A) Erosion score

The van der Heijde modification of the Sharp erosion score includes 16 areas from each hand and wrist, 10 metatarsophalangeal joints on both sides and two interphalageal joints of the big joints. The maximum erosion score is 160 for hands:

• 5 metacarpophalangeal joints (MCP)
• 4 proximal interphalangeal joints (PIP)
• interphalangeal joint of the thumb (IP)
• radius
• ulna
• trapezium and trapezoideum as one unit (multangular)
• scaphoid
• lunate

and 120 for feet:

The original Sharp score included erosion score and joint space narrowing score for each evaluated joint. The number of evaluated joints was later decreased to reflect more accurately the extent of abnormalities and to shorten the amount of time required to read the films.
This modification considers 17 areas for erosion for each hand:

• five proximal interphalageal joints (PIP)
• five metacarpophalangeal (MCP)
• base of the first metacarpal bone (MCB)
• multangular bone
• navicular bone
• lunate bone

Larsen's scoring system atributes 0 to 5 points to each synovial joint evaluated on a radiograph. As each synovial joint can be included in the score, description of scored joints and maximum attainable score should be reported.

The original method from 1977 included hands, wrists, and feet with a maximum possible score of 250 (10 joints per hand or foot + 2 x 5 x wrist) x 5. The wrist is considered as one unit and the score is multiplied by five:

• 5 distal interphalangeal joints (DIP)
• 4 proximal interphalangeal joints (PIP)