The Scotland prop Allan "Chunk" Jacobsen needs shoulder surgery that will sideline him for up to four months after being injured during yesterday's 26-6 Six Nations victory over Italy at Murrayfield.

"Chunk has damaged the pectoralis major muscle adjacent to his right shoulder," said the Scotland team doctor James Robson, announcing the results of tests on the prop today. "It will require repair and the operation will be carried out later this week by surgeon Richard Nutton at the Spire Murrayfield Hospital."

The loss of the Edinburgh forward for the remainder of the Six Nations is a major blow to the head coach Frank Hadden. Jacobsen, 30, played in all 10 of Scotland's internationals in 2008 and has also been ever-present in the tournament so far.

"Chunk has been in a rich vein of form and we wish him a speedy recovery," said Hadden, who at least received better news on his lock Alastair Kellock and his centre Max Evans.

Kellock, who was recalled in the absence of the injured Nathan Hines and Jim Hamilton, strained ankle ligaments during the Murrayfield victory but he will be fit for the visit of Ireland on 14 March.

Dr Robson said: "He is now wearing an immobilising boot and will begin his rehabilitation under the care of the Glasgow Warriors physiotherapy staff tomorrow with a view to being able to resume training in around seven days."

There were fears that his Glasgow team-mate Evans had suffered a fractured cheekbone but X-ray results allayed those. "Max has severe bruising to his right cheek but, happily, the X-ray has indicated there is no break," added Dr Robson.