Table 1.

Subtle radiographic signs which should not be overlooked.

Diagnosis	Specific radiographic clues
Primary hyperparathyroidism	Diffuse osteopenia Subperiosteal resorption - fraying and lace-like appearance of outer cortex of bone Subchondral resorption (can be confused with erosions in an inflammatory arthritis) Trabecular resorption – “salt and pepper” calvarium Subligamentous and subtendinous changes Brown tumours Chondrocalcinosis
Osteomalacia	Fuzzy or dirty appearance of bone density Pseudo-fractures in pelvis, scapula and ribs Decreased vertebral body height Bowing of long bones
Rickets	Widened bulky physeal plates Irregularity and splaying of bone at the junction of metaphysis and physis Slipped capital femoral epiphysis Bowing of long bones
X-linked hypophosphatemia or familial vitamin D-resistant rickets	Stress fracture with pronounced enthesopathic changes
Renal osteodystrophy	Diffuse osteosclerosis Biconcave vertebral bodies, with insufficiency fractures Rugger-jersey spine Soft tissue and vascular calcifications
Fluorosis	Diffuse osteosclerosis (most common), can present with osteopenia Ossification of the attachments of tendons, ligaments and muscles Interosseous membrane ossification Ossification of the posterior longitudinal ligament Periosteal bone formation
DISH	No osteosclerosis Flowing ossification along the anterior or right anterolateral aspects of at least four contiguous vertebrae Usually well preserved disc spaces Interdigitating areas of protruding disc material in the flowing ossifications Absence of sacroiliac joint erosions, sclerosis or joint space narrowing however, juxtra and or intraarticular bridging ossification can be present No apophyseal joint or costovertebral joint ankylosis Large osteophyte at the lateral margin of acetabulum
Alkaptonuria	Severe osteoporosis Multi-level intervertebral disc calcification Multi-level disc space narrowing Syndesmophyte formation Early marked osteoarthritic changes