Additionally , the ulnar-most portion of the tendon inserts into the little finger 's digital cord .
The muscle thus forms part of a structure that flexes the metacarpophalangeal joint and extends the interphalangeal joints .
Additionally , the ulnar-most portion of the tendon inserts into the little finger 's digital cord , and the muscle thus forms part of a structure that flexes the metacarpophalangeal joint and extends the interphalangeal joints .