This article on the basic principles of anatomy and physiology aims to provide insight into medical notes, medical report writing and questions to medical practitioners.
Fractures to limbs
Limb fractures are a common form of injury. They are often associated with those mechanisms of injury seen in personal injury claims. Road traffic accidents (RTAs) account for a significant part of personal injury practice, and the forces at work in high-speed collisions are sufficient to cause fractures within the long bones.
The upper limb comprises three long bones: the humerus in the upper arm, which articulates with the radius and the ulna.
Types of fracture
The way a long bone fractures depends on how the injurious force is applied to it. Therefore, the twisting motion within a ski boot may result in a spiral fracture of the tibia.
Spiral fractures in the upper limb bones are less common. In children there is a well-documented association between the development of spiral fractures and deliberate harm.
The way a fracture is identified will relate to its position, which can be head, mid-shaft or distal (the furthest point of the bone from the centre of the body). It will also depend on how the fracture appears when seen by the clinician and on x-ray.
Humerus, radius and ulna
The humerus, being the largest of the upper limb bones, has several muscular attachments, needed to produce the complex range of movements at the shoulder and the elbow. The bone is widest at its two ends and has a waist. Fractures caused by trauma in the humerus can occur at the upper end (the head of the humerus) or just below it (the neck of the humerus).
The long bones of the upper limb all have a hard outer layer with a honeycomb-like core. In adulthood, blood-cell production from the bone marrow largely retreats to the spine, the ribs and the sternum. The material within the core in adults is a more fatty substance, and can be associated with significant complications in fractures of long bones (primarily within the leg).
The radius and ulna provide the structural support for the flexion and extension of the muscles of the wrist and fingers. Fractures of the radius and ulna are usually encountered in the extremes of life. Both are associated with falls on the outstretched hand. In the young this tends to give rise to a ‘greenstick’ fracture, while in the elderly the fracture tends to be a displaced fracture of the radius at the wrist joint. The most common of such fractures is the Colles’ fracture, which is a frequent injury in the winter months, particularly for the elderly and those with osteoporosis.
Femur, tibia and fibula
The femur can be injured at any age. However, with the exceptions of the elderly and where there is an underlying illness, the femur is sufficiently large to mean that considerable force is necessary to cause fracture. This is also the case for the tibia.
In the young, fractures of the femur are associated with considerable impact forces, and so are encountered in RTAs and in farming or horse-riding. The femur contains a considerable amount of fatty tissue in its core. In the case of femoral fractures, there is a clear association with the development of a fat embolus.
In a fat embolus the fatty material contained in the honeycomb core (matrix) of the femur can enter the circulation. Small fragments of the fatty material then enter the veins in the bone and then the veins draining the leg. From this source the fatty material travels through the right side of the heart and into the lungs.
A fat embolus is a potentially life-threatening complication of a femoral fracture.
Fractures of the femur and the pelvis can also be life-threatening purely because of the potential for blood loss. As a general rule, pelvic fractures are associated with the loss of up to two litres of blood into the pelvis, without any apparent external blood loss. In femoral fractures there can be a loss of up to one litre of blood into the tissues around the femur.
Tibial fractures, like those of the femur, are associated with considerable force in the young and in the absence of underlying disease. The tibia can be injured in compression when falling from height, and such injuries can result in significant disruption of the knee joint. Fractures of the tibia or femur that extend into the joint and onto the joint surface are associated with a lifetime risk of osteoarthritis.
Fibula fractures can occur with much less injury. It can be a complication of a significant ankle sprain. Further, the bone is not weight-bearing, so its fracture tends to be a less significant injury.
Treatment of fractures
The basic principle of fracture management is immobilisation. This to surrounding tissue is significantly reduced. Finally, it assists in healing.
In relation to the upper limb, fractures of the humerus can be treated with complex (aeroplane) casts, which hold the arm clear of the chest wall, with plaster on the chest as well as the arm. This is clearly a situation which most patients would not tolerate. Therefore, where possible, humeral fractures are treated by open reduction, which entails an operation to bring the edges of the broken bone back together. To assist this healing process and to reduce the possibility of parts of the bone (ORIF) can be applied. In addition, the long-proven art of plaster application is still widely used. Here the intention is to immobilise the length of the bone by reducing the scope for movement in the joint above and below the fracture.
As the femur and tibia are weight-bearing bones and early mobilisation of the patient is necessary to prevent any complications, such as the development of deep venous thrombosis, ORIF is frequently applied.
In the next article I will deal with bone healing and the development of pathology within joints.
Varieties of fracture
Simple: undisplaced and comprising of no more than two broken ends of the same bone.
Comminuted: a more complex fracture with multiple bone fragments.
Compound: the fracture has breached the skin, and bone may be visible to the naked eye.
Displaced: the position of the distal part of the fracture has been shifted relative to the proximal portion (for example, the two components may override each other, producing a Colles’ fracture).
Greenstick: this is not so much a fracture as a defect in the covering of the bone (the periosteum) and is commonly seen in children.
This article has been written by Dr. David Thomas, a barrister.