Differences in Topographical Location of Sacroiliac Joint MRI Lesions in Patients With Early Axial Spondyloarthritis and Mechanical Back Pain

Rosa Marie Kiil; Clara E. Mistegaard; Anne Gitte Loft; Anna Zejden; Oliver Hendricks; Anne Grethe Jurik

Arthritis Res Ther. 2022;24(75)

Abstract and Introduction

Abstract

Background: Early diagnostics of axial spondyloarthritis (axSpA) remains a challenge. Traditional imaging one-plane sacroiliac joint (SIJ) MRI assessment is used. By introducing a two-plane assessment system, the objective was to analyse the differences in SIJ MRI changes in early axSpA compared with changes in patients with mechanical back pain (MBP) by exploring the differences in volume and location.

Methods: MRIs in the early diagnostic state of 25 axSpA patients (mean age 31.3 years) and 59 MBP patients (mean age 32.3 years) were included. The MRIs were assessed by two readers regarding the distribution of bone marrow edema (BME) in 14 joint portions and structural changes in six joint portions in addition to SIJ anatomical variations and lumbar spine disc degeneration.

Results: AxSpA patients had a significantly higher overall BME sumscore (volume) of 25.1 compared to MBP patients 6.8, p < 0.005. The MBP group had the highest prevalence (66%) and sumscore (5.7) in the middle anterior sacrum. The axSpA group had significantly higher prevalence and sumscores in all joint portions except the three cartilaginous anterior sacral joint portions, including the ligamentous compartments (prevalence 40–60% compared to 8–15%, p both < 0.005). The axSpA group had also a significantly higher prevalence of erosions and fatty marrow disposition, but there were no differences in the prevalence of anatomical variations except the bipartite iliac bony plate.

Conclusions: AxSpA patients demonstrated a widespread distribution of both inflammatory and structural changes, including high BME occurrence in the ligamentous joint portions whereas patients with MBP had the highest occurrence of BME in the middle anterior sacrum. These findings may help differentiate axSpA patients from other back pain conditions in the early diagnostic phase.

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Arthritis Res Ther. 2022;24(75) © 2022 BioMed Central, Ltd.
Copyright to this article is held by the author(s), licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original citation.

Abstract and Introduction
Background
Methods
Results
Discussion
Conclusions
References

Table 1. Demographic, biochemical and clinical data. N (%) if not otherwise stated
	axSpA (n = 25)	MBP (n = 59)
Male gender	15 (60%)*	19 (32%)
Age (years), mean (SD)	31.6 (5.7)	32.3 (5.8)
HLA-B27 positivity	18 (72%)*	11 (19%)
BMI (kg/m²), mean (SD)	26.4 (4.2)	26.5 (4.4)^a
Childbirths (number), mean (SD) if female (n = 50)	1.6 (1.1)	1.7 (1.2)
Time since last childbirth (years), mean (SD) (n = 40)	5.3 (4.2)	4.0 (4.2)
Fulfilment of the 2009 ASAS criteria [3]	24 (96%)*	36 (61%)
Sacroiliitis according to the 2009 ASAS criteria [4]	24 (96%)	49 (83%)
Inflammatory back pain (ASAS definition [3])	20 (80%)*	30 (51%)
Buttock pain	23 (92%)*	41 (69%)

ASAS Assessment of SpondyloArthritis International Society, axSpA axial spondyloarthritis, BMI body mass index, HLA-B27 human leucocyte antigen subtype B27, N number, SD standard deviation
*p < 0.05 for test for between-group differences
^a n = 57

Table 2. The mean axial spondyloarthritis (axSpA) confidence scores for the likelihood of axSpA ranging between − 5.0 and 5.0 in MBP and axSpA patients based on MRI assessment only. N (%) if not otherwise stated
	axSpA (n = 25)	MBP (n = 59)
− 5.0 to − 3.0	4 (16%)	36 (61%)
− 2.5 to − 0.5	4 (16%)	12 (20%)
0	2 (8%)	4 (7%)
0.5 to 2.5	2 (8%)	2 (3%)
3.0 to 5.0	13 (52%)	5 (8%)

axSpA axial spondyloarthritis, MBP mechanical back pain, N number

Table 3. Prevalence of four atypical SIJ morphologies, transitional vertebra and disc degenerative changes. Furthermore, BME and/or structural changes in relation to these. N (%) if not otherwise stated
	axSpA (n = 25)	MBP (n = 59)
Any atypical SIJ morphology	20 (80%)	53 (90%)
Accessory SIJ	9 (36%)	27 (46%)
With BME^a	6 (67%)	7 (26%)
With structural changes^b	4 (44%)	9 (33%)
Iliosacral complex	15 (60%)	35 (59%)
With BME^a	10 (67%)	5 (14%)
With structural changes^b	5 (33%)	1 (3%)
Dysmorphic cartilaginous facets	10 (40%)	22 (37%)
With BME^a	10 (100%)	18 (82%)
With structural changes^b	9 (90%)	9 (41%)
Bipartite iliac bony plate	1 (4%)*	15 (25%)
With BME^a	0	1 (7%)
With structural changes^b	0	0
Transitional vertebra	2 (8%)	3 (5%)
With BME^a	2 (100%)	1 (33%)
With structural changes^b	2 (100%)	3 (100%)
Disc degeneration (0–3)	1.6	1.7
Disc extrusion (disc degeneration = 3)	6 (24%)	16 (27%)
Vertebral corner changes (BME/FMD)	3 (12%)*	1 (2%)
Vertebral end plate changes (BME/FMD)	6 (24%)	20 (34%)

axSpA axial spondylarthritis, BME bone marrow edema, MBP mechanical back pain, N number, SIJ sacroiliac joint
*p < 0.05 for the test for between-group differences
^aPercent of atypical morphologies accompanied by BME
^bPercent of atypical morphologies with structural changes in form of FMD and/or sclerosis in relation to an atypical morphology

Table 4. Univariate logistic and, when appropriate, linear regressions of the association between MRI patterns and axSpA diagnosis, anatomical sacroiliac joint variations, gender, childbirths, age and body mass index. Odds radios (confidence intervals) if other not stated
	axSpA	acc SIJ	ISC	Dysm CF	BIBP	Extrusion	Gender	Childbirths	Age^a	BMI^a
Unilateral BME	0.6 (0.2–1.8)	0.5 (0.2–1.3)	0.6 (0.2–1.4)	0.6 (0.2–1.7)	1.0 (0.3–3.2)	1.8 (0.7–5.1)	0.5 (0.2–1.5)	1.4 (0.6–3.6)	0.0 (− 2.7–2.7)	− 1.1 (− 3.2–0.9)
Bilateral BME	2.0 (0.7–5.8)	1.4 (0.5–3.4)	1.6 (0.7–4.1)	2.0 (0.8–5.4)	1.2 (0.4–3.9)	0.4 (0.2–1.1)	1.5 (0.6–3.7)	0.8 (0.3–1.9)	− 0.8 (− 3.5–1.8)	1.5 (− 0.4–3.5)
Unilateral FMD	0.6 (0.2–2.1)	0.3 (0.1–1.0)	0.8 (0.3–2.3)	6.4 (2.0–20.5)*	2.8 (0.9–9.2)	1.1 (0.3–3.6)	0.1 (0.0–0.6)*	3.8 (1.2–11.8)*	0.9 (− 2.1–4.0)	− 0.6 (− 2.9–1.7)
Bilateral FMD	4.8 (1.8–13.1)*	1.4 (0.6–3.5)	0.8 (0.3–1.9)	0.8 (0.3–2.0)	0.8 (0.3–2.7)	0.5 (0.2–1.4)	1.6 (0.7–4.1)	1.0 (0.4–2.6)	− 0.8 (− 3.4–1.8)	1.9 (− 0.1–3.9)
Unilateral sclerosis	0.6 (0.2–2.1)	1.4 (0.5–4.1)	1.5 (0.5–4.4)	1.4 (0.5–4.0)	1.3 (0.4–4.6)	0.1 (0.0–1.0)	0.1 (0.0–0.6)*	2.0 (0.7–5.8)	− 1.7 (− 4.8–1.3)	− 0.8 (− 3.1–1.6)
Bilateral sclerosis	1.4 (0.4–4.3)	0.7 (0.2–2.0)	2.6 (0.8–8.9)	1.6 (0.5–4.7)	3.1 (0.9–10.3)	0.5 (0.1–2.1)	0.2 (0.1–0.9)*	4.8 (1.4–16.3)*	1.2 (− 2.9–4.3)	2.2 (− 0.1–4.5)
Unilateral erosion(s)	2.6 (0.9–7.9)	0.3 (0.1–1.1)	1.0 (0.3–2.8)	2.2 (0.7–6.3)	1.4 (0.4–5.1)	0.5 (0.1–2.1)	0.2 (0.1–0.9)*	1.8 (0.6–5.1)	− 0.5 (− 3.7–2.6)	− 1.1 (− 3.5–1.3)
Bilateral erosion(s)	5.9 (2.0–17.4)*	1.5 (0.5–4.0)	1.0 (0.4–2.9)	0.6 (0.2–1.8)	0.4 (0.1–1.9)	0.2 (0.1–1.2)	2.2 (0.8–6.0)*	0.9 (0.3–2.4)	− 1.3 (− 4.2–1.6)	1.2 (− 1.0–3.4)
Ligamentary BME	7.0 (2.5–19.6)*	1.9 (0.8–4.8)	2.8 (1.0–7.6)*	0.9 (0.3–2.2)	1.3 (0.4–3.9)	0.4 (0.1–1.2)	1.4 (0.6–3.6)	1.2 (0.5–2.9)	1.3 (− 1.4–3.9)	1.4 (− 0.6–3.4)
BME depth	5.9 (2.1–16.3)*	0.7 (0.3–1.8)	1,2 (0.5–3.2)	3.7 (1.4–9.7)*	1.0 (0.3–3.1)	0.4 (0.1–1.3)	1.0 (0.4–2.6)	0.8 (0.4–2.1)	0.2 (− 2.5–2.9)	0.0 (− 1.1–3.1)
FMD depth	4.7 (1.7–13.1)*	1.2 (0.5–3.1)	2.0 (0.7–5.5)	1.6 (0.6–4.1)	0.8 (0.2–2.8)	0.3 (0.1–1.2)	1.4 (0.5–3.5)	0.9 (0.4–2.3)	0.1 (− 2.7–2.9)	1.0 (− 1.1–3.1)

Acc SIJ accessory sacroiliac joint, axSpA axial spondyloarthritis, BIBP bipartite iliac bony plate, BME bone marrow edema, BMI body mass index, dysm CF dysmorphic cartilaginous facets, extrusion lumbar disc extrusion, FMD fatty marrow deposition, ISC iliosacral complex
*p < 0.05
^aLinear regressions and results reported as regression coefficients (confidence intervals)