior annulus.

Computerized Tomographic Morphometric Analysis of Subaxial Cervical Spine Pedicles in Young Asymptomatic Volunteers

BACKGROUND Although cervical spine pedicle screws have been shown to provide excellent fixation, widespread acceptance of their use is limited because of the risk of injury to the spinal cord, nerve roots, and vertebral arteries. The risks of pedicle screw insertion in the cervical spine can be mitigated by a three-dimensional appreciation of pedicle anatomy. Normative data on three-dimensional subaxial pedicle geometry from a large, young, and asymptomatic North American population are lacking. The purpose of the present study was to determine three-dimensional subaxial pedicle geometry in a large group of young volunteers and to determine level and sex-specific morphologic differences. METHODS Helical computerized tomography scans were made from the third cervical to the seventh cervical vertebra in ninety-eight volunteers (sixty-three men and thirty-five women) with an average age of twenty-five years. Pedicle width, height, length, and transverse and sagittal angulations were measured bilaterally. Pedicle screw insertion positions were quantified in terms of mediolateral and superoinferior offsets relative to readily identifiable landmarks. RESULTS The mean pedicle width and height at all subaxial levels were sufficient to accommodate 3.5-mm screws in 98% of the volunteers. Pedicle width and height dimensions of <4.0 mm were rare (observed in association with only 1.7% of the pedicles), with 82% occurring in women and 72% occurring unilaterally. Screw insertion positions generally moved medially and superiorly at caudal levels. Transverse angulation was approximately 45 degrees at the third to fifth cervical levels and was less at more caudal levels. Sagittal angulation changed from a cranial orientation at superior levels to a caudal orientation at inferior levels. Mediolateral and superoinferior insertion positions and sagittal angulations were significantly dependent (p < 0.05) on sex and spinal level. Transverse angulation was significantly dependent (p < 0.05) on spinal level. CONCLUSIONS Pedicle screw insertion points and orientation are significantly different (p < 0.05) at most subaxial cervical levels and between men and women. Preoperative imaging studies should be carefully templated for pedicle size in all patients on a level-specific basis. Although the prevalence was low, women were more likely to have pedicle width and height dimensions of <4.0 mm.