Sacroiliac joint bridging: demographical and anatomical aspects

Lumbosacral zone features in individuals with nonspecific chronic low back pain are unique compared to controls and correlate with pain and dysfunction

OBJECTIVES

To compare the lumbosacral nerve distances (LNDs) and sacroiliac joint (SIJ) morphology in individuals with nonspecific chronic low back pain (NSCLBP) and control and examine their correlations with pain and dysfunction in the former.

MATERIALS AND METHODS

The sample includes 200 adult patients (ranging from 20 to 50 years old) referred for computerized abdominal tomography (CT): 100 individuals with NSCLBP (50 males and 50 females) and 100 individuals without NSCLBP (50 males and 50 females). CT scans were assessed for LNDs, degenerative sacroiliac changes, and joint bridging. Those factors were correlated to the outcomes of three self-reported questionnaires about pain and function (Oswestry, Fear-Avoidance, and Numerical Pain Rating Scale) in the NSCLBP group.

RESULTS

Individuals with NSCLBP tend to have reduced LNDs from the sacral part of the SIJ compared to controls (males: right Δ = 5.8 mm, left Δ = 6.03 mm; females: right Δ = 7.9 mm, left Δ = 7.73 mm, two-way ANOVA, p < 0.01), with moderate significant negative correlations with all three questionnaires (-0.38 < Pearson's r < - 0.57, p < 0.02, i.e., reduced LNDs with greater disability and pain). The NSCLBP group had more significant SIJ degeneration severity that moderately correlated with two questionnaires (0.39 < Pearson's r < 0.66, p < 0.04, i.e., greater SIJ degeneration with greater disability and pain). In males, the existence of SIJ bridging strongly correlated with all three questionnaires (0.38 < Pearson's r < 0.78, p < 0.03), and in females, only the Fear-Avoidance Questionnaire and Numerical Pain Scale (0.29 < Pearson's r < 0.41, p < 0.04).

CONCLUSION

Compared to controls, individuals with NSCLBP have reduced LNDs and worse SIJ degenerative changes that correlate with function and pain.

KEY POINTS

• Individuals with nonspecific low back pain tend to have reduced lumbosacral nerve distances than healthy controls. This may be due to entrapments or inflammation of the nerves or surrounding tissues. • Individuals with nonspecific low back pain tend to have more severe degeneration of their sacroiliac joint than healthy controls. • The above findings significantly correlated with the scores of three self-reported questionnaires about pain and function, implicating that they may be of clinical significance.

Posterior intra-articular fixation stabilizes both primary and secondary sacroiliac joints: a cadaveric study and comparison to lateral trans-articular fixation literature

BACKGROUND

Posterior and lateral techniques have been described as approaches to sacroiliac joint arthrodesis. The purpose of this study was to compare the stabilizing effects of a novel posterior stabilization implant and technique to a previously published lateral approach in a cadaveric multidirectional bending model. We hypothesized that both approaches would have an equivalent stabilizing effect in flexion-extension and that the posterior approach would exhibit better performance in lateral bending and axial rotation. We further hypothesized that unilateral and bilateral posterior fixation would stabilize both the primary and secondary joints.

METHODS

Ranges of motion (RoMs) of six cadaveric sacroiliac joints were evaluated by an optical tracking system, in a multidirectional flexibility pure moment model, between ± 7.5 N-m applied moment in flexion-extension, lateral bending, and axial rotation under intact, unilateral fixation, and bilateral fixation conditions.

RESULTS

Intact RoMs were equivalent between both samples. For the posterior intra-articular technique, unilateral fixation reduced the RoMs of both primary and secondary joints in all loading planes (flexion-extension RoM by 45%, lateral bending RoM by 47%, and axial RoM by 33%), and bilateral fixation maintained this stabilizing effect in both joints (flexion-extension at 48%, lateral bending at 53%, and axial rotation at 42%). For the lateral trans-articular technique, only bilateral fixation reduced mean RoM of both primary and secondary sacroiliac joints, and only under flexion-extension loads (60%).

CONCLUSION

During flexion-extension, the posterior approach is equivalent to the lateral approach, while producing superior stabilization during lateral bend and axial rotation.

Sacroiliac Joint Ankylosis Decreases Intervertebral Fusion Rate in L5/S1 Single Intervertebral Transforaminal Lumbar Interbody Fusion

Background Transforaminal lumbar interbody fusion (TLIF) is a common surgical procedure for lumbar spondylolisthesis and intervertebral foraminal stenosis. Sacroiliac joint ankylosis is also known to occur in patients without axial spondyloarthritis. When sacroiliac joint bony ankylosis occurs and sacroiliac joint mobility is lost, stresses from the lower extremities to the lumbar spine are no longer buffered and are expected to be concentrated between the fifth lumbar (L5) and the first sacral (S1) vertebrae. We hypothesized that sacroiliac joint bony ankylosis could adversely affect L5/S1 intervertebral fusion and investigated the postoperative intervertebral fusion rate in single intervertebral TLIF on L5/S1 among patients with bony ankylosis of the sacroiliac joint. Methods Seventy-two patients who had undergone TLIF in the L5/S1 single intervertebral segment since 2014 and had a follow-up of at least one year after surgery were included in the study. Seventy-two patients were divided into the following two groups for comparison: group A consisted of 17 patients with bony ankylosis of the sacroiliac joint on either side on preoperative CT, and group N consisted of 55 patients without ankylosis. We investigated the intervertebral segment fusion rate one year postoperatively. Fisher's exact tests were used for statistical analysis, with a significance level of P < 0.05. Results Twelve patients (71%) in group A and 50 patients (91%) in group N had a fusion of the L5/S1 intervertebral segment one year after TLIF surgery, with a significantly lower rate in group A (P = 0.049). Conclusions We conclude that the presence of preoperative sacroiliac joint bony ankylosis is a risk factor for postoperative intervertebral fusion failure after single-segment TLIF at L5/S1.

Association of Inflammation, Ectopic Bone Formation, and Sacroiliac Joint Variation in Ossification of the Posterior Longitudinal Ligament

Ossification of the posterior longitudinal ligament (OPLL) is considered a multifactorial condition characterized by ectopic new bone formation in the spinal ligament. Recently, its connections with inflammation as well as sacroiliac (SI) joint ankylosis have been discussed. Nevertheless, whether inflammation, spinal ligament ossification, and SI joint changes are linked in OPLL has never been investigated. In this study, whole-spinal computed tomography and serum high-sensitive C-reactive protein (hs-CRP) levels were obtained in 162 patients with cervical OPLL. Ossification lesions were categorized as plateau and hill shapes. Accordingly, patients were divided into plateau-shaped (51 males and 33 females; mean age: 67.7 years) and hill-shaped (50 males and 28 females; mean age: 67.2 years) groups. SI joint changes were classified into four types and three subtypes, as previously described. Interactions among ossification shapes, hs-CRP levels, and morphological changes in the SI joint were investigated. The plateau shape was more common in the vertebral segments (59.5%), compared to the hill shape, which was predominant in the intervertebral regions (65.4%). Serum hs-CRP levels in the plateau-shaped group (0.11 ± 0.10 mg/dL) were significantly higher than those in the hill-shaped group (0.07 ± 0.08 mg/dL). SI joint intra-articular fusion was the main finding in the plateau-shaped group and showed significantly higher hs-CRP levels compared to the anterior para-articular bridging, which more frequently occurred in the hill-shaped group. Our findings suggested a possible inflammation mechanism that might contribute to the new bone formation in OPLL, particularly the plateau shape.

Spontaneous ankylosis of the sacroiliac joint: prevalence and risk factors

PURPOSE

Evidence on spontaneous sacroiliac joint (SIJ) ankylosis is lacking. The aim of this analysis was to assess the prevalence of spontaneous SIJ ankylosis and examined different ankylosis patterns and risk factors for spontaneous SIJ ankylosis.

METHODS

Pelvic computed tomography (CT) data of 102 consecutive patients with spinal pathologies were compared to CT of a control group consisting of 102 consecutive patients without spinal pathologies. SIJ ankylosis patterns and risk factors for SIJ ankylosis, such as age, sex, and previous spinal fusion surgery were examined.

RESULTS

Overall, 117 men and 86 women were examined between 2019 and 2020. Non-spinal patients were significantly older (mean age 70.5 years, standard deviation [SD] 11.4) than those in the spinal group (mean age 65.3 years, SD 14.3; p = 0.005). The prevalence of SIJ ankylosis was 24.5% in the non-spinal group and 23.5% in the spinal group. The anterior ankylosis type prevalence was 91.7% in the spinal group, compared to 48.0% in the non-spinal group. Factors associated with SIJ ankylosis were older age (odds ratio [OR] 1.04, 95% confidence interval [CI] 1.01-1.07, p = 0.004) and male sex (OR 5.14, 95% CI 2.29-11.55, p < 0.001).

CONCLUSION

Spontaneous ankylosis of the SIJ was a frequent phenomenon in patients with and without spinal pathologies and more likely with older age and male sex. Anterior type SIJ ankylosis was substantially more frequent in patients with spinal pathologies. This may be due to strain exerted on the anterior SIJ aspects in patients with compromised posture due to spine degeneration.

A Cadaver-Based Biomechanical Evaluation of a Novel Posterior Approach to Sacroiliac Joint Fusion: Analysis of the Fixation and Center of the Instantaneous Axis of Rotation

Purpose

The purpose of this study was to assess the stabilizing effect of a posterior joint fixation technique using a novel cortical allograft implant in unilateral and bilateral fixation constructs. We hypothesize that fixation would reduce the joint's range of motion during flexion-extension, axial rotation, and lateral bending loads. We also hypothesize that fixation would shift the center of the instantaneous axis of rotation during the predominant flexion-extension motions towards the implant's location, and that this shift would be correlated with the reduction in flexion-extension range of motion.

Materials and Methods

Six cadaveric sacroiliac joint specimens were tested under intact, unilateral fixation, and bilateral fixation conditions. The total range of motion (ROM) of the sacroiliac joint in flexion-extension, lateral bending, and axial rotation were evaluated by an optical tracking system, in a multidirectional flexibility pure moment model, between ± 7.5 Nm applied moment loads. The centers of the instantaneous axis of rotation (cIAR) of the sacroiliac joint were evaluated during flexion-extension loading. A correlation analysis was performed between the ROM reduction in flexion-extension upon implantation and shift of the cIAR to the graft implantation site.

Results

Unilateral and bilateral fixations generated sacroiliac joint ROM reductions in flexion-extension, lateral bending, and axial rotation motions. Fixation shifted the cIAR to the graft implantation site. Reduction in the total range of motion had a moderate correlation with the shift of the cIAR.

Conclusion

Our novel posterior approach presents a multifaceted mechanism for stabilizing the joint: first, by the reduction of the total range of motion in all planes of motion; second, by shifting the centers of the instantaneous axis of rotation towards the implant's location in the predominant plane of motion, ensuring little to no motion at the implantation site, thus promoting fusion in this region.

Relationship of the sacral slope with early gait derangements in robust older women

BACKGROUND

Trunk pelvic dissociation is fundamental to the compensatory mechanism for muscle weakness during body bending. We carried out an early investigation of gait changes in a sample of community-dwelling women ≥60 years without gait complaints. The primary objective was to correlate spine and pelvic angles with performance tests and accelerometry parameters. The secondary objective was to correlate performance tests with accelerometry.

METHODS

In this cross-sectional study, 54 community-dwelling women ≥60 years were subjected to Falls Efficacy Scale-International (FES-I), performance tests (Berg Balance Scale, Timed Up and Go, and Gait analysis), and radiographic analysis of sagittal alignment (Thoracic and Lumbar Cobb, Pelvic Incidence, Sacral Slope, and Pelvic Tilt angles). Gait speed was assessed in a 10-m comfortable walk, and accelerometry parameters were obtained in a 30-m walk distance.

RESULTS

The sample, aged 72 ± 6 years, exhibited moderate correlation between Sacral Slope and Step Length (+ 0.615). Sacral Slope weakly correlated with FES-I (- 0.339), Berg Balance Scale (+ 0.367), and with further accelerometry data in the AP plane: RMS, (+ 0.439) and Stride Regularity (+ 0.475), p < 0.05, all. Lumbar Cobb weakly correlated with the following accelerometry data in the AP plane: Step Length (+ 0.405), RMS, (+ 0.392), and Stride Regularity (+ 0.345), p < 0.05, all. Additionally, Stride Regularity in AP moderately correlated with FES-I (0,561, p < 0.05), among other weak correlations between performance tests and accelerometry data in AP.

CONCLUSIONS

Early alterations in Sacral Slope and gait abnormalities in the AP plane may provide understanding of the early gait changes in robust older women.

Re-examining the Spectrum of Lumbosacral Transitional Dysmorphisms: Quantifying Joint Asymmetries and Evaluating the Anatomy of Screw Fixation Corridors

Objective

Although a wide range of sacral dysmorphisms has been documented with lumbosacral transitional vertebrae (LSTV) variations, quantitative characterization of the upper segment morphology and articular anatomy across the array of lumbosacral transitions are hardly found in the literature. This study presents LSTV anomalies as a series of sequential morphological changes (the LSTV spectrum) and quantitatively compares 6 LSTV subtypes with normative sacral dimensions including the anatomy at the upper sacral segments used for percutaneous sacroiliac screw insertion.

Methods

Seven linear dimensions were measured from LSTV subtypes and normal sacral variants from dried adult sacral specimens. The auricular, superior articular and facet surface areas were quantified. Obliquity and thickness of osseous corridors used for sacroiliac screw fixation were measured. Data were statistically compared within and between LSTV subtypes and the normal variants.

Results

LSTVs presented a wide range of morphometric differences in comparison to the normal bones. Grouping LSTV according to auricular surface positions (high, normal, and low) demonstrated significant between-group differences in the obliquity and thickness at the S1 and S2 segmental corridors.

Conclusion

Frequent occurrence of LSTV in the general population may require evaluation of anatomical parameters in these variations for safe sacroiliac instrumentation around this region.

Age-related trends of lesser pelvic architecture in females and males: a computed tomography pelvimetry study

The pelvis and the spine form a system balancing human skeleton. Within this system, the pelvis adapts to age-related changes in the spine. Previous studies were predominantly focused on changes of pelvic parameters in the sagittal plane. The aim of this study was to reveal age-related changes of lesser pelvic dimensions at different levels of the pelvic cavity in the sagittal and coronal planes and to explore sexual dimorphism in age-related tendencies. The computed tomography pelvimetry was performed on the three-dimensional workstation. The research sample included 211 females aged 18 to 84 years and 181 males aged 18 to 82 years, who underwent an examination at the Riga East University Hospital, Clinical Center “Gailezers,” Latvia. Three pelvic angles and transverse and sagittal diameters of the lesser pelvis were measured at four levels: the inlet, two axial planes in the mid-cavity, and the outlet. The results demonstrated that more pronounced age-related changes occurred in the inlet and the outlet of the lesser pelvis. The mid-cavity was less changing. The transverse diameter between acetabular centers and the sagittal diameter at the level of ischial spines were independent of age. In general, the common age-related trends were observed for pelvic parameters in females and males. A single exception was the proportion of diameters at the level of ischial spines, which decreased in males only. For parameters associated with pelvic floor diseases, age-related changes occurred in the direction of pathology.

The Assessment of Fusion Following Sacroiliac Joint Fusion Surgery

Sacroiliac joint fusions (SIJF) have been the subject of many research studies. The technical success of an SIJF is in part determined by whether osseous bridging occurs across the sacroiliac joint (SIJ). However, no validated SIJF assessment method has been described. Our objective was to document previously described SIJF assessment methods and define and validate a detailed assessment system for SIJF. Our results are only intended to establish computed tomography (CT)-based guidelines for SIJF to be used in a subsequent large clinical study to correlate them with clinical outcomes.

The SIJF literature was reviewed to document previous descriptions of SIJF assessments. A detailed system was then developed for assessing SIJF from CT exams. To provide data that can be used to address a range of research questions, the system included assessing bridging bone relative to the SIJ anatomy, bridging bone immediately adjacent to the threaded implants crossing the joint, as well as bridging bone close to but not immediately adjacent to the implants. The system was applied to assessing SIJF from thin-slice CT exams in 19 patients 12 months following surgery. Two experienced radiologists implemented the assessment system, and in the event of a disagreement, an adjudicator was used.

Most prior studies provide very little detail about how SIJF was assessed. Using the new assessment system, the agreement between the primary readers was substantial (0.67 using Gwet’s AC1 statistic). Bridging bone representing a fusion of the SIJ was identified in most patients both immediately adjacent to the threaded implants crossing the joint, as well as distant to the implants.

A detailed radiographic assessment system proved to be applicable to SIJF. The assessment system includes explicit language describing the location and extent of bridging bone across the SIJ. Standardization of the assessment of the SIJFs may allow for a more meaningful comparison of data between studies.

CT Abnormalities in the Sacroiliac Joints of Patients With Diffuse Idiopathic Skeletal Hyperostosis

OBJECTIVE

The purpose of this study is to characterize sacroiliac joints (SIJs) findings at CT of patients with diffuse idiopathic skeletal hyperostosis (DISH), a condition characterized (using the Resnick classification criteria) by ossification of at least four contiguous vertebrae in the thoracic spine and preserved disk space, but without radiographic evidence of intraarticular SIJ abnormalities.

MATERIALS AND METHODS

Pelvic CT examinations of 104 patients with DISH (fulfilling the Resnick criteria on spinal CT) and 106 age- and sex-matched control subjects whose entire spine lacked CT evidence of DISH (total, 149 men and 61 women; mean [± SD] age, 72.3 ± 8.7 years) were retrospectively evaluated for the presence of intra- and extraarticular bridging osteophytes, spurs, subchondral cystlike changes, erosions, and sclerosis of SIJs. Excluded were patients with known ankylosing spondylitis or inflammatory-related diseases. Data were analyzed using multivariate ANOVA to examine the degree of difference between patients with DISH and control subjects. Logistic regression analysis was used to generate odds ratios to examine their discriminatory ability. ROC analysis was then applied to examine the sensitivity and specificity of the results.

RESULTS

The frequency of anterior bridging, posterior bridging, entheseal bridging, and joint ankylosis was significantly higher among patients with DISH compared with control subjects (48% vs 9%, 20% vs 1%, 34% vs 4%, and 23% vs 0%, respectively; p < 0.001 for all comparisons).

CONCLUSION

Intraarticular ankylosis seen at CT, an entity not included in the Resnick classification criteria, is common among patients with DISH, which implies that the radiologic classification criteria for DISH need to be revised.

The effect of factors other than age upon skeletal age indicators in the adult

CONTEXT

Estimation of adult age from skeletal remains is problematic due to the weak and variable relationship between age indicators and age.

OBJECTIVES

To assess the proportion of variation in age indicators that is associated with factors other than age and to attempt to identify what those factors might be.

METHODS

The paper focuses on frequently used adult bony age markers. A literature search (principally using Web of Science) is conducted to assess the proportion of variation in age indicators associated with factors other than age. The biology of these age markers is discussed, as are factors other than age that might affect their expression.

RESULTS

Typically, ∼60% of variation in bony age indicators is associated with factors other than age. Factors including inherent metabolic propensity to form bone in soft tissue, vitamin D status, hormonal and reproductive factors, energy balance, biomechanical variables and genetic factors may be responsible for this variation, but empirical studies are few.

CONCLUSION

Most variation in adult skeletal age markers is due to factors other than age; dry bone study of historic documented skeletal collections and high resolution CT scanning in modern cadavers or living individuals is needed to identify these factors.

The effect of implant placement on sacroiliac joint range of motion: posterior versus transarticular

STUDY DESIGN

A human cadaveric biomechanical study of 2 sacroiliac (SI) joint fusion implant placement techniques.

OBJECTIVE

To evaluate and compare the biomechanical properties of 2 implant placement techniques for SI joint fusion.

SUMMARY OF BACKGROUND DATA

Minimally invasive placement of SI joint fusion implants is a potential treatment of SI joint disruptions and degenerative sacroiliitis. Biomechanical studies of screw fixation within the sacrum have shown that placement and trajectory are important in the overall stability of the implant. Although clinical results have been promising, there is the possibility that a more optimal arrangement of implants may exist.

METHODS

Bilateral SI joints in 7 cadaveric lumbopelvic (L4-pelvis) specimens were tested using a single leg stance model. All joints were tested intact, pubic symphysis sectioned, and treated (3 SI joint fusion implants). The implants were laterally placed using either a posterior or transarticular placement technique. The posterior technique places the implants inline in the inlet view, parallel in the outlet view, and parallel to the posterior sacral body in the lateral view. The transarticular technique places all implants across the articular portion of the SI joint. For all conditions, the range of motion was tested in flexion-extension, lateral bending, and axial rotation.

RESULTS

The posterior technique significantly reduced the range of motion in flexion-extension, lateral bending, and axial rotation by 27% ± 24% (P = 0.024), 28% ± 26% (P = 0.028), and 32% ± 21% (P = 0.008), respectively. The transarticular technique significantly reduced the range of motion in flexion-extension, lateral bending, and axial rotation by 41% ± 31% (P = 0.013), 36% ± 38% (P = 0.049), and 36% ± 28% (P = 0.015), respectively. No significant differences were detected between the posterior and transarticular placement techniques (P > 0.25).

CONCLUSION

Posterior and transarticular placement of SI joint fusion implants stabilized the SI joint in flexion-extension, lateral bending, and axial rotation.

LEVEL OF EVIDENCE

N/A.

Characterization of individuals with sacroiliac joint bridging in a skeletal population: analysis of degenerative changes in spinal vertebrae

The aim of this study was to characterize the individuals with sacroiliac joint bridging (SIB) by analyzing the degenerative changes in their whole vertebral column and comparing them with the controls. A total of 291 modern Japanese male skeletons, with an average age at death of 60.8 years, were examined macroscopically. They were divided into two groups: individuals with SIB and those without bridging (Non-SIB). The degenerative changes in their whole vertebral column were evaluated, and marginal osteophyte scores (MOS) of the vertebral bodies and degenerative joint scores in zygapophyseal joints were calculated. SIB was recognized in 30 individuals from a total of 291 males (10.3%). The average of age at death in SIB group was significantly higher than that in Non-SIB group. The values of MOS in the thoracic spines, particularly in the anterior part of the vertebral bodies, were consecutively higher in SIB group than in Non-SIB group. Incidence of fused vertebral bodies intervertebral levels was obviously higher in SIB group than in Non-SIB group. SIB and marginal osteophyte formation in vertebral bodies could coexist in a skeletal population of men. Some systemic factors might act on these degenerative changes simultaneously both in sacroiliac joint and in vertebral column.

One-year outcomes after minimally invasive sacroiliac joint fusion with a series of triangular implants: a multicenter, patient-level analysis

Background

Sacroiliac joint (SI) pain is an often-overlooked cause of lower-back pain, due in part to a lack of specific findings on radiographs and a symptom profile similar to other back-related disorders. A minimally invasive surgical (MIS) approach to SI joint fusion using a series of triangular, titanium plasma spray-coated implants has shown favorable outcomes in patients with SI joint pain refractory to conservative care. The aim of this study was to provide a multicenter experience of MIS SI joint fusion using a patient-level analysis.

Patients and methods

We report a patient-level analysis from 144 patients with a mean of 16 months postoperative follow-up. Demographic information, perioperative measures, complications, and clinical outcomes using a visual analog scale for pain were collected prospectively. Random-effects regression models were used to account for intersite variability.

Results

The mean age was 58 years, 71% of patients were female, and 62% had a history of lumbar spinal fusion. Mean (95% confidence interval [CI]) operative time was 73 minutes (25.4–118), blood loss was minimal, and hospital stay was 0.8 days (0.1–1.5). At follow-up, mean (95% CI) visual analog scale pain scores improved by 6.1 points (5.7–6.6). Substantial clinical benefit, defined as a decrease in pain by >2.5 points or a score of 3.5 or less, was achieved in 91.9% of patients (95% CI 83.9%–96.1%), and 96% (95% CI 86.3%–98.8%) of patients indicated they would have the same surgery again.

Conclusion

When conservative measures fail to relieve symptoms resulting from degeneration or disruption of the SI joint, MIS SI joint fusion using a series of triangular, porous, titanium plasma spray-coated implants is a safe and effective treatment option.

Prevalence of sacral dysmorphia in a prospective trauma population: Implications for a "safe" surgical corridor for sacro-iliac screw placement

Background

Percutaneous sacro-iliac (SI) screw fixation represents a widely used technique in the management of unstable posterior pelvic ring injuries and sacral fractures. The misplacement of SI-screws under fluoroscopic guidance represents a critical complication for these patients. This study was designed to determine the prevalence of sacral dysmorphia and the radiographic anatomy of surgical S1 and S2 corridors in a representative trauma population.

Methods

Prospective observational cohort study on a consecutive series of 344 skeletally mature trauma patients of both genders enrolled between January 1, 2007, to September 30, 2007, at a single academic level 1 trauma center. Inclusion criteria included a pelvic CT scan as part of the initial diagnostic trauma work-up. The prevalence of sacral dysmorphia was determined by plain radiographic pelvic films and CT scan analysis. The anatomy of sacral corridors was analyzed on 3 mm reconstruction sections derived from multislice CT scan, in the axial, coronal, and sagittal plane. "Safe" potential surgical corridors at S1 and S2 were calculated based on these measurements.

Results

Radiographic evidence of sacral dysmorphia was detected in 49 patients (14.5%). The prevalence of sacral dysmorphia was not significantly different between male and female patients (12.2% vs. 19.2%; P = 0.069). In contrast, significant gender-related differences were detected with regard to radiographic analysis of surgical corridors for SI-screw placement, with female trauma patients (n = 99) having significantly narrower corridors at S1 and S2 in all evaluated planes (axial, coronal, sagittal), compared to male counterparts (n = 245; P < 0.01). In addition, the mean S2 body height was higher in dysmorphic compared to normal sacra, albeit without statistical significance (P = 0.06), implying S2 as a safe surgical corridor of choice in patients with sacral dysmorphia.

Conclusions

These findings emphasize a high prevalence of sacral dysmorphia in a representative trauma population and imply a higher risk of SI-screw misplacement in female patients. Preoperative planning for percutaneous SI-screw fixation for unstable pelvic and sacral fractures must include a detailed CT scan analysis to determine the safety of surgical corridors.

Shape variation of the neural arch in the thoracic and lumbar spine: characterization and relationship with the vertebral body shape

Quantifying the human vertebral geometry is important for accurate medical procedures. We aimed to characterize the neural arch (NA) shape at T1-L5. All T1-L5 dry vertebrae (N = 4,080) of 240 individuals were measured and analyzed by age, gender, and ethnicity. A 3D digitizer was used to measure the dimensions of the spinous (SP) and transverse (TP) processes, vertebral canal (VC), laminae, and isthmus. Most parameters were independent of age and ethnicity, yet greater in males than in females. Isthmus length increases from T1 (9.8 mm) to T12 (19.87 mm) and decreases from T12 to L5 (9.68 mm) with right > left in the thorax and oppositely in the lumbar region. The SP is longer than its thickness both decreasing in the upper thorax (by ca. 4mm), increasing in the lower thoracic and upper lumbar vertebrae (by 7 mm for length and ca. 14.5 mm for thickness) and decreasing again along the lower lumbar vertebrae (both by 8 mm). The TP length decreases at T1-T12 (by 13 mm) and increases at L1-L5 with left > right at T1-L5 (P < 0.003). The laminar length decreases from T1 (8.72 mm) through T5 (4.76 mm) and increases toward L5 (8.4 mm) with right > left at T1-L5 (P < 0.003). The VC is oval-shaped at T1 and T11-L5 (width > length), rounded-shape at T2 and T10 (width = length), and inverted oval-shaped at T3-T9 (length > width). In conclusion, the NA is systematically asymmetrical and dynamic in shape along the thoracic and lumbar spine. The inter-relationship with the vertebral body and articular facets is discussed.

Variable positions of the sacral auricular surface: classification and importance

OBJECT

Although the area at the auricular surface defines the magnitude of weight transmission to the hip bones, this study proposes that the position of the auricular surfaces may also significantly influence load bearing patterns at the sacrum. This study attempts to investigate and classify variable positions of the auricular surfaces that may cause vertical shifts in weight-bearing patterns between the L-5 and S-1 segments, altering weight distribution at the lumbosacral and sacroiliac regions.

METHODS

Three hundred human sacra were studied to determine the position and extent of their auricular surfaces in relation to the sacral segments. Specimens were grouped as "normal," "high-up," and "low-down" auricular surface-bearing sacra. All bones were also scrutinized for the presence of accessory articulating facets on the ala of the sacrum and sacralization of the L-5 segment or lumbarization of the S-1 segment. Seven dimensions and 5 articular areas were measured in all sacra. Nine indices were calculated to show proportional representation of dimensions and areas in the bones. Obtained data were analyzed for differences in groups of sacra bearing different auricular surface positions.

RESULTS

Thirty-nine of the sacra (13%) showed auricular surfaces that occupied a high-up position (from upper S-1 to low S-2 segments). Forty-four of the sacra (15%) exhibited a low-down auricular surface (from the low S-1 to low S-3 sacral segments). The remaining bones demonstrated a normal position of the surface (from the S-1 to the middle of the S-3 segments). Twenty of the high-up sacra demonstrated unilateral or bilateral accessory articulating facets on the alae that articulated with extended transverse processes of the L-5 vertebrae. The low-down sacra transmitted load predominantly via lower (S2-3) segments and exhibited stouter, broader, and efficient weight-bearing lower sacral elements, and a prominent gap between the S-1 segment and the rest of the sacrum. The high-up sacra: 1) were shorter and broader in comparison with the normal sacra; 2) at times presented accessory articular facets on their alae; 3) had a smaller body span and a wider ala; 4) were found to have the plane of the facet joints nearer to the posterior aspect of the S-1 body; and 5) had the smallest of the facet areas. The low-down sacra were longer than they were broad, had a substantially broad body span at S-1, possessed the smallest interauricular distance, and showed considerable depth of the plane of the facet joints.

CONCLUSIONS

The position of the auricular surface varies in human sacra. These variations are associated with differential load bearing at the sacral joints. Only the high-up sacra demonstrated the presence of accessory articulating facets between L-5 and S-1. The position of the auricular surface can explain or possibly predict low-back pain situations.

[Non-specific lower back pain: In search of the origin of pain]

Lower back pain is a condition considered benign and with a specific cause determined only in 15% of patients. In the past years this concept has varied, because many papers have described no benign condition leading to back pain, citing their capacity to cause disability. Through many different diagnostic techniques it is possible to identify the structures capable of producing back pain. This identification, and the level of evidence of the interventional techniques, is the aim of this paper.

Vertebral body shape variation in the thoracic and lumbar spine: characterization of its asymmetry and wedging

This study was designed to characterize the vertebral body (VB) shape, focusing on vertebral wedging, along the thoracic and lumbar spine, and to look for shape variations with relation to gender, age, and ethnicity. All thoracic and lumbar (T1-L5) dissected vertebrae of 240 individuals were measured and analyzed by age, gender, and ethnicity. A 3D digitizer was used to measure all VB lengths, heights, and widths, and their ratios were calculated. This study showed that the VB size was independent of age or ethnicity. VB left lateral wedging was found in most vertebrae of most individuals, yet systematically was absent in six vertebrae (T4, T8-T9, T11, L3-L4) with a greater tendency in females than males ( approximately 92% vs. 86%). The VB was anteriorly wedged from T1 through L2 (peak at T7), nonwedged at L3, and posteriorly wedged at L4-L5 (peak at L5). VB width decreased from T1 to T4 and then increased toward L4-L5, so that the spinal configuration in the coronal plane resembled two pyramids of opposite directions, sharing an apex at T4. The inferior VB width was significantly greater than the superior width of both the same vertebra and the adjacent lower vertebra, indicating a trapezoidal shape of the VB and an inverted trapezoidal shape of the intervertebral space. In conclusion, these findings indicate that the human vertebra, in its normal condition, maintains its external dimensions with age, independent of gender or ethnic origin. Clinical and surgical implications of the unique thoracolumbar architecture are discussed.

Orientation of the human sacrum: Anthropological perspectives and methodological approaches

Discovering the nature of sacral orientation is of considerable anthropological importance. Therefore, this study aims at presenting a new anthropologically based definition for sacral anatomical orientation (SAO) angle, establishing standards of SAO for human population; examining the relationship between pelvic incidence (PI) and SAO; and associating SAO with demographic parameters. The study population consisted of 424 adult and 14 sub-adult (13-18 years, for SAO only) pelvises. Sacral orientation was measured using two different definitions: a) SAO is the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis; b) PI is the angle created between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle of the axis of the acetabulum. SAO was measured using a specially designed mechanical measurement tool and a 3D digitizer. PI was measured via the 3D digitizer. The methods developed by us for measuring SAO and PI in skeletal material are valid and reliable. SAO and PI measures were highly correlated (r = -0.824, P < 0.001). The average SAO was 49.01 degrees (SD = 10.16), and the average PI 54.08 degrees (SD = 12.64). SAO was independent of ethnicity and sex, yet age dependent. This study establishes a methodology for estimating SAO and PI in skeletal material and furnishes the anthropological milieu with base line data regarding these parameters. Future studies in human evolution can greatly benefit from this study.

The association of sacroiliac joint bridging with other enthesopathies in the human body

STUDY DESIGN

A descriptive study of the association between sacroiliac joint (extra-articular) bridging and other enthesopathies.

OBJECTIVES

To examine the relationship between sacroiliac joint bridging with other entheseal reaction sites in the skeleton, and its prognostic value in spinal diseases.

SUMMARY OF BACKGROUND DATA

Sacroiliac joint bridging is considered a hallmark of spinal diseases (e.g., ankylosing spondylitis). Nevertheless, its association with other enthesopathies has never been quantified and analyzed.

METHODS

A total of 289 human male skeletons with sacroiliac joint bridging and 127 without (of similar demographic structure) were evaluated for the presence of entheseal ossification, cartilaginous calcification, and other axial skeleton joint fusion (a total of 18 anatomic sites). The presence of diffuse idiopathic skeletal hyperostosis and spondyloarthropathy was also recorded.

RESULTS

Sacroiliac joint bridging was strongly associated with entheseal reactions in other parts of the body. Of the sacroiliac joint bridging group, 24.91% had diffuse idiopathic skeletal hyperostosis, and 8.05% had spondyloarthropathy.

CONCLUSIONS

The presence of sacroiliac joint bridging indicates an intensive general entheseal process in the skeleton.

Sacroiliac joint fusion and the implications for manual therapy diagnosis and treatment

The present paper examines gender differences and changes in prevalence of ankylosed sacroiliac joint (SIJ) with age. SIJs of 287 patients (159 males and 128 females), aged 22-93 years, were examined for fusion, using 3-D CT images. Presence, side and location of the fusion along the joint borders were recorded. Fusion of the SIJ was found to be gender and age dependent; present in 27.7% of all males in contrast to only 3.0% in females (p<0.001). The phenomenon increased with age in the male population from 5.8% in the 20-39 age cohorts to 46.7% in the 80+ cohort. As mobilization and/or manipulation of a dysfunctional SIJ are common procedures used by manual therapists, the effect that aging has on SIJ mobility requires therapists to alter or change their method with advancing age.