This can lead to the instauration of automaticity in ischemic tissue. Re-entry
The role of re-entry or circus motion was demonstrated separately by G. R. Mines and W. E. Garrey. Mines created a ring of excitable tissue by cutting the atria out of the ray fish. Garrey cut out a similar ring from the turtle ventricle. They were both able to show that, if a ring of excitable tissue was stimulated at a single point, the subsequent waves of depolarisation would pass around the ring. The waves eventually meet and cancel each other out, but, if an area of transient block occurred with a refractory period that blocked one wavefront and subsequently allowed the other to proceed retrogradely over the other path, then a self-sustaining circus movement phenomenon would result. For this to happen, however, it is necessary that there be some form of non-uniformity. In practice, this may be an area of ischemic or infarcted myocardium, or underlying scar tissue.It is possible to think of the advancing wave of depolarisation as a dipole with a head and a tail. The length of the refractory period and the time taken for the dipole to travel a certain distance—the propagation velocity—will determine whether such a circumstance will arise for re-entry to occur. Factors that promote re-entry would include a slow-propagation velocity, a short refractory period with a sufficient size of ring of conduction tissue.
Elbow fractures are any broken bone around the elbow joint.They include among others:
Olecranon fractures
Supracondylar humerus fractures
Radial head fracturesThe terrible triad of the elbow (not to be confused with the terrible triad of the knee) is a combination of:
A fracture of the head of radius
A fracture of the coronoid process of the ulna
Humeroulnar dislocation (generally posterior or posterolateral)The terrible triad of the elbow is confers joint instability and a major risk of developing osteoarthritis. == References ==