Fig. 3

The distance between the entry point and MP (green points) is illustrated. The 12 mm area around the MP was divided into six parts: 47% of the entry points (total 57, left 33, right 24) were located within 0–2 mm lateral to the MP (red bar), 25% of the entry points (total 30, left 11, right 19) were located within 0–2 mm medial to the MP (blue bar), 18.3% of the entry points (total 22, left 11, right 11) were located within 2–4 mm lateral to the MP (blue bar), and only 9.2% of the entry points were located in the remaining area (green bar)