Quantitative analysis of misplaced pedicle screws in the thoracic spine: how much pullout strength is lost?

2010 ◽  
Vol 12 (5) ◽  
pp. 503-508 ◽  
Author(s):  
Leonardo B. C. Brasiliense ◽  
Nicholas Theodore ◽  
Bruno C. R. Lazaro ◽  
Zafar A. Sayed ◽  
Fatih Ersay Deniz ◽  
...  
Keyword(s):  
Pedicle Screws ◽  
Thoracic Vertebrae ◽  
Pullout Strength ◽  
Mineral Density ◽  
Insertion Depth ◽  
Screw Insertion ◽  
Significant Difference ◽  
Thoracic Pedicle Screws ◽  
The Mean ◽  
Cortical Perforation

Object The object of this study was to investigate the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of thoracic pedicle screws. Methods Forty human thoracic vertebrae (T6–11) from human cadavers were studied. Before pedicle screws were inserted, the specimens were separated into 4 groups according to the type of screw used: 1) standard pedicle screw (no cortical perforation); 2) screw with medial cortical perforation; 3) screw with lateral cortical perforation; and 4) “airball” screw (a screw that completely missed the vertebral body). Consistency among the groups for bone mineral density, pedicle diameter, and screw insertion depth was evaluated. Finally, each screw was pulled out at a constant displacement rate of 10 mm/minute while ultimate strength was recorded. Results Compared with well-placed pedicle screws, medially misplaced screws had 8% greater mean pullout strength (p = 0.482) and laterally misplaced screws had 21% less mean pullout strength (p = 0.059). The difference in mean pullout strength between screws with medial and lateral cortical perforations was significant (p = 0.013). Airball screws had only 66% of the mean pullout strength of well-placed screws (p = 0.009) and had 16% lower mean pullout strength than laterally misplaced screws (p = 0.395). Conclusions This in vitro study showed a significant difference in mean pullout strength between medial and lateral misplaced pedicle screws. Moreover, airball screws were associated with a significant loss of pullout strength.

Biomechanical Effects of Lumbar Pedicle Screw Insertion Depth on Screw Loosening and Fulcrum Location

2013 ◽  
Author(s):  
Laura E. Buckenmeyer ◽  
Kristophe J. Karami ◽  
Ata M. Kiapour ◽  
Vijay K. Goel ◽  
Constantine K. Demetropoulos ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Screw Loosening ◽  
Pullout Strength ◽  
Insertion Depth ◽  
Bone Implant ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Increased Risk ◽  
Screw Length

Osteoporosis is a critical challenge in orthopedic surgery. Osteoporotic patients have an increased risk of loosening and failure of implant constructs due to a weaker bone-implant interface than with healthy bone. Pullout strength of pedicle screws is enhanced by increased screw insertion depth. However, more knowledge is needed to define optimal pedicle screw insertion depth in relation to screw-bone interface biomechanics and the resulting loosening risk. This study evaluates the effects of screw length on loosening risk in the osteoporotic lumbar spine.

Fixation Strength of Pedicle and Cortical Lumbar Vertebral Screws after Laminectomy: A Cadaver Study

2018 ◽  
Vol 79 (04) ◽  
pp. 273-278
Author(s):  
Dai-Soon Kwak ◽  
Ho-Jung Cho ◽  
Ho Chang ◽  
Moon Park ◽  
In-Sung Kim ◽  
...  
Keyword(s):  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Cadaver Study ◽  
Fixation Strength ◽  
Pullout Strength ◽  
Screw Insertion ◽  
Cortical Screw ◽  
Significant Difference ◽  
Midline Approach ◽  
Biomechanical Strength

Background and Study Aim Cortical screws were proposed as an alternative to the traditional pedicle screws. Diverse experimental results support the biomechanical superiority of cortical screws compared to pedicle screws. Laminectomy is often part of multilevel lumbar surgeries. Laminectomy might weaken the medial bony edge at the entry of the divergently oriented screw and, thereby, the screw purchase. This study investigated the biomechanical strength of lumbar cortical screw after laminectomy. Objective To compare the fixation strength of cortical screws and traditional pedicle screws after lumbar laminectomy. Material and Methods A total of 120 pedicles from 60 lumbar vertebrae of 12 cadavers (8 men, 4 women) were assessed. The mean age of the cadavers was 73.4 ± 6.2 years (range: 62–82 years). Using a posterior midline approach, we inserted the traditional pedicle screws into one and the cortical screws into the other side of each vertebra. Laminectomy was performed after screw insertion. Vertical pullout strength and toggle strength testing were performed to compare the fixation strength between the two sides. Results After laminectomy, the pullout strength of the cortical screws was 718.92 ± 340.76 N, and that of the pedicle screws was 625.78 ± 287.10 N (p = 0.183). The toggle strength of the cortical screws was 544.83 ± 329.97 N; that of the pedicle screws was 613.17 ± 311.70 N (p = 0.145). No significant difference was found in biomechanical strength between the two types of screws. Conclusion Despite laminectomy, lumbar cortical screws offers comparable pullout and toggle biomechanical strength as traditional pedicle screws.

Increased pedicle screw pullout strength with vertebroplasty augmentation in osteoporotic spines

2002 ◽  
Vol 96 (3) ◽  
pp. 309-312 ◽  
Author(s):  
John S. Sarzier ◽  
Avery J. Evans ◽  
David W. Cahill
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Pullout Strength ◽  
Mineral Density ◽  
Content Type ◽  
Pullout Force ◽  
Grade Ii ◽  
The Mean ◽  
Grade Iii ◽  
Fine Print

Object. The authors conducted a biomechanical study to evaluate pedicle screw pullout strength in osteoporotic cadaveric spines. Nonaugmented hemivertebrae were compared with pressurized polymethylmethacrylate (PMMA)—augmented hemivertebrae. Methods. Six formalin-fixed cadaveric thoracolumbar spines at least two standard deviations below the mean bone mineral density (BMD) for age were obtained. Radiographic and BMD studies were correlated to grades I, II, and III osteoporosis according to the Jekei scale. Each of the 21 vertebrae underwent fluoroscopic placement of 6-mm transpedicular screws with each hemivertebra serving as the control for the contralateral PMMA-augmented hemivertebra. Pedicle screws were then evaluated for biomechanical axial pullout resistance. Augmented hemivertebrae axial pullout forces were increased (p = 0.0005). The mean increase in pullout force was 181% for Grade I, 206% for Grade II, and 213% for Grade III osteoporotic spines. Augmented Grade I osteoporotic spines demonstrated axial pullout forces near those levels reported in the literature for nonosteoporotic specimens. Augmented Grade II osteoporotic specimens demonstrated increases to levels found in nonaugmented vertebrae with low-normal BMD. Augmented Grade III osteoporotic specimens had increases to levels equal to those found in nonaugmented Grade I vertebrae. Conclusions. Augmentation of osteoporotic vertebrae in PMMA-assisted vertebroplasty can significantly increase pedicle screw pullout forces to levels exceeding the strength of cortical bone. The maximum attainable force appears to be twice the pullout force of the nonaugmented pedicle screw for each osteoporotic grade.

Using lamina screws as a salvage technique at C-7: computed tomography and biomechanical analysis using cadaveric vertebrae

2009 ◽  
Vol 11 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Mario J. Cardoso ◽  
Anton E. Dmitriev ◽  
Melvin D. Helgeson ◽  
Frederick Stephens ◽  
Victoria Campbell ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Cervical Spine ◽  
Pedicle Screw ◽  
Bone Mineral ◽  
Pedicle Screws ◽  
Pullout Strength ◽  
Mineral Density ◽  
The Mean ◽  
The Right ◽  
Pedicle Width

Object Transpedicular instrumentation at C-7 has been well accepted, but salvage techniques are limited. Lamina screws have been shown to be a biomechanically sound salvage technique in the proximal thoracic spine, but have not been evaluated in the lower cervical spine. The following study evaluates the anatomical feasibility of lamina screws at C-7 as well as their bone-screw interface strength as a salvage technique. Methods Nine fresh-frozen C-7 cadaveric specimens were scanned for bone mineral density using dual energy x-ray absorptiometry. Prior to testing, all specimens were imaged using CT to obtain 1-mm axial sections. Caliper measurements of both pedicle width and laminar thickness were obtained. On the right side, pedicle screws were first inserted and then pulled out. Salvage intralaminar screws were inserted into the left lamina from the right spinous process/lamina junction and then pulled out. All screws were placed by experienced cervical spine surgeons under direct fluoroscopic visualization. Pedicle and lamina screws were 4.35- and 3.5-mm in diameter, respectively. Screws sizes were chosen based on direct and radiographic measurements of the respective anatomical regions. Insertional torque (IT) was measured in pounds per inch. Tensile loading to failure was performed in-line with the screw axis at a rate of 0.25 mm/sec using a MiniBionix II system with data recorded in Newtons. Results Using lamina screws as a salvage technique generated mean pullout forces (778.9 ± 161.4 N) similar to that of the index pedicle screws (805.3 ± 261.7 N; p = 0.796). However, mean lamina screw peak IT (5.2 ± 2.0 lbs/in) was significantly lower than mean index pedicle screw peak IT (9.1 ± 3.6 lbs/in; p = 0.012). Bone mineral density was strongly correlated with pedicle screw pullout strength (r = 0.95) but less with lamina screw pullout strength (r = 0.04). The mean lamina width measured using calipers (5.7 ± 1.0 mm) was significantly different from the CTmeasured mean lamina width (5.1 ± 0.8 mm; p = 0.003). Similarly, the mean pedicle width recorded with calipers (6.6 ± 1.1 mm) was significantly different from the CT-measured mean pedicle width (6.2 ± 1.3 mm; p = 0.014). The mean laminar width measured on CT at the thinnest point ranged from 3.8 to 6.8 mm, allowing a 3.5-mm screw to be placed without difficulty. Conclusions These results suggest that using lamina screws as a salvage technique at C-7 provides similar fixation strength as the index pedicle screw. The C-7 lamina appears to have an ideal anatomical width for the insertion of 3.5-mm screws commonly used for cervical fusions. Therefore, if the transpedicular screw fails, using intralaminar screws appear to be a biomechanically sound salvage technique.

scholarly journals SAT0462 ASSESSMENT OF BONE MINERAL DENSITY IN INFLAMMATORY BOWEL DISEASE

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1188.1-1188
Author(s):  
C. Daldoul ◽  
N. El Amri ◽  
K. Baccouche ◽  
H. Zeglaoui ◽  
E. Bouajina
Keyword(s):  
Bone Mineral Density ◽  
Inflammatory Bowel Disease ◽  
Bone Mineral ◽  
Bowel Disease ◽  
Mineral Density ◽  
Femoral Site ◽  
Significant Difference ◽  
History Of ◽  
Inflammatory Bowel ◽  
The Mean

Background:Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), is considered as a risk factor of low bone mineral density (BMD). In fact, the prevalence of osteoporosis ranges from 17% to 41% in IBD patients. The possible contributing factors may include malabsorption, glucocorticoid treatment and coexisting comorbiditiesObjectives:The purpose of our work was to determine the frequency and the determinants of osteoporosis in patients with IBD and to assess whether there is a difference in BMD status between UC and CD.Methods:This is a retrospective study, over a period of 5 years (from January 2014 to December 2018) and including patients followed for IBD who had a measurement of BMD by DEXA. Clinical, anthropometric and densitometric data (BMD at the femoral and vertebral site) were recorded. The WHO criteria for the definition of osteoporosis and osteopenia were applied.Results:One hundred and five patients were collected; among them 45 were men and 60 were women. The average age was 45.89 years old. The average body mass index (BMI) was 25.81 kg/m2 [16.44-44.15]. CD and UC were diagnosed in respectively 57.1% and 42.9%. A personal history of fragility fracture was noted in 4.8%. Hypothyroidism was associated in one case. Early menopause was recorded in 7.6%. 46.8% patients were treated with corticosteroids. The mean BMD at the vertebral site was 1.023 g/cm3 [0.569-1.489 g/cm3]. Mean BMD at the femoral site was 0.920g/cm3 [0.553-1.286g / cm3]. The mean T-score at the femoral site and the vertebral site were -1.04 SD and -1.27 SD, respectively. Osteoporosis was found in 25.7% and osteopenia in 37.1%. Osteoporosis among CD and UC patients was found in respectively 63% and 37%. The age of the osteoporotic patients was significantly higher compared to those who were not osteoporotic (52.23 vs 43.67 years, p = 0.01). We found a significantly higher percentage of osteoporosis among men compared to women (35.6% vs 18.3%, p=0.046). The BMI was significantly lower in the osteoporotic patients (23.87 vs 26.48 kg/m2, p=0.035) and we found a significant correlation between BMI and BMD at the femoral site (p=0.01). No increase in the frequency of osteoporosis was noted in patients treated with corticosteroids (27.9% vs 21.6%, p=0.479). Comparing the UC and CD patients, no difference was found in baseline characteristics, use of steroids or history of fracture. No statistically significant difference was found between UC and CD patients for osteoporosis(p=0.478), BMD at the femoral site (p=0.529) and at the vertebral site (p=0.568).Conclusion:Osteoporosis was found in 25.7% of IBD patients without any difference between CD and UC. This decline does not seem to be related to the treatment with corticosteroids but rather to the disease itself. Hence the interest of an early screening of this silent disease.Disclosure of Interests:None declared

Optimization of Pedicle Screw Depth in the Lumbar Spine

2013 ◽  
Author(s):  
Laura E. Buckenmeyer ◽  
Kristophe J. Karami ◽  
Ata M. Kiapour ◽  
Vijay K. Goel ◽  
Teck M. Soo ◽  
...  
Keyword(s):  
Lumbar Spine ◽  
Pedicle Screw ◽  
Pedicle Screws ◽  
Fixation Strength ◽  
Osteoporotic Patient ◽  
Insertion Depth ◽  
Anterior Cortex ◽  
Screw Insertion ◽  
Clinical Challenge ◽  
Series Of Experiments

Optimization of pedicle screw insertion depth for ideal fixation and fusion remains a clinical challenge. Improved screw purchase may improve fixation strength 1, which is especially critical in an osteoporotic patient population. Extended screw insertion depths, up to and through the anterior cortex, have yet to be compared to more commonly used shorter pedicle screws in a laboratory controlled series of experiments. The purpose of this study is to evaluate screw purchase in the osteoporotic lumbar spine as a function of insertion depth, which may be used to optimize pedicle screw-rod constructs.

scholarly journals Influence of Contrast Media on Bone Mineral Density (BMD) Measurements from Routine Contrast-Enhanced MDCT Datasets using a Phantom-less BMD Measurement Tool

2017 ◽  
Vol 189 (06) ◽  
pp. 537-543 ◽  
Author(s):  
Andrea Toelly ◽  
Constanze Bardach ◽  
Michael Weber ◽  
Rui Gong ◽  
Yanbo Lai ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Bone Mineral ◽  
Intraclass Correlation ◽  
Arterial Phase ◽  
Measurement Tool ◽  
Mineral Density ◽  
Contrast Enhanced ◽  
Significant Difference ◽  
Venous Phase ◽  
The Mean

Aim To evaluate the differences in phantom-less bone mineral density (BMD) measurements in contrast-enhanced routine MDCT scans at different contrast phases, and to develop an algorithm for calculating a reliable BMD value. Materials and Methods 112 postmenopausal women from the age of 40 to 77 years (mean age: 57.31 years; SD 9.61) who underwent a clinically indicated MDCT scan, consisting of an unenhanced, an arterial, and a venous phase, were included. A retrospective analysis of the BMD values of the Th12 to L4 vertebrae in each phase was performed using a commercially available phantom-less measurement tool. Results The mean BMD value in the unenhanced MDCT scans was 79.76 mg/cm³ (SD 31.20), in the arterial phase it was 85.09 mg/cm³ (SD 31.61), and in the venous phase it was 86.18 mg/cm³ (SD 31.30). A significant difference (p < 0.001) was found between BMD values on unenhanced and contrast-enhanced MDCT scans. There was no significant difference between BMD values in the arterial and venous phases (p = 0.228). The following conversion formulas were calculated using linear regression: unenhanced BMD = -2.287 + 0.964 * [arterial BMD value] and -4.517 + 0.978 * [venous BMD value]. The intrarater agreement of BMD measurements was calculated with an intraclass correlation (ICC) of 0.984 and the interobserver reliability was calculated with an ICC of 0.991. Conclusion Phantom-less BMD measurements in contrast-enhanced MDCT scans result in increased mean BMD values, but, with the formulas applied in our study, a reliable BMD value can be calculated. However, the mean BMD values did not differ significantly between the arterial and venous phases. Key points  Citation Format

scholarly journals Relationship Between Insertion Torque, and Pullout Strength Depending on the Size of the Pilot Hole and Biodegradable Suture Anchor in Osteoporotic Humeral Head

2012 ◽  
Vol 15 (1) ◽  
pp. 8-15 ◽  
Author(s):  
Yong Min Chun ◽  
Young Han Lee ◽  
Sung Hwan Kim ◽  
Yoo Jung Park ◽  
Sung Jae Kim
Keyword(s):  
Humeral Head ◽  
Suture Anchor ◽  
Region Of Interest ◽  
Insertion Torque ◽  
Pullout Strength ◽  
Mineral Density ◽  
Pilot Hole ◽  
Significant Difference ◽  
Group A ◽  
The Difference

PURPOSE: The object of this study was to investigate the difference in torque and pullout strength between the standard anchor insertion (5.0 mm) with a small awl (3.7 mm) and larger anchor insertion (6.5 mm), with a standard awl (5.0 mm) in osteoporotic humeral head.MATERIALS AND METHODS: The embalmed 24 paired cadaveric shoulders were assigned to either Group A or B. After measuring the bone mineral density (BMD) of the ROI (region of interest) in the humeral head, 5.0 mm suture anchors were inserted using a 3.7 mm awl in Group A1, and the same 5.0 mm anchors were inserted using a 5.0 mm awl in Group A2. The 5.0 mm anchors were inserted using a 5.0 mm awl in Group B1, and 6.5 mm anchors were inserted using a 5.0 mm awl in Group B2. We measured the torques at the time of the anchor insertion and pullout strengths.RESULTS: There was no significant difference in the BMD between the groups. The torque of A1 (20.6 cN.m) was significantly higher than that of A2 (13.2 cN.m), and the torque of B2 (20.8 cN.m) was significantly higher than that of B1(12.1 cN.m). However, the difference in the increased torque between group A and B was not significant. The pullout strength of A1 (204.2 N) was significantly higher than that of A2 (152.9 N), and the pullout strength of B2 (210.9 N) was significantly higher than that of B1 (149.5 N). However, the difference in the increased pullout strength between Group A and B was not significant.CONCLUSION: In severe osteoporosis, the use of a larger suture anchor with a standard awl increased the torque and pullout strength significantly, in comparison to the use of the same sized suture anchor and awl. If there is an inadequate interval between the anchors on the greater tuberosity, the use of a 3.7 mm awl and 5.0 mm anchor will be beneficial compared to that of a 5.0 mm awl and 6.5 mm anchor, considering that an increase in the pullout strength does not depend on the awl size.

scholarly journals Correlation between the Computed Tomography Values of the Screw Path and Pedicle Screw Pullout Strength: An Experimental Study in Porcine Vertebrae

2020 ◽  
Vol 14 (3) ◽  
pp. 265-272
Author(s):  
Atsushi Ikeura ◽  
Taketoshi Kushida ◽  
Kenichi Oe ◽  
Yoshihisa Kotani ◽  
Muneharu Ando ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Bone Mineral Density ◽  
Pedicle Screw ◽  
Bone Mineral ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Mineral Density ◽  
Screw Insertion ◽  
Pull Out ◽  
Pull Out Strength

Study Design: Biomechanical study.Purpose: To assess the correlation between the computed tomography (CT) values of the pedicle screw path and screw pull-out strength.Overview of Literature: The correlation between pedicle screw pull-out strength and bone mineral density has been well established. In addition, several reports have demonstrated a correlation between bone mineral density and CT values. However, no previous biomechanical studies investigated the correlation between CT values and pedicle screw pull-out strength.Methods: Sixty fresh-frozen lumbar vertebrae from 6-month-old pigs were used. Before screw insertion, the CT values of the screw path were obtained for each sample. Specimens were then randomly divided into three equal groups. Each group had one of three pedicle screws inserted: 4.0-mm LEGACY (4.0-LEG), 4.5-mm LEGACY (4.5-LEG), or 4.5-mm SOLERA (4.5-SOL) (all from Medtronic Sofamor Danek Inc., Memphis, TN, USA). Each screw had a consistent 30-mm thread length. Axial pull-out testing was performed at a rate of 1.0 mm/min. Correlations between the CT values and pedicle screw pull-out strength were evaluated using Pearson’s correlation coefficient analysis.Results: The correlation coefficients between the CT values of the screw path and pedicle screw pull-out strength for the 4.0-LEG, 4.5-LEG, and 4.5-SOL groups were 0.836 (<i>p</i> <0.001), 0.780 (<i>p</i> <0.001), and 0.873 (<i>p</i> <0.001), respectively. Greater CT values were associated with greater screw pull-out strength.Conclusions: The CT values of the screw path were strongly positively correlated with pedicle screw pull-out strength, regardless of the screw type and diameter, suggesting that the CT values could be clinically useful for predicting pedicle screw pull-out strength.

scholarly journals Comparison of intraoperative O-arm- and conventional fluoroscopy (C-arm)-assisted insertion of pedicle screws in the treatment of fracture of thoracic vertebrae

2017 ◽  
Vol 25 (1) ◽  
pp. 230949901668409 ◽  
Author(s):  
Hao Liu ◽  
Yimeng Wang ◽  
Bin Pi ◽  
Zhonglai Qian ◽  
Xiaoyu Zhu ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Screw Placement ◽  
Thoracic Vertebrae ◽  
Pedicle Screw Placement ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Computed Tomography Images ◽  
Hospitalization Time ◽  
Time Required

Purpose: To introduce the intraoperative O-arm-assisted pedicle screw insertion without any navigation system in the treatment of thoracic vertebrae fracture and compare it to conventional fluoroscopy (C-arm)-assisted pedicle screw insertion technique. Methods: About 156 pedicle screws were inserted in 23 patients (C-arm group), and 208 pedicle screws were inserted in 30 patients (O-arm group). The postoperative computed tomography images were analyzed for pedicle violation based on Gertzbein classification. The total surgery time, the average time required for inserting a screw, the mean action times of adjusting guide probe and pedicle screw, and the hospitalization time were compared in both groups, respectively. The American Spinal Injury Association (ASIA) was used for evaluating the health outcomes pre- and postoperatively. Results: There are the higher accuracy rate of satisfactory pedicle screw placement (grades 0 and 1) and the less incidence of medial perforation in the O-arm group compared to the C-arm group ( p < 0.05). The average time required for inserting a screw, the action times of adjusting the guide probe and pedicle screw, and the hospitalization time in the O-arm group are less than the respective ones in the C-arm group ( p < 0.05). There was no significant difference for the total surgery time between both groups. No further damage of the nerve function postoperatively is found according to the ASIA grade. Conclusion: The O-arm-assisted pedicle screw insertion without navigation we described provides higher accuracy of pedicle screw placement and better clinical efficacy compared to conventional fluoroscopy (C-arm) technique.

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