Page 214 - Adams and Stashak's Lameness in Horses, 7th Edition

180 Chapter 2

point of the olecranon. A 3.5‐inch (8.9‐cm), 18‐ to 20‐
gauge spinal needle is directed distomedially through
VetBooks.ir of the limb into the olecranon fossa (Figure 2.182).
the triceps musculature at a 45° angle to the long axis
Alternatively, the spinal needle may be directed down­
ward along the lateral shaft of the olecranon process to Infraspinatus tendon
enter the joint. The injection site is 3 cm distal and 2 cm
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cranial to the point of the olecranon, and the needle is Glenoid
directed distally and cranially to enter the caudal joint
pouch just proximal to the anconeal process.
Lateral
tuberosity
Scapulohumeral (Shoulder) Joint of humerus
Arthrocentesis of the shoulder can be difficult due to Bicipital Deltoid tuberosity
the depth of the joint. It is a large joint, and 20–40 mL of bursa
anesthetic is usually used for diagnostic purposes. It is Biceps
always performed with the horse standing, and many brachii
clinicians now utilize ultrasound to guide the injection. muscle
Ultrasound‐guided injections of the scapulohumeral
joint and bicipital and infraspinatus bursae have been Figure 2.183. Lateral view of the shoulder demonstrating the
reported to be highly reliable and more accurate than injection sites for the craniolateral (cranial to the infraspinatus
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conventional blind techniques. The shoulder joint may tendon) and lateral (caudal to the infraspinatus tendon) approaches.
communicate with the bicipital bursa in a small percent­ Ultrasound guidance of the needles can be advantageous with
age of horses, and temporary anesthesia of the supras­ these approaches.
capular nerve and paralysis of the infraspinatus and
supraspinatus muscles may occur with periarticular Bicipital Bursa
injection of anesthetic. 48,75
The bicipital bursa lies cranial to the shoulder and
humerus under the biceps brachii muscle. It is a rela­
Craniolateral Approach tively large synovial structure (20–30 mL of anesthetic)
The site for the craniolateral approach to the shoulder but can be difficult to enter because of its depth and the
joint is located in the notch formed between the cranial landmarks for injection are not easily palpable. In a
and caudal prominences of the lateral tuberosity of the recent study that compared two different injection tech­
humerus. The caudal prominence (point of the shoulder) niques (distal and proximal) to enter the bicipital bursa,
is easiest to palpate, and by exerting deep finger pressure, the accuracy of injecting the bursa was only 28% and
the depression for needle insertion can be palpated 39%, respectively. The authors concluded that clini­
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3.5–4 cm cranial to the caudal prominence. This notch is cians without previous experience of injecting the bicipi­
not as readily palpable in heavily muscled horses. A 3.5‐ tal bursa were unlikely to be successful with either
inch (8.8‐cm), 18‐ to 20‐gauge spinal needle is inserted approach. This study confirmed the difficulty of inject­
into this notch and directed parallel to the ground in a ing the bicipital bursa and is why ultrasound guidance is
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caudomedial direction toward the opposite elbow. 48,75 recommended to improve the accuracy of injections.
The depth of penetration depends on the size of the Alternatively, radiographic examination after injecting
horse, but the joint capsule is usually entered at a depth radiopaque contrast medium may be used to assess the
of 2–3 inches (5–7 cm). Synovial fluid can usually be success of centesis if synovial fluid is not obtained. The
aspirated and is the only definitive method to document proximal and distal approaches to the bursa are usually
correct needle placement. Alternatively, the spinal needle performed with the limb weight‐bearing, but the proxi­
may be inserted slightly more proximal on the limb in a mal approach may be done with the limb held.
distinct depression located 1–1.5 cm cranial to the
infraspinatus tendon and slightly proximal and cranial to Distal Approach
the point of the shoulder. The needle is placed parallel to
the ground or slightly downward and directed caudome­ The cranial prominence of the lateral tuberosity of
dially at a 45° angle until bone is contacted (Figure 2.183). the humerus is used as the landmark, as was done for
the shoulder joint. The site of injection is 2.5 inches
(5–6 cm) distal and 3 inches (7–8 cm) caudal to
Lateral Approach
this prominence. A 3.5‐inch (8.9‐cm), 18‐ to 20‐gauge
The landmarks for the lateral approach to the shoul­ spinal needle is directed proximomedially toward the
der are the lateral humeral tuberosity and the infraspi­ intertubercular groove until it contacts the humerus
natus tendon. A 3.5‐inch (8.9‐cm), 18‐ to 20‐gauge (Figure 2.184). The depth of the needle depends on the
spinal needle is inserted 1–2 cm caudal and distal to the size of the horse, but a 3.5‐inch (8.9‐cm) spinal needle is
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infraspinatus tendon in line with the lateral humeral usually inserted to the hub in most mature horses.
tuberosity (Figure 2.183). 3,75 The needle is directed Alternatively, the deltoid tuberosity of the humerus can
slightly caudally and upward toward the lateral aspect be palpated and used as a landmark. A 3.5‐inch (8.9‐cm),
of the humeral head. In general, this approach is more 18‐ to 20‐gauge spinal needle is inserted 1.5 inches
difficult than the craniolateral approach. (3–4 cm) proximal to the distal aspect of the deltoid