Re: Rear breakdowns/ SIGHTSOUND'S VET STUDY POST (562 Views)
Posted by:
marcus (IP Logged)
Date: June 07, 2006 06:43PM
PT 2 OF SIGHTSOUND RE-POST ( along w/ subsequent threard )
sighthound Wrote:
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> The horse leg is a fascinating display of
> integrated biomechanics. Certainly there's ample
> evidence that some condylar fractures are the
> final culmination of previous small, cumulative
> microfractures. Failure of one small component
> leads to disaster of the whole. Barbaro's bones
> didn't all shatter in one stride.
>
> In the end, the only people able to knowledgably
> search their hearts about a possible prior warning
> of a problem would be the man that rode the horse
> daily and felt every movement and breath, and the
> trainer who afterwards ran his hands over every
> tendon and joint. Matz has been the man on the
> back of 1100 pounds landing on one coffin bone
> after clearing a 6-foot wide oxer.
>
> We're armchair quarterbacks <g> that can
> emotionally walk away. They are the only folks
> having to bear forever the "what if?" self-doubts.
> My heart goes out to them for that.
>
> Scanning electron microscopic examination of third
> metacarpal/third metatarsal bone failure surfaces
> in thoroughbred racehorses with condylar
> fracture.
> Vet Surg 33[1]:2-10 2004 Jan-Feb Stepnik MW,
> Radtke CL, Scollay MC, Oshel PE, Albrecht RM,
> Santschi EM, Markel MD, Muir P
> Comparative Orthopaedic Research Laboratory,
> School of Veterinary Medicine, University of
> Wisconsin-Madison, Madison, WI 53706, USA.
> OBJECTIVE : To examine the fracture failure
> surfaces from Thoroughbred horses that had
> sustained a catastrophic condylar fracture. SAMPLE
> POPULATION : Bone specimens from the failure
> surface were obtained from 12 Thoroughbred
> racehorses with catastrophic injury and 2
> non-racing horses with accidental long bone
> fracture. METHODS : Bone specimens from the
> failure surface of each fracture were incubated
> with gold microspheres to label microcracks before
> examination at x50 to x60,000 using scanning
> electron microscopy. Microcracking at the failure
> surface was assessed using a visual analog scale.
> RESULTS : Branching arrays or clusters of
> microcracks were seen over a range of
> magnifications in adapted subchondral bone in the
> distal end of the MC3/MT3 bone from racing
> Thoroughbreds with a catastrophic displaced
> condylar fracture. In the palmar/plantar region,
> microcracking was associated with the formation of
> an array of macroscopic cracks in the condylar
> groove. A different pattern of microcracking was
> seen in specimens of bone from distal metaphyseal
> and diaphyseal MC3/MT3 failure surfaces from
> Thoroughbred racehorses with catastrophic fracture
> and non-racing horses with an accidental
> diaphyseal long bone fracture. Few microcracks
> were seen and typically did not form branching
> arrays. *** CONCLUSION : These data suggest that
> propagation of condylar fracture in Thoroughbred
> racehorses is initiated by the formation of
> nanoscale microcracks in adapted subchondral bone
> that form during exercise-induced bone adaptation.
> CLINICAL RELEVANCE : Accumulation and coalescence
> of branching microcracks into arrays or clusters
> appears to eventually lead to the development of
> macroscopic subchondral cracks in the condylar
> groove and initiation of a condylar fracture.
>
> Macroscopic changes in the distal ends of the
> third metacarpal and metatarsal bones of
> Thoroughbred racehorses with condylar fractures.
> Am J Vet Res 64[9]:1110-6 2003 Sep Radtke CL,
> Danova NA, Scollay MC, Santschi EM, Markel MD, Da
> Costa Gomez T, Muir P
> Comparative Orthopaedic Research Laboratory,
> Department of Surgical Sciences, School of
> Veterinary Medicine, University of Wisconsin,
> Madison, WI 53706, USA. OBJECTIVE: To determine
> changes in the distal ends of the third metacarpal
> and metatarsal bones (MCIII and MTIII) of
> Thoroughbred racehorses that had sustained a
> catastrophic condylar fracture during high-speed
> exercise. SAMPLE POPULATION: Fractured and
> contralateral MCIIIs and MTIIIs from 11
> Thoroughbred racehorses that sustained a displaced
> condylar fracture during racing, both MCIIIs from
> 5 Thoroughbred racehorses euthanized because of a
> catastrophic injury other than a condylar
> fracture, and both MCIIIs from 5 horses of other
> breeds that had not been professionally trained or
> raced. PROCEDURE: Macroscopic observations were
> made of the distal ends of the bones before and
> after digestion of the articular cartilage with
> NaOH. RESULTS: In all 11 racehorses with a
> displaced condylar fracture, the fracture was
> associated with a branching array of cracks in the
> condylar groove. In this region, fracture margins
> were smooth, and there was loss of subchondral
> bone. Comminution of the dorsal cortex was also
> seen. Parasagittal linear wear lines in the
> articular cartilage, erosions in the articular
> cartilage of the condyles, loss of the underlying
> subchondral bone, and cracking of condylar grooves
> were all more severe in the Thoroughbred
> racehorses than in the horses that had not been
> professionally trained or raced. ***CONCLUSIONS
> AND CLINICAL RELEVANCE: Results suggest that
> condylar fractures in horses are pathologic
> fatigue or stress fractures that arise from a
> preexisting, branching array of cracks in the
> condylar groove of the distal end of MCIII or
> MTIII.
>
> Biomechanical investigation of the association
> between suspensory ligament injury and lateral
> condylar fracture in thoroughbred racehorses.
> Vet Surg 32[6]:585-97 2003 Nov-Dec Le Jeune SS,
> Macdonald MH, Stover SM, Taylor KT, Gerdes M
> Veterinary Medical Teaching Hospital, Department
> of Surgical and Radiological Sciences, School of
> Veterinary Medicine, University of California,
> Davis, CA 95616, USA. Objective-To determine
> whether partial transection of the medial branch
> of the suspensory ligament (MBSL) alters equine
> third metacarpal bone (MC3) condylar surface
> strains and forelimb, distal joint angles in a
> manner consistent with promotion of lateral
> condylar fracture. Study Design-In vitro
> biomechanical experiment. Sample Population-Right
> forelimbs from 7 Thoroughbred horse cadavers.
> Methods-Lateral and medial MC3 condylar, dorsal
> and abaxial, bone surface strains and distal joint
> angles were measured both before and after partial
> transection of the MBSL during in vitro axial limb
> compression. Dorsal, principal bone strains and
> abaxial, uniaxial, and proximodistal strains were
> compared before and after MBSL partial transection
> at 1,400-, 3,000-, and 5,600-N loads. Results-Bone
> strains increased in all locations with increasing
> axial load. All lateral condylar bone strains were
> significantly higher, and abaxial surface medial
> condylar bone strain was significantly lower,
> after partial transection of the MBSL. Respective
> distal joints became more flexed or extended as
> axial load increased but were not significantly
> different after partial transection of the MBSL.
> Conclusions-Partial transection of the MBSL
> increases in vitro MC3 lateral condylar bone
> surface strains. ***Clinical Relevance-Loss of
> integrity of the medial branch of the suspensory
> ligament could increase the risk for lateral
> condylar fracture in Thoroughbred horses by
> amplifying bone strain in the lateral condyle.
>
>
Edited 4 time(s). Last edit at 06/07/2006 07:05PM by marcus.