How to Perform a Successful Sacroiliac Joint Region Injection

1. Introduction

The sacroiliac joint is often cited as the source of lower back discomfort in performance horses. The rider or trainer may perceive that a horse has lower back pain from a number of clinical signs. These may include sensitivity to grooming, resistance to rider weight, stiffness in work, pain on manual palpation of the back, and poor performance. Many of these symptoms may arise as issues secondary to other lameness problems, particularly of the hind limb, and frequently the difficulty is determining the origin of the problem. A thorough physical examination, coupled with a complete therapeutic approach, can most frequently relieve symptoms of lumbosacral and sacroiliac pain.

Lumbosacral and sacroiliac strain is common in jumping, dressage, and Western performance horses. There is far more motion in the lumbosacral joint than in the sacroiliac, and the pain may be coming from this joint instead of the sacroiliac. The sacroiliac joint, however, has multiple ligamentous attachments to the axial skeleton that may be subject to trauma. Many horses are mildly affected on a chronic basis and continue to perform, although soreness in the region is evident on palpation. In more severe cases, performance is usually significantly compromised and the horse is distinctly lame, usually more obviously on one leg. Horses that were good performers suddenly don’t want to jump; dressage horses often refuse to “sit” and collect. The horse often stands with a stretched out posture and may rest one hind limb. Palpation over the lumbosacral area produces a painful response. Pain may be perceived by exerting more pressure on one sacral tuberosity. There may be considerable resistance on the part of the horse to have one of the hind legs picked up.¹  Rocking the pelvis may cause the horse to grunt. In cases of sacroiliac pain, lameness may be apparent in the opposite hind limb after an upper limb flexion test. The horse may be observed to have one more prominent tuber sacrale when viewed from behind, but this is not a certain indicator of recent injury. The appearance of a “jumper’s bump” has been associated with sacroiliac strain; however, this may be more of a conformational matter than a sign of pathology. Some veterinarians report being able to reduce lameness or temporarily alter the horse’s way of going with local anesthetic infiltrated deeply over the sacroiliac joint region, but this can be tricky, with a misplaced injection causing difficulty for the horse to stand. Nuclear scintigraphy can be useful in assessing if significant inflammation is present in the area. Ultrasound can be used to visualize lesions of the lower lumbar ligamentous structures, dorsal articular facets, and more superficial sacroiliac ligaments. Using rectal ultrasound, the ventral aspect of the sacroiliac and lumbosacral joints may be visualized as well as the foramina for the last lumbar and sacral nerve roots. Local pathology may be identified.²  

Rest and time are the two most significant factors in treating serious injuries of the sacroiliac joint region. In the case of severe strain, which is likely to be accompanied by sudden-onset lameness, healing of the injured tissue probably will require 6 months or longer. The horse should be stall-rested for 30 days, followed by 2 to 3 months of controlled paddock rest (tranquilized at first, if necessary). After this, light exercise on flat surfaces with a gradual increase in the amount of work over the next 3 months will allow time for healing and regaining strength in the affected area. Deep injection of the sacroiliac joint region may be of additional benefit and will be described herein.

2. Materials and Methods

Preparation of Sacroiliac Injection

Horses with less severe injuries of the lumbosacral and sacroiliac joints may continue in work and receive local therapy for soreness. Peri-articular injection of corticosteroids over the sacroiliac region may significantly reduce pain and allow for continued work. Various injection techniques have been described utilizing blind and ultrasound-guided methods.^3–5 There are two more commonly used techniques for injection of the lumbosacral and sacroiliac joints that will be outlined in this article. The first technique will describe a blind injection technique and the second will outline the steps for an ultrasound-guided technique.

Proper site preparation is essential for success in any deep injection of the sacroiliac region. Clipping of the injection site(s) may provide for a more complete aseptic prep and allow for better ultrasound visualization, but this may not be acceptable for some performance horses. Horses with a fine coat can be adequately cleansed for injection, and ultrasound images will be adequate. Heavy hair coats should be clipped for both blind and ultrasoundguided techniques. For ultrasound-guided procedures, the ultrasound probe should be covered with a sterile probe cover or surgical glove to minimize potential contamination and unnecessary damage to the probe surface. Sterile lubricant can be used within the cover for ultrasound coupling, and alcohol will suffice for cleaning the skin surface.

Restraint

Appropriate sedation and restraint is indicated for a safe sacroiliac injection procedure. The author prefers a combination of detomidine hydrochloride (0.01 mg/kg IV)^a and butorphanol (0.01 mg/kg IV)^b and restraint in stocks if available. Otherwise, a nose twitch and a nonslip surface should be used in addition to adequate sedation. The author typically administers gentamicin (6 mg/kg IV)c and flunixin meglumine (1 mg/kg IV)d as premedications as well.

Injection Technique

The first of the two more commonly used techniques was described by Engeli et al (2002).³ This involves a blind dorsomedial technique using a 6- to 10-inch (12.5 to 25 cm), 15- to 18-gauge needle that is placed along the cranial edge of one contralateral tuber sacrale and directed obliquely and slightly caudally across the midline to the medial aspect of the opposite tuber sacrale. Not directing the needle sufficiently caudally may result in hitting the spinous process of the sixth lumbar vertebra. Longer needles will obviously be required in larger horses. The needle is then directed along the medial surface of the ilium toward the sacrum as deeply as possible. Most 18-gauge needles will “follow” the medial surface of the ilium. This may require bending the needle slightly to accommodate placement for largergauge needles. The needle should stop firmly against bone to ensure proper placement (Fig. 1 and Fig. 2). The area is then infiltrated with 10 to 15 mL of a corticosteroid mixture. The author’s preference is isoflupredone (10 to 20 mg)^e with or without methylprednisolone acetate (100 mg)^f and diluted with physiological saline or a pain-relieving agent^g to a total volume of 30 to 35 mL. This technique may produce successful results, but the margin for error is significant due to lack of visualization. The use of the larger needle may require local anesthetic infiltration and a small stab incision to facilitate the injection. Use of a lighter-gauge needle (smaller than 18 gauge) may result in excessive bending of the needle and an inaccurately placed injection. Experience will provide the operator with more confidence in the “feel” of needle placement.
 

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