Maturation of pelvic ossification centers on computed tomography in normal children.

BACKGROUND: The pelvis is composed of three paired primary ossification centers: the pubis, the ischium and the ilium. During maturation, multiple secondary ossification centers can be seen in the synchondroses between these bones and in the pelvic apophyses. The fragmented appearance of these centers can be confused with pathology. OBJECTIVE: To examine development of pelvic ossification centers by CT and determine normal appearance throughout childhood. MATERIALS AND METHODS: Three pediatric radiologists reviewed 325 pelvic CT scans in children and young adults 5-18 years old and graded 6 pelvic ossification centers to evaluate maturational changes in critical structures. RESULTS: Rate and progression of ossification and age at complete fusion vary with gender at the different ossification centers in the growing pelvis. CONCLUSION: Knowledge of the normal CT appearance of ossification centers throughout childhood is important to differentiate the normal appearance from pathology.

Benefits of integration of radiology services across a pediatric health care system with locations in multiple states.

BACKGROUND: Integration was implemented of previously independently practicing pediatric radiology services across a pediatric health care system with sites 1,000 miles apart. OBJECTIVE: The purpose of this manuscript is to describe the process utilized to integrate imaging services across our enterprise and to study the direct effects on report turnaround time and other parameters. MATERIALS AND METHODS: Parameters were evaluated both the year before integration as well as the 2 years following integration and compared for improvement. Parameters studied included report turnaround time, academic productivity (as measured by peer review publications per year), and degree of sub-subspecialization within pediatric radiology (as measured by the percentage of neuroimaging CT and MRI studies read by pediatric neuroradiologists). RESULTS: Comparing pre- to post-integration measures, the median report turnaround time decreased from 2.3 h to 1.1 h (52.1% improvement), the percentage of neuroimaging studies read by neuroimaging faculty increased from 15.0% to 86.6% (477% improvement), and peer review publication by calendar year increased from 3 to 30 (1,000% improvement). Other benefits included increased hours of in-house coverage and execution on multiple quality improvement efforts. CONCLUSION: A pediatric health care system successfully integrated radiology services across multiple previously non-integrated locations into one functional group. This integration was associated with a positive effect on multiple parameters.

Benefits and unexpected artifacts of biplanar digital slot-scanning imaging in children.

Biplanar digital slot-scanning allows for relatively low-dose orthopedic imaging, an advantage in imaging children given the growing concerns regarding radiosensitivity. We have used this system for approximately 1 year for orthopedic imaging of the spine and lower extremities. We have noted advantages of using the digital slot-scanning system when compared with computed radiographic and standard digital radiographic imaging systems, but we also found unexpected but common imaging artifacts that are the direct result of the imaging method and that have not been reported. This pictorial essay serves to familiarize radiologists with the advantages of the digital slot-scanning system as well as imaging artifacts common with this new technology.

Flexion-extension cervical spine MRI in children with skeletal dysplasia: is it safe and effective?

BACKGROUND: Skeletal dysplasias may be associated with cervical spinal instability or stenosis. Cervical spine flexion-extension plain radiographs in children with skeletal dysplasia are difficult to interpret. The purpose of this study was to review the indications, efficacy, and safety of performing flexion-extension magnetic resonance imaging (MRI) under sedation/anesthesia in these children. METHODS: Retrospective, Institutional Review Board-approved review of 31 children with skeletal dysplasia who underwent 38 cervical spine flexion-extension MRI studies under sedation/anesthesia. Indications included abnormal neurological examination, suspected instability, stenosis, or inconclusive findings on flexion-extension radiographs. Studies were performed by the radiology technologist as directed by the radiologist with an anesthesiologist present. MRI was evaluated for odontoid hypoplasia, os odontoideum, cerebrospinal fluid effacement, cord compression, spinal cord changes, cervical canal narrowing in the neutral, flexion, and extension positions. Neurological examinations were recorded before and after MRI to assess safety. RESULTS: The average age at MRI was 3 years, 2 months. In 6 patients whose plain radiographs showed C1-C2 or subaxial instability, flexion-extension MRI showed no cord compression. Nine patients with inconclusive plain radiographs had abnormal MRI findings. An os odontoideum not seen on plain radiographs was diagnosed in 3 patients on flexion-extension MRI. On the basis of the MRI findings, 14 patients underwent surgery, 9/14 had increased cord compression in flexion or extension compared with neutral, and observation was continued in 17 others. Patients who underwent surgery had significant cord compression on MRI. There were no significant changes in the neurological examinations after MRI. CONCLUSIONS: Cervical spine flexion-extension MRI under sedation/anesthesia in children with skeletal dysplasia is safe under adequate supervision and is necessary to guide accurate medical and surgical decision making. Flexion-extension MRI is useful for identifying dynamic changes in canal diameter resulting in cord compression not seen on plain radiographs, and it is also useful for identifying patients with suspected plain film instability who may not have stenosis or cord compression on MRI. STUDY DESIGN: Level IV-retrospective case series.

Protocol for MRI of the hips after spica cast placement.

BACKGROUND: In reduction of hip displacement in developmental dysplasia, concentric placement of the femoral head within the acetabulum is key. Magnetic resonance imaging (MRI) is an effective modality to assess the adequacy of the reduction, but sedation may be required due to the length of the examination. MRI is also more expensive than other imaging modalities. Our goal was to provide an MRI protocol that does not require sedation and can be performed in <15 minutes. METHODS: We retrospectively reviewed 34 consecutive MRI studies performed without sedation after spica cast placement in 24 developmental hip dysplasia patients. The MRI examinations were performed with a variety of techniques. Sequences used were evaluated for contrast, resolution, and motion artifact. RESULTS: Ninety-seven percent of studies were diagnostic, although 18% of examinations had significant motion artifact. Seven sequences were analyzed. T2-weighted fast spin echo sequences had the best overall scores and were performed in <3 minutes. T1 and fat-suppressed T2-weighted fast spin echo sequences did not score as well, and also required <3 minutes. Single-shot fast spin echo sequences scored poorly due to decreased contrast and resolution, despite shorter acquisition times of 20 to 40 seconds. Three-dimensional (3D) gradient recovery imaging scored poorly due to lower contrast and increased motion due to longer acquisition times of approximately 4 minutes. Both coronally and axially oriented sequences satisfactorily assessed femoral head position within the acetabulum. CONCLUSIONS: MRI is a useful tool in evaluating the hips without radiation exposure and without sedation in infants and toddlers after spica cast placement. Both axial and coronal T2 fast spin echo MRI sequences provided excellent anatomic definition and required ≤3 minutes per sequence. Orthopaedic surgeons can request these 2 sequences for accurate assessment of concentric reduction with a potential study time of 15 minutes, obviating the need for sedation. LEVEL OF EVIDENCE: Level II.

Fracture after bisphosphonate treatment in children with cerebral palsy: the role of stress risers.

BACKGROUND: In the nonambulatory cerebral palsy (CP) population with a prior history of fracture, the use of pamidronate is not always effective in preventing further fractures. OBJECTIVE: To test the hypothesis that when fractures occur after cyclic pamidronate, they will be at the proximal or distal end of a pamidronate band. MATERIALS AND METHODS: Retrospective review of our CP patient database revealed 53 children who had received one or more complete courses of pamidronate therapy (five cycles over 12 months). Medical records were screened to identify children who had sustained a fracture or fractures after completing treatment. RESULTS: Of 53 patients treated with pamidronate, only 14 sustained fractures after treatment. Radiographs were available for 11 patients, showing 19 fractures. Sixty-three percent of these fractures were located at a junction with pamidronate bands but not within the bands. CONCLUSIONS: We propose stress risers as the mechanism for fractures that have occurred where bone mineral density abruptly changes as a result of cyclic administration of pamidronate. We show a theoretical example of how alternative dosing might reduce the ratio and therefore decrease the chance of formation of a stress riser.

Developmental anatomy of the atlas and axis in childhood by computed tomography.

OBJECT: The CT modality plays a central role in the diagnosis of cervical spine fractures. In childhood, radiolucent synchondroses between ossification centers can resemble fractures, and they can be the sites of fractures as well. Recognition of cervical spine fractures in children requires familiarity with normal developmental anatomy and common variants as they appear on CT scans. METHODS: A convenience sample of 932 CT scans of the cervical spine accessible on the picture archiving and communications system (known as PACS) at a single children's hospital was examined. Scans were excluded from further analysis if they did not include the atlantoaxial region or were otherwise technically unsatisfactory; if the patient carried the diagnosis of a skeletal dysplasia; or if there were developmental lesions noted at other levels of the spine. No more than 1 scan per patient was analyzed. Synchondroses were graded as radiolucent, not totally radiolucent but still visible, or no longer visible. Their locations and symmetries were noted. The presence or absence of the tubercles of the transverse ligament was noted as well. RESULTS: After exclusions, 841 studies of the atlas and 835 studies of the axis were analyzed. The 3 common ossification centers of the atlas arose in the paired neural arches and the anterior arch, but in as many as 20% of cases the anterior arch developed from paired symmetrical ossification centers. The 5 common ossification centers of the axis arose in the paired neural arches, in the basal center, in the dentate center (from which most of the dentate process develops), and in the very apex of the dentate process. The appearance of each synchondrosis was noted at sequential ages. The tubercles for the transverse ligament generally did not appear until the ossification of the synchondroses of the atlas was far advanced. Anomalies of the atlas included anterior and posterior spina bifida, absence of sectors of the posterior arch, and anomalous ossification centers and synchondroses. Anomalies of the axis were much less common. What appeared possibly to be chronic, incompletely healed fractures of the atlas were discovered on review for this analysis in 6 cases. No fractures of the axis were discovered. CONCLUSIONS: There is substantial variation in the time course and pattern of development of the atlas, and anomalies are common. Some fractures of the atlas may escape recognition without manifest sequelae. Variation in the time course of the development of the axis is notable as well, but anomalies seem much less common.

High-signal T2 changes of the bone marrow of the foot and ankle in children: red marrow or traumatic changes?

BACKGROUND: High-signal T2-weighted bone marrow changes can be found in both bone marrow edema and hematopoietic marrow and are often seen on pediatric MR images of the feet and ankle. OBJECTIVE: To evaluate whether high-signal T2 changes of the bone marrow seen on pediatric MRI of feet and ankles represent residual hematopoietic marrow. MATERIALS AND METHODS: A total of 402 bones in 41 pediatric MRI studies of feet and ankles (34 children, 1-18 years) were reviewed by two observers who were blinded to the patients' ages. The studies were reviewed for the presence of high-signal changes of the bone marrow on sagittal fluid-sensitive images. The frequency and location of these foci were correlated with the patients' ages. RESULTS: High-signal T2 changes of the bone marrow were seen in 45/402 bones (11%) and in 24/41 patients younger than 16 years (59%). The changes were most commonly located in the calcaneus (54%), followed by the talus (35%) and navicular bone (35%), invariably at the endosteal surface. In 16 ankles, such foci were seen in the feet but not in the distal tibia/fibula. Symmetric presence (two ankles) or absence (four ankles) of high-signal marrow were seen in six of seven patients with bilateral ankles. CONCLUSION: High-signal T2 changes of the bone marrow in pediatric feet and ankle MRIs have a symmetric, fairly consistent pattern and disappear after the age of 15 years. We believe that these high-signal areas are normal and represent residual hematopoietic marrow.

Bone densitometry in pediatric patients treated with pamidronate.

BACKGROUND: Increasing numbers of children are being treated with the bisphosphonate pamidronate for low bone mineral density, particularly children with increased risk of fractures caused by bone disorders or low/non-weight bearing. OBJECTIVE: To determine the effect of intravenous pamidronate on the bone mineral density of children with osteogenesis imperfecta and spastic quadriplegic cerebral palsy. MATERIALS AND METHODS: Charts of 38 children with osteogenesis imperfecta (n=20) and spastic quadriplegic cerebral palsy (n=18) treated with pamidronate were retrospectively reviewed. Patients were selected for treatment because of prior fracture and/or abnormally low bone mineral density. All received intravenous pamidronate at two-month to eight-month intervals and were periodically examined using dual energy X-ray absorptiometry. RESULTS: All patients had abnormally low bone mineral density prior to treatment. Lumbar spine bone mineral density and z-scores showed serial improvement in 31 of 32 patients. Spine bone mineral density increased 78+/-38.1% in OI and 47.4+/-39.0% in children with cerebral palsy. The area of greatest lateral distal femur bone mineral density improvement was in the metaphysis adjacent to the growth plate, with a 96+/-87.8% improvement in the osteogenesis imperfecta group and 65.7+/-55.2% improvement in the cerebral palsy group. Increases in bone mineral density exceeded that expected for age-specific growth. This was demonstrated by improvement in both spine and femur z-scores for both groups. No children with spastic quadriplegic cerebral palsy experienced fractures after the first week of treatment, whereas patients with osteogenesis imperfecta continued to have fractures but at a decreased rate. CONCLUSIONS: Intravenous pamidronate given at 3- to 4-month intervals proved to be effective in increasing bone mineral density in patients with osteogenesis imperfecta and spastic quadriplegic cerebral palsy. The greatest gains in bone mineral density were observed in the children with osteogenesis imperfecta, but they did continue to fracture, albeit at a decreased rate. Children with cerebral palsy gained bone mineral density and did not continue to fracture.

Radiographic characteristics of lower-extremity bowing in children.

Lower-extremity bowing is common in infants and children and can result from a variety of conditions. At radiography, developmental bowing shows varus angulation centered at the knee, "metaphyseal beaking," thickening of the medial tibial cortices, and tilted ankle joints. Tibia vara (Blount disease) demonstrates genu varum and depression of the proximal tibia medially. Congenital bowing manifests as posteromedial bowing with cortical thickening along the concavity of the curvature and, in some cases, diaphyseal broadening. In rickets, radiographic changes occur primarily at sites of rapid growth and are predominantly metaphyseal, with widening of the zone of provisional calcification. Achondroplasia is characterized by shortening and thickening of the long bones with metaphyseal flaring and cupping. In neurofibromatosis, there may be anterolateral bowing of the tibia, and there is often focal narrowing and intramedullary sclerosis or cystic change at the apex of the angulation. The tibia is typically involved at the junction of the middle and distal thirds. Osteogenesis imperfecta demonstrates bowing from softening due to osteoporosis and multiple fractures and typically involves the entire skeleton. In camptomelic dysplasia, lower-extremity bowing is associated with a short trunk, short limbs, and deficiencies in pelvic bone development. Recognition of these pathologic conditions is important for differentiating those that will resolve spontaneously from those that require surgery or other treatment.

Radiographic features of bisphosphonate therapy in pediatric patients.

BACKGROUND: Pediatric patients are being treated with bisphosphonates for low bone mineral density. Skeletal radiographic findings have been described with bisphosphonates given orally and intravenously. OBJECTIVE: To determine and describe the radiographic findings of cyclic intravenous bisphosphonate therapy in the growing skeleton. MATERIALS AND METHODS: Retrospective review of radiographs of 32 patients with osteogenesis imperfecta or cerebral palsy treated with intravenous bisphosphonates on a quarterly schedule. RESULTS: Principal observations were metaphyseal bands and increased bone mineral density. The bands varied in spacing according to the age of the patient, rate of growth, and the location of the metaphysis. Fractures continued to be seen in patients with osteogenesis imperfecta. CONCLUSION: Cyclic bisphosphonate therapy results in distinctive radiographic findings in the growing skeleton.

Developmental Dysplasia of the Pediatric Hip with Emphasis on Sonographic Evaluation.

Developmental dislocation and/or dysplasia of the hip (DDH), formerly referred to as congenital dislocation of the hip, is a frequent problem of the neonatal and infant hip. At that age, the femoral head and acetabulum consist of cartilage components that are not visible on plain radiography but readily identified by ultrasound. Realtime sonography allows for assessment of the hip in multiple planes, both at rest and with movement. Ultrasound can replace radiographic studies and thereby reduce radiation exposure to the young infant.