BROKEN FOREARM

(ULNA or MONTEGGIA FRACTURE)


our website is for educational purposes only.  the information provided is not a substitution for seeing a medical doctor.  for the treatment of a medical condition, see your doctor.  we update the site frequently but medicine also changes frequently.  thus the information on this site may not be current or accurate. 

related talks: radius fracture (another type of broken forearm); children's broken forearm (both bone forearm fracture); radial head fracture (type of broken elbow); broken wrist; broken elbowbroken armswollen elbow
 

What is a Forearm Fracture of the Ulna?

Your forearm has two bones, like the buffalo wings you eat watching football.  The ulna is one of your forearm bones (the other is the radius).  When you feel the pointy bone that makes up your elbow, you are feeling the ulna.  The ulna joins up with the arm bone (humerus) to make the elbow joint (the other forearm bone contributes very little to the elbow joint).  As you move toward the wrist, the ulna gets thinner and smaller as the radius becomes bigger, so that at your wrist, the radius makes up the larger portion of the wrist joint.   The two forearm bones work together closely, so its typical for both to be injured during an accident (and important to look for injury to the other bone, even when just one appears injured)

There is a common fracture called a "Nightstick" injury which occurs when we use our forearm to protect our face (like with an assault at night with a big stick, or a car accident).  In this injury only the middle portion ulna will be broken (the radius can be ok).

In kids, its common for both the ulna and the radius to break at the same time in the middle of the forearm.  This is because these two bones are so closely related that they react to a high speed injury the same way. Adults also experience both bone forearm fractures (not as commonly as kids) but its seen in high energy car accidents and other blunt trauma.

As you move closer to the elbow, the ulna gets thicker, and so a larger force is required to break it. If the Ulna breaks near the elbow, usually a high energy force will travel through both bones, so the ulna bone breaks (the first 1/3 of the bone) and the radius bone often dislocated at the elbow (called a radial head dislocation).  This injury pattern is so common that it got its own name: A Monteggia fracture. A Monteggia fracture is most common in kids, but can also be seen in adults.  

 

How is a Forearm Fracture of the Ulna diagnosed?

The diagnosis of an ulna fracture, or a Monteggia fracture, is made by first listening to the history of a person's injury and their symptoms.  People report elbow and forearm pain, with swelling and a possible bent forearm (it just doesnt look straight).  Doctors will get X-rays of the elbow and forearm to definitively diagnose the injury. Diagnosis can be difficult because the injury may be very subtle. In kids, their bone is very resilient, like the green twig of a young tree, and the bone doesn’t always break, but sometimes gets bends instead.  A doctor can miss this because they are looking for cracks in the bone and a small bend is not always noticed.

In a Monteggia fracture, the ulna break is usually easy to identify but the radial head dislocation can be easily overlooked.  There are varying degrees of dislocation of the radial head, and sometimes it is out of position, but just barely, this is called a “subluxation” in medical terms. A subluxation means that the alignment of a joint is not normal, but there is still some contact between the bones, they are not completely separated as seen with a dislocation.  When a Monteggia fracture identified, it is then classified based on what direction the radial head has moved based on the x-rays.  A Type I, which is most common in kids, the radial head has moved upwards. A type II, which is most common in adults, the radial head has moved downwards. A type III the radial head moves to the side and the ulna is broken very close to the elbow joint. A type IV, the radius and ulna bones are both broken, plus the radial head is dislocated.  This is the most severe type of injury.

How is a Forearm Fracture of the Ulna treated?

Treatment depends on the age of the patient, and the severity of the injury.

In kids, most of the broken forearms, even the Monteggia type fractures, can be treated successfully without surgery because kids bones are still growing so they heal very well.  The injury is fixed by re-aligning the bones (in a Monteggia that means straightening out the ulna, and putting the dislocated radius back into place) while the child is sedated (put to sleep with medicine).  A splint or cast is then used to hold the break in normal alignment while the bone heals over the next few weeks.  It is very important for Monteggia fractures to be diagnosed and treated as soon as possible because the radial head gets very comfortable once its dislocated, and doesnt like to return to its normal position if left out for a few days (think happy gilmore).  

Adult bones are a different story.  They have less healing potential and therefore more of these injuries require surgery (but not always).  

An isolated ulna fracture (the "Nightstick" injury) can heal in a short arm cast.  We can expect over 95% healing as long as the bones fragments have 50% contact with each other and the bone is bent less than 10 degrees.  This indicates that the bone is stable despite being broken and there is a low chance it will move out of place once put in a cast.  

However, any angulation over 10 degrees, or anything less than <50% contact between the bone fragments and the ulna has a high risk of continuing to move once splinted.  This instability can prevent the bone from healing, or it may cause to bone to heal in an abnormal position that will  prevent you from turning your wrist (ie unable to turn a doorknob).  

Most adult Monteggia fractures need surgery because they are very unstable.  

Surgery uses plates and screws to hold the bone in position while it heals.  

What is the long term outcome?  

People heal from these injuries very well, as long as they are diagnosed soon after the injury.

The biggest complication occurs in kids, when the diagnosis is missed. Usually a subtle radial head dislocation ("subluxation") is missed and the child will be treated for a simple broken forearm (with a basic splint) and the arm will heal with the radial head dislocated.  Once the arm heals, it is impossible to re-locate the radial head, and surgery is required to rebreak the ulna and align it properly so that the radial head can return to its position within the elbow joint.

Reference

Isolated Ulna

1) Dymond IW. The treatment of isolated fractures of the distal ulna. JBJS 1984; 66: 408-10. full article. cadaveric study 50% cortical contact leads to low risk displacement.

2) Zych GA et al. Treatment of isolated ulnar shaft fractures with prefabricated functional fracture braces. CORR 1987; 219: 194-200. full article. angle <10deg low risk progression treated in brace.

3) Atkin DM et al. Treatment of ulnar shaft fractures: a prospective, randomized study. Orthopedics 1995; 18: 543-7. full article.  no advantage to above elbow immobilizataion.  treat: 8 weeks short arm cast.  

4) Mackay D et al. The treatment of isolated ulnar fractures in adults: a systematic review. Injury 2000; 31: 565-70. full article. review

5) McKee MD et al. The application of the limited contact dynamic compression plate in the upper extremity: an analysis of 114 consecutive cases. Injury 1995; 26: 661-666. full article. good outcome plate for displaced fx :10 wks to union, <5% nonunion.

5) Anderson LD et al. Compression plate fixation in the acute diaphyseal fractures of the radius and ulna. JBJS 1975; 57: 287-297. full article. 50 pt, 85% good-excellent outcome, 9 weeks to union. 

Monteggia Adults

6) Ring D et al. Monteggia fractures in children and adults. JAAOS 1998; 6: 215-24. full article.  review.

7) Bado JL. The Monteggia lesion. CORR 1967; 50: 71-86. full article. classic article on classification system. 

12) Bruce HE et al. Monteggia fractures. JBJS 1974; 56: 1563-1576. full article.  historical: poor outcome in adults with old rx approach: imn or nonop had high nonunion, chronic radial sublux rates.  highlights the value of current locked plates.

11) Boyd HB, Boals JC. The Moneteggia lesion: a review of 159 cases. Clin Ortho 1969; 66: 94-100. full article. historical: poor outcome nonop; pruj disrupted by annular/quadrate lig. tear. reduction ulna reduces radiocapitellar joint b/c interosseus membrane intact.

8) Ring D et al. Monteggia fractures in adults. JBJS 1998; 80: 1733-44. full article. 90% good-excellent outcome in adults with early orif. fair outcomes had radial head fx. shows improved plating causes improved outcomes.  

8) Konrad GG et al. Monteggia fractures in adults: long-term results and prognostic factors.  JBJS Br 2007; 89: 354-60. full article. 25% reoperation, 20% fair-poor outcome at 8 yrs, esp. bado 2, or radial head fx.

Monteggia Kids

9) Ring D, Waters PM. Operative fixation of Monteggia fractures in children. JBJS Br 1996; 78: 734-9. full article. good outcome monteggia kids. all complete ulna fx treated w. orif. 3/11 incomplete orif.  9/11 incomplete rx nonop long arm cast did well. all early rx had excellent outcome. 

10) Olney BW et al. Monteggia and equivalent lesions in childhood. JPO 1989; 9: 219-23. full article. large series, most nonop did well. risk varus deformity.