Table 4.
Impact of RA disease duration on bone strength and structure
| Disease duration | RA+ | RA− | ||||
| ≤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.