Bastian Welke1, Michael Schwarze2, Christof Hurschler2, Dennis Nebel2, Nadine Bergmann3, Dorothea Daentzer3. 1. Laboratory for Biomechanics and Biomaterials, Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625, Hannover, Germany. welke.bastian@mh-hannover.de. 2. Laboratory for Biomechanics and Biomaterials, Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625, Hannover, Germany. 3. Department of Orthopaedic Surgery, Spine Section, Hannover Medical School, Diakovere Annastift, Anna-von-Borries-Str. 1-7, 30625, Hannover, Germany.
Abstract
PURPOSE: Instrumentation of the lumbar spine is a common procedure for treating pathologic conditions. Studies have revealed the risks of pathologies in the adjacent segments, with the incidence rate being up to 36.1%. Revision procedures are often required, including extension of the instrumentation by the use of connectors to adjacent levels. The aim of this study was to determine the stiffness of side-to-side and end-to-end connectors for comparison with the use of continuous rods. METHODS: Ten human lumbar spine specimens (L1-S1) were tested about the three axes under pure moment loading of ± 7.5 Nm. Nine conditions were used to investigate the functions of the extensions for different instrumentation lengths (L3-S1 and L2-S1) and different connector levels (L3/4 and L2/3). The intersegmental range of motion (iROM) and intersegmental neutral zone as well as total range of motion (tROM) and total neutral zone (tNZ) were analyzed. RESULTS: The application of the spinal system significantly decreased the tROMs (- 44 to - 83%) and iROMs in levels L2/3 (- 56 to - 94%) and L3/4 (- 68 to - 99%) in all the tested directions, and the tNZ under flexion/extension (- 63 to - 71%) and axial rotation (- 34 to - 72%). These decreases were independent of the employed configuration (p < 0.05). The only significant changes in the iROM were observed under lateral bending between the continuous rod and the side-to-side connector at level L3/4 (p = 0.006). CONCLUSION: From a biomechanical viewpoint, the tested connectors are comparable to continuous rods in terms of ROM and NZ. These slides can be retrieved under Electronic Supplementary Material.
PURPOSE: Instrumentation of the lumbar spine is a common procedure for treating pathologic conditions. Studies have revealed the risks of pathologies in the adjacent segments, with the incidence rate being up to 36.1%. Revision procedures are often required, including extension of the instrumentation by the use of connectors to adjacent levels. The aim of this study was to determine the stiffness of side-to-side and end-to-end connectors for comparison with the use of continuous rods. METHODS: Ten human lumbar spine specimens (L1-S1) were tested about the three axes under pure moment loading of ± 7.5 Nm. Nine conditions were used to investigate the functions of the extensions for different instrumentation lengths (L3-S1 and L2-S1) and different connector levels (L3/4 and L2/3). The intersegmental range of motion (iROM) and intersegmental neutral zone as well as total range of motion (tROM) and total neutral zone (tNZ) were analyzed. RESULTS: The application of the spinal system significantly decreased the tROMs (- 44 to - 83%) and iROMs in levels L2/3 (- 56 to - 94%) and L3/4 (- 68 to - 99%) in all the tested directions, and the tNZ under flexion/extension (- 63 to - 71%) and axial rotation (- 34 to - 72%). These decreases were independent of the employed configuration (p < 0.05). The only significant changes in the iROM were observed under lateral bending between the continuous rod and the side-to-side connector at level L3/4 (p = 0.006). CONCLUSION: From a biomechanical viewpoint, the tested connectors are comparable to continuous rods in terms of ROM and NZ. These slides can be retrieved under Electronic Supplementary Material.
Entities:
Keywords:
Connector; In vitro biomechanics; Lumbar spine; Rod system; Spinal fixation
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