Kirschner wire creates more microdamage than standard or acrylic drill bits in the rabbit (Oryctolagus cuniculi) femur.

Objective: Histologically evaluate damage to rabbit femur after the creation of bicortical 1.5-mm-diameter holes using a standard surgical drill bit, an acrylic drill bit, and a Kirschner wire (K-wire).

Methods: 10 femora (5 pairs) from skeletally mature female intact New Zealand white rabbits were used.

Computed tomography-derived structural analysis for the likelihood of pathologic fracture in canine antebrachial osteosarcoma.

Determining the risk of pathologic fracture in dogs with a primary bone tumor would aid in case selection for in-situ treatment options. Prior research found strong relationships between in vitro strength of canine antebrachii with primary bone tumors and CT-derived metrics. This study assesses the prognosis for pathologic fracture in dogs with distal radial bone tumors using CT-derived structural analysis metrics.

Condylar fracture location is correlated to exercise history in Thoroughbred racehorses.

Background: Condylar fractures are a major cause of morbidity and mortality in Thoroughbred racehorses. Condylar fractures have a variety of fracture configurations that suggest there may be differences in aetiopathogenesis.

Objective: To determine if exercise history differs with condylar fracture location in a population of Thoroughbred racehorses.

K-wire is more damaging than standard or acrylic drill bits when evaluating torsional properties of rabbit (Oryctolagus cuniculi) femurs.

Objective: The objective of this study is to compare drilling variables and torsional mechanical properties of rabbit femora after bicortical drilling with a 1.5-mm standard surgical drill bit, acrylic drill bit, and K-wire.

Samples: 24 pairs of rabbit femora.

Ex vivo biomechanical evaluation of an adhered fiberglass and polymethyl methacrylate sole-hoof wall cast on stabilization of type III distal phalanx fractures under simulated physiologic midstance loads.

Objective: To evaluate the effect of the application of a novel fiberglass-glue cast (FGC) on the fracture gap width in experimentally created type III distal phalanx fractures in cadaveric specimens under simulated physiologic loads.

Study Design: Ex vivo biomechanical laboratory study.

Animals: Nine unilateral adult equine cadaver forelimbs.

Hoof Expansion, Deformation, and Surface Strains Vary with Horseshoe Nail Positions.

Racehorses are susceptible to underrun heel hoof conformation. Racehorses are often shod with nails placed toward the heel. It is unknown if palmar nails restrict or alter hoof deformation in a manner that could promote the development of underrun heel conformation over time with repeated loading.

Effects of Jumping Phase, Leading Limb, and Arena Surface Type on Forelimb Hoof Movement.

During the stance phase of equine locomotion, ground reaction forces are exerted on the hoof, leading first to rapid deceleration ("braking") and later to acceleration ("propulsion") as the hoof leaves the ground. Excessive hoof deceleration has been identified as a risk factor for musculoskeletal injury and may be influenced by arena surface properties. Therefore, our objective was to evaluate the effect of arena surface type (dirt, synthetic) on hoof translation of the leading and trailing forelimbs during jump takeoff and landing.

Biomechanical comparison of compact versus standard flute drill bits, and interlocking versus buttress thread self-tapping cortical bone screws in cadaveric equine third metacarpal condyle.

Objectives: To compare (1) performance of compact versus standard flute drill bits, (2) screw insertion properties and (3) pullout variables between interlocking thread (ITS) and buttress thread (BTS) self-tapping screws in third metacarpi.

Study Design: In vitro experimental study.

Sample Population: Paired third metacarpi from 11 Thoroughbreds aged 2-4 years.

Training drives turnover rates in racehorse proximal sesamoid bones.

Focal bone lesions are often found prior to clinically relevant stress-fractures. Lesions are characterized by low bone volume fraction, low mineral density, and high levels of microdamage and are hypothesized to develop when bone tissue cannot sufficiently respond to damaging loading. It is difficult to determine how exercise drives the formation of these lesions because bone responds to mechanical loading and repairs damage.

Biomechanical evaluation of locking versus nonlocking 2.0-mm malleable L-miniplate fixation of simulated caudal mandibular fractures in cats.

Objective: To evaluate the biomechanical properties of the mandibles of cats with experimentally created osteotomies simulating oblique ramus fractures, which were stabilized with malleable L-miniplates with either locking screws [locking construct (LC)] or nonlocking screws [nonlocking construct (NLC)], compared with those for intact mandibles.

Samples: 20 mandibles from 10 adult cat cadavers.

Procedures: A block study design was adopted to allocate the mandibles of each cadaver to 2 of the 3 test groups (LC, NLC, or intact mandible).

A Coupled Biomechanical-Smoothed Particle Hydrodynamics Model for Horse Racing Tracks.

Distal limb injuries are common in racing horses and track surface properties have been associated with injury risk. To better understand how track surfaces may contribute to equine limb injury, we developed the first 3D computational model of the equine hoof interacting with a racetrack and simulated interactions with model representations of 1) a dirt surface and 2) an all-weather synthetic track. First, a computational track model using the Smoothed Particle Hydrodynamics (SPH) method with a Drucker-Prager (D-P) elastoplastic material model was developed.

Exercise history predicts focal differences in bone volume fraction, mineral density and microdamage in the proximal sesamoid bones of Thoroughbred racehorses.

Medial proximal sesamoid bones (PSBs) from Thoroughbred racehorses that did (Case) or did not (Control) experience unilateral biaxial PSB fracture were evaluated for bone volume fraction (BVF), apparent mineral density (AMD), tissue mineral density (TMD), and microdamage in Case fractured, Case contralateral limb intact, and Control bones. A majority of Case bones had a subchondral lesion with high microdamage density, and low BVF, AMD, and TMD. Lesion microdamage and densitometric measures were associated with training history by robust linear regression.

In vitro motions of the medial and lateral proximal sesamoid bones under mid-stance load conditions are consistent with racehorse fracture configurations.

Proximal sesamoid bone (PSB) fractures in racehorses are likely fatigue fractures that occur due to repetitive loads and stress remodeling. The loading circumstances that may induce damage in the PSBs are not well understood. The goal of this study was to determine in three-dimensions, PSB motions relative to the opposing metacarpal condyle during simulated mid-stance loads.

Sudden death caused by spinal cord injury associated with vertebral fractures and fetlock failure in a Thoroughbred racehorse.

The most prevalent causes of death in racehorses are musculoskeletal injuries, causing ~83% of deaths within the racing industry in California and elsewhere. The vast majority of these injuries have preexisting lesions that predispose to fatal injury. A 4-y-old Thoroughbred colt suffered an acute suspensory apparatus failure, including biaxial proximal sesamoid bone fractures of the right front fetlock, causing loss of support of the fetlock joint and consequent fall with fractures of the cervical and sacral spine.

How does bone strain vary between the third metacarpal and the proximal phalangeal bones of the equine distal limb?

Strain parameters at injury prone sites of the equine third metacarpal (MC3) and proximal phalangeal (P1) bones were investigated with the aim of improving understanding of injury pathogenesis. We hypothesized that dorsal principal and shear strain patterns, magnitudes and directions would differ from proximal-to-distal; and would be similar from medial-to-lateral across each bone. Unilateral limbs from nine equine cadavers were instrumented with rosette strain gauges during limb loading to 10,500 N.

Influence of interlocking thread screws to repair simulated adult canine humeral condylar fractures.

Objective: To determine the influence of interlocking screw threads on the biomechanical properties of repaired canine humeral condylar fractures.

Study Design: Ex vivo biomechanical study.

Sample Population: Thirty-six humeral condyles.

In vitro assessment of the motion of equine proximal sesamoid bones relative to the third metacarpal bone under physiologic midstance loads.

Objective: To assess the motion of the proximal sesamoid bones (PSBs) relative to the third metacarpal bone (MC3) of equine forelimbs during physiologic midstance loads.

Sample: 8 musculoskeletally normal forelimbs (7 right and 1 left) from 8 adult equine cadavers.

Procedures: Each forelimb was harvested at the mid-radius level and mounted in a material testing system so the hoof could be moved in a dorsal direction while the radius and MC3 remained vertical.

Characteristics of complete tibial fractures in California racehorses.

Background: Tibial fractures cause ~3% of racehorse deaths. Pre-existing stress fractures have been associated with multiple racing and training fractures, but not complete tibial fractures.

Objectives: To describe racehorse tibial fractures and compare signalment and exercise histories of affected and control racehorses.

Comparison of torsional properties between a Fixateur Externe du Service de Santé des Armées and an acrylic tie-in external skeletal fixator in a red-tailed hawk () synthetic tibiotarsal bone model.

Objective: To compare the torsional mechanical properties of 2 external skeletal fixators (ESFs) placed with 2 intramedullary pin (IP) and transfixation pin (TP) size combinations in a model of raptor tibiotarsal bone fracture.

Sample: 24 ESF-synthetic tibiotarsal bone model (polyoxymethylene) constructs.

Procedures: Synthetic bone models were fabricated with an 8-mm (simulated fracture) gap.

Subchondral focal osteopenia associated with proximal sesamoid bone fracture in Thoroughbred racehorses.

Background: Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress-related process. However, the aetiopathogenesis of PSB fracture is poorly understood.

Kinematic analysis of mandibular motion before and after mandibulectomy and mandibular reconstruction in dogs.

Objective: To evaluate and quantify the kinematic behavior of canine mandibles before and after bilateral rostral or unilateral segmental mandibulectomy as well as after mandibular reconstruction with a locking reconstruction plate in ex vivo conditions.

Sample: Head specimens from cadavers of 16 dogs (range in body weight, 30 to 35 kg).

Procedure: Specimens were assigned to undergo unilateral segmental (n = 8) or bilateral rostral (8) mandibulectomy and then mandibular reconstruction by internal fixation with locking plates.

Comparative histomorphometric analysis of cellular phenotype in canine stifle ligaments and tendon.

Objective: To measure the density of cellular phenotypes in canine caudal cruciate ligament (CaCL), cranial cruciate ligament (CrCL), medial collateral ligament (MCL), and long digital extensor tendon (LDET).

Study Design: Ex-vivo study.

Methods: Ten CaCL, CrCL, MCL, and LDET obtained from 1 stifle of 10 dogs with no gross pathology were analyzed histologically.

A natural energy absorbent polymer composite: The equine hoof wall.

The equine hoof has been considered as an efficient energy absorption layer that protects the skeletal elements from impact when galloping. In the present study, the hierarchical structure of a fresh equine hoof wall and the energy absorption mechanisms are investigated. Tubules are found embedded in the intertubular matrix forming the hoof wall at the microscale.

Effects of Hole Diameter on Torsional Mechanical Properties of the Rabbit Femur.

Objective:  The aim of this study was to evaluate and compare the effect of three clinically applicable screw hole diameters on rabbit femoral torsional structural properties.

Sample:  Eighteen pairs of skeletally mature New Zealand White rabbit femora (36 bones).

Materials And Methods:  Femora with a bicortical hole at mid-diaphysis from one of the 3-drill bit sizes, 1.