Biomedical subjects

William J Hurst

Publications and source records attributed to William J Hurst.

5 recordsLinked to original sources

PubMed2006

Predicting zygoma fractures from baseball impact.

The purpose of this study is to develop injury risk functions that predict zygoma fracture based on baseball type and impact velocity. Zygoma fracture strength data from published experiments were mapped with the force exerted by a baseball on the orbit as a function of ball velocity. Using a normal distribution, zygoma fracture risk functions were developed. Experimental evaluation of these risk functions was performed using six human cadaver tests and two baseballs of different stiffness values. High speed video measured the baseball impact velocity. Post test analysis of the cadaver skulls was performed using CT imaging including three-dimensional reconstruction as well as autopsy. The developed injury risk functions accurately identify the risk of zygoma fracture as a result of baseball impact. The experimental results validated the zygoma risk functions at the lower and upper levels. The injuries observed in the post test analysis included fractures of the zygomatic arch, frontal process and the maxilla, zygoma suture, with combinations of these creating comminuted, tripod fractures of the zygoma. Tests with a softer baseball did result in injury but these had fewer resulting zygoma bone fragments and occurred at velocities 50% higher than the major league ball.

Baseball↗

PubMed2004

Spring-mediated cranial reshaping for craniosynostosis.

The evolution of modern craniofacial surgery has come full circle from the early strip craniectomies to the complete calvarial remodeling and now back to attempts at minimally invasive surgical interventions. The goal of the craniofacial surgeon has always been the correction of form and function with minimization of associated morbidity and mortality. Particularly problematic has been the ability to maintain the anatomical correction beyond the result seen on the operating room table secondary to changes with growth. The ability to improve the clinical result in a growing and developing child has been the impetus for dynamic treatment modalities. Dr Claes Lauritzen's pioneering work in this area has been particularly successful using internal springs to correct craniofacial deformities. The purpose of this study is to assess this treatment modality clinically in terms of safety and efficacy and to develop a methodology for the spring formation that would be easily reproducible. This is an institutional review board-approved prospective study of 15 children (11 male, 4 female) with non-syndromic sagittal suture synostosis. All patients were treated with a sagittal strip craniectomy and placement of 2 omega-shaped stainless steel springs at a mean age of 3.9 months. Patients were followed clinically and with cephalograms; after reossification of the intervening bone, the springs were removed at a mean age of 8.2 months. The mean force applied at initial placement of the springs was 6.9 N, and the mean spring deflection at formation was 6.87 cm. All patients completed the study protocol without any significant morbidity or any mortality. Perioperative variables, including blood loss, transfusion rate, operative time, intensive care unit stay, hospital stay, and hospital charges, were all significantly less (P < 0.05) in this study group compared with children with the same diagnosis treated with cranial vault reshaping during the same period. Furthermore, the preoperative mean cephalic index of 64.3 corrected to 77.6 after surgery and was maintained over time. Spring-mediated cranial reshaping is efficacious and safe for the treatment of sagittal synostosis. Long-term study of cranial development and clinical morphology are ongoing to validate further the effectiveness of this treatment modality.

Cephalometry↗

PubMed2004

Lateral and posterior dynamic bending of the mid-shaft femur: fracture risk curves for the adult population.

The purpose of this study was to develop injury risk functions for dynamic bending of the human femur in the lateral-to-medial and posterior-to-anterior loading directions. A total of 45 experiments were performed on human cadaver femurs using a dynamic three-point drop test setup. An impactor of 9.8 kg was dropped from 2.2 m for an impact velocity of 5 m/s. Five-axis load cells measured the impactor and support loads, while an in situ strain gage measured the failure strain and subsequent strain rate. All 45 tests resulted in mid-shaft femur fractures with comminuted wedge and oblique fractures as the most common fracture patterns. In the lateral-to-medial bending tests the reaction loads were 4180 +/- 764 N, and the impactor loads were 4780 +/- 792 N. In the posterior-to-anterior bending tests the reaction loads were 3780 +/- 930 N, and the impactor loads were 4310 +/- 1040 N. The difference between the sum of the reaction forces and the applied load is due to inertial effects. The reaction loads were used to estimate the mid-shaft bending moments at failure since there was insufficient data to include the inertial effects in the calculations. The resulting moments are conservative estimates (lower bounds) of the mid-shaft bending moments at failure and are appropriate for use in the assessment of knee restraints and pedestrian impacts with ATD measurements. Regression analysis was used to identify significant parameters, and parametric survival analysis was used to estimate risk functions. Femur cross-sectional area, area moment of inertia (I), maximum distance to the neutral axis (c), I/c, occupant gender, and occupant mass are shown to be significant predictors of fracture tolerance, while no significant difference is shown for loading direction, bone mineral density, leg aspect and age. Risk functions are presented for femur cross-sectional area and I/c as they offer the highest correlation to peak bending moment. The risk function that utilizes the most highly correlated (R2 = 0.82) and significant (p = 0.0001) variable, cross-sectional area, predicts a 50 percent risk of femur fracture of 240 Nm, 395 Nm, and 562 Nm for equivalent cross-sectional area of the 5(th) percentile female, 50(th) percentile male, and 95(th) percentile male respectively.

Journal Article↗

PubMed2002

Synchronization and phase-resetting by glutamate of an immortalized SCN cell line.

SCN 2.2 cultures were stably transfected with luciferase reporter constructs driven by Ca(2+)/cAMP response element, E-box, or vasoactive intestinal peptide promoter to probe the circadian properties of this clock cell line. SCN 2.2 reporter lines displayed approximately 24-h rhythms of transcriptional activation after serum-shock. Serum-shocked cultures pulsed with glutamate exhibited phase-gated induction of phospho-CREB and of VIP, CRE, and E-box promoter activity. Glutamate-induced CRE promoter activity displayed restricted sensitivity to inhibitors of nitric oxide synthase and cGMP-dependent protein kinase. The temporal pattern of these sensitivities paralleled those of the SCN to light and glutamate during the night. Taken together, our data indicate that serum-shock can synchronize the circadian clock of SCN 2.2 cells to a state consistent with the day/night transition and, thus, establishes a temporal context for this cell line.

Biological Clocks↗

PubMed2002

Immortalized suprachiasmatic nucleus cells express components of multiple circadian regulatory pathways.

We undertook an extensive antigenic characterization of the SCN 2.2 cell line in order to further evaluate whether the line expresses components of circadian regulatory pathways common to the hypothalamic suprachiasmatic nucleus (SCN), the central circadian clock in mammals. We found that differentiated SCN 2.2 cultures expressed a broad range of putative clock genes, as well as components of daytime, nighttime, and crepuscular circadian regulatory pathways found within the SCN in vivo. The line also exhibits several antigens that are highly expressed in a circadian pattern and/or differentially localized in the SCN relative to other hypothalamic regions. Expression of a broad complement of circadian regulatory proteins and putative clock genes further support growing evidence in recent reports that the SCN 2.2 cell line is an appropriate model for investigating the regulation of central mammalian pacemaker.

Animals↗