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Alexander R. Vaccaro

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Ali Nourbakhsh, Shashikant Patil, Prasad Vannemreddy, Alan Ogden, Debi Mukherjee and Anil Nanda

Object

Anterior screw fixation of the Type II odontoid fracture stabilizes the odontoid without restricting the motion of the cervical spine. The metal screw may limit bone remodeling because of stress shielding (if not placed properly) and limit imaging of the fracture. The use of bioabsorbable screws can overcome such shortcomings of the metal screws. The purpose of this study was to compare the strength of a 5-mm bioabsorbable screw with single 4-mm metal and double 3.5-mm lag screw fixation for Type II fractures of the odontoid process.

Methods

Three different modalities of anterior screw fixation were used in 19 C-2 vertebrae. These fixation methods consisted of a single 5-mm cannulated bioabsorbable lag screw (Group A), a single 4-mm cannulated titanium lag screw (Group B), and two 3.5-mm cannulated titanium lag screws (Group C). Anteroposterior (AP) stiffness and rotational stiffness were evaluated in all constructs.

Results

There was no statistical difference among the ages of the cadavers in each group (p = 0.52). The AP bending stiffness in Groups A, B, and C was 117 ± 86, 66 ± 43, and 305 ± 130 Nm/mm, respectively. The AP bending stiffness in Group C was significantly higher than that in Groups A and B (p = 0.01 and p = 0.001, respectively). The difference in AP bending stiffness values of bioabsorbable and 4-mm metal screws was not statistically significant (p = 0.23). The rotational stiffness of the double 3.5-mm metal screws was significantly greater than that of the 5-mm bioabsorbable and the 4-mm titanium screws.

Conclusions

Double screw fixation with 3.5-mm screws provides the stiffest construct in Type II odontoid fractures. Bioabsorbable lag screws (5 mm) have the same AP bending and rotational stiffness as the single titanium lag screw (4 mm) in odontoid fractures.

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Ali Nourbakhsh, Prashant Chittiboina, Prasad Vannemreddy, Anil Nanda and Bharat Guthikonda

Object

Transpedicular thoracic vertebrectomy (TTV) is a safe alternative to the more standard transthoracic approach. A TTV is most commonly used to address vertebral body fractures due to tumor or trauma.

Transpedicular reconstruction of the anterior column with cage/bone traditionally requires unilateral thoracic nerve root sacrifice. In a cadaveric model, the authors evaluated the feasibility of transpedicular anterior column reconstruction without nerve root sacrifice. If feasible, this may be a reasonable approach that could be extended to the lumbar spine where nerve root sacrifice is not an option.

Methods

A TTV was performed in 8 fixed cadaveric specimens. In each specimen, an alternate vertebra (either odd or even) was removed so that single-level reconstruction could be evaluated. The vertebrectomy included facetectomy, adjacent discectomies, and laminectomy; however, the nerve roots were preserved. The authors then evaluated the feasibility of inserting a titanium mesh cage (Medtronic Sofamor Danek) without neural sacrifice.

Results

Transpedicular anterior cage reconstruction could be safely performed at all levels of the thoracic spine without nerve root sacrifice. The internerve root space varied from 18 mm at T2–3 to 27 mm at T11–12; thus, the size of the cage that was used also varied with level.

Conclusions

Cage reconstruction of the anterior column could be safely performed via the transpedicular approach without nerve root sacrifice in this cadaveric study. Removal of the proximal part of the rib in addition to a standard laminectomy with transpedicular vertebrectomy provided an excellent corridor for anterior cage reconstruction at all levels of the thoracic spine without nerve root sacrifice.

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Ali Nourbakhsh, Jinping Yang, Sean Gallagher, Anil Nanda, Prasad Vannemreddy and Kim J. Garges

Object

The purpose of this study was to find a landmark according to which the surgeon can dissect the cervical spine safely, with the lowest possibility of damaging the vertebral artery (VA) during anterior approaches to the cervical spine or the VA.

Methods

The “safe zone” for each level of the cervical spine was described as an area where the surgeon can start from the midline in that zone and dissect the soft tissue laterally to end up on the transverse process and cross the VA while still on the transverse process. In other words, safe zone signifies the narrowest width of the transverse process at each level. In such an approach, the VA is protected from the inadvertent deep penetration of the instruments by the transverse process. The surgical safe zone for each level was the common area among at least 95% of the safe zones for that level. For the purpose of defining the upper and lower borders of the safe zone for each level, the line passing from the upper vertebral border perpendicular to the midline (upper vertebral border line) was used as a reference.

Cervical spines of 64 formalin-fixed cadavers were dissected. The soft tissue in front of the transverse process and intertransverse space was removed. Digital pictures of the specimens were taken before and after removal of the transverse processes, and the distance to the upper and lower border of the safe zone from the upper vertebral border line was measured on the digital pictures with Image J software. The VA diameter and distance from the midline at each level were also measured. To compare the means, the authors used t-test and ANOVA.

Results

The surgical safe zone lies between 1 mm above and 1 mm below the upper vertebral border at the fourth vertebra, 2 mm above and 1 mm below the upper vertebral border at the fifth vertebra, and 1 mm above and 2 mm below the upper vertebral border of the sixth vertebra. The VA was observed to be tortuous in 13% of the intertransverse spaces. There is a positive association between disc degeneration and tortuosity of the VA at each level (p < 0.001). The artery becomes closer to the midline (p < 0.001) and moves posteriorly during its ascent.

Conclusions

Dissection of the soft tissue off the bone along the surgical safe zone and removal of the transverse process afterward can be a practical and safe approach to avoid artery lacerations. The findings in the present study can be used in anterior approaches to the cervical spine, especially when the tortuosity of the artery mandates exposure of the VA prior to uncinate process resection, tumor excision, or VA repair.

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Christina Notarianni, Prasad Vannemreddy, Gloria Caldito, Papireddy Bollam, Esther Wylen, Brian Willis and Anil Nanda

Object

Hydrocephalus is a notorious neurosurgical disease that carries the adage “once a shunt always a shunt.” This study was conducted to review the treatment results of pediatric hydrocephalus.

Methods

Pediatric patients who underwent ventriculoperitoneal shunt surgery over the past 14 years were reviewed for shunt revisions. Variables studied included age at shunt placement, revision, or replacement; programmable shunts; infection; obstruction; and diagnosis (congenital, posthemorrhagic, craniospinal dysraphism, and others including trauma, tumors, and infection). Multiple regression analysis methods were used to determine independent risk factors for shunt failure and the number of shunt revisions. The Kaplan-Meier method of survival analysis was used to compare etiologies on the 5-year survival (revision-free) rate and the median 5-year survival time.

Results

A total of 253 patients were studied with an almost equal sex distribution. There were 92 patients with congenital hydrocephalus, 69 with posthemorrhagic hydrocephalus, 48 with craniospinal dysraphism, and 44 with other causes. Programmable shunts were used in 73 patients (other types of shunts were used in 180 patients). A total of 197 patients (78%) underwent revision surgeries due to shunt failures. The mortality rate was 1.6%. Age at first revision, the 5-year survival rate, and the median 5-year survival time were significantly less for both posthemorrhagic and craniospinal dysraphism than for either the congenital or “other” group (p < 0.05). The failure rate and number of revisions were not significantly reduced with programmable shunts compared with either pressure-controlled or no-valve shunts (p > 0.5).

Conclusions

Posthemorrhagic hydrocephalus and craniospinal dysraphism hydrocephalus had significantly earlier revisions than congenital and other etiologies. Programmable systems did not reduce the failure rate or the average number of shunts revisions.

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Ali Nourbakhsh, Runhua Shi, Prasad Vannemreddy and Anil Nanda

Object

The purpose of this study was to evaluate the feasibility of the criteria described in the literature as the indications for surgery for acute Type II odontoid fractures.

Methods

The authors searched the PubMed database for studies in which the fusion rate of acute Type II odontoid fractures following external immobilization (halo vest or collar) or surgery (posterior C1–2 fusion or anterior screw fixation) was reported. The only studies included reported the fusion rate for either 1) groups of patients whose age was either more or less than a certain age range (45–55 years); or 2) groups of patients with a fracture displacement of either more or less than a certain odontoid fracture displacement (4–6 mm) or the direction of displacement (see Methods section of text for more details). A meta-analysis in which the random effect model was used was conducted to analyze the data.

Results

There was a statistically significantly higher fusion rate for operative management compared with external immobilization (85 vs 60%, p = 0.01) for the patients > 45–55 years. However, the overall fusion rate was > 80% for the patients whose age was < 45–55 years, regardless of treatment modality, and no significant differences were observed between surgically and nonsurgically treated patients (89 and 81%, respectively; p = 0.29). The result of operation (overall fusion rate 89%) was superior to external immobilization (44%) when the fracture was posteriorly displaced (p < 0.001), but for anteriorly displaced fractures, the results of operative and nonoperative management were identical (p = 0.15). The overall fusion rate of operative management of both anteriorly and posteriorly displaced fractures proved to be > 85%, and no statistically significant difference was observed (p = 0.50). For all degrees of displacement (either > or < 4–6 mm) the operation proved to provide significantly better results than conservative treatment. The fusion rate of conservatively treated fractures with < 4–6 mm displacement was significantly better than in fractures with > 4–6 mm displacement (76 vs 41%, p = 0.002).

Conclusions

Operative treatment (posterior C1–2 fixation or anterior screw fixation) provides a better fusion rate than external immobilization for acute odontoid Type II fractures, although in certain situations, such as anterior displacement of the fracture and for younger (< 45–55 years of age) patients, conservative management (halo vest or collar immobilization) can be as effective as surgery. Operative management is recommended in older patients, in cases of posterior displacement of the fracture, and when there is displacement of > 4–6 mm.

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Prashant Chittiboina, Esther Wylen, Alan Ogden, Debi P. Mukherjee, Prasad Vannemreddy and Anil Nanda

Object

Surgical management of unstable traumatic spondylolisthesis of the axis includes both posterior and anterior fusion methods. The authors performed a biomechanical study to evaluate the relative stability of anterior fixation at C2–3 and posterior fixation of C-1 through C-3 in hangman's fractures.

Methods

Fresh-frozen cadaveric spine specimens (occipital level to T-2) were subjected to stepwise destabilization of the C1–2 complex, replicating a Type II hangman's fracture. Intact specimens, fractured specimens, and fractured specimens with either anterior screw and plate or posterior screw and rod fixation were each tested for stability. Each spine was subjected to separate right and left rotation, bending, flexion, and extension testing.

Results

Anterior fixation restored stiffness in flexion and extension movements to values greater than those for intact specimens. For other movement parameters, the values approximated those for intact specimens. Posterior fixation increased the stiffness to above those values seen for anterior fixation specimens.

Conclusions

In cadaveric spine specimens subjected to a Type II hangman's fracture, both anterior fixation at C2–3 and posterior fixation with C-1 lateral mass screws and C-2 and C-3 pedicle screws resulted in a consistent increase in stiffness, and hence in stability, over intact specimens.

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Brian Willis, Vijayakumar Javalkar, Prasad Vannemreddy, Gloria Caldito, Junko Matsuyama, Bharat Guthikonda, Papireddy Bollam and Anil Nanda

Object

The aim of the study was to analyze the outcome of surgical treatment for posthemorrhagic hydrocephalus in premature infants.

Methods

From 1990 to 2006, 32 premature infants underwent surgical treatment for posthemorrhagic hydrocephalus, and their charts were retrospectively reviewed to analyze the complications and outcome with respect to shunt revisions. Multivariate analysis and time series were used to identify factors that influence the outcome in terms of shunt revisions.

Results

The mean gestational age was 27 ± 3.3 weeks, and mean birth weight was 1192 ± 660 g. Temporary reservoir placement was performed in 15 patients, while 17 underwent permanent CSF diversion with a ventriculoperitoneal (VP) shunt. In 2 patients, reservoir tapping alone was sufficient to halt the progression of hydrocephalus; 29 patients received VP shunts. The mean follow-up period was 37.3 months. The neonates who received VP shunts first were significantly older (p = 0.02) and heavier (p = 0.04) than those who initially underwent reservoir placement. Shunts were revised in 14 patients; 42% of patients in the reservoir group had their shunts revised, while 53% of infants who had initially received a VP shunt required a revision. The revision rate per patient in the reservoir group was half that in the direct VP shunt group (p = 0.027). No patient in the reservoir group had > 2 revisions. Shunt infections developed in 3 patients (10.3%), and 2 patients in the reservoir group died of nonneurological issues related to prematurity.

Conclusions

Birth weight and age are useful parameters in decision making. Preterm neonates with low birth weights benefit from initial CSF drainage procedures followed by permanent CSF diversion with respect to the number of shunt revisions.

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Nima Majlesi, Howard Greller and Mark Su

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Prasad Vannemreddy, Gloria Caldito, Brian Willis and Anil Nanda

Object

The purpose of this study was to determine whether cocaine use is a significant prognostic factor for outcome measures such as Hunt and Hess grade and Glasgow Outcome Scale (GOS) score among patients presenting with ruptured intracranial aneurysms (IAs).

Methods

The authors performed a MEDLINE/PubMed search for cases of ruptured IAs associated with cocaine use. Fourteen cases from the authors' experience were combined with 50 from a literature review, for a total of 64 cases associated with cocaine use. These 64 cases were compared with 65 cases without cocaine use (controls), which had been obtained from an aneurysm database. Logistic regression analysis was performed to determine significant prognostic factors for a poor Hunt and Hess grade and a poor GOS score, and a general linear model was applied to identify significant factors for these measures among cocaine users.

Results

There were 40 women in each group. The mean age was 32.3 ± 8.1 years in the cocaine group and 49.7 ± 10.6 years in the control group; thus, patients in the cocaine group were significantly younger (p < 0.01). Cocaine was snorted in 21% of cases, smoked in 55%, and intravenously injected or taken in through a combination of routes in 24%. Fifty-one percent of cocaine users and 7.7% of nonusers presented with a poor GOS score (p < 0.01). Fifty-six percent had ictus during cocaine abuse. At the end of a 30-day follow-up, 51% of the patients in the cocaine group had a good GOS score compared with 92% in the control group (p < 0.01). Controlling for the effects of other significant factors, cocaine use had a significant effect on Hunt and Hess grade (p < 0.03) and GOS score (p < 0.01). The odds of having a poor Hunt and Hess grade among cocaine users were 4.2 times greater than those in nonusers, and the odds of having a poor GOS score among cocaine users were 38.8 times greater.

Conclusions

Aneurysms were significantly smaller and ruptured at a younger age among cocaine users compared with nonusers. Although the poor clinical grade was not significantly different between the 2 groups, outcome was significantly worse in cocaine users.