Low back sprain: The sacroiliac syndrome

Abstract

D ISABILITY due to pain in the Iower back is being drawn to our attention more and more frequentIy. We see cases constantIy in Iarge orthopedic chnics, especiahy the type with involvement of the sacroiIiac joint and of traumatic origin. Interest in the Iatter cases has undoubtedly been stimuIated by their frequent appearance at Compensation Commission hearings. Even a casua1 survey of the Iiterature on sacroiIiac disease in the past five years reveaIs that it is becoming more and more recognized as a distinct syndrome. We shah here consider onIy the traumatic and relaxed types of sacroiliac syndromes. Many etiological factors enter into these low back disabiIities, varying from static strain on the ligaments due to constant standing with muscIes of the back relaxed, as with many young women, producing the sacroiliac reIaxation described by Baer, to the vioIent attempts to Itft heavy weights, producing the severe sacroiIiac subIuxations or arthritis and back strains of a different type. They vary from faIIs to obstetric Iabors. Many patients awake from an anesthetic to compIain bitterIy of pain in the Iower back after lying on a flat tabIe a protracted time. The number of wrenched backs occurring in wrestIing, footbaI1 and in the industries is Iegion. Before anything can be said concerning sacroiliac subIuxation or arthritis or syndrome, caI1 it what you wiI1, essential points in anatomy must be brought out for a clearer understanding of the mechanics of the disturbance. We are concerned here with a true diarthrodia1 joint (Figs. I and 2), in which the opposing surfaces are partIy in contact but, in the main, are separated by synovia1 fluid. This has been brought out by GoIdthwait, Albee, Roberts of EngIand and others. As the sacrum is broader in front than behind and above than beIow, the joint surface faces backward, outward and downward and is compIeteIy covered by the overhanging posterior superior spine of the iIium. The joint surfaces mesh like two oyster shelIs pIaced one within the other; especiahy is this so in the maIe. They are covered with cartilage, thicker on the sacral than on the iIiac side. The capsuIe of the synovia1 cavity is formed by the surrounding ligaments. Of these the most important structure, for it receives a11 the weight of the erect body above the peIvis, is the posterior sacroiIiac Iigament. It not only is the suspensory ligament of the body but the pivot ligament of the sacroiIiac joint itself. It pIays an important r6Ie in the mechanics of subluxation. It arises from the posterior superior spine of the iIium and runs forward to the sacrum, fanning out and fihing in the notch formed by the overhanging posterior superior spine of the iIium and the body of the sacrum. This ligament, especiaIIy the horizontal and main segment, forms one of the strongest fiber masses in the body. No amount of force has been abIe to tear it without fracturing the bony structures of its insertions. The upper part of the sacrum is, therefore, abso1uteIy prevented from moving forward. Two other Iigaments have an important bearing on the mechanism of sacroiliac syndrome. They are the greater and Iesser sacrosciatic Iigaments. The former is attached by a broad base to the posterior inferior spine of the ilium, to the fourth and fifth transverse tubercIes of thesacrum,