Bone Abstracts

Objective: Childhood onset Crohn’s disease (CO-CD) is associated with musculoskeletal deficits. However, there are limited data regarding muscle-bone outcomes in adults with CO-CD. The current study aimed to comprehensively assess the muscle-fat-bone unit in young adults with CO-CD, using novel methods of MRI, in comparison with healthy controls.

Methods: Trabecular microarchitecture and cortical geometry of the distal femur were assessed using 3T microMRI. Muscle cross sectional area (CSA) and fat infiltration (FF) were assessed using six-point VIBE Dixon pulse sequence. CSA was adjusted for FF to measure contractile muscle CSA (CM-CSA). Lumbar spine bone marrow adiposity (BMAT) was measured using ¹H-MRS. Grip strength, general health and disease history data were also collected. Results expressed as median (range).

Results: Twenty-six adults with CO-CD (42% male), median age 23.2 years (18.0 to 36.1) and median 10 years (5 to 22) since diagnosis, were compared with 26 age- and gender-matched controls. CD status was in remission (73%) or mildly active (27%). Apparent trabecular bone volume fraction (0.556 (0.471 to 0.640) vs 0.558 (0.521 to 0.594)), trabecular thickness (0.299 (0.238 to 0.368) vs 0.292 (0.265 to 0.356) mm), trabecular number (1.88 (1.62 to 2.21) vs 1.90 (1.61 to 2.12) /mm), and trabecular separation (0.242 (0.181 to 0.289) vs 0.232 (0.199 to 0.275) mm) were not different between CO-CD and controls, respectively. After adjustment for height, there were no differences in cortical geometry between CO-CD and controls. BMAT was 30.1% (9.6 to 58.8) and 31.3% (11.0 to 68.5) in CO-CD and controls, respectively. CO-CD had 1451 mm² (95% CI: 613 – 2289; P=.001) lower CM-CSA than controls, after adjustment for sex and height. CO-CD had higher muscle FF than controls (5.2% (0.6 – 9.7) vs 4.1% (0.5 – 9.2); P=.045). Grip strength was 5.0 kg (95% CI: 2.1 – 7.9; P=.001) lower in CO-CD after adjustment for sex and height.

Conclusion: This high-resolution MRI study found no differences in femur trabecular microarchitecture or cortical geometry between young adults with well controlled CO-CD and healthy controls. However, these subjects had reduced muscle mass, muscle function, and increased muscle fat infiltration in spite of low disease activity.

Disclosure: Richard K Russell has received speaker’s fees, travel support, or has performed consultancy work with: Nestlé, AbbVie, Takeda, Napp, Mead Johnson, Nutricia and Janssen. Daniel R Gaya has received travel grants and speaker honoraria from Vifor, Ferring, Pfizer, Abbvie, Takeda & Janssen.