Independent effects of denervating the cricothyroid muscle and stenting on the anterior cricoid split: canine model.

The anterior cricoid split (ACS) has gained in popularity since its introduction in 1980, for the treatment of the difficult to extubate child. The procedure allows a successful extubation and avoids a tracheotomy about 75% of the time. How the ACS allows extubation remains poorly understood. Animal research has shown that in the canine model the ACS results in a gap in the cricoid cartilage with a subjective increase in the subglottic space (Senders and Eisele, 1978). This gap in the cricoid cartilage develops whether or not an endotracheal tube stent is used. This experiment was designed to quantitatively evaluate the effect of the ACS on the subglottic space with or without the use of the stent, and to evaluate the effect of the cricothyroid muscle on the ACS procedure. The results show that the ACS does result in an increase in the subcricoid space, and that the use of an endotracheal tube stent does result in a larger increase. The cricothyroid muscle has a strong immediate effect on the gap in the cricoid cartilage, which is eliminated by sectioning the external laryngeal nerve. The long-term effects of sectioning the external laryngeal nerve on the gap in the cricoid cartilage were not conclusive.

Observations about the normal and abnormal embryogenesis of the canine lip and palate.

Twenty-three puppies with cranofacial and limb abnormalities from a family of Australian shepherd dogs were studied anatomically. Limb abnormalities included lumbar scoliosis, short malformed tibias and fibulas, and polydactyly. Craniofacial abnormalities consisted of retronathia, cleft palate, and cleft lip. The clefts can be separated into three categories: group I, cleft of the secondary palate associated with a midline cleft lip; group II, unilateral cleft of the lip and primary and secondary palate; and group III, complete bilateral cleft of the lip and primary and secondary palate. Comparing human clefts with the canine clefts suggests that the development of the secondary palate is similar whereas the development of the upper lip is different. In the dog, the maxillary processes fuse in the midline to produce the majority of the upper lip, whereas in the human the upper lip is composed of fused maxillary and medial nasal processes.