Table 1.
The biomechanical properties of uninjured and healing (injured) Achilles tendons in rats treated with NO-paracetamol, paracetamol, or vehicle at day 10 postoperation
| Failure load (N) | Cross-sectional area (mm2) | Displacement (mm) | Maximum energy | Total energy | Length (mm) | Stiffness (N/mm) | Ultimate stress (MPa) | Strain (%) | |
|---|---|---|---|---|---|---|---|---|---|
| Uninjured | |||||||||
| Vehicle | |||||||||
| Mean | 70 | 2.8 | 3.6 | 134 | 333 | 8.6 | 7.6 | 25 | 42 |
| SD | 24 | 0.1 | 1.5 | 69 | 145 | 1.0 | 2.7 | 9 | 14 |
| n | 5 | 5 | 5 | 5 | 5 | 4 | 4 | 5 | 4 |
| Paracetamol | |||||||||
| Mean | 76 | 2.8 | 3.3 | 141 | 364 | 10.1 | 7.5 | 27 | 33 |
| SD | 15 | 0.1 | 0.9 | 76 | 99 | 0.4 | 1.6 | 5 | 9 |
| n | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Controls | |||||||||
| Mean | 68 | 2.8 | 3.3 | 120 | 346 | 8 | 8 | 24 | 30 |
| SD | 31 | 1.2 | 1.3 | 66 | 208 | 2.9 | 2.8 | 10 | 14 |
| n | 11 | 11 | 11 | 11 | 11 | 10 | 10 | 11 | 10 |
| NO-paracetamol | |||||||||
| Mean | 93 | 3 | 2.9 | 138 | 527 | 9.2 | 10.1 | 32 | 31 |
| SD | 7 | 0 | 0.3 | 18 | 208 | 0.7 | 1.1 | 4 | 4 |
| n | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| T-tests | |||||||||
| Vehicle vs paracetamol | 0.64 | 0.69 | 0.72 | 0.89 | 0.71 | 0.02 | 0.95 | 0.62 | 0.26 |
| Controls vs NO-paracetamol | 0.05 | 0.24 | 0.29 | 1.00 | 0.06 | 0.58 | 0.02 | 0.10 | 0.35 |
| Injured | |||||||||
| Vehicle | |||||||||
| Mean | 40 | 7.9 | 5 | 119 | 172 | 10.2 | 4.5 | 5 | 51 |
| SD | 18 | 0.5 | 2 | 84 | 57 | 0.5 | 1.6 | 2 | 21 |
| n | 5 | 5 | 5 | 5 | 5 | 4 | 4 | 5 | 4 |
| Paracetamol | |||||||||
| Mean | 35 | 7.2 | 4 | 79 | 131 | 11.5 | 3.0 | 5 | 31 |
| SD | 12 | 0.5 | 1 | 37 | 34 | 0.8 | 1.0 | 1 | 10 |
| n | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Controls | |||||||||
| Mean | 37 | 7.5 | 4 | 97 | 150 | 10.0 | 3.6 | 5 | 36 |
| SD | 14 | 0.6 | 2 | 63 | 49 | 3.4 | 1.4 | 2 | 20 |
| n | 11 | 11 | 11 | 11 | 11 | 11 | 10 | 11 | 11 |
| NO-paracetamol | |||||||||
| Mean | 49 | 6.0 | 4 | 116 | 169 | 11.3 | 4.4 | 8 | 37 |
| SD | 16 | 0.6 | 2 | 67 | 52 | 1.0 | 1.7 | 2 | 15 |
| n | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| T-tests | |||||||||
| Vehicle vs paracetamol | 0.57 | 0.04 | 0.41 | 0.33 | 0.18 | 0.02 | 0.11 | 0.81 | 0.08 |
| Controls vs NO-paracetamol | 0.15 | 0.0002 | 0.99 | 0.57 | 0.44 | 0.39 | 0.32 | 0.007 | 0.92 |
SD = standard deviation, n = sample size. Statistical analysis using unpaired two-tailed Student’s t-tests. The alpha level was set at 0.01 in order to account for multiple comparisons. P values that meet these criteria are in bold.