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Article: Effect of the degree of osteoporosis on the biomechanical anchoring strength of the sacral pedicle screws: An in vitro comparison between unaugmented bicortical screws and polymethylmethacrylate augmented unicortical screws

TitleEffect of the degree of osteoporosis on the biomechanical anchoring strength of the sacral pedicle screws: An in vitro comparison between unaugmented bicortical screws and polymethylmethacrylate augmented unicortical screws
Authors
Keywordsbiomechanics
lumbosacral fusion
osteoporosis
PMMA augmentation.
sacral pedicle screw fixation
Issue Date2010
PublisherLippincott, Williams & Wilkins. The Journal's web site is located at http://www.spinejournal.com
Citation
Spine, 2010, v. 35 n. 19, p. E925-E931 How to Cite?
AbstractStudy Design.: An in vitro laboratory study. Objective.: (i) To evaluate the effect of osteoporotic degree in determining the strength of sacral screw fixation and (ii) to compare the strength of unaugmented bicortical pedicle screw and polymethylmethacrylate (PMMA) augmented unicortical pedicle screw in sacral fixation. Summary of Background Data.: Screw loosening is a clinical problem in lumbosacral fusions, especially in osteoporotic patients. To improve the screw anchoring strength of sacrum, bicortical and PMMA augmented sacral pedicle screw fixation techniques are widely used in clinical practice. However, the biomechanical strength of the bicortical and PMMA augmented sacral screw fixations remains undetermined in different degrees of osteoporosis. Methods.: Twenty-five fresh osteoporotic cadavers were used in this study. According to the value of lumbar bone mineral density (BMD) assessed by DEXA, specimens were divided into 3 groups: group A (N = 9): BMD = 0.7 to 0.8 g/cm, group B (N = 8): BMD = 0.6 to 0.7 g/cm, and group C (N = 8): BMD < 0.6 g/cm. In each specimen, S1 pedicle screw was inserted bicortically on the left side, and S1 pedicle screw with PMMA augmentation was inserted unicortically on the right side of the sacrum. Following a dynamic cyclic loading from 30 to 250 N on the screw head for 2000 cycles, the subsidence displacement and axial pull-out strength of each screw were measured. Results.: No anchoring failure (defined as the subsidence displacement exceeding 2 mm within 2000 loading cycles) occurred in group A and B. However, in group C, 6 cases (75%) in bicortical fixation and 5 cases (63%) in PMMA augmented fixation failed during cyclic loading. In group A, no significant difference between the bicortical and PMMA augmented fixations was detected in terms of the subsidence and maximal pull-out strength. In group B, significantly less subsidence and higher maximal pull-out strength were demonstrated in the PMMA augmented technique than that in the bicortical fixation. Both techniques exhibited lower subsidence of the screw in group A than in group B. The bicortical technique exhibited higher maximum pull-out strength in group A than that in group B. However, statistical difference in terms of PMMA augmentation was not detected between group A and B. Conclusion.: For BMD value more than 0.70 g/cm, bicortical sacral pedicle screw fixation could obtain sufficient anchoring strength comparable with the PMMA augmented technique. When BMD value is within 0.6 to 0.7 g/cm, the PMMA augmented technique would be more beneficial in improving the fixation strength than the bicortical fixation. For BMD values less than 0.6 g/cm, early screw loosening may occur in both bicortical and PMMA augmented fixations. © 2010, Lippincott Williams & Wilkins.
Persistent Identifierhttp://hdl.handle.net/10722/142443
ISSN
2015 Impact Factor: 2.439
2015 SCImago Journal Rankings: 1.459
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhuang, XMen_HK
dc.contributor.authorYu, BSen_HK
dc.contributor.authorZheng, ZMen_HK
dc.contributor.authorZhang, JFen_HK
dc.contributor.authorLu, WWen_HK
dc.date.accessioned2011-10-28T02:46:07Z-
dc.date.available2011-10-28T02:46:07Z-
dc.date.issued2010en_HK
dc.identifier.citationSpine, 2010, v. 35 n. 19, p. E925-E931en_HK
dc.identifier.issn0362-2436en_HK
dc.identifier.urihttp://hdl.handle.net/10722/142443-
dc.description.abstractStudy Design.: An in vitro laboratory study. Objective.: (i) To evaluate the effect of osteoporotic degree in determining the strength of sacral screw fixation and (ii) to compare the strength of unaugmented bicortical pedicle screw and polymethylmethacrylate (PMMA) augmented unicortical pedicle screw in sacral fixation. Summary of Background Data.: Screw loosening is a clinical problem in lumbosacral fusions, especially in osteoporotic patients. To improve the screw anchoring strength of sacrum, bicortical and PMMA augmented sacral pedicle screw fixation techniques are widely used in clinical practice. However, the biomechanical strength of the bicortical and PMMA augmented sacral screw fixations remains undetermined in different degrees of osteoporosis. Methods.: Twenty-five fresh osteoporotic cadavers were used in this study. According to the value of lumbar bone mineral density (BMD) assessed by DEXA, specimens were divided into 3 groups: group A (N = 9): BMD = 0.7 to 0.8 g/cm, group B (N = 8): BMD = 0.6 to 0.7 g/cm, and group C (N = 8): BMD < 0.6 g/cm. In each specimen, S1 pedicle screw was inserted bicortically on the left side, and S1 pedicle screw with PMMA augmentation was inserted unicortically on the right side of the sacrum. Following a dynamic cyclic loading from 30 to 250 N on the screw head for 2000 cycles, the subsidence displacement and axial pull-out strength of each screw were measured. Results.: No anchoring failure (defined as the subsidence displacement exceeding 2 mm within 2000 loading cycles) occurred in group A and B. However, in group C, 6 cases (75%) in bicortical fixation and 5 cases (63%) in PMMA augmented fixation failed during cyclic loading. In group A, no significant difference between the bicortical and PMMA augmented fixations was detected in terms of the subsidence and maximal pull-out strength. In group B, significantly less subsidence and higher maximal pull-out strength were demonstrated in the PMMA augmented technique than that in the bicortical fixation. Both techniques exhibited lower subsidence of the screw in group A than in group B. The bicortical technique exhibited higher maximum pull-out strength in group A than that in group B. However, statistical difference in terms of PMMA augmentation was not detected between group A and B. Conclusion.: For BMD value more than 0.70 g/cm, bicortical sacral pedicle screw fixation could obtain sufficient anchoring strength comparable with the PMMA augmented technique. When BMD value is within 0.6 to 0.7 g/cm, the PMMA augmented technique would be more beneficial in improving the fixation strength than the bicortical fixation. For BMD values less than 0.6 g/cm, early screw loosening may occur in both bicortical and PMMA augmented fixations. © 2010, Lippincott Williams & Wilkins.en_HK
dc.languageengen_US
dc.publisherLippincott, Williams & Wilkins. The Journal's web site is located at http://www.spinejournal.comen_HK
dc.relation.ispartofSpineen_HK
dc.subjectbiomechanicsen_HK
dc.subjectlumbosacral fusionen_HK
dc.subjectosteoporosisen_HK
dc.subjectPMMA augmentation.en_HK
dc.subjectsacral pedicle screw fixationen_HK
dc.subject.meshBone Cements - therapeutic use-
dc.subject.meshLumbar Vertebrae - injuries - radiography - surgery-
dc.subject.meshOsteoporosis - complications - radiography-
dc.subject.meshPolymethyl Methacrylate/*therapeutic use-
dc.subject.meshSpinal Fusion - instrumentation-
dc.titleEffect of the degree of osteoporosis on the biomechanical anchoring strength of the sacral pedicle screws: An in vitro comparison between unaugmented bicortical screws and polymethylmethacrylate augmented unicortical screwsen_HK
dc.typeArticleen_HK
dc.identifier.emailLu, WW:wwlu@hku.hken_HK
dc.identifier.authorityLu, WW=rp00411en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1097/BRS.0b013e3181c5fb21en_HK
dc.identifier.pmid20098349-
dc.identifier.scopuseid_2-s2.0-77956414426en_HK
dc.identifier.hkuros197075en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-77956414426&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume35en_HK
dc.identifier.issue19en_HK
dc.identifier.spageE925en_HK
dc.identifier.epageE931en_HK
dc.identifier.isiWOS:000281656400020-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridZhuang, XM=35436325900en_HK
dc.identifier.scopusauthoridYu, BS=25633299000en_HK
dc.identifier.scopusauthoridZheng, ZM=7403007434en_HK
dc.identifier.scopusauthoridZhang, JF=35098035200en_HK
dc.identifier.scopusauthoridLu, WW=7404215221en_HK

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