Elsevier

Clinical Biomechanics

Volume 18, Issue 2, February 2003, Pages 99-105
Clinical Biomechanics

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

https://doi.org/10.1016/S0268-0033(02)00179-1Get rights and content

Abstract

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.

Objective. 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.

Introduction

In the majority of cases low back pain (LBP) manifests itself in the lower lumbar region, with pain radiating to the iliac crest, into the buttocks or even the leg. Therefore, most studies on the etiology of LBP focus on the mechanical behaviour of the lumbosacral area and specifically on the intervertebral discs (Adams and Hutton, 1982; Nachemson, 1981; Keller et al., 1990; Brinckman, 1986). However, modern imaging techniques have shown that spinal abnormalities such as disk herniation are common in persons without back pain (Riihimaki, 1991). Furthermore, in the majority of LBP patients, only rarely a specific cause can be identified (Waddell, 1987). For these LBP patients the expression non specific LBP is used (Waddell, 1987).

Recently, several anatomical, biomechanical and neurophysiological studies on the lumbopelvic region have supported the view that loss of stability of the sacroiliac joints (SIJ) can be crucial in the aetiology of non specific LBP (Vleeming et al., 1996; Richardson et al., 2002; Pool-Goudzwaard et al., 1998). Main conclusions from these studies are: (a) in all loading conditions muscle forces are necessary for lumbosacral stability (Snijders et al., 1997, Snijders et al., 1993a, Snijders et al., 1993b); (b) mechanoreceptors in the massive ligamentous system of the lumbosacral area are important for the activation of muscles for posture control (Richardson et al., 2002; Indahl et al., 1999; Hides et al., 1994; Jull and Richardson, 1999; Richardson and Jull, 1995) and (c) ligaments that restrict the range of motion of the SIJ play an important role in the stability of the SIJ (Vleeming et al., 1996; Wingerden et al., 1993; Vleeming et al., 1989).

Stability can be interpreted in multiple ways. In this study we define stability as the ability of a joint to bear loading without uncontrolled displacements. Stability depends on the relative positions of the respective bones: in certain positions the joint can bear loading, in others it cannot. Uncontrolled displacements will allow the joint to adopt positions in which the joint cannot bear loading. Ligaments contribute to stability by controlling the relative positions of the joint, restricting the mobility of the joint to those positions in which the joint can bear loading. Hence, the ligaments contribute to stability by restriction of mobility.

To assess the contribution of the ligamentous system to stability of the SIJ, all relevant ligaments in the lumbosacral area have to be taken into consideration. Surprisingly, the function of one of the major ligaments in this region, the iliolumbar ligament (IL), is poorly understood. Several authors describe its influence on flexion–extension, lateroflexion in the L5-S1 facet joint and torsional stability of the L5-S1 facet joint (Yamamoto et al., 1990; Leong et al., 1987; Yamamoto et al., 1989; Chow et al., 1989). However, no study exists in relation to the mechanics of the SIJ. This is remarkable since the IL actually crosses the SIJ (Pool-Goudzwaard et al., 2001).

Knowledge of the function of the IL is of special interest since the assumption has been made that the IL is the primary cause of many cases of LBP (Sims and Moorman, 1996; Naeim et al., 1982; Broudeur et al., 1982; Broadhurst, 1989).

In the present study we analyse whether the IL is able to contribute to SIJ stability by restricting SIJ mobility.

Section snippets

Methods

In this study we consider an increase of SIJ mobility after sectioning the IL, as evidence that the IL is able to restrict SIJ mobility. To test the SIJ mobility we applied different moments of force to the SIJ and measured the amount of rotation in the sagittal plane. The relation between SIJ rotation and load is shown in Fig. 1 (thick S-curve). After sectioning of the IL the same moments of force have been applied to the SIJ. We hypothesize that section of the IL results in a steeper S-curve,

Results

Comparing the data of the intact specimens with those after a total cut of both ILs, the paired t-test showed a significantly steeper slope (P=0.021) of the load deformation curves after the total cut (Table 1). The mean increase of the normalised values in specimens with the IL totally cut was 28.1%. Also after transection of exclusively the ventral bands of the ILs, the paired samples t-test showed a significantly steeper slope (P=0.002) (Table 1). Transection of both dorsal bands as well as

Discussion

A significant increase of SIJ mobility in the sagittal plane occurs after a total cut of both ILs, as shown by the significantly steeper slope of the load deformation curves. This increase in SIJ mobility was not due to changes over time since four subsequent tests in intact specimens without transection did not show significant changes. Obviously, the IL restricts SIJ mobility in the sagittal plane (nutation and counternutation). This finding does expand the biomechanical functions of the IL

Conclusions

Based on this study we conclude the following:

  • 1.

    the ILs restrict sagittal SIJ mobility,

  • 2.

    especially the ventral band of the IL contributes to this restriction,

  • 3.

    no important role restricting sagittal SI joint mobility could be attributed to the sacroiliac part and the dorsal band of the IL.

Acknowledgements

The authors would like to thank the “Vereniging Trustfonds Erasmus Universiteit” for their financial support. The authors would like to thank J. Velkers and C. Entius for their effort, and J. Twisk for his advice.

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