The visible rate of the LPM on sagittal and CLPM imaging of TMJ is presented in Paper I (Tables 1and 2 in Paper I). The results indicated that the visible rate of the LPM on sagittal images was significantly affected by the degree of mouth opening and the location of the imaging plane. CLPM images could show the LPM constantly. In 325 patients (650 TMJs), the visibility of the LPM on 580 oblique sagittal images, 274 sagittal images and 92 CLPM images of TMJ was compared (Table 1). In 102 patients (204 TMJs) both sagittal and oblique sagittal images were taken. In 46 patients (92TMJs) both CLPM and oblique sagittal images were taken. The clear visible rates of the LPM in different projections, with the two bellies being clearly observed (Fig. 2), are presented in Table 2. It showed that the clear visible rate of the LPM was significantly higher in CLPM images (100% 92/92) and oblique sagittal images (74.5%, 432/580) than in sagittal images (27.8%, 76/274). The very significant differences (P < 0.001, Pearson Chi-square test) were found between each group ( Table 2).
Table 1. Visibility of LPM in MRI with Different Projections
| Projections | V2 | V1 | V0 | Total |
|---|---|---|---|---|
| CLPM | 92 | 0 | 0 | 92 |
| Oblique Sagittal | 432 | 98 | 50 | 580 |
| Sagittal | 76 | 39 | 159 | 274 |
| Total | 600 | 137 | 209 | 946 |
| LPM = lateral pterygoid muscle; CLPM = condyle-LPM projection; V2 = both bellies can be observed on image; V1 = only one belly can be seen in image; V0 = non-belly can be seen in image. P < 0.001 Pearson Chi-square test (df = 4). | ||||
Table 2. Clear Visible Rate of the LPM in MRI with Different Projections
| Projections | χ2 | ||
|---|---|---|---|
| V2-Rate % | Sagittal | Oblique Sagittal | |
| CLPM | 100 (92/92) | 144.835*** | 30.106*** |
| Oblique Sagittal | 74.5 (432/580) | 254.806*** | |
| Sagittal | 27.8 (76/274) | ||
| LPM = lateral pterygoid muscle; CLPM = condyle-LPM projection; V2 = both bellies can be observed on image; χ2 = Pearson Chi-square value. ***P < 0.001. | |||