Curtis A. Dickman

Posterior C1-C2 transarticular screw fixation for atlantoaxial arthrodesis

OBJECTIVE To assess the outcomes associated with C1-C2 transarticular screw fixation. METHODS The clinical outcomes of 121 patients treated with posterior C1-C2 transarticular screws and wired posterior C1-C2 autologous bone struts were evaluated prospectively. Atlantoaxial instability was caused by rheumatoid arthritis in 48 patients, C1 or C2 fractures in 45, transverse ligament disruption in 11, os odontoideum in 9, tumors in 6, and infection in 2. RESULTS Altogether, 226 screws were placed under lateral fluoroscopic guidance. Bilateral C1-C2 screws were placed in 105 patients; each of 16 patients had only one screw placed because of an anomalous vertebral artery (n = 13) or other pathological abnormality. Postoperatively, each patient underwent radiography and computed tomography to assess the position of the screw and healing. Most screws (221 screws, 98%) were positioned satisfactorily. Five screws were malpositioned (2%), but none were associated with clinical sequelae. Four malpositioned screws were reoperated on (one was repositioned, and three were removed). No patients had neurological complications, strokes, or transient ischemic attacks. Long-term follow-up (mean, 22 mo) of 114 patients demonstrated a 98% fusion rate. Two nonunions (2%) required occipitocervical fixation. In comparison, our C1-C2 fixations with wires and autograft (n = 74) had an 86% union rate. CONCLUSION Rigidly fixating C1-C2 instability with transarticular screws was associated with a significantly higher fusion rate than that achieved using wired grafts alone. The risk of screw malpositioning and catastrophic vascular or neural injury is small and can be minimized by assessing the position of the foramen transversaria on preoperative computed tomographic scans and by using intraoperative fluoroscopy and frameless stereotaxy to guide the screw trajectory.

A new technique for determining 3-D joint angles: the tilt/twist method

OBJECTIVE To develop a new method of representing 3-D joint angles that is both physically meaningful and mathematically stable. DESIGN The two halves of a joint are modeled as overlapping cylinders. This simple physical model is easily understood and yields mathematically stable angle equations. BACKGROUND Two currently-used methods are the Euler/Cardan (joint coordinate system) method and the projection angle method. Both of these methods approach a singularity at 90 degrees that limits their use. The helical angle (attitude vector) method is mathematically stable but has limited physical meaning and is difficult to communicate. METHODS Calculation of the tilt/twist angles is described. Tilt/twist angles are compared to Euler/Cardan, projection, and helical angles in terms of behavior and stability. RESULTS Through a small range of angulation, tilt/twist angles match the specific projection and Euler/Cardan angles previously found to be appropriate for describing spinal motion. Through larger ranges, tilt/twist angles do not match the other angles studied. Although not as stable as helical angles, tilt/twist angles are twice as stable as Euler/Cardan and projection angles, reaching a singularity only at 180 degrees. CONCLUSIONS Because of their mathematical stability and simple physical interpretation, tilt/twist angles are recommended as a standard in describing angular joint motion.

Traumatic atlantooccipital dislocation with survival.

Survival after traumatic atlantooccipital dislocation is rare. Only long-term survivors have been reported in the literature; however, improved prehospital care is likely responsible for the increase in the number of these patients seen at neurotrauma centers over the last decade. Associated severe and persistent neurological deficits are common in the few survivors. We report the case of a 10-year-old boy with traumatic atlantooccipital dislocation and a severe neurological injury. Low-field magnetic resonance imaging provided the additional diagnosis of an associated cervicomedullary epidural hematoma. The patient underwent emergency operative evacuation of the hematoma and an occipital-cervical fusion with internal fixation. He had a remarkable recovery in neurological function and achieved stable bony fusion 3 months postoperatively. With early recognition of this entity, improved neuroradiological imaging techniques, and aggressive treatment, patients may survive with significant neurological recovery.

Methods for determining spinal flexion/extension, lateral bending, and axial rotation from marker coordinate data: Analysis and refinement

Abstract Angular coupling patterns in the spine are often described by quantifying flexion/extension, lateral bending, and axial rotation angles as functions of one another. The most common methods for calculating these angles from marker coordinate data are the Euler method and the projection method. Both methods have the problem that they may be applied to spinal motion in a variety of ways, depending on the sequence chosen for Euler rotations or the vectors chosen for projection. The spinal angles calculated by each permutation of both methods vary significantly, leading to difficulties in reporting and comparing results between studies. The ambiguities of the Euler and projection techniques may be resolved and the two techniques standardized for application to the spine by considering vertebral symmetry. Using symmetry considerations, unique vectors may be chosen for determining the planar projection angles that best describe coupling in the spine. Because of the close relationship, presented herein, between projection angles and Euler angles, the same considerations allow one Euler rotation sequence to be chosen over the five alternate sequences. To validate the need for standardization of these techniques and to demonstrate the utility of the method presented, the results from a published study describing angular coupling patterns in the upper cervical spine are reexpressed in terms of the newly chosen Euler sequence and projection angle set. The reevaluated angles are consistent in both methods and lead to a conclusion different from the published conclusion with regard to the pattern of lateral bending coupling at C1C2 during axial rotation.

Self-inflicted orbital and intracranial injury with a retained foreign body, associated with psychotic depression: case report and review.

Reports of intracranial self-mutilation by psychotic individuals are associated with severe mental disorders, criminality, or both. We describe a psychotically depressed male who drove a ballpoint pen through his right medial canthus and into his intracranial compartment. The patient developed a cavernous sinus syndrome and a traumatic dissection of the cavernous portion of the carotid artery. The pen was removed intraoperatively. Postoperatively, the patient was placed on a course of broad-spectrum antibiotics, antidepressants, and antipsychotic medications, and he has received long-term psychiatric follow-up. The literature related to these unusual cases is reviewed, and relevant surgical, medical, and psychiatric aspects of treatment are discussed.

Amyloidoma of the Cervical Spine: A Case Report

This is the first published report of an amyloidoma localized to the cervical spine. Primary amyloidosis of bone is rare. Only 5 cases involving the spine have been described. We present a 74-year-old man with cervical and occipital radicular pain as the manifestations of an amyloidoma involving the 2nd cervical vertebra. The signs and symptoms of this disease, when localized to the vertebrae, are nonspecific and result from bony destruction and compression of neural structures. Diagnosis requires a high index of suspicion and, ultimately, adequate tissue biopsy for histopathological studies. Curative resection is possible for well-localized lesions. Additionally, external immobilization with a halo vest and bony grafting for fusion may be indicated when the cervical spine is involved.

Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating

BACKGROUND CONTEXT Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. PURPOSE To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. STUDY DESIGN/SETTING A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. PATIENT SAMPLE Six human cadaveric specimens were studied. OUTCOME MEASURES Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. METHODS Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. RESULTS The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. CONCLUSIONS Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.

Tension Hydrothorax from Intrapleural Migration of a Ventriculoperitoneal Shunt

A male newborn underwent a myelomeningocele repair, with subsequent placement of a ventriculoperitoneal shunt for treatment of hydrocephalus. Five days after shunt surgery, the infant acutely developed a deeply sunken fontanel, pallor, tachypnea, bradycardia, and irritability. Chest radiographs revealed intrathoracic migration of the distal shunt tubing and a tension hydrothorax. Treatment consisted of tube thoracostomy and temporary externalization of the distal shunt tubing. The patient fully recovered. The acute onset of shock in association with a sunken fontanel in a neonate with a shunt should raise the suspicion of tension hydrothorax. For critically ill infants immediate needle aspiration or thoracostomy is suggested. In less severely ill children, exposure of the shunt tubing in the neck and withdrawal of the pleural effusion by the distal shunt tubing may be performed as an emergency measure. The early recognition and urgent management of this problem are emphasized.

Surgery and permanent 125I seed paraspinal brachytherapy for malignant tumors with spinal cord compression.

PURPOSE To evaluate the functional outcome, predictors of response, and toxicity from spinal surgery and 125I brachytherapy in patients with malignant tumors resulting in spinal cord compression. METHODS AND MATERIALS Between July 1985 and September 2001, after surgical resection, 30 patients underwent 31 intraoperative paraspinal brachytherapy procedures at Barrow Neurological Institute. Twenty-four (with 25 procedures) had follow-up at our clinic and form the basis for this report. Surgical procedures were based on the location of the impinging lesion: corpectomy or spondylectomy in 13 cases and laminectomy in 12. Permanent 125I seeds in absorbable suture were placed with open exposure after resection. RESULTS Spinal cord compression was cervical in 4 (16%), thoracic in 14 (56%), and lumbar in 7 (28%) of the 25 cases. One patient underwent two separate procedures at different spinal sites. Of the 25 brachytherapy sites, 22 also received external beam radiotherapy (EBRT): 5, EBRT with a planned brachytherapy boost; 4, brachytherapy and prompt EBRT after recovery; and 13, brachytherapy as salvage for local failure after prior EBRT. Three had no EBRT: 1 had lymphoma treated with chemotherapy, 1 had remote previous EBRT for a childhood tumor, and 1 refused EBRT. The mean follow-up was 19.8 months. The 2- and 3-year actuarial local control rate was 87.4% and 72.9%, respectively. Four sites (16.0%) experienced local failure. The mean time to recurrence for these 4 patients was 20.3 months. Three of the four had failed prior EBRT, with surgery and brachytherapy used for salvage. The 2- and 3-year actuarial overall survival rates were 24.0% and 16.0%, mean 19.2 months. An ambulatory function score was assigned pre- and postoperatively: I, normal ambulation; II, abnormal not requiring assistance; III, abnormal requiring assistance; and IV, unable to ambulate. All patients with score I, 91% of those with score II, 67% of those with score III, and 67% of those with score IV were ambulatory after the procedure; 84% had either normal or improved ambulation postoperatively. Morbidity was restricted to four postoperative events: one cerebrospinal fluid leak, two wound infections treated in situ without removal of seeds or instrumentation, and one pulmonary embolus. No myelopathies or other neurologic sequelae were encountered. CONCLUSION This is the largest series in the literature exploring surgery and 125I brachytherapy in the treatment of malignant spinal cord compression. We found this to be well tolerated and to result in durable local control and ambulatory function. Our results suggest a benefit to aggressive local therapy in selected patients with spinal cord compression.

Techniques of anterior cervical plating

Several pathological processes affecting the cervical spine ultimately require management with rigid internal fixation of the vertebral column. The use of anterior cervical screw-plate systems for fixation has been associated with improved fusion, greater postoperative comfort, and a more expedient return to work compared with patients who do not receive these implants. Five cervical screw-plate systems are discussed: four are widely available, and the fifth system is completing final stages of a clinical trial before its commercial release. We describe the preferences and techniques that have evolved at our institution for successful cervical fusion and fixation procedures and compare the features of the different plating systems.