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

Introduction. Periprosthetic joint infection (PJI) remains the main cause of failure in primary and revision total knee arthroplasties (TKAs). Local delivery of antibiotics, mainly antibiotic-loaded bone cement (ALBC), is commonly employed to prevent PJI. Over the past decade, tantalum and porous titanium have been successfully utilized as metaphyseal fixation devices to address bone loss and improve biologic fixation during revision TKA. However, no study has examined the antimicrobial properties compared to bone cement. The purpose of this study was to compare the ability of tantalum, 3D porous titanium, antibiotic-loaded bone cement (ALBC) and smooth titanium alloy (STA) to inhibit Staphylococci bacterial agents in an in vitro medium environment, based on the evaluation of the zone of inhibition (ZOI) and the antibacterial activity duration. Our study hypothesis was that we will found no significant difference between groups to inhibit Methicillin-Sensitive or Methicillin-Resistant Staphylococcus aureus (MSSA/MRSA) agents. Methods. Thirty beads made of 3 different materials (tantalum/ 3D porous titanium/ STA) were bathed during 1hour inside of a solution made of 1g vancomycin with 20-mL of sterile water for injection (bath concentration: 50 mg/mL). Ten 1cm. 3. cylinders were also created mixing standard surgical cement with 1g of Vancomycin in standardized sterile molds (ALBC beads). Finally, thirty beads made of tantalum/ 3D porous titanium/ STA were bathed in phosphate buffered saline solution to act as a control group. Cylinders were then placed on agar plates inoculated with MSSA and MRSA. Inhibition zone diameters were measured each day and cylinders were transferred onto a new inoculated plate. Inhibition zones were measured with a manual Vernier caliper and with automated software. The mean inhibition zones between groups were compared using the Wilcoxon Test. Results. The inter-class coefficient correlation values indicated an optimal intra-observer and inter-observer reproducibility for ZOI measurement (ICC 0.96 and ICC 0.98). For MSSA and MRSA, no inhibitory effect was found in the control group and antibiotic-loaded STA beads exhibited a short inhibitory effect until day 2. For MSSA, both tantalum and 3D porous titanium beads exhibited larger inhibition zones than cement beads (all p<0.01) each day until day 7 for tantalum and until day 3 for 3D porous titanium. After 6 days, ALBC presented larger inhibition zone than the 3D porous titanium, but no difference was found with tantalum. For MRSA, both tantalum and 3D porous titanium beads had significantly larger inhibition zones than ALBC each day until day 6 for tantalum (all p<0.01) and until day 3 for 3D porous titanium (all p<0.04). ALBC presented larger inhibition zone than tantalum and 3D porous titanium from day 7 to 9 (all p<0.04). Conclusion. Our results demonstrate that porous metal implants can deliver local antibiotics over slightly varying time frames based on our in vitro analysis. Antibiotic-impregnated tantalum and 3D porous titanium constructs exhibited superior antimicrobial properties when compared to STA. Future goals include impregnating porous metals with antibiotics for intraoperative use during revision TKA. For figures, tables, or references, please contact authors directly

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

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

Introduction. Reconstructing acetabular defects in revision hip arthroplasty can be challenging. Small, contained defects can be successfully reconstructed with porous-coated cups without bone grafts. With larger uncontained defects, a cementless cup even with screws, will not engage with sufficient host bone to provide enough stability. Porous titanium augments were originally designed to be used with cementless porous titanium cups, and there is a scarcity of literature on their usage in cemented cups with bone grafting. Methods. We retrospectively reviewed five hips (four patients – 3 women, 1 man; mean age 65 years) in which we reconstructed the acetabulum with a titanium augment (Biomet, IN, USA) as a support for impaction bone grafting and cemented acetabular cups (Figure 1). All defects were classified according to Paprosky classification. Radiographic signs of osseointegration were graded according to Moore grading. Quality of life was measured with the Oxford Hip Score. Results. At a minimum of one year follow-up, none of the patients required any further surgery for aseptic loosening or re-revision. The Oxford Hip Scores generally improved and two of the patients were very satisfied with the overall outcome of the surgery and would have undergone the surgery again for a similar problem. The patient that underwent bilateral acetabular reconstruction during a period one month, scored lowered than the other patients and was less satisfied with the outcome. Radiographs at the latest follow-up revealed incorporation of the augment with mean change in acetabular component inclination of less than 1° and cup migration of less than 5 mm in both horizontal and vertical axes. Discussion. Acetabular reconstruction using porous titanium augments as a support for bone grafting and cemented acetabular cups can be an effective way of managing uncontained structural acetabular defect, with biocompatibility and osteoinducive characteristics. The early results are promising but longer follow-up is required

INTRODUCTION. Rotator cuff tears are common injuries which often require surgical repair. Unfortunately, repairs often fail [1] and improved repair strength is essential. P2 Porous titanium (DJO Surgical, Austin TX) has been shown to promote osseointegration [2,3] and subdermal integration [4]. However, the ability of P2Porous titanium to aid in supraspinatus tendon-to-bone repair has not been evaluated. Therefore, the purpose of this study was to investigate P2 implants used to augment supraspinatus tendon-to-bone repair in a rat model [5]. We hypothesized that supraspinatus tendon-to-bone repairs with P2 implants would allow for ingrowth and increased repair strength when compared to standard repair alone. METHODS. Thirty-four adult male Sprague-Dawley rats were used (IACUC approved). Rats received bilateral supraspinatus detachment and repair with one limb receiving P2 implant. Animals were sacrificed at time 0 (n=3), 2 weeks (n=8), 4 weeks (n=9) and 12 weeks (n=14). Limbs were either dissected for histological and SEM analysis or mechanical testing as described previously [5]. Specimens for histology and SEM were embedded in PMMA for tissue-implant interface analysis. Specimens were first viewed in SEM under BSE to detect bony ingrowth, then stained with Sanderson's Rapid Bone Stain and viewed under transmitted and polarized light for tissue ingrowth. Comparisons were made using Student's t-tests with significance at p≤0.05. RESULTS. No differences in cross-sectional area were detected at any time point (Fig 1A). Percent relaxation was significantly increased in the P2 group at 2 weeks, but not at 4 and 12 weeks (Fig 1B). Maximum load was significantly increased in the P2 group at 2 weeks, but not at 4 weeks (Fig 1C – maximum load not reported due to failure at grip at 12 weeks). Modulus was significantly increased in the P2 group at 4 weeks, but not at 2 or 12 weeks (Fig 1D). No differences were detected in stiffness at any time point (data not shown). BSE analysis demonstrated bone ingrowth (Fig 2) and histological analysis showed soft tissue integration (Fig 3). DISCUSSION. Results indicate superior mechanical properties in the P2 group at 2 and 4 weeks, and tissue ingrowth at all time points. Importantly, at 2 weeks, the P2group had 76% increased maximum load compared to standard repair. As supraspinatus tendon re-tears are extremely common early [1] and occur at the tendon-to-bone interface, this finding supports the reduction of re-tear risk with the P2 implant. Although no differences were detected in maximum load at 4 weeks, the increase at 2 weeks denotes that P2 implants improved early tendon-to-bone healing. Additionally, at 4 weeks, the P2 implant group had significantly increased elastic modulus, further supporting increased mechanical properties due to the P2 implant. Clinically, improved early healing might allow faster rehabilitation and associated recovery. This study demonstrates that the P2 implant improves tendon-to-bone healing up to 4 weeks (with no detrimental effects at longer time points), suggesting that P2 porous titanium may be of benefit for use in clinical rotator cuff repairs

The efficacy of saline irrigation for the treatment of periprosthetic infection (PJI) is limited in the presence of infected implants. This study evaluated the efficacy of vancomycin/tobramycin-doped polyvinyl alcohol (PVA)/ceramic composites (PVA-VAN/TOB-P) after saline irrigation in a mouse pouch infection model. 3D printed porous titanium (Ti) cylinders (400, 700 and 100 µm in pore size) were implanted into mice pouches, then inoculated with S. aureus at the amounts of 1X10. 3. CFU and 1X10. 6. CFU per pouch, respectively. Mice were randomized into 4 groups (n=6 for each group): (1) no bacteria; (2) bacteria without saline wash; 3) saline wash only, and (4) saline wash+PVA-VAN/TOB-P. After seven days, pouches were washed out alone or with additional injection of 0.2 ml of PVA-VAN/TOB-P. Mice were sacrificed 14 days after pouch wash. Bacteria cultures of collected Ti cylinders and washout fluid and histology of pouch tissues were performed. The low-grade infection (1X10. 3. CFU) was more significant in 400 µm Ti cylinders than that in Ti cylinders with larger pore sizes (700 and 1000 µm (p<0.05). A similar pattern of high-grade infection (1X10. 6. CFU) was observed (p<0.05). For the end wash, the bacteria burden (0.49±0.02) in saline wash group was completely eradicated by the addition of PVA-VAN/TOB-P (0.005±0.001, p<0.05). We noticed that 400 µm Ti cylinders have the highest risk of implant infection. Our data supported that the effect of saline irrigation was very limited in the presence of contaminated porous Ti cylinders. PVA-VAN/TOB-P was biodegradable, biocompatible, and was effective in eradicating bacteria retention after saline irrigation in a mouse model of low grade and high-grade infection. We believe that PVA-VAN/TOB-P represents an alternative to reduce the risk of PJI by providing a sustained local delivery of antibiotics

Introduction. Bone loss management represents one of the most challenging issues for the orthopaedic surgeon. In most cases, stems, structural allograft, TMcones, and sleeves are adequate to allow optimal implant stability and durable fixation. In selected cases of wide metadiaphyseal bone defects, these devices do not provide proper intraoperative stability. In such scenarios, further steps are needed and include complex modular reconstruction, substitution with megaprosthesis (exposing patients at high risk of early failure) or joint arthrodesis that can yield unacceptable results. The aim of this paper is to present early results obtained with a new custom-made implant for complex metadiaphyseal bone defects management in knee revision surgery. By means of case presentations the authors would highlight the possibilities and technical notes of this novel device in complex knee revision surgery. Methods. Since2015, 8 custom-made porous titanium devices were implanted for massive bone defect management in 6 knee arthroplasty revision procedures. Five patients were staged revision for periprosthetic joint infection (PJI) and one patient underwent a staged revision for post-traumatic septic arthritis. Main demographic and surgical data were collected. Clinical (Range of Movement [ROM], Knee Society Score [KSS] and Oxford Knee Score [OKS]), radiological findings and complications were recorded at different time points and statistically evaluated. Mean follow up was 19.5 ± 9.6months. Results. The study group included 4 males and 2 females with a mean age of 63.7 ± 5.5 years and a mean Body Mass Index of 29.3 ± 4.1. Globally, the mean number of previous surgeries was 4.8 ± 2.7. The custom made device was combined with a hinged prosthesis in 5 cases and with a constrained condylar implant in 1 patient. Hybrid fixation was used in all cases. The mean KSS and OKS of the entire population improved significantly from 35.3 ±6.5 and 19.2 ±3.5 preoperatively to 85.8 ±4.0 and 39.3 ±3.1 at the time of last follow-up evaluation (p<0.01). The range of motion improved from 46.7 ±9.8 of mean preoperative flexion and 7.8 ±6.8 of mean preoperative flexion contracture to 93.3 ±10.3 and 1.2 ±2.9 respectively (p<0.01). Radiological analysis showed no migration or implant loosening. No intraoperative or postoperative complication was recorded. One patient required a prolonged antibiotic therapy for positive culture samples of sonication of the retrieved spacer. No implant mismatch between the preoperative planning and the final implant was reported. Conclusion. The presented custom-made implant showed promising early clinical and radiological results. In extremely selected cases, this new device can be considered a safe and effective surgical step between “off the shelf” reconstruction implants and knee substitution with a tumor megaprosthesis. Accurate surgical planning and intraoperative management of soft tissues and residual bone stock are of paramount importance

Summary Statement. The modulation of both quantity and quality of peri-implant bone with either PTH or loading may be viable options to improve implant fixation and patient outcomes. A strong bone-implant interface is essential for successful joint replacement surgery. This study investigated the differences in bone surrounding and within a porous titanium implant after single or combined treatment with two anabolic bone therapies: intermittent parathyroid hormone (teriparatide) and mechanical loading. Porous titanium implants were inserted bilaterally on the distal lateral femurs of rabbits. The right implant was loaded daily (1 MPa, 50 cycles/day) while the left implant was not. Rabbits received daily PTH injections (20 ug/kg) or saline vehicle. Periprosthetic cancellous bone 0.5, 1.0, and 2.0 mm below the implant surface, bone at the 0.25 mm bone-implant interface and total bone within each implant were examined using tissue-level analyses (quantitative backscattered electron microscopy), cellular analyses (immunohistochemistry staining of osteoblasts with procollagen-1 and TRAP staining of osteoclasts), and shear testing (implant-bone interface). Statistical significance was determined using GEE models (p<0.05). For tissue located 0.5 mm below the implant, significant increases in bone area per total area (BA/TA) were observed with PTH treatment (56%) and with loading (27%). Further, an 18% increase in mineralization density with PTH treatment and a 20% increase in mineralization density with loading was found. Loading effects were not present beyond the 0.5 mm periprosthetic region, but PTH significantly increased BA/TA 2.0 mm below and mineralization density 1.0 mm below the implant. Tissue-level changes were supported by increases in osteoblast activity 0.5 mm below the implant with PTH (79%) and loading (34%), as well as by minimal osteoclast changes. At the 0.25 mm implant-bone interface PTH and loading increased BA/TA (16% and 23%, respectively), but only loading increased mineralization density (7%). Further, total integrated bone area was increased 35% with PTH. Both PTH and loading enhanced the mechanical integrity of the implant-bone; shear strength increased 34% and 60%, respectively. Although combined treatment was not synergistic, both PTH and loading individually enhanced the amount and mineralization density of bone at the implant interface and immediately below the interface, thereby increasing the mechanical strength of the metal-bone interface. This research suggests that modulation of both quantity and quality of peri-implant bone may be viable options to improve implant fixation and patient outcomes

Introduction. The use of cementless TKA's has been gradually increasing over the past several years given the increasing life expectancy of our patient population. Cementless TKA's have not been rapidly adopted due to the challenges and uncertainty of tibial fixation especially in elderly patients. With the advent of new technologies, the results of cementless TKA's with the potential for long term biologic fixation may now be equivalent or better than cemented TKA's. A highly porous tibial baseplate was developed based on proximal tibial anatomy using CT scans using 3D printing technology with focus on length, location and design of press-fit pegs. Objectives. The purpose of this study was to review the early results with respect to fixation and complications using a new, highly porous cementless tibial baseplate designed for biologic fixation. Methods. One hundred primary cementless TKAs were retrospectively reviewed using a highly porous titanium tibial baseplate. The femoral and patella components were also press-fit using peri-apetite beaded technology. Patients were evaluated at 2 weeks, 3 months, 1 and 2 year for clinical and radiographic outcomes along with any early (within 90 day) and 2 year complications. Postoperative protocol consisted of immediate full weightbearing, as tolerated. Radiographs were evaluated for biological fixation and radiolucent lines. Results. There were 68 females and 32 males with 7 undergoing bilateral TKA. The mean age was 63.8 yrs (range 40–84). The mean BMI was 33.7. Diagnosis in all patients was osteoarthritis. The mean follow up was 24.8 months (range 15 to 33). The mean hospital length of stay was 3.2 days (range 2–7). The mean pre operative flexion was 105.8 degrees which improved to 117.9 degrees at latest follow up. KSS scores improved significantly in all patients. There were no postoperative transfusions in this group. All patients developed good radiographic fixation and stability of the tibial baseplate (Figure 1). There were no cases of loosening of the baseplate or infections in this series. Within 90 days, one patient developed a non fatal DVT and one patient was revised due to instability from a CR to a PS femur with the baseplate intact. At 8 months post-op, one patient had a liner exchange for MPFL rupture with a subluxating patella. At 18 months post-op, one patient had a liner exchange due to instability and extensor mechanism rupture. In both cases the baseplate was not revised. Conclusions. Study results indicate cementless fixation using this baseplate is a viable option with good short term clinical results and no cases of aseptic loosening at 2 years. Early stability, pain relief and good ROM were shown. Long term data will be required to determine the overall benefits of this highly porous TKA with biologic fixation versus cemented arthroplasty

Cementless total knee replacement (TKR) is at the present date a controversial topic. Aim of the study was to compare the effect on tibial periprosthetic bone mineral density (BMD) between different implant materials and designs. During the two-year period between January 2005 and December 2006, we analysed data of 45 patients who underwent consecutively cementless TKR (49 implants) at our Institution for primary osteoarthritis. Data was divided in 2 groups: A) 26 implants with tantalium tibial component (Zimmer NexGen Trabecular Metal. TM. Monoblock); B) 23 implants with porous titanium tibial component (Lima MultiGen. TM. ). Data was comparable per sex, age, BMI, post-op alignment, post-op KSS > 75, absence of major post-op complications. Standard AP x-rays were taken 4 months post-op and 8 years post-op. In order to quantify the reduction of BDM, we determined using ImageJ (an open source software) the Mean Grey Value (MGV) of a specific area on the 4 months- and 8 yrs-postop AP x-rays. Group A and Group B had an average MGV variation of, respectively, 11.79% and 10.51%; there was no statistically significant difference between the two groups. Reduction of BMD in a TKR is known to be a biomechanical response to load and it is conditioned by the alignment of the components and their design. Our study shows that the different materials (porous titanium vs. tantalium), in relation to the different implant design, have a similar effect on the surrounding bone. The overall results show a valid osseointegration in both group of patients

Introduction. Acetabular revision surgery remains a technically demanding procedure with higher failure rates than primary total hip arthroplasty (THA). An acetabular component with three dimensional porous titanium and anatomic screw holes (Figure 1) was designed to allow the cup to be positioned anatomically and provide reliable fixation. Methods. A prospective multicenter study of 193 cases (190 patients) was conducted to assess the midterm clinical outcomes of the revision titanium acetabular shell. Radiographs, demographics, Harris Hip Score (HHS), and Short Form 36 (SF-36) were collected preoperatively, at 6 weeks, 3 months, and annually thereafter to 5 years. The mean duration of follow-up was 3.36 years. The Paprosky classification was assessed intraoperatively. Short Form 6D (SF-6D) utility values were obtained by transforming SF-36 scores through the Brazier method and were analyzed for effect size. Results. At time of surgery, mean patient age was 63.5 years and mean BMI was 28.1. 69 of the 193 cases were graded as 3A or 3B according to the Paprosky classification method. For all cases, Harris Hip Scores improved significantly (p < 0.001) from a preoperative mean score of 53.60 to a mean score of 86.15 at 1 year. These significant gains were maintained through 5 years, with a mean score of 87.35 at the 5-year time point. The Harris Hip Scores for Paprosky 3A and 3B cases also improved significantly (p < 0.001) from a preoperative mean score of 48.11 to a mean score of 85.45 at 1 year. These significant gains were maintained through 5 years, with a mean score of 85.65 at the 5-year time point. Among the radiographs independently reviewed to date, no cup migration or unstable cups have been identified. There were 12 acetabular shell re-revisions reported, for infection (7), aseptic loosening (4) and recurrent dislocation (1). Three of the cases revised for aseptic loosening were Paprosky type 3A, and one was 3B. For all cases, a clinically significant improvement in health utility was achieved by 3 months postoperative, with an effect size of 0.54. Clinically significant scores were maintained throughout the follow-up period, reaching an effect size of 0.64 at 5 years. Effect sizes were larger for cases with Paprosky classifications of 3A and 3B than the overall study population at all time points, reaching clinical significance at 3 months with an effect size of 0.64, and continuing to increase to an effect size of 1.19 at 5 years. Conclusion. Even in patients with severe acetabular defects, next generation highly porous acetabular components with three dimensional porous titanium and anatomic screw holes provide excellent stability, predictable midterm biologic fixation, pain, and reduction, and improved clinical function and health utility

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.

Bone impaction grafting (BIG) is a surgical technique for the restoration of bone stock loss with impaction of autograft or allograft bone particles (BoP). The goal of a series in-vitro and in-vivo experiments was to assess the suitability of deformable pure Ti (titanium) particles (TiP, FONDEL MEDICAL BV, Rotterdam, The Netherlands) for application as a full bone graft substitute in cemented revision total hip arthroplasty. TiP are highly porous (interconnective porosity before impaction 85 to 90%). In-vitro acetabular reconstructions were made in Sawbones (SAWBONES EUROPE, Malmö, Sweden) to evaluate migration by roentgen stereo photogrammetric analysis and shear force resistance by a lever out experiment. In-vitro femoral TiP reconstructions (SAWBONES, Malmö, Sweden) were used to evaluate micro-particle release and subsidence. Mature Dutch milk goats were used for two in-vivo experiments.

A non-loaded femoral defect model was used to compare osteoconduction of bioceramic coated TiP with BoP and ceramic particles (CeP).

Blood samples were taken for toxicological analysis.

In-vitro: TiP were as deformable as BoP and created an entangled graft layer (porosity after impaction 70 to 75%). Acetabular TiP reconstructions were more stable and resistant to subsidence and shear force than BoP reconstructions (lever-out moment 56 ± 12 Nm respectively 12 ± 4 Nm, p < 0.001). After initial setting, femoral subsidence rates were smaller than seen in femoral bone impaction grafting (0.45 ± 0.04 mm after 300 000 loading cycles). Impaction generated 1.3 mg particles/g TiP (particle Ø 0.7–2 000 μm, tri-modal size distribution). In-vivo: Bioceramic coated (10 −40 μm) TiP showed bone ingrowth rates comparable to BoP and CeP. Reconstructed acetabular defects showed rapid bone ingrowth into the layer of TiP. Serum titanium concentrations slowly increased from 0.60 ± 0.28 parts per billion (ppb) preoperatively to 1.06 ± 0.70 ppb at fifteen weeks postoperatively (p = 0.04).

Mechanical studies showed very good initial mechanical properties of TiP reconstructed defects. The in-vitro study showed micro-particle generation, but in the short-term goat studies, histology showed very few particles and no negative biological effects were found. The in-vivo acetabular study showed very favorable bone ingrowth characteristics into the TiP layer and a much thinner interface with the cement layer compared to similar defects reconstructed with BoP or mixtures of BoP with CeP. Further analysis in a human pilot study should proof that TiP is an attractive and safe alternative for allograft bone in impaction grafting revision arthroplasty.

The osteointegration of a new three-dimensional reticular titanium material, Trabecular Titanium™, was assessed using a bilateral cancellous (distal femur, proximal tibia) and cortical (tibia diaphysis) bone drill hole model in 18 sheep. TT is a novel Ti6Al4V material characterized by a high open porosity and composed of multi-planar regular hexagonal cells. Two 5.0 mm diameter, 12 mm long cylinders (TT1 & TT2) of two different porosities (TT1:650 μm, TT2:1250 μm) were tested and compared to two solid predicate 5.0 mm diameter, 12 mm long Ti cylinders (PT1 & PT2) coated with porous Ti (PT1: vacuum-plasma spray coating; PT2: inert-gas shielding arc spray coating).

Each implant type was surgically implanted at 4 separate locations in each sheep (16 implants per sheep). Three timepoints of 4, 16 and 52 weeks (n=6 sheep per timepoint) were used. Bone-implant interface was analyzed ex vivo by the determination of: 1) the shear strength (SS) measured during a push out test, 2) the percentage of bone in-growth (%B) using histomorphometry, 3) the bone apposition rate using fluorochrome labelling analysis and 4) the bone-implant contact using backscattered scanning electron microscopy (SEM). An ANOVA with a Bonferroni Post hoc test were used to detect differences between tested and predicate implants. P values 0.05 were considered significant.

At 4 weeks, 5 out of the 6 TT1 could be pushed out of the cortical bone (COB) samples. The remaining TT1 collapsed during testing. All TT1 could be pushed of the cancellous bone (CAB) samples. Four out of the 6 TT2 could be pushed out of CAB and of the COB samples. At 16 and 52 weeks, only one TT1 and one TT2 could be pushed out of the bone samples, the remaining implants collapsed during testing. All the PTs were successfully pushed out at all timepoints.

The mean %B of PT1 and PT2 did not significantly increase over time. For both materials, the mean %B ranged between 1.7% and 4.4% at 4 weeks and between 5.7% and 6.5% at 52 weeks. The mean %B of TT1 significantly increased over time in both COB (10.2% at 4 weeks, 46.2% at 16 weeks, 50.5% at 52 weeks) and CAB (5.8%, 23.9%, 24.3%). Similarly, the mean %B of TT2 significantly increased over time in both COB (7.8%, 48.6%, 65%) and CAB (4.5%, 24.1%, 38.6%). Bone apposition rates for the TT implants remained superior to 2 μm/day for the entire duration of the study. SEM showed an intimate bone-implant contact for all implant types at all timepoints.

At 16 and 52 weeks, histomorphometry revealed an extensive osteointegration of the TT specimens. Bone-implant interface strength was so high for the TT implants that they could not be pushed out of the bone samples. The results of this study would indicate that the TT implants provide a good scaffold for bone in-growth.

The last two decades have seen remarkable technological advances in total hip arthroplasty (THA) implant design. Porous ingrowth surfaces and highly crosslinked polyethylene (HXLPE) have been expected to dramatically improve implant survivorship. The purpose of the present study was to evaluate survival of contemporary cementless acetabular components following primary THA. 16,421 primary THAs performed for osteoarthritis between 2000 and 2019 were identified from our institutional total joint registry. Patients received one of 12 contemporary cementless acetabular designs with HXLPE liners. Components were grouped based on ingrowth surface into 4 categories: porous titanium (n=10,952, mean follow-up 5 years), porous tantalum (n=1223, mean follow-up 5 years), metal mesh (n=2680, mean follow-up 6.5 years), and hydroxyapatite (HA) coated (n=1566, mean follow-up 2.4 years). Kaplan-Meier analyses were performed to assess the survivorship free of acetabular revision. A historical series of 182 Harris-Galante-1 (HG-1) acetabular components was used as reference. The 15-year survivorship free of acetabular revision was >97% for all 4 contemporary cohorts. Compared to historical control, porous titanium (HR 0.06, 95% CI 0.02–0.17, p<0.001), porous tantalum (HR 0.09, 95%CI 0.03–0.29, p<0.001), metal mesh (HR 0.11, 95%CI 0.04–0.31, p<0.001), and HA-coated (HR 0.14, 95%CI 0.04–0.48, p=0.002) ingrowth surfaces had significantly lower risk of any acetabular revision. There were 16 cases (0.1%) of acetabular aseptic loosening that occurred in 8 (0.07%) porous titanium, 5 (0.2%) metal mesh, and 3 (0.2%) HA-coated acetabular components. 7 of the 8 porous titanium aseptic loosening cases occurred in one known problematic design. There were no cases of aseptic loosening in the porous tantalum group. Modern acetabular ingrowth surfaces and HXLPE liners have improved on historical results at the mid-term. Contemporary designs have extraordinarily high revision-free survivorship, and aseptic loosening is now a rare complication. At mid-term follow-up, survivorship of contemporary uncemented acetabular components is excellent and aseptic loosening occurs in a very small minority of patients

Objectives. In order to address acetabular defects, porous metal revision acetabular components and augments have been developed, which require fixation to each other. The fixation technique that results in the smallest relative movement between the components, as well as its influence on the primary stability with the host bone, have not previously been determined. Methods. A total of 18 composite hemipelvises with a Paprosky IIB defect were implanted using a porous titanium 56 mm multihole acetabular component and 1 cm augment. Each acetabular component and augment was affixed to the bone using two screws, while the method of fixation between the acetabular component and augment varied for the three groups of six hemipelvises: group S, screw fixation only; group SC, screw plus cement fixation; group C, cement fixation only. The implanted hemipelvises were cyclically loaded to three different loading maxima (0.5 kN, 0.9 kN, and 1.8 kN). Results. Screw fixation alone resulted in up to three times more movement (p = 0.006), especially when load was increased to 100% (p < 0.001), than with the other two fixation methods (C and SC). No significant difference was noted when a screw was added to the cement fixation. Increased load resulted in increased relative movement between the interfaces in all fixation methods (p < 0.001). Conclusion. Cement fixation between a porous titanium acetabular component and augment is associated with less relative movement than screw fixation alone for all implant interfaces, particularly with increasing loads. Adding a screw to the cement fixation did not offer any significant advantage. These results also show that the stability of the tested acetabular component/augment interface affects the stability of the construct that is affixed to the bone. Cite this article: N. A. Beckmann, R. G. Bitsch, M. Gondan, M. Schonhoff, S. Jaeger. Comparison of the stability of three fixation techniques between porous metal acetabular components and augments. Bone Joint Res 2018;7:282–288. DOI: 10.1302/2046-3758.74.BJR-2017-0198.R1

Objectives. An experimental rabbit model was used to test the null hypothesis, that there is no difference in new bone formation around uncoated titanium discs compared with coated titanium discs when implanted into the muscles of rabbits. Methods. A total of three titanium discs with different surface and coating (1, porous coating; 2, porous coating + Bonemaster (Biomet); and 3, porous coating + plasma-sprayed hydroxyapatite) were implanted in 12 female rabbits. Six animals were killed after six weeks and the remaining six were killed after 12 weeks. The implants with surrounding tissues were embedded in methyl methacrylate and grinded sections were stained with Masson-Goldners trichrome and examined by light microscopy of coded sections. Results. Small amounts of bone were observed scattered along the surface of five of the 12 implants coated with porous titanium, and around one out of 12 porous coated surfaces with Bonemaster. No bone formation could be detected around porous coated implants with plasma-sprayed hydroxyapatite. Conclusion. Porous titanium coating is to some degree osteoinductive in muscles

Introduction. Total shoulder arthroplasty is the fastest growing joint replacement in recent years, with projected compound annual growth rates of 10% for 2016 through 2021 – higher than those of both the hip and knee combined. Reverse total shoulder arthroplasty (RTSA) has gained particular interest as a solution for patients with irreparable massive rotator cuff tears and failed conventional shoulder replacement, for whom no satisfactory intervention previously existed. As the number of indications for RTSA continues to grow, so do implant designs, configurations, and fixation techniques. It has previously been shown that continuous implant migration within the first two years postoperatively is predictive of later loosening and failure in the hip and knee, with aseptic loosening of implant components a guaranteed cause for revision in the reverse shoulder. By identifying implants with a tendency to migrate, they can be eliminated from clinical practice prior to widespread use. The purpose of this study is to, for the first time, evaluate the pattern and magnitude of implant component migration in RTSA using the gold standard imaging technique radiostereometric analysis (RSA). Methods. Forty patients were prospectively randomized to receive either a cemented or press-fit humeral stem, and a glenosphere secured to the glenoid with either autologous bone graft or 3D printed porous titanium (Aequalis Ascend Flex, Wright Medical Group, Memphis, TN, USA) for primary reverse total shoulder arthroplasty. Following surgery, partients are imaged using RSA, a calibrated, stereo x-ray technique, at 6 weeks (baseline), 3 months, 6 months, 1 year, and 2 years. Migration of the humeral stem and glenosphere at each time point is compared to baseline. Preliminary results are presented, with 15 patients having reached the 6-month time point by presentation. Results. Implant migration of ten participants at the 3-month time point is presented. Maximum total point motion (MTPM) is a measure of translation and rotation of the point on the implant that has moved the most from baseline. Average MTPM ± SD of the humeral stem is 1.18 ± 0.65 mm and 0.98 ± 0.46 mm for press-fit (n = 6) and cemented (n = 4) stems, respectively; and 0.25 ± 0.09 mm and 0.47 ± 0.24 mm for bone graft (n = 4) and porous titanium (n = 6) glenosphere fixations, respectively, at the 3-month time point. Conclusion. There is a trend towards increased migration with the use of press-fit humeral stems and porous titanium glenosphere fixation, though no conclusions can be made from the current sample size. Further, though differences in migration magnitude may be observed at early postoperative time points, it is expected that all fixation techniques will show stability from 1 to 2 years postoperatively

Introduction. Varus alignment in total knee replacement (TKR) results in a larger portion of the joint load carried by the medial compartment. [1]. Increased burden on the medial compartment could negatively impact the implant fixation, especially for cementless TKR that requires bone ingrowth. Our aim was to quantify the effect varus alignment on the bone-implant interaction of cementless tibial baseplates. To this end, we evaluated the bone-implant micromotion and the amount of bone at risk of failure. [2,3]. Methods. Finite element models (Fig.1) were developed from pre-operative CT scans of the tibiae of 11 female patients with osteoarthritis (age: 58–77 years). We sought to compare two loading conditions from Smith et al.;. [1]. these corresponded to a mechanically aligned knee and a knee with 4° of varus. Consequently, we virtually implanted each model with a two-peg cementless baseplate following two tibial alignment strategies: mechanical alignment (i.e., perpendicular to the tibial mechanical axis) and 2° tibial varus alignment (the femoral resection accounts for additional 2° varus). The baseplate was modeled as solid titanium (E=114.3 GPa; v=0.33). The pegs and a 1.2 mm layer on the bone-contact surface were modeled as 3D-printed porous titanium (E=1.1 GPa; v=0.3). Bone material properties were non-homogeneous, determined from the CT scans using relationships specific to the proximal tibia. [2,4]. The bone-implant interface was modelled as frictional with friction coefficients for solid and porous titanium of 0.6 and 1.1, respectively. The tibia was fixed 77 mm distal to the resection. For mechanical alignment, instrumented TKR loads previously measured in vivo. [5]. were applied to the top of the baseplate throughout level gait in 2% intervals (Fig.1a). For varus alignment, the varus/valgus moment was modified to match the ratio of medial-lateral force distribution from Smith et al. [1]. (Fig.1b). Results. For both alignments and all bones, the largest micromotion and amount of bone at risk of failure occurred during mid stance, at 16% of gait (Figs.2,3). Peak micromotion, located at the antero-lateral edge of the baseplate, was 153±32 µm and 273±48 µm for mechanical and varus alignment, respectively. The area of the baseplate with micromotion above 40 µm (the threshold for bone ingrowth. [3]. ) was 28±5% and 41±4% for mechanical and varus alignment, respectively. The amount of bone at risk of failure at the bone-implant interface was 0.5±0.3% and 0.8±0.3% for the mechanical and varus alignment, respectively. Discussion. The peak micromotion and the baseplate area with micromotion above 40 µm increased with varus alignment compared to mechanical alignment. Furthermore, the amount of bone at risk of failure, although small for both alignments, was greater for varus alignment. These results suggest that varus alignment, consisting of a combination of femoral and tibial alignment, may negatively impact bone ingrowth and increase the risk of bone failure for cementless tibial baseplates of this TKR design