• Journal of Korean Neurosurgical Society
• /
• v.39 no.4
• /
• pp.251-255
• /
• 2006

Objective : To determine the clinical and radiological safety of 15 consecutive patients managed with plate and screw fixation systems applied to the cervical lateral mass. Methods : 15 patients who underwent posterior cervical and T1 arthrodesis were reviewed from Jan 2002 to Dec 2004. Posterior cervical screw and plate fixation was applied on the lateral mass of the cervical spine. The authors have tried lateral mass screw fixation using a modified Magerl's technique [$20^{\circ}$ lateral and $20{\sim}30^{\circ}$ rostral screw trajectory] under preliminary radiological study. The average patient age was $39.73^{\circ}{\pm}11.00\;years$, and the average follow-up period was $9.73^{\circ}{\pm}6.77\;months$. Computed tomography scans taken after surgery were reviewed to confirm the attempted screw trajectory correct and safety. Results : Three of 93 lateral mass screws were malpositioned but clinical damage was not noted. Two of 8 pedicle screws on the T1 vertebrae were not placed on the correct pedicle area. Screw and plate loosening was observed in one case but was not subjected to an additional procedure because of maintained screw position observed during follow-up periods. Conclusion : The results of this study indicate that lateral mass screw fixation using the Modified Magerl's technique on the cervical lateral mass may provide safe and effective application on the patients. In addition, the chance of incorrectly placed screws was higher in T1 pedicle screw fixation than in lateral mass screw fixation of the cervical area.

• Journal of Korean Neurosurgical Society
• /
• v.52 no.2
• /
• pp.120-125
• /
• 2012

Objective : To investigate the feasibility of C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion to treat various atlantoaxial instabilities. Methods : After posterior atlantoaxial fixation with lateral mass screw in the atlas and pedicle screw in the axis, we used 2 miniplates to fixate interlaminar iliac bone graft instead of sublaminar wiring. We performed this procedure in thirteen patients who had atlantoaxial instabilities and retrospectively evaluated the bone fusion rate and complications. Results : By using this method, we have achieved excellent bone fusion comparing with the result of other methods without any complications related to this procedure. Conclusion : C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion may be an efficient alternative method to treat various atlantoaxial instabilities.

• Journal of Korean Neurosurgical Society
• /
• v.44 no.3
• /
• pp.124-130
• /
• 2008

Objective : Our purpose of this study is to compare insertion angles and screw lengths from Roy-Camille, Magerl, and our designed method for cervical lateral mass screw fixation in the Korean population by quantitative measurement of reformatted two dimensional (2D) computed tomography (CT) images. Methods : We selected thirty Korean patients who were evaluated with thin section CT scans and reconstruction program to obtain reformatted 2D-CT images of the transversal plane passing the cranio-caudal angle using three different techniques. We measured the minimum angle to avoid vertebral artery (VA) injury, the ideal angle and depth for bicortical screwing of cervical lateral mass. Morphometric measurements of the lateral masses from C3-C7 were also taken. Results : In all three techniques, the mean safety angles from the VA were less than 8 degrees and the necessary depth of the screw was about 14 mm for safety to the VA and for the bicortical purchase. In our designed technique, the mean $\beta$ angles of each level from C3 to C7 were 29.0. 29.8. 29.5. 26.3. and 23.9 degrees, respectively. Conclusion : Results of this study and data from the literature indicate that differences may exist between the Korean and Western people in the length and angle for ideal lateral mass screw fixation. In addition, our technique needs further cadaveric and clinical study for safety and efficacy for being performed as alternative method for cervical lateral mass fixation.

• Journal of Korean Neurosurgical Society
• /
• v.30 no.2
• /
• pp.131-136
• /
• 2001

Object : The clinical uses of screws are increasing with broader applications in spinal disorders. When screws are inserted repeatedly to achieve optimal position, tips of screw pitch may become damaged during insertion even though there are significant differences in the moduli of elasticity between bone and titanium. The effect of repeated screw insertion on pullout resistance was investigated. Methods : Three different titanium screws(cortical lateral mass screw, cancellous lateral mass screw and cervical vertebral body screw) were inserted into the synthetic cancellous material and then extracted axially at a rate of 2.4mm/min using Instron(Model TT-D, Canton, MA). Each set of screws was inserted and pulled out three times. There were six screws in each group. The insertional torque was measured with a torque wrench during insertion. Pullout strength was recorded with a digital oscilloscope. Results : The mean pullout force measurements for the cortical lateral mass screws($185.66N{\pm}42.60$, $167.10N{\pm}27.01$ and $162.52 N{\pm}23.83$ for first, second and third pullout respectively : p=0.03) and the cervical vertebral body screws($386.0N{\pm}24.1$, $360.2N{\pm}17.5$ and $330.9N{\pm}16.7$ : p=0.0024) showed consecutive decrease in pullout resistance after each pullout, whereas the cancellous lateral mass screws did not($194.00N{\pm}36.47$, $219.24N{\pm}26.58$ and 199.49N(36.63 : p=0.24). The SEM after insertion and pullout three times showed a blunting in the tip of the screw pitch and a smearing of the screw surface. Conclusions : Repetitive screw insertion and pullout resulted in the decrease of pullout resistance in certain screws possibly caused by blunting the screw tip. This means screw tips suffer deformations during either repeated insertion or pullout. Thus, the screws that have been inserted should not be used for the final construct.

• Journal of Korean Neurosurgical Society
• /
• v.50 no.4
• /
• pp.341-347
• /
• 2011

Objective : The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Methods : Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle $30^{\circ}$ to $45^{\circ}$ toward the midline in the transverse plane and $40^{\circ}$ to $50^{\circ}$ cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. Results : There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Conclusion : Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

• Journal of Korean Neurosurgical Society
• /
• v.43 no.2
• /
• pp.111-113
• /
• 2008

Recently, Harms and Melcher modified Goel's approach, the C1 lateral mass and C2 pedicle screw fixation, and the new technique is currently in favor among neurosurgeons. Comparing to the advantages of Harms construct, the disadvantages were not extensively investigated. We experienced a patient with severe occipital pain developed after the C1 lateral mass screw placement for the traumatic atlantoaxial instability. We reviewed literatures about Harms construct with focus on the occipital neuralgia as a postoperative complication and suggest here technical tips to avoid the troublesome pain.

• Journal of Korean Neurosurgical Society
• /
• v.52 no.2
• /
• pp.114-119
• /
• 2012

Objective : The purpose of this study was 1) to analyze clinically-executed cervical lateral mass screw fixation by the Kim's technique as suggested in the previous morphometric and cadaveric study and 2) to examine various complications and bicortical purchase that are important for b-one fusion. Methods : A retrospective study was done on the charts, operative records, radiographs, and clinical follow up of thirty-nine patients. One hundred and seventy-eight lateral mass screws were analyzed. The spinal nerve injury, violation of the facet joint, vertebral artery injury, and the bicortical purchases were examined at each lateral mass. Results : All thirty-nine patients received instrumentations with poly axial screws and rod systems, in which one hundred and seventy-eight screws in total. No vertebral artery injury or nerve root injury were observed. Sixteen facet joint violations were observed (9.0%). Bicortical purchases were achieved on one hundred and fifty-six (87.6%). Bone fusion was achieved in all patients. Conclusion : The advantages of the Kim's technique are that it is performed by using given anatomical structures and that the complication rate is as low as those of other known techniques. The Kim's technique can be performed easily and safely without fluoroscopic assistance for the treatment of many cervical diseases.

• Journal of Korean Neurosurgical Society
• /
• v.56 no.6
• /
• pp.475-481
• /
• 2014

Objective : To evaluate the anatomical feasibility of 3.5 mm screw into the cervical spine in the pediatric population and to establish useful guidelines for their placement. Methods : A total of 37 cervical spine computerized tomography scans (24 boys and 13 girls) were included in this study. All patients were younger than 10 years of age at the time of evaluation for the period of 2007-2011. Results : For the C1 screw placement, entry point height (EPH) was the most restrictive factor (47.3% patients were larger than 3.5 mm). All C2 lamina had a height larger than 3.5 mm and 68.8% (51/74) of C2 lamina had a width thicker than 3.5 mm. For C2 pedicle width, 55.4% (41/74) of cases were larger than 3.5 mm, while 58.1% (43/74) of pedicle heights were larger than 3.5 mm. For pedicle width of subaxial spine, 75.7% (C3), 73% (C4), 82.4% (C5), 89.2% (C6), and 98.1% (C7, 1/54) were greater than 3.5 mm. Mean lamina width of subaxial cervical spine was 3.1 (C3), 2.7 (C4), 2.9 (C5), 3.8 (C6), and 4.0 mm (C7), respectively. Only 34.6% (127/370) of subaxial (C3-7) lamina thickness were greater than 3.5 mm. Mean length of lateral mass for the lateral mass screw placement was 9.28 (C3), 9.08 (C4), 8.81 (C5), 8.98 (C6), and 10.38 mm (C7). Conclusion : C1 lateral mass fixation could be limited by the morphometrics of lateral mass height. C2 translamina approach is preferable to C2 pedicle screw fixation. In subaxial spines, pedicle screw placement was preferable to trans-lamina screw placement, except at C7.

• Journal of Korean Neurosurgical Society
• /
• v.49 no.6
• /
• pp.351-354
• /
• 2011

Objective : This investigation was conducted to evaluate a new, safe entry point for the C2 pedicle screw, determined using the anatomical landmarks of the C2 lateral mass, the lamina, and the isthmus of the pars interarticularis. Methods : Fifteen patients underwent bilateral C1 lateral mass-C2 pedicle screw fixation, combined with posterior wiring. The C2 pedicle screw was inserted at the entry point determined using the following method : 4 mm lateral to and 4 mm inferior to the transitional point (from the superior end line of the lamina to the isthmus of the pars interarticularis). After a small hole was made with a high-speed drill, the taper was inserted with a 30 degree convergence in the cephalad direction. Other surgical procedures were performed according to Harm's description. Preoperatively, careful evaluation was performed with a cervical X-ray for C1-C2 alignment, magnetic resonance imaging for spinal cord and ligamentous structures, and a contrast-enhanced 3-dimensional computed tomogram (3-D CT) for bony anatomy and the course of the vertebral artery. A 3-D CT was checked postoperatively to evaluate screw placement Results : Bone fusion was achieved in all 15 patients (100%) without screw violation into the spinal canal, vertebral artery injury, or hardware failure. Occipital neuralgia developed in one patient, but this subsided after a C2 ganglion block. Conclusion : C2 transpedicular screw fixation can be easily and safely performed using the entry point of the present study. However, careful preoperative radiographic evaluation, regardless of methods, is mandatory.

• Journal of Korean Neurosurgical Society
• /
• v.50 no.3
• /
• pp.166-172
• /
• 2011

Objective : The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. Methods : A total of 120 patients (60 men and 60 women) with an average age of $51.7{\pm}13.6$ years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. Results : At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, $33.9{\pm}3.1$ mm; ILS, $30.8{\pm}3.1$ mm; LMS, $10.6{\pm}1.3$; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, $6.8{\pm}1.2$ mm; lamina, $6.2{\pm}1.2$ mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, $18.6{\pm}2.0$ mm; pedicle, $8.7{\pm}1.3$ mm; p<0.01). The ideal screw trajectory at C7 was also measured ($47.8{\pm}4.8^{\circ}$ for ILS and $35.1{\pm}8.1^{\circ}$ for PS). Conclusion : Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.