The effect of external coaptation on plate deformation in an ex vivo model of canine pancarpal arthrodesis

Summary

Objectives: Since external coaptation is applied clinically to prevent plate failure during healing in canine pancarpal arthrodesis (PCA), we tested the hypothesis that external coaptation does not significantly reduce plate strain in an experimental ex vivo model of canine PCA.

Methods: Ten thoracic limbs from healthy Greyhounds euthanatized for reasons un- related to the study were harvested and the carpus was stabilised with a dorsally applied 2.7/3.5 mm hybrid PCA plate. The strain in the plate adjacent to the most distal radial screw hole (R4) and the radial carpal bone (RCB) screw hole was measured as the limbs were loaded axially to a load that approximated that of controlled walking. Each limb was tested with and without external coaptation in place.

Results: Mean strain amplitude at the RCB was –177.2 με (± 20.78) without external coaptation. Following cast application, strain reduced significantly to –34.7 με (± 9.84) (p <0.002). Mean strain at R4 was –89.4 με (± 22.10) without external support and –66.9 με (± 10.74) following application of a cast. This reduction in recorded strain was not statistically significant.

Clinical significance: The application of a cast to the distal portion of the limb significantly reduced strain in the 2.7/3.5 mm hybrid PCA plate, but the magnitude of the measured strain was low, suggesting that fatigue damage is unlikely to accumulate as a result of this type of loading and that external coaptation may not be necessary to prevent fatigue failure of the plate.

Keywords

Pancarpal arthrodesis - hybrid plate - strain - external coaptation - implant failure

• References

• 1 Parker RB, Brown SG, Wind AP. Pancarpal arthrodesis in the dog: a review of forty-five cases. Vet Surg 1981; 10: 35-43.
• 2 Johnson AL, Houlton JEF. Arthrodesis of the carpus. In: Johnson AL, Houlton JEF, Vannini R. editors. AO Principles of Fracture Management in the Dog and Cat. Davos Platz, Switzerland: AO Publishing; Stuttgart : Distribution by Thieme; 2005. pg. 446-457.
• 3 Fractures and other orthopedic conditions of the carpus, metacarpus, and phalanges. In: Piermattei DL, Flo GL, DeCamp CE. editors. Brinker, Piermattei, and Flo's Handbook of Small Animal Orthopedics and Fracture Repair. St. Louis, Mo.: Saunders/Elsevier; 2006. pg. 382-428.
• 4 Johnson KA. Carpal arthrodesis in dogs. Aust Vet J 1980; 56: 565-573.
• 5 Penwick RC. Arthrodesis. Vet Clin N Am Sm Anim Pract 1987; 17: 821-840.
• 6 Buote NJ, McDonald D, Radasch R. Pancarpal and partial carpal arthrodesis. Compend Contin Educ Vet 2009; 31: 180-192.
• 7 Chambers JN, Bjorling DE. Palmar surface plating for arthrodesis of the canine carpus. J Am Anim Hosp Assoc 1982; 18: 875-882.
• 8 Li A, Gibson N, Carmichael S. et al. Thirteen pancarpal arthrodeses using 2.7/3.5 mm hybrid dynamic compression plates. Vet Comp Orthop Traumatol 1999; 12: 102-107.
• 9 Guerrero TG, Montavon PM. Medial plating for carpal panarthrodesis. Vet Surg 2005; 34: 153-158.
• 10 Lewis DD, Radasch RM, Beale BS. et al. Initial clinical experience with the IMEXTM circular external skeletal fixation system. Part I: Use in fractures and arthrodeses. Vet Comp Orthop Traumatol 1999; 12: 108-117.
• 11 Lotsikas PJ, Radasch RM. A clinical evaluation of pancarpal arthrodesis in nine dogs using circular external skeletal fixation. Vet Surg 2006; 35: 480-485.
• 12 Benson JA, Boudrieau RJ. Severe carpal and tarsal shearing injuries treated with an immediate arthrodesis in seven dogs. J Am Anim Hosp Assoc 2002; 38: 370-380.
• 13 Denny HR, Barr ARS. Partial carpal and pancarpal arthrodesis in the dog: a review of 50 cases. J Small Anim Pract 1991; 32: 329-334.
• 14 Clarke SP, Ferguson JF, Miller A. Clinical evaluation of pancarpal arthrodesis using a CastLess plate in 11 dogs. Vet Surg 2009; 38: 852-860.
• 15 Whitelock RG, Dyce J, Houlton JE. Metacarpal fractures associated with pancarpal arthrodesis in dogs. Vet Surg 1999; 28: 25-30.
• 16 Parente EJ, Nunamaker DM. Stress protection afforded by a cast on plate fixation of the distal forelimb in the horse in vitro. Vet Surg 1995; 24: 49-54.
• 17 Arnott JL, Bailey R, Shields A. et al. An in vitro comparison of a 2.7/3.5 mm hybrid plate alone and combined with crossed K-wires for canine pancarpal arthrodesis. Vet Comp Orthop Traumatol 2008; 21: 307-311.
• 18 Anderson DM, White RA. Ischemic bandage injuries: a case series and review of the literature. Vet Surg 2000; 29: 488-498.
• 19 Meeson RL, Davidson C, Arthurs GI. Soft-tissue injuries associated with cast application for distal limb orthopaedic conditions. A retrospective study of sixty dogs and cats. Vet Comp Orthop Traumatol 2011; 24: 126-131.
• 20 Piermattei DL, Johnson KA. Approach to the distal radius and carpus through a dorsal incision. In: Piermattei DL, Johnson KA. editors. An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. Philadelphia, Pa: Saunders; 2004. pg. 254-257.
• 21 DeCamp CE. Kinetic and kinematic gait analysis and the assessment of lameness in the dog. Vet Clin N Am Small Anim Pract 1997; 27: 825-840.
• 22 Roush JK, McLaughlin Jr. RM. Effects of subject stance time and velocity on ground reaction forces in clinically normal greyhounds at the walk. Am J Vet Res 1994; 55: 1672-1676.
• 23 Guillou RP, Demianiuk RM, Sinnott MT. et al. In vitro mechanical evaluation of a limited contact dynamic compression plate and hybrid carpal arthrodesis plate for canine pancarpal arthrodesis. Vet Comp Orthop Traumatol 2012; 25: 83-88.
• 24 Diaz-Bertrana C, Darnaculleta F, Durall I. et al. The stepped hybrid plate for carpal panarthrodesis - Part I: relationship between plate and bone surfaces. Vet Comp Orthop Traumatol 2009; 22: 380-388.
• 25 Diaz-Bertrana C, Darnaculleta F, Durall I. et al. The stepped hybrid plate for carpal panarthrodesis - Part II: a multicentre study of 52 arthrodeses. Vet Comp Orthop Traumatol 2009; 22: 389-397.
• 26 Clarke S. New plate design for pancarpal arthrodesis. In: Baines S. editor. Proceedings of the 19th Annual Scientific Meeting, European College of Veterianry Surgeons. 2010. July 1-3 Helsinki, Finland: 2010. pg. 210-211.
• 27 Kirsch JA, Dejardin LM, DeCamp CE. et al. In vitro mechanical evaluation on the use of an intramedullary pin-plate combination for pantarsal arthrodesis in dogs. Am J Vet Res 2005; 66: 125-131.
• 28 Hulse D, Hyman W, Nori M. et al. Reduction in plate strain by addition of an intramedullary pin. Vet Surg 1997; 26: 451-459.
• 29 Dueland RT, Vanderby R, McCabe RP. Fatigue study of six and eight mm diameter interlocking nails with screw holes of variable size and number. Vet Comp Orthop Traumatol 1997; 10: 194-199.
• 30 Meeson RL, Goodship AE, Arthurs GI. A Biomechanical evaluation of a hybrid dynamic compression plate and a CastLess arthrodesis plate for pancarpal arthrodesis in dogs. Vet Surg. In press 2012