Biomechanical comparison of static and dynamic cervical plates in terms of the bone fusion, tissue degeneration, and implant behavior.

INTRODUCTION: Using an anterior cervical fixation device in the anterior cervical discectomy and fusion (ACDF) has evolved to various systems of static and dynamic cervical plates (SCP and DCP). Dynamic cervical plates have been divided into three categories: the rotational (DCP-R), translational (DCP-T), and hybrid (DCP-H) joints. However, little studies have been devoted to systematically investigate the biomechanical differences of dynamic cervical plates. MATERIALS AND METHODS: The biomechanical tests of load-deformation properties and failure modes between the SCP and DCP systems are implemented first by using the UHMWPE blocks as the vertebral specimens. The CT-based C2-C7 model simulates the strategies of cervical plate in ACDF surgery is developed with finite-element analyses. One intact, one SCP and two DCP systems are evaluated for their biomechanical properties of bone fusion and tissue responses. RESULTS: In the situation of biomechanical test, The mean values of the five ACDSP constructs are 393.6% for construct stiffness (p < 0.05) and 183.0% for the first yielding load (p < 0.05) less than those of the SCP groups, respectively. In the situation of finite-element analysis, the rigid-induced ASD is more severe for the SCP, followed by the DCP-H, and the DCP-R is the least. DISCUSSION AND CONCLUSIONS: Considering the degenerative degree of the adjacent segments and osteoporotic severity of the instrumented segments is necessary while using dynamic system. The mobility and stability of the rotational and translational joints are the key factors to the fusion rate and ASD progression. If the adjacent segments have been degenerative, the more flexible system can be adopted to compensate the constrained mobility of the ACDF segments. In the situation of the osteoporotic ACDF vertebrae, the stiffer system is recommended to avoid the cage subsidence.

Endoscopically assisted presigmoid retrolabyrinthine approach to the lateral mesencephalic sulcus: a cadaveric study with comparison to the variant supracerebellar infratentorial approaches.

The supracerebellar infratentorial (SCIT) approach is commonly used to gain access to the lateral mesencephalic sulcus (LMS), which has been established as a safe entry point into the posterolateral midbrain. This study describes a lateral variant of the SCIT approach, the supreme-lateral SCIT approach, for accessing the LMS through the presigmoid retrolabyrinthine craniectomy and quantitatively compares this approach with the paramedian and extreme-lateral SCIT approaches. Anatomical dissections were performed in four cadaveric heads. In each head, the supreme-lateral SCIT approach was established on one side, following a detailed description of each step, whereas the paramedian and supreme-lateral SCIT approaches were established on the other side. Quantitative measurements of the exposed posterolateral midbrain, the angles of LMS entry, and the depth of surgical corridors were recorded and compared between the three SCIT approach variants. The supreme-lateral (67.70 ± 23.14 mm2) and extreme-lateral (70.83 ± 24.99 mm2) SCIT approaches resulted in larger areas of exposure anterior to the LMS than the paramedian SCIT approach (38.61 ± 9.84 mm2); the supreme-lateral SCIT approach resulted in a significantly smaller area of exposure posterior to the LMS (65.24 ± 6.81 mm2) than the other two variants (paramedian = 162.75 ± 31.98 mm2; extreme-lateral = 143.10 ± 23.26 mm2; both P < .001). Moreover, the supreme-lateral SCIT approach resulted in a surgical corridor with a shallower depth and a smaller angle relative to the horizontal plane than the other two variants. The supreme-lateral SCIT approach is a more lateral approach than the extreme-lateral SCIT approach, providing a subtemporal approach with direct LMS visualization. The supreme-lateral SCIT offers the benefits of both subtemporal and SCIT approaches and represents a suitable option for the management of selected midbrain pathologies.

Biomechanical evaluation of a novel tri-blade titanium implantable vertebral augmentation device.

BACKGROUND CONTEXT: Titanium implantable vertebral augmentation device (TIVAD) are regarded as having potential in the treatment of vertebral compression fractures (VCFs). However, improper design in current TIVADs results in the inability to effectively restore VCF height and maintain stability. There is still an unmet clinical need for improvement. PURPOSE: The authors tested a newly developed a TIVAD (Tri-blade fixed system) that can provide enough endplate collapse support to restore the vertebral body height in a safe retraction mechanism for VCFs using minimally invasive surgery (MIS). STUDY DESIGN: The performed biomechanical tests included blade expansion force, lifetime of cement embedded and vertebral height restoration efficiency of porcine osteoporosis VCFs for its feasibility. METHODS: A cylinder with 3 surface cuts that form blades that can be expanded into a conical space was designed (Tri-blade fixed system). The 3 blades can be expanded outward with angles between blades as 105°/ 105°/150° for lower left/lower right/upper arms, respectively that reach 15mm in height and 14.8 mm in width. A frame was specifically designed to measure the contact force using force sensing resistors during blade expansion. The Tri-blade fixed system was embedded into a cement block to perform fatigue testing under 2000N pressure (5*106 cycles) for understanding the device lifetime limitation. The Tri-blade system was then inserted into porcine osteoporosis VCFs to examine the vertebral height restoration efficiency. RESULTS: The average maximum contact force for the top, bottom left and right blades were 299.0N, 283.5N and 279.3N, respectively with uniformly outward expansion forces. The fatigue test found that there were no obvious cracks or damage to the cement block. The porcine osteoporosis vertebral body at the anterior, middle, and posterior heights can be restored to 21.9%, 12.6% and 6.4%, respectively. CONCLUSIONS: This study developed a novel TIVAD with conical shape that can provide a more stable structure with sufficient/uniform expansion force, passing the fatigue test with bone cement and high effective in vertebral height restoration tests for porcine osteoporosis VCFs. CLINICAL SIGNIFICANCE: The new 3D Tri-blade TIVAD may offer a new treatment option for VCFs.

A parametric investigation on traditional and cortical bone trajectory screws for transpedicular fixation.

BACKGROUND: Many studies have been conducted to compare traditional trajectory (TT) and cortical bone trajectory (CBT) screws; however, how screw parameters affect the biomechanical properties of TT and CBT screws, and so their efficacy remains to be investigated. METHODS: A finite element model was used to simulate screws with different trajectories, diameters, and lengths. Responses for implant and tissues at the adjacent and fixed segments were used as the comparison indices. The contact lengths and spanning areas of the inserted screws were defined and compared across the varieties. RESULTS: The trajectory and diameter had a greater impact on the responses from the implant and tissues than the length. The CBT has shorter length than the TT; however, the contact length and supporting area of the CBT within the cortical bone were 19.6%. and 14.5% higher than those of the TT, respectively. Overall, the TT and CBT were equally effective at stabilizing the instrumented segment, except for bending and rotation. The CBT experienced less adjacent segment compensations than the TT. With the same diameter and length, the TT was considerably less stressed than the CBT, especially for flexion and extension. CONCLUSIONS: The CBT may provide less stress at adjacent segments compared with the TT. The CBT may provide more stiffer in osteoporotic segments than the TT due to greater contact with cortical bone and a wider supporting base between the paired screws. However, both entry point and insertion trajectory of the CBT should be carefully executed to avoid vertebral breach and ensure a stable cone-screw purchase.

Oblique lateral interbody fusion in heterogenous lumbar diseases: Anterolateral screw fixation vs. posterior percutaneous pedicle screw fixation - A single center experience.

Background: Oblique lateral interbody fusion (OLIF) is a type of minimally invasive lateral lumbar interbody fusion technique used for treating lumbar degenerative diseases. This study aimed to analyze the clinical and radiographic efficacy of OLIF with anterolateral screw fixation alone and OLIF requiring fixation with conventional posterior percutaneous pedicle screws for lumbar diseases. Methods: Medical records of consecutive patients admitted to Cheng-Hsin Hospital who received OLIF between January 2019 and December 2020 were retrospectively reviewed. Patients were divided into two groups by screw fixation: patients who received anterolateral screw fixation alone were defined as one-stage OLIF (n = 9) and patients who received fixation with conventional posterior percutaneous pedicle screw were defined as two-stage OLIF (n = 16). Patient clinical characteristics, medical history, intraoperative blood loss, length of hospital stay, peri-operative, and post-operative complications were evaluated in all patients. Results: During the study period, a total of 25 patients were successfully treated with OLIF (n = 9 one-stage; n = 16 two-stage). Two-stage OLIF was associated with longer operation times, longer hospital stays, shorter bed-rest time, and a greater likelihood of having a blood transfusion compared with the one-stage OLIF group. A higher proportion of grade I subsidence was observed at 6 months and 1 year after surgery in the two-stage group compared with the one-stage group. Post-operative complications included ileus, dystonia, and dystonia were higher in the two-stage OLIF group. Improvements in radiographic parameters were demonstrated after OLIF, and the improvements were comparable between one-stage and two-stage OLIF. Conclusions: One-stage OLIF is a feasible and efficacious treatment method for single- and multiple-level degenerative lumbar diseases. Additional clinical follow-up is necessary to confirm long-term outcomes.

Unusual Cerebral Aneurysm after Stereotactic Radiosurgery to Treat Trigeminal Neuralgia.

Stereotactic radiosurgery is a treatment option for trigeminal neuralgia. This procedure is minimally invasive, but tumor development and facial numbness have been reported. Here, we report an unusual presentation after stereotactic radiosurgery to treat trigeminal neuralgia. A 60-year-old man demonstrated typical signs for type 1 trigeminal nerve neuralgia and was treated with medication for 5 years. Owing to an intolerance to that medication, he received stereotactic radiosurgery with 66 Gy. During a 9-year follow-up exam, dizziness with a spinning sensation was reported and a right superior cerebellar thrombosed aneurysm was diagnosed. He received transarterial embolization with coiling of aneurysm and subsequently reported no complications on follow-up exams. Although stereotactic radiosurgery is a promising treatment for trigeminal neuralgia, aneurysm development may be considered a possible complication. Long-term follow-up care of these patients should be considered. To understand the relationship between radiosurgery and the potential development of a cerebral aneurysm, further research is needed.

Endoscopic transcanal transpetrosal approach to the petroclival region: a cadaveric study with comparison to the Kawase approach.

This study introduces expanded application of the endoscopic transcanal approach with anterior petrosectomy (ETAP) in reaching the petroclival region, which was compared through a quantitative analysis to the middle fossa transpetrosal-transtentorial approach (Kawase approach). Anatomical dissections were performed in five cadaveric heads. For each head, the ETAP was performed on one side with a detailed description of each step, while the Kawase approach was performed on the contralateral side. Quantitative measurements of the exposed area over the ventrolateral surface of the brainstem, and of the angles of attack to the posterior margin of the trigeminal nerve root entry zone (CN V-REZ) and porus acusticus internus (PAI) were obtained for statistical comparison. The ETAP provided significantly larger exposure over the ventrolateral surface of the pons (93.03 ± 21.87 mm2) than did the Kawase approach (34.57 ± 11.78 mm2). In contrast to the ETAP, the Kawase approach afforded greater angles of attack to the CN V-REZ and PAI in the vertical and horizontal planes. The ETAP is a feasible and minimally invasive procedure for accessing the petroclival region. In comparison to the Kawase approach, the ETAP allows for fully anterior petrosectomy and larger exposure over the ventrolateral surface of the brainstem without passing through the cranial nerves or requiring traction of the temporal lobe.

Quantitative comparison of endoscopically assisted endonasal, sublabial and transorbital transmaxillary approaches to the anterolateral skull base.

OBJECTIVES: The aim of this anatomical study is to make quantitative comparison among three endoscopic approaches, encompassing contralateral endonasal transseptal transmaxillary transpterygoid approach (contralateral EEA), endoscopic sublabial transmaxillary transalisphenoid (Caldwell-Luc) approach and endoscopic transorbital transmaxillary approach through inferior orbital fissure (ETOA), to the anterolateral skull base for assisting preoperative planning. DESIGN & PARTICIPANTS: Anatomical dissections were performed in four adult cadaveric heads bilaterally using three endoscopic transmaxillary approaches described above. SETTING: Skull Base Laboratory at the National Defense Medical Center. MAIN OUTCOME MEASURES: The area of exposure, angles of attack and depth of surgical corridor of each approach were measured and obtained for statistical comparison. RESULTS: The ETOA had significantly larger exposure over middle cranial fossa (731.40 ± 80.08 mm2 ) than contralateral EEA (266.60 ± 46.74 mm2 ) and Caldwell-Luc approach (468.40 ± 59.67 mm2 ). In comparison with contralateral EEA and Caldwell-Luc approach, the ETOA offered significantly greater angles of attack and shorter depth of surgical corridor (P < .05 for all comparisons). CONCLUSIONS: The ETOA is the superior choice for target lesion occupying multiple compartments with its epicentre located in the middle cranial fossa or superior portion of infratemporal fossa.

Association of early vertebroplasty with risk of hip replacement: A nationwide population-based cohort study in Taiwan.

Studies show that vertebral fractures could predict the risk of hip fractures. We aimed to evaluate the potential benefits of whether the timing of vertebroplasty (VP) for vertebral fracture associated with the risk of hip fracture for hip replacement.We identified 142,782 patients from the Taiwan National Health Insurance Database with thoracolumbar vertebral fracture (International Classification of Diseases, Ninth Revision, Clinical Modification:805.2-805.9) who were followed up from 2000 to 2013. These patients were divided into those who underwent VP (VP group) (International Classification of Diseases, Ninth Revision, Clinical Modification : 78.49) within 3 months and those who did not (non-VP group). After adjusting for the confounding factors, the Cox proportional hazards analysis was used to estimate the effect of early VP on reducing the risk of hip fracture. The difference in the risk of hip replacement, between the VP group and non-VP group was estimated using the Kaplan-Meier method with the log-rank test.In the 14-year follow-up, the cumulative incidence rate of hip replacement in the VP group was lower than that in the non-VP group (0.362% and 0.533%, respectively, long-rank P < .001). There was a significant difference between the 2 groups since the first-year follow-up.Our study showed that early VP performed to avoid progression of the kyphotic changes following thoracolumbar vertebral fracture may reduce the risk of hip fracture. These results, obtained from retrospective data, indicate that a prospective study is warranted.

Endoscopic transorbital approach to anterolateral skull base through inferior orbital fissure: a cadaveric study.

BACKGROUND: Endoscopic transorbital approach (eTOA) has been announced as an alternative minimally invasive surgery to skull base. Owing to the inferior orbital fissure (IOF) connecting the orbit with surrounding pterygopalatine fossa (PPF), infratemporal fossa (ITF), and temporal fossa, the idea of eTOA to anterolateral skull base through IOF is postulated. The aim of this study is to access its practical feasibility. METHODS: Anatomical dissections were performed in five human cadaveric heads (10 sides) using 0-degree and 30-degree endoscopes. A stepwise description of eTOA to anterolateral skull base through IOF was documented. The anterosuperior corner of the maxillary sinus in the horizontal plane of the upper edge of zygomatic arch was defined as reference point (RP). The distances between the RP to the foramen rotundum (FR), foramen ovale (FO), and Gasserian ganglion (GG) were measured. The exposed area of anterolateral skull base in the coronal plane of the posterior wall of the maxillary sinus was quantified. RESULTS: The surgical procedure consisted of six steps: (1) lateral canthotomy with cantholysis and preseptal lower eyelid approach with periorbita dissection; (2) drilling of the ocular surface of greater sphenoid wing and lateral orbital rim osteotomy; (3) entry into the maxillary sinus and exposure of PPF and ITF; (4) mobilization of infraorbital nerve with drilling of the infratemporal surface of the greater sphenoid wing and pterygoid process; (5) exposure of middle cranial fossa, Meckel's cave, and lateral wall of cavernous sinus; and (6) reconstruction of orbital floor and lateral orbital rim. The distances measured were as follows: RP-FR = 45.0 ± 1.9 mm, RP-FO = 55.7 ± 0.5 mm, and RP-GG = 61.0 ± 1.6 mm. In comparison with the horizontal portion of greater sphenoid wing, the superior and inferior axes of the exposed area were 22.3 ± 2.1 mm and 20.5 ± 1.8 mm, respectively. With reference to the FR, the medial and lateral axes of the exposed area were 11.6 ± 1.1 mm and 15.8 ± 1.6 mm, respectively. CONCLUSIONS: The eTOA through IOF can be used as a minimally invasive surgery to access whole anterolateral skull base. It provides a possible resolution to target lesion involving multiple compartments of anterolateral skull base.

Endoscopic transorbital transtentorial approach to middle incisural space: preclinical cadaveric study.

BACKGROUND: Endoscopic transorbital approach is a novel development of minimally invasive skull base surgery. Recently, anatomical studies have started to discuss the expanded utilization of endoscopic transorbital route for intracranial intradural lesions. The goal of this cadaveric study is to assess the feasibility of endoscopic transorbital transtentorial approach for exposure of middle incisural space. METHODS: Anatomical dissections were performed in four human cadaveric heads (8 sides) using 0- and 30-degree endoscopes. A stepwise description of endoscopic transorbital transtentorial approach to middle incisural space and related anatomy was provided. RESULTS: Orbital manipulation following superior eyelid crease incision with lateral canthotomy and cantholysis established space for bone drilling. Extradural stage consisted of extensive drilling of orbital roof of frontal bone, lessor, and greater wings of sphenoid bone. Intradural stage was composed of dissection of sphenoidal compartment of Sylvian fissure, lateral mobilization of mesial temporal lobe, and penetration of tentorium. A cross-shaped incision of tentorium provided direct visualization of crural cistern with anterolateral aspect of cerebral peduncle and upper pons. Interpeduncular cistern, prepontine cistern, and anterior portions of ambient and cerebellopontine cisterns were exposed by 30-degree endoscope. CONCLUSION: The endoscopic transorbital transtentorial approach can be used as a minimally invasive surgery for exposure of middle incisural space. Extensive drilling of sphenoid wing and lateral mobilization of mesial temporal lobe are the main determinants of successful dissection. Further studies are needed to confirm the clinical feasibility of this novel approach.

Impact of global spine balance and cervical regional alignment on determination of postoperative cervical alignment after laminoplasty.

The aim of this study is to analyze the combined impact of preoperative T1 slope (T1S) and C2-C7 sagittal vertical axis (C2-C7 SVA) on determination of cervical alignment after laminoplasty.Forty patients undergoing laminoplasty for cervical spondylotic myelopathy (CSM) with more than 2 years follow-up were enrolled. Three parameters, including cervical lordosis, T1S, and C2-C7 SVA, were measured by preoperative and postoperative radiographs. Receiver operating characteristics (ROC) curve analysis was used to determine the optimal cut-off values of preoperative T1S and C2-C7 SVA for predicting postoperative loss of cervical lordosis. Patients were classified into 4 categories based on cut-off values of preoperative T1S and C2-C7 SVA. The primary outcome was postoperative C2-C7 SVA. Change in radiographic parameters between 4 groups were compared and analyzed.Optimal cut-off values for predicting loss of cervical lordosis were T1S of 20 degrees and C2-C7 SVA of 22 mm. Patients with small C2-C7 SVA, no matter what the value of T1S, got slight loss of cervical lordosis and increase in C2-C7 SVA. Patients with low T1S and large SVA (T1 ≤20° and SVA >22 mm) got postoperative correction of kyphosis and decrease of C2-C7 SVA. However, patients with high T1S and large SVA (T1 >20° and SVA >22 mm) got mean postoperative C2-C7 SVA value of 37.06 mm, close to the threshold value of 40 mm.Determination of cervical alignment after laminoplasty relies on the equilibrium between destruction of cervical structure, kyphotic force, and adaptive compensation of whole spine, lordotic force. Lower T1S means bigger compensatory ability to adjust different severity of cervical sagittal malalignment, and vice versa.

Preoperative grading of intracranial meningioma by magnetic resonance spectroscopy (1H-MRS).

Although proton magnetic resonance spectroscopy (1H-MRS) is a common method for the evaluation of intracranial meningiomas, controversy exists regarding which parameter of 1H-MRS best predicts the histopathological grade of an intracranial meningioma. In this study, we evaluated the results of pre-operative 1H-MRS to identify predictive factors for high-grade intracranial meningioma. Thirteen patients with World Health Organization (WHO) grade II-III meningioma (confirmed by pathology) were defined as high-grade; twenty-two patients with WHO grade I meningioma were defined as low-grade. All patients were evaluated by 1H-MRS before surgery. The relationships between the ratios of metabolites (N-acetylaspartate [NAA], creatine [Cr], and choline [Cho]) and the diagnosis of high-grade meningioma were analyzed. According to Mann-Whitney U test analysis, the Cho/NAA ratio in cases of high-grade meningioma was significantly higher than in cases of low-grade meningioma (6.34 ± 7.90 vs. 1.58 ± 0.77, p<0.05); however, there were no differences in age, Cho/Cr, or NAA/Cr. According to conditional inference tree analysis, the optimal cut-off point for the Cho/NAA ration between high-grade and low-grade meningioma was 2.409 (sensitivity = 61.54%; specificity = 86.36%). This analysis of pre-operative 1H-MRS metabolite ratio demonstrated that the Cho/NAA ratio may provide a simple and practical predictive value for high-grade intracranial meningiomas, and may aid neurosurgeons in efforts to design an appropriate surgical plan and treatment strategy before surgery.

The Efficacy of Therapeutic Plasma Exchange in Antiphospholipid Antibody-positive Patients With Spontaneous Intracerebral Hemorrhage and High D-dimer Levels.

OBJECTIVE: We investigated the efficacy of plasma exchange (PE) in antiphospholipid antibody (aPL)-positive patients with a spontaneous intracerebral hemorrhage (ICH) and high D-dimer levels. MATERIALS AND METHODS: From May 2013 to May 2016, we evaluated 32 patients who were below the age of 50 and presented with spontaneous ICH. Five patients were positive for aPL antibody and 3 had a higher level of D-dimer. These 3 patients underwent 5 sessions of PE using fresh frozen plasma as replacement fluid. We analyzed the days postadmission until PE-start, the days of intensive care unit (ICU) hospitalization, D-dimer series, Glasgow Coma Scale (GCS) scores, and modified Rankin scale (mRS) scores. D-dimer levels and GCS scores were recorded at both pre-PE and post-PE stages. The mRS scores were recorded at pre-PE stage and 3 months post-PE. RESULTS: The mean postadmission period until PE-start was 8.33 days. The mean ICU hospitalization was 17.33 days. The D-dimer level pre-PE ranged from 2.34 to 5.44 mg/L fibrinogen equivalent unit (FEU). The D-dimer level post-PE ranged from 1.05 to 3.30 mg/L FEU. The amount of decline of the D-dimer level between pre-PE and post-PE ranged from 0.65 to 2.14 mg/L FEU. The GCS score pre-PE was between 7 and 8. The highest post-PE GCS score was 14. The improved GCS scores post-PE ranged from 3 to 6. The improved mRS scores of 3 months post-PE ranged from 3 to 4. CONCLUSIONS: The concurrent presence of positive aPL and a higher D-dimer level may worsen the neurological outcome of patients with a spontaneous ICH. Aggressive PE is effective for the treatment of such patients, decreasing the extent of the ICU hospitalization.

Analysis of volumetric response of pituitary adenomas receiving adjuvant CyberKnife stereotactic radiosurgery with the application of an exponential fitting model.

Tumor control rates of pituitary adenomas (PAs) receiving adjuvant CyberKnife stereotactic radiosurgery (CK SRS) are high. However, there is currently no uniform way to estimate the time course of the disease. The aim of this study was to analyze the volumetric responses of PAs after CK SRS and investigate the application of an exponential decay model in calculating an accurate time course and estimation of the eventual outcome.A retrospective review of 34 patients with PAs who received adjuvant CK SRS between 2006 and 2013 was performed. Tumor volume was calculated using the planimetric method. The percent change in tumor volume and tumor volume rate of change were compared at median 4-, 10-, 20-, and 36-month intervals. Tumor responses were classified as: progression for >15% volume increase, regression for ≤15% decrease, and stabilization for ±15% of the baseline volume at the time of last follow-up. For each patient, the volumetric change versus time was fitted with an exponential model.The overall tumor control rate was 94.1% in the 36-month (range 18-87 months) follow-up period (mean volume change of -43.3%). Volume regression (mean decrease of -50.5%) was demonstrated in 27 (79%) patients, tumor stabilization (mean change of -3.7%) in 5 (15%) patients, and tumor progression (mean increase of 28.1%) in 2 (6%) patients (P = 0.001). Tumors that eventually regressed or stabilized had a temporary volume increase of 1.07% and 41.5% at 4 months after CK SRS, respectively (P = 0.017). The tumor volume estimated using the exponential fitting equation demonstrated high positive correlation with the actual volume calculated by magnetic resonance imaging (MRI) as tested by Pearson correlation coefficient (0.9).Transient progression of PAs post-CK SRS was seen in 62.5% of the patients receiving CK SRS, and it was not predictive of eventual volume regression or progression. A three-point exponential model is of potential predictive value according to relative distribution. An exponential decay model can be used to calculate the time course of tumors that are ultimately controlled.

Quantitative analysis of anatomical relationship between cavernous segment internal carotid artery and pituitary macroadenoma.

Cavernous segment internal carotid artery (CSICA) injury during endoscopic transsphenoidal surgery for pituitary tumor is rare but fatal. The aim of this study is to investigate anatomical relationship between pituitary macroadenoma and corresponding CSICA using quantitative means with a sense to improve safety of surgery.In this retrospective study, a total of 98 patients with nonfunctioning pituitary macroadenomas undergoing endoscopic transsphenoidal surgeries were enrolled from 2005 to 2014. Intercarotid distances between bilateral CSICAs were measured in the 4 coronal levels, namely optic strut, convexity of carotid prominence, median sella turcica, and dorsum sellae. Parasellar extension was graded and recorded by Knosp-Steiner classification.Our findings indicated a linear relationship between size of pituitary macroadenoma and intercarotid distance over CSICA. The correlation was absent in pituitary macroadenoma with Knosp-Steiner grade 4 parasellar extension.Bigger pituitary macroadenoma makes more lateral deviation of CSICA. While facing larger tumor, sufficient bony graft is indicated for increasing surgical field, working area and operative safety.

Hybrid Strategy of Two-Level Cervical Artificial Disc and Intervertebral Cage: Biomechanical Effects on Tissues and Implants.

This numerical study aimed to evaluate tissue and implant responses to the hybrid surgery (HS) of cervical artificial disc replacement (C-ADR) and anterior cervical discectomy and fusion (ACDF).Four hybrid strategies of two-level C-ADR and ACDF were compared in terms of adjacent segment degeneration (ASD) and implant failure.The rotary C-ADR and semirigid ACDF have been extensively used in the multilevel treatment of cervical instability and degeneration, but the constrained mobility at the ACDF segments can induce postoperative ASD problems. Hybrid surgery of C-ADR and ACDF has been an alternative to provide the optimal tradeoff between surgical cost and ASD problems. The biomechanical effects of hybrid strategies warrant thorough investigation for the two-level instrumentation.Based on computed tomography imaging, a nonlinear C2-C7 model was developed and validated by cadaveric and numerical data. Four strategies of inserting the C-ADR and ACDF into the C4-C6 segments were systematically arranged as PP (2 peek cages), AA (2 artificial discs), PA, and AP. The biomechanical behavior of these 4 strategies was evaluated in terms of motion and stresses of discs, facet forces, stresses of C-ADR and ACDF, and C-ADR motion.The constrained mobility of the ACDF segment worsened the kinematic and mechanical demands of the adjacent segments and artificial discs. The C-ADR articulation provided higher mobility than the replaced disc of the intact construct, making it an effective buffer to accommodate the compensated mobility and load from the ACDF segment. Consequently, the ASD progression of the AA construct was most restricted, followed by the PA, AP, and PP construct.The PA strategy is a tradeoff to preserve mobility and reduce cost. The C-ADR of the PA construct preserves the mobility of the C5/C6 segment and shares the transferred motion and loads of the fused C4/C5 segment. The PA construct shows optimal biomechanical results for minimizing ASD and implant failure, whereas the AP strategy is only recommended when cranial degeneration is the major concern.

Biomechanical effects of cage positions and facet fixation on initial stability of the anterior lumbar interbody fusion motion segment.

STUDY DESIGN: An in vitro biomechanical study using porcine lumbar segments as specimens. OBJECTIVE: To evaluate the effects of interbody cage support and endplate strength on the stability of instrumented segments. SUMMARY OF BACKGROUND DATA: The anterior lumbar interbody fusion (ALIF) cage is widely used to restore disc height and support the anterior column. Transpedicle or posterior spinal fusion or facet screw fixation (FSF) can improve the stability of the vertebra-instrumented segments. The cage position can affect the anterior support and initial stability of the ALIF region, but there is no consistent data on its biomechanical effects on ALIF and ALIF/FSF segments. METHODS: Nine variations of 3 instrumentation modes (intact, ALIF, ALIF/FSF) and 3 cage positions (type I, anterolateral; type II, mediolateral; and type III, posteromedial) are tested under 5 lumbar motions. The range of motion and axial displacement are used as comparison indices for the different variations. RESULTS: The cage placement serves as support for the intervertebral loads while the posterior fixation behaves as lever to further enhance the anterior support. At the endplate-cage interfaces, the endplate strength directly affects the cage subsidence. Type III exhibits higher stability for standing due to the greater strength of the endplate in the posterior region. Otherwise, type I consistently has higher stability for all other types of motion. CONCLUSION: The initial stability of the ALIF region is affected by the moment arm and the mechanical strength of the engaged endplates. Type I has greater moment arm and provides more efficient support to the instrumented segments. Endplate strength provides an ability to withstand lumbar loads and suppress the cage subsidence. Bone quality at the endplate-cage interfaces must therefore be cautiously evaluated preoperatively. LEVEL OF EVIDENCE: N/A.

Risks of subsequent epilepsy among patients with hypertensive encephalopathy: a nationwide population-based study.

BACKGROUND: To determine whether the diagnosis of hypertensive encephalopathy (HE) is linked to an increased risk of subsequent epilepsy by using a nationwide population-based retrospective study. METHODS: Our study featured a study cohort and a comparison cohort. The study cohort consisted of all patients with newly diagnosed HE between 1997 and 2010, compiled from universal insurance claims data on patients with hypertension taken from the National Health Insurance Research Database. The comparison cohort comprised the remaining hypertensive patients without encephalopathy. The follow-up period was terminated following the development of epilepsy, death, withdrawal from the National Health Insurance system, or the end of 2010. We determined the cumulative incidences and hazard ratios (HRs) of epilepsy development. RESULTS: The incidence of subsequent epilepsy was 2.25-fold higher in the patients with HE than in comparisons (4.17 vs. 1.85 per 1000 person-years), with an adjusted HR of 2.06 (95% CI=1.66-2.56) in the multivariable Cox proportional-hazards regression analysis. The incidence of epilepsy was higher in men, younger patients with HE, and those with brain disorders. CONCLUSIONS: We found that, in Taiwan, patients with HE are at an increased risk of subsequent epilepsy. Physicians should be aware of HE's link to epilepsy when assessing patients with HE.