Nuclear scintigraphy:
- A focal area of increased radiopharmaceutical uptake is identified within the mid aspect of the glenoid cavity extending to the infraglenoid tubercle and proximally to the caudal border of the scapular neck (yellow circle).
- A mild increase in radiopharmaceutical uptake is seen along the palmar aspect of the proximal interphalangeal joints bilaterally.
- Increased radiopharmaceutical uptake is noted in the regions of the physes and active bony remodeling compatible with the young age of the horse.
Left shoulder radiographs:
- Associated with the caudal aspect of the mid glenoid cavity, within the subcentral bone at the level of the articular margin, there is a medium-sized, well-defined, smoothly marginate lucency (green outline) with surrounding sclerosis.
- In the region of the infraglenoid tubercle and caudal scapular neck, irregular and well defined osseous proliferation is seen. No other abnormalities are detected.
Conclusions:
- Subchondral cyst, left glenoid cavity.
- Enthesopathy in the origin of the teres minor or long head of the triceps, left scapula.
Case outcome:
- In this case, the lesions was traumatic as the horse ran into fence post several month ago and has been extremely lame (4-5/5) since then. This is similar to a case report by Corraretti et al.
- The horse was euthanized and necropsy revealed:
- Arthritis, synovitis, periarthritis and cellulitis, suppurative, marked, chronic, with multifocal cartilagenous defects on the humeral head and glenoid cavity, left scapulohumeral joint.
- Subchondral bone loss with marked osteosclerosis, chronic/ active, focal, severe, glenoid cavity of left scapula.
- Hemorrhage, multifocal, moderate to extensive, subcutaneous tissue and deep muscles around left
scapulohumeral joint.
A little bit more…
- Osseous cyst-like lesions can be articular or extra-articular. Those that result in lameness tend to be articular (Kay et al.).
- More commonly reported in young horses <3 yrs of age (Kay et al., Corraretti et al.).
- Multiple etiologies have be proposed. The following two are the most accepted causes (Kay et al., Corraretti et al.):
- Disruption of endochondral ossification in the metaphysis or epiphysis results in altered calcification and
retention of cartilage matrix. - Articular trauma results in microfracture of subchondral bone within
the epiphysis and subsequent bone resorption. Synovial fluid enters the defect, and the repeated forces during movement causes fluid to be pushed into the lesions.
- Disruption of endochondral ossification in the metaphysis or epiphysis results in altered calcification and
- Most frequently occurs at the medial femoral condyle in the stifle joint (Kay et al.). The glenoid cavity is a less commonly affected area.
- Little synovial effusion is usually palpable due to the degree of muscular and tendinous coverage over the joint (Kay et al.).
- Positive and double contrast arthrography may be considered to assess for communication of the cyst with the articular surface (Kay et al.).
- Arthroscopy is ultimately the gold standard to assess for join communication, and for curettage (Kay et al.).
- Glenoid subchondral cysts have a poorer prognosis compared with other locations, regardless of lesion size and type of therapy (Kay et al.).
- Return to athletic soundness after arthroscopic debridement of OCD lesions of the shoulder is
approximately 50%. Given that subchondral cystic lesions are often accompanied by OCD lesions of the humeral head, the prognosis for these horses is much worse (Kay et al.). - Placement of a translesional cortical bone screw has been described with success in a horse that regained full athletic function (Corraretti et al.).
References:
- Kay AT. An acute subchondral cystic lesion of the equine shoulder causing lameness. Equine Veterinary Education. 2006 Dec;18(6):316-9.
- Corraretti G, Meulyzer M, Simon O. Treatment of a subchondral cystic‐like lesion in the distal scapula with a translesional bone screw in a horse. Equine Veterinary Education. 2021 Jul;33(7):e205-9.
