Fractures of the Humeral Shaft and Distal Humerus

 

 

Fractures of the humerus include those near the shoulder (known as proximal humeral fractures), shaft fractures, and fractures near the elbow (known as distal humeral fractures). Although the humerus is an analog of the femur, the humerus is not often a weight-bearing bone and is also remarkably tolerant of post-fracture deformity. Thus, fractures of the humeral shaft, unlike those of the femoral shaft, are usually amenable to treatment with simple immobilization rather than surgery. One major exception is fracture of the distal humerus. Because immobilization of distal humeral fractures might lead to intolerable elbow stiffness, and because precise anatomic reduction of articular surface might be needed to preserve elbow motion as well, distal humeral fractures are more likely to be treated surgically.

 

 

Structure and Function

Humeral Shaft

The humeral shaft is defined as the diaphyseal region of the bone, spanning from a point distal to the insertion of the pectoralis major muscle and proximal to the supracondylar ridge.

 

The proximal portion of the humeral shaft is cylindrical. More distally, the shaft narrows and tapers to a triangular shape with the apex anterior. The tapered shape of the distal humerus is unlike the flaring of the metaphysis at the knee, ankle, and other joints, and limits the use of intramedullary nails for the fixation of some humeral shaft fractures.

 

The humerus is surrounded by richly vascularized muscles, an anatomic feature which aids healing. Medial and lateral muscular septa divide the arm into anterior and posterior muscle compartments. The median nerve, musculocutaneous nerve, and brachial artery are in the anterior compartment. The ulnar nerve begins proximally in the anterior compartment but passes through the medial intermuscular septum to enter the posterior compartment near the distal third of the humerus. The radial nerve begins in the posterior compartment and crosses the posterior aspect of the humerus obliquely in the spiral groove, (approximately 20 cm proximal to the medial epicondyle and 15 cm proximal to the lateral epicondyle), and then passes through the lateral intermuscular septum to enter the anterior compartment just proximal to the lateral epicondyle.

 

Distal Humerus

The humeral diaphysis flares into medial and lateral columns. Each column has an epicondyle and a condyle. These columns flank the olecranon fossa and distally support the trochlea -- a smooth spool of articular cartilage clasped by the proximal ulna to form the humeral side of the elbow’s hinge mechanism. The distal part of the lateral column, the capitellum, articulates with the head of the radius to complete the elbow joint (see Figure 1).

  

Figure 1: The anterior and posterior views of the humerus, with attention to the landmarks of the distal humerus, labeled as follows: (A) capitellum; (B) lateral epicondyle; (C) radial head; (D) coronoid process of the ulna; (E) trochlea; (F) medial epicondyle; (G) olecranon. (Modified from https://www.researchgate.net/figure/Anatomy-of-the-humerus-Modified-from-Wikimedia-This-file-is-licenced-under-the-Creative_fig3_342476171)
 

The distal part of the medial column is the medial epicondyle. The ulnar nerve passes through the cubital tunnel just distal to the medial epicondyle. The common wrist flexors originate from the medial epicondyle, and the extensors from the lateral epicondyle.

 

 

Patient Presentation

Humeral Shaft Fractures

In younger patients, humeral shaft fractures are usually due to direct high energy impact (e.g., vehicular accident, sporting injury, or penetrating trauma), while in the elderly they are usually low energy injuries sustained after a fall. (In that setting, owing to bone fragility, there may be other broken bones elsewhere as well.)

 

In newborns, a humeral shaft fracture may occur because of trauma during delivery.

 

Patients will typically present with arm pain, swelling, weakness. Commonly there is a visible deformity and patients often report a snapping or cracking sound at the time of injury. The pain is immediate, enduring, and exacerbated by the slightest movements, though patients are generally comfortable if the arm is immobilized.

 

Displaced fractures of the humerus shaft are often associated with shortening of the upper arm due to muscle contraction. The affected region swells, and bruising appears a day or two after the fracture.

 

A detailed neurovascular exam should be performed and documented. Particular attention should be paid to radial nerve function (i.e., wrist and finger extension; dorsal forearm and hand sensation) as injury to the radial nerve is seen in ~20% of these fractures.

 

Vascular injury is rare but constitutes an emergency when present and may be evidenced by a diminished pulse at the wrist and reduced perfusion with coolness of the hand and fingertips.

 

Distal Humerus

Fractures of the distal humerus are less common. They make up about one-third of humeral fractures and about 2% of all fractures in adults. Condyle-splitting (intercondylar) fractures are the most common type and are generally due to direct impact on the flexed elbow.

 

Patients present with pain, deformity and swelling, making palpation of bony landmarks difficult. Any attempt at active or passive elbow movement is very painful.

 

When there is a break of the skin in the setting of a fracture, further investigation should be undertaken to determine whether the open injury communicates with the joint. If the joint has been violated the injury should be treated with urgent administration of antibiotics, and irrigation of the wound and joint to prevent infection.

 

Complete nerve injuries are rare with fractures of the distal humerus, but numbness and weakness of the small and ring fingers, caused by compromise of the ulnar nerve, is not uncommon and should be carefully documented at initial presentation.

 

 

Objective Evidence

Imaging is essential for diagnosis and classification. X-rays, including AP and lateral views of the entire humerus, including the humeral head and elbow on a single radiograph, are often sufficient (see Figure 2).

 

Figure 2: An oblique fracture of the humeral shaft (red arrow). (From https://upload.wikimedia.org/wikipedia/commons/7/7c/MidShaftHumerousMark.png)
(MELLICK: if you have access to x-rays, perhaps we should have figure 2a, 2b etc and show a collection of fractures, showing some of the various patterns…)

 

In cases where distal humerus fractures are suspected, standard AP, lateral, and oblique x-rays of the elbow should be obtained. If the distal humerus is found to be comminuted on initial x-rays, CT scan may be helpful to characterize the fracture pattern. A CT scan can also reveal violation of the joint capsule, a so-called traumatic arthrotomy, if air is seen in the elbow joint.

 

Sometimes, especially in children, a distal humeral fracture may be present in the absence of obvious cortical irregularity. In these cases, an anterior or posterior "fat pad sign" may be evident on the lateral x-ray view. A fat pad sign is caused by bleeding into the elbow joint, displacing the layer of fat that normally lies adjacent to the bone. The anterior fat pad sign is common and sensitive for a joint swelling but not ‘fracture-specific’ whereas the posterior fat pad sign, while not always present (less sensitive), is fairly fracture-specific.

 

Fractures of the distal humerus can be classified descriptively by location: supracondylar, intercondylar, transcondylar, condylar, capitellar, trochlear, medial epicondylar, or lateral epicondylar.

 

 

Epidemiology

Humerus fractures are common. Humeral shaft fractures comprise 5-10% of all fractures in adults. There is a bimodal distribution of these fractures, with a small peak in the third decade (especially in males) from high energy trauma and a much larger peak in the seventh decade (especially in females) related to osteoporosis.

 

Although distal humerus fractures – particularly extra-articular supracondylar fractures – are common in children, they are relatively rare among adults. While distal humeral fractures can occur in isolation, they are often associated with proximal radial and ulnar fractures or complex ligamentous injuries to the elbow.

 

 

Differential Diagnosis

Distal humerus fractures are often associated with other injuries.

 

Other important injuries can occur around the elbow in the absence of a distal humerus fracture and deserve mention here. The so called ‘terrible triad’ injury is fracture/dislocation around the elbow caused by mechanisms similar to those which cause distal humeral fractures. It includes (1) a fracture of the radial head fracture, (2) a fracture of the coronoid process of ulna, and (3) a dislocation of the elbow joint.

 

Elbow dislocations can also occur in the absence of a fracture and will often spontaneously re-locate prior to presentation and imaging. A high index of suspicion is therefore necessary to diagnose these injuries in combination with a targeted history and examination. Dynamic radiography or fluoroscopy can help make the diagnosis and will demonstrate incongruent and widened joint spaces.

 

Distal biceps avulsion, anterior capsular strain, and collateral ligament injury can all occur acutely in the absence of fracture. MRI imaging is useful in diagnosing these soft tissue injuries.

 

 

Red Flags

In the elderly patient, a fall itself is a red flag and needs to be investigated. Various medical comorbidities (e.g. anemia, syncope, cardiac arrhythmias) may have contributed to the fall.

 

In very young patients with a broken arm, the possibility of child abuse must always be considered and carefully excluded with extreme sensitivity.

Compartment syndrome is a potentially catastrophic complication that can occur with distal humerus fractures and should be carefully checked for - particularly in children with supracondylar fractures.

 

Radial nerve palsy occurs in ~20% of distal third humerus fractures. A radial nerve palsy can develop after a splint or brace is applied. As such, a carefully documented neurological examination must both precede and follow any intervention.

 

(The strong recommendation for performing and documenting the neurological examination goes beyond the avoidance of legal liability – liability that poor documentation can only enhance. Rather, a careful pre- and post- treatment neurological exam can alert you to the presence of an iatrogenic [doctor-caused] injury, which may be easily reversed by reversing the treatment [i.e., removing the splint].)

 

Radial nerve palsy can also result from iatrogenic injury during open reduction and internal fixation, and close post-operative monitoring is needed too.

 

 

Treatment Options and Outcomes

Humeral shaft fractures can tolerate considerable angulation without compromising function or cosmetic appearance. Further, these injuries seem to “want to heal,” most likely because of the excellent blood supply to the muscles that surround the bone (Figure 3). Hence, most humeral shaft fractures are successfully treated without surgery. The wide range of motion of the shoulder joint allows the patient to compensate for up to 20 degrees of fracture angulation, if not more; and because the arms, unlike the legs, are not impeded by a discrepancy in length, up to 3cm of shortening is well tolerated as well.

 

Figure 3: A humeral shaft fracture with callus formation (red brackets). As shown, the edges of the fracture (green lines) do not have to touch for the healing process to begin. (Modified from Wikipedia)
  

The standard non-operative treatment is initial splint immobilization followed by functional bracing once initial swelling has subsided (Figure 4). The rationale of the brace treatment (popularized by A Sarmiento and colleagues in a landmark 1977 paper, Functional Bracing of Fractures of the Shaft of the Humerus, hence known to many as “Sarmiento bracing”) is that compression of the surrounding soft tissues generates hydrostatic pressure that can stabilize the fracture itself, even though the brace does not contact the bone. The force of gravity acting on the arm helps to re-establish length.

 

Figure 4: Functional bracing of the humerus. Compression of the soft tissues in turn stabilize the bone, without need for heavy plaster, or, for that matter, a need to immobilize the elbow and shoulder. (Photo at left from https://bmjopen.bmj.com/content/7/7/e014076. X-ray at right courtesy of Christopher Domes, MD)
 

Functional bracing might be needed for at least 3 months for the bone to fully unite, but after 6 weeks of non-operative treatment, there should be at least some callous (primitive bone healing, as seen on radiographs) at the fracture site. In the absence of callous at 6 weeks, operative treatment might be considered.

 

Although the majority of humeral shaft fractures may be successfully treated without surgery, indications for operative intervention, typically with surgical plate (Figure 5) might include transverse or short oblique fracture lines (as a small fracture surface may generate inadequate callous to adequately stabilize the fracture); intraarticular extension; segmental or open fractures, injuries associated with compartment syndrome; brachial plexus injury; vascular injury requiring repair, and polytrauma cases, in which upper extremity weight bearing would facilitate recovery (e.g., a humerus fracture with an associated lower extremity fracture).

 

Figure 5: A humeral fracture after it has been fixed with a plate and screws. (Image courtesy of Christopher Domes, MD)
 

Regardless of treatment strategy, prolonged immobilization of the elbow joint should be avoided, and frequent range of movement elbow exercises should be encouraged to prevent stiffness.

 

When a patient presents with a closed fracture and radial nerve palsy, immediate radial nerve exploration is not obligatory, as approximately 85-90% of radial nerve neuropraxias will improve within 3 months of injury. Surgeons, however, may opt for open reduction and internal fixation to ensure that the nerve is not caught up in the fracture site. While full recovery of the nerve may require six months, if there is no evidence of recovery by 10 weeks, EMG studies should be arranged, as the absence of nerve function on EMG suggests that further recovery will not occur without surgical intervention.

 

When a patient presents with an open humeral shaft fracture and radial nerve palsy, the management will usually include surgical debridement and fracture stabilization. During that surgery, the radial nerve should be explored. If the nerve is lacerated, primary repair is usually possible.

 

Radial nerve function must be assessed immediately after surgery, to verify that the radial nerve was not compressed by the surgical hardware (see Figure 6).

 

Figure 6: The radial nerve courses posterior to the humerus but then wraps around it to emerge anterior/lateral near the distal 1/3rd of the shaft (A). Fractures near there can entrap the nerve; also, the nerve can be inadvertently caught under a surgical plate (B, anterior view; C lateral view). (Modified from https://www.researchgate.net/figure/The-abridged-general-view-of-the-distalthird-diaphyseal-humerus-fracture-fixed-with_fig2_327286667)
 

For distal humeral fractures the goal of treatment is stable reduction with anatomic restoration of the articular surfaces and restoration of alignment. This often requires surgical fixation which allows early range of motion exercises, with good-to-excellent results achieved in 70-80% of patients.

 

While most patients regain a functional arc of motion, complications are not uncommon. Approximately 10% to 30% will experience some combination of stiffness, non-union, malunion, infection, ulnar nerve palsy, or post-traumatic arthritis. Some degree of elbow stiffness is difficult to avoid. This is usually caused by simple soft tissue contracture, but heterotopic ossification (excess formation of calcified tissue) or post-traumatic arthritis may contribute.

 

In elderly patients with significant articular comminution, elbow arthroplasty (Figure 7) may be preferable to attempted fracture repair if the articular surface and osteoporotic bone cannot be solidly fixed with sufficient stability to allow immediate range of motion. (For this injury in younger, more active patients, arthrodesis – that is, joint fusion – deserves consideration, as elbow arthroplasty is more likely to wear out prematurely in this patient population.)

 

Figure 7: Lateral view comminuted distal humerus fracture in an elderly person after total elbow arthroplasty. (Courtesy of OrthopaedicsOne: Treatment Options for Distal Humerus Fractures)
 

In the newborn, humeral shaft fractures are generally managed with a makeshift sling: pinning the long sleeve of clothing worn on the injured arm to restrict motion.

 

 

Risk Factors and Prevention

Contact sports such as football, or those associated with falling, such as gymnastics, skiing, bicycling, and skateboarding, are associated with a risk for a humeral fracture. Elbow pads can help to reduce the risk of distal humeral fractures.

 

In older patients, all disease or condition that poses a risk for falling should be considered a risk for fracture. A systematic approach to risk assessment and fall prevention, coupled with optimal medical management of bone health, can reduce the likelihood of fracture.

 

 

Miscellany

The medial aspect of distal humerus is called the “funny bone” because paresthesias (“funny feelings”) might be produced when tapping this area, as the ulnar nerve contacts the bone.

 

 

Key Terms

Humerus fracture, elbow fracture, humeral shaft fracture, distal humerus fracture, functional bracing, elbow arthroplasty, elbow arthrodesis

 

 

Skills

Perform and accurately document a neurovascular exam of the upper extremity. Recognize the spectrum of humeral fractures and the distinct issues that pertain to them by anatomic location.

Perform application of a humeral immobilization splint.