Case reveal

Findings:

• The intermediate tubercle is flattened. The lateral (1) and medial (2) intertubercular grooves, as well as the tubercles, are moderately diffusely irregular, most severe medially.
• The lateral (A) and medial (B) lobes of the bicipital tendon are moderately thickened and severely heterogeneous with small hypoechoic regions and loss of normal fiber alignment, most severe medially.

• The bicipital bursa is moderately thickened with extensive synovial proliferations and contains mild effusion. Multifocally within the bursa/regional soft tissues, mild mineralization is identified (yellow circle).

Conclusions:

• The combined severe right bicipital tendinopathy, moderate proliferative bicipital bursitis, right shoulder and osteomyelitis are most compatible with septic bicipital bursitis and tendinitis, likely secondary to prior penetrating trauma.
  

Radiographs (3 weeks prior):

Findings: Within the greater tubercle and intertubercular grooves, moderate moth-eaten osteolysis is identified. Best seen on the skyline projections, the margins of the greater, lesser, and intermediate tubercles, as well as the corresponding intertubercular grooves are mildly to moderately irregularly margimated, with associated mild osseous proliferation, with the greater and intermediate tubercles, as well as the corresponding medial intertubercular groove being more affected. On all projections, there is moderate soft tissue thickening identified along the region of the biceps brachii tendons and corresponding muscle. 

Conclusions: Aggressive lesions of the right humeral tubercles, with associated moderate diffuse soft tissue edema, cellulitis, and/or phlegmon. Consider septic bicipital bursitis, tendinitis and myositis, with associated proximal humeral osteomyelitis.  

More information/follow-up:

• The patient ran through a fence on the inside of a track while training, split a PVC rail resulting in punctures or the chest/shoulder region.
• The reported soft tissue swelling was associated with the presence of an abscess. The abscess and intermediate tubercle were debrided.
• The patient developed compensatory laminitis of the contralateral supporting limb.

A little bit more…

• Bicipital injuries in horses are more commonly secondary to direct trauma +/- associated with a penetrating wound (Hawe et al.)
• Depending on the extent of the wound, trauma to the bicipital bursa and underlying bone is described.

Normal biceps anatomy:

• Biceps brachii (red) originates from the supraglenoid tubercle of the scapula. Proximally, it is mostly tendinous and forms two lobes (medial and lateral) as it courses over the most proximal portion of the humerus. The intertubercular (bicipital) bursa lies between the tendon and humerus at this site (Hawe et al.).
• The proximal humerus has 3 tubercles (greater, intermediate and lesser tubercles from lateral to medial) with associated inter tubercular grooves, which cradle the bilobed portion of the biceps tendon. The mid portion of the biceps tendon run over the intermediate ridge of the humeral (Hawe et al., Reef et al.).
• The remainder of the biceps brachii is mostly muscle (Hawe et al., Reef et al.).
• The biceps brachii tendon extends through the muscle and splits into 2 small branches distally, which… (Hawe et al.)
  1. Joins with the medial collateral ligament of the elbow joint and inserts onto the radial tuberosity
  2. Blends with the fascia of the forearm and the tendon of the extensor carpi radialis

• Radiographs of the shoulder are preferred for a more comprehensive evaluation of the bone. nuclear scintigraphy may be helpful to localize lameness to the shoulder joint. Ultrasonography remains the preferred modality for evaluation of the soft tissues and may be used to direct therapy.
• Radiographic are most beneficial to screen for osteomyelitis, sequestrum formation, fractures and embedded foreign material.

• Most common ultrasonographic abnormalities (Spiesshofer et al.):
  • Synovial thickening (most often severe)
  • Variable degree of bicipital bursa effusion
  • Can sometimes see track between cutaneous wound and bicipital bursa (+/- gas in the bursa)
  • Irregularity of the bone margins = osteomyelitis
  • If bicipital tendon is affected, it may become enlarged, heterogeneously hypoechoic/have a focal hypoechoic core lesion or longitudinal tear
• Bursoscopy of the bicipital bursa may improve prognosis (Spiesshofer et al.).

References:

• Hawe, C., and A. M. McDiarmid. “Tendonitis of the biceps brachii and intertubercular (bicipital) bursitis in a Thoroughbred racehorse.” Equine Veterinary Education 11.2 (1999): 60-62.
• Spiesshofer, Pius, et al. “Septic inflammation of the bicipital bursa: clinical, imaging, and surgical findings in nine horses.” Journal of the American Veterinary Medical Association 261.9 (2023): 1380-1387.
• Reef, Virginia B., Mark Whittier, and Lila Griswold Allam. “Joint ultrasonography.” Clinical techniques in equine Practice 3.3 (2004): 256-267.
• Tnibar, Mohamed A., Joerg A. Auer, and Saoussane Bakkali. “Ultrasonography of the equine shoulder: technique and normal appearance.” Veterinary Radiology & Ultrasound 40.1 (1999): 44-57.
• Riccio, Barbara. “Ultrasonography of the elbow and shoulder.” Atlas of Equine Ultrasonography (2022): 148-172.