X-ray Appearances.—In periosteal tumours that do not ossify, there is merely erosion of bone, and the shadow is not unlike that given by caries; in ossifying tumours, the arrangement of the new bone on the surface is characteristic, and when it takes the form of spicules at right angles to the shaft, it is pathognomic.
In soft central tumours, there is disappearance of bone shadow in the area of the tumour, while above and below or around this, the shadow is that of normal bone right up to the clear area. In many respects the X-ray appearances resemble those of myeloma. In tumours in which there is a considerable amount of imperfectly formed new bone, this gives a shadow which barely replaces that of the original bone, in parts it may even add to it—the resulting picture differing widely in different cases; but it is usually possible to differentiate it from that caused by bacterial infections of the bone and from lesions of the adjacent joint.
Fig. 151.—Radiogram of Osteo-Sarcoma of Upper Third of Femur.
Skiagraphy is not only of assistance in differentiating new growths from other diseases of bone, but may also yield information as to the situation and nature of the tumour, which may have important bearings on its treatment by operation.
Fig. 152.—Radiogram of Chondro-Sarcoma of Upper End of Humerus in a woman æt. 29.