Is it safe to stop at C7 during multilevel posterior cervical decompression and fusion? - multicenter analysis

Abstract

Background context: Despite a number of studies addressing the anatomical and biomechanical challenges of long segment, posterior cervical fusion surgery, recommendations for appropriate caudal "end level" vary widely.

Purpose: Compare revision rates, patient reported outcomes and radiographic outcomes in patients in whom 3+ level posterior fusions ended in the cervical spine versus those in whom the fusion was extended into the thoracic spine.

Study design: Multicenter retrospective analysis.

Outcome measures: Visual analog scale (VAS), Oswestry disability index (ODI), cervical lordosis, C2-C7 sagittal plumbline, T1 slope, and revision rate.

Methods: We assembled a radiographic and clinical database of patients that had undergone three or more level posterior cervical fusions for degenerative disease from January 2013 to May 2015 at one of four busy spine centers. Only those patients with at least 2 years of postoperative (postop) follow-up were included. Patients were divided into two groups: group I (fusion ending at C6 or C7) and group II (fusion extending into the thoracic spine). All radiographic measurements (cervical lordosis, T1 slope, and C2-C7 sagittal plumbline) were performed by an independent experienced clinical researcher.

Results: Two hundred and sixty-four patient cases were reviewed and sorted into the two outlined groups, Group I (n=168) and Group II (n=96). Demographically, mean age, percentage of females, non-smokers and anterior support were greater in Group II than in Groups I (p<.05). Mean estimated blood loss (EBL), operative time (OR) and length of hospital stay (LOS) were significantly higher in Group II (p<.05). Rate of revision was not clinically or statistically significantly different (p>.05) between Group I (11.1%) and Group II (9.4%). The majority of the revision surgeries occurred between 2 to 5 years postop. A greater number of subjacent degeneration/spondylolisthesis events were noted in Group I compared with Group II (3.6% vs. 1.2%). There were significant improvements in mean clinical outcomes (ie, VAS and ODI) at two years postop in both groups, but there were no statistically significant differences between the groups (p>.05). Mean cervical lordosis at 2 years postop improved in all groups (12.8° vs. 14.1°); however, there was no significant statistical difference in change for mean cervical lordosis (2 weeks vs. 2 year postop) between the two groups. Similary, there were no significant statistical differences in change for mean C2-C7 sagittal plumbline and T1 slope (2 weeks vs. 2 year postop) between the two groups(p>.05).

Conclusions: Caudal end level did not significantly affect revision rates, patient reported outcomes or radiographic outcomes. Higher EBL, OR, and LOS in group II suggest that, absent focal C7-T1 pathology, extension of posterior cervical fusions into the thoracic spine may not be necessary. Extension of posterior cervical fusions into the thoracic spine may be recommended for higher risk patients with limitations to strong C7 bone anchorage. In others, it is safe to stop at C7.

Keywords: Cervicothoracic fusion; Cervicothoracic junction; Multilevel posterior cervical fusion; Outcomes; Posterior cervical fusion.