Univariate analysis: MRI variables at baseline and associations with time to RTS in univariate analysis
| All cases | MRI-positive cases | |||||||
|---|---|---|---|---|---|---|---|---|
| MRI measures | N | Baseline measures | Mean RTS | β-Coefficient (95% CI) | N | Baseline measures | Mean RTS | β-Coefficient (95% CI) |
| Distance ischial tuberosity (cm)§ | 179 | 9.2 (±8.7) | – | 0.2 (−0.02 to 0.4) | 140 | 11.8 (±8.2) | – | −0.2 (−0.4 to 01) |
| Craniocaudal (cm) | 180 | 11.0 (±8.8) 9.8 (14.9)† | – | 0.6 (0.4 to 0.8) | 141 | 14.0 (±7.5) – | – | 0.4 (0.2 to 0.7) |
| Anteroposterior (cm) | 180 | 1.8 (±1.6) | – | 3.4 (2.4 to 4.4) | 141 | 2.2 (±1.4) | – | 2.6 (1.3 to 3.9) |
| Mediolateral (cm) | 180 | 1.7 (±1.4) | – | 3.7 (2.6 to 4.8) | 141 | 2.2 (±1.2) | – | 2.8 (1.2 to 4.3) |
| Volume of oedema (cm3) | 180 | 47.1 (±78.7) 13.8 (54.1)† | – | 0.1 (0.0 to 0.1) | 141 | 60.2 (±84.4) 27.7 (64.2)† | – | 0.1 (0.0 to 0.1) |
| Cross-sectional area (%)‡ | 179 | 18.2 (±22.7) 9.5 (23.6)† | – | 0.2 (0.1 to 0.3) | 140 | 23.2 (±23.2) 14.1 (26.3)† | – | 0.2 (0.1 to 0.2) |
| Negative vs positive MRI | 180 | 11.0 (7.2 to 14.9) | 141 | |||||
| Positive | 141 (78) | 24 (±12) | 140 (100) | 24 (±12) | – | |||
| Negative* | 39 (22) | 13 (±8) | – | |||||
| Muscle most involved¶ | 141 | 0.2 (−4.7 to 5.0) | 141 | 0.2 (−4.7 to 5.0) | ||||
| Lateral (BFLH and BFSH) | 113 (80) | 24 (±11) | 113 (80) | 24 (±11) | ||||
| Medial (SM and ST)* | 28 (20) | 24 (±12) | 28 (20) | 24 (±12) | ||||
| Presence of central tendon disruption | 180 | 9.6 (6.0 to 13.2) | 141 | 7.1 (3.2 to 10.1) | ||||
| Yes | 50 (28) | 28 (±11) | 50 (35) | 28 (±11) | ||||
| No* | 130 (72) | 19 (±11) | 91 (65) | 21 (±11) | ||||
| Overall grading | 180 | 141 | 6.6 (2.8 to 10.3) | |||||
| Grade 2 | 59 (33) | 28 (±12) | 14.9 (10.6 to 19.1) | 59 (58) | 28 (±12) | |||
| Grade 1 | 82 (45) | 21 (±11) | 8.3 (4.3 to 12.3) | 82 (42) | 21 (±11) | |||
| Grade 0* | 39 (22) | 13 (±8) | 0§ | – | – | |||
| Number of muscles involved | 180 | 141 | 5.0 (0.2 to 9.7) | |||||
| 2 or 3 muscles involved | 28 (15) | 28 (±11) | 15.1 (9.8 to 20.3) | 28 (20) | 28 (±11) | |||
| 1 muscle involved | 113 (63) | 23 (±12) | 10.1 (6.1 to 14.0) | 113 (80) | 23 (±12) | |||
| No muscles involved* | 39 (22) | 13 (±8) | 0§ | – | – | |||
Data are presented as the mean time to RTS within each group (±SD). For categorical data, the distribution of cases within each group is presented (valid percentage). Regression coefficients are presented as unadjusted unstandardised β-coefficients with 95% CIs.
*Reference category.
†Not normally distributed, median values (IQR) are presented additionally.
‡For one athlete, the cross-sectional area could not be calculated, due to reduced image sequences. Statistical significant (p≤0.05) associations are presented in bold and italics.
§For one athlete, the distance from ischial tuberosity could not be measured.
¶Only MRI positive cases.
BFLH, biceps femoris long head; BFSH, biceps femoris short head; RTS, return to sport; SM, semitendinosus; ST, semitendinosus.