The hip series is comprised of an anteroposterior (AP) and lateral radiograph of the hip joint. The series is requested for a myriad of reasons from trauma to atraumatic hip pain.
Hip radiographs are performed for a variety of indications including
- hip pain
- abnormal gait
- inability to weight bear
- knee pain
- AP view
- demonstrates the hip joint in the AP plane, with the limb internally rotated so the neck of the femur is in profile
- often only performed in follow up studies
- lateral view
- standard rolled lateral view demonstrating the femoral neck and acetabular rim can only be performed on non-trauma patients
Modified trauma projections
- horizontal beam lateral view
- lateral projection demonstrating the neck of the femur without movement of the affected limb
- can only be conducted on unilateral hip trauma
- Clements-Nakayama view
- lateral projection demonstrating the neck of the femur without movement of the either limb
- the ideal projection for bilateral hip or femur trauma
- Pelvic AP radiograph
- Dunn view
- lateral projection to aid and diagnose femoroacetabular impingement (FAI) due to its increased sensitivity for detecting femoral head-neck asphericity.
- frog leg view
- bilateral examination allows for better visualisation of the hip joints and femoral neck. It is almost exclusively used in the paediatric population to assess for slipped upper femoral epiphysis (SUFE) and Perthes disease.
Many of the measurements can be conceptualised as follows in the frontal and horizontal plane.
- Acetabulum coverage frontal plane - lateral centre edge etc
- Acetabulum coverage horizontal plane - acetabular version. However there are some signs on the frontal plane (crossover sign etc).
- Femoral neck frontal plane - angle of inclination
- Femoral neck horizontal plane - femoral neck torsion.
Acetabular morphology is assessed by looking at the following
- Orientation – Posterior wall sign, crossover sign, ischial spine sign
- Depth – coxa profunda, protrusion acetabuli, acetabular depth
- Coverage – L-CEA, A-CEA, tonnis angle, sharp angle, extrusion index
Acetabular Orientation and Morphology
Acetabular Depth and Coverage Calculations
Normal is 75% coverage
- Acetabular depth ratio
- Lateral centre edge angle L-CEA – normal 20-45 (Wiberg variant W-CEA is to edge of sourcil, 18-42). Confusingly the W-CEA is connected with Ogata et al, and the L-CEA with wiberg
- Femoral extrusion – normal less than 25%
- Lequesnes anterior centre edge angle – normal 25-50
- Tonnis Angle – draw towards most medial sclerotic edge (the sourcil).
- Normal: 0-10 degrees
- Dysplasia: >10 degrees
- Pincer FAI risk: <0 degrees
- Sharp angle – draw from distal part of teardrop (total acetabulum)
- Dysplasia: >45 degrees
- Lim SJ, Park YS. Plain Radiography of the Hip: A Review of Radiographic Techniques and Image Features. Hip Pelvis. 2015 Sep;27(3):125-34. doi: 10.5371/hp.2015.27.3.125. Epub 2015 Sep 30. PMID: 27536615; PMCID: PMC4972716.
- Sutter et al.. New developments in hip imaging. Radiology 2012. 264:651-67. PMID: 22919039. DOI.