James Harder

Bone mineral density during puberty in western Canadian children.

To assess the influence of puberty and its associated changes in body weight and height on bone mineral density (BMD), lumbar spine (L2-L4) and femoral neck BMD were measured in 74 healthy, active children (9-16 years) using dual-photon absorptiometry. Competitive swimmers were recruited to minimize the potential effect variability in mechanical loading regime may have on bone density of the lumbar spine. Tanner staging was used to assess stage of puberty. Current dietary calcium intake was assessed by analysis of 6-day dietary records. Significant differences in spinal and femoral neck BMD occurred between early (Tanner 1 and 2) and late stages of puberty (Tanner 4 and 5), P < 0.05. A significant correlation was found between bone density and dietary calcium intake. However stepwise regression analyses demonstrated stage of puberty or body weight were the only factors which significantly affected spinal BMD, accounting for 77% and 68% of the variability respectively; while at the femoral neck, body weight accounted for 52% of the variability. These results demonstrate that when potential interacting factors are controlled for through regression analyses, differences in BMD occur mainly as a function of puberty and the associated gains in body weight.

Perioperative blood transfusion requirements in pediatric scoliosis surgery: The efficacy of tranexamic acid

Background: Previous studies have noted that the use of antifibrinolytic medications can help reduce blood loss and transfusion requirements during cardiac, total joint arthroplasty, and spine surgery. Tranexamic acid (TXA) has been investigated in these patient groups but consensus with respect to the dosing regimen has not been achieved, especially in the pediatric scoliosis literature. The purpose of this study was to compare the effects of 2 TXA dosing regimens on reducing transfusion requirements. Methods: A retrospective chart review was performed on all idiopathic scoliosis patients undergoing posterior spinal instrumentation and fusion from 2005 to 2006 to determine total perioperative transfusion requirements. Transfusion requirements for those patients receiving either a low (10 mg/kg loading, 1 mg/kg/h infusion) or high (20 mg/kg loading, 10 mg/kg/h infusion) dose of TXA were compared. Results: High-dose TXA (n = 11) showed a trend toward a reduction in transfusion requirements compared with the low dose (n = 15) for idiopathic scoliosis patients undergoing posterior only instrumentation and fusion (687.9 ± 778.1 mL vs 1372.6 ± 1077.3 mL; P = 0.07; 95% confidence interval for the mean difference, −66.3 mL to 1435.7 mL). Although substantial, this difference was underpowered to show a difference. Conclusions: The use of the higher dose of TXA resulted in a 50% reduction in transfusion requirements for idiopathic scoliosis patients. Given previous studies, there appears to be a dose-response effect. A prospective dose-ranging study is now required to determine the optimal dose for pediatric patients with idiopathic scoliosis. Level of Evidence: III, retrospective cohort study.

Indices of torso asymmetry related to spinal deformity in scoliosis.

OBJECTIVE To develop indices that quantify 360 degrees torso surface asymmetry sufficiently well to estimate the Cobb angle of scoliotic spinal deformity within the clinically important 5-10 degrees range. DESIGN Prospective study in 48 consecutive adolescent scoliosis patients (Cobb angles 10-71 degrees ). BACKGROUND Scoliotic surface asymmetry has been quantified on the back surface by indices such as back surface rotation (BSR) and curvature of the spinous process line and torso centroid line, though with limited success in spinal deformity estimation. Quantification of 360 degrees torso shape may enhance surface-spine correlation and permit reduced use of harmful X-rays in scoliosis. METHODS For each patient a 3D torso surface model was generated concurrently with postero-anterior X-rays. We computed indices describing principal axis orientation, back surface rotation, and asymmetry of the torso centroid line, left and right half-areas and the spinous process line. We calculated correlations of each index to the Cobb angle and used stepwise regression to estimate the Cobb angle. RESULTS Several torso asymmetry indices correlated well to the Cobb angle (r up to 0.8). The Cobb angle was best estimated by age, rib hump and left-right variation in torso width in unbraced patients and by centroid lateral deviation in braced patients. A regression model estimated the Cobb angle from torso indices within 5 degrees in 65% of patients and 10 degrees in 88% (r=0.91, standard error=6.1 degrees ). CONCLUSION Consideration of 360 degrees torso surface data yielded indices that correlated well to the Cobb angle and estimated the Cobb angle within 10 degrees in 88% of cases. RELEVANCE The torso asymmetry indices developed here show a strong surface-spine relation in scoliosis, encouraging development of a model to detect scoliosis magnitude and progression from the surface shape with minimal X-ray radiation.

Deep wound infection following pediatric scoliosis surgery: incidence and analysis of risk factors

BACKGROUND Deep wound infection after spinal surgery is a severe complication that often requires prolonged medical and surgical management. It can compromise the outcome of the deformity correction, especially in patients requiring surgical intervention with subsequent removal of implants. Ascertaining the incidence and risk factors leading to infection may help to prevent this problem. METHODS We reviewed the hospital charts of all patients who underwent spinal deformity correction from 1996 to 2005. RESULTS In all, 227 patients were identified (139 idiopathic, 57 neuromuscular, 8 syndromic, 6 congenital, 17 other); 191 patients were treated with posterior instrumentation and fusion, 11 with anterior-only procedures and 24 with combined anterior and posterior procedures. Final follow-up ranged from 1 to 9.5 years. Infection developed in 14 patients. The overall incidence of infection was 6.2%. Drainage and back pain were the most common presenting symptoms. The incidence of infection was higher among patients with nonidiopathic diagnoses (risk ratio [RR] 8.65, p < 0.001). Use of allograft bone was associated with a higher rate of infection (RR 9.66, p < 0.001) even when stratified by diagnosis (nonidiopathic diagnoses, RR 7.6, p = 0.012). Higher volume of instrumentation was also a risk factor for infection (p = 0.022). Coagulase-negative Staphyloccocus was the most commonly identified organism, followed by Propionibacterium acnes and Pseudomonas. CONCLUSION Development of infection following scoliosis surgery was found to be associated with several risk factors, including a nonidiopathic diagnosis, the use of allograft and a higher volume of instrumentation. Preventative measures addressing these factors may decrease the rate of infection.

Estimation of spinal deformity in scoliosis from torso surface cross sections

Study Design. Correlation of torso scan and three-dimensional radiographic data in 65 scans of 40 subjects. Objectives. To assess whether full-torso surface laser scan images can be effectively used to estimate spinal deformity with the aid of an artificial neural network. Summary of Background Data. Quantification of torso surface asymmetry may aid diagnosis and monitoring of scoliosis and thereby minimize the use of radiographs. Artificial neural networks are computing tools designed to relate input and output data when the form of the relation is unknown. Methods. A three-dimensional torso scan taken concurrently with a pair of radiographs was used to generate an integrated three-dimensional model of the spine and torso surface. Sixty-five scan–radiograph pairs were generated during 18 months in 40 patients (Cobb angles 0–58°): 34 patients with adolescent idiopathic scoliosis and six with juvenile scoliosis. Sixteen (25%) were randomly selected for testing and the remainder (n = 49) used to train the artificial neural network. Contours were cut through the torso model at each vertebral level, and the line joining the centroids of area of the torso contours was generated. Lateral deviations and angles of curvature of this line, and the relative rotations of the principal axes of each contour were computed. Artificial neural network estimations of maximal computer Cobb angle were made. Results. Torso–spine correlations were generally weak (r < 0.5), although the range of torso rotation related moderately well to the maximal Cobb angle (r = 0.64). Deformity of the torso centroid line was minimal despite significant spinal deformity in the patients studied. Despite these limitations and the small data set, the artificial neural network estimated the maximal Cobb angle within 6° in 63% of the test data set and was able to distinguish a Cobb angle greater than 30° with a sensitivity of 1.0 and specificity of 0.75. Conclusions. Neural-network analysis of full-torso scan imaging shows promise to accurately estimate scoliotic spinal deformity in a variety of patients.

Reconstruction of laser-scanned 3D torso topography and stereoradiographical spine and rib-cage geometry in scoliosis

Assessments of scoliosis are routinely done by means of clinical examination and full spinal x-rays. Multiple exposure to ionization radiation, however, can be hazardous to the child and is costly. Here, we explain the use of a noninvasive imaging technique, based on laser optical scanning, for quantifying the three-dimensional (3D) trunk surface topography that can be used to estimate parameters of 3D deformity of the spine. The laser optical scanning system consisted of four BIRIS laser cameras mounted on a ring moving along a vertical axis, producing a topographical mapping of the entire torso. In conjunction with the laser scans, an accurate 3D reconstruction of the spine and rib cage were developed from the digitized x-ray images. Results from 14 scoliotic patients are reported. The digitized surfaces provided the foundation data to start studying concordance of trunk surface asymmetry and spinal shape in idiopathic scoliosis.

Femoral Fractures in Children Younger Than Three Years : The Role of Nonaccidental Injury

Background: Nonaccidental injury (NAI) in children is a major cause of morbidity and mortality, with fractures being the second most common presentation. The presence of a femur fracture has been reported to be suggestive of nonaccidental trauma in 30% to 60% of young children. The purpose of this study was to determine the percentage of NAI in children younger than 3 years presenting with a femur fracture to a single institution within a western Canadian population. Methods: A retrospective cohort study was performed for children younger than 3 years who presented to the Alberta Childrens Hospital during the years 1994 to 2005. The primary outcome variable was the percentage of NAI associated with femur fracture. Secondary outcome variables included patient demographics, injury characteristics, radiological and other workup, and suspicion of NAI. Results: The overall percentage of NAI was 11% (14/127 patients) and 17% (10/60 patients) in children younger than 12 months. Age younger than 12 months (P = 0.04), nonambulatory status (P = 0.004), delayed presentation (P = 0.002), mechanism of injury unwitnessed or inconsistent (P = 0.008), and other associated injuries (P = 0.006) were significant risk factors for NAI. Conclusions: Children younger than 3 years who present with femoral fracture are at risk for associated NAI, although perhaps this risk is not as high as previously thought. Regardless, a high index of suspicion is mandatory when these children are encountered, and careful screening with a thorough history, physical examination, and other investigations, where indicated, is warranted to rule out associated NAI. Level of Evidence: Retrospective cohort study, level IV.

Normative ground reaction force data for able-bodied and trans-tibial amputee children during running

The purpose of this investigation was to develop normative ground reaction force data for able-bodied (AB) and trans-tibial amputee (TTA) children during running. Two hundred AB (mean age 9.4 years, range 7–12) and 21 TTA (mean age 11.1 years, range 5–17) children ran (2.2 m/s±10%) over a force platform. Ground reaction force data were normalized, averaged within groups and plotted to produce force-time curves characterizing the different leg types (i.e. able-bodied, non-prosthetic and prosthetic). In addition, discrete variables characterizing the leg type differences were determined. One way ANOVA determined significant differences between variables and a TukeyB Post Hoc analysis defined which variables were significantly different (p < 0.05). Results generally indicated differences between the three leg types with the non-prosthetic leg indicating greater forces than the prosthetic and AB legs. The results of this investigation provide normative ground reaction force data for both AB and TTA children during running and can be used for comparison with other groups of children.

Genetic Algorithm–Neural Network Estimation of Cobb Angle from Torso Asymmetry in Scoliosis

Scoliosis severity, measured by the Cobb angle, was estimated by artificial neural network from indices of torso surface asymmetry using a genetic algorithm to select the optimal set of input torso indices. Estimates of the Cobb angle were accurate within 5 degrees in two-thirds, and within 10 degrees in six-sevenths, of a test set of 115 scans of 48 scoliosis patients, showing promise for future longitudinal studies to detect scoliosis progression without use of X-rays.

A CAD CAM method for custom below-knee sockets.

The purpose of this investigation was to develop a numerical method for fabricating prosthetic sockets for below-knee amputees. An opticalllaser digitiser scans an amputees stump and collects three dimensional numerical data describing the surface of the limb and describing specific modification site locations. The numerical data from the laser camera representing the stump and modification sites are altered by the prosthetist using a custom computer aided design software system running on a personal computer. Using the altered numerical data a programme is created for a high resolution numerically controlled milling machine and a mould is made. The prosthetist then fabricates a socket. While the system has been tested with below-knee amputees it has been designed for application in most areas of prosthetics and orthotics. Utilising this method 15 patients were fitted. All patients sujectively stated that their “computer designed” socket fitted better than their conventionally made socket. As the research progressed and experience was gained with the system patients were normally fitted with the first socket iteration. The system overcomes five limitations existing with some of the other numerical systems: 1) accurate high resolution surface topography, 2) specific identification of subject modification sites, 3) flexible, user friendly software, 4) high resolution numerically controlled milling, and 5) integrated expansion to other prosthetic and orthotic areas.