SLR - February 2018 - Matthew Fernandez

Muscle Deficits in Rheumatoid Arthritis Contribute to Inferior Cortical Bone Structure and Trabecular Bone Mineral Density

Reference: Joshua F. Baker, Jin Long, Sogol Mostoufi-Moab, Michele Denburg, Erik Jorgenson, Prerna Sharma, Babette S. Zemel, Elena Taratuta, Said Ibrahim and Mary B. Leonard. Muscle Deficits in Rheumatoid Arthritis Contribute to Inferior Cortical Bone Structure and Trabecular Bone Mineral Density. The Journal of Rheumatology, 2017; 44 (12) 1777–1785.

Scientific Literature Review

Reviewed By: Matthew Fernandez, DPM
Residency Program: UF Health Jacksonville, Jacksonville, FL

Podiatric Relevance: Rheumatoid arthritis (RA) is a fairly common and challenging condition faced by podiatrists on a daily basis. It is well known that patients with RA also suffer from a decreased bone density leading to pathologic fractures. This is also an important and challenging issue when it comes to surgical planning. This study aims to examine the associations between skeletal muscle mass, strength and quality, trabecular and cortical bone deficits in patients with RA and healthy controls.

Methods: Patient with RA ages 18 to 75 who met the 2010 American College of Rheumatology classification criteria were recruited from UPENN and the Philadelphia VA Medical Center Rheumatology practices and were compared to adult controls ages 21 to 78 who were enrolled as healthy reference participants for multiple bone studies at UPENN. In the RA cohort, older patients were excluded to avoid confounding by advanced age, as were those who had juvenile idiopathic arthritis (or other inflammatory arthritis), active cancer, a history of chronic disease known to affect bone health, were pregnant or with a weight > 300lbs. In the control group, exclusion criteria included history of chronic disease or medications known to affect nutrition or bone health (diabetes, chronic kidney disease, liver disease, malignancy, thyroid disease). All study participants (RA and controls) underwent scans at the same laboratory using identical equipment and methods. Assessment parameters included BMI, muscle, fat and bone measurements in the lower leg by peripheral quantitative computed tomography (pQCT). Bone measurements included cortical bone structure and trabecular volumetric bone mineral density (vBMD). Subjects also underwent DEXA assessments, muscle strength measurements, physical activity questionnaires and screenings for disease and inflammatory markers (ESR, CRP).

Results: Participants with RA were generally older but were otherwise similar demographically. Participants with RA had greater BMI and were more likely to be obese. They also were observed to have a greater FMI (fat mass index) and VAT (visceral adipose tissue). RA patients had similar ALMI (appendicular lean mass index) and significantly lower ALMI when adjusting for greater FMI. RA patients had significantly lower muscle CSA (cross-sectional area), as well as lower muscle density and muscle strength. Patients with RA tended to have lower trabecular vBMD with adjustment for BMI. A greater ALMI strongly correlated with a greater trabecular vBMD and cortical thickness. Patients with RA had a low lean mass for their age, substantially lower cortical thickness and trabecular vBMD.

Conclusion: The authors concluded that patients with RA have deficits in muscle mass, quality and strength as well as modest deficits in trabecular vBMD and cortical structure compared to what would be expected for the BMI. The deficits in muscle mass, density and strength observed in RA may contribute to bone deficits through a loss of mechanical loading. Further study needs to be performed to determine if muscle-strengthening regimens in those with RA would have positive correlation with improved bone structure.

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