arachnodactyly

Imaging of

Marfans syndrome. X-ray of both hands showing long and slender metacarpals suggestive of arachnodactyly.

Inclusion of

joint laxity, recurrent patellar dislocation, and short distal ulnae as a feature of Van Den Ende-Gupta syndrome: a case report. X-Rays of the Right (a) and Left (b) hands of the male sibling showing the classic arachnodactyly with long, slender bones. Also note the bilateral short distal ulnae with abnormal configuration of the distal ulnar epiphyses

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Arachnodactyly refers to the physical finding of elongated, thin "spider-like" fingers, which are a classic feature of Marfan disease, but by no means pathognomonic .

Radiographic features

The metacarpal index was historically-used as a radiographic criterion for arachnodactyly. To obtain it, the length of the second, third, fourth and fifth metacarpals is divided by their width at the mid shaft. An index of greater than 8.4 is considered the upper limit of normal . It is no longer used due to its poor specificity and sensitivity.