RADIOGRAPHIC CHARACTERISTICS OF THE FORELIMB DISTAL PHALANX AND MICROSCOPIC MORPHOLOGY OF THE LATERAL PALMAR PROCESS IN FOALS 332 WEEKS OLD
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Developmental morphology of the forelimb distal phalanges and lateral palmar processes of 9 Thoroughbred foals aged 332 weeks was assessed using radiography, microradiography and histology. For inclusion in the study, all distal phalanges had no pathologic radiographic abnormalities. Vascular channels that are characteristically found in the dorsal region of the distal phalanx were not evident radiographically in the palmar process. The proximal and distal angles of the palmar processes were separated by a lucent line continuous with the incisure in foals only through 12 weeks of age. The distal phalanges were triangularshaped in foals 312 weeks of age, and were ovalshaped in older foals. The palmar aspect of the distal phalanx was the major contributor to growth of the distal phalanx in the sagittal plane, especially between 3 and 12 weeks of age. Growth of the lateral palmar process occurred through the means of endochondral ossification. The body and cortices of the lateral palmar process were composed of coarse cancellous bone. Porosity within the lateral palmar process was greater in regions sampled axial, compared to abaxial, to the parietal sulcus and did not change with age. A fracture was identified microradiographically and/or histologically in 9 of 18 (50%) and 10 of 17 (59%), respectively, of the lateral palmar processes examined. The fracture line was consistently associated with the parietal sulcus on the dorsal cortical surface and was always immediately abaxial to the deep digital flexor tendon attachment. No agerelated morphological changes of the lateral palmar processes were identified with microradiography or histological examinations. Copyright 1995, Wiley Blackwell. All rights reserved
