Does contiguous multilevel pedicle screws offer added curve correction over alternate level screw strategy in AIS patients when curve flexibility is taken into account?

Abstract

SUMMARY: This study assessed the radiographic and cost analysis of contiguous multilevel pedicle screws to alternate level pedicle screw strategy (ALSS) in the context of the fulcrum bending correction index (FBCI) in AIS patients treated with titanium instrumentation. The study noted similar FBCIs between strategy-types, but significant cost reductions associated with ALSS. INTRODUCTION: With the use of each pedicle screw in AIS surgery, there is an increase in instrumentation-related costs, operative time, risk of complications and health-care expenses. As such, alternate level screw strategy (ALSS) is an alternative to contiguous multilevel screw strategy (CMSS). Moreover, studies have demonstrated the importance in accounting for the flexibility of the curve based on the fulcrum bending radiograph when assessing postoperative curve correction. Therefore, being cognizant of curve flexibility, the following study addressed a radiographic and cost analysis comparing CMSS to ALSS for the treatment of thoracic AIS with titanium instrumentation. METHODS: Seventy-seven AIS patients underwent surgery (range: 6-15 levels). Thirty-five patients received CMSS, characterized as bilateral screw fixation at every level. Forty-two patients underwent ALSS, which entailed bilateral screw fixation at alternate levels. Titanium rods were utilized in all cases. Pre- and postoperative postero-anterior and fulcrum bending radiographic Cobb angles were obtained of all patients. The fulcrum flexibility and the fulcrum bending correction index (FBCI) were assessed. Cost analysis was also performed. RESULTS: There was a statistically significant difference between screw strategy-type to that of pre- and postoperative Cobb angles, and postoperative curve correction (p<0.05). No statistically significant difference was noted between screw strategy-type and fulcrum flexibility (CMSS mean, 66.9%; ALSS mean, 62.7%; p>0.05). The mean FBCIs of the CMSS and ALSS were 126.1% and 122.1%, respectively, and did not statistically differ (p=0.734). In comparison to the CMSS, the ALSS was associated with pedicle screw cost reductions of up to 46.2%. CONCLUSION: This study is the first to illustrate that regardless of curve rigidity, ALSS utilizing less pedicle screws can achieve comparable FBCI as CMSS. We attribute this to the relatively flexible titanium rods used in this study. Thus in this context, ALSS is as effective as CMSS in terms of coronal curve correction, it has the added benefits of reducing operative time and neurological complication risk, as well as the possibility of better kyphosis restoration compared to the lordosing effect of CMSS.