A Detailed Analysis of the Association between Urate Deposition and Erosions and Osteophytes in Gout

Monosodium urate crystal depletion and bone erosion remodeling during pegloticase treatment in patients with uncontrolled gout: Exploratory dual-energy computed tomography findings from MIRROR RCT

OBJECTIVE

Monosodium-urate (MSU) crystal deposits can be visualized and quantified with dual-energy CT (DECT). Pegloticase lowers serum urate (SU) in uncontrolled gout patients, with methotrexate (MTX) co-therapy recommended to increase SU-lowering response rate and decrease infusion reaction risk. The literature on serial DECT-imaging during pegloticase+MTX co-therapy is sparse, with only 2 prior cases of rapid MSU deposition depletion with subsequent bone-erosion remodeling reported from a small open-label trial. Here, we report DECT findings during pegloticase treatment in a larger number of patients from a randomized controlled trial to confirm bone-erosion remodeling that follows MSU depletion with pegloticase. The influence of length-of-therapy is also explored.

METHODS

Patients received pegloticase (8mg every 2weeks)+MTX (15mg/week orally) or pegloticase+placebo (PBO) during the MIRROR RCT trial. A subset underwent DECT-imaging on Day1 (first pegloticase infusion) and at Weeks 14, 24, and 52. Patients with paired baseline-Week 52 images were included. Imaged regions with baseline MSU-crystal volume (VMSU)<0.5cm3 were excluded to minimize artifact contributions. VMSU and bone-erosion remodeling were assessed.

RESULTS

Eight patients (6 MTX, 2 PBO) were included. Included patients had received 52weeks (5 MTX), 42weeks (1 PBO), and 6weeks (1 MTX, 1 PBO) of pegloticase therapy. Patients who prematurely discontinued pegloticase maintained SU<6mg/dL on allopurinol (n=2)/febuxostat (n=1). At Week 52, VMSU had markedly decreased in both the pegloticase+MTX and pegloticase+PBO treatment groups, with faster depletion during pegloticase therapy. Bone-erosion remodeling was observed in 29/42 (69%) evaluated erosions: 29 (69%) size decrease, 4 (9.5%) recortication, 3 (7.1%) new bone formation.

CONCLUSION

Rapid VMSU depletion during pegloticase therapy was observed with concomitant bone remodeling within 1year. Following pegloticase discontinuation, VMSU reduction slowed or stopped even when SU was maintained<6mg/dL with oral ULT.

CLINICAL TRIAL REGISTRATION

NCT03994731.

Ultrasound imaging in crystal arthropathies: a pictorial review

OBJECTIVE

The prevalence of crystal arthropathies in the general population is rising. The purpose of this pictorial study is to describe the sonographic elements of the most prevalent crystal arthropathies by emphasizing particular sonographic findings using illustrative images and cases while considering technical details and common pitfalls.

METHODS

Using established recommendations, specialists in the fields of sonography and crystal arthropathies agreed by consensus on the unique ultrasound signs associated with each of the conditions.

RESULTS

Gout, calcium pyrophosphate deposition arthropathy, and hydroxyapatite arthropathy are the three most prevalent crystal arthropathies. Today's high-resolution sonography enables reliable evaluation of the underlying crystal deposits, post-inflammatory changes, and a precise description of joint inflammation.

CONCLUSIONS

High-prevalence crystal arthropathies are reliably detectable by ultrasound with current ultrasound equipment. It is necessary to have extensive ultrasound training, know specific sonographic findings, and understand all possible differential diagnoses for disorders affecting the musculoskeletal system.

Detailed analysis of the association between urate deposition and bone erosion in gout: a dual-energy computed tomography study

Objective

This study aimed to analyze the effect of urate deposition (UD) on bone erosion and examine the association between the volume of monosodium urate (MSU) crystals and an improved bone erosion score method, as measured in the metatarsophalangeal (MTP) joints of patients with gout.

Materials and methods

Fifty-six patients diagnosed with gout using the 2015 European League Against Rheumatism and American College of Rheumatology criteria were enrolled. MSU crystals volume at each MTP joint was measured using dual-energy computed tomography (DECT) images. The degree of bone erosion was evaluated with the modified Sharp/van der Heijde (SvdH) erosion scoring system based on CT images. Differences in clinical features between patients with (UD group) and without (non-UD group) UD were assessed, and the correlation between erosion scores and urate crystal volume was analyzed.

Results

The UD and non-UD groups comprised 30 and 26 patients, respectively. Among the 560 MTP joints assessed, 80 showed MSU crystal deposition, and 108 showed bone erosion. Bone erosion occurred in both groups but was significantly less severe in the non-UD group (p <0.001). Both groups had equivalent levels of serum uric acid (p=0.200). Symptom duration was significantly longer in the UD group (p=0.009). The UD group also had a higher rate of kidney stones (p=0.023). The volume of MSU crystals was strongly and positively associated with the degree of bone erosion (r=0.714, p <0.001).

Conclusion

This study found that patients with UD show significant increased bone erosion than those without UD. The volume of MSU crystals is associated with the improved SvdH erosion score based on CT images, regardless of serum uric acid level, demonstrating the potential of combining DECT and serum uric acid measurements in helping optimize the management of patients with gout.

Dual-energy CT assessment of rapid monosodium urate depletion and bone erosion remodelling during pegloticase plus methotrexate co-therapy

OBJECTIVES

Pegloticase rapidly lowers serum urate in uncontrolled/refractory gout patients, with ≥1 tophus resolution in 70% of pegloticase responders and 28% of non-responders. Dual-energy computed tomography (DECT) non-invasively detects MSU deposition, including subclinical deposition, quantifies MSU volumes and depicts bone erosions. This report presents DECT findings in MIRROR open-label trial participants receiving pegloticase+MTX co-therapy.

METHODS

Serial DECT scans were obtained during pegloticase (8 mg biweekly infusions)+oral MTX (15 mg/week) co-therapy. Bilateral hand/wrist, elbow, foot/ankle and knee images were analysed with default post-processing settings. MSU volumes were quantified and bone erosions were identified and evaluated for remodelling (decreased size, sclerosis, new bone formation). DECT and physical examination findings were compared.

RESULTS

2 patients underwent serial DECT. Patient 1 (44-year-old male) completed 52 weeks of pegloticase+MTX co-therapy (26 infusions). Baseline examination detected 4 tophus-affected joints while DECT identified 73 MSU-affected joints (total MSU volume: 128.76 cm3). At end-of-treatment, there were no clinically-affected joints and 4 joints with DECT-detected MSU deposition. MSU volume decreased by 99% and bone erosion remodelling was evident. Patient 2 (51-year-old male) had 10 weeks of therapy (5 infusions), discontinuing because of urate-lowering response loss. Baseline examination detected 7 tophus-affected joints while DECT identified 55 MSU-affected joints (total MSU volume: 59.20 cm3). At end-of-treatment, there were 5 clinically affected joints and 42 joints with DECT-detected MSU deposition. MSU volume decreased by 58% and bone erosion remodelling was evident.

CONCLUSION

DECT detected subclinical MSU deposition and quantified changes over time. Rapid tophus resolution and bone erosion remodelling occurred during pegloticase+MTX co-therapy.

TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT03635957.

Development of a radiographic scoring system for new bone formation in gout

Background

Features of new bone formation (NBF) are common in tophaceous gout. The aim of this project was to develop a plain radiographic scoring system for NBF in gout.

Methods

Informed by a literature review, scoring systems were tested in 80 individual 1st and 5th metatarsophalangeal joints. Plain radiography scores were compared with computed tomography (CT) measurements of the same joints. The best-performing scoring system was then tested in paired sets of hand and foot radiographs obtained over 2 years from an additional 25 patients. Inter-reader reproducibility was assessed using intraclass correlation coefficients (ICC). NBF scores were correlated with plain radiographic erosion scores (using the gout-modified Sharp-van der Heijde system).

Results

Following a series of structured reviews of plain radiographs and scoring exercises, a semi-quantitative scoring system for sclerosis and spur was developed. In the individual joint analysis, the inter-observer ICC (95% CI) was 0.84 (0.76–0.89) for sclerosis and 0.81 (0.72–0.87) for spur. Plain radiographic sclerosis and spur scores correlated with CT measurements (r = 0.65–0.74, P < 0.001 for all analyses). For the hand and foot radiograph sets, the inter-observer ICC (95% CI) was 0.94 (0.90–0.98) for sclerosis score and 0.76 (0.65–0.84) for spur score. Sclerosis and spur scores correlated highly with plain radiographic erosion scores (r = 0.87 and 0.71 respectively), but not with change in erosion scores over 2 years (r = −0.04–0.15).

Conclusion

A semi-quantitative plain radiographic scoring method for the assessment of NBF in gout is feasible, valid, and reproducible. This method may facilitate consistent measurement of NBF in gout.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02683-9.