Posterior Bending Research Articles

The Effect of Twisted Wire Configuration on the Stability of External Fixator: A Biomechanical Study

The Ilizarov fixator is a type of external fixator that is used to treat patients who have suffered injuries from accidents, bone shortening, or nonunion of the bone. The principle behind the Ilizarov fixator is that thin wires (called Kirschner wires) are used to support the bones and connect them to framed rings. Before being fastened to the rings, the wires are tensioned and drilled through the bones. This study suggests using a new parallel wires configuration at the same level on the same ring and two revised versions, which are divergent and convergent models, and compare them with standard wires, 60 angle wires model. All models were designed using SolidWorks, a computer-aided design (CAD) software, and then analyzed in four conditions (axial compression, medial bending, posterior bending, and torsion) with Finite Element Analysis (FEA) using Ansys Workbench 2020 R2. Mechanical testing was conducted to validate the FEA results, A simple model consisting of a single ring, two K-wires, and polylactic acid (PLA) cylinders was utilized in a tensile test. It has been concluded from the results that the parallel model and its improvement have higher stiffness to axial compression, medial bending, and torsion, but a lower posterior bending stiffness, except the divergent model with 8-hole separation which has a relatively acceptable stiffness for posterior bending.

Cadaveric biomechanical assessment of different configurations for a novel pin and plate fixation method in distal humerus fractures

Use of dual pre-contoured plates has been accepted as the treatment of choice in distal humerus fractures despite challenges especially in very distal or highly fragmented fractures. Aiming to improve results in such instances, our newly proposed method uses several K-wires fixated by a small reconstruction plate. Drawing on the results of previous finite element studies, the current study aims to compare the stiffness of three clinically common variations of this method using biomechanical testing in cadaveric humeri. 24 samples were divided into three groups and fractures were simulated. Groups I and II used 1.5 mm K-wires in differing configurations while 2 mm wires were used in group III. All samples underwent compression, anterior and posterior bending, and torsional testing as well as failure testing. Our results indicated that Group III had significantly higher stiffness in flexion, extension, and torsion (p < 0.05). In failure, group III had the highest mean stiffness in anterior bending and torsion (861.2 N, 30.9 Nm). Based on previous and current results, this new Persian fixation method, especially when implemented using 2 mm K-wires, shows promise in achieving suitable stability and may be useful as an alternative approach in complex distal humerus fractures.

Comparative study of mechanical performance of various fixation constructs in multifragmentary distal humeral shaft fracture: a finite element analysis.

There has been no scientific mechanical assessment demonstrating the optimal fixation technique in multifragmentary fractures of the distal humeral shaft. The purpose of the present study was to compare the biomechanical performance of 5 fixation constructs as used in minimally invasive plating osteosynthesis (MIPO) for distal humeral shaft fractures. Three-dimensional (3D) humerus model with 20mm distal humeral shaft fracture gap simulating multifragmentary fracture was created from computed tomography data and virtually fixed by 5 fixation techniques as MIPO, i.e., anterior narrow dynamic compression plate (DCP), anterior narrow locking compression plate (LCP), anterior reversed proximal humeral internal locking system (R-PHILOS), extra-articular distal humerus locking compression plate (LCP-EADH), and anteromedial LCP. All constructs were biomechanically tested under 6 loading conditions by means of finite element analysis, i.e., 250-N axial compression, 7.5-Nm internal rotation, 7.5-Nm external rotation, 10-Nm posterior bending, 10-Nm valgus rotation, and 10-Nm varus rotation. In addition, A 3D model of each construct was fabricated as 3D printed models. Fixations were applied to the 3D printing model which were later mechanically tested to validate the FE results. EQV stress exhibited on anterior narrow LCP and anterior R-PHILOS were comparable which were lower than other constructs under axial compression and valgus-varus bending. Anterior R-PHILOS produced lower EQV stress than other constructs under internal-external rotation and posterior bending. On the whole, R-PHILOS demonstrated a comparable fracture displacement to those LCP with anterior or anteromedial approaches, that achieved the lowest displacement values. In addition, the experimental mechanical test values shared a correlation with the FE model results. Overall, the anterior R-PHILOS was considered as a potential candidate for multifragmentary distal humeral shaft fractures. It demonstrated efficacious biomechanical performance in terms of implant stress and distal fragment displacement.

Analysis of Biomechanical Characteristics of External Fixators with Steel and Composite Frames during Anterior–Posterior Bending

This paper presents a comparative analysis of the biomechanical characteristics of an external fixator with a frame made of two different materials (stainless steel and composite material) during anterior–posterior bending. Before the test itself, two representative configurations of the Sarafix fixator were selected for application on the lower leg and upper extremities under the designations B50 and C50, which are most widely used in orthopedic practice. The examination of the biomechanical characteristics of the external fixator was carried out using the structural analysis of the construction performance of the Sarafix fixator using the finite element method, the results of which were verified through experimental tests. The developed experimental and FEM models study the movement of the fracture crack and enable the determination of the stiffness of structural designs as well as the control of the generated stresses at the characteristic locations of the fixator. The results show that the fixator with a carbon frame has lower stresses at critical points in the construction compared to the fixator with a steel frame, in the amount of up to 49% (at the measuring point MT+) or up to 46% (at the measuring point MT−) for both fixture test configurations. The fixator with a carbon frame has greater displacements at the fracture site compared to the fixator with a steel frame, in the amount of up to 45% (for configuration B50) or up to 31% (for configuration C50). The stiffness of the structure for both test configurations of the fixator is lower in the fixator with a carbon frame compared to the fixator with a steel frame by up to 27%. Based on the findings of this study, we can conclude that a fixator with a steel frame has better biomechanical characteristics compared to a carbon frame.

Effect of bone cement augmentation with different configurations of the dual locking plate for femoral allograft fixation: finite element analysis and biomechanical study

AimsImplant failure in allograft reconstruction is one of the most common problems after treating a large bone defect for a primary bone tumor. The study aimed to investigate the effect of bone cement augmentation with different configurations of dual locking plates used for femoral allograft fixation.MethodsFour finite element (FE) models of the femur with a 1-mm bone gap were developed at the midshaft with different configurations of the 10-hole fixation dual locking plate (LP) with and without intramedullary bone cement augmentation. Model 1 was the dual LP at the lateral and medial aspect of the femur. Model 2 was Model 1 with bone cement augmentation. Model 3 was the dual LP at the anterior and lateral aspect of the femur. Finally, Model 4 was Model 3 with bone cement augmentation. All models were tested for stiffness under axial compression as well as torsional, lateral–medial, and anterior–posterior bending. In addition, the FE analyses were validated using biomechanical testing on a cadaveric femur.ResultsModel 2 had the greatest axial compression stiffness, followed by Models 1, 4, and 3. Bone cement augmentation in Models 2 and 4 had 3.5% and 2.4% greater axial stiffness than the non-augmentation Models 1 and 3, respectively. In the bone cement augmentation models, Model 2 had 11.9% greater axial compression stiffness than Model 4.ConclusionThe effect of bone cement augmentation increases construct stiffness less than the effect of the dual LP configuration. A dual lateral–medial LP with bone cement augmentation provides the strongest fixation of the femur in terms of axial compression and lateral bending stiffness.

Does the Posterior Bending Osteotomy in Bilateral Sagittal Split Osteotomy Affect the Condyle Position in Asymmetric Patients?

To measure and compare changes in postoperative condylar position following bilateral sagittal split osteotomy in patients with asymmetry treated using a posterior bending osteotomy (PBO) and conventional methods (shaving of premature contacts). Participants were randomized to either the PBO or conventional group. The inclusion criteria were the need for bilateral sagittal split osteotomy or bimaxillary asymmetric surgery (menton deviation >4mm). The primary outcome variable was changes in the condylar position in the axial, coronal, and sagittal planes 6months after surgery, whereas the secondary outcome variable was changes in temporomandibular joint symptoms. Covariates included surgery type, deformity type, age, and sex. Categorical and numerical variables were analyzed using Fisher exact χ2 test and 2-way analysis of covariance. The study sample comprised 42 patients with a mean age of 23.3years; 57.5% were women. The alteration in the coronal condyle angle was 0.8⁰ ± 0.86⁰ in the PBO and 2.72⁰ ± 0.81⁰ in the conventional group. The differences in the condylar position in the coronal plane were not statistically significant (P=.129). The alteration in the axial condyle angle was 2.31⁰ ± 1.74⁰ in the PBO group and 5.65⁰±1.65⁰ in the conventional group. The alteration in the sagittal plane was 0.44⁰ ± 1.52⁰ in PBO and 0.47⁰ ± 1.44⁰ in the conventional group. Alterations in axial (P=.194) and sagittal (P=.976) condylar positions were insignificant. In the conventional group, statistically significant differences were found in the axial (P=.002) and coronal (P=.002) planes, and the condyle turned inward in both planes. There were no statistically significant differences between the groups or within the groups in the sagittal plane (P>0,5). In PBO and conventional groups, joint noise examination revealed positive results in 11 and 6 patients preoperatively and 1 and 2 patients postoperatively, respectively. A statistically significant decrease in joint noise was detected in the PBO group (P=0,04). The maximum mouth opening without pain was 5.95±1.47 in the PBO group and 7.91±1.39 in the conventional group, respectively. The alteration was not statistically significant between the groups but was significant within the groups (P<.001). PBO effectively prevents premature contact between mandibular segments in facial asymmetry.

Implementasi Pemeriksaan Lumbosacral pada Kasus Scoliosis di Instalasi Radiologi BLUD Rumah Sakit Umum Daerah Cut Nyak Dhien Meulaboh

The aim of this study was to find out how the implementation of the lumbosacral examination in cases of Scoliosis and how to describe the quality of radiographic images on lumbosacral examination using Anterior Posterior (AP) Projection, Lateral Projection, and Anterior Posterior Projection bending left and right in terms of detail and sharpness. This study was conducted with three exposures to one patient who was diagnosed with lumbosacral scoliosis using the same distance but with different projections. The results of this study are in the form of lumbosacral radiographs and distribution frequency tables of ten radiographer respondents. The results showed that the lumbosacral examination in cases of scoliosis at the Radiology Installation BLUD, Cut Nyak Dhien Hospital, Meulaboh, West Aceh can use three different projections, namely anterior posterior projection, lateral projection and anterior posterior bending left right projection. The quality of the lumbosacral radiograph images produced in cases of scoliosis is clear and good in detail and has a sharpness level from the distance, patient movement, and the use of the viewing box.

Biomechanical comparison of three internal fixation configurations for low transcondylar fractures of the distal humerus

BackgroundWe aimed to evaluate the biomechanical stiffness and strength of different internal fixation configurations and find suitable treatment strategies for low transcondylar fractures of the distal humerus. Methods and materialsThirty 4th generation composite humeri were used to create low transcondylar fracture models that were fixed by orthogonal and parallel double plates as well as posterolateral plate and medial screw (PPMS) configurations (n=10 in each group) using an anatomical locking compression plate-screw system and fully threaded medial cortical screws. Posterior bending (maximum 50 N), axial loading (maximum 200 N) and internal rotation (maximum 10 N·m) were tested, in that order, for each specimen. Stiffness under different biomechanical settings among different configurations were compared. Another 18 sets of fracture models were created using these three configurations (n=6 in each group) and the load to failure under axial loading among different configurations was compared. ResultsUnder posterior bending, the stiffness of parallel group was higher than orthogonal group (P<0.001), and orthogonal group was higher than PPMS group (P<0.001). Under axial loading, the stiffness of parallel group was higher than orthogonal group (P=0.001) and PPMS group (P<0.001); however, the difference between orthogonal and PPMS group was not statistically significant (P>0.05). Under internal rotation, the stiffness of parallel group was higher than orthogonal group (P=0.044), and orthogonal group was higher than PPMS group (P=0.029). In failure test under axial loading, the load to failure in the orthogonal group was lower than parallel group (P=0.009) and PPMS group (P=0.021), but the difference between parallel group and PPMS group was not statistically significant (P>0.05). All specimens in orthogonal group demonstrated “distal medial failure”; most specimens had “distal medial and trochlear failure” in the parallel group; most specimens exhibited “contact failure” in the PPMS group. ConclusionFor treating low transcondylar fractures, the overall stiffness and strength of the parallel configuration were superior to those of the orthogonal and PPMS configurations. Nevertheless, the PPMS configuration can provide adequate stability and stiffness comparable to double-plate configurations under axial loading. Therefore, the PPMS construct may have certain clinical value.

Outcomes and experience after open reduction for chronic Monteggia fracture in children.

BackgroundThe treatment of chronic Monteggia fracture-dislocation (CMF) remains controversial and challenging for surgeons. We describe our initial experience with ulnar osteotomy and angulation on correction with modified open surgery and evaluate outcomes from clinical and radiographic findings.MethodsWe retrospectively reviewed 18 children with a mean age of 6.78±2.67 years old who underwent surgical treatment because of CMF. Electronic medical records of Bado type, complaints, Kim scores, and complications were recorded. Radiographic parameters of maximum interosseous distance (MID), proportional ulnar length (PUL), lengthening, and bending angle of the ulna were summarized. The final reduction statuses of the radial head were reviewed. Parameters were compared at the time of pre-operation and the last follow-up. The relationship between the lengthening and angulation of ulna and the interval was calculated.ResultsThe mean interval was 11.1 [1–48] months and the follow-up time was 46.6 [24–96] months. A good reduction was observed in 15 (83.33%) patients, while 3 (16.67%) patients were fair. Postoperatively, the Kim scores were improved, from 59.17±18.17 to 90±6.64 (P=0.000). The mean posterior bending angle was 12.88° (range, 3 to 25°), and the mean amount of elongation of the ulna was 8.78 mm (range, 3.61 to 17.52 mm). The lengthening of the ulna was proportional to the magnitude of angulation of the ulna (r=0.648, P=0.004), and a positive correlation was also seen between the lengthening and the interval (r=0.632, P=0.005) and the angulation and the interval (r=0.502, P=0.034). The PUL and MID were significantly increased from 1.06±0.03 and 1.11±0.26 to 1.13±0.11 (P=0.047) and 1.28±0.27 (P=0.021), separately.ConclusionsWe highlight ulnar osteotomy as the essential procedure during reconstruction surgeries. Stabilization of the radial head with adequate elongation and balanced angulation of the osteotomy through direct observation is the main way to ensure and maintain satisfactory outcomes. With the extension of the interval, it is more necessary to increase the lengthening and angulation in positive proportion. PUL is a useful parameter in evaluating the mismatch between ulna and radius in CMF.

Comparison of the Effect of Two Dynamic Loading Rates on Fracture Characteristics of Human Ribs in Bending

Recent years have seen an increase in contributions to the criminal justice system through expert testimony regardingskeletal trauma analysis and interpretation. In order to scientifically validate skeletal trauma analysis methods and ensure the dependability of interpretations to support expert testimonies, the reliability of generally accepted concepts must be determined. This research focused on the traditional assumption that extrinsic factors influence fracture characteristics in human bone. The objective of this study was to investigate the influence of loading rate on fracture characteristics by evaluating the effect of two dynamic loading rates in blunt-force trauma to human ribs. The sample consisted of mid-level human ribs in which fracture characteristics were evaluated in bilateral rib pairs experimentally tested in precisely the same loading scenario (anterior to posterior bending) at different dynamic loading rates. These comparisons demonstrated that the difference between 1 m/s and 2 m/s had no independent influence on fracture characteristics, despite the large difference in impact energy associated with these rates (27.2 J and 108.8 J, respectively). The general assumption that greater impact speed and energy leads to increased injury severity and more complex fracture characteristics was not supported in ribs loaded at 1 m/s versus 2 m/s.

Modified pin and plate fixation for low intercondylar fractures of the humerus: biomechanical study corroborated with a case series.

Establishing fracture union of low and comminuted intercondylar fractures of the humerus is inherently challenging. The purposes of the present study were to investigate the biomechanical effectiveness of pin & plate (PP) fixation compared to other dual-plating techniques by finite element analysis, and to present a technical description as well as retrospectively review the outcomes of PP fixation in such difficult fractures. Low-level intercondylar fracture 3D models of the humerus were virtually stabilized with three fixations on lateral side including PP, lateral pre-contoured locking compression plate (L-LCP), and variable angle lateral pre-contoured locking plate (VA-L-LCP) whereas medial pre-contoured locking compression plate (M-LCP) on medial side. Loading conditions under consideration were axial compression, internal rotation, posterior bending, and valgus rotation. Regarding the clinical series, eight patients with intra-articular and comminuted fractures of the distal humerus (6 intercondylar fractures, 1 fracture-subluxation, and 1 isolated lateral condylar fracture) were operated by isolated PP fixation or combinations of PP and the other standard implants. Data were collected on fracture union, perioperative complications, and objective clinical outcomes. Biomechanical results revealed the most instability of the fracture occurring under posterior bending. PP fixation presented comparable fracture stability and fragment displacement compared to other dual-plating fixations, except stress on the Kirschner wire under internal rotation which was higher than other fixations. Regarding the clinical series, fracture union was achieved in all cases with an average union time of 17weeks (range 12-20). All except one patient had good-to-excellent MEPS results with an average Disabilities of the Arm, Shoulder, and Hand (DASH) score of 14.6 (range 0-45) and an average arc of elbow motion of 107.5 degrees (range 60-140). By the biomechanical performance, PP fixation is a reliable technique for fixation of low intercondylar fractures of the humerus. Supported by the clinical outcomes, the present technique could be an alternative for this particular fracture especially when severe comminution prevents the use of the standard dual plating technique.

Computed tomography-based selection of transseptal puncture site for percutaneous left atrial appendage closure.

An inferoposterior transseptal puncture (TSP) is generally recommended for percutaneous left atrial appendage (LAA) closure. However, the LAA is a highly variable anatomical structure. This may have an impact on the preferred TSP site. This study aimed to determine the optimal TSP site for percutaneous LAA closure in different LAA morphologies. In this prospective study, 182 patients undergoing percutaneous LAA closure were included. The spatial relationship of the LAA to the fossa ovalis and its consequence for TSP was assessed at preprocedural cardiac computed tomography (CCT). Based on CCT analysis, it was predicted that coaxial alignment between the delivery sheath and the LAA would be obtained by an inferoposterior, inferocentral, or inferoanterior TSP in 75%, 16% and 8% of cases, respectively. This was also confirmed by procedural LAA angiogram in 175 cases (96%) with <30° angle between the delivery sheath and the LAA central axis. Multivariate logistic regression analysis identified reverse chicken wing LAA (odds ratio [OR] 6.36 [1.85-29.3]; p=0.005) and posterior bending of the proximal LAA (OR 17.2 [3.3-96.2]; p<0.001) as independent predictors of a central or anterior TSP - this to increase the chance of obtaining coaxial alignment between the delivery sheath and the LAA. An inferoposterior TSP is recommended in the majority of percutaneous LAA closure procedures in order to obtain coaxial alignment between the delivery sheath and the LAA. An inferior but more central/anterior TSP should be recommended in case of a reverse chicken wing LAA or posterior bending of the proximal LAA, which occurs in 20-25% of cases.

Does posterior configuration have similar strength as parallel configuration for treating comminuted distal humerus fractures? A cadaveric biomechanical study

BackgroundThe posterior plating technique could be used as a clinical alternative to parallel plating for treating comminuted distal humerus fractures (DHFs) successfully with good clinical results. However, the biomechanical characteristics for posterior fixation are still unclear. The purpose of this study is to evaluate the biomechanical properties of the posterior fixation and to make comparisons between the parallel and the posterior fixation systems.Materials and methodsWe performed a cadaveric biomechanical testing with two posterior plating systems (a posterior two plating and a single posterior pre-contoured Y plating system) and one parallel two plating system to treat AO/OTA type-C2.3 DHFs. Among three groups, we compared construct stiffness, failure strength, and intercondylar width changes after 5000-cycle fatigue loading and failure loads and failure modes after destructive tests in both the axial compression and (sagittal) posterior bending directions. The correlations between construct failure loads and bone marrow density (BMD) were also compared.ResultsIn axial direction, there were no significant differences in the stiffness and failure load between the posterior and the parallel constructs. However, in sagittal direction, the two-plate groups (posterior two plating and parallel plating group) had significant higher stiffness and failure loads than the one-plate group (single posterior Y plating). There was no fixation failure after 5000-cyclic loading in both directions for all groups. Positive correlation was noted between BMD and failure loads on parallel fixation.ConclusionsWe found that when using two plates for treating comminuted DHFs, there were no significant differences in terms of most biomechanical measurements between posterior and parallel fixation. However, the single pre-contoured posterior Y plate construct was biomechanically weaker in the sagittal plane than the parallel and the posterior two-plate constructs, although there was no fixation failure after the fatigue test for all groups regardless of the fixation methods.Level of evidenceBiomechanical study

Posterior bending osteotomy: An effective measure to secure facial symmetry in orthognathic surgery

This study aimed to compare the effectiveness of posterior bending osteotomy and grinding techniques for orthognathic surgery in patients with facial asymmetry. Patients who had undergone Le Fort I osteotomy and bilateral sagittal split ramus osteotomy, and who presented with a menton shift and setback difference exceeding 4 mm, were enrolled. Cone-beam computed tomography was performed before surgery (T0), immediately after surgery (T1), and 6 months after surgery (T2). Overall, 38 patients were included and divided into posterior bending osteotomy (n = 23) and grinding (n = 15) groups.Significant differences were observed between the posterior bending osteotomy and grinding groups on the treated side. In the grinding group, the gonion on the treated side was displaced slightly outward, resulting in a significant difference between both sides (non-treated side: 50.52 ± 4.20 [T0] and 48.67 ± 4.37 [T2]; treated side: 50.88 ± 4.55 [T0] and 51.00 ± 3.95 [T2]; p = 0.038). In the posterior bending osteotomy group, bilateral inward movements of the gonion were observed, and the distance from the midsagittal plane to the gonion did not differ significantly between the sides (non-treated side: 46.74 ± 4.41 [T0] and 45.54 ± 3.95 [T2]; treated side: 47.43 ± 4.93 [T0] and 45.18 ± 3.52 [T2]; p = 0.224). The yawing movement of the proximal segment was greater in the grinding group than in the posterior bending osteotomy group (non-treated side: p = 0.839; treated side: p = 0.025).Posterior bending osteotomy is recommended over the grinding method for patients with severe facial asymmetry, in order to ensure a symmetric and esthetic facial profile by allowing passive adaptation between the mandibular segments.

Biomechanical evaluation of a modified proximal humeral locking plate application for distal extra-articular diaphyseal humeral fractures.

The extra-articular distal humerus locking plate (EADHP) is widely used for distal extra-articular diaphyseal humeral fracture fixation. However, it occasionally causes skin prominence and discomfort. The upside-down use of a proximal humerus internal locking system (PHILOS) plate is suggested as an alternative option, but it lacks biomechanical evidence. The purpose of this study was to compare the biomechanical performance between two different fixation methods: themodified use of the PHILOS plate on the anterior cortex versus conventional use of an EADHP on the posterior cortex. Twelve pairs of fresh-frozen cadaveric humeri were used and 7 mm gap osteotomy was performed at 50 mm proximal to the lateral epicondyle to simulate an AO/OTA 12-C1.3 fracture type. Single load to failure was measured after five stiffness tests of the plate-bone constructs in anterior/posterior bending, internal/external torsion, and axial compression. There were no significant differences in metrics between the two groups, except for the load to failure in posterior bending, which was significantly higher for PHILOS (1589.3 ± 234.5) compared to EADHP (1430.1 ± 188.6), p < .023. In conclusion, the modified use of the PHILOS plate showed comparable biomechanical performance compared to the conventional EADHP. The new fixation method offers potential clinical advantages, considering the patient's position and surgical approach at the time of surgery as well as postoperative soft tissue irritation. Therefore, this could be an option for distal humeral extra-articular diaphyseal fracture fixation when the use of EADHP is not suitable or preferred.

A new surgical method for posterior bending of the uterus (abdominal strengthening of the uterus without opening the abdominal cavity)

The operation of suturing the uterus to the abdominal walls about its posterior bending, proposed for the first time by Olshausen in 1886, soon attracted general attention and became widespread with only small changes in suture imposition (Czerny, Leopold, Snger, etc.).

G.I. Thomson. The current status of the issue of the treatment of retroversio - retroflexio uteri. (South Russian Medical Newspaper, 1894, No. 3-4)

Noting the frequency of posterior bending of the uterus and the severity of local and general symptoms caused by this incorrect position of the uterus, the author considers the treatment of this disease to be one of the most interesting gynecological issues of the day.

Identification of the origin of force-feedback signals influencing motor neurons of the thoraco-coxal joint in an insect.

Force feedback from Campaniform sensilla (CS) on insect limbs helps to adapt motor outputs to environmental conditions, but we are only beginning to reveal the neural control mechanisms that mediate these influences. We studied CS groups that affect control of the thoraco-coxal joint in the stick insect Carausius morosus by applying horizontal and vertical forces to the leg stump. Motor effects of ablation of CS groups were evaluated by recording extracellularly from protractor (ProCx) and retractor (RetCx) nerves. Extracellular recordings showed that the effects of stimulating the sensilla were consistent with their broad ranges of directional sensitivity: for example, RetCx firing in response to posterior bending could be reduced by ablating several groups of trochanteral CS, whereas ablation of tibial and femoral sensilla had little effect. In contrast, ProCx motor neuron activity upon anteriorly directed stimuli was affected mainly by ablating a single CS group (G2). Dye fills of trochanteral, femoral and tibial CS groups with fluorescent dyes revealed a common projection pattern with little group specificity. These findings support the idea that the influences of CS feedback are determined by the activities of pre-motor interneurons, facilitating fast and task-dependent adaptation to changing environmental conditions.

Development of an easy-to-assemble external fixation system for bone transport

We developed a monolateral external fixation system for bone elongation easier to assemble than commercial systems since the clamps can be laterally assembled to the rail in contrast to the commercial systems where the clamps can only be assembled from the ends. The system is formed by clamps, screws, and a rail. The rail is composed of two carbon fiber circular rods of ½” diameter and 42-cm length. The clamps can slide with respect to the rail to allow bone distraction or may be fixed to the rail by using a wedge and a screw. The prototype was mechanically evaluated under the ASTM F1541 standard. The stiffness in axial, Medio Lateral bending (ML), Antero Posterior bending (AP), and flexo-torsional load were 117 N/mm, 46 N/mm, 8.7 N/mm, and 5.8 N-mm/°, respectively, which are on the range of stiffness of commercial systems.

Biomechanical comparison of orthogonal versus parallel double plating systems in intraarticular distal humerus fractures

ObjectivesIn intraarticular distal humerus fractures, internal fixation with double plates is the gold standard treatment. However the optimal plate configuration is not clear in the literature. The aim of this study was to compare the biomechanical stability of the parallel and the orthogonal anatomical locking plating systems in intraarticular distal humerus fractures in artificial humerus models. MethodsIntraarticular distal humerus fracture (AO13-C2) with 5 mm metaphyseal defect was created in sixteen artificial humeral models. Models were fixed with either orthogonal or parallel plating systems with locking screws (Acumed elbow plating systems). Both systems were tested for their stiffness with loads in axial compression, varus, valgus, anterior and posterior bending. Then plastic deformation after cyclic loading in posterior bending and load to failure in posterior bending were tested. The failure mechanisms of all the samples were observed. ResultsStiffness values in every direction were not significantly different among the orthogonal and the parallel plating groups. There was no statistical difference between the two groups in plastic deformation values (0.31 mm–0.29 mm) and load to failure tests in posterior bending (372.4 N–379.7 N). In the orthogonal plating system most of the failures occurred due to the proximal shaft fracture, whereas in the parallel plating system failure occurred due to the shift of the most distal screw in proximal fragment. ConclusionOur study showed that both plating systems had similar biomechanical stabilities when anatomic plates with distal locking screws were used in intraarticular distal humerus fractures in artificial humerus models.