False about 1st metacarpal is

The base of the 1st metacarpal bone is occupied by a convexo-concave ave aicular surface for the trapezium. It is the shoest and stoutest of all metacarpal bones. The first metacarpal bone is rotated medially through 90degrees relative to other metacarpals. As a result of this rotation, the movements of the thumb take place at right angles to those of other digits. REF: BD Chaurasia 7th edition Page no: 28 and 29.