• Journal of Korean Neurosurgical Society
• /
• 제65권6호
• /
• pp.779-789
• /
• 2022

Objective : To analyze the effects of the number and shape of fenestrations on the mechanical strength of pedicle screws and the effects of bone cement augmentation (BCA) on the pull-out strength (POS) of screws used in conventional BCA. Methods : For the control group, a conventional screw was defined as C1, a screw with cannulated end-holes was defined as C2, a C2 screw with six pinholes was defined as C3, and the control group type was set. Among the experimental screws, T1 was designed using symmetrically placed thru-hole type fenestrations with an elliptical shape, while T2 was designed with half-moon (HM)-shaped asymmetrical fenestrations. T3 and T4 were designed with single HM-shaped fenestrations covering three pitches and five pitches, respectively. T5 and T6 were designed with 0.6-mm and 1-mm wider fenestrations than T3. BCA was performed by injecting 3 mL of commercial bone cement in the screw, and mechanical strength and POS tests were performed according to ASTM F1717 and ASTM F543 standards. Synthetic bone (model #1522-505) made of polyurethane foam was used as a model of osteoporotic bone, and radiographic examinations were performed using computed tomography and fluoroscopy. Results : In the fatigue test, at 75% ultimate load, fractures occurred 7781 and 9189 times; at 50%, they occurred 36122 and 82067 times; and at 25%, no fractures occurred. The mean ultimate load for each screw type was 219.1±52.39 N for T1, 234.74±15.9 N for T2, 220.70±59.23 N for T3, 216.45±32.4 N for T4, 181.55±54.78 N for T5, and 216.47±29.25 N for T6. In comparison with C1, T1, T2, T3, T4, and T6 showed significantly different ultimate load values (p<0.05). However, when the values for C2 and the fenestrated screws were evaluated with an unpaired t test, the ultimate load value of C2 significantly differed only from that of T2 (p=0.025). The ultimate load value of C3 differed significantly from those of T1 and T2 (C3 vs. T1 : p=0.048; C3 vs. T2 : p<0.001). Linear correlation analysis revealed a significant correlation between the fenestration area and the volume of bone cement (Pearson's correlation coefficient r=0.288, p=0.036). The bone cement volume and ultimate load significantly correlated with each other in linear correlation analysis (r=0.403, p=0.003). Conclusion : Fenestration yielded a superior ultimate load in comparison with standard BCA using a conventional screw. In T2 screws with asymmetrical two-way fenestrations showed the maximal increase in ultimate load. The fenestrated screws can be expected to show a stable position for the formation of the cement mass.

• Journal of Trauma and Injury
• /
• 제19권2호
• /
• pp.164-172
• /
• 2006

Background: The authors conducted a retrospective study to evaluate the mechanism of injury, the surgical techniques, the clinical features, the combined injuries, the treatment results, and the surgical complications in patients with atlantoaxial fracture/subluxations. Methods: The authors reviewed 71 cervical fracture/dislocations during a four-year period from September 2002 to August 2006. Among them, there were twenty one C1,2 fracture/subluxations. There were thirteen men (mean age : 43.5 years) and eight women (mean age : 50 years). Their follow-up period was at least 6 months, and the mean follow-up period was 9.6 months. Gardner-Wells tongs traction was used in all patients immediately on presentation. Surgical treatment was performed, depending on the pathologic conditions. Results: Of all 21 cases, 14 cases were injured in motor vehicle accidents, 5 were falls, and 2 were miscellaneous. There were four C1 fracture (5.6%), fourteen C2 fracture (66.7%), one C1 and 2 combined fracture (4.8%), and one C1-2 subluxation (4.8%). The C1 fractures in our series were classified as two Jefferson's fractures and two C1 lateral mass fracture. The C2 fractures were classified as one odontoid type I fracture, two odontoid type II fractures, five odontoid type III fractures, one hangman's fracture, and four C2 body tear-drop fractures. Atlantoaxial fractures were associated with six (28.6%) head injuries, four (19.0%) other spinal injuries, two (9.5%) chest injuries, and three (14.3%) spinal cord injuries. Surgical treatment was performed in nine cases, which included anterior odontoid screw fixation in two cases, transarticular screw fixation with iliac bone graft in one case, posterior fixation by using C2 pedicle screw and C3 lateral mass screw in three cases, lateral mass screw fixation C1-2 with iliac bone graft in one case, O(occipito)-C1-3-4 screw fixation in one case, posterior C2-3 wiring with allograft in one case, and halo vest in six cases. Conservative management was used in the rest of the patients in our trials. Bone fusion was complete in all cases. There were no operation-related complication, except one pin site infection in the case of halo vest. Conclusion: In this study, the choice of appropriate treatment according to the fracture types resulted in safe and effective management of unique atlantoaxial fracture/subluxations.

• Journal of Korean Neurosurgical Society
• /
• 제54권1호
• /
• pp.25-29
• /
• 2013

Objective : To clarify the landmark for deciding the entry point for C1 lateral mass screws via the posterior arch by using 3-dimensional (3D) computed images. Methods : Resnick insisted that the C1 posterior arch could be divided into pure posterior and lateral lamina (C1 pedicle). Authors studied where this transition point (TP) is located between the posterior lamina and the C1 pedicle and how it can be recognized. The 3D computed images of 86 cadaver C1s (M : F=45 : 41) were used in this study. Results : The superior ridge of the C1 posterior arch had 2 types of orientation. One was in the vertical direction in the C1 posterior lamina and the other was in the horizontal direction in the C1 pedicle. The TP was located at the border between the 2 areas, the same site as the posterior end of the groove of the vertebral artery. On posterior-anterior projection, the posterior arch was sharpened abruptly at TP. We were unable to identify the TP in 6.4% of specimens due to complete or partial osseous bridges. A total of 93.8% of the TP were located between the most enlarged point of the spinal canal and the medial wall of the vertebral artery. Conclusion : The anatomic entry zone of C1 lateral laminar screws was clarified and identified based on the TP by using preoperative 3D computed images.

• Journal of Korean Neurosurgical Society
• /
• 제40권1호
• /
• pp.22-27
• /
• 2006

Objective : The purpose of this study is to investigate the clinical results of anterior and posterior stabilization by one stage posterolateral approach for the unstable fracture of thoracolumbar and lumbar spine. Methods : By posterolateral approach with curved skin incision, unilateral facet and pedicle were removed. Through this route, corpectomy was performed, and then this space was replaced with mesh cage filled up with autologous bone graft. Both side pedicle screw fixation was followed to upper and lower levels. Results : Six of seven patients of this study showed neurological improvement. The other one patient showed no neurological change. One patient had postoperative infection, another patient had postoperative kyphosis. The other patient had epidural hematoma on operation site after surgery. And all patinets on this study made to have spinal stability except one patient happened postoperative kyphosis. Conclusion : In the unstable fracture of thoracolumbar and lumbar spine, one stage anterior and posterior stabilization and fusion by posterolateral approach seems to be an effective procedure, if we have more care and supplementation.

• 대한의용생체공학회:의공학회지
• /
• 제29권2호
• /
• pp.139-145
• /
• 2008

Many recent studies suggest that the posterior dynamic stabilization(PDS) can be a more physiologically-relevant alternative to the rigid fixation for the patients suffering from low back pain. However, its biomechanical effects or clinically proven efficacies still remain unknown. In this study, we evaluated kinematic behaviors of the lower lumbar spine with the PDS system and then compared to those of the rigid fixation system using finite element (FE) analysis. A validated FE model of intact lumbar spine(L2-L5) was developed. The implanted model was then constructed after modification from the intact to simulate two kinds of pedicle screw systems (PDS and the rigid fixation). Hybrid protocol was used to flex, extend, laterally bend and axially rotate the FE model. Results showed that the PDS systems are more flexible than rigid fixation systems, yet not flexible enough to preserve motion. PDS system allowed $16.2{\sim}42.2%$ more intersegmental rotation than the rigid fixation at the implanted level. One the other hand, at the adjacent level it allowed more range of motion ($2.0%{\sim}8.3%$) than the rigid fixation. The center of rotation of the PDS model remained closer to that of the intact spine. These results suggest that the PDS system could be able to prevent excessive motion at the adjacent levels and restore the spinal kinematics.

• Journal of Korean Neurosurgical Society
• /
• 제62권4호
• /
• pp.422-431
• /
• 2019

Objective : In an aging society, the number of patients with symptomatic degenerative spondylolisthesis (DS) is increasing and there is an emerging need for fusion surgery. However, few studies have compared transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF) for the treatment of patients with DS. The purpose of this study was to investigate the clinical and radiological outcomes between TLIF and LLIF in DS. Methods : We enrolled patients with symptomatic DS at L4-5 who underwent TLIF with open pedicle screw fixation (TLIF group, n=41) or minimally invasive LLIF with percutaneous pedicle screw fixation (LLIF group, n=39) and were followed-up for more than one year. Clinical (visual analog scale and Oswestry disability index) and radiological outcomes (spondylolisthesis rate, segmental sagittal angle [SSA], mean disc height [MDH], intervertebral foramen height [FH], cage subsidence, and fusion rate) were assessed. And we assessed the changes in radiological parameters between the postoperative and the last follow-up periods. Results : Preoperative radiological parameters were not significantly different between the two groups. LLIF was significantly superior to TLIF in immediate postoperative radiological results, including reduction of spondylolisthesis rate (3.8% and 7.2%), increase in MDH (13.9 mm and 10.3 mm) and FH (21.9 mm and 19.4 mm), and correction of SSA ($18.9^{\circ}$ and $15.6^{\circ}$) (p<0.01), and the changes were more stable from the postoperative period to the last follow-up (p<0.01). Cage subsidence was observed significantly less in LLIF (n=6) than TLIF (n=21). Fusion rate was not different between the two groups. The clinical outcomes did not differ significantly at any time point between the two groups. Complications were not statistically significant. However, TLIF showed chronic mechanical problems with screw loosening in four patients and LLIF showed temporary symptoms associated with the surgical approach, such as psoas and ileus muscle symptoms in three and two cases, respectively. Conclusion : LLIF was more effective than TLIF for spondylolisthesis reduction, likely due to the higher profile cage and ligamentotactic effect. In addition, LLIF showed mechanical stability of the reduction level by using a cage with a larger footprint. Therefore, LLIF should be considered a surgical option before TLIF for patients with unstable DS.

• Journal of Korean Neurosurgical Society
• /
• 제56권1호
• /
• pp.5-10
• /
• 2014

Objective : When the pedicle screw insertion technique is failed or not applicable, C7 intralaminar screw insertion method has been used as an alternative or salvage fixation method recently. However, profound understanding of anatomy is required for safe application of the bilaterally crossing laminar screw at C7 in clinic. In this cadaveric study, we evaluated the anatomic feasibility of the bilateral crossing intralaminar screw insertion and especially focused on determination of proper screw entry point. Methods : The C7 vertebrae from 18 adult specimens were studied. Morphometric measurements of the mid-laminar height, the minimum laminar thickness, the maximal screw length, and spino-laminar angle were performed and cross-sectioned vertically at the screw entry point (spino-laminar junction). The sectioned surface was equally divided into 3 parts and maximal thickness and surface area of the parts were measured. All measurements were obtained bilaterally. Results : The mean mid-laminar height was 13.7 mm, mean minimal laminar thickness was 6.6 mm, mean maximal screw length was 24.6 mm, and mean spinolaminar angle was $50.8{\pm}4.7^{\circ}$. Based on the measured laminar thickness, the feasibility of 3.5 mm diameter intralaminar screw application was 83.3% (30 sides laminae out of total 36) when assuming a tolerance of 1 mm on each side. Cross-sectional measurement results showed that the mean maximal thickness of upper, middle, and lower thirds was 5.0 mm, 7.5 mm, and 7.3 mm, respectively, and mean surface area for each part was $21.2mm^2$, $46.8mm^2$, and $34.7mm^2$, respectively. Fourteen (38.9%) sides of laminae would be feasible for 3.5 mm intralaminar screw insertion when upper thirds of C7 spino-laminar junction is the screw entry point. In case of middle and lower thirds of C7 spino-laminar junction, 32 (88.9%) and 28 (77.8%) sides of laminae were feasible for 3.5 mm screw insertion, respectively. Conclusion : The vertical cross-sectioned area of middle thirds at C7 spinolaminar junction was the largest area and 3.5 mm screw can be accommodated with 77.8 % of feasibility when lower thirds were the screw entry point. Thus, selection of middle and lower thirds for each side of screw entry point in spino-laminar junction would be the safest way to place bilateral crossing laminar screw within the entire lamina. This anatomic study result will help surgeons to place the screw safely and accurately.

• Journal of Korean Neurosurgical Society
• /
• 제55권5호
• /
• pp.289-292
• /
• 2014

A case of total spondyloptosis of the cervical spine at C6-7 level with cord compression is described in a 51-year-old male. Because the bodies of C6 and 7 were tightly locked together, cervical traction failed. Then the patient was operated on by a posterior approach. Posterior stabilization and fusion were performed by C4-5 lateral mass and C7-T1 pedicle screw fixation and rod instrumentation with bridging both C4-5's rods to the C7-T1's extended ones. After C6 total laminectomy and foraminotomy, the C6 body was returned to its proper position. Secondly, anterior stabilization and fusion were performed by C6-7 discectomy with a screw-plate system. A postoperative lateral plain radiograph showed good realignment. In this case, we report the clinical presentation and discuss the surgical modalities of C6-7 total spondyloptosis and the failed close reduction.

• Journal of Korean Neurosurgical Society
• /
• 제37권2호
• /
• pp.154-156
• /
• 2005

We present a case of chondroblastoma in the thoracic vertebra. A 40-year-old patient with upper back pain and lower extremity weakness was admitted to our clinic. On neurological examination, the patient exhibited lower extremity spastic paraparesis. Magnetic resonance imaging revealed a mass infiltrating the 7th thoracic vertebra and its adjacent structures with concomitant compression of the epidural space. After right upper lung tuberculoma was resected through the transthoracic approach, T7 total corpectomy was done with anterior stabilization using a MESH cage and T7 rib bone graft. Two weeks after the first operation, remained part of vertebra was removed and posterior stabilization was performed using a pedicle screw fixation and cross linkage bar with the assistance of the navigation system. The final pathologic diagnosis of the vertebral lesion was benign chondroblastoma.

• 대한정형외과학회지
• /
• 제56권5호
• /
• pp.419-426
• /
• 2021

목적: 화농성 요추부 추체 감염의 수술적 치료 시 이환된 추체에 척추경 나사를 삽입하는 수술법은 균막의 형성 및 감염 치료 실패의 위험성으로 기피되었다. 저자들은 이환된 추체에 척추경 나사를 삽입하여 고정 분절수를 최소화하면서도 감염 치료에 성공하였는바, 이를 분석하여 해당 술식의 유용성에 대하여 알아보고자 하였다. 대상 및 방법: 2000년 1월부터 2018년 6월까지 본원 척추센터에서 제1저자에 의해 수술적으로 치료한 화농성 요추부 척추 감염 환자 중, 이환된 추체에 직접 척추경 나사를 삽입하여 유합술을 시행한 환자군을 그룹 A, 이환된 추체 척추경의 골파괴 소견으로 인접 정상 추체에 척추경 나사를 삽입하여 유합술을 시행한 환자군을 그룹B로 분류하여 임상적 결과를 후향적으로 연구하였다. 모든 환자들은 후방 접근법으로 수술하였으며, 이환된 추간판을 제거하고 부골화된 추체의 소파술 및 추체 간 자가 지주골 이식술 후 척추경 나사 고정술을 시행한 48예(그룹A 28예, 그룹B 20예)를 대상으로 두 그룹 간의 입원 기간, 수술 시간, 출혈량 및 수술 후 1개월째 EQ-5D 지수, 주사 항생제 투여 기간, 혈액학적 결과, 임상적 결과, 방사선학적 결과를 종합적으로 분석하였다. 결과: 그룹 A에서 고정 분절 수, 수술 시간, 출혈량 및 술 후 1개월째 EQ-5D 지수에서 그룹 B에 비하여 통계적으로 유의하게 향상된 결과를 보였으며, 항생제 사용 기간, 입원 기간, 방사선학적 골유합의 시기, 시상각의 교정률 및 재발률에서는 유의한 차이를 보이지 않았다. 결론: 후방 도달법을 통한 이환된 추체에 직접 척추경 나사를 삽입하는 최소 분절 고정술은 수술 시간 및 출혈량이 줄어들고, 고정분절을 최소화하여 요추부의 운동성을 보전하면서도, 감염의 확산이나 재발 없이 빠른 회복을 보였기에, 요추부 화농성 척추염 환자의 수술적 치료 시 권장할 만한 술식으로 생각된다.