Effects of manipulations of oblique pulling on the biomechanics of the sacroiliac joint: a cadaveric study

BACKGROUND: There are many reports on the treatment of sacroiliac joint dysfunction by manipulation of oblique pulling (MOP). However, the specific mechanism of MOP on the sacroiliac joint remains unclear. This study aimed to investigate the effect of MOP on the biomechanics of the sacroiliac joint and the effect of the anterior sacroiliac ligament on the stability of the sacroiliac joint. METHODS: First, MOP-F1 (F: force) and MOP-F2 were applied to nine cadaveric pelvises. Then, segmental resection of the anterior sacroiliac ligament was performed. The range of motion of the sacroiliac joint was observed in all procedures. RESULTS: Under MOP-F1 and F2, the average total angles were 0.84° ± 0.59° and 1.52° ± 0.83°, and the displacements were 0.61 ± 0.21 mm and 0.98 ± 0.39 mm, respectively. Compared with MOP-F1, MOP-F2 caused greater rotation angles and displacements of the sacroiliac joint (p = 0.00 and p = 0.01, respectively). In addition, the rotation angles and displacements of the sacroiliac joint significantly increased after complete resection of the anterior sacroiliac ligament (p = 0.01 and p = 0.02, respectively). The increase was mainly due to the transection of the upper part of the anterior sacroiliac ligament. CONCLUSIONS: MOP-F2 caused greater rotation angles and displacements of the sacroiliac joint and was a more effective manipulation. The anterior sacroiliac ligament played an important role in maintaining the stability of the sacroiliac joint; the upper part of the anterior sacroiliac ligament contributed more to the stability of the joint than the lower part.