Musculoskeletal abnormalities of the tibia in juvenile rheumatoid arthritis.
OBJECTIVE
To characterize local bone geometry, density, and strength, using peripheral quantitative computed tomography (pQCT), compared with general bone characteristics as measured using dual x-ray absorptiometry (DXA), and to assess their relationship to disease-related factors in children with juvenile rheumatoid arthritis (JRA).


METHODS
Forty-eight children ages 4-18 years with JRA (17 pauciarticular, 23 polyarticular, 8 systemic) were compared with age-matched healthy controls (n = 266). Measurements included cortical and trabecular bone geometry, density, and strength at the distal and midshaft tibia determined by pQCT, and whole-body, lumbar spine, and femoral neck measurements by DXA.


RESULTS
Methotrexate (MTX) was prescribed to 23 of 48 patients (47.9%) and glucocorticoids and MTX were prescribed to 15 of 48 patients (31.3%), with the greatest use in children with systemic JRA. All JRA patients had decreased tibia trabecular bone density, cortical bone size and strength, and muscle mass. Children with systemic JRA had lower femoral neck densities. Systemic JRA was associated with a shorter, less mineralized skeleton, while a narrower, less mineralized skeleton was observed in polyarticular JRA. The tibia diaphysis was narrower with decreased muscle mass, but normal, size-adjusted bone mineral in all subtypes indicated a localized effect of JRA on bone. Patients exposed to glucocorticoids and MTX or to glucocorticoids or MTX alone had greatly reduced trabecular density, cortical bone geometry properties, and bone mineral content, muscle mass, and bone strength.


CONCLUSIONS
Children with JRA have decreased skeletal size, muscle mass, trabecular bone density, cortical bone geometry, and strength. Not surprisingly, these bone abnormalities are more pronounced in children with greater disease severity.
Felin
Elena M O
EM
University of Utah, Salt Lake City, UT 84158, USA.
Prahalad
Sampath
S
Askew
E Wayne
EW
Moyer-Mileur
Laurie J
LJ
D015502:Absorptiometry, Photon; D000293:Adolescent; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001171:Arthritis, Juvenile / Q000150:complications / Q000188:drug therapy / Q000473:pathology*; D015519:Bone Density; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D005272:Femur Neck / Q000473:pathology; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use; D009141:Musculoskeletal System / Q000473:pathology*; D012720:Severity of Illness Index; D013977:Tibia / Q000473:pathology*; D014057:Tomography, X-Ray Computed
D018501:Antirheumatic Agents; D005938:Glucocorticoids; D008727:Methotrexate