Biomechanical evaluation of cervical lateral mass fixation: a comparison of the Roy-Camille and Magerl screw techniques

2004 ◽  
Vol 100 (3) ◽  
pp. 268-276 ◽  
Author(s):  
Cédric Barrey ◽  
Patrick Mertens ◽  
Claude Rumelhart ◽  
François Cotton ◽  
Jérôme Jund ◽  
...  
Keyword(s):  
Testing Machine ◽  
Biomechanical Study ◽  
Lateral Mass ◽  
Mineral Density ◽  
Vertebral Level ◽  
Content Type ◽  
Pullout Force ◽  
Significant Difference ◽  
The Difference ◽  
Fine Print

Object. The purpose of this study was to assess human cervical spine pullout force after lateral mass fixation involving two different techniques: the Roy-Camille and the Magerl techniques. Although such comparisons have been conducted previously, because of the heterogeneity of results and the importance of this procedure in clinical practice, it is essential to have data derived from a prospective and randomized biomechanical study involving a sufficient sample of human cervical spines. The authors also evaluated the influence of the sex, the vertebral level, the bone mineral density (BMD), the length of bone purchase, and the thickness of the anterior cortical purchase. Methods. Twenty-one adult cervical spines were harvested from fresh human cadavers. Computerized tomography was performed before and after placing 3.5-mm titanium lateral mass screws from C-3 to C-6. Pullout forces were evaluated using a material testing machine. The load was applied until the pullout of the screw was observed. A total of 152 pullout tests were available, 76 for each type of screw fixation. The statistical analysis was mainly performed using the Kaplan—Meier survival method. The mean pullout force was 266 ± 124 N for the Roy-Camille technique and 231 ± 94 N for the Magerl technique (p < 0.025). For the C3–4 specimen group, Roy-Camille screws were demonstrated to exert a significantly higher resistance to pullout forces (299 ± 114 N) compared with Magerl screws (242 ± 97 N), whereas no difference was found between the two techniques for the C5–6 specimen group (Roy-Camille 236 ± 122 N and Magerl 220 ± 86 N). Independent of the procedure, pullout strengths were greater at the C3–4 level (271 ± 114 N) than the C5–6 level (228 ± 105 N) (p < 0.05). No significant correlation between the cancellous BMD, the thickness of the anterior cortical purchase, the length of bone purchase, and maximal pullout forces was found for either technique. Conclusions. The difference between pullout forces associated with the Roy-Camille and the Magerl techniques was not as significant as has been previously suggested in the literature. It was interesting to note the influence of the vertebral level: Roy-Camille screws demonstrated greater pullout strength (23%) at the C3–4 vertebral level than Magerl screws but no significant difference between the techniques was observed at C5–6.

Biomechanical properties of expander compared with conventional screws

2002 ◽  
Vol 97 (3) ◽  
pp. 346-349 ◽  
Author(s):  
Aziz Rassi-Neto ◽  
Antonio Shimano
Keyword(s):  
Maximum Load ◽  
Biomechanical Properties ◽  
Biomechanical Study ◽  
Intergroup Difference ◽  
Content Type ◽  
Significant Difference ◽  
Group 2 ◽  
The Comparative Study ◽  
Screw Group ◽  
Fine Print

Object. A pullout strength biomechanical study was performed in 20 fresh swine vertebral bodies in which titanium expander (Group 1) and conventional screws (Group 2) were placed. Methods. The screws were inserted into the anterosuperior portion of the anterior spine, and assessment was performed after application of loads. The expander screw is composed of two parts: 1) a cover with an external portion comprising tight thin threads; and 2) a compact internal screw inserted through the cover that allows expansion. In the comparative study between the screws in Groups 1 and 2 maximum load was assessed, and the intergroup difference was significant (p = 0.00001 [t-test]); regarding load at the elasticity threshold, a significant difference was also observed (p = 0.0063). With regard to rigidity (stiffness), there was a tendency in both groups toward significance (p = 0.069). With regard to absorbed energy in the elastic phase, statistical analysis showed a significant intergroup difference (p = 0.00439). The expander screw showed a greater load-bearing capacity than the conventional screw. Adhesion to bone in relation to the applied load and displacement was greater (significant tendency) in the expander screw group than in the conventional screw group. Conclusions. The expander screws exhibited a greater capacity to absorb energy in the elastic phase. They adhered better to bone, were easy to insert, and, if necessary, were simple to remove.

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.

Sacral Endplate Penetrating Screw for Lumbosacral Fixation: A Cadaveric Biomechanical Study

2019 ◽  
Vol 17 (4) ◽  
pp. 396-402 ◽  
Author(s):  
Grigor Grigoryan ◽  
Serkan Inceoglu ◽  
Olumide A Danisa ◽  
Wayne Cheng
Keyword(s):  
Cyclic Loading ◽  
Bone Quality ◽  
Force Measurement ◽  
Biomechanical Study ◽  
Osteoporotic Bone ◽  
Mineral Density ◽  
Pullout Force ◽  
Normal Bone ◽  
Normal Bone Mineral Density ◽  
The Difference

Abstract BACKGROUND Cortical bone trajectory is a relatively new alternative for instrumentation of the lumbar spine. When performing lumbosacral instrumentation, a novel S1 endplate penetrating screw (EPS) has been recently shown to have higher insertional torque than the traditional trajectory screw, but the biomechanical properties of this new trajectory are yet to be verified with the cadaveric studies. OBJECTIVE To evaluate 2 screw trajectories in sacra using cyclic loading and pullout tests, and to determine whether bone quality had different effects on the 2 trajectories. METHODS Nine cadaveric sacra were used, 5 of which had normal bone mineral density (BMD) and 4 were osteoporotic. Each side of the sacra was randomly assigned to either EPS trajectory or S1-alar screw (S1AS) trajectory. Each screw then underwent cyclic loading followed by pullout force measurement. A mixed-design 2 way ANOVA test was used to detect differences between the groups. RESULTS The EPS group had less relative rotation at the bone–screw interface during cyclic loading than the S1AS group (P = .016) regardless of bone quality. The pullout force following the cyclic loading was significantly higher in the EPS group (2349 ± 838 N) than the S1AS group (917 ± 909 N) in normal bone (P < .0001). The difference was more pronounced in osteoporotic bone with the EPS (1075 ± 216 N) compared to the S1AS (365 ± 422 N; P < .0001). CONCLUSION The S1 EPS trajectory is significantly more stable against loosening and has a higher pullout force compared to the S1AS trajectory. The difference between the 2 trajectories is more pronounced in osteoporotic bone.

Biomechanical comparison of C1–2 posterior fixation techniques

2005 ◽  
Vol 2 (2) ◽  
pp. 175-181 ◽  
Author(s):  
Jonathan S. Hott ◽  
James J. Lynch ◽  
Robert H. Chamberlain ◽  
Volker K. H. Sonntag ◽  
Neil R. Crawford
Keyword(s):  
Screw Fixation ◽  
Graft Fixation ◽  
Lateral Mass ◽  
Transarticular Screw ◽  
Content Type ◽  
Transarticular Screw Fixation ◽  
Significant Difference ◽  
Pars Interarticularis ◽  
Flexion And Extension ◽  
Fine Print

Object. In a nondestructive, repeated-measures in vitro flexibility experiment, the authors compared the acute stability of C1–2 after placement of C-1 lateral mass and C-2 pars interarticularis (LC1—PC2) instrumentation with that of C1–2 transarticular screw fixation. Methods. The effect of C-1 laminectomy and C1–2 interspinous cable/graft fixation on LC1—PC2 stability was studied. Screw pullout strengths were also compared. Seven human cadaveric occiput—C3 specimens were loaded nondestructively with pure moments while measuring nonconstrained atlantoaxial motion. Specimens were tested with graft alone, LC1—PC2 alone, LC1—PC2 combined with C-1 laminectomy, and graft-augmented LC1—PC2. Interspinous cable/graft fixation significantly enhanced LC1—PC2 stability during extension. After C-1 laminectomy, the LC1—PC2 construct allowed increased motion during flexion and extension. There was no significant difference in lax zone or range of motion between LC1—PC2 fixation and transarticular screw fixation, but graft-assisted transarticular screws yielded a significantly smaller stiff zone during extension. The difference in pullout resistance between C-1 lateral mass screws and C-2 pars interarticularis screws was insignificant. The LC1—PC2 region restricted motion to within the normal range during all loading modes. Atlantal laminectomy reduced LC1—PC2 stability during flexion and extension. Conclusions. The instrumentation-augmented LC1—PC2 construct performed biomechanically similarly to the C1–2 transarticular screw fixation. The LC1—PC2 construct resisted flexion, lateral bending, and axial rotation well. The weakness of the LC1—PC2 fixation in resisting extension can be overcome by adding an interspinous graft to the construct.

Insertion torque and pullout force of rescue screws for anterior cervical plate fixation in a fatigued initial pilot hole

2004 ◽  
Vol 1 (2) ◽  
pp. 198-201 ◽  
Author(s):  
Tobias Pitzen ◽  
Frederick Franta ◽  
Dragos Barbier ◽  
Wolf-Ingo Steudel
Keyword(s):  
Strong Correlation ◽  
Peak Torque ◽  
Insertion Torque ◽  
Mineral Density ◽  
Content Type ◽  
Pullout Force ◽  
Pilot Hole ◽  
The Mean ◽  
Rescue Screw ◽  
Fine Print

Object. The purpose of this study was to investigate whether thicker-core-diameter screws increase fixation strength in the cervical spine. Methods. Bone mineral density (BMD) was determined for each vertebral body (VB) obtained in six human C4–7 segments. Based on their BMD, the specimens were assigned to one of two groups in which torque and pullout force were tested. Two initial pilot holes were drilled into the VBs and tests were first performed using a standard screw. The test was repeated using a thicker rescue screw inserted into the same initial pilot hole. The mean value of peak torque and pullout force resulting from the single left/right measurements was used for statistical analysis. A t-test was performed to determine the effect of screw design on peak torque and pullout force. Moment correlation coefficients were calculated to determine the effect of BMD on peak torque and pullout force. Mean insertional peak torque for the standard screw was 82.1 N/cm and that for the rescue screw was 47.6 Ncm (p < 0.001). There was a strong correlation between insertional peak torque and BMD for both standard screws (r = 0.71, p = 0.02) and rescue screws (r = 0.59, p = 0.07). The mean pullout force for standard screws was 464.7 N, whereas it was 164.5 N for rescue screws (p < 0.001). There was a strong correlation between pullout force and BMD for both standard (r = 0.75, p = 0.0081) and rescue screws (r = 0.7, p = 0.025). Conclusions. Uncemented rescue screws that have been inserted into a fatigued hole in the cervical VB do not strengthen the screw—bone interface compared with the strength initially conferred by a standard screw.

Unilateral progressive alterations in the lumbar spine: a biomechanical study

2005 ◽  
Vol 2 (3) ◽  
pp. 298-302 ◽  
Author(s):  
Gabriel C. Tender ◽  
Scott Kutz ◽  
Richard Baratta ◽  
Rand M. Voorhies
Keyword(s):  
Lumbar Spine ◽  
Testing Machine ◽  
Main Concern ◽  
Foraminal Stenosis ◽  
Content Type ◽  
Biomechanical Behavior ◽  
Significant Difference ◽  
Pars Interarticularis ◽  
Intact Condition ◽  
Fine Print

Object. Lumbar radiculopathy secondary to foraminal stenosis can be treated by unilateral removal of the overlying pars interarticularis. The main concern after this procedure is spinal stability. In this study the authors evaluate the biomechanical behavior of the lumbar spine under torsional loading after unilateral progressive alterations, including resection of the pars. Methods. Six human cadaveric L5—sacrum functional spinal units were tested while intact and then after the following sequential unilateral alterations: excision of the pars, capsulectomy, facetectomy, and discectomy. Specimens were tested in rotation by using a biomechanical testing machine, with an axial load of 280 N and torques of ± 7.5 Nm. The specimens remained in the machine throughout testing, and the angular displacements were recorded after each set of trials. No statistically significant difference in any of the measured parameters was found between intact spines and those undergoing resection of the pars. For positive displacement (toward the side of the lesion), a significant difference from the intact condition was found after facetectomy and discectomy. For overall displacement (range of motion), spines treated with capsulectomy, facetectomy, and discectomy were significantly different from those in the intact condition. Conclusions. Unilateral removal of the pars interarticularis does not increase spinal mobility in a statistically significant fashion. The clinical implication is that the spine may not become acutely unstable after unilateral resection of the pars.

Gamma knife radiosurgery for intracranial metastatic melanoma: a 6-year experience

2002 ◽  
Vol 97 ◽  
pp. 494-498 ◽  
Author(s):  
Jorge Gonzalez-martinez ◽  
Laura Hernandez ◽  
Lucia Zamorano ◽  
Andrew Sloan ◽  
Kenneth Levin ◽  
...  
Keyword(s):  
Prognostic Factors ◽  
Brain Metastases ◽  
Metastatic Melanoma ◽  
Gamma Knife Radiosurgery ◽  
Tumor Control ◽  
Karnofsky Performance Scale ◽  
Content Type ◽  
Significant Difference ◽  
The Mean ◽  
Fine Print

Object. The purpose of this study was to evaluate retrospectively the effectiveness of stereotactic radiosurgery for intracranial metastatic melanoma and to identify prognostic factors related to tumor control and survival that might be helpful in determining appropriate therapy. Methods. Twenty-four patients with intracranial metastases (115 lesions) metastatic from melanoma underwent radiosurgery. In 14 patients (58.3%) whole-brain radiotherapy (WBRT) was performed, and in 12 (50%) chemotherapy was conducted before radiosurgery. The median tumor volume was 4 cm3 (range 1–15 cm3). The mean dose was 16.4 Gy (range 13–20 Gy) prescribed to the 50% isodose at the tumor margin. All cases were categorized according to the Recursive Partitioning Analysis classification for brain metastases. Univariate and multivariate analyses of survival were performed to determine significant prognostic factors affecting survival. The mean survival was 5.5 months after radiosurgery. The analyses revealed no difference in terms of survival between patients who underwent WBRT or chemotherapy and those who did not. A significant difference (p < 0.05) in mean survival was observed between patients receiving immunotherapy or those with a Karnofsky Performance Scale (KPS) score of greater than 90. Conclusions. The treatment with systemic immunotherapy and a KPS score greater than 90 were factors associated with a better prognosis. Radiosurgery for melanoma-related brain metastases appears to be an effective treatment associated with few complications.

Gamma knife radiosurgery for metastatic brain tumors from lung cancer: a comparison between small cell and non—small cell carcinoma

2002 ◽  
Vol 97 ◽  
pp. 484-488 ◽  
Author(s):  
Toru Serizawa ◽  
Junichi Ono ◽  
Toshihiko Iichi ◽  
Shinji Matsuda ◽  
Makoto Sato ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Brain Tumors ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Small Cell ◽  
Metastatic Brain Tumors ◽  
Cell Lung Carcinoma ◽  
Content Type ◽  
Significant Difference ◽  
Fine Print

Object. The purpose of this retrospective study was to evaluate the effectiveness of gamma knife radiosurgery (GKS) for the treatment of metastatic brain tumors from lung cancer, with particular reference to small cell lung carcinoma (SCLC) compared with non-SCLC (NSCLC). Methods. Two hundred forty-five consecutive patients meeting the following five criteria were evaluated in this study: 1) no prior brain tumor treatment; 2) 25 or fewer lesions; 3) a maximum of three tumors with a diameter of 20 mm or larger; 4) no surgically inaccessible tumor 30 mm or greater in diameter; and 5) more than 3 months of life expectancy. According to the same treatment protocol, large tumors (≥ 30 mm) were surgically removed and the other small lesions (< 30 mm) were treated with GKS. New lesions were treated with repeated GKS. Chemotherapy was administered, according to the primary physician's protocol, as aggressively as possible. Progression-free, overall, neurological, qualitative, and new lesion—free survival were calculated with the Kaplan—Meier method and were compared in the SCLC and NSCLC groups by using the log-rank test. The poor prognostic factors for each type of survival were also analyzed with the Cox proportional hazard model. Conclusions. Tumor control rate at 1 year was 94.5% in the SCLC group and 98% in the NSCLC group. The median survival time was 9.1 months in the SCLC group and 8.6 months in the NSCLC group. The 1-year survival rates in the SCLC group were 86.5% for neurological survival and 68.9% for qualitative survival; those in the NSCLC group were 87.9% for neurological and 78.9% for qualitative survival. The estimated median interval to emergence of a new lesion was 6.9 months in the SCLC group and 9.8 months in the NSCLC group. There was no significant difference between the two groups for any type of survival; this finding was verified by multivariate analysis. The results of this study suggest that GKS appears to be as effective in treating brain metastases from SCLC as for those from NSCLC.

Evaluation of endorphin content in the CSF of patients with trigeminal neuralgia before and after Gasserian ganglion thermocoagulation

1981 ◽  
Vol 55 (6) ◽  
pp. 935-937 ◽  
Author(s):  
Giuseppe Salar ◽  
Salvatore Mingrino ◽  
Marco Trabucchi ◽  
Angelo Bosio ◽  
Carlo Semenza
Keyword(s):  
Cerebrospinal Fluid ◽  
Trigeminal Neuralgia ◽  
Control Group ◽  
Gasserian Ganglion ◽  
Content Type ◽  
Group Of Seven ◽  
Idiopathic Trigeminal Neuralgia ◽  
Significant Difference ◽  
Before And After ◽  
Fine Print

✓ The β-endorphin content in cerebrospinal fluid (CSF) was evaluated in 10 patients with idiopathic trigeminal neuralgia during medical treatment (with or without carbamazepine) and after selective thermocoagulation of the Gasserian ganglion. These values were compared with those obtained in a control group of seven patients without pain problems. No statistically significant difference was found between patients suffering from trigeminal neuralgia and those without pain. Furthermore, neither pharmacological treatment nor surgery changed CSF endorphin values. It is concluded that there is no pathogenetic relationship between trigeminal neuralgia and endorphins.

Associated change in plantar temperature and sweating after transthoracic endoscopic T2–3 sympathectomy for palmar hyperhidrosis

2001 ◽  
Vol 95 (1) ◽  
pp. 58-63 ◽  
Author(s):  
Han-Jung Chen ◽  
Cheng-Loong Liang ◽  
Kang Lu
Keyword(s):  
Skin Temperature ◽  
Temperature Change ◽  
The Body ◽  
Palmar Hyperhidrosis ◽  
Compensatory Sweating ◽  
Content Type ◽  
Postoperative Changes ◽  
The Face ◽  
The Difference ◽  
Fine Print

Object. Transthoracic endoscopic T2–3 sympathectomy is currently the treatment of choice for palmar hyperhidrosis. Compensatory sweating of the face, trunk, thigh, and sole of the foot was found in more than 50% of patients who underwent this procedure. The authors conducted this study to investigate the associated intraoperative changes in plantar skin temperature and postoperative plantar sweating. Methods. One hundred patients with palmar hyperhidrosis underwent bilateral transthoracic endoscopic T2–3 sympathectomy. There were 60 female and 40 male patients who ranged in age from 13 to 40 years (mean age 21.6 years). Characteristics studied included changes in palmar and plantar skin temperature measured intraoperatively, as well as pre- and postoperative changes in plantar sweating and sympathetic skin responses (SSRs). In 59 patients (59%) elevation of plantar temperature was demonstrated at the end of the surgical procedure. In this group, plantar sweating was found to be exacerbated in three patients (5%); plantar sweating was improved in 52 patients (88.1%); and no change was demonstrated in four patients (6.8%). In the other group of patients in whom no temperature change occurred, increased plantar sweating was demonstrated in three patients (7.3%); plantar sweating was improved in 20 patients (48.8%); and no change was shown in 18 patients (43.9%). The difference between temperature and sweating change was significant (p = 0.001). Compared with the presympathectomy rate, the rate of absent SSR also significantly increased after sympathectomy: from 20 to 76% after electrical stimulation and 36 to 64% after deep inspiration stimulation, respectively (p < 0.05). Conclusions. In contrast to compensatory sweating in other parts of the body after T2–3 sympathetomy, improvement in plantar sweating was shown in 72% and worsened symptoms in 6% of patients. The intraoperative plantar skin temperature change and perioperative SSR demonstrated a correlation between these changes.

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