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Jae-Won Doh, Andrea L. Halliday, Nevan G. Baldwin and Edward C. Benzel

✓ The authors describe the case of a 41-year-old man with high-grade chondrosarcoma who presented with a paraspinous mass extending into three thoracic vertebrae (T10–12). Crossfixed long anterior and posterior instrumentation was placed after three complete spondylectomies (T10–12). This technique augments spinal stability with an outrigger effect by using crossfixators placed between paired dorsal rods, as well as between the anterior and posterior hardware components. This technique may be used as an alternative when multiple vertebrae or all three spinal columns are involved by radioresistant malignant tumors in patients in whom there is a relatively long life expectancy.

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Cary D. Alberstone, Stephen L. Skirboll, Edward C. Benzel, John A. Sanders, Blaine L. Hart, Nevan G. Baldwin, Charles L. Tessman, John T. Davis and Roland R. Lee

Object. The availability of large-array biomagnetometers has led to advances in magnetoencephalography that permit scientists and clinicians to map selected brain functions onto magnetic resonance images. This merging of technologies is termed magnetic source (MS) imaging. The present study was undertaken to assess the role of MS imaging for the guidance of presurgical planning and intraoperative neurosurgical technique used in patients with intracranial mass lesions.

Methods. Twenty-six patients with intracranial mass lesions underwent a medical evaluation consisting of MS imaging, a clinical history, a neurological examination, and assessment with the Karnofsky Performance Scale. Magnetic source imaging was used to locate the somatosensory cortex in 25 patients, the visual cortex in six, and the auditory cortex in four. The distance between the lesion and the functional cortex was determined for each patient.

Twenty-one patients underwent a neurosurgical procedure. As a surgical adjunct, a frameless stereotactic navigational system was used in 17 cases and a standard stereotactic apparatus in four cases. Because of the results of their MS imaging examination, two patients were not offered surgery, four underwent a stereotactic biopsy procedure, 10 were treated with a subtotal surgical resection, and seven were treated with complete surgical resection. One patient deteriorated before a procedure could be scheduled and, therefore, was not offered surgery, and two patients were offered surgery but declined. Three patients experienced surgery-related complications.

Conclusions. Magnetic source imaging is an important noninvasive neurodiagnostic tool that provides critical information regarding the spatial relationship of a brain lesion to functional cortex. By providing this information, MS imaging facilitates a minimum-risk management strategy and helps guide operative neurosurgical technique in patients with intracranial mass lesions.

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Sait Naderi, Edward C. Benzel and Nevan G. Baldwin

Cervical spondylotic myelopathy can produce a variety of clinical signs and symptoms secondary to neural compromise and biomechanical involvement of the spine. The surgical treatment of cervical spondylotic myelopathy remains a controversial issue after many years of study, evolution, and refinement. Several ventral, dorsal, or combined approaches have been defined. The complications associated with ventral approaches and the concerns about kyphosis following dorsal approaches led to the development of a variety of laminoplasty procedures. This paper reviews the biomechanical basis of cervical spondylotic myelopathy and its effect on choosing the appropriate surgical approach.

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Sait Naderi, Cary D. Alberstone, Frederick W. Rupp, Edward C. Benzel and Nevan G. Baldwin

Forty-four patients with cervical spondylotic myelopathy who underwent a ventral surgical approach were evaluated with respect to the results of surgery. The neurological status of the patients was categorized according to the modified Japanese Orthopedic Association scale (0-18). Three patients had a functional score of 8, one patient 9, five patients 10, five patients 11, seven patients 12, seven patients 13, seven patients 14, and nine patients had a functional score of 15, preoperatively. Twenty-three patients underwent a one-level corpectomy, 15 patients a two-level corpectomy, and six patients underwent a three-level corpectomy. Forty-one (93.1%) of the 44 patients underwent ventral cervical plate fixation. Complications among the 44 patients included graft-and instrumentation-related complications in seven cases, iliac crest donor-site infection in three cases, and respiratory complications in three cases. The follow-up periods ranged between 7 and 60 months (mean 42.3 months). Overall, the fusion rate was 97.72%. Three patients showed no functional change (6.8%), two patients were worse (4.5%), and 39 patients (88.6%) showed functional improvement in their score between +1 and +6 points (mean 2.16 points). There was no statistically significant difference in the functional improvement score in patients younger or older than 60 years old. The mean improvement in the functional score was found to be +2.857 ± 1.352, +2.400 ± 1.454, and +0.5000 ± 1.871 following one-level corpectomy, two-level, and three-level corpectomies, respectively. There were statistically significant differences in the neurological improvement observed between patients with one-level corpectomy and three-level corpectomy (p < 0.01), as well as between those with two-level and three-level corpectomy (p < 0.05). There was no statistically significant difference in the neurological outcome between patients with one-level and two-level corpectomy (p > 0.05). The results of this study demonstrate a high rate of solid bone fusion and a high rate of functional (neurological) improvement. Five patients underwent reoperation, predominantly for instrumentation failure. The use of instrumentation dictates careful consideration of the risk/benefit ratio associated with its use in each case.

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Edward C. Benzel, Blaine L. Hart, Perry A. Ball, Nevan G. Baldwin, William W. Orrison and Mary C. Espinosa

✓ Because it is often difficult to diagnose accurately the structurally intact cervical spine after acute trauma, a series of patients was evaluated with magnetic resonance (MR) imaging to assess its efficacy for the evaluation and clearance of the cervical spine in a trauma victim in the early posttrauma period. Ultralow-field MR imaging was used to evaluate 174 posttraumatic patients in whom physical findings indicated the potential for spine injury or minor radiographic findings indicated injury. This series includes only those patients who did not appear to harbor disruption of spinal integrity on the basis of a routine x-ray film. None had clinically obvious injury.

Of the 174 patients, 62 (36%) had soft-tissue abnormalities identified by MR imaging, including disc interspace disruption in 27 patients (four with ventral and dorsal ligamentous injury, three with ventral ligamentous injury alone, 18 with dorsal ligamentous injury alone, and two without ventral or dorsal ligamentous injury). Isolated ligamentous injury was observed in 35 patients (eight with ventral and dorsal ligamentous injury, five with ventral ligamentous injury alone, and 22 with dorsal ligamentous injury alone). One patient underwent a surgical fusion procedure, 35 patients (including the one treated surgically) were placed in a cervical collar for at least 1 month, and 27 patients were placed in a thermoplastic Minerva jacket for at least 2 months. All had a satisfactory outcome without evidence of instability.

The T2-weighted sagittal images were most useful in defining acute soft-tissue injury; axial images were of minimal assistance. Posttraumatic soft-tissue cervical spine injuries and disc herniations (most likely preexisting the trauma) are more common than expected. A negative MR image should be considered as confirmation of a negative or “cleared” subaxial cervical spine. Diagnostic and patient management algorithms may be appropriately tailored by this information. Thus, MR imaging is useful for early acute posttrauma assessment in a very select group of patients.

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Nevan G. Baldwin, Gregg P. Hartman, Martin W. Weiser and Edward C. Benzel

✓ The authors present the case of a failed titanium anterior cervical spine plate. The plate was contoured during implantation. Analysis of the failed implant with electron microscopy showed no metallurgical flaw to have caused the plate fracture. A crack was apparently initiated with the contouring of the plate. It was located at the weakest point in the plate (the position of the intermediate screw hole), and with subsequent stress, it propagated and led to fracture. Techniques for avoiding failure of this type are discussed.

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Edward C. Benzel and Nevan G. Baldwin

✓ An ideal spinal construct should immobilize only the unstable spinal segments, and thus only the segments fused. Pedicle fixation techniques have provided operative stabilization with the instrumentation of a minimal number of spinal segments; however, some failures have been observed with pedicle instrumentation. These failures are primarily related to excessive preload forces and limitations caused by the size and orientation of the pedicles.

To circumvent these problems, a new technique, the crossed-screw fixation method, was developed and is described in this report. This technique facilitates short-segment spinal fixation and uses a lateral extracavitary approach, which provides generous exposure for spinal decompression and interbody fusion. The technique employs two large transverse vertebral body screws (6.5 to 8.5 mm in diameter) to bear axial loads, and two unilateral pedicle screws (placed on the side of the exposure) to restrict flexion and extension deformation around the transverse screws and to provide three-dimensional deformity correction. The horizontal vertebral body and the pedicle screws are connected to rods and then to each other via rigid crosslinking. The transverse vertebral body screws are unloaded during insertion by placing the construct in a compression mode after the interbody bone graft is placed, thus optimizing the advantage gained by the significant “toe-in” configuration provided and further decreasing the chance for instrumentation failure.

The initial results of this technique are reported in a series of 10 consecutively treated patients, in whom correction of the deformity was facilitated. Follow-up examination (average 10.1 months after surgery) demonstrated negligible angulation. Chronic pain was minimal. The crossed-screw fixation technique is biomechanically sound and offers a rapid and safe form of short-segment three-dimensional deformity correction and solid fixation when utilized in conjunction with the lateral extracavitary approach to the unstable thoracic and lumbar spine. This approach also facilitates the secure placement of an interbody bone graft.

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Edward C. Benzel, Blaine L. Hart, Perry A. Ball, Nevan G. Baldwin, William W. Orrison and Mary Espinosa

✓ Vertical C-2 body fractures are presented in 15 patients with clinical and imaging correlations that suggest the existence of a variety of mechanisms of injury. In these patients, clinical and imaging correlations were derived by: 1) defining the point of impact by clinical examination; 2) defining the point of impact by soft-tissue changes on cranial magnetic resonance (MR) imaging or computerized tomography (CT); 3) obtaining an accurate history of the mechanism of injury; and 4) spine imaging (x-ray studies, CT, and MR imaging) of the C-2 body fracture and surrounding bone and soft tissue.

The cases presented involve the region located between the dens and the pars interarticularis of the axis. Although these fractures are rarely reported, they are not uncommon. An elucidation of their pathological anatomy helps to further the understanding of the mechanistic etiology of upper cervical spine trauma.

A spectrum of mechanisms of injury causing upper cervical spine fractures was observed. The type of injury incurred is determined predominantly by the force vector applied during impact and the intrinsic strength and anatomy of C-2 and its surrounding spinal elements. From this clinical experience, two types of vertical C-2 body fractures are defined and presented: coronally oriented (Type 1) and sagittally oriented (Type 2). A third type of C-2 body fracture, the horizontal rostral C-2 fracture (Type 3), is added for completeness; this Type 3 fracture is the previously described Type III odontoid process fracture described by Anderson and D'Alonzo.