Physical examination
Physical examination was performed by one investigator (TM) on both legs in order to directly compare the operated leg with the unaffected leg. (1) The range of motion (ROM) of the hip joint was measured using a goniometer and given as angular degrees for the following directions of movement: flexion/extension, abduction/adduction, and interior rotation/external rotation. (2) The muscle strength during hip flexion was determined using the muscle function test according to Janda [