Myotomy of the lateral pterygoid muscle and condylar cartilage growth.

The influence of lateral pterygoid muscle activity on growth of the condylar cartilage of the mandible remains controversial. As a case in point, two recent studies involving total resection (myectomy) and sectioning (myotomy) of this muscle have come to contradictory conclusions. In the study reported here, it was found that young growing rats in which the lateral pterygoid muscle was bilaterally cut experienced significantly retarded mitotic activity and bone formation relative to their sham-operated counterparts. Changes in the shape and topographical distribution of cartilage over the condylar head, as well as the distribution of labelled cells, were also noted in myotomy animals at 4 days following surgery. Considerable resorption at the insertion of the muscle on the mandibular ramus was apparent at 14 days after surgery. However, the myotomy surgery was accompanied by a significant post-operative loss of body weight and incisal supra-eruption indicative of feeding difficulties, thereby complicating interpretation of the results.