Synthetic Bone Model Research Articles

Elastic properties of 3D printed clavicles are closer to cadaveric bones of elderly donors than commercial synthetic bones

Synthetic bone models have increasing utility in orthopaedic research due to their low cost and low variability and have been shown to be biomechanically equivalent to human bones in a variety of ways. The rise in additive manufacturing (AM) for orthopaedic applications presents an opportunity to construct synthetic whole-bone models for biomechanical testing applications, but there is a lack of research comparing these AM models to cadaveric or commercially available bone surrogates. This study compares the mechanical properties of 3D printed clavicle models to commercially available (4th generation Sawbones) and human cadaveric clavicles via nondestructive cyclic 4-point bending, axial compression, and torsion, and a final axial compression test to failure. Commercially available synthetic clavicles had 57.8–203% higher superior-inferior bending rigidity (p < 0.0001), 80.9–198% higher axial stiffness (p < 0.001), and 314–557% higher torsional rigidity (p < 0.05) on average than AM and cadaveric clavicles. Cadaveric and AM clavicles printed from a BoneMatrix/VeroWhite composite material had similar failure mechanisms under axial compression while AM VeroWhite clavicles experienced catastrophic failure, but these groups did not have significantly different ultimate failure loads. Together, these results demonstrate that current commercially available synthetic clavicles may be too rigid to emulate the mechanical properties of elderly cadaveric clavicles, and that AM bone models can closely mimic these cadaveric bones in a variety of biomechanical loading schemes. These results show promising applications for future work using 3D printed bone surrogates for biomechanical analysis of orthopaedic implants and other surgical repair techniques.

Nail–Plate Constructs for Treating Distal Femur Fractures: A Systematic Review of Biomechanical Studies

The biomechanical efficacy of nail–plate constructs (NPCs) used in the treatment of traumatic distal femur fractures (DFFs) remains understudied compared to traditional approaches. This systematic review examines the biomechanical efficacy of NPCs compared to alternative approaches for the surgical fixation of DFFs to guide surgical decision-making and improve patient outcomes. This systematic review searched the PubMed, CINAHL, MEDLINE, Web of Science, and SPORT Discus databases from inception until 24 January 2024. Inclusion criteria were biomechanical studies that involved nail–plate combination constructs for DFFs. Six observational studies were included. Of the included studies, five studies utilized synthetic bone models in testing, and one study used both synthetic and cadaveric bone models. All studies found NPCs to have significantly higher axial and torsional stiffness and resistance to loading than distal lateral femoral locking plate (DLFLP) constructs. The 11 mm NPCs were significantly stiffer than the 9 mm NPCs under torsional and axial loading. Only one of two studies found NPCs to have greater axial stiffness than dual-plate (DP) constructs. NPCs and DP constructs had greater torsional and axial stiffness than the plate-only or DP with medial distal tibial plate constructs. NPCs had less displacement and torque than the plate- or nail-only constructs under axial and torsional loads. NPCs demonstrate superior axial and torsional stiffness and resistance to mechanical loads compared to DLFLP. The varying performance between 11 mm and 9 mm NPCs suggests that construct diameter plays a role in mechanical stability. NPCs and DP constructs performed better than plate-only constructs. Future research should explore the impact of varying nail diameters and plate configurations on stability, as well as the clinical efficacy of NPCs across different patient populations, particularly those with varying bone densities, to better understand their performance in real-world scenarios.

Biomechanical evaluation of Gamma 3 nail with anti-rotation screw fixation for unstable femoral neck fractures: a biomechanical study

This study aims to evaluate the biomechanical performance of the Gamma 3 nail with an anti-rotation screw (GNS) and compare it to two established gold-standard methods for treating unstable femoral neck fractures (UFNFs). Synthetic bone models were prepared with Pauwels’ type III osteotomy and an additional posterior wedge. Three different implant configurations were tested: three cannulated crews (3CS) in an inverted triangle configuration, a dynamic hip screw with an anti-rotation screw (DHSS), and GNS. Non-destructive cyclic axial loading was applied at 7° adduction, with 1000 cycles ranging from 100 to 1000 N. Subsequently, a construct failure test was conducted using progressive axial compression, and fracture reduction loss was recorded. The average axial stiffness was 321 ± 52 N/mm for 3CS, 430 ± 71 N/mm for DHSS, and 519 ± 104 N/mm for GNS. The average ultimate failure loads were 2699.3 N for 3CS, 3427.1 N for DHSS, and 3758.9 N for GNS. GNS demonstrated significantly greater axial stiffness compared to the other two groups (P < 0.05). Both DHSS and GNS exhibited similar failure loading, which were greater than those of 3CS (P < 0.05). GNS offers the advantages of a minimally invasive and intramedullary implant with comparable stability to the DHSS system. Moreover, GNS demonstrated superior biomechanical performance compared to 3 CS configuration.

Biomechanical Analysis of Pedicle Screw Reinsertion Along the Same Trajectory in a Validated 3D-Printed Synthetic Bone Model

To investigate the biomechanical properties of pedicle screw reinsertion along the same trajectory in a previously validated synthetic bone model. Twenty identical acrylonitrile butadiene styrene models of lumbar vertebrae were three-dimensional-printed. Screws were placed in the standard fashion into each pedicle. Models were separated into 2 equal groups, control and experimental. Experimental group screws were completely removed from their testing block and reinserted once. All screws in both groups were then forcibly removed. Continuous torque monitoring was collected on screw insertion torque (IT), removal torque, and reinsertion torque. Pullout strength (PO), screw stiffness (STI), and strain energy (STR) were calculated. There was no significant difference between control and experimental groups for PO (P=0.26), STI (P=0.55), STR (P=0.50), or IT (P=0.24). There was a significant decrease in reinsertion torque (54.5 N-cm±8.2 N-cm) from control IT (62.9 N-cm±8.4 N-cm, P=0.045) and experimental IT (67.5 N-cm±7.6 N-cm, P=0.0026). Strong correlations (Pearson's r>0.80) were seen between control IT against STR and PO, between each of the experimental torque measurements, and between experimental PO and STI. Despite a significant decrease in insertion torque, there is no significant loss of pedicle screw performance when a screw is removed and reinserted along the same trajectory.

Biomechanical validation of novel polyurethane-resin synthetic osteoporotic femoral bones in axial compression, four-point bending and torsion

In addition to human donor bones, bone models made of synthetic materials are the gold standard substitutes for biomechanical testing of osteosyntheses. However, commercially available artificial bone models are not able to adequately reproduce the mechanical properties of human bone, especially not human osteoporotic bone.To overcome this issue, new types of polyurethane-based synthetic osteoporotic bone models have been developed. Its base materials for the cancellous bone portion and for the cortical portion have already been morphologically and mechanically validated against human bone. Thus, the aim of this study was to combine the two validated base materials for the two bone components to produce femur models with real human geometry, one with a hollow intramedullary canal and one with an intramedullary canal filled with synthetic cancellous bone, and mechanically validate them in comparison to fresh frozen human bone.These custom-made synthetic bone models were fabricated from a computer-tomography data set in a 2-step casting process to achieve not only the real geometry but also realistic cortical thicknesses of the femur. The synthetic bones were tested for axial compression, four-point bending in two planes, and torsion and validated against human osteoporotic bone.The results showed that the mechanical properties of the polyurethane-based synthetic bone models with hollow intramedullary canals are in the range of those of the human osteoporotic femur. Both, the femur models with the hollow and spongy-bone-filled intramedullary canal, showed no substantial differences in bending stiffness and axial compression stiffness compared to human osteoporotic bone. Torsional stiffnesses were slightly higher but within the range of human osteoporotic femurs.Concluding, this study shows that the innovative polyurethane-based femur models are comparable to human bones in terms of bending, axial compression, and torsional stiffness.

A Novel Bone-Screw-Fastener Demonstrates Greater Maximum Compression Force Before Failure Compared With a Traditional Buttress Screw.

This study compared the maximal compression force before thread stripping of the novel bone-screw-fastener (BSF) with the traditional buttress screw (TBS) in synthetic osteoporotic and cadaveric bone models. The maximum compression force of the plate-bone interface before loss of screw purchase during screw tightening was measured between self-tapping 3.5-mm BSF and 3.5-mm TBS using calibrated load cells. Three synthetic biomechanical models were used: a synthetic osteoporotic diaphysis (model 1), a 3-layer biomechanical polyurethane foam with 50-10-50 pounds-per-cubic-foot layering (model 2), and a 3-layer polyurethane foam with 50-15-50 pounds-per-cubic-foot layering (model 3). For the cadaveric metaphyseal model, 3 sets of cadaveric tibial plafonds and 3 sets of cadaveric tibial plateaus were used. A plate with sensors between the bone and plate interface was used to measure compression force during screw tightening in the synthetic bone models, while an annular load cell that measured screw compression as it slid through a guide was used to measure compression in the cadaver models. Across all synthetic osteoporotic bone models, the BSF demonstrated greater maximal compression force before stripping compared with the TBS [model 1, 155.51 N (SD = 7.77 N) versus 138.78 N (SD = 12.74 N), P = 0.036; model 2, 218.14 N (SD = 14.15 N) versus 110.23 N (SD = 8.00 N), P < 0.001; model 3, 382.72 N (SD = 20.15) versus 341.09 N (SD = 15.57 N), P = 0.003]. The BSF had greater maximal compression force for the overall cadaver trials, the tibial plafond trials, and the tibial plateau trials [overall, 111.27 N vs. 97.54 N (SD 32.32 N), P = 0.002; plafond, 149.6 N versus 132.92 N (SD 31.32 N), P = 0.006; plateau, 81.33 N versus 69.89 N (SD 33.38 N), P = 0.03]. The novel bone-screw-fastener generated 11%-65% greater maximal compression force than the TBS in synthetic osteoporotic and cadaveric metaphyseal bone models. A greater compression force may increase construct stability, facilitate early weight-bearing, and reduce construct failure.

Compressive Strength of Midfoot Fusion Nail vs Midfoot Fusion Bolt and Role of Subtalar Fusion in Midfoot Charcot Fixation Model.

Operative management of midfoot Charcot arthropathy often involves an extended midfoot arthrodesis with intramedullary bolts for fixation, a method called "beaming." Recently intramedullary nails have been introduced for the same indication, presumably providing stronger fixation. This study compares midfoot fusion nails to bolts with regard to stiffness and compressive ability. Additionally, we assessed how the addition of a subtalar fusion affects the construct. Medial column fusions were performed on 10 matched cadaver foot specimens with either a midfoot fusion nail or bolt. Specimens underwent cyclical compression loading, and displacement was measured. Separately, compressive forces produced were compared between the 2 fixation constructs using a synthetic bone block model. Lastly, another 10 matched specimens with midfoot fusion nails were evaluated with or without subtalar fusions. No differences in stiffness were found in comparing matched specimens between nail vs bolt or comparing nail only without subtalar fusion (STF) vs nail with STF. The compressive force produced by the nail specimens was significantly and substantially greater than the bolted specimens (751.7 vs 139.0 N, P = .01). The accumulated height drop at the midfoot after cycling was 0.5 mm more in the nail group than in the bolt group (1.72 vs 1.22 mm, P = .008). The nail with STF group had greater initial height drop at the midfoot than the nail-only group (0.68 vs 0.34 mm, P = .035) with similar initial height drop at the ankle. However, there were no differences in strength among the matched pairs of midfoot nail-only vs midfoot nail with STF as measured by displacement after fatigue or maximum force at load to failure. The overall cadaveric comparisons between matched pairs of nails vs bolts, and nail-only vs nail with STF, did not provide noteworthy differences between the groups with regard to strength or stiffness. However, the compressive force of the midfoot fusion nail was far superior to the bolt in a synthetic bone model. These data provide valuable insight comparing implants used in Charcot midfoot arthrodesis.

Fluoroscopically calibrated 3D-printed patient-specific instruments improve the accuracy of osteotomy during bone tumor resection adjacent to joints

BackgroundInadequate surface matching, variation in the guide design, and soft tissue on the skeletal surface may make it difficult to accurately place the 3D-printed patient-specific instrument (PSI) exactly to the designated site, leading to decreased accuracy, or even errors. Consequently, we developed a novel 3D-printed PSI with fluoroscopy-guided positioning markers to enhance the accuracy of osteotomies in joint-preserving surgery. The current study was to compare whether the fluoroscopically calibrated PSI (FCPSI) can achieve better accuracy compared with freehand resection and conventional PSI (CPSI) resection.MethodsSimulated joint-preserving surgery was conducted using nine synthetic left knee bone models. Osteotomies adjacent to the knee joint were designed to evaluate the accuracy at the epiphysis side. The experiment was divided into three groups: free-hand, conventional PSI (CPSI), and fluoroscopically Calibrated PSI (FCPSI). Post-resection CT scans were quantitatively analyzed. Analysis of variance (ANOVA) was used.ResultFCPSI improved the resection accuracy significantly. The mean location accuracy is 2.66 mm for FCPSI compared to 6.36 mm (P < 0.001) for freehand resection and 4.58 mm (P = 0.012) for CPSI. The mean average distance is 1.27 mm compared to 2.99 mm (p < 0.001) and 2.11 mm (p = 0.049). The mean absolute angle is 2.16° compared to 8.50° (p < 0.001) and 5.54° (p = 0.021). The mean depth angle is 1.41° compared to 8.10° (p < 0.001) and 5.32° (p = 0.012). However, there were no significant differences in the front angle compared to the freehand resection group (P = 0.055) and CPSI (P = 0.599) group. The location accuracy observed with FCPSI was maintained at 4 mm, while CPSI and freehand resection exhibited a maximum deviation of 8 mm.ConclusionThe fluoroscopically calibrated 3D-printed patient-specific instruments improve the accuracy of osteotomy during bone tumor resection adjacent to joint joints compared to conventional PSI and freehand resection. In conclusion, this novel 3D-printed PSI offers significant accuracy improvement in joint preserving surgery with a minimal increase in time and design costs.

Pedicle screw pull-out testing in polyurethane foam blocks: Effect of block orientation and density.

Synthetic bone models such as polyurethane (PU) foam are a well-established substitute to cadaveric bone for screw pull-out testing; however, little attention has been given to the effect of PU foam anisotropy on orthopaedic implant testing. Compressive and screw pull-out performance in three PU foam densities; 0.16 g/cm3 (PCF 10), 0.32 g/cm3 (PCF 20) and 0.64 g/cm3 (PCF 40) were performed in each of the X, Y or Z orientations. The maximum compressive force, stiffness in the linear region, maximum stress and modulus were determined for all compression tests. Pedicle screws were inserted and pulled out axially to determine maximum pull-out force, energy to failure and stiffness. One-way ANOVA and post hoc tests were used to compare outcome variables between PU foam densities and orientations, respectively. Compression tests demonstrated the maximum force was significantly different between all orientations for PCF 20 (X, Y and Z) while stiffness and maximum stress were different between X versus Y and X versus Z. Maximum pull-out force was significantly different between all orientations for PCF 10 foam. No significant differences were noted for other foam densities. There is potential for screw pull-out testing results to be significantly affected by orientation in lower density PU foams. It is recommended that a single, known orientation of the PU foam block be used for experimental testing.

Additive-manufactured synthetic bone model with biomimicking tunable mechanical properties for evaluation of medical implants

Additive manufacturing has enabled the customization of biomedical systems, including transplantable medical devices, to achieve mechanical biocompatibility. For bone implants, patient-specific bone models must be used to evaluate the mechanical properties of implant compression and subsidence. This study proposes a methodology for designing and fabricating bone models to evaluate patient-specific bone implants. The method involves three-dimensional printing of infill-varied structure, with alternating high-low-high infill density regions, which undergo sequential deformation from the surficial region during compression with an implant. Based on this deformation behavior, the relationship between infill density parameters and mechanical properties was confirmed with the tunability of mechanical properties involving stiffness and failure load. The infill-varied design was applied to the inner structures of artificial vertebra models based on computed tomography scans for cadaver specimens. By tailoring the infill density conditions, the stiffness and failure load were approximated to those of the natural vertebrae. Furthermore, this infill-varied artificial vertebra could be used to evaluate additive-manufactured patient-specific implants. The patient-specific implant had greater resistance to subsidence than the commercial implant, suggesting the feasibility of a biomimicking bone model. The bone-mimetic infill-varied structure could be used to evaluate patient-specific manufactured implants and could be applied to other bone engineering structures with optimized biomechanical properties.

Biomechanical comparison of headless compression screws versus independent locking screw for intra-articular fractures

PurposeHeadless compression screws (HCS) have a variable thread pitch and headless design enabling them to embed below the articular surface and generate compression force for fracture healing without restricting movement. Locking screws have greater variety of dimensions and a threaded pitch mirroring the design of the HCS. The objective of this study is to determine whether locking screws can generate compression force and compare the compressive forces generated by HCS versus locking screws.MethodA comparison between 3.5-mm HCS versus 3.5-mm locking screws and 2.8-mm HCS versus 2.7-mm locking screws was performed using a synthetic foam bone model (Synbone) and FlexiForce sensors to record the compression forces (N). The mean peak compression force was calculated from a sample of 3 screws for each screw type. Statistical analysis was performed using the one-way ANOVA test and statistical significance was determined to be p = < 0.05.ResultsThe 3.5-mm Synthes and Smith and Nephew locking screws generated similar peak compression forces to the 3.5-mm Acutrak 2 headless compression screws with no statistically significant difference between them. The smaller 2.7-mm Synthes and Smith and Nephew locking screws initially generated similar compressive forces up to 1.5 and 2 revolutions, respectively, but their peak compression force was less compared to the 2.8-mm Micro Acutrak 2 HCS.ConclusionLocking screws are able to generate compressive forces and may be a viable alternative to headless compressive screws supporting their use for intra-articular fractures.

Comparison of antegrade and retrograde cross pin fixation in the surgical treatment of pediatric supracondylar femur fractures: A biomechanical study

PurposeThe aim of this study is to compare biomechanical stability of Kirschner wires (K-wires) sent with antegrade and retrograde technique in the fixation of pediatric supracondylar femur fractures. Materials and MethodsA transverse fracture model was created two centimeters above the physis in 24 synthetic bone models suitable for the pediatric femur bone structure. The models were randomly divided into two groups as 12 bones each. In the first group (Group 1), 12 bone fracture models were retrogradely fixed with two cross K-wires. In the second group (Group 2), the fracture was fixed antegradely. In Group 2, both wire ends were allowed to protrude three millimeters from the femoral condyles. The stability of the groups was tested biomechanically by exposing them to varus and extension forces. The forces corresponding to 1 mm, 2 mm, 3 mm and 4 mm displacement and failure loads were calculated in two groups. ResultsAccording to the test results regarding displacements and failure loads, the retrograde group was found to be significantly stronger than the antegrade group against varus loads (p < 0.05). When the groups were compared in terms of extension strength, the results of the two groups were similar and there was no statistical difference between them (p > 0.05). ConclusionRetrograde cross K-wires fixation provides a more stable fixation against varus forces. This is important to prevent varus deformity, which is a clinically less tolerable deformity. However, considering that full-weight mobilization of patients is not allowed after surgery in pediatric supracondylar femur fractures, the surgeon should consider that K-wires can also be sent antegrade to decrease the risk of septic arthritis.

Usefulness of a drill stopper to prevent iatrogenic soft tissue injury in orthopedic surgery

ObjectiveThis study introduces a novel technique utilizing a drill stopper to limit drill penetration depth and to prevent iatrogenic injuries, specifically neurovascular damage, in orthopedic surgeries. Orthopedic surgeries frequently involve the use of drills, which are essential tools for various procedures. However, improper handling of drills can lead to iatrogenic soft tissue injuries, causing severe consequences such as permanent disability or life-threatening complications. To address this issue, we propose the use of a drill stopper as a safeguard to prevent excessive drill penetration and reduce the risk of soft tissue damage during surgery. Materials and MethodsThe study involved 32 orthopedic surgeons, half of whom were experienced and the other half inexperienced. Synthetic femur bone models (Synbone) were used for drilling exercises, employing four configurations: a sharp drill bit without a stopper (SF, Sharp Free), a sharp drill bit with a stopper (SS, Sharp Stopper), a blunt drill bit without a stopper (BF, Blunt Free), and a blunt drill bit with a stopper (BS, Blunt Stopper). Each participant conducted three trials for each configuration, and the penetration depth was measured after each trial. ResultsFor experienced surgeons, the average penetration depths were 3.83 (±1.826)mm for SF, 11.02 (±3.461)mm for BF, 2.88 (±0.334)mm for SS, and 2.75 (±0.601)mm for BS. In contrast, inexperienced surgeons had average depths of 8.52 (±4.608)mm for SF, 18.75 (±4.305)mm for BF, 2.96 (±0.683)mm for SS, and 2.83 (±0.724)mm for BS. ConclusionThe use of a drill stopper was highly effective in controlling drill penetration depth and preventing iatrogenic injuries during orthopedic surgeries. We recommend its incorporation, particularly when using a blunt drill bit or when an inexperienced surgeon operates in an anatomically unfamiliar area. Using the drill stopper, the risk of severe injuries from excessive drill penetration can be minimized, leading to improved patient safety and better surgical outcomes.

Does the type of medial plate fixation matter for supplemental fixation of distal femur fractures manage with a lateral pre-contoured locked plate? A Biomechanical study.

Fixation of distal femur fractures with a lateral pre-contoured locking plate provides stable fixation and is the standard treatment in most cases, allowing early range of motion with a high rate of union. However, in situations, the stability achieved with the lateral plate alone may be insufficient, predisposing to fixation failure. The objective of the study was to compare, in synthetic bone models, the biomechanical behaviour of the fixation with a distal femur lateral pre-contoured locking plate solely and associated with a 3.5mm proximal humeral locking plate applied upside down or a 4.5mm helical locking compression plate on the medial side. A total of 15 solid synthetic left femur samples were used. A metaphysical defect at the level of the medial cortex was simulated. The samples were randomly distributed into three groups equally. All groups received a 4.5/5.0mm single lateral 9-hole distal femur lateral pre-contoured locking plate. Group 1 had no supplementary plate. Group 2 received a supplementary 6-hole 3.5mm proximal humeral locking plate and Group 3 received a supplementary 4.5/5.0mm helical 14-hole narrow locking compression plate. Both supplementary plate types used in groups 2 and 3 contributed to increase the apparent stiffness of the construct, but pairwise comparison showed statically significant difference only between group 1 and 3. No significant difference was observed between groups 2 and 3. Both supplementary plates might be considered for improving the fixation in distal femur fracture in selected cases.

Evaluation of polyethylene terephthalate glycol (PETG), Simubone™, and photopolymer resin as 3D printed temporal bone models for surgical simulation

ObjectivesAmong types of 3D printing, fused deposition modeling (FDM) and digital light processing (DLP) are the most accessible, making them attractive, low-cost options for simulating surgical procedures. This study characterized and compared inexpensive, synthetic temporal bone models printed using Resin, PETG, and Simubone™. Materials and methodsThis study compared models made of polyethylene terephthalate glycol (PETG), Simubone™ produced from a FDM printer, and photopolymer resin from a DLP printer. These temporal bone models were processed by: (1) DICOM files from a patient's CT scan were segmented to define critical parts expected in a temporal bone surgery. (2) The model was appended with a base that articulates with a 3D-printed temporal bone holder. (3) The refined, patient-specific model was manufactured using FDM and DLP printing technologies. (4) The models were sent to evaluators, who assessed the models based on anatomic accuracy, dissection experience, and its applicability as a surgical simulation tool for temporal bone dissection. ResultsThe photopolymer resin outperformed PETG and Simubone™ in terms of anatomical accuracy and dissection experience. Additionally, resin and PETG were evaluated to be appropriate for simple mastoidectomy and canal wall down mastoidectomy while Simubone™ was only suitable for simple mastoidectomy. All models were unsuitable for posterior tympanotomy and labyrinthectomy. ConclusionsPhotopolymer resin and PETG have shown to be suitable materials for dissection models with 3D-printed resin models showing more accuracy in replicating anatomical structures and dissection experience. Hence, the use of 3D-printed temporal bones may be a suitable low-cost alternative to cadaveric dissection.

A biomechanical comparison of three fixation methods for unstable femoral neck fractures with medial calcar defect

BackgroundUnstable femoral neck fractures with medial calcar defects are difficult to manage. The optimal fixation methods for these fractures have been a subject of ongoing debate among orthopedic surgeons. In this study, three different fixation techniques for vertical, medial defected femoral neck fractures were compared.MethodsIn this study, a biomechanical analysis was conducted to compare three fixation methods: cannulated screws (Group 1), cannulated screws combined with a medial buttress plate (Group 2), and intramedullary nails (Group 3). Synthetic composite bone models representing vertical collum femoris fractures with medial calcar defects were used. Each group consisted of seven specimens, and, to maintain consistency, a single surgeon performed the surgical procedure. Biomechanical testing involved subjecting the specimens to axial loading until failure, and the load to failure, stiffness, and displacement values were recorded. Normality was tested using the Shapiro–Wilk test. One-way ANOVA and Tukey’s HSD post hoc test were used for comparisons.ResultsThe difference in the load to failure values was statistically significant among the groups, with Group 2 exhibiting the highest load to failure value, followed by Group 3 and Group 1. Stiffness values were significantly higher in Group 2 than in the other groups. Displacement values were not significantly different between the groups. Fracture and displacement patterns at the point of failure varied across the groups.ConclusionThe results of this study indicate that fixation with a medial buttress plate in combination with cannulated screws provides additional biomechanical stability for vertical femoral neck fractures with medial calcar defects. Intramedullary nail fixation also demonstrated durable stability in these fractures. These findings can be used to better understand current management strategies for these challenging fractures to promote the identification of better evidence-based recommendations.

A Novel Plate for Vertical Shear Fractures of Medial Malleolus: A Biomechanical Study.

This study aims to evaluate and compare stiffness and the load to failure values of our novel medial malleolus compression plate (MP) and 3,5mm 1/3 tubular plate (TP) in the treatment of vertical shear fractures of medial malleolar fractures. Fourteen identical synthetic third generation composite polyurethane bone models of right distal tibia were randomly separated into two groups. Fracture models were created with a custom-made osteotomy guide to provide the same fracture characteristics in every sample (AO OTA type 44A2). Fractures were reduced and novel medial malleolus compression plate was applied to bone models in MP group and tubular plate was applied to TP group. All samples were evaluated biomechanically, force/displacement and the load to failure values were recorded. The force required to create displacement in MP group was twice of that of the TP group. There was a significant difference between two groups in all amounts of displacement (p = .006, p = .005, p = .007 and .015 for 0.5, 1.0, 1.5, and 2.0 mm, respectively). In the treatment of vertical shear fractures of the medial malleolus, the strength of fixation with the novel medial malleolar compression plate is biomechanically higher than the one-third semi-tubular plate.

Statistical Shape and Bone Property Models of Clinical Populations as the Foundation for Biomechanical Surgical Planning: Application to Shoulder Arthroplasty.

This work developed, validated, and compared statistical shape, statistical intensity, and statistical shape and intensity models (SSMs, SIMs, SSIMs) of scapulae from a clinical population. SSMs efficiently describe bone shape variation while SIMs describe bone material property variation, and SSIM's combine description of both variables. This work establishes these models' efficacy and whether they can be used in surgical planning. Models were developed using shoulder arthroplasty data of patients with bone erosion, which is challenging to treat and would benefit from improved surgical planning. Models were created using previously validated nonrigid registration and material property assignment processes that were optimized for scapula characteristics. The models were assessed using standard metrics, anatomical measurements, and correlation analyses. The SSM and SIM specificity and generalization error metrics were 3.4 mm and <1 mm and 184 HU and 156 HU, respectively. The SSIM did not achieve the same level of performance as the SSM and SIM in this study (e.g., shape generalization: SSIM-2.2 mm versus SSM-<1 mm). Anatomical correlation analysis showed that the SSM more effectively and efficiently described shape variation compared to the SSIM. The SSM and SIM modes of variation were not strongly correlated (e.g., rmax = 0.56 for modes explaining ≤2.1% of variance). The SSIM is outperformed by the SSM and SIM and the latter two are not strongly correlated; therefore, using the SSM and SIM in conjunction will generate synthetic bone models with realistic characteristics and thus can be used for biomechanical surgical planning applications.

Is the construct stability of the acetabular cup affected by the acetabular screw configuration in bone defect models?

BackgroundIn revision surgery with significant segmental acetabular defects, adequate implant selection and fixation methods are critical in determining successful bony ingrowth. Commercially available total hip prosthesis manufacturers generally offer additional multi-hole options of acetabular shells with identical designs for use in revision THAs where screw holes configurations vary from product to product. This study aims to compare the mechanical stability of the two types of acetabular screw constructs for the fixation of acetabular components: spread-out and pelvic brim-focused configurations.MethodsWe prepared 40 synthetic bone models of the male pelvis. In half of the samples with acetabular defects, identical curvilinear bone defects were manually created using an oscillating electrical saw. On the right side, multi-hole-cups in which the direction of the screw holes are centered on the pelvic brim (brim-focused) and, on the left side, multi-hole-cups with the direction of the screw hole spread throughout the acetabulum (spread-out) were implanted into the pelvic synthetic bones. Coronal lever-out and axial torsion tests were performed with a testing machine, measuring load versus displacement.ResultsThe average torsional strengths were significantly higher in the spread-out group over the brim-focused group regardless of the presence of the segmental defect of the acetabulum (p < 0.001). But for the lever-out strength, the spread-out group exhibited significantly higher average strength over the brim-focused group for the intact acetabulum (p = 0.004), whereas the results were reversed in the brim-focused group when the defects were generated (p < 0.001). The presence of acetabular defects reduced the average torsional strengths of the two groups by 68.66% versus 70.86%. In comparison, the decrease in the average lever-out strength was less significant for the brim-focused group than the spread-out group (19.87% vs. 34.25%) (p < 0.001).ConclusionConstructs of multi-hole acetabular cups with the spread-out screw holes configuration exhibited statistically better axial torsional strength and coronal lever-out strength. With the presence of posterior segmental bone defects, the spread-out constructs demonstrated significantly better tolerance to axial torsional strength. Still, they exhibited inverted results of higher lever-out strength in the pelvic brim-focused constructs.

Development and preclinical evaluation of a cable-clamp fixation device for a disrupted pubic symphysis

BackgroundTraumatic separation of the pubic symphysis can destabilize the pelvis and require surgical fixation to reduce symphyseal gapping. The traditional approach involves open reduction and the implantation of a steel symphyseal plate (SP) on the pubic bone to hold the reposition. Despite its widespread use, SP-fixation is often associated with implant failure caused by screw loosening or breakage.MethodsTo address the need for a more reliable surgical intervention, we developed and tested two titanium cable-clamp implants. The cable served as tensioning device while the clamp secured the cable to the bone. The first implant design included a steel cable anterior to the pubic symphysis to simplify its placement outside the pelvis, and the second design included a cable encircling the pubic symphysis to stabilize the anterior pelvic ring. Using highly reproducible synthetic bone models and a limited number of cadaver specimens, we performed a comprehensive biomechanical study of implant stability and evaluated surgical feasibility.ResultsWe were able to demonstrate that the cable-clamp implants provide stability equivalent to that of a traditional SP-fixation but without the same risks of implant failure. We also provide detailed ex vivo evaluations of the safety and feasibility of a trans-obturator surgical approach required for those kind of fixation.ConclusionWe propose that the developed cable-clamp fixation devices may be of clinical value in treating pubic symphysis separation.