Page 552 - Adams and Stashak's Lameness in Horses, 7th Edition

518 Chapter 4

distal aspect of P1 but do occur rarely in the proximal
aspect of P2 (Figure 4.94). SCLs due to OA occur with
VetBooks.ir Malformation of the condyles of the distal aspect of P1
equal frequency in distal P1 and proximal P2.
without fragmentation has also been recognized by the
author and may represent another form of OC that
leads to early OA within the PIP joint.

Etiology
The cause of OC within the PIP joint is assumed to be
due to similar factors that cause the condition in other
locations within the horse. However, traumatic frag-
mentation and articular cartilage or subchondral bone
damage leading to SCLs can also occur within the PIP
joint, and it may be difficult to differentiate between
developmental and traumatic causes. Developmental
lesions tend to occur in younger horses, whereas trauma
can occur in any age horse. In addition, more severe
clinical signs related to the PIP joint may be identified
associated with trauma vs. OC.

Clinical Signs
As stated above, developmental lesions tend to occur
in young horses and may cause variable signs of lame-
ness, even within the same horse on a different day.
Physical examination findings are similar to other prob-
lems within the PIP joint and include no abnormalities,
enlargement of the pastern, pain with flexion and
manipulation of the pastern region, and positive
response to flexion tests. Horses with SCLs of the distal Figure 4.94. Dorsoplantar radiograph of a young horse
aspect of P1 tend to be more lame than those with osteo- demonstrating an SCL of the proximal aspect of P2 (arrow). This
chondral fragmentation. SCLs are also more common in abnormality was not considered to be the cause of the lameness in
this horse.
the hindlimb than in the forelimb. Due to the variable
71
lameness that may be associated with OC in the PIP
joint, it is important to identify the true source of lame- developing within the joint. SCLs of distal P1
ness using diagnostic anesthesia in many cases. (Figure 4.95) are often clinically significant and can be
managed conservatively or surgically, depending on the
severity of lameness. Surgical management includes
Diagnosis trans‐cyst screw application, transcortical cyst debride-
The diagnosis is confirmed with radiographs of the ment, corticosteroid injection, or pastern arthrodesis
pastern region. Osteochondral fragmentation can usu- (Figure 4.96). Conservative management with NSAIDs
ally be seen on both lateral and dorsopalmar/plantar and IA medication usually resolves the lameness tempo-
views (Figure 4.93), whereas SCLs are often only visible rarily, but recurrence is common. Therefore, most horses
on the dorsopalmar/plantar radiographic projection with SCLs and PIP joint OA are best treated surgically.
(Figure 4.94) or only with cross‐sectional imaging such
as CT or MRI (Figure 4.95). Some lesions, particularly Prognosis
osteochondral fragmentations, may be incidental find-
ings on radiographs. Most SCLs that involve the distal The prognosis following removal of OC fragmenta-
condyle of P1 are clinically significant and often lead to tion is usually very good, and many horses can perform
lameness and OA. Radiography of the opposite PIP joint athletically. The prognosis for SCLs of distal P1 after
should be performed because OC lesions can be bilat- trans‐cyst screw placement or transcortical debridement
eral, similar to other locations. has not yet been reported in the literature, but if it is
similar to SCLs in other locations, it will be good. SCLs
of distal P1 typically do well following arthrodesis, and
Treatment these horses can be used as athletes.
The treatment of choice for osteochondral fragments
within the PIP joint that cause clinical problems is LUXATION/SUBLUXATION OF THE PROXIMAL
arthroscopic removal. Both the dorsal and palmar/plan- INTERPHALANGEAL (PIP) JOINT
tar pouches of the PIP joint are accessible with the
arthroscope, but the surgery can be difficult. 44,52 An Luxation of the PIP joint is uncommon and can occur
arthrotomy can be performed but is associated with in the medial/lateral or palmar/plantar direction. Medial/
more soft tissue damage and increased likelihood of OA lateral luxation is usually seen after severe injury to one