In rapidly growing animals there are numerous selective pressures and developmental constraints underpinning the ontogenetic development of muscle-tendon morphology and mechanical properties. Muscle force generating capacity, tendon stiffness, elastic energy storage capacity and efficiency were calculated from muscle and tendon morphological parameters and in vitro tendon mechanical properties obtained from a growth series of ostrich cadavers. Ontogenetic scaling relationships were established using reduced major axis regression analysis. Ostrich pelvic limb muscle mass and cross-sectional area broadly scaled with positive allometry, indicating maintained or relatively greater capacity for maximum isometric force generation in larger animals. The length of distal limb tendons was found to scale with positive allometry in several tendons associated with antigravity support and elastic energy storage during locomotion. Distal limb tendon stiffness scaled with negative allometry with respect to body mass, with tendons being relatively more compliant in larger birds. Tendon material properties also appeared to be size-dependent, suggesting that the relative increased compliance of tendons in larger ostriches is due in part to compensatory distortions in tendon material properties during maturation and development, not simply from ontogenetic changes in tendon geometry. Our results suggest that the previously reported increase in locomotor economy through ontogeny in the ostrich is due to greater potential for elastic energy storage with increasing body size. In fact, the rate of this increase may be somewhat greater than the conservative predictions of previous studies, thus illustrating the biological importance of elastic tendon structures in adult ostriches.
Reasons for performing study Perineural analgesia of the equine maxillary nerve is used for diagnostic and surgical procedures. Little data exists to evaluate accuracy and complication rates with current techniques. Objectives This study compared 2 previously described approaches to maxillary nerve analgesia, and a novel needle guidance positioning system (SonixGPS™, Ultrasonix Medical Corporation, Richmond, British Columbia, Canada), assessing relative accuracy and complication rates of each method when performed by inexperienced operators. Study design Cadaver study. Methods Clinical veterinary students performed surface landmark, ultrasound and GPS guided contrast injections, to simulate maxillary nerve blocks in 38 equine cadaver heads. Computed tomography was then used to assess accuracy (successful deposition of contrast in contact with the maxillary nerve), and complication rate (contrast identified within surrounding vasculature or periocular structures), associated with each method. Results Perineural injection of contrast around the maxillary nerve was attempted 76 times, with an overall success rate of 65.8% (50/76), and complication rate of 53.9% (41/76). Success rates were 50% (13/26) with surface landmark, 65.4% (17/26) with ultrasound and 83.3% (20/24) with GPS guided approaches (Fisher's exact P = 0.046). No significant difference in complication rate was found between the 3 methods. Conclusions Ultrasound guided maxillary nerve blocks are significantly more accurate than surface landmark approaches when performed by inexperienced operators, and best success rates are achieved with GPS needle guidance. All 3 methods were equivalent in terms of complication rates when performed in cadavers. Ethical animal research: This study was authorised by the Ethics and Welfare Committee of the Royal Veterinary College. The study was performed on material obtained from abattoirs. Source of funding: Royal Veterinary College. Competing interests: None declared. Acknowledgements: We thank the technical teams of the Equine Referral Hospital Diagnostic Imaging and Pathology departments and the clinical veterinary students.
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