X-ray of hip dysplasia

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Hip dysplasia with right-sided hip dislocation.

Authors: Mikael Häggström; Authors of integrated Creative Commons article[1] [notes 1]

Projectional radiography ("X-ray") of dysplasia of the hip joint (also termed developmental dysplasia of the hip (DDH)) is where the socket portion does not fully cover the ball portion, resulting in an increased risk for joint dislocation.[2]


Choice of modality

ACR Appropriateness Criteria for hip dysplasia[3]
Age Scenario Usual appropriate initial imaging
<4 weeks Equivocal physical examination or risk factors No imaging
Physical findings of DDH Ultrasonography
4 weeks - 4 months Equivocal physical examination or risk factors Ultrasonography
4 - 6 months Concern for DDH X-ray. Ultrasonography may be appropriate[notes 2]
>6 months X-ray
  • Ultrasonography of hip dysplasia is generally the investigation of choice at up to 4 months due to limited ossification of the skeleton.[3][notes 2]
  • X-ray of hip dysplasia is generally the initial imaging of choice thereafter.[3][notes 2]


  • Anteroposterior view including both hip joints.[4]
  • Some guidelines also recommend a Lauenstein ("frog leg") projection.[5]

Image quality checking

Image quality checking.
  • Obturator foramen diameter ratio (of Tönnis): A quotient of rotation that can be evaluated by dividing the horizontal diameter of the obturator foramen of the right side and that of the left. In neutral rotation the ratio is 1 but is considered to be acceptable when it is between 0.56 and 1.8.[1]
  • Symphysis os-ischium angle (of Tönnis): This evaluates the pelvic position in the sagittal plane. Lines are drawn from the highest point of the ischium to the most prominent point of the symphysis, joining at the inside of the pelvis. The range of normal values is from 90 to 135° and is related to the infant’s age.[1]

Measurements in children

The most useful lines and angles that can be drawn in the pediatric pelvis assessing DDH are as follows:[1]

  • (A) Hilgenreiner line, connects the inferior tips of the iliac bones,[6] at the triradiate cartilage. This line is used to measure the acetabular angle and as a reference for Perkin line.
  • (B) Perkin line is perpendicular to Hilgenreiner line, touching the lateral margin of the acetabulum. This leads to four quadrants and a normal femoral head has to be located in the inferomedial quadrant. We can measure the lateral displacement of the femoral head with regard to the Perkin line by dividing the width of the head that crosses the Perkin line by the diameter of the head. The value for patients under 3 years must be 0 and in older children this ranges from 0 to 22%.
  • (C) Shenton line is a continuous arc drawn from the inner edge of the femoral neck to the superior margin of the obturator foramen. In children over about 3 to 4 years of age, this line should be smooth and undisrupted, otherwise it may indicate a fracture or hip dysplasia.[7]
  • (D) The acetabular index measures the acetabular roof slope. It is the most useful measure of acetabular dysplasia until 6 years of age. It is formed between Hilgenreiner line and the acetabular roof. In newborns, values of 30° ±4° in females and 26° ±5° in males are considered normal. Gradually this angle becomes smaller, with a mean value of 20° ±3° in females and 18° ±4° in males at 1 year of age.

  • (E) The medial articular joint space is measured between the medial border of the femoral head or neck (when epiphysis is not ossified) and the acetabular platform. Normal values range between 5 and 12 mm. Differences greater than 1.5 mm between the two sides are considered abnormal.

Also check for any asymmetric or age-inconsistent ossification of the femoral heads.

Further workup

Reimer's migration index.

In case of hip dysplasia, also perform the following:

  • Reimer's migration index (MI), also called the femoral extrusion index,[1] in order to detect and quantify any hip dislocation. It is the horizontal distance (parallel to the Hilgenreiner Line) between the Perkin line and the lateral border of the ossification center of the femoral head, divided by the horizontal width of the ossification center. The migration index is normally less than 33% by most sources,[9] but 25% and 30% has also been suggested.[10]


  • Absence or presence of signs of hip dysplasia, including at least any abnormal measurement.
  • If hip dysplaia, also report:
  • Reimer's migration index, with a subjective grading of lateralization.
  • Even normal ossification of the femoral heads.


X-ray of measurements in hip dysplasia, with numbers.jpg Left-sided hip dysplasia, with normal acetabular index. Mild lateralization, with Reimer's migration index of 35%. Normal ossification of the femoral heads.
This example is Public Domain, and can be copied without any need for author attribution.
See also: General notes on reporting

Measurements in adults


In the adult hip there are important landmarks to be recognized on plain film radiographs:[1]

Iliopectineal line, ilioischial line, tear drop, acetabular fossa, and anterior and posterior wall of the acetabulumi.jpg
X-ray of the hips of a 40-year-old female, with dysplasia of her right hip.
  • The iliopectineal or iliopubic line is formed by the arcuate line of the ilium and the superior border of the superior pubic ramus up to the pubic symphysis. It conforms to the inner margin of the pelvic ring and it is part of the anterior column of the acetabulum.
  • The ilioischial line of Köhler begins at the medial border of the iliac wing and extends along the medial border of the ischium to end at the ischial tuberosity. It is part of the posterior column of the acetabulum.
  • The acetabular floor.
  • The teardrop represents a summation of shadows. Its medial aspect corresponds to the inner cortex of the pelvis and the lateral edge with the acetabular notch and the anteroinferior portion of the quadrilateral plate. It is not present at birth but gradually develops due to pressure of the femoral head.


  • Fossa/ilioischial relationship: In normal conditions the floor of the acetabular fossa is lateral to the ilioischial line by 2 mm in men and 1 mm in women. When the acetabular floor overlaps or overpasses the ilioischial line, the diagnosis of coxa profunda can be made. Nevertheless, coxa profunda had been found in 76% of asymptomatic hips, mainly in women. Therefore, this as an isolate criterion is not enough to make the diagnosis of pincer-type impingement. A more severe condition is protrusio acetabuli, diagnosed when the femoral head overlaps or overpasses the ilioischial line.[1]
  • Joint space: In the adult hip, normal joint space ranges from 3 to 5 mm and must be uniform. Values under 2 mm are consistent with joint space narrowing.[1]
Other measurements in adult hip.[notes 3][1]
Measurement Image Target Normal value
Acetabular depth ratio Acetabular depth ratio.jpg Deepness of acetabulum.
  • The width is measured between the inferior margin of the teardrop and the lateral rim of the acetabulum.[11]
  • The depth is measured perpendicularly from the midpoint of the width line.[11]
  • Less indicates a dysplastic hip
Center-edge angle of Wiberg
Center-edge angle of Wiberg.jpg
The superior-lateral coverage of the femoral head.
  • >20° (<55 years old)[notes 4]
  • <24° (>55 years old)[notes 4]
  • >40° indicates overcoverage
Reimer's migration index[9] Femoral extrusion index.jpg The percentage of the femoral head that lies outside of the acetabular roof. It is also called the femoral extrusion index. <25%
Tönnis angle Tönnis angle of the hip.jpg Slope of the sourcil (the sclerotic weight-bearing portion of the acetabulum) 0 to 10°
  • >10° is a risk factor for instability
  • <0° is a risk factor for pincer impingement
Caput-sourcil angle[12] Caput-sourcil angle.jpg Superior to the Tönnis angle in cases without joint space narrowing or subluxation.[12] The medial point of the sourcil is defined as being at the same height as the most superior point of caput femoris. −6 to 12°[12]
  • >12° is a risk factor for instability
  • <-6° is a risk factor for pincer impingement
Sharp angle Sharp angle of the hip.jpg Acetabular slope <45°
  • Greater indicates acetabular dysplasia
Cervical diaphyseal angle Cervical diaphyseal angle of the hip.jpg The angle formed between the femoral neck and femoral diaphysis 120° to 140°
  • Higher indicates coxa valga
  • Lower indicates coxa vara

On CT, the anterior center-edge Lequesne’s angle can be measured in a false profile view of the hip or in a sagittal CT scan. In this case the tangent line touches the anterior rim of the acetabulum. Values under 20° indicate undercoverage of the femoral head.[1]

The sciatic spine and posterior wall signs are other signs associated with acetabular retroversion. The first one is considered positive when the sciatic spine is projected medial to the iliopectineal line in an AP radiography of the spine, indicating that it is not just the acetabulum but the whole hemipelvis that is twisted into retroversion. The second sign is considered positive when the posterior wall edge is medial to the center of the femoral head, indicating deficiency of the posterior wall.[1]

Although femoral version or torsion can be measured by radiographs, CT overcomes the inconsistencies demonstrated in the measurements made by biplane radiography.[1]


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.
  2. 2.0 2.1 2.2 Ultrasonography is the imaging method of choice up to 6 months for the nonoperative surveillance imaging in harness of known diagnosis of DDH.
    - . ACR Appropriateness Criteria - Developmental Dysplasia of the Hip (DDH)–Child. American College of Radiology. Revised 2018
  3. Unless otherwise specified in boxes, reference is the one marked in header.
  4. 4.0 4.1 This can also be used in children. At between 5 and 10 years, the minimum normal value is 15°.


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 Initially largely copied from: Ruiz Santiago, Fernando; Santiago Chinchilla, Alicia; Ansari, Afshin; Guzmán Álvarez, Luis; Castellano García, Maria del Mar; Martínez Martínez, Alberto; Tercedor Sánchez, Juan (2016). "Imaging of Hip Pain: From Radiography to Cross-Sectional Imaging Techniques ". Radiology Research and Practice 2016: 1–15. doi:10.1155/2016/6369237. ISSN 2090-1941.  Attribution 4.0 International (CC BY 4.0) license
  2. . Your Orthopaedic Connection: Developmental Dysplasia of the Hip (October 2013).
  3. 3.0 3.1 3.2 . ACR Appropriateness Criteria - Developmental Dysplasia of the Hip (DDH)–Child. American College of Radiology. Revised 2018
  4. Page 317 in: Fritz Hefti (2015). Pediatric Orthopedics in Practice . Springer. ISBN 9783662468104. 
  5. Sandra M. Rua Ventura, Altino Monteiro (2010). Radiographic Outcomes and Evaluation of Developmental Dysplasia of the Hip in Children . Polytechnic Institute of Porto. Archived from the original. . 
  6. Page 298 in: Rebecca Stein-Wexler, Sandra L. Wootton-Gorges, M.B. Ozonoff (2014). Pediatric Orthopedic Imaging . Springer. ISBN 9783642453816. 
  7. Page Page 1000 in: Wood W. Lovell, Robert B. Winter, Raymond T. Morrissy, Stuart L. Weinstein (2006). Lovell and Winter's Pediatric Orthopaedics . Lippincott Williams & Wilkins. ISBN 9780781753586. 
  8. 8.0 8.1 Akel, İbrahim (2013). "Acetabular index values in healthy Turkish children between 6 months and 8 years of age: a cross-sectional radiological study ". Acta Orthopaedica et Traumatologica Turcica 47 (1): 38–42. doi:10.3944/AOTT.2013.2832. ISSN 1017995X. 
  9. 9.0 9.1 . Hip subluxation and dislocation in cerebral palsy: Outcome of bone surgery in 21 hips (2008).
  10. Stott, N Susan; Piedrahita, Luis (2007). "Effects of surgical adductor releases for hip subluxation in cerebral palsy: an AACPDM evidence report* ". Developmental Medicine & Child Neurology 46 (9): 628–645. doi:10.1111/j.1469-8749.2004.tb01029.x. ISSN 00121622. 
  11. 11.0 11.1 Laborie, Lene Bjerke; Engesæter, Ingvild Øvstebø; Lehmann, Trude Gundersen; Sera, Francesco; Dezateux, Carol; Engesæter, Lars Birger; Rosendahl, Karen (2013). "Radiographic measurements of hip dysplasia at skeletal maturity—new reference intervals based on 2,038 19-year-old Norwegians ". Skeletal Radiology 42 (7): 925–935. doi:10.1007/s00256-013-1574-y. ISSN 0364-2348. 
  12. 12.0 12.1 12.2 Fa, Liangguo; Wang, Qing; Ma, Xiangxing (2014). "Superiority of the modified Tönnis angle over the Tönnis angle in the radiographic diagnosis of acetabular dysplasia ". Experimental and Therapeutic Medicine 8 (6): 1934–1938. doi:10.3892/etm.2014.2009. ISSN 1792-0981.