Document Detail

Biomechanical analysis of corrective forces in spinal instrumentation for scoliosis treatment.
MedLine Citation:
PMID:  23151872     Owner:  NLM     Status:  In-Data-Review    
STUDY DESIGN.: Computer modeling and simulations to analyze correction forces at the bone-screw interface in scoliosis instrumentation. OBJECTIVE.: To derive the minimum corrective forces applied on vertebrae through pedicle screws to achieve desired scoliosis corrections and evaluate the actual bone-screw forces associated with 3 types of pedicle screws (monoaxial, polyaxial, and dorsoaxial). SUMMARY OF BACKGROUND DATA.: The optimum screw pattern has not been established in the literature. The final bone-screw forces in scoliosis instrumentation consist of "true corrective forces" (i.e., the minimum forces required to achieve the desired corrections without considering adequate rod seating at all pedicle screws) and "extra forces" (EF) (i.e., supplementary forces applied to ensure proper rod seating when the attachment of some screws is not in compliance with the attachment of their neighboring screws; they have no benefit to overall corrections). METHODS.: Using patient-specific computer models, true corrective forces were estimated for 10 spinal instrumentation cases. EF were computed by simulating the instrumentations of the 10 cases using respectively monoaxial, polyaxial, and dorsoaxial screws. RESULTS.: The average true corrective forces were 50 ± 30 N. The average bone-screw forces were 229 ± 140 N, 141 ± 99 N, and 103 ± 42 N, respectively, for monoaxial, polyaxial, and dorsoaxial screws; the averages of the EF magnitudes were 205 ± 136 N, 125 ± 93 N, and 65 ± 39 N, respectively. CONCLUSION.: Bone-screw forces to achieve desired corrections can be minimized. However, EF are inevitable to secure the locking of all screws. Higher EF were associated with pedicle screws, with less degrees of freedom for connecting screw body to rod, that is, monoaxial followed by polyaxial and then by dorsoaxial screws.
Xiaoyu Wang; Carl-Eric Aubin; Hubert Labelle; Stefan Parent; Dennis Crandall
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Spine     Volume:  37     ISSN:  1528-1159     ISO Abbreviation:  Spine     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7610646     Medline TA:  Spine (Phila Pa 1976)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  E1479-87     Citation Subset:  IM    
*Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Montreal, Canada †Research Center, Sainte-Justine University Hospital Center, Montreal, Canada ‡Sonoran Spine Center, Phoenix, AZ.
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