Patients undergoing revision surgery of a primary total hip arthroplasty often exhibit bone loss and poor bone quality, which make achieving stable fixation and osseointegration challenging. Implant components coated in porous metals are used clinically to improve mechanical stability and encourage bone in-growth. We compared ultra-porous titanium coatings, known commercially as Gription and Porocoat, in an intra-articular model by press-fitting coated cylindrical implants into ovine femoral condyles and evaluating bone in-growth and fixation strength 4, 8 and 16 weeks post-operatively. Bilateral surgery using a mini-arthrotomy approach was performed on twenty-four Dorset-Rideau Arcott rams (3.4 ± 0.8 years old, 84.8 ± 9.3 kg) with Institutional Animal Care Committee approval in accordance with the Canadian Council on Animal Care. Cylindrical implants, 6.2 mm in diameter by 10 mm in length with surface radius of curvature of 35 mm, were composed of a titanium substrate coated in either Porocoat or Gription and press-fit into 6 mm diameter recipient holes in the weight-bearing regions of the medial (MFC) and lateral (LFC) femoral condyles. Each sheep received 4 implants; two Gription in one stifle (knee) and two Porocoat in the contralateral joint. Biomechanical push-out tests (Instron ElectroPuls E10000) were performed on LFCs, where implants were pushed out relative to the condyle at a rate of 2 mm/min. Force and displacement data were used to calculate force and displacement at failure, stiffness, energy, stress, strain, elastic modulus, and toughness. MFCs were fixed in 70% ethanol, processed undecalcified, and polished sections, approximately 70 µm thick (Exakt Micro Grinding system) were carbon-coated. Backscattered electron images were collected on a scanning electron microscope (Hitachi SU3500) at 5 kV and working distance of 5 mm. Bone in-growth within the porous coating was quantified using software (ImageJ). Statistical comparisons were made using a two-way ANOVA and Fisher's LSD post-hoc test (Statistica v.8). Biomechanical evaluation of the bone-implant interface revealed that by 16 weeks, Gription-coated implants exhibited higher force (2455±1362 N vs. 1002±1466 N, p=0.046) and stress (12.60±6.99 MPa vs. 5.14±7.53 MPa, p=0.046) at failure, and trended towards higher stiffness (11510±7645 N/mm vs. 5010±8374 N/mm, p=.061) and modulus of elasticity (591±392 MPa vs. 256±431 MPa, p=0.61). Similarly, by 16 weeks, bone in-growth in Gription-coated implants was approximately double that measured in Porocoat (6.73±3.86 % vs. 3.22±1.52 %, p=0.045). No statistically significant differences were detected at either 4 nor 8 weeks, however, qualitative observations of the exposed bone-implant interface, made following push-out testing, showed more bony material consistently adhered to Gription compared to Porocoat at all three time points. High variability is attributed to implant placement, resulting from the small visual window afforded during surgery, unique curvatures of the condyles, and presence of the extensor digitorum longus tendon which limited access to the LFC. Ultra-porous titanium coatings, know commercially as Gription and Porocoat, were compared for the first time in a challenging intra-articular ovine model. Gription provided superior fixation strength and bone in-growth, suggesting it may be beneficial in hip replacement surgeries where bone stock quality and quantity may be compromised

Dorr bone type is both a qualitative and quantitative classification. Qualitatively on x-rays the cortical thickness determines the ABC type. The cortical thickness is best judged on a lateral x-ray and the focus is on the posterior cortex. In Type A bone it is a thick convex structure (posterior fin of bone) that can force the tip of the tapered implant anteriorly – which then displaces the femoral head posteriorly into relative retroversion. Fractures in DAA hips have had increased fractures in Type A bone because of the metaphyseal-diaphyseal mismatch (metaphysis is bigger than diaphysis in relation to stem size). Quantitatively, Type B bone has osteoclastic erosion of the posterior fin which proceeds from proximal to distal and is characterised by flattening of the fin, and erosive cysts in it from osteoclasts. A tapered stem works well in this bone type, and the bone cells respond positively. Type C bone has loss of the entire posterior fin (stove pipe bone), and the osteoblast function at a low level with dominance of osteoclasts. Type C is also progressive and is worse when both the lateral and AP views show a stove pipe shape. If just the lateral x-ray has thin cortices, and the AP has a tapered thickness of the cortex a non-cemented stem will work, but there is a higher risk for fracture because of weak bone. At surgery Type C bone has “mushy” cancellous bone compared to the hard structure of type A. Tapered stems have high risk for loosening because the diaphysis is bigger than the metaphysis (opposite of Type A). Fully coated rod type stems fix well, but have a high incidence of stress shielding. Cemented fixation is done by surgeons for Type C bone to avoid fracture, and insure a comfortable hip. The large size stem often required to fit Type C bone causes an adverse-stem-bone ratio which can cause chronic thigh pain. I cement patients over age 70 with Type C bone which is most common in women over that age.

Introduction

Aligning the tibial tray is a critical step in total knee arthroplasty (TKA). Malalignment, (especially in varus) has been associated with failure and revision surgery. While the link between varus malalignment and failure has been attributed to increased medial compartmental loading and generation of shear stress, quantitative biomechanical evidence to directly support this mechanism is incomplete. We therefore constructed and validated a finite element model of knee arthroplasty to test the hypothesis that varus malalignment of the tibial tray would increase the risk of tray subsidence.

Background

Recent advances in materials and manufacturing processes for arthroplasty have allowed fabrication of intricate implant surfaces to facilitate bony attachment. However, refinement and evaluation of these new design strategies is hindered by the cost and complications of animal studies, particularly during early iterations in development process. To address this problem, we have constructed and validated an ex-vivo bone bioreactor culture system to enable empirical testing of candidate structures and materials. In this study, we investigated mineralization of a titanium wire mesh scaffold under both static and dynamic culturing using our ex vivo bioreactor system.

This study aimed to analyze the effect of two different techniques of cement application: cement on bone surface (CoB) versus cement on bone surface and implant surface (CoBaI) on the short-term effect of radiolucent lines (RLL) in primary fully cemented total knee arthroplasties (TKA) with patella resurfacing. 379 fully cemented TKAs (318 patients) were included in this monocentric study. Preoperative and postoperative at week 4 and 12 month after surgery all patients had a clinical and radiological examination and were administered the Oxford Knee Score (OKS). Cement was applied in two different ways among the two study groups: cement on bone surface (CoB group) or cement on bone surface and implant surface (CoBaI group). The evaluation of the presence of RLL or osteolysis was done as previously described using the updated Knee Society Radiographic Evaluation System. The mean OKS and range of motion improved significantly in both groups at the 4-week and 12-month follow-up, with no significant difference between the groups (CoB vs. CoBaI). RLL were present in 4.7% in the whole study population and were significantly higher in the CoBaI group (10.5%) at the 4-week follow-up. At the 12-month follow-up RLL were seen in 29.8% of the TKAs in the CoBaI group, whereas the incidence was lower in the CoB group (24.0% (n.s.)). There were two revisions in each group. None of these due to aseptic loosening. Our study indicated that the application of bone cement on bone surface only might be more beneficial than onto the bone surface and onto the implant surface as well in respect to the short-term presence of RLL in fully cemented primary TKA. The long-term results will be of interest, especially in respect to aseptic loosening and might guide future directions of bone cement applications in TKA

Aim. Several local antibiotic-eluting drug delivery systems have been developed to treat bacterial bone infections. However, available systems have significant shortcomings, including suboptimal drug-release profiles with a burst followed by subtherapeutic release, which may lead to treatment failure and selection for drug resistance. Here, we present a novel injectable, biocompatible, in situ-forming depot, termed CarboCells, which can be fine-tuned for the desired antibiotic-release profile. The CarboCell technology has flexible injection properties that allow surgeons to accurately place antibiotic-eluting depots within and surrounding infectious sites in soft tissue and bones. The CarboCell technology is furthermore compatible with clinical image-guided injection technologies. These studies aimed to determine the therapeutic potential of CarboCell formulations for treatment of implant-associated osteomyelitis by mono- and dual antimicrobial therapy. Methods. The solubility and stability of several antibiotics were determined in various CarboCell formulations, and in vitro drug release was characterized. Lead candidates for antimicrobial therapy were selected using a modified semi-solid biofilm model with 4-day-matured Staphylococcus aureus biofilm (osteomyelitis-isolate, strain S54F9). Efficacy was investigated in a rat implant-associated osteomyelitis model established in the femoral bone by intraosseous implantation of a stainless-steel pin with 4-day-old in vitro-matured S. aureus biofilm. CarboCells were injected subcutaneously at the femur, and antimicrobial efficacy was evaluated 7 days post-implantation. Lead formulations were subsequently tested in a well-established translational implant-associated tibial S. aureus osteomyelitis pig model. Infection was established for 7 days before revision surgery consisting of debridement, washing, implantation of a new stainless-steel pin, and injection of antibiotic-releasing CarboCells into the debrided cavity and in the surrounding bone- and soft-tissue. Seven days post-revision, pigs were euthanized, and samples were collected for microbial and histopathological evaluation. Results. Lead antimicrobial agents were soluble in high concentrations and were stable in CarboCell formulations. Three combinations completely eradicated bacteria in the in vitro semi-solid biofilm model. In the rat osteomyelitis model, CarboCell formulations of the lead combinations also eradicated bacteria in bone and implant in several rats and significantly reduced infection in all treated rats. In the pig model, CarboCell antimicrobial monotherapy demonstrated promising therapeutic efficacy, including complete eradication of infection in bone and implants in several pigs and significantly reduced bacterial burden in others. Conclusions. Using the CarboCell technology for antimicrobial delivery exert substantial loco-regional efficacy. The attractive sustained high-dose antibiotic release profile combined with the flexible injection technology allows surgeons to accurately place effective drug-eluting depots in key areas not accessible to competing technologies

Ligament reconstruction following multi-ligamentous knee injuries involves graft fixation in bone tunnels using interference screws (IS) or cortical suspensory systems. Risks of IS fixation include graft laceration, cortical fractures, prominent hardware, and inability to adjust tensioning once secured. Closed loop suspensory (CLS) fixation offers an alternative with fewer graft failures and improved graft-to-tunnel incorporation. However, graft tensioning cannot be modified to accommodate errors in tunnel length evaluation. Adjustable loop suspensory (ALS) devices (i.e., Smith & Nephew Ultrabutton) address these concerns and also offer the ability to sequentially tighten each graft, as needed. However, ALS devices may lead to increased graft displacement compared to CLS devices. Therefore, this study aims to report outcomes in a large clinical cohort of patients using both IS and CLS fixation. A retrospective review of radiographic, clinical, and patient-reported outcomes following ligament reconstruction from a Level 1 trauma centre was completed. Eligible patients were identified via electronic medical records using ICD-10 codes. Inclusion criteria were patients 18 years or older undergoing ACL, PCL, MCL, and/or LCL reconstruction between January 2018 and 2020 using IS and/or CLS fixation, with a minimum of six-month post-operative follow-up. Exclusion criteria were follow-up less than six months, incomplete radiographic imaging, and age less than 18 years. Knee dislocations (KD) were classified using the Schenck Classification. The primary outcome measure was implant removal rate. Secondary outcomes were revision surgery rate, deep infection rate, radiographic fixation failure rate, radiographic malposition, Lysholm and Tegner scores, clinical graft failure, and radiographic graft failure. Radiographic malposition was defined as implants over 5 mm off bone or intraosseous deployment of the suspensory fixation device. Clinical graft failure was defined as a grade II or greater Lachman, posterior drawer, varus opening at 20° of knee flexion, and/or valgus opening at 20° of knee flexion. Radiographic failure was defined when over 5 mm, 3.2 mm, and/or 2.7 mm of side-to-side difference occurred using PCL gravity stress views, valgus stress views, and/or varus stress views, respectively. Descriptive statistics were used. Sixty-three consecutive patients (mean age = 41 years, range = 19-58) were included. A total of 266 CLS fixation with Ultrabuttons and 135 IS were used. Mean follow-up duration was 383 days. Most injuries were KD type II and III. Graft revision surgery rate was 1.5%. Intraosseous deployment occurred in 6.2% and 17% had implants secured in soft tissue, rather than on bone. However, the implant removal rate was only 6.2%. Radiographic PCL gravity stress views demonstrated an average of 1.2 mm of side-to-side difference with 6.2% meeting criteria for radiographic failure. A single patient met radiographic failure criteria for collateral grafts. Mean Lysholm and Tegner scores were 87.3 and 4.4, respectively, with follow-up beyond one year. Both IS and CLS fixation demonstrate an extremely low revision surgery rate, a high rate of implant retention, excellent radiographic stability, and satisfactory patient-reported outcome scores. Incorrect implant deployment was seen in a total of 17% of patients, yet none required implant removal. A single patient required graft revision due to implant failure

Aim. Galleria mellonella larvae is a well-known insect infection model that has been used to test the virulence of bacterial and fungal strains as well as for the high throughput screening of antimicrobial compounds against infections. Recently, we have developed insect infection model G. mellonella larvae to study implant associated biofilm infections using small K-wire as implant material. Here, we aimed to further expand the use of G. mellonella to test other materials such as bone cement with combination of gentamicin to treat implant-associated infections. Method. The poly methyl methacrylate (PMMA) with and without gentamicin and liquid methyl methacrylate (MMA) were kindly provided by Heraeus Medical GmbH, Wehrheim. To make the bone cement implants as cubes, Teflon plate (Karl Lettenbauer, Erlangen) with specified well size was used. The Radiopaque polymer and monomer were mixed well in a bowl, applied over on to the Teflon plate and pressed with spatula to form fine and uniform cubes. After polymerization, the bone cement implants were taken out of the Teflon well plate with the help of pin. For the infection process, bone cement cubes were pre-incubated with S. aureus EDCC 5055 culture at 5×10. 6. CFU/ml for 30 min at 150 rpm shaking conditions. Later, these implants were washed with 10ml PBS and implanted in the larvae as mentioned. Survival of the larvae were observed at 37°C in an incubator. To analyze the susceptibility of the bacterial infections towards gentamicin, survival of the larvae compared with control group implanted only with bone cement. The effect of gentamicin was also measured in terms of S. aureus load in larvae on 2. nd. day. SEM analysis was performed to see the effect of gentamicin on biofilm formation on bone cement. Results. Our experiments established the G. mellonella as an excellent model to screen bone cement with antimicrobial compounds against bacterial infections. The gentamicin bone cement samples showed excellent S. aureus bacterial load reduction after the implantation in G. mellonella model. The bone cement with gentamicin showed better survival of larvae infected with S. aureus compared to control. Finally, the gentamicin also affected the biofilm formation on the bone cement surface with S. aureus. Conclusions. Thus, our work showed G. mellonella is a rapid, cheap economical pre-clinical model to study the bone cement associate bacterial infections as well as screening of the various antimicrobial compounds

Aim. Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty that typically requires revision surgery for treatment. Systemic antibiotics are usually held prior to surgery to improve yield of intraoperative cultures. However, recent studies suggest that preoperative aspirations have a high concordance with intraoperative cultures, which may allow surgeons to initiate antibiotic treatment earlier. The purpose of the study was to investigate the effect of Pre-surgical systemic antibiotic therapy on the bacterial burden within the periprosthetic space and systemic immune reaction. Method. PJI was induced with MSSA (Xen36) S. aureus in the right knee of 16-week old, female, C57BL6 mice using a previously validated murine model. Mice were randomized to three groups (n=8, each): control; Vanc, receiving systemic vancomycin (110mg/kg, SQ, twice daily); or VancRif receiving vancomycin same as in Vanc group, plus rifampin (12mg/kg dose, IV, once daily). Following 2 weeks of treatment, mice were euthanized and periprosthetic bone, soft tissue and the implant were harvested. Bacterial burden, colony forming units (CFUs), was quantified in soft tissue, tibial bone, and on the implant. Specifically, tissues were homogenized and serially plated for CFUs, while the implant was sonicated and then plated for CFUs. The host immune response was analysed through weighing inguinal and iliac lymph nodes and through measuring serum amyloid A (SAA). Non-parametric pairwise group comparisons of the three outcome measures were performed using a Mann-Whitney U test. Results. VancRif, the combined treatment significantly reduced bacterial burden in the periprosthetic soft tissue, bone, and implant compared to control (p<0.001) and Vanc alone (p<0.001). While not significant, Vanc alone did reduce bacterial load as compared to control. The ipsilateral weight of the iliac lymph nodes was significantly reduced in Vanc and VancRif mice compared to controls (p<0.001), was well as in VancRif versus Vanc alone (p<0.001). Interestingly, SAA levels did not significantly differ among all groups. During tissue harvesting, minimal purulence was observed in antibiotic treatment groups, unlike controls. Conclusions. Treating active PJI with vancomycin alone decreases periprosthetic bacterial loads and reduces the local immunological response. This effect is significantly enhanced with the combined rifampin use. These findings could suggest that when culture positive PJI is diagnosed, pre-surgical treatment with antibiotics may decrease immunosuppression and soft tissue infiltration, leading to a better chance of infection cure with subsequent surgical debridement. Histological investigations and repeat experiments involving subsequent surgical treatment are underway. Acknowledgements. Funding comes from internal institutional grants

Aim. To make an inoculum for induction of Implant-Associated Osteomyelitis (IAO) in pigs based on bacterial aggregates resembling those found on the human skin, i.e. aggregates of 5–15 µm with low metabolic activity. The aggregates were evaluated and compared to a standard planktonic bacterial inoculum. Method. The porcine Staphylococcus aureus strain S54F9 was cultured in Tryptone Soya Broth for seven days. Subsequently, the culture was filtered through cell strainers with pore sizes of 15 µm and 5 µm, respectively. The fraction of 5–15 µm aggregates in the top of the 5 µm filter was collected as the aggregate-inoculum. The separation of aggregates into different size fractions was evaluated by light microscopy. The metabolism of the aggregate-inoculum and a standard overnight planktonic inoculum was evaluated with isothermal microcalorimetry. In total, six female minipigs were allocated into three groups (n=2), receiving different inoculums. Group A: overnight planktonic inoculum; 10. 4. CFU S. aureus (S54F9), Group B: seven days old 5–15 µm aggregate-inoculum; 10. 4. CFU S. aureus (S54F9), Group C: saline. All inoculums were placed in a pre-drilled implant cavity in the right tibia of the pig and a sterile stainless-steel implant was inserted. The pigs were euthanized seven days after surgery. Postmortem macroscopic pathology, microbiology, computed tomography and histopathology were performed. Results. The separation of aggregates into different size fractions was done successfully by the filtering method. Isothermal microcalorimetry showed, a delayed Time-to-peak metabolic activity of the aggregate-inoculum compared to the planktonic inoculum. S. aureus was isolated from subcutis, bone and implants from all animals in groups A and B. Both group A animals showed osteomyelitis at gross inspection with suppuration and sequestration, while groups B and C animals had no macroscopic lesions. From CT scans, both group A animals also showed positive signs of osteomyelitis, i.e., osteolysis, while only one animal in group B did, and none in group C. Histopathological examination of the bones showed more extensive inflammation in group A animals compared to those in group B, which showed more osteoid formation. Conclusions. Formation and separation of low metabolism bacterial aggregates into different size fractions was possible. The aggregates can be used as inoculum in the porcine IAO model, with microbiological re-isolation from both implants and tissue. Furthermore, the aggregates caused a less aggressive IAO, than the planktonic counterparts. Using aggregated bacteria as inoculum appears to be more relevant to the clinical situation of infecting bacteria

Introduction. Treatment of non-union in open tibial fractures Gustilo-Anderson(GA)-3A/3B fractures remains a challenging problem. Most of these can be dealt using treatment methods that requires excision of the non-union followed by bone grafting, masquelet technique, or acute shortening. Circular fixators with closed distraction or bone transport also remains a useful option. However, sometimes due to patient specific factors these cannot be used. Recently antibiotic loaded bone substitutes have been increasingly used for repairing infected non-unions. They provide local antibiotic delivery, fill dead space, and act as a bone conductive implant, which is resorted at the end of a few months. We aimed to assess the outcome of percutaneous injection of bone substitute while treating non-union of complex open tibial fractures. Materials & Methods. Three cases of clinical and radiological stiff tibial non-union requiring further intervention were identified from our major trauma open fracture database. Two GA-3B cases, treated with a circular frame developed fracture-related-infection(FRI) manifesting as local cellulitis, loosened infected wires/pins with raised blood-markers, and one case of GA-3A treated with an intramedullary nail. At the time of removal of metalwork/frame, informed consent was obtained and Cerament-G. TM. (bone-substitute with gentamicin) was percutaneously injected through a small cortical window using a bone biopsy(Jamshedi needle). All patients were allowed to weight bear as tolerated in a well-fitting air-cast boot and using crutches. They were followed up at 6 weekly intervals with clinical assessment of their symptoms and radiographs. Fracture union was assessed using serial radiographs with healing defined as filling of fracture gap, bridging callus and clinical assessment including return to full painless weight bearing. Results. Follow-up at 6 months showed all fractures had healed with no defect or gaps with evidence of new trabecular bone and significant resorption of Cerament-G. TM. at final follow-up. There was no evidence of residual infection with restoration of normal limb function. Fractures with no internal fixation showed a mild deformity that had developed during the course of the healing, presumed due to mild collapse in the absence of fixation. These were less than 10 degrees in sagittal and coronal planes and were clinically felt to be insignificant by the patients. Conclusions. Cerament-G's unique combination of high dose antibiotics and hydroxy apatite matrix provided by calcium sulphate might help provide an osteoconductive environment to allow these stiff non-unions to heal. The matrix appears to provide a scaffold-like structure that allows new bone in-growth with local release of antibiotics helping reduce deep-seated infections. The final deformation at fracture site underlines the need for fixation- and it is very unlikely that this technique will work in mobile nonunions. Whilst similar fractures may heal without the use of bone substitute injections, the speed of healing in presence of significant fracture gap suggests the use of these bone substitutes did help in our cases. Further studies with a larger cohort, including RCTs, to evaluate the effectiveness of this technique compared to other methods are needed

Aim. In the context of total knee arthroplasty (TKA), trauma with perigenicular fracture fixation or oncological surgical treatment, soft tissue defects can expose critical structures such as the extensor apparatus, the knee joint, bone or implants. This work compares soft tissue reconstruction (STR) between a classical pedicled gastrocnemius (GC) muscle flap and a pedicled chimeric sural artery perforator (SAP) musculocutaneous GC flap in complex orthoplastic scenarios. Method. A retrospective study was conducted on prospectively maintained databases in three University Hospitals from January 2016 to February 2021 after orthopaedic, traumatological or oncological treatment. All patients with a perigenicular soft tissue defect and implant-associated infection were included undergoing STR either with a pedicled GC flap or with a pedicled chimeric SAP-GC flap. The outcome analysis included successful STR and flap related complications. The surgical timing, preoperative planning and surgical technique are discussed together with the postoperative rehabilitation protocol. Results. 43 patients were included (22 GC muscle flaps, 21 SAP-GC musculocutaneous flaps). The GC and SAP-GC patient group were comparable in terms of age, comorbidities, defect size and follow-up. The incidence of flap related complications was comparable among the two groups. Specifically, in the SAP-GC group 1 wound dehiscence at the recipient site occurred as well as 1 distal muscle flap necrosis, 1 distal skin flap necrosis, 1 donor site infection and 1 donor site wound dehiscence. Furthermore, the donor site was closed in 9 patients while a skin graft was used in 12 patients. A significant difference was recorded with regard to re-raising the flap for further orthopaedic treatment: In the SAP-CG group (re-raise in 11 patients) no problems occurred while in the GC group (re-raise in 14 patients) in 6 patients the soft tissue did not heal completely. Conclusions. According to our clinical experience, the pedicled chimeric SAP-CG musculocutaneous flap is a relevant further development of the classical GC workhorse flap for perigenicular STR, in multiple staged procedures

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

Safety concerns surrounding osseointegration are a significant barrier to replacing socket prosthesis as the standard of care following limb amputation. While implanted osseointegrated prostheses traditionally occur in two stages, a one-stage approach has emerged. Currently, there is no existing comparison of the outcomes of these different approaches. To address safety concerns, this study sought to determine whether a one-stage osseointegration procedure is associated with fewer adverse events than the two-staged approach.

Introduction. Untreated hip osteoarthritis is a debilitating condition leading to pain, bone deformation, and limited range of motion. Unfortunately, studies have not been conducted under in vivo conditions to determine progressive kinematics variations to a hip joint from normal to pre-operative and post-operative THA conditions. Therefore, the objective was this study was to quantify normal and degenerative hip kinematics, compared to post-operative hip kinematics. Methods. Twenty unique subjects were analyzed; 10 healthy, normal subjects and 10 degenerative, subjects analyzed pre-operatively and then again post-operatively after receiving a THA. During each assessment, the subject performed a gait (stance and swing phase) activity under mobile, fluoroscopic surveillance. The normal and diseased subjects had CT scans in order to acquire bone geometry while implanted subjects had corresponding CAD models supplied. Femoral head and acetabular cup centers were approximated by spheres based on unique geometries while the component centers were pre-defined as the center of mass. These centers were used to compare femoral head sliding magnitudes on the acetabular cup during the activity for all subjects. Subjects were noted to have separation with changes in center magnitudes of more than 1 mm during gait. Utilizing 3D-to-2D registration techniques, the hip joint kinematics were derived and assessed. This allowed for visualization of normal subject positioning, pre-op bone deterioration, and implant placement within the bones. Results. None of the normal, experienced femoral head sliding (FHS) within the acetabulum. Two of the normal subjects revealed tendencies more similar to a degenerative hip. However, 4/10 of the degenerative subjects saw significant FHS with an average maximum of 1.344 0.522 mm. It was interesting to note that none of the implanted subjects experienced FHS, demonstrating improved kinematic trends more normal-like and revealing better kinematic patterns post-operative compared to their pre-operative conditions. Discussion. Overall, analysis has revealed trends of degenerative hips experiencing more abnormal hip kinematics due to lower surface area and greater magnitudes of femoral center head displacement. The implanted subjects saw decreased amounts of displacement which correlated to increases in contact area. These results more closely matched normal hip kinematics and showed an improvement over their diseased condition. It seems that the surgeon in this study better replicated the stem version angle to the pre-operative conditions, leaving less transverse stress of the femoral head on the acetabular cup, possibly leading to the femoral head remaining within the acetabular cup and the subjects not experiencing FHS. Significance. Pre-operative, degenerative hip subjects displayed abnormal femoral hip displacement at greater magnitudes to normal hip subjects. After THA, these subjects saw reduced magnitudes of displacement more in line with normal hip kinematics. For any figures or tables, please contact authors directly

The use of endoprosthesis implants is frequent for tumours involving the proximal third of the femur and not amenable to primary arthroplasty or internal fixation. In this population, these implants are preferentially cemented given poor bone quality associated with systemic diseases and treatments. Loosening is a common complication of these implants that have been linked to poor bone quality, type of implants and importantly cementing technique. Thus, these techniques vary between different surgeons and based mainly on previous experience. One of the most successful cementing techniques in the arthroplasty literature is the French paradox. This technique involves removing the cancellous bone of the proximal femoral metaphysis and selects the largest stem to tightly fit the created cavity delineated by cortical bone. Cementing the implant results in a very thin cement layer that fills the inconsistent gaps between the metal and the bone. To our knowledge, no previous report exists in the literature assessing loosening in proximal femur replacement using the French paradox cementing technique. In this study, we sought to examine (1) rates of loosening in proximal femur replacement, and (2) the oncological outcomes including tumour recurrence and implant related complications. A retrospective study of 42 patients underwent proximal femur replacement between 1990 and 2018 at our institution. Of these, 30 patients met our inclusion criteria. Two independent reviewers have evaluated the preoperative and the most recent postoperative radiographs using the International Society of Limb Salvage (ISOLS) radiographic scoring system and Gruen classification for femoral stem loosening. Additionally, the acetabulum was evaluated for erosion according to the criteria of Baker et al. The mean age of this cohort was 60.5 (19–80), with 60% being males. The primary origin was metastatic in 17 (56.7%) patients, bone sarcoma in 10 (33.3%) patients and soft tissue sarcoma in 3 (10%) patients. Pathological fractures were present in 11 (36.7%) patients. Seven (23.3%) patients had prior intramedullary nailing. Preoperative radiotherapy was used in 8 (26.7%) and postoperative radiotherapy in 17 (56.7%) patients. The mean clinical follow-up was 25.2±26.3 months and the mean radiographical follow-up was 24.8±26 months. The mean ISOLS score for both reviewers was found to be 89±6.5% and 86.5±6.1%, respectively. Additionally, the first reviewer found two patients to be possibly loos (6.7%) compared to one (3.3%) patient for the second reviewer. No components scored as probably or definitely loose and non-required revision for either loosening or metal failure. Furthermore, both reviewers showed no acetabular erosion in 25 (83.3%) and 24 (80%) patients, respectively. On the other hand, the overall rate of complications was 36.6% with 11 complications reported in 30 patients. Local recurrence occurred in five (16.6%) patients. Prosthetic Dislocation was the most frequent complications with eight dislocations in four patients. Despite complications, our results showed no radiographic evidence of stem loosening. Cementing proximal femur prosthesis with a tight canal fit and with a thin cement mantle appears to be a viable option at short and medium term

Aim. Chronic bone infections and infected fractures are often treated with excision of the dead bone and implantation of biomaterials which elute antibiotics. Gentamicin has been a preferred drug for local delivery, but this could induce renal dysfunction due to systemic toxicity. This is a particular concern in patients with pre-existing chronic renal disease treated with new antibiotic carriers which achieve very high peak levels of gentamicin in the first few days after surgery. Method. 163 patients (109 males; average age 51.6 years) with Cierny-Mader Type 3 or 4 chronic osteomyelitis had a single-stage operation with excision of the dead bone, filling of the osseous defect with a calcium sulphate-hydroxyapatite carrier, containing gentamicin and immediate soft tissue closure. 2. No patient was given systemic gentamicin or other renal toxic antibiotics. Mean carrier volume was 10.9mls (range 1–30mls) and mean gentamicin dosing was 190.75mg (maximum 525mg). Seven patients had pre-existing renal disease (4 diabetic nephropathy, 1 nephrotic syndrome, 1 renal transplant and 1 previous acute kidney injury). Serum creatinine levels were collected pre-operatively and during the first seven days post-operatively. Glomerular filtration rate (GFR) was calculated using the CKD-epi creatinine equation. Renal function was defined using the Chronic Kidney Disease (CKD) Staging system. Results. 155 cases had adequate data to allow calculation of pre- and post-operative GFR. Pre-operative CKD staging demonstrated 118 Class I (normal renal function), 30 Class II, 3 Class IIIa, 3 Class IIIb, and 1 Class V disease. Mean pre-operative GFR (99.7ml/min/1.73m. 2. , SD 21.0) was no different to post-operative GFR (103.2ml/min/1.73m. 2. , SD 21.3), p= 0.0861. Four cases had a >10% decline in GFR below normal, with only one case dropping a CKD stage, from I (normal) to II (mildly decreased). Only 1/7 cases with pre-existing renal disease had a GFR drop of >10% (from 11ml/min/1.73m. 2. to 8ml/min/1.73m. 2. ). 70/155 (45.2%) had a temporary GFR drop post-operatively, with the biggest drop occurring a mean 3.06 days following surgery (SD 2.1). No patient had clinical signs of new acute renal impairment post-operatively. Conclusions. Renal function is not significantly affected by local implantation of gentamicin up to 525mg. The presence of pre-existing renal disease is not a contraindication to local gentamicin therapy

The treatment of critical-sized bone defects still remains today a challenge, especially when the surrounding soft, vascularized and innervated tissues have been damaged - a lack of revascularization within the injured site leading to physiological disorders, from delayed healing to osteonecrosis. The axial insertion of a vascular bundle (e.g. arterio-venous loop, AVL) within a synthetic bone filler to initiate and promote its revascularization has been foreseen as a promising alternative to the current strategies (e.g., vascularized free flaps) for the regeneration of large bone defects. In a previous work, we showed that the insertion of a vein in a 3D-printed monetite scaffold induced its higher revascularization than AVL, thus a possible simplification of the surgical procedures (no microsurgery required). Going further, we investigate in this study whether or not the presence of a vein could stimulate the formation of mineralized tissue insides a synthetic scaffold filled with bone marrow and implanted in ectopic site. Monetite scaffolds were produced by additive manufacturing according to a reactive 3D-printing technique co-developed by the authors then thoroughly characterized. Animal study was performed on 14 male Wistar rats. After anesthesia and analgesia, a skin medial incision in rat thigh allowed the site on implantation to be exposed. Bone marrow was collected on the opposite femur through a minimally invasive procedure and the implant was soaked with it. For the control group (N=7), the implant was inserted in the incision and the wound was closed whereas the femoral bundle was dissected and the vein inserted in the implant for the experimental group (N=7). After 8 weeks animals were sacrificed, the implant collected and fixed in a 4% paraformaldehyde solution. Explants were characterized by µCT then embedded in poly-methyl methacrylate prior SEM, histology and immunohistochemistry. Images were analyzed with CT-Analyzer (Bruker) and ImageJ (NIH) and statistical analyses were carried out using SPSS (IBM). Implants were successfully 3D-printed with a +150 µm deviation from the initial CAD. As expected, implants were composed of 63%wt monetite and 37%wt unreacted TCP, with a total porosity of 44%. Data suggested that scaffold biodegradation was significantly higher when perfused by a vein. Moreover, the latter allowed for the development of a dense vascular network within the implant, which is far more advanced than for the control group. Finally, although mineralized tissues were observed both inside and outside the implant for both groups, bone formation appeared to be much more important in the experimental one. The ectopic formation of a new mineralized tissue within a monetite implant soaked with bone marrow seems to be highly stimulated by the simple presence of a vein alone. Although AVL have been studied extensively, little is known about the couple angiogenesis/osteogenesis which appears to be a key factor for the regeneration of critical-sized bone defects. Even less is known about the mechanisms that lead to the formation of a new bone tissue, induced by the presence of a vein only. With this in mind, this study could be considered as a proof of concept for further investigations

Introduction. The treatment of chronic bone infection often involves excision of dead bone and implantation of biomaterials which elute antibiotics. Gentamicin is a preferred drug for local delivery, but its systemic use carries a well-established risk of nephrotoxicity. We aim to establish the risk of renal injury with local delivery in a ceramic carrier. Materials and Methods. 163 consecutive patients with Cierny-Mader Type 3 or 4 chronic osteomyelitis were treated with a single-stage operation which included filling of the osseous defect with a calcium sulphate-hydroxyapatite carrier containing gentamicin. The mean carrier volume used was 10.9mls, leading to a mean implanted gentamicin dose of 191.3mg (maximum 525mg). Serum creatinine levels were collected pre-operatively and during the first seven days post-operatively. Renal impairment was graded using the Chronic Kidney Disease (CKD) Staging system, and AKI was assessed using the RIFLE criteria. Results. 155 cases had adequate data to allow calculation of pre- and post-operative GFR. 7 patients had pre-existing renal disease. 70 patients (45.2%) had a temporary eGFR drop post-operatively, with the greatest decrease occurring a mean 3.06 days following surgery. Twenty cases had a >10% decline in eGFR, but 12 resolved within 7 days. 7 patients transiently fell into the “Risk” category according to RIFLE criteria, but no patient had a change consistent with “Injury”, “Failure” or “Loss” of renal function and none had clinical signs of new acute renal impairment post-operatively. Conclusions. The implantation of up to 525mg of gentamicin contained within Cerament G, as part of the surgical treatment of osteomyelitis, is safe and carries minimal risk of significant acute kidney injury. A small, transient increase in serum creatinine may be observed in the early post-operative period, and attention should be paid to limit patients exposure to other nephrotoxic agents. The majority of patients will return to their baseline renal function within 7 days following the operation. The presence of pre-existing renal disease is not a contraindication to local gentamicin therapy

Biodegradable metals as orthopaedic implant materials receive substantial scientific and clinical interest. Marketed cardiovascular products confirm good biocompatibility of iron. Solid iron biodegrades slowly in vivo and has got supra-physiological mechanical properties as compared to bone and porous implants can be optimized for specific orthopaedic applications. We used Direct Metal Printing (DMP)3 to additively manufacture (AM) scaffolds of pure iron with fine-tuned bone-mimetic mechanical properties and improved degradation behavior to characterize their biocompatibility under static and dynamic 3D culture conditions using a spectrum of different cell types. Atomized iron powder was used to manufacture scaffolds with a repetitive diamond unit cell design on a ProX DMP 320 (Layerwise/3D Systems, Belgium). Mechanical characterization (Instron machine with a 10kN load cell, ISO 13314: 2011), degradation behavior under static and dynamic conditions (37ºC, 5% CO2 and 20% O2) for up of 28 days, with μCT as well as SEM/energy-dispersive X-ray spectroscopy (EDS) (SEM, JSM-IT100, JEOL) monitoring under in vivo-like conditions. Biocompatibility was comprehensively evaluated using a broader spectrum of human cells according to ISO 10993 guidelines, with topographically identical titanium (Ti-6Al-4V, Ti64) specimen as reference. Cytotoxicity was analyzed by two-way ANOVA and post-hoc Tukey's multiple comparisons test (α = 0.05). By μCT, as-built strut size (420 ± 4 μm) and porosity of 64% ± 0.2% were compared to design values (400 μm and 67%, respectively). After 28 days of biodegradation scaffolds showed a 3.1% weight reduction after cleaning, while pH-values of simulated body fluids (r-SBF) increased from 7.4 to 7.8. Mechanical properties of scaffolds (E = 1600–1800 MPa) were still within the range for trabecular bone, then. At all tested time points, close to 100% biocompatibility was shown with identically designed titanium (Ti64) controls (level 0 cytotoxicity). Iron scaffolds revealed a similar cytotoxicity with L929 cells throughout the study, but MG-63 or HUVEC cells revealed a reduced viability of 75% and 60%, respectively, already after 24h and a further decreased survival rate of 50% and 35% after 72h. Static and dynamic cultures revealed different and cell type-specific cytotoxicity profiles. Quantitative assays were confirmed by semi-quantitative cell staining in direct contact to iron and morphological differences were evident in comparison to Ti64 controls. This first report confirms that DMP allows accurate control of interconnectivity and topology of iron scaffold structures. While microstructure and chemical composition influence degradation behavior - so does topology and environmental in vitro conditions during degradation. While porous magnesium corrodes too fast to keep pace with bone remodeling rates, our porous and micro-structured design just holds tremendous potential to optimize the degradation speed of iron for application-specific orthopaedic implants. Surprisingly, the biological evaluation of pure iron scaffolds appears to largely depend on the culture model and cell type. Pure iron may not yet be an ideal surface for osteoblast- or endothelial-like cells in static cultures. We are currently studying appropriate coatings and in vivo-like dynamic culture systems to better predict in vivo biocompatibility