3D printed models can guide safe halo pin placement in patients with diastrophic dysplasia.

PURPOSE: To trial the use of three-dimensional (3D) printed skull models to guide safe pin placement in two patients with diastrophic dysplasia (DTD) requiring prolonged pre-fusion halo-gravity traction (HGT). METHODS: Two sisters aged 8 (ML) and 4 (BL) with DTD were planned for staged fusion for progressive kyphoscoliosis. Both sisters were admitted for pre-fusion HGT. Models of their skulls were generated from computer tomography (CT) scans using Mimics Innovation Suite and printed on a Guider II in polylactic acid. The 3D models were cut axially proximal to the skull equator, in-line where pins are usually inserted, allowing identification of the thickest skull portion to guide pin placement. RESULTS: Eight pins were inserted into each patient's skull. Postoperative CT scans demonstrated adequate pin position. Pre-traction Cobb angles were 122° and 128° for ML and BL, improving to 83° and 86° following traction. Duration of HGT was 182 and 238 days for ML and BL. Prior to fusion, both patients returned to theatre twice for exchange of loose pins and there was one incidence of pin site infection. Surgery was performed via a posterior instrumented fusion. Postoperatively, both patients remained in their halos for 3 months. One pin in BL was removed for loosening. Both patients achieved fusion union by 9 months. CONCLUSION: 3D models of the skull can be a useful tool to guide safe pin placement in patients with skeletal dysplasias, who require prolonged pre-fusion HGT for severe deformity correction.

Risk factors for postoperative pulmonary complications in children with severely compromised pulmonary function secondary to severe scoliosis.

OBJECTIVES: After corrective surgery for scoliosis, postoperative pulmonary complications lead to increases in morbidity, length of hospital stay (LOS) and mortality. This study aimed to identify associations with such respiratory complications, and to assess the utility of noninvasive ventilation (NIV) in children with severe scoliosis METHODS: This retrospective cohort study included all children aged ≤17 years who underwent spinal surgery for scoliosis between January 2009 and January 2012 at a quaternary pediatric hospital. Data were collated regarding polysomnography (PSG) and NIV use, before and after corrective surgery. Factors associated with severely compromised pulmonary function (SCPF) were established and correlations with the occurrence of postoperative pulmonary complications and LOS were identified. RESULTS: Altogether, 133 children had corrective surgery for scoliosis, aged 12.7 (range: 2-17) years at operation. Scoliosis causes were identified as: idiopathic (39.8%), neuromuscular disease (32.2%), syndrome (15.7%), and congenital (12%). Correlates with SCPF (forced vital capacity [FVC] <40% predicted, n = 10) included markers of sleep hypoventilation, including serum bicarbonate ≥29 mmol/L, morning pCO2 > 50mm Hg (P = .003), and overnight, episodic CO2 retention of >7 mm Hg. Using these parameters an additional eight children with SCPF were identified making a total of 18 out of 133 (13.5%) of the patients. Postoperative pulmonary complications were seen in 24 children (18%) and their occurrence correlated with higher Cobb angle (>90°), lower pulmonary function (FVC), higher serum bicarbonate and underlying neuromuscular disease. Amongst the 18 children with SCPF, regular use of NIV preoperatively was associated with reduced rate of postoperative pulmonary complications (P = .02) and reduced LOS by 6.4 days (P = .01). CONCLUSION: Nocturnal hypoventilation on PSG identifies children with SCPF. Use of NIV in children with SCPF was linked to fewer postoperative pulmonary complications and reduced duration of hospital stay.

The Natural History of Scoliosis in Females With Rett Syndrome.

STUDY DESIGN: Population-based longitudinal observational study. OBJECTIVE: To describe the prevalence of scoliosis in Rett syndrome, structural characteristics and progression, taking into account the influences of age, genotype, and ambulatory status. SUMMARY OF BACKGROUND DATA: Scoliosis is the most common orthopedic comorbidity in Rett syndrome yet very little is known about its natural history and influencing factors such as age, genotype, and ambulatory status. METHODS: The infrastructure of the Australian Rett Syndrome Database was used to identify all cases with confirmed Rett syndrome in Australia and collect data on genotype and walking status. We identified radiological records and described the Cobb angle of each curve. Time to event analysis was used to estimate the median age of onset of scoliosis and the log-rank test to compare by mutation type. Latent class group analysis was used to identify groups for the trajectory of walking status over time and a multilevel linear model used to assess trajectories of scoliosis development by mutation type and walking status. We used a logistic regression model to estimate the probability of developing a scoliosis with a Cobb angle >60° at 16 years in relation to Cobb angle and walking status at 10 years of age. RESULTS: The median age of scoliosis onset was 11 years with earliest onset in those with a p.Arg255 mutation or large deletion. Scoliosis was progressive for all mutation types except for those with the p.Arg306Cys mutation. Scoliosis progression was reduced when there was capacity to walk independently or with assistance. Cobb angle and walking ability at age 10 can be reliably used to identify those who will develop a very severe scoliosis by age 16. CONCLUSION: These data on prognosis of scoliosis inform clinical decision making about the likelihood of progression to very severe scoliosis and the need for surgical management. LEVEL OF EVIDENCE: 4.

Zoledronic acid improves bone mineral density, reduces bone turnover and improves skeletal architecture over 2 years of treatment in children with secondary osteoporosis.

There are limited data on the use of bisphosphonate therapy for secondary osteoporoses in childhood, and no previous reports of the use of zoledronic acid in this group. We report 20 children with a variety of underlying primary diagnoses with associated secondary osteoporosis, who were treated with 3 monthly zoledronic acid for 2 years (annualised dose 0.1mg/kg/year). There was a significant improvement in lumbar spine (by 1.88 SD±1.24 over first 12 months, p<0.001) and total bone mineral density as assessed by dual energy absorptiometry (DXA) scans, with a similar increase in bone mineral content for lean tissue mass (mean increase 1.34 SD in first 12 months, p<0.001). Bone turnover was reduced with a suppression of both osteocalcin and alkaline phosphatase in the first 12 months of treatment. Skeletal architecture was improved, with increased second metacarpal cortical thickness from 2.44mm to 2.72mm (p<0.001) and improved vertebral morphometry, with 7 patients who had vertebral wedging at baseline showing improved anterior (p=0.017) and middle (p=0.001) vertebral height ratios. Aside from well reported transient side effects with the first dose, there were no adverse effects reported. No adverse effects on anthropometric parameters were seen over the course of the study. Despite all patients having sustained fragility fractures prior to treatment, no fractures were reported during the study period. Further evidence is required to confirm efficacy, with long term follow up required to assess the impact of treatment on fracture risk.

Atlantoaxial and craniocervical arthrodesis in children: a tomographic study comparing suitability of C2 pedicles and C2 laminae for screw fixation.

STUDY DESIGN: Analysis of C1-C2 tomographic anatomy in a cohort of healthy children. OBJECTIVE: Compare suitability of C2 laminae and C2 pedicles for screw placement. SUMMARY OF BACKGROUND DATA: Surgeons have applied several techniques for craniocervical and atlantoaxial spondylodesis to address congenital or developmental abnormalities in children. Constructs with pedicle or transarticular screws are effective to stabilize the craniocervical junction; however, these fixation points are not suitable in all patients. Translaminar screw placement in C2 has been safely performed in children; yet, suitability of C2 laminae and C2 pedicles has not been systematically compared. METHODS: Applying chi2 test, we compared suitability for screw placement in 46 C2 pedicles and 46 C2 laminae on digital images of axial reconstructions of cervical CT scans of 23 children who had been admitted to the same hospital due to head or neck injury. On the same scans, we estimated suitability for screw placement in 46 lateral masses of C1. RESULTS: Twenty-four percent of C2 pedicles and 65% of C2 laminae were deemed suitable for 3.5-mm screw placement, and the difference was statistically significant (P < or = 0.0001, chi2 15.88). Forty-one percent of C2 pedicles and 80% of C2 laminae were deemed suitable for 3.0-mm screw placement, and the difference was statistically significant (P < or = 0.0001, chi2 14.78). Ninety-five percent of C1 lateral masses were deemed suitable for 3.5-mm screw placement. CONCLUSION: C2 laminae represent a viable fixation point for C1-C2 and craniocervical arthrodesis in children. This information can be useful for preoperative planning.