In silico comparative biomechanical analysis of oblique and chevron medial displacement calcaneal osteotomies for pes planus deformity.

BACKGROUND: Medializing displacement calcaneal osteotomy is commonly performed as part of reconstructive surgery for patients with valgus hindfoot and progressive pes planus deformity. Among several types of calcaneal osteotomies, the oblique and Chevron osteotomy patterns have been commonly described in the literature and gained popularity as they are easily reproducible through percutaneous techniques. Currently, there is scarce evidence in the literature on which cut pattern is superior in terms of stability. To investigate the impact of cut pattern and posterior fragment medialization level on foot biomechanics, computational methods are employed. METHODS: Ankle weightbearing computer tomography (CT) scans of seven patients diagnosed with stage II pes planus deformity are segmented and converted into 3D computational models. Oblique and Chevron osteotomy patterns are modeled independently for each patient. The posterior fragments are medially translated by 8-, 10- and 12-mm and subsequently fixated to the anterior calcaneus with two screws. A total of 42 models are exported to finite element software for biomechanical simulations. Among the investigated parameters, the higher stiffness and lower von Mises stress at the osteotomy interface and the screw site are assumed to be precursors of better stability. RESULTS: It is recorded that as the medialization level increases, the stiffness decreases, and overall stresses increase. Also, it is observed that the Chevron cut produces a stiffer construct while the overall stresses are lower, indicating better stability when compared to the oblique cut. The statistical comparisons of the relevant groups that support these trends are found to be significant (p < 0.05). CONCLUSION: Chevron osteotomy showed superior stability compared to the oblique osteotomy while underscoring the negative impact of increased medialization of the posterior fragment. CLINICAL RELEVANCE: Opting for a lower medialization level and implementing the Chevron technique may facilitate union and earlier weightbearing.

Comparison between achilles tendon reinsertion and dorsal closing wedge calcaneal osteotomy for the treatment of insertional achilles tendinopathy: A meta-analysis.

BACKGROUND: The debridement and Achilles tendon reinsertion (DATR) have been the most common surgical approach for the treatment of Insertional Achilles Tendinopathy (IAT), while dorsal closing wedge calcaneal osteotomy (DCWCO) has recently gained popularity as an alternative surgical option. This study aimed to systematically review the published literature on both surgical techniques and compare their clinical outcomes and complication rates. METHODS: A systematic review was performed according to the PRISMA guidelines using Medline, Embase, and Scopus databases. The inclusion criteria encompassed clinical studies reporting functional outcomes and complications, with a minimum of 10 patients and at least 12 months of follow-up. RESULTS: Seven studies (n = 169) were included for the analysis of DATR, and eight studies (n = 227) were included for the analysis of open DCWCO. Both groups showed a similar improvement in AOFAS score. The overall complication rates were 16.6% in the DATR group and 9.2% in the DCWCO group, but the difference was not statistically significant. However, there was a significantly higher incidence of wound complications in the DATR group (10.1%, 95% C.I.: 4.7-15.6) compared to the DCWCO group (2.5%, 95% C.I.: 0.6-4.4) as the confidence intervals did not overlap. CONCLUSIONS: Clinical outcomes and overall complication rates of both techniques were comparable, although DCWCO had a lower incidence of wound complications. Further research should be focused on prospective studies comparing the two techniques to corroborate the current findings. LEVEL OF EVIDENCE: Level IV; meta-analysis.

In silico analysis of rib force distribution in postscapulothoracic arthrodesis model.

Scapulothoracic arthrodesis (STA) is carried out by fixing the scapula to thoracic ribs which in turn allows the patient suffering from Facioscapulohumeral Muscular Dystrophy to carry out shoulder-joint dependent activities of daily living. A biomechanical analysis of this procedure has not been conducted in the literature and, for the first time, this study investigates the finite element calculated glenohumeral-applied load distributions on ribs by creating a post-STA model. Three loading directions on the glenohumeral joint are designated: anterior-posterior, superior-inferior, and lateral-medial. Reaction forces on the ribs are calculated based on the glenoid force percent. Simulations are repeated by removing a singular rib contact to observe the change in force distributions in the case of missing levels or failed bonding as well as the impact of clavicle osteotomy. Total load distribution is observed highest at T2 followed by T3 and T6. In the T2 missing scenario, total loads on T3 and T4 increase. In the T4 missing case, the most affected level is T3. In the T6 missing scenario, total loads on T5 and T7 increase. In the clavicular osteotomy scenario, all levels' loads increase; the highest is recorded in T7 by 460%, followed by T5, T4, T2, T6, and T3. While all levels contribute to fixation strength, T2 is subjected to the highest loads, and, in the missing level scenarios, the loads are tolerated sufficiently by the remaining levels. Missing T4 scenario has the least effect on the system, which is interpreted as potentially the only skippable level of fixation. Clavicular osteotomy has the highest effect on the arthrodesis site.

Intraoperative fluoroscopic safety assessment of femoral head implants with 3-dimensional risk parameters to minimize cut-out.

OBJECTIVE: This study aimed to introduce a method to extract the 3-dimensional spatial position of the femoral head implant from 2-dimensional fluoroscopic projections, allowing surgeons to assess fixation much more accurately and prevent cut-out complications in proximal femoral nailing. METHODS: To define a safety region for the tip in the femoral head, a novel 3-dimensional distance-based risk parameter called TSD3D was introduced. An intersection algorithm was developed that solely takes the fluoroscopic anteroposterior and lateral distances to reveal the 3-dimensional location of the screw or Kirschner wire tip, enabling the utilization of the 3-dimensional parameter. Orthogonal per- spectives of 6 femur proximal bone substitutes with randomly inserted Kirschner wires were imaged under fluoroscopy. The developed algorithm was used to calculate the implant tip location in 3-dimensional from 2-dimensional images for each case. Algorithm accuracy was validated with the computed tomography-obtained 3-dimensional models of the same femur substitutes. RESULTS: The newly introduced risk parameter successfully visualizes 3-dimensional safety regions. Utilizing the 2-dimensional fluoro- scopic distances as inputs to the algorithm, the 3-dimensional position of the implanted Kirschner wire tip is calculated with a maximum of 9.8% error for a single Cartesian-coordinate measurement comparison. CONCLUSION: By incorporating the newly introduced 3-dimensional risk parameter, surgeons can more precisely evaluate the position of the implant and avoid cut-out complications, instead of relying solely on misleading 2-dimensional fluoroscopic projections of the femoral head.

Investigation of lattice infill parameters for additively manufactured bone fracture plates to reduce stress shielding.

BACKGROUND: Stress shielding is a detrimental phenomenon caused by the stiffness mismatch between metallic bone plates and bone tissue, which can hamper fracture healing. Additively manufactured plates can decrease plate stiffness and alleviate the stress shielding effect. METHODS: Rectilinear lattice plates with varying cell sizes, wall thicknesses, and orientations are computationally generated. Finite element analysis is used to calculate the four-point bending stiffness and strength of the plates. The mechanical behaviors of three different lattice plates are also simulated under a simple diaphyseal fracture fixation scenario. RESULTS: The study shows that with different combinations of lattice infill parameters, plates with up to 68% decrease in stiffness compared to the 100% infill plate can be created. Moreover, in the fixation simulations, the least stiff lattice plate displays 53% more average stress distribution at the healing callus region compared to the 100% infill plate. CONCLUSIONS: Using computational techniques, it has been demonstrated that additively manufactured stiffness-reduced bone plates can successfully address stress shielding with the strategic modulation of lattice infill parameters. Lattice plates with design versatility have the potential for use in various fracture fixation scenarios.

A new checklist surgical hand scrub to replace time-based methods - A pixel intensity analysis.

BACKGROUND: Hand scrubbing is an absolute precaution to avoid surgical site infections. World Health Organization (WHO) recommends 4-min overall scrubbing (4MS) for surgical hand hygiene. However, we hypothesize that the more methodical 10-stroke counting technique (10SS) via locational partitioning of the arm is superior to WHO's superficial guideline dictating only the duration. PURPOSE: The mechanical efficiency of 4MS and 10SS techniques are compared. METHODS: 24 healthcare professionals were recruited for the study. A novel methodology was devised to quantify the average brightness change of skin-applied UV ink before and after scrubbing via pixel intensity analysis. A black-box setup is constructed with an integrated high-resolution camera to photograph the UV-stained dorsal arm. Each stain was then digitally isolated for brightness comparison. RESULTS: It was observed that the 10SS technique was overall more successful in removing the UV ink in comparison to the 4MS method (p = 0.014). In addition, a bias was observed in removing more percentage of the proximal stains when compared to middle and distal stains with the 4MS technique (p = 0.0027), while location-based brightness change averages were statistically equal with the 10SS technique (p = 0.423). CONCLUSIONS AND CLINICAL RELEVANCE: 10SS provided not only a more mechanically efficient scrubbing but also a more homogenous cleaning than 4MS. We recommend the use of the 10SS technique to achieve more effective pre-surgical hand hygiene.

A novel lower bound for tip-apex distance.

PURPOSE: The cut-out of the cephalomedullary nail is among the most common post-surgery complications for intertrochanteric fractures. As a risk predictor, a tip-apex distance (TAD) below 25 mm, observed from orthogonal fluoroscopic views, is recommended in the literature. This study aims to demonstrate that TAD < 25 mm is a mathematically insufficient risk definition and to complement the TAD upper bound with an appropriate lower bound, with the introduction of a novel distance parameter, TADX, based on the orthogonal projection of the nail tip on the central femoral midline. METHOD: Through a mathematical simulation software, all the possible points that lie inside the AP and lateral views of the proximal femoral hemisphere are utilized to create a 3D grid that is sorted into geometrically safe and risk-bearing regions. Extending this methodology, TAD < 25 mm, 10 mm < TAD < 25 mm, and the ideal tip position volumes are simulated. Finally, intersection volumes are created by a combination of different candidate lower TADX bounds and TAD < 25 mm upper bound to determine satisfactory TADX limits. RESULTS: Simulation of TAD-bound zones exposed that TAD is only a mathematically suitable parameter for defining the upper boundary but not the lower boundary for the optimal region. However, using a TADX lower limit creates a 3D volume that is much closer to the optimal tip region volumetrically and can still be as quickly calculated from 2D AP and lateral views. CONCLUSIONS: According to the mathematical simulations, the use of a TADX lower bound of 9 mm for small, 7.5 mm for medium, and 7 mm for large femoral heads in conjunction with a TAD upper bound of 25 mm is suggested.

In silico analysis of modular bone plates.

BACKGROUND: Inventory management or immediate availability of fracture plates can be problematic since for each surgical intervention a specific plate of varying size and functionality must be ordered. Modularization of the standard monolithic plate is proposed to address this issue. METHODS: The effects of four different unit module design parameters (type, degree of modularization, connector screw diameter, sandwich ratio) on the plate bending stiffness and failure are investigated in a finite element four-point-bending analysis. A chosen, best-performing modular plate is then tested in silico for a simple diaphyseal tibial fracture scenario under anatomical compressional, torsional, and bending loads. RESULTS: A modularization strategy is proposed to match the monolithic plate bending properties as closely as possible. With the best combination of design parameters, a fully modularized equivalent length plate with a 42.3% decrease in stiffness and 46.2% decrease in strength could be assembled. The chosen modular plate also displayed sufficient mechanical performance under the fracture fixation scenarios for a potentially successful osteosynthesis. CONCLUSIONS: Via computational methods, the viability of the modularization strategy as an alternate to the traditional monolithic plate is demonstrated. As a further realized advantage, the modular plates can alleviate stress shielding thanks to the reduced stiffness.

In Silico Analysis of Elastomer-Coated Cerclage for Reducing Sternal Cut-Through in High-Risk Patients.

BACKGROUND: AISI 316 L stainless steel wire cerclage routinely used in sternotomy closure causes lateral cut-through damage and fracture, especially in cases of high-risk patients, which leads to postoperative complications. A biocompatible elastomer (Pellethane®) coating on the standard wire is proposed to mitigate the cut-through effect. METHODS: Simplified peri-sternal and transsternal, sternum-cerclage contact models are created and statically analyzed in a finite element (FE) software to characterize the stress-reduction effect of the polymer coating for thicknesses between 0.5 and 1.125 mm. The performance of the polymer-coated cerclage in alleviating the detrimental cortical stresses is also compared to the standard steel cerclage in a full sternal closure FE model for the extreme cough loading scenario. RESULTS: It was observed via the simplified contact simulations that the cortical stresses can be substantially decreased by increasing the coating thickness. The full closure coughing simulation on the human sternum further corroborated the simplified contact results. The stress reduction effect was found to be more prominent in the transsternal contacts in comparison to peri-sternal contacts. CONCLUSIONS: Bearing in mind the promising numerical simulation results, it is put forth that a standard steel wire coated with Pellethane will majorly address the cut-through complication.

The safety and accuracy of the fluoroscopic imaging during proximal femoral fixation: A computerized 3D reappraisal of the joint penetration risk.

BACKGROUND: To assess the success of proximal cephalomedullary nailing operations for treating trochanteric fractures, surgeons utilize 2D fluoroscopy to observe the relative positions of the femoral head and the implant. One distance-based risk parameter, observed from the AP and Lateral projections, is the Tip-Surface Distance(TSD) that dictates how close to the outer cortex should the implant tip be residing to avoid post-surgical complications such as cut-out or joint penetration. In this study, the safety and the accuracy of the orthogonal fluoroscopic imaging were evaluated. METHODS: A femoral head model was created and the risk zone was defined as a hemispherical shell of 5 mm thickness beneath the subchondral cortex, which should not be violated during screw insertion. The remaining hemisphere beneath the risk zone was designated as the safe zone. To assess the effect of head size, each simulation was conducted for 34, 47, and 60 mm diameter(Dfemur) femoral heads. The rate of safe zone violation was calculated for all possible screw endpoints with a TSD of at least 5 mm on fluoroscopic orthogonal views (TSDAP and TSDLat). RESULTS: The minimum risk of joint penetration was achieved when the TSDAP/TSDLat ratio was 1. For Dfemur of 34 mm there was a risk of 91.7% of the safe zone violation when each TSDAP and TSDLat were 5 mm and 0% for 9 mm. For Dfemur of 47 mm, the risk was 92.2% for 5 mm and 0% for 11 mm. For Dfemur of 60 mm, the risk was 92.3% for 5 mm and 0% for 13 mm. Safety maps were constructed for all possible TSD combinations for 34, 47, and 60 mm femoral heads. CONCLUSIONS: Depending solely on the orthogonal fluoroscopic images is not a safe and accurate technique for assessing joint penetration risk during proximal femoral fixation due to the spherical geometry of the femoral head. The screw tip can lie completely outside of the femoral head even when it appears inside, in both orthogonal fluoroscopic views. Evidently, when using TSD, more stringent distance limits should be chosen, contrary to the recommended 5 mm limit. Our safety maps for TSD combinations may be used to check the security of the implantation.

In silico analysis of Superelastic Nitinol staples for trans-sternal closure.

BACKGROUND: Superelastic Nitinol staples, utilized routinely in foot surgeries, are proposed to be used for sternal closure application in this study. It is hypothesized that the shape memory induced superelasticity will allow multiple staples placed along the sternum to promote fast and safe recovery by maintaining constant clamping pressure at the sternotomy midline. METHODS: Two different Nitinol staples of different alloying compositions, one representing the metal formed wire geometry and, the other, powder metallurgy manufactured rectangular geometry, are chosen from the literature. Austenite finish temperatures of both materials are confirmed to be appropriately below the body temperature for superelastic shape memory activation. The adopted finite element superelasticity model is first validated and, via design optimization of parametrized dimensions, the staple geometries for producing maximal clamping forces are identified. The performances of the optimized staples for full trans-sternal closure (seven staples for each) are then tested under lateral sternal loading in separate computational models. RESULTS: The optimized metal formed staple exerts 70.2 N and the optimized powder metallurgy manufactured staple exerts 245 N clamping force, while keeping the maximum localized stresses under the yield threshold for 90° leg bending. Testing the staple-sternum constructs under lateral sternal loading revealed that the former staple can be utilized for small-chested patients with lower expected physiological loading, while the latter staple can be used for high-risk patients, for which high magnitude valsalva maneuver is expected. CONCLUSION: Computational results prove that superelastic Nitinol staples are promising candidates as alternatives to routinely performed techniques for sternal closure.

A novel adjustable locking plate (ALP) for segmental bone fracture treatment.

A novel Ti6Al4V adjustable locking plate (ALP) is designed to provide enhanced bone stability for segmental bone fractures and to allow precise positioning of disconnected segments. The design incorporates an adjustable rack and pinion mechanism to perform compression, distraction and segment transfer during plate fixation surgery. The aim of this study is to introduce the advantages of the added feature and computationally characterize the biomechanical performance of the proposed design. Structural strength of the novel plate is analyzed using numerical methods for 4-point bending and fatigue properties, following ASTM standards. An additional mechanical failure finite element test is also conducted on the rack and pinion to reveal how much torque can be safely applied to the mechanism by the surgeon. Simulation results predict that the new design is sufficiently strong to not fail under regular anatomical loading scenarios with close bending strength and fatigue life properties to clinically used locking compression plates. The novel ALP design is expected to be a good candidate for addressing problems regarding fixation of multi-fragmentary bone fractures.