VN September 2023

September 2023 33 Technical I Article o Compression deformities of the mandible are most commonly seen in macaws up to 5 weeks of age. o Other malformations are often associated with Cnemidocoptes infection, trauma, PBFD, etc. • Aetiology o Congenital malformations are thought to be associated with incorrect incubation parameters (temperature, humidity, ventilation, or turning of the egg) or parental nutrition. o Acquired malformations are thought to be due to damage to all, or part of, the germinal epithelium of the beak or the poorly calcified beaks of neonates. • Treatment o Conservative treatment may be effective in very young chicks. Applying gentle digital pressure for 10 minutes 2 – 3 times daily may straighten a deviated maxilla, or lift the maxilla up and forward in prognathic chicks. o Cases that do not respond to this treatment, or older birds with calcified beaks, will need more aggressive therapy: o Deviated maxilla  Beak trimming. Grinding the overgrown gnathotheca on the side contralateral to themaxillary deviation and the overgrown tomia on the maxilla allows the maxilla to move back into a normal position. At the same time, the occlusal ledge inside the maxilla has to be re-shaped so that it is perpendicular to the lateral walls of the rhinotheca. The bird should then be encouraged to chew hard objects (e.g. branches) frequently and the beak re-shaped every 2 weeks till normal.  Acrylic ramps or prostheses can be used to augment the trimming described above. An acrylic ramp is built up on the gnathotheca on the same side as the maxillary deviation, forcing the maxilla into a normal position. The ramp needs to be high enough so that the bird cannot open its mouth wide enough to get its maxilla over the top of the ramp. This technique, not infrequently, fails due to damage to the gnathotheca during the attachment of the ramp.  Trans-sinus pinning is an ‘orthodontic’ procedure, designed to provide constant lateral tension on the deviated maxilla to guide it into a more anatomically normal position. • A K-wire or small Steinmann pin is placed perpendicular to the skull, through the frontal sinuses just caudal to the craniofacial hinge joint on a line between the lateral canthus of the eye and the cere. Care must be taken not to position this pin too caudally or too low. In macaws, a small bony protuberance marks the point where the pin is introduced on one side and exits on the other. • On the side of the beak, contralateral to the direction of the deviation, the pin is bent 90º as it leaves the skin. The pin should run the length of the maxilla, and the end (level with the beak tip) is curled over on itself. • The other end of the pin is trimmed and curled over on itself so that it is flush against the skin and cannot be pulled through the skull. • The tip of the beak is then placed under tension by means of a rubber band around the beak and the distal end of the wire. In older birds, this rubber band is replaced by a piece of wire running through a hole in the distal rhinotheca. • This tension is maintained until the beak has straightened. In young birds, this can be as soon as 10 – 14 days; older birds may require 10 – 14 months. The tension can be adjusted by loosening or tightening the wire/rubber band as required. • Once the beak has straightened the wire/rubber band should be removed. If, after several days, the beak has remained in a normal position, the pin can be removed.  Prognathism • An acrylic prosthesis can be placed over the rhinotheca. One or two small pins can be placed through the rhinotheca to provide ‘anchor points’ to prevent the prosthesis from falling off. The goal is to force hyperextension of the craniofacial hinge joint into amore normal range of motion, allowing for a“firming”up of the joint enough so that the upper mandible cannot be over-flexed to the point of mandibular prognathism. There is no correction of “growth”of the beak, but rather, guidance and reduction of the abnormal range of motion of the craniofacial hinge joint. The prosthesis must be long enough to prevent the bird from opening its mouth wide enough to place the prosthesis inside the gnathotheca. >>> 34