ESTABLISHING REFERENCE VALUES
A critical part of surgically correcting angular limb deformities of any bone is having a reference for what constitutes normal
in that particular patient so that objective goals for surgical correction can be established. If an animal is affected unilaterally,
the opposite, unaffected side can be used to obtain measurements of normal anatomical and mechanical axes and their relationship
to the associated joints for that patient. However, if a dog is affected bilaterally, reference values should be used. Numerous
studies are now being completed at umcvmth to report such reference values in dogs based on breed. For example, the canine
radius possesses a normal procurvatum of about 25 degrees and is angled within the antebrachium in the frontal plane by about
2.7 degrees.2 The canine femur is similarly complex in shape, exhibiting a normal distal varus of about 4 to 8 degrees depending on breed.3
THE CORA METHODOLOGY AND SURGICAL CORRECTION
Angular alterations of canine long bones are among the most common orthopedic surgeries performed. Examples include radial-ulnar
deformity correction,2 excessive distal femoral varus correction in the treatment of patellar luxation,4 and tibial plateau leveling osteotomy for the treatment of cranial cruciate ligament rupture.5 Each of these surgeries is similar in that the success of the procedures depends on the accuracy of deformity localization,
preoperative planning using normal standard references, and correct execution of bone realignment through osteotomies. The
cora principles as outlined by Paley and others help to accomplish these tasks by providing a usable vocabulary and repeatable
and consistent methodologies of correction.
Through the studies completed and currently under way at UMCVMTH, we hope to optimize angular limb deformity correction outcomes
in small-animal patients by fully developing a common vocabulary regardless of the affected bone, more accurately defining
the common types of angular deformities seen in dogs and cats, and demonstrating the utility and effect of the various osteotomies
used for long bone correction.
The information for "On the Forefront" was provided by Derek B. Fox, DVM, PhD, DACVS, Department of Veterinary Medicine
and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211.
1. Paley D. Principles of deformity correction. Berlin: Springer-Verlagg, 2002.
2. Fox DB, Tomlinson JL, Cook JL, et al. Principles of uniapical and biapical radial deformity correction using dome osteotomies
and the center of rotation of angulation methodology in dogs. Vet Surg 2006;35:67-77.
3. Tomlinson JL. Tibial and femoral angles in normal dogs, in Proceedings. Am Coll Vet Surg Vet Symp 2006;390-391.
4. Peruski AM, Kowaleski MP, Pozzi, et al. Treatment of medial patellar luxation and distal femoral varus by femoral wedge osteotomy
in dogs: 30 cases (2000-2005), in Proceedings. 33rd Annu Vet Orthop Soc Meet, Keystone 2006;240.
5. Slocum B, Slocum TD. Tibial plateau leveling osteotomy for cranial cruciate ligament rupture. In Bojrab MJ, ed. Current techniques in small animal surgery. 4th ed. Baltimore, Md: Williams & Wilkins, 1998;1209-1215.