The Effect of Increasing Fracture Site Stiffness on Bone–Pin Interface Stress and Foot Contact Pressure within the Equine Distal Limb Transfixation Cast: A Finite Element AnalysisFunding This work was supported by the State of Indiana, Purdue University College of Veterinary Medicine Research account funded by the Total Wagers tax. This work was also part of an animal health project supported by USDA-NIFA, project no. IND020784AH1.
Objective The aim of this study was to determine how increasing stiffness of fracture site tissues distal to the pins in an equine distal limb transfixation cast influences stress at the bone–pin interface, within the bones distal to the transcortical pins, and contact pressure between the foot and the cast.
Study Design A transfixation cast finite element model was used to compare the bone–pin interface stress, pin stress, bone stress distal to the pins and contact pressure between the foot and the cast, using six stiffness values for a composite tissue block representing progressive stages of fracture healing.
Results Increasing stiffness of the composite tissue block resulted in a decrease in the maximum stresses at the bone–pin interface, an increase in stresses distal to the transcortical pins and a decrease in the maximum pin stresses. As the composite tissue block stiffness was increased, contact pressure between the bottom of the composite tissue block and the cast increased and the stress patterns surrounding the pin holes became less focal.
Conclusion The findings of this study illustrate that with good foot to cast contact within a transfixation cast, increases in tissue stiffness due to progressive fracture healing are expected to reduce bone-pin interface stresses, and increase fracture site loading and stress. Increasing the contact pressure between the foot and the cast could reduce transfixation casting complications such as pin loosening, pin hole fracture and poor fracture healing, if these results transfer to ex vivo and in vivo settings.
Timothy Lescun contributed to the conception of study, study design, acquisition of data and data analysis and interpretation. Stephen Adams contributed to data analysis and interpretation. Eric Nauman contributed to study design, data analysis and interpretation. Gert Breur contributed to conception of study, study design and data analysis and interpretation. All authors drafted, revised and approved the submitted manuscript.
Received: 31 May 2019
Accepted: 23 May 2020
14 August 2020 (online)
© 2020. Thieme. All rights reserved.
Georg Thieme Verlag KG
Stuttgart · New York
- 1 Schneider RK, Ratzlaff MC, White KK, Hopper SA. Effect of three types of half-limb casts on in vitro bone strain recorded from the third metacarpal bone and proximal phalanx in equine cadaver limbs. Am J Vet Res 1998; 59 (09) 1188-1193
- 2 Kraus BM, Richardson DW, Nunamaker DM, Ross MW. Management of comminuted fractures of the proximal phalanx in horses: 64 cases (1983-2001). J Am Vet Med Assoc 2004; 224 (02) 254-263
- 3 Joyce J, Baxter GM, Sarrafian TL, Stashak TS, Trotter G, Frisbie D. Use of transfixation pin casts to treat adult horses with comminuted phalangeal fractures: 20 cases (1993-2003). J Am Vet Med Assoc 2006; 229 (05) 725-730
- 4 Lescun TB, McClure SR, Ward MP. , et al. Evaluation of transfixation casting for treatment of third metacarpal, third metatarsal, and phalangeal fractures in horses: 37 cases (1994-2004). J Am Vet Med Assoc 2007; 230 (09) 1340-1349
- 5 McClure S, Honnas CM, Watkins JP. Managing equine fractures with external skeletal fixation. Compend Contin Educ Pract Vet 1995; 17: 1054-1063
- 6 Williams JM, Elce YA, Litsky AS. Comparison of 2 equine transfixation pin casts and the effects of pin removal. Vet Surg 2014; 43 (04) 430-436
- 7 Huiskes R, Chao EY, Crippen TE. Parametric analyses of pin-bone stresses in external fracture fixation devices. J Orthop Res 1985; 3 (03) 341-349
- 8 Huiskes R, Chao EY. Guidelines for external fixation frame rigidity and stresses. J Orthop Res 1986; 4 (01) 68-75
- 9 Markel MD, Wikenheiser MA, Chao EY. A study of fracture callus material properties: relationship to the torsional strength of bone. J Orthop Res 1990; 8 (06) 843-850
- 10 Zioupos P, Currey JD, Mirza MS, Barton DC. Experimentally determined microcracking around a circular hole in a flat plate of bone: comparison with predicted stresses. Philos Trans R Soc Lond B Biol Sci 1995; 347 (1322): 383-396
- 11 Brianza S, Brighenti V, Lansdowne JL, Schwieger K, Bouré L. Finite element analysis of a novel pin-sleeve system for external fixation of distal limb fractures in horses. Vet J 2011; 190 (02) 260-267
- 12 Schileo E, Taddei F, Cristofolini L, Viceconti M. Subject-specific finite element models implementing a maximum principal strain criterion are able to estimate failure risk and fracture location on human femurs tested in vitro. J Biomech 2008; 41 (02) 356-367
- 13 Pai S, Ledoux WR. The compressive mechanical properties of diabetic and non-diabetic plantar soft tissue. J Biomech 2010; 43 (09) 1754-1760
- 14 Bartel DL, Davy DT, Keaveny TM. Chapter 4: Tissue Mechanics II Soft tissue. In: Orthopaedic Biomechanics: Mechanics and Design in Musculoskeletal Systems. Upper Saddle River, NJ: Pearson/Prentice Hall; 2006: 121-167
- 15 Les CM, Stover SM, Taylor KT, Keyak JH, Willits NH. Ex vivo simulation of in vivo strain distributions in the equine metacarpus. Equine Vet J 1998; 30 (03) 260-266
- 16 Gibson VA, Stover SM, Gibeling JC, Hazelwood SJ, Martin RB. Osteonal effects on elastic modulus and fatigue life in equine bone. J Biomech 2006; 39 (02) 217-225
- 17 McClure SR, Glickman LT, Glickman NW, Weaver CM. Evaluation of dual energy x-ray absorptiometry for in situ measurement of bone mineral density of equine metacarpi. Am J Vet Res 2001; 62 (05) 752-756
- 18 Les CM, Keyak JH, Stover SM, Taylor KT, Kaneps AJ. Estimation of material properties in the equine metacarpus with use of quantitative computed tomography. J Orthop Res 1994; 12 (06) 822-833
- 19 Morgan EF, Bayraktar HH, Keaveny TM. Trabecular bone modulus-density relationships depend on anatomic site. J Biomech 2003; 36 (07) 897-904
- 20 Chen Q, Thouas GA. Metallic implant biomaterials. Mater Sci Eng Rep 2015; 87: 1-57
- 21 Stevenson M, Barkey M, Bradt R. Fatigue failures of austenitic stainless steel orthopedic fixation devices. Pract Fail Anal 2002; 2: 57-64
- 22 McClure SR, Watkins JP, Hogan HA. In vitro evaluation of four methods of attaching transfixation pins into a fiberglass cast for use in horses. Am J Vet Res 1996; 57 (07) 1098-1101
- 23 Mihalko WM, Beaudoin AJ, Krause WR. Mechanical properties and material characteristics of orthopaedic casting material. J Orthop Trauma 1989; 3 (01) 57-63
- 24 Rossignol F, Vitte A, Boening J. Use of a modified transfixation pin cast for treatment of comminuted phalangeal fractures in horses. Vet Surg 2014; 43 (01) 66-72
- 25 Lescun TB, Baird DK, Oliver LJ, Adams SB, Hawkins JF, Moore GE. Comparison of hydroxyapatite-coated and uncoated pins for transfixation casting in horses. Am J Vet Res 2012; 73 (05) 724-734