Introduction
The humerus, or the upper arm bone, is a long bone of the upper extremity extending from the shoulder joint to the elbow joint. It articulates with the glenohumeral joint (the ball and socket joint between the shoulder blade and the collar bone) proximally and distally with the radius and the ulna bones (bones of the forearm). It consists of the shaft (diaphysis), humeral neck, and proximal and distal ends. The humeral shaft is the mid portion of the humerus bone, distal to the humeral neck and proximal to the epicondyles. The proximal half of the shaft is cylindrical, and the distal half is triangular in shape. The humeral shaft serves as a site of attachment for various muscles that help in the movement of the shoulder and elbow. The radial nerve located in the radial groove may be mostly injured in these fractures leading to decreased or loss of sensation in the majority of the cases.
What Is a Humeral Shaft Fracture?
A break or discontinuity in the central portion of the humerus bone (diaphysis) is called a humeral shaft fracture. These fractures are common orthopedic injuries, usually having a bimodal distribution. It occurs in young patients (21 to 30 years) due to high-impact injuries and in elderly people, especially females (60 to 80 years), due to low-impact injuries. The radial nerve, situated in the spiral groove, proximal to the lateral and medial epicondyles, has a high risk of injury and accounts for about three percent of all fractures. Most humeral shaft fractures are unstable fractures and can be classified based on the location, type, and open or closed status. Humeral shaft fractures may require around four months to heal and have a nonunion rate of around 1 to 12 percent.
What Are the Types of Humeral Shaft Fractures?
The classification of humeral shaft fractures was developed by the orthopedic trauma association (OTA) in 1996 and revised in 2007 and 2018; it is classified based on the number of bones or bone segments involved and divided into three types:
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Type A - Simple Fractures: It is determined by the angle of fracture and may be further determined as oblique (more than 30 degrees), spiral, and transverse fractures (less than 30 degrees). Based on the location of the fractures, humeral shaft fractures may be further subdivided into proximal third, middle third, and distal third fractures.
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Type B - Wedge Fractures: It is also called compression fracture, which is unstable compared to simple fractures and can be further subdivided into intact wedge fractures and fragmentary wedge fractures.
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Type C - Multifragmentary Fractures: These are complex fractures caused by high-energy trauma, which results in multiple irregular bone fragments associated with damage to the soft tissues. It may be further subdivided into proximal diaphyseal-metaphyseal, pure diaphyseal, and distal diaphyseal-metaphyseal fractures.
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Holstein - Lewis Fracture: It is a type of spiral fracture involving the distal third of the humeral shaft, which commonly results in the entrapment of the radial nerve and leads to loss of sensation and wrist drop deformity, requiring surgical management.
What Are the Causes of Humeral Shaft Fracture?
Some of the causes of humeral shaft fractures include:
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Road traffic accidents.
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A direct blow to the upper arm due to falls.
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In elderly people due to falls on an outstretched arm.
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Indirect trauma due to sports activities such as arm wrestling which involves twisting action resulting in spiral fractures.
What Are the Signs and Symptoms of Humeral Shaft Fracture?
Some of the signs and symptoms of humeral shaft fractures include:
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Severe arm pain and weakness of the extremity following the injury.
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Swelling and bruising.
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Restricted movement of the upper arm.
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Numbness or loss of sensation in case of radial nerve injury.
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A significant deformity of the upper arm.
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Break in skin integrity and lacerations in case of severe motor injuries.
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Shortening of the arm on the affected side.
What Are the Complications of Humeral Shaft Fractures?
Some of the complications of humeral shaft fractures include:
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Injury to the radial nerve or entrapment is a common complication associated with 20 percent of humeral shaft fractures. It causes neuropraxia, characterized by demyelination of the nerve at the site of injury, which leads to blockage in nerve conduction resulting in loss of sensation. Radial nerve palsy may occur in some cases following the treatment of humerus shaft fractures by open reduction and internal fixation via a lateral or posterior approach.
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Non-union of the fracture segments following treatment, even after six weeks from injury or mal union (abnormal union) of the fractured fragments. It may be due to advanced age, obesity, diabetes, poor nutrition or soft tissue interposition, or inadequate shoulder immobilization.
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Limited range of motion following the treatment.
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Infection at the fracture site may lead to poor bone healing.
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Injury to the brachial artery can occur but is a rare complication.
How Is a Humeral Shaft Fracture Diagnosed?
In the case of high-impact injuries, patients usually present with severe arm pain and swelling, which may be associated with lacerations, bleeding or bruises, and deformity of the upper arm. Skin lacerations associated with skin tenting or a break in the skin integrity suggest an open fracture. The doctor performs an overall alignment of the limb to check the presence of deformity or shortening of the arm. A neurovascular examination is performed to check numbness or loss of sensation to diagnose the involvement of the radial nerve.
Radiological imaging of the humerus bone, including anteroposterior (AP) and lateral views along with the clavicle, forearm, and wrist, must be considered to rule out their involvement. Traction radiographs can be taken in case of severely comminuted or displaced fractures with significant shortening of the arm or proximal or distal extension. A computed tomography (CT scan) is rarely advised in humeral shaft fractures. In case of high-impact trauma and evidence of vascular injury, hemoglobin levels must be assessed to estimate the blood loss. In case of suspected injury to the radial nerve, electromyography (EMG) can be performed to determine the extent of nerve damage.
How Is a Humeral Shaft Fracture Managed?
Humeral shaft fractures are usually managed by conservative treatment, and an appropriate alignment and union of the fractured segments can be achieved in most cases.
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The presence of any skin lacerations, abrasions, and bleeding is managed, followed by reduction, which is performed immediately after adequate control of pain or through sedation. Splinting the humerus shaft fracture is challenging as it must be performed along with the shoulder and the elbow joint to achieve mobilization. A coaptation splint followed by a sling or functional braces, a long arm splint, a shoulder immobilizer, or a hanging arm cast are some options for splinting humerus shaft fractures. On follow-up, a long-term cast may be applied to immobilize the fractured bone, which is usually done 12 days after the injury. By conservative treatment, effective healing can be achieved in 10 to 12 weeks, followed by a range of motion exercises of the shoulder, elbow, wrist, and fingers.
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Surgical management is required in cases of neurovascular injury, severe comminuted or open fractures, multiple fractures, inability to tolerate a splint or cast for long periods, or failure (non-union) of the conservative treatment. Open reduction and internal fixation (ORIF) by metal screws and plates are performed through the posterior or the anterolateral approach. Care is taken to avoid excessive soft tissue stripping and prevent damage to the radial nerve. Intramedullary nailing may be performed in some cases but may result in loss of shoulder motion or nerve injury.
Conclusion
A break or discontinuity in the diaphysis of the humerus bone is called a humeral shaft fracture. It is associated with severe pain, swelling, decreased movement, and loss of sensation in case of radial nerve involvement. It is usually managed conservatively, but multiple fractures or severe neurovascular injuries require surgical intervention followed by physical therapy to improve strength and range of motion. The patient can recover completely in a few months with appropriate care and treatment.
