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Paul A. Gardner, Juan C. Fernandez-Miranda, Carl H. Snyderman and Eric W. Wang

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George A. C. Mendes, Curtis A. Dickman, Nestor G. Rodriguez-Martinez, Samuel Kalb, Neil R. Crawford, Volker K. H. Sonntag, Mark C. Preul and Andrew S. Little

OBJECT

The primary disadvantage of the posterior cervical approach for atlantoaxial stabilization after odontoidectomy is that it is conducted as a second-stage procedure. The goal of the current study is to assess the surgical feasibility and biomechanical performance of an endoscopic endonasal surgical technique for C1–2 fixation that may eliminate the need for posterior fixation after odontoidectomy.

METHODS

The first step of the study was to perform endoscopic endonasal anatomical dissections of the craniovertebral junction in 10 silicone-injected fixed cadaveric heads to identify relevant anatomical landmarks. The second step was to perform a quantitative analysis using customized software in 10 reconstructed adult cervical spine CT scans to identify the optimal screw entry point and trajectory. The third step was biomechanical flexibility testing of the construct and comparison with the posterior C1–2 transarticular fixation in 14 human cadaveric specimens.

RESULTS

Adequate surgical exposure and identification of the key anatomical landmarks, such as C1–2 lateral masses, the C-1 anterior arch, and the odontoid process, were provided by the endonasal endoscopic approach in all specimens. Radiological analysis of anatomical detail suggested that the optimal screw entry point was on the anterior aspect of the C-1 lateral mass near the midpoint, and the screw trajectory was inferiorly and slightly laterally directed. The custommade angled instrumentation was crucial for screw placement. Biomechanical analysis suggested that anterior C1–2 fixation compared favorably to posterior fixation by limiting flexion-extension, axial rotation, and lateral bending (p > 0.3).

CONCLUSIONS

This is the first study that demonstrates the feasibility of an endoscopic endonasal technique for C1–2 fusion. This novel technique may have clinical utility by eliminating the need for a second-stage posterior fixation operation in certain patients undergoing odontoidectomy.

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Daniel D. Cavalcanti, Nikolay L. Martirosyan, Ketan Verma, Sam Safavi-Abbasi, Randall W. Porter, Nicholas Theodore, Volker K. H. Sonntag, Curtis A. Dickman and Robert F. Spetzler

Object

Schwannomas occupying the craniocervical junction (CCJ) are rare and usually originate from the jugular foramen, hypoglossal nerves, and C-1 and C-2 nerves. Although they may have different origins, they may share the same symptoms, surgical approaches, and complications. An extension of these lesions along the posterior fossa cisterns, foramina, and spinal canal—usually involving various cranial nerves (CNs) and the vertebral and cerebellar arteries—poses a surgical challenge. The primary goals of both surgical and radiosurgical management of schwannomas in the CCJ are the preservation and restoration of function of the lower CNs, and of hearing and facial nerve function. The origins of schwannomas in the CCJ and their clinical presentation, surgical management, adjuvant stereotactic radiosurgery, and outcomes in 36 patients treated at Barrow Neurological Institute (BNI) are presented.

Methods

Between 1989 and 2009, 36 patients (mean age 43.6 years, range 17–68 years) with craniocervical schwannomas underwent surgical resection at BNI. The records were reviewed retrospectively regarding clinical presentation, radiographic assessment, surgical approaches, adjuvant therapies, and follow-up outcomes.

Results

Headache or neck pain was present in 72.2% of patients. Cranial nerve impairments, mainly involving the vagus nerve, were present in 14 patients (38.9%). Motor deficits were found in 27.8% of the patients. Sixteen tumors were intra- and extradural, 15 were intradural, and 5 were extradural. Gross-total resection was achieved in 25 patients (69.4%). Adjunctive radiosurgery was used in the management of residual tumor in 8 patients; tumor control was ultimately obtained in all cases.

Conclusions

Surgical removal, which is the treatment of choice, is curative when schwannomas in the CCJ are excised completely. The far-lateral approach and its variations are our preferred approaches for managing these lesions. Most common complications involve deficits of the lower CNs, and their early recognition and rehabilitation are needed. Stereotactic radiosurgery, an important tool for the management of these tumors as adjuvant therapy, can help decrease morbidity rates.

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Eric M. Horn, Iman Feiz-Erfan, Gregory P. Lekovic, Curtis A. Dickman, Volker K. H. Sonntag and Nicholas Theodore

Object

Although rare, traumatic occipitoatlantal dislocation (OAD) injuries are associated with a high mortality rate. The authors evaluated the imaging and clinical factors that determined treatment and were predictive of outcomes, respectively, in survivors of this injury.

Methods

The medical records and imaging studies obtained in 33 patients with OAD were reviewed retrospectively. Clinical factors that predicted outcomes, especially neurological injury at presentation and imaging findings, were evaluated.

The most sensitive method for the diagnosis of OAD was the measurement of basion axial–basion dens interval on computed tomography (CT) scanning. Five patients with severe traumatic brain injuries (TBIs) were not treated and subsequently died. Of the 28 patients in whom treatment was performed, 23 underwent fusion and five were fitted with an external orthosis. Abnormal findings of the occipitoatlantal ligaments on magnetic resonance (MR) imaging, associated with no or questionable abnormalities on CT scanning, provided the rationale for nonoperative treatment. Of the 28 patients treated for their injuries, perioperative death occurred in five, three of whom had presented with severe neurological injuries. The mortality rate was highest in patients with a TBI at presentation. The mortality rate was lower in patients presenting with a spinal cord injury, but in this group there was a higher rate of persistent neurological deficits.

Conclusions

The spines in patients with CT-documented OAD are most likely unstable and need surgical fixation. In patients for whom CT findings are normal and MR imaging findings suggest marginal abnormalities, nonoperative treatment should be considered. The best predictors of outcome were severe brain or upper cervical injuries at initial presentation.

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Eric M. Horn, Nicholas Theodore, Iman Feiz-Erfan, Gregory P. Lekovic, Curtis A. Dickman and Volker K. H. Sonntag

Object

The risk factors of halo fixation in elderly patients have never been analyzed. The authors therefore retrospectively reviewed data obtained in the treatment of such cases.

Methods

A discharge database was searched for patients 70 years of age or older who had undergone placement of a halo device. In a search of cases managed between April 1999 and February 2005, data pertaining to 53 patients (mean age 79.9 years [range 70–97 years]) met these criteria. Forty-one patients were treated for traumatic injuries. Ten patients had deficits ranging from radiculopathy to quadriparesis, and 43 had no neurological deficit. Adequate follow-up material was available in 42 patients (mean treatment duration 91 days). Halo immobilization was the only treatment in 21 patients, and adjunctive surgical fixation was undertaken in the other 21 patients. There were 31 complications in 22 patients: respiratory distress in four patients, dysphagia in six, and pin-related complications in 10. Eight patients died; in two of these cases, the cause of death was clearly unrelated to the halo brace. The other six patients died of respiratory failure and cardiovascular collapse (perioperative mortality rate 14%). Three patients who died had sustained acute trauma and three had undergone surgical stabilization.

Conclusions

External halo fixation can be used safely to treat cervical instability in elderly patients. The high complication rate in this population may reflect the significant incidence of underlying disease processes.

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Dean Chou, Adolfo Espinoza Larios, Robert H. Chamberlain, Mary S. Fifield, Roger Hartl, Curtis A. Dickman, Volker K. H. Sonntag and Neil R. Crawford

Object

A flexibility experiment using human cadaveric thoracic spine specimens was performed to determine biomechanical differences among thoracolumbar two-screw plate, single-screw plate, and dual-rod systems. A secondary goal was to investigate differences in the ability of the systems to stabilize the spine after a one- or two-level corpectomy.

Methods

The authors evaluated 21 cadaveric spines implanted with a titanium mesh cage and three types of anterior thoracolumbar supplementary instrumentation after one-level thoracic corpectomies. Pure moments were applied quasistatically while three-dimensional motion was measured optoelectronically. The lax zone, stiff zone, and range of motion (ROM) were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Corpectomies were expanded to two levels, and testing was repeated with longer hardware.

Biomechanical testing showed that the single-bolt plate system was no different from the dual-rod system with two screws in limiting ROM. The single-bolt plate system performed slightly better than the two-screw plate system. Across the same two levels, there was an average of 19% more motion after a two-level corpectomy than after a one-level corpectomy. In general, however, the difference across the different loading modes was insignificant.

Conclusions

Biomechanically, the single-screw plate system is equivalent to a two-screw dual-rod and a two-screw plate system. All three systems performed similarly in stabilizing the spine after one- or two-level corpectomies.

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L. Fernando Gonzalez, Jeffrey D. Klopfenstein, Neil R. Crawford, Curtis A. Dickman and Volker K. H. Sonntag

✓ Occipitoatlantal dislocation and atlantoaxial vertical distraction are caused by similar mechanisms, and few individuals survive these injuries. It is hypothesized that the injurious vertical force manifests as a traumatic lesion at different levels of the same ligamentous complex. The authors report the cases of two patients who presented with this combined lesion, describe surgical alternatives for stabilization, and introduce a new technique that combines the use of transarticular screws in a “dual” construct, without involving the unaffected spine.

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L. Fernando Gonzalez, Neil R. Crawford, Robert H. Chamberlain, Luis E. Perez Garza, Mark C. Preul, Volker K. H. Sonntag and Curtis A. Dickman

Object. The authors compared the biomechanical stability resulting from the use of a new technique for occipitoatlantal motion segment fixation with an established method and assessed the additional stability provided by combining the two techniques.

Methods. Specimens were loaded using nonconstraining pure moments while recording the three-dimensional angular movement at occiput (Oc)—C1 and C1–2. Specimens were tested intact and after destabilization and fixation as follows: 1) Oc—C1 transarticular screws plus C1–2 transarticular screws; 2) occipitocervical transarticular (OCTA) plate in which C1–2 transarticular screws attach to a loop from Oc to C-2; and (3) OCTA plate plus Oc—C1 transarticular screws.

Occipitoatlantal transarticular screws reduced motion to well within the normal range. The OCTA loop and transarticular screws allowed a very small neutral zone, elastic zone, and range of motion during lateral bending and axial rotation. The transarticular screws, however, were less effective than the OCTA loop in resisting flexion and extension.

Conclusions. Biomechanically, Oc—C1 transarticular screws performed well enough to be considered as an alternative for Oc—C1 fixation, especially when instability at C1–2 is minimal. Techniques for augmenting these screws posteriorly by using a wired bone graft buttress, as is currently undertaken with C1–2 transarticular screws, may be needed for optimal performance.

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James Guest, Mohammed A. Eleraky, Paul J. Apostolides, Curtis A. Dickman and Volker K. H. Sonntag

Object. The authors compare clinical outcomes demonstrated in patients with traumatic central cord syndrome (CCS) who underwent early (< 24 hours after injury) or late (> 24 hours after injury) surgery.

Methods. The clinical characteristics, radiographic findings, surgery-related results, length of hospital stay (LOS), and clinical outcomes obtained in 50 patients with surgically treated traumatic CCS were reviewed retrospectively. Shorter intensive care unit (ICU) stay and LOS were observed in all patients who underwent early surgery compared with those who underwent late surgery. In patients with CCS secondary to acute disc herniation or fracture/dislocation who underwent early surgery significantly greater overall motor improvement was observed than in those who underwent late surgery (p = 0.04). Overall motor outcome in patients with CCS secondary to spinal stenosis or spondylosis who underwent early surgery was not significantly different from that in those who underwent late surgery (p = 0.51). Worse motor outcomes were found in patients who were older than 60 years of age and in whom initial bladder dysfunction was present (p = 0.03 and 0.02, respectively) compared with younger patients without bladder dysfunction.

Conclusions. Early surgery is safe and more cost effective than late surgery for the treatment of traumatic CCS, based on ICU stay and LOS and improved overall motor recovery, in patients whose CCS was related to acute disc herniation or fracture. In the setting of spinal stenosis or spondylosis, early surgery was safe but did not improve motor outcome compared with late surgery.

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Neil R. Crawford, Sedat Çagli, Volker K. H. Sonntag and Curtis A. Dickman

Object. The authors sought to create and to evaluate an in vitro model of Grade I degenerative (closed-arch) spondylolisthesis.

Methods. The model of spondylolisthesis was created by two primary procedures: 1) resection of the disc; and 2) stripping of anterior and posterior longitudinal ligaments away from the vertebral bodies (VBs). In 13 vertebral levels obtained from three cadaveric lumbar spines, the tissues were resected sequentially in alternating order to determine the relative contribution of each resection to spinal instability. The entire specimens were loaded with nonconstraining torques and then individual levels were loaded with anteroposterior shear forces. The motion values were measured optoelectronically for each specimen at individual levels.

Conclusions. The integrity of the disc was more important than attachment of the ligaments to the VB, but the resection of both structures was necessary to achieve substantial destabilization. The structures of the spine are highly resilient, and destabilization is difficult to achieve without performing extensive resection. Using the techniques described in this paper to alter normal spines, a level of spinal instability (Grade I; 25% slippage) that may represent spondylolisthesis can be modeled in vitro.