Biomechanics Research Articles

Cold Storage of Human Femoral Arteries for Twelve Months: Impact on Mechanical Properties

This biomechanical pre-clinical study aimed to assess the consequences on mechanical properties of long term cold storage (+2/+8 °C) of arterial allografts. Femoropopliteal arterial segments were collected from multiorgan donors and stored at +2/+8 °C for 12 months in saline solution with added antibiotics. Mechanical characterisation was carried out using two different tests, with the aim of defining the physiological modulus and the maximum stress and strain borne by the sample before rupture. These characterisations were carried out after 0, 6, and 12 months of storage for each sample (T0, T6, and T12, respectively). For comparison, the same tests were performed on cryopreserved popliteal femoral segments after thawing. Twelve refrigerated allografts (RAs), each divided into three segments, and 10 cryopreserved allografts (CAs) were characterised. The median (interquartile range [IQR]) Young's modulus was not statistically significantly different between the storage times for cold stored allografts: RAT0, 164 (150, 188) kPa; RAT6, 178 (141, 185) kPa; RAT12, 177 (149, 185) kPa. The median (IQR) Young's modulus of the CA group (153 [141, 185] kPa) showed no significant differences from the RA groups, irrespective of storage time. Furthermore, median (IQR) maximum stress and strain values were not significantly different between the different groups: for maximum stress: RAT0, 1.58 (1.08, 2.09) MPa; RAT6, 1.74 (1.55, 2.36) MPa; RAT12, 2.25 (1.87, 2.53) MPa; CA, 2.25 (1.77, 2.61) MPa; and for maximum strain: RAT0, 64% (50, 90); RAT6, 79% (63, 84); RAT12, 72% (65, 86); CA, 67% (50, 95). Cold storage for up to 12 months appears to have no impact on the mechanical characteristics of human arterial allografts. Therefore, this preservation method, which would greatly simplify routine care, seems feasible. Other indicators are being studied to verify the safety of this preservation process before considering its use in vivo.

Technical aspects of rod-insertion forceps (persuader) application in reducing construct failure after lumbar spine fusion surgery: a biomechanical cadaveric study in Germany.

A prospective experimental study. This biomechanical in vitro study aimed to examine the extent to which the use of a rod persuader (RP) leads to additional mechanical stress on the screw-rod system and determine its influence on the bony anchoring of primary pedicle screws. Degenerative spine diseases and deformities are the most common indications for the stabilization and fusion of spinal segments. The pedicle screw-rod system is considered the gold standard for dorsal stabilization, and an RP is also increasingly being considered to fit the spondylodesis material. Ten lumbar spines from body donors were examined. Bisegmental dorsal spinal lumbar interbody fusion of the L3-L5 segments was performed using a pedicle screw-rod system (ROCCIA Multi-LIF Cage; Silony Medical, Germany). In group 1, the titanium rod was inserted without tension, whereas in group 2, the rod was attached to the pedicle screws at the L4 and L5 levels, creating a 5-mm gap. To attach the rod, the RP was used to press the rod into the pedicle screw. The rod was left in place for 30 minutes and then removed. The rod reduction technique significantly increased the mechanical load on the overall construct measured by strain gauges (p<0.05) and resulted in outright implant failure with pedicle screw pullout in 88.9%. In cases where the spondylodesis material is not fully attached within the pedicle screw, an RP can be used with extreme caution, particularly in osteoporotic bones, to avoid pedicle screw avulsion and screw anchor failure.

Modular baseplate augmentation: a simple and effective method for addressing eccentric glenoid wear

BackgroundAugmented baseplates can be effective at addressing eccentric glenoid wear in reverse total shoulder arthroplasty (rTSA). However, these implants often come in a limited number of predetermined shapes that require additional reaming to ensure adequate glenoid seating. This typically involves complex instrumentation and can have a negative impact on implant stability. Modular baseplate augmentation based on intra-operative measurements may allow for more precise defect filling while preserving glenoid bone. The purpose of this investigation was to assess the stability of a novel ringed baseplate with modular augmentation in comparison to non-augmented standard and ringed baseplate designs. MethodsIn this biomechanical study, baseplate micromotion was tested for three constructs according to American Society for Testing and Materials (ASTM) guidelines. The constructs included a non-augmented curved baseplate, a non-augmented ringed baseplate and ringed baseplate with an 8 mm locking modular augmentation peg. The non-augmented constructs were mounted flush onto polyurethane (PU) foam blocks, while the augmented baseplate was mounted on a PU block with a simulated defect. Baseplate displacement was measured prior to and after 100,000 cycles of cyclic loading. ResultsPrior to cyclic loading, the non-augmented and augmented ringed baseplates both demonstrated significantly less micromotion than the non-augmented curved baseplate design (81.1 μm vs 97.2 μm vs 152.7 μm; p=0.009). After cyclic loading, both ringed constructs continued to have significantly less micromotion compared to the curved design (105.5 μm vs 103.2 μm vs 136.6 μm; p<0.001). The micromotion for both ringed constructs remained below the minimum threshold required for bony ingrowth (150 μm) at all time points. ConclusionIn the setting of a simulated glenoid defect, locked modular augmentation of a ringed baseplate does not result in increased baseplate micromotion when compared to full contact, non-augmented baseplates. This design offers a simple method for tailored baseplate augmentation that can match specific variations in glenoid anatomy, limiting the need for excessive reaming and ultimately optimizing the environment for long term implant stability. Level of EvidenceBasic Science Study; Biomechanics

Comparative Biomechanical Study of Fragment-Specific Plates and Headless Screws for Radial Styloid and Lunate Facet Fixation in Distal Radius Fracture Evaluated in a Synthetic Composite

To evaluate the compressive stiffness (ability to resist compression under an applied load) of fragment-specific plate and headless screw fixation for radial styloid and volar lunate facet fractures in a synthetic composite distal radius. A simulated radial styloid fracture (AO type B1.1) and simulated volar lunate facet fracture (AO type B3.3) were created in synthetic composite distal radii and fixed with a fragment-specific plate (FSP) using a radial styloid or lunate facet plate or with two- or three-headless screws (2HS, 3HS), creating 6 fixation models: B1.1/FSP, B1.1/2HS, B1.1/3HS, B3.3/FSP, B3.3/2HS, and B3.3/3HS. Compressive stiffness of fixation constructs under initial static load, cyclic load, and final static load was investigated. Nonaxial loadings, including shearing and rotation, were not evaluated. Regarding AO type B1.1, the mean stiffness of the B1.1/FSP construct was not significantly different from the intact radius, and the mean stiffness was greatest in the B1.1/3HS and lowest in the B1.1/2HS construct. For AO type B3.3, the mean stiffness of the B3.3/3HS construct was not significantly different from the intact radius, and the mean stiffness of the B3.3/FSP and B3.3/2HS construct was greatest and lowest, respectively. Minimal differences in stiffness between initial and final static loads confirmed that there was no evidence of failure implant under cyclic compressive loads. Fragment-specific plates and two- or three-headless screw fixation maintained mechanical stability through compressive cyclic loading for radial styloid and volar lunate facet fractures. The FSPs and three-headless screws fixations provided superior stiffness over the two-headless screws fixation. There was no articular fracture failure in all fixation constructs with initial static compression, cyclic loading, and final compression. Fragment-specific plates and headless screws can both be considered as adequate fixation for radial styloid and volar lunate facet fractures.

Computational biomechanical study on hybrid implant materials for the femoral component of total knee replacements

Multifunctional materials have been described to meet the diverse requirements of implant materials for femoral components of uncemented total knee replacements. These materials aim to combine the high wear and corrosion resistance of oxide ceramics at the joint surfaces with the osteogenic potential of titanium alloys at the bone-implant interface. Our objective was to evaluate the biomechanical performance of hybrid material-based femoral components regarding mechanical stress within the implant during cementless implantation and stress shielding (evaluated by strain energy density) of the periprosthetic bone during two-legged squat motion using finite element modeling. The hybrid materials consisted of alumina-toughened zirconia (ATZ) ceramic joined with additively manufactured Ti–6Al–4V or Ti–35Nb–6Ta alloys. The titanium component was modeled with or without an open porous surface structure. Monolithic femoral components of ATZ ceramic or Co–28Cr–6Mo alloy were used as reference. The elasticity of the open porous surface structure was determined within experimental compression tests and was significantly higher for Ti–35Nb–6Ta compared to Ti–6Al–4V (5.2 ± 0.2 GPa vs. 8.8 ± 0.8 GPa, p < 0.001). During implantation, the maximum stress within the ATZ femoral component decreased from 1568.9 MPa (monolithic ATZ) to 367.6 MPa (Ti–6Al–4V/ATZ), 560.9 MPa (Ti–6Al–4V/ATZ with an open porous surface), 474.9 MPa (Ti–35Nb–6Ta/ATZ), and 648.4 MPa (Ti–35Nb–6Ta/ATZ with an open porous surface). The strain energy density increased at higher flexion angles for all models during the squat movement. At ∼90° knee flexion, the strain energy density in the anterior region of the distal femur increased by 25.7 % (Ti–6Al–4V/ATZ), 70.3 % (Ti–6Al–4V/ATZ with an open porous surface), 43.7 % (Ti–35Nb–6Ta/ATZ), and 82.5% (Ti–35Nb–6Ta/ATZ with an open porous surface) compared to monolithic ATZ. Thus, the hybrid material-based femoral component decreases the intraoperative fracture risk of the ATZ part and considerably reduces the risk of stress shielding of the periprosthetic bone.

Unveiling individuality in the early phase of motor learning: a machine learning approach for analysing weightlifting technique in novices.

Despite the growing body of evidence highlighting the individuality in movement techniques, predominant models of motor learning, particularly during the acquisition phase, continue to emphasise generalised, person-independent approaches. Biomechanical studies, coupled with machine learning approaches, have demonstrated the uniqueness of movement techniques exhibited by individuals. However, this evidence predominantly pertains to already stabilised movement techniques, particularly evident in cyclic daily activities such as walking, running, or cycling, as well as in expert-level sports movements. This study aims to evaluate the hypothesis of individuality in whole-body movements necessitating intricate coordination and strength among novice participants at the very beginning of an acquisition phase. In a within-subject design, sixteen highly active male participants (mean age: 23.1 ± 2.1 years), all absolute novices in the learning task (i.e., power snatch of Olympic weightlifting), participated in randomised snatch learning bouts. These bouts comprised 36 trials across various motor learning models: differential learning contextual interference (serial, sCIL; and blocked, bCIL), and repetitive learning. Kinematic and kinetic data were collected from three standardised snatch trials performed following each motor learning model bout. The time-continuous data were input to a linear Support Vector Machine (SVM). We conducted analyses on two classification tasks: participant and motor learning model. The Support Vector Machine classification revealed a notably superior participant classification compared to the motor learning model classification, with an averaged prediction accuracy of 78% (in average ≈35 out of 45 test trials across the folds) versus 27.3% (in average ≈9 out of 36 test trials across the folds). In specific fold and input combinations, accuracies of 91% versus 38% were respectively achieved. Methodically, the crucial role of selecting appropriate data pre-processing methods and identifying the optimal combinations of SVM data inputs is discussed in the context of future research. Our findings provide initial support for a dominance of individuality over motor learning models in movement techniques during the early phase of acquisition in Olympic weightlifting power snatch.

Biomechanical study between percutaneous vertebroplasty combined with cement pedicle plasty improves vertebral biomechanical stability: A finite element analysis

ObjectiveTo investigate the biomechanical effects of percutaneous vertebroplasty combined with cement pedicle plasty (PVCPP) on the unstable osteoporotic vertebral fractures (OVFs) through finite element (FE) analysis. The study compares the biomechanical stability of finite element models between percutaneous vertebroplasty (PVP) and percutaneous vertebroplasty combined with cement pedicle plasty.MethodsTwo patients with unstable OVFs underwent computed tomography (CT) examination at the thoracolumbar vertebral body levels, respectively. The CT images were reconstructed into three-dimensional finite element models to simulate stress conditions across six dimensions and to evaluate the vertebral von Mises stress before and after bone cement reinforcement.ResultsThe study found that stress distribution differed between groups mainly at the pedicle base. In the surgical vertebral bodies, the maximum stress in the PVP group decreased during flexion and left bending, while it increased in other states. In the PVCPP group, all maximum stresses decreased. In the inferior vertebral bodies, the maximum stress in the PVP group generally increased, while it decreased in the PVCPP group. In the superior vertebral bodies, postoperatively, the maximum stress in the PVP group generally increased, while it almost remained unchanged in the PVCPP group. PVP group had higher cement stress and displacement.ConclusionPVCPP is an effective treatment method for patients with unstable OVFs. It can quickly relieve pain and enhance the stability of the three columns, thereby reducing the risk of some complications.

Influence of the transverse tarsal arch on radiological components of progressive collapsing foot deformity.

The importance of the transverse tarsal arch (TTA) has recently been extensively reevaluated and has even been considered to play a greater role in foot stability than the medial longitudinal arch (MLA). However, the relevance of this observation in the context of common clinical foot disorders, such as progressive collapsing foot deformity (PCFD), has not yet been fully clarified. In this biomechanical study, we examined ten pairs of human cadaveric feet by serial weight-bearing cone-beam computed tomography under controlled loading using a custom-designed testing machine. The MLA and TTA were transected separately, alternating the order in two study groups. A semiautomated three-dimensional evaluation of their influence on three components of PCFD, namely collapse of the longitudinal arch (sagittal Meary's angle), hindfoot alignment (sagittal talocalcaneal angle), and forefoot abduction (axial Meary's angle), was performed. Both arches had a relevant effect on collapse of the longitudinal arch, however the effect of transecting the MLA was stronger compared to the TTA (sagittal Meary's angle, 7.4° (95%CI 3.8° to 11.0°) vs. 3.2° (95%CI 0.5° to 5.9°); p = 0.021). Both arches had an equally pronounced effect on forefoot abduction (axial Meary's angle, 4.6° (95%CI 2.0° to 7.1°) vs. 3.0° (95%CI 0.6° to 5.3°); p = 0.239). Neither arch showed a consistent effect on hindfoot alignment. In conclusion, weakness of the TTA has a decisive influence on radiological components of PCFD, but not greater than that of the MLA. Our findings contribute to a deeper understanding and further development of treatment concepts for flatfoot disorders.

Biomechanical analysis of patient specific cone vs conventional stem in revision total knee arthroplasty

BackgroundIn revision total knee arthroplasty, addressing significant bone loss often involves the use of cemented or press-fit stems to ensure implant stability and long-term fixation. A possible alternative to stem was recently introduced utilizing custom-made porous metaphyseal cones, designed to reconstruct the missing tibial and femoral geometries. Early clinical and radiological assessments have shown promising results. The objective of this research was to biomechanically evaluate the performances of these custom-made cones.MethodsThe biomechanical study was conducted using a validated finite element model. The bone geometries of a patient (selected for their history of four knee revisions due to infection and periprosthetic fractures, followed by a successful treatment with custom-made 3D-printed metaphyseal cones) were employed for the study. On these bone models, different revision scenarios were simulated and examined biomechanically: (A) custom-made cementless metaphyseal cones; (B) cemented stems; (C) press-fit stems; (D) distal femoral reconstruction with press-fit stem. All the models were analyzed at 0 °and 90 °of flexion, under physiological load conditions simulating daily activities; stress distribution, average Von-Mises stresses and risk of fracture were then analyzed and compared among configurations.ResultsThe use of custom-made 3D-printed cones exhibited the most favorable stress distribution in both femoral and tibial bones. Tibial bone stress was evenly distributed in custom-made cone configurations, while stress concentration was observed in distal regions for the other scenarios. Additionally, custom-made cones displayed overall homogeneity and lower stress levels, potentially contributing to limit pain. Symmetrical stress distribution was observed between the lateral and medial proximal tibia in custom-made cone models, whereas other scenarios exhibited uneven stress, particularly in the anterior tibial bone.ConclusionsThe biomechanical analysis of porous custom-made metaphyseal cones in re-revision arthroplasties is in agreement with the positive clinical and radiological outcomes. These findings provide valuable insights into the potential benefits of using custom-made cones, which offer more uniform stress distribution and may contribute to improve patient outcomes in revision TKA procedures. Further studies in this direction are warranted to validate these biomechanical findings.

Clinical and Radiographic Outcomes of Nitinol Compression Staples for Midfoot and Chopart Arthrodesis

Nitinol staple use in orthopedic surgery has increased in recent years. Biomechanical studies provide useful data for use in foot/ankle; however, clinical data is limited. This study's purpose is to determine the efficacy of nitinol staples to achieve stable, bony arthrodesis in midfoot and Chopart joints, and examine their clinical outcomes and pain scores. A retrospective chart review was performed on 127 midfoot/Chopart joint arthrodeses (71 patients) using nitinol staples in isolation. The primary outcome variable was radiographic evidence of healing. Radiographs were blinded, randomized, and independently reviewed by three board certified foot and ankle surgeons. Complete/partial union was seen in 89% of all joints (113/127), increasing to 93% when including only midfoot joints (98/106). Chopart joints had significantly lower healing rates (15/21; 71%) compared to all midfoot joints (p = 0.01) and isolated tarsometatarsal joints (86/91; 95%) (p = 0.006). Neuropathy and smoking did not affect arthrodesis, but diabetes did (p = 0.004). Joints requiring bone grafting had worse rates of arthrodesis (38/49; 76%) (p = 0.002). For all joints, post-operative visual analog scale scores were significantly lower than pre-operative (p < 0.001). Pre-operative midfoot and Chopart pain scores were similar (p= 0.30). Midfoot joints had significantly lower pain scores post-operatively than pre-operatively (p < 0.001). No such significance existed in Chopart joints (p = 0.07). Isolated nitinol staples are a viable option for midfoot arthrodesis, especially tarsometatarsal joints, and offer significant pain improvement. Chopart joints may require more rigid fixation than nitinol staples, given the lower healing rate. Level of Clinical EvidenceIV

Effect of macrophages combined with supernatant of mesenchymal stem cell culture and macrophage culture on wound healing in rats

Wound healing is an orderly sequence of events restoring the integrity of the damaged tissue. It consists of inflammatory, proliferation, and remodeling phases. The objective of the current study was to investigate the effect of local transplantation of cultured macrophage loaded with mesenchymal stem cell/macrophage culture supernatants on wound healing. Sixty-four healthy adult male Wistar rats were randomized into 4 groups of sixteen animals each: 1) SHAM group. 2) MAC-MSC/SN group: One-milliliter application of a mixture comprising mesenchymal stem cell and macrophage culture supernatants in a 1:1 ratio was administered locally to the wound bed. 3) MAC group: Local transplantation of macrophage cells cultured in the wound bed. 4) MAC + MAC-MSC/SN group: Local transplantation of cultured macrophage in combination with mesenchymal stem cell/ macrophage culture supernatants in the wound bed. An incisional wound model was used for biomechanical studies, while an excisional wound model was used for biochemical, histopathological, and planimetric assessments. The wound area was significantly reduced in the MAC + MAC-MSC/SN group compared to other groups (P < 0.05). Biomechanical measurements from the MAC + MAC-MSC/SN group were significantly higher compared to other experimental groups (P < 0.05). Biochemical and quantitative histopathological analyses revealed a significant difference between MAC + MAC-MSC/SN and other groups (P < 0.05). MAC + MAC-MSC/SN showed the potential to improve wound healing significantly. This appears to work by angiogenesis stimulation, fibroblast proliferation, inflammation reduction, and granulation tissue formation during the initial stages of the healing process. This accelerated healing leads to earlier wound area reduction and enhanced tensile strength of the damaged area due to the reorganization of granulation tissue and collagen fibers.

A Biomechanical Study of Potential Plants for Erosion Control and Slope Stabilization of Highland in Thailand

A Biomechanical Study of Potential Plants for Erosion Control and Slope Stabilization of Highland in Thailand

Biomechanical analysis of load distribution in porcine hip joints at different acetabular coverages

BackgroundDevelopmental dysplasia of the hip causes secondary osteoarthritis. Finite element analysis suggests high hip joint contact pressure in patients with hip dysplasia and a reduction in contact pressure after periacetabular osteotomy. However, few biomechanical studies have examined the load distribution in the hip joint. This study aimed to investigate the biomechanical properties of load distribution in porcine hip joints at different acetabular coverages.MethodsSix porcine hip joints were analyzed using three models: 1) neutral coverage, 2) 15° under-coverage (defined as dysplasia model), and 3) 15° over-coverage created by varying the acetabular coverage. The load distribution was assessed using a pressure-mapping sensor system after applying a loading force of 100 N to the hip joint.ResultsIn the dysplasia model, the load was concentrated at the acetabular rim; in the neutral and over-coverage models, it was dispersed. The average contact pressure was significantly higher in the dysplasia model than in the neutral coverage model ([0.42 vs. 0.3 MPa]; p = 0.004). The contact area was significantly smaller in the dysplasia model than in the neutral coverage model ([250.7 vs. 345.0 mm2]; p = 0.004). No significant differences were observed in contact pressure or area between the neutral and over-coverage models.ConclusionsInsufficient acetabular coverage in the dysplasia model demonstrated higher contact pressure and smaller contact area than the neutral model. Conversely, the contact pressure and area in the over-coverage model did not differ significantly from those in the normal model. Therefore, surgeons should note that acetabular coverage overcorrection has limited effect; normalization is crucial during periacetabular osteotomy.

OUTCOMES OF DISTAL FEMUR FRACTURE IN THE ELDERLY TREATED WITH EITHER SINGLE PLATE OR DUAL PLATING OR NAIL-PLATE COMBINATION: A RETROSPECTIVE ANALYSIS FROM A SINGLE CENTRE

IntroductionDistal femur fracture fixation in elderly presents significant challenges due to osteoporosis and associated comorbidities. There has been an evolution in the management of these fractures with a description of various surgical techniques and fixation methods; however, currently, there is no consensus on the standard of care. Non-union rates of up to 19% and mortality rates of up to 26 % at one year have been reported in the literature. Delay in surgery and delay in mobilisation post-operatively have been identified as two main factors for high rate of mortality. As biomechanical studies have proved better stability with dual plating or nail-plate combination, a trend has been shifting for past few years towards rigid fixation to allow early mobilisation. Our study aims to compare outcomes of distal femur fractures managed with either single plate (SP), dual plating (DP) or nail-plate construct (NP).MethodsA retrospective review of patients aged above 65 years with distal femur fractures (both native and peri-prosthetic) who underwent surgical management between June 2020 and May 2023 was conducted. Patients were divided into three groups based on mode of fixation - single plate or dual plating or nail-plate construct. AO/OTA classification was used for non-periprosthetic, and Unified classification system (UCS) was used for periprosthetic fractures. Data on patient demographics, fracture characteristics, surgical details, postoperative complications, re-operation rate, radiological outcomes and mortality rate were evaluated. Primary objective was to compare re-operation rate and mortality rate between 3 groups at 30 days, 6 months and at 1 year.ResultsA cohort of 32 patients with distal femur fractures were included in this study. 91% were females and mean age was 80.97 (range 68–97). 18 (53%) were non-periprosthetic fracture and 14 (47%) were periprosthetic fractures.18 patients underwent single plate fixation (AO/OTA 33A – 8, 33B/C – 2, UCS V3B – 5, V3C – 3),10 patients had dual plate fixation (AO/OTA 33A – 1, 33B/C – 4, UCS V3B – 3, V3C – 2) and 4 patients underwent nail-plate combination fixation (AO/OTA 33A – 4). 70.5% patients had surgery within 36 hours of admission and 90% within 48 hours. Analysis showed no re-operation at 30 days, 6 months in all 3 groups. At 1 year one patient had re-operation in dual-plating periprosthetic group (Distal femur replacement done for failed fixation). Three patients (16%) in single plate group had re-operation at 2 years (2 for peri-implant fracture and 1 for infection). None of the patients treated with Nail-plate combination had re-operation. Mortality rate at 30 days was 0% in among all the 3 groups. At 6 months, it was 16% in single plate group and 0% in DP and NP groups at 6 months and at 1 year mortality rate was 27% in SP group, 10% in DP and 0% in NP group. Combined mortality rate was 0% at 30 days, 9% at 6 months and 18.7% at one year.ConclusionOur analysis provides insights into fixation methods of distal femur fractures in elderly patients. We conclude that a lower re-operation rate and mortality rate can be achieved with early surgery and rigid fixation with either dual plating or nail-plate construct to allow early mobilisation. Further prospective studies are warranted to confirm these findings and guide the selection of optimal surgical strategies for these challenging fractures.

Biomechanical study of effect of tibial posteromedial defect depth and area on primary TKA implant stability

BackgroundMedial tibial defects are common in patients who underwent primary total knee arthroplasty for varus deformity. Previous clinical studies have categorized tibial defects according to the depth of the defects and recommended different ways of addressing them. This study aimed to perform a biomechanical FE analysis to investigate the role of depth and surface area of the medial tibial plateau defects in the stability of the tibial component in primary TKA implants. MethodForty posteromedial tibial defect models with eight different depths (including 2, 4, 6, 8, 11, 13, 16, and 18 mm) and five different surface areas (including 10, 20, 30, 40, and 50% medial surface involvement) were used to create the FE models. Loads were applied to ellipses on tibial tray with 70–30% mediolateral distribution. The resulting relative motion of the bone and implant was measured to evaluate the tibial tray instability. ResultsFor defects with less than 20% surface involvement, the amount of relative motion had a moderately increasing fashion; however, in more significant percentages of surface involvement of the medial tibial plateau, especially in 50%, the graphs revealed a nonlinear increasing pattern which means that the depth would affect the amount of relative motion only when defect area is large. ConclusionIn defects with less than 20% surface involvement approaches like graft and cement augmentation would suffice whereas it would be essential to consider a more appropriate method like stem or metal augments for defects with more than 20% of medial surface involvement as the instability increased nonlinearly.

On the suitability of additively manufactured gyroid structures and their potential use as intervertebral disk replacement - a feasibility study.

Intervertebral disk degeneration is a growing problem in our society. The degeneration of the intervertebral disk leads to back pain and in some cases to a herniated disk. Advanced disk degeneration can be treated surgically with either a vertebral body fusion or a disk prosthesis. Vertebral body fusion is currently considered the gold standard of surgical therapy and is clearly superior to disk prosthesis based on the number of cases. The aim of this work was the 3D printing of Gyroid structures and the determination of their mechanical properties in a biomechanical feasibility study for possible use as an intervertebral disc prosthesis. Creo Parametric 6.0.6.0 was used to create models with various Gyroid properties. These were printed with the Original Prusa i3 MK3s+. Different flexible filaments (TPU FlexHard and TPU FlexMed, extrudr, Lauterach, Austria) were used to investigate the effects of the filament on the printing results and mechanical properties of the models. Characterization was carried out by means of microscopy and tension/compression testing on the universal testing machine. The 3D prints with the FlexHard and FlexMid filament went without any problems. No printing errors were detected in the microscopy. The mechanical confined compression test resulted in force-deformation curves of the individual printed models. This showed that changing the Gyroid properties (increasing the wall thickness or density of the Gyroid) leads to changes in the force-deformation curves and thus to the mechanical properties. The flexible filaments used in this work showed good print quality after the printing parameters were adjusted. The mechanical properties of the discs were also promising. The parameters Gyroid volume, wall thickness of the Gyroid and the outer wall played a decisive role for both FlexMed and FlexHard. All in all, the Gyroid structured discs (Ø 50mm) made of TPU represent a promising approach with regard to intervertebral disc replacement. We would like to continue to pursue this approach in the future.

Improved restoration of biomechanical factors using a narrow-box shaped reconstruction compared to a wide one in superior capsular reconstruction for irreparable supraspinatus tendon tears: a biomechanical study using a static shoulder simulator

PurposeTo biomechanically compare superior glenohumeral translation, subacromial contact pressures and area in a box-shape reconstruction using the long head of biceps tendon (LHBT) in an irreparable supraspinatus tendon tear model. MethodsSeven cadaveric shoulders (mean age 61 years; range 32-84 years; SD 22.3) were tested with a custom testing rig used to evaluate superior translation, subacromial contact pressures and areas at 0°, 30° and 60° of glenohumeral abduction. Conditions tested included the native state, a complete tear of the supraspinatus tendon, a wide box-shaped, double-bundle LHBT superior capsular reconstruction (wide BS-SCR), and a narrow box-shaped, double-bundle LHBT superior capsular reconstruction (narrow BS-SCR). ResultsCompared to the wide box-shape SCR, the narrow box-shape SCR had statistically significant lower median contact pressure at 30° and 60°. The subacromial contact area showed a statistically significant difference at 0° (p=0.001) and 30° (p=0.004) for the narrow compared to wide box-shape SCR. At an abduction angle of 0°, the narrow SCR could restore superior translation statistically significant better compared to the wide construct. For all angles, the wide and narrow box-shaped SCR increased the median subacromial distance statistically significantly. The contact areas in 30° and 60° of abduction were higher for all scenarios, both peaking in the intact state in 30° with approximately 600 mm2. ConclusionsIn comparison to a wide box-shape, a narrow box-shape SCR using the LHBT has biomechanical advantages in regard of subacromial contact pressures, the subacromial contact areas as well as the acromiohumeral distance. The width of the reconstruction therefore has direct influence in the success of the technique.

Trends and predictors of reporting social determinants of health in shoulder surgery

IntroductionThe role of social determinants of health (SDH) in patient outcomes, quality of life, and overall well-being has been well documented. However, the inclusion of these variables in randomized control trials (RCTs) remains limited; thus, the extent of generalizability from such trials is brought into question. The purpose of this study is to explore the rates of reporting SDH variables in RCTs focused on shoulder surgery from the past decade. MethodsThe PubMed database was searched for RCTs with a focus on shoulder surgery from 2013-2023. Duplicates, responses to the editor, biomechanical studies, and non-shoulder studies were excluded. Each article was reviewed and data pertaining to patient demographics, socioeconomic covariates. Journal of publication was recorded, and studies from the five most common journals were analyzed. These journals were the Journal of Shoulder and Elbow Surgery (JSES), the Journal of Bone and Joint Surgery (JBJS), the American Journal of Sports Medicine (AJSM), the Bone and Joint Journal (BJJ), and The Journal of the American Medical Association (JAMA). Multivariate logistic regression was performed to determine the independent effect of study characteristics on the reporting rates of SDH. ResultsA total of 255 articles were reviewed. Of these, 93.3% and 90.2% of articles reviewed reported age and sex, respectively. Employment status was reported in 11.8% of articles. Fewer than 10% reported race, ethnicity, income, insurance, and housing, with even less performing formal analyses on these variables. Studies that were conducted in the United States (US), multicenter, had a sample size 251+, and had a combination of public and private funding were significantly more likely to report on race and ethnicity. Reporting employment status was significantly associated with being European-based, multicenter, sample size 251+, double-blinded, and published in AJSM, Newer studies were significantly less likely to report education. Only publication in AJSM was significant for reporting income. Study intervention and topic were not significant for any SDH reporting. DiscussionThis data reflects how small of a proportion of RCTs report and analyze on SDH variables. These findings reflect a need for future RCTs to accurately report SDH variables that influence outcomes, such as race, ethnicity, education, employment, income, housing status, and insurance.. ConclusionsSDH are infrequently reported and analyzed in RCTs pertaining to shoulder surgery. Academic medical journals should incorporate guidelines to encourage studies to include such variables and enable the assessment of outcomes to apply to a broader population.

Finite element analysis of the treatment of a minimally invasive approach combined with a novel anatomical locking plate for scapular body fractures

BackgroundThe minimally invasive approach for the treatment of displaced scapular neck or body fractures has the advantages of less trauma and minimal muscle dissection. In clinical practice, the minimally invasive approach combined with an anatomical locking plate has been used to treat scapular body fractures. In addition, we have made minor modifications to the minimally invasive approach. However, the biomechanical study about the approach combined with an anatomical locking plate in treating scapular body fractures was limited.MethodsFinite element analysis (FEA) was used to conduct the biomechanical comparison between the anatomical locking plate (AP model) and reconstructive plate (RP model) in the treatment of scapular body fractures through the modified minimally invasive approach. A healthy male volunteer with no history of scapula or systemic diseases was recruited. High-resolution computed tomography images of his right scapula were obtained. Two scapula models were constructed and analyzed by the software of Mimics 21.0, Geomagic Wrap 2021, SolidWorks 2021, and ANSYS Workbench 2022, respectively.ResultsThrough static structural analysis, in terms of equivalent von Mises stress, equivalent elastic strain, and total deformation, the AP model exhibited superior safety characteristics, enhanced flexibility, and anticipated stability compared with the RP model. This was evidenced by lower maximum stress, lower maximum strain and displacement.ConclusionThe minimally invasive approach combined with an anatomical locking plate for scapular body fractures had better biomechanical stability. The study provided a biomechanical basis to guide the clinical treatment of scapular body fractures.

Cyclic testing of standalone ALIF versus TLIF in lumbosacral spines of low bone mineral density: an ex vivo biomechanical study.

Screwed anterior lumbar interbody fusion (SALIF) alleviates the need for supplemental posterior fixation leading to reduction of perioperative morbidity. Specifically, elderly and multimorbid patients would benefit from shorter operative time and faster recovery but tend to have low bone mineral density (BMD). The current study aimed to compare loosening, defined as increase of ROM and NZ, of SALIF versus transforaminal lumbar interbody fusion (TLIF) under cyclic loading in cadaveric spines with reduced BMD. Twelve human spines (L4-S2; 6 male 6 female donors; age 70.6 ± 19.6; trabecular BMD of L5 84.2 ± 24.4mgHA/cm3, range 51-119mgHA/cm3) were assigned to two groups. SALIF or TLIF were instrumented at L5/S1. Range of motion (ROM) and neutral zone (NZ) were assessed before and after axial cyclic loading (0-1150N, 2000 cycles, 0.5Hz) in flexion-extension (Flex-Ext), lateral bending, (LB), axial rotation (AR). ROM of the SALIF specimens increased significantly in all loading directions (p ≤ 0.041), except for left AR (p = 0.053), whereas for TLIF it increased significantly in left LB (p = 0.033) and Flex (p = 0.015). NZ of SALIF showed increase in Flex-Ext and LB, whereas NZ of TLIF did not increase significantly in any motion direction. Axial compression loading caused loosening of SALIF in Flex-Ext and LB, but not TLIF at L5/S1 in low BMD specimens. Nevertheless, Post-cyclic ROM and NZ of SALIF is comparable to TLIF. This suggests that, neither construct is optimal for the use in patients with reduced BMD.