Supracondylar fractures constitute approximately 50% of all elbow fractures. The supracondylar region is thin and weak and thus can fracture easily. These fractures are classified into two different types: extension and flexion.
Extension type fractures are the most common type, occurring approximately 95% of the time. Extension fractures typically occur due to falling onto an outstretched hand. With extension fractures, the distal fragment of the humerus displaces posteriorly. Anterior interosseous neurapraxia is the most common nerve palsy occurring with supracondylar fractures. Injury to the anterior interosseous nerve will lead to weakness of the flexor digitorum profundus muscle to the index finger and the flexor pollicis longus muscle. The patient will not be able to make an “OK” sign or bend the tip of his index finger. Radial nerve neurapraxia is the second most common palsy and is evident by weakness in wrist and finger extension.
The second type of fractures, flexion type fractures are rare and occurs due to falling directly on a flexed elbow. In flexion type fractures, the distal fragment is displaced anteriorly. This type of fracture may be accompanied with ulnar nerve neurapraxia. Injury to the ulnar nerve will lead to a loss of sensation along the little finger. Later on, the patient may also have weakness of the intrinsic hand muscles and clawing.
Gartland Classification System
The Gartland Classification System provides physicians with a way to categorize supracondylar humerus fractures. There are four classifications and are as follows: Type I fractures are nondisplaced fractures; Type II are angulated with an intact posterior cortex; Type III are completely displaced; and Type IV has complete periosteal disruption with instability in both flexion and extension.
Plain AP and lateral x-rays should be obtained. A posterior fat pad sign seen on a lateral view x-ray should increase your suspicion of an occult fracture around the elbow. On a lateral view x-ray, the anterior humeral line is drawn along the anterior border of the distal humerus. Normally, the anterior humeral line should run through the middle third of the capitellum. In extension type fractures, the capitellum will be displaced posteriorly, relative to the anterior humeral line.
The Baumann’s Angle is formed by a line perpendicular to the axis of the humerus and a line going through the physis of the capitellum. Normally, the Baumann’s angle should measure at least 11° (variable).
It is important to assess the neurovascular structures. The anterior interosseous nerve is assessed by asking the patient to do the “OK” sign with their hand. The radial nerve is assessed by asking the patient to extend their wrist and fingers. Ulnar nerve damage is usually indicated by the loss of sensation along the little finger; however, later on the patient may have weakness of the intrinsic hand muscles and clawing.
Nonoperative treatment is usually indicated for type I fractures. This treatment usually consists of splinting or casting the elbow for a duration of 3-4 weeks. It is very important to remember not to flex the elbow in the splint or cast beyond 90° in order to avoid vascular compromise and compartment syndrome.
Operative treatment is usually indicated for Types II and III, and are usually treated by a closed reduction and percutaneous pinning. During reduction, pronation of the forearm during elbow flexion helps to correct a varus deformity. After reduction, the surgeon will want to check for a gap in the fracture, as the neurovascular bundle may be trapped there. The surgeon will need to free the brachialis muscle from the fracture site if it is interpositioned there. Fixation is usually achieved with 2-3 divergent lateral pins, depending on stability. Medial pins may also be added depending on stability; however, the surgeon will need to be aware of the ulnar nerve when placing the medial pin.
Open reductions are only performed when closed techniques are unable to achieve the appropriate reduction of the fracture. The surgeon will want to avoid posterior dissection in order to preserve the vascularity of the fractured segment. Fracture reduction and fixation should be done emergently in cases of vascular compromise.
Neurapraxia is a common complication of supracondylar fractures and usually resolves on its own—thus, treatment is observation only. A cubitus varus deformity may occur due to a malunion of the fracture. This only presents as a cosmetic problem since it does not affect the function of the arm or elbow. Additionally, this deformity can be corrected later on by a supracondylar valgus osteotomy. Vascular problems, such as compartment syndrome, may also occur. Volkmann’s ischemic contracture may occur due to a compression of the brachial artery with then patient is placed in a cast with the arm in hyperflexion (more than 90°).
A patient may present with a Displaced Type III fracture and a pulseless hand. He may have adequate circulation—which is evident by the normal temperature and color of the hand—or he may have inadequate circulation—indicated by a cold blue hand. In both cases, an urgent closed reduction and percutaneous pinning is required. Once this has been performed and the circulation is adequate, the surgeon can observe the patient and place them in a splint that is at a 45° angle. However, if the patient continues to have inadequate circulation after the closed reduction, then the patient will require a vascular exploration and repair.