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Study Design: Prospective case series of nine children with early-onset scoliosis (EOS) treated by a single surgeon with a novel implant, the magnet-driven growing rod (MdGR) in a publicly funded health care service accounting for "payer costs" (PC) incurred., Objective: The aim of this study was to compare the cost-effectiveness of MdGR versus conventional growing rods (CGRs) with respect to the PC incurred for treating EOS at 5 years., Summary of Background Data: Cost estimate and mathematical modeling study projections of MdGR have shown despite high insertional costs, it breaks even with CGR by 3 to 4 years. However, no clinical study to date exists either supporting or refuting this hypothesis., Methods: Nine patients with EOS secondary to idiopathic (two), congenital (one), syndromic (three), and neuromuscular (three) etiologies treated by submuscular insertion of MdGR against stringent inclusion criteria formed the study cohort. We collected costs incurred with all aspects of care over the lifetime of device (or at least 5 years) from payers' perspective to compute and report average PC incurred per patient. We performed this cost analysis by comparing the MdGR PC against literature reported PC for CGR at 5 years., Results: There were five single rod (SR) and two dual rod (DR) de novo MdGR insertions, while two patients had conversion of CGR to MdGR. MdGR alone accounted for at least 50% of overall budget. The MdGR was at least 40% more cost-effective in comparison to the CGR (£34,741 vs. £52,293) and there were seven MdGR graduates., Conclusion: The first study reporting direct PC incurred in EOS treated by MdGR that is devoid of any mathematical modeling and deterministic sensitivity analysis is presented. The true societal/human cost savings taking into consideration indirect costs are likely to be significantly higher. MdGR is a promising novel implant that may eventually become the "standard of care" for certain EOS etiologies., Level of Evidence: 4.

Study Design: A cross-sectional survey of surgeon members of the Scoliosis Research Society (SRS)., Objective: This study sought to characterize the incidence, clinical presentation, diagnostic workup, treatment, and neurologic prognosis following delayed postoperative neurologic deficit (DPND) in patients undergoing spinal deformity surgery., Summary of Background Data: DPND is a potentially devastating condition following spinal surgery, characterized by the development of a neurological deficit within hours or days of the surgical procedure. To date, only case reports and small case series have been published on the topic., Methods: We developed a survey to characterize DPND following spinal deformity surgery. This survey was distributed to surgeon members of the SRS through email and standard mail. The overall response rate was 38% (352/929)., Results: Our results suggest an estimated DPND incidence of 1 of 9910 cases (0.01%). Eighty-one surgeons (23%) experienced at least 1 DPND in the past 10 years (92 total cases). Most common diagnoses were scoliosis (69%), kyphosis (23%), and spondylolisthesis (14%); 20% were revision surgeries. The number of hours to deficit onset was as follows: 1 to 12 (36%), 13 to 24 (27%), 25 to 48 (27%), more than 48 (10%). The most commonly cited sources of injury included ischemic injury (38%) and cord compression (15%). Forty-one percent experienced complete neurologic recovery, 26% partial, and 33% no recovery. Twenty-one percent of patients achieved final neurologic status within 1 week, 38% by 1 month, and 73% by 6 months. Patients with compression-related DPND had a significantly greater likelihood of experiencing some neurologic recovery (≥1 ASIA Grade) than ischemia-related DPND (86% versus 51%, P = 0.049)., Conclusions: DPND occurs at an estimated incidence of 0.01%. Sixty-three percent of DPND cases occurred within the first 24 hours and 90% within 48 hours. Complete (41%) or partial (26%) neurologic recovery may be expected, especially in compression-related DPND, emphasizing the need for perioperative vigilance, prompt recognition, and early intervention., Level of Evidence: 4.

Study Design: Therapeutic level II cohort study., Objective: To evaluate the safety of adjunctive local application of vancomycin powder (VP) for infection prophylaxis in posterior instrumented thoracic and lumbar spine wounds in pediatric patients weighing more than 25 kg., Summary of Background Data: Spine surgeons have largely turned to vancomycin prophylaxis in an attempt to decrease the incidence of late surgical site infection and acute surgical site infection from methicillin-resistant Staphylococcus aureus. In adult patients, the adjunctive local application of VP with an intravenous cephalosporin has been shown to decrease postsurgical wound infection rates significantly; however, the safety of VP as an adjunct in pediatric spine surgery has not been reported., Methods: We reviewed data collected under a systematic protocol specifically designed to monitor the safety profile of VP. We measured changes in creatinine and systemic vancomycin levels after intrawound application of 500 mg of unreconstituted VP during spine deformity correction surgery in patients weighing more than 25 kg (patients also received routine intravenous cephalosporin prophylaxis). Laboratory values were measured preoperatively and on postoperative days 1 and 4. Any adverse reactions and infections through available follow-up (2-8 mo) were recorded., Results: Eighty-seven consecutive pediatric patients with spinal deformity weighing more than 25 kg who received intraoperative VP during a 9-month period were identified. Sixty-three percent of the patients in this series had adolescent idiopathic scoliosis, 15% congenital scoliosis, 15% neuromuscular scoliosis, and 5% spondylolisthesis. The average change in creatinine levels between the preoperative and postoperative day 1 draw was -0.03 and between the preoperative and postoperative day 4 draw was -0.075. The postoperative systemic vancomycin levels remained undetectable. None of the patients experienced nephrotoxicity or red man syndrome. Three of the 87 patients developed a surgical site infection., Conclusion: In this cohort there were no clinically significant changes in creatinine level or systemic vancomycin level caused by use of intraoperative VP., Level of Evidence: 2.

Study Design: Retrospective cohort study using the Pediatric Health Information System database., Objective: To describe longitudinal patterns of prophylactic antibiotic use and determinants of antibiotic choice for spinal fusion surgical procedures performed at US children's hospitals., Summary of Background Data: Surgical site infections (SSIs) account for a significant proportion of post-spinal surgery complications, particularly among children with complex conditions such as neuromuscular disease. Antimicrobial prophylaxis with intravenous cefazolin or cefuroxime has been a standard practice, but postoperative infections caused by organisms resistant to these antibiotics are increasing in prevalence. Studies describing the choice of antibiotic prophylaxis for pediatric spinal surgery are lacking., Methods: We included children 6 months to 18 years of age discharged from 37 US children's hospitals between January 1, 2006, and June 30, 2009, with (1) an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure code indicating a spinal fusion and (2) combinations of diagnosis codes indicating adolescent idiopathic scoliosis (AIS) (n = 5617) or neuromuscular scoliosis (NMS) (n = 3633). After identifying antibiotics ordered on the operative day, we described variation in broad-spectrum antibiotic use over time and measured associations between patient/surgery characteristics and antibiotic choice., Results: Prophylactic antibiotic choice varied across hospitals and over time. Broad-spectrum antibiotics were used in 37% of AIS and 52% of NMS operations. Seven (19%) hospitals used broad-spectrum coverage for more 80% of all cases. For NMS procedures, broad-spectrum antibiotic use was associated with patient characteristics known to be associated with high SSI risk. Use of vancomycin and broad gram-negative agents increased over time., Conclusion: Broad-spectrum antimicrobial prophylaxis varied across hospitals and was often associated with known risk factors for SSI. These results highlight the need for future studies comparing the effectiveness of various prophylaxis strategies, particularly in high-risk subgroups. This research can inform the development of best practice for SSI prevention in spinal fusion procedures.

Study Design: A multicenter retrospective analysis., Objective: To evaluate outcomes of closed-suction wound drainage after posterior spinal fusion with instrumentation for adolescent idiopathic scoliosis and to identify surgeon patterns of drain use in this cohort., Summary of Background Data: There is little evidence on the use of drains in spinal surgery, particularly for repair of adolescent idiopathic scoliosis. Studies on hip and knee arthroplasty suggest no advantage to draining. There are few published reports on surgeon technique and rationale for drain use in spinal surgery., Methods: Patients were divided into drain and no drain cohorts and followed for 2 years. Primary outcome was complication rate. A separate survey was conducted from surgeons in the Spinal Deformity Study Group to evaluate drain practice patterns., Results: There were 324 drained and 176 undrained patients. Complication rate did not differ between the drain and no drain cohorts in any of the 4 categories (wound infection, neural injury, other infection, and other complication) at any time (all P > 0.1). More drained patients received postoperative transfusions compared with those without a drain (43% vs. 22%, P < 0.001). Of the 50 surgeons in the group, 36 used drains. Half of these did so out of habit. Surgeons tended to place deep drains with bulb suction, without drain manipulation. Half removed drains on the basis of output, whereas half removed them after 1 to 3 days., Conclusion: More patients tended to receive wound drains than not receive wound drains. Drains did not impact complication rate and drained patients received more blood product. There are no universal criteria for draining and practice patterns vary widely.

Study Design: Focused review of the literature., Objective: Assist spine specialists in diagnosis and treatment of cervical spine anomalies found in selected genetic syndromes., Summary of Background Data: Cervical spine instability and/or stenosis are potentially debilitating problems in many genetic syndromes. These problems can be overlooked among the other systemic issues more familiar to clinicians and radiologists evaluating these syndromes. It is imperative that spine specialists understand the relevant issues associated with these particular syndromes., Methods: The literature was reviewed for cervical spine issues in 10 specific syndromes. The information is presented in the following order: First, the identification and treatment of midcervical kyphosis in Larsen syndrome and diastrophic dysplasia (DD). Next, the upper cervical abnormalities seen in Down syndrome, 22q11.2 Deletion syndrome, pseudoachondroplasia, Morquio syndrome, Goldenhar syndrome, spondyloepiphyseal dysplasia congenita, and Kniest dysplasia. Finally, the chin-on-chest deformity of fibrodysplasia ossificans progressiva., Results: Midcervical kyphosis in patients with Larsen syndrome and DD needs to be evaluated and imaged often to track deformity progression. Upper cervical spine instability in Down syndrome is most commonly caused by ligamentous laxity at C1 to C2 and occiput-C1 levels. Nearly 100% of patients with 22q11.2 deletion syndrome have cervical spine abnormalities, but few are symptomatic. Patients with pseudoachondroplasia and Morquio syndrome have C1 to C2 instability related to odontoid dysplasia (hypoplasia and os odontoideum). Morquio patients also have soft tissue glycosaminoglycan deposits, which cause stenosis and lead to myelopathy. Severely affected patients with spondyloepiphyseal dysplasia congenita are at high risk of myelopathy because of atlantoaxial instability in addition to underlying stenosis. Kniest syndrome is associated with atlantoaxial instability. Cervical spine anomalies in Goldenhar syndrome are varied and can be severe. Fibrodysplasia ossificans progressiva features severe, deforming heterotopic ossification that can become life-threatening., Conclusion: It is important to be vigilant in the diagnosis and treatment of cervical spine anomalies in patients with genetic syndromes.

Study Design: Prospective consecutive multicenter case series., Objective: To compare fixation type and amount to curve correction controlled for curve flexibility., Summary of Background Data: The enhanced spinal purchase from segmental fixation should increase the force implants can exert without failure. This study evaluates whether this translates into correction beyond that expected from preoperative bending radiographs in thoracic curves where maximum correction was feasible (1A, 1B, and nonselective 1C fusions)., Methods: One hundred seventy-one Lenke type 1 curves (118 1A, 36 1B, 23 1C) with 2-year follow-up were evaluated for the number and type of fixation points within the main curves compared to the correction obtained on preoperative bend films. SRS scores were compared to the amount of correction., Results: The number of fixation points both within the curve (P = 0.01) and for each vertebral body (P = 0.002) was larger for curves with greater correction compared to the bend films than those with less correction. Overall absolute correction was best for all screw and screw and wire constructs, followed by hook and screw, and least with hooks. However, compared to the bend films, these differences were not significant (P = 0.132). For all groups, the SRS scores significantly improved (P < 0.001), and was slightly more notable for the all screw constructs than other instrumentation patterns (P = 0.023). However, there were no significant difference in this improvement between those correcting more and those correcting less than the bend films (P = 0.578)., Conclusion: Absolute curve correction improved most with all pedicle screw and screw and wire constructs, but, when compared to bending films, the number of fixation points is more important than fixation type for curve correction. Although SRS scores improved the most in those with all screw constructs, the significance of this improvement is uncertain, and the SRS scores did not relate to whether curve correction was more or less than the bend films.

Study Design: Retrospective review., Objective: To report on the safety of repetitive transcranial electric stimulation (RTES) for eliciting motor-evoked potentials during spine surgery., Summary of Background Data: Theoretical concerns over the safety of RTES have hindered broader acceptance of transcranial electric motor-evoked potentials (tceMEP), despite successful implementation of spinal cord monitoring with tceMEPs in many large spine centers, as well as their apparent superiority over mixed-nerve somatosensory-evoked potentials (SSEP) for detection of spinal cord injury., Methods: The records of 18,862 consecutive patients who met inclusion criteria and underwent spine surgery with tceMEP monitoring were reviewed for RTES-related complications., Results: This large retrospective review identified only 26 (0.14%) cases with RTES-related complications; all but one of these were tongue lacerations, most of which were self-limiting., Conclusions: The results demonstrate that RTES is a highly safe modality for monitoring spinal cord motor tract function intraoperatively.

Study Design: Literature review., Objective: This article presents a critical examination of standard of care (SOC) related to intraoperative neurophysiologic monitoring during spine surgery. Definition of SOC and its applications in the surgical setting is accompanied by discussions on SOC for neuromonitoring, credentialing of neuromonitoring personnel, off-site remote monitoring, and unattended surgeon-controlled neuromonitoring devices., Methods: A literature review of neuromonitoring and SOC over the past 10 years was performed. This information, in conjunction with the author's experience and evidence-based medicine, was used to formulate a framework for critique and discussion., Conclusion: An appropriate SOC as it relates to neuromonitoring is difficult to devise because of national variance with regard to qualifications of neurophysiologic technical and professional personnel, different levels of training and certification, and anesthesia protocols. A unified group of surgeons working in collaboration with a multidisciplinary group of experienced doctoral level nonphysician and physician professional surgical neurophysiologists is needed to define a protocol for providing and interpreting such data. In addition to ensuring that only the most qualified and experienced personnel are delivering and/or interpreting neuromonitoring services, surgeons, hospital administrators, and insurance company medical directors need to understand the different service delivery models and their respective strengths and limitations with particular attention to the qualifications and competencies of all respective parties. Only then can a well-defined SOC be established, thus improving the treatment of surgical patients for whom neuromonitoring is required.

Study Design: A retrospective study of 61 patients with cerebral palsy (CP) and neuromuscular scoliosis treated by either a combined anterior-posterior spinal arthrodesis or a posterior-only arthrodesis with the unit rod., Objectives: Compare coronal and sagittal plane radiographic outcomes in patients undergoing either a combined anterior-posterior spinal fusion (PSF) or a posterior-only fusion with the unit rod for neuromuscular scoliosis in patients with CP., Summary of Background Data: Although an anterior release before posterior spinal arthrodesis is commonly done for larger and stiffer neuromuscular curves, it is unclear whether or not an all-posterior construct produces similar correction in pelvic obliquity as that seen with an anterior-posterior spinal fusion., Methods: Sixty-one consecutive children with CP and scoliosis were treated at a single institution between 1991 and 2003 with PSF using the unit rod with an anterior release (group A: 19 patients; average = 14.4 years) or without an anterior release (group B: 42 patients; average = 13.7 years). Side-bending, AP, and lateral radiographs were used to assess various sagittal and coronal plane parameters at baseline, after surgery, and at 2 years. RESULTS.: Before surgery, group A had larger major curves (91 degrees A vs. 72 degrees B; P = 0.001), less flexible major curves (21% A vs. 40% B; P = 0.01), with greater pelvic obliquity (26 degrees A vs. 19 degrees B, P = 0.02) than group B. In the subset of patients with a more severe preoperative pelvic obliquity (>20 degrees ), percent correction in pelvic obliquity was equivalent between groups A (71%) and B (74%, P = 0.91). With respect to coronal and sagittal plane radiographic outcomes, there were no significant group differences in major curve correction (58% A vs. 60% B), but group A trended toward greater % correction from preop bending films. At most recent follow-up, there were no differences with respect to loss of curve correction (7.6 A vs. 8.1 degrees B, P = 0.80). The rate of major complications was 26% for both groups, but group A patients had significantly longer operative times., Conclusion: We demonstrate that excellent correction in severe pelvic obliquity can be achieved in smaller, more flexible curves using an all-posterior PSF, and in larger, less flexible curves using an anterior release with PSF.

Study Design: Retrospective case series from a multicenter database., Objective: To evaluate the risk of neurologic injury during growing rod surgeries and to determine whether intraoperative neuromonitoring is necessary for all growing rod procedures., Summary of Background Data: Although the use of growing rod constructs for early-onset spinal deformity has become a commonly accepted treatment, the incidence of neurologic events during growing rod surgeries remains unknown., Methods: We reviewed data from a multicenter database on 782 growing rod surgeries performed in 252 patients. VEPTR devices and any constructs with rib attachments were excluded. A questionnaire was sent to all surgeons contributing cases requesting detailed information about all neurologic events associated with any growing rod surgery., Results: There were 782 growing rod surgeries performed on 252 patients including 252 primary growing rod implantations, 168 implant exchanges, and 362 lengthenings. Five hundred sixty-nine of 782 (73%) cases were performed with neuromonitoring. Only one clinical injury occurred in the series, resulting in an injury rate of 0.1% (1/782). This deficit occurred during an implant exchange while attempting pedicle screw placement, and resolved within 3 months. There were 2 cases with neuromonitoring changes during primary implant surgeries (0.9%, 2/231), 1 change during implant exchanges (0.9%, 1/116), and 1 neuromonitoring change during lengthenings (0.5%, 1/222). The single monitoring change that occurred during a lengthening was in a child with an intracanal tumor who also had a monitoring change during the primary surgery. There are anecdotal cases (outside this study group series) of neuromonitoring changes during simple lengthenings in children with uneventful primary implantations., Conclusion: Based on our study, the largest reported series of growing rod surgeries, the rate of neuromonitoring changes during primary growing rod implantation (0.9%) and exchange (0.9%) justifies the use of intraoperative neuromonitoring during these surgeries. As there were no neurologic events in 361 lengthenings in patients with no previous neurologic events, the question may be raised as to whether intraoperative neuromonitoring is necessary for simple lengthenings in these patients. However, caution should be maintained when interpreting our results as anecdotal cases of neurologic changes from simple lengthenings do exist outside of this series.

Study Design: Review., Objective: To review and outline the preoperative evaluation and approach in assessing children with congenital vertebral malformation., Summary of Background Data: Congenital vertebral malformations encompass a broad spectrum of conditions. A high association of renal, cardiac, and intraspinal anomalies with congenital vertebral malformation has been well documented in the literature. Vertebral malformation with involvement of the thoracic cage may lead to the development of thoracic insufficiency. The natural history, the character, and location of the deformity ultimately influence the propensity for progression and the necessity for treatment. Multiple factors should be considered before treatment with the goal of treatment aimed at providing the best possible care to be able to optimize the child's overall function and potential for growth., Methods: Narrative and review of literature., Conclusion: Congenital scoliosis is a multifaceted condition. The presentation of the condition can be quite varied from those presenting with an isolated hemivertebrae to those with severe malformations, complicated by multiple medical conditions. A thorough preoperative evaluation is necessary before the institution of any treatment protocol. The presence of any medical condition must be addressed; the treatment should be tailor-made for each patient putting into consideration the patients' age and the effects of treatment on pulmonary function at maturity.

Study Design: Retrospective case series., Objective: To evaluate the axial cross-sectional dimensions of the spinal cord and cerebrospinal fluid (CSF) column in children with Klippel-Feil Syndrome (KFS) versus an age-matched cohort of control subjects., Summary of Background Data: Neurologic sequelae and chronic pain are known to occur in KFS and factors implicated include spinal cord compression from canal stenosis, segmental instability, vascular disruption, and central nervous system abnormalities including tethered cord, syrinx, and diastomyelia. No study to date, however, has examined the role of spinal cord size as a contributing factor to neurologic sequelae in KFS., Methods: We retrospectively reviewed the plain radiographic, magnetic resonance imaging (MRI), and clinical records of 12 consecutive patients between 2 and 18 years with KFS (average age 9.5 +/- 5.3 years) and 14 age-matched controls (average age 8.3 +/- 5.1 year). For each patient, plain film radiography was reviewed to compare Torg ratios at each cervical level, and axial T1-weighted MRI was used to compare spinal cord and CSF column cross-sectional area calculations., Results: The Torg-Pavlov ratios were identical between the 2 groups (0.77 +/- 0.15 vs. 0.77 +/- 0.19). Analysis of axial T1-weighted MRI cross-sectional spinal cord area revealed that the cord was smaller in KFS patients at each level from C2-C7 compared with controls. These differences were statistically significant at C4 (P = 0.016), C5 (P = 0.035), and C6 (P = 0.032). Subset analysis of abnormal (fused) levels compared with controls revealed the same findings, although these differences were not significant due to the limited numbers available at each level. Analysis of the CSF column, however, revealed that overall the canal was slightly larger in KFS patients compared with controls, although this difference was not statistically significant. Four of the 12 KFS patients presented with neurologic symptoms, all of which improved after posterior cervical stabilization., Conclusion: In our cohort of patients we have noted statistically significant differences in axial cord dimensions, with no differences in CSF column, suggesting that the cord size is smaller in KFS children compared with age-matched controls.

Study Design: Prospective, sequential enrollment., Objective: We report the development and testing of the Spinal Appearance Questionnaire (SAQ) for reliability, validity, and responsiveness in patients with idiopathic scoliosis., Summary of Background Data: The SAQ was designed to measure patients' and their parents' perception of their spinal deformity's appearance using standardized drawings and questions. This study was designed to test the instrument's psychometric properties., Methods: The SAQ was administered as a test-retest to idiopathic scoliosis patients and parents for reliability and initial validity assessment (Group I). It was then administered to patients before surgery and 1 year after surgery (Group II) for responsiveness and further validity testing. Finally, both the SAQ and SRS instruments were administered to adolescent idiopathic patients before surgery and 1 year after surgery (Group III) for comparison of the 2 instruments., Results: Group I: The individual scale items had good to excellent reliability (Spearman's rho, 0.57-0.99) and high internal scale consistency (Cronbach's alpha >0.7). The mean scale scores differentiated between curves greater than 30 degrees and lesser curves (P < 0.01). Surgery improved scores compared with those with "surgery recommended." Group II: The domains correlated with clinical and radiographic aspects of the deformity before surgery. All of the domains showed significant difference after surgery (P < 0.0001) and large effect size for all domains except for the patient chest domain. Group III: Both the SAQ and the SRS instruments had significant improvement in all of their domains except for the SRS Activity scale. The relative efficiency of the SAQ domains to the SRS appearance domain (the most responsive SRS domain) was greater for 5 SAQ domains., Conclusion: The SAQ is reliable, responsive to curve improvement, and shows strong evidence of validity. It provides more detail than the SRS in the appearance domain, and provides explanation of spinal deformity's concerns and improvements.

Study Design: This study measured active cervical spine range of motion (ROM) in children ages 3-12 years using 2 methodologies: (1) a cervical spine ROM instrument, and (2) a digital videography based technique., Objective: To determine the active cervical spine ROM, as defined by flexion/extension, lateral bending, and horizontal rotation, for children ages 3-12 years., Summary of Background Data: Review of current literature reveals limited studies of cervical spine ROM in children, many of which do not provide data on children younger than 8 years of age when many of the structural changes of the cervical spine are thought to occur., Methods: A total of 67 children (39 girls) within 3 age groups, 3-5 years (26 children), 6-8 years (22), and 9-12 years (19), were tested in flexion/extension, lateral bending, and horizontal rotation. The subjects repeated the neck movements 3 times for each direction in each method (ROM instrument and videography), and the maximum ROM values were recorded. Within each age group, the mean, standard deviation, and range for each ROM was calculated, and ROM values from the 2 methods were compared. The effect of age and gender on ROM was assessed via analysis of variance., Results: For the ROM instrument, only flexion and right and left rotation were shown to increase with age (P < 0.05). This difference resulted in an increase in ROM of approximately 7 degrees between the youngest and oldest age group. No age effects were present in the videography data. No significant differences between the genders were detected for any of the ROM measures using either method (minimum P = 0.22). In general, the videography method resulted in higher values for flexion, extension, and rotation, and lower values for lateral bending. These differences were greater for the younger children., Conclusions: This study contributes valuable normative data for pediatric cervical spine ROM in children that can be used as a clinical reference and for biomechanical applications. In children 3-12 years of age, both flexion and rotation increased slightly with age. Of interest, there were no differences in ROM with gender, which contradicts adult literature where females have been shown to have more cervical spine ROM than males.

Study Design: Prospective study., Objective: To compare variability in Cobb angle between digitally and traditionally acquired scoliosis radiographs., Summary of Background Data: Previous studies have shown that the 95% confidence interval for Cobb angle can vary from 2.6 degrees to 8.8 degrees. No study directly comparing Cobb angles measured from traditional and digitally acquired radiographs has been reported., Methods: A spine model simulating 25 single right thoracic curves (range, 20 degrees-60 degrees) was imaged using traditional and digital techniques. Traditional films and miniaturized printed digital films were each measured twice manually. Digital films were also measured twice using computer imaging software., Results: Overall mean angle and (95% confidence interval) were 41.7 degrees (39.1 degrees-44.3 degrees) for traditional, 40.6 degrees (37.4 degrees-43.8 degrees) for digital, and 39.7 degrees (36.3 degrees-43.1 degrees) for computer measurements. Overall correlation was 0.994 for traditional and digital, 0.987 for traditional and computer, and 0.993 for digital and computer. Fixed effect model analysis demonstrated that, although a statistically significant difference existed between the 3 methods of measuring the Cobb angle (P < 0.0001), the difference between methods was less than 2 degrees., Conclusions: Any of the 3 evaluated methods of measurement can be used to measure Cobb angles. Additionally, the methods can be used interchangeably.

Study Design: Retrospective case series., Objective: Evaluate the change in lordosis at the occipitocervical junction occurring during growth in skeletally immature children treated with posterior occipitocervical arthrodesis versus patients skeletally mature at arthrodesis., Summary of Background Data: Posterior occipitocervical arthrodesis is often indicated for children who have instability of the upper cervical spine develop. Theoretically, in skeletally immature children, this approach retards the growth of the posterior spinal elements but allows the anterior spinal column to continue to grow with the risk of excessive lordosis of the cervical spine developing., Methods: There were 21 children, younger than 11 years (range 1.9-10.9) at surgery and expected to have normal spinal growth, followed radiographically for an average of 6.3 years (range 2.0-12.4). Postoperative lateral neutral radiographs were compared to those at most recent follow-up to measure the change in occipitocervical angle. These results were then compared to a series of control patients who were skeletally mature at surgery., Results: Average overall change in lordosis at the occipitocervical junction was -4.6 degrees (range -12.8 degrees to +6.5 degrees). Average annualized change was -0.28 degrees per vertebral level per year (range -1.13 degrees to +0.67 degrees). This annualized change in angle was statistically significant compared to the average change of +0.01 degrees (range -0.09 degrees to +0.11 degrees) measured in the control series of patients skeletally mature at surgery (P = 0.01)., Conclusions: Increasing lordosis occurs at the occipitocervical junction following fusion in skeletally immature children. If occipitocervical arthrodesis is indicated in a skeletally immature child, fusion in excessive extension and overtightening of posterior wires should be avoided.

Study Design: Retrospective analysis of our experience with os odontoideum at the Children's Hospital of Philadelphia., Objective: To review the origin of os odontoideum and provide evidence for two separate etiologies., Summary of Background Data: The etiology of os odontoideum has been debated in the literature. Most authors support a post-traumatic etiology; however, some evidence exists to support a congenital origin., Methods: We reviewed all 519 abnormal cervical spine radiographs performed from 1991 to 2004 to identify os odontoideum. Medical records and imaging studies were examined to determine: history of trauma, severity of injury, interval from injury to presentation, coexisting syndromes, and associated congenital cervical spine anomalies., Results: Sixteen of 519 patients (3.1%) had os odontoideum. Only 8 of 16 patients reported previous trauma. Only 3 of these 8 injuries occurred with an interval remote enough to allow remodeling of the dens to an ossicle by the time of presentation. Six of 16 patients had associated congenital anomalies in the cervical spine. Three of 16 had a coexisting genetic syndrome., Conclusion: Our data supports two separate etiologies for the os odontoideum: post-traumatic and congenital. The data should raise awareness that some children with preexisting syndromes may develop os odontoideum without previous trauma.

Study Design: Details of presentation and approach to the treatment of scoliosis in a case of a Rigid Spine Syndrome (RSS)., Objective: To report on the results of conservative and operative treatment of scoliosis associated with RSS, and, based on this, to propose an assessment and treatment protocol for this condition., Summary of Background Data: Congenital muscular dystrophies (CMD) are a group of disorders marked by hypotonia at birth and a generally nonprogressive course of muscle weakness. Spinal rigidity is present in a number of patients with CMD. RSS is classified as a CMD, and is characterized by early rigidity of the spine, limb contractures, and restrictive respiratory dysfunction. An approach to the treatment of scoliosis in RSS has not been established., Methods: Details of history, diagnostic tests, and treatment of an adolescent with RSS associated with progressive scoliosis and cervical spine extension contracture is presented. The role of brace treatment, Botox (Allergan, Inc., Irvine, CA), and details of operative correction, including histology of back muscles, is defined., Results: In this case of RSS with rigid scoliosis nonresponsive to brace therapy and Botox injections, an anterior thoracolumbar spine fusion with instrumentation was successfully performed for correction of the scoliosis, and the cervical spine was addressed through a posterior approach and an occiput-cervical fusion. We outline the details of surgical procedure and restoration of spinal balance in both sagittal and coronal planes., Conclusions: The chromosomal bases of CMD and characteristic features of RSS, including diagnostic tests, have been reviewed. Surgical intervention with spinal deformity fusion, correction, and instrumentation is indicated in RSS with progressive spinal imbalance not responding to conservative therapy is safe and can give promising results.

Study Design: A radiographic analysis of the cervical spine of 70 patients diagnosed with fibrodysplasia ossificans progressiva (FOP) and 33 diagnosed with Klippel-Feil (KF) syndrome was conducted., Objectives: The objectives of this study were to describe cervical spine abnormalities in patients with FOP, to compare and contrast those findings with the malformations in patients with KF syndrome, and to examine the possible etiology of these abnormalities., Summary of Background Data: Congenital features of diseases often provide seminal clues to underlying etiology and developmental pathways. While progressive metamorphosis of connective tissue to heterotopic bone is the most dramatic and disabling feature of FOP, less severe congenital anomalies of the skeleton are also present. Vertebral fusions observed in KF are consistent with defects in embryonic segmentation., Methods: The cervical spine plain films of 70 FOP patients and 33 KF patients with documented congenital abnormalities were reviewed., Results: Generalized neck stiffness and decreased range of motion were noted in most children with FOP. In the FOP patient group, characteristic anomalies, including large posterior elements, tall narrow vertebral bodies,and fusion of the facet joints between C2 and C7, were observed. Most notably, these characteristic anomalies of the cervical spine in patients with FOP were distinctly different from those of 33 patients with KF that were examined but were strikingly similar to those seen in mice with homozygous deletions of the gene-encoding noggin, a bone morphogenetic protein (BMP) antagonist., Conclusions: FOP patients exhibit a characteristic set of congenital spine malformations. While the noggin gene (NOG) is not mutated in patients who have FOP, these findings extend a growing body of evidence implicating overactivity of the BMP signaling pathway in the molecular pathogenesis of FOP.

Study Design: A case report on cervical instability detected in a patient with Sotos syndrome, along with a review of the literature on Sotos syndrome and associated spinal findings., Objective: To present the case of a patient with a C3-C4 anterolisthesis occurring in the setting of Sotos syndrome and explore a possible association between the two., Summary of Background Data: Sotos syndrome, a rare overgrowth syndrome with slightly more than 300 cases reported in the English literature to date, is characterized by a unique constellation of symptoms and signs including musculoskeletal findings such as scoliosis, pes planus, generalized ligamentous laxity, and increased growth rates. Cervical instability as part of this syndrome is unreported and rarely presents as a C3-C4 anterolisthesis., Methods: A case report detailing the evaluation and treatment of a cervical instability in a 3-year-old with Sotos syndrome., Results: A previously unreported cervical spine instability in Sotos syndrome is described. The patient underwent a posterior spinal fusion of C3 and C4 to avoid complications from the instability. The surgery achieved good results., Conclusion: We outline a possible connection between Sotos syndrome and cervical instability, which may be associated with the unique features of this syndrome including ligamentous laxity or macrosomia and/or with unrecognized injury. Awareness of this occurrence is important for enhancing early detection and correction of this condition.

Study Design: Retrospective study of patients with scoliosis and an Arnold Chiari I malformation requiring operative management., Objectives: Determine the factors that could predict whether a particular spinal deformity might progress despite neurosurgical management of Arnold Chiari I malformation., Summary of Background Data: Few studies have documented the relationship between diagnosis and treatment of Arnold Chiari I malformation and associated spinal deformities. Most studies mix neural axis abnormalities and contain limited information about the spinal deformity., Methods: Medical records, radiographs, and magnetic resonance images of patients were evaluated focusing on age and findings at presentation, characteristics of presenting and follow-up spinal deformities, and the specifics of neurosurgical and orthopedic management. Patients were divided into two groups: those whose curves progressed >10 degrees or to surgical range (largest curve >45 degrees ) after neurosurgical intervention (progressors) and those whose curves stabilized or decreased (nonprogressors)., Results: Eight progressors presented at an average age of 11.4 years (range 2-19) and were followed for 6.3 years (range 2-15). Seven nonprogressors presented at 6.5 years of age (range 5-10) and were followed for 6.6 years (range 3.5-14). Neurosurgical procedures were equivalent in both groups; however, surgical revisions were required in 3 out of 8 progressors and 1 out of 7 nonprogressors. All progressors had a double scoliosis curve; but only one nonprogressor had a double curve. Six out of 8 progressors and 0 out of 7 nonprogressors had a rotation >or=2+ and 50% of progressors had a thoracic kyphosis >50 degrees compared to 1 out of 7 nonprogressors., Conclusions: In this series, progression of spinal deformity after neurosurgical management of Arnold Chiari I malformation was associated with later age at neurosurgical decompressions and initial neurologic symptoms, double scoliosis curve patterns, kyphosis, rotation, and larger curve at presentation.

Study Design: A case report of a child with Langerhans cell histiocytosis of the posterior elements of the cervical spine treated conservatively and with long-term follow-up is described., Objectives: To describe the unique diagnostic and therapeutic challenges of treating Langerhans cell histiocytosis located atypically in the posterior elements of the spine., Summary of Background Data: Langerhans cell histiocytosis involves the spine in approximately 20% of children with the disease. In nearly 95% of cases, spinal Langerhans cell histiocytosis results in destruction of the vertebral body, sparing the posterior elements. Confident diagnosis of vertebral body lesions is often made based on plain radiographs and MRI; however, the diagnosis of posterior element disease is not so straight forward. The natural history of isolated skeletal Langerhans cell histiocytosis is benign in most cases., Methods: The clinical and radiographic presentation of a child with Langerhans cell histiocytosis involving the posterior elements of C3 is described. A soft tissue mass was observed on magnetic resonance imaging; however, a biopsy confirmed the benign diagnosis of Langerhans cell histiocytosis. No further surgical treatment was needed, and conservative therapy incorporating a short course of cervical bracing and low-grade chemotherapy was begun., Results: Within a year, reconstitution of the posterior elements of C3 was apparent on radiographs. By 9 years after diagnosis, the child had near full reconstitution of the posterior elements of C3 and resolution of anterior pseudosubluxation of C3 on C4 that was present at diagnosis. Although diagnosis of Langerhans cell histiocytosis was made difficult by an atypical location in the posterior elements of the spine, after biopsy, conservative treatment led to excellent vertebral reconstitution., Conclusions: Isolated involvement of the posterior spine in Langerhans cell histiocytosis has not been described in detail previously. The reported case illustrates the diagnostic challenges of isolated posterior spine Langerhans cell histiocytosis. Despite an unusual presentation, posterior spine Langerhans cell histiocytosis should be treated conservatively in a similar manner to anterior lesions.

Study Design: A retrospective radiographic review was performed on 41 patients with scoliosis associated with a Chiari I malformation and/or syringomyelia., Objectives: To characterize curve patterns and curve features in this population and possibly refine the radiographic indications for magnetic resonance imaging in patients with a normal history and physical examination., Summary of Background Data: A subset of patients with "idiopathic" scoliosis may have an underlying neurologic abnormality. The radiographic indications for magnetic resonance imaging in asymptomatic patients with a normal clinical examination are not well defined., Methods: Data were collected from standing posteroanterior and lateral radiographs. The curve pattern and specific curve features were recorded and compared with historic controls. Thoracic kyphosis and total lumbar lordosis were also measured., Results: Fifty-one percent of patients were male. Ten curve patterns were identified, and, based on our criteria, approximately 50% of patients had an "atypical" pattern (left thoracic, double thoracic, triple, long right thoracic). A subset of those with "typical" patterns (right thoracic, right thoracic/left lumbar) had atypical features including a superior or inferior shift of the apex and/or the upper or lower end vertebrae. The mean kyphosis (T3-T12) was 41.8 degrees., Conclusions: Although the decision to obtain magnetic resonance imaging in a patient with scoliosis should be based on both clinical and radiographic criteria, we suggest that a heightened index of suspicion is warranted with certain curve patterns (left thoracic, double thoracic, triple, and a long right thoracic curve with end vertebra caudal to T12), and with a high or low apex and/or end vertebra, especially in males and patients with a normal to hyperkyphotic thoracic spine.

Study Design: A case report of a child with quadriplegia as a result of neurofibromatosis type I who had cervical laminectomy for spinal cord decompression followed by occipitocervical instrumentation is described., Objectives: To describe the consequences of severe neurofibromatosis type I and an effective surgical technique of occipitocervical instrumentation., Summary of Background Data: Neurofibromatosis type I is one of the most commonly inherited genetic disorders in the human population. Extensive intraspinal involvement by neurofibromas can cause significant distortion of normal spinal structure as well spinal cord compression. Extensive laminectomy (with subsequent risk of postsurgical kyphosis) is often required for adequate decompression of the spinal cord., Methods: The clinical and radiographic presentation of a child with severe neurofibromatosis type I resulting in quadriplegia is described. The severe neurologic deficit was caused by compression of the spinal cord by intraspinal neurofibromas. Extensive laminectomy was required to adequately decompress the spinal cord. Occipitocervical fusion from the occiput to C6 was done to stabilize the spine and prevent future kyphosis., Results: Decompression of the spinal cord led to complete neurologic recovery, and instrumentation of the cervical spine was successful in preventing the development of postlaminectomy kyphosis in this pediatric patient., Conclusions: The reported case emphasizes the need for treating acute neurologic symptoms caused by spinal cord compression in neurofibromatosis type I as well as addressing the future risk of spinal deformity following laminectomy.

Study Design: Retrospective review of records and radiographs with postoperative questionnaire of patients with Marfan syndrome receiving surgical correction for spinal deformity., Objective: To characterize and analyze the challenges of surgical correction for spinal deformity in Marfan syndrome and to present recommendations that may reduce morbidity and increase success for these procedures., Summary of Background Data: Spinal deformities are common in Marfan syndrome and usually refractory to conservative management. The few, smaller studies of surgical intervention reported on earlier surgical techniques but suggested increased complication rates., Methods: Records and radiographs of 39 patients with confirmed Marfan syndrome who underwent surgical management at either of two institutions for primary scoliosis (n = 26), kyphosis (n = 7), or deformity secondary to previous surgery elsewhere (n = 6) were reviewed. Presentation features, complications, and therapeutic results were analyzed. Low back outcome scores were generated from a questionnaire given to patients after surgery., Results: Increased blood loss and rates of infection (10%), dural tear (8%), instrumentation fixation failure (21%), pseudarthrosis (10%), and coronal (8%) and sagittal (21%) curve decompensation were noted. Infection was often associated with dural tear and decompensation with extreme correction. One patient died of valvular insufficiency 11 weeks after surgery., Conclusion: The cardiopulmonary condition of patients with Marfan syndrome should be evaluated and planned for before surgery. Preoperative computed tomograph to assess bony adequacy for fixation and magnetic resonance imaging to evaluate dural ectasia are indicated. Attention paid to the sagittal profile, extension of fusion to vertebrae neutral and stable in both planes, minimization of soft tissue dissection, and avoidance of extreme correction may prevent curve decompensation.

Study Design: A retrospective chart analysis of pediatric trauma patients with suspected cervical spine injury was performed., Objectives: This study was designed to evaluate the efficacy and cost-efficiency of a magnetic resonance imaging (MRI) protocol for cervical spine clearance in pediatric trauma patients., Summary of Background Data: The evaluation of cervical spine injury in the pediatric trauma population can be difficult. In obtunded or uncooperative children, MRI can be valuable in defining injuries of the cervical spine not detected by plain radiographs and computed tomography., Methods: In 1993, a protocol was instituted at a pediatric trauma center using MRI to evaluate the cervical spine of children who could not be cleared within 72 hours. Using the trauma registry from February 1989 through September 1996, children with suspected cervical spine injury who were intubated at the time of hospital admission and who remained in the intensive care unit for at least 3 days were identified. The patients were divided into two cohorts: a "preprotocol group" and a "postprotocol group," consisting of patients before or after institution of the MRI protocol in September 1993. Medical records were reviewed to determine the time to cervical spine clearance, the number of days in the intensive care unit, and hospital days for each group. Biostatistical analysis was performed by an independent professional statistician., Results: Fifty-one patients in each group met the inclusion criteria. In the preprotocol group, 19 patients underwent MRI at an average of 6.8 days after admission. In the postprotocol group, 31 MRIs were performed at an average of 2.5 days from admission. Time to cervical spine clearance decreased from 5.1 days in the preprotocol group to 3.2 days in the postprotocol group (P = 0.003). The average intensive care unit stay decreased from 9.2 days in the preprotocol group to 7.3 days in the postprotocol group (P = 0.122). The average hospital stay decreased from 20.1 days in the preprotocol group to 15.5 days in the postprotocol group (P = 0.106). Factoring charges for MRI, intensive care unit beds, and hospital beds, savings of $7,700 per patient were estimated., Conclusions: In obtunded and intubated pediatric trauma patients with suspected cervical spine injury, the clearance protocol using cervical spine MRI was effective and cost-efficient.

Study Design: Description of an operative technique with an illustrative case report., Objectives: The technique is presented to provide an alternative to iliac crest graft procedures for achieving occipitocervical fusion in children. This technique is particularly useful in children with instability after extensive decompression or laminectomy and in children with a large protuberant occiput., Summary of Background Data: The majority of techniques previously described for occipitocervical fusion in children rely on corticocancellous iliac crest autograft. Results generally have been promising; however, it can be difficult to harvest enough graft to span large defects after extensive decompression or to contour an iliac crest graft to a protuberant occiput. Structural rib autograft is superior in terms of availability and its unique and modifiable contour. Theoretical benefits of rib graft include superior strength and lower donor site morbidity., Methods: The surgical technique is described. A case of a 2-year-old boy with Down's syndrome and myelopathy secondary to cervical instability is reviewed., Results: The patient underwent occipitocervical arthrodesis using the technique described. The child made a full neurologic recovery, and at the 2-years follow-up evaluation, the graft had incorporated and the spine was stable., Conclusion: A technique of occipitocervical arthrodesis in children is described using autologous rib graft. This procedure was designed to span large defects or to deal with a large protuberant occiput; however, it is also useful for less demanding cases and may offer several advantages compared with procedures relying on iliac crest graft.

Study Design: This in vitro biomechanical study examines segmental anterior vertebral screw strain and solid rod construct stiffness with and without the addition of multilevel, threaded cortical bone dowels in a bovine model., Objective: To determine whether strain at the bone-screw interface is higher at the end levels during physiologic range loading, and whether solid interspace support decreases segmental strain on the implant., Summary of Background Data: Anterior instrumentation provides greater correction and preserves distal motion segments. However, nonunion and implant failure are observed more frequently than with posterior segmental instrumentation, and when observed, loss of fixation occurs at the end levels., Methods: Eight calf spines underwent mechanical testing in the following sequence: 1) intact condition, 2) anterior release with anterior solid rod and bicortical rib grafts, and 3) anterior release with anterior solid rod and threaded cortical bone dowels (L2-L5). Instrumented vertebral screws were used to assess strain within the vertebral body by the near cortex, whereas an anterior extensometer spanning the instrumented segments was used to measure segmental displacements to calculate construct stiffness. The protocol included axial compression (-400 N), right lateral bending (4 Nm (Newton-meter), away from the implant), and left lateral bending (4 Nm, toward the implant). Statistical analysis included a one-way analysis of variance and a Student-Newman-Keuls post hoc test. A pilot study was performed using four additional specimens loaded for 4000 cycles to investigate macroscopic loosening after fatigue loading., Results: In lateral bending toward the implant, the strain was higher at both end levels, with no differences between the rib and dowel reconstructions. The stiffness values were greater than the intact values for both groups. In lateral bending away from the implant, the strain also was higher at both end screws, and the dowel group had less strain at these levels than the rib group. Both groups were stiffer than the intact condition, and the dowel group was stiffer than the rib group. Axial compressive strain also was higher at the end levels, but this difference did not reach statistical significance. The rib group did not reach intact stiffness values, whereas the dowel group was stiffer than the intact condition. The fatigue study showed gross loosening at one or both end levels in all cases., Conclusions: Higher strain was observed at the bone-screw interface in both end screws of an anterior solid rod construct during lateral bending, which correlates with the clinically observed failure location. This suggests that physiologic range loading may predispose to failure at the end levels. Disc space augmentation with solid implants increased construct stiffness in all three load paths and decreased strain at the end levels in lateral bending away from the implant. Future implant modifications should achieve better fixation at the end screws, and the current model provides a means to compare different strategies to decrease strain at these levels.

Study Design: Retrospective review of a defined Marfan population with traditional indications for bracing., Objectives: To determine the success rate of brace treatment in keeping curves from progressing by more than 5 degrees or exceeding 45 degrees., Summary of Background Data: Few studies exist regarding brace treatment of Marfan syndrome, and they include many patients with curves of more than 45 degrees, as well as some who are near maturity. All of the prior studies risk the possibility of some selection bias., Methods: Patients were selected from support groups and several institutions. Inclusion criteria were: Definite diagnosis of Marfan syndrome, curve of 45 degrees or less, Risser sign 2, 1, or 0 at inception of bracing, recommended wear of 18 hours or more per day, and follow-up until maturity or surgery (minimum, 2 years). Success was defined as curve progression of 5 degrees or less and final curve remaining 45 degrees or less. Failure was a final curve of more than 45 degrees. Twenty-four patients met the criteria. There were 15 girls and 9 boys. Twenty-two patients wore a brace as recommended. Two additional patients were unable to tolerate it., Results: Mean age at inception of bracing was 8.7 years (range, 4-12 years). There were 14 double major, 6 thoracic, and 4 thoracolumbar curves with a mean size of 29 degrees at the beginning of bracing. The stated wearing time averaged 21 hours per day. Five patients had significant pain over bony prominences. Although correction of the curve in brace was good (45%), only 4 of the patients had success, and in 20 of the 24 treatment was considered a failure. Mean progression was 6 degrees +/- 8 degrees per year, for a final mean curve of 49 degrees. Sixteen of the patients had, or were advised to have, surgical correction. The difference in age and degree of curvature were not statistically significant between the success and nonsuccess groups., Conclusions: The success rate for brace treatment of Marfan scoliosis is 17%, which is lower than that reported for idiopathic scoliosis. Possible reasons include increased progressive forces, altered transmission of corrective pressure to the spine, and younger age at inception of bracing. Because there was no control group, it is unknown whether bracing slowed curve progression. Physicians should understand that most patients with Marfan syndrome who have a curve of more than 25 degrees and a Risser sign of 2 or less will reach the surgical range, even with brace treatment.

Study Design: This static, nondestructive, in vitro biomechanical study examines anterior solid rod construct stiffness following the addition of multilevel, threaded cortical bone dowels in a bovine model. A comparison is made with a clinically relevant posterior construct with and without an anterior release., Objectives: To determine if the addition of solid, multilevel disc space implants will increase construct rigidity, while maintaining or enhancing anterior column length., Summary of Background Data: Anterior instrumentation for thoracolumbar and lumbar scoliosis has achieved greater correction and preserved distal motion segments; however, kyphosis over the instrumented segments and nonunion have been observed more frequently than with posterior segmental spinal instrumentation., Method: Fifteen calf spines underwent mechanical testing. Group A (n = 7) included anterior constructs: 1) intact, 2) anterior release/rod/rib graft (L2-L5), and 3) anterior release/rod/dowels (L2-L5). Group B (n = 8) included posterior constructs: 1) intact, 2) posterior rod without anterior release (T13-L5), 3) posterior rod (T13-L5)/anterior release/rib graft (L2-L5). The protocol included axial compression (-600 N), axial rotation (+7 Nm), flexion/extension (+7.5 Nm), and lateral bending (+7.5 Nm). An anterior extensometer measured segmental displacements to calculate construct stiffness. Lateral radiographs evaluated alignment for the anterior constructs. Statistical analysis involved a one way analysis of variance (ANOVA) and a Student-Newman-Keuls post hoc test., Results: All reconstructions restored stiffness to intact values with the exception of the dowels alone in axial rotation. The rod/dowel construct was stiffer than all other groups in axial compression, flexion/extension, and lateral bending, with the exception of the posterior rod without discectomy, which was superior in flexion and statistically similar in extension, lateral bending, and axial rotation. The anterior construct with rib graft was equivalent to the posterior construct with rib graft in all modes of testing. The dowels created greater lordosis than the bicortical rib grafts., Conclusions: Disc space augmentation increased stiffness except in axial rotation, in which values were restored to the intact level. Stiffness was superior to a clinically relevant posterior instrumentation comparison group following anterior release, and was equivalent to a posterior construct without anterior release except in anterior flexion. In addition, the implants enhanced lordosis. Increased rigidity should improve rates of arthrodesis, while maintenance of sagittal alignment may prevent pathologic compensatory curves in adjacent spinal segments. Further research is required to determine the optimal method of achieving structural interspace support.

Study Design: A basic science biomechanical study involving an animal model., Objectives: To evaluate the effect of varying angles of halo pin insertion on the force generated at the pin-bone interface, and thereby the stability of the halo pin-bone interaction during insertion., Background Data: Because of variations in the shape and size of the pediatric skull, halo pins often are inserted at various angles rather than perpendicular to the skull. Concern exists that the high complication rate associated with pediatric halo use may result in part from less than ideal structural properties at the halo pin-bone interface., Methods: The authors used a fetal calf skull model to simulate the thickness and structural properties of the pediatric skull. Halo pins were inserted at angles of 0 degree (perpendicular), 10 degrees, 15 degrees, and 30 degrees into skull segments via a halo ring. Load generated at the pin-bone interface was measured using a modified mechanical testing device. Twenty trials were conducted per angle, with the endpoint being specimen failure, pin penetration, or maximum load., Results: Mean maximum loads per unit thickness were 82.15 +/- 7.54 N/mm at 0 degree, 68.80 +/- 4.79 N/mm at 10 degrees, 51.49 +/- 5.08 N/mm at 15 degrees, and 42.38 +/- 3.51 N/mm at 30 degrees, There was a significant difference between perpendicular insertion (0 degree) and 15 degrees angles of insertion. There was also a significant difference between the 10 degrees and 30 degrees angles of insertion., Conclusions: Perpendicular halo pin insertion in an immature skull model was shown to result in increased load at the pin-bone interface. This improved structural behavior may help to reduce the incidence of complications of halo application in children.