The metacarpal index (MCI) is a radiographic measurement that can be used to confirm the presence of disproportionate metacarpal length. It was first introduced by Sinclair in 1960 for diagnosis of Marfan syndrome 6. The metacarpal index is no longer used for the diagnosis of Marfan syndrome due to low sensitivity and specificity.
At least two methods exist for the calculation of the metacarpal index. These two methods are not mathematically identical, and a statistically significant difference has been noted between them. The first method of MCI calculation is by obtaining the average of the ratios of length / width of metacarpals 2-5.
The second method involves dividing the sum of the lengths by the sum of the widths of these metacarpals. Values of between 8.4 and 9.4 have been used as cut-off for abnormal values.
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