A 13 year old male was brought to the emergency department after injuring his right hip at a soccer game. He was running down the field when he heard and felt a crack in his right hip. He was not struck by another player. He did not twist his hip. He was not kicking at the time. He clearly felt the crack before he fell to the ground.
He was unable to get up and since then, he has not been able to bear weight on his right leg. He denied any pain in his thigh or knee. He denied any tingling, numbness, or weakness distally. He had been complaining of pain in his right hip for the past two weeks, but he did not seek medical attention for this.
T37.0 (tympanic), P100, R20, BP 114/53, weight (by history) 105 kg (230 pounds).
He was very large for his age of 13 years. He was moderately obese and husky. He was comfortable lying down.
Head without signs of trauma. Neck full range of motion. Heart regular without murmurs. Lungs clear. Chest wall without signs of injury. Abdomen benign.
His right hip was very tender on palpation externally. Range of motion testing was not performed because the patient indicated that this would be very painful. There were no visible deformities or bruises. His thigh and knee were not tender. His neuromuscular function below the thigh was normal. Radiographs of his hips were obtained.
His history did not indicate the presence of a sudden impact severe enough to cause a fracture unless this was a pathological fracture. His obesity and age made the diagnosis of slipped capital femoral epiphysis a high likelihood.
In examining his radiographs, his femoral physis is nearly fused. There is no difference in the appearance of the right and left femoral growth plates. It does not appear that his radiographs are consistent with a slipped capital femoral epiphysis. This was very confusing at the time since the clinician was almost certain that the radiographs would confirm the diagnosis of slipped capital femoral epiphysis.
An orthopedic consultation was obtained since an occult slip of the capital femoral epiphysis was still suspected. The radiographs were interpreted as showing an avulsion fracture of the lateral aspect of the right acetabulum. This is visible as a very faint and indistinct bony fragment (there may actually be two fragments) just above the hip joint lateral and superior to the superior margin of the acetabulum. The following radiograph, points it out.
The black arrows point to the two fracture fragments. If you can’t see the black arrows, then you need to adjust the contrast on your monitor. This fracture probably occurred because of the extreme forces borne by the acetabulum. It is likely that his history of hip pain for the previous two weeks was the result of weakening of the acetabulum which finally resulted in a fracture.
Since this patient’s history and clinical appearance was a classic description of a patient with a slipped capital femoral epiphysis, this expectation clouded the physician’s ability to consider an alternative diagnosis. The radiographic characteristics of slipped capital femoral epiphysis are described in another case.
This case presents a good opportunity to review the anatomy of the bony pelvis. This knowledge is important when describing the location of abnormalities over the phone when discussing a patient with an orthopedic surgeon who is relying on your verbal description of the patient’s radiographs.
Identify the labeled structures in the radiograph of the pelvis.
A. Iliac crest
B. Sacroiliac joint
C. Femur head
E. Femoral capital physis
F. Obturator foramen
G. Pubic symphysis
H. Lumbosacral junction
I. Iliac fossa
J. Pubic ramus
K. Ischial tuberosity
L. Femur neck
M. Greater trochanter
N. Anterior superior iliac spine