Eight weeks ago I fell and fractured my upper arm. The X-ray shows very little new bone at the site of the fracture. I'll have to keep the cast on another two to four weeks. The doctor mentioned nerve damage. How will I know if there is nerve damage?

The radial nerve is the one most likely injured when there's a fracture of the humeral shaft (upper arm bone). Damage can affect the motor and/or sensory function of the nerve.

With motor loss there is weakness of the wrist extensors. You will notice difficulty extending the wrist. Sensory loss is more likely to cause symptoms of numbness, tingling, or pain.

Most patients know by the end of 12 weeks if there has been some nerve damage. Most of the time a clinical exam by the doctor is all that's needed to tell. The type of fracture is the first tip-off that there may be a problem. Nerve laceration is most common with spiral or comminuted (many small pieces of bone) fractures.

Special nerve tests can be done to confirm the changes. Surgery may be needed to find out what's wrong and repair it.