Case Study

ORTHO – Fibrosing myopathy of the infraspinatus muscle with insertional tendinopathy and bursitis of the infraspinatus tendon in a 10 year old MN English setter

This 10 year old MN English Setter dog has a 6 month history of left front lameness

DX

• Bilateral fibrosing myopathy of the infraspinatus muscle • Bilateral insertional tendinopathy and bursitis of the infraspinatus tendon (likely secondary to the myopathy) • Leftsided deltoid muscle atrophy (likely due to disuse) • Bilateral mild biceps tenosynovitis (grade 1)

Sonographic Differential Diagnosis

Ultrasound of the left and right shoulder –

Left shoulder:
The infrapinatus muscle presents uniform increase in echogenicity with marked loss of volume and uniform loss of the regular echotexture. Moderate enthesiophyte formations are noted at the distal insertion tendon as well as moderate enlargement of the bursa and minor loss of the tendon fibre pattern.
The overlying deltoid muscle belly reveals a marked loss of volume.
Mild generalized thickening of the synovial lining as well as mild anechoic effusion are noted surrounding the biceps tendon. The tendon fibre pattern is within normal limits.
Both the supraspinatus insertion tendon and biceps origin reveal only minor modeling.
A mild amount of anechoic effusion is noted for the shoulder joint.

Right shoulder:
The infrapinatus muscle presents non-uniform increase in echogenicity with mild increase volume and marked loss of the regular echotexture. Mild enthesiophyte formations are noted at the distal insertion tendon as well as mild enlargement of the bursa.
The overlying deltoid muscle belly is within normal limits except for thickening of the muscle fascia.
Mild generalized thickening of the synovial lining as well as mild anechoic effusion are noted surrounding the biceps tendon. The tendon fibre pattern is within normal limits.

Outcome

Overall the findings are more advanced in degree and stage on the left side. The changes are consistent with chronic and nearly complete fibrotic replacement and contracture on the left side whereas the changes on the right side are represent an earlier subacute stage of replacement with paralleling presence of hematoma/granulation and scar tissue.

The prognosis for regain of function is poor on the left side. Surgical therapy is indicated.
Maintainance of function may be strived for the right side by means of conservative management with physical therapy (rest, passive stretching, deep heat ultrasound or laser treatment, injection of PRP) and systemic anti-inflammatory treatment. Application of methocarbamole may be considered as well. However, the prognosis remains guarded.