Quantitative examination of isolated finger flexion associated with function of the flexor digitorum superficialis.
Yudai Watanabe, Rikiya Shirato, Takuro Wada and 3 others
PMID 33281291WHAT IT FOUND
In 100 healthy adults, middle and ring fingers flexed more than the index, and small fingers that could flex on their own flexed less than the others; 32.5% of small fingers could not flex on their own.
Key findings
01In 100 healthy Japanese volunteers, all index, middle and ring fingers had independent FDS function, while 135 of 200 small fingers did and 65 of 200 did not.
02Mean isolated flexion angles were 152.4 degrees and 154.8 degrees for the right and left index, 161.1 degrees and 160.4 degrees for the middle, 160.6 degrees and 158.2 degrees for the ring, and 129.4 degrees and 134.6 degrees for small fingers with independent FDS function.
03Middle and ring fingers flexed more than the index; small fingers with independent FDS function flexed less than the index, middle and ring fingers but more than small fingers with common or absent FDS function.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The participants were healthy Japanese adults aged 20-69 years, so these are reference values, not patient outcomes. The authors did not use dissection, electrophysiologic tests, ultrasound or MRI, so other anatomical variations or silent disease could have been missed. All testing was done by one examiner, so the paper does not show whether another examiner would obtain the same angles. Small finger function was asymmetric in 35.0%, so the opposite hand is not always a reliable reference. Further studies are needed to assess the test's usefulness in patients and its effect on hand dexterity.
Declared interests
No funding or conflicts of interest were declared.
The easy way to misread this
Do not read these values as evidence that the Q-FDS test improves hand function or that absent independent small finger flexion is abnormal. The study measured healthy adults, not patients, and 32.5% of small fingers in healthy adults showed no independent FDS function.