How long does a broken arm take to heal completely after surgery?

Depends. Location, degree of injury, tupe of fixation, age, general health all come into play but in most adults farctuers on average take 6-8 weeks to heal with respect to a united bone.
6-10 weeks to heal. Generally speaking broken bones (fractures) heal after undergoing surgery to reduce and stabilize the fracture with plates and screws in 6-10 weeks. Clinical healing, based upon examination of the broken bone in the office, is complete when there is no more tenderness with palpation of the broken bone. X-rays are used to check for healing as well and should correlate with your md's clinical exam.