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  • Journal of Neurosurgery: Spine x
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Doniel Drazin, Mir Hussain, Jonathan Harris, John Hao, Matt Phillips, Terrence T. Kim, J. Patrick Johnson and Brandon Bucklen


Abnormal sacral slope (SS) has shown to increase progression of spondylolisthesis, yet there exists a paucity in biomechanical studies investigating its role in the correction of adult spinal deformity, its influence on lumbosacral shear, and its impact on the instrumentation selection process. This in vitro study investigates the effect of SS on 3 anterior lumbar interbody fusion constructs in a biomechanics laboratory.


Nine healthy, fresh-frozen, intact human lumbosacral vertebral segments were tested by applying a 550-N axial load to specimens with an initial SS of 20° on an MTS Bionix test system. Testing was repeated as SS was increased to 50°, in 10° increments, through an angulated testing fixture. Specimens were instrumented using a standalone integrated spacer with self-contained screws (SA), an interbody spacer with posterior pedicle screws (PPS), and an interbody spacer with anterior tension band plate (ATB) in a randomized order. Stiffness was calculated from the linear portion of the load-deformation curve. Ultimate strength was also recorded on the final construct of all specimens (n = 3 per construct) with SS of 40°.


Axial stiffness (N/mm) of the L5–S1 motion segment was measured at various angles of SS: for SA 292.9 ± 142.8 (20°), 277.2 ± 113.7 (30°), 237.0 ± 108.7 (40°), 170.3 ± 74.1 (50°); for PPS 371.2 ± 237.5 (20°), 319.8 ± 167.2 (30°), 280.4 ± 151.7 (40°), 233.0 ± 117.6 (50°); and for ATB 323.9 ± 210.4 (20°), 307.8 ± 125.4 (30°), 249.4 ± 126.7 (40°), 217.7 ± 99.4 (50°). Axial compression across the disc space decreased with increasing SS, indicating that SS beyond 40° threshold shifted L5–S1 motion into pure shear, instead of compression-shear, defining a threshold. Trends in ultimate load and displacement differed from linear stiffness with SA > PPS > ATB.


At larger SSs, bilateral pedicle screw constructs with spacers were the most stable; however, none of the constructs were significantly stiffer than intact segments. For load to failure, the integrated spacer performed the best; this may be due to angulations of integrated plate screws. Increasing SS significantly reduced stiffness, which indicates that surgeons need to consider using more aggressive fixation techniques.

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Wouter I. Schievink, Ray M. Chu, M. Marcel Maya, J. Patrick Johnson and Hart C. M. Cohen


The goal of the study was to elucidate the spinal manifestations of spontaneous intracranial hypotension.


The authors reviewed the medical records and imaging studies of 338 consecutive patients with spontaneous intracranial hypotension who were evaluated at their institution between 2001 and 2010.


Twenty patients (6%; mean age 35.8 [range 16 to 60 years]; 5 males and 15 females) had convincing signs or symptoms referable to the spinal cord or spinal nerve roots. The spinal manifestations consisted of radiculopathy in 11 patients (unilateral in 8 and bilateral in 3), myelopathy in 8 patients, and bibrachial amyotrophy in 1 patient. The cervical spine was involved in 12 patients, the thoracic spine in 5, and the lumbosacral spine in 3. The spinal symptoms were positional in only 3 patients. The spinal manifestations occurred around the time of the headache onset in 16 patients, and months to years after the positional headache had resolved in 4 patients. A large extrathecal CSF collection causing compression of the spinal cord or nerve root was responsible for the spinal manifestations in the majority of patients. Treatment of the spinal CSF leak resulted in resolution of the spinal manifestations along with the headache, except for those in the patient with bibrachial amyotrophy.


Spinal manifestations are uncommon in cases of spontaneous intracranial hypotension, occurring in about 6% of patients, but myelopathy and radiculopathy involving all spinal segments do occur. Unlike the headache, the spinal manifestations usually are not positional and are caused by mass effect from an extradural CSF collection.

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Srinath Samudrala, Shoshanna Vaynman, Ty Thiayananthan, Samer Ghostine, Darren L. Bergey, Neel Anand, Robert S. Pashman and J. Patrick Johnson


Sagittal plane deformities can be subdivided into kyphotic and lordotic forms and further characterized according to their global or regional (focal) presentation. Regional deformities of a significant magnitude constitute a gibbous deformity. Pedicle subtraction osteotomy (PSO) and interlaminar Smith-Petersen osteotomies have been used to correct sagittal plane deformities in the cervical, thoracic, and lumbar spine. By resecting a portion of the vertebral body and closing in the gap of this vertebra, the spine is placed in local lordosis and kyphosis is corrected. These osteotomies have generally been carried out in the lumbar or less frequently in the thoracic area. While PSO has been performed in the mid and lower thoracic spine, there have been no case series of patients undergoing PSO at the CTJ. Specifically, a PSO approach that addresses the challenges of the CTJ is needed. Here, the authors review their case series of PSOs performed in the CTJ. Their goal in the treatment of these patients was to correct the regional CTJ kyphosis, restore forward gaze, and reduce the pain associated with the deformity.


Eight patients (5 males and 3 females, mean age 63 years) underwent PSO for the correction of CTJ kyphosis. Pedicle subtraction osteotomy was performed at C-7 or the upper thoracic vertebrae and was facilitated by a computer-guided intraoperative monitoring system. Surgical indications included postlaminectomy kyphosis, spinal cord tumor resection, posttraumatic kyphosis, and degenerative cervical spondylosis.


The mean follow-up was 15.3 months (range 12–20 months), and the mean preoperative CTJ kyphosis was 38.67° (range 25°–60°). Clinically satisfactory correction of the regional deformity was accomplished in all patients, achieving a mean correction of 35.63° (range 15°–66°) at the CTJ, with restoration of forward gaze and significant reduction in pain.


A CTJ deformity is a distinctive form of kyphosis that presents as a variable local deformity and requires complex spinal reconstructive techniques to restore sagittal balance and forward gaze. Pedicle subtraction osteotomy allows for significant correction through one spinal segment, and it can be used safely to correct the regional sagittal alignment of the cervical spine and head in relation to the pelvis. Pedicle subtraction osteotomy can be used alone or in combination with other techniques as some patients may require multistage procedures with anterior and posterior spinal reconstruction to obtain stable sagittal correction. All deformities in these patients were kyphotic in nature with only mild elements of scoliosis or coronal plane deformity. This is unlike lumbar and thoracic curves where the kyphosis is frequently associated with scoliosis.

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Robert L. Tiel and David G. Kline

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Langston T. Holly, Orin Bloch and J. Patrick Johnson


Paired point matching alone and paired point matching combined with surface matching are the two techniques used for the registration step in preoperative computerized tomography–based spinal image guidance. In the present study the authors sought to compare paired point–matching registration alone with paired point matching supplemented with surface matching to determine if the addition of surface matching improves navigational accuracy.


Pedicle screws were placed in three embalmed human cervicothoracic spinal specimens during image guidance to serve as a reference points. The specimens were then rescanned, and each level was registered using paired point matching alone and then by paired point supplemented with surface matching. Navigational accuracy was assessed by placing the stereotactic probe in the center of the screw head, and measuring the apparent distance between the screw head and probe on the computer monitor. Statistical analysis was used to compare the registration error and navigational error between the two techniques.

Seventy-five screws were placed at 46 vertebral levels. The mean registration error for the paired point matching/surface matching technique (0.5 mm) was significantly lower (p < 0.001) than that of the paired point matching alone technique (1.2 mm); however, the intertechnique difference in navigational error was nearly equivalent (1.3 mm compared with 1.4 mm) and statistically insignificant (p > 0.05).


Although the addition of surface matching to paired point registration significantly decreased the mean registration error, the actual navigational accuracy between the two techniques was equivalent when easily distinguishable points were meticulously selected. The use of paired point matching alone did not compromise the accuracy of navigation and is likely to result in decreased operating time.

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Rod J. Oskouian and J. Patrick Johnson

Object. The purpose of this clinical study was to evaluate prospectively surgical and neurological outcomes after endoscopic thoracic disc surgery.

Methods. The authors assessed the following quantifiable outcome data in 46 patients: operative time, blood loss, duration of chest tube insertion, narcotic use, hospital length of stay (LOS), and long-term follow-up neurological function and pain-related symptoms.

In patients who presented with myelopathy there was a postoperative improvement of two Frankel grades. Pain related to radiculopathy was improved by 75% and in one patient it worsened postoperatively. The authors also present operative data, surgical outcomes, and complications.

Conclusions. Thoracoscopic discectomy can be used to achieve acceptable results. It has several distinct advantages such as reduced postoperative pain, morbidity, and LOS compared with traditional open procedures.

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J. Patrick Johnson, Robert S. Pashman, Carl Lauryssen, Neel Anand, John J. Regan and Robert S. Bray

✓ Spinal deformity has classically and historically been studied by those in the discipline of orthopedic surgery. This may be attributable to the orthopedic interventionalists' experience with osseous fixation for long-bone and other skeletal fractures. Neurosurgeons have maintained a long-standing interest in complex cervical spinal disorders, and their interest in the larger field of complex spinal deformity has been expanding.

An understanding of spinal deformity disorders, biomechanics, bone biology, and metallurgy is necessary before clinical, teaching, and research activities can be undertaken within neurosurgery.

The authors describe basic and advanced concepts of spinal deformity management with cases to illustrate teaching points.

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Aaron G. Filler, Jodean Haynes, Sheldon E. Jordan, Joshua Prager, J. Pablo Villablanca, Keyvan Farahani, Duncan Q. Mcbride, Jay S. Tsuruda, Brannon Morisoli, Ulrich Batzdorf and J. Patrick Johnson

Object. Because lumbar magnetic resonance (MR) imaging fails to identify a treatable cause of chronic sciatica in nearly 1 million patients annually, the authors conducted MR neurography and interventional MR imaging in 239 consecutive patients with sciatica in whom standard diagnosis and treatment failed to effect improvement.

Methods. After performing MR neurography and interventional MR imaging, the final rediagnoses included the following: piriformis syndrome (67.8%), distal foraminal nerve root entrapment (6%), ischial tunnel syndrome (4.7%), discogenic pain with referred leg pain (3.4%), pudendal nerve entrapment with referred pain (3%), distal sciatic entrapment (2.1%), sciatic tumor (1.7%), lumbosacral plexus entrapment (1.3%), unappreciated lateral disc herniation (1.3%), nerve root injury due to spinal surgery (1.3%), inadequate spinal nerve root decompression (0.8%), lumbar stenosis (0.8%), sacroiliac joint inflammation (0.8%), lumbosacral plexus tumor (0.4%), sacral fracture (0.4%), and no diagnosis (4.2%).

Open MR—guided Marcaine injection into the piriformis muscle produced the following results: no response (15.7%), relief of greater than 8 months (14.9%), relief lasting 2 to 4 months with continuing relief after second injection (7.5%), relief for 2 to 4 months with subsequent recurrence (36.6%), and relief for 1 to 14 days with full recurrence (25.4%). Piriformis surgery (62 operations; 3-cm incision, transgluteal approach, 55% outpatient; 40% with local or epidural anesthesia) resulted in excellent outcome in 58.5%, good outcome in 22.6%, limited benefit in 13.2%, no benefit in 3.8%, and worsened symptoms in 1.9%.

Conclusions. This Class A quality evaluation of MR neurography's diagnostic efficacy revealed that piriformis muscle asymmetry and sciatic nerve hyperintensity at the sciatic notch exhibited a 93% specificity and 64% sensitivity in distinguishing patients with piriformis syndrome from those without who had similar symptoms (p < 0.01).

Evaluation of the nerve beyond the proximal foramen provided eight additional diagnostic categories affecting 96% of these patients. More than 80% of the population good or excellent functional outcome was achieved.

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Fred H. Geisler, Scott L. Blumenthal, Richard D. Guyer, Paul C. McAfee, John J. Regan, J. Patrick Johnson and Bradford Mullin

Object. Arthrodesis is the gold standard for surgical treatment of lumbar degenerative disc disease (DDD). Solid fusion, however, can cause stress and increased motion in the segments adjacent to the fused level. This may initiate and/or accelerate the adjacent-segment disease process. Artificial discs are designed to restore and maintain normal motion of the lumbar intervertebral segment. Restoring and maintaining normal motion of the segment reduces stresses and loads on adjacent level segments. A US Food and Drug Administration Investigational Device Exemptions multicentered study of the Charité artificial disc was completed. The control group consisted of individuals who underwent anterior lumbar interbody fusion involving BAK cages and iliac crest bone graft. This is the first report of Class I data in which a lumbar artificial disc is compared with lumbar fusion.

Methods. Of 304 individuals enrolled in the study, 205 were randomized to the Charité disc-treated group and 99 to the BAK fusion—treated (control) group. Neurological status was equivalent between the two groups at 6, 12, and 24 months postoperatively. The number of patients with major, minor, or other neurological complications was equivalent. There was a greater incidence of both major and minor complications in the BAK fusion group at 0 to 42 days postoperatively. Compared with data reported in the lumbar fusion literature, the Charité disc—treated patients had equivalent or better mean changes in visual analog scale and Oswestry Disability Index scores.

Conclusions. The Charité artificial disc is safe and effective for the treatment of single-level lumbar DDD, resulting in no higher incidence of neurological complications compared with BAK-assisted fusion and leading to equivalent or better outcomes compared with those obtained in the control group and those reported in the lumbar fusion literature.