Table 4

Impact of RA disease duration on bone strength and structure

Disease duration	RA+			RA−
Disease duration	≤2 years	>2–<6 years	≥6 years	≤2 years	>2–<6 years	≥6 years
N	24	18	54	43	21	20
Age, years	49.2±14.4	54.6±11.6	56.3±10.8	49.7±12.6*†	57.5±11.9	59.0±8.3
Sex, n male/n female	9/15	4/14	13/41	9/34	7/14	6/14
µFEA
Stiffness, kN/mm	43.4±10.6*†	33.2±13.4	34.4±14.5	42.6±12.0	40.2±10.2	40.5±16.0
Failure load, N	2065±433*†	1615±620	1693±652	2023±542	1935±475	1942±754
Bone structure (HR-pQCT)
Volumetric bone mineral density
Dtotal, mg HA/cm³	283±55†	251±60	246±57	292±56	284±53	276±79
Dtrab, mg HA/cm³	165±40†	133±42	113±42	152±37	155±30	139±58
Dmeta, mg HA/cm³	223±35*†	191±41	186±43	210±34	213±33	195±58
Dinn, mg HA/cm³	129±36*†	95±41	85±42	112±41	114±30	100±59
Dcomp, mg HA/cm³	772±98	752±100	740±106	830±63	802±74	793±74
Meta/Inn, %	1.79±0.35*†	2.25±0.79	2.50±1.21	2.04±0.51	1.95±0.41	2.24±1.07
Bone microstructure
BV/TV, %	0.14±0.03*†	0.11±0.03	0.11±0.03	0.13±0.03	0.13±0.03	0.12±0.05
Tb.N, 1/mm	2.04±0.30*†	1.70±0.48	1.74±0.41	1.96±0.24	2.01±0.30	1.75±0.58
Tb.Th, mm	0.07±0.01†	0.07±0.01‡	0.06±0.01	0.06±0.01	0.06±0.01	0.06±0.01
Tb.Sp, mm	0.43±0.09*†	0.57±0.20	0.57±0.27	0.45±0.07	0.44±0.08	0.61±0.40
Tb.1/N.SD, mm	0.19±0.06*†	0.34±0.27	0.31±0.28	0.20±0.05	0.19±0.06	0.34±0.28
Ct.Th, mm	0.61±0.20	0.56±0.22	0.59±0.21	0.71±0.18	0.66±0.18	0.66±0.24

Bonferroni-Holm adjustment: critical P values indicating significant results for all investigated parameters were as follows: P1=0.0167, P2=0.025, P3=0.05.
*Significance between ≤2 years’ and >2–<6 years’ disease duration.
†Significance between ≤2 years’ and ≥6 years’ disease duration.
‡Significance between >2–<6 years’ and ≥6 years’ disease duration.
BV/TV, trabecular bone volume per tissue volume; Ct.Th, cortical thickness; Dcomp, compact (cortical) volumetric bone mineral density (vBMD); Dinn, inner trabecular vBMD; Dmeta, meta-trabecular vBMD; Dtotal, total vBMD; Dtrab, trabecular vBMD; HR-pQCT, high-resolution peripheral CT; Meta/Inn, ratio of meta-to-inner density; RA+, anti-citrullinated protein autoantibody positive rheumatoid arthritis (RA); RA−, anti-citrullinated protein autoantibody negative RA; Tb.N, trabecular number; Tb.1/N.SD, inhomogeneity of network; Tb.Sp, trabecular separation; Tb.Th, trabecular thickness; µFEA, micro-finite element analysis.