The acetabular roof is the superior weight-bearing area of the acetabulum, which includes a portion of both the anterior and posterior columns. The upper femoral epiphysis should be below Hilgenreiner’s line and medial to Perkin’s line in the inferomedial quadrant. Pelvic radiograph shows Hilgenreiner’s line (horizontal line) and Perkin’s line (vertical lines). These are used to diagnose developmental dysplasia of the hip. Perkin’s line is perpendicular to Hilgenreiner’s line and traverses the lateral most portion of the acetabular roof.( 3) The upper femoral epiphysis lies underneath Hilgenreiner’s line and medial to Perkin’s line, in the inferomedial quadrant. The line of Klein runs along the superior margin of the femoral neck and traverses the lateral portion of the femoral head epiphysis.( 2) It is useful in the detection of SUFE, where the line does not cross the epiphysis (Trethowan’s sign).( 2) Hilgenreiner’s line passes horizontally through the superior portion of the bilateral triradiate cartilages.( 3) It is used to measure the acetabular angle and as a reference for Perkin’s line. These fat stripes may bulge away from the femoral neck or become effaced if a hip joint effusion is present.

The iliopsoas fat stripe is the lucency seen immediately adjacent to the iliopsoas tendon.

Interruption of the Shenton arc or line may indicate the presence of a femoral neck fracture or developmental dysplasia of the hip.( 1) The gluteal fat stripe runs along the femoral neck superior portion and denotes the fat between the gluteal minimus tendon and ischiofemoral ligament. The Shenton arc or line runs along the inferior border of the superior pubic ramus and inferomedial border of the femoral neck. The arcuate line should be smooth and symmetrical discontinuity may be caused by sacral fractures. The sacral arcuate line defines the inferior surface of the costal element that forms the anterior sacral canal roof and neural groove. It delineates the pelvic posterior column. The ilioischial line starts from the iliac wing medial margin and extends to the ischial tuberosity along the medial margin of the ischial bone. It delineates the pelvic anterior column. The iliopectineal line extends from the iliac wing medial margin, along the superior margin of the superior pubic ramus, to the pubic symphysis. Numerous lines, arcs and stripes make up the pelvic radiograph (Figs. There are four articulations within the pelvis, excluding the hips: the bilateral sacroiliac joints, which join the ilia and sacrum the pubic symphysis, which joins the two pubic bones and the sacrococcygeal joint or symphysis, between the sacrum and coccyx. In childhood, they are joined by the triradiate cartilage that unites at puberty to compose the acetabulum, which articulates with the proximal femur at the hip joint. The innominate bones are formed from three separate bones – the pubis, ilium and ischium. The bony pelvis consists of the sacrum, coccyx and a pair of innominate bones. Understanding pelvic anatomy and utilising the pelvic reference lines, arcs and stripes are therefore useful and can translate to better patient care. This may aid in early detection of potentially debilitating abnormalities, particularly in relation to paediatric hip pathology, and help prevent long-term adverse sequelae. By correctly utilising these reference guides, very subtle abnormalities may be detected and further appropriate imaging and treatment can be initiated. For example, when assessing for the presence of a fracture in an elderly patient, one should not reference the line of Klein, which is used for evaluating the presence of slipped upper femoral epiphysis (SUFE) on a pelvic radiograph. Some of the reference guides are used for age-specific populations, some for symptom-specific scenarios and some for problem solving. This pictorial essay reviews pertinent reference guides that are utilised for reporting plain radiographs of the pelvis and demonstrates various pathologies that distort their appearance. The overlapping and complex configuration of pelvic anatomic structures form the bases of the lines, arcs and stripes concept in assessment of pelvic radiographs.

Other more dedicated pelvic radiograph projections are often only performed for problem solving and usually requested by specialist orthopaedic surgeons. The conventional pelvic radiograph remains the primary imaging modality for the assessment of osseous structures related to the pelvic girdle and hips in both adult and paediatric populations.

Normal xray of the hip xray