Preliminary mechanical evaluation of two novel veterinary angle-stable-threaded interlocking nail systems

ABSTRACT: The interlocking nail represents an excellent option as a surgical approach to treat fractures in long bones in veterinary medicine. However, failures were reported mainly due to a slack present in the interface of the rod with the screws. The present study tested and mechanically compare axial compression loads of two novel models of stable angle interlocking nails with threaded holes. Among the two models, one was uniplanar and the other was multiplanar with orthogonally arranged distal holes. Twenty-one specimens made of polylactic acid were used for the implantation of interlocking nail´s rods, divided into three groups: conventional interlocking nail (G1), novel interlocking nail with a stable angle with holes arranged in a single plane (G2), and novel interlocking nail with a stable angle in two planes, with the penultimate hole at 90 degrees from the others (G3). Biomechanical tests were performed using axial, cyclic, and destructive compression load for comparison between them. All the specimens showed plastic deformation in the screws after destructive tests, in both proximal and distal sides, being highly intense in G1. G2 and G3 of the stable angle rods supported higher loads than G1 in all tests performed (P<0.05). The novel stems did not differ statistically from each other (P>0.05). The initial hypothesis that the novel models would provide increased stability was confirmed; however, no differences were demonstrated between them. The screw locking system on the rods allowed high resistance values in the tests performed, proving to be effective and potentially applicable in real clinical situations.

Biomechanical Tests and Finite Element Analyses of Pelvic Stability using Bilateral Single Iliac Screw with Different Channels in Lumbo-iliac Fixation

Background: In lumbo-iliac fixation, the iliac screw can be placed in a number of locations and directions, and multiple screws can be placed to enhance the fixation effect. At present, there is no uniform standard for the placement of single iliac screw. Biomechanical tests and finite element analyses were used to compare the effect of bilateral single iliac screw with three channels on pelvic stability in lumbo-iliac fixation, so as to provide a basis for determining the best single iliac screw channel.Methods: Five adult embalmed cadaver pelvic specimens were selected. Unstable Tile C1 pelvic injury model (pubic symphysis separation and left sacral Denis II fracture) was established. The pubic symphysis was fixed with five-hole reconstruction plate. Lumbo-iliac fixation for the treatment of pelvic posterior ring injury: three channels of bilateral single iliac screw (channel A from PSIS to AIIS, channel B from 1 cm medial and 1 cm caudal of PSIS to AIIS, channel C from 2 cm below PSIS to AIIS). At the same time, the finite element model of unstable pelvic posterior ring injury treated with lumbo-iliac fixation was established, which were used to analyze and explore the effect of bilateral single iliac screw with three channels on the biomechanical stability of the pelvis, including the stress distribution and the maximum Von Mises stress of internal fixation, vertebral body and ilium.Results: Biomechanical tests revealed that under vertical compression load, the compressive stiffness of pelvic specimens fixed with three channels of bilateral single iliac screw was lower than that of complete pelvic specimens (P < 0.05). The vertical displacement fixed by channel B was smaller than that fixed by channel A and channel C; however, there was no significant difference between channel B and channel A (P > 0.05). The compressive stiffness fixed by channel B was better than that fixed by channel A and channel C. Under torsional load, the torsional stiffness fixed by channel B was stronger than that fixed by channel A and channel C. Finite element analyses conformed that the maximum Von Mises stress of the internal fixator fixed in channel B under the conditions of vertical, forward bending, backward extension, left bending, left rotating and right bending were significantly lower than that fixed in channel A and channel C. Under various working conditions, the maximum Von Mises stress of the internal fixture of channel B was less than that of channel A. In terms of the maximum Von Mises stress of the vertebral body and iliac, compared with the other two iliac screw channels, the overall stress distribution fixed by channel B was more reasonable.Conclusions: Bilateral single iliac screw with three channels in lumbo-iliac fixation could effectively restore pelvic stability. The construct stiffness of the channel from 1cm medial and 1cm caudal of PSIS to AIIS is better than that of the other two channels. This channel has the advantages of good biomechanical stability, reasonable stress distribution, small maximum Von Mises stress of internal fixation, strong fatigue resistance and not easy to break screws and robs.

Experimental Analysis of Fabricated Synthetic Midthoracic Paediatric Spine as Compared to the Porcine Spine Based on Range of Motion (ROM)

The present study is aimed at investigating the mechanical behaviour of fabricated synthetic midthoracic paediatric spine based on range of motion (ROM) as compared to porcine spine as the biological specimen. The main interest was to ensure that the fabricated synthetic model could mimic the biological specimen behaviour. The synthetic paediatric spine was designed as a 200% scaled-up model to fit into the Bionix Servohydraulic spine simulator. Biomechanical tests were conducted to measure the ROM and nonlinearity of sigmoidal curves at six degrees of freedom (DOF) with moments at ±4 Nm before the specimens failed. Results were compared with the porcine spine (biological specimen). The differences found between the lateral bending and axial rotation of synthetic paediatric spine as compared to the porcine spine were 18% and 3%, respectively, but was still within the range. Flexion extension of the synthetic spine is a bit stiff in comparison of porcine spine with 45% different. The ROM curves of the synthetic paediatric spine exhibited nonlinearities for all motions as the measurements of neutral zone (NZ) and elastic zone (EZ) stiffness were below “1.” Therefore, it showed that the proposed synthetic paediatric spine behaved similarly to the biological specimen, particularly on ROM.

Fractions of Shen-Sui-Tong-Zhi Formula Enhance Osteogenesis Via Activation of β-Catenin Signaling in Growth Plate Chondrocytes

Background: Shen-sui-tong-zhi formula (SSTZF) has been used to treat osteoporosis for decades and shows excellent clinical efficacy. This article aims to explore the optimal anti-osteoporotic ingredient and its precise mechanisms in mice models.Methods: In this study, we first screened the optimal anti-osteoporosis fraction of SSTZF extract in vivo, and then further explored the mechanism of its effects both in vivo and in vitro. Ten-week-old female C57BL/6J mice were administrated with each fraction of SSTZF. At 10 weeks after ovariectomy (OVX), femurs were collected for tissue analyses, including histology, micro-CT, biomechanical tests, and immunohistochemistry for ALP, FABP4, and β-catenin. Additionally, we also evaluated the mRNA expression level of ALP and FABP4 and the protein expression level of β-catenin after being treated with SSTZF extract in C3H10T1/2 cells. Moreover, we investigated the anti-osteoporosis effect of SSTZF extract on mice with β-catenin conditional knockout in growth plate chondrocytes (β-cateninGli1ER mice) through μCT, histology, and immunohistochemistry analyzes.Results: At 10 weeks after treatment, osteoporosis-like phenotype were significantly ameliorated in SSTZF n-butanol extract (SSTZF-NB) group mice, as indicated by increased trabecular bone area and ALP content, and decreased lipid droplet area and FABP4 content. No such improvements were observed after being treated with other extracts, demonstrating that SSTZF-NB is the optimal anti-osteoporosis fraction. Additionally, the elevated β-catenin was revealed in both OVX mice and C3H10T1/2 cells with SSTZF-NB administered. Furthermore, a significant osteoporosis-like phenotype was observed in β-cateninGli1ER mice as expected. However, SSTZF-NB failed to rescue the deterioration in β-cateninGli1ER mice, no significant re-upregulated ALP and downregulated FABP4 were observed after being treated with SSTZF-NB, demonstrating that SSTZF-NB prevents bone loss mainly via β-catenin signaling.Conclusion: SSTZF-NB enhances osteogenesis mainly via activation of β-catenin signaling in growth plate chondrocytes. SSTZF-NB is the optimal anti-osteoporosis fraction of SSTZF and it can be considered a salutary alternative therapeutic option for osteoporosis.

Murine femur micro-computed tomography and biomechanical datasets for an ovariectomy-induced osteoporosis model

The development of new effective and safer therapies for osteoporosis, in addition to improved diagnostic and prevention strategies, represents a serious need in the scientific community. Micro-CT image-based analyses in association with biomechanical testing have become pivotal tools in identifying osteoporosis in animal models by assessment of bone microarchitecture and resistance, as well as bone strength. Here, we describe a dataset of micro-CT scans and reconstructions of 15 whole femurs and biomechanical tests on contralateral femurs from C57BL/6JOlaHsd ovariectomized (OVX), resembling human post-menopausal osteoporosis, and sham operated (sham) female mice. Data provided for each mouse include: the acquisition images (.tiff), the reconstructed images (.bmp) and an.xls file containing the maximum attenuations for each reconstructed image. Biomechanical data include an.xls file with the recorded load-displacement, a movie with the filmed test and an.xls file collecting all biomechanical results.

COMPARATIVE EFFECTIVENESS OF ROBOT-INTERACTIVE GAIT TRAINING WITH AND WITHOUT ANKLE ROBOTIC CONTROL IN PATIENTS WITH BRAIN DAMAGE

Although ankle robotic control has emerged as a critical component of robot-interactive gait training (RIGT), no study has investigated the neurophysiological and biomechanical effects on ankle muscle activity and joint angle kinematics in healthy adults and participants with brain damage, including stroke and cerebral palsy (CP). This study compared the effects of RIGT, with and without ankle control actuator, on ankle muscle activity and joint angle kinematics in healthy adults and participants with brain damage. Ten patients ([Formula: see text], left hemiparetic [Formula: see text], [Formula: see text]) underwent standardized surface electromyography (EMG) neurophysiological and kinematics biomechanical tests under the RIGT with and without ankle control actuator conditions. Outcome measures included the EMG amplitudes of the tibialis anterior and gastrocnemius muscle activity, and ankle movement angles recorded with a two-axis digital inclinometer. Descriptive statistical analysis demonstrated that RIGT with ankle control actuator showed superior effects on EMG (30%) and kinematics angles (25%) than RIGT without ankle control actuator. Our results provided novel, promising clinical evidence that RIGT with ankle control actuator can more effectively improve the neurophysiological EMG data and ankle dorsiflexion and plantarflexion movements than RIGT without ankle control actuator in participants with stroke and CP.

Optimizing the layer thickness of sol–gel-derived TiO2 coating on polyetheretherketone

Sol–gel-derived TiO2 coatings have been confirmed to effectively promote bone-bonding behavior on polyetheretherketone (PEEK) surfaces; however, the optimal layer thickness to maximize the osseointegration and adhesive performance has not been yet determined. In this study, we applied sol–gel-derived TiO2 coatings with different layer thicknesses (40 and 120 nm) on PEEK implants to determine the effects of layer thickness on the surface characteristics, adhesive strength, and bone bonding capabilities (including histological osseointegration). The surface analysis results of both coated implants indicated no significant differences concerning the water contact angle, layer adhesion strength, and apatite formation ability in a simulated body fluid. Additionally, the in vivo biomechanical tests revealed a higher bone-bonding strength for both coated PEEK implants (compared with that of the uncoated sample). It was thus concluded that the factor of layer thickness marginally influences the bioactive advantages attained by sol–gel-derived TiO2 coatings on PEEK surfaces, highlighting the significant versatility and clinical availability of this coating technology.

Biomechanical study of transsacral-transiliac screw fixation versus lumbopelvic fixation and bilateral triangular fixation for “H”- and “U”-type sacrum fractures with traumatic spondylopelvic dissociation: a finite element analysis study

Objective To compare the biomechanical stability of transsacral-transiliac screw fixation and lumbopelvic fixation for “H”- and “U”-type sacrum fractures with traumatic spondylopelvic dissociation. Methods Finite element models of “H”- and “U”-type sacrum fractures with traumatic spondylopelvic dissociation were created in this study. The models mimicked the standing position of a human. Fixation with transsacral-transiliac screw fixation, lumbopelvic fixation, and bilateral triangular fixation were simulated. Biomechanical tests of instability were performed, and the fracture gap displacement, anteflexion, rotation, and stress distribution after fixation were assessed. Results For H-type fractures, the three kinds of fixation ranked by stability were bilateral triangular fixation > lumbopelvic fixation > transsacral-transiliac screw fixation in the vertical and anteflexion directions, bilateral triangular fixation > transsacral-transiliac S1 and S2 screw fixation > lumbopelvic fixation in rotation. The largest displacements in the vertical, anteflexion, and rotational directions were 0.57234 mm, 0.37923 mm, and 0.13076 mm, respectively. For U-type fractures, these kinds of fixation ranked by stability were bilateral triangular fixation > lumbopelvic fixation > transsacral-transiliac S1 and S2 screw fixation > transsacral-transiliac S1 screw fixation in the vertical, anteflexion, and rotational directions. The largest displacements in the vertical, anteflexion, and rotational directions were 0.38296 mm, 0.33976 mm, and 0.05064 mm, respectively. Conclusion All these kinds of fixation met the mechanical criteria for clinical applications. The biomechanical analysis showed better bilateral balance with transsacral-transiliac screw fixation. The maximal displacement for these types of fixation was less than 1 mm. Percutaneous transsacral-transiliac screw fixation can be considered the best option among these kinds of fracture fixation.

Whether sutures reduce the graft laceration caused by interference screw in anterior cruciate ligament reconstruction? A biomechanical study in vitro

Background Interference screw is commonly used for graft fixation in anterior cruciate ligament (ACL) reconstruction. However, previous studies had reported that the insertion of interference screws significantly caused graft laceration. The purposes of this study were to (1) quantitatively evaluate the graft laceration from one single insertion of PEEK interference screws; and (2) determine whether different types of sutures reduced the graft laceration after one single insertion of interference screws in ACL reconstruction. Methods The in-vitro ACL reconstruction model was created using porcine tibias and bovine extensor digitorum tendons of bovine hind limbs. The ends of grafts were sutured using three different sutures, including the bioabsorbable, Ethibond and ultra-high molecular weight polyethylene (UHMWPE) sutures. Poly-ether-ether-ketone (PEEK) interference screws were used for tibial fixation. This study was divided into five groups (n = 10 in each group): the non-fixed group, the non-sutured group, the absorbable suture group, the Ethibond suture group and the UHMWPE suture group. Biomechanical tests were performed using the mode of pull-to-failure loading tests at 10 mm/min. Tensile stiffness (newtons per millimeter), energy absorbed to failure (in joules) and ultimate load (newtons) were recorded for analysis. Results All prepared tendons and bone specimens showed similar characteristics (length, weight, and pre-tension of the tendons, tibial bone mineral density) among all groups (P > 0.05). The biomechanical tests demonstrated that PEEK interference screws significantly caused the graft laceration (P < 0.05). However, all sutures (the bioabsorbable, Ethibond and UHMWPE sutures) did not reduce the graft laceration in ACL reconstruction (P > 0.05). Conclusions Our biomechanical study suggested that the ultimate failure load of grafts was reduced of approximately 25 % after one single insertion of a PEEK interference screw in ACL reconstruction. Suturing the ends of the grafts using different sutures (absorbable, Ethibond and UHMWPE sutures) did not decrease the graft laceration caused by interference screws.