Effects of attentional focus strategies in drop landing biomechanics of individuals with unilateral functional ankle instability.

Background: Functional Ankle Instability (FAI) is a pervasive condition that can emerge following inadequate management of lateral ankle sprains. It is hallmarked by chronic joint instability and a subsequent deterioration in physical performance. The modulation of motor patterns through attentional focus is a well-established concept in the realm of motor learning and performance optimization. However, the precise manner in which attentional focus can rehabilitate or refine movement patterns in individuals with FAI remains to be fully elucidated. Objective: The primary aim of this study was to evaluate the impact of attentional focus strategies on the biomechanics of single-leg drop landing movements among individuals with FAI. Methods: Eighteen males with unilateral FAI were recruited. Kinematic and kinetic data were collected using an infrared three-dimensional motion capture system and force plates. Participants performed single-leg drop landing tasks under no focus (baseline), internal focus (IF), and external focus (EF) conditions. Biomechanical characteristics, including joint angles, ground reaction forces, and leg stiffness, were assessed. A 2 × 3 [side (unstable and stable) × focus (baseline, IF, and EF)] Repeated Measures Analysis of Variance (RM-ANOVA) analyzed the effects of attentional focus on biomechanical variables in individuals with FAI. Results: No significant interaction effects were observed in this study. At peak vertical ground reaction force (vGRF), the knee flexion angle was significantly influenced by attentional focus, with a markedly greater angle under EF compared to IF (p < 0.001). Additionally, at peak vGRF, the ankle joint plantarflexion angle was significantly smaller with EF than with IF (p < 0.001). Significant main effects of focus were found for peak vGRF and the time to reach peak vGRF, with higher peak vGRF values observed under baseline and IF conditions compared to EF (p < 0.001). Participants reached peak vGRF more quickly under IF (p < 0.001). Leg Stiffness (kleg) was significantly higher under IF compared to EF (p = 0.001). Conclusion: IF enhances joint stability in FAI, whereas EF promotes a conservative landing strategy with increased knee flexion, dispersing impact and minimizing joint stress. Integrating these strategies into FAI rehabilitation programs can optimize lower limb biomechanics and reduce the risk of reinjury.

Standardized Bench Test Evaluation of Biomechanical Characteristics of Stents Used in Right Ventricular Outflow Tract Revalvulation.

PURPOSE: Pre-stenting of the right ventricular outflow tract (RVOT) is commonly performed before percutaneous pulmonary valve implantation (PPVI), to relieve obstruction, prevent valved stent fractures, and provide a landing zone. This study aimed to evaluate the biomechanical characteristics of the stents currently used to perform pre-stenting of the RVOT. METHODS: We assessed five commercially available stents: Cheatham-Platinum Stent ("CP Stent"), AndraStent XL, AndraStent XXL, Optimus XL, and Optimus XXL. Following stent deployment at nominal pressure, radial and longitudinal elastic recoils and radial resistance were measured. The bending stiffness of the stents crimped onto the balloons was also evaluated. RESULTS: Three samples were tested for each stent. Our study showed no significant difference between the stent platforms in terms of radial elastic recoil, which was relatively low (< 10%). The longitudinal elastic recoil was also low for all the devices (< 5%). Significant differences were observed in radial resistance (P < 0.001). CP Stent and AndraStent XL exhibited the highest radial resistances. The bending stiffnesses of the stents crimped on their balloons were significantly different (P < 0.00001). Optimus XL and XXL were more flexible than the other stents. CONCLUSION: This study highlights the significant differences between the stents currently used in RVOT pre-stenting. Stents with good radial resistance are preferred, especially for calcified vessels, and flexibility is crucial for tortuous vessels. We proposed an algorithm for selecting the most suitable stent according to the need for radial force and flexibility, which will help inform clinicians considering RVOT revalvulation.

Effects of dynamic and rigid implantation on biomechanical characteristics of different sagittal alignment lumbar after single- or double-level spinal fixations: a finite-element modeling study.

BACKGROUND: Although it is critical to understand the accelerated degeneration of adjacent segments after fusion, the biomechanical properties of the spine have not been thoroughly studied after various fusion techniques. This study investigates whether four Roussouly's sagittal alignment morphotypes have different biomechanical characteristics after different single- or double-level spinal fixations. METHODS: The parametric finite element (FE) models of Roussouly's type (1-4) were developed based on the radiological data of 625 Chinese community population. The four Roussouly's type models were reassembled into four fusion models: single-level L4-5 Coflex fixation model, single-level L4-5 Fusion (pedicle screw fixation) model, double-level Coflex (L4-5) + Fusion (L5-S1) model, and double-level Fusion (L4-5) + Fusion (L4-5) model. A pure moment of 7.5 Nm was applied to simulate the physiological activities of flexion, extension, lateral bending and axial rotation. RESULTS: Both single-level and double-level spinal fixation had the greatest effect on lumbar range of motion, disc pressure, and annulus fibrosis stress in flexion, followed by lateral bending, extension, and axial rotation. In all models, the upper adjacent segment was the most influenced by the implantation and bore the most compensation from the fixed segment. For Type 2 lumbar, the L4-L5 Coflex effectively reduced the disc pressure and annulus fibrosis stress in adjacent segments compared to the L4-L5 Fusion. Similarly, the L4-L5 Coflex offered considerable advantages in preserving the biomechanical properties of adjacent segments for Type 1 lumbar. For Type 4 lumbar, the L4-L5 Coflex did not have superiority over the L4-L5 Fusion, resulting in a greater increase in range of motion at adjacent segments in flexion and extension. The difference between the two fixations was not apparent in Type 3 lumbar. Compared to the single-level Fusion, the changes in motion and mechanics of the lumbar increased after both the double-level Coflex + Fusion and Fusion + Fusion fixations, while the differences between two double-level fixation methods on adjacent segments of the four lumbar models were similar to that of the single-level fixation. CONCLUSION: Type 3 and Type 4 lumbar have good compensatory ability and therefore allow for a wider range of surgical options, whereas surgical options for small lordotic Type 1 and Type 2 lumbar are more limited and severe.

Effect of Erbium:YAG Laser Recycling on Mechanical Characteristics of Retrieved Orthodontic Mini-screws.

Introduction: This study aimed to evaluate the influence of two recycling methods on the mechanical and surface characteristics of orthodontic mini-screws. Methods: Thirty-six retrieved mini-screws were randomly classified into two equal groups. In the first group (laser recycled group (LG)), the Er:YAG laser (2940 nm, 5.5 W, 275 mJ, perpendicular to the mini-screws at a distance of 7-10 mm, 25 s) was used to recycle mini-screws. In the second group (phosphoric acid and sodium hypochlorite recycled group (ASG)), the mini-screws were kept in 37% phosphoric acid gel (10 minutes) and then placed in 5.25% sodium hypochlorite for 30 minutes. Eighteen new mini-screws were selected as the control group (CG). Maximum insertion torque (MIT), maximum removal torque (MRT), and fracture torque (FT) of all mini-screws were measured. A sample from each group was examined for the surface changes of the mini-screw and tissue remnants under a scanning electron microscope (SEM). Results: The mean MIT was significantly higher in both LG and ASG groups than the CG (P<0.001 and P=0.002, respectively). However, no significant difference was shown between the LG and ASG groups. The mean values of MRT and FT showed no significant difference between the groups. The amount of tissue remnants in the ASG group was significantly higher than that in the LG group. The evidence of porosity and corrosion was observed on the ASG mini-screw surface, and there was an increase in roughness on the LG mini-screw surface. Conclusion: The Er:YAG laser recycling of mini-screws is a proper method causing minimum damage to the screw surface.

Basic and clinical study of the effect of exogenous hyaluronic acid on the quality of acellular dermal matrix combined with thin intermediate split thickness skin graft.

BACKGROUND: To promote wound recovery in the recipient region, we studied the impact of exogenous hyaluronic acid (HA) on acellular dermal matrix (ADM) paired with thin intermediate-thickness skin transplant. METHODS: This study contains animal and clinical experiments. 50 Japanese big ear rabbits were separated into HA1, HA2, PADM, TS, and NS groups. Clinical part included 50 scar patients dividing into 5 groups (TS + HA + ADM 1, TS + ADM2, TS, TS + ADM and normal skin (NS)). RESULTS: In the animal trial, after 56 days, the grafts contracted least in the HA2 group; HA2 had the highest microvascular density (MVD), HA concentration, and collagen I and III expression. In clinical work, ADM > HA + ADM2 > HA + ADM1 > TS > NS; Type I and III collagen: HA + ADM1 and HA + ADM2 were higher than ADM; HA content: TS > HA + ADM1 > HA + ADM 2 > ADM. CONCLUSIONS: ADM, exogenous hyaluronic acid mixed with thin skin autograft has better biomechanical qualities and therapeutic impact than acellular dermal matrix alone, and the reconstructive result is near to self-thick skin autograft in all indexes.

Osteotomies around the knee alter alignment of the ankle and hindfoot: a systematic review of biomechanical and clinical studies.

Purpose: Emerging reports suggest an important involvement of the ankle/hindfoot alignment in the outcome of knee osteotomy; however, a comprehensive overview is currently not available. Therefore, we systematically reviewed all studies investigating biomechanical and clinical outcomes related to the ankle/hindfoot following knee osteotomies. Methods: A systematic literature search was conducted on PubMed, Web of Science, EMBASE and Cochrane Library according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on international prospective register of systematic reviews (PROSPERO) (CRD42021277189). Combining knee osteotomy and ankle/hindfoot alignment, all biomechanical and clinical studies were included. Studies investigating knee osteotomy in conjunction with total knee arthroplasty and case reports were excluded. The QUality Appraisal for Cadaveric Studies (QUACS) scale and Methodological Index for Non-Randomized Studies (MINORS) scores were used for quality assessment. Results: Out of 3554 hits, 18 studies were confirmed eligible, including 770 subjects. The minority of studies (n = 3) assessed both high tibial- and distal femoral osteotomy. Following knee osteotomy, the mean tibiotalar contact pressure decreased (n = 4) except in the presence of a rigid subtalar joint (n = 1) or a talar tilt deformity (n = 1). Patient symptoms and/or radiographic alignment at the level of the ankle/hindfoot improved after knee osteotomy (n = 13). However, factors interfering with an optimal outcome were a small preoperative lateral distal tibia angle, a small hip-knee-ankle axis (HKA) angle, a large HKA correction (>14.5°) and a preexistent hindfoot deformity (>15.9°). Conclusions: Osteotomies to correct knee deformity alter biomechanical and clinical outcomes at the level of the ankle/hindfoot. In general, these changes were beneficial, but several parameters were identified in association with deterioration of ankle/hindfoot symptoms following knee osteotomy.

Effects of tDCS on Foot Biomechanics: A Narrative Review and Clinical Applications.

In recent years, neuro-biomechanical enhancement techniques, such as transcranial direct current stimulation (tDCS), have been widely used to improve human physical performance, including foot biomechanical characteristics. This review aims to summarize research on the effects of tDCS on foot biomechanics and its clinical applications, and further analyze the underlying ergogenic mechanisms of tDCS. This review was performed for relevant papers until July 2023 in the following databases: Web of Science, PubMed, and EBSCO. The findings demonstrated that tDCS can improve foot biomechanical characteristics in healthy adults, including proprioception, muscle strength, reaction time, and joint range of motion. Additionally, tDCS can be effectively applied in the field of foot sports medicine; in particular, it can be combined with functional training to effectively improve foot biomechanical performance in individuals with chronic ankle instability (CAI). The possible mechanism is that tDCS may excite specific task-related neurons and regulate multiple neurons within the system, ultimately affecting foot biomechanical characteristics. However, the efficacy of tDCS applied to rehabilitate common musculoskeletal injuries (e.g., CAI and plantar fasciitis) still needs to be confirmed using a larger sample size. Future research should use multimodal neuroimaging technology to explore the intrinsic ergogenic mechanism of tDCS.

Finite element analysis of a novel anatomical locking plate for scapular neck fracture.

OBJECTIVES: Reconstruction plates (RPs) are commonly used in scapular neck fractures (SNFs): however, RPs have many defects. In this study, we evaluated a newly designed scapular neck anatomical locking compression plate (SNALCP). METHODS: An SNF finite element model (Miller-type IIB) was constructed. Plates were subsequently implanted into the scapula and fixed with screws that were grouped according to the plate used: SNALCP (A) and RP (B). Finally, loads were applied to record and analyze performance. RESULTS: Under lateral, anteroposterior, and vertical compression loads, the maximum von Mises stresses on the scapula and implants of group A were smaller than those of group B. There were some differences in stress distribution between the two groups. CONCLUSIONS: SNALCP can effectively reduce the stress of the scapula and implant, making stress distribution more uniform and continuous, and has mechanical conduction advantages. Compared to RP, it provides improved stability and more reliable fixation.

The Biomechanical Characteristics of Swallowing in Tracheostomized Patients with Aspiration following Acquired Brain Injury: A Cross-Sectional Study.

Objectives: Investigate the biomechanical characteristics in tracheostomized patients with aspiration following acquired brain injury (ABI) and further explore the relationship between the biomechanical characteristics and aspiration. Methods: This is a single-center cross-sectional study. The tracheostomized patients with aspiration following ABI and age-matched healthy controls were recruited. The biomechanical characteristics, including velopharynx (VP) maximal pressure, tongue base (TB) maximal pressure, upper esophageal sphincter (UES) residual pressure, UES relaxation duration, and subglottic pressure, were examined by high-resolution manometry and computational fluid dynamics simulation analysis. The penetration−aspiration scale (PAS) score was evaluated by a videofluoroscopic swallowing study. Results: Fifteen healthy subjects and fifteen tracheostomized patients with aspiration following ABI were included. The decreased VP maximal pressure, increased UES residual pressure, and shortened UES relaxation duration were found in the patient group compared with the control group (p < 0.05). Furthermore, the subglottic pressure significantly decreased in patients (p < 0.05), while no significant difference was found in TB maximal pressure between groups (p > 0.05). In addition, in the patient group, VP maximal pressure (rs = −0.439; p = 0.015), UES relaxation duration (rs = −0.532; p = 0.002), and the subglottic pressure (rs = −0.775; p < 0.001) were negatively correlated with the PAS score, while UES residual pressure (rs = 0.807; p < 0.001) was positively correlated with the PAS score (p < 0.05), the correlation between TB maximal pressure and PAS score (rs = −0.315; p = 0.090) did not reach statistical significance. Conclusions: The biomechanical characteristics in tracheostomized patients with aspiration following ABI might manifest as decreased VP maximal pressure and subglottic pressure, increased UES residual pressure, and shortened UES relaxation duration, in which VP maximal pressure, UES relaxation duration, subglottic pressure, and UES residual pressure were correlated with aspiration.

Influence of different fixation modes on biomechanical conduction of 3D printed prostheses for treating critical diaphyseal defects of lower limbs: A finite element study.

Background: Applying 3D printed prostheses to repair diaphyseal defects of lower limbs has been clinically conducted in orthopedics. However, there is still no unified reference standard for which the prosthesis design and fixation mode are more conducive to appropriate biomechanical conduction. Methods: We built five different types of prosthesis designs and fixation modes, from Mode I to Mode V. Finite element analysis (FEA) was used to study and compare the mechanical environments of overall bone-prosthesis structure, and the maximum stress concentration were recorded. Additionally, by comparing the maximum von Mises stress of bone, intramedullary (IM) nail, screw, and prosthesis with their intrinsic yield strength, the risk of fixation failure was further clarified. Results: In the modes in which the prosthesis was fixed by an interlocking IM nail (Mode I and Mode IV), the stress mainly concentrated at the distal bone-prosthesis interface and the middle-distal region of nail. When a prosthesis with integrally printed IM nail and lateral wings was implanted (Mode II), the stress mainly concentrated at the bone-prosthesis junctional region. For cases with partially lateral defects, the prosthesis with integrally printed wings mainly played a role in reconstructing the structural integrity of bone, but had a weak role in sharing the stress conduction (Mode V). The maximum von Mises stress of both the proximal and distal tibia appeared in Mode III, which were 18.5 and 47.1 MPa. The maximum peak stress shared by the prosthesis, screws and IM nails appeared in Mode II, III and I, which were 51.8, 87.2, and 101.8 MPa, respectively. These peak stresses were all lower than the yield strength of the materials themselves. Thus, the bending and breakage of both bone and implants were unlikely to happen. Conclusion: For the application of 3D printed prostheses to repair diaphyseal defects, different fixation modes will lead to the change of biomechanical environment. Interlocking IM nail fixation is beneficial to uniform stress conduction, and conducive to new bone regeneration in the view of biomechanical point. All five modes we established have reliable biomechanical safety.

Biomechanical Evaluation of Seven Fixation Methods for Sagittal Split Ramus Osteotomy with Four Advancement Levels by Finite Element Analysis.

Background: Mandibular sagittal split ramus osteotomy (SSRO) is a routine surgery to correct mandibular deformities, such as mandibular retrusion, protrusion, deficiency, and asymmetry. However, nonunion/malunion of the fragments and relapse caused by fixation failure after SSRO are major concerns. Rigid fixation to maintain postosteotomy segmental stabilization is critical for success. Additionally, understanding the biomechanical characteristics of different fixation methods in SSRO with large advancements is extremely important for clinical guidance. Therefore, the aim of the present study was to evaluate the biomechanical characteristics of different SSRO methods by finite element analysis. Methods: SSRO finite element models with 5-, 10-, 15-, and 20-mm advancements were developed. Seven fixation methods, namely, two types of bicortical screws, single miniplate, dual miniplates, grid plate, dual L-shaped plates, and hybrid fixation, were positioned into the SSRO models. Molar and incisal biomechanical loads were applied to all models to simulate bite forces. We then investigated the immediate postoperative stability from four aspects, namely, the stability of the distal osteotomy segment, osteotomy regional stability, stress distribution on the mandible, and implant stress performance. Results: The stability of the distal osteotomy segment and osteotomy region decreased when the advancement increased. All seven fixation methods displayed favorable biomechanical stability under minor advancement (5 mm). With large advancements, bicortical screws, dual miniplates, and grid plates provided better stability. The von Mises stress was concentrated around the screws close to the osteotomy region for the proximal segment for all fixation methods, and the von Mises stress on implants increased with larger advancements. With small advancements, five fixation methods endured tolerable maximum stresses of <880 MPa. A single miniplate and dual L-shaped plates generally suffered high stresses using larger advancements. The biomechanical characteristics were similar under molar and incisal loads. Conclusions: The current study investigated the biomechanical properties of seven fixation devices after SSRO under molar and incisal loads. Generally, bicortical screws, grid plates, and dual miniplates provided better biomechanical stability using finite element analysis.

Biomechanics of the lead straight punch of different level boxers.

We analyze and compare the differences in the biomechanical parameters between the lead straight punch and the index of force development of the lower extremities of boxers of different levels of ability. This can bridge the technical gap and provide insight and information for training strategies and athlete selection. To this end, a synchronized Vicon infrared 3D motion-capture system, two Kistler force platforms, and Kistler 8 target sensors were used for analysis. Sixteen boxers were recruited and sorted into an elite group (height 181.14 ± 3.01 cm, body mass 76.00 ± 10.028 kg) and a junior group (179.67 ± 5.84 cm, body mass 75.47 ± 12.19 kg), and their lead straight punch was then compared and analyzed. Three punch velocity indexes-peak velocity, contact velocity and Punching deceleration rate-six strength indexes-impulse, peak force, relative strength, peak time (frame), rate of force development (RFD), and movement time-and five exertion of both legs indexes- peak force, peak force/body mass, peak time, RFD index, and RFD/body mass index-were selected for analysis. Significant differences in the peak punch velocity and contact velocity were found between the two groups (7.162 ± 0.475 m•s-1vs. 6.317 ± 0.415 m•s-1, Cohen's d = 1.89, p < 0.01, 5.557 ± 0.606 m•s-1 vs. 4.874 ± 0.385 m•s-1, Cohen's d = 1.34, p < 0.05). Furthermore, significant differences were noted in the peak force [(1507.99 ± 411) N vs. (1035.45 ± 220) N, Cohen's d = 1.43, p < 0.01], relative strength [(21.04 ± 5.88) N•kg-1 vs. (15.61 ± 2.53) N•kg-1, Cohen's d = 1.19, p < 0.05], impulse [(88.61 ± 25.88) N•ms-1 and (60.53 ± 9.03) N•ms-1, Cohen's d = 1.45, p < 0.05], and RFD [(88.61 ± 25.88) N•ms-1 and (60.53 ± 9.03) N•ms-1, Cohen's d = 1.45, p < 0.05]. Among the four indexes of the lower extremities from two embedded Kistler force platforms, there were significant differences in the lead leg's peak force/body mass [(19.68 ± 4.096) N•kg-1vs. (13.320 ± 2.223) N•kg-1, t = 3.902, Cohen's d = 1.92, p < 0.01], RFD index [(16.90 ± 3.269) N•ms-1vs. (10.28 ± 4.313) N•ms-1, Cohen's d = 1.72, p < 0.01], and RFD/body mass index [(23.47 ± 4.09%) N•ms-1Kg-1 vs. (15.38 ± 5.65%) N•ms-1Kg-1, Cohen's d = 1.64, p < 0.01]. There were no significant differences in the four indexes on the rear leg between the two groups (p > 0.05). Based on the disparity in the effect of the lead straight punch and the biomechanical parameters of both lower extremities, the boxers must attach importance to sequential acceleration-braking training to improve the terminal velocity of the hand, and thus improve the contact velocity. Furthermore, it is advised that coaches and practitioners carefully consider increasing start-up strength training of the lead leg and attempt to improve the peak velocity of the lead straight punch. In addition, these biomechanical parameters can be used as criteria for the selection of boxers.

Effects of biomechanical parameters of spinal manipulation: A critical literature review.

Spinal manipulation is a manual treatment technique that delivers a thrust, using specific biomechanical parameters to exert its therapeutic effects. These parameters have been shown to have a unique dose-response relationship with the physiological responses of the therapy. So far, however, there has not been a unified approach to standardize these biomechanical characteristics. In fact, it is still undetermined how they affect the observed clinical outcomes of spinal manipulation. This study, therefore, reviewed the current body of literature to explore these dosage parameters and evaluate their significance, with respect to physiological and clinical outcomes. From the experimental studies reviewed herein, it is evident that the modulation of manipulation's biomechanical parameters elicits transient physiological responses, including changes in neuronal activity, electromyographic responses, spinal stiffness, muscle spindle responses, paraspinal muscle activity, vertebral displacement, and segmental and intersegmental acceleration responses. However, to date, there have been few clinical trials that tested the therapeutic relevance of these changes. In addition, there were some inherent limitations in both human and animal models due to the use of mechanical devices to apply the thrust. Future studies evaluating the effects of varying biomechanical parameters of spinal manipulation should include clinicians to deliver the therapy in order to explore the true clinical significance of the dose-response relationship.

Biomechanical Evaluation of the Transcortical and Transpedicular Trajectories for Pedicle Screw Insertion in Thoracolumbar Fracture Fixation for Ankylosing Spondylitis.

Background: Ankylosing spondylitis (AS) is a chronic disorder characterized by an imbalance between bone formation and resorption. Spinal fractures often occur after minor trauma in patients with AS. For thoracolumbar fractures, transpedicular screw (TPS) fixation through the posterior approach has been suggested. The cortical bone trajectory (CBT) technique has also been used to prevent screw pull-out in patients with poor bone quality. The aim of current study was to assess the biomechanical characteristics of the TPS and CBT technique in thoracolumbar AS fracture fixation by finite element analysis. Methods: The three-dimensional finite element models of the AS spine were created. The CBT and TPS methods of screw insertion were used in AS spinal fracture models. An intact AS spine model was considered the control. An axial force and torsion in rotation, flexion/extension and lateral flexion were applied in all models in CBT, TPS, and control groups. Results: The AS spine showed similar construct stiffness after posterior fixation by CBT and TPS techniques under axial, rotational, and flexion/extension loading conditions. The TPS technique showed better intact stability under all loading conditions. Similarly, the TPS technique provided superior fracture regional stability against axial and rotational loads than did the CBT technique. The maximum von Mises stresses were 1714.4 ± 129.8 MPa and 1208.7 ± 107.3 MPa (p < 0.001), which occurred in the CBT and TPS groups under compressive loading. Conclusions: The TPS technique provides better biomechanical strength under axial, rotational, flexion/extension, and lateral flexion loading than does the CBT technique. Compared with CBT, TPS is more effective in maintaining the stability of AS thoracolumbar fractures from a finite element analysis perspective.

The Transverse Process Trajectory Technique: An Alternative for Thoracic Pedicle Screw Implantation-Radiographic and Biomechanical Analysis.

BACKGROUND: This study evaluates the accuracy, biomechanical profile, and learning curve of the transverse process trajectory technique (TPT) compared to the straightforward (SF) and in-out-in (IOI) techniques. SF and IOI have been used for fixation in the thoracic spine. Although widely used, there are associated learning curves and symptomatic pedicular breaches. We have found the transverse process to be a reproducible pathway into the pedicle. METHODS: Three surgeons with varying experience (experienced [E] with 20 years in practice, surgeon [S] with less than 10 years in practice, and senior resident trainee [T] with no experience with TPT) operated on 8 cadavers. In phase 1, each surgeon instrumented 2 cadavers, alternating between TPT and SF from T1 to T12 (n = 48 total levels). In phase 2, the E and T surgeons instrumented 1 cadaver each, alternating between TPT and IOI. Computed tomography scans were analyzed for accuracy of screw placement, defined as the percentage of placements without critical breaches. Axial pullout and derotational force testing were performed. Statistical analyses include paired t test and analysis of variance with Tukey correction. RESULTS: Overall accuracy of screw placement was comparable between techniques (TPT: 92.7%; SF: 97.2%; IOI: 95.8%; P = .4151). Accuracy by technique did not differ for each individual surgeon (E: P = .7733; S: P = .3475; T: P = .4191) or by experience level by technique (TPT: P = .1127; FH: P = .5979; IOI: P = .5935). Pullout strength was comparable between TPT and SF (571 vs 442 N, P = .3164) but was greater for TPT versus IOI (454 vs 215 N, P = .0156). There was a trend toward improved derotational force for TPT versus SF (1.06 vs 0.93 Nm/degrees, P = .0728) but not for TPT versus IOI (1.36 vs 1.16 Nm/degrees, P = .74). Screw placement time was shortest for E and longest for T for TPT and SF and not different for IOI (TPT: P = .0349; SF: P < .0001; IOI: P = .1787) but did not vary by technique. CONCLUSIONS: We describe the TPT, which uses the transverse process as a corridor through the pedicle. TPT is an accurate method of thoracic pedicle screw placement with potential biomechanical advantages and with acceptable learning curve characteristics. CLINICAL RELEVANCE: This study provides the surgeon with a new trajectory for pedicle screw placement that can be used in clinical practice.

Comparison of Three Different Internal Brace Augmentation Techniques for Scapholunate Dissociation: A Cadaveric Biomechanical Study.

Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. However, there is no detailed information about the direction, location, or number of IBs required for scapholunate interosseous ligament (SLIL) injury repair. Thus, this study compared the biomechanical characteristics of short-transverse IB, long-oblique IB, and the combination of short-transverse and long-oblique (Combo) IB for SLIL injury in a biomechanical cadaveric model. We prepared nine fresh-frozen full upper extremity cadaveric specimens for this study. The scapholunate distance, scapholunate angle, and radioscaphoid angle were measured using the MicroScribe digitizing system with the SLIL intact, after scapholunate dissociation and the three different reconstructions. Three-dimensional digital records were obtained in six wrist positions in each experimental condition. Short-transverse IB had a similar effect compared with long-oblique IB in addressing the widening of the scapholunate distance. However, both were less effective than Combo IB. For scaphoid flexion deformity, short-transverse IB had minimal effect, while long-oblique IB had a similar effect compared to Combo IB. Combo IB was the most effective for improving distraction intensity and rotational strength. This study provides important information about the biomechanical characteristics of three different IB methods for SLIL injury and may be useful to clinicians in treating scapholunate dissociation.

Finite element analysis of an intramedulary anatomical strut for proximal humeral fractures with disrupted medial column instability: A cohort study.

BACKGROUND: Lateral locking plate (LLP) fixation has gained popularity for the treatment of proximal humeral fractures (PHFs); however, complications can occur due to loss of the medial cortical buttress from fracture comminution. MATERIALS AND METHODS: We designed a novel intramedullary anatomical medial strut with allograft bone (IAMSAB) using MIMICS software to specifically fill the intramedullary canal of the proximal humeral bone. We used finite element analysis to evaluate the biomechanical characteristics of a LLP, LLP-intramedullary fixation system (IFS), LLP-anatomical medial locking plate (AMLP), or the combined application of a LLP and IAMSAB (LLP-IAMSAB) fixation construct in patients with a PHF and an unstable medial column. RESULTS: For axial or rotational loads, under (normal) Nor or osteoporotic (Ost) bone conditions, the LLP-IAMSAB fixation construct was significantly stiffer than the LLP-IFS fixation construct, and displacement at the fracture site after LLP-IAMSAB fixation was significantly less than after LLP or LLP-IFS fixation (P < 0.05). Stiffness of the LLP-IAMSAB and LLP-AMLP fixation constructs and displacement at the fracture site after LLP-IAMSAB and LLP-AMLP fixation were not significantly different. The IFS, AMLP, and IAMSAB shared the load in the LLP and decreased the risk of implant failure. There were no significant differences in von Mises stress and stress distribution after fixation with the LLP-IFS, LLP-AMLP, and LLP-IAMSAB constructs. CONCLUSION: These data suggest that the IAMSAB can provide direct medial support or resistance to rotation and augment the biomechanics of the LLP. The combined application of the IAMSAB and LLP may achieve functional outcomes that are similar to the LLP-AMLP fixation construct.

Correlation Between the Myopic Retinal Deformation and Corneal Biomechanical Characteristics Measured With the Corvis ST Tonometry.

PURPOSE: We previously reported that the retinal deformation due to myopia was represented by the peripapillary retinal arteries angle (PRAA). In this study, we investigated the relationship between the PRAA and biomechanical properties measured with Corvis ST (CST) tonometry. METHODS: Thirty-four normative eyes of 34 subjects who underwent CST measurement were enrolled. The PRAA was calculated from a fundus photograph. Variables related to the PRAA were identified from age, axial length, spherical equivalent refractive error, and 10 CST parameters using model selection with the second-order bias-corrected Akaike information criterion index. RESULTS: The PRAA was best described with axial length (coefficient = -5.66, P < 0.0001), maximum deflection amplitude (mm; coefficient = 130.5, P = 0.0004), and deflection amplitude ratio (DA ratio) 2 mm (coefficient = -25.8, P = 0.0032), where mm was the amount of the maximum corneal apex movement and DA ratio 2 mm was the ratio between the deformation amplitudes at the apex and 2 mm away from the apex. The optimal model was significantly better than the model only with axial length (P = 0.0014, analysis of variance). CONCLUSIONS: The PRAA was significantly better described with the CST parameters compared to the axial length model only; eyes with small PRAA (larger myopic retinal deformation) showed narrow and shallow maximum corneal deflection. TRANSLATIONAL RELEVANCE: The Corvis ST parameters, which represents corneal biomechanical characteristics, were associated with myopic retinal deformation.

The Proteins of Keratoconus: a Literature Review Exploring Their Contribution to the Pathophysiology of the Disease.

INTRODUCTION: Keratoconus (KC) is a complex, genetically heterogeneous multifactorial degenerative disorder characterized by corneal ectasia and thinning. Its incidence is approximately 1/2000-1/50,000 in the general population. KC is associated with moderate to high myopia and irregular astigmatism, resulting in severe visual impairment. KC structural abnormalities primarily relate to the weakening of the corneal collagen. Their understanding is crucial and could contribute to effective management of the disease, such as with the aid of corneal cross-linking (CXL). The present article critically reviews the proteins involved in the pathophysiology of KC, with particular emphasis on the characteristics of collagen that pertain to CXL. METHODS: PubMed, MEDLINE, Google Scholar and GeneCards databases were screened for relevant articles published in English between January 2006 and June 2018. Keyword combinations of the words "keratoconus," "risk factor(s)," "genetics," "genes," "genetic association(s)," "proteins", "collagen" and "cornea'' were used. In total, 272 articles were retrieved, reviewed and selected, with greater weight placed on more recently published evidence. Based on the reviewed literature, an attempt was made to tabulate the up- and down-regulation of genes involved in KC and their protein products and to delineate the mechanisms involved in CXL. RESULTS: A total of 117 proteins and protein classes have been implicated in the pathogenesis and pathophysiology of KC. These have been tabulated in seven distinct tables according to their gene coding, their biochemistry and their metabolic control. CONCLUSION: The pathogenesis and pathophysiology of KC remain enigmatic. Emerging evidence has improved our understanding of the molecular characteristics of KC and could further improve the success rate of CXL therapies.