Table 3.
Distribution of outcomes, demographics, clinical characteristics, and biomarkers across identified k-means clusters.
| Variable | Cluster 1 (n = 243) | Cluster 2 (n = 306) | Cluster 3 (n = 182) | p-value |
|---|---|---|---|---|
| Outcomes | ||||
| OST, n (%) | 214 (88%) | 255 (83%) | 146 (80%) | 0.0801 |
| DSN, n (%) | 196 (81%) | 209 (68%) | 135 (74%) | 0.0047ABC |
| FOA, n (%) |
202 (83%) |
227 (74%) |
149 (82%) |
0.0213AB |
| OST with LBP, n (%) | 72 (31%) | 76 (26%) | 58 (33%) | 0.1967 |
| DSN with LBP, n (%) | 65 (28%) | 66 (22%) | 50 (28%) | 0.2245 |
| FOA with LBP, n (%) |
65 (28%) |
75 (25%) |
65 (37%) |
0.0234BC |
| LBP, n (%) | 0.337 | |||
| None | 155 (66%) | 207 (69%) | 103 (58%) | |
| Mild | 27 (11%) | 30 (10%) | 26 (15%) | |
| Moderate | 35 (15%) | 42 (14%) | 34 (19%) | |
| Severe |
19 (8%) |
19 (6%) |
14 (8%) |
|
| Demographics and Clinical Characteristics | ||||
| Mean age (SD) | 69.5 (7.54) | 64.2 (6.78) | 65.5 (7.31) | <0.0001AC |
| Sex, n (%) | <0.0001ABC | |||
| Female | 149 (61%) | 207 (68%) | 152 (84%) | |
| Male | 94 (39%) | 99 (32%) | 30 (16%) | |
| Race, n (%) | ||||
| White | 202 (83%) | 208 (68%) | 77 (42%) | <0.0001ABC |
| Black | 41 (17%) | 98 (32%) | 105 (58%) | |
| Knee osteoarthritis, n (%) | 105 (44%) | 93 (31%) | 86 (49%) | <0.0001ABC |
| Mean body mass index (SD) | 31.3 (6.24) | 30.6 (5.62) | 33.2 (6.47) | 0.0001BC |
| Depressive symptoms present, n (%) | 37 (16%) | 45 (15%) | 36 (20%) | 0.3023 |
| Pressure-pain threshold (≤4 kg), n (%) | 65 (28%) | 69 (23%) | 62 (36%) | 0.0148ABC |
| Biomarkers, mean (SD) | ||||
| Structural | ||||
| N-cadherin | 120.8 (24.18) | 106.1 (18.78) | 113.9 (28.75) | <0.0001AC |
| Lumican | 132.2 (18.75) | 125.9 (17.62) | 148.4 (36.35) | <0.0001ABC |
| CTX-II | 421 (390.27) | 236.3 (131.05) | 705.9 (975.86) | <0.0001ABC |
| Inflammatory | ||||
| OPG | 112.5 (44.98) | 80 (31.46) | 106.2 (38) | <0.0001AB |
| RANTES | 126051.5 (64739.59) | 187199.5 (87143.3) | 243385.8 (102088.31) | <0.0001ABC |
| IL-6 | 2.7 (5.4) | 1.4 (1.21) | 2.4 (6.32) | <0.0001AB |
| CXCL6 | 201.3 (107.65) | 265.9 (174.52) | 466.7 (1316.27) | <0.0001ABC |
| HA | 108.6 (133.01) | 45.3 (27.48) | 67.8 (42.2) | <0.0001ABC |
| Pain | ||||
| NPY | 23.7 (7.78) | 24.0 (10.18) | 20.4 (7.24) | <0.0001BC |
| BDNF | 24803.4 (6082.02) | 32705.4 (8028.68) | 36312.8 (9689.92) | <0.0001ABC |
OST = vertebral osteophytes; DSN = disc space narrowing; FOA = facet joint osteoarthritis; LBP = low back pain; CTX-II = type II collagen; OPG = osteoprotegerin; RANTES = C–C Motif Chemokine Ligand 5; IL-6 = interleukin-6; CXCL6 = C-X-C Motif Chemokine Ligand 6; HA = hyaluronic acid; NPY = neuropeptide-Y; BDNF = brain derived neurotrophicfactor. Pairwise comparisons: A = p-value for Cluster 1 vs Cluster 2; B = p-value for Cluster 2 vs Cluster 3; C = p-value for Cluster 1 vs Cluster 3.