VN September 2023

Vetnuus | September 2023 32 Technical I Article Early recognition and correction is important; once skeletal ossification occurs conservative techniques such as splinting or hobbling are unlikely to be effective. Very young birds can have their legs hobbled into a normal position to guide the leg into a normal position during growth. Various techniques have been used to achieve this goal, including tying the feet together with bandages or placing the chick’s legs into a foam block. However, if the chick is not presented until after ossification is complete, surgical de-rotational osteotomies may be required. o Angular limb deformities (ALDs) occur when more weight is borne on one side of the growth plate than the other. On this side of the physis, growth is inhibited, while on the other side, growth continues normally. Common causes include incubation problems, nutritional imbalances and trauma. In precocious chick (e.g. ratites), ALDs may occur for a range of reasons including insufficient exercise, high-energy diets, trauma, and heated flooring. The result is a deviation of the growth of the limb from the midline: if the growth is directed laterally it is termed a valgus deformity; if medial to the midline it is termed a varus deformity. The deformity may be the bowing or rotation of the affected bone. This then has a cascading effect on the muscles, tendons and joints of the affected leg. Corrective surgery, in the form of de-rotational osteotomies, is the treatment of choice, but it must be done sooner rather than later. Timing is essential when addressing affected joints – waiting till the bird has finished growing may result in irreversible tendon and joint contracture. o Pathological fractures commonly occur in chicks with nutritional secondary hyperparathyroidism or rickets. The fractures most commonly occur in the long bones – the humerus, the radius and ulna, the femur and the tibiotarsus. Some of these fractures will heal with minimal intervention, but this invariably results in some degree of bone deformity. Attempts to repair these fractures surgically can be frustrating when the contralateral limb is required to support the bird’s weight and lacks the cortical strength to do so – resulting in another fracture or bowing of that limb. Slinging the chick tominimise this problem can cause other problems, such as compression of the sternum and ribs. These factors need to be considered before undertaking such a procedure. o Toe malpositions - anteroflexion of P4 is a developmental issue in psittacine paediatrics, more often encountered where there has been sub-clinical stunting or substrate mismanagement. Once the first phalangeal bone has ossified normally, it is fused to the tarsometatarsus and becomes less flexible. If the anteroflexion has not been corrected (by splinting) by the time, the anteroflexion may be permanent. The affected digit can be splinted out into a normal position, but the abnormal angulation of P1 means that, once the splint has been removed, the digit will return to an abnormal position. o Slipped Tendon - the gastrocnemius tendon ‘slips’ medially or laterally out of the intercondylar groove on the back of the hock, causing a valgus or varus deformity of the lower limb. This is associated with trauma, poor diet, poor conformation and perhaps a genetic influence. It is most commonly seen in ratites and gallinaceous birds but can be seen in any species. Simple surgical repair of the tendon sheath is usually unrewarding, and a rotational osteotomy or arthrodesis may be required. Beak malformations • Types o Congenital  Lateral deviations of the maxilla (Wry/Scissor beak)  Mandibular prognathism o Acquired  Lateral deviations of the maxilla (Wry/Scissor beak)  Compression deformities of the mandible  Other malformations, often associated with a ‘softening’ of the beak due to malnutrition  Clinical description o Lateral deviations of the maxilla (Wry/Scissor beak). The maxillary beak is deviated laterally from the level of the cere or beak tip. The side of the mandible is no longer in wear and the maxilla often overgrows. This condition is most common in macaws up to 2 months of age, but acquired scissor beak can occur in any species at any age. o Mandibular prognathism is most common in cockatoos aged 1-2 weeks. The maxilla sits inside mandible.