Screw System Research Articles

Biomechanical Comparison of Double 2.3-mm Headless Cannulated Self-Compression Screws and Single 3.5-mm Cortical Screw in Lag Fashion in a Canine Sacroiliac Luxation Model: A Small Dog Cadaveric Study.

The aim of this study was to evaluate the feasibility of safe positioning of double 2.3-mm headless cannulated self-compression screws (HCS) in a small dog cadaveric sacroiliac luxation model and to compare the static rotational biomechanical properties of fixation repaired using two different screw systems with a minimally invasive osteosynthesis technique: double 2.3-mm HCS and a single 3.5-mm standard cortical screw placed in a lag fashion. A unilateral small dog sacroiliac luxation model was stabilized using double 2.3-mm HCS (n = 11) or a single 3.5-mm cortical screw (n = 11). Radiographic and computed tomography (CT) imaging analyses and biomechanical testing of rotational force on the sacroiliac joint of both fixations were performed. The maximum load at failure and failure modes of each fixation were recorded and compared. Fluoroscopically guided percutaneous application of double HCS was safe in a unilateral sacroiliac luxation model in small dogs without violation of the vertebral and ventral sacral foramen. Furthermore, resistance to rotational force applied on fixation of the sacroiliac joint repaired with double 2.3-mm HCS estimated by maximum failure load was significantly higher than that of a single 3.5-mm cortical screw (p < 0.001). Although this was an experimental cadaveric study, based on our results, the use of smaller double HCS may be beneficial as an alternative to the conventional single lag screw for stabilization of sacroiliac luxation in small dogs.

OSTEOSYNTHESIS OF FRACTURES NECK FEMUR: A SYSTEMATIC REVIEW

Introduction: US hip fractures exceed 250,000 each year. Femoral neck and intertrochanteric fractures are equally diagnosed. This number will double by 2050. Cannulated screws, hip screw systems, proximal femur plates, and cephalomedullary nails can treat femoral neck fractures. These procedures are evaluated for biomechanical stability. The aim: This article discusses osteosynthesis in patients with femoral neck fractures. Methods: By comparing itself to the standards set by the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020, this study was able to show that it met all of the requirements. So, the experts were able to make sure that the study was as up-to-date as it was possible to be. For this search approach, publications that came out between 2013 and 2023 were taken into account. Several different online reference sources, like Pubmed and SagePub, were used to do this. It was decided not to take into account review pieces, works that had already been published, or works that were only half done. Result: In the PubMed database, the results of our search brought up 123 articles, whereas the results of our search on SagePub brought up 72 articles. The results of the search conducted for the last year of 2013 yielded a total 75 articles for PubMed and 16 articles for SagePub. In the end, we compiled a total of 24 papers, 17 of which came from PubMed and seven of which came from SagePub. We included five research that met the criteria.

Biomechanical evaluation and optimal design of a pedicle screw with double bent rods internal fixation system based on PE-PLIF fusion

Problems, such as broken screws, broken rods, and cage subsidence after clinical spinal fusion surgery affect the success rate of fusion surgery and the fixation effect of fusion segments, and these problems still affect the treatment and postoperative recovery of patients. In this study, we used the biomechanical finite element analysis method to analyze and study the fixation effect of three kinds of spinal internal fixation systems on L4–L5 lumbar spine segments in percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF). The three different fixation systems compared in this study include bilateral pedicle screw fixation (M1); bilateral pedicle screw with cross-link fixation (M2); bilateral pedicle screws with double bent rods fixation (M3). The internal fixation systems with different structures were analyzed with the help of Hypermesh, and Abaqus. It was found that the internal fixation system with double bent rods reduced screw stresses by 23.8 and 22.2% in right and left axial rotation than the traditional bilateral pedicle screw system, while titanium rod stresses were reduced by 9.6, 3.7, 9.6, and 2.9% in flexion, left and right lateral bending, and right axial rotation, respectively, and L5 upper endplate stresses were reduced by 35.5, 18.9, 38.4, 10.2, and 48.3% in flexion, left and right lateral bending, and left and right axial rotation, respectively. The spinal range of motion (ROM) of the M3 internal fixation system was less than that of the M1 and M2 internal fixation systems in left lateral bending, left lateral rotation, and right axial rotation, and the intact vertebral ROM was reduced by 93.7, 94.9, and 90.9%, respectively. The double bent rod structure of the spinal internal fixation system has better biomechanical properties, which can effectively reduce the risk of screw breakage, loosening, cage subsidence, and endplate collapse after fusion surgery.

Biomechanical analysis of a novel screw system with a variable locking angle in mandible angle fractures.

Locking plates nowadays represent an important treatment in bone trauma and bone healing due to its strong biomechanical properties. The purpose of this study was to both computationally and experimentally validate a novel screw locking system by comparing it to another locking system from state-of-the-art and to apply it in an environment of a fractured mandible. FEA was used to test both systems prior to experimental tests. The systems were locked in the plate holes at 0°, 10°, 15°, and 20°. Cyclic bending tests and push-out tests were performed in order to determine the stiffness and push-out forces of both locking systems. Finally, newly designed locking system was implemented in mandibular angle fracture. Control locking system was biomechanically superior in push-out test, but with no greater significance. In contrast, the new locking system showed greater stiffness by 17.3% at the deflection angle of 20° in cyclic tests, with lower values for other deflection angles. Similar values were displayed in fractured mandible angle environment. Greater stiffness of the new locking system in cyclic loading tests, together with polyaxiallity of the new locking screw, could lead to easier application and improved biomechanical stability of the mandible angle fractures.

A locally modified phantom model for assessing the worst-case heating configuration of orthopedic implants under MRI.

This paper proposes a locally modified phantom model to numerically assess the worst-case configuration of orthopedic implants under magnetic resonance imaging (MRI). The proposed model is developed based on the standard American Society for Testing and Materials (ASTM) phantom and bone models with cancellous or cortical materials. Three orthopedic implant families, metallic rods, a nail and screw system, and a plate and screw system, are studied. The worst-case configurations of orthopedic implants are identified inside the proposed model and ASTM phantom. These worst-case heating configurations are then implanted in a human body model to evaluate the RF-induced heating in terms of peak SAR1g. For the orthopedic implants fully inside the bone, like the rod and the nail and screw systems, the peak SAR1g values of worst-case configurations obtained from the proposed phantom model are higher than those obtained inside the ASTM phantom. For the orthopedic implants that are mainly outside the bone, such as the plate and screw system, similar worst-case configurations lead to a negligible variation of peak SAR1g inside the human body model.Clinical Relevance- The new phantom model leads to more accurate predictions of the worst-case configuration of orthopedic implants for MR conditional labeling.

Femoral neck system vs. cannulated screws on treating femoral neck fracture: a meta-analysis and system review.

This meta-analysis aimed to compare the relative safety and efficacy of cannulated compression screw (CCS) and femoral neck system (FNS) in treating patients with femoral neck fractures and to provide evidence-based medical evidence for FNS in treating femoral neck fractures. PubMed, Embase, Cochrane, and China National Knowledge Infrastructure databases were searched to collect outcomes related to femoral neck fractures treated with FNS and CCS, including time to fracture healing, incidence of non-union, incidence of osteonecrosis of the femoral head, incidence of failure of internal fixation, rate of femoral neck shortening, Harris hip score, Barthel index, operative time, intraoperative blood loss, fluoroscopy frequency, and complications. A meta-analysis was performed using RevManv5.4 (The Cochrane Collaboration) and Stata v14.0 software. This analysis included 21 studies involving 1,347 patients. The results showed that FNS was superior to CCS in terms of fracture healing time [mean difference (MD) = -0.75, 95% CI = (-1.04, -0.46), P < 0.05], incidence of bone non-union [odds ratio (OR) = 0.53, 95% CI = (0.29, 0.98), P = 0.04], incidence of osteonecrosis of the femoral head [OR = 0.49, 95% CI = (0.28, 0.86), P = 0.01], incidence of internal fixation failure [OR = 0.30, 95% CI = (0.18, 0.52), P < 0.05], rate of femoral neck shortening [OR = 0.38, 95% CI = (0.27, 0.54), P > 0.05], Harris hip score [MD = 3.31, 95% CI = (1.99, 4.63), P < 0.001], Barthel index [MD = 4.31, 95% CI = (3.02, 5.61), P < 0.05], intraoperative bleeding [MD = 14.72, 95% CI = (8.52, 20.92), P < 0.05], fluoroscopy frequency [OR = 0.53, 95% CI = (0.29, 0.98), P = 0.04], and complications [OR = 0.31, 95% CI = (0.22, 0.45), P < 0.05]. The difference between FNS and CCS in operative time was not statistically significant [MD = -2.41, 95% CI = (-6.88, 2.05), P = 0.29]. FNS treatment of femoral neck fracture can shorten the fracture healing time; reduce the incidence and translucent rate of bone non-union, osteonecrosis of the femoral head, and internal fixation failure; reduce intraoperative blood loss and postoperative complications; and improve hip joint function and activity. We are confident in the findings that FNS, an effective and safe procedure for internal fixation of femoral neck fractures, is superior to CCS.

Comparison of bleeding during trochanteric fracture fixation with mini-invasive or conventional side plate fixation: A randomized controlled trial

BackgroundTrochanteric fractures are a public health issue due to the aging of the population. Treatment aims to reduce their related morbidity and mortality and to allow an early return to independence. Postoperative anemia is associated with poorer functional recovery and an increased mortality rate. The aim of this study was to assess whether minimally invasive side plate fixation (Minimal Invasive Screw System, MISS™) resulted in reduced perioperative bleeding compared with conventional fixation (Pertrochanteric Hip Screw, PHS™). HypothesisWe hypothesized that minimally invasive side plate fixation (MISS) would result in reduced perioperative bleeding compared with conventional fixation (PHS). Patients and methodsWe conducted an open randomized controlled trial with blinded assessment of the primary outcome. Inclusion criteria were patients aged over 65 years with isolated reducible trochanteric fracture. The 2 surgical implants were of the same shape, the only difference between them being the locking mode of the femoral neck screw on the plate of the MISS device, allowing a percutaneous approach. Primary outcome was perioperative bleeding evaluated with Mercuriali's formula. Secondary outcomes included operating time, scar length, length of hospital stay, radiological criteria such as quality of fracture reduction, implant positioning, bone healing, complications and functional recovery compared between the 2 groups. ResultsOne hundred and eight patients met the inclusion criteria and were randomized to receive either PHS (n=54) or MISS (n=54). Osteosynthesis with MISS significatively reduced perioperative bleeding (median 243mL, interquartile range [152–410] vs. 334mL [247–430] [p=0.0299]), operating time (65min [57–73] vs. 79min [66–89] [p=0.0002]) and scar length after 45 days (7cm [5–8] vs. 14cm [12–15] [p<0.0001]). There was no statistically significant difference between groups in postoperative complications, revision surgery or serious adverse events. ConclusionCompared with PHS, MISS reduced operating time, perioperative bleeding and scar length with no observed functional difference. Level of evidenceI.

Augmented Reality-Supported Rod Bending in Multilevel Spinal Fusion Using the ADVISE Software

One of the most common reasons for poor patient outcomes and revision surgery in spinal fusion is hardware failure. Screw loosening or pullout occurs in up to one-quarter of all cases. It is known that even small screw-rod misalignments can cause significant mechanical overloads during rod fixation, which can result in hardware failure. To address this crucial surgical step, a novel augmented reality-assisted software was developed to generate custom rod templates that are precisely adapted to the individual patient. The novel software, which runs on a tablet, is used in spinal fusion surgery and is based on the use of a specific pedicle screw system, in which the polyaxial screw heads are connected to detachable guides. These guides can be recognized by the tablet camera and a light detection and ranging scanner. This image information is processed to determine the spatial positions of the screw heads and to calculate an ideally fitting rod template. The calculated rod template is displayed in a 1-to-1 scale on the tablet screen. This template is used to cut and bend the rods of the pedicle screw system. Finally, the custom bent rod can be inserted into the screw heads without tension. The augmented reality-assisted software is intended to give surgeons access to patient-specific intraoperative real-time data, helping them in bending rods that are more precisely adapted to the individual patient compared with the freehand technique.

Effect of implant abutment screw materials and tightening protocols on reverse tightening values: An in vitro study

Statement of ProblemImplant abutment screw loosening is the most common prosthetic complication of implant-supported single crowns. However, few studies have objectively evaluated the effectiveness of different tightening protocols on reverse tightening values (RTVs). PurposeThe purpose of this in vitro study was to determine the optimal tightening protocol for implant abutment screws with different screw materials. Material and methodsSixty implants from 2 implant systems (Keystone and Nobel Biocare) with different definitive screw materials were selected. One group used diamond-like carbon (DLC) coated screws (DLC Group), and the other used titanium nitride (TiN) screws (TiN Group). Each group consisted of 30 implants. The implants in each group were distributed randomly into 3 subgroups (n=10). The implants from both manufacturers were mounted in resin blocks by following a clinical component connection protocol: a cover screw was placed, then an impression coping, and finally an original manufacturer prefabricated abutment. The abutment screws were tightened to the manufacturer’s recommended tightening value using 3 different protocols: tighten the screw once (1T); tighten the abutment screw to the recommended tightening value, wait 10 minutes, and then retighten (2T); and tighten the abutment screw to the recommended tightening value, countertighten, tighten, countertighten, and then tighten (3TC). RTVs were measured after 3 hours. The Shapiro-Wilk test was performed to test for normal distribution of the data. The Kruskal-Wallis test was applied to each system’s group that was not normally distributed (P<.05). Where differences existed, a post hoc analysis using the Dwass-Steel-Critchlow-Flinger (DSCF) pairwise comparisons test was conducted. ResultsNo significant differences were found among the 3 different tightening groups in the TiN group (P>.05). However, significant differences were found among the 3 different tightening protocols in the DLC group (P<.05). ConclusionsAbutment screw systems from different manufacturers behave differently with respect to how they are tightened. For the TiN screw group, statistically similar RTVs were found for the 3 tightening protocols. The most efficient tightening protocol for the DLC-coated screw was the 3TC-DLC.

Modeling and Experimental Validation of the Performance of Electromechanical Height Adjustment Vehicle Suspension with Eccentric Mounted Screw System

This paper describes the modeling and experimental validation of the performance of two height adjustment suspensions with concentrically and eccentrically mounted screws. In the former solution, an anti-rotation system is required for the generation of reaction torque on the power screw–nut mechanism. The anti-rotation represents the main drawback of such mechanisms. In contrast, the eccentric solution attempts to solve this problem by placing the screw–nut mechanism eccentrically with respect to the shock absorber tube axis. In this paper, the working principle of the eccentric solution is explained. Its performance is compared to the concentric counterpart through simulations and experiments. Although the efficiencies of eccentric and concentric systems are very similar at the power screw, overall efficiencies differ substantially. During lifting, average efficiencies are around 3.4% and 6.5% for concentric and eccentric systems, respectively. When lowering, these values are 6.2% and 26%. The higher overall efficiency of the eccentric screw system is attributed to the anti-rotation system and the balancing of the bending moment due to the offset application of the load. To yield a complete perspective on the eccentric mounted screw solution, four prototypes are installed and tested on a demo vehicle.

Surgical treatment of craniocervical instability: comparison of two constructs regarding clinical and radiological outcomes of 100 patients

PurposeThere is an increased demand for surgical solutions to treat craniocervical instability. This retrospective study demonstrates the clinical and radiological outcomes of unstable craniocervical junction treated with occipitocervical fusion.Material and methodsThe mean age of 52 females and 48 males was 56.89 years. The clinical and radiological outcomes were assessed, including NDI, VAS, ASIA score, imaging, complications and bony fusion in two used constructs: a modern occipital plate–rod–screw system (n = 59) and previous bilateral contoured titanium reconstruction plates–screws (n = 41).ResultsClinically and on imaging, patients presented with neck pain, myelopathy, radiculopathy, vascular symptoms and craniocervical instability. The mean follow-up was 6.47 years. A solid bony fusion was achieved in 93.81% of the patients. The NDI and the VAS improved significantly from 28.3 and 7.67 at the presentation to 16.2 and 3.47 at the final follow-up. The anterior and posterior atlantodental interval (AADI and PADI), the clivus canal angle (CCA), the occipitoaxial angle (OC2A) and the posterior occipitocervical angle (POCA) improved significantly. Six patients required early revision.ConclusionOccipitocervical fusion can yield excellent results regarding clinical improvement and long-term stability with a high fusion rate. Simple reconstruction plates, though more demanding surgically, achieve similar results. Preserving a neutral patient’s position for fixation avoids postoperative dysphagia and may help prevent adjacent segment disease development.

Clinical efficacy of femoral neck screw system combined with supported hollow screw in treatment of femoral neck fractures with posterometral comminution in young and middle-aged patients

Objective: To investigate the clinical efficacy of dynamic cross screw system (FNS) for femoral neck fractures in young and middle-aged patients with posterior medial comminution. Methods: A retrospective cohort study. Clinical data of 197 young and middle-aged patients with femoral neck fractures accompanied by posterior medial comminution treated with closed reduction FNS and internal fixation with anti-rotation cannulated screws in Beijing Luhe Hospital, Beijing Jishuitan Hospital and Beijing Tongren Hospital from October 2019 to October 2021 were analyzed retrospectively. According to different surgical methods, the patients were divided into two groups. There were 102 patients in the FNS group, included 55 males and 47 females with a mean age of (40.49±19.79) years; and there were 95 patients in the FNS plus anti-rotation hollow screw group (combined group), included 51 males and 44 females with an average age of (40.03±18.82) years. All patients were followed-up for at least 1 year after surgery. The general clinical data, surgical conditions and Harris score of the hip joint at the last follow-up of the two groups were compared. And the clinical efficacy of the two surgical schemes were evaluated and compared. After surgery, routine X-ray and CT examinations were performed to evaluate the fracture reduction and internal fixation, and the shortening of the femoral neck on the affected side was compared to that of healthy side according to the Zlowodzki method. Results: At the last follow-up, the incidence of fracture reduction loss, screw resection and coxa vara in the combined group were all significantly lower than those in the FNS group [10 (10.5%) vs 28 (27.4%), 1 (1.0%) vs 7 (6.8%) and 9 (9.4%) vs 21 (20.5%), respectively, all P<0.05]. The incidence of nonunion and necrosis of the femoral head in the combined group were both lower than those in the FNS group, but there was no significant difference between two groups (both P>0.05). The postoperative mild, moderate and severe femoral neck shortening in the combined group were all lower than those in the FNS group, and the difference were not statistically significant (all P>0.05). At the last follow-up, the Harris score in the combined group was 84.60±2.08, and it was higher than that in the FNS group (79.57±4.31), but the difference was not statistically significant (P=0.403). Conclusion: FNS plus supporting hollow screw has a good clinical effect on femoral neck fractures in young and middle-aged adults with posterior medial comminution.

Let's think beyond the pedicle: A biomechanical study of a new conceptual extra pedicular screw and hook construct

BackgroundTranspedicular screws have proven the test of time, yet they are not devoid of complications. Many newer techniques such as 2 D and 3D fluoroscopy,O arm Navigation assisted surgery, robotic assisted surgery have come into existence to the increase precision in pedicle screw insertion. But, complications do occur in their presence. We propose an Extra pedicular screw and hook system (EPSH) system with similar biomechanical property, better safety profile and short learning curve compared to traditional pedicle screw. PurposeTo Compare the pull out strength of Traditional Pedicle screw Vs Extra pedicular screw and hook system(EPSH). MethodsBiomechanical testing was conducted according ASTM F543 guidelines to compare the pull-out strength of EPSH based construct and traditional pedicle screw construct. Six saw bone samples in each group considered. Screw of 5.5 mm diameter and length of 35 mm was used in both the groups. Pull out strength assessed by giving 5 mm/min axial load. The axial load Vs displacement of the screw were recorded and plotted. The maximum load required for screw failure is noted in both the group. Statistical analysis was done. ResultsThe mean peak load of pedicle screw group was found to be 1670.9 ± 393.2 N with mean displacement at peak load was found to be 13.44 ± 1.7 mm and in EPSH group it was 1416.4 ± 341.4 N and 15.78 ± 3.9 mm respectively. A paired t-test showed no statistical difference(p < 0.05) between 2 groups. ConclusionEPSH has shown to have almost similar biomechanical property as that pedicle screw construct. With Addition of the hook, it provides an extra rotational stability as well. Being an extra-pedicular screw it has high safety profile and needs less expertise for insertion.

Technical Notes and Clinical Outcomes of Full-Endoscopic Interbody Fusion Via Transforaminal Approach for Hard Disc Herniations in Thoracolumbar Junction.

Obtaining sufficient decompression and solid fusion and avoiding approach-related injuries simultaneously are still challenging for the treatment of hard disc herniation in thoracolumbar junction. A combined full-endoscopic decompression and interbody fusion via a transforaminal approach was used to achieve this goal. The purpose of this study was to introduce the technical notes and clinical outcomes of this novel technique. Twenty segments of hard disc herniations in the thoracolumbar junction of 14 patients treated with full-endoscopic interbody fusion via the transforaminal approach between January 2018 and September 2021 were analyzed. The patients were an average age of 43.3 years. Full-endoscopic interbody fusion and discectomy via the transforaminal approach were performed under local anesthesia, followed by percutaneous pedicle screw system fixation under general anesthesia. Imaging, including magnetic resonance imaging (MRI), computed tomography (CT), and X-ray, was carried out. MRI was performed on the second day and 3 months postoperatively. CT was performed on the second day, 6 months, and 1 year (as needed) postoperatively. Back and radicular pain, neurological function, and thoracic spine function were scored using a visual analog scale, the Nurick scale, and modified Japanese Orthopaedic Association (mJOA) scale, and the Oswestry disability index at 1 week, 3 months, 6 months, and 1 year postoperatively. All the operations were successfully completed, and no intraoperative conversion of the surgical methods occurred. Postoperative thoracolumbar junction MRI and CT examinations of all the patients revealed a sufficiently decompressed spinal cord or cauda equina, without any residual compression. At the 1-year follow-up, all the surgical segments were fused. Back and radicular pain was relieved in all the patients, and neurological function was restored. The average recovery rate of the mJOA was 72.5%, including seven excellent, five good, and two fair cases. Although dural tears occurred in two cases during the operation, no cerebrospinal fluid leakage or pseudomeningocele occurred during follow-up. No other surgical complications were noted. A combined full-endoscopic decompression and interbody fusion via a transforaminal approach can achieve complete spinal canal decompression and solid interbody fusion with fewer approach-related injuries. It is a safe and effective minimally invasive spine surgery for treating hard disc herniation in the thoracolumbar junction.

Novel uniplanar pedicle screw systems applied to thoracolumbar fractures: a biomechanical study.

Objective: In this study, the advantages of the internal fixation configuration composed of uniplanar pedicle screws in the treatment of thoracolumbar fractures were verified by biomechanical experimental methods, which provided the basis for subsequent clinical experiments and clinical applications. Methods: A total of 24 fresh cadaveric spine specimens (T12-L2) were utilized to conduct biomechanical experiments. Two different internal fixation configurations, namely, the 6-screw configuration and the 4-screw/2-NIS (new intermediate screws) configuration, were tested using fixed-axis pedicle screws (FAPS), uniplanar pedicle screws (UPPS), and polyaxial pedicle screws (PAPS) respectively. The spine specimens were uniformly loaded with 8NM pure force couples in the directions of anteflexion, extension, left bending, right bending, left rotation, and right rotation, and the range of motion (ROM) of the T12-L1 and L1-L2 segments of the spine was measured and recorded to access biomechanical stability. Results: No structural damage such as ligament rupture or fracture occurred during all experimental tests. In the 6-screw configuration, the ROM of the specimens in the UPPS group was significantly better than that of the PAPS group but weaker than those of the FAPS group (p < 0.01). In the 4-screw/2-NIS configuration, the results were identical to the biomechanical test results for the 6-screw configuration (p < 0.01). Conclusion: Biomechanical test results show that the internal fixation configuration with UPPS can maintain the stability of the spine well, and the results are better than that of PAPS. UPPS has both the biomechanical advantages of FAPS and the superiority of easy operation of PAPS. We believe it is an optional internal fixation device for minimally invasive treatment of thoracolumbar fractures.

Analysis of the causes and clinical results of vertebral fracture during oblique lateral lumbar interbody fusion

To analyze the causes of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy, summarize the clinical results, and propose preventive measures. Retrospective analysis was made on the data of 8 cases of lumbar spondylopathy and vertebral fracture treated by oblique lateral interbody fusion in three medical centers from October 2014 to December 2018. All were female, aged from 50 to 81 years with an average of 66.4 years. Disease types included 1 case of lumbar degenerative disease, 3 cases of lumbar spinal stenosis, 2 cases of lumbar degenerative spondylolisthesis and 2 cases of lumbar degenerative scoliosis. Preoperative dual energy X-ray bone mineral density test showed that 2 cases had T-value >-1 SD, 2 cases had T-value -1 to -2.5 SD, and 4 cases had T-value <-2.5 SD. Single segment fusion was in 5 cases, two segment fusion in 1 case and three segment fusion in 2 cases. Four cases were treated with OLIF Stand-alone and 4 cases were treated with OLIF combined with posterior pedicle screw fixation. Postoperative imaging examination showed vertebral fracture, and all of them were single vertebral fracture. There were 2 cases of right lower edge fracture of upper vertebral body at fusion segment, 6 cases of lower vertebral body fracture at fusion segment, and 6 cases with endplate injury and fusion cage partially embedded in vertebral body. Three cases of OLIF Stand-alone were treated with pedicle screw fixation via posterior intermuscular approach, while one case of OLIF Stand-alone and four cases of OLIF combined with posterior pedicle screw fixation were not treated specially. The 5 cases of initial operation and 3 cases of reoperation did not show wound skin necrosis or wound infection. The follow-up time was from 12 to 48 months with an average of 22.8 months. Visual analogue scale (VAS) of low back pain was preoperative decreased from 4 to 8 points (averagely 6.3 points) and postoperative 1 to 3 points (averagely 1.7 points) at the final follow-up. Oswestry disability index (ODI) was preoperative 39.7% to 52.4% (averagely 40.2%), and postoperative 7.9% to 11.2% (averagely 9.5%) at the final follow-up. During the follow-up, there was no loosening or fracture of the pedicle screw system, and no lateral displacement of the fusion cage;however, the fusion cage at the vertebral fracture segment had obvious subsidence. The intervertebral space height of vertebral fracture segment was preoperaive 6.7 to 9.2 mm (averagely 8.1 mm), and postoperative 10.5 to 12.8 mm (averagely 11.2 mm). The improvement rate after operation was 37.98% compared to preoperative. The intervertebral space height at final follow-up was 8.4 to 10.9 mm (averagely 9.3 mm), and the loss rate was 16.71% compared with that after operation. At the final follow-up, interbody fusion was achieved in all cases except for one that could not be identified. The incidence of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy is lower, and there are many reasons for fracture, including preoperative bone loss or osteoporosis, endplate injury, irregular shape of endplate, excessive selection of fusion cage, and osteophyte hyperplasia at the affected segment. As long as vertebral fracture is found in time and handled properly, the prognosis is well. However, it still needs to strengthen prevention.

Fixation-induced surgical segment’s high stiffness and the damage of posterior structures together trigger a higher risk of adjacent segment disease in patients with lumbar interbody fusion operations

BackgroundAdjacent segment disease (ASD) is a commonly reported complication after lumbar interbody fusion (LIF); changes in the mechanical environment play an essential role in the generation of ASD. Traditionally, fixation-induced high stiffness in the surgical segment was the main reason for ASD. However, with more attention paid to the biomechanical significance of posterior bony and soft structures, surgeons hypothesize that this factor may also play an important role in ASD.MethodsOblique and posterior LIF operations have been simulated in this study. The stand-alone OLIF and OLIF fixed by bilateral pedicle screw (BPS) system have been simulated. The spinal process (the attachment point of cranial ligamentum complex) was excised in the PLIF model; the BPS system has also been used in the PLIF model. Stress values related to ASD have been computed under physiological body positions, including flexion, extension, bending, and axial rotations.ResultsCompared to the stand-alone OLIF model, the OLIF model with BPS fixation suffers higher stress values under extension body position. However, there are no apparent differences under other loading conditions. Moreover, significant increases in stress values can be recorded in flexion and extension loading conditions in the PLIF model with posterior structures damage.ConclusionsFixation-induced surgical segment’s high stiffness and the damage of posterior soft tissues together trigger a higher risk of ASD in patients with LIF operations. Optimizing BPS fixation methods and pedicle screw designs and reducing the range of posterior structures excision may be an effective method to reduce the risk of ASD.

Biomechanical analysis of a novel bone cement bridging screw system combined with percutaneous vertebroplasty for treating Kummell's disease.

Kummell's Disease (KD) was originally proposed by Dr. Hermann Kummell in 1891 as a type of delayed posttraumatic vertebral collapse, which is a clinical phenomenon. The purpose of this experiment is to compare the strength of bone cement and the novel bone cement bridging screw in the treatment of thoracolumbar Kummell disease (KD) with other treatment methods. Thirty sheep spine specimens were selected. T12 to L2 segments were selected, and a KD intravertebral vacuum cleft model was made at the L1 segment. According to the ways of cement filling, the specimens were divided into percutaneous vertebroplasty (PVP), PVP combined with unilateral percutaneous pediculoplasty (PPP), PVP combined with bilateral PPP, unilateral novel bone cement bridging screw system combined with PVP, and bilateral cement bridging screw system combined with PVP groups. There were two experiments: three-dimensional biomechanical strength test and axial compression test. In the three-dimensional biomechanical strength test, we measured the strength of bone cement in specimens under six motion states, including flexion, extension, left bending, right bending, and left and right axial rotations. In the axial compression test, we detected the maximum axial pressure that the bone cement could withstand when it was under pressure until the bone cement was displaced. The unilateral or bilateral novel bone cement bridging screw with PVP groups had the best strength under flexion, extension, left bending, right bending, and had better biomechanical strength, with a significant difference from the other three groups (p < 0.05). There was no significant difference between the unilateral or bilateral novel bone cement bridging screw with PVP groups (p > 0.05). Unilateral and bilateral novel bone cement bridging screw could achieve similar bone cement strength. Compared with the other three groups, the unilateral or bilateral novel bone cement bridging screw with PVP groups are higher 136.35%, 152.43%; 41.93%, 51.58%; 34.37%, 43.50% respectively. The bilateral novel bone cement bridging screw with PVP could bear the largest pressure under vertical force. To conclude, the novel bone cement bridging screw can increase the strength of bone cement and avoid the loosening and displacement of bone cement in the treatment of KD of the thoracolumbar spine.

Treatment of Trochanteric Hip Fractures with Cephalomedullary Nails: Single Head Screw vs. Dual Integrated Compression Screw Systems.

Extracapsular hip fractures are very common in the elderly. They are mainly treated surgically with an intramedullary nail. Nowadays, both endomedullary hip nails with single cephalic screw systems and interlocking double screw systems are available on the market. The latter are supposed to increase rotational stability and therefore decrease the risk of collapse and cut-out. A retrospective cohort study was carried out, in which 387 patients with extracapsular hip fracture undergoing internal fixation with an intramedullary nail were included to study the occurrence of complications and reoperations. Of the 387 patients, 69% received a single head screw nail and 31% received a dual integrated compression screw nail. The median follow-up was 1.1 years, and in that time, a total of 17 reoperations were performed (4.2%; 2.1% for single head screw nails vs. 8.7% for double head screws). According to the multivariate logistic regression model adjusted for age, sex and basicervical fracture, the adjusted hazard risk of reoperation required was 3.6 times greater when using double interlocking screw systems (p = 0.017). A propensity scores analysis confirmed this finding. In conclusion, despite the potential benefits of using two interlocking head screw systems and the increased risk of reoperation in our single center, we encourage to other researchers to explore this question in a wider multicenter study.

Lumbar Pedicle Morphometry of Dry Vertebral Columns in Relation to Transpedicular Fixation: A Cross-Sectional Study From Central India.

The lumbar vertebrae are the largest vertebrae of the vertebral column, which support the maximum body weight. There has been an increased focus on transpedicular spinal fixation for addressing various lumbar spine pathology. However, its safety and efficacy require precise knowledge of the lumbar pedicle anatomy. Mismatched size of screw and pedicle may lead to failure of instrumentation. It may result in cortex perforation or pedicle fracture and loosening of the pedicle screw. The oversizing of the pedicle screw can result in dural tears, leakage of the cerebrospinal fluid, and injuries to the nerve root. As the racial variations in the anatomy of a pedicle are well known, this study was performed to assess the morphological parameters of the lumbar vertebrae pedicles in the Central Indian population so that the appropriate sizes of pedicular implants can be selected. The present study was conducted at a tertiary-level hospital and medical college on dry lumbar vertebrae specimens available in the department of anatomy. The measurement of morphometric parameters of the lumbar vertebrae pedicles was performed in 20 dry lumbar specimens using vernier calipers and a standard goniometer. The morphometric parameters included in the study are pedicle transverse external diameter (pedicle width), pedicle sagittal external diameter (pedicle height), transverse angle of the pedicle, and sagittal angle of the pedicle.Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) system version 25 (Chicago, IL: SPSS Inc.). The broadest external transverse diameter was at the L5 level, with a mean of (17.54±1.6 mm) in the lumbar vertebrae. The broadest external sagittal pedicle diameter was at the L1 level (13.7±0.88 mm). The maximum transverse angle of the pedicle was at L5 with a mean of 25.39±3.10°. The maximum sagittal angle was at L1 with a mean of 5.44±0.71°. The increased concern regarding the internal fixation of the spine with pedicle screw systems created the need to have almost accurate anatomical knowledge of lumbar pedicles. Due to the dynamic nature of the lumbar spine and the body's load, maximum degeneration occurs at this spine segment, making it the most commonly operated region of the vertebral column. In our study, pedicle dimensions are comparable to populations of other Asian countries. However, the pedicle dimension of our population is lower than the White American population. This morphological variation of pedicle anatomy will help surgeons choose appropriate size screws and optimum angulations to insert the implant, decreasing complications.