A surgical clip used to control bleeding was left in the arm of a patient after an operation - one of 21 medical errors reported in the final three months of last year. The Hospital Authority said the 1.5cm clip was found to be missing in an instrument check after the operation. An X-ray showed it was still in the patient's left arm and was surgically removed. In another case reported in its risk alert bulletin, published yesterday, the broken tip of a screw holder was found in a patient's spine but removal was not necessary.