Twenty-eight recovered Sars patients have been diagnosed with a degenerative bone disease linked to the heavy dosage of steroids used in their treatment, the Hospital Authority disclosed yesterday. Some may require hip replacement surgery. So far, 418 people have been screened for the bone disease avascular necrosis with MRI (magnetic resonance imaging) scans. Forty-nine were found to have abnormal bone conditions, said Vivian Wong Taam Chi-woon, a director of the authority. Of those 49, 28 were diagnosed with avascular necrosis. The authority has contacted about 1,200 of the 1,456 people recorded as having recovered from Sars. All Sars survivors will be offered free MRI scans to check for the disease. Avascular necrosis occurs when blood stops flowing to the bone, causing it to die and finally collapse. The disease has been linked to the use of steroids in treating Sars patients. The Hospital Authority yesterday launched a new hotline service for recovered Sars patients - 2300 6393.