Page 681 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 647

cause may increase the likelihood of the development of cysts, and alteration in the humeral head contour. In
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secondary OA. 72,93 another report a flattening of the glenoid without changes
VetBooks.ir Etiology ponies. Other radiographic changes associated with OA
in the contour of the humeral head was seen in Shetland
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include osteophyte and enthesophyte formation
OA of the SH joint can have multiple causes. In younger (Figures 5.54 and 5.55). Contrast arthrography may
horses a developmental role due to OC may be the cause, improve the chances of identifying a SH joint lesion. 41,72
whereas in older horses trauma may be causative. A radi- The normal ultrasonographic anatomy of the shoul-
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ographic study comparing Shetland ponies diagnosed der region has been described. Although the detection
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with OA, skeletally mature Shetland ponies without a his- of humeral head OC has been reported, its major value
tory of lameness, and skeletally mature horses found that appears to be in identifying injury to the soft tissue sup-
ponies had a flattening (dysplasia) of the glenoid contour, port structures surrounding the SH joint. 38,78,100
which was thought to make them more susceptible to the Evaluation of the glenoid cavity with ultrasound also
development of OA. A recent study showed that 6 of 20 appears limited. Ultrasonography has been used to
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ponies had radiographic evidence of dysplasia with diag- diagnose the condition in Shetland ponies when radio-
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nosed shoulder OA. Other case reports of SH joint OA graphs were non‐diagnostic and only revealed dysplasia
have indicated that the glenoid cavity is relatively dysplas- or flattening of the glenoid cavity. Joint distension and
tic in Shetland ponies. Other causes of OA include intra‐ capsulitis provide the diagnosis. 53
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articular fracture and injury to the joint capsule resulting Nuclear medicine may be useful to diagnose a subtle
in synovitis and capsulitis. shoulder lameness with focal intense uptake of the radi-
oisotope, most commonly in the humeral head. 31,32
Clinical Signs
Treatment
A history of trauma is relatively common. In one report,
8 of 15 horses that had subtle OC lesions in the SHJ had a Conservative treatment may be indicated in horses
history of a traumatic insult. Where mild swelling may be that have no radiographic lesions and that respond
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apparent over the shoulder region in the acute case, muscle favorably to intrasynovial anesthesia. Treatment involves
atrophy is variable and may not reflect chronicity or sever- rest, controlled exercise, anti‐inflammatory drugs, and
ity of the lameness. 38,41 Disuse atrophy of the extensor relevant intra‐articular therapy including corticosteroids,
carpi radialis muscle may be apparent in the affected limb HA, and IRAP. Rest periods may be as short as a few
in some cases, and an upright narrow foot may also be weeks to 3 months.
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observed in the affected limb. In contrast, in another Horses that do not respond to the conservative treat-
study, only a small proportion (fewer than 5%) of the cases ment or have radiographic or scintigraphic changes and
with shoulder problems had a smaller foot on the affected
limb, although a severely lame horse may have abnormal
toe wear. 38,41 Deep thumb pressure applied just cranial to
the tendon of the infraspinatus muscle may elicit a painful
response in young and light muscled mature horses. Upper
limb manipulation (flexion, extension, adduction, and
abduction) may also result in a painful response. 41
The signs of lameness are typical of shoulder lame-
ness, and the degree depends on the severity of the prob-
lem. At a trot, the height of the foot flight and the flexion
of the carpus are decreased during the swing phase of
the stride compared to the contralateral limb. The cra-
nial phase of the stride of the lame limb is often short-
ened, and as the lame limb is advanced, a prominent
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lifting of the head and neck occurs on the affected side.
Additionally, the horse appears to “fix” the SH joint on
the affected side. The lameness grade in one study ranged
from subtle and intermittent to 4 on a scale of 5. 32

Diagnosis
Diagnostic anesthesia can assist in localizing the prob-
lem to the shoulder region. 32,38,41,85 Radiography, ultra-
sound, nuclear medicine, and/or arthroscopy may be
required to make a definitive diagnosis of the problem. 32,38,78
Radiography, although important in evaluating abnor-
malities of the shoulder joint, often underestimates the
full extent of the changes involving the glenoid cavity and
the humeral head. 38,40 Radiographic changes identified
in one report in horses with subtle lesions in the SH joint Figure 5.54. Severe OA of the scapulohumeral joint. Source:
included glenoid sclerosis, focal glenoid lysis, glenoid Reprinted with permission from Redding and Pease. .
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