TY - JOUR
T1 - Which salvage fixation technique is best for the failed initial screw fixation at the cervicothoracic junction? A biomechanical comparison study
AU - Hong, Jae Taek
AU - Tomoyuki, Takigawa
AU - Jain, Ashish
AU - Orías, Alejandro A.Espinoza
AU - Inoue, Nozomu
AU - An, Howard S.
N1 - Funding Information:
Acknowledgements This study is funded by the Clinical Research Fund of St. Vincent’s Hospital in 2014 and 2015.
Funding Information:
This study is funded by the Clinical Research Fund of St. Vincent?s Hospital in 2014 and 2015. The authors declare that they have no competing interests.
Publisher Copyright:
© 2017, Springer-Verlag GmbH Germany.
PY - 2017/9/1
Y1 - 2017/9/1
N2 - Purpose: The pedicle screw construct is the most widely used technique for instrumentation at cervicothoracic junction (CTJ) because of its high biomechanical stability. However, we may need salvage fixation options for it as there might be a situation when pedicle screw is not available or it initially fails in order to obviate the need to instrument an additional motion segment. We aimed to evaluate the ability of using salvage screw fixations at CTJ (C7, T1, T2), when the initial fixation method fails. Methods: Fifteen fresh-frozen cadaveric specimens (C7–T2) were tested for pull-out strength (POS, N) and insertion torque (IT, Nm) of three C7 fixation techniques (lateral mass, pedicle and laminar screw) and three upper thoracic spine instrumentation (pedicle screws with straight trajectory, anatomical trajectory pedicle screws and laminar screw). Data are shown as mean ± standard deviation (SD). Results: C7 pedicle screws generated statistically greater IT and POS than other C7 fixation techniques (P < 0.05). Similar trends were observed with pedicle fixation as a salvage procedure (P < 0.05). Laminar screws yielded significantly higher POS values than lateral mass fixation when applied as a salvage C7 fixation (mean POS: lateral mass screw—299.4 ± 173.8 N, laminar screw—629.3 ± 216.1, P = 0.013). Significant relationship was established between IT and POS for all screws using Pearson correlation coefficient analysis (r = 0.624, P < 0.01). Pedicle screw with different trajectory (anatomical vs straightforward) did not show any significant difference in terms of POS as the initial and salvage fixation of upper thoracic spine. As a salvage fixation technique, there was no significant difference between laminar screw and a pedicle screw with different trajectory (P > 0.05). Conclusion: Laminar screws appear to provide stronger and more reproducible salvage fixation than lateral mass screws for C7 fixation, if pedicle screw should fail. If failure of initial pedicle screw is verified at the upper thoracic spine, both laminar screw and pedicle screw with different trajectory could be an option of salvage fixation. Our results suggest that pedicle screws and laminar screw similarly provide a strong fixation for salvage applications in the cervicothoracic junction.
AB - Purpose: The pedicle screw construct is the most widely used technique for instrumentation at cervicothoracic junction (CTJ) because of its high biomechanical stability. However, we may need salvage fixation options for it as there might be a situation when pedicle screw is not available or it initially fails in order to obviate the need to instrument an additional motion segment. We aimed to evaluate the ability of using salvage screw fixations at CTJ (C7, T1, T2), when the initial fixation method fails. Methods: Fifteen fresh-frozen cadaveric specimens (C7–T2) were tested for pull-out strength (POS, N) and insertion torque (IT, Nm) of three C7 fixation techniques (lateral mass, pedicle and laminar screw) and three upper thoracic spine instrumentation (pedicle screws with straight trajectory, anatomical trajectory pedicle screws and laminar screw). Data are shown as mean ± standard deviation (SD). Results: C7 pedicle screws generated statistically greater IT and POS than other C7 fixation techniques (P < 0.05). Similar trends were observed with pedicle fixation as a salvage procedure (P < 0.05). Laminar screws yielded significantly higher POS values than lateral mass fixation when applied as a salvage C7 fixation (mean POS: lateral mass screw—299.4 ± 173.8 N, laminar screw—629.3 ± 216.1, P = 0.013). Significant relationship was established between IT and POS for all screws using Pearson correlation coefficient analysis (r = 0.624, P < 0.01). Pedicle screw with different trajectory (anatomical vs straightforward) did not show any significant difference in terms of POS as the initial and salvage fixation of upper thoracic spine. As a salvage fixation technique, there was no significant difference between laminar screw and a pedicle screw with different trajectory (P > 0.05). Conclusion: Laminar screws appear to provide stronger and more reproducible salvage fixation than lateral mass screws for C7 fixation, if pedicle screw should fail. If failure of initial pedicle screw is verified at the upper thoracic spine, both laminar screw and pedicle screw with different trajectory could be an option of salvage fixation. Our results suggest that pedicle screws and laminar screw similarly provide a strong fixation for salvage applications in the cervicothoracic junction.
KW - Anatomical trajectory pedicle screws
KW - Biomechanics
KW - Cervicothoracic junction
KW - Insertion torque
KW - Laminar screw
KW - Lateral mass screw
KW - Pedicle screw
KW - Pull-out strength
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U2 - 10.1007/s00586-017-5239-8
DO - 10.1007/s00586-017-5239-8
M3 - Article
C2 - 28752245
AN - SCOPUS:85026908264
VL - 26
SP - 2417
EP - 2424
JO - European Spine Journal
JF - European Spine Journal
SN - 0940-6719
IS - 9
ER -