Page 671 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 637

support of the tendinous insertions of the deltoid, bra- remind the clinician to consider neoplasia as a differen-
chiocephalicus, supraspinatus, and occasionally the tial diagnosis as a cause of lameness.
VetBooks.ir 2–3 4.5‐ or 5.5‐mm cortical or 6.5‐mm cancellous described in an adult Quarter horse mare. Chronic sig-
Primary osteosarcoma has been diagnosed and
infraspinatus muscles. Generally all that is needed are
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44
nificant and progressive lameness was noted; discomfort
screws placed in lag fashion that engage the transcor-
tex. This has been performed with success as a stand- was isolated by palpation to the scapulohumeral joint.
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ing procedure. In heavy horses a narrow DCP may be Arthrocentesis was normal and diagnostic analgesia was
54
used to provide a tension band effect. 66 uneventful. Radiographs revealed an aggressive bone
Fractures of the condyles or epicondyles of the distal lesion in the proximal humerus. Euthanasia was elected
humerus occur infrequently in horses, but small articu- due to the poor prognosis and lack of improvement
lar fragments involving the condyles should be removed despite therapy. Histological examination provided a
arthroscopically. 62,64 If the fragment is nonarticular, definitive diagnosis. Osteosarcoma is rarely reported in
conservative therapy is considered. More extensive the horse and when so more frequently in the head. 49
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fractures of the condyles or epicondylar region may A primary hemangiosarcoma was diagnosed in an
require internal fixation with lag screws. 11‐year‐old Clydesdale gelding. Local palpation of the
16
proximal humerus revealed discomfort and diagnostic
analgesia was unhelpful. In this case nuclear scintigra-
Prognosis phy was performed, resulting in significant uptake of
The prognosis for stress fractures, nondisplaced com- isotope in the proximal humerus. Radiographs revealed
plete or incomplete fractures, or minimally displaced a radiolucent area with areas of sclerosis and some
complete nonarticular fractures managed conservatively irregular new bone formation. Bone biopsies were per-
appears very good. 14,80,96 formed but considered non‐diagnostic. A definitive diag-
The prognosis for complete displaced nonarticular nosis was made after histopathological examination of
fractures is guarded but appears better for horses man- the tissue subsequent to euthanasia. Hemangiosarcoma
41
aged conservatively. In one study in which conservative has been reported in the horse; however, in this report
management was used in 17 horses, 9 (53.9%) were con- only one of 11 cases was reported to be involving bone
sidered successful, 4 horses became athletically sound, in a limb.
and 5 horses became pasture sound; younger horses may Metastatic lesions in the bone from intestinal adeno-
do better. In this same study, 13 horses were treated carcinomas are unusual and reported in a horse with
14
surgically with a variety of internal fixation methods; lameness associated with sequestrum formation and a
38
3 of 13 horses survived and became athletically sound. pathologic fracture. A tentative diagnosis of osteomy-
The successful outcomes were all surgically treated with elitis had been provided, but postmortem histopa-
stacked pinning and all were young foals. In another thology provided a definitive diagnosis of metastatic
study, conservative management was used in 10 horses, 7 adenocarcinoma with primary lesions in the colon.
of which were able to be ridden 5–12 months after the
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diagnosis was made. The horses’ ages in the successful
group ranged from 2 to 60 months. Of the 3 horses PARALYSIS OF THE RADIAL NERVE
treated surgically, 1 became pasture sound 10 months
after surgery. The conclusion was that the best candi- Paralysis of the radial nerve as a primary cause of
dates for nonsurgical treatment are nonarticular humeral lameness is an uncommon condition that results in the
fractures with minimal displacement that involve the inability to extend the elbow, carpus, and digit. Similar
midshaft and are spiral and oblique with minimal over- dysfunction may also be observed with other conditions
riding of the ends of the bone. involving the upper forelimb; therefore, differentiation
For fractures involving the greater tubercle and del- can be difficult, particularly shortly after injury occurs.
toid tuberosity, the prognosis appears good for conserv- The radial nerve, often the largest branch of the bra-
ative management of nondisplaced and surgically treated chial plexus, derives its origin chiefly from the eighth cer-
displaced greater tubercle and deltoid tuberosity frac- vical and first thoracic nerve roots of the plexus. In 10%
tures. 14,22,60 A recent report of 19 cases of treated con- of horses the seventh cervical nerve root contributes to
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servatively resulted in 13 horses returning to athletic the radial nerve. The radial nerve innervates the exten-
function with no lameness. In one report, 9 out of 10 sor muscles of the elbow, carpus, and digit and supplies
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horses with greater tubercle fractures treated surgically the lateral flexor of the carpus (ulnaris lateralis). Paralysis
returned to athletic use. Of these, 7 had the fragment of the radial nerve inactivates these muscles.
removed and 2 had internal fixation. There are few
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reports of epicondylar fractures, but in one case of a Etiology
fracture of the epicondyle and supracondylar crest, the
horse returned to athletic use after the fracture frag- In most cases, paralysis of the radial nerve is due to
ments were removed. 62 trauma of the shoulder region caused by hyperextension
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of the forelimb or extreme abduction of the shoulder.
Fractures of the humerus, the seventh cervical, and first
NEOPLASTIC LESIONS OF THE HUMERUS thoracic vertebrae can all result in radial nerve paraly-
sis. Tumors, abscesses, and enlarged axillary lymph
50
There have been several reports in the recent litera- nodes that occur in the cranial thoracic region along the
ture of both primary and metastatic bone tumors in the course of the nerve and tumors of the brachial plexus
proximal humerus of the horse. 16,38,44 These lesions and radial nerve themselves may also result in radial