Document Detail

Could Junctional Problems at the End of a Long Construct be Addressed by Providing a Graduated Reduction in Stiffness? - A Biomechanical Investigation.
MedLine Citation:
PMID:  21540778     Owner:  NLM     Status:  Publisher    
STRUCTURED ABSTRACT: Study Design. The effect of long rigid fixation on adjacent level hypermobility was investigated in a human cadaver model with and without a transitional posterior dynamic stabilization (PDS) device placed at the last caudal level.Objective. To evaluate if PDS devices are useful in the setting of scoliosis to restore increased adjacent level motions which occur in long constructs. The hypothesis is that load-sharing benefits of these devices will be most suitable in long constructs and may reduce thoracolumbar junctional effects. The PDS device evaluated has a compressive spacer and flexion-dampening bumper.Summary of Background Data. Mechanical factors such as excessive mobility, increased disc height due to instrumentation, and abnormal loading are thought to accentuate distal level problems which occur in extended instrumentation. Specifically adjacent level degeneration and distal junctional kyphosis are known to occur in these cases.Methods. Seven cadaver spines were tested from T7-L3. Long instrumentation was applied in two rigid groups, R1: Rigid(T8-L2) and R2: Rigid(T8-L1) and PDS to the last caudal level of each, RP1: Rigid(T8-L1)+PDS(L1-L2), and RP2: Rigid(T8-T12)+PDS(T12-L1). Range of motion was evaluated at surgical and distal adjacent levels after displacement controlled loading in a spine tester.Results. Distal adjacent level motion was increased following five and six level rigid fixation in flexion-extension, lateral bending, and axial rotation. Most of the increases were seen in axial rotation and lateral bending. Replacing the last caudal instrumented level with the PDS test device was able to alleviate hypermobile conditions of the adjacent non-instrumented level, closer to intact (24%, 12% reduction in RP2, RP1, respectively).Conclusion. Reduction of hypermobility caused by extended arthrodesis may represent a new and ideally suited function for PDS devices. Mechanically, the devices were seen to kinematically restore abnormal distal motion, especially with placement of the PDS at the thoracolumbar junction.
Atiq Durrani; Viral Jain; Rasesh Desai; Brandon Bucklen; Aditya Ingalhalikar; Aditya Muzumdar; Mark Moldavsky; Saif Khalil
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-5-2
Journal Detail:
Title:  Spine     Volume:  -     ISSN:  1528-1159     ISO Abbreviation:  -     Publication Date:  2011 May 
Date Detail:
Created Date:  2011-5-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7610646     Medline TA:  Spine (Phila Pa 1976)     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Center for Advanced Spine Technologies, Cincinnati, OH 2University of Louisville Hospital, Louisville, KY 3Globus Medical, Inc. Valley Forge Business Center, Audubon, PA.
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