2.5 Diaphyseal fractures
Author Klaus Dresing
2.5 Diaphyseal fractures
2.5.1 Introduction
The diaphysis is the shaft section of a long bone. Its function is the transmission of load between the two ends (epiphysis and meta-physis) of the bone (Fig 2.5-1). Diaphyseal bone is cortical and designed not only to transmit load between the joints but also to be strongly resistant to bending. Bones have both an internal (en-dosteal) blood supply through a nutrient artery and an external blood supply from the overlying periosteum.
In this chapter the principles of management of diaphyseal fractures are examined and the characteristics of the different long bones are briefly presented.
Most of the principles apply equally to children and adults. Although with children’s quicker healing and much greater potential for remodeling and correction of any deformity, their fractures are much less likely to require surgical intervention.
All fractures have to be evaluated in the context of the patient as a whole, taking into account local factors including the state of the soft tissues, the quality of the bone, whether fractures are isolated, or the patient has had multiple injuries. General patient factors, such as age, health, occupation, daily activities, and treatment expectations also need to be considered.
Mechanical considerations
Inaccurately reduced diaphyseal fractures result in malunion. The bone can heal in a shortened, angled, or malrotated postition, or any combination of the three. The effect of a malunion depends on its severity and the bone affected.
The function of the legs is to move the body (locomotion), efficiently transmitting body weight to the ground. To optimize this, the leg has a mechanical axis defined as a line between the center of the femoral head and the center of the ankle joint. This line should pass through the center of the knee joint (Fig 2.5-2). Any lower limb diaphyseal fracture that heals with persistent angulation will alter the mechanical axis which will change the way weight is distributed across the knee and ankle. In practical terms, angulation of more than 10° in the coronal plane or 5° in the sagittal plane is likely to increase the risk of developing secondary osteoarthritis. In younger patients even smaller degrees of deformity may cause trouble. However, most patients will tolerate up to 1 cm of shortening and 10° of malrotation in the leg.
A much greater degree of residual deformity can be tolerated in the humerus, as it does not bear weight and angular deformities can be compensated by the mobility of the shoulder. Up to 30° of angulation, 20° of malrotation, and 3 cm of shortening is usually considered acceptable.
In contrast, any deformity after a diaphyseal fracture of the forearm will lead to a loss of forearm rotation. Perfect function (pronation and supination) requires the radius to rotate around the ulna, and this is prevented by any loss of shape in either bone. For this reason, the whole forearm is regarded as a joint. Therefore all adult forearm fractures require anatomical reduction wherever possible.
Aims of treatment
The treatment aim in diaphyseal fractures (with the exception of the forearm) is to restore the joint surfaces at each end of the bone to their correct orientation relative to each other. In practical terms this means aiming to restore the length, rotation, and overall alignment of the bone. It is however not usually necessary or desirable to achieve perfect reduction of every fracture fragment, as attempting to do so may cause damage to the blood supply to the fracture (particularly when it is multifragmentary), and result in delayed healing.
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