Evaluation of subchondral bone mineral density associated with articular cartilage structure and integrity in healthy equine joints with different functional demands.
OBJECTIVE
To determine and correlate subchondral bone mineral density and overlying cartilage structure and tensile integrity in mature healthy equine stifle (low magnitude loading) and metacarpophalangeal (high magnitude loading) joints.


METHODS
8 healthy horses, 2 to 3 years of age.


METHODS
Osteochondral samples were acquired from the medial femoral condyle (FC) and medial trochlear ridge (TR) of the stifle joint and from the dorsal (MC3D) and palmar (MC3P) aspects of the distal medial third metacarpal condyles of the metacarpophalangeal joint. Articular cartilage surface fibrillation (evaluated via India ink staining) and tensile biomechanical properties were determined. The volumetric bone mineral density (vBMD) of the underlying subchondral plate was assessed via dual-energy x-ray absorptiometry.


RESULTS
Cartilage staining (fibrillation), tensile moduli, tensile strength, and vBMD were greater in the MC3D and MC3P locations, compared with the FC and TR locations, whereas tensile strain at failure was less in MC3D and MC3P locations than FC and TR locations. Cartilage tensile moduli correlated positively with vBMD, whereas cartilage staining and tensile strain at failure correlated negatively with vBMD.


CONCLUSIONS
In areas of high joint loading, the subchondral bone had high vBMD and the articular cartilage surface layer had high tensile stiffness but signs of structural wear (fibrillation and low failure strain). The site-dependent variations and relationships in this study support the concept that articular cartilage and subchondral bone normally adapt to physiologic loading in a coordinated way.
Lewis
Chad W
CW
Department of Mechanical Engineering, College of Engineering, Colorado State University, Fort Collins, CO 80523, USA.
Williamson
Amanda K
AK
Chen
Albert C
AC
Bae
Won C
WC
Temple
Michele M
MM
Wong
W Van
WV
Nugent
Gayle E
GE
James
Susan P
SP
Wheeler
Donna L
DL
Sah
Robert L
RL
Kawcak
Chris E
CE
D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology*; D002358:Cartilage, Articular / Q000033:anatomy & histology; D005269:Femur / Q000033:anatomy & histology* / Q000502:physiology; D006736:Horses / Q000033:anatomy & histology* / Q000502:physiology; D007596:Joints / Q000033:anatomy & histology; D050279:Metacarpal Bones / Q000033:anatomy & histology* / Q000502:physiology; D013264:Stifle / Q000033:anatomy & histology