69.5 Fractures of the shafts of long bones

The shafts of long bones heal in four stages:

(1) Injury

When a patient breaks one of his long bones, he injures the soft tissues round it, and tears the periosteum away from at least one of the fragments. This deprives the bone next to the fracture of its blood supply, and kills it.

(2) Callus formation

During the next few weeks the periosteum and endosteum near the fracture produce soft vascular callus full of active spindle cells. Cancellous bone only forms a significant amount of callus when the two bony fragments are close together; cortical bone can form callus when they are not so close. Gentle movement stimulates callus formation in a fractured long bone; complete lack of movement depresses it. The non–operative school welcomes callus, and encourages gentle movements. The newly formed callus forms a sheath round the broken bone, and is fixed to the fragments above and below the fracture, but not to the bone at the fracture site itself. The bone here is ischaemic and dead, and does not unite until it has been revascularized later.

After two weeks enough calcium has been deposited in the callus for you to see it on an X–ray. This calcified callus is slowly converted into loose open ’woven bone’ which makes the bone ends ’sticky’, and prevents them moving sideways on one another, although it still allows them to angulate.

(3) Clinical or bony union

As time passes the woven bone round the patient’s fracture becomes harder, and so firmly fixed to the fragments that they move as a single unit. This is clinical union and is a critical milestone in the healing of a broken long bone. It is the indication for a change in management, and is more important than the appearance of his X–ray. It usually occurs 4 to 8 weeks after the injury, but in the tibia it can take much longer.

EXAMINING A LONG BONE FOR CLINICAL UNION

(1) Feel the fracture site for tenderness, looking at the patient’s face as you do so. If it is not tender, his fracture has probably united.

(2) Feel the fracture site for warmth. if it feels warm, it has probably not united.

(3) Put one hand over the callus and grasp it firmly. Ask the patient to keep his limb muscles loose. With your other hand, move the lower end of his broken bone from side to side. If his fracture has united, the upper end of the bone should move in the opposite direction. Don’t be too gentle, but don’t move the bone so vigorously that you cause pain, or refracture it.

Pain, particularly pain at night, is a sign that a fracture has not united. Repeatedly examining a fracture in this way it useful, especially in the early days, because it promotes callus formation. if manipulation is painless and there is no movement, the fracture has united.

When a patient’s fracture has united clinically, you can reduce splinting, but you must continue to protect it from stress, and especially from stresses that are likely to break it. For example, a patient must protect a fracture of the shaft of his humerus from the angulation stresses that dangling it out of a sling will cause while his elbow is still stiff (71.17).

(4) Consolidation and remodelling

Bone continues to heal during this stage, which lasts several months. The broken fragments remain firmly held by callus, while the dead bone the end of each fragment is slowly removed, and their ends joined by more callus and finally by solid bone. The more a patient uses his limb, the stronger this new bone becomes. Excess is slowly removed until his injured limb is as strong, or even stronger, than it was before. Consolidation takes as long again as clinical union, so if union took 8 weeks, consolidation will take 16 weeks. Don’t allow him to do any violent sport until consolidation is complete.