Throwing enhances humeral shaft cortical bone properties in pre-pubertal baseball players: a 12-month longitudinal pilot study

Objectives: To explore throwing athletes as a prospective, within-subject controlled model for studying the response of the skeleton to exercise. Methods: Male pre-pubertal throwing athletes (n=12; age=10.3±0.6 yrs) had distal humerus cortical volumetric bone mineral density (Ct.vBMD), cortical bone mineral content (Ct.BMC), total area (Tt.Ar), cortical area (Ct.Ar), medullary area (Me.Ar), cortical thickness (Ct.Th) and polar moment of inertia (IP) assessed within their throwing (exercised) and nonthrowing (control) arms by peripheral quantitative computed tomography at baseline and 12 months. Throwing-to-nonthrowing arm percent differences (i.e. bilateral asymmetry) were compared over time. Results: Over 12 months, the throwing arm gained 4.3% (95% Cl=1.1% to 7.5%), 2.9% (95% Cl=0.3% to 5.4%), 3.9% (95% Cl=0.7% to 7.0%), and 8.2% (95% Cl=2.0% to 6.8%) more Ct.BMC, Ct.Ar, Tt.Ar, and IP than the nonthrowing arm, respectively (all p<0.05). There was no significant effect of throwing on Ct.vBMD, Ct.Th and Me.Ar (all p=0.18-0.82). Conclusion: Throwing induced surface-specific cortical bone adaptation at the distal humeral diaphysis that contributed to a gain in estimated strength. These longitudinal pilot data support the utility of throwing athletes as a within-subject controlled model to explore factors influencing exercise-induced bone adaptation during the critical growing years

Alien Registration- Warden, Fred J. (Gorham, Cumberland County)

https://digitalmaine.com/alien_docs/31603/thumbnail.jp

Tibial Bone Strength is Enhanced in the Jump Leg of Collegiate-Level Jumping Athletes: A Within-Subject Controlled Cross-Sectional Study

An efficient method of studying skeletal adaptation to mechanical loading is to assess side-to-side differences (i.e., asymmetry) within individuals who unilaterally exercise one side of the body. Within-subject controlled study designs have been used to explore skeletal mechanoadaptation at upper extremity sites; however, there is no established model in the lower extremities. The current study assessed tibial diaphysis and distal tibia asymmetry in collegiate-level jumping athletes (N = 12). To account for normal crossed asymmetry, data in jumping athletes were compared to asymmetry in a cohort of athletic controls not routinely exposed to elevated unilateral lower extremity loading (N = 11). Jumpers exhibited side-to-side differences between their jump and lead legs at both the tibial diaphysis and distal tibia, with differences at the former site persisting following comparison to dominant-to-nondominant leg differences in controls. In particular, jump-to-lead leg differences for cortical area and thickness at the tibial diaphysis in jumpers were 3.6% (95% CI 0.5-6.8%) and 3.5% (95% CI 0.4-6.6%) greater than dominant-to-nondominant differences in controls, respectively (all p < 0.05). Similarly, jump-to-lead leg differences in jumpers for tibial diaphysis maximum second moment of area and polar moment of inertia were 7.2% (95% CI 1.2-13.2%) and 5.7% (95% CI 1.7-9.8%) greater than dominant-to-nondominant differences in controls, respectively (all p < 0.05). Assessment of region-specific differences of the tibial diaphysis in jumpers indicated that the jump leg had greater pericortical radii on the medial and posterior sides and greater radial cortical thickness posteromedially when compared to the lead leg. These data suggest that athletes who perform repetitive and forceful unilateral jumping may be a useful and efficient within-subject controlled model for studying lower extremity skeletal mechanoadaptation

Shrapnel-Induced Mandibular Hypomobility

Mandibular hypomobility can develop from direct injury to, or as a result of disorders affecting, the supporting structures of the temporomandibular joint. This can be subdivided into intra-articular and extraarticular processes. Ankylosis is commonly associated with trauma (31% to 98%), followed by infections (10% to 49%) and systemic disease (10%). Temporomandibular joint ankylosis is an intra-articular process characterized by fibrous, fibro-osseous, or osseous obliteration of the joint space. Pseudoankylosis involves extracapsular causes of restricted jaw motion that include, but are not limited to, coronoid-zygomatic fusion, coronoid hypertrophy, and muscular fibrosis. Shrapnel injuries can be as devastating as high-velocity gunshot wounds, with functional and esthetic consequences, depending on the velocity, size, shape, and jagged edges of the fragments. Traumatic life support measures are paramount during the immediate postinjury setting. The airway and hemodynamic status must be maintained, because the oxygen-carrying capacity is essential for wound healing and the prevention of infection. A secure airway controlled with an endotracheal tube or tracheostomy needs early consideration because bleeding and edema can result in airway compromise. The securing of the airway should be followed by a comprehensive examination of the patient to reveal additional injuries

Exercise during growth provides lifelong benefit to bone structure and strength: a case study

poster abstractExercise induces greatest gains in bone health during skeletal development, yet reduced bone strength is predominantly an age-related phenomenon. This dichotomy has raised the question of whether exercise-induced changes in bone health when young persist into late adulthood where they may have benefits on bone health and fracture risk. Previous work has suggested exercise-induced gains in bone mass are lost with aging; however, 1) exercise during growth predominantly influences bone structure rather than mass to increase bone strength and 2) mechanisms exist for the long-term maintenance of exercise effects on bone structure. The aim of the current case was to explore whether exercise-induced gains in bone structure and strength accrued when young persist lifelong. The subject was a 94-year-old former Major League Baseball (MLB) pitcher who played competitively for 20 years before ceasing play in 1955. Throwing athletes are a unique model to investigate the skeletal effects of exercise as: 1) the unilateral upper extremity loading associated with throwing enables the contralateral side to serve as an internal control site and 2) throwing athletes have large dominant-to-nondominant (D-to-ND) differences in midshaft humeral bone properties. Peripheral quantitative computed tomography slices of the subject’s dominant and nondominant humerii were taken at 50% humeral length, and D-to-ND percent differences in bone properties calculated and compared to those observed previously in non-throwing controls. Exercise when young had no lasting effects on D-to-ND difference in cortical bone mass or area; however, Dto-ND difference in total area was nearly 3-times that observed in controls. The maintenance of exercise effects on total area resulted from persistence of benefits on periosteal perimeter, with the loss of cortical bone mass and area benefits being due to greater endosteal expansion (perimeter). As a result of the maintenance of exercise-induced benefits on bone structure, D-to-ND difference in ability to resist torsional forces (polar moment of inertia) was nearly double that observed due to habitual loading associated with arm dominance in controls. The maintenance of exercise-induced benefits on bone structure in the current case, despite exercise ceasing 56 years ago, supports the hypothesis that exercise when young can have lasting benefits on bone strength independent of maintenance of bone mass effects. This question is being further explored in a cohort of 100 former MLB players and 100 matched controls

Inconsistency in 9 mm bullets : correlation of jacket thickness to post-impact geometry measured with non-destructive X-ray computed tomography

Fundamental to any ballistic armour standard is the reference projectile to be defeated. Typically, for certification purposes, a consistent and symmetrical bullet geometry is assumed, however variations in bullet jacket dimensions can have far reaching consequences. Traditionally, characteristics and internal dimensions have been analysed by physically sectioning bullets – an approach which is of restricted scope and which precludes subsequent ballistic assessment. The use of a non-destructive X-ray computed tomography (CT) method has been demonstrated and validated Kumar et al., 2011); the authors now apply this technique to correlate bullet impact response with jacket thickness variations. A set of 20 bullets (9 mm DM11) were selected for comparison and an image-based analysis method was employed to map jacket thickness and determine the centre of gravity of each specimen. Both intra- and inter-bullet variations were investigated, with thickness variations of the order of 200 um commonly found along the length of all bullets and angular variations of up to 50 um in some. The bullets were subsequently impacted against a rigid flat plate under controlled conditions (observed on a high-speed video camera) and the resulting deformed projectiles were re-analysed. The results of the experiments demonstrate a marked difference in ballistic performance between bullets from different manufacturers and an asymmetric thinning of the jacket is observed in regions of pre-impact weakness. The conclusions are relevant for future soft armour standards and provide important quantitative data for numerical model correlation and development. The implications of the findings of the work on the reliability and repeatability of the industry standard V50 ballistic test are also discussed

Anti-Rotation Device Releasable by Insertion of a Tool

A drive mechanism enables a socket-type wrench to rotate a shaft and prevents accidental rotation of the shaft when the wrench is not coupled to the shaft. In the original intended application, the shaft would be part of an attachment mechanism on a spacecraft, and the purpose to be served by the drive is to prevent back-driving of the shaft by launch vibrations while enabling an astronaut equipped with the appropriate wrench to actuate the shaft while in orbit. The design could also be adapted to terrestrial applications in which it is necessary to prevent rotational back-driving. The mechanism includes a gear near the tip of the shaft, and a drive nut that constitutes the tip of the shaft. The gear and drive nut are positioned in a recess in a housing. The recess is sized to receive the wrench socket that mates with the drive nut. Also contained in the housing are four linkages that include pins that are spring-loaded into engagement with the gear to prevent rotation of the shaft. When the wrench socket is inserted in the recess, it pushes on the linkages in such a manner as to disengage the pins from the gear