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Steven W. Hwang, Amer F. Samdani, and Patrick J. Cahill

Object

Idiopathic scoliosis is a pathological process influencing the spinal column in 3 dimensions. Initial surgical treatment focused primarily on correction in the coronal plane, and with improved instrumentation, increasing attention has targeted balancing the sagittal profile. Newer surgical techniques now permit operative corrective forces to also directly address axial rotation. Although several technical variations of direct vertebral body derotation (DVBD) have been devised, no studies have compared outcomes from the differing techniques. The purpose of this study was to describe and compare the differences between segmental and en bloc DVBD.

Methods

A large prospectively collected database was queried for patients with adolescent idiopathic scoliosis (AIS) who underwent posterior spinal fusion and for whom there was a minimum of 2 years of follow-up. In all patients some type of DVBD maneuver was performed (segmental, en bloc, or both). Any patients with concurrent thoracoplasties were excluded.

Results

The authors identified 188 patients, of whom 120 underwent segmental derotation, 17 en bloc derotation, and 51 both. No significant radiographic or clinical differences existed among the groups preoperatively. The mean preoperative thoracic curve in the entire cohort was 53.1° ± 14.1° and the mean thoracic rib prominence was 14.0° ± 5.5°, whereas the respective postoperative values were 19.3° ± 8.3° and 7.2° ± 4.0°. No significant difference was identified between the various techniques postoperatively, either. However, when comparing intraoperative variables, significant differences were found for operative duration (p = 0.0001), estimated blood loss (p = 0.0081), and volume of blood transfusions (p = 0.041).

Conclusions

Although each surgical technique of DBVD may have theoretical benefits and risks, no apparent difference in outcomes was observed between techniques. The concurrent use of both techniques was associated with increased blood loss and operative duration without any appreciable benefit. The surgeon should adopt the derotation technique with which he or she is most comfortable, but concurrent use of both does not appear to improve results.

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Andrew C. Vivas, Steven W. Hwang, and Joshua M. Pahys

Phrenic stimulators offer an alternative to standard mechanical ventilation as well as the potential for ventilator independence in select patients with chronic respiratory failure. Young patients (< 10 years old) with high cervical spinal cord injuries often develop paralytic scoliosis due to loss of muscle tone caudal to their spinal cord lesion. Growing rod systems allow for stabilization of spinal deformity while permitting continued growth of the spine and thoracic cavity. Magnetically controlled growing rods (MCGRs) offer the advantage of noninvasive expansion, as opposed to the operative expansion required in traditional growing rod systems. To the authors’ knowledge, this is the first reported case of MCGRs in a patient with a diaphragmatic pacemaker (DP). A 7-year-old boy with ventilator dependence after a high cervical spinal cord injury presented to the authors’ institution with paralytic scoliosis that progressed to > 120°. The patient had previously undergone insertion of phrenic nerve stimulators for diaphragmatic pacing. The decision was made to insert MCGRs bilaterally to stabilize his deformity, because the planned lengthening surgeries that are necessary with traditional growing rods would be poorly tolerated in this patient. The patient’s surgery and postoperative course were uneventful. The DP remained functional after insertion and lengthening of the MCGRs by using the external magnet. The DP had no effect on the expansion capability of the MCGRs. In conclusion, the MCGRs appear to be compatible with the DP. Further studies are needed to validate the long-term safety and compatibility of these 2 devices.

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Daniel H. Fulkerson, Steven W. Hwang, Akash J. Patel, and Andrew Jea

External orthosis is the accepted and historical management of odontoid synchondrosis fractures; however, this conservative therapy carries a significant complication and fracture nonunion rate among young children. The purpose of this study was to evaluate the authors' own experience in the context of the literature, to explore surgical fixation as a primary treatment for unstable fractures. The authors retrospectively reviewed 2 cases of unstable odontoid synchondrosis fractures treated at their institution; both showed radiographic progression of deformity and subsequently underwent an open surgical reduction and fusion. A literature review was conducted to compare the authors' management strategy with those in published data. External orthosis for treatment of odontoid synchondrosis fractures has a strong history of success. However, in the literature, patients treated with a halo orthosis had a 43.3% rate of complications and an 11.4% risk of nonunion. There are radiographic findings that suggest instability, such as severe angulation and displacement of the odontoid process. Both patients in the present report underwent successful fusion without complication, as documented on CT scans obtained 3 months after surgery. Given the high rate of fusion attained with conservative therapy, it is recommended for most synchondrosis fractures. However, there is a recognized subgroup of synchondrosis fractures with severe angulation (> 30°) and displacement suggestive of significant ligamentous injury. In these patients, surgical fixation may be a safe and efficacious alternative to halo orthosis as the primary treatment.

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Steven W. Hwang, Rafeeque A. Bhadelia, and Julian Wu

✓Iophendylate (Pantopaque or Myodil) was commonly used from the 1940s until the late 1980s for myelography, cisternography, and ventriculography. Although such instances are rare, several different long-term sequelae have been described in the literature and associated with intrathecal iophendylate. The authors describe an unusual case of arachnoiditis caused by residual thoracic iophendylate imitating an expansile intramedullary lesion on magnetic resonance images obtained 30 years after the initial myelographic injection.

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Guillermo Aldave, Daniel Hansen, Steven W. Hwang, Amee Moreno, Valentina Briceño, and Andrew Jea

OBJECTIVE

Tethered cord syndrome is the clinical manifestation of an abnormal stretch on the spinal cord, presumably causing mechanical injury, a compromised blood supply, and altered spinal cord metabolism. Tethered cord release is the standard treatment for tethered cord syndrome. However, direct untethering of the spinal cord carries potential risks, such as new neurological deficits from spinal cord injury, a CSF leak from opening the dura, and retethering of the spinal cord from normal scar formation after surgery. To avoid these risks, the authors applied spinal column shortening to children and transitional adults with primary and secondary tethered cord syndrome and report treatment outcomes. The authors' aim with this study was to determine the safety and efficacy of spinal column shortening for tethered cord syndrome by analyzing their experience with this surgical technique.

METHODS

The authors retrospectively reviewed the demographic and procedural data of children and young adults who had undergone spinal column shortening for primary or secondary tethered cord syndrome.

RESULTS

Seven patients with tethered cord syndrome caused by myelomeningocele, lipomyelomeningocele, and transitional spinal lipoma were treated with spinal column shortening. One patient with less than 24 months of follow-up was excluded from further analysis. There were 3 males and 4 females; the average age at the time was surgery was 16 years (range 8–30 years). Clinical presentations for our patients included pain (in 5 patients), weakness (in 4 patients), and bowel/bladder dysfunction (in 4 patients). Spinal column osteotomy was most commonly performed at the L-1 level, with fusion between T-12 and L-2 using a pedicle screw-rod construct. Pedicle subtraction osteotomy was performed in 6 patients, and vertebral column resection was performed in 1 patient. The average follow-up period was 31 months (range 26–37 months). Computed tomography–based radiographic outcomes showed solid fusion and no instrumentation failure in all cases by the most recent follow-up. Five of 7 patients (71%) reported improvement in preoperative symptoms during the follow-up period. The mean differences in initial and most recent Scoliosis Research Society Outcomes Questionnaire and Oswestry Disability Index scores were 0.26 and –13%, respectively; minimum clinically important difference in SRS-22 and ODI were assumed to be 0.4% and –12.8%, respectively.

CONCLUSIONS

Spinal column shortening seems to represent a safe and efficacious alternative to traditional untethering of the spinal cord for tethered cord syndrome.

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Mina G. Safain, Jordan Talan, Adel M. Malek, and Steven W. Hwang

Vertebral artery (VA) occlusion is a serious and potentially life-threatening occurrence. Bow hunter's syndrome, a mechanical occlusion of the VA due to physiological head rotation, has been well described in the medical literature. However, mechanical VA compression due to routine flexion or extension of the neck has not been previously reported. The authors present the unique case of a woman without any history of trauma who had multiple posterior fossa strokes and was found to have dynamic occlusion of her right VA visualized via cerebral angiogram upon extension of her neck. This occlusion was attributed to instability at the occipitocervical junction in a patient with a previously unknown congenital fusion of both the occiput to C-1 and C-2 to C-3. An occiput to C-3 fusion was performed to stabilize her cervical spine and minimize the dynamic vascular compression. A postoperative angiogram showed no evidence of restricted flow with flexion or extension of the neck. This case emphasizes the importance of considering symptoms of vertebrobasilar insufficiency as a result of physiological head movement. The authors also review the literature on VA compression resulting from physiological head movement as well as strategies for clinical diagnosis and treatment.

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Maria Zuccaro, James Zuccaro, Amer F. Samdani, Joshua M. Pahys, and Steven W. Hwang

OBJECTIVE

Intraoperative neuromonitoring (IONM) involves the use of somatosensory evoked potentials (SSEPs) and transcranial electric motor evoked potentials (TceMEPs). In this retrospective study the authors examined the sensitivity and specificity of both SSEPs and TceMEPs during pediatric spinal deformity surgeries.

METHODS

The authors performed a retrospective quantitative analysis of data obtained in 806 patients (197 males and 609 females) treated from December 2011 until October 2015. All patients were diagnosed with scoliosis that was classified as one of the following: adolescent idiopathic scoliosis (AIS) (38%), congenital scoliosis (22%), or syndromic scoliosis (40%). Also, 53 patients underwent vertebral column resection (VCR). All surgeries were monitored by high-level neuromonitoring specialists and were performed with total intravenous anesthesia. Alerts were described as a decrease in amplitude by 50% or greater (bilateral or unilateral) in SSEPs, TceMEPs, or both.

RESULTS

True-positive alerts for TceMEPs were observed in 60 of the 806 patients (7.4%). True-positive alerts for SSEPs were observed in 7 of the 806 patients (0.9%). In contrast, there were no false-positive or false-negative outcomes. Only 1 case (0.1%) was reported with a permanent postoperative deficit. No reported false negatives or false positives were observed, and thus sensitivity was 100% and specificity was 93%–100% for TceMEPs. The rate of sensitivity was 13.2% and the rate of specificity was 100% for SSEPs. The breakdown of total alert was as follows: 6.6% in AIS cases, 24.5% in congenital scoliosis cases, and 10.2% in syndromic scoliosis cases. Neurological injury rates were significantly lower than in previous studies, as there were 0% for AIS cases (p = 0.12), 0.6% for congenital scoliosis cases (p = 0.17), and 0% for syndromic scoliosis cases (p = 0.07). One injury in a patient with congenital scoliosis occurred during a VCR procedure, which brought the injury rate to 1.9% (p < 0.005). IONM alerts occurred during 34% of rod/correction cases, 25% of thoracic screw placements, 20% of the osteotomies, 17% of the resections, 3% of the cage insertions, and 2% of the sublaminar wiring procedures.

CONCLUSIONS

The authors hypothesize that the results of this study will support the necessity, as a standard of care, of multimodality neuromonitoring during high-risk pediatric spinal deformity surgery because of the decrease in postoperative deficits. Their data suggest that the TceMEPs are more sensitive than SSEPs, but when used in combination, they offer the patient a level of safety that would otherwise not exist. Last, these findings support the notion that better outcomes are achieved with high-level IONM professionals.

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Brandon J. Toll, Amer F. Samdani, M. Burhan Janjua, Shashank Gandhi, Joshua M. Pahys, and Steven W. Hwang

OBJECTIVE

High rates of perioperative complications are associated with deformity correction in neuromuscular scoliosis. The current study aimed to evaluate complications associated with surgical correction of neuromuscular scoliosis and to characterize potential risk factors.

METHODS

Data were retrospectively collected from a single-center cohort of 102 consecutive patients who underwent spinal fusions for neuromuscular scoliosis between January 2008 and December 2016 and who had a minimum of 6 months of follow-up. A subgroup analysis was performed on data from patients who had at least 2 years of follow-up. Univariate and multivariate regression analyses, as well as binary correlational models and Student t-tests, were employed for further statistical analysis.

RESULTS

The present cohort had 53 boys and 49 girls with a mean age at surgery of 14.0 years (± 2.7 SD, range 7.5–19.5 years). The most prevalent diagnoses were cerebral palsy (26.5%), spinal cord injury (24.5%), and neurofibromatosis (10.8%). Analysis reflected an overall perioperative complication rate of 27% (37 complications in 27 patients), 81.1% of which constituted major complications (n = 30) compared to a rate of 18.9% for minor complications (n = 7). Complications were predicted by nonambulatory status (p = 0.037), increased intraoperative blood loss (p = 0.012), increased intraoperative time (p = 0.046), greater pelvic obliquity at follow-up (p = 0.028), and greater magnitude of sagittal profile at follow-up (p = 0.048). Pulmonary comorbidity (p = 0.001), previous operations (p = 0.013), history of seizures (p = 0.046), diagnosis of myelomeningocele (p = 0.046), increase in weight postoperatively (p < 0.005), and increased lumbar lordosis at follow-up (p = 0.015) were identified as risk factors for perioperative infection.

CONCLUSIONS

These results suggest that in neuromuscular scoliosis, patients with preexisting pulmonary compromise and greater intraoperative blood loss have the greatest risk of experiencing a major perioperative complication following surgical deformity correction.

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Steven W. Hwang, Loyola V. Gressot, Joshua J. Chern, Katherine Relyea, and Andrew Jea

Object

Occipitocervical stabilization in the pediatric age group remains a challenge because of the regional anatomy, poor occipital bone purchase, and, in some instances, significant thinning of the occipital bone. Multiple bicortical fixation points to the occipital bone may be required to increase construct rigidity. The authors evaluated the complications of bicortical occipital screw placement in children with occipital fusion constructs.

Methods

The records of 20 consecutive pediatric patients who had undergone occipitocervical fusion between September 1, 2007, and November 30, 2010, at Texas Children's Hospital were reviewed.

Results

The patients consisted of 10 girls and 10 boys, ranging in age from 10 months to 16 years (mean ± SD, 7.7 ± 5.1 years). Two patients were lost to follow-up, 2 died for reasons unrelated to the surgery, and the remaining patients had at least 3 months of follow-up (mean 14 ± 11.8 months) with evaluation via dynamic radiography and CT. Four patients experienced 8 complications: 2 CSF leaks, 2 vigorous venous bleedings, worsening of quadriparesis, wound infection, radiographic pseudarthrosis, and transient dysphagia. Among 114 screws, there were 2 cases of intraoperative dural venous sinus injury and 2 cases of intraoperative CSF leakage, without clinical sequelae from these complications. Only 1 case of radiographic pseudarthrosis was identified in a patient with skeletal dysplasia and a prior failed C1–2 posterior arthrodesis. There were no difficulties with wound healing because of prominent occipital instrumentation, and there was only 1 wound infection.

Conclusions

Data in this report confirm that including bicortical occipital screw placement in occipitocervical constructs in children may result in a high fusion rate but at the cost of a notable complication rate.

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Leonardo Rangel-Castilla, Steven W. Hwang, George Al-Shamy, Andrew Jea, and Daniel J. Curry

The surgical treatment of refractory epilepsy has evolved as new innovations have been created. Disconnective procedures such as hemispherectomy have evolved. Presently, hemispherotomy has replaced hemispherectomy to reduce complication rates while maintaining good seizure control. Several disconnective techniques have been described including the Rasmussen, vertical, and lateral approaches. The lateral approach, or periinsular hemispherectomy, was derived from modifications on the functional hemispherectomy and involves removal of the temporal lobe mesial structures, exposure of the atrium via the circular sulcus, internal capsule transection under the central sulcus, intraventricular callosotomy, and frontobasal disconnection. The purpose of this article is to describe and illustrate in detail the anatomy and operative technique for periinsular hemispherotomy, as well as to discuss the nuances and issues involved with this procedure.