Sixteen patients with paralysis of the anterior interosseous nerve (AI
N) in 19 limbs who were treated in a single unit were reviewed at a me
an of 6.4 years (range 2-14 years) following onset of the paralysis. T
here was a high incidence of incomplete lesions (seven limbs) and of a
ssociated neurological lesions (six limbs) in the same or opposite upp
er extremity. Patients treated conservatively and with surgical explor
ation showed no difference in the time of onset of recovery, the time
taken to achieve complete recovery or the extent of recovery. Those wi
th incomplete lesions recovered well irrespective of the type of treat
ment. A distinct cause of compression of the ALN or visible changes in
the AIN mere seen in just three of the eight limbs that were explored
. Surgery is indicated in complete lesions with no evidence of recover
y for at least 6 months; incomplete lesions and other neurological sig
ns are indications for conservative management in the first instance.