Dataset Information

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement.

ABSTRACT:

Background

Funnel technique is a method used for the insertion of screw into thoracic pedicle.

Aim

To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology.

Methods

14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique group (n = 7) and Magerl technique group (n = 7). The displacement-stiffness and pull-out strength in all kinds of position were tested and compared.

Results

Two fixed groups were significantly higher than that of the intact state (P < 0.05) in the spinal central axial direction, compression, anterior flexion, posterior bending, lateral bending, axial torsion, but there were no significant differences between two fixed groups (P > 0.05). The mean pull-out strength in Funnel technique group (789.09 ± 27.33) was lower than that in Magerl technique group (P < 0.05).

Conclusions

The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement. It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. Therefore, the funnel technique in the thoracic spine affords an alternative for the standard screw placement.

SUBMITTER: Huang YJ

PROVIDER: S-EPMC4209655 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Publications

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement.

Huang Yi-Jiang YJ Peng Mao-Xiu MX He Shao-Qi SQ Liu Liang-Le LL Dai Ming-Hai MH Tang Chenxuan C

African health sciences 20140901 3

<h4>Background</h4>Funnel technique is a method used for the insertion of screw into thoracic pedicle.<h4>Aim</h4>To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology.<h4>Methods</h4>14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique gr ...[more]

PMID: 25352893

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Project description:STUDY DESIGN: Systematic review. OBJECTIVE: To determine the effectiveness of using electromyography (EMG) during intraoperative pedicle screw placement in patients with thoracic deformity. METHODS: A systematic review of the English-language literature was undertaken for articles published between 1970 and July 2011. For our first question, we identified all articles that were designed to evaluate the diagnostic test characteristics (ie, measures of validity such as sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV]) of EMG for thoracic deformities in adolescent and adult patients. For our second question, we attempted to identify all articles that reported complication rates (pedicle wall breach or new neurological event) after pedicle screw placement in the same population comparing patients who did and did not undergo intraoperative EMG. Articles were excluded if they did not report or give raw data to calculate at least one of the four primary diagnostic test characteristics: sensitivity, specificity, PPV, or NPV for study question one. Articles were excluded if they did not have a "no EMG" control group for study question two. Other exclusions were reviews, editorials, case reports, non-English written studies, and animal studies. We rated the overall body of evidence with respect to each key question using a modified Grades of Recommendation Assessment, Development and Evaluation (GRADE) system for diagnostic and therapeutic studies. RESULTS: The overall strength of evidence evaluating the diagnostic characteristics was low due to inconsistent findings between studies and uncertainty of the impact of false-negatives. The fairly low sensitivity may lead to a high-false negative rate. It is unclear what the impact of false-negatives would be since no neurological injuries were identified in the studies summarized. A higher specificity would suggest a fairly low false-positive rate; however, the rates could be as high as 30%. If sudden changes in treatment are required in the absence of any adverse event, this could be considered a limitation of such testing. The overall strength of evidence for evaluating the efficacy of EMG compared with no EMG was insufficient because of literature shortage on this topic. CONCLUSION: The overall strength of evidence evaluating the diagnostic characteristics was low due to inconsistent findings between studies and uncertainty of the impact of false-negatives. Given the low sensitivity and potential high rate of false-negatives, pedicle wall breaches may occur, without EMG notification. These undetected breaches may lead to loose or weak screw position which may lead to neurovascular complications during or after a translation-rotation maneuver, especially in rigid deformities. The higher sensitivity would suggest a lower rate of false-positives. We recommend considering the use of intraoperative EMG-monitoring method to help identify potential complications based upon available technology, personal experiences and preferences; however, surgeons should keep in mind that false-positive results may lead to increased surgery time and increased blood loss. The surgeon should not depend solely on EMG since it can also render false-negatives.

Project description:PurposeThe purpose of this study was to investigate finite element biomechanical properties of the novel transpedicular transdiscal (TPTD) screw fixation with interbody arthrodesis technique in lumbar spine.MethodsAn L4-L5 finite element model was established and validated. Then, two fixation models, TPTD screw system and bilateral pedicle screw system (BPSS), were established on the validated L4-L5 finite element model. The inferior surface of the L5 vertebra was set immobilised, and moment of 7.5 Nm was applied on the L4 vertebra to test the range of motion (ROM) and stress at flexion, extension, lateral bending and axial rotation.ResultsThe intact model was validated for prediction accuracy by comparing two previously published studies. Both of TPTD and BPSS fixation models displayed decreased motion at L4-L5. The ROMs of six moments of flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in TPTD model were 1.92, 2.12, 1.10, 1.11, 0.90 and 0.87°, respectively; in BPSS model, they were 1.48, 0.42, 0.35, 0.38, 0.74 and 0.75°, respectively. The screws' peak stress of above six moments in TPTD model was 182.58, 272.75, 133.01, 137.36, 155.48 and 150.50 MPa, respectively; and in BPSS model, it was 103.16, 129.74, 120.28, 134.62, 180.84 and 169.76 MPa, respectively.ConclusionBoth BPSS and TPTD can provide stable biomechanical properties for lumbar spine. The decreased ROM of flexion, extension and lateral bending was slightly more in BPSS model than in TPTD model, but TPTD model had similar ROM of axial rotation with BPSS model. The screws' peak stress of TPTD screw focused on the L4-L5 intervertebral space region, and more caution should be put at this site for the fatigue breakage.The translational potential of this articleOur finite element study provides the biomechanical properties of novel TPTD screw fixation, and promotes this novel transpedicular transdiscal screw fixation with interbody arthrodesis technique be used clinically.

Project description:BackgroundCurrent methods of measuring vertebral rotation by plain radiographs rely on anatomic landmarks that are not present in the postoperative spine or require advanced imaging. Furthermore, there are few studies on the incidence of crankshaft with modern pedicle instrumentation.Questions/purposesWe sought to (1) describe and validate a method of vertebral rotation measurement using plain radiographs and (2) measure postoperative rotation in a series of patients treated for adolescent idiopathic scoliosis.MethodsPatients with adolescent idiopathic scoliosis treated with surgery over a 6-year period were reviewed. Patients with computed tomography (CT) scans and radiographs within 60 days of another were included. Vertebral rotation was calculated by radiographic measurements and measured directly by CT scan. As an internal control, patients with two apical pedicle screws on all radiographs were analyzed. Rotation was measured for all patients with at least 1 year of radiographic follow-up.ResultsThree thousand five hundred fifty-two instrumented spinal levels in 308 consecutive patients were reviewed. Ten patients with 93 screws were analyzed by CT and radiographs. The average discrepancy between computed tomography (CT) and radiographs was 3.3?±?1.9°, with 81.7% (76/93) within 5°. Intra- and inter-rater reliabilities for measured axial rotation were excellent (intra-class correlation coefficient (ICC)?=?0.879 and 0.900, respectively). One hundred swventy-eight patients were eligible with an average follow-up of 2.3?±?1.2 years; 84.8% (151/178) had screw(s) visible on all images at the major curve apex. The average postsurgical rotation was 3.5?±?2.9°; 19.2% (29/151) were measured to have a rotation over 5°, and 4.0% (6/151) demonstrated a rotation over 10°. Only 4.6% (7/151) of patients demonstrated a postoperative Cobb angle change over 10°.ConclusionsMost major curves have apical pedicle screw instrumentation that can be followed by radiographs alone to measure rotation. Vertebral rotation measurement requires only plain radiographs and is a more sensitive determination for subtle postoperative crankshaft than change in Cobb angle.

Dataset Information

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement.

Background

Aim

Methods

Results

Conclusions

Publications

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement.

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