Quantification and age-related distribution of articular cartilage degeneration in the equine fetlock joint.
BACKGROUND
The equine fetlock joint has the largest number of traumatic and degenerative lesions of all joints of the appendicular skeleton.


OBJECTIVE
To gain insight into the distribution of cartilage degeneration across the articular surface in relation to age in order better to understand the dynamic nature and progression of osteoarthritis (OA).


OBJECTIVE
That there would be a specific age-related distribution pattern of cartilage degeneration in the equine metacarpophalangeal joint.


METHODS
The proximal articular cartilage surfaces of the first phalanges (P1) of 73 slaughter horses (age range 0.4-23 years) with different stages of osteoarthritis were scored semiquantitatively on a 0 to 5 scale and also assessed quantitatively using the cartilage degeneration index (CDI(P1)), which ranges from 0 to 100%. Furthermore, CDI values were determined for special areas of interest; medial dorsal surface (CDI(mds)), lateral dorsal surface (CDI(lds)), medial central fovea (CDI(mcf)) and lateral central fovea (CDI(lcf)). Correlations were calculated for CDI(P1) values and CDI values at the specific areas of interest with macroscopic scores and with age.


RESULTS
There was a high correlation between the semiquantitative macroscopic score and the quantitative CDI(P1) values (r = 0.92; P < 0.001). A macroscopic score of 0 (i.e. no obvious cartilage degeneration) corresponded with a CDI(P1) mean +/- s.e. value of 25 +/- 2.8% and a macroscopic score of 5 (i.e. severe cartilage degeneration in localised areas) with a mean +/- s.e. value of 38.1 +/- 7.9%. There was a moderate but highly significant correlation between the CDI(P1) value and the age of the horses (r = 0.41; P < 0.001). Highest CDI values were calculated for the medial dorsal surface (from 10.6 +/- 2.8% at macroscopic Grade 0 to 63.1 +/- 8.4% at Grade 5). At the lateral dorsal surface, these values were 5.9 +/- 1.4% and 47.2 +/- 10.4%, respectively. The CDI(mcf) and CDI(lcf) were significantly lower (P < 0.05) than the CDI(mds) and CDI(lds) at all grades. The CDI(mcf) ranged from 1.0 +/- 2.9% at Grade 0 to 43.7 +/- 9.1% at Grade 5; laterally, these values were 1.5 +/- 2.6% and 15.2 +/- 6.2%, respectively.


CONCLUSIONS
CDI grading increased from lateral to medial and from central to dorsal. This specific distribution pattern confirms the heterogeneous nature of the OA process and strongly supports an important role for biomechanical loading, superimposed on age-related changes, in the spread of the disorder over the joint.


CONCLUSIONS
Knowledge of the development of OA across the articular surface is essential for understanding the dynamic nature and progression of the disease and can form a basis for improvements in diagnostic and therapeutic approaches to degenerative joint disease.
Brommer
H
H
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 12, 3584 CM Utrecht, The Netherlands.
van Weeren
P R
PR
Brama
P A J
PA
Barneveld
A
A
D017677:Age Distribution; D000367:Age Factors; D000375:Aging / Q000473:pathology*; D000818:Animals; D001696:Biomechanical Phenomena; D002357:Cartilage Diseases / Q000453:epidemiology / Q000473:pathology / Q000662:veterinary*; D002358:Cartilage, Articular / Q000473:pathology*; D006734:Horse Diseases / Q000453:epidemiology / Q000473:pathology*; D006736:Horses; D007596:Joints / Q000473:pathology; D010003:Osteoarthritis / Q000453:epidemiology / Q000473:pathology / Q000662:veterinary*