Aims. The purpose of this study was to evaluate the biological fixation of a 3D printed porous implant, with and without different hydroxyapatite (HA) coatings, in a canine model. Materials and Methods. A canine transcortical model was used to evaluate the characteristics of bone ingrowth of Ti6Al4V cylindrical implants fabricated using laser rapid manufacturing (LRM). At four and 12 weeks post-implantation, we performed histological analysis and mechanical push-out testing on three groups of implants: a HA-free control (LRM), LRM with precipitated HA (LRM-PA), and LRM with plasma-sprayed HA (LRM-PSHA). Results. Substantial bone ingrowth was observed in all LRM implants, with and without HA, at both time periods. Bone ingrowth increased from 42% to 52% at four weeks, to 60% to 65% at 12 weeks. Mechanical tests indicated a minimum shear fixation strength of 20 MPa to 24 MPa at four weeks, and 34 MPa to 40 MPa at 12 weeks. There was no significant difference in the amount of bone ingrowth or in the shear strength between the three implant types at either time period. Conclusion. At four and 12 weeks, the 3D printed porous implants exhibited consistent bone ingrowth and high mechanical shear strength. Based on the results of this study, we confirmed the suitability of this novel new additive manufacturing porous material for biological fixation by bone ingrowth. Cite this article: Bone Joint J 2019;101-B(6 Supple B):62–67

Abstract. Objectives. Young patients receiving metallic bone implants after surgical resection of bone cancer require implants that last into adulthood, and ideally life-long. Porous implants with similar stiffness to bone can promote bone ingrowth and thus beneficial clinical outcomes. A mechanical remodelling stimulus, strain energy density (SED), is thought to be the primary control variable of the process of bone growth into porous implants. The sequential process of bone growth needs to be taken into account to develop an accurate and validated bone remodelling algorithm, which can be employed to improve porous implant design and achieve better clinical outcomes. Methods. A bone remodelling algorithm was developed, incorporating the concept of bone connectivity (sequential growth of bone from existing bone) to make the algorithm more physiologically relevant. The algorithm includes adaptive elastic modulus based on apparent bone density, using a node-based model to simulate local remodelling variations while alleviating numerical checkerboard problems. Strain energy density (SED) incorporating stress and strain effects in all directions was used as the primary stimulus for bone remodelling. The simulations were developed to run in MATLAB interfacing with the commercial FEA software ABAQUS and Python. The algorithm was applied to predict bone ingrowth into a porous implant for comparison against data from a sheep model. Results. The accuracy of the predicted bone remodelling was verified for standard loading cases (bending, torsion) against analytical calculations. Good convergence was achieved. The algorithm predicted good bone remodelling and growth into the investigated porous implant. Using the standard algorithm without connectivity, bone started to remodel at locations unconnected to any bone, which is physiologically implausible. The implementation of bone connectivity ensures the gradual process of bone growth into the implant pores from the sides. The bone connectivity algorithm predicted that the full remodelling required more time (approximately 50% longer), which should be considered when developing post-surgical rehabilitation strategies for patients. Both algorithms with and without bone connectivity implementation converged to same final stiffness (less than 0.01% difference). Almost all nodes reached the same density value, with only a limited number of nodes (less than 1%) in transition areas with a strong density gradient having noticeable differences. Conclusions. An improved bone remodelling algorithm based on strain energy density that modelled the sequential process of bone growth has been developed and tested. For a porous metallic bone implant the same final bone density distribution as for the original adaptive elasticity theory was predicted, with a slower and more fidelic process of growth from existing surrounding bone into the porous implant. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Revision surgeries for orthopaedic infections are done in two stages – one surgery to implant an antibiotic spacer to clear the infection and another to install a permanent implant. A permanent porous implant, that can be loaded with antibiotics and allow for single-stage revision surgery, will benefit patients and save healthcare resources. Gyroid structures can be constructed with high porosity, without stress concentrations that can develop in other period porous structures [1] [2]. The purpose of this research is to compare the resulting bone and prosthesis stress distributions when porous versus solid stems are implanted into three proximal humeri with varying bone densities, using finite element models (FEM). Porous humeral stems were constructed in a gyroid structure at porosities of 60%, 70%, and 80% using computer-aided design (CAD) software. These CAD models were analyzed using FEM (Abaqus) to look at the stress distributions within the proximal humerus and the stem components with loads and boundary conditions representing the arm actively maintained at 120˚ of flexion. The stem was assumed to be made of titanium (Ti6Al4V). Three different bone densities were investigated, representing a healthy, an osteopenic, and an osteoporotic humerus, with an average bone shape created using a statistical shape and density model (SSDM) based on 75 cadaveric shoulders (57 males and 18 females, 73 12 years) [3]. The Young's moduli (E) of the cortical and trabecular bones were defined on an element-by-element basis, with a minimum allowable E of 15 MPa. The Von Mises stress distributions in the bone and the stems were compared between different stem scenarios for each bone density model. A preliminary analysis shows an increase in stress values at the proximal-lateral region of the humerus when using the porous stems compared to the solid stem, which becomes more prominent as bone density decreases. With the exception of a few mesh dependent singularities, all three porous stems show stress distributions below the fatigue strength of Ti-6Al-4V (410 MPa) for this loading scenario when employed in the osteopenic and osteoporotic humeri [4]. The 80% porosity stem had a single strut exceeding the fatigue strength when employed in the healthy bone. The results of this study indicate that the more compliant nature of the porous stem geometries may allow for better load transmission through the proximal humeral bone, better matching the stress distributions of the intact bone and possibly mitigating stress-shielding effects. Importantly, this study also indicates that these porous stems have adequate strength for long-term use, as none were predicted to have catastrophic failure under the physiologically-relevant loads. Although these results are limited to a single boney geometry, it is based on the average shape of 75 shoulders and different bone densities are considered. Future work could leverage the shape model for probabilistic models that could explore the effect of stem porosity across a broader population. The development of these models are instrumental in determining if these structures are a viable solution to combatting orthopaedic implant infections

Aims. The use of a porous metal shell supported by two augments with the ‘footing’ technique is one solution to manage Paprosky IIIB acetabular defects in revision total hip arthroplasty. The aim of this study was to assess the medium-term implant survival and radiological and clinical outcomes of this technique. Methods. We undertook a retrospective, two-centre series of 39 hips in 39 patients (15 male, 24 female) treated with the ‘footing’ technique for Paprosky IIIB acetabular defects between 2007 and 2020. The median age at the time of surgery was 64.4 years (interquartile range (IQR) 54.4 to 71.0). The median follow-up was 3.9 years (IQR 3.1 to 7.0). Results. The cumulative medium-term survival of the acetabular construct was 89%. Two hips (5.1%) required further revision due to shell loosening, one hip (2.6%) due to shell dislocation, and one hip (2.6%) due to infection. The median Harris Hip Score improved significantly from 47 points (IQR 41.5 to 54.9) preoperatively to 80 points (IQR 73.5 to 88.6) at the latest follow-up (p < 0.001). Conclusion. The reconstruction of Paprosky IIIB acetabular defects with porous tantalum shells and two augments using the ‘footing’ technique showed excellent medium-term results. It is a viable option for treating these challenging defects. Cite this article: Bone Joint J 2024;106-B(5 Supple B):54–58

Previous studies have reported excellent results with tapered, titanium alloy, porous plasma-sprayed components in patients undergoing uncemented primary total hip arthroplasty (THA). The purpose of this study was to examine survival and clinical results at minimum 25-year follow-up. We reviewed all patients who underwent primary THA at our center through 1995 with a specific femoral component, the Mallory-Head Porous (MHP; Zimmer Biomet, Warsaw, IN). This device, marketed in the U.S. until December 2021, was essentially unchanged since its 1984 introduction, except the porous coating was continued circumferentially along the lateral aspect in 1987, a hydroxyapatite-coated option was offered in 1988, and an offset option was added in 1999 after the study period. Three hundred thirty-two patients (396 THA) had a minimum of 25-year follow-up. Mean age at surgery was 47.6 years (range, 21–70 years). Mean follow-up in non-failed patients was 28.7 years (range, 25 to 37 years). There were 31 femoral revisions (7.8%): 9 infection, 3 failure of ingrowth, 5 aseptic loosening, 8 osteolysis revised well-fixed, 2 periprosthetic fracture, 2 polyethylene wear with trochanteric avulsion, 1 component breakage, and 1 malalignment well-fixed. Kaplan-Meier survival with endpoint of stem revision for all causes was 94.8% (95% CI: ±0.9%) at 36.7 years, and survival with endpoint of aseptic loosening/failure of ingrowth was 98.7% (95% CI: ±0.5) at 36.7 years. Harris hip scores improved significantly from 43 preoperatively to 76 most recently. This tapered, titanium, porous plasma spray-coated femoral component continues to demonstrate high long-term survival with a low rate of femoral component revision for any reason or aseptic loosening/failure of ingrowth

First-time revision acetabular components have a 36% re-revision rate at 10 years in Australia, with subsequent revisions known to have even worse results. Acetabular component migration >1mm at two years following revision THA is a surrogate for long term loosening. This study aimed to measure the migration of porous tantalum components used at revision surgery and investigate the effect of achieving press-fit and/or three-point fixation within acetabular bone. Between May 2011 and March 2018, 55 patients (56 hips; 30 female, 25 male) underwent acetabular revision THR with a porous tantalum component, with a post-operative CT scan to assess implant to host bone contact achieved and Radiostereometric Analysis (RSA) examinations on day 2, 3 months, 1 and 2 years. A porous tantalum component was used because the defects treated (Paprosky IIa:IIb:IIc:IIIa:IIIb; 2:6:8:22:18; 13 with pelvic discontinuity) were either deemed too large or in a position preventing screw fixation of an implant with low coefficient of friction. Press-fit and three-point fixation of the implant was assessed intra-operatively and on postoperative imaging. Three-point acetabular fixation was achieved in 51 hips (92%), 34 (62%) of which were press-fit. The mean implant to host bone contact achieved was 36% (range 9-71%). The majority (52/56, 93%) of components demonstrated acceptable early stability. Four components migrated >1mm proximally at two years (1.1, 3.2, 3.6 and 16.4mm). Three of these were in hips with Paprosky IIIB defects, including 2 with pelvic discontinuity. Neither press-fit nor three-point fixation was achieved for these three components and the cup to host bone contact achieved was low (30, 32 and 59%). The majority of porous tantalum components had acceptable stability at two years following revision surgery despite treating large acetabular defects and poor bone quality. Components without press-fit or three-point fixation were associated with unacceptable amounts of early migration

Aims. BoneMaster is a thin electrochemically applied hydroxyapatite (HA) coating for orthopaedic implants that is quickly resorbed during osseointegration. Early stabilization is a surrogacy marker of good survival of femoral stems. The hypothesis of this study was that a BoneMaster coating yields a fast early and lasting fixation of stems. Methods. A total of 53 patients were randomized to be treated using Bi-Metric cementless femoral stems with either only a porous titanium plasma-sprayed coating (P group) or a porous titanium plasma-sprayed coating with an additional BoneMaster coating (PBM group). The patients were examined with radiostereometry until five years after surgery. Results. At three months, the mean total translation (TT) was 0.95 mm (95% confidence interval (CI) 0.68 to 1.22) in the P group and 0.57 mm (95% CI 0.31 to 0.83) in the PBM group (p = 0.047). From two to five years, the TT increased by a mean of 0.14 mm (95% CI 0.03 to 0.25) more in the P group than in the PBM group (p = 0.021). In osteopenic patients (n = 20), the mean TT after three months was 1.61 mm (95% CI 1.03 to 2.20) in the P group and 0.73 mm (95% CI 0.25 to 1.21) in the PBM group (p = 0.023). After 60 months, the mean TT in osteopenic patients was 1.87 mm (95% CI 1.24 to 2.50) in the P group and 0.82 mm (95% CI 0.30 to 1.33) in the PBM group (p = 0.011). Conclusion. There was less early and midterm migration of cementless stems with BoneMaster coating compared with those with only a porous titanium plasma-sprayed coating. Although a BoneMaster coating seems to be important for stem fixation, especially in osteopenic patients, further research is warranted. Cite this article: Bone Joint J 2022;104-B(6):647–656

In primary total hip arthroplasty (THA) for patients with Crowe II or higher classes developmental dysplasia of the hip (DDH) or rapidly destructive coxopathy (RDC), the placement of the cup can be challenging due to superior and lateral acetabular bone defects. Traditionally, bone grafts from resected femoral heads were used to fill these defects, but bulk graft poses a risk of collapse, especially in DDH with hypoplastic femoral heads or in RDC where good quality bone is scarce. Recently, porous metal augments have shown promising outcomes in revision surgeries, yet reports on their efficacy in primary THA are limited. This study retrospectively evaluated 27 patients (30 hips) who underwent primary THA using cementless cups and porous titanium acetabular augments for DDH or RDC, with follow-up periods ranging from 2 to 10 years (average 4.1 years). The cohort included 22 females (24 hips) and 5 males (6 hips), with an average age of 67 years at the time of surgery. The findings at the final follow-up showed no radiographic evidence of loosening or radiolucency around the cups and augments, indicating successful biological fixation in all cases. Clinically, there was a significant improvement in the WOMAC score from an average of 39.1±14.7 preoperatively to 5.1±6.4 postoperatively. These results suggest that the use of cementless cups and porous titanium acetabular augments in primary THA for DDH and RDC can lead to high levels of clinical improvement and reliable biological fixation, indicating their potential as a viable solution for managing challenging acetabular defects in these conditions

Aims. The efficacy of saline irrigation for treatment of implant-associated infections is limited in the presence of porous metallic implants. This study evaluated the therapeutic efficacy of antibiotic doped bioceramic (vancomycin/tobramycin-doped polyvinyl alcohol composite (PVA-VAN/TOB-P)) after saline wash in a mouse infection model implanted with titanium cylinders. Methods. Air pouches created in female BalBc mice by subcutaneous injection of air. In the first of two independent studies, pouches were implanted with titanium cylinders (400, 700, and 100 µm pore sizes) and inoculated with Staphylococcus aureus (1 × 10. 3. or 1 × 10. 6. colony-forming units (CFU)/pouch) to establish infection and biofilm formation. Mice were killed after one week for microbiological analysis. In the second study, pouches were implanted with 400 µm titanium cylinders and inoculated with S. aureus (1 × 10. 3. or 1 × 10. 6. CFU/pouch). Four groups were tested: 1) no bacteria; 2) bacteria without saline wash; 3) saline wash only; and 4) saline wash plus PVA-VAN/TOB-P. After seven days, the pouches were opened and washed with saline alone, or had an additional injection of PVA-VAN/TOB-P. Mice were killed 14 days after pouch wash. Results. The first part of the study showed that low-grade infection was more significant in 400 µm cylinders than cylinders with larger pore sizes (p < 0.05). The second part of the study showed that saline wash alone was ineffective in eradicating both low- and high-grade infections. Saline plus PVA-VAN/TOB-P eradicated the titanium cylinder-associated infections, as manifested by negative cultures of the washouts and supported by scanning electron microscopy and histology. Conclusion. Porous titanium cylinders were vulnerable to bacterial infection and biofilm formation that could not be treated by saline irrigation alone. Application of PVA-VAN/TOB-P directly into the surgical site alone or after saline wash represents a feasible approach for prevention and/or treatment of porous implant-related infections. Cite this article: Bone Joint Res 2024;13(11):622–631

This paper presents an ongoing review of the use of a wedge-shaped porous metal augments in the shoulder to address glenoid retroversion as part of anatomical total shoulder arthroplasty (aTSA). Seventy-five shoulders in 66 patients (23 women and 43 men, aged 42 to 85 years) with Walch grade B2 or C glenoids underwent porous metal glenoid augment (PMGA) insertion as part of aTSA. Patients received either a 15º or 30º PMGA wedge (secured by screws to the native glenoid) to correct excessive glenoid retroversion before a standard glenoid component was implanted using bone cement. Neither patient-specific guides nor navigation were used. Patients were prospectively assessed using shoulder functional assessments (Oxford Shoulder Score [OSS], American Shoulder and Elbow Standardized Shoulder Assessment Form [ASES], visual analogue scale [VAS] pain scores and forward elevation [FE]) preoperatively, at three, six, and 12 months, and yearly thereafter, with similar radiological surveillance. Forty-nine consecutive series shoulders had a follow-up of greater than 24 months, with a median follow-up of 48 months (range: 24–87 months). Median outcome scores improved for OSS (21 to 44), ASES (24 to 92), VAS (7 to 0), and FE (90º to 140º). Four patients died, but no others were lost to follow-up. Apart from one infection at 18 months postoperatively and one minor peg perforation, there were no complications, hardware failures, implant displacements, significant lucency or posterior re-subluxations. Radiographs showed good incorporation of the wedge augment with correction of glenoid retroversion from median 22º (13º to 46º) to 4º. All but four glenoids were corrected to within the target range (less than 10º retroversion). The porous metal wedge-shaped augments effectively addressed posterior glenoid deficiency as part of aTSA for rotator cuff intact osteoarthritis, producing satisfactory clinical outcomes with no signs of impending future failure

Although 3D-printed porous dental implants may possess improved osseointegration potential, they must exhibit appropriate fatigue strength. Finite element analysis (FEA) has the potential to predict the fatigue life of implants and accelerate their development. This work aimed at developing and validating an FEA-based tool to predict the fatigue behavior of porous dental implants. Test samples mimicking dental implants were designed as 4.5 mm-diameter cylinders with a fully porous section around bone level. Three porosity levels (50%, 60% and 70%) and two unit cell types (Schwarz Primitive (SP) and Schwarz W (SW)) were combined to generate six designs that were split between calibration (60SP, 70SP, 60SW, 70SW) and validation (50SP, 50SW) sets. Twenty-eight samples per design were additively manufactured from titanium powder (Ti6Al4V). The samples were tested under bending compression loading (ISO 14801) monotonically (N=4/design) to determine ultimate load (F. ult. ) (Instron 5866) and cyclically at six load levels between 50% and 10% of F. ult. (N=4/design/load level) (DYNA5dent). Failure force results were fitted to F/F. ult. = a(N. f. ). b. (Eq1) with N. f. being the number of cycles to failure, to identify parameters a and b. The endurance limit (F. e. ) was evaluated at N. f. = 5M cycles. Finite element models were built to predict the yield load (F. yield. ) of each design. Combining a linear correlation between FEA-based F. yield. and experimental F. ult. with equation Eq1 enabled FEA-based prediction of F. e. . For all designs, F. e. was comprised between 10% (all four samples surviving) and 15% (at least one failure) of F. ult. The FEA-based tool predicted F. e. values of 11.7% and 12.0% of F. ult. for the validation sets of 50SP and 50SW, respectively. Thus, the developed FEA-based workflow could accurately predict endurance limit for different implant designs and therefore could be used in future to aid the development of novel porous implants. Acknowledgements: This study was funded by EU's Horizon 2020 grant No. 953128 (I-SMarD). We gratefully acknowledge the expert advice of Prof. Philippe Zysset

The advent of modular porous metal augments has ushered in a new form of treatment for acetabular bone loss. The function of an augment can be seen as reducing the size of a defect or reconstituting the anterosuperior/posteroinferior columns and/or allowing supplementary fixation. Depending on the function of the augment, the surgeon can decide on the sequence of introduction of the hemispherical shell, before or after the augment. Augments should always, however, be used with cement to form a unit with the acetabular component. Given their versatility, augments also allow the use of a hemispherical shell in a position that restores the centre of rotation and biomechanics of the hip. Progressive shedding or the appearance of metal debris is a particular finding with augments and, with other radiological signs of failure, should be recognized on serial radiographs. Mid- to long-term outcomes in studies reporting the use of augments with hemispherical shells in revision total hip arthroplasty have shown rates of survival of > 90%. However, a higher risk of failure has been reported when augments have been used for patients with chronic pelvic discontinuity. Cite this article: Bone Joint J 2024;106-B(4):312–318

The aim of this study is to print 3D polycaprolactone (PCL) scaffolds at high and low temperature (HT/LT) combined with salt leaching to induced porosity/larger pore size and improve material degradation without compromising cellular activity of printed scaffolds. PCL solutions with sodium chloride (NaCl) particles either directly printed in LT or were casted, dried, and printed in HT followed by washing in deionized water (DI) to leach out the salt. Micro-Computed tomography (Micro-CT) and scanning electron microscope (SEM) were performed for morphological analysis. The effect of the porosity on the mechanical properties and degradation was evaluated by a tensile test and etching with NaOH, respectively. To evaluate cellular responses, human bone marrow-derived mesenchymal stem/stromal cells (hBMSCs) were cultured on the scaffolds and their viability, attachment, morphology, proliferation, and osteogenic differentiation were assessed. Micro-CT and SEM analysis showed that porosity induced by the salt leaching increased with increasing the salt content in HT, however no change was observed in LT. Structure thickness reduced with elevating NaCl content. Mass loss of scaffolds dramatically increased with elevated porosity in HT. Dog bone-shaped specimens with induced porosity exhibited higher ductility and toughness but less strength and stiffness under the tension in HT whereas they showed decrease in all mechanical properties in LT. All scaffolds showed excellent cytocompatibility. Cells were able to attach on the surface of the scaffolds and grow up to 14 days. Microscopy images of the seeded scaffolds showed substantial increase in the formation of extracellular matrix (ECM) network and elongation of the cells. The study demonstrated the ability of combining 3D printing and particulate leaching together to fabricate porous PCL scaffolds. The scaffolds were successfully printed with various salt content without negatively affecting cell responses. Printing porous thermoplastic polymer could be of great importance for temporary biocompatible implants in bone tissue engineering applications

As compared to magnesium (Mg) and iron (Fe), solid zinc (Zn)-based absorbable implants show better degradation rates. An ideal bone substitute should provide sufficient mechanical support, but pure Zn itself is not strong enough for load-bearing medical applications. Modern processing techniques, like additive manufacturing (AM), can improve mechanical strength of Zn. To better mimic the in vivo situation in the human body, we evaluated the degradation behavior of porous Zn implants in vitro under dynamic conditions. Our study applied selective laser melting (SLM) to build topographically ordered absorbable Zn implants with superior mechanical properties. Specimens were fabricated from pure Zn powder using SLM and diamond unit cell topological design. In vitro degradation was performed under both static and dynamic conditions in a custom-built set-up under cell culture conditions (37 °C, 20% O2 and 5% CO2) for up to 28 days. Mechanical properties of the porous structures were determined according to ISO 13314: 2011 at different immersion time points. Modified ISO 10993 standards were used to evaluate biocompatibility through direct cell seeding and indirect extract-based cytotoxicity tests (MTS assay, Promega) against identically designed porous titanium (Ti-6Al-4V) specimens as reference material. Twenty-four hours after cell seeding, its efficacy was evaluated by Live-Dead staining (Abcam) and further analyzed using dual channel fluorescent optical imaging (FOI) and subsequent flow cytometric quantification. Porous Zn implants were successfully produced by means of SLM with a yield strength and Young's modulus in the range of 3.9–9.6 MPa and 265–570 MPa, respectively. Dynamic flow significantly increased the degradation rate of AM porous Zn after 28 days. Results from Zn extracts were similar to Ti-6Al-4V with >95% of cellular activity at all tested time points, confirming level 0 cytotoxicity (i.e., This study clearly shows the great potential of AM porous Zn as a bone substituting material. Moreover, we demonstrate that complex topological design permits control of mechanical properties and degradation behavior

Aims. Massive endoprostheses rely on extra-cortical bone bridging (ECBB) to enhance fixation. The aim of this study was to investigate the role of selective laser sintered (SLS) porous collars in augmenting the osseointegration of these prostheses. Materials and Methods. The two novel designs of porous SLS collars, one with small pores (Ø700 μm, SP) and one with large pores (Ø1500 μm, LP), were compared in an ovine tibial diaphyseal model. Osseointegration of these collars was compared with that of a clinically used solid, grooved design (G). At six months post-operatively, the ovine tibias were retrieved and underwent radiological and histological analysis. Results. Porous collars provided a significantly greater surface (p < 0.001) for the ingrowth of bone than the standard grooved design. Significantly greater extracortical pedicle formation was seen radiologically around the grooved design (length p = 0.002, thickness p < 0.001, surface area p = 0.002) than around the porous collars. However, the ingrowth of bone occurred from the transection site into the porous structure of both types of collar. A fivefold increase in integration was seen with the SP and a threefold increase in the LP design when compared with G (p < 0.001). Conclusion. SLS porous collars allow the direct ingrowth of more bone and are better than current designs which rely on surface ongrowth and ECBB. Cite this article: Bone Joint J 2017;99-B:276–82

Production of porous titanium bone implants is a highly promising research and application area due to providing high osseointegration and achieving the desired mechanical properties. Production of controlled porosity in titanium implants is possible with laser powder bed fusion (L- PBF) technology. The main topics of this presentation includes the L-PBF process parameter optimization to manufacture thin walls of porous titanium structures with almost full density and good mechanical properties as well as good dimensional accuracy. Moreover, the cleaning and coating process of these structures to further increase osseointegration and then in-vitro biocompatibility will be covered

First-time revision acetabular components have a 36% re-revision rate at 10 years in Australia, with subsequent revisions known to have even worse results. Acetabular component migration >1mm at two years following revision THA is a surrogate for long term loosening. This study aimed to measure the migration of porous tantalum components used at revision surgery and investigate the effect of achieving press-fit and/or three-point fixation within acetabular bone. Between May 2011 and March 2018, 55 patients (56 hips; 30 female, 25 male) underwent acetabular revision THR with a porous tantalum component, with a post-operative CT scan to assess implant to host bone contact achieved and Radiostereometric Analysis (RSA) examinations on day 2, 3 months, 1 and 2 years. A porous tantalum component was used because the defects treated (Paprosky IIa:IIb:IIc:IIIa:IIIb; 2:6:8:22:18; 13 with pelvic discontinuity) were either deemed too large or in a position preventing screw fixation of an implant with low coefficient of friction. Press-fit and three-point fixation of the implant was assessed intra-operatively and on postoperative imaging. Three-point acetabular fixation was achieved in 51 hips (92%), 34 (62%) of which were press-fit. The mean implant to host bone contact achieved was 36% (range 9–71%). The majority (52/56, 93%) of components demonstrated acceptable early stability. Four components migrated >1mm proximally at two years (1.1, 3.2, 3.6 and 16.4mm). Three of these were in hips with Paprosky IIIB defects, including 2 with pelvic discontinuity. Neither press-fit nor three-point fixation was achieved for these three components and the cup to host bone contact achieved was low (30, 32 and 59%). The majority of porous tantalum components had acceptable stability at two years following revision surgery despite treating large acetabular defects and poor bone quality. Components without press-fit or three-point fixation were associated with unacceptable amounts of early migration

Introduction. Long term data on the survivorship of cemented total knee arthroplasty (TKA) has demonstrated excellent outcomes; however, with younger, more active patients, surgeons have a renewed interest in improved biologic fixation obtained from highly porous, cementless implants. Early designs of cementless total knees systems were fraught with high rates of failure for aseptic loosening, particularly on the tibial component. Prior studies have assessed the bone ingrowth extent for tibial tray designs reporting near 30% extent of bone ingrowth . (1,2). While these analyses were performed on implants that demonstrated unacceptably high rates of clinical failure, a paucity of data exists on the extent on bone ingrowth in contemporary implant designs with newer methods for manufacturing the porous surfaces. We sought to evaluate the extent of attached bone on retrieved cementless tibial trays to determine if patient demographics, device factors, or radiographic results correlate to the extent of bone ingrowth in these contemporary designs. Methods. Using our IRB approved retrieval database, 17 porous tibial trays were identified and separated into groups based on manufacturer: Zimmer Natural Knee (1), Zimmer NexGen (10), Stryker Triathlon (4) and Biomet Vanguard Regenerex (2). Differences in manufacturing methods for porous material designs were recorded. Patient demographics and reason for revision are described in Table 1. Radiographs were used to measure tibiofemoral alignment and the tibial mechanical axis alignment. Components were assessed using visual light microscopy and Photoshop to map bone ingrowth extent across the porous surface. ImageJ was used to threshold and calculate values for bone, scratched metal, and available surface for bone ingrowth (Fig. 1). Percent extent was determined as the bone ingrowth compared to the surface area excluding any scratched regions from explantation. Statistics were performed among tray designs as well as between the lateral and medial pegs, if designs had pegs available for bony ingrowth. Results. Mean bone ingrowth extent was 51.4% for the tibial tray for the entire cohort. Bone ingrowth extent was statistically greater in the Zimmer NexGen design (63.8%; p=.027) compared to the other three designs (Table 2). Four sets of pegs were excluded from analysis due to lack of porous coatings or pegs having been removed at revision surgery. Across all designs, the medial peg had 45.2% ingrowth and the lateral peg had 66.1% ingrowth. The medial peg for the NexGen design had significantly less bone ingrowth compared to the lateral peg (58.7% vs. 75.4%; p=0.044). No significant differences were found in tibiofemoral alignment or tibial mechanical axis alignment between the implant groups. No significant differences were found among implants revised for aseptic loosening versus any other reason for revision (54% vs 30%; p=.18). Discussion. Our results demonstrate high rates of bone ingrowth extent in contemporary designs, further supporting porous design rationales and a role for additive manufacturing to form enhanced porosity. We plan on exploring staining techniques to confirm our visual inspection. Contemporary designs have shown successful rates for improved longevity for cementless total knee systems. For any figures or tables, please contact the authors directly

Porous surfaces on orthopaedic implants have been shown to promote tissue ingrowth. This study evaluated biological fixation of novel additively manufactured porous implants with and without hydroxyapatite coatings in a canine transcortical model. Laser rapid manufacturing (LRM) Ti6Al4V cylindrical implants were built with a random interconnected architecture mimicking cancellous bone (5.2 mm diameter, 10mm length, 50–60% porous, mean pore size 450μm). Three groups were investigated in this study: as-built with no coating (LRM), as-built coated with solution precipitated hydroxyapatite (LRM-PA), and as-built coated with a plasma sprayed hydroxyapatite (LRM-PSHA). Implants were press-fit into a 5mm unicortical, perpendicular drill hole in the femoral diaphysis of the left and right femurs in 12 canines. Right femora were harvested for histology (SEM, bone ingrowth into implant within cortical region) and left femora for mechanical push-out testing (shear strength of bone-implant interface) at 4 and 12 weeks (N=6, un-paired Student's t-test, p=0.05). For mean bone ingrowth, there was no significant difference between groups at 4 weeks (LRM, LRM-PA, LRM-PSHA: 41.5+8.6%, 51+5.5% and 53.2+11%, respectively) or 12 weeks (LRM, LRM-PA, LRM-PSHA: 64.4+2.8%, 59.9+7.6%, 64.9+6.4%, respectively). LRM and LRM-PA implants had more bone ingrowth at 12 weeks than 4 weeks (p < 0 .05). Mean shear strength of all implants at 12 weeks (LRM, LRM-PA, LRM-PSHA: 39.9+3.6MPa, 33.7+4.6MPa, 36+4.1MPa respectively) were greater than at 4 weeks (LRM, LRM-PA, LRM-PSHA: 21.6+2.8MPa, 20.7+1.1MPa, 20.2+2.5MPa respectively) (p < 0 .05). No significant difference was observed between all groups at 4 or 12 weeks. Overall, this canine study confirmed the suitability of this novel additive manufacturing porous material for biological fixation by bone ingrowth. All implants exhibited high bone ingrowth and mechanical shear strength in this canine model. No difference was observed between uncoated and hydroxyapatite coated implants

Aims. To compare the in vivo long-term fixation achieved by two acetabular components with different porous ingrowth surfaces using radiostereometric analysis (RSA). Methods. This was a minimum ten-year follow-up of a prospective randomized trial of 62 hips with two different porous ingrowth acetabular components. RSA exams had previously been acquired through two years of follow-up. Patients returned for RSA examination at a minimum of ten years. In addition, radiological appearance of these acetabular components was analyzed, and patient-reported outcome measures (PROMs) obtained. Results. In all, 15 hips were available at ten years. There was no statistically significant difference in PROMS between the two groups; PROMs were improved at ten years compared to preoperative scores. Conventional radiological assessment revealed well-fixed components. There was minimal movement for both porous surfaces in translation (X, Y, Z, 3D translation in mm (median and interquartile range (IQR)), StikTite (Smith and Nephew, Memphis, Tennessee, USA): 0.03 (1.08), 0.12 (0.7), 0.003 (2.3), 0.37 (0.30), and Roughcoat (Smith and Nephew): -0.6 (0.59),–0.1 (0.49), 0.1 (1.12), 0.48 (0.38)), and rotation (X, Y, Z rotation in degrees (median and IQR), (Stiktite: -0.4 (3), 0.28 (2), -0.2 (1), and Roughcoat: - 0.4 (1),–0.1 (1), 0.2 (2)). There was no statistically significant difference between the two cohorts (p-value for X, Y, Z, 3D translation - 0.54, 0.46, 0.87, 0.55 and for X, Y, Z rotation - 0.41, 0.23, 0.23 respectively) at ten years. There was significant correlation between two years and ten years 3D translation for all components (r = 0.81(p =< 0.001)). Conclusion. Both porous ingrowth surfaces demonstrated excellent fixation on plain radiographs and with RSA at ten years. Short-term RSA data are good predictors for long-term migration data