The man alleges the remnant wire caused a golden staph infection and permanent injury.

The patient had been standing on a stool in August 2008 to change a light bulb.

He fell and injured his hand, later undergoing surgery at the Canberra Hospital.

Doctors placed multiple K-wires, or Kirschner wires, in his hand to stabilise it.

The patient went back about three weeks later to have the wires removed, and again the next week for a review.

But he soon began to experience pain and swelling, and went back to the hospital a week later with an abscess.

Doctors realised a piece of wire had been left in his hand, and operated again on October 2.

The man took the ACT to court three years later, in July 2011, claiming the negligence had caused his infection and permanent injury.

The man claimed the hospital failed to have a proper system in place to make sure all the wire was removed, failed to take steps to prevent infection, and failed to tell him how to care for his wound and about the risk of post-surgery infection.

In March last year, his lawyers wrote to the hospital asking for all scans and imaging they held on the patient.

They received image intensifier films which showed that a fragment of K-wire was visible inside the plaintiff's hand on the day of the surgery, meaning it was left in there during the operation and not in a later procedure.

That prompted the man to try to expand his negligence claim against the hospital, asserting it failed to detect and remove the fragment during the initial operation and again when the wires were removed or when he presented to hospital with pain and swelling.

The man's application to change his claim outside of the time limit was heard by Supreme Court master David Mossop earlier this year.

The patient argued he had not been aware of the existence of the image intensifier films earlier because the ACT had not mentioned them in the list of discoverable documents originally provided to the plaintiff.

He said the change should also be allowed because the new claim was based largely on the same facts as the original.

But the ACT fought the application to amend the claim on a range of grounds.

The defendant argued there was no evidence that the remnant K-wire fragment actually caused the man's injury.

An expert report was tendered suggesting the timing of the infection meant it must have developed overtly some time between his review on September 23 and his presentation to the hospital a week later.

The defendant said the new claim against the hospital did not arise out of the same facts as the original, and should not be allowed.

That was because, it argued, the original procedure to insert the wires was separate from the later operation, which involved different surgeons and different techniques.

Master Mossop ruled against the patient's attempt to amend his claim in a judgment handed down last week.

He said the expert evidence used by the plaintiff in support of his amended claim, provided by a doctor and a nurse, was ''incoherent'' and left the court with a sense of unease.

Master Mossop said there was no expert evidence indicating that a failure to find and remove the wire fragment was a breach of the doctor's duty of care.

''Leaving broken bits of fixation devices inside the body of a patient and apparently failing to see them when they are clearly shown on the image intensifier films are clearly matters which give rise to concern,'' he wrote.

''However … the fact that an item is incorrectly left inside a patient does not necessarily prove negligence on the part of the surgeon.''

The matter is expected back before the ACT Supreme Court early next month for directions and to decide who pays costs for the application.