Summary: Thoracic pedicle screws has been proven to be safe and effective in the treatment of AIS. However, the influence of the instrumentation alloy has not yet been investigated. We revised 143 AIS patients surgically treated. Our results showed that when a stainless steel instrumentation is used, non segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is Titanium, an implant density of >60 % should be guaranteed so as to achieve similar results.
Introduction: Objective of our study was to compare segmental versus non segmental thoracic pedicle screw instrumentations in posterior fusion for adolescent idiopathic scoliosis (AIS) patients.
Methods: A consecutive series of 143 AIS patients (Lenke 1‐4) surgically treated from 1998 through 2005 by means of thoracic pedicle screws only constructs were retrospective reviewed. Considering implant density (number of fixation anchors placed per available anchors sites; segmental>60%, non segmental<40%) and implant alloy used (Ti:titanium vs SS:stainless steel) we divided the aforementioned cohort in four groups: Ti‐S=48 cases; Ti‐NS=34; SS‐S:35;SS‐NS=26. Groups were similar for preoperative average age, gender distribution, Risser sign, main thoracic curve and thoracic kyphosis. Pearson correlation coefficient and univariate analysis of variance were used.
Results: At a mean follow‐up of 6.2 years (range,3 to 10) the overall final main thoracic curve correction averaged 61.4% (20‐89), whereas the implant density within the major curve averaged 71% (15‐100). A significant correlation between implant density and percent major curve correction was observed (r =0.41, p <0.002); when the four distinct groups were compared we found that according to percent correction observed the SS‐S group showed the greatest average correction (75%), followed by the Ti‐S, SS‐NS, and Ti‐NS. We found no statistically significant differences between SS‐S vs Ti‐S vs SS‐NS (r= 0.002, p >0.05; r = 0.13, p> 0.05; r=0.07, p > 0.01), whereas the Ti‐NS group showed a statistically significant inferior percent correction when compared to all other groups (average 52%; p<0.001). Nevertheless, no significant difference between groups was found on the SRS‐30 assessment showing a postoperative improvement in both self‐image and satisfaction.
Conclusion: According to these results, when a SS instrumentation is used, non segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is Titanium, an implant density of >60% should be guaranteed so as to achieve similar results.
Significance: Level 3