Stiffness of modified Type 1a linear external skeletal fixators

H. F. Reaugh; M. C. Rochat; C. W. Bruce; D. S. Galloway; M. E. Payton

doi:10.1160/VCOT-06-05-0045

Veterinary and Comparative Orthopaedics and Traumatology, Table of Contents

Vet Comp Orthop Traumatol 2007; 20(04): 264-268
DOI: 10.1160/VCOT-06-05-0045

Original Research

Schattauer GmbH

Stiffness of modified Type 1a linear external skeletal fixators

Authors

H. F. Reaugh

¹Dallas Veterinary Surgical Center, Dallas, Texas, USA
M. C. Rochat

²Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, Oklahoma, USA
C. W. Bruce

³Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Ontario, Canada
D. S. Galloway

⁴US Army Veterinary Service, Okinawa, Japan
M. E. Payton

⁵Department of Statistics, College of Arts and Sciences, Oklahoma State University, Stillwater, Oklahoma, USA

Abstract

Summary

Modifications of a Type1a external skeletal fixator (ESF) frame were evaluated by alternately placing transfixation pins on opposite sides of the connecting rod (Type 1a-MOD) or by placing additional connecting rods on either of the two inside (Type 1a-INSIDE) or two outside (Type 1a-OUTSIDE) transfixation pins. The objective of this study was to evaluate the stiffness of these modifications in terms of axial compression (AC), cranial-caudal bending (CCB), and medial-lateral bending (MLB). We hypothesized that these designs would allow significant increase in unilateral frame stiffness, over Type 1a, without proportional increase in frame complexity or technical difficulty of application. All of the ESF frames were constructed using large IMEX SK™ clamps, 3.2 mm threaded fixation pins, 9.5 mm carbon fibre connecting rods and Delrin rods as bone models. Nine, eight pin frames of each design were constructed, and subjected to repetitive non-destructive loading forces (AC, CCB, MLB) using a materials testing machine. Frame construct stiffness for each force (AC, CCB, MLB) was derived from load-deformation curve analysis and displayed in N/mm. Data revealed the 1a-MOD and 1a-OUTSIDE constructs had significantly increased stiffness in CCB and AC as compared to the Type 1a constructs while all of the modified constructs were significantly stiffer in MLB than the Type 1a constructs.

Keywords

External skeletal fixation - biomechanics - Type 1a - Type 1b

Full Text

References

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