Surgery of the Spine
Spinal surgery used to be a common procedure for small animal orthopaedic surgeons in the UK but as time passes and with the availability of more neurologists experienced in spinal surgery with the availability of facilities for on-site advanced imaging, spinal surgery is gradually shifting away from main-steam orthopaedics and into the domain of surgical neurology. Spinal surgery can be very rewarding, and it is still possible to perform it successfully with relatively modest equipment, but there are a number of critical factors to achieving a successful outcome.
Making the correct diagnosis: Patient signalment and neurological examination should lead to gross localisation of the neurological lesion i.e. upper motor neuron vs. lower motor neuron, central vs. peripheral neuropathy, the most likely spinal segment affected i.e. C1-C5, C6-T2, T3-L3 and L4-S3, and left vs. right sided.
Most patients requiring spinal surgery have spinal cord compression caused by intervertebral disc extrusion or protrusion, soft tissue hypertrophy associated with instability, spinal fracture or luxation, or neoplasia. Plain radiographs may indicate the location of a fracture, luxation or neoplasia, but are rarely sufficiently to reliably identify location and lateralisation of intervertebral disc disease.
Myelography can be used for precise lesion localisation and was successfully used for many years, but it comes with a number of drawbacks including risks and side effects associated with cisternal or lumbar puncture, and injection of contrast agents into the subarachnoid space.
Over the last decade, MRI has become established as the technique of choice for imaging the spinal canal and cord, with CT +/-contrast coming a close second. Given the choice, both CT and MRI are preferable to myelography as they are safer, arguably quicker, have far fewer risks or side effects, and are much less likely to result in a false diagnosis. For example, a low volume high velocity (LVHV) disc extrusion or Fibro-Cartilaginous Embolus (FCE) cannot be definitively diagnosed using myelography, but the diagnosis can be made from good quality MR images, particularly a high field unit. This increases diagnostic accuracy, closely guides prognosis, decision making and treatment options, and potentially avoids unnecessary surgery from a misleading myelogram.
With experience, some spinal surgeries are relatively straightforward to perform. For example, thoracolumbar hemilaminectomy for spinal decompression caused by intervertebral disc extrusion is not technically difficult. In addition to a standard orthopaedic kit, specific equipment required includes a burr system to remove the bulk of the laminar bone, rongeurs for fine removal of bone as the spinal cord is approached, a set of probes, hooks and curettes for exploring adjacent to the spinal cord and retrieval of extruded disc material.
The critical parts to making spinal surgery a success are:
comprehensive neurological and orthopaedic assessment of the patient
accurate lesion localisation, ideally by MRI or CT scan
training and familiarity with the procedure to be undertaken
familiarity with the surgical anatomy
accurate surgical technique with careful dissection at the correct disc space
in particular, very gentle exploration and probing of the spinal canal; the spinal cord and nerve roots do not tolerate rough handling. This requires very careful technique in order to avoid slippage of the hand that could lead to concussion of the spinal cord with potentially irreversible damage.
Veterinary Instrumentation is pleased to offer a full range of equipment with which to perform routine spinal surgery, including general surgical equipment, (see Chapter 2), Gelpis and Odd-legged Gelpis for retraction and visualisation, Burrs, Rongeurs, Nerve Hooks and Curettes for retrieval of extruded disc material, and Bone wax and Lyostypt for haemostasis.
Sharp and Wheeler’s textbook “Small Animal Spinal Disorders” is an excellent read for anybody interested in spinal surgery and neurology, whether you are a beginner, or wanting to increase your knowledge and competence.
For more challenging cases such as fractures and luxations, then a full range of implants are also available, including screws, external skeletal fixator pins, locking plates.