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Biomechanical Analysis of Revision Strategies for Rod Fracture in Pedicle Subtraction Osteotomy.
MedLine Citation:
PMID:  21336218     Owner:  NLM     Status:  Publisher    
BACKGROUND:: Pseudoarthrosis after pedicle subtraction osteotomy (PSO) can require revision surgery due to posterior rod failure, and the stiffness of these revision constructs has not been quantified. OBJECTIVE:: To compare the multidirectional bending stiffness of 7 revision strategies following rod failure. METHODS:: 7 fresh-frozen human spines (T11-pelvis) were tested as follows: 1) posterior instrumentation from T12-S1 (excluding L3) with iliac fixation and L3 PSO; 2) inline connectors after rod breakage at L3 (L2 screws removed for access); 3) crosslinks connecting rods above and below inline connectors; satellite rods 4) parallel 5) 45° anterior 6) 45° posterior to original rods; 45°posterior with crosslinks connecting 7) original and 8) satellite rods. Groups 3-8 were tested in random order. Non-destructive pure moment flexion/extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted to 7.5 Nm. 3D motion tracking monitored primary range-of-motion. RESULTS:: Addition of inline connectors alone restored stiffness in FE and LB, but not in AR (p<0.05). Satellite rods (groups 4-6) restored stiffness in FE and LB, but not in AR (p<0.05) and were not significantly different between one another (p>0.05). Addition of crosslinks (groups 3, 7, 8) restored stiffness in all bending modes (p>0.05) and were significantly greater than inline connectors alone in AR (p<0.05). CONCLUSION:: The results suggest these revision strategies can restore stiffness without entire rod replacement. Failure of AR stiffness restoration can be mitigated with crosslinks. The positioning of the satellite rods is not an important factor in strengthening the revision.
Justin K Scheer; Jessica A Tang; Vedat Deviren; Jenni M Buckley; Murat Pekmezci; R Trigg McClellan; Christopher P Ames
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-2-16
Journal Detail:
Title:  Neurosurgery     Volume:  -     ISSN:  1524-4040     ISO Abbreviation:  -     Publication Date:  2011 Feb 
Date Detail:
Created Date:  2011-2-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7802914     Medline TA:  Neurosurgery     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Biomechanical Testing Facility, Orthopaedic Trauma Institute, San Francisco General Hospital, San Francisco, CA 94110, USA; 2Department of Orthopaedic Surgery, University of California, San Francisco, CA 94110, USA; 3Department of Neurological Surgery, University of California, San Francisco, CA 94110, USA.
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