PMID- 21228695
OWN - NLM
STAT- MEDLINE
DCOM- 20110506
LR  - 20220321
IS  - 1528-1159 (Electronic)
IS  - 0362-2436 (Linking)
VI  - 36
IP  - 2
DP  - 2011 Jan 15
TI  - Biomechanical comparison of force levels in spinal instrumentation using 
      monoaxial versus multi degree of freedom postloading pedicle screws.
PG  - E95-E104
LID - 10.1097/BRS.0b013e3181f07cca [doi]
AB  - STUDY DESIGN: biomechanical analysis and simulations of correction mechanisms and 
      force levels during scoliosis instrumentation using two types of pedicle screws 
      and primary correction maneuvers. OBJECTIVES: to biomechanically analyze 
      implant-vertebra and inter-vertebral forces during scoliosis correction, to 
      address the hypothesis that multi degree of freedom (MDOF) postloading screws 
      with a direct incremental segmental translation (DIST) correction technique 
      significantly reduce the loads as compared with monoaxial (MA) tulip-top design 
      screws with a rod derotation technique (RDT). SUMMARY OF BACKGROUND DATA: MA 
      screw is widely used for spinal instrumentation. The MDOF screw was introduced as 
      a refinement of the correction philosophy based on multiaxial screws. The 
      kinematics of the MDOF construct is fundamentally different and offers more 
      degrees of freedom than that of the MA construct; however, a systematic 
      comparison of their biomechanics has not been done so far. METHODS: a 
      biomechanical model was developed to simulate the instrumentation of six 
      scoliotic patients, first with the MDOF screws and DIST. Then, the 
      instrumentation with MA screws and RDT was simulated using the same cases. Thirty 
      more simulations were done to study the force-level sensitivity to small implant 
      placement variation. RESULTS: there was a small average difference of 7 degrees , 5 degrees , and 
      4 degrees  between the two simulated systems for the computed main thoracic Cobb angle, 
      kyphosis, and apical axial rotation, respectively. On average, the mean, standard 
      deviation (SD), and maximum values of the implant-vertebra forces for MDOF screws 
      were 56%, 59%, and 59%, respectively, lower than those for the MA screws, while 
      the intervertebral forces for the MDOF screws were 31%, 37%, and 36% lower, 
      respectively. Under the same set of random small implant placement changes, the 
      mean, SD, and maximum values of implant-vertebra force magnitude changes for MDOF 
      screws were 93%, 92%, and 95%, respectively, lower than those for MA screws. 
      CONCLUSION: with MDOF screws and DIST, it is possible for spinal deformity to be 
      reduced similarly as with the MA screws and RDT, but with lower forces and better 
      load distributions, and the force level is less sensitive to implant placement 
      variation.
FAU - Wang, Xiaoyu
AU  - Wang X
AD  - Ecole Polytechnique de Montreal, Department of Mechanical Engineering, PO Box 
      6079, Downtown Station, Montreal, Quebec, Canada.
FAU - Aubin, Carl-Eric
AU  - Aubin CE
FAU - Crandall, Dennis
AU  - Crandall D
FAU - Labelle, Hubert
AU  - Labelle H
LA  - eng
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Spine (Phila Pa 1976)
JT  - Spine
JID - 7610646
SB  - IM
MH  - Adolescent
MH  - Biomechanical Phenomena
MH  - *Bone Screws
MH  - Computer Simulation
MH  - Humans
MH  - Models, Biological
MH  - Scoliosis/physiopathology/*surgery
MH  - Spinal Fusion/*instrumentation/*methods
EDAT- 2011/01/14 06:00
MHDA- 2011/05/07 06:00
CRDT- 2011/01/14 06:00
PHST- 2011/01/14 06:00 [entrez]
PHST- 2011/01/14 06:00 [pubmed]
PHST- 2011/05/07 06:00 [medline]
AID - 00007632-201101150-00017 [pii]
AID - 10.1097/BRS.0b013e3181f07cca [doi]
PST - ppublish
SO  - Spine (Phila Pa 1976). 2011 Jan 15;36(2):E95-E104. doi: 
      10.1097/BRS.0b013e3181f07cca.