Paravertebral Muscle Mechanical Properties in Patients with Axial Spondyloarthritis or Low Back Pain: A Case-Control Study.

Different musculoskeletal disorders are a source of pain in the spinal region; most of them can be divided into mechanical, such as low back pain (LBP), or inflammatory origins, as is the case of axial spondyloarthritis (axSpA). Nevertheless, insufficient information is available about the muscle negative consequences of these conditions. Thus, the objective of this study was to identify whether mechanical muscle properties (MMPs) of cervical and lumbar muscles are different between patients with axSpA, subacute LBP (sLBP), and healthy controls. Furthermore, we aimed identify whether MMPs were related to sociodemographic and clinical variables in various study groups. The MMPs, sociodemographic, and clinical variables were obtained in 43 patients with axSpA, 43 subjects with sLBP, and 43 healthy controls. One-way ANOVAs and ROC curves were applied to identify whether the MMPs could differentiate between the study groups. Intra-group Pearson r coefficients to test the associations between MMPs and the rest of the variables were calculated. The results showed that axSpA subjects have a higher tone and stiffness and a lower relaxation and creep than sLBP and healthy ones (p < 0.05). All lumbar and cervical MMPs, except for decrement, could correctly classify axSpA and healthy subjects and axSpA and sLBP patients (in both cases, Area Under the Curve > 0.8). However, no MMP could differentiate between sLBP and healthy subjects. Each group had a different pattern of bivariate correlations between MMPs and sociodemographic and clinical data, with a worse state and progression of the axSpA group associated with a higher tone and stiffness in both spinal regions. This study supports that MMPs are different and show different patterns of correlations depending on the type of spinal pain.

Mechanical Properties of Lumbar and Cervical Paravertebral Muscles in Patients with Axial Spondyloarthritis: A Case-Control Study.

BACKGROUND: Axial spondyloarthritis (axSpA) affects spinal muscles, due to inflammation and structural damage. The mechanical properties of the muscles, such as tone or stiffness, could be altered in axSpA. The aim of this work is to analyze the mechanical properties of cervical and lumbar spine muscles in axSpA patients and their relationship with metrology measures, function, disease activity, structural damage and quality of life. METHODS: axSpA patients and age/gender/BMI matched healthy controls were recruited. The muscle mechanical properties (MMPs), such as tone or frequency, stiffness, decrement (linear elastic properties), relaxation and creep (viscoelastic properties), of cervical (semispinalis capitis) and lumbar (erector spinae) muscles were bilaterally measured at rest using myotonometry. Additionally, conventional metrology, BASMI (metrology index), BASDAI (disease activity index), mSASSS (radiological structural damage index) and SF-12 (health-related quality of life questionnaire) were used in the axSpA group. Between-groups comparison, intra-group correlations and multivariable regression analyses were performed to achieve the study aims. RESULTS: Thirty-four axSpA patients (mean age: 46.21 ± 8.53 y) and 34 healthy volunteers (mean age: 43.97 ± 8.49 y) were recruited. Both in cervical and lumbar spine, linear elastic parameters were significantly higher in axSpA patients in comparison with controls, while viscoelastic parameters were significantly lower. Lumbar muscle frequency, stiffness, relaxation, creep and cervical muscle elasticity were fair to strongly correlated (|0.346| < r < |0.774|) with age, functional status, activity of disease, structural damage and quality of life in axSpA patients. Furthermore, moderate to good fitted multivariate models (0.328 < R2 < 0.697) were obtained combining age, conventional metrology, activity of the disease and function for the estimation of cervical and lumbar MMPs. CONCLUSION: Mechanical properties of spinal muscles of axSpA patients differ from controls. Lumbar and cervical muscles exhibit greater linear elastic properties and lower viscoelastic properties, which are related with age, clinical and psychophysiological features of axSpA.

Patients with Axial Spondyloarthritis Show an Altered Flexion/Relaxation Phenomenon.

Axial spondyloarthritis (axSpA) is a chronic rheumatic disease characterized by the presence of inflammatory back pain. In patients with chronic low back pain, the lumbar flexion relaxation phenomenon measured by surface electromyography (sEMG) differs from that in healthy individuals. However, sEMG activity in axSpA patients has not been studied. The purpose of this study was to analyze the flexion relaxation phenomenon in axSpA patients. A study evaluating 39 axSpA patients and 35 healthy controls was conducted. sEMG activity at the erector spinae muscles was measured during lumbar full flexion movements. sEMG activity was compared between axSpA patients and the controls, as well as between active (BASDAI ≥ 4) and non-active (BASDAI < 4) patients. The reliability (using intraclass correlation coefficients (ICC)), criterion validity and discriminant validity using the area Under the curve (AUC) for the inverse flexion/relaxation ratio (1/FRR) were evaluated. Significant differences (p < 0.05) were observed between axSpA patients and the control group in lumbar electric activity, especially during flexion, relaxation, and extension and in FRR and 1/FRR (0.66 ± 0.39 vs. 0.25 ± 0.19, respectively). In addition, significant differences were found between active and non-active but also between non-active and healthy subjects. The sEMG showed good reliability (ICC > 0.8 for 1/FRR) and criterion validity. ROC analysis showed good discriminant validity for axSpA patients (AUC = 0.835) vs. the control group using 1/FRR. An abnormal flexion/relaxation phenomenon exists in axSpA patients compared with controls. sEMG could be an additional objective tool in the evaluation of patient function and disease activity status.

Measuring Spinal Mobility Using an Inertial Measurement Unit System: A Validation Study in Axial Spondyloarthritis.

Portable inertial measurement units (IMUs) are beginning to be used in human motion analysis. These devices can be useful for the evaluation of spinal mobility in individuals with axial spondyloarthritis (axSpA). The objectives of this study were to assess (a) concurrent criterion validity in individuals with axSpA by comparing spinal mobility measured by an IMU sensor-based system vs. optical motion capture as the reference standard; (b) discriminant validity comparing mobility with healthy volunteers; (c) construct validity by comparing mobility results with relevant outcome measures. A total of 70 participants with axSpA and 20 healthy controls were included. Individuals with axSpA completed function and activity questionnaires, and their mobility was measured using conventional metrology for axSpA, an optical motion capture system, and an IMU sensor-based system. The UCOASMI, a metrology index based on measures obtained by motion capture, and the IUCOASMI, the same index using IMU measures, were also calculated. Descriptive and inferential analyses were conducted to show the relationships between outcome measures. There was excellent agreement (ICC > 0.90) between both systems and a significant correlation between the IUCOASMI and conventional metrology (r = 0.91), activity (r = 0.40), function (r = 0.62), quality of life (r = 0.55) and structural change (r = 0.76). This study demonstrates the validity of an IMU system to evaluate spinal mobility in axSpA. These systems are more feasible than optical motion capture systems, and they could be useful in clinical practice.

How to calculate the ASDAS based on C-reactive protein without individual questions from the BASDAI: the BASDAI-based ASDAS formula.

OBJECTIVES: To develop a new equation to calculate the Ankylosing Spondylitis Disease Activity Score based on CRP (ASDAS-CRP) using only the BASDAI total score and CRP. METHODS: Axial SpA (axSpA) patients from the Cordoba Spondyloarthritis Registry cohort were recruited as a derivation cohort, while a retrospective sample from the Spanish Rheumatology Society National Registry of Spondyloarthropathies and Ibero American Spondyloarhtritis Registry registers was used as a validation cohort. We built a new equation based only on the BASDAI and CRP, defining a new formula: the BASDAI-based ASDAS (BASDAS). Linear regression analysis was used to determine the coefficients of the equation in the derivation cohort and it was subsequently validated in the validation cohort. RESULTS: A total of 52 axSpA patients in the derivation cohort and 3359 patients in the validation cohort were included. In the derivation cohort, the mean BASDAS [2.24 (s.d. 0.90)] was very similar to the ASDAS-CRP [2.23 (s.d. 0.95)], with a very strong correlation (r = 0.96, P < 0.001). In the validation cohort, the mean BASDAS was 3.31 (s.d. 1.37) and the ASDAS-CRP was 3.19 (s.d. 1.27), which also had a very strong correlation (r = 0.95, P < 0.001). Intraclass correlation coefficients were excellent in both cohorts (0.963 and 0.947, respectively). CONCLUSION: The BASDAS performs similarly to the ASDAS-CRP and can be calculated with only the BASDAI total score and CRP, allowing evaluation of disease activity in retrospective studies where the individual items of the BASDAI are not available.

Diagnostic validity of Doppler ultrasound in giant cell arteritis.

OBJECTIVES: To assess the validity of Doppler ultrasound in the diagnosis of giant cell arteritis (GCA), using the American College of Rheumatology (ACR) criteria and biopsy and using as gold standard the patient's definitive clinical diagnosis. METHODS: An observational, descriptive and analytical study of 451 consecutive patients with suspected GCA was conducted, and the clinical history and ultrasound findings of the patients were reviewed. The validity of ACR criteria, temporal arteritis biopsy (TAB) and Doppler ultrasound in the diagnosis of GCA was calculated using the final diagnosis of the doctor in charge as the gold standard. RESULTS: The validity and security of the diagnostic tests used were as follows: ACR criteria had 65.37% sensitivity and 62.89% specificity; positive predictive value [PPV] 70%; negative predictive value [NPV] 57.82%, likelihood ratio [LR] + 1.7619 and LR - 0.5506. Doppler ultrasonography had 91.60% sensitivity and 95.83% specificity; PPV 96.62%; NPV 89.76%, LR + 21.81 and LR - 0.0876; TA biopsy 42.86% sensitivity and 100% specificity; PPV 100%; NPV 35.71% and LR - 0.5714. CONCLUSIONS: The halo sign, especially if bilateral, is a strong predictor of GCA with a level of accuracy sufficient to recommend its introduction into clinical practice and, in our opinion, should be considered in future classification criteria sets.