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

Objectives. We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells. Materials and Methods. We seeded mouse skeletal muscle cells C2C12 on the hydroxyapatite/calcium sulphate biomaterial and the phenotype of the cells was analysed. To mimic surgical conditions with leakage of extra cellular matrix (ECM) proteins and growth factors, we cultured rat bone cells ROS 17/2.8 in a bioreactor and harvested the secreted proteins. The secretome was added to rat muscle cells L6. The phenotype of the muscle cells after treatment with the media was assessed using immunostaining and light microscopy. Results. C2C12 cells differentiated into osteoblast-like cells expressing prominent bone markers after seeding on the biomaterial. The conditioned media of the ROS 17/2.8 contained bone morphogenetic protein-2 (BMP-2 8.4 ng/mg, standard deviation (. sd. ) 0.8) and BMP-7 (50.6 ng/mg, . sd. 2.2). In vitro, this secretome induced differentiation of skeletal muscle cells L6 towards an osteogenic lineage. Conclusion. Extra cellular matrix proteins and growth factors leaking from a bone cavity, along with a ceramic biomaterial, can synergistically enhance the process of ectopic ossification. The overlaying muscle acts as an osteoinductive niche, and provides the required cells for bone formation. Cite this article: D. B. Raina, A. Gupta, M. M. Petersen, W. Hettwer, M. McNally, M. Tägil, M-H. Zheng, A. Kumar, L. Lidgren. Muscle as an osteoinductive niche for local bone formation with the use of a biphasic calcium sulphate/hydroxyapatite biomaterial. Bone Joint Res 2016;5:500–511. DOI: 10.1302/2046-3758.510.BJR-2016-0133.R1

Aims. Biofilm formation is intrinsic to prosthetic joint infection (PJI). In the current study, we evaluated the effects of silver-containing hydroxyapatite (Ag-HA) coating and vancomycin (VCM) on methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation. Methods. Pure titanium discs (Ti discs), Ti discs coated with HA (HA discs), and 3% Ag-HA discs developed using a thermal spraying were inoculated with MRSA suspensions containing a mean in vitro 4.3 (SD 0.8) x 10. 6. or 43.0 (SD 8.4) x 10. 5. colony-forming units (CFUs). Immediately after MRSA inoculation, sterile phosphate-buffered saline or VCM (20 µg/ml) was added, and the discs were incubated for 24 hours at 37°C. Viable cell counting, 3D confocal laser scanning microscopy with Airyscan, and scanning electron microscopy were then performed. HA discs and Ag HA discs were implanted subcutaneously in vivo in the dorsum of rats, and MRSA suspensions containing a mean in vivo 7.2 (SD 0.4) x 10. 6.   or 72.0 (SD 4.2) x 10. 5.   CFUs were inoculated on the discs. VCM was injected subcutaneously daily every 12 hours followed by viable cell counting. Results. Biofilms that formed on HA discs were thicker and larger than those on Ti discs, whereas those on Ag-HA discs were thinner and smaller than those on Ti discs. Viable bacterial counts in vivo revealed that Ag-HA combined with VCM was the most effective treatment. Conclusion. Ag-HA with VCM has a potential synergistic effect in reducing MRSA biofilm formation and can thus be useful for preventing and treating PJI. Cite this article:Bone Joint Res. 2020;9(5):211–218

The success of long-term transcutaneous implants depends on dermal attachment to prevent downgrowth of the epithelium and infection. Hydroxyapatite (HA) coatings and fibronectin (Fn) have independently been shown to regulate fibroblast activity and improve attachment. In an attempt to enhance this phenomenon we adsorbed Fn onto HA-coated substrates. Our study was designed to test the hypothesis that adsorption of Fn onto HA produces a surface that will increase the attachment of dermal fibroblasts better than HA alone or titanium alloy controls. . Iodinated Fn was used to investigate the durability of the protein coating and a bioassay using human dermal fibroblasts was performed to assess the effects of the coating on cell attachment. Cell attachment data were compared with those for HA alone and titanium alloy controls at one, four and 24 hours. Protein attachment peaked within one hour of incubation and the maximum binding efficiency was achieved with an initial droplet of 1000 ng. We showed that after 24 hours one-fifth of the initial Fn coating remained on the substrates, and this resulted in a significant, three-, four-, and sevenfold increase in dermal fibroblast attachment strength compared to uncoated controls at one, four and 24 hours, respectively

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.

Bone defects require implantable graft substitutes, especially porous and biodegradable biomaterial for tissue regeneration. The aim of this study was to fabricate and assess a 3D-printed biodegradable hydroxyapatite/calcium carbonate scaffold for bone regeneration. Materials and methods:. A 3D-printed biodegradable biomaterial containing calcium phosphate and aragonite (calcium carbonate) was fabricated using a Bioplotter. The physicochemical properties of the material were characterised. The materials were assessed in vitro for cytotoxicity and ostegenic potential and in vivo in rat intercondylar Φ3mm bone defect model for 3 months and Φ5mm of mini pig femoral bone defects for 6 months. The results showed that the materials contained hydroxyapatite and calcium carbonate, with the compression strength of 2.49± 0.2 MPa, pore size of 300.00 ± 41mm, and porosity of 40.±3%. The hydroxyapatite/aragonite was not cytotoxic and it promoted osteogenic differentiation of human umbilical cord matrix mesenchymal stem cells in vitro. After implantation, the bone defects were healed in the treatment group whereas the defect of controlled group with gelatin sponge implantation remained non-union. hydroxyapatite/aragonite fully integrated with host bone tissue and bridged the defects in 2 months, and significant biodegradation was followed by host new bone formation. After implantation into Φ5mm femoral defects in mini pigs hydroxyapatite/aragonite were completed degraded in 6 months and fully replaced by host bone formation, which matched the healing and degradation of porcine allogenic bone graft. In conclusion, hydroxyapatite/aragonite is a suitable new scaffold for bone regeneration. The calcium carbonate in the materials may have played an important role in osteogenesis and material biodegradation

Introduction. To evaluate the effect of hydroxyapatite coating, two same shape cementless stems were compared in this randomized control trial study. Methods. Between May 2003 and February 2010, 88 patients had a primary cementless total hip arthroplasty with two different types of cementless stems. Forty-three patients had Proarc stems (P group) (Kyocera Medical, Osaka, Japan), and Forty-five patients had Proarc HA stems (HA group) (Kyocera Medical, Osaka, Japan) which was coated with thin (20 micrometer) hydroxyapatite on Proarc rough porous coating. Gender distribution, average age at surgery, average weight and average follow-up period were same in the two groups. The average follow-up period was 8.5 years (range, 5 to 13 years). The average age at the time of surgery was 63 years. Porous acetabular shells and highly crosslinked polyethylene liners made by Kyocera Medical corporation were implanted into all hips. Stems were implanted with a modified Hardinge surgical approach without trochanteric osteotomy. Harris Hip Score was used for clinical evaluation. Post-op radiographs of these patients were evaluated. Fisher's exact probability test was used for statistical analysis. P values of less than 0.05 were considered to be significant. Results. The mean preoperative score and postoperative score of P group were 39 points and 86 points, respectively. The mean preoperative score and postoperative score of HA group were 46 points and 87 points, respectively. All stems were evaluated as bone-ingrown fixation in both groups. The rate of varus inclination was not different between two groups. The rate of severe stress shielding was not different. Discussion. However hydroxyapatite coating is useful for early fixation, the adverse effect, such as delamination for long-term in vivo situation is questionable. There was no significant difference between P-group and HA group in the present study. Longer follow-up is required to evaluate hydroxyapatite coating

Targeted delivery of drugs is a major challenge in diseases such as infections and tumors. The aim of this study was to demonstrate that hydroxyapatite (HA) particles can act as a recruiting moiety for various bioactive molecules and as a proof-of-concept demonstrate that the affinity of drugs to hydroxyapatite can exert a biological effect. A bisphosphonate, zoledronic acid (ZA), was used as a model drug. Experiment 1 (ZA seeks HA): Calcium sulphate (CaS)/hydroxyapatite (HA) biomaterial pellets (diameter¸=5 mm, height=2 mm) were implanted in the abdominal muscle pouch of rats. After 2-weeks of implantation, a sub-cutaneous injection of 14C-ZA (0.1 mg/kg) was given. 24 h later, the animals were sacrificed and the uptake of ZA determined in the pellets using scintillation counting. Experiment 2 (Systemically administered ZA seeks HA and exerts a biological effect): A fenestrated implant was filled with the CaS/HA biomaterial and inserted in the proximal tibia of rats. 2-weeks post-op, a subcutaneous injection of ZA (0.1 mg/kg) was given. Animals were sacrificed at 6-weeks post-op. Empty implant was used as a control. Peri-implant bone formation was evaluated using different techniques such as micro-CT, mechanical testing and histology. Welch's t-test was used for mechanical testing and Mann-Whitney U test for micro-CT data analysis. Experiment 1: Uptake of radioactive ZA in the CaS/HA biomaterial was confirmed. Almost no ZA was present in the surrounding muscle. These results show high specific binding between systemically administered ZA and synthetic particulate HA. Experiment 2: Significantly higher peri-implant bone was measured using micro-CT in the group wherein the implant contained the CaS/HA biomaterial and ZA was administered systemically (This study presents a method for biomodulating HA in situ by different bioactive molecules. The approach of implanting a biomaterial capable of recruiting systemically given drugs and thereby activate the material is novel and may present a possibility to treat bone infections or tumors

Aims. This study reports the results of 38 total hip arthroplasties (THAs) in 33 patients aged less than 50 years, using the JRI Furlong hydroxyapatite ceramic (HAC)-coated femoral component. Methods. We describe the survival, radiological, and functional outcomes of 33 patients (38 THAs) at a mean follow-up of 27 years (25 to 32) between 1988 and 2018. Results. Of the surviving 30 patients (34 THAs), there were four periprosthetic fractures: one underwent femoral revision after 21 years, two had surgical fixation as the stem was deemed stable, and one was treated nonoperatively due to the patient’s comorbidities. The periprosthetic fracture patients showed radiological evidence of change in bone stock around the femoral stem, which may have contributed to the fractures; this was reflected in change of the canal flare index at the proximal femur. Two patients (two hips) were lost to follow-up. Using aseptic loosening as the endpoint, 16 patients (18 hips; 48%) needed acetabular revision. None of the femoral components were revised for aseptic loosening, demonstrating 100% survival. The estimate of the cumulative proportion surviving for revisions due to any cause was 0.97 (standard error 0.03). Conclusion. In young patients with high demands, the Furlong HAC-coated femoral component gives excellent long-term results. Cite this article: Bone Jt Open 2024;5(4):286–293

Hydroxyapatite (HAp) is a well-known synthetic biomaterial that has been extensively employed in orthopedic fields as bone grafts or coating of metallic implants. During recent years, ion doping or ionic substitution has been used to improve the performance of bioceramics. Owing to the benefits of a bioactive element such as boron (B) in bone health, and reported impaired bone growth or abnormal development of bone in case of boron deficiency, it was expected that doping of boron could make a positive effect on physicochemical and biological properties of HAp. In this study, boron-doped hydroxyapatite (BHAp) was synthesized successfully through utilizing microwaved assisted wet precipitation route. X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry were used to characterize the phase purity, lattice parameters, degree of crystallinity, particle size and elemental composition of synthesized BHAp powders. Substitution of borate (BO. 3. 3-. ) ion with the phosphate (PO. 4. 3-. ) in HAp crystal caused lattice distortion due to radius difference between the dopant and the replaced element, which also led to smaller crystalline size and lower crystallinity degree in doped samples (∼ 91 % in 0.5 mol doped BHAp compared to 95 % of pure HAp). In vitro results revealed that although there was no significant difference in biodegradability of doped BHAp, after submerging samples in simulated body fluid for 14 days, intense growth of apatite particles (Ca/P ratio of 1.74) was observed on the surface of BHAp pellets, especially in samples with 0.25 and 0.5 mole B. Observed higher bioactivity was expected due to lower crystallinity degree of BHAp samples. Due to the results of this study, incorporation of B into the structure of HAp could be considered as a positive step to improve the bioactivity and biological performance of these biomaterials in orthopedic applications

The long-term results of grafting with hydroxyapatite granules for acetabular deficiency in revision total hip replacement are not well known. We have evaluated the results of revision using a modular cup with hydroxyapatite grafting for Paprosky type 2 and 3 acetabular defects at a minimum of ten years’ follow-up. We retrospectively reviewed 49 acetabular revisions at a mean of 135 months (120 to 178). There was one type 2B, ten 2C, 28 3A and ten 3B hips. With loosening as the endpoint, the survival rate was 74.2% (95% confidence interval 58.3 to 90.1). Radiologically, four of the type 3A hips (14%) and six of the type 3B hips (60%) showed aseptic loosening with collapse of the hydroxyapatite layer, whereas no loosening occurred in type 2 hips. There was consolidation of the hydroxyapatite layer in 33 hips (66%). Loosening was detected in nine of 29 hips (31%) without cement and in one of 20 hips (5%) with cement (p = 0.03, Fisher’s exact probability test). The linear wear and annual wear rate did not correlate with loosening. These results suggest that the long-term results of hydroxyapatite grafting with cement for type 2 and 3A hips are encouraging

Aims. There is a lack of biomaterial-based carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotics for bone infections. RIF is also known for causing rapid development of antibiotic resistance when given as monotherapy. This in vitro study evaluated a clinically used biphasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN). Methods. The CaS/HA composites containing RIF/GEN/VAN, either alone or in combination, were first prepared and their injectability, setting time, and antibiotic elution profiles were assessed. Using a continuous disk diffusion assay, the antibacterial behaviour of the material was tested on both planktonic and biofilm-embedded forms of standard and clinical strains of Staphylococcus aureus for 28 days. Development of bacterial resistance to RIF was determined by exposing the biofilm-embedded bacteria continuously to released fractions of antibiotics from CaS/HA-antibiotic composites. Results. Following the addition of RIF to CaS/HA-VAN/GEN, adequate injectability and setting of the CaS/HA composites were noted. Sustained release of RIF above the minimum inhibitory concentrations of S. aureus was observed until study endpoint (day 35). Only combinations of CaS/HA-VAN/GEN + RIF exhibited antibacterial and antibiofilm effects yielding no viable bacteria at study endpoint. The S. aureus strains developed resistance to RIF when biofilms were subjected to CaS/HA-RIF alone but not with CaS/HA-VAN/GEN + RIF. Conclusion. Our in vitro results indicate that biphasic CaS/HA loaded with VAN or GEN could be used as a carrier for RIF for local delivery in clinically demanding bone infections. Cite this article: Bone Joint Res 2022;11(11):787–802

Aims. The primary aim of this study is to assess the survival of the uncemented hydroxyapatite (HA) coated Trident II acetabular component as part of a hybrid total hip arthroplasty (THA) using a cemented Exeter stem. The secondary aims are to assess the complications, joint-specific function, health-related quality of life, and radiological signs of loosening of the acetabular component. Methods. A single-centre, prospective cohort study of 125 implants will be undertaken. Patients undergoing hybrid THA at the study centre will be recruited. Inclusion criteria are patients suitable for the use of the uncemented acetabular component, aged 18 to 75 years, willing and able to comply with the study protocol, and provide informed consent. Exclusion criteria includes patients not meeting study inclusion criteria, inadequate bone stock to support fixation of the prosthesis, a BMI > 40 kg/m. 2. , or THA performed for pain relief in those with severely restricted mobility. Results. Implant survival, complications, functional outcomes and radiological assessment up to ten years following index THA (one, two, five, seven, and ten years) will be performed. Functional assessment will include the Oxford Hip Score, Forgotten Joint Score, 12-Item Short Form Health Survey, EuroQol five-dimension health questionnaire, and pain and patient satisfaction. Radiological assessment with assess for acetabula lucent lines, lysis, and loosening according to DeLee and Charnley zones. Conclusion. This study is part of a stepwise introduction of a new device to orthopaedic practice, and careful monitoring of implants should be carried out as part of the Beyond Compliance principles. The results of this study will provide functional, radiological, and survival data to either support the ongoing use of the HA acetabulum or highlight potential limitations of this new implant before wide adoption. Cite this article: Bone Jt Open 2023;4(10):782–790

Bone is a dynamic tissue with a quarter of the trabecular and a fifth of the cortical bone being replaced continuously each year in a complex process that continues throughout an individual’s lifetime. Bone has an important role in homeostasis of minerals with non-stoichiometric hydroxyapatite bone mineral forming the inorganic phase of bone. Due to its crystal structure and chemistry, hydroxyapatite (HA) and related apatites have a remarkable ability to bind molecules. This review article describes the accretion of trace elements in bone mineral giving a historical perspective. Implanted HA particles of synthetic origin have proved to be an efficient recruiting moiety for systemically circulating drugs which can locally biomodulate the material and lead to a therapeutic effect. Bone mineral and apatite however also act as a waste dump for trace elements and drugs, which significantly affects the environment and human health. Cite this article: Bone Joint Res 2020;9(10):709–718

Abstract. INTRODUCTION. Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer which has found increasing application in orthopaedic implant devices and has a lot of promise for ‘made-to-measure’ implants produced through additive manufacturing [1]. However, a key limitation of PEEK is that it is bioinert and there is a requirement to functionalise its surface to make the material osteoconductive to ensure a more rapid, improved and stable fixation, in vivo. One approach to solving this issue is to modify PEEK with bioactive materials, such as hydroxyapatite (HA). OBJECTIVE. To 3D PEEK/HA composite materials using a Fused Filament Fabrication (FFF) approach to enhance the properties of the PEEK matrix. METHODS. PEEK/HA composites (0–30% w/w HA/PEEK) were 3D printed using a modified Ultimaker 2+ 3D printer. The mechanical, thermal, physical, chemical and in vitro properties of the 3D printed samples were all studied as part of this work. RESULTS. The CT images of both the filament and the 3D printed samples showed that the HA material was evenly dispersed throughout the bulk all the samples. SEM/EDX measurements highlighted that HA was homogenously distributed across the surface. As the HA content of the samples increases, so does the tensile modulus, ranging from 4.2 GPa (PEEK) to 6.1 GPa (30% HA/PEEK) and are significantly higher than datasheet information of injected molded PEEK samples. All materials supported the growth of osteoblast cells on their surface. CONCLUSIONS. The results clearly show that we can successfully and easily 3D print HA/PEEK composite materials up to 30% w/w HA/PEEK. The samples produced have a homogeneous distribution of HA in both the bulk and surface of all the samples, and their mechanical performance of the PEEK is enhanced by the addition of HA

Abstract. Objectives. The objective of this study is to investigate the effect of solvents and rheological properties of PCL/Hydroxyapatite ink on the shape fidelity of the 3D printed scaffolds for bone tissue engineering. Methods. A series of inks were made consisting of 50% (w/v) of polycaprolactone (PCL) filled with 0%, 3.5% and 12.5% (w/V) of hydroxyapatite (HA) in dichloromethane (DCM) and chloroform (CHF). Steady and oscillatory shear rheological tests were performed on a rheometer (Discovery HR-3). Solvent-cast direct ink writing was performed with a custom-made 3D printer for the fabrication of PCL/HA scaffold structures with 2–8 layers. Optical microscope and scanning electron microscopy (SEM) were used to assess the shape fidelity. Results. Shape fidelity of the inks was quantitively assessed on the 3D printed scaffold structures allowing subjective comparisons. The addition of HA particles increased zero-shear viscosity by up to 900%. For oscillatory tests, plateau of storage modulus was observed in the low-frequency region which is attributed to good dispersion of the HA particles inside the matrix that leads to the formation of filler networks, resulting in pseudo-solid behavior and shape fidelity improvement. As the HA concentration increases, the plateau becomes more pronounced and the shape fidelity increases. With the same concentration, all DCM inks also show higher viscosity (from 10% to 200%) and better shape fidelity than CHF inks. As DCM has a lower boiling point (39.6 °C) than CHF (61.2°C), DCM evaporates quicker reducing the fusion and diffusion of deposited ink filaments before solidification which is observed in SEM images. Conclusions. This study reveals insights into using rheological characterizations as a tool for evaluation of shape fidelity of solvent-based DIW inks and also provides fundamental information on the influence of different solvents on the fidelity of 3D printed scaffolds. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Carbonate-substituted hydroxyapatite (CHA) is more osteoconductive and more resorbable than hydroxyapatite (HA), but the underlying mode of its action is unclear. We hypothesised that increased resorption of the ceramic by osteoclasts might subsequently upregulate osteoblasts by a coupling mechanism, and sought to test this in a large animal model. Defects were created in both the lateral femoral condyles of 12 adult sheep. Six were implanted with CHA granules bilaterally, and six with HA. Six of the animals in each group received the bisphosphonate zoledronate (0.05 mg/kg), which inhibits the function of osteoclasts, intra-operatively. After six weeks bony ingrowth was greater in the CHA implants than in HA, but not in the animals given zoledronate. Functional osteoclasts are necessary for the enhanced osteoconduction seen in CHA compared with HA

Osseointegration has been shown to be directly affected by surface roughness and bioactive coatings. This report compares bone response to hydroxyapatite coatings on differing substrate treatments. Titanium cylinders was implanted bilaterally in the distal femora of 30 rabbits. One of three surface treatments was applied to each implant: plasma sprayed titanium surface without hydroxyapatite coating (P), plasma sprayed titanium surface with hydroxyapatite coating (PHA), and acid-etched surface with hydroxyapatite coating (CHA). Osseointegration was measured at 6 and 12 weeks, by histomorphometry of scanning electron microscopy images of histologic sections taken through the implant at three levels: diaphysis, metaphysis, and intermediate. Bone growth was measured up to 3 mm from the edge of the implant to determine changes in patterns of bone growth. Overall, bone response was greatest in the diaphyseal sections. Mean osseointegration was significantly different between hydroxyapatite coated and non-hydroxyapatite coated implants (CHA: 74+10%, PHA: 65+12%, and P: 39+10%, p< 0.01). Both hydroxyapatite coated implants demonstrated increased bone growth closer to the implant which dropped off with increasing distance from the implant. Lower and relatively unchanging levels of bone growth were seen in non-hydroxyapatite coated implants. Osseointegration and bone growth was higher in both hydroxyapatite coated surfaces confirming previous reports. The differences in substrates (acid etched vs. plasma sprayed titanium) did not yield a significant difference in bone growth, suggesting that the hydroxyapatite coating provided a much larger benefit. This study supports the hypothesis that enhanced osseointegration is primarily due to the bioactive coating

The aseptic loss of bone after hip replacement is a serious problem leading to implant instability. Hydroxyapatite coating of joint replacement components produces a bond with bone and helps to reduce loosening. However, over time bone remodeling at the implant interface leads to loss of hydroxyapatite. One possible solution would be to develop a coating that reduces hydroxyapatite and bone loss. Hydroxyapatite can be chemically modified through the substitution of ions to alter the biological response. Zinc is an essential trace element that has been found to inhibit osteoclast-like cell formation and decrease bone resorption. It was hoped that by substituting zinc into the hydroxyapatite lattice, the resultant zinc-substituted hydroxyapatite (ZnHA) would inhibit ceramic resorption and the resorption of bone. The aim of this work was to investigate the effect of ZnHA on the number and activity of osteoclasts. Discs of phase pure hydroxyapatite (PPHA), 0.37wt% ZnHA and 0.58wt% ZnHA were produced, sintered at 1100 degrees Celsius and ground with 1200 grit silicon carbide paper. They were cultured in medium containing macrophage colony stimulating factor and receptor activator of nuclear factor kappa B ligand (RANKL) for 11 and 21 days. A control disc of PPHA cultured in medium containing no RANKL was also used. On the required dates the discs were removed and the cells stained for actin with phalloidin-TRITC and the cell nuclei with 4',6-Diamidino-2-phenylindole dihydrochloride. Cells with 3 or more nuclei were classed as osteoclasts and counted using ImageJ. On day 21 after the cells had been counted, the cells were removed and the discs coated in platinum before viewing with a scanning electron microscope. Resorption areas were then measured using ImageJ. The addition of zinc was observed to significantly decrease the number of differentiated osteoclasts after 21 days (p<0.005 for 0.58wt% ZnHA compared to PPHA and p<0.01 for 0.37wt% ZnHA compared to PPHA). The area of resorption was also significantly decreased with the addition of zinc (p<0.005 for the comparison of 0.58wt% ZnHA with PPHA). The work found that zinc substituted hydroxyapatite reduced the number and subsequent activity of osteoclasts

Two calcium phosphate cements, brushite and hydroxyapatite, have been recently developed as bone substitution materials. The brushite cement is biocompatible, resorbable, osteoconductive and injectable since it hardens in physiological conditions. In contrast, hydroxyapatite is less resorbable and is not injectable. However, hydroxyapatite presents a higher strength, which may open the perspective of use in weight-bearing regions of the skeleton subjected to multi-axial stresses. The purpose of this work is a full characterization of the multiaxial elastic and failure behaviour of these two cements in a moist environment. The brushite cement was prepared by mixing three phosphate powders in presence of water. A mixture of monetite and calcite powders in presence of water was used to obtain hydroxyapatite self-setting cement. Cylindrical, hollow specimens (Øext=18mm, Øint=14mm, L=40mm) were manufactured to apply uniaxial and torsional deformations. The specimens were cast with a custom mould, avoiding any machining, and thus, residual stresses. Scanning electron microscopy and x-ray diffraction were used to examine the cement microstructures and to determine their final material phases. An MTS axial-torsional machine was used for all mechanical tests. Compression, tension and torsion tests were performed each on five brushite and five hydroxyapatite specimens under moist conditions. Uniaxial and biaxial extensometers were used to measure the elastic moduli and the Poisson ratio. The brushite cement exhibited failure properties comparable or below those of average human cancellous bone and confirmed its indication as a bone filling material (Brushite failure strength : 1.3±0.3 MPa in tension, 2.9±0.4 MPa in shear and 10.7±2.0 MPa in compression). The hydroxyapatite cement had an order of magnitude larger compressive strength (75±4.2 MPa), comparable tensile (3.5±0.9 MPa) and shear (4.8±0.3 MPa) strengths as average human cancellous bone. As expected, the latter cement seems to be more compatible with a multiaxial weight-bearing function in bone substitution

The feasibility of bone transport with bone substitute and the factors which are essential for a successful bone transport are unknown. We studied six groups of 12 Japanese white rabbits. Groups A to D received cylindrical autologous bone segments and groups E and F hydroxyapatite prostheses. The periosteum was preserved in group A so that its segments had a blood supply, cells, proteins and scaffold. Group B had no blood supply. Group C had proteins and scaffold and group D had only scaffold. Group E received hydroxyapatite loaded with recombinant human bone morphogenetic protein-2 and group F had hydroxyapatite alone. Distraction osteogenesis occurred in groups A to C and E which had osteo-conductive transport segments loaded with osteo-inductive proteins. We conclude that scaffold and proteins are essential for successful bone transport, and that bone substitute can be used to regenerate bone

Introduction: Polyethylene wear debris is the main contributing factor that leads to aseptic loosening and osteolysis. The main objective of this study was to evaluate the role of hydroxyapatite (HA) in third-body polyethylene wear in total hip arthroplasty. Materials: 199 primary cementless THA’s (174 patients) performed by a single surgeon were enrolled in a prospective randomized study comprising hydroxyapatite and non-hydroxyapatite coated femoral implants. The femoral component had metaphyseal-diaphyseal fit design with proximal plasma sprayed titanium circumferential porous coating. The hydroxyapatite coating was 50 – 75 micrometers over the porous surface with the components of identical design. The acetabular component was plasma sprayed titanium porous coated shell without hydroxyapatite. T he polyethylene liners were machined molded from ram extruded Hi-fax 1900H polyethylene resin gamma-sterilized in argon (inert) gas. Clinical and Radiographic evaluation was performed employing HSS scores and Engh criteria. Results: At a mean follow-up of 5 years, the radiographs of 83 HA and 73 Non-HA hips were evaluated by two independent observers utilizing computer-assisted wear analysis on digitized standardized radiographs described by Martell et al (1997). The radiographs were also evaluated for osteolysis or aseptic loosening. The mean linear wear rate in HA group was 0.19mm/yr and in the non-HA group was 0.21mm/yr, which was not significant (p> 0.05). There was no case of osteolysis or aseptic loosening of any component. Both groups had comparable outcomes in terms of HSS scores, walking ability and sports participation. Discussion: This study has attempted to demonstrate through an appropriately controlled in vivo study that hydroxyapatite does not play a significant role in third-body polyethylene wear in THA at a mean follow-up of five years. The concern of three-body wear with hydroxyapatite coating is no greater than porous coated cementless implants

Aim. Treatment principles of chronic osteomyelitis include debridement, clean sampling, excision of dead bone, stabilization, dead space management, soft tissue closure and systemic antibiotic therapy. Dead space management becomes very complicated, if the bone infection is caused by multi-resistant bacteria. The aim of this investigation was to evaluate the effect of a new vancomycin-loaded hydroxyapatite / calcium sulfate composite. *. in the treatment of chronic osteomyelitis (OM) caused by multi-resistant bacteria. Method. From June 2015 to November 2015, 7 patients (4 males, 3 females, average age 52.6y) were treated according to the above mentioned principles using the new vancomycin-loaded hydroxyapatite / calcium sulfate composite. *. Infections were caused by methicillin-resistant Staphylococcus aureus (MRSA), multi-resistant Staphylococcus epidermidis (MRSE) and polymicrobial, vancomycin-sensitive bacteria. We used a two-stage protocol with debridement, excision of bone and external stabilization in the first stage, followed by bone defect reconstruction. To fill the residual bone defects, in 3 patients the new vancomycin-loaded hydroxyapatite / calcium sulfate composite. *. (10mL) was used on its own and in 4 patients combined with 18mL of an unloaded calcium sulfate / hydroxyapatite composite. **. Post-operative follow-up was evaluated clinically and by radiographs and CT scans at 6, 14 and 24 weeks. Results. In 6 of 7 patients rapid control of infection was achieved. Soft tissue reactions and prolonged white wound drainage (caused by calcium sulfate dissolution) was seen in 3 of 7 patients. In 6 of 7 patients recurrence of infection has not been observed so far. Radiographs showed different elution intervals of the radiocontrast agent (Iohexol), depending on anatomical location. Bone remodelling or replacement of the composite by new bone was not uniform in the patients and showed specific radiographic signs. In addition to the so-called „puddle sign“, we found septae, membranes, vacuoles and sometimes arc-like structures. Therefore, we suggest the name “arc-sign” for these formations. Conclusions. During the follow-up of the first 7 patients treated with the unloaded calcium sulfate / hydroxyapatite composite. **. in 6 of 7 cases no recurrence of infection was observed. This is very promising in the difficult situation of bone infections caused by multi-resistant bacteria. Follow-up radiographs and CT-scans showed specific patterns during the resorption of the composite and the formation of new bone, which have not been described in other bone graft substitutes so far. The bone defects are not completely filled yet, but the affected bones are clinically stable and patients can ambulate with full weight bearing

A longitudinal study was done assessing the latest radiographs available in a series of collarless Corail uncemented stems which have reported survival rates of 95% at 20 years. Parameters scored included the degree of “Ghosting” or delamination, the Gruen, the stem fit in the femoral canal and the degree of calcar resorption. Patient and implant demographics were noted. At 3 years the loosening rate was 23% reaching 64% at 6 years after the index procedure. It was present in all age groups, with a peak in the 24 to 49 year age group. Males and females had the same occurrence. When it was present this was always in zone 1. It was present in 6% of patients in zone 7, but then always associated with zone 1 changes. High and standard off-set stems had the same loosening rates. The looser fit of the stem the higher the incidence of loosening. There was no correlation to the type of bearing surface or the degree of calcar resorption. Those patients with a BMI of 25 – 35 had lower loosening rates compared to those with higher or lower BMI's. We postulate that cancellous bone on-growth onto the hydroxyapatite coating associated with loading flexural micro-motion leads to hydroxyapatite being pulled off the smooth stem substrate in zone 1. Progressive delamination of the hydroxyapatite then occurs. The triple-tapered design though imparts continued stability. We report high loosening rates in the Corail stem and suggest a mechanism for its development

Introduction: The aetiology of dystrophic disc calcification in adult humans is unknown but a well-described clinical disorder with hydroxyapatite as the single mineral phase. Comparable but age-related pathology in the sheep could serve as a model for the human disorder. The objective of this study was to investigate the mineral phase, its mechanisms of formation/association with degeneration in a naturally-occurring animal model of disc calcification. Methods: Adult sheep lumbar intervertebral discs (n=134) from animals aged 6 (n=4), 8 (n=12) and 11 years (n=2) were evaluated using radiography, morphology, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, histology, immunohistology and proteoglycan analysis. Results: Half of the 6 yr, 84% of the 8 yr and 86% of the 11 yr old discs had calcific deposits. These were not well delineated by plain radiography. They were either:. punctate deposits in the outer annulus,. diffuse deposits in the transitional zone or inner annulus fibrosus with occasional deposits in the nucleus, or. large deposits in the transitional zone extending variably into the nucleus. Their maximal incidence was in the lower lumbar discs (L4/5-L6/7) with no calcification seen in the lumbosacral or lower thoracic discs. All deposits were hydroxyapatite with large crystallite sizes (800–1300 angstrom) compared to cortical bone (300–600 angstrom). No type X-collagen, osteopontin or osteonectin, were detected in calcific deposits although positive staining for bone sialoprotein was evident. Calcified discs had less proteoglycan of smaller hydrodynamic size than non-calcified discs. Discussion: Disc calcification in ageing sheep is due to hydroxyapatite deposition. The variable but large crystal size, lack of protein markers indicate that this does not occur by an ordered endochondral ossification-like process. The decrease in disc proteoglycan content and size suggests an association between calcification and disc degeneration in ageing sheep. There are notable dissimilarities between hydroxyapatite deposition disorder in humans and sheep. No mechanistic explanation can be offered for the different spinal distributions, thoracic and upper lumbar in the former and lumbar in the latter; hydroxyapatite deposition disorder has occasionally been seen in the lumbar spines of four year old sheep during the course of other studies but not at an earlier age. Diffferences in spinal biomechanics may be implicated but hydroxyapatite deposition does not primarily affect the most or least mobile discs in either species. Neither can an explanation be offered for the apparent immunity of the ovine lumbosacral disc to calcification. However, it is known that proteoglycan turnover is faster at this spinal level than at more proximal lumbar discs. While we have been unable to elucidate the mechanism of hydroxyapatite deposition disorder in sheep, clearly it is different from that in normal osteogenesis. We contend this animal provides a useful, naturally-occurring model for investigation of the aetiology and pathogenesis of human hydroxyapatite deposition disorder, notwithstanding obvious differences between sheep and man

In revision THA, the solid acetabular reconstruction in the true acetabulum is often challenging. We are using the Kerboull acetabular reinforcement devices after packing hydroxyapatite granules for acetabular bone defects. We report our 3–7 year clinical and roentgenographical results. Twenty-one acetabuli in 20 patients were reconstructed in the true acetabuli with Kerboull-type acetabular reinforcement devices and porous hydroxyapatite granules (Sumitomo Pharmaceutical Co. Ltd.). The mean age of the patients at operation was 68 years. The mean follow-up period was 5 years and 3 months (38–88 months). Acetabular bone deficiencies were evaluated according to AAOS classification (type II: 5 hips, type III: 16 hips). Porous hydroxyapatite granules (20–60 grams) were grafted to all the acetabuli. Autologous cortico-cancellous bone grafts or hydroxyapatite blocks were used to reconstruct the segmental defects in 6 hips. All the acetabuli were reinforced with Ker-boull-type reinforcement devices and Charnley-type cemented prostheses were implanted. Clinical and roent-genographical results were evaluated using Japanese Orthopaedic Association hip score and Hodgkinson classification. Average hip score was improved from 42 points to 75 points. No re-revision was done. No infection was noted. The roentgenograms showed neither migration nor loosening of the acetabular components. Porous hydroxyapatite granules are one of the best bone substitutes because of their mechanical and biochemical properties. Oonishi reported very good results of his acetabular reconstruction using this material. The Kerboull-type acetabular devices are very effective to the reconstruction in the true acetabulum. Excellent results of these devices were reported by Kerboull. Ace-tabular reconstrution using both of them showed very good clinical and roentgenographical results during 3 to 7 post-operative years in our series

Sixty-two consecutive primary total hip arthroplasties were prospectively randomized to receive either hydroxyapatite coated (thirty-five hips) or nonhydroxy-apatite coated (twenty-seven hips) femoral prostheses. At a minimum eleven-year followup fifty-one hips (forty-four patients) were evaluated. Only one femoral stem had been revised (secondary to traumatic periprosthetic fracture). Radiographs were available for thirty-nine hips. None of these femoral stems were loose. Harris Hip scores were evaluated for thirty-six unrevised hips and did not differ significantly between the two groups. There appears to be no significant advantage to hydroxyapatite coating for this femoral prosthesis at an average follow-up of thirteen years. There are a paucity of long term randomized controlled trials on results of hydroxapatite coating of femoral prostheses. The purpose of this study was to update the results of a prospective randomized study of a proximally pourous coated, tapered titanium femoral component with and without hydroxyapatite coating. Sixty-two consecutive primary total hip arthroplasties done by one surgeon in fifty-five patients were prospectively randomized to receive either hydroxyapatite coated (thirty-five hips) or nonhydroxyapatite coated (twenty-seven hips) femoral prostheses. At a minimum eleven year followup, three hips (three patients) were lost to followup, and a further eight patients had expired (eight hips). The remaining surviving cohort of fifty-one hips (forty-four patients) were evaluated clinically, including Harris Hip Scores, and radiographically. At an average of thirteen years followup, only one femoral stem had been revised (secondary to traumatic periprosthetic fracture), that being in the hydroxyapatite group. There were eight acetabular revisions in the hydroxyapatite group (thirty-four percent) and four acetabular revisions in the nonhydroxyapatite group (sixteen percent). Radiographs were available for thirty-nine hips. None of these femoral stems were loose. Harris Hip scores were evaluated for thirty-six unrevised hips and did not differ significantly between the two groups. Using endpoints of femoral revision, radiographic loosening, and Harris Hip Scores there appears to be no significant advantage to hydroxyapatite coating for this femoral prosthesis at an average follow-up of thirteen years. Funding: Biomet, Warsaw IN

Introduction: Polyethylene wear debris is the main contributing factor that leads to aseptic loosening and osteolysis. The main objective of this study was to evaluate the role of hydroxyapatite (HA) in third-body polyethylene wear in total hip arthroplasty. Materials: 199 primary cementless THA’s (174 patients) performed by a single surgeon were enrolled in a prospective randomized study comprising Hydroxyapatite and non-hydroxyapatite coated femoral implants. The femoral component had metaphyseal-diaphyseal fit design with proximal plasma sprayed titanium circumferential porous coating. The hydroxyapatite coating was 50 – 75 micrometers over the porous surface with the components of identical design. The acetabular component was plasma sprayed titanium porous coated shell without hydroxyapatite

Surgical failure, mainly caused by loosening implants, causes great mental and physical trauma to patients. Improving the physicochemical properties of implants to achieve favourable osseointegration will continue to be the focus of future research. Strontium (Sr), a trace element, is often incorporated into hydroxyapatite (HA) to improve its osteogenic activity. Our previous studies have shown that miR-21 can promote the osteogenic differentiation of mesenchymal stem cells by the PI3K/β-catenin pathway. The aim of this study is to fabricate a SrHA and miR-21 composite coating and it is expected to have a favorable bone healing capability. Ti discs (20 mm diameter and one mm thickness for the in vitro section) and rods (four mm diameter and seven mm length for the in vivo section) were prepared by machining pure Ti. The Ti cylinders were placed in a Teflon-lined stainless-steel autoclave for treating at 150°C for 24 h to form SrHA layer. The miR-21 was encapsulated in nanocapsules. The miR-21 nanocapsules were mixed with CMCS powder to form a gel-like sample and uniformly coated on the SrHA modifed Ti. Osteoblast-like MG63 cells were cultured on SrHA and miR-21 modified Ti, Cell proliferation activity and osteogenesis-related gene expression were evaluated. A bone defect model was established with mature New Zealand to evaluate the osseointegration. Cylindrical holes (four mm in diameter) were created at the distal femur and tibial plateau. Each rabbit was implanted with four of the aforementioned rods (distal femur and tibial plateau of the hind legs). After implantation for one, two and three months, the rabbits were observed by X-ray and scanned using u-CT. Histological and Immunohistochemical analysis were performed to examine the osteogenic markers. A biomechanical push-in test was used to assess the bone-implant bonding strength. Both SrHA nanoparticles with good superhydrophilicity and miR-21 nanocapsules with uniform sizes were distributed evenly on the surface of the Ti. In vitro experiments revealed that the composite coating was beneficial to osteoblast proliferation, differentiation and mineralization. In vivo evaluations demonstrated that this coating could not only promote the expression of angiogenic factor CD31 but also enhance the expression of osteoblastic genes to facilitate angio-osteogenesis. In addition, the composite coating also showed a decreased RANKL expression compared with the miR-21 coating. As a result, the SrHA/miR-21 composite coating promoted new bone formation and mineralization and thus enhanced osseointegration and bone-implant bonding strength. A homogeneous SrHA and miR-21 composite coating was fabricated by generating pure Ti through a hydrothermal process, followed by adhering miR-21 nanocapsules. This coating combined the favorable physicochemical properties of SrHA and miR-21 that synergistically promoted angiogenesis, osteogenesis, osseointegration, bone mineralization and thus bone-implant bonding strength. This study provided a new strategy for surface modification of biomedical implants

The aim of this study was to evaluate the trochlear bone and cartilaginous regeneration of rabbits using a composite based on platelet rich plasma (PRP), chitosan and hydroxyapatite. The study was approved by the ethics committee of the Federal University of Campina Grande under number 72/2017. Surgical holes measuring four millimetres in diameter were performed in rabbit trochleae, one surgical hole in each animal remained empty and another one was filled with the composite. Clinical-orthopaedic and radiographic evaluations were carried out for 60 days, after which the animals were euthanized for histomorphometric evaluations. Clinical-evaluations exhibited lameness of two members of the treatment (T) group and one member of control (C) group. The radiographic evaluation of T group exhibited absence of subchondral bone reaction (33%); nonetheless, presence of moderate subchondral bone reaction was more frequently reported in group C with 67%. Microscopic evaluation revealed the presence of tissue neoformation, composed of dense connective tissue. Microscopic findings were similar in both groups, with a difference in the amount of neoformed tissue, which was confirmed after the morphometric analysis, revealing a significant difference in the quantity of newly formed tissue at the bone / cartilage / implant interface in the T group. The results indicate that the composite based on chitosan, hydroxyapatite and PRP enhanced bone and cartilage healing

Aims: To investigate if coralline hydroxyapatite conduct bone formation in human spine. Methods: During revision surgery specimens were taken from the fusion mass from 13 patients, who received spinal instrumentation (Titanium alloy) and fusion with coralline hydroxyapatite. The age of patients at the time of revision surgery was 46±20 years. The time lapsed from the implantation of coralline hydroxyapatite (ProOsteon) was 11±11 months. The indication for revision was infection, pseudarthrosis, technical error, and pain related to hardware. The diagnosis for primary fusion was degenerative disease, spinal trauma and scoliosis. Coralline hydroxyapatite was applied on the posterior decorticated elements of the instrumented spine without any mixture with bone graft. Material from ten different places from the fusion mass was intraoperatively taken and the histological evaluation was made using the Hematoxylin-eosin histological stain. Results: There was a concentration of foreign-body like giant cells & development inflammatory granulomatous tissue around hydroxyapatite granules, which was gradually replaced by dense connective collagen tissue. Both inflammatory granulomatous and collagen tissue showed areas with foreign body reaction. In the cases, where bone has developed, the most initial finding was the presence of osteoblasts & apposition of osteoid in contact to hydroxyapatite granules. In a later phase, cancellous and lamellar bone has developed as a result of secondary ossification. Bone formation was observed in 11/15 cases. Conclusion: Coralline hydroxy-apatite conducts bone and osteoid formation around the implanted coralline hydroxyapatite granules in different areas of the human spine operated for different disorders

Aims. Hydroxyapatite (HA)-coated collars have been shown to reduce aseptic loosening of massive endoprostheses following primary surgery. Limited information exists about their effectiveness in revision surgery. The aim of this study was to radiologically assess osteointegration to HA-coated collars of cemented massive endoprostheses following revision surgery. Methods. Retrospective review of osseointegration frequency, pattern, and timing to a specific HA-coated collar on massive endoprostheses used in revision surgery at our tertiary referral centre between 2010 to 2017 was undertaken. Osseointegration was radiologically classified on cases with a minimum follow-up of six months. Results. In all, 39 patients underwent radiological review at mean 43.5 months; 22/39 (56.4%) showed no osseointegration to the collar. Revision endoprostheses for aseptic loosening were less likely to show osseointegration compared with other indications for revision. Oncological cases with previous or current infection were more likely to show osseointegration to ≥ 1 collar side than those without evidence of prior infection. Conclusion. This seven-year review identified osseointegration of HA-coated collars after revision surgery is less likely (43.6%, 17/39) than after primary surgery. Young patients who undergo revision surgery following initial oncological indication may benefit the most from this collar design. Use in revision oncological cases with a history of infection may be beneficial. HA-coated collars showed limited benefit for patients undergoing revision for failed arthroplasty with history of infection. Cite this article: Bone Jt Open 2021;2(6):371–379

Bone fractures are highly observed clinical situation in orthopaedic treatments. In some cases, there might be non-union problems. Therefore, recent studies have focused on tissue engineering applications as alternative methods to replace surgical procedures. Various biopolymer based scaffolds are produced using different fabrication techniques for bone tissue engineering applications. In this study, hydroxyapatite (HAp) and loofah containing carboxymethyl chitosan (CMC) scaffolds were prepared. In this regard, first 4 ml of CMC solution, 0.02 g of hydroxyapatite (HAP) and 0.06 g of poly (ethylene glycol) diglycidyl ether (PEGDE) were mixed in an ultrasonic bath until the HAp powders were suspended. Next, 0.04 g of loofah was added to the suspension and with the help of PEGDE as the cross-linking agent, then, the mixture was allowed to cross-link at 40. o. C overnight. Finally, the three-dimensional, porous and sponge-like scaffolds were obtained after lyophilization (TELSTAR - LyoQuest −85) at 0.1 mbar and −25°C for 2 days. Morphologies, chemical structures and thermal properties of the scaffolds were characterized by scanning electron microscopy (SEM), Fourier Transform infrared spectroscopy (FT-IR) and thermogravimetric differential thermal analysis (TGA/DTA), respectively. In addition, swelling behavior and mechanical properties of the scaffolds under compression loading were determined. In order to investigate biocompatibility of the scaffolds, WST-1 colorimetric assay at days 0, 1, 3, 5 and 7 was conducted by using human dermal fibroblast. Also, histological and morphological analysis were performed for cell attachment at day 7. In conclusion, the produced scaffolds showed no cytotoxic effect. Therefore, they can be considered as a candidate scaffold for bone tissue regeneration. Further studies will be performed by using bone marrow and periosteum derived mesenchymal stem cells with these scaffolds

Objective: To determine if a porous, coralline-derived hydroxyapatite block (ProOsteon 500. TM. , Interpore, Irvine, CA) is a suitable substitute for tricortical iliac crest autograft in cervical interbody fusion. Design: A prospective randomised trial with two-year follow-up comparing clinical and radiographic outcomes in patients receiving either iliac crest or hydroxyapatite grafts in cervical interbody fusion. Subjects: Twenty-nine patients undergoing cervical fusion and anterior plating were randomised to receive either iliac crest (Group I) or hydroxyapatite (Group II) interbody grafts. Fourteen patients (19 grafts) in Group I and twelve patients (18 grafts) in Group II were available for final analysis. Both groups were similar with respect to age, sex, diagnosis and levels fused. Outcome Measures: The SF-36 and Oswestry Disability Index were used to measure clinical outcome. Post-op and final follow-up radiographs were analysed for graft fragmentation, loss of height, loss of angular alignment and hardware failure to assess structural integrity of the graft. Computed or plain tomography was used to evaluate fusion. Results: Groups I and II demonstrated improvement in preoperative scores for bodily pain (p=. 016 and. 016 respectively) and physical functioning (p=. 050 and. 016 respectively) at final follow-up. There was no significant difference in SF-36 and Oswestry scores between the two groups. Successful radiographic fusion was similar in both groups (79% in Group I and 76% in Group II). Graft fragmentation occurred in 89% of the hydroxyapatite grafts and 11% of the autografts (p=. 001). Greater than 2mm of graft height and 3° of segmental lordosis were lost in 55% of hydroxyapatite grafts vs. 11% of autografts (p=. 009). One patient in Group II and none in Group I required revision surgery for graft failure. The high rate of early radiographic failure in the hydroxyapatite grafts prompted suspension of further enrolment in the clinical trial. Conclusions: ProOsteon 500 coralline hydroxyapatite blocks do not possess adequate structural integrity to resist axial loading and maintain disc height or segmental lordosis during cervical interbody fusion

Aim. Bone and implant-associated infections caused by microorganisms that grow in biofilm are difficult to treat because of persistence and recurrence. Systemic administration of antibiotics is often inefficient because the poor vascularization of the site of infection. This issue has led to the development of biomaterials capable to locally deliver high doses of therapeutic agents to the injured bone with minimal systemic effects. In this context, calcium sulphate/hydroxyapatite (CS/HA) bone graft substitutes are widely used being safe, osteoconductive and resorbable biomaterials that can be easily enriched with consistent amounts of antibiotics. In this in vitro study, the capability of the eluted antibiotics to select the tested bacterial strains for antibiotic resistance was evaluated to confirm the safe use of the product. Method. S. aureus, S. epidermidis and P. aeruginosa isolated in our Institute from bone and joint infection with different resistance phenotypes were used. 6 × 2.5 mm CS/HA discs were generated by pouring the antibiotic loaded formulations in a mold and were used as a modified disk diffusion test. The resistance selection was evaluated by subculturing cells growing on the edge of the zone of inhibition (ZOI) for seven days. Minimum inhibitory concentrations (MICs) of gentamicin and vancomycin were determined by broth microdilution method before and after the selection of resistance assay. In addition, MICs were assessed after seven day passage on antibiotic free agar plates to evaluate if eventual decrease of antibiotic susceptibility was stable or only transient. Results. Commonly, no adaptation in presence of both CS/HA formulations was observed by analysing ZOI on agar medium. The kinetic of decrease of the ZOI was similar between the strains, with the exception of gentamicin resistant staphylococci in presence of gentamicin loaded CS/HA, which was faster with respect to the susceptible strains. Conclusions. The present study shows that elution of gentamicin and vancomycin from CS/HA bone graft substitutes did not induce a decrease in susceptibility to these antibiotics in an in vitro setting, suggesting the safe use of the product

Aims: The bone – conductive proparties of hydroxyapatite (HA) coatings are attractive in revision surgery with bone loss. The purpose of this study is to analyse the clinical and radiological results of 55 cases of revision hip arthroplasty using hydroxyapatite femoral stems. Methods: Between May 1995 and October 2000 we performed 55 patients total hip replacements in 50 patients (5 bilateral) using hydroxyapatite (HA) – coated femoral stem. The average age of the patients at the time of the index revision was 67 years (range 44–84). Clinical evaluation was by a Merle d’Aubigne Score (preoperative 6.54 points). Radiological evaluation used the AAOS system for preoperative films and scaring system after Engh for the postoperative films. Bone grafts was required in 35 cases. Results: Postoperative Merle d’Aubigne score was 17.25 points. Complications: 3 dislocations, one transitory nerve palsy and 14 associated intraoperative fractures. All grafts consolidated. None of the femoral stem components required revision because of aseptic loosening. No radiologically progressive lucency or signs indicating a loose implant were visible in anycases. There were no cases of femoral stem migration. Conclusions: We conclude that the hydroxyapatite femoral stem is suitable for implantation at revision hip arthroplasty and can give good results in the short to medium term, because the clinical and radilogical results are excellent, with a early consolidate fractures

Purpose: Hinged knee prostheses are mainly used for reconstruction after major tumour resection. Aseptic loosening is the main problem with these implants. One of the solutions proposed to reduce the rate of loosening is to add a hydroxyapatite collar on the shaft stems. This work was conducted to study bone ingrowth with a new hinged implant with a hydroxyapatite collar at the junction between the zone of resection and the shaft. Material and methods: Twenty-nine massive prostheses with a hydroxyapatite collar were implanted between 1998 and 2001. Nine patients were excluded from the analysis because follow-up was less than two years. This retrospective analysis thus compared twenty massive prostheses with twenty matched hinged GUEPAR prostheses without a collar. Bony ingrowth was measured on plain x-rays (two orthogonal views) at 6, 12, 24, and 36 months. Filling of the gap between the bone and the implant was also assessed. Signs of loosening were noted. Results: Mean bony ingrowth in implants with a hydroxyapatite collar was 6.58 mm at 6 months 9.84 mm at 12 months, 12.3 mm at 24 months and 13.25 mm at 36 months. Mean bony ingrowth in the implants without a hydroxyapatite collar was 1.65 mm at 6 months, 3.31 mm at 12 months, 4.8 mm at 24 months and 4.35 mm at 36 months. In the implants with a collar, gap filling was partial in five cases and total in 15. In implants without a collar, there was no gap filling in eight cases, partial filling in two cases and total filling in fifteen cases. Discussion: Prostheses with a hydroxyapatite collar enable better radiological bony ingrowth than observed in implants without a hydroxyapatite collar. Gap filling is better for prostheses with a collar. There was no case of loosening at last follow-up for implants with a hydroxyapatite collar. Conclusion: In light of these results, shaft anchorage appears to be better with implants with a hydrosyapatite collar. Confirmation of improvement in clinical outcome and lower rate of aseptic loosening will require longer follow-up

Purpose: Despite excellent histological and biomechanical results proving the real efficacy of “biological” implant-bone fixation, use of hydroxyapatite surfacing, widely used for hip implants, remains largely unemployed for knee prostheses. We analysed our ten years experience with hydroxyapatite coated knee implants in a prospective study of 384 cases. Material and methods: Among the 384 prostheses, 361 were primary implantations, and 331 (92%) were still “in place” after ten years experience. Nineteen patients had died and only one (0.3%) was lost to follow-up; three patients were excluded from the analysis due to other major handicaps. There were five revision procedures including three (0.8%) related to deep infection and two (0.6%) to failure with loosening and pain. Mean age of the patients was 70.4 years (40–89). Indications were basically degenerative disease (91%), inflammatory rheumatoid disease (6.9%) and necrosis (1.7%). Results: Mean IKS score at five years minimal follow-up for primary surgery patients was 95.4 and 84.2 points for the overall knee score and the functional score respectively, giving 81.1% and 73.1% good and excellent results for the knee and functional score. Discussion: These clinical results compare well with the best studies reported on total knee arthroplasty with or without cement. Radiographically, we did not have any cases with evidence of an implant-bone interface problem, for femoral or tibial components with the exception of two knees (0.55%) with severe osteolysis and loosening leading to revision surgery. In addition, hydroxyapatite demonstrated its capacity to progressively fill bone-implant gaps over time, confirming the experimental work by Søballe. Cumulative survival was 96.6±0.0688% and 97.37 ± 0.0324% taking ablation and prosthesis-related failure as the endpoint respectively. Conclusion: These results allow renewed confidence in hydroxyapatite as a prosthesis fixation mode, for the knee as well as for the hip

The success of uncemented arthroplasty depends on the achievement and maintenance of implant stability. Despite the use of modern instrumentation to obtain an accurate implant fit during total knee replacement, small gaps often remain visible at the bone-prosthesis interface on high quality fluroscopically-assisted radiographs. Although the clinical significance of these gaps is unclear, their presence delays bony fixation of the implant. In uncemented total hip arthroplasty, hydroxyapatite costing has been used to enhance early stability of the implant: bony apposition has been shown to occur rapidly even in the presence of a small gap between the implant and the bone. In addition, recent RSA (Radio-stereo-photogrammateric analysis) studies have shown reduced micromotion and enhanced implant stability with hydroxyapatite coating of both hip and knee prostheses. The following study was designed to observe and investigate the phenomenon of ‘gap-healing’ around hydroxyapatite coated uncemented total knee prostheses. Over a 15-month period a hydroxyapatite coated uncemented total knee prosthesis was implanted in 99 patients undergoing 108 primary knee arthroplasties. The patients were prospectively reviewed at regular intervals with an average follow up of 18 months and a minimum of 12 months. The implant-bone interface was evaluated by obtaining serial fluroscopically-assisted radiographs. On the immediate postoperative radiographs, small gaps between the implant and bone were seen in most knee. These gaps were visible on average in 2.16 AKS (American Knee Society)zones per knee. Most of the gaps were seen in Femoral zones 2,3,5 and Tibial zones 1 & 4. The majority of the gaps were under 1mm depth. Gaps> 2mm were seen only in 6 patients. Healing of the gaps was first seen at 3 months postoperatively, the average number of zones involved per knee dropping to 1.54. There was good evidence of ‘gap healing’ occurring at all the bone-implant interface zones. At the end of the first postoperative year, only 0.8 zones per knee were involved.2mm gaps remained visible in 3 patients. In animal experiments, hydroxyapatitie coated porous surfaces have shown an increased the rate of bone ingrowth for as many as 52 weeks after implantation. In our study, progressive bone ingrowth and gap-healing has been observed beyond this period, the average involved zones on 2 –year radiographs being 0.4 per knee. During the study period, the American knee score improved from 39.52 preoperatively to 89.97 at 1 year postoperatively. No relation was found between the clinical scores and the presence or absence of gaps on follow-up radiographs. This study demonstrates the phenomenon of ‘gap-healing’ following uncemented hydroxyapatitie coated primary total knee arthroplasty in an unselected group of patients. Gaps under 1 mm at the implant –bone interface heal readily. Healing of gaps> 2mm is less predictable

Introduction and Aims: Titanium foam implants simulate the trabecular structure of bone to maximise porous space for bone ingrowth. Plasma-sprayed hydroxyapatite coatings work well on non-porous substrates but do not coat the inner surfaces of open-porous substrates. Chemical deposition is an attractive alternative that produces consistent coats on porous surfaces. Method: Titanium foam cylinders (5mm diameter by 25mm length) were implanted bilaterally in 40 rabbit femurs. Twenty implants were coated with 20 microns of hydroxyapatite (T-HA) by electrochemical deposition while 20 implants had no hydroxyapatite coat (T). Osseointegration was measured at six and 12 weeks by automated computerised histomorphometry of scanning electron microscopy images of sections taken through the implant at two levels: diaphyseal and metaphyseal. Bone ingrowth was quantified in the pores and was also measured up to 1mm beyond the surface of the implant to determine the pattern of bone growth. Results: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response. Conclusion: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response

Aims. Coatings for endo-osseous implants have been developed based on phospholipids. Such coatings promote the formation of a very thin superficial layer which is highly enriched with calcium phosphates. Aim of this study is a comparison of such coatings with an hydroxyapatite coating. Methods. Two phospholipid-based preparations have been compared with a standard hydroxyapatite coating. Preparation S was based on phosphatidyl-serine; preparation C was based on a mixture of phosphatidyl-serine, phosphatidyl-choline and cholesterol. Titanium cylinders wrapped with titanium foam were the metallic substrate for the coatings; they were implanted in the femural canal of New Zealand White rabbits and retrieved after 4, 8 and 26 weeks. A Back Scattered Electron Microscopy analysis followed. Results. Both phospholipid preparations showed to have no inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction. Pictures of bone in-growth into the cavities of the titanium foam were present. A tight apposition between bone and coating was evident only in the comparative group sprayed with hydroxyapatite, but this latter coating was often fragmented and its constituent granules were evident. Conclusion. Phospholipid-based coatings showed no inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction

Porous blocks of calcium hydroxyapatite ceramic were evaluated as delivery systems for the sustained release of antibiotics. We tested gentamicin sulphate, cefoperazone sodium, and flomoxef sodium in powder form placed in a cylindrical cavity in calcium hydroxyapatite blocks, using in vitro studies of elution and in vivo studies in rats. Gentamicin sulphate gave a maximum concentration within the first week, which gradually decreased but was still effective at 12 weeks, when 70% of the antibiotic had been released. Even at this stage the antibiotic concentration from a 75 mg dose was five times the minimum inhibitory concentration for staphylococci. In the in vivo studies the release of gentamicin sulphate into the normal bone of rats was at similar rates and levels. The bacteriocidal activity of the drugs was not affected by packing into calcium hydroxyapatite ceramic and the blocks were completely biocompatible on histology. This new system overcomes the disadvantages of other drug delivery systems, avoiding thermal damage to the antibiotics and a second operation for the removal of the carrier. Some mechanical strength is provided by the ceramic and healing may be accelerated by bone ingrowth into its micropores

Introduction. We have investigated middle-term clinical results of total hip arthroplasty (THA) cemented socket with improved technique using hydroxyapatite (HA) granules. IBBC (interfacial bioactive bone cement method, Oonishi) (1) is an excellent technique for augmenting cement-bone fixation in the long term. However, the technique is difficult and there are concerns over some points, such as bleeding control, disturbance of cement intrusion to anchoring holes by granules, difficulty of the uniform granular dispersion to the acetabular bone. To improve the original technique, we have modified IBBC (M-IBBC), and investigated the middle-term clinical results and radiographic changes. Materials and Methods. K-MAX HS-3 THA (Kyocera, Japan), with tapered cemented stem with small collar and all polyethylene cemented socket, was used for THA implants (Fig.1). Basically the third generation cementing technique was used for THA using bone cement. The socket fixation was performed with bone cement (Endurance, DePuy) and HA granules (Ca10(PO4)6(OH)2, Boneceram P; G-2, 0.3–0.6mm in size, Olympus, Japan) (Fig.2). In original IBBC technique, HA granules were dispersed on reamed acetabulum before cementing. In M-IBBC technique, HA granules were attached to bone cement on plastic plate, then inserted to reamed acetabulum and pressurized (Fig.3). 112 hip joints (95 cases) were operated between June 2010 and March 2014, and followed. The average follow-up period was 6.5 years, and average age at operation was 66.5 years. The clinical results were evaluated by Japan Orthopaedic Association Hip Score (JOA score), and X-p findings were evaluated using antero-posterior radiographs. The locations of radiolucent lines were identified according to the zones described by Delee and Charnley for acetabular components, and Zone 1 was divided into two parts, outer Zone 1a and inner Zone 1b. Results and Discussion. Revision was not performed. JOA score improved from 47 to 88. Socket and stem loosening was not observed. X-p findings of sockets demonstrated radiolucent line in Zone 1a/1b/2/3 in 0.9/0/0/0% immediately after the operation, 6.3/1.8/0/0.9% at 2 years postoperatively. After 2 years there was no progressive change, however, improvement of radiolucent line in Zone 1a was observed in two cases after 3 years postoperatively. Accordingly, at 5 years radiolucent line in Zone 1a/1b was observed in 4.4/1.8%. Oonish has reported excellent clinical results of THA with IBBC (1). To easily perform IBBC, we have modified the technique, improving the problems of IBBC. In this study, radiolucent line was observed at the margin of the socket in a small number of cases, and there was no progressive change. In addition, improvement of radiolucent line was observed in M-IBBC in this study, which was not observed in conventional cementing technique. Conclusions. It is demonstrated that M-IBBC provides stable socket cement fixation for THA. The interesting finding in M-IBBC cases was the improvement of radiolucent line, suggesting osteoconductive property of hydroxyapatite granules at the interface after the operations. The promising long-term clinical results of M-IBBC method, were expected. For any figures or tables, please contact the authors directly

We report the histological findings in post-mortem specimens obtained ten days, 17 days and seven weeks after implantation of hydroxyapatite-coated femoral components of hip arthroplasties. There was early deposition of woven bone on the hydroxyapatite ceramic, identical to that deposited on surviving cancellous trabeculae. The space between these deposits became bridged from both sides by new trabeculae, and there was no evidence of an inflammatory reaction or of fibrous tissue formation. The use of an hydroxyapatite coating seems to allow early, sound, secondary fixation of implants

A silver-containing hydroxyapatite (Ag-HA) coating has been developed using thermal spraying technology. We evaluated the osteoconductivity of this coating on titanium (Ti) implants in rat tibiae in relation to bacterial infection in joint replacement. At 12 weeks, the mean affinity indices of bone formation of a Ti, an HA, a 3%Ag-HA and a 50%Ag-HA coating were 97.3%, 84.9%, 81.0% and 40.5%, respectively. The mean affinity indices of bone contact of these four coatings were 18.8%, 83.7%, 77.2% and 40.5%, respectively. The indices of bone formation and bone contact around the implant of the 3%Ag-HA coating were similar to those of the HA coating, and no significant differences were found between them (bone formation, p = 0.99; bone contact, p = 0.957). However, inhibition of bone formation was observed with the 50%Ag-HA coating. These results indicate that the 3%Ag-HA coating has low toxicity and good osteoconductivity, and that the effect of silver toxicity on osteoconductivity depends on the dose

The durable fixation of an uncemented cup is due to two major factors: the primary stability obtained by the design of the cup and the secondary fixation obtained by the features of the surface of the cup. The CSF (cancellous screws fixation) cup is an emispheric press-fit Hydroxyapatite coated cup that has 5 holes for screws. This permit to insert screws not only in the superior part of the acetabulum but also in the inferior and supero-medial. This theoretically guarantee, also in those cases in which a perfect press-fit was non achievable, a good primary fixation. This primary fixation permit the osteo-conductive function of the HA coating in order to gain secondary e more stable fixation. From january 1999 to september 2003 we per-formed130 uncemented THR with the CSF cup and the Furlong stem. In the first 100we always insert three screws. In the next 30 only in case of a non perfect-press-fit (10). The mean age was 65 years (14–80). The follow-up varying from 5 years to 6 months. The study is retrospective. At the last follow-up all implants resulted well integrated.. The formation of new trabecular bone bonding the cup was noted on the X-ray since the third month’s control. There was no complication due to the position of the screws. All patients regained full authonomy. Primary stability is mandatory in order to obtain a good secondary fixation by osteointegration. The possibility to insert additional screws in a triaxial fashion permit to obtain good primary stability. in all the cases. The screws must be inserted carefully under X-ray in order to avoid complications. Hydroxyapatite, guiding the growth of new trabecular bone bonding the cup to the pelvic bone, guarantee a good secondary fixation

Introduction We report the clinical and radiographic outcome of a consecutive series of 138 hydroxyapatite coated total knee replacements with a mean follow up of 11 years (10–13 years). Method and Results These patients were entered into a prospective study. There were 74 females and 32 males. Indications for surgery were osteoarthritis in 131 knees, rheumatoid arthritis in 5 knees and pigmented villo-nodular synovitis in 2 knees. The mean age of the patient was 72.5 years at the time of surgery. All living patients (76 knees) were examined and X rayed. A current Hospital for Special Surgery knee score (mean 83 points) was obtained for comparison with the preoperative profile (mean 55 points).The knee status of deceased patients was known within the year of death. No patient was lost to follow up. Radiological evaluation, assessed according to the method described by the Knee Society, revealed no loosening in surviving patients, and there are no impending revisions. Seven prostheses have been revised, giving a cumulative survival rate of 93 percent at 13 years. Discussion. We believe this to be the longest follow up report available for an hydroxyapatite coated knee replacement, and the first using the Insall Burstein knee. Results can thus be compared with the identical prosthesis using cemented fixation. Further modifications would be likely to improve reliability

The material most widely used in orthopaedics is hydroxyapatite (HA), anyway many differences are still present between synthetic HA and biological HA. The aim of this study was to compare adhesion, proliferation and differentiation of human osteoblast-like cells on hydroxyapatite discs with different porosity and on plastic cultures. Human osteoblast-like cells were isolated from 4 young patients (mean age 24.5 years old), treated with collagenase and maintained in Dulbecco’s modified essential medium-10% fetal calf serum. Cells were plated on hydroxyapatite discs with 3 different porosities (35%, 35–55% e 55%) and on plastic cultures used as control. The proliferation was determined by the MTT colorimetric method, and alkaline phosphatase (ALP) activity was measured by a spettrophotometric method. Type I collagen and osteonectin production were demonstrated with fluorescence microscopy and osteoblast adhesion was studied by scanning electron microscopic (SEM) analysis. Results were analysed by one-way analysis of variance (ANOVA). Osteoblast proliferation on HA was three- to six-fold lower then on plastic. At 28 days, 2141 (± 350) cells/well grew on the most porous disks, with highly significant differences from controls. The ALP production was 2–3 fold lower on HA than on plastic. In the most porous disks, the mean ALP activity was of 2.95 (± 0.07) UI/well after 28 days, higher than in the other two groups. The type-I collagen and the osteonectin fluorescence reaction evidenced a cytoplasmic and a matrix labeling on HA at different porosities. SEM analysis showed osteoblasts with a flattened morphology and only few of them were metabolic active. At 21 and 28 days, proliferation rate and ALP activity on the three HA cultures were significantly different (p< 0.05). A decrease in cell population and increased ALP activity were observed on the most porous material, and high proliferation and poor differentiation rates on the less porous disks

Introduction. The addition of hydroxyapatite in cementless total knee arthroplasty is believed to reduce the time for implant fixation and rehabilitation, reduce the incidence of RLLs and provide long lasting implant stability, through improved osseointegration. We report the results of a prospective, randomised controlled single blinded study comparing the post operative pain, biological fixation and clinical outcomes with the LCS Complete Porocoat and the hydroxyapatite-coated, LCS Complete Duofix mobile-bearing knee systems. Methods. Two hundred and four patients for TKA were prospectively recruited into the study between November 2006 and November 2008. Subjects were randomly assigned to receive the LCS Complete Duofix or LCS Complete Porocoat knee systems. Outcomes including VAS pain scores, American Knee Society scores and Oxford knee scores were performed pre-operatively and at 3 months. X-rays were analysed by an independent reviewer for the presence of radiolucent lines. Results. At no time point from immediately post-operatively to 3 months post-operatively was there a statistically significant difference between groups, in terms of reduction in pain, as measured by the VAS pain score (p=0.9575). American Knee Society and Oxford Knee scores showed similar results between groups. In terms of fixation of the prostheses, radiological analysis revealed a statistical difference between the study groups, Odds Ratio 28.17 (3.670, 216.3), with Duofix having fewer radiolucent lines than Porocoat. 25% of the Porocoat tibias were assessed as not fixated at 3 months whereas only 1% of the Duofix tibias were considered not fixated. There was no significant difference in pain between the fixated and not fixated groups (p=0.293). Conclusions. The addition of hydroxyapatite did not make a significant difference in terms of pain or functional outcomes in the early post-operative period, but did reduce the incidence of radiolucent lines. The presence of radiolucent lines was not associated with increased pain

We studied two groups of femoral hip prostheses: 43 TiAlV ridged press-fit stems, and 26 with similar stems coated with hydroxyapatite on the proximal half. At one year, radiological measurement showed a mean downward migration of 0.99 mm for the TialV prostheses and 0.12 mm for the HA-coated prostheses (p = 0.0002). Hydroxyapatite coating appeared to provide effective bio-active supplementary fixation