The biomechanical functions of the iliolumbar ligament in maintaining stability of the lumbosacral junction

Factors associated with an increased risk of developing postoperative symptomatic lumbar spondylolisthesis after decompression surgery: an explorative two-centre international cohort study

PURPOSE

Symptomatic lumbar spinal stenosis can be treated with decompression surgery. A recent review reported that, after decompression surgery, 1.6-32.0% of patients develop postoperative symptomatic spondylolisthesis and may therefore be indicated for lumbar fusion surgery. The latter can be more challenging due to the altered anatomy and scar tissue. It remains unclear why some patients get recurrent neurological complaints due to postoperative symptomatic spondylolisthesis, though some associations have been suggested. This study explores the association between key demographic, biological and radiological factors and postoperative symptomatic spondylolisthesis after lumbar decompression.

METHODS

This retrospective cohort study included patients who had undergone lumbar spinal decompression surgery between January 2014 and December 2016 at one of two Spine Centres in the Netherlands or Switzerland and had a follow-up of two years. Patient characteristics, details of the surgical procedure and recurrent neurological complaints were retrieved from patient files. Preoperative MRI scans and conventional radiograms (CRs) of the lumbar spine were evaluated for multiple morphological characteristics. Postoperative spondylolisthesis was evaluated on postoperative MRI scans. For variables assessed on a whole patient basis, patients with and without postoperative symptomatic spondylolisthesis were compared. For variables assessed on the basis of the operated segment(s), surgical levels that did or did not develop postoperative spondylolisthesis were compared. Univariable and multivariable logistic regression analyses were used to identify associations with postoperative symptomatic spondylolisthesis.

RESULTS

Seven hundred and sixteen patients with 1094 surgical levels were included in the analyses. (In total, 300 patients had undergone multilevel surgery.) ICCs for intraobserver and interobserver reliability of CR and MRI variables ranged between 0.81 and 0.99 and 0.67 and 0.97, respectively. In total, 66 of 716 included patients suffered from postoperative symptomatic spondylolisthesis (9.2%). Multivariable regression analyses of patient-basis variables showed that being female [odds ratio (OR) 1.2, 95%CI 1.07-3.09] was associated with postoperative symptomatic spondylolisthesis. Higher BMI (OR 0.93, 95%CI 0.88-0.99) was associated with a lower probability of having postoperative symptomatic spondylolisthesis. Multivariable regression analyses of surgical level-basis variables showed that levels with preoperative spondylolisthesis (OR 17.30, 95%CI 10.27-29.07) and the level of surgery, most importantly level L4L5 compared with levels L1L3 (OR 2.80, 95%CI 0.78-10.08), were associated with postoperative symptomatic spondylolisthesis; greater facet joint angles (i.e. less sagittal-oriented facets) were associated with a lower probability of postoperative symptomatic spondylolisthesis (OR 0.97, 95%CI 0.95-0.99).

CONCLUSION

Being female was associated with a higher probability of having postoperative symptomatic spondylolisthesis, while having a higher BMI was associated with a lower probability. When looking at factors related to postoperative symptomatic spondylolisthesis at the surgical level, preoperative spondylolisthesis, more sagittal orientated facet angles and surgical level (most significantly level L4L5 compared to levels L1L3) showed significant associations. These associations could be used as a basis for devising patient selection criteria, stratifying patients or performing subgroup analyses in future studies regarding decompression surgery with or without fusion.

Identifying the relationship between lumbar sacralization and adjacent ligamentous anatomy in patients with Bertolotti syndrome and healthy controls

OBJECTIVE

Bertolotti syndrome is a diagnosis given to patients experiencing low-back pain due to a lumbosacral transitional vertebra (LSTV). LSTVs cause altered biomechanics at the lumbosacral junction, predisposing these patients to degenerative disease. It has been proposed that these patients have additional non-osseous variation such as ligamentous differences in the lumbar spine. The iliolumbar ligament, which attaches from the iliac crest to the transverse process of L4 and L5, plays a significant role in reducing lumbar motion in all six degrees of freedom; therefore, altered ligament anatomy can have a significant impact on stability. The purpose of this study was to examine the iliolumbar ligament complex in patients with Bertolotti syndrome and anatomically normal controls to determine if underdevelopment of the iliolumbar ligament complex is seen in Bertolotti syndrome.

METHODS

This is a retrospective analysis of patients with Bertolotti syndrome and anatomically normal controls who received care at the authors' institution between 2010 and 2020. Axial thickness of the iliolumbar ligament at the L5 vertebral level was assessed via MRI. Results were compared between the defective and normal side within unilaterally affected (Castellvi types IIa and IIIa) Bertolotti syndrome patients, between defective sides in bilaterally affected Bertolotti syndrome patients (Castellvi types IIb, IIIb, and IV), and between the affected side in Bertolotti syndrome patients and the corresponding location in normal controls.

RESULTS

A total of 173 patients were included in the study, 102 with Bertolotti syndrome and 71 controls. Among the Bertolotti patients, 49 had left LSTVs, 29 had right LSTVs, and 24 had bilateral LSTVs. For patients with unilateral defects, defective side ligaments were thinner than ligaments on the normal side (p < 0.05). For bilateral LSTVs, ligament thickness on each side was considered statistically equivalent (p < 0.05) and not significantly different from that in controls.

CONCLUSIONS

Bertolotti syndrome correlates to significant underdevelopment of the iliolumbar ligament corresponding to the side of the LSTV as compared to the ligament on the contralateral side. In patients with bilateral LSTVs, no difference in the iliolumbar ligament compared to that in controls was seen. Developmental changes in the iliolumbar ligament may further exacerbate the altered lumbosacral biomechanics seen in patients with unilateral LSTV, whereas bilateral LSTVs may still allow normal development of the ligament complex. Further research should be done to examine the discrepancies seen in this study.

Delayed Treatment of a Traumatic Lumbosacral Dislocation With Associated Injuries: A Case Report

CASE

A 41-year-old woman sustained a degloving injury over her lumbosacral and perineal region with fractures of her right tibia and fibula. After diversion colostomy and osteosynthesis for the fractures at a primary center, a missed grade 2 lumbosacral dislocation was diagnosed at a tertiary center and the degloving injury was treated with debridement and skin grafting. After 5 months, the dislocation had progressed to grade 4 and she underwent delayed posterior lumbosacral reduction, interbody fusion, and L4-S1 fixation, with superior gluteal artery perforator flap and subsequent colostomy closure, with good outcomes (Oswestry Disability Index 10%) at the 3-year follow-up.

CONCLUSION

A rare, missed, progressive traumatic L5-S1 spondylolisthesis with associated injuries is described.

Is L5-S1 motion segment different from the rest? A radiographic kinematic assessment of 72 patients with chronic low back pain

PURPOSE

The relationship between biomechanical instability and degenerative changes in the lumbar spine in chronic low back pain (CLBP) patients remains controversial. The main objective of this retrospective radiographical study was to evaluate changes in kinematics at different lumbar levels (in particular the L5-S1 level) with progressive grades of disc degeneration and facet joint osteoarthritis in CLBP patients.

METHODS

Using standing neutral and dynamic flexion/extension (Fx/Ex) radiographs of the lumbar spine, in vivo segmental kinematics at L1-L2 through L5-S1 were evaluated in 72 consecutive CLBP patients. Disc degeneration was quantified using changes in signal intensity and central disc height on mid-sagittal T2-weighted magnetic resonance (MR) scans. Additionally, the presence or absence of facet joint osteoarthritis was noted on T2-weighted axial MR scans.

RESULTS

Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level (p = 0.188), but an association was observed between the two at L4-L5 (p < 0.001) and L3-L4 (p < 0.05) levels. In the absence of facet joint osteoarthritis, the L5-S1 segment showed a greater range of motion (ROM) in Ex (3.3° ± 3.6°) and a smaller ROM in Fx (0.6° ± 4.2°) compared with the upper lumbar levels (p < 0.05), but the differences diminished in the presence of it. In the absence of facet joint osteoarthritis, no change in L5-S1 kinematics was observed with progressive disc degeneration, but in its presence, restabilisation of the L5-S1 segment was observed between mild and severe disc degeneration states.

CONCLUSION

The L5-S1 motion segment exhibited unique degenerative and kinematic characteristics compared with the upper lumbar motion segments. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level, but not at the other lumbar levels. Severe disc degeneration in the presence of facet joint osteoarthritis biomechanically restabilised the L5-S1 motion segment.

Effect of lumbar fasciae on the stability of the lower lumbar spine

The biomechanical effect of tensioning the lumbar fasciae (LF) on the stability of the spine during sagittal plane motion was analysed using a validated finite element model of the normal lumbosacral spine (L4-S1). To apply the tension in the LF along the direction of the fibres, a local coordinate was allocated using dummy rigid beam elements that originated from the spinous process. Up to 10 Nm of flexion and 7.5 Nm of extension moment was applied with and without 20 N of lateral tension in the LF. A follower load of 400 N was additionally applied along the curvature of the spine. To identify how the magnitude of LF tension related to the stability of the spine, the tensioning on the fasciae was increased up to 40 N with an interval of 10 N under 7.5 Nm of flexion/extension moment. A fascial tension of 20 N produced a 59% decrease in angular motion at 2.5 Nm of flexion moment while there was a 12.3% decrease at 10 Nm in the L5-S1 segment. Its decrement was 53 and 9.6% at 2.5 Nm and 10 Nm, respectively, in the L4-L5 segment. Anterior translation was reduced by 12.1 and 39.0% at the L4-L5 and L5-S1 segments under 10 Nm of flexion moment, respectively. The flexion stiffness shows an almost linear increment with the increase in fascial tension. The results of this study showed that the effect of the LF on the stability of the spine is significant.

Lumbosacral Transitional Vertebra: Possible Role in the Pathogenesis of Adolescent Lumbar Disc Herniation

OBJECTIVE

To investigate the role of lumbosacral transitional vertebra (LSTV) in the pathogenesis of adolescent lumbar disc herniation (ALDH) and the association between LSTV type and the herniation level of ALDH.

METHODS

This study was a retrospective case-control analysis of roentgenographic images. All adolescent patients who received surgical treatment for L4/5 or L5/S1 single level lumbar disc herniation in our department from 2010 to 2015 were eligible for the ALDH group. All adolescent patients admitted to our hospital during the same period and who had ever undergone a plain anteroposterior radiologic examination of the abdomen and met the inclusion criteria that ensured the absence of any spinal disorders were selected into the control group. The anteroposterior lumbar or abdomen roentgenograms were collected to identify the LSTV. The incidence of LSTV in the ALDH group and the control group were compared. Among the ALDH group, the association between LSTV type (sacralization or lumbarization) and the herniation level of ALDH were evaluated.

RESULTS

A total of 80 adolescent patients were included in the ALDH group and 92 asymptomatic adolescents were included in the control group. LSTV was found in 24 patients (30%) in ALDH group compared with 7 patients (7.6%) in the control group (P < 0.001; odds ratio, 5.2; 95% confidence interval 2.1, 12.9). Among the adolescent patients with sacralization, the L4/5 disc herniation was significantly more common than L5/S1 (81.3% vs. 18.7%; P = 0.019).

CONCLUSIONS

The LSTV is associated with LDH in adolescents and the sacralization of L5 may contribute to the L4/5 disc herniation in adolescent patients.

Lumbar Disk Herniation in Children and Adolescents: The Significance of Configurations of the Lumbar Spine

BACKGROUND

Lumbar disk herniation in adults is thought to be caused by repetitive overloading and age-rated degenerative changes. However, these causes are absent in children and adolescent patients. We assume that structural malformations in the lumbar spine could predispose intervertebral disks to early degeneration and hence need to be surgically fused. This issue has never been raised before.

OBJECTIVE

To investigate the assumption that structural malformations in the lumbar spine could predispose intervertebral disks to early degeneration and hence need to be surgically fused.

METHODS

Lumbar spine configurations, including the height of the intercrestal line, the length of L5 transverse processes, and the presence of transitional vertebrae, were recorded from anteroposterior radiographs taken from 63 consecutive pediatric patients with lumbar disk herniation admitted to our hospital over a period of 8 years. Each configuration was compared in relation to the level of disk herniation. Diskectomy alone was performed in 36 cases; arthrodesis was added in the remaining 27 cases. Patients' back and leg pain visual analog scale scores and frequency and their Oswestry Disability Index scores were recorded before surgery and at follow-up. The results were compared for assessment of outcome.

RESULTS

Patients with high intercrestal lines and long L5 transverse processes had a significantly higher incidence of L4/5 disk herniation, whereas low intercrestal line and lumbarization were associated with L5/S1 disk herniation. Patients' visual analog scale scores, pain frequency, and Oswestry Disability Index score all improved significantly after surgery, but there was no significant difference with or without arthrodesis.

CONCLUSION

Pediatric lumbar disk herniation is significantly associated with structural malformations of the lumbar spine, but arthrodesis does not improve the clinical outcome.

ABBREVIATIONS

ICL, intercrestal lineLDH, lumbar disk herniationL5TP, L5 transverse processODI, Oswestry Disability IndexTV, transitional vertebraeVAS, visual analog scale.

An International Multicenter Study Assessing the Role of Ethnicity on Variation of Lumbar Facet Joint Orientation and the Occurrence of Degenerative Spondylolisthesis in Asia Pacific: A Study from the AOSpine Asia Pacific Research Collaboration Consortium

Study Design A multinational, multiethnic, cross-sectional image-based study was performed in 33 institutions, representing 10 countries, which were part of the AOSpine Asia Pacific Research Collaboration Consortium. Objective Lumbar facet joint orientation has been reported to be associated with the development of degenerative spondylolisthesis (DS). The role of ethnicity regarding facet joint orientation remains uncertain. As such, the following study was performed across a wide-ranging population base to assess the role of ethnicity in facet joint orientation in patients with DS in the Asia Pacific region. Methods Lateral standing X-rays and axial magnetic resonance imaging scans were obtained for patients with lumbar DS. The DS parameters and facet joint angulations were assessed from L3-S1. Sex, age, body mass index (BMI), and ethnicity were also noted. Results The study included 371 patients with known ethnic origin (mean age: 62.0 years; 64% males, 36% females). The mean BMI was 25.6 kg/m(2). The level of DS was most prevalent at L4-L5 (74.7%). There were 28.8% Indian, 28.6% Japanese, 18.1% Chinese, 8.6% Korean, 6.5% Thai, 4.9% Caucasian, 2.7% Filipino, and 1.9% Malay patients. Variations in facet joint angulations were noted from L3 to S1 and between patients with and without DS (p < 0.05). No differences were noted with regards to sex and overall BMI to facet joint angulations (p > 0.05); however, increasing age was found to increase the degree of angulation throughout the lumbar spine (p < 0.05). Accounting for age and the presence or absence of DS at each level, no statistically significant differences between ethnicity and degree of facet joint angulations from L3-L5 were noted (p > 0.05). Ethnic variations were noted in non-DS L5-S1 facet joint angulations, predominantly between Caucasian, Chinese, and Indian ethnicities (p < 0.05). Conclusions This study is the first to suggest that ethnicity may not play a role in facet joint orientation in the majority of cases of DS in the Asia-Pacific region. Findings from this study may facilitate future comparative studies in other multiethnic populations. An understanding of ethnic variability may assist in identifying those patients at risk of postsurgical development or progression of DS. This study also serves as a model for large-scale multicenter studies across different ethnic groups and cultural boundaries in Asia.

Bilateral Pars Defects at the L4 Vertebra Result in Increased Degeneration When Compared With Those at L5: An Anatomic Study

BACKGROUND

Cadaveric studies have examined disc degeneration at the L4-L5 and L5-S1 motion segments; however, we are not aware of another study that has examined the relationship between bilateral spondylolysis and its effect on degenerative disc disease at those levels. This may have been overlooked by researchers owing to the majority of spondylolysis occurring at the L5 vertebra.

QUESTIONS/PURPOSES

Using osteologic specimens from a collection that included individuals who died in one city in the USA between 1893 and 1938, we asked: (1) do specimens with bilateral spondylolysis (bilateral pars defects) have increased levels of disc degeneration, at their respective motion segments, when compared with matched controls without spondylolysis, and (2) is the finding of a bilateral pars defect associated with more severe arthritis at L4-L5 than at L5-S1?

METHODS

An observational study was performed on 665 skeletal lumbar spines from the Hamann-Todd Osteologic Collection at the Cleveland Museum of Natural History (Cleveland, OH, USA). The specimens included 534 males and 131 females ranging from 17 to 87 years old, with a nearly bell-shaped distribution of ages for males and a larger proportion of younger ages in the female specimens. Of those with spondylolysis, 81 had a defect at L5 and 14 had a defect at L4. The gross specimens were examined subjectively for evidence of arthrosis. At the time of examination, specific attention was not paid to the coexisting presence or absence of spondylolysis nor was the examiner blinded to the age of the specimens. Disc degeneration was measured by the classification of Eubanks et al., a modified version of the Kettler and Wilke classification. Linear regression was performed to derive a formula that would predict the amount of disc degeneration at L4-L5 and L5-S1 for the normal control population given a specimen's age, sex, and race. We then used this formula to evaluate the difference in disc degeneration at the corresponding level of the pars defect that is greater than the predicted amount for a control without spondylolysis. This allowed us to conclude that any significant differences found between the L4-L5 and L5-S1 cohorts were attributable to factors not simply inherent to their functional position in the spine of an individual without a bilateral pars defect.

RESULTS

L4 spondylolysis and L5 spondylolysis showed greater amounts of degeneration compared with that of matched controls (L4 controls: mean = 1.52, SD = 0.74; L4 spondylolysis: mean = 3.21, SD = 0.87; p < 0.001; L5 controls: mean = 0.97, SD = 0.48; L5 spondylolysis: mean = 2.06, SD = 0.98; p < 0.001). When we controlled for the expected amount of degenerative disc disease at each level in controls, the observed degeneration was more severe at L4-L5 than at L5-S1 (p = 0.008, R-squared = 18.6).

CONCLUSIONS

L4-L5 and L5-S1 bilateral spondylolysis groups had increased presence of degenerative disc disease compared with those without bilateral spondylolysis. For the same degree of spondylolysis, the observed amount of disc degeneration was greater at the L4-5 motion segment compared with L5-S1.

CLINICAL RELEVANCE

Although not as common as the spondylolysis at L5-S1, we believe that our findings support that patients with L4-L5 spondylolysis can expect a greater degree of degenerative disc disease and increasing clinical symptoms. Multiple factors in the sacropelvic geometry of an individual, facet morphologic features at L4-L5, and the absence of the iliolumbar ligament at this level are possible contributing factors to the findings of this study.

The Surgical Anatomy of the Lumbosacroiliac Triangle: A Cadaveric Study

OBJECTIVE

The anatomic area delineated medially by the lateral part of the L4-L5 vertebral bodies, distally by the anterior-superior surface of the sacral wing, and laterally by an imaginary line joining the base of the L4 transverse process to the proximal part of the sacroiliac joint, is of particular interest to spine surgeons. We are referring to this area as the lumbo-sacro-iliac triangle (LSIT). Knowledge of LSIT anatomy is necessary during approaches for L5 vertebral and sacral fractures, sacral and iliac tumors, and extraforaminal decompression of the L5 nerve roots.

METHODS

We performed an anatomic dissection of the LSIT in 3 embalmed cadavers (6 triangles), using an anterior and posterior approach.

RESULTS

We identified 3 key tissue planes: the neurological plexus plane, constituted by L4 and L5 nerve roots; an intermediate level constituted by the ileosacral tunnel; and posteriorly, by the lumbosacral ligament, and the posterior muscular plane.

CONCLUSIONS

Improving anatomic knowledge of the LSIT may help surgeons decrease the risk of possible complications. When LSIT pathology is present, a lateral approach corresponding to the tip of the L4 transverse process, medially, is suggested to decrease the risk of vessel and nerve root damage.

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.

Survival rates and risk factors for cephalad and L5-s1 adjacent segment degeneration after L5 floating lumbar fusion : a minimum 2-year follow-up

OBJECTIVE

Although the L5-S1 has distinct structural features in comparison with other lumbar spine segments, not much is known about adjacent segment degeneration (ASD) at the L5-S1 segment. The aim of study was to compare the incidence and character of ASD of the cephalad and L5-S1 segments after L5 floating lumbar fusion.

METHODS

From 2005 to 2010, 115 patients who underwent L5 floating lumber fusion were investigated. The mean follow-up period was 46.1 months. The incidence of radiological and clinical ASD of the cephalad and the L5-S1 segments was compared using survival analysis. Risk factors affecting ASD were analyzed using a log rank test and the Cox proportional hazard model.

RESULTS

Radiological ASD of the L5-S1 segment had a statistically significant higher survival rate than that of the cephalad segment (p=0.001). However, clinical ASD of the L5-S1 segment was significantly lower survival rates than that of the cephalad segment (p=0.038). Risk factor analysis showed that disc degeneration of the cephalad segment and preoperative spinal stenosis of the L5-S1 segment were risk factors.

CONCLUSION

In L5 floating fusion, radiological ASD was more common in the cephalad segment and clinical ASD was more common in the L5-S1 segment. At the L5-S1 segment, the degree of spinal stenosis appears to be the most influential risk factor in ASD incidences, unlike the cephalad segment.

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.

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.

Unilateral lumbosacral dislocation: case report and a comprehensive review

Lumbosacral fracture-dislocation is a rare occurrence. There are more than 73 cases reported in the English literature. We report on the imaging findings and surgical treatment in a patient suffered of unilateral traumatic L5-S1 dislocation associated with severe disruption of the posterior ligamentous complex. The patient underwent open reduction and stabilization of L4-S1 vertebrae with posterior instrumentation system. Open reduction and internal fixation was mandatory as post-traumatic ligamentous insufficiency would lead to abnormal motion. Operative treatment managed to produce a solid arthrodesis and restore stability of the lumbosacral junction. Follow-up revealed excellent results. This study reports a rare injury of the lumbosacral junction, and the literature concerning this unusual condition is extensively reviewed.

Clinical and radiological outcomes of unilateral facetectomy and interbody fusion using expandable cages for lumbosacral foraminal stenosis

OBJECTIVE

Surgical treatment of lumbosacral foraminal stenosis requires an understanding of the anatomy of the lumbosacral area in individual patients. Unilateral facetectomy has been used to completely decompress entrapment of the L5 nerve root, followed in some patients by posterior lumbar interbody fusion (PLIF) with stand-alone cages.

METHODS

We assessed 34 patients with lumbosacral foraminal stenosis who were treated with unilateral facetectomy and PLIF using stand-alone cages in our center from January 2004 to September 2007. All the patients underwent follow-up X-rays, including a dynamic view, at 3, 6, 12, 24 months, and computed tomography (CT) at 24 months postoperatively. Clinical outcomes were analyzed with the mean numeric rating scale (NRS), Oswestry Disability Index (ODI) and Odom's criteria. Radiological outcomes were assessed with change of disc height, defined as the average of anterior, middle, and posterior height in plain X-rays. In addition, lumbosacral fusion was also assessed with dynamic X-ray and CT.

RESULTS

Mean NRS score, which was 9.29 prior to surgery, was 1.5 at 18 months after surgery. The decrease in NRS was statistically significant. Excellent and good groups with regard to Odom's criteria were 31 cases (91%) and three cases (9%) were fair. Pre-operative mean ODI of 28.4 decreased to 14.2 at post-operative 24 months. In 30 patients, a bone bridge on CT scan was identified. The change in disc height was 8.11 mm, 10.02 mm and 9.63 mm preoperatively, immediate postoperatively and at 24 months after surgery, respectively.

CONCLUSION

In the treatment of lumbosacral foraminal stenosis, unilateral facetectomy and interbody fusion using expandable stand-alone cages may be considered as one treatment option to maintain post-operative alignment and to obtain satisfactory clinical outcomes.

Scoliosis after extended hemipelvectomy

STUDY DESIGN

Retrospective review plus 2 representative case reports.

OBJECTIVE

To evaluate the prevalence of scoliosis after extended hemipelvectomy (EH) and illustrate the problem's severity.

SUMMARY OF BACKGROUND DATA

No published series has analyzed this problem. Data are needed to decide the potential need for and timing of spine fusion in these patients.

METHODS

We treated 14 patients with EH over 10 years. Mean age was 47 years. Diagnoses included osteosarcoma (6); chondrosarcoma (4); metastatic cancer (2); and MFH and undifferentiated sarcoma (1 each). Operating time ranged from 7 to 15 hours, and mean estimated blood loss was 8 L. Patients were observed for scoliosis, functional results, and for oncological outcome (survival, disease progression). Two patients who became scoliotic after EH illustrate the problem: a 31-year-old man underwent EH for pelvic osteosarcoma and progressively developed a painful 44° scoliotic curve; and a 27-year-old woman who developed a 60° painful scoliotic curve and radiculopathy years after EH including L5-S1 disc disruption.

RESULTS

Of 12 patients, 8 died within 7 months of EH. Only 2 of 12 patients are long-term survivors free of disease (3 and 6 years after surgery), and 2 are alive with disease more than 1 year after surgery. In patients >1 year survival, 3 of 4 patients had curves greater than 20°. Of 10 evaluable patients, 2 developed a curve greater than 30° that warranted fusion. Four others had curves between 20° and 30°. Of these 6, 5 developed a sharp-angled lumbar curve with the concavity away from the operated side. Risk factors for symptomatic scoliosis after EH include disc disruption, paraspinal muscle/ligament resection, or facetectomies in ambulatory patients with a lengthy survival.

CONCLUSION

Primary spinal fixation should be avoided because of the high morbidity and early mortality of EH. Selected high-risk patients can be stabilized later if they develop painful instability.

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.

Invasive and minimally invasive surgical techniques for back pain conditions

This article summarizes current issues related to invasive and minimally invasive surgical techniques for back pain conditions. It describes pain generators and explains theories about how discs fail. The article discusses techniques for treating painful sciatica, painful motion segments, and spinal stenosis. Problems related to current imaging are also presented. The article concludes with a discussion about physical therapy.

Invasive and minimally invasive surgical techniques for back pain conditions

Back pain is a ubiquitous problem for developed countries. It is a source of disability for society and is a financial drain through lost wages and productivity. The treatment of spine-related pain has changed over the years: minimally invasive approaches are now favored. Despite this trend, surgeons still rely on decompressions of compressed neurological structures and the fusion of painful motion segments. The history of treatments of spine-related pain as well as modern and minimally invasive techniques are reviewed.

Vibration testing of a fresh-frozen human pelvis: The role of the pelvic ligaments

A biodynamic model of the human pelvis is being developed in the frame of a research project on low back pain. In order to validate such model, the dynamic behaviour of the human pelvis needs to be investigated. In this study, a human fresh-frozen specimen comprising the three bones of the pelvic girdle and its ligamentous system has been used to perform vibration testing. In such test the response of the system to vibrations is measured at various points on the structure for frequencies between 10 and 340 Hz. The vibration testing is performed a first time on the specimen with intact ligamentous system. The measurements are taken two more times after subsequent bilateral resection of both the sacrotuberous and the sacrospinous ligaments first, and the iliolumbar ligaments afterwards. A comparison between the system response obtained in the three configurations provides information on the role of the resected ligaments in the dynamics of the system, thus on their relevance in the model. Results indicate that the sacrospinous, the sacrotuberous and the iliolumbar ligaments do not play a role in the pelvis dynamics as measured in this study, and will therefore not be represented in the biodynamic model.

Radiological Risk Factors of Pseudoarthrosis and/or Instrument Breakage After PLF With the Pedicle Screw System in Isthmic Spondylolisthesis

OBJECTIVE

Several studies have reported favorable results of posterolateral fusion (PLF) with pedicle screw systems (PSs) for isthmic spondylolisthesis. However, the best indication and limitations of this method still remain unclear. The present study aimed to analyze the radiological risk factors of pseudoarthrosis and/or instrumentation failure after PLF with PSs in isthmic spondylolisthesis, and to determine the limitations of this method.

METHODS

The study group comprised of 101 patients with isthmic spondylolisthesis who underwent PLF with PSs. Follow-up was performed for more than 5 years. Statistical analyses with multivariate logistic regression models were used to identify risk factors of pseudoarthrosis and/or instrument failures associated with PLF with PSs.

RESULTS

Average follow-up was 8 years. Fusion rate was 95%. There were instrument breakage in 6 patients, and pseudoarthrosis in 5. Statistical analysis with a logistic regression model revealed that preoperative % disc height (odds ratio: 3.60 per 10%, P<0.01) and slip angle (odds ratio: 4.48 per 10 degrees kyphosis, P<0.05) were the most crucial risk factors of pseudoarthrosis and/or instrument breakage when performing PLF for isthmic spondylolisthesis.

CONCLUSIONS

In conclusion, PLF with PSs provided satisfactory results with high fusion rate. However, there were complications including pseudoarthrosis or instrument breakage in specific conditions. Preserved disc height and presence of segmental kyphosis were risk factors of these complications. Statistically, % disc height within 20% without segmental kyphosis was the best indication for PLF with PSs.

Intervertebral disc degeneration associated with lumbosacral transitional vertebrae

We studied 52 patients, each with a lumbosacral transitional vertebra. Using MRI we found that the lumbar discs immediately above the transitional vertebra were significantly more degenerative and those between the transitional vertebrae and the sacrum were significantly less degenerative compared with discs at other levels. We also performed an anatomical study using 70 cadavers. We found that the iliolumbar ligament at the level immediately above the transitional vertebra was thinner and weaker than it was in cadavers without a lumbosacral transitional vertebra.

Instability of the vertebral segment above the transitional vertebra because of a weak iliolumbar ligament could lead to subsequent disc degeneration which may occur earlier than at other disc levels. Some stability between the transitional vertebra and the sacrum could be preserved by the formation of either an articulation or by bony union between the vertebra and the sacrum through its transverse process. This may protect the disc from further degeneration in the long term.

The mechanics of back-extensor torque production about the lumbar spine

The purpose of this study was to develop and evaluate a biomechanical model of lumbar back extension over a wide range of positions for the lumbar spine, incorporating the latest information on muscle geometry and intra-abdominal pressure (IAP). Analysis of the Visible Human data was utilised in order to obtain anatomical information unavailable from the literature and magnetic resonance imaging was used to generate subject-specific anatomical descriptions. The model was evaluated by comparisons with measured maximal voluntary static back-extension torques. Predicted maximal specific muscle tensions agreed well with in vitro measurements from the literature. When modelling the maximal static back-extension torque production, it was possible to come fairly close to simultaneous equilibrium about all the lumbar discs simply by a uniform muscle activation of all back-extensor muscles (the caudal part showed, however, less agreement). This indicates that equilibrium in the lumbar spine is mainly regulated by passive mechanical properties, e.g. muscle length changes due to postural changes, rather than due to complex muscle coordination, as earlier proposed. The model showed that IAP (measured during torque exertions) contributes about 10% of the total maximal voluntary back-extensor torque and that it can unload the spine from compression. The spinal unloading effect from the IAP was greatest with the spine held in a flexed position. This is in opposition to the effects of changed muscle lever arm lengths, which for a given load would give the largest spinal unloading in the extended position. These findings have implications for the evaluation of optimal lifting techniques.

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.

Does the morphology of the iliolumbar ligament affect lumbosacral disc degeneration?

STUDY DESIGN

An anatomic study of the iliolumbar ligament was performed in association with lumbosacral disc degeneration.

OBJECTIVES

To determine whether the morphology of the iliolumbar ligament contributes to lumbosacral disc degeneration.

SUMMARY OF BACKGROUND DATA

There have been few reports concerning the clinical significance of the iliolumbar ligament.

METHODS

We dissected 25 male and 27 female cadavers and measured the length and cross-sectional area of the anterior and posterior bands of the iliolumbar ligament. The specimens were classified into three groups based on the grade of L4-L5 and L5-S1 disc degeneration: the L4-L5 disc was more degenerated than the L5-S1 disc (group L), the L4-L5 disc was less degenerated than the L5-S1 disc (group S), and both discs were equally degenerated (group E). The results were statistically compared among the three groups.

RESULTS

The length of the posterior bands and the summation of the length of the anterior and posterior bands were significantly shorter in group L than in group S, and the cross-sectional area of the posterior bands and the summation of the cross-sectional area of the anterior and posterior bands were significantly larger in group L than in groups S or E in the male cadaver specimens.

CONCLUSION

If the iliolumbar ligaments (especially the posterior band of the ligament) of a male patient are short and have a large cross-sectional area, the lumbosacral junction can be stabilized by the ligaments, with the L5-S1 disc being protected from degeneration. The L4-L5 disc may be prone to degeneration.

Radiographic classification of L5 isthmic spondylolisthesis as adolescent or adult vertebral slip

STUDY DESIGN

A radiographic and morphologic study was conducted to investigate low-grade spondylolisthesis in cases with preexisting isthmic spondylolysis of L5.

OBJECTIVE

To distinguish radiographically between vertebral slips before and after skeletal maturity as determined by deformities of the sacral endplate.

SUMMARY AND BACKGROUND DATA

Very few reports have shown that spondylolisthesis with preexisting isthmic defects of L5 develops frequently in adulthood. The prognostic factors of the vertebral slip have remained unclear. It is hard to determine the onset time of low-grade spondylolisthesis.

METHODS

This study examined plain radiographs of 367 adult patients with pars defects of L5 (213 without slippage and 154 with Grade 1 or 2 spondylolisthesis) and 310 control subjects, ages 20 to 59 years at the first visit. The following parameters were measured and analyzed for each age decade: the sacral table index (anteroposterior width of the sacral endplate expressed as a percentage of the anteroposterior diameter of the upper L5 endplate), the sacral table angle (formed by the sacral endplate with the posterior wall of S1), the relative thickness of the L5 transverse process, and the iliac crest height.

RESULTS

The prevalence of patients with slippage who met deformity criteria (sacral table index > 102% [the mean plus 2 standard deviations of the controls] and sacral table angle </=97 degrees [the mean of the controls]) remained almost one fourth during all decades. On the contrary, the prevalence of patients with slippage who met normal-shape criteria (sacral table index </=102% and sacral table angle >/=89 degrees [mean minus 2 standard deviations of the controls]) was 0% in the third decade, but increased remarkably in the fifth and sixth decades. Of the 213 patients without slippage, 8 patients in whom new slippage developed during long-term follow-up evaluation all had a normally-shaped sacral table. The prevalence of patients without slippage decreased gradually with age, and elderly patients had relatively broader transverse processes and a higher iliac crest line.

CONCLUSIONS

The authors considered that the slips with and those without deformities of the sacral table had developed in adolescence and adulthood, respectively. Using new radiographic parameters that indicate widening and tilting of the sacral table, low-grade isthmic spondylolis thesis can be categorized into "adolescent and adult vertebral slips."

Disorders of the Sacroiliac Joint

Controversies have surrounded the sacroiliac joint. The sacroiliac joint (SIJ) is a considerably complex and strong joint with limited mobility, mechanically serving as a force transducer and a shock absorber. Anatomical changes are seen in the SIJ throughout an individual's lifetime. The ligamentous system associated with the SIJ serves to enhance stability and offer proprioceptive feedback in context with the rich plexus of articular receptors. Stability in the SIJ is related to form and force closure. Movement in the SIJ is 3-D about an axis outside of the joint. The functional examination of the SIJ is related to a clinical triad.

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.

The effect of disc degeneration and facet joint osteoarthritis on the segmental flexibility of the lumbar spine

STUDY DESIGN

A biomechanical and imaging study of human cadaveric spinal motion segments.

OBJECTIVE

To investigate the effect of both disc degeneration and facet joint osteoarthritis on lumbar segmental motion.

SUMMARY OF BACKGROUND DATA

Spinal degeneration includes the osteoarthritic changes of the facet joint as well as disc degeneration. Disc degeneration has been reported to be associated with spinal motion. The association of facet joint osteoarthritis with lumbar segmental motion characteristics and the combined influence of disc degeneration and facet osteoarthritis has not yet been investigated.

METHODS

A total of 110 lumbar motion segments (52 female, 58 male) from 44 human lumbar spines were studied (mean age = 69 years). Magnetic resonance images were used to assess the disc degeneration from Grade I (normal) to Grade V (advanced) and the osteoarthritic changes in the facet joints in terms of cartilage degeneration, subchondral sclerosis, and osteophytes. Disc height, endplate size, and facet joint orientation and width also were measured from the computed tomographic images. Rotational movements of the motion segment in response to the flexion, extension, lateral bending, and axial rotational moments were measured using a three-dimensional motion analysis system.

RESULTS

Female motion segments showed significantly greater motion (lateral bending: P < 0. 001, flexion: P < 0.01, extension: P < 0.05) and smaller endplate size (P < 0.001) than male ones. The segmental motion increased with increasing severity of disc degeneration up to Grade IV, but decreased in both genders when the disc degeneration advanced to Grade V. In male segments, the disc degeneration-related motion changes were significant in axial rotation (P < 0.001), lateral bending (P < 0.05), and flexion (P < 0.05), whereas female segments showed significant changes only in axial rotation (P < 0.001). With cartilage degeneration of the facet joints, the axial rotational motion increased, whereas the lateral bending and flexion motion decreased in female segments. In male segments, however, motion in all directions increased with Grade 3 cartilage degeneration and decreased with Grade 4 cartilage degeneration. Subchondral sclerosis significantly decreased the motion (female: axial rotation, P < 0. 05; extension, P < 0.05 vs.- male:flexion,P < 0.05). Severity of osteophytes had no significant association with the segmental motion.

CONCLUSION

Axial rotational motion was most affected by disc degeneration, and the effects of disc degeneration on the motion were similar between genders. Facet joint osteoarthritis also affected segmental motion, and the influence differed for male and female spines. Further studies are needed to clarify whether the degenerative process of facet joint osteoarthritis differs between genders and how facet joint osteoarthritis affects the stability of the spinal motion segment.

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.

Biomechanical functions of the iliolumbar ligament in L5 spondylolysis

Abiomechanical study of the functions of the iliolumbar ligament in L5 spondylolysis was performed. Five fresh cadaveric specimens were used. The bilateral ilia and sacrum were fixed. Four kinds of pure moments (10 Nm) were applied to the specimens at the top (L4) vertebra: flexion, extension, and right and left axial rotations. The three-dimensional position of the L5 vertebra was measured after serial transections in: (1) the intact condition; (2) bilateral pars interarticulares of L5 transected; (3) anterior bands of the iliolumbar ligaments transected; and (4) posterior bands of the iliolumbar ligaments transected. In L5 spondylolysis, flexion and axial rotation of L5 on S1 are significantly regulated by the anterior and posterior bands of the iliolumbar ligaments (especially by the posterior bands of the ligaments). The integrity of the ligament may determine the stability of the lumbosacral junction and the amount of forward slipping of the L5 vertebra.

Cineradiographic motion analysis of normal lumbar spine during forward and backward flexion

STUDY DESIGN

Motion characteristics of the lumbar spine in the sagittal plane were investigated in vivo using cineradiography.

OBJECTIVES

To evaluate the differences in motion characteristics of the normal lumbar spine between forward and backward flexion.

SUMMARY OF BACKGROUND DATA

Despite previous lumbar kinematic studies, differences in motion characteristics of the lumbar spine between forward and backward flexion remain unclear.

METHODS

Cineradiographic motion analysis was performed in 10 asymptomatic healthy male volunteers for two different lumbar motions. The motions consisted of active forward flexion (from maximum extension to maximum flexion) and active backward flexion (from maximum flexion to maximum extension). Displacements of the anterior and posterior vertebral corners from L3/L4 to L5/S1 were measured continuously in reference to the local coordinate system. Parameters investigated were onset of segmental motion, velocity of segmental motion, and continuous motion profiles of the vertebral corners during the two different motions.

RESULTS

During forward flexion, initial lumbar motion started stepwise from the upper level (L3/L4) to the lower levels with phase lags. Angular velocity at the onset of motion increased as the level descended. On the contrary, during backward flexion, initial motion started from the lower level (L5/S1) to the upper levels. There was no relation between velocity and spinal levels during backward flexion. Motion profiles of both anterior and posterior vertebral corners at L3/L4 and L4/L5 segments during forward flexion were similar to those during backward flexion. However, the motion profiles at L5/S1 segment during forward flexion were different from those during backward flexion.

CONCLUSIONS

During forward flexion of the lumbar spine, initial motion started from upper segments to the lower segments with phase lags. During backward flexion, initial motion started from the lower segments to the upper segments. Motion profiles of the vertebral corners during forward flexion were similar to those during backward flexion at L3/L4 and L4/L5. The motion profiles at L5/S1 were different between both flexions.

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.

Radiographic analysis of lumbar motion in relation to lumbosacral stability. Investigation of moderate and maximum motion

STUDY DESIGN

This in vivo study was performed to examine active lumbar motion without any support.

OBJECTIVES

To establish the behavior of segmental flexibility according to the degree of whole lumbar motion and to clarify the correlation between bony characteristics of the lumbosacral junction and stability in the segment.

SUMMARY OF BACKGROUND DATA

In previous studies, the full mobility of the lumbar segments has been investigated. The details of motion commonly seen with the activities of daily living have not been clarified. It has been reported that the iliolumbar ligaments have an influence on lumbosacral stability and that the relative thickness of the transverse process of L5 could indicate the functional strength of the iliolumbar ligaments. However, the effects of the iliolumbar ligaments on the lumbosacral range of motion have not been studied in vivo.

METHODS

Ninety adults, aged 20-39 years, were requested to perform motion commonly associated with activities of daily living, defined as moderate motions of the lumbar spine. The subjects then were asked to perform maximal motion of the lumbar spine. The segmental ranges of motion, segmental flexion, and extension at every level of the lumbar spine were calculated by using functional radiographs. The correlation between the relative thickness of the transverse process of L5 and the motion seen at the lumbosacral junction was also determined.

RESULTS

The greatest segmental range of motion was found at L2-L3 in moderate motion and at L4-L5 in maximal motion. It shifted gradually from the upper to lower lumbar levels with the increase in total lumbar motion. With an increase in lumbar spine motion, maximum segmental flexion shifted from L2-L3 to L3-L4, then to L4-L5. Segmental extension changed only at L5-S1, increasing with total lumbar spine motion. There was an inverse statistical correlation between lumbosacral motion and relative thickness of the L5 transverse process.

CONCLUSIONS

The greatest segmental flexibility induced by the moderate lumbar motion, usually seen with the activities of daily living, occurred more in the upper segments of the lumbar spine, especially in flexion. Further, the iliolumbar ligaments regulate lumbosacral motion especially flexion.

Comparative morphometric study of the australopithecine vertebral series Stw-H8/H41

Lower spinal structure correlates well with positional behavior among mammals. Nonetheless, the functional morphology of the axial post-crania of australopithecines has received less attention than their appendicular skeletons. This paper presents a detailed description and comparative morphometric analysis of the australopithecine thoracolumbar vertebral series Stw-H8/H41, and examines spinal mechanics in early hominids. Stw-H8/H41 is an important specimen, as the australopithecine vertebral sample is small, and vertebral series are more useful than isolated elements for the interpretation of spinal function. Results of the study support the interpretation that australopithecine species are highly sexually dimorphic. The study also reveals a considerable amount of morphometric variation other than size among australopithecine vertebrae, though the sample is too small and incomplete to ascertain whether this indicates significant interspecific differences in spinal function. Most importantly, structural and metric observations confirm that the morphology of the lower spine in australopithecines has no modern analogue in its entirety. Aspects of zygapophyseal structure, numerical composition of the lumbar region, and centrum wedging suggest that the australopithecine vertebral column was adapted to human-like intrinsic lumbar lordosis and stable balance of the trunk over the pelvis in sustained bipedal locomotion. However, relative centrum size in australopithecines indicates that either they had a different mechanism for channeling vertical forces through the vertebral column than humans, or differed behaviorally from humans in ways that produced smaller increments of compression across their centra. These findings have important implications for hypotheses of australopithecine positional behavior, and demonstrate that larger samples and more complete vertebral series are needed to improve our understanding of australopithecine spinal function.

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

Data of the postmortem studies of the iliolumbar ligament are controversial because of the number, complexity, and variability of the structures present in the lumbosacral region. The objective of this work was to study the anatomy of the iliolumbar ligament to resolve some clinical problems: (1) do anatomic bases exist that can explain the lumbar painful syndrome termed "iliolumbar syndrome?" (2) do iliolumbar ligament varieties exist that can influence lumbosacral joint stability? Magnetic resonance was used to analyze the anatomic structure of the iliolumbar ligament of live human beings. Thirty iliolumbar ligaments of 15 volunteers were analyzed with magnetic resonance. The images were acquired along the transversal and coronal planes (respectively, superoinferior and anteroposterior). The portion of the iliolumbar ligament originating from the L-5 transverse process is made up of two bands (anterior and posterior). The anterior band is broad and flat and has two different anatomic varieties. Type 1 originates from the anterior aspect of the inferolateral portion of the L-5 transverse process and fans out widely before inserting on the anterior portion of the iliac tuberosity. Type 2 originates anteriorly, laterally, and posteriorly from inferolateral aspect of the L-5 transverse process and fans out before inserting on the anterior portion of the iliac tuberosity. The posterior band of the iliolumbar ligament originates from the apex of the L-5 transverse process and is fusiform. Just before inserting on the anterior margin and apex of the iliac crest it widens, assuming the aspect of a small cone. On the transaxial plane, the anterior band of the iliolumbar ligament was placed along the horizontal line passing through the transverse processes, whereas the posterior band formed an angle of approximately 45 to 55 degrees opened posterolaterally with this line. On the coronal plane, the spatial disposition of the iliolumbar ligament varies greatly with the size of the L-5 vertebra and its position in the pelvis: (1) when L-5 is situated low in the pelvis, the bands of the iliolumbar ligament are longer and oblique; (2) when L-5 is situated high in the pelvis, the bands of the iliolumbar ligament are shorter and horizontal. The insertion manner of iliolumbar ligament posterior band in the iliac crest allows us to confirm the possibility of existence of the lumbar painful syndrome termed iliolumbar syndrome and confirms the possibility of examining its insertional site manually. Being accessible manually, various drugs can be injected directly into it or deep friction can be applied. This posterior band is thinner than the anterior, with a smaller insertional base on the iliac crest, which explains its lesser resistance to torsional overloading and also explains the frequency of this painful syndrome. It is probable that the spatial disposition of the iliolumbar ligament influences its antitorsional role. Further anatomic and biomechanic studies are needed.

The role of the iliolumbar ligament in low back pain

Low back pain is caused by a variety of etiologies. Some clinicians have postulated that much low back pain is due to trauma to the iliolumbar ligament. The iliolumbar ligament is one of the three pelvic-lumbar ligaments and develops during the 12th week of gestation. The iliolumbar ligament appears to be a major stabilizing component between the vertebral spine and the pelvis. The innervation of the iliolumbar ligament appears similar to the posterior lumbar ligaments. Our hypothesis is: micro-trauma to the iliolumbar ligament is the primary cause of many cases of chronic low back pain because (1) it is the weakest component of the multifidus triangle; (2) there is increased susceptibility to injury due to its angulated attachment; (3) it is a primary inhibitor of excess sacral flexion; (4) it is a highly innervated nociceptive tissue; and (5) it plays an increased role with progressive disc degeneration.

Variations in the lumbosacral ligament and associated changes in the lumbosacral region resulting in compression of the fifth dorsal root ganglion and spinal nerve

Sixty-five lumbosacral regions from adult cadavers were dissected and the position and relations of the lumbosacral ligament noted. The lumbosacral ligament was present in all specimens; in 22 (34%) it extended medially across the ventral ramus of the fifth lumbar nerve, and in six (9%) of these the underlying nerve was compressed and visibly flattened. On two of these specimens the nerve, together with its dorsal root ganglion, was removed, processed, and stained with Masson's trichrome. The compressed nerve showed increased thickness of endoneurial and perineurial connective tissue, and the cells of the dorsal root ganglion were smaller and surrounded by increased connective tissue, particularly at the periphery of the ganglion. Observation of the lumbosacral ligament and surrounding anatomical structures suggests that anatomical variation in this region may be attributed to the health of the lumbosacral articular elements. In those specimens showing compression of the fifth lumbar spinal nerve there was also narrowing of the lumbosacral interspace. In these the disc itself was compressed and showed degenerative changes. The articular processes at the lumbosacral joint were irregular, with thinning and fissuring of the artiuclar cartilage. It is suggested that the processes which lead to the further development of the ligament, by the formation of additional fibrous bands, are mechanical in nature and result from instability at the lumbosacral region itself. Instability subsequently leads to the initiation of a chain of degenerative changes, involving pathology at the lumbosacral disc and zygapophyseal joints.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcome after laminectomy for lumbar spinal stenosis. Part II: Radiographic changes and clinical correlations

The pre- and postoperative lumbar spine radiographs of 119 patients who underwent decompressive lumbar laminectomy were studied to evaluate radiographic changes and to correlate them with clinical outcome. An accurate and reproducible method was used for measuring pre- and postoperative radiographs that were separated by an average interval of 4.6 years. Levels of the spine that underwent laminectomy showed greater change in spondylolisthesis, disc space angle, and disc space height than unoperated levels. Outcome correlated with radiographic changes at operated and unoperated levels. This study demonstrates that radiographic changes are greater at operated than at unoperated levels and that some postoperative symptoms do correlate with these changes. Lumbar fusion should be considered in some patients who undergo decompressive laminectomy. The efficacy of and unequivocal indications for lumbar fusion can only be determined from randomized, prospective, controlled trials, however, and these studies have not yet been undertaken.

The sacroiliac joint: review of anatomy, mechanics, and function

The purpose of this paper is to review the anatomy and function of the pelvis in order to enhance the clinical understanding of this closed chain kinematic complex. The relevant bony and soft tissue anatomy is discussed with an emphasis on the complex and unique features of the related parts of the pelvis. Osteokinematics of the pelvis and the sacroiliac joints are discussed relevant to functional movements of the spine and lower extremities. Intrapelvic joint surface motion is presented in light of past and more recent experimental work. Questions regarding the validity of clinical sacroiliac models and future research are posed. J Orthop Sports Phys Ther 1991;13(2):71-84.