Musculoskeletal ImagingErosion
a destruction of the surface of or breakdown of tissue. Bone erosions occur in various musculoskeletal disorders, including rheumatoid arthritis and gout.
In rheumatoid arthritis, three types of bone erosion are recognized in the hand and wrist (Table 1).
Erosion, Table 1. Types of bone erosion in the hand and wrist in rheumatoid arthritis.
| Type | Mechanism |
|---|
| Marginal | Pannus destruction of bare areas of bone (e.g. without protective cartilage) |
| Compressive | Collapse of osteoporotic bone by muscle forces |
| Surface | Erosion of bone beneath inflamed tendons |
These types of erosion typically involve different joints and bones of the hands and wrists. Marginal erosions are seen in the metacarpophalangeal and proximal interphalangeal joints, radial styloid, midportion of the scaphoid, triquetrum, capitate and trapezium. Compressive erosions involve the metacarpophalangeal joints. Surface erosions are typically seen in the outer aspect of the distal end of the ulna, the dorsal aspect of the first metacarpal bone, and the proximal phalanx of the first digit.
Bone erosions also occur as a late manifestation of juvenile chronic arthritis and in psoriatic arthritis, ankylosing spondylitis and gout. In ankylosing spondylitis the erosions that involve the discovertebral junction may be of various types and are termed Andersson lesions. The erosions in psoriatic arthritis frequently involve the small joints of the hands and feet; a pencil-and-cup appearance may result from destruction or whittling of the head of a phalanx. Gouty arthritis produces tophaceous deposits that lead to erosions that may have a sclerotic border and "punched out" appearance. In addition, an elevated bone margin or lip covers the tophaceous nodule.
In mixed connective tissue disease, the erosions resemble those of rheumatoid arthritis or sometimes psoriatic arthritis but may also involve the distal interphalangeal joints.
DR