Souter defined criteria for functional status of a finger affected by the Boutonniere deformity. This can be used to evaluate a patient before and after a surgical intervention. The author is from the Derbyshire Royal Infirmary in Derby, England.
Parameters:
(1) loss of extension in degrees at the proximal interphalangeal (PIP) joint
(2) distance in inches between the tip of the flexed finger and distal palmar crease (in a clenched fist)
(3) flexion at the PIP joint (3a) in percent and (3b) as percent of normal ("summated flexion")
Loss of extension in degrees
Distance in inches
Flexion at PIP joint
Functional Class
none
none
both normal
perfect
1 - 9 degrees
< 0.75 inch
at least one > 90, neither < 80
very good
1 - 19 degrees
< 1.0 inch
> 80 degrees and > 80 percent
good
1 - 39 degrees
< 1.5 inch
at least one > 75, neither < 60
fair
>= 40 degrees
>= 1.5 inch
< 75 degrees and < 75%
poor
loss of extension =
= 180 - (angle of extension)
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