Stephen J. Tredwell

The genotype–phenotype correlation of hereditary multiple exostoses

Hereditary multiple exostoses (HME) is an autosomal dominant condition with a wide spectrum of clinical presentations. The purpose of this study was to determine the relationship between the genotype and the phenotype in HME. Thirty‐two affected individuals from 10 families participated in the study. An extensive description of HME phenotype in terms of the anatomical burden of disease involved clinical and radiographic examinations and evaluation of 76 parameters. Mutations were determined by sequencing the EXT 1 and EXT 2 genes. Mutations were found in eight families (26 individuals), with one mutation previously reported in the literature and seven novel mutations. There were seven subjects with an EXT 1 mutation and 16 with an EXT 2 mutation. Patients with EXT 1 mutation were found to have more exostoses, more limb malalignment with shorter limb segments and height, and more pelvic and flatbone involvement. A genotype–phenotype correlation exists in HME, with patients with EXT 1 mutations having a higher degree of anatomical burden.

Treatment of idiopathic clubfoot utilizing botulinum A toxin: a new method and its short-term outcomes.

A pivotal point in most clubfoot management protocols is Achilles tendon lengthening or tenotomy to address hindfoot deformity. The effectiveness of botulinum A toxin (BTX-A) in attenuating the function of the triceps surae muscle complex as an alternative to tenotomy was investigated. Fifty-one patients with 73 idiopathic clubfeet were recruited. Outcome measures included surgical rate, Pirani clubfoot score, ankle dorsiflexion with knee in flexion and extension, and recurrences. Patients were divided according to age: group 1 (<30 days old) and group 2 (>30 days and <8 months old). Ankle dorsiflexion in knee flexion and extension remained above 20 degrees and 15 degrees, respectively, and Pirani scores below 0.5 following BTX-A injection for both groups. One of the 51 patients required limited posterior release and 9 patients required repeat manipulation and casting plus or minus BTX-A injection. The use of BTX-A as an adjunctive therapy in the noninvasive approach of manipulation and casting in idiopathic clubfoot is a safe and effective treatment.

Cervical Spine Anomalies in Fetal Alcohol Syndrome

Fifty cases of well-documented fetal alcohol syndrome were reviewed with the intent of describing the cervical vertebral anomalies. Thirty-eight cases had adequately detailed x-ray examination to be included in this study. Of these, 19 or 53% showed congenital fusion of two or more cervical vertebrae. The associated findings were minor anomalies on the intravenous pyelogram (IVP) in three of 18 IVPs done, mild to moderate microcephaly in 53%, and significant congenital heart anomalies in 41%. Although the vertebral anomalies bear a resemblance to the Klippel Feil syndrome, it is thought that the two syndromes are separate. The patterns of occurrence of the vertebral anomalies are different in the two groups, and the visceral expression of the disorder is also different. The major visceral anomaly in the Klippel Feil syndrome being in the genitourinary system and in the fetal alcohol syndrome being in the cardiovascular system. The patterns, however, are close enough to imply teratogenic event as the etiology in the Klippel Feil group. The occurrence of neck fusion in the fetal alcohol syndrome is common enough for it to be used in making the diagnosis.

Clinical usefulness of somatosensory evoked potentials for detection of brachial plexopathy secondary to malpositioning in scoliosis surgery.

Study Design. A retrospective longitudinal study of 434 consecutive pediatric patients who underwent surgical correction of scoliosis, while being monitored for positional brachial plexopathy. Objective. To evaluate the effectiveness of intermittent monitoring of ulnar nerve somatosensory evoked potentials (SSEPs) for detecting brachial plexus injury caused by malpositioning during scoliosis surgery. Summary of Background Data. Continuous intraoperative SSEP monitoring for spinal cord function has been well reported, and is widely accepted as the standard for spinal deformity correction surgery to detect and avoid neurologic injury. The use of SSEPs for the monitoring of ulnar nerve function intraoperatively as an indicator of brachial plexus function is becoming more accepted as a valid and useful technique to minimize intraoperative neurologic injuries during deformity corrections. Methods. A review was conducted to assess the effect of ulnar nerve SSEP monitoring, as a measure of brachial plexus function, during anterior, posterior, or combined approach surgeries. The type of scoliosis, type of surgery and positioning, and surgical event at noted amplitude decrease were included in an analysis of variance for repeated measures, and a Student t test was performed for significant differences. Results. A total of 27 patients had ulnar nerve amplitude decreases of ≥30%, resulting in a point prevalence of 6.2% for positional brachial plexopathy during positioning for all scoliosis surgeries. A significant difference was noted between the types of positioning, with prone positioning accounting for a higher rate of brachial plexopathy compared with anterior approach positioning (P < 0.01). No statistical difference exists as to the type of scoliosis present and the incidence of brachial plexopathy (P < 0.01). Conclusions. Avoidance of neurologic injury to the brachial plexus during scoliosis surgery is possible by early detection with ulnar nerve SSEP monitoring.

The mutant guppy syndrome Curveback as a model for human heritable spinal curvature

Study Design. This study investigated the morphology, pathogenesis, and inheritance of idiopathic-like spinal curvature in the guppy syndrome, curveback. Objective. To determine whether curveback could be applied as a model for the primary factors that contribute to heritable spinal curvature in humans, specifically, the etiopathogenesis of human familial idiopathic scoliosis. Summary of Background Data. Although a genetic basis is accepted, phenotypic complexity and the lack of an animal model with noninduced curvature have made identification of idiopathic scoliosis etiology difficult. It is well established that humans and fish share many genes with similar tissue and temporal expression characteristics, and comparisons between human and fish genomes have proven to be valuable for understanding the genetics of diseases affecting humans. Methods. The curveback lineage of guppies was constructed from a single curved male crossed to a normal female. Offspring (103) from the original cross were scored from birth until death for the presence and magnitude of spinal curvature. Genetic architecture was investigated through selective inbreeding, analysis of the distribution of curve magnitude in the mature population, and assessment of curve dynamics during development. Computed tomography assessed vertebral detail. Results. Computed tomography reveals that vertebral breakage or fusion is not associated with the curveback syndrome. Inbreeding demonstrates a strong genetic influence on curveback, and the distribution of curve magnitude among adult fish suggests polygenic inheritance. There is a female bias for curves of high magnitude and curves that resolve before maturity. There is developmental variability for the age of curve onset, curve progression, and final curve magnitude. Conclusions. Observed parallels between the curveback syndrome and human idiopathic scoliosis suggest that the guppy model is an unexploited resource for the identification of primary etiological factors involved in curvature. As models for biomedical research, teleosts offer great potential regarding spinal stability and deformity.

The effect of interbody cage positioning on lumbosacral vertebral endplate failure in compression.

Study Design. A biomechanical investigation using a human cadaver, multisegmental lumbosacral spine model. Objectives. To determine if 2 small, posterolaterally positioned titanium mesh interbody cages would provide superior construct strength and stiffness in compression compared to central cage placement. In addition, determine construct stiffness with interbody cages as opposed to an intact spine and assess the effect of bone mineral density (BMD). Summary of Background Data. Previous work has shown that the posterolateral corners of the lumbosacral endplates are stronger than the anterior and central regions. Information to suggest appropriate interbody cage positioning to avoid subsidence into adjacent vertebrae would be valuable for spine surgeons and implant designers. Methods. A total of 27 functional spinal units from L3 to S1 were dual x-ray absorptiometry scanned for BMD, instrumented with pedicle screw systems, and tested to failure in compression with titanium mesh interbody cages placed in 1 of 3 positions: 2 small posterolateral, 2 small central, or 1 large central. Analysis of covariance was conducted to compare failure load and stiffness across the different cage configurations. Repeated measures analysis of variance was used to analyze stiffness between functional spinal units with intact disc, discectomy, or interbody cages. Failure load was correlated against BMD. Results. Of the 3 placement patterns, 2 small titanium mesh cages in the posterolateral corners had 20% higher failure loads, although the difference was not significant (P = 0.20). Stiffness in compression for the 3 cage positions was not significantly different (P = 0.82). All intact discs with posterior instrumentation were significantly stiffer than any of the cage patterns (P = 0.0001). BMD of the vertebrae significantly correlated with failure loads (P = 0.007). Conclusions. The placement of 2 small interbody cages posterolaterally tended to result in higher failure loads than central cage placement, although the results were not statistically significant. It is noteworthy that cage placement in any position resulted in a less stiff construct in compression than with an intact disc.

Pediatric tourniquets: analysis of cuff and limb interface, current practice, and guidelines for use.

There are few clear guidelines on the proper use of tourniquets in pediatric surgery, in particular on how to set the tourniquet pressure, how to select the most appropriate cuff, and whether to use some type of soft padding beneath the cuff for limb protection. The authors could find only one published study specifically addressing pediatric cuff pressures, and no studies showing what types of cuff and/or padding create the smoothest skin surface under the cuff. Of 46 pediatric orthopaedic surgeons surveyed, 44 use a tourniquet 4.6 times per week on average and 2 have discontinued their use as a result of complications. To set cuff pressure, 13 of 44 use a standard value, 14 of 44 base pressure on age, extremity, and size, and 17 of 44 base cuff pressure on blood pressure. Thirty-four of 44 use skin protection under the cuff, but damage to the skin is common, accounting for 21 of the 67 reported complications. Nerve (15/67) and muscle (8/67) complications, related to both pressure and tourniquet time, were also reported. Using a molding and digital measurement technique, the authors compared the maximum wrinkle heights and the sums of all wrinkle heights in the skin surface under four different cuff/padding configurations. In a total of 44 trials on the upper arms and thighs of two healthy child volunteers, one type of pediatric cuff with a matching limb-protection sleeve designed and recommended by the manufacturer (Delfi) produced significantly fewer, less severe pinches and wrinkles in the skin surface than a second type of tourniquet cuff (Zimmer) with or without two layers of commonly available cast padding, and a third type (Kidde) with padding. With the second type of cuff, using cast padding reduced skin wrinkling compared to applying the same cuff on unprotected skin. In view of the survey, clinical literature, and results of this study, a guideline for use of pediatric tourniquets is proposed.

The Epidemiology of Nonaccidental Trauma in Children

BackgroundAbuse of children is abhorrent in Western society and, yet, is not uncommon. Nonaccidental trauma (NAT) is the result of a complex sociopathology. Not all of the causative factors of NAT are known, many are incompletely described, not all function in each case, and many are secondary to preexisting pathology in other areas.Questions/purposesWe therefore addressed the following questions in this review: (1) what is the general incidence of NAT; (2) what factors are intrinsic to the abused child, family, and society; and (3) what orthopaedic injuries are common in NAT?MethodsWe searched Medline, Medline In Process & Other Non-Indexed Citations, and Embase using OVID. Only one article fit our inclusion criteria; therefore, this is a descriptive generalized review of the epidemiology of NAT.ResultsThe general incidence of NAT ranges from 0.47 per 100,000 to 2000 per 100,000. Younger children are at greater risk of NAT than older children. Parents are often the perpetrators of the abuse. Rib fractures are highly indicative of NAT in young children.ConclusionsIt is important to consider child, family, and societal factors when confronted with suspicions of child abuse. Our review demonstrates the currently limited information on the true incidence of NAT. To determine a much more accurate incidence of NAT, there needs to be a population-based surveillance program conducted through primary care providers.

Pediatric lumbar Chance fractures in British Columbia: chart review and analysis of the use of shoulder restraints in MVAs.

Chance fractures of the skeletally immature spine classically occur in frontal motor vehicle accidents (MVAs) when the occupants are restrained by a lap belt only and undergo traumatic hyperflexion of the torso during the impact. We retrospectively examined all MVA-related Chance fractures at British Columbias Childrens Hospital since 1986, by collecting injury and seat-belt use information from chart data and imaging studies. Twenty-six patients were included in the study, 14 wore a lap belt only, seven wore a three-point restraint properly, and five were reportedly misusing the shoulder portion of a three-point restraint. The subjects ranged in age from 3 to 16 with a mean age of 10.6 years. Eleven of the 26 (42%) patients sustained abdominal viscera injuries, seven of the 26 patients suffered neurologic injury (spinal cord and/or spinal nerve injury) associated with their spinal fracture, with two cases of complete paralysis, and there was a 38% incidence of head injury. Concomitant injuries (i.e. to the head, abdomen and abdominal contents) tended to be mitigated by the presence of a properly worn shoulder restraint. This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.

Effects of Three-dimensional Assessment on Surgical Correction and on Hook Strategies in Multi-hook Instrumentation for Adolescent Idiopathic Scoliosis

Study Design. A prospective study using intraoperative stereophotogrammetry to analyze change during the correction of scoliosis. Objective. To examine the relation between the number of hooks used during segmental instrumentation and the amount of correction achieved. Summary of Background Data. An intraoperative stereophotogrammetric technique was developed at our center. Vertebral translations and rotations can be measured at several stages during scoliosis surgery. Methods. Thirty‐two patients with right thoracic adolescent idiopathic scoliosis were studied using our stereophotogrammetry technique during surgical correction. Correlations were determined between apical vertebral movements and the hook ratio (number of vertebrae/number of hooks used). Results. Mean curve Cobb angle correction was 66%. Correction occurred in all three planes but primarily along the x and y axes. Scoliotic deformity was corrected by translation of the vertebra along the y axis and rotation about the x; physiologic kyphosis was restored by translation along the x axis and rotation about the y. The plane of maximum deformity as compared with the sagittal plane of the patient corrected from 57° to 25° as an indication of detorsion of the scoliotic deformity. Conclusions. Increasing the number of hooks per vertebral segment significantly enhances the correction of the coronal scoliotic deformity and enhances the z axis derotation, but does not significantly change the reestablishment of the kyphosis, nor does it result in significant elongation of the spine.