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Eduardo Martinez-del-Campo, Jay D. Turner, Leonardo Rangel-Castilla, Hector Soriano-Baron, Samuel Kalb and Nicholas Theodore

OBJECTIVE

If left untreated, occipitocervical (OC) instability may lead to serious neurological injury or death. Open internal fixation is often necessary to protect the neurovascular elements. This study reviews the etiologies for pediatric OC instability, analyzes the radiographic criteria for surgical intervention, discusses surgical fixation techniques, and evaluates long-term postoperative outcomes based on a single surgeon's experience.

METHODS

The charts of all patients < 18 years old who underwent internal OC fixation conducted by the senior author were retrospectively reviewed. Forty consecutive patients were identified for analysis. Patient demographic data, OC junction pathology, radiological diagnostic tools, surgical indications, and outcomes are reported.

RESULTS

The study population consisted of 20 boys and 20 girls, with a mean age of 7.3 years. Trauma (45% [n = 18]) was the most common cause of instability, followed by congenital etiologies (37.5% [n = 15]). The condyle-C1 interval had a diagnostic sensitivity of 100% for atlantooccipital dislocation. The median number of fixated segments was 5 (occiput–C4). Structural bone grafts were used in all patients. Postsurgical neurological improvement was seen in 88.2% (15/17) of patients with chronic myelopathy and in 25% (1/4) of patients with acute myelopathy. Preoperatively, 42.5% (17/40) of patients were neurologically intact and remained unchanged at last follow-up, 42.5% (17/40) had neurological improvement, 12.5% (5/40) remained unchanged, and 2.5% (1/40) deteriorated. All patients had successful fusion at 1-year follow-up. The complication rate was 7.5% (3/40), including 1 case of vertebral artery injury.

CONCLUSIONS

Occipitocervical fixation is safe in children and provides immediate immobilization, with excellent survival and arthrodesis rates. Of the radiographic tools evaluated, the condyle-C1 interval was the most predictive of atlantooccipital dislocation.

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Ali M. Elhadi, Samuel Kalb, Nikolay L. Martirosyan, Abhishek Agrawal and Mark C. Preul

Within a few months of Wilhelm Conrad Röntgen's discovery of x-rays in 1895, Fedor Krause acquired an x-ray apparatus and began to use it in his daily interactions with patients and for diagnosis. He was the first neurosurgeon to use x-rays methodically and systematically. In 1908 Krause published the first volume of text on neurosurgery, Chirurgie des Gehirns und Rückenmarks (Surgery of the Brain and Spinal Cord), which was translated into English in 1909. The second volume followed in 1911. This was the first published multivolume text totally devoted to neurosurgery. Although Krause excelled in and promoted neurosurgery, he believed that surgeons should excel at general surgery. Importantly, Krause was inclined to adopt technology that he believed could be helpful in surgery. His 1908 text was the first neurosurgical text to contain a specific chapter on x-rays (“Radiographie”) that showed roentgenograms of neurosurgical procedures and pathology. After the revolutionary discovery of x-rays by Röntgen, many prominent neurosurgeons seemed pessimistic about the use of x-rays for anything more than trauma or fractures. Krause immediately seized on its use to guide and monitor ventricular drainage and especially for the diagnosis of tumors of the skull base. The x-ray images contained in Krause's “Radiographie” chapter provide a seminal view into the adoption of new technology and the development of neurosurgical technique and are part of neurosurgery's heritage.

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Eduardo Martinez-del-Campo, Jay D. Turner, Hector Soriano-Baron, Anna G. U. S. Newcomb, Samuel Kalb and Nicholas Theodore

OBJECTIVE

The authors assessed the rate of vertebral growth, curvature, and alignment for multilevel constructs in the cervical spine after occipitocervical fixation (OCF) in pediatric patients and compared these results with those in published reports of growth in normal children.

METHODS

The authors assessed cervical spine radiographs and CT images of 18 patients who underwent occipitocervical arthrodesis. Measurements were made using postoperative and follow-up images available for 16 patients to determine cervical alignment (cervical spine alignment [CSA], C1–7 sagittal vertical axis [SVA], and C2–7 SVA) and curvature (cervical spine curvature [CSC] and C2–7 lordosis angle). Seventeen patients had postoperative and follow-up images available with which to measure vertebral body height (VBH), vertebral body width (VBW), and vertical growth percentage (VG%—that is, percentage change from postoperative to follow-up). Results for cervical spine growth were compared with normal parameters of 456 patients previously reported on in 2 studies.

RESULTS

Ten patients were girls and 8 were boys; their mean age was 6.7 ± 3.2 years. Constructs spanned occiput (Oc)–C2 (n = 2), Oc–C3 (n = 7), and Oc–C4 (n = 9). The mean duration of follow-up was 44.4 months (range 24–101 months). Comparison of postoperative to follow-up measures showed that the mean CSA increased by 1.8 ± 2.9 mm (p < 0.01); the mean C2–7 SVA and C1–7 SVA increased by 2.3 mm and 2.7 mm, respectively (p = 0.3); the mean CSC changed by −8.7° (p < 0.01) and the mean C2–7 lordosis angle changed by 2.6° (p = 0.5); and the cumulative mean VG% of the instrumented levels (C2–4) provided 51.5% of the total cervical growth (C2–7). The annual vertical growth rate was 4.4 mm/year. The VBW growth from C2–4 ranged from 13.9% to 16.6% (p < 0.001). The VBW of C-2 in instrumented patients appeared to be of a smaller diameter than that of normal patients, especially among those aged 5 to < 10 years and 10–15 years, with an increased diameter at the immediately inferior vertebral bodies compensating for the decreased width. No cervical deformation, malalignment, or detrimental clinical status was evident in any patient.

CONCLUSIONS

The craniovertebral junction and the upper cervical spine continue to present normal growth, curvature, and alignment parameters in children with OCF constructs spanning a distance as long as Oc–C4.

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Ali M. Elhadi, Samuel Kalb, Luis Perez-Orribo, Andrew S. Little, Robert F. Spetzler and Mark C. Preul

The field of anatomy, one of the most ancient sciences, first evolved in Egypt. From the Early Dynastic Period (3100 bc) until the time of Galen at the end of the 2nd century ad, Egypt was the center of anatomical knowledge, including neuroanatomy. Knowledge of neuroanatomy first became important so that sacred rituals could be performed by ancient Egyptian embalmers during mummification procedures. Later, neuroanatomy became a science to be studied by wise men at the ancient temple of Memphis. As religious conflicts developed, the study of the human body became restricted. Myths started to replace scientific research, squelching further exploration of the human body until Alexander the Great founded the city of Alexandria. This period witnessed a revolution in the study of anatomy and functional anatomy. Herophilus of Chalcedon, Erasistratus of Chios, Rufus of Ephesus, and Galen of Pergamon were prominent physicians who studied at the medical school of Alexandria and contributed greatly to knowledge about the anatomy of the skull base. After the Royal Library of Alexandria was burned and laws were passed prohibiting human dissections based on religious and cultural factors, knowledge of human skull base anatomy plateaued for almost 1500 years. In this article the authors consider the beginning of this journey, from the earliest descriptions of skull base anatomy to the establishment of basic skull base anatomy in ancient Egypt.

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Nestor G. Rodriguez-Martinez, Amey Savardekar, Eric W. Nottmeier, Stephen Pirris, Phillip M. Reyes, Anna G. U. S. Newcomb, George A. C. Mendes, Samuel Kalb, Nicholas Theodore and Neil R. Crawford

OBJECTIVE

Transvertebral screws provide stability in thoracic spinal fixation surgeries, with their use mainly limited to patients who require a pedicle screw salvage technique. However, the biomechanical impact of transvertebral screws alone, when they are inserted across 2 vertebral bodies, has not been studied. In this study, the authors assessed the stability offered by a transvertebral screw construct for posterior instrumentation and compared its biomechanical performance to that of standard bilateral pedicle screw and rod (PSR) fixation.

METHODS

Fourteen fresh human cadaveric thoracic spine segments from T-6 to T-11 were divided into 2 groups with similar ages and bone quality. Group 1 received transvertebral screws across 2 levels without rods and subsequently with interconnecting bilateral rods at 3 levels (T8–10). Group 2 received bilateral PSR fixation and were sequentially tested with interconnecting rods at T7–8 and T9–10, at T8–9, and at T8–10. Flexibility tests were performed on intact and instrumented specimens in both groups. Presurgical and postsurgical O-arm 3D images were obtained to verify screw placement.

RESULTS

The mean range of motion (ROM) per motion segment with transvertebral screws spanning 2 levels compared with the intact condition was 66% of the mean intact ROM during flexion-extension (p = 0.013), 69% during lateral bending (p = 0.015), and 47% during axial rotation (p < 0.001). The mean ROM per motion segment with PSR spanning 2 levels compared with the intact condition was 38% of the mean intact ROM during flexion-extension (p < 0.001), 57% during lateral bending (p = 0.007), and 27% during axial rotation (p < 0.001). Adding bilateral rods to the 3 levels with transvertebral screws decreased the mean ROM per motion segment to 28% of intact ROM during flexion-extension (p < 0.001), 37% during lateral bending (p < 0.001), and 30% during axial rotation (p < 0.001). The mean ROM per motion segment for PSR spanning 3 levels was 21% of intact ROM during flexion-extension (p < 0.001), 33% during lateral bending (p < 0.001), and 22% during axial rotation (p < 0.001).

CONCLUSIONS

Biomechanically, fixation with a novel technique in the thoracic spine involving transvertebral screws showed restoration of stability to well within the stability provided by PSR fixation.

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Corinna C. Zygourakis, A. Karim Ahmed, Samuel Kalb, Alex M. Zhu, Ali Bydon, Neil R. Crawford and Nicholas Theodore

The Excelsius GPS (Globus Medical, Inc.) was approved by the FDA in 2017. This novel robot allows for real-time intraoperative imaging, registration, and direct screw insertion through a rigid external arm—without the need for interspinous clamps or K-wires. The authors present one of the first operative cases utilizing the Excelsius GPS robotic system in spinal surgery. A 75-year-old man presented with severe lower back pain and left leg radiculopathy. He had previously undergone 3 decompressive surgeries from L3 to L5, with evidence of instability and loss of sagittal balance. Robotic assistance was utilized to perform a revision decompression with instrumented fusion from L3 to S1. The usage of robotic assistance in spinal surgery may be an invaluable resource in minimally invasive cases, minimizing the need for fluoroscopy, or in those with abnormal anatomical landmarks.

The video can be found here: https://youtu.be/yVI-sJWf9Iw.

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Eduardo Martinez-del-Campo, Samuel Kalb, Hector Soriano-Baron, Jay D. Turner, Matthew T. Neal, Timothy Uschold and Nicholas Theodore

OBJECT

Atlantooccipital dislocation (AOD) in adults cannot be diagnosed with adequate specificity and sensitivity using only CT or plain radiography, and the spine literature offers no guidelines. In children, the most sensitive and specific radiographic measurement for the diagnosis of AOD is the CT-based occipital condyle–C1 interval (CCI). The goal of the current study was to identify the normal CCI in healthy adults and compare it with the CCI in adults with AOD to establish a highly sensitive and specific cutoff value for the neuroimaging diagnosis of AOD.

METHODS

A total of 81 patients, 59 without AOD and 22 with AOD, were included in this study. Measurements obtained from thin-slice CT scans of the craniovertebral joint to assess atlantooccipital dislocation included the CCI, condylar sum, the Wholey and Harris intervals, Powers and Sun ratios, Wackenheim line, and Lee X-lines.

RESULTS

The group of patients without AOD included 30 men (50.8%) and 29 women (49.2%) with a mean age of 42.4 ± 16 years (range 19–87 years). The group of patients with AOD included 10 men (45.5%) and 12 women (54.5%) with a mean age of 38.2 ± 9.7 years (range 20–56 years). Interrater reliabilities within a 95% CI were all greater than 0.98 for CCI measurements. A total of 1296 measurements of the CCI were made in 81 patients. The mean CCI for non-AOD patients was 0.89 ± 0.12 mm, the single largest CCI measurement was 1.4 mm, and the largest mean for either right or left CCI was 1.2 mm. The mean condylar sum was 1.8 ± 0.2 mm, and the largest condylar sum value was 2.2 mm. Linear regression with age predicted an increase in CCI of 0.001 mm/year (p < 0.05). The mean CCI in AOD patients was 3.35 ± 0.18 mm (range 1.5 mm–6.4 mm). The shortest single CCI measurements in the AOD patients were 1.1 mm and 1.2 mm. The mean condylar sum for all 22 AOD patients was 6.7 ± 2.7 mm and the shortest condylar sums were 3.0 mm. Cutoff values for AOD were set at 1.5 mm for the CCI and 3.0 mm for the condylar sum, both with a sensitivity of 1 and false-negative rate of 0. Sensitivity for the Powers, Wholey, Harris, Sun, Wackenheim, and Lee criteria were determined to be 0.55, 0.46, 0.27, 0.23, 0.41, and 0.41, respectively.

CONCLUSIONS

The CCI is shorter in adult patients as opposed to the pediatric population. The revised CCI (1.5 mm) and condylar sum (3.0 mm) cutoff values have the highest sensitivity and specificity for the diagnosis of AOD in the adult population.

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Samuel Kalb, Nikolay L. Martirosyan, Luis Perez-Orribo, M. Yashar S. Kalani and Nicholas Theodore

Object

Ossification of the posterior longitudinal ligament (OPLL) is a rare disease that results in progressive myeloradiculopathy related to pathological ossification of the ligament from unknown causes. Although it has long been considered a disease of Asian origin, this disorder is increasingly being recognized in European and North American populations. Herein the authors present demographic, radiographic, and comorbidity data from white patients with diagnosed OPLL as well as the outcomes of surgically treated patients.

Methods

Between 1999 and 2010, OPLL was diagnosed in 36 white patients at Barrow Neurological Institute. Patients were divided into 2 groups: a group of 33 patients with cervical OPLL and a group of 3 patients with thoracic or lumbar OPLL. Fifteen of these patients who had received operative treatment were analyzed separately. Imaging analysis focused on signal changes in the spinal cord, mass occupying ratio, signs of dural penetration, spinal levels involved, and subtype of OPLL. Surgical techniques included anterior cervical decompression and fusion with corpectomy, posterior laminectomy with fusion, posterior open-door laminoplasty, and anterior corpectomy combined with posterior laminectomy and fusion. Comorbidities, cigarette smoking, and previous spine surgeries were considered. Neurological function was assessed using a modified Japanese Orthopaedic Association Scale (mJOAS).

Results

A high-intensity signal on T2-weighted MR imaging and a history of cervical spine surgery correlated with worse mJOAS scores. Furthermore, mJOAS scores decreased as the occupying rate of the OPLL mass in the spinal canal increased. On radiographic analysis, the proportion of signs of dural penetration correlated with the OPLL subtype. A high mass occupying ratio of the OPLL was directly associated with the presence of dural penetration and high-intensity signal. In the surgical group, the rate of neurological improvement associated with an anterior approach was 58% compared with 31% for a posterior laminectomy. No complications were associated with any of the 4 types of surgical procedures. In 3 cases, symptoms had worsened at the last follow-up, with only a single case of disease progression. Laminoplasty was the only technique associated with a worse clinical outcome. There were no statistical differences (p > 0.05) between the type of surgical procedure or radiographic presentation and postoperative outcome. There was also no difference between the choice of surgical procedure performed and the number of spinal levels involved with OPLL.

Conclusions

Ossification of the posterior longitudinal ligament can no longer be viewed as a disease of the Asian population exclusively. Since OPLL among white populations is being diagnosed more frequently, surgeons must be aware of the most appropriate surgical option. The outcomes of the various surgical treatments among the different populations with OPLL appear similar. Compared with other procedures, however, anterior decompression led to the best neurological outcomes.

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M. Yashar S. Kalani, Samuel Kalb, Nikolay L. Martirosyan, Salvatore C. Lettieri, Robert F. Spetzler, Randall W. Porter and Iman Feiz-Erfan

Object

Resection of cancer and the involved artery in the neck has been applied with some success, but the indications for such an aggressive approach at the skull base are less well defined. The authors therefore evaluated the outcomes of advanced skull base malignancies in patients who were treated with bypass and resection of the internal carotid artery (ICA).

Methods

The authors retrospectively reviewed the charts of all patients with advanced head and neck cancers who underwent ICA sacrifice with revascularization in which an extracranial-intracranial bypass was used between 1995 and 2010 at the Barrow Neurological Institute.

Results

Eighteen patients (11 male and 7 female patients; mean age 46 years, range 7–69 years) were identified. There were 4 sarcomas and 14 carcinomas that involved the ICA at the skull base. All patients underwent ICA sacrifice with revascularization. One patient died of a stroke after revascularization. A second patient died of the effects of a fistula between the oral and cranial cavities (surgery-related mortality rate 11.1%). Eight months after the operation, 1 patient developed occlusion of the bypass and died. Complications associated with the bypass surgery included 1 case of subdural hematoma (SDH) with blindness, 1 case of status epilepticus, and 1 case of asymptomatic bypass occlusion (bypass-related morbidity 16.7%). Complications associated with tumor resection included 3 cases of CSF leakage requiring repair and shunting, 1 case of hydrocephalus requiring shunting, 1 case of SDH, and 1 case of contralateral ICA injury requiring a bypass (tumor resection morbidity rate 33.3%). In 1 patient treated with adjuvant therapy before surgery, the authors identified only a radiation effect and no tumor on resection. In a second patient the bypass was occluded, and her tumor was not resected. The other 16 patients underwent gross-total resection of their tumor. Excluding the surgery-related deaths, the mean and median lengths of survival in this series were 13.2 and 8.3 months, respectively (range 1.5–48 months). Including the surgery-related deaths, the mean and median lengths of survival were 11.8 and 8 months, respectively (range 17 days–48 months). At last follow-up all patients had died of cancer or cancer-related causes.

Conclusions

Despite maximal surgical intervention, including ICA sacrifice at the skull base with revascularization, patient survival was dismal, and the complication rate was significant. The authors no longer advocate such an aggressive approach in this patient population. On rare occasions, however, such an approach may be considered for low-grade malignancies.

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Nestor G. Rodriguez-Martinez, Luis Perez-Orribo, Samuel Kalb, Phillip M. Reyes, Anna G. U. S. Newcomb, Jeremy Hughes, Nicholas Theodore and Neil R. Crawford

OBJECT

The effects of obesity on lumbar biomechanics are not fully understood. The aims of this study were to analyze the biomechanical differences between cadaveric L4–5 lumbar spine segments from a large group of nonobese (body mass index [BMI] < 30 kg/m2) and obese (BMI ≥ 30 kg/m2) donors and to determine if there were any radiological differences between spines from nonobese and obese donors using MR imaging.

METHODS

A total of 168 intact L4–5 spinal segments (87 males and 81 females) were tested using pure-moment loading, simulating flexion-extension, lateral bending, and axial rotation. Axial compression tests were performed on 38 of the specimens. Sex, age, and BMI were analyzed with biomechanical parameters using 1-way ANOVA, Pearson correlation, and multiple regression analyses. MR images were obtained in 12 specimens (8 from obese and 4 from nonobese donors) using a 3-T MR scanner.

RESULTS

The segments from the obese male group allowed significantly greater range of motion (ROM) than those from the nonobese male group during axial rotation (p = 0.018), while there was no difference between segments from obese and nonobese females (p = 0.687). There were no differences in ROM between spines from obese and nonobese donors during flexion-extension or lateral bending for either sex. In the nonobese population, the ROM during axial rotation was significantly greater for females than for males (p = 0.009). There was no significant difference between sexes in the obese population (p = 0.892). Axial compressive stiffness was significantly greater for the obese than the nonobese population for both the female-only group and the entire study group (p < 0.01); however, the difference was nonsignificant in the male population (p = 0.304). Correlation analysis confirmed a significant negative correlation between BMI and resistance to deformation during axial compression in the female group (R = −0.65, p = 0.004), with no relationship in the male group (R = 0.03, p = 0.9). There was also a significant negative correlation between ROM during flexion-extension and BMI for the female group (R = −0.38, p = 0.001), with no relationship for the male group (R = 0.06, p = 0.58). Qualitative analysis using MR imaging indicated greater facet degeneration and a greater incidence of disc herniations in the obese group than in the control group.

CONCLUSIONS

Based on flexibility and compression tests, lumbar spinal segments from obese versus nonobese donors seem to behave differently, biomechanically, during axial rotation and compression. The differences are more pronounced in women. MR imaging suggests that these differences may be due to greater facet degeneration and an increased amount of disc herniation in the spines from obese individuals.