I had a recent pelvic MRI done which successfully ruled out endometrial cancer, so I took the opportunity to look at the images of my pelvic joints to see what kind of shape they were in. When I examined the coronal view of the L5-S1 joint (where the lumbar spine meets the sacrum) I discovered this intriguing scene:
I’ve never viewed a pelvic MRI before, but I could clearly see that the left sacral ala had a crooked split in it (black arrow) starting at L5/S1 and moving all the way across to the sacroiliac joint. The right side was one continuous chunk of bone with no split. I think the reasonable person would be curious about such an anomaly, so I sought out the advice of an orthopedic doctor.
I never knew that a doctor’s office could take on the proportions of a multilevel airport terminal. Dozens of doctors and hundreds of patients filed through the place each day. The doctor they assigned me to was fresh out of med school and looked younger than my 25-year-old daughter. I told her of my history of EDS, hypermobility type and separation of the pubic symphysis during childbirth. She took one look at the MRI image above and then said, “I don’t know what that is, but don’t worry about it.” She went on to say that she does not read MRI’s. She reads x-rays. After taking a pelvic x-ray, She concluded that it’s my ligament laxity I need to be concerned with, not my bones.
Clearly unimpressed, I took matters into my own hands and did my own research. The closest thing in Internet Land I could find is a Castellvi type IV lumbosacral transitional vertebra (LSTV). Type IV is enlarged transverse processes of L5 that fuse with the sacrum on one side and articulate on the other.
I learned that anywhere from 4-30% of the population has some form of LSTV and that, for the most part, it really is nothing to be concerned about. The type IV that mine looks like is less common and is correlated with lower back pain and higher incidence of L4/L5 disc degeneration.
That crooked crease in the sacral ala is an “anomalous articulation,” and it can cause pain (which I’ve had on and off for years, once bad enough to send me to the ER). When I saw a picture of a flouroscope guided needle into an anomalous articulation to inject anesthetic/steroids to relieve pain, I decided that my lower back pain was not significant enough to warrant that kind of treatment just yet.
My, oh, my… The wonders of modern medicine never cease to entertain and enlighten me…