Arthroscopy of the Equine Cervical Articular Process Joints

Introduction
The equine cervical articular process joints (APJs) are subject to developmental defects, osteochondrosis, fractures and degenerative joint disease. Cervical arthropathy has been documented as a cause of neck pain, neck stiffness, ataxia and, less frequently, forelimb lameness therefore the development of a technique for investigating APJs is warranted. In the last 25 years, arthroscopy has become a useful tool for diagnosing and treating a variety of articular disorders in horses, and today it can be considered to be one of the most useful techniques in equine joint surgery. It has also been proven to provide more anatomical detail of the cartilage and other synovial structures. Arthroscopy of the APJs has not been reported in horses. Therefore, the purposes of this presentation is to describe the arthroscopic technique of cervical APJs, using the current equine arthroscopic instrumentation via a lateral neck approach.

Surgical Technique
The horse is positioned in right or left lateral recumbency, with a slight ventroflexion of the cervical spine and mild lateral flexion using a rest located between the necks and the surgery table. The area corresponding to the cervical vertebrae (C1–C7) is clipped and cleaned. Two articular recesses can be explored in each APJ, one located cranioventrally and one caudodorsally. For each cervical vertebra, landmarks for the identification of the APJs are developed by palpation of the transverse processes. The cranioventral articular recess for each APJs is situated 3–4 cm dorsal to the caudal border of the dorsal tubercle of the transverse process. A 21 gauge 7 cm needle is introduced 3–5 cm dorsal to the caudal border of the dorsal tubercle of the transverse process into the cranioventral articular recess under ultrasound control (3.5–5 MHz convex probe). Joint distension is achieved with 12–20 ml of sterile lactated Ringer’s solution to facilitate insertion of the arthroscope. A 10 mm skin incision with a No. 21 blade is made that corresponded with the position of the needle introduced in the cranioventral recess. A deep stab incision through the most superficial muscular structures (cutaneous colli, splenius cervicis and longissimus cervicis) is made with a No. 11 blade. The arthroscopic sleeve (2.7 or 4.0 mm) and a blunt conical obturator are inserted into the cranioventral articular recess. The insertion of the arthroscopic sleeve can be performed under ultrasound guidance in some cases. If ultrasound guidance is used then the arthroscope is inserted cranial (cranioventral recess) or caudal (caudodorsal recess) to the transducer and advanced until the tip of the arthroscope is visible inside the recesses. Joint entry is confirmed by backflow of irrigation fluid and flow is adjusted (100-150 mmHg) to produce joint distension while limiting fluid extravasation. The caudodorsal recess is evaluated by inserting the arthroscope about 1 cm dorsally and 4 cm caudally to the cranioventral recess portal, with the same slope but in the opposite direction (caudocranial) to that of the cranioventral recess of the APJ under investigation.  [...]