Humeral Shaft Fractures
Humeral shaft fractures represent 3-5 percent of all fractures. As many as 10 percent are open fractures. Most involve the middle third of the long bone (60 percent), while 30 percent are proximal third fractures, and 10 percent are distal third fractures. They are most commonly seen in males in their 20s and women in their 60s. Those in younger people are most likely due to a major trauma, while those in younger people are pathologic or due to osteoporosis and minor trauma.
The most common cause of a humeral shaft fracture is a direct blow to the arm from a motor vehicle accident. This usually results in a comminuted fracture or a simple transverse fracture. Indirect injuries are likely from a fall on the outstretched hand or from rotational injuries. Sometimes this type of fracture is seen in a throwing injury that involves severe muscle contraction.
The types of humeral shaft fractures include:
- Compression on the humeral shaft
- Bending of the humeral shaft
- Torsion, leading to spiral fractures of the shaft of the humerus
- Torsion and bending both, leading to an oblique fracture and a butterfly fragment
Evaluation of a Humeral Shaft Fracture
People who have a humeral shaft fracture often present with pain, shortening, swelling and deformity of the affected arm. It is important to check the nerves and blood vessel supply to the arm because the fracture can disrupt the nerve supply and blood vessel to the rest of the arm. Radial nerve function can be particularly damaged. There is often obvious instability of the fracture site and crepitus is common. The doctor also needs to look out for the possibility of an open fracture as well as fractures extending into the proximal or distal joint, which can lead to arthritis and a reduction in range of motion of the arm after it heals.
Classification of Humeral Shaft Fractures
Humerus fractures are divided into open or closed fractures, location (proximal, middle, and distal), angulation, and degree (displaced or nondisplaced). They are also classified as being transverse, oblique, spiral, or comminuted and whether or not they involve a joint.
Humerus shaft fractures can be treated with or without having to do surgery. In non-operative cases, the limb can be casted, splinted, immobilized with a dressing, casted with a spica cast or braced.
About 90 percent of humerus fractures can be treated this way. Ideally, the patient must be mobile and upright and there must be close supervision to make sure the bones are healing well. Up to 20 degrees of angulation is considered acceptable and the fracture can be foreshortened by up to 3 cm if it is to be treated without surgery. The humerus fracture needs to be acceptably reduced in a relatively normal position in order to be treated non-operatively.
These are the types of non-operative ways to handle a humerus fracture cast.
- Hanging cast. This uses the weight of the arm and cast in order to keep the humerus reduced. It can be used to treat fractures that have shortened the humerus as well as spiral or oblique fractures. The patient needs to be upright at all times for this to work. About 95 percent of the time, this fracture is healed without difficulty.
- Coaptation Splint. This uses hydrostatic pressure and traction to keep the bones in place. It is good for fractures that have not shortened much. The splint can slip and can irritate the axilla in some cases but it can be replaced with a functional brace after a week or two.
- Valpeau dressing. This is often used in the elderly or in kids. It involves using a bulky dressing and keeping the arm still next to the thorax in cases where there is minimal displacement of the fracture. Passive range of motion can be undertaken after a week or two following the fracture and can be exchanged for a brace in one to two weeks.
- Shoulder spica cast. This cast isn’t used much. It is bulky and uncomfortable and holds the upper arm in an inconvenient position. The arm is held away from the body and is externally rotated when this cast is placed.
- Functional bracing. This uses soft tissue compression and hydrostatic pressure to hold the fracture segments in place. It is not usually used right away but after other types of casting or splinting have been used for a couple of weeks. The patient is held in a shell-shaped brace that is attached using Velcro. The patient must be upright and it must be tightened every day. It can’t be used in situations where there isn’t a lot of soft tissue swelling or if the patient is unreliable and won’t keep the brace on. A collar and cuff are used to support the forearm but a sling might unacceptably angulate the fracture. It is worn for about 8 weeks or until it appears obvious that the bone has healed.
Surgery for Humerus Fractures
Surgery is necessary in the following situations:
- Unacceptable malunion
- Multiply traumatized patient
- Pathological fracture of the humerus
- Floating elbow
- Segmental fracture
- Vascular injury
- Joint involvement
- Bilateral fractures
- Neurological injuries
- Open fractures
- Non union
- Radial nerve palsy
Surgery involves the use of plates and screws, intramedullary rods, flexible nails, and interlocked nails. When flexible nails are used, the canal of the bone is filled with multiple nails the keep the bone fracture together. If a plate and screws are use, a plate goes along the length of the bone with multiple screws holding the fracture in place. They aren’t very stable but will hold the humerus together until the bone heals.
External fixation can be used using pins on the outside of the body to hold the fracture together. This is used whenever the fracture is infected or when the patient has also suffered from burns or an open fracture with a lot of loss of soft tissue.
Complications of a humerus fracture include radial nerve injury (18 percent), especially in middle third fractures. Usually function returns within a few months, unless the radial nerve is lacerated. Then it can take longer. If vascular injury occurs, then surgery is required. It is usually the brachial artery that is disrupted in this type of fracture. This is an orthopedic emergency requiring surgery in order to regain circulation to the arm. The artery must be repaired within 6 hours in order for it to be effective in saving the limb.
Nonunion happens in 15 percent of humerus fractures. This may require surgery with bone grafting in order to allow the bones to knit together. Malunion is also possible, with problems moving the arm after healing, arthritis, and angulation of the fracture after healing. Usually, exercises to strengthen the muscles can help fix any malunion problems after the bone has healed.