Biomechanical comparison of strategies to adjust axial stiffness of a hybrid fixator

M. J. Socie; G. L. Rovesti; D. J. Griffon; O. Elkhatib; R. N. Mudrock; P. Kurath

doi:10.3415/VCOT-11-04-0053

Veterinary and Comparative Orthopaedics and Traumatology, Table of Contents

Vet Comp Orthop Traumatol 2012; 25(03): 224-230
DOI: 10.3415/VCOT-11-04-0053

Original Research

Schattauer GmbH

Biomechanical comparison of strategies to adjust axial stiffness of a hybrid fixator

M. J. Socie

¹Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Illinois, USA

,

G. L. Rovesti

²Clinica Veterinaria M. E. Miller, Cavriago, Italy

,

D. J. Griffon

³College of Veterinary Medicine, Western University of Health Sciences, Pomona, California, USA

,

O. Elkhatib

¹Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Illinois, USA

,

R. N. Mudrock

¹Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Illinois, USA

,

P. Kurath

¹Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Illinois, USA

› Author Affiliations

Abstract

Summary

Objectives: To evaluate strategies for increasing the axial stiffness of a hybrid external bone fixator.

Materials and methods: Type Ia hybrid fixators, consisting of a uniplanar linear component connected to a circular ring, were tested in displacement controlled loading in axial compression. The basic hybrid construct was modified to explore strategies considered to increase fixator stiffness including: decreasing ring diameter, increasing ring thickness, adding pins to the ring fixation, and adding struts between the ring and vertical post components of the device. Stiffness in the initial phase of loading was compared between the groups.

Results: The addition of a single diagonal bar between the ring and linear connecting rail did not significantly improve the stiffness of constructs. However, the addition of two half-pins to the ring, the addition of two struts between the ring and linear connecting rail, or decreasing the internal ring diameter from 115 to 85 mm progressively increased the stiffness of the frame. The most effective strategy consisted of increasing the thickness of the ring from 6 to 12 mm, thereby increasing the stiffness of the control frame by 335%.

Clinical significance: Modulating the ring thickness, adding two struts between the ring and linear connecting rail, and reducing the ring diameter appear to be the most effective, simple, and clinically versatile ways to increase axial stiffness, most likely due to their impact on reducing ring bending.

Keywords

External skeletal fixation - hybrid fixation - biomechanical properties

Full Text

References

References
1 Marcellin-Little DJ. Fracture treatment with circular external fixation. Vet Clin North Am Small Anim Pract 1999; 29: 1153-1170.
2 Watson TJ, Ripple S, Hoshaw SJ. et al. Hybrid external fixation for tibial plateau fractures. Clinical and biomechanical correlation. Orthop Clin North Am 2002; 33: 199-209.
3 Savolainen VT, Pajarinen J, Hirvensalo E. et al. Hybrid external fixation in treatment of proximal tibial fractures: a good outcome in AO/ASIF type-C fractures. Arch Orthop Trauma Surg 2010; 130: 897-901.
4 Babis GC, Evangelopoulos DS, Kontovanezitis P. et al. High energy tibial plateau fractures treated with hybrid external fixation. J Orthop Surg Res. 2011 6. 35.
5 Marcellin-Little DJ. External skeletal fixation. In: Slatter D. editor. Textbook of Small Animal Surgery. Philadelphia: WB Saunders; 2002. pg. 1818-1834.
6 Kirkby KA, Lewis DD, Lafuente MP. et al. Management of humeral and femoral fractures in dogs and cats with linear-circular hybrid external skeletal fixators. J Am Anim Hosp Assoc 2008; 44: 180-197.
7 Phelps HA, Lewis DD, Aiken-Palmer C. et al. Use of a linear-circular hybrid external fixator for stabilization of a juxta-physeal proximal radial fractures in a deer (Odocoileus virginianus). J Zoo Wildl Med 2010; 41: 688-696.
8 Pugh KJ, Wolinsky PR, Pienkowski D. et al. Comparative biomechanics of hybrid external fixation. J Orthop Trauma 1999; 13: 418-425.
9 Caja VL, Kim W, Larsson S. et al. Comparison of the mechanical performance of three types of external fixators: linear, circular and hybrid. Clin Biomech 1995; 10: 401-406.
10 Khalily C, Voor MJ, Seligson D. Fracture site motion with Ilizarov and “hybrid” external fixation. J Orthop Trauma 1998; 12: 21-26.
11 Yilmaz E, Belhan O, Karakurt L. et al. Mechanical performance of hybrid Ilizarov external fixator in comparison with Ilizarov circular fixator. Clin Biomech 2003; 18: 518-522.
12 Roberts CS, Dodds JC, Perry K. et al. Hybrid external fixation of the proximal tibia: strategies to improve frame stability. J Orthop Trauma 2003; 17: 415-420.
13 Voor M, Antoci V, Kam B. et al. Hybrid external fixation of proximal tibia fractures: biomechanical analysis of four commercial systems. Orthopedics 2007; 30: 1033-1038.
14 Hildreth BE, Marcellin-Little DJ, Roe SC. et al. In vitro evaluation of five canine tibial plateau leveling methods. Am J Vet Res 2006; 67: 693-700.
15 Welch RD, Radasch RM, Toombs JP. Small Animal Hybrid Circular ESF course [Handouts distributed during course]. Proceedings of the American College of Veterinary Surgeons Symposium. 2003. October 11 Washington DC, USA: pg. 1-16.
16 Lewis DD, Bronson DG, Cross AR. et al. Axial characteristics of circular external skeletal fixator single ring constructs. Vet Surg 2001; 30: 386-394.
17 Cross RA, Lewis DD, Murphy ST. et al. Effects of ring diameter and wire tension on the axial biomechanics of four-ring circular external skeletal fixator constructs. Am J Vet Res 2001; 62: 1025-1030.
18 Griffon DJ. Fracture healing. In: Johnson AL, Houlton JEF, Vannini R. editors. AO principles of fracture management in small animals. Davos, Switzerland: AO Publishing; 2005. pg. 72-98.
19 Budsberg SC, Verstraete MC, Soutas-Little RW. Force plate analysis of the walking gait in healthy dogs. Am J Vet Res 1987; 48: 915-918.
20 Budsberg SC, Verstraete MC, Brown J. et al. Vertical loading rates in clinically normal dogs at the trot. Am J Vet Res 1995; 56: 1275-1280.
21 Ragetly CA, Griffon DJ, Mostafa AA. et al. Inverse dynamics analysis of the hindlimbs in Labrador Retrievers with and without cranial cruciate ligament disease. Vet Surg 2010; 39: 513-522.
22 Fragomen AT, Rozbruch SR. The Mechanics of external fixation. HSS J 2007; 3: 13-29.
23 Bouvy BM, Markel MD, Chelikani S. et al. Ex Vivo biomechanics of the Kirschner-Ehmer external skeletal fixation applied to canine tibiae. Vet Surg 1993; 22: 194-207.
24 Kummer FJ. Biomechanics of the Ilizarov external fixator. Clin Orthop 1992; 280: 11-14.
25 Podolsky A, Chao EY. Mechanical performance of Ilizarov external fixators in comparison with other external fixators. Clin Orthop 1993; 293: 61-70.
26 Babis GC, Kontovazenitis P, Evangelopoulos DS. et al. Distal tibial fractures treated with hybrid external fixation. Injury 2010; 41: 253-258.
27 Singh GR, Aithal HP, Saxena RK. et al. In vitro biomechanical properties of linear, circular, and hybrid external skeletal fixation devices for use in large ruminants. Vet Surg 2007; 36: 80-87.
28 Sereda CW, Lewis DD, Radasch RM. et al. Descriptive report of antebrachial growth deformity correction in 17 dogs from 1999 to 2007, using hybrid linear-circular external fixator constructs. Can Vet J 2009; 50: 723-732.
29 Yang L, Nayagam S, Saleh M. Stiffness characteristics and inter-fragmentary displacements with different hybrid external fixators. Clin Biomech 2003; 18: 166-172.
30 Grala P, Zielinski W. Hybrid external fixation for neglected fractures of the distal radius: results after one year. J Orthop Traumatol 2008; 9: 195-200.
31 Hulse D, Hyman B. Fracture biology and biomechanics. In: Slatter D. editor. Textbook of Small Animal Surgery. Philadelphia Saunders; 2003. pg. 1785-1793.