Respiratory syncytial virus hospitalization trends in infants with chronic lung disease of infancy, 1998-2008.

OBJECTIVE: Infants with chronic lung disease of infancy (CLDI) are at high risk for severe respiratory syncytial virus (RSV) illness requiring hospitalization. Palivizumab was first licensed in 1998 for the prevention of RSV disease in high-risk infants, including those with CLDI. We performed a retrospective cohort study of all hospitalized children with CLDI aged <2 years between 1998 and 2008 in the USA to determine trends in rates of hospitalizations due to RSV (RSVH) since the launch of palivizumab. MATERIALS AND METHODS: Data from the United States National Hospital Discharge Survey, a multistage systematic survey sample of US hospitals, were assembled. We defined RSVH using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes of 079.6 (RSV), 466.11 (acute bronchiolitis due to RSV), and 480.1 (pneumonia due to RSV). Quarterly rates of RSVH were assessed for children with CLDI (ICD-9-CM code 770.7) and calculated between 1998 and 2008. Because RSV may be miscoded, the analysis was repeated after expanding the definition of RSVH to include all acute bronchitis and acute bronchiolitis (ABH) (ICD-9-CM = 466). Trends were described using linear regression with seasonal indicators included in the model. RESULTS: On average, about 966 RSVH (range 98-1373 RSVH) per year were found for children <2 years with CLDI in the USA between 1998 and 2008. Over the 11-year period, the predicted rate of RSVH statistically significantly decreased by 48% (from 93.78 to 49.06 RSVH per 1 million children) (P = 0.013). Addition of ABH resulted in a nonstatisically significant decrease of 32% over the 10-year period (P = 0.102). CONCLUSION: These results suggest that there has been a decrease in the rate of RSVH in infants with CLDI between 1998 and 2008. The reasons for this decrease may include improved neonatal intensive care unit and outpatient management of CLDI, and possibly increased use of palivizumab in this high-risk population.

Biomechanical evaluation of kyphoplasty with calcium phosphate cement in a 2-functional spinal unit vertebral compression fracture model.

BACKGROUND CONTEXT: Kyphoplasty is used to treat vertebral compression fractures (VCFs) by inflating a balloon within the vertebral body (VB) to create a void, thereby reducing the fracture, and then depositing polymethylmethacrylate (PMMA) into that void to augment the VB. Calcium phosphate (CaP) may be preferable to PMMA because it is resorbable and nontoxic, although there are concerns about its compressive strength during the setting process. PURPOSE: To evaluate the ability of a particular self-setting CaP cement to restore the structural integrity of a VCF in a 2-functional spinal unit (2FSU) cadaver model under physiologically relevant loading. STUDY DESIGN/SETTING: Repeated-measures compressive testing on a cadaver thoracolumbar 2FSU VCF model. METHODS: Ten 2FSU thoracolumbar specimens were tested to evaluate structural integrity under compressive loading during initial anterior VCF creation (in the central VB), after fracture, and after kyphoplasty treatment. Bipedicular kyphoplasty treatment was performed in a 37 degrees C chamber to reduce the fracture and create a void, which was filled with CaP (n=5) or PMMA (n=5) and allowed to cure for at least 15 minutes. Using fluoroscopic imaging, the sagittal area of the VB (SAVB), the minimum central VB height (MCVBH), and the wedge angle were measured on the central VB for each condition at a 1,000-N compressive load. A repeated-measures linear model was used to determine if the differences in these parameters among the various experimental conditions were statistically significant (p< .05). RESULTS: Compared with the fractured condition, there was a significant improvement in the SAVB, MCVBH, and wedge angle under a physiologically relevant 1,000-N compressive load applied after kyphoplasty. There was no statistically significant difference between treatment with CaP or PMMA. CONCLUSIONS: The structural properties of CaP-augmented VBs are similar to those of PMMA-augmented VBs. Our study indicated that, after at least 15 minutes of setting, a fractured 2FSU specimen treated with kyphoplasty with PMMA or CaP could withstand physiologically relevant loading.

Wear and corrosion in retrieved thoracolumbar posterior internal fixation.

STUDY DESIGN: Posterior thoracolumbar spine implants retrieved as part of routine clinical practice over a 2-year period were analyzed to identify wear and corrosion. OBJECTIVE: Engineering analyses of retrieved posterior instrumentation for indications of performance and failure and correlation of this information with clinical factors. SUMMARY OF BACKGROUND DATA: Recent studies have reported spinal instrumentation particulate wear debris and have noted the importance of design considerations at implant connector interfaces. METHODS: A total of 57 implants were analyzed from patients (39 female, 18 male) whose average age at implantation was 43.9 years (range, 13.7-77.4 years). Time of implantation ranged from 2 months to 13.5 years. The top 3 implantation diagnoses were radiculopathy (33%), scoliosis (30%), and back pain (25%). Metallurgical analyses were performed to characterize the wear and/or corrosion, and fractures of the implants. RESULTS: Wear was present in 75%, corrosion in 39%, and fractures in 7% of the retrieved implants. Wear and/or corrosion was more prevalent, with respect to the total number of implants retrieved, in implants that had been in service at least 1 year. There was no evidence of corrosion in any of the Ti implants, whereas corrosion was present (with wear) in 58% of the stainless steel (SS) implants. Wear and corrosion were more frequently observed in long rods than in short rods. Implantation times were longer for SS implants than for Ti implants. CONCLUSIONS: Retrieved rods exhibited corrosion, wear, and fracture, with wear and corrosion mainly located at the interfaces with hooks, screws, or cross-connectors. The mechanisms causing this material loss in situ, as well as what local or systemic responses it may stimulate are of clinical significance and should be studied further.

Incidence of thoracic and lumbar spine injuries for restrained occupants in frontal collisions.

The increased utilization of three-point restraint systems has greatly reduced the incidence of spinal injuries in motor vehicle accidents. Nevertheless, several studies which rely upon the National Automotive Sampling System (NASS) have documented lower thoracic and upper lumbar fractures in restrained occupants involved in frontal collisions of moderate severities. Although it has been postulated that the injury mechanism may be related to the occupant being out-of-position or sitting in an unusual posture, conclusions with regard to the precise mechanism of injury are difficult due to the lack of information contained in the NASS database. In addition, previous studies have not reported statistical significance of these injuries. In this study, we combined statistical analysis of frontal collisions in the NASS database with the analysis of data acquired from sled and crash tests, which utilized anthropomorphic test devices (ATDs), in order to evaluate the incidence and potential injury mechanisms underlying thoracic and lumbar spine fractures in moderate frontal impacts. In the first portion of the study, we performed a statistical analysis of the NASS database to estimate the incidence rate of spinal fracture. This was complemented with measurements and analysis of lumbar spine load data derived from frontal sled and crash tests. Analysis of the NASS database demonstrated that thoracolumbar spinal injuries are rare when an occupant is restrained by a lap and shoulder belt, and are often accompanied by abdominal injury. The spinal loads measured during frontal impacts with restrained and nominally positioned ATDs were found to be well below injury thresholds. Our results also suggest that the potential for isolated fracture is increased when the geometry of occupant-to-restraint interaction is compromised, as occurs when an occupant submarines the lap belt.

Implications of vehicle roll direction on occupant ejection and injury risk.

Vehicle roll direction and occupant position have been shown to affect occupant kinematics. Data from NASS-CDS were analyzed for risk of serious or greater injuries and ejection with respect to the position of the occupant (near side or far side). The risk of AIS 3+ injuries was higher for unrestrained occupants, for ejected occupants, for occupants involved in rollovers with higher numbers of quarter turns, and for far side occupants. Near side occupants had an increased risk of partial ejection in rollovers consisting of one complete roll or less. Occupant roll direction did not affect risk of complete ejection.

Biomechanical factors and injury risk in high-severity rollovers.

The number of rolls, as well as other factors, has been associated with increased injury risk in rollovers. Data from NASS-CDS from 1995-2003 were used to evaluate the biomechanical implications of vehicle kinematics during multiple rolls and to evaluate the risk of injuries to different body regions during rollovers. The data showed that the risk of injury increased with increasing number of rolls. The rate of increase in risk varied by the region of the body affected and injury severity. The increased risk was particularly great when a vehicle rolled more than two complete rolls.