The iliolumbar ligament: its influence on stability of the sacroiliac joint

STUDY DESIGN: In human specimens the influence of the iliolumbar ligament on sacroiliac joint stability was tested during incremental moments applied to the sacroiliac joints. OBJECTIVES: To assess whether the iliolumbar ligament is able to restrict sacroiliac joint mobility in embalmed cadavers. BACKGROUND: Firstly, the sacroiliac joint can play an important role in non-specific low back pain; hence, its mobility and stability are of special interest. Secondly, the iliolumbar ligament is considered to be an important source of chronic low back pain. Data on a functional relation between the iliolumbar ligament and sacroiliac joint mobility are lacking. METHODS: In 12 human specimens an incremental moment was applied to the sacroiliac joint to induce rotation in the sagittal plane. After the assessment of the relationship between rotation angle and moment in the intact situation, specific parts of the iliolumbar ligaments were transected. After each partial transection the measurements were repeated. RESULTS: Sacroiliac joint mobility in the sagittal plane was significantly increased after a total cut of both iliolumbar ligaments. This increase was in particular due to the transection of a specific part of the iliolumbar ligament, the ventral band. CONCLUSIONS: The main conclusions are: (a) the iliolumbar ligaments restrict sacroiliac joint sagittal mobility; (b) the ventral band of the iliolumbar ligament contributes most to this restriction. RELEVANCE: In embalmed human cadavers, the mobility of the sacroiliac joint increases after sequential cutting of specific parts of the iliolumbar ligaments. It can be expected that severance of this ligament during surgery will lead to increase of mobility and hence loss of stability of the sacroiliac joint. As a consequence adjacent structures will be affected. This may well be a cause of pain in patients with failed back surgery.