Functional construction of the sacroiliac ligamentous apparatus

Selective pressures in the human bony pelvis: Decoupling sexual dimorphism in the anterior and posterior spaces

OBJECTIVES

Sexual dimorphism in the human bony pelvis is commonly assumed to be related to the intensity of obstetrical selective pressures. With intense obstetrical selective pressures, there should be greater shape dimorphism; with minimal obstetrical selective pressures, there should be reduced shape dimorphism. This pattern is seen in the nondimorphic anterior spaces and highly dimorphic posterior spaces. Decoupling sexual dimorphism in these spaces may in turn be related to the differential influence of other selective pressures, such as biomechanical ones.

MATERIALS AND METHODS

The relationship between sexual dimorphism and selective pressures in the human pelvis was examined using five skeletal samples (total female n = 101; male n = 103). Pelvic shape was quantified by collecting landmark coordinate data on articulated pelves. Euclidean distance matrix analysis was used to extract the distances that defined the anterior and posterior pelvic spaces. Sex and body mass were used as proxies for obstetrical and biomechanical selective pressures, respectively.

RESULTS

MANCOVA analyses demonstrate significant effects of sex and body mass on distances in both the anterior and the posterior spaces. A comparison of the relative contribution of shape variance attributed to each of these factors suggests that the posterior space is more influenced by sex, and obstetrics by proxy, whereas the anterior space is more influenced by body mass, and biomechanics by proxy.

CONCLUSIONS

Although the overall shape of the pelvis has been influenced by obstetrical and biomechanical selective pressures, there is a differential response within the pelvis to these factors. These results provide new insight into the ongoing debate on the obstetrical dilemma hypothesis.

A partial hominoid innominate from the Miocene of Pakistan: description and preliminary analyses

We describe a partial innominate, YGSP 41216, from a 12.3 Ma locality in the Siwalik Group of the Potwar Plateau in Pakistan, assigned to the Middle Miocene ape species Sivapithecus indicus. We investigate the implications of its morphology for reconstructing positional behavior of this ape. Postcranial anatomy of extant catarrhines falls into two distinct groups, particularly for torso shape. To an extent this reflects different although variable and overlapping positional repertoires: pronograde quadrupedalism for cercopithecoids and orthogrady for hominoids. The YGSP innominate (hipbone) is from a primate with a narrow torso, resembling most extant monkeys and differing from the broader torsos of extant apes. Other postcranial material of S. indicus and its younger and similar congener Sivapithecus sivalensis also supports reconstruction of a hominoid with a positional repertoire more similar to the pronograde quadrupedal patterns of most monkeys than to the orthograde patterns of apes. However, Sivapithecus postcranial morphology differs in many details from any extant species. We reconstruct a slow-moving, deliberate, arboreal animal, primarily traveling above supports but also frequently engaging in antipronograde behaviors. There are no obvious synapomorphic postcranial features shared exclusively with any extant crown hominid, including Pongo.

The extent of ligament injury and its influence on pelvic stability following type II anteroposterior compression pelvic injuries--A computer study to gain insight into open book trauma

Surgical stabilization of the pelvis following type II anteroposterior compression pelvic injuries (APCII) is based on the assumption that the anterior sacroiliac, sacrospinous, and sacrotuberous ligaments disrupt simultaneously. Recent data on the ligaments contradict this concept. We aimed at determining the mechanisms of ligament failure in APCII computationally. In an individual osteoligamentous computer model of the pelvis, ligament load, and strain were observed for the two-leg stance, APCII with 100-mm symphyseal widening and for two-leg stance with APCII-related ligament failure, and validated with body donors. The anterior sacroiliac and sacrotuberous ligaments had the greatest load with 80% and 17% of the total load, respectively. APCII causes partial failure of the anterior sacroiliac ligament and the pelvis to become horizontally instable. The other ligaments remained intact. The sacrospinous ligament was negligibly loaded but stabilized the pelvis vertically. The interosseous sacroiliac and sacrotuberous ligaments are likely responsible for reducing the symphysis and might serve as an indicator of vertical stability. The sacrospinous ligament appears to be of minor significance in APCII but plays an important role in vertical stabilization. Further research is necessary to determine the influence of alterations in ligament and bone material properties.

Ligamentous influence in pelvic load distribution

BACKGROUND CONTEXT

The influence of the posterior pelvic ring ligaments on pelvic stability is poorly understood. Low back pain and sacroiliac joint (SIJ) pain are described being related to these ligaments. Computational approaches involving finite element (FE) modeling may aid to determine their influence. Previous FE models lacked in precise ligament geometries and material properties, which might have influence on the results.

PURPOSE AND STUDY DESIGN

The aim of this study is to investigate ligamentous influence in pelvic stability by means of FE using precise ligament material properties and morphometries.

METHODS

An FE model of the pelvis bones was created from computer tomography, including the pubic symphysis joint (PSJ) and the SIJ. Ligament data were used from 55 body donors: anterior (ASL), interosseous (ISL), and posterior (PSL) sacroiliac ligaments; iliolumbar (IL), inguinal (IN), pubic (PL), sacrospinous (SS), and sacrotuberous (ST) ligaments; and obturator membrane (OM). Stress-strain data were gained from iliotibial tract specimens. A vertical load of 600 N was applied. Pelvic motion related to altered ligament and cartilage stiffness was determined in a range of 50% to 200%. Ligament strain was investigated in the standing and sitting positions.

RESULTS

Tensile and compressive stresses were found at the SIJ and the PSJ. The center of sacral motion was at the level of the second sacral vertebra. At the acetabula and the PSJ, higher ligament and cartilage stiffnesses decrease pelvic motion in the following order: SIJ cartilage>ISL>ST+SS>IL+ASL+PSL. Similar effects were found for the sacrum (SIJ cartilage>ISL>IL+ASL+PSL) but increased ST+SS stiffnesses increased sacral motion. The influence of the IN, OM, and PL was less than 0.1%. Compared with standing, total ligament strain was reduced to 90%. Increased strains were found for the IL, ISL, and PSL.

CONCLUSIONS

Posterior pelvic ring cartilage and ligaments significantly contribute to pelvic stability. Their effects are region- and stiffness dependent. While sitting, load concentrations occur at the IL, ISL, and PSL, which goes in coherence with the clinical findings of these ligaments serving as generators of low back pain.

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.

Novel insights into the sacroiliac joint ligaments

STUDY DESIGN

The ligaments of the human sacroiliac joint (SIJ) were investigated morphometrically.

OBJECTIVE

A macroscopical study was performed to measure the anterior sacroiliac ligament (ASL), the interosseous sacroiliac ligament (ISL), and the posterior sacroiliac ligament (PSL), applying different methods of ligament visualization.

SUMMARY OF BACKGROUND DATA

Little is known about the SIJ ligaments, especially about the ISL. Pelvic computer simulations neglect these ligaments due to the lack of information. Computer simulations of the SIJ ligaments may help to improve the clinical outcome of SIJ operations.

METHODS

Seven-Tesla MR images, CT images, and corresponding thin slice plastinates of the SIJ of 1 male and 1 female specimen were obtained. Serial sections of the SIJ of 32 frozen specimens (13 males, 19 females) were generated to gather measurements of the SIJ ligaments.

RESULTS

By means of the MR images and the plastinates, a virtual reconstruction of the SIJ ligaments was accomplished. Parallelepipeds were attributed to the cranial, middle, and caudal parts of all SIJ ligaments. This allowed precise measurements and statistical comparison including positional relationships. The ISL volumes and origin surfaces were the largest. Statistically, the ASL and PSL parameters were larger in males, while the ISL parameters were larger in females. The height of the cranial ASL part showed large negative correlations in spite of positive correlations of the other heights.

CONCLUSION

The combined use of high-resolution MRI and thin slice plastination allows precise reconstructions of the SIJ ligaments. With these techniques, the ligaments can be visualized in situ and described morphometrically if based on substantive data. The SIJ ligaments are gender-dependent. This has to be taken into account for pelvic computer simulations.

Diagram specific to sacroiliac joint pain site indicated by one-finger test

BACKGROUND

The sacroiliac joint (SIJ) can be a source of low back and lower limb pain. The SIJ pain can originate not only from the joint space but also from the ligaments supporting the joint. Its diagnosis has been difficult because the physical and radiological examinations have proved less than satisfactory. Thus, to know the specific sites of SIJ pain, if these exist, could be very useful for making the diagnosis. The purpose of the present study was to identify the main site of SIJ pain according to the patient's pointing with one finger and to confirm the site by a pain-provocation test and periarticular lidocaine injection.

METHODS

Forty-six of 247 consecutive patients with low back pain at our outpatient clinic, who could indicate with one finger the main site of the pain, which presented at only one site and was reproducible, were the subjects of this study. The main site of pain was anatomically confirmed by fluoroscopy. Then, a periarticular SIJ injection was performed. The patients were blindly assessed and a diagram of the main site of the SIJ pain was made.

RESULTS

There were 19 males and 27 females and the age averaged 50 years. Eight patients showed a positive placebo response and were excluded from this study. Twenty-five of the remaining 38 patients indicated the main site of pain at the posterior-superior iliac spine (PSIS) or within 2 cm of the PSIS, and 18 of these patients showed a positive effect with periarticular SIJ block. The other 13 patients, including 2 patients with a positive response to the periarticular block, did not show the PSIS as the main site of pain.

CONCLUSIONS

Our study clearly indicated that when patients point to the PSIS or within 2 cm of it as the main site of low back pain, using one finger, the SIJ should be considered as the origin of their low back pain.

The Neuroarticular Lesion in the Elderly: A Condensed Literature Review

OBJECTIVE

This condensed literature review was performed to show how inappreciably known are the aging effects of the neuromuscular system, especially the neuroarticular function. To give a needed perspective on the aging process of the musculoskeletal system of a rapidly aging population that is all-important to the chiropractor.

DATA SOURCES

An online search of several databases (MEDLINE and MANTIS) provided several guidelines for review. Comparison among the guidelines was made on different aspects: format, focus, significance of aging of the neuroarticular process, and primary diagnostic considerations. For brevity, no tables were cited for comparisons on the aspects covered and supported by the references.

DATA SYNTHESIS

Condensed literature review from abstracts and full-length articles were used to establish the review conclusions.

RESULTS

The data and information found in this literature search are insufficient to draw primary conclusions about the aging process and the neuroarticular complex.

CONCLUSION

It may be simply concluded that there needs to be additional concentrated research in the area of the neuroarticular process and the lesion that occurs at some point in time to a significant majority of individuals. As a large portion of chiropractic patients are elderly, this perspective should be read by all chiropractors. There were several criteria in mind when the project began, especially to improve the chiropractic care of the aged patient, to review and to develop needed data, and to understand the neuroarticular process involvement. This article was to accomplish the understanding and build interest in the degeneration ramifications in the neuroarticular complex of the elderly. This interest may stimulate more attention on the subject with an extensive literature search of the topic and additional research needed.

Side-to-side weight-bearing asymmetry in subjects with low back pain

The purpose of this project was to determine if subjects with low back pain (LBP) exhibit greater side-to-side weight-bearing (WB) asymmetry compared to healthy control subjects without LBP. This study utilized an observational double cohort design and consisted of 35 subjects with LBP and 31 healthy control subjects. Side-to-side WB asymmetry was calculated as the average of the absolute value of the difference between the right and left lower extremity from three trials. The percentage of the average side-to-side WB asymmetry relative to the total body weight was calculated to normalize expected differences in magnitude of asymmetry based on a subject's total body weight. An 11-point numeric pain rating scale was used to represent the subject's current level of pain. Patients with LBP demonstrated significantly greater normalized side-to-side WB asymmetry than healthy control subjects (8.8% vs. 3.6%, respectively, P<0.001). In patients with LBP, higher magnitudes of side-to-side WB asymmetry were significantly associated with increased pain (r=0.39, P=0.021). In conclusion patients with LBP exhibited increased side-to-side WB asymmetry compared to healthy control subjects without LBP. This asymmetry was associated with increased levels of pain. This finding is relevant for planning future studies that will attempt to provide evidence for the construct validity of manipulation by determining if side-to-side WB asymmetry normalizes after a manipulation intervention and if this improvement is associated with improvements in pain and function.

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.

Ventral sacroiliac ligament. Anatomic and pathologic considerations

RATIONALE AND OBJECTIVES

The ventral sacroiliac ligament (VSL), which bridges the sacroiliac (SI) joint anteriorly, has been described as an important stabilizing structure of the joint, but no data exist regarding its assessment with routine and advanced imaging methods. The authors determine the imaging appearance of the normal and abnormal VSL using close anatomic-histologic-imaging correlation.

METHODS

Eight and 10 cadaveric SI joints were examined with magnetic resonance imaging in axial and coronal planes, respectively; and in four computed tomography scanning in both planes was obtained. Anatomic sectioning with histologic correlation at levels corresponding to those of imaging planes was performed. Representative examples of diseases that produce abnormalities of the VSL and connective tissue about the SI joint were reviewed.

RESULTS

Magnetic resonance images showed the VSL-anterior capsular complex as a hypointense, linear, or minimally curved structure of approximately 2 mm thickness traversing the SI joint anteriorly. The VSL could not be separated from the anterior joint capsule by imaging studies, but such differentiation by histology could be determined based upon the orientation of its collagen fibers. Any disease process that affects the ligament or the site of ligamentous attachment to bone produces characteristic imaging alterations.