Research & Reviews: Journal of Veterinary Sciences
Menue-ISSN No.:2581-3897
e-ISSN No.:2581-3897
Jan-Hein Swagemakers*, S. Schmidt
Department of Orthopedics, Tierklinik Luesche GmbH, Bakum, Germany
Received: 17-May-2024, Manuscript No.JVS-24-135978; Editor assigned: 21-May-2024, PreQC No. JVS-24-135978 (PQ); Reviewed: 04-Jun-2024, QC No. JVS-24-135978; Revised: 11-Jun-2024, Manuscript No. JVS-24-135978 (R); Published: 18-Jun-2024, DOI: 10.4172/2581-3897.8.02.003
Citation: Swagemakers JH, et al. Uniportal, Full Endoscopic Foraminotomy as Treatment of Cervical Radiculopathy in Horses. J Vet Sci. 2024;8:003.
Copyright: © 2024 Swagemakers JH, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Equine cervical radiculopathy can express itself in a wide variety of symptoms. Empirically, conservative treatment has not produced consistent, lasting results. The innovative uniportal, full endoscopic surgical for aminotomy procedure, widening the Inter Vertebral Foramen (IVF), eliminates the pressure on the exiting spinal nerve. The procedure has a low complication rate and the marked advantage of limited after care and rapid return to performance.
Radiculopathy; Equine; Foraminotomy; Endoscopic surgery; Cervical; Foramen stenosis; Neurology
Interest in the cervical spine as a cause of pain or dysfunction is increasingly becoming the focus of many equine practitioners. Many affected horses are presented for poor performance, related to lameness, neck pain, restricted motion or neurological deficits. Severe cases will present with dramatic, sometimes dangerous behaviour [1]. Osteochondrosis and osteoarthritis are the two primary disorders that affect the cervical articular processes in horses and cervical APJ osteoarthritis is a relatively common problem in horses, particularly in the caudal cervical region [2-4]. It has been reported that 25% of warmblood jumpers (n = 104) have radiographic evidence of moderate to severe osteoarthritis at C6-7 [5]. Enlarged or encroaching articular processes associated with osteoarthritis can cause narrowing of the intervertebral foramen. This stenosis may cause radiculopathy, characterized by irritation and compression of the entrapped nerve root leading to inflammation and pain, as well as vascular congestion causing neurogenic symptoms.
These may vary from local pain, claudication, proprioceptive deficits or reduced motoric function. The latter may affect neck range of motion or front limb movement. Equine radiculopathy is challenging to diagnose even using advanced diagnostic imaging, as clinical symptoms cannot reliably be correlated to the extent of imaging findings. The only treatment option so far has been local injections with anti-inflammatory, mostly steroid, agents. However, conservative treatment often does not produce satisfactory outcomes. Either only alleviating symptoms temporarily requiring repeated treatment, which often loses efficacy over time, or leading to no improvement at all.
Technique
The procedure is performed under general anaesthesia, with the head and neck positioned on a fiberglass extension of the surgical table, as described previously [6]. The targeted IVF is positioned uppermost. After identifying the margins of the IVF using a fluoroscope, the spinal cannula is placed under ultrasound guidance aiming for the ventral margin of the APJ, which constitutes the dorsal border of the IVF. Localizing the facet joint margin, the outline of the APJ can be traced ventrally to identify its ventral margin. Significant anatomical structures to be avoided are the vertebral artery and the nerve root. The optimal approach would be a slight ventrolateral to dorsomedial angle, which may need to be adapted depending on the extent of the lateral tubercle. The surgical instruments are manufactured and designed for human spinal surgery (Riwospine GmbH). The cannula is inserted until bone contact is established (Figure.1).
Figure 1: Ultra sonographic controlled placement of the cannula at the dorsal margin of the IVF.
After confirmation of the position by fluoroscope, the trocard of the spinal cannula is replaced by a K-wire, which is fixed to the dorsal margin of the IVF using a surgical hammer. Following a 1,5 cm skin incision around the cannula a dilator followed by a working sleeve are placed over the K-wire (Figure. 2-4). Initially, the asymmetrical working sleeve is positioned with the tip in bone contact dorsally. The dilator is removed, and the endoscope (207 mm long, 6,9 mm diameter, eccentrically located lens) is inserted under visual control and continuous irrigation with 0,9% saline solution. Soft tissue is removed using a radio ablator (Trigger-Flex® Bipolar System, RIWO Spine) until the ventral edge of the facet is clearly visible. The sleeve is then rotated 180°, positioning the tip ventrally, thus protecting soft tissue structures, in particular the exiting nerve root and vertebral artery. Using different 3 mm burrs and bone punches, bone is removed, until visualization of the spinal canal is established, and both the cranial and caudal margins of the facet are distinguished. The amount of bone needing to be removed is determined beforehand on the CT images, by measuring the excessive bone in three dimensions. Additionally, intraoperative radiographic control images are obtained to estimate the increase of IVF space. Once the images suggest a satisfactory result all instruments are removed, and the skin incision is closed in two layers.
Figure 2: Endoscope placed through the sleeve.
Figure 3: Pre- surgery transverse- and sagittal CT image of a right sided C67 foramen stenosis.
Figure 4: Post- surgery transverse and sagittal CT image of the same horse as in above figure.
Post-surgical care and rehabilitation
Typically, patients receive phenylbutazone as a loading dose post-surgery (4,4 mg/kg), followed by 2,2 mg/kg BID for another three to five days depending on clinical presentation. From our clinical experience there is an increased risk of airway infection due to the long anaesthesia time and lateral recumbence. Therefore, prophylactic antimicrobial treatment with penicillin for three to five days is indicated.
After two days of stall rest post surgically, the first phase of rehabilitation consists of daily hand walking and active stretching of the neck. One-week post-surgery training and physiotherapeutically exercise is progressively increased. The horses are started on the lunge line in all three gaits on a halter, introducing proprioceptive training such as pole work, resistance bands and side reins. Additionally, neck stability is enhanced by static exercises on balance pads. Work under tack can be resumed six weeks after surgery. Sufficient to say that the rehabilitation should be adapted to the condition of the individual patient.
Main objective of the described minimally invasive uniportal technique is to achieve decompression of the spinal nerve root. Main advantage being continuous visualization with minimisation of operation-related trauma and its possible consequences such as bleeding or nerve injury.
Suitable candidates for this procedure are horses that have been diagnosed with spinal nerve root injury caused by IVF narrowing, that has not responded to intraarticular or per neural medication. IVF narrowing may be caused by remodelling of the cervical APJ’s as a result of ongoing osteoarthritis.
Diagnosis of IVF stenosis is challenging, as local anaesthesia of the exiting nerve is not conclusive, since this would affect general motor function of the front limb. Correlation of typical symptoms with corresponding CT findings and exclusion of other possible causes forms the decision to proceed to surgery. Typical findings are lameness, which does not respond to local anaesthesia of the complete limb; restricted protraction of one or both front limbs; local neck pain; reduced function or Range of Motion (ROM) of the neck or the affected front limb; proprioceptive deficits such as stumbling or falling down. Part of the patients show symptoms continuously, others intermittently. In cases with non-continuous presentation, examination should include flexion, extension and lateral bending of the neck, as the size of the IVF is known to alter depending on neck position [4]. In our opinion this could also explain why in some cases clinical signs do not correlate with the extent of CT findings as the intervertebral foramen remains a dynamic structure.
CT images of the included clinical cases showed stenosis of the IVF particularly at the cranial aspect. As the cervical spinal nerve exits the foramen at the caudal half of the IVF in horses, bony proliferation secondary to APJ osteoarthritis at the cranial aspect of IVF is less likely to cause spinal nerve compression [1,6]. However, we would like to note that nerve compression may also result from increase in soft tissue density in the IVF as a sequel of the osteoarthritic proliferation and capsulitis. In addition, we have perceived variation in the exit location of the nerve root in several patients making detailed anatomic studies essential to further optimize surgical technique by reducing direct or indirect manipulation.
We assume that the clinical effectiveness of this technique, both short-term and long-term, can be attributed to the decompression of the nerve root. Also, continuous flushing during the endoscopic procedure may have a positive effect on the chemically-induced neuritis of the nerve roots by removing the inflammatory mediators associated with APJ degeneration. Chemically- induced neuritis may be difficult to confirm in vivo, but histological evidence of nerve root injury has been noted at post-mortem examination in horses with unexplained forelimb lameness [1-8]. Therefore, we believe that in cases where satisfactory widening of the IVF is not completely achieved, clinical signs can still improve following this procedure.
More detailed anatomical and biomechanical studies of the equine cervical IVFs are required for comprehensive understanding of mechanisms of spinal nerve compression.
We consider this technique described to be a sufficient and safe novel surgical option when conservative therapy proves insufficient. This validated and established procedure in humans has now been successfully adapted for equine medicine allowing sustainable treatment of cervical radiculopathy caused by foraminal stenosis.
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