Is magnetic resonance imaging necessary for normal plain radiography evaluation of contralateral non-traumatic asymptomatic femoral head in high osteonecrosis risk patient.

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.