Synthetic Bone Model Research Articles

Cerclage wire or positional cortical screw for the treatment of intraoperative calcar fractures during primary total hip arthroplasty? A biomechanical study

BackgroundDuring primary total hip arthroplasty, intra-operative calcar fractures have been historically treated with cerclage wires. However, interfragmentary screw fixation technique can possibly achieve the same results with technical advantages. The aim of this biomechanical study was to assess stability of calcar fractures fixed using interfragmentary screw technique compared to a traditional cerclage system specifically in context of total hip arthroplasty. MethodsThirty-two periprosthetic fractures were reduced using either a single cerclage cable or an intracortical positional screw perpendicular to the fracture line. Axial and torsional load testing was terminated after experimental model failure. FindingsNo significant difference was obtained for all output parameters when comparing cerclage wires versus interfragmentary screw fixation respectively. Load at failure: 8043 ± 712 N vs 7425 ± 854 N (p = 0.115). Load at calcar fracture propagation: 6240 ± 2207 N versus 6220 ± 966 N (p = 0.668). Maximum stiffness before failure: 617 ± 115 N/mm vs 839 ± 175 N/mm (p = 0.100) and stiffness at calcar fracture propagation reached 771 ± 153 Nmm vs 886 ± 129 N/mm (p = 0.197). Torque to failure levels obtained were 59.4 ± 7.1 N*m vs 60.9 ± 12.0 N*m (p = 0.908). Torque to calcar fracture propagation, 51.6 ± 6.1 N*m vs 48.5 ± 9.8 N*m (p = 0.298). Torsional stiffness at failure, 0.38 ± 0.03 N*m\\deg. vs 0.43 ± 0.13 N*m\\deg. (p = 0.465). Torsional stiffness at calcar fracture propagation were 0.37 ± 0.03 N*m\\deg. vs 0.45 ± 0.17 N*m\\deg. (p = 0.462). InterpretationThe strength of fixation and stability of the implant were similar for both techniques. In the synthetic bone model tested, using an interfragmentary screw conveyed similar stability to the constructs in the management of an intra-operative medial calcar fractures. Thus, potentially giving surgeons an alternative option for intraoperative fracture fixation during primary total hip arthroplasty.

Experience using immersive virtual reality simulation during an AO trauma regional course in Latin America

Virtual reality has been used in orthopedics for several years now, both as a training and assessment tool. The use of extended reality technologies in surgical training and simulation is the most developed and validated of all the current applications. However, formal and massive implementation in continuous orthopedic education has yet to happen. This report aimed to present our experience during the first AO trauma regional courses in Latin America that incorporated the use of immersive virtual reality (IVR) simulation as a hands-on activity as part of the program. IVR was used for the first time as part of a course activity during the advanced principles of fracture treatment course as part of the AO regional courses in Rio de Janeiro, Brazil, in 2022. The activity was implemented for 120 participants in a back-to-back fashion. Each participant used the IVR simulation for the trochanteric nail application and did a traditional hands-on exercise with a synthetic bone model. An appreciation survey was answered by participants. Seventy-four persons answered the survey. About 62% considered that the IVR simulation was like reality, and 76.38% thought that IVR was helpful in the learning process. The majority (91.6%) would like to use IVR for training, and 93% would be willing to use IVR again. This was the first time, IVR simulation was implemented as a massive and structured educational activity during the principles of fracture treatment course. Participant feedback was positive, and most people would use IVIR again. A systematic way of implementing IVR simulation sessions with educational goals needs to be developed for these activities.

Biomechanical Comparison of Headless Compression Screws, Kirschner Wires and Bioabsorbable Pins in Distal Oblique Metatarsal Osteotomy for Correction of Hallux Valgus.

Distal osteotomy of the first metatarsal is a widely used method for the correction of mild-to-moderate hallux valgus deformities. The objective of this study was to compare the stability of headless compression screws, kirschner wires and absorbable pins in terms of stiffness and maximum load in distal oblique metatarsal osteotomy. A total of 30 4th generation first metatarsal synthetic bone models were divided into three groups according to the fixation techniques. The stiffness of the first metatarsal was calculated as the slope of the linear curve that fit with the first linear part of the force displacement curve. The failure strength was recorded as the maximum load. The stiffness and maximum load values in the axillary and transverse configurations were compared between the three fixation groups. The stiffness was statistically higher in Group K and Group C compared to Group B in both axial and transverse loading. Similarly, the maximum load was significantly higher in both Group K and Group C compared to Group B in both loading conditions. No significant difference was found between Group K and Group C in stability. The higher failure strength was obtained with headless compression screws (113.34±35.88 N) in the axial loading. The lowest failure strength was found in the absorbable pins technique (16.17±7.72 N) in the transverse loading. No significant difference was found between the Kirschner wires and headless compression screws techniques, although the highest strength was obtained with headless compression screws that are increasingly used in orthopedic practice.

Optimizing the Orientation of a Suture Button to Stabilize the Distal Radioulnar Joint in a Sawbones Model

When left untreated, distal radioulnar joint (DRUJ) instability leads to prolonged wrist pain and weakness during pronosupination. Current treatment options are technically demanding and result in mixed outcomes. This study used a synthetic bone model to evaluate the potential of using a suture button to stabilize the DRUJ and find its optimal configuration. A suture button was placed between the radius and ulna of a synthetic bone model with DRUJ instability. The suture button was placed straight across or in an oblique orientation while the forearm was in 60° of pronation, neutral, or 60° of supination for 6 configurations. The range of motion, dislocation events, dorsal translation, volar translation, and gaps between the radius and ulna were measured and compared among these 6 configurations. Full range of motion (ROM) was achieved in all configurations except for suture buttons placed while the forearm was in 60 pronation. Obliquely placed suture buttons led to more dislocations than straight across suture buttons. The 2 configurations that offered full ROM with the greatest stability were straight across 60° supination and straight across neutral configuration, with the supinated configuration slightly improving stability. In this model, suture buttons restored DRUJ stability while maintaining full ROM, indicating that suture buttons have the potential to be used as a treatment option for stabilization of DRUJ. The optimal configuration of a suture button is likely in the straight across 60° supinated configuration, as it provides the greatest stability without sacrificing ROM compared with the other suture button configurations. Additional treatment options for the stabilization of DRUJ are needed. Suture buttons may be of use.

An Experimental Study on the Biomechanical Effectiveness of Bone Cement-Augmented Pedicle Screw Fixation with Various Types of Fenestrations.

To analyze the effects of the number and shape of fenestrations on the mechanical strength of pedicle screws and the effects of bone cement augmentation (BCA) on the pull-out strength (POS) of screws used in conventional BCA. For the control group, a conventional screw was defined as C1, a screw with cannulated end-holes was defined as C2, a C2 screw with six pinholes was defined as C3, and the control group type was set. Among the experimental screws, T1 was designed using symmetrically placed thru-hole type fenestrations with an elliptical shape, while T2 was designed with half-moon (HM)-shaped asymmetrical fenestrations. T3 and T4 were designed with single HM-shaped fenestrations covering three pitches and five pitches, respectively. T5 and T6 were designed with 0.6-mm and 1-mm wider fenestrations than T3. BCA was performed by injecting 3 mL of commercial bone cement in the screw, and mechanical strength and POS tests were performed according to ASTM F1717 and ASTM F543 standards. Synthetic bone (model #1522-505) made of polyurethane foam was used as a model of osteoporotic bone, and radiographic examinations were performed using computed tomography and fluoroscopy. In the fatigue test, at 75% ultimate load, fractures occurred 7781 and 9189 times; at 50%, they occurred 36122 and 82067 times; and at 25%, no fractures occurred. The mean ultimate load for each screw type was 219.1±52.39 N for T1, 234.74±15.9 N for T2, 220.70±59.23 N for T3, 216.45±32.4 N for T4, 181.55±54.78 N for T5, and 216.47±29.25 N for T6. In comparison with C1, T1, T2, T3, T4, and T6 showed significantly different ultimate load values (p<0.05). However, when the values for C2 and the fenestrated screws were evaluated with an unpaired t test, the ultimate load value of C2 significantly differed only from that of T2 (p=0.025). The ultimate load value of C3 differed significantly from those of T1 and T2 (C3 vs. T1 : p=0.048; C3 vs. T2 : p<0.001). Linear correlation analysis revealed a significant correlation between the fenestration area and the volume of bone cement (Pearson's correlation coefficient r=0.288, p=0.036). The bone cement volume and ultimate load significantly correlated with each other in linear correlation analysis (r=0.403, p=0.003). Fenestration yielded a superior ultimate load in comparison with standard BCA using a conventional screw. In T2 screws with asymmetrical two-way fenestrations showed the maximal increase in ultimate load. The fenestrated screws can be expected to show a stable position for the formation of the cement mass.

Biomechanical study of rod stress in lumbopelvic fixation with lateral interbody fusion: an in vitro experimental study using synthetic bone models.

Despite improvements in surgical techniques and instruments, high rates of rod fracture following a long spinal fusion in the treatment of adult spinal deformity (ASD) remain a concern. Thus, an improved understanding of rod fracture may be valuable for better surgical planning. The authors aimed to investigate mechanical stress on posterior rods in lumbopelvic fixation for the treatment of ASD. Synthetic lumbopelvic bone models were instrumented with intervertebral cages, pedicle screws, S2-alar-iliac screws, and rods. The construct was then placed in a testing device, and compressive loads were applied. Subsequently, the strain on the rods was measured using strain gauges on the dorsal aspect of each rod. When the models were instrumented using titanium alloy rods at 30° lumbar lordosis and with lateral interbody fusion cages, posterior rod strain was highest at the lowest segment (L5-S1) and significantly higher than that at the upper segment (L2-3) (p = 0.002). Changing the rod contour from 30° to 50° caused a 36% increase in strain at L5-S1 (p = 0.009). Changing the rod material from titanium alloy to cobalt-chromium caused a 140% increase in strain at L2-3 (p = 0.009) and a 28% decrease in strain at L5-S1 (p = 0.016). The rod strain at L5-S1 using a flat bender for contouring was 23% less than that obtained using a French bender (p = 0.016). In lumbopelvic fixation in which currently available surgical techniques for ASD are used, the posterior rod strain was highest at the lumbosacral junction, and depended on the contour and material of the rods.

The addition of cerclage wiring does not improve proximal bicortical fixation of locking plates for Type C periprosthetic fractures in synthetic humeri

BackgroundTreatment of proximal humerus periprosthetic fractures is challenging. It remains difficult to achieve robust fixation of the proximal fragment to the locking plate using cerclage wiring and/or unicortical screws. Use of polyaxial tangentially directed bicortical locking screws increases screw purchase, but it is unclear if this option provides robust fixation. This biomechanical study compares fixation of constructs using cerclage wires, bicortical locking screws, and a hybrid method utilizing both methods. MethodsUncemented humeral stems were implanted into synthetic humeri and Type C periprosthetic fractures were simulated with a 1 cm transverse osteotomy. Distal ends of locking plates were secured with bicortical non-locking screws. The proximal ends were supported by either isolated cerclage wires, polyaxial locking screws, or a hybrid combination of both (n = 6 for each group). A universal test frame was used for non-destructive torsion and cyclic axial compression tests. 3-D motion tracking was employed to determine stiffnesses and relative interfragmentary motions. FindingsIsolated screw constructs showed significantly increased resistance against torsional movement, bending, and shear, (p < 0.05) in comparison to cerclage constructs. The hybrid construct provided no significant changes in stability over the isolated screw construct. InterpretationAddition of cerclage wires in this synthetic bone model of Type C periprosthetic humerus fractures did not add significant stability to proximal bicortical locking plate fixation. Considering risks of tissue stripping and nerve injury, usage of cerclage wires in a similar clinical setting should be chosen carefully, especially when bicortical fixation around the prosthetic stem can be achieved.

Evaluation of a customized 3D-printed saw guide for tibial plateau leveling osteotomy: An ex vivo study.

To determine whether a tibial plateau leveling osteotomy (TPLO) performed with a customized 3D-printed guide and jig is more accurate than the traditional technique using a jig alone. In vitro study. Cadaveric canine pelvic limbs (n=10) and 20 synthetic bone models. Tibial plateau leveling osteotomy using a jig with (n=10) and without (n=10) a customized 3D-printed guide were performed in bone models, and TPLO using a jig with (n=5) and without (n=5) a customized 3D-printed guide were performed in cadaveric limbs. Angulation of the osteotomy, angulation of the proximal jig pin, angular/torsional deformity and medial cortex damage were measured from photographs of the specimens and compared. In the bone models, there were differences with and without the 3D guide for mean osteotomy inclination (-0.06° vs. -1.74°, P < .001), osteotomy torsion (5268 vs. 10 469 visible osteotomy pixels, P < .001), and medial cortical damage (2970 vs. 18 562 pixels, P < .001). In the cadaveric study, osteotomy inclination (-1.1° vs. 1.01°, P < .01), induced angular deformity (0.17° vs. -3.01°, P < .001) and angulation of the proximal jig pin (-0.27° vs. 0.80°, P < .001) differed between groups. The 3D-printed guide during TPLO resulted in slightly more accurate osteotomies and proximal jig pin placement, and reduced medial cortex damage. A customized 3D-printed guide may improve intraoperative accuracy for TPLO, although the clinical significance of the small benefits is unknown.

Migration of Subtalar Implants in Paediatric Flatfoot Correction: A Pilot Study in Synthetic Bone Models.

Subtalar implant migration as a complication following subtalar arthroeresis has been described in the scientific literature. However, clinical studies do not allow for unequivocally determining the underlying causes. The aim of the study is to determine the risk of migration of two geometric types of subtalar implants. Biomechanical tests were carried out on a synthetic bone model with a soft tissue substitute, which allowed for reduction of variability of results caused by biological differences. A foot model mirroring natural anatomy was made from synthetic bone and a silicone soft tissue substitute with the same hardness as that of the soft tissues of the foot. Two types of 11 mm Ti6Al4V titanium alloy implants were studied, namely, a rectangular subtalar screw and a cylindrical subtalar screw, a type commonly used in flatfoot reconstruction surgery in children. The screws were placed in the sinus tarsi and subjected to cyclic loading (up to 1,000,000 cycles at a frequency of 5 Hz, with a maximum load of 500 N). Comparative pull-out force tests were performed immediately following implantation and after the dynamic loading test. Wyniki. Following the dynamic loading test, all 12 samples were qualified for the pull-out force test. Cylindrical screws demonstrated higher pull-out force values both for the samples tested immediately following implantation and for those that underwent dynamic loading. Implants of the same shape did not show statistically significant differences in the Mann-Whitney U test (p &gt;0.05). Wniosek. The synthetic research model produces reproducible results in the assessment of risk of implant migration. Long-term loading does not significantly affect the risk of implant migration.

Biomechanical Comparison of Use of Two Screws versus Three Screws Per Fragment with Locking Plate Constructs under Cyclic Loading in Compression in a Fracture Gap Model

Abstract Objectives The aim of this study was to measure and compare the stiffness and cyclic fatigue of two plate-bone model constructs, with either two or three locking screws per fragment, under cyclic compression. Methods A 10-hole 3.5 mm stainless steel locking compression plate (LCP) was fixed 1 mm from a synthetic bone model in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled compression test until failure. Results The three-screw constructs were stiffer than the two-screw constructs (196.75 ± 50.48 N/mm and 102.43 ± 22.93 N/mm, respectively) and the actuator displacements of the two-screw constructs were higher (18.02 ± 1.07 mm) than those of the three-screw constructs (14.48 ± 2.25 mm). The number of cycles to failure of the two-screw constructs was significantly lower (38,337.50 ± 2,196.98) than the that of the three-screw constructs (44,224.00 ± 1,515.24). Load at irreversible deformation was significantly lower in the two-screw constructs (140.93 ± 13.39 N) than in the three-screw constructs (184.27 ± 13.17 N). All constructs failed by plate bending at the gap between the two cylinders. Clinical Significance Omission of the third innermost locking screw during bridging osteosynthesis subjected to compression forces led to a 13.3% reduction in the number of cycles to failure and a 23.5% reduction of the load withstood by the plate before plastic deformation occurred.

Torque acting on biodegradable magnesium screws during intramedullary insertion into a metacarpal bone – a biomechanical study

Recently, biodegradable implants made from magnesium (Mg) alloys have been developed to obviate the need for later implant removal. Mg-based cannulated compression screws (CCS) are ideal for intramedullary screw (IMS) fixation of metacarpal fractures. The present study aimed at investigating the torque acting on Mg-based CCS at failure and at intramedullary metacarpal insertion. The devices were CE certified Magnezix 2.7 and 3.2 mm CCSs (Syntellix®, Hannover, Germany). Torque at failure was measured in a synthetic bone model using a standardized polyurethane foam block. In a second assessment, insertional torque was measured in ten cadaveric metacarpal bones. Mean torque at failure for the 2.7 mm and 3.2 mm CCSs was 42.8 Ncm (±1.9 Ncm) and 63.0 Ncm (±2.2 Ncm), respectively. In the human cadaver model, the torque distribution curve at metacarpal insertion showed three peaks. The highest reached 53.6% of the lowest torque at failure measured in the synthetic bone model for the 3.2 CCS (31.4 vs. 58.6 Ncm). The mean difference between peak torque at metacarpal insertion and torque at failure was 38.3 Ncm (99% CI [33.6, 43.0 Ncm], p < 0.0001). In terms of torque load, Mg-based CCSs are suitable for IMS fixation of metacarpal fractures. Biodegradable implants may represent an important improvement of this treatment method; confirmation by in-vivo studies is needed.

Evaluation of a crescent saw guide for tibial plateau-leveling osteotomy: An ex vivo study.

To evaluate the effectiveness of a novel crescent-shaped tibial plateau-leveling osteotomy (TPLO) saw guide (crescent guide) to assist with saw control in novice participants. Ex vivo study. Synthetic bones (n=54) and medium sized dog pelvic limbs (n=36). The 6 participants (interns and residents) without any prior experience performing a TPLO each performed 9 osteotomies on synthetic tibia models, and 6 osteotomies in cadaveric limbs of medium-sized dogs. Osteotomies made with the crescent guide were compared with those made with a standard jig and a radial saw guide with a jig. Osteotomy angulation, distance of eccentricity (DOE), and medial tibial cortical damage (synthetic bone models only) were measured from calibrated photographs. Participants rated their experiences with each technique. There was no difference in the DOE, coronal or axial osteotomy angulation between the 3 alignment devices for synthetic bone models or cadavers. Average medial cortical damage with the crescent guide (3.8 ± 7.3 mm2 ) was lower than with the radial guide (35.7 ± 27 mm2 ) and standard jig (51.2 ± 63.2 mm2 ) guides (P=<.01). Five of 6 participants preferred the crescent guide over the standard jig and radial guide. There was no difference in accuracy of osteotomy positioning but using the crescent guide resulted in lower cortical damage and more favorable participant perceptions. The crescent guide may improve control of the radial saw during TPLO in novice surgeons but does not appear to aid accurate osteotomy positioning.

Optimal blocking screw placement for retrograde IM nail fixation of distal femur fracture: a standardized biomechanical study of "osteoporotic" synthetic bone.

Intramedullary (IM) nail use for metaphyseal fracture management is problematic in long bones like the femur because the larger medullary cavity allows increased fracture motion and potentially increased implant failure and malunion/nonunion risk; Achieving effective distal femur fracture fixation is even more difficult in osteoporotic bone. Blocking screws to control IM nail movement are known to be effective for tibia fracture management. Few studies have evaluated IM nail and blocking screw use efficacy for distal femur fracture fixation in osteoporotic bone. This study used an osteoporosis simulation synthetic bone model to evaluate retrograde IM nail fixation of a standardized non-comminuted, extra-articular distal femur fracture with and without blocking screws. The hypothesis was that use of one or two blocking screws would increase IM nail fixation stability as evidenced by greater peak IM nail load and lesser movement. A servohydraulic device under displacement control collected loading force versus movement deflection data. Shapiro-Wilk tests confirmed data normality. One-way analysis of variance and Tukey post hoc tests were used to compare condition specific loading force and movement differences. In the coronal plane, blocking screw conditions displayed greater loading ranges (38.3 ± 2 vs. 19.1 ± 2N, 100.5% difference) (p < 0.0001) and lesser movement (2.0 ± 0.3 vs. 6.86 ± 0.4mm, 243% difference) (p < 0.0001). In the sagittal plane, the two blocking screw condition displayed a significantly greater loading magnitude (29.9 ± 6 vs. 20.8 ± 2.3N, 43.8% difference) than the identical control condition without blocking screws (p = 0.018); however, movements were comparable (p = 0.82). Long-axis rotational loading failed to reveal load magnitude differences (p = 0.28); however, two different blocking screw conditions displayed decreased movement (1.32 ± 0.2 vs. 2.05 ± 0.3mm, 53.8% difference) compared to other conditions (p ≤ 0.018). Use of one or two blocking screws on the medial and lateral sides of the IM nail decreased coronal plane movement in the intramedullary canal. Combining retrograde IM nail implantation with blocking screws reduced medial-lateral IM nail movement and increased fracture stability. These characteristics may help prevent fixation failure, malunion, and even nonunion in patients with a distal femur fracture in osteoporotic bone.

The Effect of Prophylactic Femoral Neck Fixation in a Synthetic Osteoporosis Bone Model

The Effect of Prophylactic Femoral Neck Fixation in a Synthetic Osteoporosis Bone Model

Can the design of the instruments used for undersized osteotomies influence the initial stability of implants installed in low-density bone? An in vitro pilot study.

ObjectivesThe aims of this study were to compare the initial implant stability obtained using four different osteotomy techniques in low-density synthetic bone, to evaluate the instrument design in comparison to the implant design, and to determinate a possible correlation between the insertion torque and initial stability quotient (ISQ).Materials and methodsFour groups were identified in accordance with the osteotomy technique used (n = 10 implants per group): group G1, osteotomy using the recommended drilling sequence; group G2, osteotomy using an undersized compactor drill; group G3, osteotomy using an undersized drill; and group G4, osteotomy using universal osseodensification drills. Two polyurethane blocks were used: block 1, with a medullary portion of 10 pounds per cubic foot (PCF 10) and with a 1 mm cortical portion of PCF 40, and block 2, with a medullary of PCF 15 and with a 2 mm cortical portion of PCF 40. Tapered implants of 4 mm in diameter and 11 mm in length were used. The insertion torque (IT) and ISQ were measured. The dimensions of the final instrument used in each group and the dimensions of the implant were used to calculate the total area of each part, and these data were compared.ResultsDifferences between the four groups were found for IT and ISQ values depending on the technique used for the osteotomy in the two synthetic bone models (p < 0.0001). All groups showed lower values of initial stability in block 1 than in block 2.ConclusionsUndersized osteotomies with instruments designed according to the implant body significantly increased the initial stability values compared to beds prepared with universal drills and using the drilling sequence standardized by the manufacturer.

Simulation on synthetic bone: A tool for teaching thoracolumbar pedicle screw placement

IntroductionSimulation workshops for surgical training of residents are becoming popular. The gold standard for teaching thoracolumbar pedicle screw placement are cadaver labs; however, the availability of human bodies is limited. The primary objective of this study was to determine if training on a synthetic bone model improves the apprenticeship of accurate pedicle screw placement. The secondary objective was to check the influence of residents’ previous experience in spine surgery. HypothesisThe main hypothesis was that theoretical learning with practical application on synthetic bone was superior to theoretical learning alone. MethodsTwenty-three orthopedic residents were taught about free-hand pedicle screw placement using a theoretical presentation. Six residents had previous experience with screwing techniques. After randomization in two groups, 11 residents (group 1) participated in a workshop on synthetic bone, whereas 12 residents received only theoretical instruction (group 2). Each resident was asked to place two thoracic screws (T7-T11) and two lumbar screws (L1-L5) on a cadaver. Screw placement accuracy was analyzed using the Gertzbein classification on computed tomography (grades 0 and 1=accurate positioning; grades 2 and 3=malposition>2mm). ResultsRates of accurate screw positioning were 64.0% and 62.5% for thoracic levels, and 72.7% and 66.6% for lumbar levels in group 1 and 2, respectively. There was no significant difference in malposition rates on cadavers between the groups (p=0.1809). A resident who was first trained by simulation had a chance of decreasing the Gertzbein score with an odds-ratio of 1.7714 [0.7710–4.1515]. The odds ratio was 4.5188 [0.0456–0.8451] when comparing residents with previous experience in spinal surgery to novice residents. DiscussionTheoretical teaching associated with a simulation model is relevant for learning a surgical technique. A single simulation workshop on synthetic bone seems insufficient to improve pedicle screw placement accuracy compared to theoretical teaching alone. Progressive experience and the repetition of technical gestures during hands-on supervised learning in spine surgery with a senior surgeon had an influence on the accuracy of pedicle screw placement. Level of evidenceII.

The Potential of Stereolithography for 3D Printing of Synthetic Trabecular Bone Structures.

Synthetic bone models are used to train surgeons as well as to test new medical devices. However, currently available models do not accurately mimic the complex structure of trabecular bone, which can provide erroneous results. This study aimed to investigate the suitability of stereolithography (SLA) to produce synthetic trabecular bone. Samples were printed based on synchrotron micro-computed tomography (micro-CT) images of human bone, with scaling factors from 1 to 4.3. Structure replicability was assessed with micro-CT, and mechanical properties were evaluated by compression and screw pull-out tests. The overall geometry was well-replicated at scale 1.8, with a volume difference to the original model of <10%. However, scaling factors below 1.8 gave major print artefacts, and a low accuracy in trabecular thickness distribution. A comparison of the model–print overlap showed printing inaccuracies of ~20% for the 1.8 scale, visible as a loss of smaller details. SLA-printed parts exhibited a higher pull-out strength compared to existing synthetic models (Sawbones ™), and a lower strength compared to cadaveric specimens and fused deposition modelling (FDM)-printed parts in poly (lactic acid). In conclusion, for the same 3D model, SLA enabled higher resolution and printing of smaller scales compared to results reported by FDM.

Knotless Suture Anchors: A Comparative Biomechanical Study of Acetabular Rim Anchor Fixation with Implications for Hip Labral Repair

AbstractThe purpose of this study was to analyze relevant initial-implantation biomechanical properties of five knotless suture anchors available for use in acetabular labral repair. Five knotless suture anchor constructs were tested: Arthrex PushLock 2.9, Arthrex PushLock 2.4, Arthrex SutureTak 3.0, Stryker CinchLock SS 2.4, and Stryker CinchLock Flex 2.4. Anchors were placed in synthetic bone blocks and in acetabular bone of cadaveric specimens. Constructs were subjected to cyclic and load-to-failure (LTF) testing. Displacement at 1, 100, 250, and 500 cycles, yield load, ultimate load, and failure mode were compared with statistically significant (p &lt; 0.005) differences. PushLock 2.9 mm and CinchLock SS 2.4 anchor constructs had significantly less displacement than PushLock 2.4 mm after 1 cycle (p = 0.017) and 500 cycles (p = 0.043). Excluding “tare” displacement after the first cycle, all anchor constructs were associated with less than 2.0 mm of displacement after 500 cycles. Arthrex PushLock 2.4 and SutureTak 3.0 had the highest number of failures prior to completing cyclic loading. Arthrex PushLock 2.9 was associated with the highest LTF in cadaver (p = 0.00013) and synthetic (p = 0.009) bone models. Most common failure mode in cadaver bone was eyelet failure for all anchor types. Knotless suture anchors used for arthroscopic hip surgery (2.9 mm PushLock, 2.4 mm PushLock, 3.0 mm SutureTak, 2.4 mm CinchLock SS, and 2.4 mm CinchLock Flex) were associated with material properties that met or exceeded the reported thresholds for successful periarticular soft tissue repair surgeries. Based on cyclic and LTF testing in synthetic bone blocks and cadaveric acetabulums, 2.9 mm PushLocks and 2.4 mm CinchLock SS anchors may have potential biomechanical advantages over the other constructs tested. Further functional ex vivo and preclinical animal model studies are recommended to further characterize suture anchor constructs designed for acetabular labrum repair. These results provide novel and relevant biomechanical testing data that contribute to assessing knotless suture anchor constructs for use in acetabular labral repair.

Comparison of different fixation techniques for periprosthetic fractures: a biomechanical study of a new implant.

The ideal treatment method for periprosthetic fractures is controversial due to the risks of current methods. Single-cortex screw fixation in prosthesis may lead to implant failure. Therefore, we aimed to develop an implant that lowers the risk for complications. For this study, we designed and tested two new implant models. The first model was a plate with a combination of U nails and cerclage holes. The second model was a U nail plate with a screw, which combines a plate screw with U nail (staples). Our study aimed to compare the stability of two newly designed implants with classical treatment modalities. We used 27 (in 3 groups) artificial bone models and 9 different test models. The ISO 7206-4:2010 (E) standards were used for 27 bones in nine groups tested under laboratory conditions. In our study, we examined nine different groups. In group 1, hipthe prosthesis was extracted, and a revision femoral stem was embedded. In group 2, periprosthetic fractures were repaired with a plate and cable. In group 3, periprosthetic fractures were repaired with a plate and stapler. In group 4, periprosthetic fractures were repaired with a plate and stapler cable. In group 5, periprosthetic fractures were repaired with a plate stapler and screw. Groups 6 and 7 were the control groups. Group 6 was the only artificial bone group, and group 7 was the prosthesis embedded bone group. Group 8 was periprosthetic fractures treated with unicortical screw fixation with cerclage, and group 9 was periprosthetic fractures treated with unicortical screw fixation. Axial loading was applied to the bones. The yield strength of the system was determined by loading the synthetic bone models with a constant compression speed of 5 mm/min through the centre of motion using the Geratech SH 2000 testing system. During the tests, load and displacement values were recorded, and the stiffness of the models was calculated based on those values. According to our results, the greatest durability was found in the revision hip prosthesis group (1511 N), and the weakest performance was found in the plate with the stapler implant group (163N). When comparing the data of groups according to compression, significant differences were found in group 2 with groups 1, 4, 5, and 7; group 3 with group 1; group 8 with groups 1 and 5; and group 9 with 1, 5, 7, and according to breakage, significant differences were found in group2 with groups 1, 3, 5, and 7; group 3 with group 1; group 8 with groups 1 and 5; and group 9 with groups 1, 5, and 7 (p<0.001). The revision hip prosthesis treatment for periprosthetic fractures showed the best performance, followed by the plate with stapler screw. In older patients, U nail-augmented implants may be a good alternative for periprosthetic fractures. Unicortical screw and cerclage wire combination fixation results were unsatisfactory results in this study. This is an experimental study, so further studies, especially patient-specific studies, should be made to expand the findings of this study.

Biomechanical Analysis of Sagittal Plane Pin Placement Configurations for Pediatric Supracondylar Humerus Fractures

Anterior to posterior (AP) pinning is the recommended sagittal pin configuration in divergent lateral entry coronal pinning of pediatrics supracondylar fractures. However, there was still a lack of evidence regarding alternative sagittal pins configurations. We aimed to compare the construct stiffness of alternative sagittal pin configurations by using synthetic bone models. Sixty synthetic pediatric humeri were osteotomized to create a supracondylar fracture. After the fracture reduction, all specimens were fixed in the coronal plane with divergent lateral entry pin configurations in four different patterns in the sagittal plane: AP, crossed, divergent and parallel sagittal pin configuration. Each configuration was tested with five loading patterns. The AP sagittal pin had significantly lower construct stiffness than the divergent (p = 0.003) and the parallel sagittal pin configuration (p = 0.005) in external rotation loading tests. The divergent sagittal pin had the highest construct stiffness in extension, valgus, and external rotation loads, but the parallel sagittal pin had lower construct stiffness under extension load than the divergent and crossed sagittal pin configurations. The divergent sagittal pin configuration provides greater construct stiffness than other sagittal pin configurations due to the maximal pin spreading distance at the fracture site and the pin angle lock mechanism.