The ZSO: A Novel Approach to the Pedicle Subtraction Osteotomy
Authors: Zavatsky Joseph M. , Briski David C. 
Published: May 2015

Introduction

PSOs are technically demanding given the proximity of neural structures and association with increased blood loss secondary to epidural and cancellous bleeding. Traditionally, straight osteotomes have been utilized to perform PSOs, which can result in a variable amount of correction achieved. This can lead to longer operative times and increased blood loss. We report a novel technique, where fixed-angled (25, 30, and 35 degrees) triangular shavers are utilized to perform the PSO resulting in more reproducible and time efficient osteotomies, which can ultimately lead to decreased blood loss.

Methods

A retrospective review of all patients who underwent an isolated single-level PSO, regardless of previous surgical history from August 2010 to January 2014 was performed. Patients were divided into two groups depending on the PSO technique utilized. Group 1 included all patients before August 2012, in which traditional straight osteotomes were utilized. Group 2 included patients where fixed-angled triangular shavers were used after their adoption in August 2012. Fusion levels, number of Smith–Peterson osteotomies (SPOs), number of revision surgeries, previous fusion mass and the need for osteoclasis and fusion takedown, total operative time, PSO associated operative time, total operative blood loss, PSO associated blood loss, utilization of blood products, ICU requirements, length of stay, major medical complications, and requirement for revision surgery were recorded.

Results

There were 18 patients who had an isolated single-level PSOs performed during this time period. There were 8 patients in group 1, and there were 10 patients in group 2. No difference was found between the two groups in relation to mean age, height, weight, total operative time, total estimated blood loss, or number of levels fused. There was a difference in the number of osteoclasis and fusion takedowns among the revision patients. Group 1 included two patients who had fusion takedowns (two of six revisions, 33%), group 2 included eight patients (eight of eight revisions, 100%), ( p = 0.018). Group 1 included 4 patients (four of eight, 50%) who underwent Smith–Peterson osteotomies (SPOs), whereas group 2 included 10 patients (10/10, 100%), ( p = 0.008). Among all the patients with SPOs, there was no difference in the number of SPOs performed (mean = 4.5). There was a statistical difference in PSO associated blood loss and osteotomy time between the two groups. Mean PSO time for group 1 was 52 minutes, whereas group 2 was 33 minutes, ( p = 0.032). Mean PSO associated blood loss for group 1 was 1,018 mL, whereas group 2 was 463 mL ( p = 0.047). Group 2 had shorter ICU LOS (3 vs. 6 days, p = 0.030), as well as a shorter overall hospital LOS (6.1 vs. 9.3, p = 0.041). There was a statistical difference in major complications between groups 1 and 2. Group 1 had six patients with eight major complications, and group 2 had three patients with three major complications ( p = 0.029).

Conclusion

We report our experience of a novel and highly reproducible ZSO technique to perform PSOs utilizing fixed-angled, triangular shavers, which decreased associated PSO times by 37%, PSO blood loss by 55%, LOS by 34%, and perioperative morbidity.