Ken Gall

Background: Trapeziectomy with suture button suspensionplasty (SBS) is a common treatment for thumb carpometacarpal (CMC) osteoarthritis. This study aimed to evaluate the effect of bone tunnel configuration and suture count on the construct stability. Methods: Twelve matched specimens underwent trapeziectomy and randomization to either a 2-strand 1-tunnel (single SBS) or divergent 4-strand 2-tunnel suture button (crossed dual SBS) construct. Mechanical stiffness was measured using material testing machine with a semiconstrained axial load over 5-mm displacement. Trapezial space was measured under no load and in a light and heavy physiologic pinch grip models. Subsequently, specimens were randomized to undergo single SBS or divergent 2-strand 2-tunnel suture (crossed suture) constructs, and loaded pinch testing was performed. Primary outcomes were analyzed using matched-pair t -tests. Results: The crossed dual SBS construct showed significantly higher stiffness compared to the single SBS construct in elastic deformation (19.9 vs 15.5 N/mm, P = .010) and maintained trapezial height better in both light (82% vs 71%, P = .021) and heavy (73% vs 46%, p = .004) pinch grips. The crossed suture technique also preserved trapezial height better than the single SBS construct in light (79% vs 64%, P = 0.021) and heavy (60% vs 44%, P = 0.039) pinch grips. Conclusions: In the immediate postoperative period, a crossed dual SBS construct was stiffer to axial load and more stable in pinch grip compared to a single SBS construct. The novel crossed suture construct better preserved trapezial height then the singe SBS, suggesting that the crossed configuration may be more relevant than suture count in postoperative stability.

Introduction Periprosthetic joint infections are relatively rare complications of total joint replacements. The standard of care for these infections involves the placement of a temporary spacer made of poly (methyl methacrylate) (PMMA) bone cement combined with antibiotics. The rate of major complication can be as high as 12% for PMMA spacers. Therefore, this study was designed to identify an alternative resin material that could be 3D printed, provide mechanical support necessary for ambulation, and deliver a therapeutic dose of antibiotics over an extended period. Methods Test substrates were photochemically printed out of Biomed Clear (BMC) loaded with up to 16% gentamicin or 10% vancomycin (wt%). PMMA and BMC composites were characterized using differential scanning calorimetry, dynamic mechanical analysis, compression testing, and a 30-day antibiotic elution study. Results The thermoset properties of the BMC allowed for the compressive properties to remain unchanged (post-elution = compressive strength 84–94 MPa) as antibiotics were added to the resin (0–16 wt%). However, antibiotic elution was influenced by the type and concentration of the antibiotic in the composite. In contrast, the thermoplastic properties of PMMA led to a decrease in compressive properties with the addition of antibiotics, but PMMA was able to elute relatively more antibiotics. Discussion This study described a novel method to 3D print load bearing materials that can release antibiotics over 30 days. BMC composites have some advantages and disadvantages compared to PMMA that need to be considered when developing new treatments for orthopaedic infections.

Background Tensioning and relaxation of grafts in tendon and ligament reconstruction surgeries significantly influence operation success, yet there are no clinically available technologies that can effectively measure both graft tension intra-operatively and during post-surgical recovery and rehabilitation. Objective To address the lack of an effective technology to measure graft tension intra-operatively and post-operatively, an implantable sensor was developed to provide real-time suture loading biofeedback both during reconstruction for surgeons and during rehabilitation exercises for physical therapists. Methods This paper introduces a passively powered wireless sensor designed to monitor tension of tendon and ligament sutures fixed in orthopedic reconstruction surgeries. The inductive-capacitive-resistive (LCR) based sensor was designed to be used along with commercially available suture buttons to monitor loading in reconstructed tendons and ligaments. Results Sensor loading experiments demonstrated a detection range from 5 N to 180 N with high repeatability (1.8 % change in sensitivity over 10,000 cycles). Additionally, the effects of depth, alignment, and orientation on signal transmission between the implantable sensor and an external detection device were characterized. Finally, the sensor was deployed in an anterior cruciate ligament reconstructed cadaver knee and used to detect graft loading during various knee joint movements. Conclusion This study established the design and basic functionality of a suture button accessory loading sensor to potentially assist orthopedic surgeons with surgical technique and help physical therapists with optimizing rehabilitation protocols for enhanced recovery in an effort to reduce failure rates.

Porous media, ranging from bones to concrete and from batteries to architected lattices, pose difficult challenges in fully harnessing for engineering applications due to their complex and variable structures. Accurate and rapid assessment of their mechanical behavior is both challenging and essential, and traditional methods such as destructive testing and finite element analysis can be costly, computationally demanding, and time consuming. Machine learning (ML) offers a promising alternative for predicting mechanical behavior by leveraging data-driven correlations. However, with such structural complexity and diverse morphology among porous media, the question becomes how to effectively characterize these materials to provide robust feature spaces for ML that are descriptive, succinct, and easily interpreted. Here, we developed an automated methodology to determine porous material strength. This method uses scalar morphological descriptors, known as Minkowski functionals, to describe the porous space. From there, we conduct uniaxial compression experiments for generating material stress-strain curves, and then train an ML model to predict the curves using said morphological descriptors. This framework seeks to expedite the analysis and prediction of stress-strain behavior in porous materials and lay the groundwork for future models that can predict mechanical behaviors beyond compression.

Bone cement is an adhesive commonly used to bond orthopedic implants to bone during a surgical procedure. Total joint replacements such as total knee, hip, shoulder, or ankle arthroplasties have metal or polymer components that are commonly cemented. However, implant failures can occur via debonding at the implant-cement interface, suggesting sub-optimal adhesion of the cement to the implant. In parallel, the orthopedic implant industry is seeing a significant rise in additive manufacturing (AM), which enables the seamless integration of surface porosity enhanced osseointegration in cementless procedures. However, there is a lack of foundational data or understanding of how bone cement adheres to 3D printed surfaces as a function of varying topography. This study evaluates adhesion of cement to clinically relevant printed implant surfaces, porous topographies, and materials. Adhesion strength of cemented samples was tested in shear. Surface porous layers were compared to traditional implant surface finishes (blasted, machined, polished). The impact of 3D printed surface porosity size and depth was also investigated. Testing revealed that the adhesive strength of porous surfaces (26.3 ± 3.1 MPa) was more than double the adhesive strength of all non-porous surfaces (the highest being the as-printed surface with a strength of 11.3 ± 2.5 MPa). The study also demonstrated porosity and layer-depth dependent performance trade-offs, with the best performing group having a 2x2x2 mm 3 unit cell size and 0.50 mm layer depth and a shear strength of 26.31 ± 3.10 MPa. These results provide a foundation for improving designs of emerging 3D printed orthopedic implants that can be both cemented and cementless.

In light of the increasing prevalence of reverse shoulder arthroplasty, it has become clear that standard off the shelf implants provide insufficient glenoid fixation in challenging primary and revision cases. Recent advancements in computed tomography scanning, software automation tools, and additive manufacturing have paved the way for patient specific implants in difficult cases for reverse shoulder arthroplasty. This review article aims to provide an overview of the current state of patient specific implants in reverse shoulder arthroplasty, discussing their design principles, manufacturing techniques, short-term clinical outcomes, and future directions.

Multi-material jetting (MMJ) allows for printed parts with intricate distributions of photopolymer materials deposited through hundreds of tiny nozzles at the voxel design scale. In this study, the mechanical tensile performance of various two-material composite designs is compared with respect to various volumetric ratios of two constituent materials, one rigid and strong and the other soft and ductile. Layered samples exhibited convergent, alternating layer failure due to interfacial bonding and fracture mechanisms of the dissimilar materials. To assist with predicting deformation profiles and explaining this behavior, a multilayer composite model was developed. Additionally, newly accessible voxel-scale digital material creation software was used to create custom “digital material” (DM) composites with a greater range of tunable strength , stiffness, and modulus of toughness over multilayer composites and manufacturer preset DM composites. Specifically, custom DMs increased the tunable ranges of ultimate strength and Young's modulus by 25.8 % and 5.5 %, respectively, and the achievable modulus of toughness by 56.3 % over the other composites. This study highlights the benefit of utilizing the full potential of MMJ by creating composite geometries designed at the voxel scale and provides groundwork for future comparative studies where customized voxel-scale material distributions can be tuned to achieve a desired mechanical performance over traditional composite designs.

Complications following surgical repair of pelvic organ prolapse (POP) with polypropylene mesh (PPM) are common. Recent data attributes complications, in part, to stiffness mismatches between the vagina and PPM. We developed a 3D printed elastomeric membrane (EM) from a softer polymer, polycarbonate urethane (PCU). EMs were manufactured with more material given the low inherent material strength of PCU. We hypothesized that the EMs would be associated with an improved host response as compared to PPM. A secondary goal was to optimize the material distribution (fiber width and device thickness) within EMs, in regards to the host response. EM constructs (2 × 1 cm 2 ) with varied polymer stiffness, fiber width, and device thickness were implanted onto the vagina of New Zealand white rabbits for 12 weeks and compared to similarly sized PPMs. Sham implanted animals served as controls. Mixed effects generalized linear models were used to compare the effect of construct type accounting for differences in independent variables. EMs had an overall superior host response compared to PPM as evidenced by preservation of vaginal smooth muscle morphology ( p -values<0.01), decreased total cellular response to construct fibers ( p -values<0.001), and a reduced percent of macrophages ( p -values<0.02) independent of how the material was distributed. Both PPM and EMs negatively impacted vaginal contractility and glycosaminoglycan (GAG) content relative to Sham (all p -values<0.001) with EMs having less of an impact on GAGs ( p -values<0.003). The results suggest that softer PCU EMs made with more material are well tolerated by the vagina and comprises a future material for POP repair devices. Prolapse is a debilitating condition in which loss of support to the vagina causes it and the organs supported by it to descend from their normal position in the pelvis. Surgical solutions to rebuild support involves the use of polypropylene mesh which is orders of magnitude stiffer than the vagina. This mismatch results in complications including exposure of the mesh into the vagina and pain. To provide an innovative solution for women, we have developed an elastomeric membrane from a soft polymer that matches the stiffness of the vagina. Here, we show in a rabbit animal model that this device incorporates better into the vagina and is associated with an overall improved host response as compared to polypropylene mesh.

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: Recently, there has been a gradual rise in the utilization of patient-specific metallic implants within foot and ankle orthopedics, with the total ankle/total ankle replacement (TATTR) serving as a prime example. A critical decision made by surgeons in conjunction with the TATTR procedure involves the potential arthrodesis of the subtalar joint. This decision hinges upon numerous factors encompassing surgeon preference, radiographic indications, and clinical evaluations. However, no study has compared surgeon decision to the true joint health. The primary aim of this study was to determine if surgeon decision correlated with true three-dimensional joint health. It was hypothesized that arthrodesis of the subtalar joint with the TATTR procedure would be correlated with measures of sinus tarsi impingement or reduced joint space evident on 3D imaging. Methods: In this retrospective study, a 172 TATTR dataset was analyzed. Each patient underwent a bilateral computed tomography (CT) scan. Cases were semi-automatically segmented, and cases involving extensive anatomical damage were excluded. To assess joint health, a semi-automated distance mapping algorithm was written in MATLAB. Specific surfaces of the subtalar joint were manually selected. This included the posterior and middle/anterior talocalcaneal facets on the talus, and the sinus tarsi, anterior, middle, and posterior facets on the calcaneus. Distance mapping was performed by projecting a vector perpendicular from one bone triangulation until it intersected with its opposing triangulation. For detailed analysis, the sinus tarsi and posterior facet were divided into four and nine regions, respectively. Statistical analysis involved calculating the difference in means and Welch's t-test to assess significance. For visual analysis, rank plots were generated to determine if there was a clear distinction in joint spacing for fused and articulating procedures. Results: A total of 46 TATTR cases were included. No significance was found between groups for the four large regions (sinus tarsi, anterior, middle, and posterior facet), but when analyzing by specific regions, significance was found on the lateral portion of the posterior sinus tarsi as well as at both the medial portion of the anterior and middle sections of the posterior facet. When analyzing on rank plots for the posterior facet (anterior/medial), a clear cutoff was found around 2mm of joint space width (Figure 2). Table 1 summaries these results, and figures 1, 2, and 3 demonstrate our findings visually. Conclusion: In this study, surgeon decision to fuse the subtalar joint along with a TATTR procedure was compared to 3D imaging data of the pre-operative joint. Our findings indicate that patients in the fused+TATTR group, there was a noticeable anterior/medial downward shift of the talus. Moreover, our initial assumption regarding sinus tarsi impingement in fused cases was validated, as there was a significant reduction in sinus tarsi JSW. Future following of individualized surgeon decision could begin to establish trends in surgeon decision. Utilizing this tool prior to surgery in conjunction with the surgeon’s clinical decision-making process could potentially enhance patient outcomes.

Powder bed fusion (PBF), including selective laser melting and electron beam melting, fabricates complex, porous, osseointegrative implants for widespread clinical use. Fatigue testing is imperative for predicting long-term strength and durability of rough and surface porous implants while bone remodels around and grows into the implant. This study analyzes different materials (Ti6Al4V and Co28Cr6Mo) with varying topographies including as-printed surface roughness and the addition of a surface porous layer common to implants. The results are compared to wrought and PBF controls that are polished and machined. Moreover, different PBF techniques for titanium result in different as-printed surface roughness (∼0.07–17 μm) and microstructure. The fatigue data demonstrates that the surface finish impact was stronger in Ti6Al4V versus CoCr and SLM Ti6Al4V HIP + surface porous gyroid samples didn't perform worse than the roughest solid sample without surface porosity (EBM Ti6Al4V). With the same mechanical surface finishes, the SLM and wrought Ti6Al4V samples display similar fatigue resistance (800 and 850 MPa respectively), while EBM samples remain inferior (350 MPa). This study provides a foundation to compare fatigue resistance across materials and surface topographies through different fabrication techniques to optimize the lifespan of orthopedic implants while incorporating rough as printed surfaces and added surface porosity, both of which are essential for osseointegration.

Creating the optimal environment for effective and long term osseointegration is a heavily researched and sought-after design criteria for orthopedic implants. A validated multimaterial finite element (FE) model was developed to replicate and understand the results of an experimental in vivo push-out osseointegration model. The FE model results closely predicted global force (at 0.5 mm) and stiffness for the 50-90% porous implants with an r2 of 0.97 and 0.98, respectively. In addition, the FE global force at 0.5 mm showed a correlation to the maximum experimental forces with an r2 of 0.90. The highest porosity implants (80-90%) showed lower stiffnesses and more equitable load sharing but also failed at lower a global force level than the low porosity implants (50-70%). The lower strength of the high porosity implants caused premature plastic deformation of the implant itself during loading as well as significant deformations in the ingrown and surrounding bone, resulting in lower overall osseointegration strength, consistent with experimental measurements. The lower porosity implants showed a balance of sufficient bony ingrowth to support osseointegration strength coupled with implant mechanical properties to circumvent significant implant plasticity and collapse under the loading conditions. Together, the experimental and finite element modeling results support an optimal porosity in the range of 60-70% for maximizing osseointegration with current structure and loading.

There is a significant need for models that can capture the mechanical behavior of complex porous lattice architectures produced by 3D printing. The free boundary effect is an experimentally observed behavior of lattice architectures including the gyroid triply periodic minimal surface where the number of unit cell repeats has been shown to influence the mechanical performance of the lattice. The purpose of this study is to use finite element modeling to investigate how architecture porosity, unit cell size, and sample size dictate mechanical behavior. Samples with varying porosity and increasing number of unit cells (relative to sample size) were modeled under an axial compressive load to determine the effective modulus. The finite element model captured the free boundary effect and captured experimental trends in the structure's modulus. The findings of this study show that samples with higher porosity are more susceptible to the impact of the free boundary effect and in some samples, the modulus can be 20% smaller in samples with smaller numbers of unit cell repeats within a given sample boundary. The outcomes from this study provide a deeper understanding of the gyroid structure and the implications of design choices including porosity, unit cell size, and overall sample size.

The use of midfoot wedges for the correction of flatfeet disorders, such as progressive collapsing foot disorder, has increased greatly in recent years. However, the wedge material/composition has yet to be standardized. Metallic wedges offer advantages such as comparable elasticity to bone, reduced infection risk, and minimized osseous resorption, but a comprehensive review is lacking in the literature. Therefore, the objective of this systematic review was to organize all studies pertaining to the use of metallic wedges for flatfoot correction to better understand their efficacy and safety. This systematic review adhered to PRISMA guidelines, and articles were searched in multiple databases (PubMED, SPORTDiscus, CINAHL, MEDLINE, and Web of Science) until August 2023 using a defined algorithm. Inclusion criteria encompassed midfoot surgeries using metallic wedges, observational studies, and English-language full-text articles. Data extraction, article quality assessment, and statistical analyses were performed. Among 11 included articles, a total of 444 patients were assessed. The average follow-up duration was 18 months. Radiographic outcomes demonstrated that patients who received metallic wedges experienced improvements in lateral calcaneal pitch angle and Meary’s angle, with an enhancement of up to 15.9 degrees reported in the latter. Success rates indicated superior outcomes for metallic wedges (99.3%) compared to bone allograft wedges (89.9%), while complications were generally minor, including hardware pain and misplacement. Notably, there were no infection complications due to the inert nature of the metallic elements. This review summarizes the effectiveness, success rates, and safety of metallic wedges for flatfoot correction. Radiographic improvements and high success rates highlight their efficacy. Minor complications, including pain and mispositioning, were reported, but the infection risk remained low. Our results demonstrate that metallic midfoot wedges may be a viable option over allograft wedges with proper planning. Future research should prioritize long-term studies and standardized measures.

Lattice structures offer desirable functionality for engineering design such as having a high strength-to-weight ratio and efficient heat exchange. Lattice parameters can be adjusted to achieve specific benchmarks such as porosity, surface area, weight, or mechanical performance. One of the biggest challenges of creating components with lattice structures is that they are difficult to fabricate with conventional methods due to their complex, highly periodic shape. Additive manufacturing (AM) techniques such as stereolithography (SLA) vat photopolymerization (VPP) have emerged as manufacturing methods for successfully creating these structures. However, a seamless characterization and subsequent understanding of the relationship between base material properties and lattice geometry across a wide range of porosity has not been fully investigated. In this study, SLA VPP was used to print structures from two distinctly different lattices, specifically the TPMS (triply periodic minimal surface) gyroid and strut-based diamond lattices, five unique photopolymer materials with varying stiffness and strength, and twenty-six levels of porosity ranging from 34% to 84%. The broad porosity sweep provides a more continuous understanding of the impact of porosity on mechanical behavior. Analysis of mechanical and volumetric properties yielded several discoveries, including substantial effects of photopolymer resin viscosity and porous volume fraction on volumetric accuracy, printability, and defects. Based on the experimental data we propose a model for predicting mechanical properties as a function of porosity that outperformed the traditional Gibson-Ashby model. The discoveries and methods included in this work provide a foundation for future analysis of mechanical and volumetric properties of 3D printed lattices across an expansive range of structural porosities and materials.

Additive manufacturing has provided the ability to manufacture complex structures using a wide variety of materials and geometries. Structures such as triply periodic minimal surface (TPMS) lattices have been incorporated into products across many fields due to their unique combinations of mechanical, geometric, and physical properties. Yet, the near limitless possibility of combining geometry and material into these lattices leaves much to be discovered. This article provides a dataset of experimentally gathered tensile stress-strain curves and measured porosity values for 389 unique gyroid lattice structures manufactured using vat photopolymerization 3D printing. The lattice samples were printed from one of twenty different photopolymer materials available from either Formlabs, LOCTITE AM, or ETEC that range from strong and brittle to elastic and ductile and were printed on commercially available 3D printers, specifically the Formlabs Form2, Prusa SL1, and ETEC Envision One cDLM Mechanical. The stress-strain curves were recorded with an MTS Criterion C43.504 mechanical testing apparatus and following ASTM standards, and the void fraction or "porosity" of each lattice was measured using a calibrated scale. This data serves as a valuable resource for use in the development of novel printing materials and lattice geometries and provides insight into the influence of photopolymer material properties on the printability, geometric accuracy, and mechanical performance of 3D printed lattice structures. The data described in this article was used to train a machine learning model capable of predicting mechanical properties of 3D printed gyroid lattices based on the base mechanical properties of the printing material and porosity of the lattice in the research article [1].

Advancements in additive manufacturing (AM) technology and three-dimensional (3D) modeling software have enabled the fabrication of parts with combinations of properties that were impossible to achieve with traditional manufacturing techniques. Porous designs such as truss-based and sheet-based lattices have gained much attention in recent years due to their versatility. The multitude of lattice design possibilities, coupled with a growing list of available 3D printing materials, has provided a vast range of 3D printable structures that can be used to achieve desired performance. However, the process of computationally or experimentally evaluating many combinations of base material and lattice design for a given application is impractical. This research proposes a framework for quickly predicting key mechanical properties of 3D printed gyroid lattices using information about the base material and porosity of the structure. Experimental data was gathered to train a simple, interpretable, and accurate kernel ridge regression machine learning model. The performance of the model was then compared to numerical simulation data and demonstrated similar accuracy at a fraction of the computation time. Ultimately, the model development serves as an advancement in ML-driven mechanical property prediction that can be used to guide extension of current and future models.

Background: The use of intervertebral cages within the interbody fusion setting is ubiquitous. Synthetic cages are predominantly manufactured using materials such as Ti and PEEK. With the advent of additive manufacturing techniques, it is now possible to spatially vary complex 3D geometric features within interbody devices, enabling the devices to match the stiffness of native tissue and better promote bony integration. To date, the impact of surface porosity of additively manufactured Ti interbody cages on fusion outcomes has not been investigated. Thus, the objective of this work was to determine the effect of implant endplate surface and implant body architecture of additive manufactured lattice structure titanium interbody cages on bony fusion. Methods: Biomechanical, microcomputed tomography, static and dynamic histomorphometry, and histopathology analyses were performed on twelve functional spine units obtained from six sheep randomly allocated to body lattice or surface lattice groups. Results: Nondestructive kinematic testing, microcomputed tomography analysis, and histomorphometry analyses of the functional spine units revealed positive fusion outcomes in both groups. These data revealed similar results in both groups, with the exception of bone-in-contact analysis, which revealed significantly improved bone-in-contact values in the body lattice group compared to the surface lattice group. Conclusion: Both additively manufactured porous titanium cage designs resulted in increased fusion outcomes as compared to PEEK interbody cage designs as illustrated by the nondestructive kinematic motion testing, static and dynamic histomorphometry, microcomputed tomography, and histopathology analyses. While both cages provided for similar functional outcomes, these data suggest boney contact with an interbody cage may be impacted by the nature of implant porosity adjacent to the vertebral endplates.

Pelvic organ prolapse (POP) is the herniation of the pelvic organs into the vaginal space, resulting in the feeling of a bulge and organ dysfunction. Treatment of POP often involves repositioning the organs using a polypropylene mesh, which has recently been found to have relatively high rates of complications. Complications have been shown to be related to stiffness mismatches between the vagina and polypropylene, and unstable knit patterns resulting in mesh deformations with mechanical loading. To overcome these limitations, we have three-dimensional (3D)-printed a porous, monofilament membrane composed of relatively soft polycarbonate-urethane (PCU) with a stable geometry. PCU was chosen for its tunable properties as it is comprised of both hard and soft segments. The bulk mechanical properties of PCU were first characterized by testing dogbone samples, demonstrating the dependence of PCU mechanical properties on its measurement environment and the effect of print pathing. The pore dimensions and load-relative elongation response of the 3D-printed PCU membranes under monotonic tensile loading were then characterized. Finally, a fatigue study was performed on the 3D-printed membrane to evaluate durability, showing a similar fatigue resistance with a commercial synthetic mesh and hence its potential as a replacement.

Vat photopolymerization is able to produce intricate composite parts at high print speed, good part fidelity, and strong mechanical properties.