[Application of MRI in diagnosis of transient dislocation of patella]

To explore the diagnostic value of MRI in the transient dislocation of the patella.

The DR and MRI data of 35 patients with acute patellar transient dislocation from January 2015 to December 2017 were retrospectively analyzed, including 12 males and 23 females, ranging in age from 10 to 23 years old, with an average of 17 years old. The differences between DR and MRI diagnosis and surgical or discharge diagnosis were compared, and the difference between them in diagnosis of knee anatomical position, bone injury, signs and soft tissue injury were compared. The R statistical software WiLcoxon signed rank test (WiLcoxon signed rank test) was used for statistical analysis.

All 35 MRI findings were completely consistent with postoperative or discharge diagnosis. According to MRI, 7 cases of high patella and 7 cases of patella subluxation were diagnosed. According to DR, 7 cases of high patella and 0 cases of patella subluxation were diagnosed. Fourteen dislocations were diagnosed by MRI and 7 dislocations were diagnosed by DR. There was statistically significant difference between the two methods in the diagnosis of abnormal position of patella(v=10, P<0.05). Total 112 cases of bone injuries were diagnosed by MRI, and 0 was diagnosed by DR. There was statistically significant difference between the two methods in the diagnosis of bone injuries(v=16, P<0.05). Total 43 cases of soft tissue injuries were diagnosed by MRI, and 0 was diagnosed by DR. There was statistically significant difference between the two methods in the diagnosis of soft tissue injuries (v=21, P<0.05). Total 35 cases of hydrops of the knee joint were diagnosed by MRI, and 30 were diagnosed by DR. There was statistically significant difference between the two methods in the diagnosis of hydrops of the knee joint(v=32, P>0.05).

MRI is superior to DR in the diagnosis of acute temporal bone dislocation. MRI should be used as the first choice for imaging diagnosis of acute temporal bone dislocation. It can avoid missed diagnosis and misdiagnosis.