OJO  Vol.3 No.2 , June 2013
A New Model to Study Healing of a Complex Femur Fracture with Concurrent Soft Tissue Injury in Sheep
Abstract: High energy bone fractures resulting from impact trauma are often accompanied by subcutaneous soft tissue injuries, even if the skin remains intact. There is evidence that such closed soft tissue injuries affect the healing of bone fractures, and vice versa. Despite this knowledge, most impact trauma studies in animals have focussed on bone fractures or soft tissue trauma in isolation. However, given the simultaneous impact on both tissues a better understanding of the interaction between these two injuries is necessary to optimise clinical treatment. The aim of this study was therefore to develop a new experimental model and characterise, for the first time, the healing of a complex fracture with concurrent closed soft tissue trauma in sheep. A pendulum impact device was designed to deliver a defined and standardised impact to the distal thigh of sheep, causing a reproducible contusion injury to the subcutaneous soft tissues. In a subsequent procedure, a reproducible femoral butterfly fracture (AO C3-type) was created at the sheep’s femur, which was initially stabilised for 5 days by an external fixator construct to allow for soft tissue swelling to recede, and ultimately in a bridging construct using locking plates. The combined injuries were applied to twelve sheep and the healing observed for four or eight weeks (six animals per group) until sacrifice. The pendulum impact led to a moderate to severe circumferential soft tissue injury with significant bruising, haematomas and partial muscle disruptions. Posttraumatic measurements showed elevated intra-compartmental pressure and circulatory tissue breakdown markers, with recovery to normal, pre-injury values within four days. Clinically, no neurovascular deficiencies were observed. Bi-weekly radiological analysis of the healing fractures showed progressive callus healing over time, with the average number of callus bridges increasing from 0.4 at two weeks to 4.2 at eight weeks. Biomechanical testing after sacrifice showed in- creasing torsional stiffness between four and eight weeks healing time from 10% to 100%, and increasing ultimate torsional strength from 10% to 64% (relative to the contralateral control limb). Our results demonstrate the robust healing of a complex femur fracture in the presence of a severe soft tissue contusion injury in sheep and demonstrate the establishment of a clinically relevant experimental model, for research aimed at improving the treatment of bone fractures accompanied by closed soft tissue injuries.
Cite this paper: M. Wullschleger, R. Steck, R. Matthys, J. Webster, M. Woodruff, D. Epari, K. Ito and M. Schuetz, "A New Model to Study Healing of a Complex Femur Fracture with Concurrent Soft Tissue Injury in Sheep," Open Journal of Orthopedics, Vol. 3 No. 2, 2013, pp. 62-68. doi: 10.4236/ojo.2013.32012.

[1]   M. Bhandari, P. Tornetta, S. Sprague, S. Najibi, B. Petrisor, L. Griffith and G. H. Guyatt, “Predictors of Reoperation Following Operative Management of fracTures of the Tibial Shaft,” Journal of Orthopaedic Trauma, Vol. 17, No. 5, 2003, pp. 3-361.

[2]   S. E. Utvag, O. Grundnes, D. B. Rindal and O. Reikeras, “Influence of Extensive Muscle Injury on Fracture Healing in Rat Tibia,” Journal of Orthopaedic Trauma, Vol. 17, No. 6, 2003, pp. 430-435. doi:10.1097/00005131-200307000-00007

[3]   L. Claes, N. Maurer-Klein, T. Henke, H. Gerngross, M. Melnyk and P. Augat, “Moderate Soft Tissue Trauma Delays New Bone Formation Only in the Early Phase of Fracture Healing,” Journal of Orthopaedic Research, Vol. 24, No. 6, 2006, pp. 1178-1185. doi:10.1002/jor.20173

[4]   S. P. Bruder, D. J. Fink and A. I. Caplan, “Mesenchymal Stem Cells in Bone Development, Bone Repair, and Skeletal Regeneration Therapy,” Journal of Cellular Biochemistry, Vol. 56, No. 3, 1994, pp. 283-294. doi:10.1002/jcb.240560303

[5]   R. Bielby, E. Jones and D. McGonagle, “The Role of Mesenchymal Stem Cells in maIntenance and Repair of Bone,” Injury, Vol. 38, No. Suppl 1, 2007, pp. S26-S32. doi:10.1016/j.injury.2007.02.007

[6]   A. Schmeling, M. Schuetz, M. Kääb, S. Rupp, K. Schaser and K. Ito, “A Realistic Experimental Model of Shaft Fractures and Concomitant Soft Tissue Trauma in the Sheep Tibia (Abstract),” ORS 46th Annual Meeting, Orlando, 12-15 March 2000, p. 276.

[7]   H. Tscherne and H. J. Oestern, “A New Classification of Soft-Tissue Damage in Open and Closed Fractures,” Unfall-Heilkunde, Vol. 85, No. 3, 1982, pp. 111-115.

[8]   M. E. Mueller, S. Nazarian and P. Koch, “The Comprehensive Classification of Fractures of Long Bones,” SpringerVerlag, Berlin, Heidelberg, New York, 1990. doi:10.1007/978-3-642-61261-9

[9]   R. Hente, J. Cordey, B. A. Rahn, M. Maghsudi, S. von Gumppenberg and S. M. Perren, “Fracture Healing of the Sheep Tibia Treated Using a uniLateral External Fixator. Comparison of Static and Dynamic Fixation,” Injury, Vol. 30, No. Suppl 1, 1999, pp. A44-A51. doi:10.1016/S0020-1383(99)00126-6

[10]   H. Schell, H, M. S. Thompson, H. J. Bail, J. E. Hoffmann, A. Schill, G. N. Duda and J. Lienau, “Mechanical Induction of Critically Delayed Bone Healing in Sheep: Radiological and Biomechanical Results,” Journal of Biomechanics, Vol. 41, No. 14, 2008, pp. 3066-3072. doi:10.1016/j.jbiomech.2008.06.038

[11]   F. Baumgaertel, S. M. Perren and B. Rahn, “Animal Experiment Studies of ‘Biological’ Plate Osteosynthesis of Multi-Fragment Fractures of the Femur,” Unfallchirurg, Vol. 97, No. 1, 2001, pp. 19-27.

[12]   A. S. Malik, O. Boyko, N. Atkar and W. F. Young, “A Comparative Study of MR Imaging Profile of Titanium Pedicle Screws,” Acta Radiologica, Vol. 42, No. 3, 2001, pp. 291-293. doi:10.1080/028418501127346846