Spine Computed Tomography Radiation Dose Reduction: Protocol Refinement Based on Measurement Variation at Simulated Lower Radiation Acquisitions.

STUDY DESIGN: Retrospective dose-simulation comparison. OBJECTIVE: To determine if sufficient detail for preoperative analysis of bony anatomy can be acquired at substantially lower doses than those typically used. SUMMARY OF BACKGROUND DATA: Computed tomography (CT) is a preoperative planning tool for spinal surgery. The pediatric population is at risk to express the harmful effects of ionizing radiation. Preoperative CT scans are presently performed at standard pediatric radiation doses not tailored for surgical planning. METHODS: We used the validated GE Noise Injection software to retrospectively modify existing spine and chest CT scans from 10 patients to create CT images that simulated a standard dose (100%), 50% dose, and 25% dose scans. 4 orthopedic surgeons and a pediatric radiologist, blinded to dose, measured minimum medial-lateral pedicle width and maximum anterior-posterior bony length along the axis of presumed pedicle screw placement. A total of 90 axial images were generated to create our sample set. Measurements were evaluated for accuracy, precision, and consistency. RESULTS: For any given rater, there was no clinically relevant difference between measurements at the different dose levels and no apparent degradation in precision at the different dose levels. Consistent variation was observed between raters, the likely result of individual differences in measurement approach. CONCLUSION: Spinal CT scans done for preoperative planning can be performed at 25% of current radiation doses without a loss in surgical planning measurement accuracy or precision. These 25% dose-reduced scans would have average Computed Tomography Dose Index volume dose levels of roughly 1.0 to 2.5 mGy (depending on patient size) and size-specific dose estimates of roughly 2.5 mGy representing a substantial dose savings compared to current practice for many sites. Standardization of consistent landmarks may be useful to further improve inter-rater concordance.

Comparison of structural bone autografts and allografts in pediatric foot surgery.

BACKGROUND: Autogenous bone has been the gold standard as the source for structural bone-graft material due to its osteogenic potential, nonimmunogenicity, and efficiency of incorporation. However, donor-site morbidity can lead to significant problems. Allograft bone is readily available and obviates the risks associated with bone-graft harvesting. However, its use raises concerns of disease transmission, infection, slower incorporation, and immunologic reaction. Despite these concerns, allograft use has become widespread. The few comparative studies of the 2 graft types used in spine and tumor surgery are promising. We sought to compare the speed and completeness of graft incorporation and the relative safety of autograft and allograft structural bone in pediatric foot surgery. METHODS: A retrospective analysis was performed on 161 children who underwent foot surgery requiring 182 allografts and 63 autografts from 1982 to 1994. Follow-up ranged from 2 to 146 months (mean=51.4). RESULTS: Graft-host union, defined as radiographic evidence of healing with a clinical lack of tenderness at graft insertion site, occurred within 12 weeks in both groups. Average time to healing in both groups was just over 7 weeks. In the allograft group, there was 1 nonunion, 3 graft displacements due to technical error requiring reoperation, and 1 partial displacement that did not require reoperation. All of these complications can be attributed to technique rather than to graft type. There were no infections or instances of disease transmission. There were no reported complications in the autograft group. CONCLUSIONS: Small, structural bone allografts provide a safe, efficient, and cost-effective alternative to iliac crest bone autograft in pediatric foot surgery. LEVELS OF EVIDENCE: Level III, therapeutic study, retrospective comparative study.

EXT2-positive multiple hereditary osteochondromas with some features suggestive of metachondromatosis.

Metachondromatosis (MC) and hereditary multiple osteochondromas (HMO) are thought to be distinct disorders, each with characteristic x-ray and clinical features. Radiographic differences are the current mainstay of differential diagnosis. Both disorders are autosomal dominant, but the majority of patients with HMO have mutations in EXT-1 or EXT 2 genes. The genetic defect in MC is unknown, although recent studies indicate a possible identifiable mutation. The cancer risk in HMO is thought to be greater than in MC, although the small number of cases make such conjecture imprecise. The purpose of this report is to review existing literature and examine whether radiographic findings in HMO and MC can be reliable as a stand-alone means of differential diagnosis. Three members of a multi-generational family with an autosomal dominant exostosis syndrome were studied by clinical examination and complete skeletal survey. The roentgenographic characteristics of all osteochondromas were analyzed. The father underwent gene sequencing for EXT-1 and EXT-2, which revealed a novel EXT-2 mutation. Typical radiographic and clinical findings of both HMO and MC were seen throughout the family as well as in individuals. These family study findings contradict many of the long-standing clinical and x-ray diagnostic criteria for differentiating MC from HMO. The phenotypic crossover between the two conditions in this family, and results of genetic analysis, suggest that in the absence of a definitive genetic diagnosis, radiographic and clinical diagnosis of past and future cases HMO and MC may not be as reliable as previously assumed.

Classic bladder exstrophy: orthopaedic surgical considerations.

Classic bladder exstrophy is an embryologic malformation that results in complex deficiency of the anterior midline, with urogenital and skeletal manifestations. Urogenital reconstruction is a challenging procedure that can be facilitated by closure of the bony pelvic ring by an orthopaedic team. Surgical options include a multiyear staged approach and the single-stage complete repair for exstrophy. The goals of urologic surgery include closure of the bladder and abdominal wall with eventual bladder continence, preservation of renal function, and cosmetic and functional reconstruction of the genitalia. Pelvic osteotomy is done at the time of bladder closure in the patient in whom the anterior pelvis cannot be approximated without tension. Traction or spica casting is used postoperatively. Good outcomes are probable with appropriate management at specialized treatment centers.