Hook Design Research Articles

A topology optimization design of a crane hook

The goal of this research was to demonstrate the effectiveness of optimization techniques and test the possibility of using ABS plastic to optimize the existing crane hooks that use these techniques. Based on the optimization results, verification of the modified hook, and structural stability, this optimization reduces the weight of the crane hook while maintaining durability. This study utilized 3D modeling software to optimize the design of an existing hook, ensuring both sufficient strength and weight reduction. The research analyzes the results, concentrating on the stress that falls within the material strength limit. The research begins by utilizing a maximum of 1 kg of ABS plastic and a 5 kg liftable load. Using topology techniques, the study proposed five models that meet technical requirements. As a result, the proposed structure is highly economical and optimized in terms of materials and time, while still ensuring working performance. This work utilizes 3D modeling software for optimization design. It was effective to combine 3D printing manufacturing technology with size considerations. This article serves as a reference for future research and hook design.

МЕТОДИЧЕСКИЕ РЕКОМЕНДАЦИИ ПО ТОПОЛОГИЧЕСКОЙ ОПТИМИЗАЦИИ СИЛОВЫХ КОНСТРУКЦИЙ С ПРИМЕНЕНИЕМ СРЕДСТВ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Methodological recommendations are proposed for the development of the process of topological optimization of load carrying structures adapted for the use of additive technologies. The stage of postprocessing of the polygonal geometry of the part generated as a result of optimization is considered in detail. The validation stage is included in the process of topological optimization by comparing the calculated and experimental data to assess the operability (strength) of the optimized structure. For the option of manufacturing load carrying structures by 3D printing, it is planned to conduct studies of the mechanical properties of the material obtained on a 3D printer, taking into account the printing settings and the orientation of the material layers relative to the applied load during testing. An example of approbation of the proposed methodological recommendations is given on the example of a load carrying hook included in the design of a wheeled transport anti-ram device. The optimization was performed in the SolidThinking Inspire software environment (Altair Engineering, USA). The results of the calculated and experimental determination of the destructive load are presented for the initial and optimized hook design. For the experiment, the hooks were made of ABS plastic using FDM technology. Finite element models of hooks were developed in the ANSYS Workbench software package (ANSYS, USA). Assignment of material properties, boundary conditions and applied load is performed in the LS-PrePost application, calculation in the LS-DYNA solver (ANSYS, USA). The calculated and experimental efficiency estimates were 44.4 and 57.8 %, i.e. their difference is within 13.4 %. The zones and the nature of the destruction identified by calculation and experimentally completely coincide. The results obtained confirm the correctness of the proposed methodological recommendations, the selected modeling approaches and the determination of the properties of the material of the structure manufactured by 3D printing.

Investigating weighted fishing hooks for seabird bycatch mitigation

Fisheries bycatch threatens the viability of some seabird populations and reduces fishing efficiency. Albatross bycatch in a US North Pacific tuna longline fishery has increased over the past decade and now exceeds 1000 annual captures. Seabirds interacting with this fishery reach hooks at depths up to 1 m. A branchline weight’s mass and distance from the hook affect seabird catch rates. We conducted experimental fishing to compare the commercial viability of a weighted hook relative to conventional gear with weights attached 0.75 m from the hook. We used a Bayesian random effects meta-analytic regression modelling approach to estimate pooled expected species-specific log relative risk of capture on conventional versus experimental gear. There was a significant 53% (95% HDI: − 75 to − 25%) decrease in retained species’ catch rates on experimental hooks, indicating an unacceptable economic cost, and no significant effect for discarded species. Using a Bayesian general linear mixed regression modelling approach, experimental hooks sank to 85 cm ca. 1.4 times (95% HDI: 1.37–1.48) faster than control hooks. Given their potential to reduce seabird catch rates, eliminate safety risks from bite-offs and facilitate robust compliance monitoring, it is a priority to find a weighted hook design with acceptable catch rates.

Multidisciplinary design optimization in design for additive manufacturing

ABSTRACT Design for additive manufacturing (AM) involves decision making in various design domains, including product design, material selection, and process planning. In practice, engineers typically adopt a sequential design process to optimize these design domains in consecutive order. However, coupling factors, e.g. shared variables, related constraints, and conflicting objectives, are not sufficiently considered within the sequential design process, resulting in an inefficient workflow and suboptimal design solutions. To address the above issues, this paper proposes a multidisciplinary design optimization framework to simultaneously optimize different domains, which enables rapid exploration and complete exploitation of the AM design space under complex constraints. More specifically, the proposed framework is based on the concurrent optimization method, which coordinates the optimization of different design domains by allowing an automated exchange of design information. Also, the framework utilizes the surrogate modeling approach to approximate high-fidelity simulations for facilitating the iterative process. The effectiveness of the proposed framework is validated with two examples, a plate with a hole design and a hook design, which involve multiple design objectives from both process and structure domains, i.e. the print time, print area, strain energy, and maximum von Mises stress.

Bungee cord related ocular trauma: An avoidable cause of ocular morbidity

To study the mechanism and clinical features of ocular injury and its outcome associated with bungee cord related eye trauma. A retrospective review of medical records was performed at our tertiary care centre to identify patients presented with bungee cord related eye injury between March 2016 to February 2017. Data collected from medical records were age, sex, mechanism of injury, clinical features, therapeutic intervention, presenting visual acuity, final visual acuity and length of follow up. Total of thirteen patients with bungee cord related trauma were identified. Ten (77%) patients presented with closed globe injury and 3(23%) presented with open globe injury. All patients were male with mean age group of 30.15±7.38 years. Presenting visual acuity ranges from 6/12 to NPL. Only seven (54%) of patients were having final visual acuity of better than or equal to 6/18 in injured eye. Three patients (23.1%) with open globe injury had final visual acuity of counting fingers or worse. Main mechanism of injury being combination of blunt and high speed projectile injury due to slippage of metal or plastic hook while the cord is stretched. Trauma with bungee cord is usually affecting working age group male with injury resulting in loss of workable vision to loss of eye hence there is need of appropriate intervention like use of printed warning on package and modification of hook design to decrease the incidence of bungee cord related trauma.

Improving the safety of two-wheeler pillion rider by modified footrest joint

Two-wheeler with higher cc engine (180 or above) or even lower cc bikes which has aerodynamic elevation for pillion section has many problems regarding safety as well vehicle’s balance at high speed with pillion riders. Sudden braking, sudden acceleration or jumping of vehicle due to road variation can be dangerous for the pillion rider. Two-wheeler especially motorbikes and scooters have extra safety hook design extension for pillion rider to hold for safety. Sudden braking causes the bike to decelerate. the upper and the lower body of the rider riding the bike will also decelerate. For the pillion rider his/her upper body will not experience the same forces as experienced by the rider. Pillion rider lower body will decelerate with the bike as its contact with the foot of the pillion rider at footrest. To properly balance his/her upper body, the pillion rider has to hold the hook extension provided, or by holding a bike structure or by holding the bike rider. Similarly, in case of acceleration, pillion rider’s upper body tends to lean backward. To balance the force again the pillion rider has to hold the hook extension or bike rider or any other bike structure for support. In this work decided to rectify this by introducing a retrofitted joint to ensure extra safety with proper seating angle for pillion rider either during acceleration or deceleration. The modification will help to reduce the drag and lift force experienced by the pillion rider. To do this have considered "TVS Apache rtr 180" beast model to carry out our simulation to find out suitable characteristics for retrofitted joint. To carry out part designing using SOLIDWORKS software. To find out suitable characteristics for retrofitted point by simulation using MATLAB software.

Reflections on the influence of a synthesis of circle‐hook evidence on the angling community and conservation policy and practice

Abstract Understanding how different forms of environmental evidence inform the actions of different stakeholders is useful to improve how we share knowledge with knowledge users. Reflections on a literature review that we published in 2004 on circle hooks as a tool for fish conservation in the recreational fishing sector identified a number of ways in which that synthesis was influential. The article has had direct influence on policy and regulations in a number of countries, but there were even more examples of where the article has been used to influence voluntary guidelines. The article also contributed to formally defining circle hooks, which was necessary from a regulatory and enforcement perspective. The recreational fishing community has also embraced the work, with numerous angling articles based on the literature review appearing in the media and with some angler organizations pushing for the adoption of circle hooks. The fishing tackle industry has also responded with evidence that circle hooks are now more widely available in stores with more hook design options to suit diverse recreational fisheries. In addition, the influence of the article has extended beyond the recreational sector to commercial fishery issues that span several taxa. The research agenda from the article helped to direct research for more than a decade and has since been updated. Overall, this review was timely in that it provided various knowledge users with credible information synthesized in a thoughtful manner at a time when there was interest and need in exploring circle hooks as a tool to enhance the conservation of angled fish. Although this was not a systematic review, it still served as a form of evidence synthesis that gave diverse knowledge users information to guide them in their decisions.

Fate of yellowfin bream, Acanthopagrus australis after ingesting offset and/or inline barbed and barbless J and circle hooks

Offset J and circle hooks (nickel-plated carbon steel) were modified by removing the barb and bending the front parallel (‘inline’) with the shaft (circle only) to assess their utility for reducing mortality after ingestion by one of Australia’s most commonly angled species—yellowfin bream, Acanthropagrus australis—and for increasing hook ejection and corrosion. One-hundred-and-fifty-one fish were angled from large holding tanks using six passively fished hook treatments (barbless and barbed offset J hooks, and barbed and barbless offset and inline circle hooks), which were all similar in size. Thirty-five fish were mouth hooked (mostly on circle hooks), while the remaining 116 ingested hooks (n = 17–24 per treatment), had their lines cut and were released in pairs into 110-l tanks and monitored along with 14 control fish (not hooked) for six weeks. One control (7%) and 26 (22%) hook-ingested fish died (16 after a vital organ was perforated), with 23 mortalities occurring within ten days. Mortalities were not affected by hook design, but were significantly greater among fish with retained (19 of 35 individuals) rather than ejected (3/81) hooks. For the fish that ejected their hooks (70%), there were no differences in frequencies among the six treatments, but both ejected and retained barbless hooks corroded significantly faster (9 and 3×, respectively) than barbed designs. Irrespective of the treatment, on average after six weeks, surviving hook-ingested fish had a lower mean weight than controls, but those that ejected hooks had greater mean weights than those that retained hooks. Notwithstanding some loss of weight (as an index of health), the data support a supposition that many hook-ingested fish released with the line cut will eventually eject hooks of varying designs and survive.

The development of length-weight relationships for four pelagic fish species in the tropical Northwest Pacific Ocean

The present study provides the length–weight relationships (LWRs) for four pelagic fish species belonging to three families sampled with the longline gear from the tropical Northwest Pacific Ocean. The sampling was conducted by the Chinese longline observers from June 2011 to September 2012 and the fishes were captured by commercial pelagic longline fleets. The circular size 4.0 sun-C-37 Japanese tuna hook design was used for this fishing operation. Length–weight relationship for one of these species is unknown to Fish Base. Additionally, a new maximum length of one fish species is identified in the study.

Hook Design Loading by The Optimization Method With Weighted Factors Rating Method

This study aims for 2-ton lifting hooks designed to be the appropriate size for using. Both of the cost, the strength, the security and the aesthetics by using the optimal designed method together with the highest weight method. In this study is divided a methodology to design the hook into three-step processes. The first step is to create a lifting hook by ISO 7597: 2013 standard (Forged Steel Lifting Hooks with Latch, Grade 8) to be an initial lifting hook. Then analyzed the axial load of 2 tons by the finite element method. The second step is to analyze by the optimal design to design the lifting hook with the higher safety value by the weight of the lifting hook remains the same or difference. The third step is to analyze the results of the second step by deciding on proper lifting hooks by highest weight method for sizing of the lifting hook. The results of the analysis showed that lifting hook that has been designed by the method presented in this research can be able to reduce the production cost of the materials by 27.5 percents per piece with increasing the safety equal to 42.16 percents. It is good looking and can be easily produced by comparing with the initial lifting hooks.

Unraveling the Sperm Bauplan: Relationships Between Sperm Head Morphology and Sperm Function in Rodents.

Rodents have spermatozoa with features not seen in other species. Sperm heads in many rodent species bear one or more apical extensions known as "hooks." The process by which hooks have evolved, together with their adaptive significance, are still controversial issues. In order to improve our understanding of the biological meaning of these sperm head adaptations, we analyzed hook curvature angles, hook length, and overall hook shape in muroid rodents by using geometric morphometrics. We also searched for relationships between hook design and measurements of intermale competition to assess whether postcopulatory sexual selection was an important selective force driving changes in this sperm structure. Finally, we sought possible links between aspects of sperm hook design and sperm velocity as a measure of sperm performance. Results showed that one hook curvature angle is under strong selective pressure. Similarly, hook length appears to be strongly selected by sexual selection, with this selective force also exhibiting a stabilizing role reducing intermale variation in this trait. The adaptive significance of changes in hook structure was supported by the finding that there are strong and significant covariations between hook dimensions and shape and between hook design and sperm swimming velocity. Overall, this study strongly suggests that postcopulatory sexual selection has an important effect on the design of the sperm head that, in turn, is important for enhancing sperm velocity, a function crucial to reaching the vicinity of the female gamete and winning fertilizations under competitive situations.

Collaborative lesson hook design in science teacher education: advancing professional practice

This article documents the process of collaboratively developing lesson hook e-resources for science teachers to establish a community of inquiry and to strengthen the pedagogy of science teaching. The authors aim to illustrate how the development and application of strategic hooks can bridge situational interest and personal interest so that lessons may become more meaningful and enduring. Qualitative data from both teacher educators and pre-service teachers involved in the design process, participant research journals, and data from six focus group sessions, illustrate the systematic reflection involved in producing effective and transformative hooks to support teachers and promote deeper student engagement and learning. Key findings reveal a pedagogical model of hook design, the complex elemental make-up of a science hook, the value that this teaching tool adds to the science classroom, and finally, the beneficial outcomes of collaborative resource design between student and staff in pre-service teacher education programmes. These hook resources aim to move beyond simply capturing student attention towards voluntary self-engagement, and have significant potential to serve as a pedagogical tool for teacher educators, as well as pre-service, newly qualified, in service, out-of-field, and experienced science teachers, to increase student academic performance, third-level science enrolments, and science careers.

Improving the Tensile Strength of a Novel Double Hook Design Manufactured by Nanosilica Epoxy Reinforced Aramid/Carbon Composites

This paper presents the novel design of a double hook manufactured with advanced composite materials and nanomaterials. For the preparation of the composite materials an epoxy resin was used while the fiber reinforcement was in the form of hybrid aramid/carbon twill fabric. The nanoparticles were silica nanospheres dispersed in the epoxy matrix. The nanospheres were in the form of a colloidal silica-sol and they were added in the epoxy resin so to form a carefully prepared masterbatch. A series of tensile and fracture toughness tests were performed in order to evaluate the effect of the nanosilica concentration as well as the strength of the hybrid aramid/carbon composites. Upon the design and the manufacture of the innovative geometry of the double hook, comparative uniaxial tensile tests were performed. The results proved that the use of the silica nanoparticles significantly increase the strength of the hook, while affect considerably its tensile fracture behavior.

Application of probabilistic finite element analysis for crane hook design

PurposeThe purpose of this paper is to report a study in which the feasibility of conducting probabilistic finite element analysis (FEA) for crane hook design has been explored.Design/methodology/approachThis paper presents the results of probabilistic analysis, where in the input random variables are varied and corresponding variations in the output parameters were observed. In this study, material properties and load have been considered as random input variables and the maximum stress, maximum deflection variations were considered as output random variables.FindingsThe probability of occurrence of output variation and the sensitivity of output variables on the input variables are the important results generated from this analysis. By performing this probabilistic analysis, the random selection of factor of safety could be avoided.Research limitations/implicationsThe implementation study has been carried out for a single product.Practical implicationsThe usage of the approach will indicate the importance of probabilistic analysis in product design and development process. This process will enable the organization to compete in the global market.Originality/valueA case study has been reported to indicate the feasibility of performing probabilistic FEA for crane hook design. Hence, the contributions are original.

Evaluation of Hook and Bait Type on the Catch Rates in the Western North Atlantic Ocean Pelagic Longline Fishery

Research was conducted in 2002 and 2003 by noaa's national Marine fisheries service, southeast fisheries science center, to investigate changes in hook design and bait type to reduce the bycatch of sea turtles on pelagic longlines in the western north atlantic ocean. The effectiveness of 18/0-20/0 circle hooks and 10/0 Japanese tuna hooks with squid (Illex spp.) and mackerel bait (Scomber scombrus linnaeus, 1758) was evaluated against the industry standard 9/0 J-hooks with squid bait with respect to reducing sea turtle and shark interactions while maintaining swordfish (Xiphias gladius linnaeus, 1758) and tuna (Thunnus spp.) catch rates. In total, 973,734 hooks were deployed during the study. Individually, circle hooks and mackerel bait significantly reduced both loggerhead [Caretta caretta (linnaeus, 1758)] and leatherback [Dermochelys coriacea (vandelli, 1761)] sea turtle bycatch. The combination of 18/0 circle hooks with mackerel bait was even more effective for loggerhead sea turtles and had a significant increase in swordfish catch by weight. The combination 18/0 circle hooks with squid bait resulted in a significant decrease in the swordfish catch and a significant increase in the catch rate of blue shark [Prionace glauca (linnaeus, 1758)] , bluefin tuna [Thunnus thynnus (linnaeus, 1758)], and albacore tuna [Thunnus alalunga (bonnaterre, 1788)]. With all hook types, mackerel bait resulted in a significant decrease in blue shark, bigeye tuna [Thunnus obesus (lowe, 1839)], and albacore tuna, but significantly increased the catch of porbeagle [Lamna nasus (bonnaterre, 1788)] and shortfin mako (Isurus oxyrinchus rafinesque, 1810).

Are circle hooks effective in reducing incidental captures of loggerhead sea turtles in a Mediterranean longline fishery?

Abstract A known fishing hot spot for loggerhead sea turtles (Caretta caretta) in the Mediterranean Sea is in the waters of the Strait of Sicily where interactions with fish hooks and branchlines are believed to be a major cause of mortality for sea turtles. Hooks with different shapes but a similar gape width (circle hook size 16/0 vs J hook size 2) were tested in order to determine the potential effectiveness of the hook design to both reduce sea turtle capture as well as to maintain acceptable levels of target species capture rates in a shallow‐set longline swordfish fishery in the Mediterranean. Seven experimental fishing trips, 30 000 hooks total, were conducted on a single commercial fishing vessel (18 m in length) in the Strait of Sicily during the months of July through October over a period of three years from 2005 to 2007. Circle and J hooks were alternated along the mainline. A total of 26 sea turtles were hooked, all immature‐size Caretta caretta. Turtles were caught at a statistically greater frequency on J hooks than on circle hooks. The capture rate, weight, and upper jaw fork length of the target species were not significantly different between the two types of hooks employed. Five sea turtles swallowed the hook and in all such cases these were J type. Circle hooks tended to be located externally and were more easily detected by fishermen, and could be removed with the correct dehooking action before returning the turtle to the sea. These findings suggest that 16/0 circle hooks can effectively reduce the incidental capture of immature loggerhead sea turtles in a Mediterranean swordfish longline fishery without affecting the catch size of the target species. Copyright © 2009 John Wiley & Sons, Ltd.

Influence of terminal rig configuration on the anatomical hooking location of line‐caught yellowfin bream, Acanthopagrus australis

Abstract Experiments were carried out to test the dependence of anatomical hooking location on terminal rig configuration, and identify strategies by which hook ingestion can be minimised to reduce post‐release mortality of angled yellowfin bream, Acanthopagrus australis (Günther). Eighty‐five anglers targeted yellowfin bream using different designs and sizes of circle and J hooks and recorded technical, environmental and biological data for each landed fish. Considerably fewer fish (16.6 and 8.5%, respectively) ingested hooks than those hooked in the mouth (82.1 and 88.6%), and a greater percentage of J hooks were ingested than circle hooks or a J hook modified with a 15‐mm horizontal bar. Irrespective of hook type, the rate of ingestion also declined with increasing hook weight and decreasing fish size. In cage experiments, significantly more hooks baited with natural soft baits (e.g. intestines and cephalopods) were ingested than those baited with artificial baits, crustaceans or teleosts, while in the field fewer hooks were ingested using artificial bait (e.g. bread and pellets) than terrestrial animals, teleosts, crustaceans, teleost or terrestrial animal intestines, cephalopods or polychaetes. Similarly, rigs with floats, short traces or a sinker only on the hook, along with angling in environments with at least some current reduced ingestion. Based on this study, anglers targeting yellowfin bream should be encouraged to use circle or modified J hooks and, regardless of the hook design, the largest hook size possible attached to short traces or a sinker only and hard baits.

Fishing methods to reduce sea turtle mortality associated with pelagic longlines

Changes in hook design and bait type were investigated as measures to reduce the bycatch of sea turtles on pelagic longlines in the western North Atlantic Ocean. Specifically, the effectiveness of 18/0 circle hooks and mackerel (Scomber scombrus) bait was evaluated with respect to reducing sea turtle interactions and maintaining swordfish (Xiphias gladius) and tuna (Thunnus spp.) catch rates. Individually, circle hooks and mackerel bait significantly reduced both loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtle bycatch. Circle hooks also significantly reduced the rate of hook ingestion by the loggerheads, potentially reducing postrelease mortality. The combination of circle hooks and mackerel bait was even more effective for loggerhead turtles and had no negative effect on swordfish catch. These modifications in fishing methods, in conjunction with tools developed to remove hooks and line from the turtles, significantly reduced the capture rate of sea turtles and potentially the post-hooking mortality of those that were caught and did not negatively impact the primary target species catch rate. In addition, these mitigation measures have the potential to reduce mortality of sea turtles and other bycatch species worldwide.

Safety of supplemental endplate screws in thoracic pedicle hook fixation.

The AO Universal Spine System thoracic pedicle hook design includes a fixation screw that passes obliquely through the inferior facet into the pedicle to engage in the posterior portion of the superior vertebral body endplate. This endplate screw provides additional purchase at the hook-bone interface. To determine the safety of this fixation system the authors reviewed the operative notes, radiographs, and outcomes of patients who underwent placement of endplate screws. Thirty-six patients (16 male and 20 female patients) who required posterior thoracic instrumentation for spinal deformity (11 cases), neoplasm (15 cases), and traumatic injury (10 cases) were included in this study. One hundred sixty-four endplate screws were placed (mean 4.3/patient) to augment pedicle hooks for posterior thoracic instrumentation. The number of instrumented levels ranged from seven to 16. The positions of the screws in relation to the pedicle, neural foramen, spinal canal, and endplate were evaluated by assessing plain radiographs and computerized tomography scans (10 cases). Eighty-two screws (56%) were in ideal position. Lateral pedicle wall perforation occurred with 51 screws (35%). Three screws violated the medial wall and nine screws violated the superior or inferior walls of the pedicle. There were no clinical sequelae associated with any of the malpositioned screws. Adequate follow-up radiographic data were not available in five patients. The mean follow-up duration was 19.8 months (range 3-61 months). Two patients required revision surgery at 3 months and 18 months, respectively, because of hook/endplate screw displacement. There was also one case of an endplate screw fracture without hook displacement that was discovered during subsequent revision surgery. The remainder of the endplate screws and associated pedicles hooks maintained their original positions. There was no case of spinal cord, nerve root, pulmonary, or vascular injury. The placement of supplemental endplate screws in conjunction with thoracic pedicle hooks can be conducted safely.

The USS Pedicle Hook System

The Universal Spine System (USS) pedicle hook design includes a fixation screw that passes obliquely in the anterocranial direction in the pedicle. The addition of the fixation screw was to address concerns with rotation of the hook and hook disengagement. This study was designed to evaluate the safety of the USS screw locked pedicle hook. Eleven cadaveric thoracic spines were instrumented posteriorly with USS pedicle hooks from T1 to T12. Spinal instrumentation was performed by a spinal surgeon experienced with the USS system. Spinal deformity was created prior to instrumentation, ranging from 0 to 55 degrees in the horizontal plane (rotation) and from 0 to 50 degrees in the frontal plane (scoliosis). Radiographs, computed tomography (CT), and segmental dissection were used for data acquisition. Morphometric CT analysis before instrumentation demonstrated that the transverse pedicular diameter was the smallest at T5 with a mean of 3.7 mm. The transverse pedicular angle (TPA) was found to always point toward the midline. The largest TPA was observed at T1 with a mean TPA of 28.4 degrees. The pedicle with the least angular deviation from the midline was T11 with a mean TPA of 7 degrees. Postinstrumentation CT analysis and segmental dissection revealed perforations of the pedicle cortex by the fixation screw in 15% of instrumented pedicles (26/172). There were 6 medial and 20 lateral perforations. Medial perforations occurred exclusively in the three most proximal spinal segments, whereas the lateral perforations occurred throughout the thoracic spine. The mean encroachment of the fixation screw was 1.67 mm medially and 1.95 mm laterally. This study demonstrates the variation in caliber and direction of the thoracic pedicles. Medial and lateral perforations of the pedicle can occur with the USS pedicle hook instrumented system.