C2 Lamina Research Articles

Image-Guided Placement of Occipitocervical Instrumentation Using a Reference Arc Attached to the Headholder

To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder. The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach. No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred. This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

Morphometric trajectory analysis for the C2 crossing laminar screw technique

This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis has been performed to confirm the accuracy of screw trajectory using this technique. In this study, morphometric analysis was performed on 100 Korean C2 three-dimensional reconstruction CT images. The reconstructive C2 vertebrae from the post-edge of the spinal canal to the spinal process were divided into several zones, 1 mm each. Each zone was chosen as the entry point to imitate a crossing laminar screw (3.5 mm diameter) placement. In each 1-mm zoned trajectory, the screw pass ratio (PR), safe screw angle range (SAR) and maximum screw length (MSL) were measured and compared with the data from the other zoned trajectories. The zone '5-6 mm posterior to the post-edge of the spinal canal' was found to be a more feasible and safer entry point for guiding a crossing laminar screw placement than the other zones because this zone could provide a trajectory with maximal PR (85%), SAR (9.57 +/- 4.36 masculine) and a larger MSL (21.74 +/- 2.44 mm) than the other areas. The recommended safe screw angle in the axial plane is 49.68 +/- 4.94 to 59.19 +/- 4.70 masculine. However, the screw angle can vary considerably according to the individual variance. A preoperative evaluation of the screw trajectory is essential for safe screw placement using this technique.

Atlantoaxial and Craniocervical Arthrodesis in Children

Analysis of C1-C2 tomographic anatomy in a cohort of healthy children. Compare suitability of C2 laminae and C2 pedicles for screw placement. Surgeons have applied several techniques for craniocervical and atlantoaxial spondylodesis to address congenital or developmental abnormalities in children. Constructs with pedicle or transarticular screws are effective to stabilize the craniocervical junction; however, these fixation points are not suitable in all patients. Translaminar screw placement in C2 has been safely performed in children; yet, suitability of C2 laminae and C2 pedicles has not been systematically compared. Applying chi2 test, we compared suitability for screw placement in 46 C2 pedicles and 46 C2 laminae on digital images of axial reconstructions of cervical CT scans of 23 children who had been admitted to the same hospital due to head or neck injury. On the same scans, we estimated suitability for screw placement in 46 lateral masses of C1. Twenty-four percent of C2 pedicles and 65% of C2 laminae were deemed suitable for 3.5-mm screw placement, and the difference was statistically significant (P < or = 0.0001, chi2 15.88). Forty-one percent of C2 pedicles and 80% of C2 laminae were deemed suitable for 3.0-mm screw placement, and the difference was statistically significant (P < or = 0.0001, chi2 14.78). Ninety-five percent of C1 lateral masses were deemed suitable for 3.5-mm screw placement. C2 laminae represent a viable fixation point for C1-C2 and craniocervical arthrodesis in children. This information can be useful for preoperative planning.

One-stage posterior resection is feasible for a holovertebral aneurysmal bone cyst of the axis: a case report and literature review

Background For cervical spine ABC, staged surgery and the combination of both anterior and posterior approaches are usually necessary for lesions involving all 3 (anterior, middle, and posterior) columns of the spine (holovertebral). Case Description A 20-year-old young man presented with quadriplegia and acute urine retention lasting for 3 days in November 2006. The diagnosis of an ABC involving the C2 vertebral body, pedicles, laminae, and spinous process was made by MRI. One-stage surgery with intralesional injection of fibrin glue via the posterior approach only was able to deliver complete resection and spinal stabilization. His neurologic function recovered well, and he was able to walk independently 10 days postoperation. At the 1-year follow-up, image studies of the cervical spine demonstrated good bone fusion without recurrence of ABC. The C2 vertebral body also showed resolution of ABC and good trabeculation. Conclusions Intralesional injection of fibrin glue during the operation for holovertebral ABC can be beneficial to (1) avoid using an anterior approach for complete resection and reconstruction, which was usually required in previous reports, and (2) effectively decrease the blood loss during surgery.

Different Types of Syringomyelia and Their Management

Surgical Procedures Posterior Fossa Decompression There are many ways to perform posterior fossa decompression (PFD), although indications for each technique are not clear, and its application depends on clinical manifestations, radiologic findings, dynamics of cerebrospinal fluid (CSF) and especially, the surgeon’s preference. OccipitalCraniectomy.This is the simplest procedure, and it consists of performinganoccipital craniectomywide enough to allow for both decompression and maintenance of the posterior fossaneural elements. The extent of bone removal is very important, because performing a wide occipital window has a high risk of formation of a pseudomeningocele and the socalled cerebellar ptosis; in these cases, symptomsmaynot only recur but even become associated with other cerebellar manifestations. Themost recommendedaverage size for the craniectomy is approximately 2.5 to 3 cm on each side of the midline immediately below the inionup to the foramenmagnumand, depending on the extension of cerebellar tonsillar herniation, it is usually associated with resection of the posterior arch of C1 and sometimes, the lamina of C2 (Figure 1). Most patients with type I Chiari malformation experience improvement in their symptomswith this simpleprocedure. This improvement is because pathologic analysis has shown an increase in collagen fibers, hyaline nodules, and calcification in thedural band of the craniovertebral junction, so bone removal promotes liberationof all these elements andallows restorationofCSF flow. However, if this procedure is chosen as the only treatment, it Different Types of Syringomyelia and Their Management: Part II

P71. Biomechanical Evaluation of a Novel Anterior Atlanto-Axial Fixation Construct

BACKGROUND CONTEXT: Atlanto-axial fixation is a necessary treatment modality in a variety of pathologies, including cervical trauma, degenerative disease and neoplasm. Several posterior fixation techniques are currently in practice, including fixation of the C1 lateral masses to the C2 pars, pedicles or lamina. Simple interspinous wiring is also an option. Anterior atlanto-axial fixation may be associated with less risk to the neurovascular structures in the upper cervical spine, particularly the vertebral arteries.

In this issue – October 2009

In this issue – October 2009

Stabilisation with dorsal and ventral fixation of a traumatic cervical instability in a dog

This case study reports the outcome of dorsal and ventral stabilisation of a traumatic cervical instability in a dog. A 2-year-old, male Pointer was admitted following a motor vehicle accident. Clinical examination revealed non-ambulatory tetraparesis, severe neck pain and upper motor neuron changes in all limbs. Deep pain response was present. Subluxation of C2/3 and fractures of the dorsal spinous process and lamina of C2 were observed on radiographs. Ventral stabilisation was performed with screws and bone cement (polymethylmethacrylate). For dorsal fixation of the fractures, screws and cerclage wire were used. The dog stood up independently after 1 month, was able to walk 1.5 months postoperatively and had recovered completely at 1 year following surgery. We conclude that combined stabilisation techniques are effective for this type of cervical fracture in which the dorsal, middle and ventral structures of the vertebra are severely disrupted.

Modification of Wright’s technique for C2 translaminar screw fixation: technical note

To describe a modification of Wright's technique for C2 translaminar screw fixation. Bilateral crossing C2 laminar screws have recently become popular as an alternative technique for C2 fixation. This technique is particularly useful in patients with anomalous anatomy, as a salvage technique where other modes of fixation have failed or as a primary procedure. However, reported disadvantages of this technique include breach of the dorsal lamina and spinal canal, early hardware failure and difficulty in bone graft placement due to the position of the polyaxial screw heads. To address some of these issues, a modified technique was used in six patients. In this technique, the upper part of the spinous process of C2 was removed and the entry point of the screw was in the base of this removed spinous process. The screw position was satisfactory in all patients. There were no intraoperative or early postoperative complications. Our modification enables placement of a bone graft on the C2 lamina and is also less likely to cause inadvertent cortical breach. Because of these advantages, it is especially suitable for patients with advanced rheumatoid arthritis with destruction of the lateral masses of C2 or as part of a hybrid construct in patients with a unilateral high-riding vertebral artery. This technique is not suitable for bilateral translaminar screw placement.

Cervical osteochondroma with postoperative recurrence: case report and review of the literature

Osteochondromas of the cervical spine are rare. We report an 8-year-old girl presenting with neck pain and a known familial predisposition for osteochondromas. Imaging revealed a presumed osteochondroma of the cervical spine located at C3. A cervical hemilaminectomy of the lesion was performed. Histopathology confirmed the lesion as an osteochondroma. Six months later, the child was found to have a recurrence of the previously resected lesion. The child was reoperated and the lesion removed along with the entire remaining lamina of C3. At 6-year follow-up, there has been no recurrence of the child's cervical lesion. We believe this to be the third reported case of recurrence of a cervical osteochondroma. Surgeons dealing with such lesions should be mindful of this complication.

TRANSLAMINAR VERSUS PEDICLE SCREW FIXATION OF C2

C2 translaminar (TL) screws rigidly capture the posterior elements of C2, avoid risk of vertebral artery injury, and are less technically demanding than C2 pedicle (PD) screws. However, a C2-TL screw breach places the spinal cord at risk, and the durability of C2-TL screws remains unknown. It is unclear if TL versus PD screw fixation of C2 is truly associated with less operative morbidity, greater accuracy of screw placement, or equivalent durability. We retrospectively reviewed the records of 167 consecutive patients undergoing posterior cervical fusion with either PD or TL screw fixation of C2. Perioperative morbidity, breach of the C2 lamina or pedicle on postoperative computed tomographic scans, and rates of operative revision were compared between PD and TL screw constructs in axial (C1-C2 or C1-C3) and subaxial (C2 and caudal) cervical fusions. In total, 152 C2-TL screws and 161 C2-PD screws were placed in 167 patients. Thirty-one (19%) cases of axial cervical fusion (C1-C2 or C1-C3) were performed (mean age, 63.8 +/- 20.6 years) with either C2-TL (16 [52%]) or C2-PD (15 [48%]) screw fixation. One hundred thirty-six (81%) cases of subaxial cervical fusion (C2-caudal) were performed (mean age, 57.9 +/- 14.7 years) with either C2-TL (66 [49%]) or C2-PD (70 [51%]) screw fixation. For both axial and subaxial cervical fusions, baseline patient characteristics and all measures of perioperative morbidity were similar between C2-TL and C2-PD screw cohorts. In total, 11 (7%) PD screws breached the pedicle (0 requiring acute revision) versus only 2 (1.3%) TL screws that breached the C2 lamina (1 requiring acute revision) (P = 0.018). By 1 year postoperatively, pseudoarthrosis or screw pullout requiring reoperation was required in 4 (6.1%) patients with C2-TL screws versus 0 (0%) patients with PD screws (P < 0.05 for subaxial constructs). No cases of C2-TL or C2-PD axial fusion required reoperation or screw pullout or pseudoarthrosis. In our experience, radiographic breach of C2 pedicle screws occurred more frequently than C2 laminar screw breach. However, this was not associated with an increase in morbidity. By 12 months postoperatively, C2-TL screws were associated with a greater incidence of operative revision when used in subaxial constructs but similarly effective for axial cervical constructs. The 1-year durability of C2-TL screws might be inferior to C2 pedicle screws for subaxial fusions, but equally effective for axial cervical fusions.

Occipitocervical fusion using a hook and rod system between cervical levels C2 and C3

We aimed to evaluate the clinical utility and safety of the hook and rod method for occipitocervical fusion. Eleven consecutive patients (3 males, 8 females; 50–78 years old, average 63.8 years; 16–77 months follow-up, average 33.7 months) with unstable lesions at the craniocervical junction who underwent occipitocervical fusion using a hook and rod system were examined. A Compact Cotrel-Dubousset cervical system (Sofamor-Danek, Memphis TN, USA) was used in all patients. The claw mechanism was applied bilaterally between the hook on the C2 lamina and the hook on the C3 inferior articular process. No complications occurred during surgery. Solid bony fusion was obtained in all patients and no patient became clinically worse postoperatively. Occipitocervical fusion using a hook and rod system is a useful procedure that allows decompression of the spinal cord and secure spinal fusion at multiple levels simultaneously.

Intramuscular myxoma of the cervical paraspinal muscle

Myxoma is a neoplasm of mesenchymal origin composed of undifferentiated stellate cells in a myxoid stroma. This tumor can develop in a variety of locations. Myxomas that arise from skeletal muscles are called intramuscular myxomas. They usually occur in large skeletal muscles. Only ten cases of these benign tumors involving the neck muscles were reported in literature. Of them, only three were located at the paraspinal muscles. A 64-year-old woman presented with occipital and neck pain over 5 years noted an expansive painful lesion located at posterior cervical region with progressive volume increase in the last 12 months. Image exams revealed a large mass located in the left posterior region of the neck in contact with the C2, C3 and C4 laminae with no invasion of the vertebrae. Tumor total removal was performed through normal muscle margins and the vertebral periosteum was scraped. The tumor was encapsulated, lobulated with a gray-white appearance. The histological examination yielded the diagnosis of intramuscular myxoma. Follow-up at 1 year showed complete resolution of preoperative symptoms and no evidence of local recurrence. In conclusion, although rare, intramuscular myxoma should be included in differential diagnosis of cervical paraspinal tumors. We reported the fourth case of intramuscular myxoma in the paraspinal musculature of the neck. Despite its benign characteristics, local recurrence was reported after subtotal resection. Tumor total removal should be the goal of surgery.

Primary medulla oblongata germinoma – an unusual posterior fossa tumors in young adults

We encountered 2 patients with germinoma arising from the medulla oblongata in whom preoperative radiological diagnosis was difficult. A 30-year-old woman presented due to aspiration pneumonia caused by bilateral lower cranial nerve palsies, and a 24-year-old man presented with headache caused by obstructive hydrocephalus. In both patients, there was a midline tumor that extended from the lower part of the fourth ventricle to the C1 lamina level. It was well-demarcated and homogeneously enhanced tumor with a slightly high density on plain CT scan. The preoperative diagnosis for both patients was ependymoma. The former patient had persistent lower cranial nerve palsies due to brain stem injury after tumor resection. Both patients achieved complete remission with adjuvant therapy. Fewer than 10 cases of germinoma affecting the medulla oblongata have been reported. Radiological findings resembling those of the pineal region germinoma were observed in the two patients reported here. We would like to stress the importance of remembering germinoma when making a preoperative differential diagnosis of fourth ventricular tumors in young adults.

Estudo anatômico dimensional do arco posterior de C2 para a instrumentação com parafuso intralaminar

INTRODUÇÃO: A articulação atlantoaxial possui mecanismos estabilizadores C1-C2, ligamentares, ósseos e capsulares, mantendo a relação anatômica adequada entre C1 e C2. A falha, traumática ou atraumática, isolada ou um conjunto destes mecanismos leva à instabilidade atlantoaxial, podendo culminar em alterações neurológicas, dor e limitação da mobilidade cervical. Casos com déficit neurológico e de instabilidade moderada a grave, são passíveis de tratamento cirúrgico. Desde 1910 inúmeras técnicas de estabilização cirúrgica C1-C2 são praticadas e mesmo recentemente novas técnicas de estabilização C1-C2 vêm sendo desenvolvidas. Novas técnicas foram desenvolvidas utilizando parafusos bilaterais na massa lateral de C1 e na lâmina de C2, conectados por barras. OBJETIVO: Mensurar as dimensões da lâmina de C2 para avaliar a segurança e dimensão do parafuso a ser utilizado, pela técnica de Wright. MÉTODOS: Estudo anatômico com 29 cadáveres adultos dissecando a lâmina de C2, aferindo medidas externa e interna da lâmina no plano sagital, coronal e axial. RESULTADOS: A média das medidas das porções médias externas das lâminas de C2 foi 5,83 mm, das quais 8,93% foram abaixo de 3,5mm. CONCLUSÃO: Sugerimos um estudo tomográfico pré-operatório, para identificar pacientes com lâminas menores e logo em maior risco.

Cervical Osteochondroma Presenting as Brown-Sequard Syndrome in a Child with Hereditary Multiple Exostosis

Cervical cord compression due to osteochondroma in hereditary multiple exostosis (HME) is a rare condition, especially in young children. In this report, we discuss a rare case of cervical osteochondroma presenting as Brown-Sequard syndrome (BSS) in a 7-year-old boy with HME. The child was admitted because of hemiparesis involving the right limbs and hypoesthesia on the left side following mild trauma. MR image revealed cord compression by osteochondroma of the C7 lamina. We removed the osteocondroma and the neurological deficit was improved.

Late Migration of Threaded Wire (Schanz Screw) from Right Distal Clavicle to the Cervical Spine

We report a 49-year-old man who had undergone osteosynthesis to treat right distal clavicular fracture with a threaded wire (Schanz screw). The wire could not be removed due to its firm fixation within the bone. Eight years later, migration of the broken wire to the right 7th cervical vertebra punctured the lamina, with no spinal cord injury noted. The threaded wire was extracted from the C7 lamina emergently. No complication occurred after pin removal or during the 1-year postoperative follow-up.

Rapid Reduction of Syrinx Associated With Traumatic Intracranial Hypotension by Direct Surgery -Case Report-

A woman in her early twenties presented with cerebellar tonsillar herniation with syrinx in the cervicothoracic spinal cord manifesting as postural headache after suffering trauma to the hip. She was treated under a diagnosis of traumatic intracranial hypotension. Cranial magnetic resonance (MR) imaging demonstrated tonsillar herniation to the upper rim of the C1 lamina, associated with effacement of the basal cisterns and flattening of the pons against the clivus, sagging of the optic chiasm, and protrusion of the pituitary gland into the suprasellar cistern. Spinal MR imaging and computed tomography (CT) myelography showed cervicothoracic syrinx and arachnoid diverticulum. Three applications of epidural blood patches produced no improvement. Surgery identified cerebrospinal fluid leakage from two small holes in the spinal dural sac, slightly proximal from the origin of the left L1 root sleeve, and arachnoid diverticulum. These two holes were sutured and a few sheets of gelatin sponge were placed around the arachnoid diverticulum and sealed with fibrin glue. The cervicothoracic syrinx was reduced significantly and tonsillar herniation disappeared within 10 days. Simple surgical repair of the dural tears may rapidly improve symptoms and imaging findings in patients with tonsillar herniation caused by traumatic intracranial hypotension.

OPEN REDUCTION OF C1–C2 SUBLUXATION WITH THE USE OF C1 LATERAL MASS AND C2 TRANSLAMINAR SCREWS

Abstract Objective: Spinal cord compression secondary to a subluxation of one vertebral body over another can be achieved with reduction of the translational deformity. Intraoperative reduction of C1–C2 subluxations can be technically challenging when one uses traditional techniques (e.g., wiring and transarticular screw fixation). The popularization of C1 lateral mass and C2 pedicle screws has allowed surgeons to achieve a more complex realignment at this region of the spine. Control of both C1 and C2 with independent fixation can be used to obtain reduction. In certain instances, placement of C2 pedicle screws is not possible. The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2 and can be used for intraoperative reduction. Clinical Presentation: A 15-year-old boy with juvenile rheumatoid arthritis presented with spinal cord compression secondary to a C1–C2 subluxation. The C2 pedicle anatomy precluded safe placement of C2 pedicle screws. An alternative method of fixation with the use of C2 translaminar screws and reduction was performed to obtain proper alignment and decompress the spinal cord. Technique: C1 lateral mass screws and C2 translaminar screws are inserted in the usual fashion. Two contoured rods, two rod holders, and two distractors, combined with C1 lateral mass screws and C2 translaminar screws, were used to achieve reduction. Concomitant distraction between the C2 translaminar screw head and the rod holder resulted in ventral translation of C2 on C1, decompressing the spinal cord. The reduction was maintained by tightening the C2 locking nut onto the rod. Conclusion: The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2. C1 lateral mass and C2 translaminar screw fixation provide a powerful means of reducing C1–C2 subluxations and maintaining alignment, achieving indirect decompression of the spinal cord.

COMBINED TRANSVENTRICULAR AND SUPRACEREBELLAR INFRATENTORIAL APPROACH PRESERVING THE VERMIS IN GIANT PEDIATRIC POSTERIOR FOSSA MIDLINE TUMORS

Abstract Objective: Giant pediatric midline tumors of the posterior fossa involving the fourth ventricle and the tectal region are difficult to approach and present a high risk of postoperative neurological deficits. Children with sequelae such as cerebellar mutism and ataxia experience a compromise in their quality of life. Here, we present our combined transventricular and supracerebellar infratentorial approach to avoid complications of vermian splitting. Methods: The combined transventricular and supracerebellar infratentorial approach described here was used in a total of four pediatric patients. A medial suboccipital craniotomy with opening of the foramen magnum and resection of the C1 lamina was performed with the patient in the semisitting position. The tumor mass filling the fourth ventricle was removed via a transventricular telovelar route through the foramen of Magendie, preserving the vermis. The rostral tumor portions in the peritectal region extruding up to the thalami were exposed and resected via an infratentorial supracere-bellar route to preserve the venous drainage of the cerebellum. Results: There were no new neurological deficits postoperatively. Two patients had low-grade astrocytomas, and two patients had malignant tumors. Complete tumor resection was achieved in two patients, and near-total tumor removal in the two others. CONCLUSION: The combined transventricular and supracerebellar infratentorial approach offers a unique possibility of safely removing giant pediatric midline tumors. Splitting of the cerebellar vermis is not necessary for removal of such tumors.