Comparison of X-ray films and MRI in early diagnosis of Perthes' disease / 中华骨科杂志

ABSTRACT

Objective To compare the difference of X-ray film and MRI in evaluating the degree of early femoral head protrusion of Perthes disease.Methods Data of 38 cases with unilateral modified Waldenstr(o)m necrosis and fragmentation stage from January 2005 to August 2016 were retrospectively analyzed.There were 35 males and 3 females with an average age of 7.2±1.4 years old.There are 21 cases at lefi side,and 17 at right side.14 cases were at necrosis stage,with an average age of 6.9±1.5 years.While 24 cases were at fragmentation stage,with an average age of 7.4±1.4 years old.Both side X-ray films and MRI femoral head extrusion index (X-rayfemoral head bony protruding acetabular part of the outer edge of the bones/femoral skull margin maximum diameter× 100％;MRIouter edge of bony cartilage protrudes the part of the rim of the acetabular cartilage/the maximum transverse diameter of the cartilage of the femoral head× 100％) were collected.Results The femoral head extrusion index of healthy side was measured on X-ray films and showed an average value of 11.6％±8.2％,and the mean value of affected side was 19.3％±9.8％.The difference between the two sides was statistically significant (t=1 1.550,P=0.000).The femoral head extrusion index of the healthy side was measured on MRI and showed an average value of 20.1％±5.5％,and the mean value of affected side was 27.8％±5.8％.The difference between the two sides was statistically significant (t=5.172,P=0.000).The mean femoral head extrusion index of affected side in necrosis stage of X-ray film was 16.3％± 10.2％,but there were no significant difference compared with the healthy side (13.0％±9.0％) (t=0.369,P=0.719).The mean value of extrusion index of affected side in fragmentation stage was 21.3％±8.8％,while there was 10.8％±1.6％ at the healthy side.The difference was statistically significant (t=4.756,P=0.000).The mean extrusion index of affected side of necrosis stage in MRI was 27.9％± 19.6％,and there was significant difference compared with the healthy side (21.6％± 1.4％) (t=2.651,P=0.018).The mean extrusion index of affected side of disintegration period was 27.8％±5.4％,which was significantly lower than that of healthy side (19.6％± 1.1％).There was statistical significance (t=4.622,P=0.000).There were 17 cases (70.8％) and 22 cases (91.7％) of MRI showed positive sign,and the difference had no statistically significance (P=0.137).Conclusion No significant increasement in femoral head extrusion was observed on the X-ray at necrosis stage in Perthes disease,while MRI showed prominent femoral head extrusion at the acetabular rim.MRI evaluation for evaluating early femoral head extrusion of Perthes disease has better clinical significance.