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Timothy J. Kovanda and Eric M. Horn

Secondary injury following initial spinal cord trauma is uncommon and frequently attributed to mismanagement of an unprotected cord in the acute time period after injury. Subacute posttraumatic ascending myelopathy (SPAM) is a rare occurrence in the days to weeks following an initial spinal cord injury that is unrelated to manipulation of an unprotected cord and involves 4 or more vertebral levels above the original injury. The authors present a case of SPAM occurring in a 15-year-old boy who sustained a T3–4 fracture-dislocation resulting in a complete spinal cord injury, and they highlight the imaging findings and optimum treatment for this rare event.

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Thomas J. Gianaris, Gregory M. Helbig and Eric M. Horn

Object

Percutaneous pedicle screw insertion techniques are commonly used to treat a variety of spinal disorders. Typically, Kirschner (K)-wires are used to guide the insertion of taps and screws during placement since the normal anatomical landmarks are not visualized. The use of K-wires adds risks, such as vascular and nerve injuries as well as increased radiation exposure given the use of fluoroscopy. The authors describe a series of patients who had percutaneous pedicle screws placed using a new computer-assisted navigation technique without the need for K-wires.

Methods

Minimally invasive percutaneous pedicle screw placement in the thoracic and lumbar spine was performed in a consecutive series of 15 patients for a variety of spinal pathologies. Intraoperative 3D CT images were obtained and used with a computer-assisted navigation system to insert an awl-tap into each pedicle. The tap location in the pedicle was marked with the navigation software, and the awl-tap was then removed. The navigation system was used to identify each landmark to insert the pedicle screw. Connecting rods were then inserted percutaneously under fluoroscopic guidance. Postoperative CT scans were obtained in each patient to evaluate screw placement.

Results

On postprocedure scanning, only 1 screw had a minor lateral and superior breach that was asymptomatic. To date, there have been no hardware failures.

Conclusions

Percutaneous pedicle screws can be placed effectively and safely without the use of K-wires.

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Kashif A. Shaikh, Gregory M. Helbig, Scott A. Shapiro, Mitesh V. Shah, Saad A. Khairi and Eric M. Horn

Object

Organ transplantation for renal, liver, cardiac, and pulmonary failure has become more common in recent years, and patients are living longer as a result of improved organ preservation methods, immunosuppressive regimens, and general posttransplant care. Some of these patients undergo spine fusion surgery following organ transplantation, and there is little available information concerning outcomes. The authors report on their experience with and the outcomes of spine fusion in this rare and unique immunosuppressed patient group.

Methods

Using the Current Procedural Terminology and ICD-9 codes for solid organ transplants, bone marrow transplantations (BMTs), and spine fusion surgeries, the authors searched their patient database between 1997 and 2008. Data points of interest included primary diagnosis, type of organ transplant, immunosuppressant drug therapy, complications from spine surgery, and radiographic analysis of spine fusion. Spine fusion was assessed with CT or radiography at the latest follow-up.

Results

The database search results revealed 5999 patients who underwent heart, lung, liver, kidney, pancreas, intestine, or bone marrow transplant between 1997 and 2008. Eighteen of the 5999 patients underwent a spine fusion surgery while receiving immunosuppressive therapy. Organ transplants included kidney, liver, heart, pancreas, and allogenic BMT. There were 3 deaths unrelated to spine fusion within 1 year of the surgery and 1 death immediately after spine surgery. Graft-versus-host disease developed in 1 patient when prednisone was stopped prior to the spine surgery. Thirteen patients underwent follow-up radiographic imaging at an average of 25 months after spine surgery; 12 demonstrated radiographic fusion.

Conclusions

The results suggest that spine fusion rates are adequate despite immunosuppressive therapy in patients undergoing spinal fusion after transplant procedures. The data also illustrate the high morbidity and mortality rates found in the organ transplant patient population.

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Jeffrey F. Lastfogel, Thomas J. Altstadt, Richard B. Rodgers and Eric M. Horn

Recent studies have demonstrated excellent results in treating isthmic spondylolisthesis via an anterior lumbar interbody fusion (ALIF). The authors describe 3 patients with isthmic spondylolisthesis at L5–S1 who experienced sacral fractures after insertion of a unique, stand-alone anterior interbody fixation device.

Three consecutive patients at a single institution were treated for Grade I spondylolisthesis at L5–S1 via a standalone ALIF with insertion of a novel biomechanical interbody device. This device is made of polyetheretherketone and has an integrated system for internal fixation into the vertebral bodies. In each patient a bone morphogenetic protein–soaked sponge was placed for the fusion. The indications for treatment in each patient were back and radicular pain that had been unsuccessfully treated with conservative measures.

All 3 patients had reduction of their spondylolisthesis and resolution of their unilateral radiculopathies immediately postoperatively. Within 1 month of surgery, all 3 patients had failure of the device and recurrence of their symptoms. In each case the failure was due to fracture of the anterior portion of the S-1 body. Each patient underwent reduction and pedicle screw fixation at L5–S1. In all cases, there was successful reduction in their recurrent spondylolisthesis and resolution of their radiculopathies.

Treatment of Grade I isthmic spondylolisthesis at L5–S1 with stand-alone ALIF and fixation can lead to sacral fracture from high stress loads at that level in the spine, and consideration should be made either for supplemental pedicle screw fixation or a completely posterior approach.

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Neal B. Patel, Matthew A. Hazzard, Laurie L. Ackerman and Eric M. Horn

Unstable pediatric cervical spine injuries present significant challenges in terms of fixation. Given the smaller cervical vertebral bodies in the preschool-aged population, commercially available pediatric cervical fixation instrumentation may be unsuitable because of the inappropriately large size of the screws and plates. The authors describe a 2-year-old girl who sustained an unstable C6–7 distraction injury during a motor vehicle accident. Because of the small size of her vertebral bodies, standard cervical spine instrumentation was not feasible, and posterior wiring alone was believed to be insufficient because of the complete distraction of all 3 spinal columns. The patient was taken to the operating room where craniofacial plates with an inherent locking mechanism were used to circumferentially stabilize the cervical spine. Follow-up examination 6 months postoperatively demonstrated stable cervical spine alignment and fusion with no evidence of the failure of either the anterior or posterior hardware. The use of craniofacial miniplates with an intrinsic locking mechanism represents a superior alternative for both anterior and posterior cervical fixations when spinal instrumentation is needed in the pediatric age group.

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Eric M. Horn, Phillip M. Reyes, Seungwon Baek, Mehmet Senoglu, Nicholas Theodore, Volker K. H. Sonntag and Neil R. Crawford

Object

The small diameter of the pedicle can make C-7 pedicle screw insertion dangerous. Although transfacet screws have been studied biomechanically when used in pinning joints, they have not been well studied when used as part of a C7–T1 screw/rod construct. The authors therefore compared C7–T1 fixation using a C-7 transfacet screw/T-1 pedicle screw construct with a construct composed of pedicle screws at both levels.

Methods

Each rigid posterior screw/rod construct was placed in 7 human cadaveric C6–T2 specimens (14 total). Specimens were tested in normal condition, after 2-column instability, and once fixated. Nondestructive, nonconstraining pure moments (maximum 1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while recording 3D motion optoelectronically. The entire construct was then loaded to failure by dorsal linear force.

Results

There was no significant difference in angular range of motion between the 2 instrumented groups during any loading mode (p > 0.11, nonpaired t-tests). Both constructs reduced motion to < 2° in any direction and allowed significantly less motion than in the normal condition. The C-7 facet screw/T-1 pedicle screw construct allowed a small but significantly greater lax zone than the pedicle screw/rod construct during lateral bending, and it failed under significantly less load than the pedicle screw/rod construct (p < 0.001).

Conclusions

When C-7 transfacet screws are connected to T-1 pedicle screws, they provide equivalent stability of constructs formed by pedicle screws at both levels. Although less resistant to failure, the transfacet screw construct should be a viable alternative in patients with healthy bone.

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Nicholas C. Bambakidis, Eric M. Horn, Peter Nakaji, Nicholas Theodore, Elizabeth Bless, Tammy Dellovade, Chiyuan Ma, Xukui Wang, Mark C. Preul, Stephen W. Coons, Robert F. Spetzler and Volker K. H. Sonntag

Object

Sonic hedgehog (Shh) is a glycoprotein molecule that upregulates the transcription factor Gli1. The Shh protein plays a critical role in the proliferation of endogenous neural precursor cells when directly injected into the spinal cord after a spinal cord injury in adult rodents. Small-molecule agonists of the hedgehog (Hh) pathway were used in an attempt to reproduce these findings through intravenous administration.

Methods

The expression of Gli1 was measured in rat spinal cord after the intravenous administration of an Hh agonist. Ten adult rats received a moderate contusion and were treated with either an Hh agonist (10 mg/kg, intravenously) or vehicle (5 rodents per group) 1 hour and 4 days after injury. The rats were killed 5 days postinjury. Tissue samples were immediately placed in fixative. Samples were immunohistochemically stained for neural precursor cells, and these cells were counted.

Results

Systemic dosing with an Hh agonist significantly upregulated Gli1 expression in the spinal cord (p < 0.005). After spinal contusion, animals treated with the Hh agonist had significantly more nestin-positive neural precursor cells around the rim of the lesion cavity than in vehicle-treated controls (means ± SDs, 46.9 ± 12.9 vs 20.9 ± 8.3 cells/hpf, respectively, p < 0.005). There was no significant difference in the area of white matter injury between the groups.

Conclusions

An intravenous Hh agonist at doses that upregulate spinal cord Gli1 transcription also increases the population of neural precursor cells after spinal cord injury in adult rats. These data support previous findings based on injections of Shh protein directly into the spinal cord.

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Eric M. Horn, Nicholas Theodore, Rachid Assina, Robert F. Spetzler, Volker K. H. Sonntag and Mark C. Preul

Object

Venous stasis and intrathecal hypertension are believed to play a significant role in the hypoperfusion present in the spinal cord following injury. Lowering the intrathecal pressure via cerebrospinal fluid (CSF) drainage has been effective in treating spinal cord ischemia during aorta surgery. The purpose of the present study was to determine whether CSF drainage increases spinal cord perfusion and improves outcome after spinal injury in an animal model.

Methods

Anesthetized adult rabbits were subjected to a severe contusion spinal cord injury (SCI). Cerebrospinal fluid was then drained via a catheter to lower the intrathecal pressure by 10 mm Hg. Tissue perfusion was assessed at the site of injury, and values obtained before and after CSF drainage were compared. Two other cohorts of animals were subjected to SCI: 1 group subsequently underwent CSF drainage and the other did not. Results of histological analysis, motor evoked potential and motor function testing were compared between the 2 cohorts at 4 weeks postinjury.

Results

Cerebrospinal fluid drainage led to no significant improvement in spinal cord tissue perfusion. Four weeks after injury, the animals that underwent CSF drainage demonstrated significantly smaller areas of tissue damage at the injury site. There were no differences in motor evoked potentials or motor score outcomes at 4 weeks postinjury.

Conclusions

Cerebrospinal fluid drainage effectively lowers intrathecal pressure and decreases the amount of tissue damage in an animal model of spinal cord injury. Further studies are needed to determine whether different draining regimens can improve motor or electrophysiological outcomes.

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Ryan P. Brennan, Philip Y. Smucker and Eric M. Horn

Lower back pain from spondylolysis historically has been treated with a variety of options ranging from conservative care to open fusion. The authors describe the novel technique of minimally invasive bilateral pars interarticularis screw placement by utilizing intraoperative 3D imaging and frameless navigation in a 17-year-old male athlete. This technique is a modification of the open technique first described in 1970 by Buck and has the advantages of minimal dissection requirements with improved screw trajectory visualization. The patient's postoperative course is discussed, followed by a brief literature review of pars interarticularis defect treatment.

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Eric M. Horn, Nicholas Theodore, Neil R. Crawford, Nicholas C. Bambakidis and Volker K. H. Sonntag

Object

Lateral mass screws are traditionally used to fixate the subaxial cervical spine, while pedicle screws are used in the thoracic spine. Lateral mass fixation at C-7 is challenging due to thin facets, and placing pedicle screws is difficult due to the narrow pedicles. The authors describe their clinical experience with a novel technique for transfacet screw placement for fixation at C-7.

Methods

A retrospective chart review was undertaken in all patients who underwent transfacet screw placement at C-7. The technique of screw insertion was the same for each patient. Polyaxial screws between 8- and 10-mm-long were used in each case and placed through the facet from a perpendicular orientation. Postoperative radiography and clinical follow-up were analyzed for aberrant screw placement or construct failure.

Results

Ten patients underwent C-7 transfacet screw placement between June 2006 and March 2007. In all but 1 patient screws were placed bilaterally, and the construct lengths ranged from C-3 to T-5. One patient with a unilateral screw had a prior facet fracture that precluded bilateral screw placement. There were no intraoperative complications or screw failures in these patients. After an average of 6 months of follow-up there were no hardware failures, and all patients showed excellent alignment.

Conclusions

The authors present the first clinical demonstration of a novel technique of posterior transfacet screw placement at C-7. These results provide evidence that this technique is safe to perform and adds stability to cervicothoracic fixation.