Abstract
Reasons for performing study Palmar/plantar osteochondral disease (POD) is a common, debilitating condition in Thoroughbred racehorses; however, training- and racing-related factors associated with this disease are unknown.Objectives To determine horse-, racing- and training-related risk factors for POD. The general hypotheses were that early training and racing, and increased intensity of racing and training, lead to increased severity of POD.Methods The metacarpo/metatarsophalangeal joints of 164 Thoroughbred racehorses were examined at post mortem and graded for third metacarpal and metatarsal POD. The relationships between training- and racing-related factors and grade of POD in each condyle were determined using multilevel, multivariable, ordinal logistic regression models.Results A total of 1288 condyles were graded. Factors associated with higher grades of POD were the total lifetime number of races, an increase in gallop sessions in the previous season, racing before import to Hong Kong and an increase in the number of short (8–16 weeks) between-race intervals per season. Horses in their first racing season were more likely to have lower POD grades, while horses that had a long between-race interval (greater than 16 weeks) in the season prior to euthanasia were also more likely to have lower POD grades. Lower POD grades were significantly more likely as days since last race increased up to 400 days. Age at first race was not significantly associated with grade of POD.Conclusions and potential relevance Cumulative racing exposure and training intensity in the previous season were associated with higher grades of POD, supporting the hypothesis that the disease is due to repetitive loading. Longer between-race intervals and increased time since racing were associated with lower POD grades, which may indicate that lesions heal. Further work is required to enable optimisation of racing and training programmes to reduce the frequency and severity of this disease.
Highlights
Palmar/plantar osteochondral disease (POD) is a degenerative condition affecting the distal condyles of the third metacarpal and metatarsal bones (Mc/MtIII) and is common in the Thoroughbred racehorse [1]
The clinical condition of pain associated with subchondral bone injury of the distal condyles of Mc/MtIII has become well recognised in most racing breeds, including Thoroughbreds [3,4]; training- and racing-related risk factors associated with the disease and with its severity have not been evaluated previously and yet are essential in order to develop strategies to prevent the onset and progression of POD
A number of hypotheses were formed prior to the study based on previous literature [2,3,4] and the authors’ knowledge of the clinical condition and its presentation in racing Thoroughbreds. These were as follows: 1) POD is more severe in horses that commence high-impact training or racing as 2-year-olds; 2) severity of POD is increased in horses raced over longer distances; 3) severity of POD is increased in horses raced and trained more frequently; 4) severity of POD is increased in heavier horses due to increased stress on joint tissues; 5) severity of POD is greater in those horses that have more short rest periods in between racing; 6) swimming as part of the training regimen has a protective effect on severity of POD
Summary
Palmar/plantar osteochondral disease (POD) is a degenerative condition affecting the distal condyles of the third metacarpal and metatarsal bones (Mc/MtIII) and is common in the Thoroughbred racehorse [1]. The clinical condition of pain associated with subchondral bone injury of the distal condyles of Mc/MtIII has become well recognised in most racing breeds, including Thoroughbreds [3,4]; training- and racing-related risk factors associated with the disease and with its severity have not been evaluated previously and yet are essential in order to develop strategies to prevent the onset and progression of POD. A number of hypotheses were formed prior to the study based on previous literature [2,3,4] and the authors’ knowledge of the clinical condition and its presentation in racing Thoroughbreds. These were as follows: 1) POD is more severe in horses that commence high-impact training or racing as 2-year-olds; 2) severity of POD is increased in horses raced over longer distances; 3) severity of POD is increased in horses raced and trained more frequently; 4) severity of POD is increased in heavier horses due to increased stress on joint tissues; 5) severity of POD is greater in those horses that have more short rest periods in between racing; 6) swimming as part of the training regimen has a protective effect on severity of POD (due to less impact damage); 7) POD is more prevalent in certain bloodlines; and 8) winnings from racing are reduced in horses with increased grades of POD
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