Heary RF, Agarwal N, Parvathreddy NK, Hansberry DR, Ferrara LA. Kinematics Following 3-Screw Integrated Interbody Spacers in the Lumbar Spine.
Oper Neurosurg (Hagerstown) 2020;
18:175-182. [PMID:
31131859 DOI:
10.1093/ons/opz102]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 01/19/2019] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND
"Stand-alone" fusion implants attempt to alleviate the need for supplemental posterior instrumentation.
OBJECTIVE
A biomechanical study was conducted to assess the stability of an integrated 3- screw interbody cage with, and without, supplemental posterior fixation.
METHODS
Nondestructive biomechanical testing was performed on 19 healthy cadaver spine segments. Specimens were tested in 6 degrees of motion and a maximum pure bending moment of 10 Nm was applied. Specimens were evaluated in the following sequence: Intact, cage, cage ± facet bolts, and cage ± pedicle screws. Nonconstrained motion was measured at both the index and adjacent levels.
RESULTS
The index levels were L2-L3 and L5-S1. The cage alone provided a significant decrease in motion at the L2-L3 level but not at L5-S1. At L2-L3, cage + pedicle screws decreased motion more effectively than cage + facet bolts, however, both the supplemented constructs outperformed intact (P < .05). At L5-S1, both posterior fixation systems appeared to have smaller degree of displacement compared to intact; however, no significant differences were observed at L5-S1 among the various constructs. Furthermore, the adjacent segments for each level (L1-L2 and L4-L5) had no significantly increased motion, compared to intact, for all 6 degrees of motion tested.
CONCLUSION
The stand-alone cage was more effective at L2-L3, than at L5-S1, in limiting motion. At L5-S1, supplemental fixation may need to be considered. No abnormal motion was identified at the adjacent, normal segments, for the stand-alone, or the circumferential constructs at either level tested.
Collapse