A Morphological and Diagnostic Imaging Study of the Distal Pelvic Limb of the Ostrich (Struthio camelus)

The ostrich (Struthio camelus) farming industry is growing rapidly in many countries. Although the ostrich is now established as a commercial species, there are still some significant gaps in our knowledge of the structure and function of this unique species. One such area where there appears to be little information available is on the morphology of the distal region of the pelvic limb. Morphological knowledge of this area is important as distal limb deformities appear to present a significant problem in the husbandry and management of these birds. The objectives of the present study in an attempt to fill this gap, were two fold: (i) To provide a detailed functional morphological account of the topographical anatomy of the distal region in the normal pelvic limb of the ostrich. (ii) To use two diagnostic imaging techniques, ultrasonography and radiography, in the identification and characterisation of the structures studied in the first part of this study, as a basis for the examination of the clinical leg deformities such as rolled toes. Chapter 1 provides information about ostriches in general, and a brief history of ostrich farming, as well as summarising available research work carried out in relation to the pelvic limb of the ostrich. There are very few studies that have been done to evaluate the morphology of the pelvic limb in the ostrich. While many uses of diagnostic ultrasound imaging techniques have been cited in other species, there is very little information on the use of this technique in ostriches. Various types of common limb abnormalities in ostriches have been described and defined. Chapter 2 provides information about ultrasonography, covering various aspects of this imaging technique. The areas covered include the development of the technique, its physical principles, types of image display modes and an explanation of image interpretation and common terminology used in ultrasonography. Ultrasonographic image artefacts, their identity, and, where possible, ways of minimising them have been explained. These artefacts include reverberations, acoustic shadows, distant enhancement, reflection and refraction, comet-tail and electronic noise. In Chapter 3, a detailed explanation of the materials and methods used in this study is given. Fresh cadaverous limbs were carefully skinned and muscles separated by blunt dissection along their connective tissue planes, during which their origins, form, course and insertions were recorded. These were then boiled out to obtain bony specimens. Eight different pre-selected levels of the limb at which cross-sectional and ultrasonographical examinations where carried out are illustrated diagrammatically. Chapter 4 presents the results of the present study. These results were classified in five categories namely: osteology, arthrology, myology, ultrasonographical and descriptive topographical anatomy, and rolled toe pathological aspects. Interesting osteological findings included the very marked cranially-projecting medial cnemial crest and a greatly reduced lateral cnemial crest of the tibiotarsus. The supratendinal groove is partially ossified while a large single hypotarsal ridge, devoid of flexor canals, is displaced slightly medially with concomitant loss of the intercotylar prominence. A unique pattern in the course of tendons and ligaments, and a special morphology of the joints, has been reviewed and illustrated diagrammatically. The former form the digital check apparatus, a structure that has not been described before in the ostrich, while the intertarsal joint was found to have only one meniscus, the lateral meniscus, and paired medial and lateral collateral ligaments. A total of 15 muscles were identified and it was interesting to note that despite the absence of the hallux (digit I), M. flexor hallucis longus was amongst the muscles present in the ostrich. A description of the normal topographic anatomy and ultrasonographic appearance of the tendons and ligaments has also been given. Cross- sectional ultrasonographic scans of normal ostrich tendons appear hyperechoic and compact, with a stippled echopattern, while longitudinal scanning images present a multiple closely-aligned highly echogenic pattern (fibrillar sonographic texture). In adult birds with rolled toes, in this study regarded as long-standing cases of rolled toes, there was partial ossification of extensor tendons, distal rotation of the tarsometatarsal bone, (as much as 35 degrees), distal rotation the first phalanx of digit III (as much as 30 degrees), and the formation of osteophytes. Most of these features in this study confirm the advanced morphological placement of the monophylectic origin of the superfamily Struthionoidea over the more primitive ratites. The overall findings of these studies are interpreted and discussed in detail in Chapter 5. There is need for more of future work to explore the usefulness of ultrasound and causal factors of musculoskeletal disorders in ostriches. There is also need for study on the normal vasculature and innervation of the ostrich hind limb in order to ascertain whether or not any injuries or damage occurs to these structures as a result of conditions such as slipped tendon, or rolled toes in these birds.