Determination of proximal femoral epiphyseal depth for repair of physeal fractures in immature dogs.

ABSTRACT

OBJECTIVE: To determine the depth that implants may be safely placed for repair of proximal femoral physeal fractures. STUDY DESIGN: Relationships were determined between the depth of the proximal femoral epiphysis (PFE) and the contralateral PFE, and the PFE and pubic bone width. ANIMALS OR SAMPLE POPULATION 20 immature dog cadavers. METHODS: Actual PFE depths were determined at the center of the physeal surface and at four other eccentric points. The contralateral intact PFE depth and the width of the cranial aspect of the public bone were measured from radiographs. RESULTS: Mean ratios of actual central PFE depth to radiographically measured (1) contralateral PFE depth and (2) pubic bone width were 1.041, and 1.091, and ratios of actual eccentric PFE depths were 0.891 and 0.931. Body weight was not useful in estimating depth of the PFE. CONCLUSIONS: For the central epiphysis, pins may safely be placed a distance equal to 75% to 80% of the contralateral intact PFE depth or pubic bone width, measured from a ventrodorsal radiograph, with minimal risk of penetration through the articular surface. Pins placed eccentrically may be safely driven a depth equal to 65% of the radiographically measured contralateral intact PFE depth or pubic bone width. CLINICAL RELEVANCE Estimating the safe depth of implant placement into the PFE avoids penetration of the articular surface.