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Can you please explain "islands of ossification in the posterior acetabulum" to me? I'm reading the MRI report on my 10-year-old son's hip. He has been complaining of pain for months and we finally decided it wasn't just "growing pains." Now I see he has islands of ossification. Could that be causing the pain?
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Hip pain in growing children isn't always from "growing pains." Children and young teens active in sports training and competition who have not yet completed their growth often develop hip pain. The bones are not fully formed yet.
Formation of the bone in the posterior (back wall) of the acetabulum (hip socket) is important because this portion of the hip socket is located at the juncture where three other bones meet (the ilium, the ischium, and the pubis). The pattern of development of the posterior acetabulum depends on the coordination and timing of development of these three bones as well.
The posterior (back) wall of the hip socket (acetabulum) develops in four distinct phases. At first (in the young child before age eight), the acetabulum is made up of 100 per cent cartilage. Around age eight or nine, the cartilage starts to turn to bone. That process is called ossification. MRI images showed a cobblestone formation with islands of bone ringed by areas of cartilage. This is the "islands of ossification" the radiologist observed and commented on in the report. It tells the surgeon (or other physician reading the report) what phase of bone formation and development your son is in.
By age 12 or 13, the three bones (ilium, ischium, pubis) that join together to form the acetabulum have met together and fused. At this point, there is still a rim of bone forming (ossification) around the upper back (posterior) portion of the acetabulum. This is referred to as the posterior rim sign. The final step is closure of the cartilage between the three bones called the triradiate cartilage. This last phase occurs in girls by age 12 and in boys by age 14.
MRI studies have made it clear that the posterior aspect of the acetabulum (hip socket) develops and progresses in an orderly fashion. It goes from cartilage to bone more slowly (and after) the same process takes place in the front (anterior) portion of the socket. But it is a predictable series of four phases. Boys tend to complete this ossification process later than girls (one to one and a half years later).
If a surgeon needs to know the shape and developmental phase of the acetabulum before that final phase (before closure of the triradiate cartilage), then an MRI (not X-rays or CT scans) will be needed. Children younger than eight won't need an MRI since it is known the socket is all cartilage. Children between nine and 14 must be evaluated on an individual basis keeping their gender in mind (remember, girls complete the fusion process at a younger age than boys).
Using only X-rays during phases two and three (ossification and fusion but before closure of the cartilage) can lead to problems. There can be false positives for femoral anteversion (twist in the angle at the top of the femur or thigh bone) and false negatives for damage to the posterior wall of the acetabulum from acute traumatic injury. Misjudging either of these signs can cause delays in diagnosis and treatment for these children.
Ask your physician to explain the MRIs and the written results to you. The observation of islands of ossification is a normal finding at this age. There may be other information contained within that report of interest in diagnosing your son's hip pain.
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*Disclaimer:*The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic. |
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