THE PROCESS OF REPAIR.—The first attempt at repair is seen in the perios teum, which throws out a layer of granu lations. These become cartilaginous and finally bony, being the only portions of the callus to pass through a cartilaginous stage. The bone and marrow also share in the separative process, but to a less extent. They throw out granulations, which combine with these from the peri osteum to fill the whole space between the bone-ends, even the medullary canal (forming the so-called "medullary plug"). The bone acts more slowly than the periostemn on account of the relative scarcity of its cellular elements, and be cause it has the added task of dissolving and making away with the thin layer of bone-substance which is infallibly de stroyed at the point of fracture. The callus thus thrown out forms a large irregular mass, whose size is increased in proportion to the degree of displacement, the amount of comminution, and the lack of immobilization. If the callus is thus rendered unduly large, it may in volve adjoining tendons, nerves, or joints, thus complicating recovery. If the line of fracture runs into a joint, it may be come permanently immobilized by osse ous union of its articular surfaces.
Fragments detached from the perios teum may regain their vital connections by revascularization of their Haversian canals, or they may remain imbedded in the callus as innocuous foreign bodies. In this condition they may ultimately lead to suppuration.
If the vital energy of the bone-forming elements is not sufficient to form bony union, the callus remains fibrous. The usual causes of fibrous union are systemic debility, separation of the fragments, faulty immobilization, and the presence of foreign bodies,—e.g., wire sutures.
Ultimately the medullary plug is ab sorbed and the callus becomes entirely bony, shrinking, in cases that have been completely reduced, almost to a simple layer between the bone-ends, any sharp angles of which are also gradually rounded off by absorption.
Repair of Compound Fraciures.—If they heal by first intention their repair follows the same course as that of simple fractures, but when suppuration occurs partly detached fragments that would otherwise have lived are cast off, and the ends of the larger fragments also die, and act often for long periods of time as for eign bodies to which sinuses run, after all active suppuration has ceased. In
such cases the dead bone should be cut down upon and removed. After sup puration none of the callus goes through a cartilaginous stage.
Prognosis.—The prognosis depends on many conditions, the extent of the in jury, the associated lesions, and the age and general condition of the patient. Again, the prognosis for certain fractures (clavicle, Colles's) is far better than for others. Among the accidents that may imperil the patient's life are embolism of a clot from an injured vein into the heart or lung, causing instant death (see EM BOLISM), or fat-embolism, a very rare con dition which occurs during the first few days after fracture. The symptoms may be those of embolism or shock, or there may be more or less characteristic signs of oedema of the lungs. Post-mortem examination reveals the fact that the pulmonary capillaries are obstructed by minute globules of fat, which have been poured into the gaping vessels from the torn bone-marrow. H the patient recov ers the diagnosis of fat-embolism cannot be made with any certainty.
Shock is a frequent cause of death, which usually occurs within the first forty-eight hours, and in compound fract ures death may occur from haemorrhage, or later from tetanus or septicaemia or pyazmia. Delirium tremens is a frequent complication. The shock, the with drawal of customary alcoholic stimula tion, and the confinement to bed all tend to induce it. Besides the customary ad ministration of hypnotics, stimulants, and nourishment, it is of the greatest importance to get such patients up and about while they are still in the premoni tory stage of restlessness and insomnia. They must be gotten out of bed at any cost. I have seen this expedient succeed in abating an attack of delirium tremens when all other means bade fair to fail. Finally, gangrene may result from lacera tion of the main vessels of a limb or from their compression, whether by the dis placed fragments or by a splint unskill fully applied.