Comparison of clinical outcomes between groups at different time intervals (n = 103).
| Early (n = 42) | Late (n = 61) | ||||
| Mean | SD | Mean | SD | P Valuea | |
| 6-mo VAS NP b | 1.0 | 1.9 | 1.5 | 2.6 | 0.023 |
| 6-mo VAS AP b | 0.3 | 1.2 | 0.9 | 1.9 | 0.027 |
| 6-mo JOA | 15.2 | 1.9 | 14.1 | 2.6 | 0.022 |
| 6-mo NS b | 14.9 | 15.1 | 24.9 | 24.1 | 0.044 |
| 6-mo NPD b | 10.1 | 12.9 | 17.1 | 15.5 | 0.042 |
| 6-mo NDI b | 8.4 | 12.0 | 15.8 | 13.2 | 0.074 |
| 6-mo PCS | 51.3 | 8.5 | 45.7 | 10.8 | 0.059 |
| 6-mo MCS | 51.7 | 10.6 | 50.6 | 11.7 | 0.015 |
| 2-y VAS NP b | 0.6 | 1.9 | 1.1 | 2.3 | 0.325 |
| 2-y VAS AP b | 0.3 | 1.0 | 1.2 | 2.6 | 0.060 |
| 2-y JOA | 15.3 | 1.5 | 14.7 | 2.3 | 0.007 |
| 2-y NS b | 13.5 | 14.3 | 22.0 | 20.6 | 0.046 |
| 2-y NPD b | 6.9 | 10.0 | 13.0 | 13.7 | 0.042 |
| 2-y NDI b | 6.8 | 10.2 | 11.7 | 13.8 | 0.036 |
| 2-y PCS | 52.1 | 6.9 | 49.4 | 9.8 | 0.008 |
| 2-y MCS | 53.1 | 9.8 | 48.7 | 13.5 | 0.057 |
Boldface indicates statistical significance.
aUsing multivariate regression to control for age, gender, body mass index, comorbidities and baseline JOA and NDI scores.
bA lower score is better.
JOA, Japanese Orthopaedic Association; MCS, Mental Component Summary; NDI, Neck Disability Index; NPD, neck pain and disability; NS, neurogenic symptoms; PCS, Physical Component Summary; RTW, return to work; VAS AM, visual analog scale arm pain; VAS NP, visual analog scale neck pain.