Mouse model for thoracic congenital scoliosis.

SUMMARY: This study sought to produce a dose-response curve for acute and chronic maternal carbon monoxide (CO) exposure versus vertebral anomalies in mouse offspring and to determine the critical day of exposure. In Part I, pregnant CD-1 mice were exposed to an acute dose of CO at 9 days of gestation. A positive dose-response relationship of acute maternal CO exposure and vertebral anomalies in the offspring was produced. In Part II, pregnant females were exposed to chronic CO for the first 11 days of gestation. Chronic exposure to CO did not produce significant vertebral anomalies. In Part III, pregnant females were exposed to an acute dose of 600 ppm of CO at gestation day 8, 9, or 10. Day 9 in this mouse breed is the critical day for maternal exposure to CO. The detected anomalies were predominately in the thoracic spine.

The induction of congenital spinal deformities in mice by maternal carbon monoxide exposure.

Carbon monoxide (CO) has been shown to be teratogenic in mice. High altitude hypoxia has also been shown to induce congenital vertebral anomalies in mice. The purpose of this study was to investigate the effect of maternal hypoxia owing to CO exposure and the production of congenital spinal deformities in the offspring. Sixty DBA-1J mice were bred using polygamous timed breeding methods. Pregnant females were exposed to 200, 400, or 600 ppm CO using a custom-designed gas blender system. Seven-hour exposures were performed on day 8.5, 9.5, or 10.5 of the 21-day gestation cycle. The neonates were euthanized at birth; the specimens were fixed, eviscerated, and radiographed. Congenital spinal deformities were observed (wedge, hemi, fused, and missing vertebrae; fused ribs) and were located in all regions of the spine. There was a statistically significant difference in the number of spinal deformities between all groups, with no defects in the controls and a 77% incidence at 600 ppm (p < 0.0001). There was no apparent correlation between the time of exposure and defect location. The most sensitive time of gestation was 9.5 days. We identified an animal model of congenital spinal deformities that compares favorably with the evidence of human congenital spinal deformities in cases of maternal exposure to CO and other gas and chemical fumes.

Hip arthroscopy using a limited anterior exposure: an alternative approach for arthroscopic access.

SUMMARY: Hip arthroscopy is a technically difficult procedure to perform. A limited anterior approach to the joint has made hip arthroscopy technically less difficult in our hands and has enabled us to treat a wide range of hip pathology. Five hip arthroscopies were performed using a modified 4-cm Smith-Petersen anterior approach to the hip exposing the joint capsule as manual traction is applied. The arthroscope is then easily introduced making visualization of the hip joint possible. The 5 hip arthroscopies resulted in either removal of loose bodies or debridement of an osteochondral fragment, synovitis, or cartilaginous debris. There were no complications postoperatively. We believe that hip arthroscopy through a limited anterior approach provides an easy and safe alternative method for arthroscopic access to the hip joint. Importantly, there is a decreased risk of neurovascular trauma and iatrogenic damage to the articular cartilage and acetabular labrum when introducing instruments into the hip joint.

The predictive value of computed tomography in the treatment of developmental dysplasia of the hip.

The use of computed tomography (CT) to confirm femoral head position after closed reduction and spica cast immobilization in the treatment of developmental dysplasia of the hip (DDH) has become a common practice. We retrospectively reviewed postreduction CT scans of 38 children younger than 24 months of age with unilateral DDH to determine whether they could predict acetabular remodeling potential. The measurements analyzed from the postreduction CT scans were the acetabular index, axial acetabular index, anterior and posterior acetabular angles, acetabular anteversion, and axial reduction index; the standard acetabular index was measured from the plain radiographs. The average age at reduction was 11 months and at follow-up was 61 months. No angle measured on the postreduction CT scan was found to be predictive of acetabular remodeling.

Nuchal cord changes in children with os odontoideum: evidence for associated trauma.

We describe nuchal cord changes in four children with os odontoideum who had cervical spine magnetic resonance imaging (MRI) before surgery. In these four children, nuchal cord changes consistent with previous trauma were seen. The presence of the nuchal cord changes supports the concept of trauma as an etiologic factor in these four cases. This study supports trauma as an associated factor in patients with os odontoideum.

Slipped capital femoral epiphysis associated with radiation therapy.

We reviewed 32 children with 41 radiation-therapy associated slipped capital femoral epiphyses (RTASCFE). Ten were from the authors' institutions and 22 from the literature. Gender distribution was equal. The age at diagnosis of the malignancy was 4.3 +/- 3.1 years; the amount of radiation was 4,240 +/- 1,445 rads. Children with RTASCFE presented younger (10.4 +/- 3.2 years) than a routine SCFE. The average symptom duration was 5 +/- 6 months. Children with RTASCFE are usually thin (median weight, 10th percentile) in contrast to children with typical SCFE, who are usually obese (<95th percentile). The majority (82%) of the slips were mild, compared to routine SCFEs (approximately 50%); 28% were bilateral. There was a positive linear relationship between the age at presentation of the SCFE and the age at diagnosis of the malignancy; there was a negative linear relationship between the age at presentation of the SCFE and the amount of radiation therapy.

Muscle and tendon size relationships in a paralyzed chick embryo model of clubfoot.

Clubfoot is a birth defect that may be related to muscle weakness or imbalance. The purpose of this study was to examine the relationships among muscle and tendon size and embryonic motility in a paralyzed chick embryo model of clubfoot and arthrogryposis. Decamethonium bromide, a neuromuscular blocking agent, was administered to a series of embryos in five dosage groups, producing a cohort of embryos with various degrees of paralysis and atrophy of tendons and muscle. Embryonic movement frequency was monitored, and after death in late gestation, the cross-sectional areas of the calf musculature and the gastrocnemius tendon proximal to the ankle were measured histologically. Significant correlations were found between embryonic motility and both muscle (r2 = 0.52) and tendon (r2 = 0.77) areas. In addition, a significant correlation (r2 = 0.74) was found between muscle and tendon areas, suggesting that a measurement of one may be used to predict the other.

Telescoping intramedullary rodding with Bailey-Dubow nails for recurrent pathologic fractures in children without osteogenesis imperfecta.

We reviewed four children with multiple, recurrent, pathologic fractures caused by bone disease, excluding osteogenesis imperfecta, and in whom multiple osteotomies with telescoping intramedullary stabilization had been performed. The diagnoses were myelomeningocele in two children and Rett syndrome and fibrous dysplasia in one child each. Five long bones were stabilized; four femora and one tibia. The average age at surgery was 6 years 6 months; the average number of fractures that had occurred in the involved bone before surgery was 3.0 per bone. At an average follow-up of 2 years 4 months, the average number of fractures that had occurred after surgery in the stabilized bones was 0.2 per bone. There were no infections, nonunions, or rod complications. We believe that in the carefully selected patient, multiple osteotomies with intramedullary telescoping rod stabilization can be quite successful in solving the problem of recurrent fractures in children with diseases other than osteogenesis imperfecta.

Slipped capital femoral epiphysis associated with renal failure osteodystrophy.

A retrospective institutional and literature review of 31 children (20 boys and 11 girls) with 58 renal failure-associated slipped capital femoral epiphyses (RFASCFEs) was performed. The average age at diagnosis of renal failure was 8.9 years, and for RFASCFE 11.5 years, with a linear correlation between these two ages. All patients had secondary hyperparathyroidism at diagnosis of the RFASCFE. The median height and weight were below the 5th percentile. The RFASCFEs were stable and bilateral in 95% of the children. Slip magnitude was mild in 53%, moderate in 8%, and severe in 39%. Avascular necrosis was associated with steroid immunosuppression in children with renal transplants. All children were treated with medical management; surgery was used in an additional 29 hips. If correction of secondary hyperparathyroidism is not achieved within 2 months, RFASCFEs are likely to progress and surgical stabilization is recommended.

Role of intentional abuse in children 1 to 5 years old with isolated femoral shaft fractures.

We reviewed 42 children, aged 1-5 years, with isolated femoral shaft fractures to investigate the possible role of intentional injury in these children. Those children with documented motor vehicle accidents or pathologic fractures were excluded. Follow-up from the Department of Social Services regarding the potential for the fractures being inflicted was obtained. The average age of the children was 3.1 +/- 1.2 years; the fracture was spiral in 28. oblique in six, and transverse in eight; history of a fall was present in 34 and absent in eight. The history was considered suspicious for intentional injury in 14 children. In all 42 children, only one fracture was documented to be inflicted; one other child had prior documentation of intentional injury. From this review, the likelihood of intentional injury to the femoral shaft appears to be low; unfortunately, there were no discriminating clinical parameters to help to determine which injuries were intentional. The clinician should continue to have a high index of suspicion and have the circumstances investigated if concern exists regarding the fracture.

Lower extremity lawn-mower injuries in children.

Lower extremity lawn-mower injuries in children result in significant morbidity with a significant financial burden to the family and society. We reviewed 24 children with lower extremity lawn-mower injuries; all mothers completed standardized psychologic assessments of their children, and 18 children were interviewed. Fifty percent of the mothers had defensive profiles on the standardized psychologic assessment, suggesting the likelihood of denial or underreporting of the child's psychologic difficulties. Therefore, we found the interview with the child to be a more accurate measure of psychologic distress. Prevention measures aimed at parents must emphasize that a child must not be allowed in a yard that is being mowed with a riding mower.

The role of melatonin in the pathogenesis of adolescent idiopathic scoliosis.

STUDY DESIGN: A matched, case-control study comparing melatonin production in female patients with and without adolescent idiopathic scoliosis. OBJECTIVES: To determine whether melatonin production is decreased in adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: A central etiology for idiopathic scoliosis has never been established. Previous authors have produced experimental scoliosis in chickens after pinealectomy, preventable by administration of melatonin. They suggested that a defect in melatonin synthesis might be involved in the pathogenesis of human idiopathic scoliosis. METHODS: Nine female adolescents with no medical problems, normal neurologic examinations, radiographic idiopathic scoliosis of 15-40 degrees, and Risser Stage I-III were in the patient group. Eighteen healthy adolescent girls with no medical problems, a negative school screening, and no family history of scoliosis were control subjects. Patients and control subjects were matched for age, weight, Tanner stage, sleep duration, and light exposure by multiple linear regression. Nighttime and daytime urine samples were analyzed for melatonin by high-performance liquid chromatography. RESULTS: Although nighttime melatonin levels were significantly higher than daytime levels in all volunteers (P < 0.00002), there were no significant differences in nighttime (P > 0.63) or daytime (P > 0.78) melatonin levels between patients and control subjects, even after matching by multiple linear regression analysis. A statistical analysis demonstrated that if a melatonin deficiency of 25% or more did exist in patients with scoliosis compared with control subjects, the likelihood that it would have been detected in this study was more than 98%. CONCLUSION: Although melatonin deficiency may cause scoliosis in the chicken, this study suggests that it is not a mechanism in the pathogenesis of adolescent idiopathic scoliosis in humans.