Young's modulus and Poisson's ratios of 6 mm-sized cubes of equine cortical bone were measured incompression using a micromechanical loading device. Surface displacements were determined by electronicspeckle pattern-correlation interferometry. This method allows for non-destructive testing of very small samples in water. Analyses of standard materials showed that the method is accurate and precise for determining both Young's modulus and Poisson's ratio. Material properties were determined concurrently in three orthogonal anatomic directions (axial, radial and transverse). Young's modulus values were found to beanisotropic and consistent with values of equine cortical bone reported in the literature. Poisson's ratios were also found to be anisotropic, but lower than those previously reported. Poisson's ratios for the radial-transverse and transverse radial directions were 0.15 +/- 0.02, for the axial-transverse and axial-radial directions 0.19 +/- 0.04, and for the transverse-axial and radial-axial direction 0.09 +/- 0.02 (mean +/- SD). Cubes located only millimetres apart had significantly different elastic properties, showing that significant spatial variation occurs in equine cortical bone. (c) 2006 Elsevier Ltd. All rights reserved.

Understanding the relations between the mechanical responses of whole entities, their materials properties and their structures, is a challenge. This challenge is greatly enhanced when the material itself is complex, and when the entity it forms has a convoluted shape. It is for these reasons that it is still beyond the state-of-the-art to predict and fully understand the mechanical functions of whole biological entities such as bones and teeth. Recent advances in optical metrology open up new opportunities as they enable the precise and accurate mapping of the manner in which the entire surface of a whole stiff mineralized tissue deforms. Furthermore these data can be obtained non-destructively and without contact with the sample. Data of this kind create the exciting possibility of relating the complex distribution of mechanical properties of loaded biological materials such as bone and teeth and their microstructures to deformations and strains. Such studies could improve our understanding of normal physiological processes such as skeletal aging, as well as disease processes such as osteoporosis. They also provide opportunities for engineers designing bio-inspired materials to study the principles, advantages, and characteristics of the behavior of hierarchical and multifunctional materials. 

In this manuscript we review optical metrology methods, highlight studies of whole body function for bones and teeth, and in particular those studies that provide insights into structure-function relations. We also outline the potential for future studies.

Endo-beta-mannanase is one of the key enzymes involved in the hydrolysis of the mannan-rich cell walls oftomato (Solanum lycopersicon) seeds. Two isoforms of endo-beta-mannanase have been characterized intomato seeds: LeMAN2 is active in the micropylar area prior to germination and LeMAN1 is active aftergermination in all endosperm cells surrounding the cotyledons. To explore whether general mannanase activity in the endosperm cap is sufficient to promote germination, the gene encoding Le.MAN3 was inserted into transgenic tomato plants under the control of a CaMV-35S promoter. Expression of LeMAN3 was evident in the endosperm cap and in the lateral endosperm of the transgenic seeds 10 min after imbibition. An activity test indicated increased activity of endo-beta-mannanase in the transgenic lines relative to thecontrol line in all seed parts, during the first 20 h of imbibition. However, overexpression of LeMAN3 intransgenic seeds inhibited seed germination at both optimal and suboptimal temperatures. Detailed RT-PCR analyses revealed the transcription patterns of the genes encoding the various mannanase isoforms, and indicated a delay in LeMAN2 transcription in the endosperm cap of the transgenic seeds. Interestingly, tissue-print assays indicated similar mannanase activity in the micropylar areas for both transgenic andcontrol seeds. These results indicate that overexpression of active endo-beta-mannanase in the endosperm cap is not sufficient to enable hydrolysis of the cell walls or to promote germination of tomato seeds. Cell-wall hydrolysis in these endosperm cells is under tight control and requires the specific activity of LeMAN2.

Objective - To evaluate the effect of tibial plateau leveling on the biomechanics of the canine stifle. 

Study Design - Analysis of a 3-dimensional (3-D) anatomically accurate theoretical model of the canine stifle. 

Methods - A 3-D, 3-segment mathematical model of the normal canine stifle was modified to simulate the effect of rotation of the tibial plateau during tibial plateau leveling osteotomy (TPLO). The model examined the normal stifle, the stifle with a tibial plateau angle (TPA) of 0 degrees, and the stifle with a TPA of 5 degrees. Analysis of the models at 10 consecutive equally spaced positions during the stance phase yielded data such as ligament forces and joint reaction forces at each position. 

Results - Rotation of the tibial plateau to a TPA of 0 degrees almost eliminates forces in the cranial cruciate ligament (CCL) throughout the stance phase. Rotation to a TPA of 5 degrees did not, however, substantially decrease the load in the CCL. Both procedures increased the load in the caudal cruciate ligament (CaCL). 

Conclusions - Cranial tibial thrust (CTT) is converted into caudal tibial thrust when the TPA is 0 degrees; however, rotating the plateau to a TPA of 5 degrees does not eliminate the CTT. 

Clinical Relevance - The TPLO procedure performed as currently recommended (rotating the tibial plateau to a TPA of 5 degrees) may not eliminate the CTT, but only reduce it. Both TPLO procedures evaluated here were found to increase the load in the CaCL. (c) Copyright 2006 by The American College of Veterinary Surgeons.

Objective - To define landmarks on the canine ilial wing for accurate, consistent insertion of implants into the1st sacral (S1) vertebral body when the sacroiliac joint is intact. 

Study Design - Anatomic study. 

Animals - Intact, cadaveric canine pelves and sacra (n=25). 

Methods - Median sections (5 specimens) were drilled from the center of S1 in a lateral direction, exiting onthe ilial wing. Landmarks on the ilial wing and shaft used to define this exit point were then used to locate this point on both wings of 20 articulated specimens, positioned and rigidly held so that the dorsal plane ofthe pelvis was aligned with a plumb line and the median plane of the pelvis was horizontal. A 2 mm hole was drilled from the marked point, parallel to the plumb line, until it exited the contralateral ilial wing. Distance ofdrill hole position from the geometric center (GC) of S1 was located on median and paramedian plane images derived from plane, computed tomographic (CT) scans. 

Results - The entire drill hole was located within S1 in 18 specimens. Mean deviation of the hole from GC (ratio of the distance of GC from the closest S1 body border) in median section was 0.40 +/- 0.29 (craniocaudal direction) and 0.29 +/- 0.23 (dorsoventral). 

Conclusions - Use of ilial wing landmarks and drilling perpendicular to the median plane will improve accuracy for insertion of implants into S1 when the sacroiliac joint is intact. 

Clinical Relevance - Ilial wing landmarks should be used to improve accuracy of implant insertion into S1. (c) Copyright 2006 by The American College of Veterinary Surgeons.

The manner in which stiff biological objects, such as whole bones and teeth, deform under load can provide direct insight into their in vivo functions, while highlighting the relations between their structure and materialsproperties. A new approach for studying the mechanical functions of such objects, using as an example the crowns of human teeth, is developed. Tooth-crown deformation under a compressive load is determined inwater using laser speckle interferometry. The deformation patterns are analyzed using a novel procedure that reveals the relative magnitudes of 3D displacements of the outer surface. Nanometer-scale deformations of natural teeth were compared to deformations of identical acrylic replicas, in order to differentiate betweencontributions of the structure-material properties from contributions of morphology. It is shown that human premolars deform in a manner that is largely controlled by shape; in natural teeth, the enamel cap appears to displace mainly as a rigid body, undergoing moderate deformation. These observations contribute to the understanding of whole-tooth performance under load. The approach for analyzing the deformation of loaded whole objects is directly applicable to the study of many stiff biological specimens, including comparisonsbetween normal and altered (repaired or genetically modified) bones.

The morphometric properties and the anatomical relationships of the entire musculature of the canine cervical spine are reported herein. These data were obtained from the dissection of cadavers of six dogs. Total muscle length, muscle weight, fascicle length and angles of pennation were recorded for each muscle comprising the canine cervical spine. Based upon these properties, physiological cross-section area (PCSA) and architectural index were estimated. When scaled by whole body mass, the values of each ofthese parameters were found to be similar between all dogs. Muscles that course from the cranial neck tothe shoulder girdle or the rib cage (e.g. brachiocephalicus and rhomboideus capitis) were found to have relatively long fascicles and low PCSA values and thus appear to be designed for rapid excursions. By contrast, muscles that primarily support the neck and shoulder against gravitational forces (e.g. serratus ventralis and trapezius) were found to have relatively high PCSA values and short fascicle lengths, and thus have the capacity to generate large forces. Differences of morphometry as well as nomenclature were found between the canine and human neck musculature. Nevertheless, many similarities exist; in particular, both species have similar muscles adapted to force generation or large excursions. We thus conclude that thecanine neck may be used as a modelling tool for biomechanical investigations of the human cervical region as long as the differences listed are borne in mind.

Hyperextension injury of the tarsometatarsal joint (TMTJ) is a debilitating injury and arthrodesis of this joint is often the only procedure that can result in full return to function. Most surgical procedures described for arthrodesis of the tarsometatarsal joint necessitate the use of external, splint or cast, to protect the implants used from fatigue failure. This report describes the successful use of type II external fixator that spans the tarsometatarsal joint in four dogs with hyperextension injury of the tarsometatarsal joint. This technique enables the patient to bear weight on the limb immediately after surgery until bony fusion is achieved, without the need for an additional protecting splint.

Objectives-To compare the expression of canine relaxin, relaxin-like factor (RLF), and relaxin receptors within the muscles of the pelvic diaphragm of dogs with perineal hernia (PH) and clinically normal dogs. 

Study Design-In vivo comparative study. 

Animals-Fifteen client-owned intact male dogs with PH were studied. Four mature intact male dogs with no evidence of perineal pathology served as controls. 

Methods-Biopsy samples from the levator am, coccygeus, and internal obturator muscles were obtained. RNA samples were reverse transcribed and analyzed by real-time PCR for the expression of canine relaxin receptor LRG7, relaxin, and RLF. 

Results-Significantly higher expression levels of canine relaxin receptors occurred in the musculature of the pelvic diaphragm and internal obturator muscle in dogs with PH compared with normal dogs. Expression of canine RLF revealed no significant difference between dogs with PH and controls. The difference in the expression of canine relaxin between groups was not statistically significant. 

Conclusions-Relaxin receptor up-regulation occurs in the coccygeus, levator ani, and internal obturator muscles of dogs with PH. 

Clinical Relevance-The higher expression of relaxin receptors within the muscles of the pelvic diaphragm in dogs with PH suggests that relaxin might play a role in the pathogenesis of PH. Atrophy of these muscles, which predisposes to PH, may be attributable to increased relaxin activity. (c) Copyright 2005 by The American College of Veterinary Surgeons.

(P) atient-specific finite element (FE) modelling is a promising technology that is expected to support clinical assessment of the spine in the near future. To allow rapid, robust and economic patient-specific modelling of the whole spine or of large spine segments, it is practicable to consider vertebral cancellous bone in the spine as a continuum material, but the elastic modulus of that continuum material must reflect the quality of the individual vertebral bone. A numerical parametric model of lattice trabecular architecture has been developed for determining the apparent elastic modulus of cancellous bone E-cb in vertebrae. The model inputs were apparent morphological parameters (trabecular thickness Tb-Th and trabecular separation Tb-Sp) and the bone mineral density (BMD), which can all be measured in vivo, using the spatial resolution of current clinical quantitative computed tomography (QCT) commercial whole-body scanners. The model predicted that Ecb values between 30 and 110 MPa represent normal morphology and BMD of human spinal cancellous bone. The present Ecb to Tb-Th, Tb-Sp and BMD relationships pave the way for automatic generation of patient-specific continuum FE spine models that consider the individual's osteoporotic or other degenerative condition of cancellous bone.

The object of this study was to obtain the anatomic and morphometric data required for biomechanical analyses of the forelimb in dogs. Following the euthanasia of four healthy, adult, crossbred dogs, 44 muscles of the right forelimb were identified and meticulously removed. Morphometric data for all muscles were collected and physiologic cross-sectional areas (PCSA) and architectural indices (AI) were calculated. The coordinates of the origin and insertion of each muscle were determined using orthogonal, right-handed coordinate systems embedded in the scapula, humerus, and radius-ulna. The PCSA and AI were calculated for all the muscles and coordinates for the origins and insertions of these muscles were determined. Results provide the morphometric and anatomic data necessary for three-dimensional biomechanical studies of the forelimb in dogs. (C) 2004 Wiley-Liss, Inc.

The clinical use of stainless steel wire in veterinary orthopaedics is common, and occurs in diverse situations. One of the most common uses of stainless steel wire is the fabello-tibial suture to stabilize the cranial cruciate deficient knee (10). Numerous reports have appeared in the literature, describing biomechanical aspects of the use of stainless steel wire. The purpose of the study presented herein was to compare the strength and performance of two methods used to fasten loops of stainless steel wire: the traditional twist-knot method and the crimp-clamp method. Both loop-fastening methods were evaluated with two diameters of wire (1.0 mm and 1.2 mm). Both static and dynamic (cyclical) testing procedures were performed. Using a materials testing machine maximum tensile strength (load to failure), loop elongation, mode of loop failure and location of loop failure were recorded. The results of the study demonstrate that loops fastened with the crimp clamp method resulted in higher load to failure than the traditional twist knot method.

Bilateral external fixator frames ore frequently preferred over unilateral frames due to their superior rigidity. The objective of this study was to compare the biomechanical features of bilateral external fixators with those of unilateral external fixators that are combined with an intra-medullary pin. Three-dimensional, solid models were created of several unilateral and bilateral external fixator frames. The callus in the fracture gap was also modeled. Biomechanical analyses of all constructs were performed by the finite element method. This modeling approach allows the determination of stresses, displacements, and strains in the components of the various constructs, and thus the calculation of their relative stiffness. In addition, local shear strain values in the fracture gap, currently thought to be one of the deciding factors in the process of bone healing, can also be determined. The concept of equivalent stiffness modulus, which represents a weighed average stiffness of a construct to various loads, was defined. Using this concept, it was shown that when the intramedullary pin is well seated in the epiphyseal bone, the various unilateral frames have an equivalent stiffness modulus that is similar or even greater than that of bilateral frames with a similar arrangement of transcortical pins.

The purpose of this study was to develop a reliable and repeatable radiographic protocol for the measurement of joint angles in the standing dog, and to use this protocol to determine all standing joint angles for dogs over a wide range of body weights. The radiographic technique and the method of joint angle measurements were found to be highly repeatable, suggesting that the technique is reliable. Most joint angles did not vary between dogs of different weights. In those few instances where significant differences (p<0.05) were found, certain trends were followed and represent differences in conformation. This paper presents a complete description of the angles defining the position of the joints in a standing dog. This information is important for biomechanical studies, for clinical assessment of dogs, and for the design of surgical procedures such as arthrodesis.

A mathematical, three-dimensional, anatomically accurate model of the canine knee was created to determine the forces in the knee ligaments and the kneejoint reaction forces during the stance phase of a slow walk. This quasi-static model considered both the tibio-femoral and patello-femoral articulations. The geometric and morphometric data of the hind limb were obtained from cadaver data. Muscle forces acting on the femur and the hip joint reaction force were determined by numerical optimization. Ligaments were modeled as non-linear-springs. Ligament material properties were obtained from the literature pertaining to the human knee. The model consists of -28 non-linear algebraic equations describing equilibrium of the femur and the patella, and geometric constraints. This system of equations was solved by a non-linear least-squares method. Results are presented for a knee with an intact cranial cruciate ligament (CCL) and for a knee with a ruptured CCL. Forces predicted to occur in the CCL by analysis of the model were found to be very similar to reported results of CCL forces measured in vivo in goats. (C) 2004 Elsevier Ltd. All rights reserved.

Objective-To report partial esophagectomy (PE) as a treatment for esophageal sarcoma in dogs. 

Study Design-Retrospective study (2000-2002). 

Animals-Six dogs with caudal thoracic esophageal tumors. 

Methods-Medical records of 6 dogs that had surgical removal of esophageal tumors were reviewed. Signalment, medical history, physical examination results, complete blood count, surgical procedure, tumor classification, postoperative treatment, and complications were retrieved. 

Results-Esophageal masses were approached by thoracotomy and esophagotomy on the side opposite the mass, removed with I cm margins by full thickness excision, and the defects closed with a single layer of interrupted sutures. All dogs recovered rapidly without major complications. Tumors were fibrosarcoma (3 dogs), undifferentiated sarcoma (1), and osteosarcoma (2). Five dogs were administered doxorubicin chemotherapy after surgery. Good quality of life was observed postoperatively in 5 dogs until deterioration necessitated euthanasia; survival ranged from 2-16 months. The remaining dog was alive, 20 months after surgery. 

Conclusions-Partial esophagectomy and closure using I suture layer, was an effective, simple, and safe technique for removal of sarcomas of the distal thoracic esophagus. 

Clinical Relevance Removal of esophageal masses by partial esophagectomy can be used reliably as a method of esophageal surgery. (C) Copyright 2004 by The American College of Veterinary Surgeons.

A wide variety of surgical techniques to stabilize the coxo-femoral joint have been described in the veterinary literature. In this paper twenty small animals (19 dogs and 1 cat) were treated successfully with open reduction and an extra-capsular suture taken between the greater trochanter of the femur and the origin of the rectus femoris muscle. The technique is simple, quick and safe, and avoids many of the potential complications associated with other methods.

The object of this study was to examine the effect of high intensity, short duration pulsed electromagnetic fields (PEMF) on the healing of full thickness skin wounds in rats. Full thickness skin wounds were surgically created in two groups of Sprague-Dawley male rats. The rats were randomly divided into two groups, each containing 20 rats. Animals in the treatment group received treatments with the PEMF device on day 0, 3, 7, 9, 12, 14, 17, and 22, while the rats in the control group were subjected to the same procedure, but with the PEMF device not activated. Photographs of the surgically created wounds were obtained on day 0, 3, 7, 9, 12, 14, 17, and 22. Wound contraction (WC), wound epithelialization (WE), non-healed wound, and contraction-epithelialization (CE) ratio were calculated for each wound. No significant difference was found between the two groups for the parameters of WC, WE, non-healed wound, and CE ratio. A significant group x time interaction was found for WE and CE ratio. This type of PEMF did not have a significantly beneficial effect on wound healing. Wounds in the PEMF treated group were relatively less contracted and showed a compensatory increase in epithelialization in the early stages of wound repair. (C) 2004 Wiley-Liss, Inc.

The long-term performance of total hip replacement is of concern to veterinary surgeons. Two of the main complications associated with this procedure ore implant loosening and stress shielding. Designs of the femoral stem which will avoid loosening and achieve maximum endurance while reducing stress shielding and periprosthetic bone loss are sought. 

In the intact femur the stress is distributed over the entire cross section of the bone. After hip replacement this pattern of stress distribution is altered because of the manner in which the load is transferred from the prosthesis to the bone. 

The objective of this study was to examine the stresses that develop in the femur and implant components of two different methods of hip replacement used clinically in dogs. Anatomic, three-dimensional finite element models of the canine femur with a cemented femoral stem and a Zurich cementless stem were constructed. The stresses and displacements were calculated by the finite element analysis method, under physiologic loads that included muscle forces and joint reaction forces. The results were compared to results obtained by a similar analysis of an intact femur. This study demonstrates that the Zurich cementless method causes less stress shielding in the proximal femoral cortex than does the cemented method. Implant stresses are higher in the Zurich cementless stem, but still within an acceptable range.

Information regarding the stresses and strains in the canine femur during various activities is important for veterinary orthopaedic surgeons, engineers designing implants for dogs, and researchers of human orthopaedics who use dogs as models. Nevertheless, such information is currently unavailable. The objective of this study is to determine the stress and strain distribution in the canine femur during mid-stance, for two loading scenarios. Three-dimensional finite element models of the canine femur were created. Two loading cases were considered: the hip joint reaction force alone, and the hip joint reaction force with all muscle forces acting on the femur. Force directions and magnitudes were obtained from the literature. Analyses were performed with NASTRAN for Windows(R) software. When all muscle forces were considered, stresses and strains were significantly reduced, peak compressive stresses were found to occur in the medial diaphysis, and peak tensile stresses occurred in the lateral diaphysis. While the canine femur seems to be, loaded primarily in bending when only the hip joint reaction force is considered, the bending moment is significantly decreased when all muscle forces are considered as well. Further in vivo and in vitro experiments are needed to validate the results of the calculations described in this paper. It is expected that future studies will be carried out, in which the stress and strain distributions in femora with different types of implants and stems will be compared to those in the normal femur. (C) 2003 IPEM. Published by Elsevier Science Ltd. All rights reserved.