How to Inject the Cervical and Thoracolumbar Articulations

1. Introduction

Topline issues are common among all disciplines in equine practice.^1–3  These problems can be divided up by anatomical location and generally involve the cervical, thoracolumbar, and sacroiliac regions. Treatment of the former two by injection will be covered in this report.

The cervical spine should be considered the conduit for all signals traveling from the control center of the brain to the rest of the body, particularly all four limbs.⁴  In the horse, issues associated with the neck may be related to its gravitationally challenged anatomical construct, functioning as a horizontally positioned boney column supported by the elastic nuchal ligament. During exercise, particularly in disciplines that require the horse to assume a collected cervical frame, excess stress may be placed on these articulations, either between the cervical bodies or the facet joints.⁵

Cervical dysfunction in people is commonly reported in orthopedic practice and is often associated with weakness and pain in the appendages or local pain restricting movement.^6,7  Most often the clinical signs are described verbally to the attending physician; the gold standard for imaging of cervical lesions in the human patient is MRI. Due to the limitations of magnet design, however, it is not currently and may never be feasible to image the caudal cervical region of the horse. Therefore, equine clinicians are limited in their imaging capacity to radiology, ultrasound, and nuclear scintigraphy. In cases in which compression is suspected, myelography enhances the radiographic study but must be conducted under general anesthesia. 

In our opinion, any horse with mild ataxia, intermittent or unrelenting forelimb lameness, or obscure hind limb lameness should be investigated for cervical issues.^8,9 The pathophysiology associated with an obscure lameness may be due to a proprioceptive deficit, nerve root compression, or pain. Proprioceptive deficits may be described by the trainer or rider simply as “being heavy on the forehand” or feeling “disjointed” between the fore and hind limbs. Furthermore, any time a generalized decrease in performance is noted without corresponding lameness, a problem affecting any part of the axial skeleton should be ruled out. Recurrence of appendicular lameness after successful treatment may also be indicative of an underlying problem with the axial skeleton. In our practice, the most common clinical signs associated with pathology in the thoracolumbar region are localized pain and aversion to saddling or mounting. More severely affected horses will react to the weight of the rider, sometimes violently, by bucking or rearing.

The physical examination of the entire axial skeleton of the horse is subjective and may be considered limited compared with examination of the limbs. Assessment of the neck includes observation of muscular development or atrophy, the response to passive cervical manipulation, and dermal stimulation. In many cases of cervical arthropathy, muscular atrophy is noted. Most horses that exhibit abnormal cervical manipulation either resist lateral flexion totally or avoid lateral flexion by offering a more ventral flexion of the head and neck. The rider often describes resistance to lateral bending, being “heavy on one rein” or resistance to achieving the frame desired. In some cases, particularly with upper-level dressage horses, the avoidance of this desired frame can even result in hypertrophy of the affected muscles along the topline. Examination of the thoracolumbar region can be even more subjective, with a painful response to direct pressure variable among horses.

It can be difficult to rule out problems in the axial skeleton without the screening tool of nuclear scintigraphy (Fig. 1), as these areas are easily highlighted by increased radiopharmaceutical uptake (IRU). In the case of myelopathy, no IRU may be noted in the cervical region. Radiography alone can be used to document some cases of cervical arthropathy. Radiography can highlight enlarged facets (Fig. 2), previous trauma (such as fracture), or entheseous bone formation and narrowing of the spinal canal, although these findings may not always carry clinical significance. Findings on ultrasound may include periarticular osteophytosis/ entheseophytosis not seen radiographically. Ultrasound is also used to identify the facet joint and to guide the needle for proper intra-articular therapy.
 

The treatment of issues associated with the axial skeleton can often be challenging. In many cases, injection of the affected area with anti-inflammatory medication (corticosteroids) or autologous conditioned serum^a (ACS) may be indicated. Injection techniques for the cervical and thoracolumbar regions are described below. [...]