@article{3149778,
    title = "Hemiepiphyseal Arrest in a Porcine Model",
    author = "Burghardt, Rolf D. and Kanellopoulos, Anastasios D. and Herzenberg, John and E.",
    journal = "Journal of Pediatric Orthopaedics",
    year = "2011",
    volume = "31",
    number = "4",
    pages = "E25-E29",
    publisher = "Lippincott, Williams & Wilkins",
    issn = "0271-6798, 1539-2570",
    doi = "10.1097/BPO.0b013e31821a5d04",
    keywords = "temporary hemiepiphysiodesis; eight-Plate; Blount staple; tibia; angular
deformity; porcine model",
    abstract = "Background: Treating angular deformities with temporary
hemiepiphysiodesis in skeletally immature patients can avoid the need
for osteotomies. Recently, newer implants have been introduced as
alternatives to the Blount staple, which was commonly used for the past
60 years. The purpose of this project was to develop a porcine model
that can be used to compare various methods of temporary hemiepiphyseal
arrest. In this pilot study, we compared the Blount staple and the
eight-Plate. We hypothesized that the Blount staple, a fixed angle
device, tethers growth immediately, whereas the eight-Plate, having
mobile arms, has a certain lead time to take the slack out of the system
until it can begin to tether growth.
Methods: A porcine model was selected due to its widespread availability
and because its size approximates human pediatric dimensions.
Thirty-day-old, 15-kg piglets underwent surgery to insert an eight-Plate
in each right proximal medial tibia and a Blount staple in each left
proximal medial tibia. The insertion technique was identical to the
surgical procedure performed in humans, including the use of image
intensification. Anteroposterior and lateral view tibial radiographs
were obtained monthly until sacrifice at 3 months after insertion to
measure the medial proximal tibial angle.
Results: At 1 month follow-up, a large varus deformity up to 30 degrees
had already occurred with both devices. In some piglets, the implants
were even dragged, by growth, through the epiphysis during the first two
months. With further follow-up, the Blount staples frequently migrated
to the proximal metaphysis. We observed rebound in four tibiae after
implant migration, with partial restoration of the normal limb
alignment.
Conclusions: The porcine model for temporary hemiepiphysiodesis seems to
have promise for future studies. However, the unusually rapid rate of
growth causes us to recommend more frequent observation periods, such as
weekly instead of monthly radiographic observation."
}