Microstructural properties of the proximal sesamoid bones of Thoroughbred racehorses in training

Ayodele, Babatunde A.; Hitchens, Peta L.; Wong, Adelene S. M.; Mackie, Eleanor J.; Whitton, R. C.

doi:10.1111/evj.13394

Cited by 9 publications

(21 citation statements)

References 37 publications

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“…To our knowledge, the microstructure of the proximal sesamoid or dorsal MCIII bone has not been examined using our methodology. Our total specimen proximal sesamoid bone volume fraction results are comparable to a study isolating the midbody dorsal sesamoid bone (mean bone volume fraction 0.86 ± 0.06, similar to our 0.83 ± 0.05); however the bone mineral density in our specimens appears higher (mean 928.29 ± 12.60 compared to 828.56 ± 19.60 mg HA/ccm) ( 13 ). This may be due to differences in site selection, resolution of imaging, or local or individual microdamage as a number of microfractures are associated with BVTV in the proximal sesamoid ( 13 ).…”

Section: Discussionsupporting

confidence: 88%

“…The differences in BVTV and BMD between studies may represent densification and remodeling due to different training volumes and microdamage burdens . Our samples were selected to have relatively low damage burdens and were therefore likely to have lower BVTV as damage and BVTV are highly correlated ( 9 , 13 ). Increasing bone mineral density with increased distance from the articular surface is a consistent feature in the palmar MCIII bone ( 16 , 20 , 32 ) and was also present in our dorsal MCIII and proximal sesamoid specimens.…”

Section: Discussionmentioning

confidence: 99%

“…Within the joint, fatigue-related SCB microdamage is most common and severe in the disto-palmar third metacarpal condyle (MCIII), a site that articulates with the proximal sesamoid bone when the joint is under extension during midstance ( 11 , 12 ). Microdamage is less severe in proximal sesamoid SCB ( 13 ), and rare in the disto-dorsal MCIII ( 14 , 15 ).…”

Section: Introductionmentioning

confidence: 99%

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Biomechanical and Microstructural Properties of Subchondral Bone From Three Metacarpophalangeal Joint Sites in Thoroughbred Racehorses

Pearce

Hitchens²,

Malekipour³

et al. 2022

Front. Vet. Sci.

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Fatigue-induced subchondral bone (SCB) injury is common in racehorses. Understanding how subchondral microstructure and microdamage influence mechanical properties is important for developing injury prevention strategies. Mechanical properties of the disto-palmar third metacarpal condyle (MCIII) correlate poorly with microstructure, and it is unknown whether the properties of other sites within the metacarpophalangeal (fetlock) joint are similarly complex. We aimed to investigate the mechanical and structural properties of equine SCB from specimens with minimal evidence of macroscopic disease. Three sites within the metacarpophalangeal joint were examined: the disto-palmar MCIII, disto-dorsal MCIII, and proximal sesamoid bone. Two regions of interest within the SCB were compared, a 2 mm superficial and an underlying 2 mm deep layer. Cartilage-bone specimens underwent micro-computed tomography, then cyclic compression for 100 cycles at 2 Hz. Disto-dorsal MCIII specimens were loaded to 30 MPa (n = 10), while disto-palmar MCIII (n = 10) and proximal sesamoid (n = 10) specimens were loaded to 40 MPa. Digital image correlation determined local strains. Specimens were stained with lead-uranyl acetate for volumetric microdamage quantification. The dorsal MCIII SCB had lower bone volume fraction (BVTV), bone mineral density (BMD), and stiffness compared to the palmar MCIII and sesamoid bone (p < 0.05). Superficial SCB had higher BVTV and lower BMD than deeper SCB (p < 0.05), except at the palmar MCIII site where there was no difference in BVTV between depths (p = 0.419). At all sites, the deep bone was stiffer (p < 0.001), although the superficial to deep gradient was smaller in the dorsal MCIII. Hysteresis (energy loss) was greater superficially in palmar MCIII and sesamoid (p < 0.001), but not dorsal MCIII specimens (p = 0.118). The stiffness increased with cyclic loading in total cartilage-bone specimens (p < 0.001), but not in superficial and deep layers of the bone, whereas hysteresis decreased with the cycle for all sites and layers (p < 0.001). Superficial equine SCB is uniformly less stiff than deeper bone despite non-uniform differences in bone density and damage levels. The more compliant superficial layer has an important role in energy dissipation, but whether this is a specific adaptation or a result of microdamage accumulation is not clear.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Biomechanical and Microstructural Properties of Subchondral Bone From Three Metacarpophalangeal Joint Sites in Thoroughbred Racehorses

Pearce

Hitchens²,

Malekipour³

et al. 2022

Front. Vet. Sci.

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“…Although palmar osteochondral disease was not analyzed in these cases, an abnormal articular surface of the third metacarpal condyle may play a role in microdamage accumulation in the articular margin of PSBs 25 . The location of microcracks at the articular subchondral margin is consistent with another study using micro‐CT as a modality for detection, where microcracks were most common in the articular mid‐body region in the calcified cartilage and subchondral bone detected at a resolution of 24.2 μm 27 . In the current study, microcracks were not detected via LUA‐stained micro‐CT with a resolution of 40 μm.…”

Section: Discussionsupporting

confidence: 81%

“…25 The location of microcracks at the articular subchondral margin is consistent with another study using micro-CT as a modality for detection, where microcracks were most common in the articular mid-body region in the calcified cartilage and subchondral bone detected at a resolution of 24.2 μm. 27 In the current study, microcracks were not detected via LUA-stained micro-CT with a resolution of 40 μm. LUA staining of the periphery could have obscured damage given that microcracks were only detected in the calcified cartilage and subchondral bone in the previous study by Ayodele et al It is also possible that microcracks were not detectable at a resolution of 40 μm.…”

Section: Discussioncontrasting

confidence: 46%

Proximal sesamoid bone microdamage is localized to articular subchondral regions in Thoroughbred racehorses, with similar fracture toughness between fracture and controls

et al. 2022

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Objective To determine whether proximal sesamoid bone (PSB) microdamage and fracture toughness differ between Thoroughbred racehorses sustaining PSB fracture and controls. Study design Cadaveric case–control. Animals Twenty‐four Thoroughbred racehorses (n = 12 PSB fracture, n = 12 control). Methods Proximal sesamoid bones were dissected, and gross pathological changes and morphological measurements were documented. High‐speed exercise history data were evaluated. Microdamage was assessed in fracture, fracture‐contralateral limb (FXCL) and control PSBs using whole bone lead uranyl acetate (LUA) staining with micro‐CT imaging or basic fuchsin histological analysis. Fracture toughness mechanical testing was carried out in 3‐point‐bending of microbeams created from PSB flexor cortices. Data were analyzed using ordinal logistic and linear regression models. Results Microdamage was detected most commonly in the articular subchondral region of PSBs via LUA micro‐CT and basic fuchsin histology. There were no differences in microdamage between FXCL and control PSBs. Fracture toughness values were similar for FXCL (1.31 MPa√m) and control (1.35 MPa√m) PSBs. Exercise histories were similar except that horses sustaining fracture spent a greater percentage of their careers in rest weeks. Conclusion Microdamage was detected in the articular region of PSBs but was not greater in horses sustaining catastrophic PSB fracture. Fracture toughness of PSB flexor cortices did not differ between FXCL and control PSBs. Clinical significance Although uncommon, microdamage is localized to the articular region of Thoroughbred racehorse PSBs. Catastrophic PSB failure is not associated with lower PSB flexor cortex fracture toughness.

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

Shaffer

Garcia

Stover

et al. 2022

Journal Orthopaedic Research

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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. Exercise intensity was negatively related to BVF (0.07 ≤ R2 ≤ 0.12) and positively related to microcrack areal density (0.21 ≤ R2 ≤ 0.29) in the lesion; however, in an undamaged site, the relationships were opposite in direction. Regardless of location, TMD decreased with event frequency for both Case and Control, suggesting increased bone remodeling with exercise. Measures of how often animals were removed from active training (layups) predicted a decrease in TMD, AMD, BVF, and microdamage at regions away from the lesion site. A steady‐state compartment model was used to organize the differences in the correlations between variables within the data set. The overall conclusions are that at the osteopenic lesion site, repair of microdamage by remodeling was not successful (e.g., lower bone mass, increased damage, and lower mineralization) but that in regions away from the lesion remodeling successfully controlled damage (e.g., higher bone mass, less microdamage, and lower mineralization).

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Microstructural properties of the proximal sesamoid bones of Thoroughbred racehorses in training

Cited by 9 publications

References 37 publications

Biomechanical and Microstructural Properties of Subchondral Bone From Three Metacarpophalangeal Joint Sites in Thoroughbred Racehorses

Biomechanical and Microstructural Properties of Subchondral Bone From Three Metacarpophalangeal Joint Sites in Thoroughbred Racehorses

Proximal sesamoid bone microdamage is localized to articular subchondral regions in Thoroughbred racehorses, with similar fracture toughness between fracture and controls

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

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