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Accuracy of a patient-specific drill guide created using computer-aided design from CT data and printed using rapid prototyping technology for placement of lumbosacral pedicle screws in dogs

Degenerative lumbosacral stenosis (DLSS) is a common cause of lumbosacral disease in dogs mostly observed in middle-aged (7–8 years), average to large breed dogs, with a clear predisposition for the German shepherd dog.

DLSS presents as lumbosacral pain, decreased ability to jump and in working dogs, is a significant cause of early retirement. Surgical treatment is indicated when the pain is severe and nonresponsive to medical treatment, when the motor or sensory deficits are present and in working dogs for whom pain-free performance is essential. Surgical decompression, combined with pedicle screw-rod fixation (PSRF) of the affected spinal segment is currently used to treat spinal stenosis, spinal instability, and degenerative disc disease in people. This surgery is challenging and risks neurologic complications during hardware placement. Great precision is essential to avoid potential complications because of the small bone geometry and the juxtaposition to the spinal cord and/or cauda equina.

In human spinal surgery, intra-operative imaging techniques have been introduced to ensure safe and accurate placement of pedicle screws but these are not routinely available in veterinary practice. Andrew Worth has developed a stabilization procedure using three-dimensional (3D) printing, also termed rapid proto-typing technology, to design implants that are patient-specific and therefore should give a higher degree of accuracy and safety for lumbosacral pedicle screw placement in dogs, compared to free-hand and conventional fluoroscopic techniques. This implant has been successfully used clinically in a small number of cases but the accuracy of pedicle screw placement has not been confirmed in these animals.

Drill guides manufactured with rapid-prototyping technology have been compared to intra-operative fluoroscopy in the human lumbar spine, but this has not yet been studied in the canine lumbosacral spine. It is important to assess if the intended accuracy of a custom LS implant can actually be replicated in a canine subject using a patient-specific drill guide. To the author’s knowledge, the proposed study will be the first to compare the accuracy of screw placement using 3D printed drill guides to traditional screw placement using only anatomic landmarks in the canine lumbosacral spine.

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