Endoscopic perineal approach to the presacral space: a feasibility study

Sacrococcygeal sinus angle: as a new anatomic landmark for the posterior approach of presacral lesions

PURPOSE

We have discussed the importance of sacrococcygeal sinus angle (SSA), which is a new anatomical landmark in the surgery of presacral lesions. Because of its anatomical structure, the sacrum limits the surgical exposure like a compact barrier for the posterior surgical approach. The main aim of this paper is to explain the anatomical description and clinical importance of SSA in the surgery of presacral lesions.

METHODS

Three groups were designated, consisting of ten patients in each group, as early childhood (group 1), late childhood (group 2) and adulthood (group 3). Patients were selected randomly. The degree of SSA measurement was performed between the line tangent to the anterior margin of the first sacral vertebra and the line from the promontorium to the tip of the coccyx. The measurement of SSA was performed on patients' lumbosacral magnetic resonance images. When the SSA forms a triangle via a parallel line starting from the inferior tip of the sacrum and running parallel to the ground, the area of the triangle also covers the field of view of the presacral region. In addition, the sacral region needed to be resected for maximum exposure is also within this area.

RESULTS

The mean SSA was measured to be 53.9 ± 11.4° in group 1, 77.8 ± 11.2° in group 2 and 74.5 ± 12.5° in group 3. Intergroup comparisons revealed a significant difference between group 1 and the other two groups statistically. It was found that the SSA was 20° less in group 1 as compared to the other age groups (p = 0.0005). The area of a triangle is calculated using the sine area formula, and according to this formula the area of a triangle increases when the degree of the angle increases, thus comprising larger part of the sacrum. This condition requires more and wide sacral resection to obtain maximum exposure in the presacral zone.

CONCLUSIONS

We have observed that the SSA is significantly smaller during early childhood compared with the other age groups. This feature provides an anatomical superiority in this age group for the posterior approach in the surgical treatment of presacral masses.

The relevant anatomy of the approach for axial lumbar interbody fusion

STUDY DESIGN

Prospective trial.

OBJECTIVE

To perform a precise anatomical study of the presacral space and to examine the approach safety of AxiaLIF (axial lumbar interbody fusion) in an anatomical aspect.

SUMMARY OF BACKGROUND DATA

AxiaLIF is a novel, minimally invasive surgery. Though there were a few clinical reports on its safety, AxiaLIF is less used in current practice because of the unfamiliarity of surgeons with the regional anatomy of presacral space. METHODS.: Sixteen adult cadaveric pelvic specimens were divided along the median sagittal plane. The presacral fascial structures, the rectosacral fascia, and the pelvic splanchnic nerves were dissected and measured. In the simulated operation, a blunt guide pin was inserted bilaterally to determine the relation of the guide pin's path with important anatomic structures. Mean distances with 95% confidence intervals (CIs) were calculated.

RESULTS

The results showed that the fascial structures of the presacral space were divided into 5 layers, and the pelvic splanchnic nerves limited the dissection of the lower rectum, the mean length of which was 2.2 cm (1.9-2.5 cm). In the simulated operation, the mean minimum distance from the guide pin to the pelvic splanchnic nerves was 0.8 cm (0.4-1.2 cm), and the mean vertical distance to the S3-S4 junction was 1.5 cm (1.2-1.7 cm).

CONCLUSION

Our study suggests that the approach for AxiaLIF is risky and requires further modification. We should choose the accurate surgical plane when performing the presacral approach.