Radiology Corner – The Ischial Tuberosity

By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, Michael S. Barry, DC, DACBR, and Chad J. Maola, DC

The Ischial Tuberosity: Normal Variant or Pathology?

History

This young female presents with pain in the area of the ischial tuberosity following running hurdles for her track team. There is an unusual appearance of the ischial tuberosity. Do you recognize this abnormality?

Figure 1. What’s the abnormality?

Figure 1. What’s the abnormality?

Diagnosis

An avulsion of the secondary growth center (apophysis) for the ischial tuberosity is identified.

Ischial Tuberosity (Rider’s Bone) 

This type of fracture represents an avulsion of the secondary growth center (apophysis) for the ischial tuberosity as a result of a forceful contraction of the hamstring group of muscles. These can be acute or chronic injuries and are frequently bilateral.With healing, an unexplained overgrowth of the avulsed apophysis occurs, often leaving a wide radiolucent gap between the avulsed fragment and the parent ischium. This overgrowth may be the effect of hyperemia upon the ischial apophysis. Occasionally, the avulsed ischial apophysis may assume a size larger than the parent ischium. This large overgrowth can be confused with an osteochondroma. Usually, the patient’s history of a previous severe hamstring injury and the fact that the lesion is asymptomatic secures the proper diagnosis. Reduction in hip mobility is common and surgical intervention has not been encouraging.These fractures are seen most commonly in cheerleaders and hurdlers.Since chronic stress often produces this lesion in horseback riders the residual bony fragment has been called ‘Rider’s’ bone.

References

  1. Sundar M, Carty H. Avulsion of the pelvis in children: a report of 32 fractures and their outcomes. Skeletal Radiol 1994; 23:85.
  2. Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 2nd ed. Baltimore: Williams & Wilkins, 1996.

About the Authors

Dr. Terry R. Yochum is a second generation Chiropractor and a cum laude graduate of the National College of Chiropractic, where he subsequently completed his radiology specialty. He is a Diplomate of the American Chiropractic Board of Radiology and served as its vice-president and president for seven years (1983-1990).

Dr. Michael S. Barry is a 1988 cum laude graduate of Palmer College of Chiropractic. He completed a three-year radiology residency at Logan College of Chiropractic following two years of clinical practice in Las Vegas, Nevada. He received his diplomate in radiology from the American Chiropractic Board of Radiology in 1992.

Dr. Chad J. Maola is a 1999 magna cum laude graduate of National College of Chiropractic.

Drs. Yochum and Barry interpret and consult with clients regarding all aspects of diagnostic imaging, including plain film and advanced imaging procedures.