The sacroiliac part of the iliolumbar ligament

Experimental characterization of motion resistance of the sacroiliac joint

BACKGROUND

The human sacroiliac joint (SIJ) in vivo is exposed to compressive and shearing stress environment, given the joint lines are almost parallel to the direction of gravity. The SIJ supports efficient bipedal walking. Unexpected or unphysiological, repeated impacts are believed to cause joint misalignment and result in SIJ pain. In the anterior compartment of the SIJ being synovial, the articular surface presents fine irregularities, potentially restricting the motion of the joints.

OBJECTIVE

To clarify how the SIJ articular surface affects the resistance of the motion under physiological loading.

METHODS

SIJ surface models were created based on computed tomography data of three patients and subsequently 3D printed. Shear resistance was measured in four directions and three combined positions using a customized setup. In addition, repositionability of SIJs was investigated by unloading a shear force.

RESULTS

Shear resistance of the SIJ was the highest in the inferior direction. It changed depending on the direction of the shear and the alignment position of the articular surface.

CONCLUSION

SIJ articular surface morphology is likely designed to accommodate upright bipedal walking. Joint misalignment may in consequence increase the risk of subluxation.

Incidence and Characteristics of Clinical L5-S1 Adjacent Segment Degeneration after L5 Floating Lumbar Fusion: A Multicenter Study

STUDY DESIGN

Retrospective study.

PURPOSE

This study aimed to evaluate the incidence, characteristics, and risk factors for clinical L5-S1 adjacent segment degeneration (ASD) after L5 floating lumbar fusion.

OVERVIEW OF LITERATURE

ASD is known to occur after lumbar spine fusion at a certain frequency. Several studies on radiological L5- S1 ASD have been reported. However, there are only a few studies on L5-S1 ASD with clinical symptoms, including back pain and/or radiculopathy.

METHODS

In total, 306 patients who received L5 floating lumbar fusion were included in this study. Clinical L5-S1 ASD was defined as newly developed radiculopathy in relation to the L5-S1 segment. Patients' medical records and imaging data were retrospectively analyzed. The risk factors for clinical ASD were assessed by an inverse probability of treatment weighting-adjusted logistic regression analysis.

RESULTS

Clinical L5-S1 ASD occurred in 17 patients (5.6%). The mean onset time of L5-S1 ASD was 12.9±7.5 months after the primary surgery. Among these patients, 10 (58.8%) presented with clinical L5-S1 ASD within 12 months. Reoperation was performed in three patients (1.0%). The severity of L5-S1 disk degeneration did not affect the occurrence of L5-S1 ASD. Logistic regression analysis showed that the number of fusion levels was a significant risk factor for clinical L5-S1 ASD.

CONCLUSIONS

The incidence and characteristics of clinical L5-S1 ASD after L5 floating lumbar fusion were retrospectively investigated. This study established that the number of fusion levels was a significant candidate factor for clinical L5-S1 ASD. Careful clinical follow-up is deemed necessary after L5 floating lumbar fusion surgery, especially for patients who received multiple-level fusions.

Anatomy and morphology of iliolumbar ligament

PURPOSE

To address limited amount of available data and contradictory statements in published works 60 Iliolumbar ligaments extracted from 30 cadavers were examined to describe their insertions and morphology.

METHODS

The ligaments were removed during the standard autopsy procedures with a use of an oscillating saw, a chisel and a scalpel. The specimens were photographed before the extraction and measured alongside their anterior margin. Next, they were preserved in formaldehyde, stripped of other soft tissues and then examined, photographed and described.

RESULTS

The mean length of the ligaments was 31.7 mm. 44 specimens were described as single-banded, 13 as double-banded and 3 as other. In 24 cases costal process of L_V has been fixed to the iliac plate by short ligamentous bands. In 38 cases there was a thick fibrous membrane connected to the ligament. No legitimate insertions on L_IV vertebra were observed.

CONCLUSIONS

Typical iliolumbar ligament consists of a single ligamentous band. Most common variability of the ligament consist of two bands. In approximately 40% of cases the costal process of L_V can be additionally stabilized to the iliac plate by short, strong ligamentous bands. In 63% of cases a connection between the iliolumbar ligament and a fibrous membrane placed in the frontal plane, superiorly to the ligament, has been observed. There seems to be no convincing proof of existence of the insertion of the iliolumbar ligament on the L_IV vertebra.

The Sacroiliac Joint as a Cause of Pain - Review of the Sacroiliac Joint Morphology and Models for Pain Genesis

INTRODUCTION

In recent years, the sacroiliac joint has become increasingly important as a generator of low back pain with and without pseudo-radicular pain in the legs. Up to 27% of reported back pain is generated by disorders in the sacroiliac joint.

METHOD

This review is based on a selective literature search of the sacroiliac joint (SIJ) as a possible pain generator. It also considers the anatomical structures and innervation of the sacroiliac joint.

RESULTS

The SIJ is a complex joint in the region of the posterior pelvis and is formed by the sacrum and the ilium bones. The SIJ is very limited in movement in all three planes. Joint stability is ensured by the shape and especially by strong interosseous and extraosseous ligaments. Different anatomical variants of the sacroiliac joint, such as additional extra-articular secondary joints or ossification centres, can be regularly observed in CT scans. There is still controversy in the literature regarding innervation. However, there is agreement on dorsal innervation of the sacroiliac joint from lateral branches of the dorsal rami of the spinal nerves S I-S III with proportions of L III and L IV as well S IV. Nerve fibres and mechanoreceptors can also be detected in the surrounding ligaments.

CONCLUSION

A closer look at the anatomy and innervation of the SIJ shows that the SIJ is more than a simple joint. The complex interaction of the SIJ with its surrounding structures opens the possibility that pain arises from this area. The SIJ and its surrounding structures should be included in the diagnosis and treatment of back and leg pain. Published literature include a number of plausible models for the sacroiliac joint as pain generator. The knowledge of the special anatomy, the complex innervation as well as the special and sometimes very individual functionality of this joint, enhance our understanding of associated pathologies and complaints.

Biomechanical analysis of sacroiliac joint motion following oblique-pulling manipulation with or without pubic symphysis injury

Background: Oblique-pulling manipulation has been widely applied in treating sacroiliac joint (SIJ) dysfunction. However, little is known about the biomechanical mechanism of the manipulation. This study aims to analyze the SIJ motion under oblique-pulling manipulation, in comparison with compression and traction loads.

Methods/Study Design: A total of six specimens of embalmed human pelvis cadavers were dissected to expose the SIJ and surrounding ligaments. Through a servo-hydraulic testing system, biomechanical tests were performed on the stable pelvis and the unstable pelvis with pubic symphysis injury (PSI). A three-dimensional (3D) photogrammetry system was employed to determine the separation and nutation in three tests: axial compression (test A), axial traction (test B), and oblique-pulling manipulation (test C).

Results: After applying the testing loads, the range of nutation was no more than 0.3° (without PSI) and 0.5°(with PSI), separately. Except for test B, a greater nutation was found with PSI (p < 0.05). Under both conditions, nutation following test A was significantly greater than that of other tests (p < 0.05). SIJ narrowed in test A and separated in tests B and C, where the range of motion did not exceed 0.1 mm (without PSI) or 0.3 mm (with PSI) separately. Under both conditions, the separation of SIJ in test C was not as apparent as the narrowness of SIJ in test A (p < 0.05). Compared to SIJ, a more significant increasing displacement was found at the site of the iliolumbar ligament (p < 0.05). Nevertheless, when the force was withdrawn in all tests, the range of nutation and separation of SIJ nearly decreased to the origin.

Conclusion: Pubic symphysis is essential to restrict SIJ motion, and the oblique-pulling manipulation could cause a weak nutation and separation of SIJ. However, the resulting SIJ motion might be neutralized by regular standing and weight-bearing load. Also, the effect on SIJ seems to disappear at the end of manipulation. Therefore, the stretching and loosening of surrounding ligaments need to be paid more attention to.

Ligaments stabilizing the sacrum and sacroiliac joint: a comprehensive review

The sacroiliac joint is a diarthrodial synovial joint in the pelvis. Anatomically, it is described as a symphysis, its synovial joint characteristics being limited to the distal cartilaginous portion on the iliac side. It is a continuous ligamentous stocking comprising interconnecting ligamentous structures and surrounding fascia. Its ligaments, the primary source of its stability, include the anterior, interosseous and dorsal sacroiliac, the iliolumbar, sacrotuberous, and sacrospinous. Structural reinforcement is also provided by neighboring fascia and muscles. Lower back pain is a common presentation of sacroiliac joint disease, the best-established treatments being corticosteroid injections, bipolar radiofrequency ablation, and sacroiliac joint fusion.

The impact of a sacroiliac joint belt on function and pain using the active straight leg raise in pregnancy-related pelvic girdle pain

INTRODUCTION

Pelvic girdle pain (PGP) is the most common musculoskeletal concern in pregnancy. The Active Straight Leg Raise (ASLR) test is diagnostic. Sacroiliac joint (SIJ) belts are included in multimodal therapy, but there is no established predictive measure to determine which pregnant women will benefit.

OBJECTIVE

To determine if the ASLR score is immediately reduced by SIJ belt application and whether PGP pain and function improves after 4 weeks of belt use.

DESIGN

Prospective observational cohort study.

SETTING

Academic medical center.

PARTICIPANTS

Pregnant women at least 18 years of age in the second or third trimester of pregnancy with posterior PGP and ASLR score of 2 to 10.

INTERVENTIONS

Four-week SIJ belt use.

MAIN OUTCOME MEASURES

ASLR, Numerical Rating Scale (NRS), Pelvic Girdle Questionnaire (PGQ), Perceived Global Impression of Improvement (PGII).

RESULTS

Sixty-three women enrolled. On multivariable analysis, immediate belted ASLR score was -2.70 points lower than the non-belted ASLR score (P < .001). Four weeks later there was significant improvement in the ASLR score with a belt (M_diff  = -0.99; P = .001) and without a belt (M_diff  = -1.94; P < .001); the decline was more precipitous for the non-belted response (M_diff  = -0.96; P = .02). Current NRS pain scores declined from baseline by approximately -0.94 points (P < .001). This decline did not depend on ASLR scores (interaction P = .43) or wearing a belt at the time of testing (interaction P = .51). Similar conclusions held for participants' usual NRS score and average PGQ score. After 4 weeks, 82% reported improvement based on the PGII.

CONCLUSIONS

SIJ belts are a safe, well-tolerated, and effective therapeutic option for pregnancy-related PGP. The ASLR score is immediately reduced following SIJ belt application but does not predict pain score 4 weeks later. SIJ belt leads to significant improvements in pain and function over time.

Does "Coronal Root Angle" Serve as a Parameter in the Removal of Ventral Factors for Foraminal Stenosis at L5-S1 In Stand-alone Microendoscopic Decompression?

STUDY DESIGN

Prospective single-center cohort study.

OBJECTIVE

The present study aims to investigate the causes of failure of L5/S1 foraminal stenosis, and it is hypothesized that the newly defined "L5 coronal root angle (CRA)" may be a parameter in the removal of ventral pathologies.

SUMMARY OF BACKGROUND DATA

Lumbar foraminal stenosis is an important cause of recurrent leg pain after central spinal stenosis surgery. Although it can be seen at all levels, L5/S1 is the level at which it is most frequently seen due to its specific characteristics, with success rate is lower than other levels after foraminal decompression.

METHODS

L5/S1 microendoscopic foraminal decompression was performed to 51 patients. According to Japanese Orthopedic Association (JOA) improvement at 12-month follow-up, those with improvement >20% were classified as Group 1 and <20% were classified as Group 2. The patients who underwent discectomy in addition to foraminotomy formed Group 3. Lumbar lordosis angle, segmental lordosis angle, anterior disc height, pelvic tilt, pelvic incidence, sacral slope, relative disc height ratio, pedicle height/vertebral body height ratio, L5 depth, L5 CRA, and anterior disc height/ posterior disc height ratio parameters were measured with lumbar radiographic views, computed tomography (CT), and magnetic resonance imaging (MRI).

RESULTS

Among the parameters compared between groups, L5 CRA, posterior disc height, anterior disc height/posterior disc height, relative disc height ratio, and lumbar lordosis angle during extension were seen to be statistically significantly related with low success rate.

CONCLUSION

Failure to remove the ventral pathologies when the L5 CRA is <112. 1º may lead to failed results. Besides, in cases wherein the posterior disc height is <2.85 mm or the anterior/posterior disc height ratio is >3.98, approaches to restoring disc height rather than stand-alone posterior decompression may reduce the possibility of failure.

LEVEL OF EVIDENCE

2.

Quantification of fat in the posterior sacroiliac joint region: fat volume is sex and age dependant

Fat is appreciated as a structural component of synovial joints. It may serve a shock-absorbing function for the incongruent surfaces, vessels and ligaments, but has not been investigated in the posterior sacroiliac joint (PSIJ). Sixty-six cadaveric hemipelves were serially-sectioned and photographed. The amount of visible fat in the PSIJ was quantified using a modified version of Cavalieri’s method. Total volume, fat volume and fat percentage of the PSIJ were calculated in predefined sub-regions. Fat is consistently present in the PSIJ (1.9 ± 1.3 cm³). Fat volume correlates with the PSIJ total volume (p < 0.0001; r = 0.73) and age (p = 0.024; r = 0.24), and is smaller in males (1.4 ± 0.8 cm³) than females (2.4 ± 1.5 cm³). Fat volumes in the middle and inferior sub-regions of the PSIJ show side- (p < 0.0001) and sex-differences (p = 0.013 females, middle sub-region). Age and PSIJ total volume correlate between sexes in various sub-regions (p = 0.05 females superior sub-region; males inferior sub-region). Fat percentage differs between sexes and sub-regions (p = 0.018 females, superior sub-region) but is independent of age and sides. The presence of fat within the PSIJ is a normal finding and shows sex-dependant and age-related differences. It is unclear whether fat is linked to age-related degeneration or has a shock-absorbing role in stress- and load-dissipation in the PSIJ.

Three-dimensional morphological analysis of the human sacroiliac joint: influences on the degenerative changes of the auricular surfaces

The sacroiliac joint (SIJ) is responsible for weight transmission between the spine and lower extremity. However, details of the structure and function of the SIJ remain unclear. In a previous study, we devised a method of quantitatively evaluating the level of degeneration of the SIJ using an age estimation procedure for the auricular surface of the ilium. Our results in that study suggested that the degree of degeneration of the joint surface may be associated with the morphology of the auricular surface of the ilium. In that study, however, the morphology of the auricular surface of the ilium was simplified for analysis, meaning that more detailed investigations were required in future. In the present study, we focused on individual differences in the shape of SIJ and carried out three-dimensional quantitative evaluation of the morphology of the auricular surface of the ilium to ascertain its association with joint degeneration. We produced three-dimensional images of the right auricular surfaces of the ilium of 100 modern Japanese men (age 19-83), and obtained the three-dimensional rectangular coordinates of 11 defined measurement points. We then calculated 16 parameters indicating the morphological characteristics of the auricular surfaces of the ilium from the three-dimensional rectangular coordinates of these measurement points, and used these to perform principal component analysis to investigate trends in the morphology of the auricular surface of the ilium. We found that the morphology of the auricular surface of the ilium could be characterized in terms of (i) size, (ii) concavity of the posterior border and (iii) amount of undulation. An investigation of the correlation between these parameters and age suggested that the amount of undulation of the auricular surface of the ilium tends to diminish with advancing age. In an investigation of the association between morphology of the auricular surface of the ilium and degeneration of the articular surface when the subjects were divided into a high-degeneration group (n = 55) and a low-degeneration group (n = 45) and the 16 parameters were compared, there was a significant difference in the amount of undulation of the auricular surface of the ilium. In an investigation limited to older subjects aged ≥ 60 (n = 47) at the time of death, there were significant differences between the high-degeneration group (n = 27) and low-degeneration group (n = 20) in terms not only of the parameters indicating the amount of undulation of the auricular surface of the ilium but also of those indicating the amount of the concavity of the posterior border. These results suggested that the amount of undulation of the auricular surface of the ilium may affect the degree of degeneration of the articular surface. In addition, in older subjects, the degree of concavity of the posterior border of the SIJ may also affect the degree of degeneration of the articular surface. It is thus likely that differences in the morphology of the auricular surface of the ilium may affect degenerative changes in the SIJ.

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.

Pelvic Belt Effects on Health Outcomes and Functional Parameters of Patients with Sacroiliac Joint Pain

Introduction

The sacroiliac joint (SIJ) is a common source of low back pain. However, clinical and functional signs and symptoms correlating with SIJ pain are widely unknown. Pelvic belts are routinely applied to treat SIJ pain but without sound evidence of their pain-relieving effects. This case-control study compares clinical and functional data of SIJ patients and healthy control subjects and evaluates belt effects on SIJ pain.

Methods

17 SIJ patients and 17 healthy controls were included in this prospective study. The short-form 36 survey and the numerical rating scale were used to characterize health-related quality of life in patients in a six-week follow-up and the pain-reducing effects of pelvic belts. Electromyography data were obtained from the gluteus maximus, biceps femoris, rectus femoris and medial vastus. Alterations of muscle activity, variability and gait patterns were compared in patients and controls along with the belts’ effects in a dynamic setting when walking.

Results

Significant improvements were observed in the short-form 36 survey of the SIJ patients, especially in the physical health subscores. Minor declines were also observed in the numerical rating scale on pain. Belt-related changes of muscle activity and variability were similar in patients and controls with one exception: the rectus femoris activity decreased significantly in patients with belt application when walking. Further belt effects include improved cadence and gait velocity in patients and controls.

Conclusions

Pelvic belts improve health-related quality of life and are potentially attributed to decreased SIJ-related pain. Belt effects include decreased rectus femoris activity in patients and improved postural steadiness during locomotion. Pelvic belts may therefore be considered as a cost-effective and low-risk treatment of SIJ pain.

Trial Registration

ClinicalTrials.gov NCT02027038

A comprehensive review of the sub-axial ligaments of the vertebral column: part I anatomy and function

BACKGROUND

As important as the vertebral ligaments are in maintaining the integrity of the spinal column and protecting the contents of the spinal canal, a single detailed review of their anatomy and function is missing in the literature.

METHODS

A literature search using online search engines was conducted.

RESULTS

Single comprehensive reviews of the spinal ligaments are not found in the extant medical literature.

CONCLUSIONS

This review will be useful to those who treat patients with pathology of the spine or who interpret imaging or investigate the anatomy of the ligaments of the vertebral column.

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.

Pelvic belt effects on pelvic morphometry, muscle activity and body balance in patients with sacroiliac joint dysfunction

Introduction

The sacroiliac joint (SIJ) is frequently involved in low back and pelvic girdle pain. However, morphometrical and functional characteristics related to SIJ pain are poorly defined. Pelvic belts represent one treatment option, but evidence still lacks as to their pain-reducing effects and the mechanisms involved. Addressing these two issues, this case-controlled study compares morphometric, functional and clinical data in SIJ patients and healthy controls and evaluates the effects of short-term pelvic belt application.

Methods

Morphometric and functional data pertaining to pelvic belt effects were compared in 17 SIJ patients and 17 controls. Lumbar spine and pelvis morphometries were obtained from 3T magnetic resonance imaging. Functional electromyography data of pelvis and leg muscles and center of pressure excursions were measured in one-leg stance. The numerical rating scale was used to evaluate immediate pain-reducing effects.

Results

Pelvic morphometry was largely unaltered in SIJ patients and also by pelvic belt application. The angle of lumbar lateral flexion was significantly larger in SIJ patients without belt application. Muscle activity and center of pressure were unaffected by SIJ pain or by belt application in one-leg stance. Nine of 17 patients reported decreased pain intensities under moderate belt application, four reported no change and four reported increased pain intensity. For the entire population investigated here, this qualitative description was not confirmed on a statistical significant level.

Discussion

Minute changes were observed in the alignment of the lumbar spine in the frontal plane in SIJ patients. The potential pain-decreasing effects of pelvic belts could not be attributed to altered muscle activity, pelvic morphometry or body balance in a static short-term application. Long-term belt effects will therefore be of prospective interest.

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.

Extraforaminal compression of the L-5 nerve root at the lumbosacral junction: clinical analysis, decompression technique, and outcome

OBJECT

Extraforaminal compression of the L-5 nerve encompasses multiple pathological entities and may result from disc herniations as well as bony (osteophytes or sacral ala) or ligamentous (sacroiliac ligament and lumbosacral band) compression. Several other factors, such as disc space collapse or coronal wedging, can also contribute to narrowing of the extraforaminal space. The extraforaminal space at L5-S1 has unique anatomical features compared with the upper lumbar levels, which makes surgical access to this region difficult. Minimally invasive techniques offer easier access to the region. The purpose of this study was to analyze the contributing factors for extraforaminal compression of the L-5 nerve and assess clinical outcome following surgical decompression.

METHODS

Fifty-two consecutive patients who underwent a minimally invasive far-lateral approach for extraforaminal compression of the L-5 nerve were retrospectively analyzed for clinical data, outcomes, and imaging features (type of disc prolapse, coronal wedging, degree of disc and facet degeneration, facet tropism, foraminal stenosis, osteophytes, and adjacent-level disease). The authors describe the surgical technique used in this study.

RESULTS

The mean age of the patient sample was 57 years. Sixteen patients each had an extraforaminal ruptured disc or contained protrusion, and the remaining 20 patients had disc protrusions extending into the foraminal region or the lateral recess. Associated foraminal stenosis was found in 38.5%, and adjacent-level stenosis was noted in 22 cases (42.3%) and spondylolisthesis in 4 (7.7%). Osteophytes were noted in 18 cases. A coronal wedging angle ≥ 3° was found in 46.2%, and the laterality of wedging corresponded to the symptomatic side in 91% of cases. Fifteen patients (28.8%) complained of postoperative dysesthesias, which completely resolved in all cases within 6 months. The incidence of dysesthesias was more common in the ruptured disc group. There were no differences in clinical outcome among the different types of disc prolapses. The mean preoperative and postoperative visual analog scale scores were 7.6 and 3.6, respectively. The mean preoperative and postoperative Japanese Orthopaedic Association (JOA) scores were 6.4 and 13.8, respectively. The mean JOA recovery rate was 86.1%. According to the Macnab functional grading system, 96% of the patients had excellent or good grades at follow-up.

CONCLUSIONS

A minimally invasive far-lateral approach to L5-S1 requires a good understanding of the regional anatomy and can provide good to excellent clinical results in properly selected cases. This approach is effective in decompressing the far-lateral and foraminal zones. Adequate preoperative diagnosis and tailoring the surgical procedure to address the relevant compressive element in each case is essential to achieving good clinical results.

The sacroiliac joint: an overview of its anatomy, function and potential clinical implications

This article focuses on the (functional) anatomy and biomechanics of the pelvic girdle and specifically the sacroiliac joints (SIJs). The SIJs are essential for effective load transfer between the spine and legs. The sacrum, pelvis and spine, and the connections to the arms, legs and head, are functionally interrelated through muscular, fascial and ligamentous interconnections. A historical overview is presented on pelvic and especially SIJ research, followed by a general functional anatomical overview of the pelvis. In specific sections, the development and maturation of the SIJ is discussed, and a description of the bony anatomy and sexual morphism of the pelvis and SIJ is debated. The literature on the SIJ ligaments and innervation is discussed, followed by a section on the pathology of the SIJ. Pelvic movement studies are investigated and biomechanical models for SIJ stability analyzed, including examples of insufficient versus excessive sacroiliac force closure.

Sacroiliac joint pain after lumbar/lumbosacral fusion: current knowledge

Recently, the sacroiliac joint (SIJ) has gained increased attention as a source of persistent or new pain after lumbar/lumbosacral fusion. The underlying pathophysiology of SIJ pain may be increased mechanical load, iliac crest bone grafting, or a misdiagnosis of SIJ syndrome. Imaging studies show more frequent degeneration of the SIJ in patients with lumbar/lumbosacral fusion than in patients without such fusion. Using injection tests, it has been shown that SIJ pain is the cause of persistent symptoms in a considerable number of patients after fusion surgery. Recent articles reporting on surgical outcomes of SIJ fusion include a high percentage of patients who had lumbar/lumbosacral fusion or surgery before, although well-controlled clinical studies are necessary to assess the efficacy of surgical treatment. Taking these findings into consideration, the possibility that the SIJ is the source of pain should be considered in patients with failed back surgery syndrome after lumbar/lumbosacral fusion.

Pregnancy-related pelvic girdle pain and its relationship with relaxin levels during pregnancy: a systematic review

PURPOSE

The present systematic review assessed the level of evidence for the association between relaxin levels and pregnancy-related pelvic girdle pain (PPGP) during pregnancy.

METHODS

PRISMA guidelines were followed to conduct this systematic review. Electronic search was carried out using six different databases. Observational cohorts, cross-sectional or case-control studies focused on the association between relaxin levels and PPGP during pregnancy were included. Studies selection was conducted by two reviewers who screened firstly for titles, then for abstracts and finally for full articles. Risk of bias was assessed using the Newcastle-Ottawa scale and the quality of evidence by the guidelines proposed by the Cochrane back review group.

RESULTS

731 references were identified. Six articles met the inclusion criteria and were considered for this systematic review. The main reason for the studies exclusion was PPGP related to gynaecological reasons. Five studies were case-control and one study was a prospective cohort. Four studies were ranked as high while two were ranked as low quality. Among the high quality studies, three found no association between PPGP and relaxin levels.

CONCLUSIONS

Based on these findings, the level of evidence for the association between PPGP and relaxin levels was found to be low. PPGP assessment and controlling for risk factors were found to increase bias leaving uncertainty in interpretation of these findings and a need for further research.

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.

Diagnostic validity of criteria for sacroiliac joint pain: a systematic review

A systematic literature review was conducted to determine the diagnostic validity of the criteria for sacroiliac (SI) joint pain as proposed by the International Association for the Study of Pain (IASP). Databases were searched up to September 2007. Quality of the studies was assessed using a Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Sensitivity, specificity, and diagnostic odds ratios (DOR) were calculated together with 95% confidence intervals (CI). Statistical pooling was conducted for results of provocative tests. Eighteen studies were included. Five studies examined the pattern of SI joint pain, whereas another 5 examined stressing test specific for SI joint pain. None of the studies evaluated the diagnostic validity of the SI joint infiltration or the diagnostic validity of the IASP criteria set as a whole. In all studies, the SI joint selective infiltration was used as a gold standard; however, the technique, medications, and required pain relief after the infiltration varied considerably between the studies. Taking the double infiltration technique as reference test, the pooled data of the thigh thrust test (DOR, 18.461; CI, 5.82 to 58.53), compression test (DOR, 3.88; CI, 1.7 to 8.9), and 3 or more positive stressing tests (DOR, 17.16; CI, 7.6 to 39) showed discriminative power for diagnosing SI joint pain.

PERSPECTIVE

This review of clinical studies focused on the diagnostic validity of the IASP criteria for diagnosing SI joint pain. A meta-analysis showed that the thigh thrust test, the compression test, and 3 or more positive stressing tests have discriminative power for diagnosing SI joint pain. Because a gold standard for SI joint pain diagnosis is lacking, the diagnostic validity of tests related to the IASP criteria for SI joint pain should be regarded with care.

Biomechanical analysis of reducing sacroiliac joint shear load by optimization of pelvic muscle and ligament forces

Effective stabilization of the sacroiliac joints (SIJ) is essential, since spinal loading is transferred via the SIJ to the coxal bones, and further to the legs. We performed a biomechanical analysis of SIJ stability in terms of reduced SIJ shear force in standing posture using a validated static 3-D simulation model. This model contained 100 muscle elements, 8 ligaments, and 8 joints in trunk, pelvis, and upper legs. Initially, the model was set up to minimize the maximum muscle stress. In this situation, the trunk load was mainly balanced between the coxal bones by vertical SIJ shear force. An imposed reduction of the vertical SIJ shear by 20% resulted in 70% increase of SIJ compression force due to activation of hip flexors and counteracting hip extensors. Another 20% reduction of the vertical SIJ shear force resulted in further increase of SIJ compression force by 400%, due to activation of the transversely oriented M. transversus abdominis and pelvic floor muscles. The M. transversus abdominis crosses the SIJ and clamps the sacrum between the coxal bones. Moreover, the pelvic floor muscles oppose lateral movement of the coxal bones, which stabilizes the position of the sacrum between the coxal bones (the pelvic arc). Our results suggest that training of the M. transversus abdominis and the pelvic floor muscles could help to relieve SI-joint related pelvic pain.

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.

Intensity mapping of pain referral areas in sacroiliac joint pain patients

OBJECTIVE

To identify differences in pain referral areas, using intensity maps, between responders and nonresponders to a double diagnostic sacroiliac joint injection with a short- and long-acting local anesthetic in patients with chronic low back pain.

METHODS

From a group of 140 consecutive patients with chronic low back pain, 60 patients who met clinical criteria were included in the study. Twenty-seven demonstrated a positive response to a double diagnostic fluoroscopically guided intra-articular sacroiliac joint block and were compared with 33 patients with a negative response. Each patient's preinjection pain diagram was used to determine areas of pain referral. The summation of these pain referral zones for both groups was used to construct intensity maps.

RESULTS

No major differences were observed between responders and nonresponders with regard to mean size and distribution of referral pain areas. Intensity maps, however, showed differences in pain referral at the buttock in the areas overlying the sacroiliac joint (100% of the responders vs 80% of the nonresponders) and the ischial tuberosity (10% of the responders vs 100% of the nonresponders).

CONCLUSIONS

Overall referred pain maps appeared not to be useful to discriminate patients with an identified sacroiliac joint pain from chronic low back pain patients with pain from other sources. Differences were only found using intensity maps. By implementing these data, it could be concluded that patients with sacroiliac joint pain are less likely to experience pain in both the 'Fortin' and 'tuber' areas. This knowledge can be used as additional selection criterion for putative sacroiliac joint patients, next to sacroiliac joint pain provocation tests.

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 influence of slouching and lumbar support on iliolumbar ligaments, intervertebral discs and sacroiliac joints

OBJECTIVE

To investigate lumbopelvic kinematics when moving into a slouch.

DESIGN

A biomechanical model was developed. Load tests in vitro verified the model.

BACKGROUND

The precise mechanism causing disc herniation and back sprain is still debated. Most biomechanical studies have focused on lifting in a stooped posture. Previous studies address instability situations due to Euler buckling of the spine under axial load. However, no studies address lumbosacral, iliolumbar and sacroiliac kinematics in slouching, i.e. flexing the spine in situations with negligible compressive spinal load.

METHODS

Modeling started with the click-clack movement, i.e. the transition from lumbar lordosis to lumbar kyphosis by the combination of backward rotation of the pelvis and ventral flexion of the spine. The flexed spine was compared with a crowbar which uses the iliolumbar ligaments as fulcrum and pivot. To analyse the click-clack movement in sitting, unembalmed erect human trunks were moved from a forward position to a backward position, recording angular changes between L5, sacrum and ilium.

RESULTS

When moving the trunk stepwise backward with support at shoulder level, L5 showed forward rotation with respect to the sacrum, but rotation of the sacrum with respect to the iliac bones was reversed (i.e. counternutation). L5 showed displacement in ventral direction with respect to the ilium. Measurements were in agreement with prediction from the crowbar model of the spine.

CONCLUSIONS

Backward rotation of the pelvis combined with flexion of the spine, i.e. slouching, results in backward rotation of the sacrum with respect to the ilium, dorsal widening of the intervertebral disc L5-S1 and strain on the iliolumbar ligaments when protection from back muscles against lumbar flexion is absent. Lumbar backrest support almost eliminates lumbosacral and sacroiliac movement.

RELEVANCE

Understanding why the iliolumbar ligaments are loaded in slouching contributes to the understanding of the biomechanics of low back pain in everyday situations with small or negligible compressive spinal load. The results recommend lumbar support: backrests with free shoulder space.

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.