Effect of cleft palate repair on the susceptibility to contraction-induced injury of single permeabilized muscle fibers from congenitally-clefted goat palates.
OBJECTIVE
Despite cleft palate repair, velopharyngeal competence is not achieved in approximately 15% of patients, often necessitating secondary surgical correction. Velopharyngeal competence postrepair may require the conversion of levator veli palatini muscle fibers from injury-susceptible type 2 fibers to injury-resistant type 1 fibers. As an initial step to determining the validity of this theory, we tested the hypothesis that, in most cases, repair induces the transformation to type 1 fibers, thus diminishing susceptibility to injury.


METHODS
Single permeabilized levator veli palatini muscle fibers were obtained from normal palates and nonrepaired congenitally-clefted palates of young (2 months old) and adult (14 to 15 months old) goats and from repaired palates of adult goats (8 months old). Repair was done at 2 months of age using a modified von Langenbeck technique.


METHODS
Fiber type was determined by contractile properties and susceptibility to injury was assessed by force deficit, the decrease in maximum force following a lengthening contraction protocol expressed as a percentage of initial force.


RESULTS
For normal palates and cleft palates of young goats, the majority of the fibers were type 2 with force deficits of approximately 40%. Following repair, 80% of the fibers were type 1 with force deficits of 20% +/- 2%; these deficits were 45% of those for nonrepaired cleft palates of adult goats (p < .0001).


CONCLUSIONS
The decrease in the percentage of type 2 fibers and susceptibility to injury may be important for the development of a functional levator veli palatini muscle postrepair.
Rader
Erik P
EP
Department of Surgery, University of Michigan, Ann Arbor, MI, USA.
Cederna
Paul S
PS
McClellan
William T
WT
Caterson
Stephanie A
SA
Panter
Kip E
KE
Yu
Deborah
D
Buchman
Steven R
SR
Larkin
Lisa M
LM
Faulkner
John A
JA
Weinzweig
Jeffrey
J
D000367:Age Factors; D000818:Animals; D001696:Biomechanical Phenomena; D002972:Cleft Palate / Q000473:pathology / Q000601:surgery*; D004195:Disease Models, Animal; D006041:Goats; D009119:Muscle Contraction / Q000502:physiology; D024510:Muscle Development / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology* / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology* / Q000502:physiology; D010156:Palatal Muscles / Q000254:growth & development / Q000473:pathology*; D010159:Palate / Q000473:pathology; D021362:Palate, Hard / Q000601:surgery; D010160:Palate, Soft / Q000601:surgery; D012518:Sarcomeres / Q000473:pathology / Q000502:physiology; D013314:Stress, Mechanical; D013997:Time Factors