Anatomy of the iliolumbar ligament: a review of its anatomy and a magnetic resonance study

Deferent Anatomical Presentations of Iliolumbar Ligament: A Cadaveric Study

This work was carried out to describe the detailed gross anatomy of the iliolumbar ligaments in human cadavers and to shed more light on these disputes regarding the configuration and direction of these ligaments. Twenty partially dissected human formalin-preserved cadavers originating from North America and Europe were investigated in this study. Blunt dissection was made through the ventral and dorsal aspects of the pelvic area of the cadavers. According to the current study, the anterior and posterior portions of the iliolumbar ligament most frequently attached to the 5th lumbar vertebra’s transverse process (70% and 80%, respectively). The body of the 4th lumbar vertebra with the 5th lumbar vertebra’ transverse process was the attachment of the anterior part (30%). The attachment of the posterior part was the body of the 5th lumbar vertebra (20%). The anterior and posterior parts of the iliolumbar ligament were inserted into the anterior tip of the iliac crest. There is an obvious variation in the morphological appearance of the iliolumbar ligament distinguished in attachments, length, width, thickness, number of bands, and the presence of accessory bands in the anterior part of the ligament. In addition, a new attachment for the anterior band was revealed in one-third of the specimens (body of the 4th lumbar vertebra) which have not been described before. Also, in one-fifth of the specimens, there was a new attachment for the posterior band (body of the 5th lumbar vertebra).

Evaluation of facet joints and segmental motion in patients with different grades of L5/S1 intervertebral disc degeneration: a kinematic MRI study

PURPOSE

This study aimed to evaluate facet joint parameters and osteoarthritis grades, and segmental angular and translational motions among different grades of L5/S1 intervertebral disc (IVD) degeneration.

METHODS

This retrospective study analysed kinematic magnetic resonance imaging (kMRI) images of the lumbar spine of 214 patients with low back pain. Degenerations of the L5/S1 IVDs and facet joints osteoarthritis were assessed using the Pfirrmann and Pathria grading scales, respectively. Facet joint parameters included facet joint angle and facet joint space width. Angular and translation segmental motions were measured using MRI Analyzer software.

RESULTS

The mean age of the studied patients was 44.1 ± 13.9 years. Patients with L5/S1 disc degeneration were associated with higher odds of facet joint osteoarthritis (odds ratio = 2.28, 95% confidence interval = 1.23-4.23, P = 0.008). There was a positive correlation between L5/S1 disc degeneration grade and the facet joint grade (r = 0.365, P > 0.001). Grade IV facet joint osteoarthritis did not appear in grades I or II disc degeneration (P > 0.001). The average facet joint width decreased significantly with increasing Pfirrmann grading (P = 0.017). The difference in facet joint angle between groups was not statistically significant (P = 0.532). The differences in the angular and translational motions were not statistically significant (P = 0.530, and 0.510, respectively).

CONCLUSION

A positive correlation exists between L5/S1 disc degeneration and facet joint osteoarthritis grades. The facet joint space width decreases significantly with increasing grade of disc degeneration.

Prevalence of Lumbosacral Transitional Vertebra in Individuals with Low Back Pain: Evaluation Using Plain Radiography and Magnetic Resonance Imaging

Study Design

Descriptive cross-sectional study.

Purpose

To determine the frequency of lumbosacral transitional vertebrae (LSTV) in patients with low back pain (LBP) and the role of iliolumbar ligament (ILL) origin from L5 in LSTV cases.

Overview of Literature

Transitional vertebrae are developmental variants of the spine. LSTV is a common congenital abnormality, and failure to recognize this anomaly may result in serious consequences during surgery.

Methods

All patients aged 11–90 years of either gender with LBP for any duration, who presented for X-ray and magnetic resonance imaging (MRI) of the lumbosacral spine, were included. X-rays of the lumbosacral spine in anteroposterior and lateral views were acquired. In addition, T1- and T2-weighted sagittal and axial MRI was performed. Images were evaluated on a workstation.

Results

Of 504 patients, transitional vertebrae were observed in 75 patients (15%). Among them, 39 (52%) patients had Castellvi type III and 36 (48%) patients had Castellvi type II. However, on MRI, 42 (56%) patients had O'Driscoll type II, 18 (24%) patients had O'Driscoll type IV, and 15 patients (20%) had O'Driscoll type III. ILL origin from L5 was significantly higher (n=429, 100%) among patients with a normal lumbosacral junction than among patients with a transitional lumbosacral junction (n=22, 29.3%) (p<0.001).

Conclusions

LSTV occurs at a high frequency in patients with LBP. Furthermore, in the presence of LSTV, the ILL is not a reliable marker for the identification of L5.

The molecular composition of the extracellular matrix of the human iliolumbar ligament

BACKGROUND CONTEXT

The human iliolumbar ligament connects the transverse process of L5 to the iliac crest and contributes to lumbosacral stability and has been associated with low back pain. However, different opinions exist regarding the functional relevance of the ligament.

PURPOSE

In the present study, we analyze the regional molecular composition of the ligament extracellular matrix.

STUDY DESIGN

Special attention is given to the attachment sites, to determine whether the ligament is subjected to a certain mechanical environment.

METHODS

Iliolumbar ligament samples, extending from one enthesis to the other, were removed from 11 cadavers and fixed in methanol. Cryosections were immunolabeled with a panel of antibodies directed against collagens, glycosaminoglycans, proteoglycans, matrix proteins, and neurofilament.

RESULTS

The mid-substance of the ligament labeled for all the molecules normally found in dense fibrous connective tissue including types I, III, and VI collagen, versican, dermatan -, chondroitin 4 -, and keratan sulfate. However, both entheses were fibrocartilaginous and labeled for type II collagen, aggrecan, and chondroitin 6- sulfate. A common feature was fat between the fiber bundles near the entheses. Occasionally this fat contained nerve fibers.

CONCLUSIONS

The existence of fibrocartilaginous entheses suggests that the insertion sites of the ligament are subject to both tensile and compressive loading-probably because of insertional angle changes between ligament and bone during loading. Our findings support the suggestion that the iliolumbar ligament might play an important role in the stabilization of the lumbosacral junction.

Is the iliolumbar ligament a reliable identifier of the L5 vertebra in lumbosacral transitional anomalies?

OBJECTIVE

Sufficiently sized studies to determine the value of the iliolumbar ligament (ILL) as an identifier of the L5 vertebra in cases of a lumbosacral transitional vertebra (LSTV) are lacking.

METHODS

Seventy-one of 770 patients with LSTV (case group) and 62 of 611 subjects without LSTV with confirmed L5 level were included. Two independent radiologists using coronal MR images documented the level(s) of origin of the ILL. The interobserver agreement was analysed using weighted kappa/kappa (wκ/κ) and a Fischer's exact test to assess the value of the ILL as an identifier of the L5 vertebra.

RESULTS

The ILL identified the L5 vertebra by originating solely from L5 in 95 % of the controls; additional origins were observed in 5 %. In the case group, the ILL was able to identify the L5 vertebra by originating solely from L5 in 25-38 %. Partial origin from L5, including origins from other vertebra was observed in 39-59 % and no origin from L5 at all in 15-23 % (wκ = 0.69). Both readers agreed that an ILL was always present and its origin always involved the last lumbar vertebra.

CONCLUSION

The level of the origin of the ILL is unreliable for identification of the L5 vertebra in the setting of an LSTV or segmentation anomalies.

KEY POINTS

• The origin of the ILL is evaluated in subjects with an LSTV. • The origin of the ILL is anatomically highly variable in LSTV. • The ILL is not a reliable landmark of the L5 vertebra in LSTV.

Osseous and ligamentous scaphoid anatomy: Part II. Evaluation of ligament morphology using three-dimensional anatomical imaging

PURPOSE

There are many controversies in the literature regarding the morphology of the scaphoid ligaments. The aim of this study was to provide a more accurate description by quantitatively describing the 3-dimensional, geometrical aspects of the scaphoid ligaments and their attachments, using cryomicrotome images of cadaveric wrists.

METHODS

Eight fresh-frozen human cadaver wrists were examined with computed tomography (CT) and an imaging cryomicrotome. A series of 2-dimensional cryoimages created a 3-dimensional anatomical data set of each test specimen. Detection of ligaments and their surface areas was performed by manually marking the course and attachment points for each ligament, using dedicated visualization software. The 3-dimensional bone surfaces were segmented from the acquired CT images and incorporated in the 3-dimensional anatomical data set of the same anatomical specimen to facilitate the detection procedure. The results of the morphological parameters and attachment areas of the scaphoid ligaments are described 3-dimensionally.

RESULTS

The mean size of the whole scaphoid surface was 1503 ± 17 mm(2), and the mean size of all ligament attachments on the scaphoid was 131 ± 14 mm(2); thus, ligament attachments consist of 9% ± 0.9% of the total scaphoid surface area. Based on the data, a 3-dimensional representation of the wrist was created to present the scaphoid ligament attachment areas and paths. The dorsal intercarpal ligament had the most individual variability between specimens in attachments.

CONCLUSIONS

The quantitative results were almost completely consistent with the findings of previous reports. The only inconsistency in ligament morphology regarded the scaphocapitate ligament, which in this study was found to be the thickest ligament attached to the scaphoid.

CLINICAL RELEVANCE

The results of this study improve our knowledge of scaphoid ligament anatomy, as they corroborate previous findings. This is important for carpal surgery and will pave the way to a better understanding of the biomechanics involved in destabilization of wrist fractures.

Osseous and ligamentous scaphoid anatomy: Part I. A systematic literature review highlighting controversies

PURPOSE

The interpretation of scaphoid anatomy and kinematics is confusing and controversial. This results from a lack of consensus on the anatomy of the ligaments attaching to the scaphoid and an overwhelming variety of substantially different anatomic descriptions and classification systems of the wrist joint in the literature. The present study systemically reviews the consistencies or inconsistencies of the various scaphoid ligament descriptions and aims to clarify and unify different concepts and classification systems.

METHODS

We performed a systematic search of the medical literature from 1950 to 2010. We included all descriptive reports of the anatomy or morphology of the scaphoid, ligaments, or both. With the aim to describe the best available evidence, we considered all anatomical descriptions but emphasized a selection of the most frequently cited articles.

RESULTS

The literature search resulted in 555 potentially eligible descriptive reports, 58 of which met the inclusion criteria and were included in the review. Variations in the anatomic descriptions appear to be mostly due to the difficulty of identifying individual interdigitating ligaments or bundles by macroscopic dissections, as well as the interindividual variability in ligament anatomy. The most important areas of controversy in the scaphoid ligament attachments include the radial collateral ligament, dorsal radiocarpal ligament, dorsal intercarpal ligament, volar scaphotriquetral ligament, and scaphotrapezium-trapezoid ligament.

CONCLUSIONS

None of the scaphoid ligaments other than the scaphocapitate ligament have been described consistently. Future research is required to verify the ligament attachments that currently have the most controversial descriptions, while addressing the interindividual variability of ligament insertions and morphology.

CLINICAL RELEVANCE

Thorough knowledge of the anatomy will enhance our understanding of the kinematics of the scaphoid.

Lumbosacral transitional vertebrae: classification, imaging findings, and clinical relevance

SUMMARY

LSTVs are common within the spine, and their association with low back pain has been debated in the literature for nearly a century. LSTVs include sacralization of the lowest lumbar vertebral body and lumbarization of the uppermost sacral segment. These vertebral bodies demonstrate varying morphology, ranging from broadened transverse processes to complete fusion. Low back pain associated with an LSTV may arise from the level above the transition, the contralateral facet when unilateral, and/or the anomalous articulation when present. Although this association is still somewhat controversial, beyond dispute is the importance of identifying an LSTV in patients in whom a surgical or interventional procedure is planned. This is essential to avoid an intervention or surgery at an incorrect level. In this article, each of these issues will be addressed with attention to identifying and correctly numbering LSTVs as well as detecting imaging findings related to the genesis of low back pain.

Clinical application of a novel assessment for lumbosacral stability

OBJECT

To evaluate the grade of lumbosacral stability, shape analysis was conducted on plain radiographs of the lumbar spine.

METHODS

One hundred twenty-six patients were classified into 2 groups: those with a single-segment disc space narrowing at L5-S1 or at L4-5. Stability was evaluated using the discriminant function (z score) derived from the analysis of radiographic parameters-that is, relative thickness of transverse process of L-5 and the sacral table angle.

RESULTS

In patients with a space narrowing at L5-S1, the author observed a significantly slender L-5 transverse process and acute obliquity of the sacral endplate; accordingly, the z score was negative. In patients with a broad transverse process and a positive z score, the segment associated with disc height loss was L4-5. Thus, a close correlation was found between the site of the disc height loss and the bony characteristics of L-5 and S-1. Furthermore, it could be expected with a high degree reliability that when young adult patients had a z score less than -2 or -3, their L-5 vertebra would develop degenerative spondylolisthesis after middle age and the L5-S1 segment could be saved from age-related alterations as long as the z score was greater than 2.5. The constitutional characteristics of the lumbosacral junction may exert a major influence on the site of disc degeneration.

CONCLUSIONS

Stability at the lumbosacral junction was thought to be quantitatively represented by the z score, with z being designated the lumbosacral stability score.

Description of the iliolumbar ligament for computer-assisted reconstruction

STUDY DESIGN

The iliolumbar ligament (IL) was examined using morphometric and virtual methods.

OBJECTIVES

A macroscopic study was performed to measure the anterior (AIL) and the posterior part of the IL (PIL).

SUMMARY OF BACKGROUND DATA

Though being a widely accepted cause of low back pain and lumbosacral instability, the IL is neglected in computer-based biomechanical studies due to the lack of morphometric information.

METHODS

Frozen sections prepared from 29 human subjects were measured and 7-tesla MR images made to distinguish the AIL and PIL. Cuboids were designated as geometric figures to both parts of the ligament, allowing computer-based calculations of length, surface, volume and angle of positional relationships.

RESULTS

Based on 7-tesla MR imaging, virtual reconstruction was conducted for one male pelvis, including the IL. While left- and right-side parameters varied at a statistically significant level, no gender-dependencies could be determined. Lengths of 30 and 25 mm were measured for the AIL and PIL, as well as heights of 17-19 mm, respectively, and a thickness of 4mm.

CONCLUSIONS

Correlations between the side-dependent parameters and the AIL and the PIL of the same side indicate close functional relationships. Additional dependencies suggest that the IL is capable of compensating age-related as well as bone-attributed alterations in lumbosacral morphology. The IL data and the visualised ligament structures contribute to determination of the influence of the IL in spinal and sacroiliac stability by means of computer-assisted biomechanics.

Immunohistochemical demonstration of nerve endings in iliolumbar ligament

STUDY DESIGN

Immunohistochemical study on fresh cadaver specimens.

OBJECTIVE

Assessment of mechanoreceptor and nociceptor levels and distribution in iliolumbar ligament.

SUMMARY AND BACKGROUND DATA

The function of iliolumbar ligament and its role in low back pain has not been yet fully clarified. Understanding the innervation of this ligament should provide a ground which enables formation of stronger hypotheses.

METHODS

Bilateral 30 iliolumbar ligaments of 15 fresh cadavers were included in the study. Morphologic properties were recorded and the ligaments were examined by focusing on 3 main parts: ligament, bone insertions, and tendon body. Assessment of mechanoreceptor and nociceptor levels and their distribution in iliolumbar ligament were performed on the basis of immunohistochemistry using the S-100 antibody specific for nerve tissue.

RESULTS

Iliac wing insertion was found to be the richest region of the ligament in terms of mechanoreceptors and nociceptors. Pacinian (type II) mechanoreceptor was determined to be the most common (66.67%) receptor followed by Ruffini (type I) (19.67%) mechanoreceptor, whereas free nerve endings (type IV) and Golgi tendon organs (type III) were found to be less common, 10.83% and 2.83%, respectively.

CONCLUSION

Immunohistochemical staining has shown that iliolumbar ligament had a rich nerve tissue. Those results indicate that ILL plays an important role in proprioceptive coordination of lumbosacral region alongside its known biomechanic support function. Moreover, the presence of type IV nerve endings suggest that the injury of this ligament might contribute to the low back pain.

Sagittal whole-spine magnetic resonance imaging in 750 consecutive outpatients: accurate determination of the number of lumbar vertebral bodies

Object

When the number of lumbar and sacral vertebrae is being assessed, variations from typical lumbosacral anatomy may confuse the practitioner, potentially leading to significant clinical errors. In this study, the authors describe the statistical variation in lumbar spine anatomy in an outpatient imaging setting, evaluate the potential implications for clinical practice based on the variation in the number of lumbar-type vertebrae identified, and recommend a method for rapidly determining the number of lumbar spine vertebral bodies (VBs) in outpatients referred for lumbar spine MR imaging.

Methods

A total of 762 patients (male and female) who presented with low back–related medical conditions underwent whole-spine MR imaging in an outpatient setting.

Results

The high-speed whole-spine evaluation was successful for determining the number of lumbar-type VBs in 750 (98%) of 762 consecutive patients. The sagittal whole-spine 3-T MR imaging system images obtained between the beginning of January 2005 and the end of February 2007 were reviewed. The VBs were counted successively from the level of C-2 inferiorly to the intervertebral disc below the most inferior lumbar-type VB. Numbers of disc herniations were also evaluated in the context of the number of VBs.

Conclusions

One in 5 of these outpatients did not have 5 lumbar-type vertebrae: 14.5% had 6; 5.3% had 4; and 1 (0.13%) had the rare finding of 3 lumbar-type vertebrae. Two-thirds of the individuals with 6 lumbar-type vertebrae were male and two-thirds of the individuals with 4 lumbar-type vertebrae were female. Sagittal whole-spine MR imaging can be performed rapidly and efficiently in the majority of patients (98%), and provides improved accuracy for the determination of the number of lumbar-type VBs. A supplementary coronal MR, Ferguson view radiograph or intraoperative fluoroscopic determination for the presence of lumbosacral transitional vertebrae may add additional information when indicated for clinical treatment or surgical planning.

Disc height and segmental motion as risk factors for recurrent lumbar disc herniation

STUDY DESIGN

Retrospective review and multivariate analysis.

OBJECTIVES

Recurrent lumbar disc herniation (rLDH) is a repeated disc herniation at a previously operated disc level in patients who experienced a pain-free interval of at least 6 months after surgery. We investigated whether the preoperative radiologic biomechanical factors (disc height index [DHI] and sagittal range of motion [sROM]) have any effect on rLDH.

SUMMARY OF BACKGROUND DATA

rLDH has been reported in 5% to 15% of patients. There have been many studies suggesting various risk factors for rLDH, such as disc degeneration, trauma, age, smoking, gender, and obesity. However, these factors did not reflect a biomechanical effect on the affected joint directly. Investigation of DHI and sROM would be helpful to understand the biomechanical impact on the occurrence of rLDH.

METHODS

This study enrolled 157 patients who underwent surgery for L4-L5 LDH. We divided the patients into the recurrent and the nonrecurrent group and compared their clinical parameters (age, sex, body-mass index, symptom duration, diabetes, smoking, herniation type, preoperative visual analogue scale) and preoperative radiologic parameters (disc degeneration, DHI, sROM).

RESULTS

rLDH occurred at 40.8+/-15.5 months (7-70 months) after primary surgery. Mean DHI was 0.37+/-0.09 and 0.29+/-0.09 in the recurrent and the nonrecurrent group, respectively (P<0.05). Mean sROM was 11.3 degrees+/-2.9 degrees and 5.9 degrees+/-3.7 degrees in the recurrent and the nonrecurrent group, respectively (P<0.05). Both smoking and disc degeneration were related with the development of rLDH (P<0.05).

CONCLUSION

Together with our data, DHI and sROM showed a significant correlation with the incidence of recurrent lumbar disc herniation, suggesting that preoperative biomechanical conditions of the spine can be an important pathogenic factor in the site of lumbar disc surgery.

Spinal mechanisms of pain control

OBJECTIVES

To demonstrate initial results using Khan Kinetic Treatment (KKT) as a chronic neck pain treatment and to present pain control mechanistic theory on which the treatment is based.

METHODS

A self-reported functional assessment, neck pain questionnaire, and pain medication dose were used as outcome measures for 44 matched patients randomly split into 2 groups ("treatment" and "control"). The treatment group underwent a treatment period consisting of several individual KKT treatments, whereas the control group continued conventional therapy.

RESULTS

Compared with a control group, the treatment group lowered both their self-recorded neck pain scores (P=0.012) and pain medication dose (P=0.048), although current functional assessment questionnaires (range of motion, overall activity, and recreation/work activities) did not detect changes (P=0.233, 0.311, and 0.472, respectively).

DISCUSSION

We address the theory of the pain control mechanisms of the device in detail. Although we await randomized placebo controlled trials and additional results from ongoing mechanistic studies, initial results show that KKT is potentially an effective treatment for chronic neck pain and may contribute to the reduction of pain relieving medication.

Numbering of lumbosacral transitional vertebrae on MRI: role of the iliolumbar ligaments

OBJECTIVE

The objective of this study was to determine whether identification of the iliolumbar ligaments is of practical use for numbering lumbosacral transitional vertebrae (LSTV).

MATERIALS AND METHODS

Five hundred consecutive lumbar spine MRI studies were reviewed. A standard protocol of sagittal and axial T1-weighted and T2-weighted spin-echo sequences was used. The sagittal images were assessed for the presence of an LSTV, and axial images were assessed for the level of origin of the iliolumbar ligaments.

RESULTS

Of the 500 patients, 433 (86.6%) had normal lumbosacral segmentation and 67 (13.4%) had a transitional lumbosacral junction. The iliolumbar ligament was identified at L5 in all patients with normal lumbosacral segmentation (n = 433), bilaterally in 432 and unilaterally in one. Using the identification of the iliolumbar ligaments as a marker of the L5 vertebral level, we numbered 46 of the 67 LSTV as L5 transitions and 21 as S1 transitions.

CONCLUSION

The iliolumbar ligament is readily identifiable on axial lumbar spine MRI and always arises from L5. We suggest that its position can be used to confidently assign lumbar levels in patients with LSTV.

Provocative sacroiliac joint maneuvers and sacroiliac joint block are unreliable for diagnosing sacroiliac joint pain

Mapping studies of pain elicited by injections into the sacroiliac joints (SIJs) suggest that sacroiliac joint syndrome (SIJS) may manifest as low back pain, sciatica, or trochanteric pain. Neither patient-reported symptoms nor provocative SIJ maneuvers are sensitive or specific for SIJS when SIJ block is used as the diagnostic gold standard. This has led to increasing diagnostic use of SIJ block, a procedure in which an anesthetic is injected into the joint under arthrographic guidance. However, several arguments cast doubt on the validity of SIJ block as a diagnostic gold standard. Thus, the effects of two consecutive blocks are identical in only 60% of cases, and the anesthetic diffuses out of the joint in 61% of cases, often coming into contact with the sheaths of the adjacent nerve trunks or roots, including the lumbosacral trunk (which may contribute to pain in the groin or thigh) and the L5 and S1 nerve roots. These data partly explain the limited specificity of SIJ block for the diagnosis of SIJS and the discordance between the pain elicited by the arthrography injection and the response to the block. The limitations of provocative maneuvers and SIJ blocks may stem in part from a contribution of extraarticular ligaments to the genesis of pain believed to originate within the SIJs. These ligaments include the expansion of the iliolumbar ligaments, the dorsal and ventral sacroiliac ligaments, the sacrospinous ligaments, and the sacrotuberous ligaments (sacroiliac joint lato-sensu). They play a role in locking or in allowing motion of the SIJs. Glucocorticoids may diffuse better than anesthetics within these ligaments. Furthermore, joint fusion may result in ligament unloading.

Imaging of lumbosacral transitional vertebrae

Lumbosacral transitional vertebrae (LSTV) are a common finding in the general population. Their clinical significance is controversial with no consensus as to their relationship to low back pain or disc prolapse. However, on magnetic resonance imaging (MRI) they may be difficult to positively identify on sagittal sequences and can lead to confusion with respect to numbering of lumbar discs and vertebrae, with the consequent risk of surgical intervention at an inappropriate level. The imaging findings of LSTV on plain radiography and MRI are reviewed and their clinical significance discussed.

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.

The sacroiliac part of the iliolumbar ligament

The iliolumbar ligament has been described as the most important ligament for restraining movement at the lumbosacral junction. In addition, it may play an important role in restraining movement in the sacroiliac joints. To help understand its presumed restraining effect, the anatomy of the ligament and its orientation with respect to the sacroiliac joints were studied in 17 cadavers. Specific dissection showed the existence of several distinct parts of the iliolumbar ligament, among which is a sacroiliac part. This sacroiliac part originates on the sacrum and blends with the interosseous sacroiliac ligaments. Together with the ventral part of the iliolumbar ligament it inserts on the medial part of the iliac crest, separate from the interosseous sacroiliac ligaments. Its existence is verified by magnetic resonance imaging and by cryosectioning of the pelvis in the coronal and transverse plane. Fibre direction, length, width, thickness and orientation of the sacroiliac part of the iliolumbar ligament are described. It is mainly oriented in the coronal plane, perpendicular to the sacroiliac joint. The existence of this sacroiliac part of the iliolumbar ligament supports the assumption that the iliolumbar ligament has a direct restraining effect on movement in the sacroiliac joints.

Anatomy of the iliolumbar ligament

Information is lacking in the literature on the precise anatomy of the iliolumbar ligament and its individual differences. The morphologic pattern, length, and width of the iliolumbar ligament were determined in 56 embalmed lumbosacral spines from human cadavers. It was possible to classify the iliolumbar ligament into two groups: Type A (74 ligaments), in which anterior and posterior ligaments had separate courses; and Type B (32 ligaments), in which anterior and posterior ligaments moved together as one band. The angle of the posterior iliolumbar ligament in Type A was oriented significantly more posteriorly than that in Type B. The posterior iliolumbar ligament was significantly shorter and oriented more posteriorly in male anatomic specimens than in female ones.

Differences in the iliolumbar ligament and the transverse process of the L5 vertebra in young white and black people

The anatomy of the iliolumbar ligament (ILL) and the spatial orientation of the transverse process of the L5 vertebra were studied in 62 young black (n = 29) and white (n = 33) men and women during routine autopsy. The aim of the study was to determine possible racial differences in the structure and attachments of the iliolumbar ligament. The present study also investigated the spatial orientation of the transverse process of the L5 vertebra since the ILL has been reported to attach to the transverse process. The measurements of the iliolumbar ligament were carried out with a digital vernier caliper while the transverse process angles were measured with an adjustable protractor. The ligament in black people was made up of a single, markedly longer band compared to white people, where the ligament was made up of two shorter bands. The ILL measured 61.8 +/- 1.3 mm in black and 33.2 +/- 1.5 mm white men, and in black women 61.3 +/- 0.9 mm versus 32.2 +/- 1.2 mm in white women (p <0.01). Further, the ILL was markedly wider in black than white subjects (p <0.01). The horizontal and vertical angle also varied greatly between black and white subjects (p <0.01). These are previously unrecognized observations. Albeit unsubstantiated, these findings may have implications for understanding the etiology of various low back stress problems.

The lumbosacral ligament. An autopsy study of young black and white people

The lumbosacral ligament (LSL), situated between the L5-vertebra and the sacrum, was studied in autopsy material. Twenty-eight cadaveric specimens from 12 black and 16 white persons aged 17-30 years were studied during routine forensic autopsies. The ligaments were measured and determined in situ. Thereafter, the ligaments were removed for histologic preparation. The ligament in the black subjects was thicker compared with the white (7.5 +/- 1.4 vs. 5.7 +/- 1.2 mm), and wider (11.7 +/- 1.6 mm in the black vs. 9.2 +/- 0.5 mm in the white), yielding a greater cross-sectional area in the black group (70.7 +/- 22.8 vs. 34.5 +/- 11.4 mm(2), p < 0.001). However, no histological differences were noted. The previously described fibro-osseus tunnel could not be detected in any of the subjects. In all instances, the ligament was situated medial to the L5 nerve. Compression of the L5 nerve under the previously presented fibro-osseus tunnel could not be confirmed.

The iliolumbar ligament: three-dimensional volume imaging and computer reformatting by magnetic resonance: a technical note

STUDY DESIGN

An assessment of magnetic resonance imaging techniques of the iliolumbar ligament.

OBJECTIVES

To identify a technique to better image the iliolumbar ligament.

SUMMARY OF BACKGROUND DATA

The iliolumbar ligament plays an important role in providing lumbosacral stability. Two-dimensional magnetic resonance imaging of the lumbar spine only provides a fragmented representation of the ligament.

METHODS

A two-part study was performed. In the first part, three cadaver pelvi were dissected, and the individual bands of the iliolumbar ligament were identified. Computer reformatting of magnetic resonance three-dimensional volume images then were performed, correlating the structural characteristics of the iliolumbar ligament to its magnetic resonance image. In the second part of the study, the lumbosacral region of three groups of patients were evaluated. Group I was studied with routine magnetic resonance imaging techniques of the intervertebral disc regions. Group II was studied with routine contiguous axial magnetic resonance imaging of the lumbosacral spine. Group III was studied with computer reformatting of three-dimensional volume images of the lumbosacral spine.

RESULTS

Accurate imaging of the iliolumbar ligament of cadaver specimens was achieved with three-dimensional volume imaging and computer reformatting. Routine imaging of the intervertebral disc region as well as contiguous axial imaging of the spine depicted only limited segments of the iliolumbar ligament. Three-dimensional volume imaging and computer reformatting allowed precise imaging of the iliolumbar ligament in all patients, demonstrating the ligament orientation as well as length, width, and depth.

CONCLUSION

Only images of the iliolumbar ligament obtained through computer reformatting of three-dimensional volume averaging from L3 to the sacral ala correlated with the ligament's structural characteristics.