X-ray of hip prostheses
Mikael Häggström [notes 1]
For X-ray of the hip joint in the presence of a prosthesis, this article first deals with the first postoperative image which is more focused at prosthesis configuration, and separately describes subsequent follow-ups which are more focused at complications.
- The referral or complementary information needs to specify the type of prosthesis and when it was inserted.
- Images that need to be available include the first postoperative ones, as well as the most recent previous exam.
First postoperative image: Configuration
Post-operative projectional radiography ("X-ray") is routinely performed to ensure proper configuration of hip prostheses.
Necessary projections are:
- Frontal and axial image of the hip joint
- Frontal image of the inferior parts of the hip bone (to include the ischium bones for measurements).
The direction of the acetabular cup influences the range of motion of the leg, and also affects the risk of dislocation. For this purpose, the acetabular inclination and the acetabular anteversion are measurements of cup angulation in the coronal plane and the sagittal plane, respectively.
Center of rotation: The horizontal center of rotation is calculated as the distance between the acetabular teardrop and the center of the head (or caput) of the prosthesis and/or the native femoral head on the contralateral side. The vertical center of rotation instead uses the transischial line for reference. The parameter should be equal on both sides.
Cement coverage is regarded as acceptable when there are no translucent zones on an anteroposterior image in at least 6 of 7 Gruen-zones. Absence of cement in zone 7 (medially-proximally) needs to be noted. On a lateral image, the distal tip of the prosthesis should be centered, and not be in contact with the cortex. The cup should not have translucent zones in zone 1 and 2. It is acceptable to have translucent zones in parts of zone 3.
The postoperative report should include:
- Prosthesis configuration. If the report is likely to undergo double reading, the parameters need to be given in numbers even if within normal limits.
- Cement coverage.
|(Total) hip replacement with unremarkable configuration and cement coverage||Post-operative images of total hip replacement with unremarkable configuration:
- See also: General notes on reporting
Further follow-ups: Complications
Further follow-ups after the initial postoperative image are focused on various complications.
Post-operative femoral fractures are graded by the Vancouver classification:
|A||Fracture in the trochanteric region|
|B1||Fracture around stem or just below, with well fixed stem|
|B2||Fracture around stem or just below, with loose stem but good proximal bone|
|B3||Fracture around stem or just below, with poor quality or severely comminuted proximal bone|
|C||Fracture below theprosthesis|
On radiography, it is normal to see thin radiolucent areas of less than 2 mm around hip prosthesis components, or between a cement mantle and bone. However, these may still indicate loosening of the prosthesis if they are new or changing, and areas greater than 2 mm may be harmless if they are stable. The most important prognostic factors of cemented cups are absence of radiolucent lines in DeLee and Charnley zone I, as well as adequate cement mantle thickness. In the first year after insertion of uncemented femoral stems, it is normal to have mild subsidence (less than 10 mm).
Further follow-up reports should include at least:
- Dates of the images used for comparison
- Absence of change in position, or a description of any change.
- Absence or of loosening, or a description of it.
- See also: General notes on reporting
- For a full list of contributors, see article Radlines:Authorship for details. . Creators of images are attributed at the image description pages, seen by clicking on the images. See
- Andrew Still (2002-11-02). Total Hip Replacement. University of Southern California. Retrieved on 2017-01-05.
- Radiologists: Torsten Boegård, Mats Geijer, Marianne Petrén-Mallmin. Orthopedic surgeons: Lennart Sanzén, Christer Strömberg, Torbjörn Ahl. Hip - Radiologic evaluation of prosthetic surgery (Swedish title: HÖFT - Radiologisk undersökning vid proteskirurgi). Swedish Orthopaedic Association (SOA). Publication #18, 2006
- Iain Watt, Susanne Boldrik, Evert van Langelaan and Robin Smithuis. Hip - Arthroplasty -Normal and abnormal imaging findings. Radiology Assistant. Retrieved on 2017-05-21.
- Vanrusselt, Jan; Vansevenant, Milan; Vanderschueren, Geert; Vanhoenacker, Filip (2015). "Postoperative radiograph of the hip arthroplasty: what the radiologist should know ". Insights into Imaging 6 (6): 591–600. doi:10.1007/s13244-015-0438-5. ISSN 1869-4101. PMID 26487647.
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- Steffen Breusch, Henrik Malchau (2005). The Well-Cemented Total Hip Arthroplasty: Theory and Practice . Springer Science & Business Media. p. 336. ISBN 978-3-540-24197-3.