Volume 37 • Number 26 December 31, 2014 Systematic Approach to the Interpretation of Pelvis and Hip Radiographs: How to Avoid Common Diagnostic Errors Through a Checklist Approach MAJ Matthew Minor, MD, and COL (Ret) Liem T. Bui-Mansfi eld, MD After participating in this activity, the diagnostic radiologist will be better able to identify the anatomical landmarks of the pelvis and hip on radiography, and become familiar with a systematic approach to the radiographic interpretation of the hip and pelvis using a checklist approach. initial imaging examination for the evaluation of hip or CME Category: General Radiology Subcategory: Musculoskeletal pelvic pain should be radiography. In addition to the com- Modality: Radiography plex anatomy of the pelvis and hip, subtle imaging fi ndings often indicating signifi cant pathology can be challenging to the veteran radiologist and even more perplexing to the Key Words: Pelvis and Hip Anatomy, Radiographic Checklist novice radiologist given the paradigm shift in radiology residency education. Radiography of the pelvis and hip is a commonly ordered examination in daily clinical practice. Therefore, it is impor- tant for diagnostic radiologists to be profi cient with its inter- The initial imaging examination for the evaluation pretation. The objective of this article is to present a simple of hip or pelvic pain should be radiography. but thorough method for accurate radiographic evaluation of the pelvis and hip. With the advent of cross-sectional imaging, a shift in residency training from radiography to CT and MR imag- Systematic Approach to the Interpretation of Pelvis ing has occurred; and as a result, the art of radiographic and Hip Radiographs interpretation has suffered dramatically. However, the Common views of the pelvis and proximal femur include the AP projection of the pelvis, anterior and posterior 45-degree oblique (Judet) projections of the pelvis, AP pro- Dr. Minor is Radiology Resident, SAUSHEC, Fort Sam Houston, Texas; and Dr. Bui-Mansfi eld is Chief, Musculoskeletal Radiology Section, Department of jection of the hip, and frog-leg lateral or straight lateral (Dan Radiology, Brooke Army Medical Center, Fort Sam Houston, Texas, and Miller) projection of the hip. More specifi c views of the hip Associate Professor, Department of Radiology, Uniformed Services University and pelvis to include pelvic inlet and outlet (Ferguson) views of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814; E-mail: liem.mansfi [email protected]. may be obtained depending on the clinical presentation. Each The authors and all staff in a position to control the content of this CME activity projection has advantages for visualization of the complex and their spouses/life partners (if any) have disclosed that they have no relation- pelvic anatomy. For example, the posterior column of the ships with, or fi nancial interests in, any commercial organizations pertaining to pelvis is best visualized on the Judet view; the sacroiliac this educational activity. joints are best appreciated on the pelvic outlet view; and the The opinions and assertions contained herein are those of the authors and should not be construed as offi cial or as representing the opinions of the Department of anterior and posterior aspects of the femoral neck are best the Army, Department of the Air Force, or the Department of Defense. seen on the frog-leg lateral view.1-3 Lippincott Continuing Medical Education Institute, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Lippincott Continuing Medical Education Institute, Inc., designates this enduring material for a maximum of 2 AMA PRA Category 1 Credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity. To earn CME credit, you must read the CME article and complete the quiz and evaluation on the enclosed answer form, answering at least seven of the 10 quiz questions correctly. This continuing medical education activity expires on March 20, 2015. 1 CCDRv37n26.inddDRv37n26.indd 1 111/17/141/17/14 99:36:36 PPMM The proximal femur, which can be divided into the fem- oral head, femoral neck, trochanters, and femoral shaft, articulates with the pelvis at the acetabulum. Normal angu- lation of the femoral head is approximately 125 to 135 degrees with respect to the long axis of the femoral shaft, with approximately 25 to 30 degrees of anteversion.3 The femoral neck, composed of the subcapital, transcervical, and basicervical segments, has characteristic compressive (vertically oriented) and tensile (arc-shaped) trabeculae. The intertrochanteric line (anterior) and the intertrochanteric crest (posterior) mark the transition between the femoral neck and the shaft. From the fusion of the 3 pelvic bones and articulation of the femur with the pelvis, several distinct Figure 1. This AP view of the pelvis shows the Hilgenreiner (H, radiographic lines, rings, and arcs are formed and are essen- horizontal dashed line) and Perkins (P, perpendicular solid line) lines on the right. On the left, the pubis (blue), ischium (yellow), tial to the analysis of pelvic radiographs. Table 1 outlines and ilium (red) are shown. the basic checklist approach for the evaluation of pelvic and hip radiographs. The complex anatomy of the pelvis derives from the sym- In the absence of trauma, an avulsion injury metric fusion of 3 pelvic bones: the ilium, ischium, and pubis of the pelvis or proximal femur in an adult at the acetabulum (Figure 1). Initially, the 3 pelvic bones are should raise concern of an underlying bone connected by a Y-shaped growth plate, the triradiate cartilage, neoplasm. which fuses at approximately 14 to 16 years of age.4-6 Anteriorly, the right and left pubis, composed of a body and superior and inferior pubic rami, articulate at the pubic sym- On every pelvic radiograph, the white cortical margins or physis. Posteriorly, the body of the ilium articulates with the lines of the pelvis and femur should be closely scrutinized sacrum forming the sacroiliac joints, which are composed of for evidence of disruption. Loss of the white cortical line is a synovial component at the lower one third and a syndes- due most commonly to fracture, followed by neoplasm, infec- motic component at the upper two thirds of the joint. Key tion, and erosion from arthritis. An example of a fracture components of the ilium include the iliac crest and the ante- disrupting the cortical white line of the ilium is an isolated rior inferior and anterior superior iliac spines. The ischium, impaction fracture or Duverney fracture7 (Figure 2). In young which forms the posterior border of the acetabulum, also is athletic individuals, traumatic pelvic avulsion injuries will composed of a body and 2 rami. Spines arising from the result in disruption of the cortical white margin; however, it ischium and ilium form the greater and lesser sciatic notches should be noted that in the absence of trauma an avulsion posteriorly. The obturator foramen, which is anterior, is injury in an adult should raise concern for an underlying bone formed by the fusion of the superior and inferior pubic rami neoplasm.8 Similarly, the pelvic and obturator rings should and the inferior ischial ramus.5 be smooth and continuous. Disruption of the pelvic or obtu- rator ring requires 2 fractures or a fracture and dislocation, most frequently described by the hard pretzel analogy. Initially, the 3 pelvic bones are connected at the Therefore, whenever a radiologist detects a fracture in either acetabulum by the triradiate cartilage, which the pelvic or obturator ring, it is incumbent upon him or her fuses at approximately age 14 to 16 years. to search for a second fracture or a diastasis of either the sacroiliac joint or symphysis pubis. The continuing education activity in Contemporary Diagnostic Radiology is intended for radiologists. EDITOR: Robert E. Campbell, M.D., Clinical Professor of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Contemporary Diagnostic Radiology (ISSN 0149-9009) is published bi-weekly by Lippincott Williams & Wilkins, Inc., 16522 Hunters Green Parkway, Hagerstown, MD 21740-2116. Customer Service: Phone (800) 638-3030; FOUNDING EDITOR: William J. 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