A "new" diaphragm following prosthetic repair of experimental hemidiaphragmatic defects in the pup.

Hemidiaphragmatic defects were created in ten pups and repaired with Silastic Sheeting (Dow-Corning .007 u) to determine the long-term results of prosthetic replacement of the diaphragm in growing subjects. All animals survived the operation without complication and grew and developed normally, weighing between 35 and 40 pounds at one year of age. The prosthesis gradually became located in the extreme left anterolateral costophrenic sulcus in nine of the ten dogs studied by sequential chest x-rays. Slight paradoxical movement was visible to fluoroscopy without eventration of the diaphragm. One animal developed an asymptomatic posterolateral diaphragmatic hernia nine months following operation. The other animals were sacrificed at one year of age. The liver, spleen and stomach were partially covered by a "new" muscle containing diaphragm having a mean area of 176 +/- 8.3 cm, compared to the original defect which measured 15.89 +/- 1.2 cm. Skeletal muscle cells extended into the margins of the prosthesis. The dorsolateral location of the "new" diaphragm is evidence that postnatal skeletal muscle growth may be derived from persisting precursor tissues.