Radiological and anatomical investigation of calcific tendinitis of the gluteus maximus tendon

: The radiological findings in four cases of gluteus maximus tendinitis were retrospectively analyzed. All the patients underwent radiographic, CT and MRI examinations. Amorphous or round calcifications were detected on lateral radiographs in three cases, and on CT in all cases. A small cortical erosion was observed in three cases on both radiographs and CT. MRI showed a thickened gluteus maximus tendon, but no other specific features. In the supine position, which is common in routine CT and MRI studies, the calcific deposits appeared to be distributed along the vastus lateralis muscle tendon. To correlate these radiographic observations with the topographic anatomy of the tendon's insertion, we investigated 14 thighs of seven cadavers, and clarified that the tendon's insertion was the main component of the lateral femoral intermuscular septum. Consequently we performed MRI on a volunteer in a prone position who was asked to maintain contraction of the gluteus maximus and quadratus femoris muscles. The images obtained showed clearly that the gluteus maximus tendon was directed dorsally. In conclusion, radiography and CT are the modalities of choice for diagnosis of this entity. Additionally, radiologists should be aware that the gluteus maximus tendons are directed laterally as a main part of the lateral femoral intermuscular septum on routine CT and MRI.