Page 206 - Adams and Stashak's Lameness in Horses, 7th Edition

172 Chapter 2

perform this block (Figure 2.164). Alternatively, the fore­ was confirmed with radiography, while ultrasound
14
50
limb can be suspended with the metacarpus placed within was used in the other study. The primary advantage of
VetBooks.ir Radiographic or fluoroscopic documentation of the nee­ DDFT, which may decrease the morbidity associated
these techniques is that the needle does not penetrate the
a padded hoof stand to help facilitate the injection.
with the injection. The disadvantages include possible
dle’s location is recommended in most cases because it is
easy to pass the needle over to the proximal border of the entry into the tendon sheath and DIP joint and the dif­
navicular bone into the DIP joint. 28,48 Including radio­ ficulty of placing the needle at the correct angulation. As
graphic contrast medium into the injection solution and with all navicular bursal injections, confirmation of cor­
taking a radiograph immediately after the injection can rect needle placement is recommended with some type
also be used to document a successful injection. The dis­ of imaging either before or after the injection.
advantage of this technique is that the needle passes A positive response to administration of local anes­
through the DDFT to gain access to the bursa and is dif­ thesia into the navicular bursa may indicate problems of
ficult to perform in the standing horse. the navicular bursa, navicular bone and/or its support­
The navicular bursa can also be entered from the lat­ ing ligaments, sole and/or toe, or distal aspect of the
eral or medial sides (abaxial or lateral position) just DDFT. 17,48,63,66 Even though diffusion of local anesthetic
proximal to the collateral cartilage of the distal phalanx. into the navicular bursa occurs following DIP joint
Two lateral techniques that do not penetrate the DDFT injection, 6–8,39,52 the converse does not occur, and analge­
have recently been described. 14,50 One technique was sia of the navicular bursa does not result in analgesia of
performed in the standing horse using radiographic the DIP joint. Pain from the DIP joint can likely be
66
guidance, and the other used ultrasound to help guide excluded as a cause of lameness if analgesia of the navic­
the needle into the bursa with the foot placed in a navic­ ular bursa improves the lameness within 10 minutes.
66
ular block. Needle entry was along the proximal and In addition, a positive response to intra‐articular analge­
dorsoproximal margin of the collateral cartilage, and an sia of the DIP joint together with a negative response to
18‐ to 20‐gauge, 3.5‐inch (8.9‐cm) needle was angled navicular bursa analgesia incriminates pain within the
approximately 45° to the horizontal plane toward the DIP joint as the cause of lameness. 18,66
10 o’clock (right front) or 2 o’clock (left front) position
(Figure 2.165). The needle was directed beneath the
14
DDFT and digital tendon sheath to enter the bursa. Proximal Interphalangeal (PIP) Joint
This technique can also be performed with the limb There are primarily two approaches (dorsolateral
unweighted (Video 2.19). In one study needle placement and palmar/plantar) for arthrocentesis of the PIP joint.
A dorsal approach has been described but is more diffi­
53
cult to perform and is not recommended by the author.
The dorsolateral approach is usually performed with the
horse standing but can be done with the limb extended
and the sole supported on the knee. The condylar emi­
nences of the distolateral aspect of P1 are identified, and
a 1.5‐inch (3.8‐cm), 20‐gauge needle is inserted parallel
to the ground surface 0.5 inches (1.2 cm) distal to the
palpable eminence. 48,75 The needle is directed beneath
the edge of the extensor tendon to enter the joint at a
depth of 0.5 inches (Figure 2.166; Video 2.20).
The palmaro/plantaroproximal approach is best per­
formed with the distal limb in a flexed position. A 1.5‐inch
(3.8cm), 20‐gauge needle is inserted perpendicular to the
limb into the palpable V‐depression formed by the palmar
aspect of P1 dorsally, the distal eminence of P1 distally, and
the lateral branch of the SDFT as it inserts on the eminence
45
of P2 palmarodistally (Figure 2.167; Video 2.21). This
corresponds to the transverse bony prominence on the
proximopalmar/plantar border of P2 that is usually easily
Deep digital palpable. The author prefers to angle the needle slightly
flexor tendon
dorsally to contact P1, and then direct the needle along the
palmar/plantar aspect of the bone. This ensures that the
needle is just behind P1 where it will enter the PIP joint
capsule at a depth of approximately 1 inch (2.5 cm). The
main disadvantage of this approach is the inadvertent
injection of the digital flexor tendon sheath (DFTS). 53
Navicular bone
Metacarpophalangeal/Metatarsophalangeal
(Fetlock) Joints
Figure 2.165. Lateral approach to the navicular bursa that
avoids penetrating the DDFT. The spinal needle is inserted just Three palmar/plantar approaches and one dorsal
above the collateral cartilage and angled at approximately 45° to the approach can be used for arthrocentesis of the fetlock
horizontal plane to enter the bursa. joint. The proximal palmar/plantar approach can be