Elbow: Supracondylar humerus fractures in children

Supracondylar elbow fractures in children are serious limb-threatening injuries. These injuries are limb threatening because the fractured bone ends can kink, stretch, or pinch the brachial artery and thus interfere with the blood supply to the forearm and the hand.

Understanding the problem

The supracondylar part of the humerus is the weak point, predisposed to break when strong enough forces are applied to the child's elbow.

In 95% of supracondylar humerus fractures, the mechanism of injury is forceful hyperextension of the elbow, usually after a fall from monkey bars. As the child's body impacts with the ground, the elbow starts out straight. As the force of the impact continues to overextend the arm, the anterior humeral cortex fails first, and a small gap is created in the front part of the humeral bone. At the same time the back part of the bone is compressed, crushed, and crumbles a little bit. As the injury progresses, the bone fragments separate, and it looks like the elbow bends backwards. In type 3 fractures, the injury continues until the broken fragments are fully separated and move independently of each other.

Glossary

Supracondylar = "above the condyles." Condyles are the prominent lumps of bone just above the joint. The word supracondylar refers to the part of the humeral bone just above the elbow joint. This is an area where the round shaft of the humerus becomes wider side-to-side, and thinner front-to-back, as it joins the ulna and radius to form the elbow joint. Volkmann's ischemic contracture is the end result of the death of the forearm and hand muscles when blood supply is interrupted.

The problem with type 3 fractures fractures is that the artery that supplies blood to the forearm and hand is right in front of the broken humeral bone. This artery can be kinked, can be draped over the end of the broken bone, or can sometimes be caught between the broken bone fragments. The nerves that control the hand can likewise be stretched, kinked, pinched, compressed, etc. This is the reason why these fractures are limb threatening, for without blood supply the muscles of the forearm may die. Volkmann's ischemic contractures is a potentially devastating consequence of these injuries. In addition, disruption of the tissues causes quite a bit of bleeding and considerable swelling: this is another factor that contributes to poor circulation of blood in the injured limb.

Thankfully, prompt realignment of the fracture often restores normal blood flow.

Flexion injuries are a minority of supracondylar fractures. Flexion injuries make up 5% of the supracondylar fractures. In my experience, they occur when the child falls directly on the elbow.

Who needs surgery for these fractures ?

Supracondylar humerus fractures are categorized as type 1, type 2, or type 3, based on the amount of fragment displacement.

Type 1 supracondylar fractures are not displaced. The front of the humeral bone has fractured, there is a crack in it, but the broken fragments are staying together. Type 1 supracondylar fractures are safely treated with splint or cast immobilization, without surgery.

In type 2 supracondylar fractures, the fragments are more displaced, but not fully. In type 2 fractures, the soft tissues behind the bone continue to provide some stability. When confronted with a type 2 fracture, it is important to realize that there is a good amount of interobserver variability in making the diagnosis. This is a nice way of saying that if you ask 2 different orthopedic surgeons "Which type of fracture is this?" they might give you 2 different answers. It turns out that it can be difficult for physicians to decide whether the fracture is a true type 2 fairly stable fracture, or more of a type 3 unstable pattern just by looking at static xrays. Therefore a consensus seems to have developed among the orthopedic profession that for type 2 supracondylar fractures, benefits of surgical treatment with pins outweigh the risks.

Type 3 supracondylar humerus fractures in children are limb threatening injuries. Treatment universally requires surgical stabilization with metallic pins.

Goals of treatment

  1. Restoration of blood flow to the hand, if compromised. This is usually accomplished by realigning the bone ends by feel, but may require open surgery if the artery is caught between bone fragments (rare).
  2. Restoring and maintaining bony alignment. This also may occasionally require open surgery if a large piece of periosteum or a tendon is in between the bones. Maintaining bony alignment while the fracture heals may require casting, pinning, or both (see discussion above on the different types of supracondylar fractures)

Other risks

  1. Nerve injury. About half of children with supracondylar humerus fractures have a certain degree of nerve damage. The child may not be able to bend the thumb joint fully, or may be unable to cross the fingers. These nerve injuries get better with time, usually about 3 months.
  2. Deformity. When the immediate blood flow issues are addressed, there is still the concern of late deformity which gets noticed as the child grows. Typically, the child develops varus at the elbow, commonly referred to as gunstock deformity. This deformity is usually without functional implications, in other words the child can use the hand well but the elbow just does not look right. Accurate fracture reduction and stable pin fixation decreases the odds of this deformity.
  3. Infection. Rarely the pin site can get infected - infection is a risk any time skin is pierced during surgery.
  4. Stiffness. Some stiffness is to be expected 100% of the time. It gets better and motion returns to normal in approximately 6 months.

A couple of examples

A type 3 extension injury

A 2 year old boy, playing on a trampoline, fell, bent the arm backwards, and was brought in by his distressed parents. The xrays below show a type 3 extension injury.

Surgery was delayed a few hours, until the kid's stomach contents moved downstream. The fracture was reduced by feel and under x-ray guidance, and transcondylar pins were placed. Typically 2 lateral pins are enough, but as you can see one of the lateral pins did not have a good far cortex purchase. An additional medial pin was placed with a small incision, for a total of 3 pins. In this particular case, alignment of the bones is very good, with acceptable imperfection. Perfect alignment of the bone fragments would have required an incision, and was not necessary for a normal looking and functioning elbow.

After pins are placed, bones are examined with live fluoroscopy xray, to make sure that the fixation is stable.

Pins are removed between 3 and 4 weeks, in the office. The child's injured elbow is placed over the parent's shoulder, as if hugging the parent, the child's head turned in the opposite direction. Pins are removed simply by twisting and pulling them out. Usually a couple of drops of blood are seen and are not a cause for concern.

Cast is removed at the same time, while a sling is continued for 3-4 more weeks.

Occasionally, a family will prefer to have a second session of general anesthesia just to remove the pins. I highly recommend removal in the office without anesthesia.

Here are the xrays at 4 months. Fracture is healed by xray. Alignment of the bone is good. Elbow looks normal and moves without any limitation. No long term problems are expected.

A flexion supracondylar fracture

The following are xrays of a 5 year old boy who fell down the stairs playing.

Fracture was reduced, pinned, and the pins were shortened and bent.

Xrays at 6 weeks show a well aligned fracture. Range of motion was fully restored by 3 months, including in extension.

Typical outcome. Note the small scar at the pin site on the side of the elbow.

For these injuries, I recommend that the child avoid contact sports for a minimum of 2 months after xrays show healing. This may be frustrating occasionally, but it is certainly the prudent thing to do.