Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

DesJardins, John D

Committee Member

LaBerge , Martine

Committee Member

Nagatomi , Jiro

Abstract

Salter-Harris fractures of the proximal tibia and distal femur are common in pediatric patients that present to orthopedic surgeons. Salter-Harris type I fractures are characterized by breaks that extend only through the physis while Salter-Harris II fractures are the most common, accounting for 85% of Salter-Harris fractures, and extend past the growth plate, exiting through the metaphyseal bone1. Fixation of these fracture types can be accomplished using a variety of methods including the use of Kirschner wires, cannulated screws, and a combination of both materials. Stability of fracture fixation is of utmost importance as persistent motion at the fracture margin leads to deformity2. Other complications resulting from unsuccessful fracture treatment include knee instability, premature physeal closure, and leg shortening causing the patient to experience a higher physiological load1,3.
The purpose of this study is to analyze the biomechanical efficacy of common fixation methods used to stabilize Salter-Harris I and II fracture patterns in both the proximal tibia and distal femur. Rotational stiffness will be used as the primary gauge of efficacy and is tested in flexion and extension, varus and valgus rotation, and internal and external rotation. Comparison of stiffness will be used to determine the optimal fixation method specific to each bone and fracture pattern.
This study utilized 39 tibia and 36 femur 4th generation synthetic bones, fractured and fixated to model Salter-Harris type I and II fractures and common fixation methods. Fixation methods used employed 6.5mm cannulated screws, 4.5mm cannulated screws, 2mm smooth k-wires, and 2mm threaded k-wires. Cyclic displacement tests were performed on a materials testing machine which recorded the torque required to reach an angulation of ±5¡ for 10 cycles. Statistical analysis was performed to compare construct stiffness and differences between groups using analysis of variance.
Results show superior stability achieved through the use of threaded k-wires for both femoral and tibial Salter-Harris type I fracture fixation. The optimal femoral Salter-Harris type II fixation method utilized two oblique screws. Methods consisting of a combination of screws and k-wires resulted in the greatest rotational stiffness for tibial Salter-Harris type II fractures. Improvements in fixation methods should be considered to enhance internal and external rotational stiffness for all fracture types.

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Biomechanics Commons

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