Iliolumbar Ligament
Anatomy of the Iliolumbar Ligaments
The iliolumbar ligament is generally documented as being split into anterior and posterior bands extending from the L5 transverse process to the ilium (Rucco et al 1996).
However Kelihues et al (2001) found in only three out of thirty cadavers was the ligament made up of clearly identifiable bands. In a majority of cases, the ligament appeared as a spreading, connective tissue complex, which could be differentiated into two (9/30), three (14/30) or four (4/30) main bands.
Sandwiched between the iliopsoas anteriorly and quadratus lumborum posteriorly the iliolumbar ligaments blends with the posterior retinaculum sheet (Willard et al 2012) and the anterior sacroiliac ligaments (Vleeming et al 2012).
Back to the traditional description Rucco et al (1996) found that whilst the iliolumbar ligament splits into anterior and posterior bands they both extend from the L5 transverse process, with some fibres blending with the intertransverse ligaments of L4-5 and L5-S1 and L4-L5 and insert on to the anterior part of the iliac tuberosity (Pool-Goudzwaard et al 2001).
The iliolumbar ligament is split into the anterior and posterior bands:
Anterior band: the whole anteroinferior border of the L5 transverse process is covered by a well-developed ligamentous band that constitute the anterior band of the iliolumbar ligament. It is broad and flat and extends from the anterocaudal L5 transverse process and sometimes the caudal aspect of the endplate of the vertebral body of L5, and extends to the anterocranial part of the iliac tuberosity below the posterior band (Basadonna et al 1996). It has two types (Rucco et al 1996):
(i). Originates from the anterior aspect of the inferolateral portion of the L5 transverse process and fans out widely before inserting on the anterior portion of the iliac tuberosity (Rucco et al 1996).
(ii). Originates anteriorly, laterally, and posteriorly from inferolateral aspect of the L5 transverse process and fans out before inserting on the anterior portion of the iliac tuberosity (Rucco et al 1996).
The anterior band also has connections to the anterior sacroiliac ligament:
(i). Originates from the anterolateral aspect of the L5 vertebral body and anteromedial part of the L5 transverse processes and inserts on to the most anterolateral part of the base of the sacrum, near the sacroiliac joint. These fibres blend with the anterior sacroiliac ligaments (Pool-Goudzwaard et al 2001).
(ii). Sacroiliac part of the iliolumbar ligament: originates from the cranial surface of the ala of the sacrum, directly caudal to the L5 transverse process, merging with the thin L5-S1 intertransverse ligament and inserts at the anteromedial part of the iliac tuberosity, together with the anterior bands of the iliolumbar ligament, and blends with the interosseous sacroiliac ligaments (Pool-Goudzwaard et al 2001).
Vertical bands of the anterior fibers can extend from the anteroinferior boarder of the L5 transverse process over the anterior sacroiliac ligaments to the upper and posterior parts of the iliac fossa inserting vertically into the posterior end of the iliopectineal line (Albatati et al 2022).
Posterior band: the posterior band of the iliolumbar ligament is thinner than the anterior section. It originates from the apex of the L5 transverse process and inserts on the iliac crest above the anterior band (Basadonna et al 1996), below the medial part of the origin of the quadratus lumborum, medial part of the iliac crest, and to the deep anterior layer of the thoracolumbar fascia (quadratus lumborum fascia) (Pool-Goudzwaard et al 2001).
Rucco et al (1996) found in the coronal plane, the spatial disposition of the iliolumbar ligament varies greatly with the size of the L5 vertebra and its position in the pelvis:
(i). When L5 is situated low in the pelvis, the bands of the iliolumbar ligament are longer and oblique.
(ii). When L5 is situated high in the pelvis, the bands of the iliolumbar ligament are shorter and horizontal.
Anatomical variations
More uncommon variations in the attachment of the iliolumbar ligament are mainly on its vertebral attachments. These include (Kelihues et al (2001):
Lateral surface of the L5 vertebral body.
Lateral surface of the L4 vertebral body and transverse process.
Lateral surface of the L3 vertebral body and transverse process.
Lateral surface of the S1 body.
Muscular and fascial attachments to the iliolumbar ligament
The muscular and fascial attachments to the iliolumbar ligament are:
Quadratus lumborum: Barker et al (2007) found the quadratus lumborum divided into a superficial and deep layer. The superficial layer descends almost vertically from rib 12 with tendons attaching to the superolateral corner of each transverse process. The deep layer is oblique originating from the iliac crest and ascending superomedially to insert to the inferolateral corner of each transverse process. This is in contrast to Tanaka et al (2022) who described the superficial layer ascending from the iliac crest to the L1-4 transverse processes; the middle layer as originating from the L1-L4 transverse processes and inserting on rib 12; and the deep layer extending from the iliac crest to rib 12. These different fascicles function differently with the transverse process attachments extending and ipsilateral sidebending the spine (Parker et al 2013) and stabilising the spine, (more so than the psoas), especially during flexion (Tanaka et al 2022) and the rib 12 attachments just responsible for ipsilateral sidebending, but may also stabilise the attachment of the diaphragm at rib 12 (Park et al 2013). The most medial muscle fibres of quadratus lumborum, mainly deriving from L4 and L5, attach to the most lateral part of the posterior bands of the iliolumbar ligament (Pool-Goudzwaard et al 2000). Whilst situated largley posteriorly to the iliolumbar ligament fibers from the quadratus lumborum can be sandwiched between the anterior and posterior portions of the iliolumbar ligament (Albatati et al 2022).
Iliocostalis lumborum: this muscle consists of four fascicles that arise from the L1-L4 transverse processes, ribs 4-12, and the middle layer of the thoracolumbar fascia adjacent to the respective transverse processes. Gilchrist et al (2003) found the iliocostalis lumborum lacks fascicle attachment to the L5 transverse process and is represented in the iliolumbar ligament posteriorly.
Deepest layer of the thoracolumbar fascia that encloses the base of the quadratus lumborum forms the superior portion of the iliolumbar ligament (Albatati et al 2022). It forms a fibrous connection between the L4 and L5 transverse process (and intertransverse ligament), iliolumbar ligament (or its insertion on the iliac crest) and sacroiliac joint capsule (Dąbrowski & Ciszek 2023).
Iliacus: the most medial fibers of the iliacus blend with the caudal part of the anterior bands of the iliolumbar ligament (Pool-Goudzwaard et al 2001).
Biomechanics of the Iliolumbar ligament
Viehofer et al (2015) found fibrocartilaginous connective tissue between the iliolumbar ligament and its bony attachment. This suggests the insertion sites of the ligament are subject to both tensile and compressive loading. This is probably because of the insertional angle changes between the ligament and bone during loading. This supports the suggestion that the iliolumbar ligament might play an important role in the stabilisation of the lumbosacral junction.
Pool-Goudzwaard et (2003) concluded the iliolumbar ligaments restrict sacroiliac joint sagittal mobility (they didn't specify nutation or counternutation) and it's the anterior band of the iliolumbar ligament that mainly contributes to this restriction.
Sims and Moorman (1996) found the iliolumbar ligament the greatest resister of sacral flexion (nutation) although no reference was cited in their study. Snijders et al (2008) found contrary to this finding the iliolumbar ligament stretched in counternutation of the pelvis and flexion of the lumbar spine (and Miyasaka et al 2000).
The anterior band restricts lateral tilting of the pelvis and sacroiliac joint movement while the posterior band restricts flexion preventing L5 vertebrae from slipping over the sacrum (Wang et al 2018).
Yamamoto et al (1990) found the iliolumbar ligament resists lumbar spine movement predominately in contralateral lateral bending, then flexion (& Miyasaka et al 2000, Snijders et al 2000), then extension and lastly contralateral axial rotation. Bilaterally the iliolumbar ligament provides significant restriction to flexion and extension while a unilateral iliolumbar ligament does not.
Innervation of the Iliolumbar ligament
There is no direct innervation for the iliolumbar ligament (Wang et al 2018) but the iliolumbar ligament is richly innervated (Kiter et al 2010) as is the fat anterior and posterior to the ligament, as well as that lodged in the ligament (Wang et al 2018). This suggests the iliolumbar ligament has an important proprioceptive coordination role in the lumbosacral region and can be a source of pain.
Palpation of the Iliolumbar ligament
Maigne and Maigne (1991) claimed the iliolumbar ligament was inaccessible to palpation. They found the insertion of the iliolumbar ligament to the pelvis was shielded by the iliac crest. They believed the area tender to palpation was in fact the dorsal rami of the L1 or L2 nerve roots not the iliolumbar ligament attachment. These nerves cross the iliac crest 7 cm from the midline as they course through the fibroosseous tunnel.
However other authors such as Harmon and Alexiev (2011), Sipko et al (2010) and Rucco et al (1996) found painful palpation of the iliolumbar ligament at the iliac crest indicative of iliolumbar ligament pathology.
Iliolumbar ligament injury
It has been hypothesized that at least 50% of low back pain is due to abnormalities of the iliolumbar ligaments. However, the fat anterior and posterior to the iliolumbar ligament is innervated and some have argued that the fat could serve as a mechano-sensory organ that conducts neural information (including proprioception), rather than the iliolumbar ligament itself. iliolumbar ligament pain could actually originate from the nervous tissue within the fat cells that are lodged inside the ligament instead of nervous tissue in the ligament itself (Wang et al 2018).
Posterior bands of the iliolumbar ligament are more prone to injury due to their weaker structure (Basadonna et al 1996 and Rucco et al 1996).
Sims and Moorman (1996) identified the iliolumbar ligament as the weakest component of the multifidus triangle which along with its angulated attachment they hypothesised lends it prone to injury.
Interestingly it is the insertional angle that changes during loading that Viehofer et al (2015) found subjected the ligament to both tensile and compressive loading.
Snijders (2004, 2008) found slouching to elongate and place excessive strain on the iliolumbar ligament.
Symptoms include chronic low back pain, with a sensitivity around the PSIS aggravated by standing or sitting upright for long periods of time and ipsilateral hip extension (Wang et al 2018).
References
Iliolumbar ligament insertions. In vivo anatomic study (1996). Basadonna PT, Gasparini D, Rucco V.
Anatomy of the iliolumbar ligament: a review of its anatomy and a magnetic resonance study. (1996). Rucco V, Basadonna PT, Gasparini D.
The molecular composition of the extracellular matrix of the human iliolumbar ligament. (2015). Viehöfer AF, Shinohara Y, Sprecher CM, Boszczyk BM, Buettner A, Benjamin M, Milz S.
Immunohistochemical demonstration of nerve endings in iliolumbar ligament. (2010). Kiter E, Karaboyun T, Tufan AC, Acar K.
The occurrence of strain symptoms in the lumbosacral region and pelvis during pregnancy and after childbirth. (2010). Sipko T, Grygier D, Barczyk K, Eliasz G.
The iliolumbar ligament: its influence on stability of the sacroiliac joint. (2003). Pool-Goudzwaard A, Hoek van Dijke G, Mulder P, Spoor C, Snijders C, Stoeckart R.
Trigger point of the posterior iliac crest: painful iliolumbar ligament insertion or cutaneous dorsal ramus pain? An anatomic study. (1991). Maigne JY, Maigne R.
The role of the iliolumbar ligament in the lumbosacral junction. (1990). Yamamoto I, Panjabi MM, Oxland TR, Crisco JJ.
Description of the iliolumbar ligament for computer-assisted reconstruction. (2010). Hammer N, Steinke H, Böhme J, Stadler J, Josten C, Spanel-Borowski K.
Sonoanatomy and Injection Technique of the Iliolumbar Ligament (2011) Harmon D and. Alexiev V
The role of the iliolumbar ligament in low back pain. (1996). Sims JA, Moorman SJ.
The influence of slouching and lumbar support on iliolumbar ligaments, intervertebral discs and sacroiliac joints. (2004). Snijders CJ, Hermans PF, Niesing R, Spoor CW, Stoeckart R.
Radiographic analysis of lumbar motion in relation to lumbosacral stability. Investigation of moderate and maximum motion. (2000). Miyasaka K, Ohmori K, Suzuki K, Inoue H
Topographic relations between the neural and ligamentous structures of the lumbosacral junction: in-vitro investigation (2001). H. Kleihues, S. Albrecht, and W. Noack
The thoracolumbar fascia: anatomy, function and clinical considerations (2012). F H Willard, A Vleeming, M D Schuenke, L Danneels, and R Schleip
The sacroiliac joint: an overview of its anatomy, function and potential clinical implications. Vleeming A, Schuenke MD, Masi AT, Carreiro JE, Danneels L, Willard FH.
The sacroiliac part of the iliolumbar ligament (2000) A. L. POOL-GOUDZWAARD, G. J. KLEINRENSINK , C. J. SNIJDERS , C. ENTIUS AND R. STOECKART
The middle layer of lumbar fascia and attachments to lumbar transverse processes: implications for segmental control and fracture (2007). Priscilla J. Barker, Donna M. Urquhart, Ian H. Story, Marius Fahrer, and Christopher A. Briggs
Muscular Control of the Lumbar Spine (2003). Russell V. Gilchrist, Michael E. Frey and Scott F. Nadler.
The Iliolumbar Ligament Does Not Have a Direct Nerve Supply (2018). Wang J, Kirkpatrick C, Loukas M
Tanaka K, Funasaki H, Kubota D, Murayama Y, Saito M, Iguchi Y. (2022). Quadratus lumborum muscle strain in a youth soccer player: a case report
Albatati AS, Khalifa AFM, El-Sherbiny M, Alfayez MA, Abualmakarim S, Ebrahim HA, Aljahdali AR, Darwish H. (2022). Deferent Anatomical Presentations of Iliolumbar Ligament: A Cadaveric Study
Dąbrowski K & Ciszek B. (2023). Anatomy and morphology of iliolumbar ligament
