Mark Reiley
Scientific Tracks Abstracts: Rheumatology & Orthopedics
I n the sacrum, congenital deformities span a huge gambit of problems including sacral agenesis all the way to complete sacralisation of L5. Therefore one would expect a large variation in the types of Sacral Deformities that can and do occur. The recently observed deformities of the sacrum may be described as being either deficiency of the anterior ala (which causes pain), posterior ala deficiency (which is likely to produce both pain and, an unstable joint with ?the knee giving way? symptoms), or both anterior and posterior deficiency which causes pain and instability. These deficiencies are particularly important when attempting to diagnose sacro-iliac pathology in the patient under 45, without a history of trauma, auto-immune disease, or spinal fusion. In patients with a pre-existing lumbar spine fusion, other radiologic findings appear to be diagnostic. A lumbar fusion increases the amount of shear force crossing the SI Joint. Since the sacrum (or rather the SI Joint) is responsible for controlling posterior shear forces to the pelvic ring, the increased demands on the joint begin to erode the posterior part of the joint, giving a sagittal alignment to the articulation. This situation is analogous and opposite to the chronologic changes observed in facets, which become sagittally aligned as the anterior shear forces deform them. In patients who have donated bone from the posterior ilium, all signs go out the window. Nearly 100% of the time, the SI Joint with a previous bone graft is the symptomatic site. All of these radiologic findings are demonstrated and discussed.
