ELBOW DISLOCATION


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related talks:  broken elbowchildren's broken elbowradial head fracture (type of broken elbow); elbow stiffnessbroken forearmbroken armswollen elbow
 

What is an Elbow Dislocation?

The elbow joint is the second most common joint to dislocate (the shoulder is the most common, see talk). 

Our elbow joint is where the 2 forearm bones (the radius and ulna) meet the arm bone (the humerus).  So there are 3 bones that form the elbow.  The interlocking of these bones gives stability to the joint.  The elbow dislocates when the forearm bones separate from the arm bone (at the ulnohumeral joint).

Therefore if you break the bones at the time of dislocation, the elbow becomes unstable.   There are two parts of the ulna that can break, the olecranon and the coronoid, which will cause the elbow to be unstable. If the olecranon breaks, the larger the broken fragment, the more instability.  If the coronoid breaks, its more black and white: if >50% of the coronoid is broken, the elbow is unstable, if <50% then the elbow should be ok.  

There are also ligaments on the inside (medial collateral ligament, "MCL") and outside (lateral collateral ligament, "LCL") of the elbow that also hold the bones together.  The MCL is a very important ligament in preventing the inside part of the joint from opening up.  The LCL prevents the outside of the joint from opening up.  When the elbow dislocates, 90% of the time the forearm goes backward and to the side.  The MCL and LCL are almost always injured.  

How is an Elbow Dislocation diagnosed?

One look at the elbow and most doctors can tell that its dislocated.  It looks bent out of place, and the elbow usually cant move (because the joint isnt working).  

X-rays are obtained to look at the position of the bones and to look for breaks in the bones.  Even though the injury looks pretty bad, its actually fairly uncommon for the bones to break, the coronoid is the most commonly broken in about 5-15% of cases.

Once the elbow is set back in place, repeat x-rays are ordered, to make sure there are no small bone fragments within the joint that will cause discomfort (like a pebble in your shoe).  

How is an Elbow Dislocation treated?

The treatment is to first re-set the bone.  

Once the elbow is back in position, its tested for stability.  The elbow is flexed and extended to see if it is easy to re-dislocate.   As we mentioned before, almost all dislocations damage the elbow ligaments, but this usually doesnt affect stability (only about 1-2% of elbows are unstable after a first time dislocation).  This is much much different than a shoulder dislocation, where injury to the surrounding ligaments puts you at a very high risk for instability.  

The elbow relies on the interlocking bones for stability.  The elbow is most stable when bent at 90 degrees (flexed), and the palm of your hand is facing the ground (pronated).  This position maximizes the interlocking of bones to provide the greast stability.  

If theres a broken ulna or radius bone, doctors are more concerned for instability.

If the elbow appears stable, especially in athletes and young people, the elbow is usually splinted for just a week (or less) for comfort, and then physical therapy is started, first using passive range of motion and quickly building to active motion to prevent stiffness and pain (this should start at least by 2 wks).

Surgery is occasionally required if the elbow is very unstable.  Broken bones (ie the olecranon or coronoid) are often repaired with screws.  If there is no break, but the elbow dislocates whenever its extended past 60%, the ligament damage is probably significant and the LCL +/- the MCL should be repaired.  

The worst form of an elbow dislocation is something called a "Terrible Triad".  This injury is an elbow dislocation + a radial head fracture + coronoid process fracture.  Its considered terrible because the elbow joint is very unstable and theres a high rate of dislocation, even when the arm is held in place with a cast.  Therefore the recommendation is for early surgical repair of the coronoid process, no matter how small it is (remember in normal elbow dislocations we only worry about the coronoid process if >50% is broken).  The radial head is also fixed.  And the ligaments are also fixed.  Yeah, its a pretty big surgery but outcomes are generally good.

What is the long term outcome?  

Most elbow dislocations heal well, and the risk of further dislocation is low (only 1-2% in your simple dislocations).  

The biggest concern is not continued instability but rather stiffness (the opposite of instability).  A lot of the surrounding tissue gets injured when the elbow moves out of place, and therefore there is a high risk that too much scar tissue will form.  Many times your body reacts so strong that calcium deposits in the surrounding tissue (almost 75% of people will get some form of this).  These deposits are called heterotopic ossification, and its like your body is turning muscle into bone.  That is why doctors try to get the elbow moving ASAP.  Even with aggressive physical therapy, its not uncommon for people to lose the ability to full straighten their arm (it will lose the terminal 5-15 degrees of extension after everything is said an done).  That arm will often times feel a little looser than the other, and this may result in a mild (about 15%) loss of strength.

But overall, people heal very well from this injury and have few lasting side effects.  

Reference

1. Cohen MS, Hastings H. Acute elbow dislocation: evaluation and management. JAAOS 1998; 6: 15-23. full article. review

2. Tashjian RZ et al. Complex elbow instability. JAAOS 2006; 14: 278-86. full article. review. 

3. McKee MD et al. The pathoanatomy of lateral ligamentous disruption in complex elbow instability. JSES 12(4): 391-6. full article. 62 elbows undergo surgery after dislocation or fx-dislocation and instability.  all had LCL tear. 41% concominant common extensor torn.

4. Mehta JA, Bain GI. Posterolateral rotatory instability of the elbow. JAAOS 2004; 12: 405-15. full article. review.

5. Tan V et al. Hinged elbow external fixators: indications and uses. JAAOS 2005; 13: 503-14. full article. review.

6. Doornberg JN, Ring DC. Fracture of the anteromedial facet of the coronoid process. JBJS 2006; 88(10); 2216-24. full article. 18 pt. 9/12 had assoc LCL injury. all cases of malalignment were assoc w. abnormal position of this facet.

7. Ring DC, Doornberg JN. Coronoid fracture patterns. J Hand Surg 2006; 31(1): 45-52. full article. predictable patterns: all terrible triad had coronoid fx <50%. anteromedial facet fx ocurred w. posteromedial instability pattern.  basic fx-dislocation had large coronoid fx. 

7. Beingessner DM et al. The effect of suture fixation of type I coronoid fractures on the kinematics and stability of the elbow with and without medial collateral ligament repair. JSES 200716:213-217. full article. coronoid fx <10% has little effect on stability.  coronoid blocks posterior sublux >30 deg flex.

8. Regan WMorrey BFractures of the coronoid process of the ulna. JBJS 198971:1348-1354. full article. classic paper on 50% coronoid creates instability.

9. Pugh DM et al. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. JBJS 2004; 86(6): 1122-30. full article. rx terrible triad.  all surgery: repair bone + LCL, 15 excellent, 13 good, 7 fair, 1 poor result, 8 req reoperation (2 HO, 4 stiffness).

10. Mathew PK et al. Terrible triad injury of the elbow: current concepts. JAAOS 2009; 17: 137-151. full article. review.