OBJECTIVE: To examine the incidence rate and extension of non-traumatic asymptomatic osteonecrosis of the contralateral femoral head (ONFH) in high-risk patient groups. MATERIAL AND METHOD: A cross-sectional design was used. We studied patients who visited at Orthopedics department, Khon Kaen hospital between January 2007 and December 2008. Only high-risk patients diagnosed with non-traumatic osteonecrosis in index side by plain radiography and asymptomatic contralateral sides with normal plain radiography evaluated for non-traumatic femoral head osteonecrosis were included in the analysis. We evaluated both hips of individual patient by MRI to determine the incidence, staging, and extension area of osteonecrosis. RESULTS: Thirty-two patients with index femoral head osteonecrosis and non-traumatic asymptomatic contralateral femoral head were studied. Average age of these patients was 46.38 years. The most common risk factors were alcohol (78.12%) and corticosteroid use (18.75%). Osteonecrosis of the contralateral femoral head (ONFH) was found in 22 patients (68.75%). These hips were in stage VI (87.5%) with 99.05% extension area of osteonecrosis, large extension, C- location, and mix intensity of MRI on index side. We found stage I in all patients (100%), 80.62% extension area of osteonecrosis, large extension, C-location and mix intensity of MRI on ONFH at contralateral side with normal plain radiographic. CONCLUSION: We found the high incidence rate and high extension area of asymptomatic osteonecrosis of the contralateral femoral head of the hip in high-risk patient. This result supported that silent aggressive disease can rapidly progress to advanced stage in a short time. Early detection of osteonecrosis in contralateral hip by MRI is considered a clinically necessary procedure in high-risk patients with unilateral hip osteonecrosis.
OBJECTIVE: To examine the incidence rate and extension of non-traumatic asymptomatic osteonecrosis of the contralateral femoral head (ONFH) in high-risk patient groups. MATERIAL AND METHOD: A cross-sectional design was used. We studied patients who visited at Orthopedics department, Khon Kaen hospital between January 2007 and December 2008. Only high-risk patients diagnosed with non-traumatic osteonecrosis in index side by plain radiography and asymptomatic contralateral sides with normal plain radiography evaluated for non-traumatic femoral head osteonecrosis were included in the analysis. We evaluated both hips of individual patient by MRI to determine the incidence, staging, and extension area of osteonecrosis. RESULTS: Thirty-two patients with index femoral head osteonecrosis and non-traumatic asymptomatic contralateral femoral head were studied. Average age of these patients was 46.38 years. The most common risk factors were alcohol (78.12%) and corticosteroid use (18.75%). Osteonecrosis of the contralateral femoral head (ONFH) was found in 22 patients (68.75%). These hips were in stage VI (87.5%) with 99.05% extension area of osteonecrosis, large extension, C- location, and mix intensity of MRI on index side. We found stage I in all patients (100%), 80.62% extension area of osteonecrosis, large extension, C-location and mix intensity of MRI on ONFH at contralateral side with normal plain radiographic. CONCLUSION: We found the high incidence rate and high extension area of asymptomatic osteonecrosis of the contralateral femoral head of the hip in high-risk patient. This result supported that silent aggressive disease can rapidly progress to advanced stage in a short time. Early detection of osteonecrosis in contralateral hip by MRI is considered a clinically necessary procedure in high-risk patients with unilateral hip osteonecrosis.