SLR - October 2020 - John R. Greaves

Rheumatoid Arthritis and Tenosynovitis at the Metatarsophalangeal Joints: An Anatomic and MRI Study of the Forefoot Tendon Sheaths

Reference: Dakkak YJ, Jansen FP, DeRuiter MC, Reijnierse M, van der Helm-van Mil AHM. Rheumatoid Arthritis and Tenosynovitis at the Metatarsophalangeal Joints: An Anatomic and MRI Study of the Forefoot Tendon Sheaths. Radiology. 2020;295(1):146-154. doi:10.1148/radiol.2020191725

Scientific Literature Review

Reviewed By: John R. Greaves, DPM 
Residency Program: Northwest Medical Center – Margate FL

Podiatric Relevance: MRI detected tenosynovitis has been shown to be associated with rheumatoid arthritis (RA) in the metacarpophalangeal joints (MCPJs) of the hand. This finding has been used as an early diagnostic criterion due to its specificity for RA. This study is relevant to podiatric medicine because it examines the anatomic structure of the forefoot tendon sheaths as well as the relationship between MRI detected tenosynovitis in the metatarsophalangeal joints (MTPJs) in RA patients.   

Methods: The anatomic study consisted of macroscopic and microscopic evaluation of the forefoot flexor and extensor tendons. The specimens for macroscopic evaluation were prepped by injecting epoxy resin into the flexor tendons and surrounding tissues and silicone rubber into the extensor tendons and surrounding tissues. Microscopic evaluation of the tendon sheaths was performed after the specimens were embedded in paraffin and hematoxylin-eosin staining was performed. Examination was performed independently by an anatomist and pathologist who were blinded. 

The imaging study involved 441 patients with clinically confirmed arthritis and symptom onset of less than two years. Tenosynovitis was scored according to the Haavardsholm method. Scoring for bone marrow edema and synovitis was done using the Outcome Measures in Rheumatology Clinical Trials Rheumatoid Arthritis MRI (OMERACT RAMRIS) Scoring system. These systems were found to be reliable when being applied to the MTPJs. The images were scored by six trained readers who were blinded to the clinical data and each image was scored by two readers independently.     
 
Results:
Anatomic Studies:
On gross examination the hardened injectables were found to be confined to sheath-like structures on both the flexor and extensor tendons that crossed the MTPJ’s distally. Microscopic evaluation showed enclosed spaces that completely surrounded the flexor and extensor tendons at the level of the MTPJs. The cell type in these structures was noted to be squamous epithelial cells representative of synoviocytes.  

MR Imaging Studies:
One hundred fifty-seven of the 441 participants were classified as having RA. The semiquantitative MRI scores were higher in RA patients then those with other arthridities. The sensitivity of MRI for the detection of tenosynovitis at the MTPJ was noted to be 41 percent. The specificity of MRI for the detection of tenosynovitis at the MTPJ was noted to be 78 percent when compared to those with other arthridities and 98 percentwhen compared to healthy individuals. 

Conclusions: The anatomic portion of this study showed that a true synovial sheath does exist around the flexor and extensor tendons at the level of the MTPJs in the forefoot. Due to these findings it can be extrapolated that MRI enhancement around these structures is consistent with the finding of tenosynovitis. 

Previous studies show a positive correlation between MRI confirmed tenosynovitis of the MCPJs and patients with RA. This study shows that MRI detected tenosynovitis is both characteristic and highly specific to RA when compared to healthy adults. This journal article has increased the scientific communities understanding of characteristic pathologic changes that are associated with the foot and ankle in patients with rheumatoid arthritis. This article should help providers confirm the diagnosis of rheumatoid arthritis in patients with pedal presentation.  

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