Myotendinous junction

Oxytetracycline and doxycycline are used in horses. Oxytetracycline is the drug of choice for Potomac horse fever, caused by Ehrlichia risticii, and equine ehrlichiosis, caused by Ehrlichia equi. It is also used to treat contracted flexor tendons in foals, where the effects may be caused by calcium chelation at the myotendinous junction resulting in the relaxation of the flexor tendons. Some clinicians use parenteral oxytetracycline or p.o. doxycycline to treat horses with EPM. 

TidbaU, J. G. 1991. Myotendinous junction injury in relation to jimction structure and molecular composition. Exerc. Sport Sci. Rev. 19 419-445. 

Because of its peculiar position between the acromioclavicular arch and the humeral head, only the distal part of the supraspinatus tendon can be examined while keeping the patient s arm in neutral position (Fig. 6.29a). To obtain a more complete visualization of this tendon, the patient is asked to extend the arm posteriorly, placing the palmar side of the hand on the superior aspect of the iliac wing with the elbow flexed, directed posteriorly and toward the midline, so that the acromion is moved away from it (Fig. 6.29b). With this maneuver (commonly known as the modified Crass or Middleton position), the tendon is depicted in its full extent, even including visualization ofits myotendinous junction (Crass et al. 1988b Middleton et al. 1992). When the patient assumes this position, the supraspinatus rotates and becomes a more anterior structure (Fig. 6.29b). Some... 

Fig. 6.28a,b. Short head of the biceps tendon, coracobrachialis and pectoralis minor. a,b Transverse 12-5 MHz US images obtained a at the level of the coracoid process of the scapula and b approximately 2 cm caudal to it. In a, the relationship of the coracoid (Co) with the humeral head (HH), the subscapularis tendon (SubS) and the deltoid muscle are illustrated. The coracoid is easily identified with US owing to its medial position relative to the humeral head and the curvilinear hyperechoic appearance of its bony surface. In b, three individual structures are seen arising from the coracoid. From lateral to medial, they are the hyperechoic tendon of the short head of the biceps (curved arrow), the hypoechoic myotendinous junction of the coracobrachialis (straight arrow) and that of the pectoralis minor (arrowheads)... 

Fig. 6.103a,b. Calcifying tendinitis of the pectoralis major tendon, a Anteroposterior radiograph shows a juxtacortical calcification (arrow) adjacent to the anterior proximal humeral shaft cortex, b Corresponding transverse 12-5 MHz US image over the myotendinous junction of the long head of the biceps (B) demonstrates a well-defined type I deposit (arrow) within the distal pectoralis major tendon (arrowheads). Hs, humeral shaft... 

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