Biomechanical comparison of the pullout strengths of C1 lateral mass screws and C1 posterior arch screws
| Autor: | Christopher Zarro, Daniel E. Gelb, Charles Seal, Steven C. Ludwig, Adam H. Hsieh |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
musculoskeletal diseases
medicine.medical_specialty Lateral mass Bone Screws Cadaver Medicine Fluoroscopy Humans Orthopedics and Sports Medicine Cervical Atlas Orthodontics medicine.diagnostic_test business.industry Soft tissue Pullout strength equipment and supplies musculoskeletal system Sagittal plane Posterior arch Surgery Biomechanical Phenomena surgical procedures operative medicine.anatomical_structure Spinal Fusion Axial load Neurology (clinical) business Cadaveric spasm |
| Zdroj: | The spine journal : official journal of the North American Spine Society. 13(12) |
| ISSN: | 1878-1632 |
| Popis: | Background context Conditions of the atlantoaxial complex requiring internal stabilization can result from trauma, malignancy, inflammatory diseases, and congenital malformation. Several techniques have been used for stabilization and fusion. Posterior wiring is biomechanically inferior to screw fixation. C1 lateral mass screws and C1 posterior arch screws are used for instrumentation of the atlas. Previous studies have shown that unicortical C1 lateral mass screws are biomechanically stable for fixation. No study has evaluated the biomechanical stability of C1 posterior arch screws or compared the two techniques. Purpose The purpose of the study was to assess the differences in the pullout strength between C1 lateral mass screws and C1 posterior arch screws. Study design Biomechanical testing of pullout strengths of the two atlantal screw fixation techniques. Methods Thirteen fresh human cadaveric C1 vertebrae were harvested, stripped of soft tissues, evaluated with computed tomography for anomalies, and instrumented with unicortical C1 lateral mass screws on one side and unicortical C1 posterior arch screws on the other. Screw placement was confirmed with postinstrumentation fluoroscopy. Specimens were divided in the sagittal plane and potted in polymethylmethacrylate. Axial load to failure was applied with a material testing device. Load displacement curves were obtained, and the results were compared with Student t test. DePuy Spine, Inc. (Raynham, MA, USA) provided the hardware used in this study. Results Mean pullout strength of the C1 lateral mass screws was 821 N (range 387−1,645 N±standard deviation [SD] 364). Mean pullout strength of the posterior arch screws was 1,403 N (range 483−2,200 N±SD 609 N). The difference was significant (p=.009). Five samples (38%) in the posterior arch group experienced bone failure before screw pullout. Conclusions Both unicortical lateral mass screws and unicortical posterior arch screws are viable options for fixation in the atlas. Unicortical posterior arch screws have superior resistance to pullout via axial load compared with unicortical lateral mass screws in the atlas. |
| Databáze: | OpenAIRE |
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