Third Carpal Bone Sclerosis Radiographic evaluation and clinical implications in Standardbred trotters

Uhlhorn, H. 2000. Third carpal bone sclerosis Radiographic evaluation and clinical implications in Standardbred trotters. Doctoral dissertation. The aims of this thesis were to evaluate the DPr-DDiO projection for the assessment of sclerosis and to study the relationships between altered third carpal bone (C3) radiopacity and previous exercise, previous carpal lameness, clinical appearance, and prognosis for future performance. Effects of positioning on radiographic appearance and depth of evaluated C3 were investigated in frozen specimens under beam-cassette angles of 15" to 45". Beam-cassette angles near 40" produced maximal depth of evaluated C3 but grading of sclerosis appeared insensitive to variations in beam-cassette angle in the range 25"-40". A comparison between grading of sclerosis and histomorphometrical bone density estimations in specimens from Standardbred trotters showed a higher bone volume density in subchondral compared to central cancellous bone. Mild sclerosis indicated that the subchondral cancellous bone had reached its maximal density while increasing sclerosis only reflected a further density-increase in central cancellous bone. The association between altered C3 radiopacity and degree of lameness and prognosis for racing was evaluated in a retrospective study of 89 Standardbred trotters diagnosed with traumatic carpitis. No significant relationships between degree of sclerosis and lameness or prognosis for racing within 30 months were found. However, radiolucencies 2 2 mm were found to significantly influence degree of lameness at presentation and time to start but did not affect chances of racing within 30 months. Factors affecting development of increased C3 radiopacity were evaluated in a longitudinal study of 14 Standardbred trotters in professional training, between the mean ages of 20 and 42 months. Carpal lameness was significantly associated with progression of sclerosis although in most cases, sclerosis developed irrespective of carpal lameness. No significant associations were found between grade of sclerosis and previous carpal lameness or between grade of sclerosis and level of performance, classified as training, qualified for racing and actively racing. Sclerosis appears to be of limited value as an indicator of clinical carpal disease or level of performance in Standardbred trotters while radiolucencies are clinically significant findings warranting further research.