Fixation Of Implants Research Articles

Using Magnetic Resonance Imaging to Identify Complications Associated with Bioabsorbable Implant Fixation of Osteochondral Lesions: A Practical Guide.

Using Magnetic Resonance Imaging to Identify Complications Associated with Bioabsorbable Implant Fixation of Osteochondral Lesions: A Practical Guide.

Canadian Spine SocietyPresentation CPSS1: Spinal insufficiency fracture in the geriatric pediatric spinePresentation CPSS2: The clinical significance of tether breakages in anterior vertebral body growth modulation: a 2-year postoperative analysisPresentation CPSS3: Anterior vertebral body growth modulation for idiopathic scoliosis: early, mid-term and late complicationsPresentation CPSS4: Ovine model of congenital chest wall and spine deformity with alterations of respiratory mechanics: follow-up from

Canadian Spine SocietyPresentation CPSS1: Spinal insufficiency fracture in the geriatric pediatric spinePresentation CPSS2: The clinical significance of tether breakages in anterior vertebral body growth modulation: a 2-year postoperative analysisPresentation CPSS3: Anterior vertebral body growth modulation for idiopathic scoliosis: early, mid-term and late complicationsPresentation CPSS4: Ovine model of congenital chest wall and spine deformity with alterations of respiratory mechanics: follow-up from

Biomechanics of Implant Fixation in Osteoporotic Bone.

The purpose of this review is to critically evaluate the current literature regarding implant fixation in osteoporotic bone. Clinical studies have not only demonstrated the growing prevalence of osteoporosis in patients undergoing total joint replacement (TJR) but may also indicate a significant gap in screening and treatment of this comorbidity. Osteoporosis negatively impacts bone in multiple ways beyond the mere loss of bone mass, including compromising skeletal regenerative capacity, architectural deterioration, and bone matrix quality, all of which could diminish implant fixation. Recent findings both in preclinical animal models and in clinical studies indicate encouraging results for the use of osteoporosis drugs to promote implant fixation. Implant fixation in osteoporotic bone presents an increasing clinical challenge that may be benefitted by increased screening and usage of osteoporosis drugs.

Fixation Using Alternative Implants for the Treatment of Hip Fractures (FAITH-2): The Clinical Outcomes of a Multicenter 2 × 2 Factorial Randomized Controlled Pilot Trial in Young Femoral Neck Fracture Patients.

To assess whether the fixation method and vitamin D supplementation affect the risk of patient-important outcomes within 12 months of injury in nongeriatric femoral neck fracture patients. A pilot factorial randomized controlled trial. Fifteen North American clinical sites. Ninety-one adults 18-60 years of age with a femoral neck fracture requiring surgical fixation. Participants were randomized to a surgical intervention (sliding hip screw or cancellous screws) and a vitamin D intervention (vitamin D3 4000 IU daily vs. placebo for 6 months). The primary clinical outcome was a composite of patient-important complications (reoperation, femoral head osteonecrosis, severe femoral neck malunion, and nonunion). Secondary outcomes included fracture-healing complications and radiographic fracture healing. Eighty-six participants with a mean age of 41 years were included. We found no statistically significant difference in the risk of patient-important outcomes between the surgical treatment arms (hazard ratio 0.90, 95% confidence interval 0.40-2.02, P = 0.80) and vitamin D supplementation treatment arms (hazard ratio 0.96, 95% confidence interval 0.42-2.18, P = 0.92). These pilot trial results continue to describe the results of current fixation implants, inform the challenges of improving outcomes in this fracture population, and may guide future vitamin D trials to improve healing outcomes in young fracture populations. Although the pilot trial was not adequately powered to detect treatment effects, publishing these results may facilitate future meta-analyses on this topic. Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Treatment of Pelvic Ring Injury with 3D Printed Patient-Specific Implant: Case Report

Rationale. The development of 3D printing technology allows the manufacture of individual implants to treat the patients with diseases and consequences of musculoskeletal system injuries. However, the use of additive technologies in the patients with multiple trauma in the acute period is limited. The purpose of study was to demonstrate the possibility of using individual implants for the definitive fixation of the anterior pelvic ring in a patient with multiple trauma.Patient concerns. A 22-year-old patient was admitted after an injury as a result of a fall from the 5th floor. The treatment was carried out in accordance with the ATLS protocol. Diagnosis: multiple trauma; closed chest, pelvis and limbs injuries; fracture of the left 2nd to 5th ribs; pelvic bones fracture AO/ OTA: 61-C1.3a; fracture of both bones of the left lower leg AO/OTA: 42-B3b; 2nd degree shock.Interventions. An emergency external fixation of the pelvis and lower leg bones was performed. An individual implant for pubic bone fixation was made using 3D printing. On the 8th day, the definitive fixation of the pelvic and left lower leg bones was performed. The patient is activated on the 1st day after the surgery.Outcomes. The early postoperative period was uneventful. The functional result on the Majeed scale in 6 months by remote filling out the questionnaire was 84 points. Lessons. The custom-made implants make it possible the successful fixation of the anterior pelvic ring. The use of 3D printing technologies for the osteosynthesis of pelvic fractures is promising, although requires further study.

Mechanical Comparison of 3D-Printed Plates and Screws for Open Reduction and Internal Fixation of Fractures

Objectives:Three-dimensional (3D) printing has emerged as a promising technology in the field of orthopaedic surgery. The purpose of this study was to evaluate the mechanical properties of 3D printed 1/3 tubular plates and cortical screws compared to standard-of-care stainless steel 1/3 tubular plates and cortical screws.Methods:Replication and modification designs were developed for both plates and screws using open-source computer-assisted design (CAD) software. Models were printed in four materials: acrylonitrile butadiene styrene (ABS), carbon fiber reinforced polylactic acid (PLA), polycarbonate (PC), and polyether ether ketone (PEEK). The implants (Figure 1) were tested and compared to surgical steel plates and screws. Plates were tested with three-point bend and torsional loading using an Instron® material testing machine. Screws were analyzed on pull-out strength in a Sawbones® bone model, shear strength, and torsional loading. Each combination of design and material was placed in its own test group with a sample size (n = 5) and compared to a steel control group (n = 5) for each mechanical test.Results:Significant interaction effects between material type and design type were observed for screw shear (p = 0.003), screw torque (p = 0.023), plate 3-point bend (p = 0.002), and plate torque (p = 0.001). A significant interaction effect was not observed for screw pull-out (p = 0.407), however, a statistically significant difference in mean force between material types (p <0.0005) was observed.Screw Shear: The highest mean force when both material and design were considered was for the CFPLA modified flat design with a mean force of 105.83 N (95% CI 88.51 to 123.14).Screw Torque: The highest mean force when both material and design were considered was for the PEEK modified tilt design with a mean force of 49.51 Ncm (95% CI 43.40 to 55.63).Plate 3-Point Bend: The highest mean force when both material and design were considered was for the PEEK modification design with a mean force of 31.93 N (95% CI 30.53 to 33.33).Plate Torque: The highest mean force when both material and design were considered was for the CFPLA modified flat design with a mean force of 46.88 Ncm (95% CI 42.95 to 50.80).Screw Pull-Out: Mean force produced was highest for PC across all test groups (Figure 2) with a total mean force of 211.86 N (95% CI 186.81 to 236.90).Conclusion:This study demonstrates that desktop 3D printers are capable of printing biocompatible materials that can replicate surgical implants. Although the current materials have significant mechanical variability, they do not approximate the properties of stainless steel. The utility of 3D printed surgical implants for internal fracture fixation provides a potential clinical application in locations where equipment is not as readily available, such as developing countries, forward operating military units, or long duration space flight missions. Furthermore, the cost for 3D printers and 3D printable materials has significantly decreased over recent years. This increase in technology and associated decrease in costs, along with numerous open-source 3D modeling software programs, could provide a low-cost alternative to more expensive and less accessible standard-of-care stainless-steel implants.Figure 1.

Polymethyl Methacrylate-Based Bone Cements Containing Carbon Nanotubes and Graphene Oxide: An Overview of Physical, Mechanical, and Biological Properties.

Every year, millions of people in the world get bone diseases and need orthopedic surgery as one of the most important treatments. Owing to their superior properties, such as acceptable biocompatibility and providing great primary bone fixation with the implant, polymethyl methacrylate (PMMA)-based bone cements (BCs) are among the essential materials as fixation implants in different orthopedic and trauma surgeries. On the other hand, these BCs have some disadvantages, including Lack of bone formation and bioactivity, and low mechanical properties, which can lead to bone cement (BC) failure. Hence, plenty of studies have been concentrating on eliminating BC failures by using different kinds of ceramics and polymers for reinforcement and also by producing composite materials. This review article aims to evaluate mechanical properties, self-setting characteristics, biocompatibility, and bioactivity of the PMMA-based BCs composites containing carbon nanotubes (CNTs), graphene oxide (GO), and carbon-based compounds. In the present study, we compared the effects of CNTs and GO as reinforcement agents in the PMMA-based BCs. Upcoming study on the PMMA-based BCs should concentrate on trialing combinations of these carbon-based reinforcing agents as this might improve beneficial characteristics.

Is Immediate Weight-Bearing Safe After Single Implant Fixation of Elderly Distal Femur Fractures?

To compare early complications in elderly patients with extra-articular distal femur fractures (DFFs) allowed to weight-bear as tolerated (WBAT) immediately versus patients prescribed initial touchdown weight-bearing (TDWB). Retrospective cohort study. Level 1 academic trauma center. One hundred thirty-five patients 60 years or older who underwent surgical fixation of an extra-articular DFF, including the OTA/AO fracture classification of 33-A1-3, and periprosthetic fractures with a stable knee prosthesis (Lewis and Rorabeck type I or II) with at least 6 months follow-up. Immediate WBAT or TDWB after surgical fixation of an extra-articular DFF with either an intramedullary nail or locked plate. The primary outcome was a major adverse event within the first 6 months, defined as (1) early fixation failure or change in alignment leading to reoperation, (2) nonunion, or (3) deep infection. Secondary outcomes included postoperative inpatient length of stay, discharge disposition (secondary facility vs. home), malunion, mortality, and patient-reported outcomes. The rate of early adverse events requiring reoperation was similar between the WBAT group (6, 10.7%) and the TDWB group (15, 19.0%; P = 0.23). There was no difference between groups with respect to length of stay, discharge disposition, malunion, and patient-reported outcomes. This study supports allowing carefully selected elderly patients, based on surgeon preference, to immediately weight-bear after operative fixation of an extra-articular DFF regardless of implant choice. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Flapless Intrascleral Knotting Technique for Suture Fixation of Intraocular Implants.

We will describe a flapless/grooveless/pocketless and minimally invasive technique for scleral suture fixation of intraocular implants. After introducing the suture into the eye, the two ends of the suture were left exterior to the globe, the free end and the end connected to a curved needle (the needle side). A back-and-forth intrascleral suture passage was performed with the aid of a curved needle. The suture was thus supported by adequate scleral tissue. The suture was fixated to the sclera by knotting it into the sclerotomy. The ends of the suture were finally anchored intrasclerally with the aid of a 30-gauge needle. The technique was used in 15 eyes of 15 patients. The mean postoperative follow-up period was 9.1 ± 4.6 months. Postoperatively, the intraoperative lenses of all the eyes remained well-positioned and stable. The postoperative visual acuities for all of the eyes were also improved. No suture erosion, suture loosening, hypotony, scleral atrophy, chronic inflammation, retinal tears, and/or detachments were observed within the follow-up period. The present technique provides minimal surgical invasion for the scleral suture fixation of intraocular implants.

Total hip replacement in femoral head osteonecrosis

The experience of hip replacement in young patients with osteonecrosis of the femoral head was analyzed in the article. The results of operations in the osteonecrosis group and osteoarthritis group in 3 years and 7 months after operations were compared. In 97.5 % of cases, cementless fixation implants with a ceramic on ceramic friction pair (45 %) and ceramic on polyethylene friction pair (45 %) were used. Surgical approaches by Moore, Hardinge and AMIS technique were applied. The clinical results of operations in the studied groups were similar, but the survival rate of endoprostheses in the osteonecrosis group was 91.5 %, and in the osteoarthritis group 97.2 %. In the osteonecrosis group an increased frequency of complications (dislocation of the endoprosthesis head, periprosthetic fracture, periprosthetic infection) and revision operations were observed. Our results show the influence of risk factors, concomitant diseases, the level of activity of young patients on the long-term total hip arthroplasty result.

EVALUATION OF RADIOLUCENCY AND SUBSIDENCE OF THE CEMENTLESS OXFORD MEDIAL UNICOMPARTMENTAL KNEE REPLACEMENT

Background: The most popular unicompartmental knee replacement(UKR) prosthesis to treat medial compartmentosteoarthritis (OA) is the Oxford knee (OUKR). This prosthesis now has cemented and cementless fixation options.The fixation of the new cementless implants has proved successful with significantly reduced radiolucent lines compared to the cemented prosthesis in the designer series. Unfortunately, some studies have reported tibial component subsidence as a specific complication to the cementless design. Aim of the Work: This study aims to review the fixation and clinical outcomes of the cementless prosthesis. We report the incidence of radiolucent lines associated with both cementless andcemented tibial prosthesis. More importantly, to study the incidence of tibial component subsidence. Materials and Methods: This is a prospective study of a consecutive series of the Oxford medial UKR. All patients had bone on bone arthritisfulfilling the criteria for anteromedial OA. All patients received cementless femur implants. The majority of patients received cementless tibial implants. Cemented tibial component was only used in elderly patients where the tibial metaphyseal bone was found potentially weak intraoperatively. Fluoroscopy-aligned radiographs were obtained post-operatively and at one-year.Radiolucent lines and subsidence were evaluated. All patients completed the Oxford kneequestionnaire (OKS) at one-year follow-up. Results: A total of 68 knees implanted in 59 patients completed the study. Fully cementless medial OUKR (n=61), and cemented tibial with cementless femur (n=7). The mean age was 67.5 years. Two patients required revision to TKR. The cemented design had higher incidence of radiolucent lines. One patient had Cementless tibial component subsidence. The median OKS was excellent in both groups. Conclusion: Both designs of the OUKR are valid treatment optionswith excellent OKS. Radiolucent lines are less frequent with the cementless design buttibial component subsidence and fracture have a higher incidence compared to the cemented prosthesis.

Treatment of Facial Deformities using 3D Planning and Printing of Patient-Specific Implants.

Technological advancements in surgical planning and patient-specific implants are constantly evolving. One can either adopt the technology to achieve better results, even in the less experienced hand, or continue without it. As technology develops and becomes more user-friendly, we believe it is time to allow the surgeon the option to plan his/her operations and create his/her own patient-specific surgical guides and fixation plates allowing him full control over the process. We present here a protocol for 3D planning of the operation followed by 3D planning and printing of surgical guides and patient-specific fixation implants. During this process we use two commercial computer-assisted design (CAD) software. We also use a fused depositionmodeling printer for the surgical guides and a selective laser sintering printer for the titanium patient-specific fixation implants. The process includes computed tomography (CT) imaging acquisition, 3D segmentation of the skull and facial bones from the CT, 3D planning of the operations, 3D planning of patient-specific fixation implant according to the final position of the bones, 3D planning of surgical guides for performing an accurate osteotomy and preparing the bone for the fixation plates, and 3D printing of the surgical guides and the patient-specific fixation plates. The advantages of the method include full control over the surgery, planned osteotomies and fixation plates, significant reduction in price, reduction in operation duration, superior performance and highly accurate results. Limitations include the need to master the CAD programs.

Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone

BackgroundWhat is the right surface for an implant to achieve biological fixation? Surface technologies can play important roles in encouraging interactions between the implant surface and the host bone to achieve osseointegration. Preclinical animal models provide important insight into in vivo performance related to bone ongrowth and implant fixation.MethodsA large animal model was used to compare the in vivo response of HA and plasma-sprayed titanium coatings in a well-reported adult ovine model to evaluate bone ongrowth in terms of mechanical properties in cortical sites, and histology and histomorphometry in cortical and cancellous sites at 4 and 12 weeks.ResultsTitanium plasma-sprayed surfaces outperformed the HA-coated samples in push-out testing in cortical sites while both surfaces supported new bone ongrowth and remodeling in cortical and cancellous sites.ConclusionsWhile both HA and Ti plasma provided an osteoconductive surface for bone ongrowth, the Ti plasma provided a more robust bone-implant interface that ideally would be required for load transfer and implant stability in the longer term.

The role of USP34 in the fixation of titanium implants in murine models.

Ubiquitin-specific protease 34 (USP34), a member of the ubiquitin-specific protease family, regulates osteogenic differentiation of bone marrow mesenchymal stem cells via bone morphogenetic protein signaling. This study aimed to investigate the role of USP34 in fixation of titanium implants in mouse models. Eight-week-old Usp34-knockout (Prx1-Cre;Usp34f/f ) mice and their Usp34 wild-type (Usp34f/f ) control littermates were used. Experimental titanium implants were inserted into the distal ends of femurs and the edentulous area of maxillae. Two and four weeks after surgery, samples of femur and maxilla were obtained, and micro-computed tomography scanning, histomorphometric analyses, and push-in tests were performed on the samples. Compared with controls, Prx1-Cre;Usp34f/f mice showed reduced bone volume for both femurs and maxillae; a decreased femoral bone-implant contact ratio (BIC) at 2wk [mean (standard error of the mean): 62.17% (2.15%) vs. 44.06% (3.45%)] and 4wk [72.46% (1.61%) vs. 64.53% (1.93%)]; decreases in femoral bone volume fraction (BV/TV) and push-in resistance; and lower BIC and BV/TV of the maxillae. Taken together, our data demonstrate that specific deletion of Usp34 in mesenchymal stem cells impairs fixation of titanium implants in mice.

Distally Based Sural Adipofascial Turnover Flap for Coverage of Complicated Wound in the Foot and Ankle Region.

Distally based perforator propeller flap from the lower leg region is a versatile local reconstructive technique for the foot and ankle defects. However, flap venous congestion remains a tough nut to crack. We hypothesize that raising an adipofascial flap with turnover mode of transposition can improve venous drainage and enhance flap safety. Based on the 2 rows of septocutaneous perforators in the posterior distal third of the lower leg, distally based adipofascial flap was raised from medial sural region nourished by 1 perforator bundle from the posterior tibial artery or from the lateral sural region from the peroneal artery. The superficial dissection was performed in subdermal plane and deep in to the subfascial space. The flap was nourished by perforator-plus-adipofascial pedicle and turned over 180 degrees upside down to reach the distal wounds. One week later, a split-skin graft was used to cover the exposed fascial flap. Postoperatively, flap survival, complications, and patient functional recovery were evaluated. Distally based sural turnover adipofascial flaps were used in 12 cases with complicated wounds of the distal third lower leg, foot, and ankle region. All wounds were caused by trauma and experienced fracture implants fixation and 5 with osteomyelitis. The comorbidities include diabetes in 9 cases and smoking in 7. There were 8 medial ural flaps and 4 lateral sural flaps. The adipofiscial flaps measured from 6.0 cm × 5.0 cm to 17.0 cm × 6.0 cm (mean, 61.3 cm). Postoperatively, all flaps survived uneventfully without any complication such as flap ischemia and/or necrosis. Two minor donor site complications were encountered, one was postoperative hematoma, and another was hyperproliferative scar. After a mean of 14.6 months of follow-up, the adipofascial flap plus skin graft showed a durable esthetic coverage, with normal shoe wearing and walking. Distally based sural adipofascial turnover flap is a simple and reliable wound coverage technique. It avoids venous congestion as usually seen in distally based fasciocutaneous flaps.

Topographic-Anatomical Validation of a New Method for Minimally-Invasive Extra-Cortical Osteosynthesis Using Plastinated Transverse Shoulder Cuts

The aim of the studywas to assess capability and benefits of this method, its technical feasibility and safety regarding a damage of the most essential anatomical structures.Material and methods.The study involved 15 natural humeral bones; their parameters - the length and shape of the plates – were measured for osteosynthesis. Bone osteosynthesis was further performed on 14 intact upper limbs taken from 7 non-fixed corpses of people died at the age of 63–77 using the discussed method; after that, the operated limbs were studied using preparating technique. Furthermore, after plate application on two shoulder sections, 12 transverse cuts with their epoxy plastination were made at three levels according to the original technology; this was followed by the preparation of histotopographic sections.Results.The results obtained have demonstrated that for the new method of bone osteosynthesis it is advisable to use metal plates 220–260 mm long with spiral twisting clockwise for the right humerus and counterclockwise for the left. Average distances from the fixed plate to the humerus, tendon of the long head of the biceps of the shoulder muscle, large blood vessels and peripheral nerves were determined using precision preparation and measurements; the measurements were also performed on transparent plate-shaped shoulder cuts. All the above validates safety of the discussed method regarding a damage of the most essential anatomical structures and allow to successfully use it in the clinical practice.Conclusion.The discussed technique of plastinated transverse shoulder cuts with further experimental fixation of metal implants for osteosynthesis ensures safety of the initial topographic and anatomical relationships of these structures with anatomical structures. In addition, high transparency of the tissues created by epoxy plastination allows determining distances between implants and important anatomical structures with high precision, the fact being of great significance in applied anatomical studies.

5 Year Follow Up Evaluation of a Third Generation Fixed Bearing Total Ankle Arthroplasty with an Intramedullary Tibial Component and a Central Sulcus Talus

Category:Ankle Arthritis, AnkleIntroduction/Purpose:Total ankle arthroplasty (TAA) has been shown to be a viable option in the treatment of end stage ankle arthritis (ESAA). Early reports demonstrated good results with intramedullary fixation implants. Third generation implants of this kind added a central sulcus to the talar component. This is a report of clinical follow up data from a prospectively collected database at a single US institution using a Third generation fixed bearing total ankle arthroplasty implant with a stemmed tibial component and a talar component with a central sulcus. To our knowledge, this is the first report of 5 year follow up data for this implant.Methods:Patients undergoing primary TAA at a single institution by one of four fellowship trained orthopedic foot and ankle surgeons with a Third generation fixed bearing implant consisting of an intramedullary stemmed tibial component and a sulcus talus that were at least 5 years postoperative were reviewed from a prospectively collected database. These patients were followed at regular intervals with history, physical examination and radiographs. All ankles were classified using the Canadian Orthopedic Foot and Ankle Society (COFAS) End-Stage Ankle Arthritis Classification System. The primary outcome was implant survivability. Secondary outcomes included pre- and postoperative coronal plane radiographic alignment, evaluation for osteolysis, and failure mode when applicable. All reoperation events were recorded using the COFAS Reoperations Coding System (CROCS).Results:126 TAA with this implant were performed in 124 patients between 2010 and 2013; 74 met inclusion criteria for our study. The mean age at surgery was 61.6 +- 10.0 years (range 38.7-84.3). Four patients died with their initial implants in place. The mean duration of follow up for living patients that retained both initial components at final follow-up was 6.2 +- .9 years (range 4.7-8.1 years). 35% (26 of 74) of ankles had a preoperative coronal plane deformity of at least 10 degrees. 11% (8 of 74) of the ankles had a preoperative coronal plane deformity of at least 20 degrees. There were 6 (8%) implant failures that occurred at a mean 2.0 +- 1.4 years postoperative. Two failures were due to deep infection. One failure was related to talar component subsidence. All failures occurred in patients with =preoperative coronal plane deformity of less than 5 degrees. 81% (60 of 74) of TAA had no reoperation events in the follow up period.Conclusion:This cohort of TAA patients with minimum 5 year follow up using a third generation fixed bearing implant demonstrates acceptable implant survival, improved reoperation rates, and maintenance of coronal plane alignment. These data also suggest tolerance of a larger preoperative deformity with improved implant design. Continued follow up and reporting is needed to ensure that these favorable outcomes are maintained. Additionally, further investigation on acceptable coronal plane alignment correction with TAA is needed to determine the possible limitations of this procedure.

Effects of porogen morphology on the architecture, permeability, and mechanical properties of hydroxyapatite whisker reinforced polyetheretherketone scaffolds

Porous polyetheretherketone (PEEK) and bioactive hydroxyapatite (HA) reinforced PEEK scaffolds have attracted recent interest for enabling biologic fixation of orthopaedic and spinal implants, such as interbody spinal fusion cages. Porous PEEK and HA-PEEK scaffolds have been prepared by compression molding and leaching a fugitive porogen, most commonly NaCl salt crystals which exhibit a cubic morphology. Ellipsoidal or spherical porogen particles have been suggested to improve pore interconnectivity and permeability in scaffolds through improved porogen particle contact compared with a cubic porogen, but a direct comparison without concomitant effects from other factors is lacking. Therefore, the objective of this study was to investigate the effects of the porogen morphology on the architecture, permeability, and mechanical properties of bioactive HA whisker reinforced PEEK scaffolds. HA whisker reinforced PEEK scaffolds were prepared using a cubic or ellipsoidal NaCl porogen of equivalent size at multiple, equivalent levels of porosity and a constant level of HA reinforcement. Scaffolds prepared with an ellipsoidal porogen exhibited greater pore interconnectivity, indicated by a lower specific surface area measured by micro-computed tomography, and greater permeability than scaffolds prepared with a cubic porogen at 75–85% porosity. Compressive mechanical properties were not affected by the porogen morphology. Thus, an ellipsoidal porogen facilitated improved pore interconnectivity and permeability without compromising mechanical properties, and offers a means to circumvent an otherwise inherent design tradeoff between the benefit of increased porosity on permeability and the detriment of increased porosity on mechanical properties.

Dual Delivery of Alendronate and E7-BMP-2 Peptide via Calcium Chelation to Mineralized Nanofiber Fragments for Alveolar Bone Regeneration.

The fixation and stability of dental implants is governed by the quality of the underlying alveolar bone. The current study investigates if the dual delivery of calcium chelating bone therapeutics from mineralized nanofiber fragments can help regenerate alveolar bone in vivo. Alendronate (ALN) or/and bone morphogenetic protein-2-mimicking peptide conjugated to a heptaglutamate moiety (E7-BMP-2) were incorporated onto mineralized nanofiber fragments of polylactide-co-glycolide-collagen-gelatin (PCG in 2:1:1 weight ratios) via calcium coupling/chelation. Two mg of the single-loaded (ALN) and coloaded (ALN + E7-BMP-2) mineralized nanofiber PCG grafts was filled into critical-sized (2 mm diameter × 2 mm depth) alveolar bone defects in rat maxillae and let heal for 4 weeks. X-ray microcomputed tomography analysis of the retrieved maxillae revealed significantly elevated new bone formation parameters for the ALN and ALN + E7-BMP-2 groups compared with the unfilled defect controls. However, no significant differences between the single and coloaded nanofiber grafts were noted. Furthermore, the histopathological analysis of the tissue sections divulged islands of new bone tissue in the ALN and ALN + E7-BMP-2 groups, whereas the control defect was covered with gingival tissue. Together, the presented strategy using mineralized nanofiber fragments in the sustained delivery of dual calcium chelating therapeutics could have potential applications in enhancing bone regeneration.

Additive manufacturing of fracture fixation implants: Design, material characterization, biomechanical modeling and experimentation

Recent advancements in additive manufacturing (AM) have motivated researchers to consider this fabrication technique as a solution for challenges in patient-specific orthopaedic needs. Although there is an increasing trend in the applications of AM in medical fields, there is a critical need to understand the biomechanical performance of AM implants. In particular, design opportunities, anisotropic material properties and resulting stability of AM implant constructs for large bone defects such as osteosarcoma, comminuted fractures and infections are unexplored. This study aims to evaluate metal AM for complex fracture fixation using both computational and experimental methods. In addition, this research highlights the role of AM in the entire workflow to fabricate metal AM fixation plates for treatment of comminuted proximal humerus fractures. A new AM-centric patient-specific implant design for reducing common postoperative complications such as varus collapse and screw cutout is investigated. Biocompatible 316L stainless steel specimens processed in laser-powder bed fusion (L-PBF) is subjected to tensile testing and post-hoc microhardness to obtain orthotropic material properties of the AM implants. Subsequently, risk of screw cut-out is evaluated using finite element modelling (FEM) of AM implant-bone constructs. Parallel experiments included synthetic bones that are evaluated using a 3D motion capture system. The biomechanical tests are analyzed to quantify the medial fracture gap displacement among study groups subject to different loading conditions. The outcomes of this study suggest that the proposed AM-centric fixation plate design reduces average varus collapse (i.e. medial fracture gap displacement) by 47.2 % and risk of screw cut-out by 14.6 % when compared to the conventional plate design. Findings from this study can be extended to other patient anatomy, loading conditions, and AM processes.