Case Study

ORTHO – Arthropathy of the antebrachiocarpal joint, inflammatory vs neoplastic, causing lameness in a 6 year old FS Labrador Retriever dog

Tnis 6 year old FS Labrador Retriever dog presented with right front lameness

Physical exam: tender right shoulder, swelling right carpus

Radiographs: Chronic periosteal reaction distal radius with concurrent severe focal soft tissue swelling. Poss OSA. FNA of area pending. Mild periarticular remodeling of the caudal aspect of the right shoulder, mineralization associated with the greater tubercle. Joint tap pending

Tnis 6 year old FS Labrador Retriever dog presented with right front lameness

Physical exam: tender right shoulder, swelling right carpus

Image Interpretation

Ultrasound of the right shoulder and right carpus – Right shoulder: The volume, echogenicity and echotexure of both the supra- and infraspinatus muscle are within normal limits. The distal insertion tendon of the supraspinatus appears to be normal in volume, small irregular shaped shadowing echogenic foci are noted next to the slightly irregular bone surface of the greater humeral tubercle. There is no impingement on the biceps tendon. The distal insertion tendon of the infraspinatus is even in width, smooth in outline and presents a regular fibre pattern. The attachment to the bone is within normal limits. The biceps tendon is even in width, slightly irregular in outline with a mildly heterogeneous fibre pattern. There is mild tendon sheath effusion and moderate thickening of the synovial lining of the tendon sheath. A semicircular bony exostosis is present within the intertuercular groove. A mild amount of periarticular new bone is seen at the visible parts of the periarticular margins of the shoulder joint. Right carpus: A large amount of periarticular & periosteal irregular new bone is seen emphasizing the antebrachiocarpal joint. Cortical bone defects are not seen. A tendon (likely consistent with a digital extensor tendon) is seen surrounded by a severely and irregularly thickened synovium and associated with loss of its regular layering and echoarchitecture. A mild amount of anechoic synovial effusion is seen as well. The aforementioned tendon itself presents a regular echoarchitecture and echogenicity.

DX

• Mild to moderate chronic biceps tenosynovitis • Mild shoulder joint osteoarthritis • Calcifying tendinopathy of the supraspinatus • Aggressive antebrachiocarpal arthropathy with severe synovial proliferation and new bone formation

Outcome

The biceps tenosynovitis and shoulder joint osteoarthritis may contribute to the clinical presentation but overall the severe arthropathy of the antebrachiocarpal joint is more likely to be the underlying cause of the lameness here.
Differentials include inflammatory – such as immune mediated/rheumatoid erosive and non-erosive arthritis – as well as an emerging neoplasia of the joint – such as synovial cell sarcoma, histiocytic sarcoma or other. However aggressive osteolytic defects are not overtly seen. The findings have to be correlated with the radiographic changes.
The findings are not typical for a primary neoplasia of the bone as the changes seem to be concentrated on the synovium and to bridge the joint.
Septic forms of arthritis are not considered very likely here too as both the amount and quality of synovial effusion are not typical.
In case the synovial aspirates reveal no definitive diagnosis synovial biopsy (and depending on the complementing radiographic changes bone biopsies) should be obtained for further definition.
The supraspinatus tendinopathy is unlikely to be of any clinical impact here.

Comments

Rescan 2 months later: no changes in the right shoulder. Right carpus still shows

Severe chronic non-infectious inflammatory antebrachiocarpal arthropathy with severe synovial proliferation/herniation and new bone formation versus severe chronic tendovaginitis of the abductor pollicis longus tendon with antebrachiocarpal osteoarthritis.
The call between the 2 aforementioned entities needs to be made based on the location of the changes.Consider aspiration of synovia and synovial membrane biopsy in case the patient remains refractory to empirical treatment if not yet done so.