Charcot-Marie-Tooth Disease of the Foot and Ankle: Imaging Features and Pathophysiology.

Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral polyneuropathy, resulting in length-dependent motor and sensory deficiencies. Asymmetric nerve involvement in the lower extremities creates a muscle imbalance, which manifests as a characteristic cavovarus deformity of the foot and ankle. This deformity is widely considered to be the most debilitating symptom of the disease, causing the patient to feel unstable and limiting mobility. Foot and ankle imaging in patients with CMT is critical for evaluation and treatment, as there is a wide range of phenotypic variation. Both radiography and weight-bearing CT should be used for assessment of this complex rotational deformity. Multimodality imaging including MRI and US is also important to help identify changes in the peripheral nerves, diagnose complications of abnormal alignment, and evaluate patients in the perioperative setting. The cavovarus foot is susceptible to distinctive pathologic conditions including soft-tissue calluses and ulceration, fractures of the fifth metatarsal, peroneal tendinopathy, and accelerated arthrosis of the tibiotalar joint. An externally applied brace can assist with balance and distribution of weight but may be appropriate for only a subset of patients. Many patients will require surgical correction, which may include soft-tissue releases, tendon transfers, osteotomies, and arthrodesis when necessary, with the goal of creating a more stable plantigrade foot. The authors focus on the cavovarus deformity of CMT. However, much of the information discussed may also be applied to a similar deformity that may result from idiopathic causes or other neuromuscular conditions. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.

Identifying trajectories of radiographic spinal disease in ankylosing spondylitis: a 15-year follow-up study of the PSOAS cohort.

OBJECTIVES: Little is known with certainty about the natural history of spinal disease progression in ankylosing spondylitis (AS). Our objective was to discover if there were distinct patterns of change in vertebral involvement over time and to study associated clinical factors. METHODS: Data were analysed from the Prospective Study of Outcomes in Ankylosing Spondylitis (PSOAS) observational cohort. All patients met modified New York Criteria for AS and had ≥2 sets of radiographs scored by modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) by two independent readers between 2002 and 2017. Group-based trajectory modelling (GBTM) was used to classify patients into distinct groups of longitudinal mSASSS considering sociodemographic and clinical covariables. The optimal trajectory model and number of trajectories was selected using Nagin's Bayesian information criterion (BIC). RESULTS: A total of 561 patients with 1618 radiographs were analysed. The optimum number of trajectory groups identified was four (BIC -4062). These groups were subsequently categorized as: non-progressors (204 patients), late-progressors (147 patients), early-progressors (107 patients) and rapid-progressors (103 patients). Baseline predictors associated with higher spinal disease burden groups included: baseline mSASSS, male gender, longer disease duration, elevated CRP and smoking history. In addition, time-varying anti-TNF use per year was associated with decreased mSASSS progression only in the rapid-progressor group. CONCLUSIONS: GBTM identified four distinct patterns of spinal disease progression in the PSOAS cohort. Male gender, longer disease duration, elevated CRP and smoking were associated with higher spinal disease groups. Independent confirmation in other AS cohorts is needed to confirm these radiographic patterns.

Risk Factors for Spinal Structural Damage in a Chinese Cohort With Ankylosing Spondylitis.

OBJECTIVES: A cross-sectional study was conducted in 270 Chinese patients with ankylosing spondylitis (AS) in order to identify potential risk factors for severity of spinal structural damage. METHODS: Two hundred seventy AS patients fulfilled the Modified New York Criteria. Computed tomography (CT) was used to scan sacroiliac and hip joints, and radiography was used to scan anteroposterior and lateral lumbar spine, as well as lateral cervical spine. Bath Ankylosing Spondylitis Radiology Index and modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) were scored in duplicate. RESULTS: One hundred eighty-three patients had low mSASSS (mSASSS, <10), and 87 patients had high mSASSS (mSASSS, ≥10). Univariate analysis revealed that AS age of onset, body mass index (BMI), smoking duration, duration of symptoms, diagnostic delay, hip involvement, and sacroiliitis grade were significantly associated with the risk of having high mSASSS after adjustment (all p's < 0.05). Hip involvement interacted significantly with BMI and smoking duration in a graded manner. Particularly, relative to patients with low BMI-negative hip involvement, those with high BMI-negative hip involvement, low BMI-positive hip involvement, and high BMI-positive hip involvement had a 1.94-fold, 3.29-fold, and 5.07-fold increased risk of high mSASSS (95% confidence interval, 0.84-4.47, 1.37-7.89, and 1.97-13.06, p = 0.118, 0.008, and 0.001, respectively). Finally, a nomogram graph based on 7 significant risk factors was generated with substantial prediction accuracy (concordance index, 0.906). CONCLUSIONS: We have identified 7 potential risk factors for the severity of spinal structural damage in Chinese AS patients. Importantly, positive hip involvement, combined with high BMI or long smoking duration, was associated with a remarkably increased risk of having severe spinal structural damage.

Longitudinal associations between depressive symptoms and clinical factors in ankylosing spondylitis patients: analysis from an observational cohort.

OBJECTIVES: Although cross-sectional studies have shown that ankylosing spondylitis-specific factors correlate with depressive symptom severity, the association of these factors over time is unresolved. We examined the demographic and clinical factors associated with longitudinal depressive symptom severity in AS patients. METHODS: We analyzed sociodemographic, clinical, behavioral and medication data from 991 patients from the Prospective Study of Outcomes in Ankylosing spondylitis cohort, and measured depression severity with the Center for Epidemiological Studies Depression (CES-D) Scale administered at approximately 6-month visit intervals. Multivariable longitudinal negative binomial regression models were conducted using generalized estimating equation modeling to assess the demographic, clinical, and medication-related factors associated with depression severity by CES-D scores over time. RESULTS: The median baseline CES-D score (possible range 0-60) was 10.0 (interquartile range = 5, 17). In longitudinal multivariable analyses, higher CES-D scores were associated with longitudinal smoking, greater functional impairment, greater disease activity, self-reported depression, and poor global health scores. Marital status (e.g., being married) was associated with lower CES-D. Adjusted mean CES-D scores in our model decreased over time, with a significant interaction between time and gender observed. CONCLUSION: This study identified longitudinal clinical factors such as greater disease activity, greater functional impairment, and poor global health to be associated with longitudinal depression severity. These factors are potentially modifiable and may help manage depressive symptoms in AS.

HLA class I and II alleles in susceptibility to ankylosing spondylitis.

OBJECTIVE: To examine associations of HLA class I and class II alleles with ankylosing spondylitis (AS) in three cohorts of patients of European, Asian and African ancestry. METHODS: HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1 and HLA-DPB1 alleles were genotyped in 1948 unrelated white and 67 African-American patients with AS from the Prospective Study of Outcomes in Ankylosing Spondylitis cohort, the North American Spondylitis Consortium and Australo-Anglo-American Spondyloarthritis Consortium, 990 white and 245 African-American Controls and HLA-B alleles in 442 Han Chinese patients with AS and 346 controls from Shanghai and Gansu, China. In addition to the case:control analyses, HLA-B*27-negative patients with AS were analysed separately, and logistic regression and 'relative predispositional effects' (RPE) analyses were carried out to control for the major effect of HLA-B*27 on disease susceptibility. RESULTS: Although numerous associations were seen between HLA alleles and AS in whites, among HLA-B*27-negative patients with AS , positive associations were seen with HLA-A*29, B*38, B*49, B*52, DRB1*11 and DPB1*03:01 and negative associations with HLA-B*07, HLA-B*57, HLA-DRB1*15:01, HLA-DQB1*02:01 and HLA-DQB1*06:02. Additional associations with HLA-B*14 and B*40 (B60) were observed via RPE analysis, which excludes the HLA-B*27 alleles. The increased frequency of HLA-B*40:01 and decreased frequency of HLA-B*07 was also seen in Han Chinese and African-Americans with AS. HLA-B*08 was decreased in whites with acute anterior uveitis. CONCLUSIONS: These data, analysing the largest number of patients with AS examined to date in three ethnic groups, confirm that other HLA class I and II alleles other than HLA-B*27 to be operative in AS predisposition.

Prevalence and Associations of Avascular Necrosis of the Hip in a Large Well-characterized Cohort of Patients With Inflammatory Bowel Disease.

OBJECTIVES: Avascular necrosis (AVN) is associated with significant morbidity potentially causing severe pain and disability; patients with inflammatory bowel disease (IBD) have a higher prevalence of AVN compared with non-IBD populations. The purpose of our study was to determine the prevalence of AVN in our IBD population and to evaluate these subjects for the presence of clinical characteristics associated with AVN on computed tomography (CT) imaging. METHODS: In 1313 IBD patients with abdomen/pelvis CT scans, we identified 27 patients (2.1%) with CT findings consistent with AVN. Through historical chart review, we confirmed that most patients had prior exposure to steroids, although 2 patients had no documented steroid exposure at all. RESULTS: We found that 59% of the concurrent radiology reports did not comment on the presence of AVN, suggesting that incidental CT findings of AVN among IBD patients are likely underreported. Notably, we found that 63% of these cases had documented complaints of low-back and/or hip pain. Using logistic regression, we found an association between anti-neutrophil cytoplasmic antibody-positive status across IBD (p = 0.007) and a smoking history in Crohn disease (p = 0.03) with the presence of AVN. CONCLUSIONS: We found that a significant proportion of IBD patients with AVN are reported in their records as having hip or low-back pain, and review of CT imaging under dedicated bone windows may identify AVN among this population. Our findings also suggest that additional etiological factors, beyond corticosteroids, contribute to the development of AVN in IBD. Further investigation is warranted regarding the mechanisms associated with AVN in IBD.

The impact of tumor necrosis factor α inhibitors on radiographic progression in ankylosing spondylitis.

OBJECTIVE: To study the effect of tumor necrosis factor α (TNFα) inhibitors on progressive spinal damage in patients with ankylosing spondylitis (AS). METHODS: All AS patients meeting the modified New York criteria who had been monitored prospectively and had at least 2 sets of spinal radiographs a minimum of 1.5 years apart were included in the study (n=334). The patients received standard therapy, which included nonsteroidal antiinflammatory drugs and TNFα inhibitors. Radiographic severity was assessed by the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Patients with a rate of AS progression that was ≥1 mSASSS unit/year were considered progressors. Univariable and multivariable regression analyses were done. Propensity score matching and sensitivity analysis were performed. A zero-inflated negative binomial (ZINB) model was used to analyze the effect of TNFα inhibitors on the change in the mSASSS with varying followup periods. Potential confounders, such as disease activity (as assessed by the Bath Ankylosing Spondylitis Disease Activity Index), the erythrocyte sedimentation rate, C-reactive protein level, HLA-B27 positivity, sex, age at onset, smoking burden (number of pack-years), and baseline damage, were included in the model. RESULTS: TNFα inhibitor treatment was associated with a 50% reduction in the odds of progression, with an odds ratio (OR) of 0.52 (95% confidence interval [95% CI] 0.30-0.88, P=0.02). Patients with a delay of >10 years in starting therapy were more likely to experience progression as compared to those who started earlier (OR 2.4 [95% CI 1.09-5.3], P=0.03). In the ZINB model, the use of TNFα inhibitors significantly reduced disease progression when the gap between radiographs was >3.9 years. The protective effect of TNFα inhibitors was stronger after propensity score matching. CONCLUSION: Treatment with TNFα inhibitors appears to reduce radiographic progression in AS patients, especially with early initiation and with longer duration of followup.

Limb-sparing surgery for distal femoral and proximal tibial bone lesions: imaging findings with intraoperative correlation.

OBJECTIVE: Our purpose is to present normal and abnormal imaging findings associated with endoprosthetic reconstruction after limb-salvage surgery. CONCLUSION: Endoprosthetic reconstruction varies with the location and size of the tumor, implant designs, and complications. Radiologists need to be aware of associated imaging findings seen in postoperative infection, tumor recurrence, and hardware failure. With a thorough understanding of the normal postoperative radiographic findings after complex reconstructions, subsequent abnormalities are readily identified and timely diagnosis can be obtained.

Why Do Some Patients Have Severe Sacroiliac Disease But No Syndesmophytes in Ankylosing Spondylitis? Data From a Nested Case-Control Study.

OBJECTIVE: Sacroiliac (SI) joint and spinal inflammation are characteristic of ankylosing spondylitis (AS), but some patients with AS have been identified who have discordant radiographic disease. We studied an AS subgroup with long-standing disease and fused SI joints. We identified factors associated with discrepant degrees of radiographic damage between the SI joints and spine. METHODS: From the Prospective Study of Outcomes in AS (PSOAS) cohort, patients with a disease duration ≥ 20 years and fused SI joints were included in a nested case-control design. Patients with and without syndesmophytes were used as cases and controls for analysis. We used classification and regression tree (CART) analysis to determine risk factors for syndesmophytes presence and reexamined the validity of the risk factors using univariable logistic regression models. RESULTS: There were 354 patients in the subgroup, 23 of whom lacked syndesmophytes. CART analysis showed females were less likely to have syndesmophytes. The next important predictor was age of symptom onset in males, with age of onset ≤ 16 years being less likely to have syndesmophytes. Univariable analysis confirmed females were less likely to have syndesmophytes (odds ratio [OR] 0.17, 95% CI 0.07-0.41). Syndesmophyte presence was associated with HLA-B27 positivity (P = 0.03) and age of symptom onset > 16 years old (OR 2.72, 95% CI 1.15-6.45). All 23 patients who lacked syndesmophytes were HLA-B27 positive. CONCLUSION: Using CART analysis and univariable modeling, women were less likely to have syndesmophytes despite advanced disease duration and SI joint disease. Patients with younger age of symptom onset were less likely to have syndesmophytes. All patients without syndesmophytes were HLA-B27 positive, indicating HLA-B27 positivity may be more associated with SI disease than spinal disease.

Ankylosing spondylitis: patterns of radiographic involvement--a re-examination of accepted principles in a cohort of 769 patients.

PURPOSE: To re-examine the patterns of radiographic involvement in ankylosing spondylitis (AS). MATERIALS AND METHODS: This prospective study had institutional review board approval, and 769 patients with AS (556 men, 213 women; mean age, 47.1 years; age range, 18-87 years) provided written informed consent. Radiographs of the cervical spine, lumbar spine, pelvis, and hips were scored by using the Bath Ankylosing Spondylitis Radiology Index (BASRI) by an experienced radiologist. Differences in sacroiliitis grade between right and left sacroiliac joints, frequency of cervical- and lumbar-predominant involvement by sex, frequency of progression to complete spinal fusion, and association between hip arthritis and spinal involvement were computed for the cohort overall and for subgroups defined according to duration of AS in 10-year increments. RESULTS: Symmetric sacroiliitis was seen in 86.1% of patients. Lumbar predominance was more common during the first 20 years of the disease, after which the cervical spine and lumbar spine were equally involved. Men and women were equally likely to have cervical-predominant involvement. Complete spinal fusion was observed in 27.9% of patients with AS for more than 30 years and in 42.6% of patients with AS for more than 40 years. Patients with BASRI hip scores of 2 or greater had significantly higher BASRI spine scores. CONCLUSION: There were no sex differences in cervical-predominant involvement in AS. Hip arthritis was strongly associated with worse spinal involvement.

Vascular lesions presenting as musculoskeletal neoplasms.

OBJECTIVE: The purpose of this article is to describe how to distinguish between vascular lesions and other soft-tissue tumors such as sarcomas on various imaging modalities. CONCLUSION: Careful attention to imaging characteristics, patient history, and presentation is essential to differentiate vascular lesions from sarcomas and other tumors.

Repeated Spinal Mobility Measures and Their Association With Radiographic Damage in Ankylosing Spondylitis.

OBJECTIVE: We sought to explore the relationship between changes in repeated mobility measures and spinal structural progression in patients with ankylosing spondylitis (AS) over time. METHODS: We studied patients with AS from the PSOAS (Prospective Study of Outcomes in AS) cohort and performed longitudinal multivariable regression modeling to assess the relationship of structural damage measured by their regional (cervical or lumbar) modified Stoke AS Spinal Score(mSASSS) and selected cervical (eg, cervical rotation, lateral bending, and occiput-to-wall distance) and lumbar spinal mobility measures (eg, Schöber's test and lumbar lateral bending) that were collected at least every 2 years from 2003 to 2019. RESULTS: The median length of follow-up for our 518 patients with cervical mSASSS measurements and 573 with lumbar mSASSS measurements was 4.08 (interquartile range [IQR] 2.25-6.67) and 4.17 (IQR 2.25-6.67) years, respectively. Among the mobility measures, based on multivariable regression models adjusting for clinical/demographic variables and C-reactive protein, we did not observe meaningful associations between changes in spinal mobility with their respective regional mSASSS. Baseline mSASSS, male sex, increased C-reactive protein (CRP), and longer disease duration were associated with increased longitudinal mSASSS in all analyses. CONCLUSION: Our study shows that 2-year changes in individual spinal mobility measures are not reliably associated with increased, longitudinal, AS-related spinal structural progression. We also confirmed the relationship of baseline mSASSS, sex, CRP, and disease duration with AS-related structural spinal progression over time.

The changing profile of ankylosing spondylitis in the biologic era.

OBJECTIVE: To compare disease characteristics, comorbidities, and medication utilization of 1141 patients with ankylosing spondylitis (AS) with short (< 20 years) and long (≥ 20 years) disease duration enrolled in the Prospective Study of Outcomes in AS (PSOAS) study over three different periods of time and followed longitudinally. METHODS: Study visits were carried out every 6 months examining disease activity (Bath AS Disease Activity Index (BASDAI), C-reactive protein, erythrocyte sedimentation rate), functional impairment, depression, and medication utilization as well as radiographic severity. Groups were compared with regression models using generalized estimating equation, linear, and Poisson regressions after adjusting for sites and for patients withdrawing from the study at less than 2 years follow-up. RESULTS: Overall, AS patients with long disease duration were more likely to be married, white, receiving disability, and to be with higher functional impairment and radiographic severity, more uveitis, diabetes, hypertension, cardiovascular disease, and osteoporosis, and with less nonsteroidal anti-inflammatory drug (NSAID) and more opioid use than those with short disease duration. Current smoking decreased between 2002 and 2019 regardless of disease duration. Lower baseline NSAID and methotrexate/sulfasalazine use and higher TNF inhibitor usage were seen only in those with shorter disease duration, though NSAID use and functional impairment decreased over time in both groups. Disease activity, depression scores, and NSAID use decreased and anti-TNF use increased in those followed > 8 years. CONCLUSIONS: Patients with AS enrolling in this multicenter longitudinal cohort have different disease profiles and medication utilization over time, perhaps reflecting innovations in treatment and increasing disease awareness. Key Points • The use of NSAIDs, nonbiologic DMARDs, and prednisone has decreased over the past 16 years in patients with AS. • The use of anti-TNF agents has dramatically increased. • In treated patients, disease activity, depression scores, and functional impairment have decreased over time.

Emergency joint aspiration: a guide for radiologists on call.

Septic arthritis is a disabling and possibly life-threatening disease that requires early diagnosis for optimal management. It is important that clinical and imaging features of septic arthritis be promptly identified. In addition, because other disease entities may have characteristics similar to those of septic arthritis, analysis of a needle biopsy specimen may be necessary for differential diagnosis. Radiologists may be asked to perform emergent aspiration of a possibly infected joint. It is important that those who perform aspiration procedures be familiar with a safe and effective imaging-guided arthrocentesis technique that is tailored to the individual patient and the specific joint affected.

Thermal ablation of osteoid osteoma: overview and step-by-step guide.

Osteoid osteoma is a small, benign but painful lesion with specific clinical and imaging characteristics. Computed tomography is the imaging modality of choice for visualization of the nidus and for treatment planning. Complete surgical excision of the nidus is curative, providing symptomatic relief, and is the traditionally preferred treatment. However, surgery has disadvantages, including the difficulty of locating the lesion intraoperatively, the need for prolonged hospitalization, and the possibility of postoperative complications ranging from an unsatisfactory cosmetic result to a fracture. Percutaneous radiofrequency (RF) ablation, which involves the use of thermal coagulation to induce necrosis in the lesion, is a minimally invasive alternative to surgical treatment of osteoid osteoma. With reported success rates approaching 90%, RF ablation should be considered among the primary options available for treating this condition.

Salmonella spondylodiscitis associated with a mycotic abdominal aortic aneurysm and paravertebral abscess.

Each year, 1.4 million people in the United States are infected with Salmonella (Beneson et al. [23] Am J Med, 110:60-63, 2001). The most common clinical presentation of Salmonella infection is gastroenteritis which is usually self-limited, lasting between one to four days (Black et al. [24] N Engl J Med, 261:811-816, 1960). Although most infections are mild-to-moderate, serious disease, and death does occur (Voetsch et al. [25] CID, 38:S127-S132, 2004). A rare but increasing number of patients present with Salmonellosis spondylodiscitis resulting from contiguous spread of infection from the adjacent abdominal aorta. Concurrent infection of these structures exacerbates morbidity, necessitating an elevated clinical suspicion in patients with appropriate risk factors, clinical signs and symptoms. Furthermore, an overall mortality rate of 67% makes mycotic abdominal aortic aneurysms highly lethal (Gonda et al. [26] Radiology, 168:343-346, 1988). Thus, early diagnosis is crucial, allowing for prompt antibiotic and surgical management. Laboratory and imaging tests obtained at the initial suspicion for infection of the spine and aorta facilitates diagnosis while minimizing or preventing more serious complications like paresis and aortic rupture. We present a patient with a mycotic abdominal aortic aneurysm infected with Salmonella enteritides that spread to the adjacent lumbar vertebra and left psoas muscle.

En bloc shoulder resection with total shoulder prosthetic replacement: indications and imaging findings.

OBJECTIVE: Our purpose was to highlight the importance of radiologic studies in assessing the appropriateness of total scapular resection and total shoulder prosthetic reconstruction and to examine the role of imaging in evaluating for postoperative complications. CONCLUSION: Evolving surgical and reconstructive techniques for treatment of shoulder girdle tumors require radiologists to familiarize themselves with novel imaging findings associated with these procedures. Readers will better understand the indications for limbsparing surgery with total shoulder prosthetic reconstruction, normal postoperative radiologic findings, and common complications.

Avulsion fractures of the knee: imaging findings and clinical significance.

The knee is an intricate joint with numerous tendinous, ligamentous, and meniscal attachments, which make it particularly vulnerable to complex injuries after trauma. A variety of avulsion fractures of the knee can occur, including Segond and reverse Segond fractures; avulsions of the anterior and posterior cruciate ligaments; arcuate complex avulsion; iliotibial band avulsion; avulsions of the biceps femoris, semimembranosus, and quadriceps tendons; Sinding-Larsen-Johansson syndrome; and Osgood-Schlatter disease. These fractures often have a subtle appearance at conventional radiography, which is typically the first imaging modality performed in these cases. Advanced imaging modalities, particularly magnetic resonance imaging, are helpful and can provide valuable additional information for adequately defining the extent of damage. The onus is on the radiologist to identify the pattern of injury and to understand the substantial underlying damage that it frequently represents. Conveying this information to the referring clinician is crucial and represents the first step toward additional evaluation and probable orthopedic referral. By recognizing the significance of these injuries at initial presentation, radiologists can facilitate appropriate patient work-up and prevent the chronic morbidity associated with delayed treatment.

Harmonization, data management, and statistical issues related to prospective multicenter studies in Ankylosing spondylitis (AS): Experience from the Prospective Study Of Ankylosing Spondylitis (PSOAS) cohort.

Ankylosing spondylitis (AS) is characterized by inflammation of the spine and sacroiliac joints causing pain and stiffness and, in some patients, ultimately new bone formation, and progressive joint ankyloses. The classical definition of AS is based on the modified New York (mNY) criteria. Limited data have been reported regarding data quality assurance procedure for multicenter or multisite prospective cohort of patients with AS. Since 2002, 1272 qualified AS patients have been enrolled from five sites (4 US sites and 1 Australian site) in the Prospective Study Of Ankylosing Spondylitis (PSOAS). In 2012, a Data Management and Statistical Core (DMSC) was added to the PSOAS team to assist in study design, establish a systematic approach to data management and data quality, and develop and apply appropriate statistical analysis of data. With assistance from the PSOAS investigators, DMSC modified Case Report Forms and developed database in Research Electronic Data Capture (REDCap). DMSC also developed additional data quality assurance procedure to assure data quality. The error rate for various forms in PSOAS databases ranged from 0.07% for medications data to 1.1% for arthritis activity questionnaire-Global pain. Furthermore, based on data from a sub study of 48 patients with AS, we showed a strong level (90.0%) of agreement between the two readers of X-rays with respect to modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). This paper not only could serve as reference for future publications from PSOAS cohort but also could serve as a basic guide to ensuring data quality for multicenter clinical studies.