Journal of Musculoskeletal Trauma

Original Articles

A Biomechanical Advantage of the Lengthening with an External Fixator Over an Intramedullary Nail: An Experimental Study in Saw Bones and Cadeveric Bones: Chang Wug Oh, Poong Taek Kim, Hae Ryong Song, Jong Keon Oh, Hyung Soo Ahn, Byung Chul Park, Byung Guk Min, Sung Ki Park, Young Heon Sohn; J Korean Fract Soc 2005;18(3):335-340. Published online July 31, 2005; DOI: https://doi.org/10.12671/jkfs.2005.18.3.335

Abstract PDF: PURPOSE
To know biomechanical differences in methods of limb lengthening between using monolateral external fixator and using external fixator over an intramedullary nail.
MATERIALS AND METHODS
In acryl rods, saw-bone, and cadeveric bone, we created two lengthening models of using monolateral external fixator and using external fixator over an intramedullary nail. The axial compression test was done on the site of osteotomy for lengthening. To fix the models, half pins of 5 mm in diameter and nails of 9 mm in diameter were used. Using MTS (Material Test System) machine, we evaluated the differences of axial stiffness according to the presence of an intramedullary nail or the numbers of half-pins which were fixed at each side of osteotomy.
RESULTS
Lengthening over an intramedullary nail, comparing to monolateral external fixator only, increased the axial stiffness by 1.1~1.2 times in acryl rods, 1.2~1.6 times in saw bones, and 15.6~15.9 times in cadeveric bones when the same numbers of half-pins were used. In saw bone and cadaveric bone, the group of two half pins in lengthening over an intramedullary nail was stiffer than the group of three pins in lengthening with monolateral external fixator.
CONCLUSION
In the distraction of the limb, the addition of an intramedullary nail may increase the axial stiffness of the frame of monolateral external fixator. In lengthening over an intramedullary nail, it is enough to distract the bone with fixing two half pins at each sides of osteotomy.

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The Biomechanics of Hybrid External Fixator: The Effect of Periarticular Half Pin on Frame Stiffness: Jong Keon Oh, Duk Young Jung, In Su Kim; J Korean Soc Fract 2002;15(2):114-122. Published online April 30, 2002; DOI: https://doi.org/10.12671/jksf.2002.15.2.114

Abstract PDF: OBJECTIVES
The purpose of this study was to identify the biomechanical effect of periarticular half pin in the hybrid external fixator.
METHODS
Simulated tibial plateau fractures were created using a polyvinylchloride pipe. Seven frame configurations were tested : a four-ring Ilizarov frame, a hybrid frame with three wires on peri-articular fragment, hybrid frames with wires and half pins on peri-articular fragment by four different configurations, a hybrid frame constructed with multiple levels of fixation in the periarticular fragment. A materials testing machine was used to apply pure compression, anterior and posterior bending, medial and lateral bending, and torsion. Stiffness values were calculated from the load deformation and torque angle curves RESULTS: The overall stiffness of the hybrid frame was increased up to 30% by replacing a coronal tension wire with a half pin placed on the sagittal plane. The hybrid frame constructed with two wires and a half pin on the sagittal plane of the periarticular fragment showed overall stiffness compatible with that of multi-level peri-articular fixation frame.
CONCLUSION
Our results show that the half pin placed on the periarticular fragment can be a effective tool to increase the stiffness of hybrid external fixators in this periarticular tibia fracture model.

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