Caudal cervical spondylomyelopathy is a common disease of the cervical vertebrae in large-breed dogs that leads to various neurologic clinical signs caused by static and dynamic compression of the spinal cord.1,2 Most of the so-called disk-associated CSMs involve IVD degeneration and prolapse between C5 and C6 and between C6 and C7.2 The pathogenesis, diagnosis, and treatment of this disease are controversial, largely because the disease is not completely understood.
Treatment for CSM can be medical or surgical.2 Surgical treatment has a better overall outcome and therefore is recommended in most cases.3 Surgical treatment may consist of direct decompression (eg, partial removal of a bulging IVD via a ventral approach) or indirect decompressive techniques (eg, distraction and fusion of the affected vertebral segment2,4). However, decompressive techniques often lead to delayed fusion of the involved segments.5 Although these surgical techniques are generally satisfactory, it has been suggested that they can promote a change in vertebral kinematics and consequently a shift of the disease toward adjacent segments (adjacent segment disease) in up to 20% of the cases.6 Canine patients are often euthanized when there is recurrence of clinical signs originating from an adjacent segment.4
With the aim of preserving vertebral kinematics after surgical intervention, there has been an increasing interest in the development of new surgical techniques for canine patients with CSM. One of these techniques involves inserting an artificial IVD into the IVD space, with the goal of reestablishing normal vertebral motion.7,a However, this technique is associated with various complications, including delayed bone ingrowth, subsidence of the implant at the bone interface, lack of osseointegration, and incomplete restoration of vertebral kinematics.8,b Such complications may arise from a mismatch between the shape of current prosthesis designs and the rather asymmetric and obliquely orientated cervical IVD space. This discrepancy between anatomy and implant design may result in abnormal loading between the prosthesis and adjacent end plates. When considering potential improvements to current prosthesis designs, an anatomically shaped prosthesis conforming to the natural shape and size of an IVD space in dogs can be expected to more closely match the dynamic properties of the disk space. However, to our knowledge, a blueprint for such a prosthesis (ie, a fundamental morphometric description of the canine caudal cervical IVD space in a neutral position and in various loading positions) has not been described.
The aims of the study reported here were to determine the shape and size of the cranial and caudal end plates of the canine C4-5, C5-6, and C6-7 IVD spaces and to calculate the intervertebral angles and dimensions (IVD width) of the C4-5, C5-6, and C6-7 spaces in neutral, flexion, extension, and lateral bending positions. We hypothesized that the size and shape of the cranial end plate would differ from those of the caudal end plate, IVD wedge angles and width would change significantly throughout the physiologic range of motion, and morphometric characteristics would not differ among the C4-5, C5-6, and C6-7 spaces.
This manuscript represents a portion of a thesis submitted by Dr. Knell to the Graduate School for Cellular and Biomedical Sciences, University of Bern, as partial fulfillment of the requirements for a Doctor of Philosophy degree.
Supported in part by the Small Animal Foundation of the University of Zurich.
Presented in abstract form at the 26th Annual Scientific Meeting of the European College of Veterinary Surgeons, Edinburgh, July 2017, and the 1st International Symposium of the Societa Culturale Italiana Veterinari per Animali da Campagnia, Bologna, Italy, April 2018; and in poster form at the 45th Annual Meeting of the Veterinary Orthopedic Society, Snowmass, Colo, March 2018.
The authors thank Jeanne Peter for technical assistance.
Caudal cervical spondylomyelopathy
Adamo PF, da Costa RC, Kroll R, et al. Cervical disc arthroplasty using the Adamo Spinal Disc in 18 dogs affected by disc associated wobbler syndrome (abstr). J Vet Intern Med 2013;27:677.
Zindl C, Adamo PF, da Costa RC, et al. Retrieval analysis of canine cervical total disc replacement implants (abstr). Vet Surg 2015;44:E27.
Kirschner-Ehmer apparatus, DePuy Synthes, Oberdorf, Switzerland.
Brilliance CT 16-slice machine, Philips AG, Zurich, Switzerland.
OsiriX imaging software, version 4.1, 64-bit, Geneva, Switzerland.
Program R, R Foundation for Statistical Computing, Vienna, Austria.
Graphpad Prism, version 6, Graphpad Software Inc, La Jolla, Calif.
DISCOVER, DePuy Synthes, Raynham, Mass.
Adamo Spinal Disc, Applied Veterinary Technology, Walnut Creek, Calif.
ActiveC, Aesculap, Tuttlingen, Germany.
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