1406 AJVR, Vol 69, No. 11, November 2008 P antarsal arthrodesis has been recommended in dogs with intractable degenerative joint disease, irrepa- rable bone and soft tissue trauma, or sciatic nerve pa- ralysis. 1–3 This procedure is often preferred to selective arthrodesis of the talocrural joint, which has been as- sociated with high complication rates in relation to its inability to achieve bone union, implant failure, and the formation of secondary degenerative changes in inter- tarsal and tarsometatarsal joints. 4–7 Plantar bone plate fixation for pantarsal arthrod- esis is biomechanically sound because the plate is ap- plied on the tension side of the construct (during the weight-bearing phase of the gait cycle) and therefore provides dynamic compression of the joint surfaces In vitro mechanical evaluation of medial plating for pantarsal arthrodesis in dogs Reunan P. Guillou, Doc Vét; Joseph D. Frank, DVM; Michael T. Sinnott, MS; Eric G. Meyer, MS; Roger C. Haut, PhD; Loïc M. Déjardin, DVM, MS Objective—To compare the bending properties of pantarsal arthrodesis constructs involving either a commercially available medial arthrodesis plate (MAP1) or a specially designed second-generation plate (MAP2) implanted in cadaveric canine limbs and evaluate the effect of calcaneotibial screw (CTS) augmentation on the structural properties of both constructs. Sample Population—5 pairs of canine hind limbs. Procedures—Within pairs, specimens were stabilized with an MAP1 or MAP2 and loaded to 80% of body weight, with and without CTS augmentation. Compliance, angular deforma- tion (AD), and plate strains were compared. Results—Construct compliance and AD did not differ between plates. Maximum plate strain was lower in the MAP2 than in the MAP1 (difference of approx 30%). Augmentation with a CTS reduced compliance, AD, and strains in MAP1 constructs but had no effect on those variables in MAP2 constructs. Conclusions and Clinical Relevance—Because of lower peak strains, the MAP2 may be less susceptible to failure than the MAP1. Furthermore, CTS augmentation was unnecessary with MAP2s, which could minimize intra- and postoperative morbidity. Compared with what is known for dorsal plates, MAP2 constructs were associated with approximately 35% less AD. As a result of improved local stability, one might anticipate earlier fusion of the talocrural joint with an MAP2. In addition, plate peak strain was approximately 3.5 times lower in MAP2s than in dorsal plate constructs, which should result in greater fatigue resistance. The use of MAP2s may be a better alternative to both MAP1s and dorsal plates and could contribute to lower patient morbidity. (Am J Vet Res 2008;69:1406–1412) during loading. 2,8,9 However, plantar plate application is surgically challenging because of the regional neuro- vascular structures 8 and has remained unpopular. Con- versely, the use of DPs for pantarsal arthrodesis, with their ease of application, is common in dogs. However, DPs are placed on the compression side of the con- struct; therefore, they bear large bending moments be- cause of the talocrural fusion angle and the long mo- ment arms provided by the tibia and tarsometatarsus on either side of the construct. 10 Such constructs are biomechanically weaker than those involving a plate placed on the tension side of the construct and are more susceptible to plastic deformation or breakage of Received November 8, 2007. Accepted February 15, 2008. From the Department of Small Animal Clinical Sciences, College of Veterinary Medicine (Guillou, Frank, Déjardin), and the Orthopae- dic Biomechanics Laboratories, College of Osteopathic Medicine (Sinnott, Meyer, Haut), Michigan State University, East Lansing, MI 48824. Supported by a grant from the AO Vet Research Fund. Presented in abstract form at the 2007 American College of Veterinary Surgeons Symposium, Chicago, October 2007, and at the 2008 Vet- erinary Orthopedic Society Winter Meeting, Big Sky, Mont, March 2008. The authors thank Cliff Beckett for technical assistance. Address correspondence to Dr. Déjardin. ABBREVIATIONS AD Angular deformation AMI Area moment of inertia CTS Calcaneotibial screw DCH Dynamic compression hole DCP Dynamic compression plate DP Dorsal plate FEA Finite element analysis IMR Intramedullary rod MAP1 First-generation medial arthrodesis plate MAP2 Second-generation medial arthrodesis plate VMS Von Mises stresses Unauthenticated | Downloaded 08/20/22 03:38 AM UTC