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Os odontoideum in children: neurological manifestations and surgical management.

The os odontoideum is a congenital anomaly of the 2nd cervical vertebra. It is an ossicle that is separated from the body of the axis by a variable transverse gap. This weakens atlantoaxial stability. When ligamentous support also fails, subluxation ensues. Compressive myelopathy and vertebral artery obliteration may occur. Eight cases, all in children, were studied prospectively. The neurological manifestations and surgical indications and treatment are discussed.

Adolescent↗

Cadaveric morphometric analysis for atlantal lateral mass screw placement.

OBJECTIVE: Atlantal lateral mass screws provide an alternative to C1/C2 transarticular screws and, in some cases, can obviate the need for extending a fusion to the occiput. For these reasons, C1 lateral mass screws are becoming increasingly popular. However, the critical local anatomy and unfamiliarity with this new technique can make C1 screw placement more challenging. METHODS: Morphometric analysis was performed on 74 cadaveric spines obtained from the Department of Anatomy at the Keck School of Medicine, University of Southern California. Critical measurements were determined for screw entry points, trajectories, and lengths for application of the technique described by Harms and Melcher. RESULTS: The mean height and width for screw entry on the posterior surface of the lateral mass were 3.9 and 7.3 mm, respectively. The maximum medialized screw trajectory ranged from 25 to 45 degrees (mean, 33 degrees). The mean maximal screw length to obtain bicortical purchase was 22.5 mm, and the mean minimum screw depth was 14.4 mm. Screw depths varied on the basis of the entry point, trajectory, and vertebral morphology. The overhang of the posterior arch averaged 11.4 mm (range, 6.9-17 mm). All specimens could accommodate 3.5-mm lateral mass screws bilaterally with proper preparation of the entry site. CONCLUSION: Significant variations in the morphology of C1 exist. However, the large size of the atlantal lateral mass makes screw placement forgiving. Preoperative computed tomographic scans and intraoperative fluoroscopy are useful in guiding proper screw placement. Close attention should be paid to preparation of the screw entry site.

Adult↗

Neurological deterioration after posterior wiring of the cervical spine.

Posterior cervical wiring is commonly performed for patients with spinal instability, but has inherent risks. We report eight patients who had neurological deterioration after sublaminar or spinous process wiring of the cervical spine; four had complete injuries of the spinal cord, one had residual leg spasticity and three recovered after transient injuries. We found no relation between the degree of spinal canal encroachment and the severity of the spinal-cord injury, but in all cases neurological worsening appeared to have been caused by either sublaminar wiring or spinous process wiring which had been placed too far anteriorly. Sublaminar wiring has substantial risks and should be used only at atlantoaxial level, and then only after adequate reduction. Fluoroscopic guidance should be used when placing spinous process wires especially when the posterior spinal anatomy is abnormal.

Adolescent↗

Atlanto-axial fusion in rheumatoid arthritis. A new method of fixation with wire and bone cement.

Twenty-eight occipito-cervical fusions performed over the past 4 years in patients with rheumatoid arthritis are discussed. All of the patients with one exception had signs of neurological involvement preoperatively due to pressure on occipital nerve roots, spinal cord and/or vertebral arteries. A surgical technique using wire, pin and bone cement and permitting early mobilization without external fixation was used and is described in detail. The clinical results were excellent in 21 cases with an additional five patients showing improvement. One patient did not benefit from surgery and one had no symptoms preoperatively. The results are encouraging and the possibility of early mobilization (the day after surgery) is of the utmost importance for this group of patients.

Adult↗

Anatomical suitability of C1-2 transarticular screw placement in pediatric patients.

OBJECT: Craniovertebral instability is a challenging problem in pediatric spinal surgery. Recently, C1-2 transarticular screw fixation has been used to assist in craniovertebral joint stabilization in pediatric patients. Currently there are no available data that define the anatomical suitability of this technique in the pediatric population. The authors report their experience in treating 31 pediatric patients with craniovertebral instability by using C 1-2 transarticular screws. METHODS: From March 1992 to October 1998, 31 patients who were 16 years of age or younger with atlantooccipital or atlantoaxial instability, or both, were evaluated at our institution. There were 21 boys and 10 girls. Their ages ranged from 4 to 16 years (mean age 10.2 years). The most common causes of instability were os odontoideum (12 patients) and ligamentous laxity (eight patients). Six patients had undergone a total of nine previous attempts at posterior fusion while at outside institutions. All patients underwent extensive preoperative radiological evaluation including fine-slice (1-mm) computerized tomography scanning with multiplanar reconstruction to evaluate the anatomy of the C1-2 joint space. Preoperatively, of the 62 possible C1-2 joint spaces in 31 patients, 55 sides (89%) were considered suitable for transarticular screw placement. In three patients the anatomy was considered unsuitable for bilateral screw placement. In three patients the anatomy was considered inadequate on one side. Fifty-five C1-2 transarticular screws were subsequently placed, and there were no neurological or vascular complications. CONCLUSIONS: The authors conclude that C1-2 transarticular screw fixation is technically possible in a large proportion of pediatric patients with craniovertebral instability.

Adolescent↗

Recurrent atlantoaxial rotatory fixation in children: a rare complication of a rare condition. Report of four cases.

Atlantoaxial rotatory fixation (AARF) is an uncommon condition of childhood. Occasionally AARF may recur. The authors describe the cases of four patients with recurrent AARF (RAARF). The probable cause of the RAARF and operative procedure selected are discussed. In three cases, attempts were made to stabilize the atlantoaxial complex rather than to perform fusion to preserve the function of the joint complex. Joint stabilization is performed by incorporating a "check ligament" into the joint construct between the axial spinous process and the atlantal lateral mass. The authors believe this technique of joint stabilization augments the strength of the joint, allowing normal, but preventing excessive, rotation, until the joint reaches physiological maturity.

Atlanto-Axial Joint↗

Atlantoaxial stabilization with the use of C1-3 lateral mass screw fixation. Technical note.

Atlantoaxial stabilization has evolved from simple posterior wiring to transarticular screw fixation. In some patients, however, the course of the vertebral artery (VA) through the axis varies, and therefore transarticular screw placement is not always feasible. For these patients, the authors have developed a novel method of atlantoaxial stabilization that does not require axial screws. In this paper, they describe the use of this technique in the first 10 cases. Ten consecutive patients underwent the combined C1-3 lateral mass-sublaminar axis cable fixation technique. The mean age of the patients was 62.6 years (range 23-84 years). There were six men and four women. Eight patients were treated after traumatic atlantoaxial instability developed (four had remote trauma and previous nonunion), whereas in the other two atlantoaxial instability was caused by arthritic degeneration. All had VA anatomy unsuitable to traditional transarticular screw fixation. There were no intraoperative complications in any of the patients. Postoperative computed tomography studies demonstrated excellent screw positioning in each patient. Nine patients were treated postoperatively with the aid of a rigid cervical orthosis. The remaining patient was treated using a halo fixation device. One patient died of respiratory failure 2 months after surgery. Follow-up data (mean follow-up duration 13.1 months) were available for seven of the remaining nine patients and demonstrated a stable construct with fusion in each patient. The authors present an effective alternative method in which C1-3 lateral mass screw fixation is used to treat patients with unfavorable anatomy for atlantoaxial transarticular screw fixation. In this series of 10 patients, the method was a safe and effective way to provide stabilization in these anatomically difficult patients.

Adult↗

[HASTE sequence and cine-MRI evaluation of the cervical spinal canal: evaluation in 11 healthy subjects].

PURPOSE: We studied 11 healthy subjects were evaluated using cine MR imaging comparing HASTE and gradient echo sequences. Materials and methods :HASTE is a high-speed turbo-spin echo T2-weighted sequence. All examinations were performed using dynamic MRI using a simple process allowing acquisition of images at different stages during flexion and extension. The cine MR evaluation was obtained by rebuilding a cine-loop sequence. RESULTS: HASTE sequence provides a myelographic effect of the cervical spine. The size, the pattern and the movements of the cervical spine, the spinal cord, as well as the functional reserve of cerebro-spinal fluid are analysable. CONCLUSION: Because of its very high speed, HASTE sequence is particularly useful for cine MR imaging.

Adult↗