Neurosurgical Management of Sacral Tumors: Review of the Literature and Operative Nuances.

BACKGROUND: Sacral tumors present a significant challenge to the spine surgeon. As new techniques have evolved in recent years, these lesions have become more amenable to aggressive surgical treatment. Although sacral tumors make up only a small minority of spinal tumors, their surgical management warrants special consideration. METHODS: Based on our experience, we highlight 3 important surgical nuances specifically for the treatment of sacral tumors: preservation and maximization of neurologic function, protection of ventral abdominal and pelvic structures, and lumbopelvic fixation. RESULTS: Two cases of patients with sacral tumors treated at our institution are presented to illustrate these points. Both patients had successful postoperative courses, and remained pain free, well-fixated, and neurologically intact at 3-4 month follow-up. They had no evidence of biomechanical instability. CONCLUSIONS: To ensure a successful outcome, a goal-directed, methodical approach is required.

Biomechanical comparison of inside-outside screws, cables, and regular screws, using a sawbone model.

Our aim was to conduct a biomechanical comparison of the pull-out strengths of inside-outside (I/O) screws, cables, and bone screws to determine whether I/O screws provide greater pull-out resistance than cables or bone screws, and their effectiveness with the screw diameter. There is no remarkable biomechanical experimental study comparing the I/O technique with conventional spinal techniques. The diameter of the screw heads were also biomechanically tested to determine the optimal size that can be used. In this study, 45 blocks of 50x50x5 mm of "sawbone" (synthetic bone, model 1137, Pacific Research Laboratories, Vashon, WA, USA) were used as bone substitutes. Fifteen sets of 14-mm inside-outside Dynalok screws and nuts, 15 wire cables, and 15 bone screws were inserted into a separate sawbone block. An MTS Bionx materials testing machine was used to measure the load to failure of each implant. The mean values and standard deviations of each group were calculated and Student's t-test was used for comparison. The load to failure of the inside-outside screws was significantly greater than that of the cables (p<0.0000004) and the regular bone screws (p<0.000002). The results also revealed that increasing the diameter of the head of the screw also increases the resistance against the pull-out strengths. Thus, using a larger screw in occipitocervical stabilization provides safe and stable fixation of the occipital bone to the cervical spine. This study also proved that sawbone is a useful and reliable alternative to allogenic fresh cadaveric bone grafts or animal bones for certain biomechanical testing.