Hydroxyapatite-coated Implants Research Articles

Dental implant osseointegration in individuals with diabetes: An in-depth analysis

Diabetes, a chronic ailment with systemic implications, extends its influence to oral health, notably contributing to periodontal disease that ranks as the sixth major diabetic complication, often resulting in tooth loss. While dental implants have gained favour for their convenience and long-term viability, their success in diabetic individuals is hampered by compromised osseointegration due to reduced healing-associated bone formation. Successful implant outcomes in such cases hinge on meticulous patient selection, appropriate implant design, and effective restorative strategies, underpinned by stringent glycemic control and oral hygiene. Innovative solutions encompass implant-supported removable dentures and hydroxyapatite-coated implants that foster bone growth and implant-bone integration. In sum, navigating diabetes-related challenges for dental implants entails a comprehensive approach encompassing careful procedural considerations and advanced interventions to bolster the chances of success.

Impact of surface characteristics on the peri-implant microbiome in health and disease.

Because little is known about the impact of implant surface modifications on the peri-implant microbiome, we aimed to examine peri-implant communities in various surface types in order to better understand the impact of these surfaces on the development of peri-implantitis (PI). One hundred and six systemically healthy individuals with anodized (AN), hydroxyapatite-coated (HA), or sandblasted acid-etched (SLA) implants that were >6 months in function were recruited and categorized into health (H) or PI. Peri-implant biofilm was analyzed using 16S rRNA gene sequencing and compared between health/disease and HA/SLA/AN using community-level and taxa-level metrics. Healthy implants did not demonstrate significant differences in clustering, alpha- or beta-diversity based on surface modification. AN and HA surfaces displayed significant differences between health and PI (p<0.05); however, such a clustering was not evident with SLA (p>0.05). AN and HA surfaces also differed in the magnitude and diversity of differences between health and PI. Six species belonging to the genera Shuttleworthia, Scardovia, and Prevotella demonstrated lower abundances in AN implants with PI, and 18 species belonging to the genera Fretibacterium, Tannerella, Treponema, and Fusobacterium were elevated, while in HA implants with PI, 20 species belonging to the genera Streptococcus, Lactobacillus, Veillonella, Rothia, and family Ruminococcaceae were depleted and Peptostreptococcaceae, Atopobiaceae, Veillonellaceae, Porphyromonadaceae, Desulfobulbaceae, and order Synergistales were enriched. Within the limitations of this study, we demonstrate that implant surface can differentially modify the disease-associated microbiome, suggesting that surface topography must be considered in the multi-factorial etiology of peri-implant diseases.

The effectiveness of fixation of hydroxyapatite-coated helical blade in preventing of the cut-out observed in treatment with proximal femoral nail of fractures of the femur intertrochanteric in elderly.

This study aimed to retrospectively evaluate the effectiveness of hydroxyapatite-coated (HA-coated) implants and other caput-collum implants in preventing cut-out observed in treatment with proximal femoral nail (PFN) of intertrochanteric femur fractures in elderly patients. A total of 98 consecutive patients (56 males and 42 females; mean age: 79.42 (61-115) years) treated with three differ-ent PFNs for intertrochanteric femoral fractures were retrospectively examined. The mean of the follow-up period was 7.87 (4-48) months. It was used a threaded lag screw in 40 patients, an HA-coated helical blade in 28 patients and a non-coated helical blade in 30 patients for PFN. The reduction quality, fracture type, and radiological outcomes among all groups were evaluated. Unstable type was seen in 50 (52.1%) patients according to AO Foundation/Orthopedic Trauma Association fracture classi-fication. An acceptable-good reduction quality was seen in 87 (88.8%) of all patients. The average of tip-apex distance (TAD) value was 27.61 mm, calcar-referenced TAD (CalTAD) value was 28.72 mm, caput-collum diaphyseal angle was 128,° Parker's anteroposterior ratio was 46.36%, and Parker's lateral ratio was 46.82%. The best suitable implant position was observed in 49 (50%) patients. Cut-out was observed in 7 (7.14%) patients, and secondary varus displacement of more than 10° was observed in 12 (12.24%) patients. Correlation analysis and multivariate logistic regression analysis showed a significant difference between HA-coated and other implants in cut-out. Furthermore, implant type was the strongest predictive factor for cut-out complications in the multivariate logistic regression analysis. HA-coated implants may reduce the long-term cut-out risk due to increased osteointegration and bone ingrowth in elderly patients with intertrochanteric femoral fractures with poor bone quality. However, this alone is not enough; a suitable screw position, optimal TAD values, and excellent reduction quality are other important factors.

Case Series of Silver Oxide–Containing Hydroxyapatite Coating in Antibacterial Cementless Total Hip Arthroplasty: Clinical Results of 50 Cases at 5-Year Follow-Up

BackgroundProsthetic joint infection, which is caused by implant treatment, is a severe complication. Consequently, silver-containing hydroxyapatite (Ag-HA)-coated implants have been developed to prevent prosthetic joint infection by combining Ag with HA. The Ag-HA-coated total hip prosthesis, which combines the antibacterial activity of Ag and the osteoconductivity of HA, is the first antibacterial cementless total hip prosthesis worldwide. This study aimed to evaluate the short-term outcomes of total hip arthroplasty (THA) with Ag-HA-coated implants. MethodsOverall, 50 hips with various disabling hip diseases and postoperative infection risks that underwent a primary THA using an Ag-HA total hip prosthesis were enrolled. The patients included 37 women (41 hips) and 8 men (9 hips), and the mean age at the time of surgery was 77 years. The clinical outcomes and hip function before and at 5 years postoperatively were measured using the Japanese Orthopaedic Association hip score. Implant stability was assessed, and postoperative complications were also examined. ResultsThe Japanese Orthopaedic Association score increased in all cases and improved from 41 to 86 points after the THA (P < .001). Radiography revealed no implant failure. Dislocation and deep vein thrombosis also occurred in 1 case each. However, there were no adverse reactions associated with Ag, and argyria was not observed in any case. Additionally, none of the patients experienced infection following the surgery. ConclusionsSilver-containing hydroxyapatite–coated implants significantly enhanced patients’ daily activities without any adverse effects on the human body attributed to Ag, and they are expected to reduce postoperative infections.

Osteoconductivity and neurotoxicity of silver-containing hydroxyapatite coating cage for spinal interbody fusion in rats.

The use of spinal instrumentation is an established risk factor for postoperative infection. To address this problem, we prepared silver-containing hydroxyapatite coating, consisting of highly osteoconductive hydroxyapatite interfused with silver. The technology has been adopted for total hip arthroplasty. Silver-containing hydroxyapatite coating has been reported to have good biocompatibility and low toxicity. However, no studies about applying this coating in spinal surgery have addressed the osteoconductivity and direct neurotoxicity to the spinal cord of silver-containing hydroxyapatite cages in spinal interbody fusion. In this study, we evaluated the osteoconductivity and neurotoxicity of silver-containing hydroxyapatite-coated implants in rats. Titanium (non-coated, hydroxyapatite-coated, and silver-containing hydroxyapatite-coated) interbody cages were inserted into the spine for anterior lumbar fusion. At 8 weeks postoperatively, micro-computed tomography and histology were performed to evaluate the osteoconductivity of the cage. Inclined plane test and toe pinch test were performed postoperatively to assess neurotoxicity. Micro-computed tomography data indicated no significant difference in bone volume/total volume among the three groups. Histologically, the hydroxyapatite-coated and silver-containing hydroxyapatite-coated groups showed significantly higher bone contact rate than that of the titanium group. In contrast, there was no significant difference in bone formation rate among the three groups. Data of inclined plane and toe pinch test showed no significant loss of motor and sensory function in the three groups. Furthermore, there was no degeneration, necrosis, or accumulation of silver in the spinal cord on histology. This study suggests that silver-hydroxyapatite-coated interbody cages produce good osteoconductivity and are not associated with direct neurotoxicity.

Evaluation of sodium alendronate drug released from TiO2 nanoparticle doped with hydroxyapatite and silver–strontium for enhancing antibacterial effect and osteoinductivity

Hydroxyapatite (HA) nanocrystalline coatings on implants increase bone/implant joint fusion, but bacteria grow on hydroxyapatite-coated implants and cause infections. To solve this problem, silver (Ag), strontium (Sr), and chitosan were used to modify the surface of the titanium dioxide nanoparticles (TNPs) coated with hydroxyapatite. Ag was used for antimicrobial properties, and Sr was used to control drug release and increase the ossification of titanium implants. Chitosan (Chit) is a natural polymer with good biocompatibility, low toxicity, and strong antibacterial properties. The results show that HA + Sr + Ag + Chit coating causes controlled and long-term release (more than 16 days) of the alendronate sodium drug, an osteoporosis drug, from the implant. Electrochemical corrosion studies reveal that the Sr + Ag + HA + Drug + Chit coating on titanium dioxide nanoparticles has reduced the corrosion penetration rate compared to pure titanium dioxide nanoparticle (TNP). The cytotoxicity analysis results show that the TNP + Sr + Ag + HA + Drug sample has the highest cell viability, equal to 99.3%. Microbial study shows that coated TNPs have more inhibition of Staphylococcus aureus growth than uncoated TNPs. Among the coated TNP samples, TNP samples with HA + Sr + Ag coating had the highest inhibition of bacterial growth.

PRF versus xenograft in sinus augmentation in case of HA-coating implant placement: A 36-month retrospective study.

Sinus lift with a simultaneous implant placement in the residual maxilla is a common technique used worldwide. Nevertheless, choosing an ideal grafting material remains an object of dispute. The use of an autologous blood-derived graft, known as platelet-rich fibrin (PRF), has not yet been recognized to be as good as xenografts and alloplastic materials. However, initial results have been promising. To conduct a clinical and radiological comparison of implantation with a simultaneous sinus lift using xenograft or PRF clots. Thirty sinus lifts with simultaneous implantation were conducted using a lateral window approach and the tent pole technique, with xenograft (group 1 (G1)) or PRF (group 2 (G2)) as a filling material. To be included in the study, patients must have had an alveolar ridge height of 4-5 mm, no signs of inflammatory processes, good oral hygiene, and no other grafting procedures performed in region of implant insertion. In each case, the measurements taken were probing pocket depth (PPD), height of keratinized tissue (HKT), clinical attachment level (CAL), recession depth/width (RD/RW), and, on panoramic X-rays, marginal bone loss (MBL), grafted sinus high (GSH), and bone gain (BG). Preand post-operative treatment was applied to reduce the chance of infection. During the study, 30 implants (hydroxyapatite-coated implants manufactured by SGS - 10 mm in length and 4.2 mm in diameter) were placed. The survival rate of implants in both groups was 100% with no implant mobility, pain, paresthesia, or inflammatory processes in the direct vicinity of the implants observed, except in 1 patient. After 36 months of follow-up, the radiological assessments for G1 were: GSH 4.5 mm, MBL 0.46 mm and BG 4.53 mm; and for G2: 3.4 mm, 0.6 mm and 3.4 mm, respectively. Results of the clinical measurements were for G1: HKT after 36 months (HKT36) 2.46 mm, CAL 0.47 mm and PPD 2 mm; and for G2: HKT36 3.13 mm, CAL 0.6 mm and PPD 2.07 mm. After 3 years of follow-up, the results of sinus lifting solely using PRF with simultaneous implantation were promising, especially in terms of soft tissue management. Therefore, PRF can be regarded as an alternative to previously used materials.

Immediate and early loading of hydrothermally treated, hydroxyapatite-coated dental implants: a 7-year prospective randomized clinical study

BackgroundExisting research on marginal bone stability around hydroxyapatite (HA)-coated implants often lacks adequate long-term follow-up. The purpose of this randomized prospective study was to evaluate the 7-year outcome of patients with immediate and early loaded single-tooth restorations supported by implants with plasma-sprayed, partially HA-coated surfaces. Forty-two patients in need of 50 single implants were treated in in the Postgraduate Periodontics Clinic of Louisiana State University School of Dentistry. Implants were randomly divided into 2 groups: Group A was immediately loaded, and Group B was early loaded. Continuous follow-up with periodic maintenance care and radiographic evaluations was performed. The primary outcome of interest was implant survival, characterized using the Kaplan–Meier method. Secondary study outcome consisted of peri-implant crestal bone level changes. Data on age, sex, bone quality, implant location, length and diameter, and prior augmentation of the site were collected. Multiple regression analyses were conducted to determine whether the independent variables were associated with bone loss.ResultsOne implant failed to maintain stability and was removed at 3 weeks. Thirty-four patients (14 males, 20 females with a total of 42 implants) completed the 7-year follow-up visit. Average age of evaluable patients was 52 in Group A and 55 in Group B. No significant difference was observed regarding sex and age distribution between the 2 groups. No significant difference was detected in the distribution of implant locations, types of bone, implant length, implant diameter, and augmentation status of the bone between the 2 groups. After 7 years of functioning for the 42 implants examined, implant survival rate was 100% for Group A and 95.5% for Group B. The results from this study of 50 implants showed that HA-coated Zimmer Tapered Screw-Vent Implants were clinically effective, with an overall cumulative 7-year survival rate of 98.0%. When comparing radiographic bone levels between 2-year and 7-year follow-ups, no significant differences in bone loss were found between Group A and Group B.ConclusionsAfter 7 years in function, implants partially coated with plasma-sprayed and hydrothermally treated HA were clinically predictable when restored in occlusion immediately after or 3 weeks after implant placement.

Effect of plasma gas atmosphere on hydroxyapatite-coated titanium-based implants

The study was designed to understand the influence of different atmospheres of plasma gas on hydroxyapatite-coated commercially pure Titanium (Ti) and titanium alloy (Ti-6Al-4V). Ti and Ti-6Al-4V were plasma spray-coated with hydroxyapatite in argon, nitrogen, argon/hydrogen, and nitrogen/hydrogen atmospheres. The microstructure, porosity, calcium to phosphate (Ca-P) ratio, surface roughness, and hardness of the coat were characterized using a scanning electron microscope, energy dispersive spectroscopy, image analyzer, profilometer, and Vickers hardness tester. The analyses of the coatings obtained in different plasma gas atmospheres showed variation in microstructure, morphology, porosity, surface roughness, and hardness. As the enthalpy decreased, an increase in porosity was observed in nitrogen/hydrogen, nitrogen, argon/hydrogen, and argon atmospheres, respectively. Peak Ca-P ratio was observed in argon, which is the most inert atmosphere compared to other tested plasma atmospheres. Atmospheres with high enthalpy presented an even surface with comparatively low surface roughness. Hardness value decreased with increasing porosity. The plasma gas atmosphere has a significant influence on Ca-P ratio, porosity, and microcracks of hydroxyapatite-coated oral implants.

Osseointegration of hydroxyapatite-coated implants with new bone in one stage sinus floor elevation without bone substitute

Osseointegration of hydroxyapatite-coated implants with new bone in one stage sinus floor elevation without bone substitute

Hydroxyapatite-coated implants provide better fixation in total knee arthroplasty. A meta-analysis of randomized controlled trials.

BackgroundThe potential advantages of hydroxyapatite (HA)-coated cementless total knee arthroplasty (TKA) implants are bone stock preservation and biological fixation. Studies comparing the outcomes of HA-coated cementless, non HA-coated cementless (uncemented) and cemented TKA implants reported contradictory data. Our aim was to provide a comparison of the effects of HA coating of tibial stem on the stability and functionality of TKA implants.MethodsA systematic literature search was performed using MEDLINE, Scopus, EMBASE and the CENTRAL databases up to May 31st, 2019. The primary outcome was Maximum Total Point Motion (MTPM) of the tibial stem. This parameter is determined by radiosterometric analysis and refers to the migration pattern of the prosthesis stems. The clinical outcomes of the implanted joints were evaluated by the Knee Society Knee Score (KSS) and the Knee Society Function Score (KFS). Weighted mean difference (WMD) with 95% confidence interval (CI) were calculated with the random-effects model.ResultsAltogether, 11 randomized controlled trials (RCTs) with 902 patients for primary TKA implants were included. There was a statistically significant difference in the MTPM values with the use of HA-coated and uncoated uncemented implants (WMD = +0.28, CI: +0.01 to +0.56, P<0.001). However, HA-coated stems showed significantly higher migration when compared with the cemented prostheses (WMD = -0.29, CI: -0.41 to -0.16, P<0.001). The KSS values of HA-coated implants were significantly higher than those for the uncemented implants; moreover, KSS and KFS outcome scores were statistically not different between the HA-coated and cemented prosthesis cases.ConclusionHA-coating yields better stability than other, uncemented prostheses. More importantly, the HA-coating is not outperformed by cemented prosthesis in providing good functional outcome.

Antibacterial Activity of Ag‐Hydroxyapatite Coating Against Hematogenous Infection by Methicillin‐Resistant Staphylococcus aureus in the Rat Femur

Several antibacterial materials have been developed to prevent periprosthetic joint infection and thus prevent serious complications for patients and surgeons. However, no study has addressed the activity of antibacterial materials against hematogenous infection. The present study evaluated the antibacterial activity of a silver-containing hydroxyapatite-coated implant against methicillin-resistant Staphylococcus aureus (MRSA) hematogenous infection. Implants coated with hydroxyapatite and silver-hydroxyapatite were inserted into rats' right and left femurs, respectively, after which the animals were infected with S. aureus via a tail vessel. About 107 colony-forming units was the optimal bacterial number for the establishment of S. aureus hematogenous infection. Bacterial loads and C-reactive protein in the blood were measured to confirm bacteremia and inflammation. Fourteen days after the infection, bacterial loads were statistically lower in the femurs containing silver-hydroxyapatite-coated implants than in those with hydroxyapatite-coated implants (p = 0.022). Thus, silver-hydroxyapatite-coated implants might provide antibacterial activity against MRSA hematogenous infection in the postoperative period. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2655-2660, 2019.

Surface Morphology and Corrosion Behavior of Hydroxyapatite-Coated Co-Cr Implant: Effect of Sintering Conditions

The surface morphology and corrosion behavior of a hydroxyapatite (HA)-coated cobalt-chromium (Co-Cr) implant after sintering posttreatment using different times and temperatures were investigated. The substrates were electrophoretically coated with calcium phosphate in solution of Ca(NO3)·4H2O and NH4H2PO4. Sintering at four different conditions was then performed on the as-deposited samples. Scanning electron microscopy, contact angle measurement, and potentiodynamic polarization studies were employed to investigate the surface morphology, porosity, wettability, and corrosion behavior of the coated samples. The results revealed that the HA-coated substrate sintered at temperature of 600°C for 20 min showed fairly uniform microstructure with the highest density and corrosion resistance compared with the other conditions. Moreover, the highest wettability was exhibited by the HA surface sintered at temperature of 500°C for 60 min.

Ballooning osteolysis in 71 failed total ankle arthroplasties

Background and purpose — Aseptic loosening is a major cause of failure in total ankle arthroplasty (TAA). In contrast to other total joint replacements, large periarticular cysts (ballooning osteolysis) have frequently been observed in this context. We investigated periprosthetic tissue responses in failed TAA, and performed an element analysis of retrieved tissues in failed TAA.Patients and methods — The study cohort consisted of 71 patients undergoing revision surgery for failed TAA, all with hydroxyapatite-coated implants. In addition, 5 patients undergoing primary TAA served as a control group. Radiologically, patients were classified into those with ballooning osteolysis and those without, according to defined criteria. Histomorphometric, immunohistochemical, and elemental analysis of tissues was performed. Von Kossa staining and digital microscopy was performed on all tissue samples.Results — Patients without ballooning osteolysis showed a generally higher expression of lymphocytes, and CD3+, CD11c+, CD20+, and CD68+ cells in a perivascular distribution, compared to diffuse expression. The odds of having ballooning osteolysis was 300 times higher in patients with calcium content >0.5 mg/g in periprosthetic tissue than in patients with calcium content ≤0.5 mg/g (p < 0.001).Interpretation — There have been very few studies investigating the pathomechanisms of failed TAA and the cause-effect nature of ballooning osteolysis in this context. Our data suggest that the hydroxyapatite coating of the implant may be a contributory factor.

Randomized controlled clinical trial of 2 types of hydroxyapatite-coated implants on moderate periodontitis patients.

PurposeThe aim of this study was to compare and analyze the peri-implant tissue conditions and prospective clinical outcomes associated with 2 types of hydroxyapatite (HA)-coated implants: (1) fully HA-coated implants and (2) partially HA-coated implants with resorbable blast medium on the coronal portion of the threads.MethodsForty-four partially edentulous patients were randomly assigned to undergo the placement of 62 HA-coated implants, and were classified as the control group (partially HA-coated, n=30) and the test group (fully HA-coated, n=32). All patients had chronic periodontitis with moderate crestal bone loss around the edentulous area. The stability and clinical outcomes of the implants were evaluated using the primary and secondary implant stability quotient (ISQ), as well as radiographic, mobility, and peri-implant soft tissue assessments around the implants. The Wilcoxon signed-rank test and the Mann-Whitney test were used to evaluate differences between and within the 2 groups, with P values <0.05 considered to indicate statistical significance.ResultsThe fully HA-coated implants displayed good retention of crestal bone, and insignificant differences were found in annual marginal bone loss between the 2 types of HA-coated implants (P>0.05). No significant differences were found in the survival rate (group I, 100%; group II, 100%) or the success rate (group I, 93.3%; group II, 93.8%). The fully HA-coated implants also did not significantly increase the risk of peri-implantitis (P>0.05).ConclusionsThe fully HA-coated implants did not lead to an increased risk of peri-implantitis and showed good retention of the crestal bone, as well as good survival and success rates. Our study suggests that fully HA-coated implants could become a reliable treatment alternative for edentulous posterior sites and are capable of providing good retention of the crestal bone.

Significance of osteogenic surface coatings on implants to enhance osseointegration under osteoporotic-like conditions.

The aim was to assess the significance of osteogenic surface coatings on implants to enhance osseointegration under osteoporotic-like (OP-like) conditions. To address the focused question "Do osteogenic surface coatings on implants enhance osseointegration under OP-like conditions?" PubMed/MEDLINE and Google-Scholar databases were searched from 1995 up to and including February 2014 using various keywords. Unpublished data, letters to the editor, review articles, and articles published in languages other than English were excluded. Of the 28 studies identified, 11 experimental studies were included. These studies were performed on bilaterally ovariectomized animals. In all studies, implant surface roughness was increased by various osteogenetic surface coatings including alumina, hydroxyapatite, calcium phosphate, and zoledronic acid. Nine studies reported that compared with non-coated surfaces, osteogenic coatings on implant surfaces increases bone volume and bone-to-implant contact (BIC) under OP-like conditions. In 2 studies, there was no difference in BIC around hydroxyapatite-coated implants placed in animals with and without OP-like conditions. Osteogenic coatings on implant surfaces enhanced osseointegration in animals with OP-like conditions. However, additional clinical studies are warranted to assess the role of osteogenic coatings in increasing osseointegration in patients with osteoporosis.

Long lasting outcome of hydroxyapatite-coated implants in primary knee arthroplasty: a continuous series of two hundred and seventy total knee arthroplasties at fifteen to twenty two years of clinical follow-up

This study is a long-term review of an hydroxyapatite (HA)-coated knee prosthesis. Our aim was to confirm that excellent previously reported results with HA knees could stand the test of time at the 15-year milestone. A total of 270 cruciate retaining HA-Omnifit knees, implanted in the same institution by a single surgeon with the same surgical procedure, were reviewed at 15-22 years of clinical follow-up (75 knees partially-coated and 195 fully-coated). At review, IKS mean values were 95.6 points for knee score and 91.19 points for function score. Radiological review confirmed an excellent long-lasting fixation over years in the long run. Taking implant failure as the end-point, the survival rate was 97.1% at 20 years. Our results were as good, and often better, than the best cemented or porous published studies. These very encouraging results at 15-22 years make us very confident in the ultimate outcome of bioconductive coatings in knee arthroplasty.

Perspective on Hydroxyapatite-Coated Collars for Bone-Bridging

The Journal of Bone & Joint Surgery: September 4, 2013 - Volume 95 - Issue 17 - p e128 doi: 10.2106/JBJS.M.00525

Periprosthetic Fractures Around a Cementless Hydroxyapatite-coated Implant: A New Fracture Pattern Is Described

Periprosthetic fractures can occur both intraoperatively and postoperatively with implantation of cementless tapered stems. In a large cohort of patients receiving cementless, proximally hydroxyapatite-coated femoral implants, we answered the following questions: What was the incidence of intraoperative and postoperative fractures associated with the implant? What were the fracture patterns as classified by the Vancouver classification system? Did the Vancouver classification represent the fracture patterns found? How were the fractures treated and what were the treatment outcomes; that is, how many fractures healed and did the stems osseointegrate? We evaluated 1039 hips (932 patients) from three prospective studies. The hips were divided into three groups: no fractures, intraoperative fractures, and postoperative fractures. Demographic differences among the groups were noted. Postoperative fractures were classified using the Vancouver classification system. We judged stem stability using Engh's criteria and fracture union was determined by the treating surgeon and confirmed by the authors. We identified 58 periprosthetic fractures in the 1039 hips (5.6%): 38 intraoperative (3.7%) and 20 postoperative (1.9%). Eleven of the postoperative fractures were classifiable by the original Vancouver classification system and nine were of the newly described "clamshell" variety, not classifiable by this system. No intraoperative fractures extended below the lesser trochanter. Twenty-five of these fractures were treated with a single cable or cerclage wire. The remaining received no specific treatment. Of the 20 postoperative fractures, five were treated nonoperatively. All stems osseointegrated. Both intraoperative and postoperative fractures can be managed with success when the stem is stabilized or found to be osseointegrated. An adjustment to the Vancouver classification is suggested to include the clamshell fracture, which has not been previously described.

A Silver Ion-doped Calcium Phosphate-based Ceramic Nanopowder-coated Prosthesis Increased Infection Resistance

Despite progress in surgical techniques, 1% to 2% of joint arthroplasties become complicated by infection. Coating implant surfaces with antimicrobial agents have been attempted to prevent initial bacterial adhesion to implants with varying success rates. We developed a silver ion-containing calcium phosphate-based ceramic nanopowder coating to provide antibacterial activity for orthopaedic implants. We asked whether titanium prostheses coated with this nanopowder would show resistance to bacterial colonization as compared with uncoated prostheses. We inserted titanium implants (uncoated [n = 9], hydroxyapatite-coated [n = 9], silver-coated [n = 9]) simulating knee prostheses into 27 rabbits' knees. Before implantation, 5 × 10(2) colony-forming units of Staphylococcus aureus were inoculated into the femoral canal. Radiology, microbiology, and histology findings were quantified at Week 6 to define the infection, microbiologically by increased rate of implant colonization/positive cultures, histologically by leukocyte infiltration, necrosis, foreign-body granuloma, and devitalized bone, and radiographically by periosteal reaction, osteolysis, or sequestrum formation. Swab samples taken from medullary canals and implants revealed a lower proportion of positive culture in silver-coated implants (one of nine) than in uncoated (eight of nine) or hydroxyapatite-coated (five of nine) implants. Silver-coated implants also had a lower rate of colonization. No cellular inflammation or foreign-body granuloma was observed around the silver-coated prostheses. Silver ion-doped ceramic nanopowder coating of titanium implants led to an increase in resistance to bacterial colonization compared to uncoated implants. Silver-coated orthopaedic implants may be useful for resistance to local infection but will require in vivo confirmation.