Mechanical effects of partial sacrectomy: when is reconstruction necessary?

Area of Science:

• Spine Surgery
• Biomechanics
• Orthopedic Research

Background:

• Transverse sacrectomy is a surgical procedure involving the removal of a portion of the sacrum.
• Understanding the biomechanical impact of sacrectomy is crucial for patient outcomes and surgical planning.

Purpose of the Study:

• To evaluate the mechanical consequences of high partial transverse sacrectomy on pelvic structural integrity.
• To determine the safe limits of sacrectomy relative to the S1 nerve root.

Main Methods:

• Ten human cadaveric pelves were divided into three groups: control, sacrectomy caudal to S1 foramina (Group I), and sacrectomy cephalad to S1 foramina (Group II).
• Pelves were subjected to vertical loading at the L4/L5 disc space until failure.
• Load to failure and stiffness were measured for each group.

Main Results:

• Group II (sacrectomy cephalad to S1 foramina) demonstrated significantly lower average load to failure (1045 N) and stiffness (100 N/mm) compared to Group I (2166 N, 222 N/mm) and controls (3014 N, 353 N/mm).
• All specimens failed via sagittal sacral fractures, primarily in Denis Zone II.
• Resection of sacroiliac joints averaged 16% in Group I and 25% in Group II.

Conclusions:

• Partial transverse sacrectomy cephalad to the S1 nerve root (Group II) compromises pelvic structural integrity, likely leading to fracture during postoperative mobilization.
• Sacrectomy caudal to the S1 nerve root (Group I) may allow for safe postoperative mobilization.
• Reconstruction should be considered for transverse partial sacrectomy performed above the S1 nerve root to maintain pelvic stability.