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Objective: To reduce surgical exposure and improve accuracy, this study evaluated the anatomical distance parameter D (including D1, D2, and D3) of the lumbar isthmus for cortical bone screw insertion., Methods: A total of 25 structurally complete lumbar dry specimens were used for lumbar anatomy measurements. The six cadaver specimens were divided into upper and lower parts on the plane of the T11-T12 vertebrae, and we use the lower parts. Therefore, six lumbar wet specimens and another four complete lumbar dry specimens were selected. The lumbar isthmus tangent point was considered a coordinate origin, and the insertion point was determined through translating the distance of D1 value to the midline of the vertebral body horizontally and then vertically moved toward inferior board of the transverse process with the distance of D3 value., Results: In four dry and six wet intact lumbar specimens, cortical bone screws were placed according to the average value of the isthmus parameter D. A total of 100 trajectories were verified in specimens by X-ray and computed topography scan to evaluate the safety, accuracy, and feasibility of the surgical use of isthmus parameter D. Using this parameter, the rates of excellent screw placement were 95% (38/40) in four dry specimens and 88.7% (53/60) in six wet specimens., Conclusion: The isthmus parameter D is easier to use by the operator, which can improve surgical accuracy and reduce operation time., Level of Evidence: Level IV, prospective study.

The objective of this study was to evaluate the effect of bone-miniscrew contact percentage (BMC%) and bone quality and quantity on orthodontic miniscrew stability and the maximum insertion torque value (ITV). Orthodontic miniscrews of five different dimensions and several bovine iliac bone specimens were used in the evaluation. Miniscrews of each dimension group were inserted into 20 positions in bovine iliac bone specimens. The experiment was divided into three parts: (1) Bone quality and quantity were evaluated using cone-beam computed tomography (CBCT) and microcomputed tomography. (2) The 3D BMC% was calculated. (3) The ITVs during miniscrew insertion were recorded to evaluate the stability of the orthodontic miniscrews. The results indicated that longer and thicker miniscrews enabled higher ITVs. CBCT was used to accurately measure cortical bone thickness (r = 0.939, P < 0.05) and to predict the bone volume fraction of cancellous bone (r = 0.752, P < 0.05). BMC% was significantly influenced by miniscrew length. The contribution of cortical bone thickness to the ITV is greater than that of cancellous bone structure, and the contribution of cortical bone thickness to BMC% is greater than that of cancellous bone structure. Finally, the higher is BMC%, the greater is the ITV. This study concludes that use of CBCT may predict the mechanical stability of orthodontic miniscrews., (© 2022. The Author(s).)

Abstract: The cortical bone trajectory screws technique (CBTT) is a popular minimally invasive spine surgery. Few studies have reported long-term outcomes. We aimed to evaluate the complication profile and long-term follow-up results of patients with lumbar degenerative disease treated with the CBTT.This retrospective analysis included the first 40 consecutive patients that underwent the CBTT. The indication for surgery was critical stenosis of the intervertebral foramen, which required removal of the entire intervertebral joint, on at least 1 side, during decompression.The last follow-up showed minimal clinically important differences in the numerical rating scale of leg pain, the numerical rating scale of back pain, and the Oswestry Disability Index, in 97%, 95%, and 95% of patients, respectively. Thirty-nine patients completed long-term radiological follow-up. Computed tomography demonstrated solid bone union on 47 (92%) operated levels, collapsed union on 2 (4%) levels, nonunion on 1 (2%) level, and 1 (2%) patient was lost to follow-up. Seven patients experienced complications (4 hardware-related). Three patients required 4 revision surgeries.The CBTT effectively achieved spinal fusion; over 90% of patients achieved clinical improvement at a mean follow-up of 4.4 years (range: 3-5.75 years)., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

With the emerging concerns for more flexible and less stiff bridge constructs in the interest of stimulating bone healing, the technique of far cortical locking has been designed to reduce the stiffness of locked plating (LP) constructs while retaining construct strength. This study utilized simulation with diaphyseal bridge plating biomechanical models to investigate whether far cortical locking causes larger screw fracture risk than LP during rehabilitation. The fracture risk of the screws in the far cortical locking constructs increases in the non-osteoporotic and osteoporotic diaphysis compared with the screws in the LP constructs.

Objective: To determine the influence of a custom 3D-printed guide for placement of cortical bone screws in the equine navicular bone., Study Design: Ex vivo study., Sample Population: Eight pairs of normal adult equine forelimbs., Methods: A 3.5 × 55 mm cortical screw was placed in the longitudinal axis of each intact navicular bone. Screws were placed with a 3D-printed guide (3D) in one bone and with a traditional aiming device (AD) in the contralateral bone within each pair. Duration of surgery and the number of fluoroscopy images were compared between techniques. Screw placement was subjectively evaluated by gross examination and scored by three boarded veterinary surgeons., Results: The use of a 3D-printed guide reduced the duration of surgery by 6.6 min (±1.5 min) compared to traditional screw placement (20.7 min ± 4.8 min, p < .01). Fewer peri-operative fluoroscopic images were obtained when the 3D guide was used (18 images ± 2.6 images vs. 40 images ± 5.1, p < .01). No difference was detected in navicular screw placement., Conclusion: The use of a 3D guide decreased the time required to place screws and the number of intraoperative images taken without affecting screw placement in intact navicular bones., Clinical Relevance: 3D-printed guides can aid in the study, practice, and execution of surgical procedures reducing surgical time and radiation exposure throughout the operative period achieving similar results to those obtained with a conventional approach., (© 2021 American College of Veterinary Surgeons.)

The strength between the cortical screw and bone following an orthopaedic implant surgery is an important determinant for the success of osteosynthesis. An excessive axial cutting force during drilling produces microcracks in the bone surface, resulting in reduced strength between the screw and bone, resulting in loosening of implant. The present work, investigates the influence of drilling parameters on microcracks generated in the drilled surface and pull-out strength of screw fixed in cortical bone of human tibia. The holes were drilled by two different techniques: conventional surgical bone drilling (CSBD) and rotary ultrasonic bone drilling (RUBD), by a recently developed operation theatre (OT) compatible machine. Cutting force generated in drilling of human tibia using RUBD was 30-40% lesser than that of CSBD. Scanning electron microscopy (SEM) also revealed that RUBD produced significantly lesser and thinner microcracks than that of CSBD in human bones. Biomechanical pull-out test results showed that, the pull-out strength of screws inserted into drilled holes by RUBD was much higher (100-150%) than that of CSBD. A significant difference in pull-out strength (p < 0.05) between RUBD and CSBD was revealed by statistical analysis at 95% confidence interval.

Background: For posterior fixation of C2 vertebra (the axis), several fixation techniques such as pedicle screw, laminar screw, and pars screw have been reported. A pedicle screw (PS) is considered the strongest among the techniques, but certain situations make PS fixation impossible or difficult. These include patients with a narrow C2 pedicle or high-riding vertebral artery. We introduced an alternative screw technique for C2 that addressed the aforementioned problems with safely placing it, which we termed a cortical screw (CS) for C2., Methods: Among a total of 28 cases using C2 CS for high cervical spine surgery, 2 cases using C2 CS were described. One patient was a 76-year old woman with a gait disturbance and myelopathic symptoms and diagnosed with C1-C2 myelopathy and translational instability. The other case was 54-year old man with posterior neck pain after traffic accident and diagnosed with C1-C2 fracture-dislocation. We used the C2 CS as an alternative technique for high cervical spine surgery in these patients and describe the ideal entry point and trajectory., Results: A postoperative computed tomography scan confirmed proper positioning of the C1 posterior arch screw and C2 CS, with satisfactory reduction of the C2 dens and adequate restoration of the C1-C2 spinal canal. The patient experienced no screw-related postoperative complications, and postoperative 1-year computed tomography images showed that solid union and good alignment of C1-2 segment was achieved., Conclusions: C2 CS can be suitable alternative for C2 screw fixation technique in posterior high cervical spine fusion surgery., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Cortical bone trajectory (CBT) can facilitate both minimum invasiveness and strong screw fixation; however, ensuring the ideal cortical trajectory is challenging due to the narrow corridor, necessitating high-level surgical skill. A patient-specific template guide for CBT screw placement may be a promising solution to improve accuracy and safety. Little has been reported on the use of a CBT screw guide in clinical practice. The aim of the present study was to evaluate the accuracy of CBT screw placement using the template guide. This study was a retrospective clinical evaluation of prospectively collected patients. Forty-three consecutively enrolled patients who underwent posterior lumbar spinal fusion using the guide system were included. First, three-dimensional planning of CBT screw placement was performed using computer simulation software. The trajectory was directed in a more anterior position of the vertebral body, compared with the original CBT, and the standard size was set as 5-6 mm in diameter and 40-45 mm in length. Then, screw guides were created for each vertebra preoperatively and used. The safety and accuracy of a total of 198 inserted screws (L1 to L5) were analyzed using postoperative computed tomography by evaluation of pedicle perforation and measurement of screw deviations between the planned and actual screw positions. A total of 193 screws (97.5%) were placed completely inside the pedicle and there was no incidence of neurovascular injuries. The mean screw deviation from the planned trajectory on the coronal plane at the midpoint of the pedicle was 0.62 ± 0.42 mm, and the mean angular deviations in the sagittal and transverse planes were 1.68 ± 1.24° and 1.27 ± 0.77°, respectively. CBT screw placement using a patient-specific template guide was accurate enough for clinical application. This technique could be an effective solution to achieve both correct screw insertion and a reduction of complications.

Cortical Bone Trajectory screws allow a limited soft tissue dissection with mechanical properties comparable to traditional pedicle screws. However, clinical results are still reported on limited samples. The study aimed to evaluate perioperative and mid-term follow up outcomes, clinical results and complications in 238 consecutive patients underwent CBT fusion for degenerative lumbosacral disease. Pre- and intraoperative data, clinical outcomes and complications were collected. The patients were stratified in three groups. The original technique was performed in the first 43 cases without a preoperative CT scan planning. The second group includes the patients who underwent preoperative CT scan for entry point and screw trajectory planning (158 patients). Surgical procedures in the last group were performed with patient-matched 3D printed guide (37 patients). The accuracy in screws positioning was evaluated on postoperative CT scan. The mean follow-up was 32.3 months. Mean ODI and VAS index improved with statistical significance. Mean procedural time was 187, 142 and 124 min in the three subgroups. The total amount of recorded complications was 4.2% (16.3%, 3.8% and 0.0% respectively). Screws entirely within the cortex of the pedicle were 78.9%, 90.5% and 93.9% in the three groups. Fusion was obtained in 92.4% of cases. The CBT technique is a safe procedure, especially with an accurate preoperative CT scan-based planning. This seems more evident with the 3D template patient-matched guide. More studies are needed to directly compare traditional pedicle screws and CBT screws on long-term outcomes., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Cortical bone trajectory (CBT) screws are popular for spinal fixation, but their ideal diameter has not been determined. Studies using postoperative computed tomography (CT) have revealed ample bone marrow space around 5.5-mm screws, which are commonly used. However, evidence indicates that a larger screw diameter provides a greater fixation strength. This study aimed to develop a generalizable formula for computing the diameter of CBT screws that could be inserted safely for fixation of the lower lumbar spine., Methods: Records of 44 consecutive patients who had undergone posterior fusion with CBT screws for single-level degenerative lumbar spondylolisthesis were retrospectively reviewed. We estimated the maximum diameter for conventional pedicle screws by the minimum diameter of the pedicle using preoperative CT (PSD). We measured the minimum endosteal diameter of the pedicle on the reconstructed plane of the postoperative CT which passed through the cannula used for the screw and estimated the maximum diameter for the CBT screws that could be inserted within the bone marrow space of the pedicle (CBTD)., Results: Among the 176 pedicles measured, there were 151 (85.8%) with a PSD of 8.5 mm and 13, 7.5 mm. Because of a slight pedicle wall breach, 13 screws were excluded from the sample. There were 64 (39.3%) screws with a CBTD of 8.5 mm; 45, 7.5 mm; and 40, 6.5 mm. Of 163 screws, 156 (95.7%) had PSD minus CBTD ≤2 mm for each pedicle. PSD minus the minimum outer cortical diameter was ≤1 mm for each pedicle in 155 (95.1%) screws., Conclusion: Our results show that CBT screws with a diameter 1 mm smaller than the endosteal diameter of the pedicle were inserted safely., Study: Design: Clinical study., (Copyright © 2019 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)

Purpose: To compare the clinical efficacy and safety between cortical bone trajectory (CBT) and pedicle screw (PS) in posterior lumbar fusion surgery., Methods: Five electronic databases were used to identify relevant studies comparing the clinical efficacy and safety between CBT and PS. The main outcomes were postoperative fusion rates and complication (especially in superior facet joint violations, symptomatic ASD, wound infection, dural tear, screw malposition and hematoma). The secondary results included operation time, intraoperative blood loss, length of hospital stay, incision length, ODI, VAS, JOA score, JOA recovery rate, patients' satisfaction and health-related quality of life., Results: The outcomes showed that there was no significant difference in terms of fusion rate (p = 0.55), back and leg VAS score (p > 0.05), JOA score (p = 0.08) and incidence of reoperation (p = 0.07). However, CBT was superior to PS with Oswestry Disability Index (ODI) (p = 0.02), JOA recovery rate (p < 0.00001) and patients' satisfaction (p = 0.001). In addition, CBT was superior to PS with significantly lower incidence of superior facet joint violation and symptomatic ASD. However, there was no significant difference regarding wound infection (p > 0.05) and screw malposition (p > 0.05). CBT group required significant shorter operation time, less blood loss, shorter incision length and shorter length of hospital stay in comparison with PS group (p < 0.05)., Conclusions: Both CBT and PS achieve similar, fusion rate and revision surgery rate. Furthermore, CBT is superior to PS with lower incidence of complications, shorter operation time, less blood loss, shorter incision length and shorter length of hospital stay. These slides can be retrieved under Electronic Supplementary Material.

The transversal screw was introduced in order to overcome some disadvantages of the transocclusal screw. However, its mechanical risk has not been studied sufficiently. The main purpose of this research was to assess and compare stress distribution in the screws and abutment of a single-crown implant with transversal and transocclusal screw models. Two 3D models were assembled to analyse a single-implant-supported prosthesis with transversal and transocclusal screws embedded in the jawbone. The crown was subjected to a static load of value 300 N with different levels of inclination. The transversal screw model, with an axial load of 15°, was the one with lowest stress values in all its components. However, the stress was greater with more inclined loads when compared with the transocclusal model. The prosthetic transversal screw showed much less stress than the rest of the components for any load inclination. The transversal screw design is the option with the lowest risk of mechanical complications, both in the prosthetic screw and in the abutment screw, when applying forces of lower inclination. The more oblique forces favoured a better biomechanical environment in the abutment and its screw in the transocclusal screw model., (© 2019 John Wiley & Sons, Ltd.)

Introduction: The aim of this study was to evaluate bone depth, cortical bone thickness, and vestibulolingual bone dimension of the mandibular retromolar trigone and anterior ramus region to evaluate what are its most suitable sites for miniscrew insertion in adults., Methods: The sample included cone-beam computerized tomography (CBCT) records of 60 adult subjects retrospectively evaluated. All CBCT examinations were performed with the use of an i-CAT CBCT scanner (Imaging Sciences International). Each exam was converted into DICOM format and processed with the use of Osirix Medical Imaging software. On reproducible sagittal scan views, bone depth and cortical bone thickness were evaluated on specific lines parallel and at a 45° angle to the occlusal plane, and at 3 mm and at 6 mm distance from it. Vestibulolingual bone dimension was computed in 4 different cross-section scans and at 3 different levels of depth (0, 6, and 11 mm)., Results: All of the considered insertion sites showed on average more than 10 mm of bone depth. Inferential statistics showed significantly (P <0.05) greater bone depth (+3 mm) in cross-sectional scans parallel to the occlusal plane compared with those at a 45° angle to it. Cortical bone thickness showed average values from 3 mm to 5 mm. Vestibulolingual bone dimension showed a significant (P <0.05) reduction (-10 mm) in the posterior region of retromolar region. No significant differences were found between subjects with and without third molars., Conclusions: The retromolar trigone and anterior ramus region showed enough bone quantity and adequate bone quality for safe miniscrew insertion in adults., (Copyright © 2018 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Background: This study aimed to explore the effect of retaining inferomedial cortical bone contact and fixation with calcar screws on the dynamic and static mechanical stability of proximal humerus fractures treated with a locking plate., Methods: Twelve Synbone prosthetic humeri (SYNBONE-AG, Switzerland) were used for a wedge osteotomy model at the proximal humerus, in four groups. In the cortex contact + screw fixation group and cortex contact group, the inferomedial cortical bone contact was retained. In the screw fixation group and control group, the inferomedial cortical bone contact was not retained. Calcar screw fixation was implemented only in the screw fixation groups. The dynamic and static mechanical stability of the models were tested with dynamic fatigue mechanics testing, quasi-static axial compression, three-point bending, and torsion testing., Results: The cortex contact + screw fixation group showed the longest fatigue life and the best stability. There was 35% difference in fatigue life between the cortex contact + screw fixation group and the cortex contact group, 43%between the cortex contact + screw fixation group and screw fixation group, and 63% between the cortex contact + screw fixation group and screw fixation group (P < 0.01). The cortex contact + screw fixation group showed the best axial compressive stiffness, bending stiffness, and torsion stiffness; these were successively decreased in the other three groups (P < 0.01)., Conclusion: Retaining inferomedial cortical bone contact and fixation with two calcar screws maintained fracture stability with the highest strength and minimum deformation. Of the two methods, restoration of the inferomedial cortical bone support showed better dynamic and static biomechanical properties than placement of calcar screws alone.

Objective: The aim of the present study was to compare the accuracy and safety of TiRobot system-assisted with those of fluoroscopy-assisted cortical bone trajectory screw placement in lumbar spinal surgery., Methods: We included 58 patients who required instrumentation in a retrospective matched-cohort study. The primary outcome measures were the accuracy of screw placement using the modified Gertzbein-Robbins scale and the incidence of proximal facet joint violation. Secondary outcome measures included operative time, intraoperative blood loss, postoperative hospital stay, radiation exposure, and complications., Results: A total of 231 screws were placed (TiRobot group [RG], 86 screws; fluoroscopy group [FG], 145 screws). In the RG, 87.2% of the screws had perfect positions (grade A). The remaining screws were grade B (8.1%) and C (4.7%). In the FG, 66.9% of the screws had perfect positions (grade A). The remaining screws were grade B (20.0%), C (9.0%), and D (4.1%). The proportion of clinically acceptable screws (grade A or B) was greater in the RG than in the FG. In the RG, the most common direction of screw deviation was cephalad endplate and was the vertebral cortex in FG. No difference was found in facet joint violation between the 2 groups. The operative time and blood loss were slightly greater in the RG than in the FG. No statistically significant difference was found in the postoperative hospital stay between the 2 groups. The mean cumulative radiation time was greater for the RG than for the FG, but the radiation exposure to the surgeon was significantly lower in the RG than in the FG., Conclusions: Robot-assisted screw placement is more accurate and safe compared with fluoroscopy-assisted placement for lumbar spinal cortical bone trajectory instrumentation., (Published by Elsevier Inc.)

Objective: To assess an alternative method of cortical bone trajectory (CBT) screw placement in the thoracic spine from T1 to T8 and to investigate the proper entry point, screw insertion angle, screw length, and diameter., Methods: Computed tomography images of 80 patients were used to measure all related parameters. Ten cadaveric spines were studied and 4.5-mm screws were inserted into both sides of the vertebrae. Computed tomography of all vertebrae previously inserted with CBT screws was performed and lateral or medial pedicle wall violation was checked., Results: Of the inserted 160 CBT screws, 41.25% (66/160) penetrated the lateral pedicle wall, and the proportion of medial pedicle wall violation accounted for 0.625% (1/160). Maximal screw length tended to gradually increase from T1 to T8 (from 24.54 mm at T1 to 29.53 mm at T8). Compared with T4 and T5, maximal screw diameters of other thoracic levels were wider, ranging from 4.63 mm at T4 to 5.53 mm at T8. The greatest lateral angle was 8.66° in men and 8.39° in women at T8, whereas the smallest lateral angle was 4.97° in men and 4.67° in women at T1. The cephalad angle ranged from 17.23° at T7 to 31.50° at T1 and it was significantly larger in men at T7 (P < 0.05), T6 and T8 (P < 0.01)., Conclusions: Based on the results of this study, we suggest that patients could be placed with 4.5 × 25.0-30.0 mm CBT screws from T1 to T8 through the pedicle or pedicle rib unit., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objective: To compare the mechanical behavior of a novel bioabsorbable cortical interference screw (BCIS) with bioabsorbable interference screw (BIS; Polylactate hydroxyapatite) used for anterior cruciate ligament (ACL) reconstruction in femoral and tibial fixation with doubled Achilles tendon graft in vitro., Patients and Methods: 30 paired goat knee specimens were harvested from 15 male sheep aged 18 months. All soft tissues were stripped from the bones of 20 paired specimens, and the last 10 paired specimens were stripped all soft tissues besides ACL (femur-ACL-tibia complex). The Achilles tendon was harvested as graft for ACL reconstruction. The specimens were divided into several groups: BCIS femoral fixation (group A, n=10), BIS femoral fixation (group B, n=10), BCIS tibial fixation (group C, n=10), BIS tibial fixation (group D, n=10), Group E is femur-ACL-tibia complex (n=10). Cyclic loading test was performed from 50 to 250 N at 1 Hz for 1000 cycles and followed by a load-to-failure test at 25 mm/sec. A paired t-test was used to compare the biomechanical properties of group A, B, E and group C, D, E., Results: No fixation structures failed during the cyclic phase. Cyclic displacement for group B was superior to group A, and showed statistically significant difference after 30, 100, 500, 1000 cycles. Group E got minimum cyclic displacements compared with group A and group B, and showed statistically significant difference after 500, 1000 cycles compared with group A. Cyclic displacement for group D was superior to group C, and showed statistically significant difference after 100, 500, 1000 cycles. Group E got minimum cyclic displacements compared with group C and group D, and showed statistically significant difference after 500,1000 cycles compared with group C. Regarding MFL, group A was superior to group B (572.10±111.12 N vs. 413.96±34.56 N, p=0.118), group E was superior to group A (599.74±85.45N vs. 572.10±111.12 N, p=0.992), and group C was superior to group D (802.88±240.07 N vs. 415.63±51.9 N, p<0.001), group C was superior to group E (802.88±240.07 N vs. 599.74±85.45 N, p=0.024). Regarding YL, group A was superior to group B (521.57±93.96 N vs. 366.99±44.66 N, p=0.109), group E was superior to group A (565.37±66.05 N vs. 521.57±93.96 N, p=0.952), and group C was superior to group D (735.63±242.91 N vs. 394.49±31.90 N, p<0.001), group C was superior to group E (735.63±242.91 N vs. 565.37±66.05 N, p=0.063). Regarding stiffness, group A was superior to group B (157.36±34.31 N/mm vs. 91.98±25.57 N/mm, p=0.001), group E was superior to group A (181.35±25.42 N vs. 157.36±34.31 N/mm, p=0.529), and group C was superior to group D (175.28±43.19 N/mm vs. 128.24±18.92 N/mm, p=0.032), group E was superior to group C (181.35±25.42 N/mm vs. 175.28±43.19 N/mm, p=0.995)., Conclusions: In vitro, this experimental study suggested the biomechanical properties of novel bioabsorbable cortical interference screw (BCIS) were superior to bioabsorbable interference screw (BIS) used for femoral and tibial anterior cruciate ligament (ACL) reconstruction in a goat knee model.

Objective: To determine whether 2.0 mm cancellous screws are superior to 2.0 mm cortical screws when inserted into cancellous and bicortical bone., Study Design: Biomechanical study., Methods: The 2.0 mm cancellous screws and 2.0 mm cortical screws were inserted according to the recommended guidelines in synthetic cancellous and bicortical blocks. Fifteen screw-block constructs per group were tested to failure in axial pullout. Axial pullout strength and yield strength were calculated. Data were analyzed using a one-way ANOVA., Results: The 2.0 mm cortical screws achieved lower axial pullout strength than 2.0 mm cancellous screws in cancellous blocks. The 2.0 mm cortical screws achieved greater pullout strength than 2.0 mm cancellous screws in bicortical blocks., Conclusion: The 2.0 mm cancellous screws may offer a biomechanical advantage in bone with thin cortices (<1 mm thick), whereas 2.0 mm cortical screws may be preferred in cortical bone with cortices measuring at least 1 mm in thickness., (© 2017 The American College of Veterinary Surgeons.)

Objective: To analyze the buccal bone thickness, bone depth, and cortical bone depth of the mandibular buccal shelf (MBS) to determine the most suitable sites of the MBS for mini-screw insertion., Materials and Methods: The sample included cone-beam computed tomographic (CBCT) records of 30 adult subjects (mean age 30.9 ± 7.0 years) evaluated retrospectively. All CBCT examinations were performed with the i-CAT CBCT scanner. Each exam was converted into DICOM format and processed with OsiriX Medical Imaging software. Proper view sections of the MBS were obtained for quantitative and qualitative evaluation of bone characteristics., Results: Mesial and distal second molar root scan sections showed enough buccal bone for mini-screw insertion. The evaluation of bone depth was performed at 4 and 6 mm buccally to the cementoenamel junction. The mesial root of the mandibular second molar at 4 and 6 mm showed average bone depths of 18.51 mm and 14.14 mm, respectively. The distal root of the mandibular second molar showed average bone depths of 19.91 mm and 16.5 mm, respectively. All sites showed cortical bone depth thickness greater than 2 mm., Conclusions: Specific sites of the MBS offer enough bone quantity and adequate bone quality for mini-screw insertion. The insertion site with the optimal anatomic characteristics is the buccal bone corresponding to the distal root of second molar, with screw insertion 4 mm buccal to the cementoenamel junction. Considering the cortical bone thickness of optimal insertion sites, pre-drilling is always recommended in order to avoid high insertion torque.

Bone drilling is one of the most common operations used to repair fractured parts of bones. During a bone drilling process, microcracks are generated on the inner surface of the drilled holes that can detrimentally affect osteosynthesis and healing. This study focuses on the investigation of microcracks and pullout strength of cortical-bone screws in drilled holes. It compares conventional surgical bone drilling (CSBD) with rotary ultrasonic bone drilling (RUBD), a novel approach employing ultrasonic vibration with a diamond-coated hollow tool. Both techniques were used to drill holes in porcine bones in an in-vitro study. Scanning electron microscopy was used to observe microcracks and surface morphology. The results obtained showed a significant decrease in the number and dimensions of microcracks generated on the inner surface of drilled holes with the RUBD process in comparison to CSBD. It was also observed that a higher rotational speed and a lower feed rate resulted in lower damage, i.e. fewer microcracks. Biomechanical axial pullout strength of a cortical bone screw inserted into a hole drilled with RUBD was found to be much higher (55-385%) than that for CSBD., (Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.)

Objectives: This study aims to assess five different cortical screw types using artificial femurs, under equated testing conditions., Materials and Methods: We investigated the maximum force needed to cause deformation at screw-bone interface using fourth generation composite femurs by conducting separate pullout tests for each screw type. We normalized obtained results with traditional methods and cross-comparison. To conduct pullout tests dependent on screw dimensions, we eliminated the effect of bicortical bone thickness by equalizing the conditions of screw insertion., Results: Non-locking screws with larger diameter and pitch depth required larger pullout forces to be extracted, showing statistically superior performance compared to locking screws with smaller dimensions. However, the statistical differences between the absolute pullout forces decreased after the traditional normalization of the results. We proposed a new normalization method based on solid geometric reasoning., Conclusion: This novel approach showed that a screw type that appeared to show average performance, in fact, did not have statistically significantly different results than the top performers. Surgeons are not required to prefer larger dimension screws in small dimension host bones.

To quantify the reference data concerning the morphometrics of the middle-upper thorax to guide the placement of cortical bone trajectory (CBT) screws.Eighty patients were studied on computed tomography (CT) scans. The reference anatomical parameters were measured. Next, 20 cadaveric specimens were implanted with CBT screws based on CT measurements. These specimens were then judged directly from the cadaveric vertebrae and X-ray.The maximum length of the trajectory, the maximum diameter, and the cephaled angle exhibited a slight increase trend while the transverse and sagittal angles of the pedicle tended to decrease from T3 to T8. We recommend that the width of CBT screw for middle-upper thoracic spine is 5.0 mm, the length is 25 to 35 mm. The cadaveric anatomical study revealed that 5/240 screws penetrated in the medial or lateral areas, 5/240 screws penetrated in the superior or inferior pedicle wall, and 2/240 screws did not fit into the superior endplate of the pedicle.The CBT screws are safe for the middle-upper thorax. This study provides a theoretical basis for clinical surgery., Competing Interests: The authors have no conflicts of interest to disclose.

The purpose of this research was to evaluate the structural stress and deformation of a newly designed onplant miniplate anchorage system compared to a standard anchorage system. A bone block integrated with a novel miniplate and fixation screw system was simulated in a three-dimensional model and subjected to force at different directions. The stress distribution and deformation of the miniplate system and cortical bone were evaluated using the three-dimensional finite element method. The results showed that the stress on the plate system and bone was linearly proportional to the force magnitude and was higher when the force was in a vertical direction (Y-axis). Stress and deformation values of the two screws (screw 1 and 2) were asymmetric when the force was added along Y-axis and was greater in screw 1. The highest deformation value of the screws was 7.5148 μm, much smaller than the limit value. The load was decreased for each single miniscrew, and the ability of the new anchorage system to bear the load was also enhanced to some degree. It was suggested that the newly designed onplant miniplate anchorage system is effective, easily implanted and minimally invasive.