Quantitative assessment of foot structure in rheumatoid arthritis by a foot digitizer: detection of deformities even in the absence of erosions.
OBJECTIVE
Foot involvement is a major feature in rheumatoid arthritis (RA), leading to structural deformities. Methods to allow a 3-dimensional (3-D) evaluation of foot structure in RA to be applicable in daily clinical practice have not been evaluated. This study assessed the use of a foot digitizer, a noninvasive 3-D scanner collecting objective quantitative data of the feet, to evaluate the presence of foot structure abnormalities in an RA outpatient cohort.


METHODS
Foot digitizer data of RA patients were compared with healthy controls. Subanalyses were performed to find relationships with erosive disease and the presence of swollen and/or tender joints. Linear mixed models were applied with correction, including sex, age, body weight and height, foot length, Disease Activity Score in 28 joints, and disease duration.


RESULTS
Forty-one percent of the patients showed >1 abnormal parameter, measured with the 3-D foot scanner. Most differences found were located in the forefoot, the most frequently affected area of the RA foot. Strikingly, even in the absence of joint erosions, marked alterations were found. Comparable differences were also observed between the patients with and without swollen and/or tender joints. Additionally, alterations were not strongly related to foot pain and disability, suggesting the capacity of the foot digitizer to detect early changes in foot structure.


CONCLUSIONS
The results highlight the impact of RA on foot structure, even in the absence of clinical signs of swelling or radiographic erosions. The foot digitizer offers a valuable tool to screen for such foot deformities before the presence of erosions.
Ghent University, Belgium.
Sophie
S
De Mits
Herman
H
Mielants
Dirk
D
De Clercq
James
J
Woodburn
Philip
P
Roosen
Dirk
D
Elewaut
D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000000981:diagnostic imaging / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging / Q000473:pathology*; D015331:Cohort Studies; D004487:Edema / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D005534:Foot Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D006214:Hallux / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods*; D007834:Lasers; D008297:Male; D008683:Metatarsophalangeal Joint / Q000000981:diagnostic imaging / Q000473:pathology; D008875:Middle Aged; D055096:Optical Devices; D011859:Radiography