Anatomical Joint Form Variation in Sacroiliac Joint Disease: Current Concepts and New Perspectives

Posterior allograft sacroiliac joint fusion with pre-operative mapping

Background

Low back pain is a highly prevalent and disabling condition. Sacroiliac joint dysfunction is prevalent in up to 62 % of some populations and is a common origin of low back pain. The posterior approach for minimally invasive sacroiliac joint fusion with an allograft is still relatively novel, with limited studies examining its safety and efficacy.

Objective

The objective of our study was to analyze changes in pain and opioid usage for patients who underwent this procedure with pre-operative mapping after exhausting conservative treatment methods.

Methods

This was a single-center, retrospective study with all cases completed by a single interventional pain physician. Outcomes regarding pain and opioid usage were extracted from electronic medical records, Georgia Prescription Drug Monitoring Program reports, and all other available state databases for 208 consecutive patients who underwent the minimally invasive sacroiliac joint fusion procedure with the LinQ Fusion Implant (PainTeq, Tampa, FL) after pre-operative mapping between August 2019 and October 2022. Pain was assessed using the Numerical Rating Scale (NRS), and opioid consumption was measured using Morphine Milligram Equivalents (MME).

Results

NRS scores decreased from 7.23 ± 1.82 at baseline to 1.16 ± 1.35 at the final available follow-up (p < 0.001). Pain improvements ranged from 40 to 100 %, and all patients reported at least some improvement post-intervention. 205 of the 208 patients reported an improvement in pain of at least 50 %. MME reduced from 20.74 ± 26.33 mg to 10.00 ± 18.69 mg (p < 0.001).

Conclusion

Posterior allograft sacroiliac joint fusion significantly reduces pain and opioid consumption. Pre-operative mapping is beneficial but requires more evidence to elucidate its role in optimizing implant placement.

Sacroiliac Joint: Mimics and Pitfalls

Sacroiliac joint pathology presents a complex diagnostic challenge due to the diverse range of conditions, both mechanical and inflammatory, that can affect the joint. Although axial spondyloarthritis-related sacroiliitis is often the most recognized pathology, numerous other conditions closely mimic axial spondyloarthritis in both clinical presentation and imaging features. This review describes key anatomical aspects of the sacroiliac joint, including its distinct morphology, ligamentous support, and histologic characteristics, essential for understanding and differentiating various pathologies. It also examines detailed imaging findings from magnetic resonance imaging, computed tomography, and radiography in relation to each pathologic condition. By providing a framework for distinguishing between common and rare sacroiliac joint disorders and axial spondyloarthritis, this article will enhance diagnostic accuracy and offer insights into the anatomical nuances that impact clinical and imaging assessments.

Influence of sacroiliac joint variation on clinical features of axial spondyloarthritis: a comparative analysis

OBJECTIVES

Anatomical variation of the sacroiliac (SI) joints is common and specific variants are associated with erosions and bone marrow oedema on imaging. Our investigation aims to evaluate whether anatomical variations influence the clinical presentation of axial spondyloarthritis (axSpA).

METHODS

In this propensity score matched post hoc analysis documented clinical data from four prospective clinical cohorts was assessed. Classification of back pain as inflammatory (=IBP), human leucocyte antigen-B27 positivity, family history, disease activity according to Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), symptom duration, elevated acute phase reactants, peripheral and extramusculoskeletal manifestations were evaluated. Statistical analyses were done using (generalised) linear models, t-tests, χ2 tests and analysis of variances. Multiple testing was corrected according to Bonferroni.

RESULTS

A total of 165 patients (86 women) were included. Atypical SI joints, defined by the presence of accessory joint facets, iliosacral complex or crescent-shaped ilii on MRI, were identified in 61 out of 165 patients with axSpA. Disease activity, assessed by BASDAI and symptom duration were similar in both groups (adjusted ß=-0.118 (95% CI -0.713, 0.476), p=0.696 and 120.0 (107.4) vs 116.5 (98.3) months, p=0.838, respectively). There was no significant difference in IBP between the groups (adjusted OR=0.614 (95% CI 0.274, 1.377), p=0.236). Sex-stratified analysis revealed no statistically significant results.

CONCLUSION

Our analysis suggests that clinical phenotypes do not significantly differ between patients with axSpA with and without atypical joints.

Clinical information on imaging referrals for suspected or known axial spondyloarthritis: recommendations from the Assessment of Spondyloarthritis International Society (ASAS)

OBJECTIVES

This study aims to establish expert consensus recommendations for clinical information on imaging requests in suspected/known axial spondyloarthritis (axSpA), focusing on enhancing diagnostic clarity and patient care through guidelines.

MATERIALS AND METHODS

A specialised task force was formed, comprising 7 radiologists, 11 rheumatologists from the Assessment of Spondyloarthritis International Society (ASAS) and a patient representative. Using the Delphi method, two rounds of surveys were conducted among ASAS members. These surveys aimed to identify critical elements for imaging referrals and to refine these elements for practical application. The task force deliberated on the survey outcomes and proposed a set of recommendations, which were then presented to the ASAS community for a decisive vote.

RESULTS

The collaborative effort resulted in a set of six detailed recommendations for clinicians involved in requesting imaging for patients with suspected or known axSpA. These recommendations cover crucial areas, including clinical features indicative of axSpA, clinical features, mechanical factors, past imaging data, potential contraindications for specific imaging modalities or contrast media and detailed reasons for the examination, including differential diagnoses. Garnering support from 73% of voting ASAS members, these recommendations represent a consensus on optimising imaging request protocols in axSpA.

CONCLUSION

The ASAS recommendations offer comprehensive guidance for rheumatologists in requesting imaging for axSpA, aiming to standardise requesting practices. By improving the precision and relevance of imaging requests, these guidelines should enhance the clinical impact of radiology reports, facilitate accurate diagnosis and consequently improve the management of patients with axSpA.

Update on Rheumatic Diseases in Clinical Practice: Recent Concepts and Developments

Diagnostic imaging is essential in the diagnostic process of rheumatic diseases. Given the heterogeneity of this group of diseases and the tremendous impact of novel therapeutic options, guidelines and recommendations regarding the optimal choice of the most appropriate technique/s are continuously revised and radiologists should always be up-to-date. Last, because of the continuous technological innovations, we will assist to the progressive application of advanced techniques and tools in rheumatology.

Association between sacroiliac joint forms and subchondral changes in patients with Crohn's disease

AIM

To assess the relationship between anatomical variants of sacroiliac joint (SIJ) and subchondral changes detected in magnetic resonance enterography (MRE) in patients with Crohn's disease (CD).

METHODS

This was a retrospective study of 60 CD patients, who were divided into two groups: with (n = 16) and without SIJ (n = 44) involvement, depending on the presence of inflammatory (bone marrow edema) and structural changes (sclerosis and erosions) in MRE. Anatomical variants of SIJ were assessed in CT of the abdomen and/or pelvis, distinguishing typical form with convex iliac surface and atypical forms. Univariate and multivariate analyses were performed to reveal an association between joint changes and forms.

RESULTS

Our study included 60 patients (38 males; mean age 38.72 years ± 13.33). Patients with SIJ changes were older (p = .044). No significant differences in CD localization and behavior were found. The most common SIJ lesions were structural changes (in 75% of patients); the main atypical form was the iliosacral complex. The univariate and multivariate analyses showed a significant association of atypical forms with total subchondral changes (odds ratio [OR]: 3.429, 95% confidence interval [CI] 1.043-11.268; p = .042; OR: 5.066, 95% CI: 1.273-20.167; p = .021, respectively), and with structural changes (OR: 4.185, 95% CI: 1.155-15.160; p = .029; OR: 5.986, 95% CI: 1.293-27.700; p = .022, respectively).

CONCLUSION

Atypical forms of SIJ are a risk factor for the occurrence of structural joint changes in CD patients. An association between bone marrow edema and atypical forms was not found.

Biomechanics in the onset and severity of spondyloarthritis: a force to be reckoned with

Increasing evidence suggests that there is a pivotal role for physical force (mechanotransduction) in the initiation and/or the perpetuation of spondyloarthritis; the review contained herein examines that evidence. Furthermore, we know that damage and inflammation can limit spinal mobility, but is there a cycle created by altered spinal mobility leading to additional damage and inflammation?Over the past several years, mechanotransduction, the mechanism by which mechanical perturbation influences gene expression and cellular behaviour, has recently gained popularity because of emerging data from both animal models and human studies of the pathogenesis of ankylosing spondylitis (AS). In this review, we provide evidence towards an appreciation of the unsolved paradigm of how biomechanical forces may play a role in the initiation and propagation of AS.

Anatomical variation of the sacroiliac joint carries an increased risk for erosion and bone marrow oedema in axial spondyloarthritis

OBJECTIVES

To assess the impact of joint shape variations on inflammatory lesions on SI joint MRIs in patients with axial spondyloarthritis (axSpA).

METHODS

A total of 1194 patients from four different prospective cohorts were evaluated, with 684 (57.3%) having sufficient imaging data for inclusion (379 axSpA, 305 controls). All images were evaluated for joint form, erosion, sclerosis, fat metaplasia and bone marrow oedema (BMO) by two independent readers. Logistic regression analyses were used to assess the association of joint form and lesions on imaging for axSpA patients and controls.

RESULTS

Atypical joint forms were common in both axSpA (43.5% [154/354]) and control patients (44.2% [134/303]); both intra-articular variants and a crescent joint shape were significantly more common in axSpA patients (18.4% vs 11.6% and 11.0% vs 5.3.%, respectively; P < 0.001). The axSpA patients with intra-articular joint form variants had 2-fold higher odds of exhibiting erosions [odds ratio (OR) 2.09 (95% CI 1.18, 3.69)] and BMO [OR 1.79 (95% CI 1.13, 2.82)]; this association was not observed in controls. Accessory joints increased the odds for sclerosis in axSpA patients [OR 2.54 (95% CI 1.10, 5.84)] and for sclerosis [OR 17.91 (95% CI 6.92, 46.37)] and BMO [OR 2.05 (95% CI 1.03, 4.07)] in controls.

CONCLUSIONS

Joint form variations are associated with the presence of inflammatory lesions on SI joint MRIs of axSpA patients. This should be taken into consideration in future research on the interplay of mechanical strain and inflammation in axSpA.

Axial Spondyloarthritis and Diagnostic Challenges: Over-diagnosis, Misdiagnosis, and Under-diagnosis

PURPOSE OF REVIEW

This article aims to review the challenges in axial spondyloarthritis diagnosis and identify the possible contributing factors.

RECENT FINDINGS

The inability to reach an accurate diagnosis in a timely fashion can lead to treatment delays and worse disease outcomes. The lack of validated diagnostic criteria and the misuse of the currently available classification criteria could be contributing. There is also significant inter-reader variability in interpreting images, and the radiologic definitions of axial spondyloarthritis continue to be re-defined to improve their positive predictive value. The role of inflammatory back pain features, serologic biomarkers, genetics, and their diagnostic contribution to axial spondyloarthritis continues to be investigated. There is still a significant amount of delay in the diagnosis of axial spondyloarthritis. Appreciating the factors that contribute to this delay is of utmost importance to close the gap. It is similarly important to recognize other conditions that may present with symptoms that mimic axial spondyloarthritis so that misdiagnosis and wrong treatment can be avoided.

Sex Disparities of the Sacroiliac Joint: Focus on Joint Anatomy and Imaging Appearance

The sacroiliac joint (SIJ) is an anatomically complex joint which, as a functional unit with the pelvis and spine, is of decisive biomechanical importance for the human body. It is also a commonly overlooked source of lower back pain. Like the entire bony pelvis, the SIJ exhibits major sexual dimorphisms; thus, the sex-dependent evaluation of this joint is becoming increasingly important in clinical practice, both anatomically with joint shape variations and biomechanical differences as well as in terms of image appearance. The influence of the SIJ shape, which differs in women and men, is crucial for the different biomechanical joint properties. These differences are important in the development of joint diseases at the SIJ, which shows a specific difference between the sexes. This article aims to provide an overview of sex disparities of the SIJ regarding different anatomical and imaging appearances to further understand the insights into the interplay of sex differences and SIJ disease.

Unexpected Sex Differences in the Relationship of Sacroiliac Joint and Lumbar Spine Degeneration

The relationship between degenerative changes of the sacroiliac joints and the lumbar spine on CT has not been studied yet. The aim of this analysis is to determine the nature of their association as well as the influence of fixed anatomical spinopelvic parameters on sacroiliac joint degeneration. For this institutional review-board-approved investigation, imaging datasets as well as electronic medical records of 719 patients without back pain from the clinical routine of our department of radiology were included. Age, sex, weight category (slim, normal, obese), parity in women and indication for imaging were noted for all patients. The presence of degenerative lesions of the lumbar spine (disc degeneration, endplate degeneration, spondylophytes, and facet joint osteoarthritis) was noted separately at each lumbar segment (L1 to L5). Sacroiliac joints were assessed for sclerosis and osteophytes. Fixed anatomical spinopelvic parameters were measured: pelvic radius = PR; pelvic incidence = PI; sacral table angle = STA. Correlation as well as regression analyses were performed; data were analyzed for males and females separately. PI increased significantly with age in both women and men, while STA decreased and PR remained constant; neither of them was associated with SIJ degeneration. SIJ degeneration correlated with disc degeneration (tau = 0.331; p < 0.001), spondylophytes (tau = 0.397; p < 0.001), and facet joint degeneration (tau = 0.310; p < 0.001) in men, but with no parameter of spinal degeneration in women. Lumbar spinal degeneration increased the risk of sacroiliac joint degeneration in men significantly (OR 7.2; 95%CI 2.8–19.0), but it was not a significant covariable in women. Fixed spinopelvic parameters have little impact on sacroiliac joint degeneration. The degeneration of the sacroiliac joints and the lumbar spine appear to be parallel processes in men, but are largely unrelated in women.

Main Diagnostic Pitfalls in Reading the Sacroiliac Joints on MRI

Magnetic resonance imaging of the sacroiliac joints is now frequently performed to help identify patients with early axial spondyloarthritis. However, differential diagnoses exist and should be recognized. The aim of this article is to review the most frequent differential diagnoses that may mimic inflammatory sacroiliitis in clinical practice.