Elbow—Distal Humerus

Maya Pring

Vidyadhar Upasani

INTRODUCTION

In our hospital, it is rare to get through a call night without at least one supracondylar fracture that needs to be fixed. The goal of this chapter is to help you recognize and treat pediatric elbow fractures while avoiding the complications that are abundant. In this chapter we will concentrate on distal humerus fractures and dislocations and in Chapter 9 will explore proximal radius and ulna fractures and associated dislocations.

“Learning is not attained by chance, it must be sought for with ardor and attended to with diligence”

—Abigail Adams

Figure 8-1 The trochlea has a spiral orientation, which brings the forearm from in-line with the humerus in flexion to a carrying angle of 15 degrees valgus in extension.

ANATOMY

The elbow is a sophisticated joint composed of three separate articulations: radio-capitellar, proximal ulnohumeral, and radio-ulnar. The spiral orientation of the trochlea allows flexion and extension about an oblique axis, which brings the forearm from a position parallel to the humerus in full flexion to a valgus carrying angle of approximately 15 degrees in extension (Fig. 8-1). The carrying angle has evolutionary significance, presumably to allow the upper extremity to carry an item with clearance of the pelvis as the arm swings.

Elbow motion also permits pronation and supination about the long axis of the forearm, allowing one to position the hand in space with close to 180 degrees of rotation. Morrey had previously shown that an arc of 100 degrees of flexion-extension and 100 degrees of pronation-supination provided a functional range of motion for an adult. However, more recent studies show that more motion may be necessary to complete normal 21st century tasks. Loss of rotation can significantly affect function: pronation is necessary for use of a computer keyboard, and supination allows talking on a cell phone in addition to self-care, feeding, and toileting (Fig. 8-2).

Figure 8-2 Loss of rotation can significantly affect function.

These complex motions require maintenance of the anatomic relationship between all three articulations. Fracture management requires an understanding of not just the bony anatomy that is visualized on the x-ray but also the ligaments, capsule, muscles, and neurovascular structures around the elbow. Unfortunately, anatomic reduction and union of the bones does not guarantee good post-injury motion and function. The elbow, more than most other joints, can become stiff following injury or surgery, and the surgeon must make the difficult decision of early motion (and risk for non-union) versus cast immobilization (and possible stiffness).

The brachial artery runs across the anterior aspect of the elbow and can be injured by the bone spikes of a distal humerus fracture. There are 2 main sources of blood supply to the trochlea. The lateral vessels are
intra-articular and the medial vessels are extra-articular—there is not a good anastomosis between the vessels. The blood supply is important to understand as supracondylar fractures and lateral condyle fractures can lead to avascular necrosis (AVN) even if the fracture is well aligned, as noted by Etier et al. (in Suggested Readings at the end of the chapter).

In addition to complex design issues, there are multiple growth plates near the elbow that fractures may disrupt, leading to growth arrest and deformity (Fig. 8-3).

Figure 8-3 Anatomy of the elbow.

ASSESSING THE PATIENT

In the busy season, we may see 50 injured and/or swollen elbows each week. As a note of caution, on the initial exam, it may be difficult to distinguish between an occult fracture and an infected elbow in a young child. At least twice a year, we see a child with a history of trauma and a swollen elbow who turns out to have a septic joint. If you do not see a clear fracture on x-ray, don’t assume there is an occult fracture until you have ruled out infection. A “soft” history of trauma may lead a young resident away from suspecting infection (a “soft” history may consist of an unwitnessed fall, “she falls a lot,” “…fell yesterday and woke up with pain this morning,” etc.).

There is immediate pain with a fracture; the timing of a fracture should not be unclear. The questions regarding the injury must be precise. “Did the child cry in pain immediately?” “Who observed this?” If there is no definitive association between a witnessed fall and pain, order a complete blood count (CBC), sedimentation rate, and C-reactive protein to rule out infection before you send the child out in a cast. If a patient diagnosed with occult fracture comes back with pain in the cast, re-assess: occult fractures typically do not hurt once they are immobilized; infections do.

Like a good radiologist reviewing a chest x-ray, start your exam away from the area of concern: the contralateral elbow should be examined to determine the normal carrying angle and the child’s natural ligamentous laxity or ability to hyperextend. Once you know the child’s normal anatomy and have narrowed down where and what the problems are, gently move to the injured elbow. Carefully examine the skin to rule out an open fracture. Check areas where the skin is tented or at-risk; the sharp bone ends of a displaced supracondylar fracture can easily penetrate the skin; a closed fracture may be only a cell layer or two from an open fracture. Use a single finger to palpate medial and lateral humerus, olecranon, and radial head to try to localize the fracture so that you can get the best x-rays for the suspected fracture(s).

Check the joint above (shoulder) and the joint below (wrist) for associated injuries. Next, proceed with vascular assessment; radial pulses should be symmetric and capillary refill less than 2 seconds. If pulses are not palpable, a Doppler can be used to check for blood flow to the hand. A dysvascular hand represents an emergency and should be immediately reduced. A compartment syndrome can also impede blood flow and must be addressed immediately (see Chapter 19).

Older children can comply with a neurologic exam (Table 8-1). Test the radial nerve by asking the child to extend the thumb. Anterior interosseous nerve testing includes flexion of the distal interphalangeal joint of the index finger and the interphalangeal joint of the thumb. The ability to grasp indicates median nerve function, whereas finger spread and ability to cross the fingers indicate ulnar nerve function. Test sensation to 2-point discrimination on the radial and ulnar sides of each digit and over the dorsum of the thenar web; light touch sensation is not sensitive enough to detect a nerve injury (Fig. 8-4). Caution:
if the median nerve is compromised, the child will not feel the pain of compartment syndrome and you lose pain as an indicator of impending disaster; for severe injuries, it is important to document 2-point discrimination in the median nerve distribution.

Table 8-1 Quick Motor Nerve Testing for the Upper Extremity

“Thumbs up”

“OK”

Radial nerve—Extension of wrist and thumb

Median nerve—Flexion of digits 2-3

Ulnar nerve—Abduction of digits 3-5

Anterior interosseous nerve—Flexion of index and thumb DIP

Figure 8-4 Sensory nerve distribution of the hand.

If a young injured child is not capable of complying or willing to comply with a neurologic exam, avoid documenting that the patient is “neurovascularly intact” (NVI) unless each test has been successfully performed. Document only what you can effectively test; if the patient has a nerve palsy post-operatively and someone wrote “NVI” on the initial exam sheet, it may be difficult to prove that the nerve injury was not caused by the reduction (or surgery). The neurovascular status of the upper extremity must be monitored carefully until definitive treatment is completed, and for at least 24 hours and sometimes even 48 hours following treatment.

RADIOGRAPHIC ISSUES

Obtaining true AP and lateral x-rays in the injured child can test even the best radiology technician. Some radiology techs will capture a “loser’s” view (Fig. 8-5), an AP view of an elbow flexed about 90 degrees, which makes accurate diagnosis difficult. Don’t be bashful about insisting on a true AP of the distal humerus and of the proximal forearm, even if two or more views must be taken. Correct diagnosis is everything.

Although many fractures are obvious on the AP and lateral x-ray, some are not. Occult fractures may be detected only by clinical suspicion and a careful study of the soft tissue on x-ray. The displacement of lateral condyle fractures is best seen on an internal oblique x-ray.

Figure 8-5 “Loser’s view”—with the elbow flexed it may be difficult to get a true AP of the distal humerus or proximal forearm.

The displacement of a medial epicondyle fracture is best seen on the axial view described by Edmonds (Table 8-2). Ordering the correct views to best evaluate the fracture is very helpful in determining if surgery should be offered or if casting is adequate treatment.

Growth plates and ossification centers cause much confusion for those who do not regularly evaluate and treat children’s fractures. Fortunately, the opposite elbow can be radiographed as a control, which is
very useful in determining the normal anatomy for a particular child. Understanding the timing of growth center ossification and fusion helps the orthopaedic surgeon in evaluating an elbow injury but is generally not part of a primary doctor’s training (Fig. 8-6).

Table 8-2 The Distal Humerus Axial View for Assessment of Medial Epicondyle Fractures

Patient and X-ray Beam Positioning	Model Positioning	Corresponding X-ray

A sawbones model was created with 10-mm anterior displacement of the medial epicondyle. The distal humerus axial view was found to be more accurate and more reproducible than traditional x-ray views.

Figure 8-6 Age at ossification of the distal humerus growth centers for males and females. (Adapted from Haraldsson.)

Even for the experienced pediatric orthopaedist, there are times when the exact diagnosis remains elusive. Ultrasound is becoming a more common tool for evaluating fractures in young children in whom much of the elbow remains as radiolucent cartilage (Fig. 8-7). An arthrogram and magnetic resonance imaging (MRI) study can also be useful but may require general anesthesia in a younger child.

X-ray Landmarks

Several x-ray landmarks help in evaluating an injured elbow: Baumann’s angle on the standard AP view assesses the angulation of the physeal line (below the lateral condyle) in relation to the long axis of the humeral shaft. A normal Baumann’s angle is approximately 20 degrees with a decrease in Baumann’s angle (0 degree for example) suggesting cubitus varus.

The anterior humeral line on the lateral view passes through the middle third of the ossification center of the capitellum for most normal elbows. The anterior humeral line of an extension-type supracondylar fracture will intersect the capitellum more anteriorly or may not intersect it at all. In a very young child, in whom much of the distal humerus remains cartilaginous, this is a less accurate test. Also, in the lateral view, the shaft-condylar angle should be about 40 degrees. A decrease in this angle suggests hyper-extension through the fracture site (Table 8-3). In the fat pad sign (often referred to as a sail sign), a small amount of fat overlies the elbow joint both anteriorly and posteriorly. With injury (or sepsis) and elbow swelling, the fat is pushed away from the bone and may be visible on a high-quality lateral view. A small anterior fat pad is a normal finding on many pediatric elbow x-rays, while a posterior fat pad sign often indicates an occult fracture about the elbow (Table 8-4).

Figure 8-7 An ultrasound can be used to evaluate displacement of a lateral condyle fracture in young children. The top image indicates the fracture (arrow), the bottom is the contralateral normal elbow with intact cartilage.

Table 8-3 X-ray Landmarks

With a posterior fat pad sign and no obvious fracture, oblique x-rays should be obtained to help identify medial or lateral condyle fractures as these may displace in a cast. Skaggs and Mirzayan prospectively examined a group of children with acute elbow trauma and a posterior fat pad sign without a visible fracture on AP and lateral x-rays. At 3 weeks, new radiographs were taken and were evaluated for signs of fracture healing; they found that 34 out of 45 patients (76%) had evidence of an elbow fracture. These included the following:

Supracondylar fracture—53%
Proximal ulna fracture—26%
Lateral condyle fracture—12%
Radial neck fracture—9%

A more recent study from Denmark (Al-Aubaidi) showed that 73% of patients with a positive fat pad sign had only a bone bruise on MRI and not a true fracture, indicating that a positive fat pad sign may not
always indicate occult fracture. However, treatment recommendation remains the same—a short period of immobilization (3 weeks) will allow both a bone bruise and a non-displaced fracture to heal without too much risk of elbow stiffness.

Table 8-4 Distal Humerus Fat Pad Sign (Sail Sign) A posterior fat pad or so-called sail sign strongly suggests an occult elbow fracture. You may not know what type of fracture for 10-14 days when callus appears.

Normal (note—a small anterior fat pad sign is often normal)
Anterior Fat Pad (Large anterior fat pad; Dx—occult supracondylar fracture)
Anterior and Posterior Fat Pad (Dx—supracondylar fracture)

TRANSPHYSEAL DISTAL HUMERUS FRACTURES

Separation of the distal humeral physis in an infant with an nonossified epiphysis can look like a dislocation on x-ray (Fig. 8-8). Remember that dislocation of the elbow without an associated fracture is very rare in children. Transphyseal distal humerus fractures are frequently associated with child abuse and warrant further investigation. They occur in young children and may also be secondary to birth trauma or a fall from a height.

Typically, the distal fragment displaces posteriorly and medially, so the alignment of the proximal radius and ulna are no longer in line with the distal humerus. In comparison (although extremely rare in young children), elbow dislocations usually have posterolateral displacement of the proximal radius and ulna (Fig. 8-9). If there is
inadequate ossification to evaluate the fracture on plane films, an ultrasound study or arthrogram can help to clarify the diagnosis.

Figure 8-8 Transphyseal fracture sustained during delivery healed with significant callus at 3 weeks. At follow-up, the patient had full range of motion at the elbow.

Figure 8-9 Transphyseal fracture.

Many of these injuries have a small piece of the distal metaphyseal bone attached to the physis and are thus technically a Salter-Harris II fracture pattern. Radiographic evidence of this small Thurston-Holland triangular fragment plus posteromedial displacement of the proximal radius and ulna helps to confirm the diagnosis.

Classification—Transphyseal Fractures

DeLee classified transphyseal fractures based on age of the child and ossification of the epiphysis (see Table 8-5).

Treatment—Transphyseal Fractures

If the fracture is diagnosed early (less than 5 days), closed reduction is recommended. Arthrogram or ultrasound is very helpful to visualize alignment, as the epiphysis may not be ossified. If the reduction is stable, casting may be adequate, or pin fixation can stabilize the reduction until there is adequate callus (3 weeks)—the technique of pinning will be reviewed later in this chapter with supracondylar fractures. It is not uncommon for transphyseal fractures to heal in varus. Although flexion and extension deformity will often remodel, varus and valgus do not remodel as well except in the very young infant where more initial deformity can be accepted.

If the fracture is diagnosed late (which is common in child abuse cases), closed reduction should not be attempted, as the physis will be
further injured. Allow the fracture to heal, and treat the resultant deformity with a supracondylar osteotomy when the child is older.

Table 8-5 DeLee Classification of Transphyseal Fractures

Group A: 0-12 months	Group B: 1-3 years	Group C: 3-7 years

No ossification of lateral condyle; usually SH I	Ossification of lateral condyle; can be SH I or SH II with small metaphyseal fragment	Ossification of lateral condyle; usually SH II with large metaphyseal fragment

Pitfalls—Transphyseal Fractures

Recognizing the injury as a “classic sign” of child abuse and completing a social work-up prior to discharge may be may be the most important issue for future safety of the child. Cubitus varus is the most common deformity following under-treatment of transphyseal fractures. Also, AVN of the trochlea or medial condyle and physeal bar/growth inhibition can be caused by displaced transphyseal distal humerus fractures.

Frequently, children are brought in late with transphyseal fractures (particularly if they are secondary to child abuse); if the fracture is more than 5 days old, or there is periosteal new bone noted on x-ray, the fracture should probably not be reduced because the reduction maneuver may cause further damage to the physis. Such fractures should be splinted or casted for comfort, and often adequate remodeling occurs in infants. If there is not sufficient remodeling, a later osteotomy can be done to correct alignment when the child is older.

SUPRACONDYLAR FRACTURES

Supracondylar fractures represent the most common elbow fracture seen in children. The bone is quite thin in the area of the olecranon fossa, making this a weak point in the upper extremity. A fall onto an outstretched hand causes the olecranon to act like a fulcrum, snapping the distal humerus into two (Fig. 8-10). This fracture is more common in children who are “loose jointed” and can hyperextend their elbows. The posterior periosteum may remain intact when the force is pure hyperextension; however, when the fracture is forcibly rotated, the periosteum is torn, permitting gross displacement (Fig. 8-11). With progressively more force, the sharp spikes of the proximal fragment can tear the brachialis, injure the neurovascular structures, and, in rare cases, come through the skin (open fracture).

Classification—Supracondylar Fractures

Most commonly, the distal fragment of supracondylar fractures go into extension (capitellum behind the anterior humeral line); only approximately 5% are in flexion. The Gartland classification of extension type supracondylar humerus fractures initially included Type I (non-displaced), Type II (extended with posterior hinge intact), and Type III (completely displaced). This classification has been modified by several authors. Extension fractures can be further subdivided as described in Table 8-6.

Figure 8-10 The olecranon forms a fulcrum in the supracondylar region, which causes a fracture when the elbow is forcibly hyperextended.

Figure 8-11 Rotation through the fracture may cause the sharp anterior spike to tear through the brachialis and skin.

Table 8-6 Classification of Supracondylar Fractures Modification of Gartland Classification


Nondisplaced, no varus or valgus.	Displaced with angulation, posterior cortex intact—no rotation.	Displaced with angulation and rotation, posterior cortex intact.

Completely displaced, no cortical contact. Medial periosteal hinge intact. Distal fragment displaces posteromedially.	Completely displaced, no cortical contact. Lateral periosteal hinge intact. Distal fragment displaces posterolaterally.	No periosteal hinge. Multidirectional instability.