Epiduroscopy of the lumbosacral vertebral canal in the horse: Technique and endoscopic anatomy.

Abstract: Back pain is a common cause of gait alterations and poor performance in horses, but the available imaging modalities are frequently insufficient to isolate the underlying pathology. In human patients, epidural endoscopy (epiduroscopy) is successfully used to diagnose and treat challenging cases of lower back pain. Endoscopy of the cervical epidural space has previously been reported in anaesthetised horses. Objective: To develop a technique for lumbosacral epiduroscopy in standing horses and to describe the endoscopic anatomy of the lumbosacral epidural space. Methods: Pilot study to assess the feasibility of lumbosacral epiduroscopy in 5 horse cadavers. Methods: The cadavers of 5 horses, weighing 457-694 kg (mean, 570 kg), were suspended in an upright position. Vascular dilators of increasing size were inserted between the first 2 moveable vertebrae caudal to the sacrum to create a minimally invasive approach into the epidural space. A flexible videoendoscope was introduced and advanced as far cranially as the length of the endoscope permitted. The lumbosacral epidural space underwent gross necropsy examination following the procedure. Results: The endoscope was successfully inserted into the epidural space in all horses. Saline injection through the working channel of the endoscope allowed the following anatomical structures to be seen: dura mater, left and right lumbosacral spinal nerves, cauda equina, epidural fat, connective tissue and blood vessels. Using the 60 cm working length of the endoscope, the epidural space could be examined as far cranial as L3-T18, depending on the size of the horse. No gross damage to epidural neurovascular structures was observed on necropsy examination. Conclusions: Lumbosacral epiduroscopy is technically feasible in standing horses and may become a valuable diagnostic tool in horses with caudal back or limb pain of unknown origin. Studies in live horses will be necessary to evaluate the safety of the procedure.