Low back pain and sciatica symptoms can arise from a number of structures that comprise the lower back like the intervertebral disc, the facet joints, the muscles and tendon attachments, the ligaments that hold bone to bone, the hip, and the sacroiliac joint. Though several of these can generate pain simultaneously, the focus of this month will center on the sacroiliac joint.
The role of the sacroiliac joint is quite unique. It has a big job. It is the transition point between the flexible axial skeleton (our spine) and the pelvis. The pelvis supports the weight of the torso, which usually accounts for about two-thirds of our body weight. The sacroiliac joint is shaped at an oblique angle that diverges or opens at the front and converges inwards at the back of the joint in order to support the weight on top of it. Because the sacrum or tailbone is “V” shaped, it fits like a wedge and is held together with very strong ligaments, making it an inflexible but sturdy joint.
Making a diagnosis of sacroiliac joint syndrome or identifying it as a pain generator can be a challenge.
Since the sacroiliac joint is not a flat and smooth oblique joint, x-ray has many limitations. However, the pubic bone, which is located in the front of the pelvis, can be easily seen on x-ray. Because the pelvis is a ring-like structure, a pubic bone that is out of alignment may indicate sacroiliac joint dysfunction.
In a recent study, two independent orthopedic surgeons analyzed the x-rays of 20 consecutive patients – 17 women and 3 men. These patients have sacroiliac joint dysfunction and low back pain. These are confirmed by sacroiliac joint injection testing. In 18 of the 20 subjects, they found osteoarthritic degeneration and subluxation or misalignment.
To contrast the above result, they also looked at the pubic bone alignment on x-rays of 20 control subjects with no sacroiliac joint dysfunction or low back pain. The control group had 16 women and 4 men. They discovered that 7 or 35% had abnormal pubic bone findings. In contrast, 18 of 20 or 90% of the ones with sacroiliac joint dysfunction and low back pain mentioned above had abnormal pubic bone alignment.
A review of the patients’ past radiology reports found that only three reports mentioned this in the patients with sacroiliac joint dysfunction and low back pain group and none reported this in the control group.
The authors concluded that pubic bone alignment findings are underreported by radiologists, and because pubic bone alignment is much easier to read or assess than the sacroiliac joint dysfunction itself, it needs to be looked at.
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