Molly Dempsey

Analysis of screw placement relative to the aorta and spinal canal following anterior instrumentation for thoracic idiopathic scoliosis

Study Design. Axial computed tomographic (CT) evaluation of the position of anterior vertebral body screws placed thoracoscopically in patients with adolescent idiopathic scoliosis (AIS). Objective. To evaluate the position of the anterior vertebral body screws relative to the spinal canal and the thoracic aorta following anterior spinal fusion and instrumentation for AIS. Summary of Background Data. Thoracoscopic anterior instrumentation and fusion is gaining more widespread use in the treatment of idiopathic scoliosis. However, the accuracy in the positioning of instrumentation has not been previously studied for this technically difficult surgery. Methods. CT examinations were performed following thoracoscopic anterior spinal fusion and instrumentation in 14 patients with right thoracic AIS. The vertebral body width (transverse dimension) and depth (anterior-posterior dimension) was measured for each thoracic vertebra. At each instrumented level, the position of the screw was analyzed to determine its proximity to the spinal canal and the aorta. The distance from the anterior cortex of the spinal canal to the posterior edge of the screw was measured. The position of each screw relative to the aorta was determined: D, the screw tip was distant to the aorta; A, the screw tip was adjacent to the aorta; C, the screw tip was felt to be against the aorta and creating some contour deformity on the outer wall of the aorta. Results. All 14 patients were female and had a single right thoracic curve. The average age of the patients was 13.3 years (range 12.4–15.1 years). The average preoperative coronal Cobb measurement was 55.9° (bending 26.4°) with correction to 8.9° at 2 years after surgery. The average number of levels fused was 6.6 (range 5–8) and a total of 106 screws were used (average 7.6/patient). The width of the vertebral bodies increased from T4 (24.0 mm) to T12 (33.6 mm), increasing an average of 1.2 mm per level, while the depth increased from 17.7 mm at T4 to 25.5 mm at T12. The average distance from the posterior aspect of the screw to the spinal canal was 5.3 mm (range−1.2 to 11.4 mm). There were no neurologic deficits in any patient. When analyzing the position of the screw tip relative to the aorta, 78 (73.6%) screws were distant from the aorta, 15 (14.2%) were adjacent to the aorta, and there were 13 (12.3%) screws that were thought to create a contour deformity of the aorta. There were no vascular complications at 2 years after surgery. Conclusions. Thoracoscopic instrumentation and fusion is technically demanding and relies on adequate visualization for accurate screw placement. The vertebral body width and depth are consistent between patients, with the vertebral body width increasing approximately 1.2 mm when progressing down the thoracic spine. Safe screw placement was achieved with adequate distance from the spinal canal; however, close screw proximity to the aorta was seen. The aorta was positioned on the left lateral aspect of the vertebral body in these patients, making anterior screw placement challenging in right thoracic AIS.

ACR Appropriateness Criteria® acute trauma to the knee

More than 500,000 visits to the emergency room occur annually in the United States, for acute knee trauma. Many of these are twisting injuries in young patients who can walk and bear weight, and emergent radiographs are not required. Several clinical decision rules have been devised that can considerably reduce the number of radiographs ordered without missing a clinically significant fracture. Although a fracture is seen on only 5% of emergency department knee radiographs, 86% of knee fractures result from blunt trauma. In patients with a fall or twisting injury who have focal tenderness, effusion, or inability to bear weight, radiographs should be the first imaging study obtained. If the radiograph shows no fracture, MRI is best for evaluating for a suspected meniscus or ligament tear, or the injuries from a reduced patellar dislocation. Patients with a knee dislocation should undergo radiographs and an MRI, as well as an angiographic study such as a fluoroscopic, CT, or MR angiogram. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures, by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

ACR Appropriateness Criteria Head Trauma—Child

Head trauma is a frequent indication for cranial imaging in children. CT is considered the first line of study for suspected intracranial injury because of its wide availability and rapid detection of acute hemorrhage. However, the majority of childhood head injuries occur without neurologic complications, and particular consideration should be given to the greater risks of ionizing radiation in young patients in the decision to use CT for those with mild head trauma. MRI can detect traumatic complications without radiation, but often requires sedation in children, owing to the examination length and motion sensitivity, which limits rapid assessment and exposes the patient to potential anesthesia risks. MRI may be helpful in patients with suspected nonaccidental trauma, with which axonal shear injury and ischemia are more common and documentation is critical, as well as in those whose clinical status is discordant with CT findings. Advanced techniques, such as diffusion tensor imaging, may identify changes occult by standard imaging, but data are currently insufficient to support routine clinical use. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

A comparison of non-contrast and contrast-enhanced MRI in the initial stage of Legg-Calvé-Perthes disease

BackgroundA prognostic indicator of outcome for Legg-Calvé-Perthes disease (LCP) is needed to guide treatment decisions during the initial stage of the disease (stage 1), before deformity occurs. Radiographic prognosticators are applicable only after fragmentation (stage II).ObjectiveWe investigated pre- and postcontrast MRI in depicting stage I femoral head involvement.Materials and methodsThirty children with stage I LCP underwent non-contrast coronal T1 fast spin-echo (FSE) and corresponding postcontrast fat-suppressed T1-weighted fast spin-echo (FSE) sequences to quantify the extent of femoral head involvement. Three pediatric radiologists and one pediatric orthopedic surgeon independently measured central head involvement.ResultsInterobserver reliability of percent head involvement using non-contrasted MR images had intraclass correlation coefficient (ICC) of 0.72. Postcontrast MRI improved interobserver reliability (ICC 0.82). Qualitatively, the area of involvement was more clearly visible on contrast-enhanced MRI. A comparison of results obtained by each observer using the two MRI techniques showed no correlation. ICC ranged from −0.08 to 0.03 for each observer. Generally, greater head involvement was depicted by contrast compared with non-contrast MRI (Pearson r = −0.37, P = 0.04).ConclusionPre- and postcontrast MRI assess two different components of stage I LCP. However, contrast-enhanced MRI more clearly depicts the area of involvement.

MR perfusion index as a quantitative method of evaluating epiphyseal perfusion in legg-calve-perthes disease and correlation with short-term radiographic outcome: A preliminary study

Background: Current radiographic prognosticators of the outcome of Perthes disease can only be applied after femoral head deformity has occurred. Quantification of femoral head perfusion using the gadolinium-enhanced subtraction magnetic resonance imaging (MRI) technique may serve as an early prognosticator of outcome. The purposes of this study were 2-fold: (1) to develop a reliable method to quantify femoral head perfusion using this MRI technique; and (2) to determine whether the perfusion at early stages of Perthes disease correlates with radiographic deformity after a 2-year follow-up. Methods: A total of 20 patients meeting the following inclusion criteria were studied: radiographs and MRI obtained of femoral heads predeformity, age between 5 and 13 years, and unilateral disease. MR perfusion index, a measure of perfusion in the epiphysis, was obtained using digital image analysis of subtraction gadolinium-enhanced MRI. Intraobserver and interobserver agreement of this index was assessed by 2 independent observers. MR perfusion index was correlated with a radiographic deformity index (a measure of femoral head deformity) obtained after a minimum of 2 years. Results: The intraobserver agreement assessed by the intraclass correlation coefficient was 0.96 for observer 1 and 0.97 for observer 2. The interobserver agreement of the MR perfusion index was 0.90 for trials 1 and 2. MR perfusion index in the early stages of Perthes disease was highly variable, ranging from 0 to 0.70. After a minimum of 2 years following MRI acquisition, radiographs were obtained and evaluated using the deformity index, a continuous measure of femoral head deformity, by 2 blinded observers. Deformity index at 2-year follow-up showed moderate correlation with predeformity MR perfusion index (r=−0.56, P=0.01, R2=0.31). In those patients who were treated nonoperatively, the correlation was stronger (r=−0.79, P=0.006, R2=0.63). Conclusions: MR perfusion index obtained from gadolinium-enhanced subtraction MR images showed a high interobserver agreement. MR perfusion index is highly variable at early stages of Perthes disease, and a lower MR perfusion index correlated with greater radiographic deformity at the 2-year follow-up. This pilot study shows the promise of predeformity MR perfusion index as a possible early prognosticator of outcome in Perthes disease. Levels of Evidence: Prognostic level II.

Magnetic resonance imaging of the congenital clubfoot treated with the French functional (physical therapy) method

The purpose of this study was to assess magnetic resonance imaging (MRI) changes that occur in clubfeet after nonoperative treatment with the French functional method, specifically pertaining to the chondro-osseous anatomy and the joint relationships. The magnetic resonance images were obtained in 6 infants before treatment and 3 months later. The MRI protocol described previously for clubfeet which were treated by the Ponseti method (J Pediatr Orthop. 2001;21:719) was closely adhered to, except that no sedation was allowed by our institutional review board. The severity of the clubfoot deformities before treatment made assessment of the tibiotalar, talonavicular, and talocalcaneal joint relationships difficult in some feet. Despite this, improvements were noted after treatment in tibiotalar plantarflexion, the talonavicular relationship, the calcaneocuboid relationship, and the varus position of the calcaneus. The wedge shape of both the navicular and distal end of the calcaneus that occasionally was noted on the MRI before treatment improved after therapy. Although improved clinically, persistent equinus of the calcaneus on MRI was significant in 2 feet and was associated with slight dorsal displacement of the cuboid on the calcaneus (MRI evidence of rocker bottom). As noted with use of the Ponseti nonoperative treatment method, the chondro-osseous abnormalities seen on MRI studies in congenital clubfoot improve after treatment with the French functional (physical therapy) method, with the exception of equinus.

Perfusion MRI in early stage of Legg-Calvé-Perthes disease to predict lateral pillar involvement: A preliminary study

BACKGROUND Current radiographic classifications for Legg-Calvé-Perthes disease cannot be applied at the early stages of the disease. The purpose of this study was to quantify the perfusion of the femoral epiphysis in the early stages of Legg-Calvé-Perthes disease with use of perfusion magnetic resonance imaging (MRI) and to determine if the extent of epiphyseal perfusion can predict the lateral pillar involvement at the mid-fragmentation stage. METHODS Twenty-nine patients had gadolinium-enhanced perfusion MRI at the initial stage or early fragmentation stage of Legg-Calvé-Perthes disease and were followed prospectively. The percent perfusion of the whole epiphysis and its lateral third was measured by four independent observers using image analysis software. The radiographs obtained at the mid-fragmentation stage were used for the lateral pillar classification. Intraclass correlation coefficient (ICC) and logistic regression analyses were performed. RESULTS The mean age (and standard deviation) at diagnosis was 7.7 ± 1.7 years (range, 5.3 to 11.3 years). The mean interval between the MRI and the time of maximum fragmentation was 8.2 ± 5.5 months. The interobserver ICC for the percent perfusion of the lateral third of the epiphysis was 0.90 (95% confidence interval [CI]: 0.83 to 0.95). The mean percent perfusion of the lateral third of the epiphysis was 92% ± 2%, 68% ± 18%, and 46% ± 12% for the hips in which the lateral pillar was later classified as A, B, and C, respectively (p = 0.001). When the perfusion level was ≥90% in the lateral third of the epiphysis, the odds ratio of the lateral pillar being later classified as group A, as opposed to B or C, was 72.0 (CI: 3.5 to 1476). With a perfusion level of ≤55% in the lateral third of the epiphysis, the odds ratio of the lateral pillar being later classified as group C, as opposed to A or B, was 33.3 (CI: 2.8 to 392). Similar results were obtained for the whole epiphysis. CONCLUSIONS Perfusion MRI measurements of the total epiphysis and its lateral third obtained at the early stages of Legg-Calvé-Perthes disease were predictive of lateral pillar involvement at the mid-fragmentation stage of the disease. LEVEL OF EVIDENCE Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

ACR Appropriateness Criteria® Suspected Physical Abuse—Child

The youngest children, particularly in the first year of life, are the most vulnerable to physical abuse. Skeletal survey is the universal screening examination in children 24 months of age and younger. Fractures occur in over half of abused children. Rib fractures may be the only abnormality in about 30%. A repeat limited skeletal survey after 2 weeks can detect additional fractures and can provide fracture dating information. The type and extent of additional imaging for pediatric patients being evaluated for suspected physical abuse depends on the age of the child, the presence of neurologic signs and symptoms, evidence of thoracic or abdominopelvic injuries, and social considerations. Unenhanced CT of the head is the initial study for suspected intracranial injury. Clinically occult abusive head trauma can occur, especially in young infants. Therefore, head CT should be performed in selected neurologically asymptomatic physical abuse patients. Contrast-enhanced CT of the abdomen/pelvis is utilized for suspected intra-abdominal or pelvic injury. Particular attention should be paid to discrepancies between the patterns of injury and the reported clinical history. Making the diagnosis of child abuse also requires differentiation from anatomical and developmental variants and possible underlying metabolic and genetic conditions. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria Osteonecrosis of the Hip

Osteonecrosis of the hip (Legg-Calvé-Perthes) is a common disease, with 10,000-20,000 symptomatic cases annually in the United States. The disorder affects both adults and children and is most frequently associated with trauma and corticosteroid usage. The initial imaging evaluation of suspected hip osteonecrosis is done using radiography. MRI is the most sensitive and specific imaging modality for diagnosis of osteonecrosis of the hip. The clinical significance of hip osteonecrosis is dependent on its potential for articular collapse. The likelihood of articular collapse is significantly increased with involvement of greater than 30%-50% of the femoral head area, which is optimally evaluated by MRI, often in the sagittal plane. Contrast-enhanced MRI may be needed to detect early osteonecrosis of the hip in pediatric patients, revealing hypoperfusion. In patients with a contraindication for MRI, use of either CT or bone scintigraphy with SPECT (single-photon emission CT) are alternative radiologic methods of assessment. Imaging helps guide treatment, which may include core decompression, osteotomy, and ultimately, need for joint replacement. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

The cross-table lateral radiograph results in a significantly increased effective radiation dose compared with the Dunn and single frog lateral radiographs.

Background: A lateral radiograph of the proximal femur is critical in the evaluation of patients with suspected femoroacetabular impingement. Positioning patients for a cross-table lateral (XTL) image is difficult, which may result in repeat exposures and increased cumulative radiation. Alternatively, the 45-degree Dunn (Dunn) and single frog lateral (SFL) views have been shown to accurately reveal proximal femoral abnormalities in femoroacetabular impingement. The purpose of this study was to compare the effective radiation doses (ERD) for 3 lateral hip projections that provide similar diagnostic information. Methods: Patients presenting to the adolescent hip clinic with indicated examinations were evaluated with a standard anteroposterior (AP) pelvic radiograph and one of 3 lateral hip radiographs: XTL (n=16), Dunn (n=17), or SFL (n=27). Technical exposure parameters and published reference data for an AP pelvic radiograph were used to extrapolate the ERD. A simple Pearson r correlation test determined the relationships between body mass index, age, and ERD. The rate of repeat exposures per study was calculated. Results: Body mass index positively correlated (r=0.34) and age and negatively correlated (r=−0.27) with ERD. ERD was increased for the XTL (0.83±0.98 mSv) over the Dunn (0.37±0.15 mSv) and SFL (0.22±0.11 mSv; P<0.05). Repeat exposures were performed in 10.4%, 4%, and 6% of XTL, Dunn, and SFL studies, respectively. Conclusions: The ERD for a single projection is highest for the XTL, and the examination is more likely to be repeated. The XTL radiograph should be avoided whenever possible and substituted with alternative images providing similar diagnostic information, such as the Dunn or SFL, to minimize lifetime cumulative radiation exposure to the patient. Level of Evidence: Level II.