Ti Pins Research Articles

Therapeutic Efficacy of an Erythromycin-Loaded Coaxial Nanofiber Coating in a Rat Model of S. aureus-Induced Periprosthetic Joint Infection.

Implant surface nanofiber (NF) coatings represent an alternative way to prevent/treat periprosthetic joint infection (PJI) via local drug release. We developed and characterized a coaxial erythromycin (EM)-doped PLGA/PCL-PVA NF coating. The purpose of this study was to determine the efficacy of EM-NF coatings (EM0, no EM, EM100 (100 mg/mL), and EM1000 (1000 mg/mL) wt/wt) in a rat PJI model. A strong bond of the EM-NF coating to the surface of titanium (Ti) pins was confirmed by in vitro mechanical testing. Micro-computed tomography (mCT) analysis showed that both EM100 and EM1000 NF effectively reduced periprosthetic osteolysis compared to EM0 at 8 and 16 weeks after implantation. Histology showed that EM100 and EM1000 coatings effectively controlled infection and enhanced periprosthetic new bone formation. The bone implant contact (BIC) of EM100 (35.08%) was higher than negative controls and EM0 (3.43% and 0%, respectively). The bone area fraction occupancy (BAFO) of EM100 (0.63 mm2) was greater than controls and EM0 (0.390 mm2 and 0.0 mm2, respectively). The BAFO of EM100 was higher than that of EM1000 (0.3 mm2). These findings may provide a basis for a new implant surface fabrication strategy aimed at reducing the risks of defective osseointegration and PJI.

Potential of Titanium Pins Coated with Fibroblast Growth Factor-2-Calcium Phosphate Composite Layers to Reduce the Risk of Impaired Bone-Pin Interface Strength in the External Fixation of Distal Radius Fractures.

Background: The risk of impaired bone-pin interface strength in titanium (Ti) pins coated with fibroblast growth factor (FGF)-calcium phosphate (CP) composite layers is yet to be evaluated in a clinical study. This retrospective study used Weibull plot analysis to evaluate bone-pin interface strength in Ti pins coated with FGF-CP layers for external distal radius fracture fixation. Methods: The distal radial fractures were treated with external fixation. The FGF-CP group comprised five patients (all women, aged 70.4 ± 5.9 (range: 62-77) years), and the uncoated pin group comprised ten patients (eight women and two men, aged 64.4 ± 11.7 (range: 43-83) years). The pins were removed after six weeks. The insertion and extraction peak torques were measured. The extraction peak torque was evaluated using Weibull plot analysis. Results: We compared the extraction torque of the two groups at or below 506 Nmm for a fair comparison using Weibull plot analysis. The Weibull plots were linear for both the FGF-CP and uncoated pin groups. The slope of the regression line was significantly higher in the FGF-CP group (1.7343) than in the uncoated pin group (1.5670) (p = 0.011). The intercept of the regression line was significantly lower in the FGF-CP group (-9.847) than in the uncoated pin group (-8.708) (p = 0.002). Thus, the two regression lines significantly differed. Conclusions: Ti pins coated with FGF-CP layers exhibit the potential to reduce the risk of impaired bone-pin interface strength in the external fixation of distal radius fractures.

ERYTHROMYCIN-DOPED NANOFIBRE COATING ENHANCES OSSEOINTEGRATION AND INHIBITS STAPHYLOCOCCUS AUREUS-INDUCED OSTEOLYSIS

Failure of osseointegration and periprosthetic joint infection (PJI) are the two main reasons of implant failure after total joint replacement (TJR). Nanofiber (NF) implant surface coating represents an alternative local drug eluting device that improves osseointegration and decreases the risk of PJI. The purpose of this study was to investigate the therapeutic efficacies of erythromycin (EM)-loaded coaxial PLGA/PCL-PVA NF coating in a rat S. aureus-infected tibia model.NF coatings with 100mg and 1000mg EM were prepared. NF without EM was included as positive control. 56 Sprague Dawley rats were divided into 4 groups. A titanium pin (1.0-mm x 8 mm) was placed into the tibia through the intercondylar notch. S. aureus (SA) was introduced by both direct injection of 10 μl broth (1 × 104 CFU) into the medullary cavity and single dip of Ti pins into a similar solution prior to insertion. Rats were sacrificed at 8 and 16 weeks after surgery. The outcome measurements include μCT based quantitative osteolysis evaluation and hard tissue histology.Results: EM-NF coating (EM100 and EM1000) reduced osteolysis at 8 and 16 weeks, compared to EM0 and negative control. The effective infection control by EM-NFs was further confirmed by hard tissue section analysis. The Bone implant contact (BIC) and bone area fraction Occupancy (BAFO) within 200 µm of the surface of the pins were used to evaluate the osseointegration and new bone formation around the implants. At 16 weeks, the bone implant contact (BIC) of EM 100 (35.08%) was higher than that of negative control (3.43%) and EM0 (0%). The bone area fraction occupancy within 200 µm (BAFO) of EM100 (0.63 mm2) was higher than that of negative control (0.390 mm2) and EM0 (0.0 mm2). The BAFO of EM100 was also higher than that of EM1000 (0.3mm2).There was much less osteolysis observed with EM100 and EM1000 NF coatings at 16 weeks, as compared to EM0 positive control, p=0.08 and p=0.1, respectively. Osseointegration and periprosthetic bone formation was enhanced by EM-NFs, especially EM100. Data from this pilot study is promising for improving implant surface fabrication strategies.

Evaluating metallic artefact of biodegradable magnesium-based implants in magnetic resonance imaging

Magnesium (Mg) implants have shown to cause image artefacts or distortions in magnetic resonance imaging (MRI). Yet, there is a lack of information on how the degradation of Mg-based implants influences the image quality of MRI examinations. In this study, Mg-based implants are analysed in vitro, ex vivo, and in the clinical setting for various magnetic field strengths with the aim to quantify metallic artefact behaviour. In vitro corroded Mg-based screws and a titanium (Ti) equivalent were imaged according to the ASTM F2119. Mg-based and Ti pins were also implanted into rat femurs for different time points and scanned to provide insights on the influence of soft and hard tissue on metallic artefact. Additionally, MRI data of patients with scaphoid fractures treated with CE-approved Mg-based compression screws (MAGNEZIX®) were analysed at various time points post-surgery. The artefact production of the Mg-based material decreased as implant material degraded in all settings. The worst-case imaging scenario was determined to be when the imaging plane was selected to be perpendicular to the implant axis. Moreover, the Mg-based implant outperformed the Ti equivalent in all experiments by producing lower metallic artefact (p < 0.05). This investigation demonstrates that Mg-based implants generate significantly lower metallic distortion in MRI when compared to Ti. Our positive findings suggest and support further research into the application of Mg-based implants including post-operative care facilitated by MRI monitoring of degradation kinetics and bone/tissue healing processes.

Resveratrol reduces the progression of titanium particle-induced osteolysis via the Wnt/β-catenin signaling pathway in vivo and in vitro.

As an activator of sirtuin 1, resveratrol has become an extensively reviewed anti-inflammatory and anti-aging drug in recent years, and it has been widely studied for the treatment of energy control and endocrine diseases. The present study attempted to characterize the role of resveratrol in osteolysis induced by titanium (Ti) alloy particles and Ti pins in vitro and in vivo. In vitro, bone marrow mesenchymal stem cells were cultured with Ti alloy particles to simulate osteolysis. Cell viability and the expression levels of proteins associated with osteogenesis and the Wnt/β-catenin signaling pathway, including Runt-related transcription factor 2 (Runx2), alkaline phosphatase, osteocalcin, β-catenin, lymphoid enhancer-binding factor 1 and transcription factor 4, were increased following treatment with resveratrol after 21 days of osteogenic differentiation. In vivo, a Ti pin model in C57BL/6J mice was used to study the anti-osteolysis effect of resveratrol on the peri-prosthetic bone. The pulling force of the Ti alloy pin was increased in a dose-dependent manner in the resveratrol groups compared with the control group. Furthermore, the results of micro-CT scanning revealed that the bone volume and the bone surface/volume ratio in the periprosthetic tissue were increased in the resveratrol-treated groups, particularly in the high-dose resveratrol group. In addition, immunohistochemistry demonstrated that Runx2 expression was upregulated in the high-dose resveratrol group. In conclusion, the results of the present study indicated that resveratrol may inhibit Ti particle-induced osteolysis via activation of the Wnt/β-catenin signaling pathway in vitro and in vivo.

Increased Staphylococcus aureus Biofilm Formation on Biodegradable Poly(3-Hydroxybutyrate)-Implants Compared with Conventional Orthopedic Implants: An In Vitro Analysis.

To compare the biofilm formation on a biodegradable material, poly(3-hydroxybutyrate) (PHB), with that on conventional titanium (Ti) and steel (St) implant material. Pins made of the different materials were incubated in Müller-Hinton broth inoculated with 2 × 10 colony-forming units (CFU)·mL of Staphylococcus aureus for 2 and 7 days and then sonicated for the disruption of the biofilms. CFU were counted to quantify the number of bacteria in the biofilm, and the cell proliferation assay 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H- tetrazolium-5-carboxanilid salt was used to evaluate their metabolic activity. Scanning electron microscopy visualized the structure of the biofilm. We found a significantly higher metabolic activity and CFU count in the biofilm of PHB pins compared with St and Ti pins (analysis of variance, P < 0.0001). Scanning electron microscopy revealed structured biofilms on PHB pins already after 2 days of incubation, which was not observed on the other tested implants. PHB implants seem to provide an environment that advantages the formation of biofilms of S. aureus, a common pathogen in implant-related infections. The amount of biofilm is higher on PHB implant compared with conventionally used orthopedic titanium and steel implants. To overcome the potential risk of surgical site infections linked to the clinical use of PHB implants, possible modifications of the material, increasing its antibacterial properties, need to be further investigated.

Improving tribological and anti-bacterial properties of titanium external fixation pins through surface ceramic conversion

In this study, an advanced ceramic conversion surface engineering technology has been applied for the first time to self-drilling Ti6Al4V external fixation pins to improve their performance in terms of biomechanical, bio-tribological and antibacterial properties. Systematic characterisation of the ceramic conversion treated Ti pins was carried out using Scanning electron microscope, X-ray diffraction, Glow-discharge optical emission spectroscopy, nano- and micro-indentation and scratching; the biomechanical and bio-tribological properties of the surface engineered Ti pins were evaluated by insertion into high density bone simulation material; and the antibacterial behaviour was assessed with Staphylococcus aureus NCTC 6571. The experimental results have demonstrated that the surfaces of Ti6Al4V external fixation pins were successfully converted into a TiO2 rutile layer (~2 μm in thickness) supported by an oxygen hardened case (~15 μm in thickness) with very good bonding due to the in-situ conversion nature. The maximum insertion force and temperature were reduced from 192N and 31.2 °C when using the untreated pins to 182N and 26.1 °C when the ceramic conversion treated pins were tested. This is mainly due to the significantly increased hardness (more than three times) and the effectively enhanced wear resistance of the cutting edge of the self-drilling Ti pins following the ceramic conversion treatment. The antibacterial tests also revealed that there was a significantly reduced number of bacteria isolated from the ceramic conversion treated pins compared to the untreated pins of around 50 % after 20 h incubation, P < 0.01 (0.0024). The results reported are encouraging and could pave the way towards high-performance anti-bacterial titanium external fixation pins with reduced pin-track infection and pin loosing.

The calcium phosphate matrix of FGF-2-apatite composite layers contributes to their biological effects.

The purpose of the present study was to fabricate fibroblast growth factor (FGF)-2-apatite composite layers on titanium (Ti) pins in one step at 25 °C using a supersaturated calcium phosphate (CaP) solution, and to evaluate the physicochemical characteristics and biological effects of the coated Ti pins compared with coated Ti pins fabricated at 37 °C. Ti pins were immersed in a supersaturated CaP solution containing 0.5, 1.0, or 2.0 µg/mL FGF-2 at 25 °C for 24 h (25F0.5, 25F1.0, and 25F2.0) or containing 4.0 µg/mL FGF-2 at 37 °C for 48 h (37F4.0). Except for the 25F0.5, the chemical compositions and the mitogenic activity levels of FGF-2 of the composite layers formed by these two methods were similar, except for the Ca/P molar ratio, which was markedly smaller at 25 °C (1.55–1.56 ± 0.01–0.02, p = 0.0008–0.0045) than at 37 °C (1.67 ± 0.11). Thus, either the apatite was less mature or the amount of amorphous calcium phosphate was higher in the composite layer formed at 25 °C. In vivo, the pin tract infection rate by visual inspection for 37F4.0 (45%) was lower than that for 25F1.0 (80%, p = 0.0213), and the rate of osteomyelitis for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0341). The extraction torque for 37F4.0 (0.276 ± 0.117 Nm) was higher than that for 25F0.5 (0.192 ± 0.117 Nm, p = 0.0142) and that for 25F1.0 (0.176 ± 0.133 Nm, p = 0.0079). The invasion rate of S. aureus for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0110). On the whole, the FGF-2-apatite composite layer formed at 25 °C tended to be less effective at improving fixation strength in the bone-pin interface and resisting pin tract infections. These results suggest that the chemistry of the calcium phosphate matrix that embeds FGF-2, in addition to FGF-2 content and activity, has a significant impact on composite infection resistance and fixation strength.

Correction: Mutsuzaki, H., et al. Improved Bonding of Partially Osteomyelitic Bone to Titanium Pins Owing to Biomimetic Coating of Apatite. Int. J. Mol. Sci. 2013, 14, 24366–24379.

In the original version of the manuscript [1] there was an inadvertent error. The words “25 °C for 48 h” should be replaced with “25 °C for 24 h”. The authors carried out the coating experiments at 25 °C for 1, 3, 6, 12, 24 and 48 h. The apatite coatings formed at 25 °C for 24 and 48 h were found to be identical in physicochemical nature, which was revealed by SEM, EDX, XRD and chemical analysis. Thus, in the animal experiments, the authors used apatite-coated Ti pins fabricated at 25 °C for 24 h. Several corrections are thus required in the abstract, the main text, the figure legends, and the figures (Table 1). The authors would like to apologize for any inconvenience this may have caused to readers of the journal. [...]

Improved Bonding of Partially Osteomyelitic Bone to Titanium Pins Owing to Biomimetic Coating of Apatite

Increased fixation strength of the bone-pin interface is important for inhibiting pin loosening after external fixation. In a previous study, an apatite (Ap) layer was formed on anodically oxidized titanium (Ti) pins by immersing them in an infusion fluid-based supersaturated calcium phosphate solution at 37 °C for 48 h. In the present study, an Ap layer was also successfully formed using a one-step method at 25 °C for 48 h in an infusion fluid-based supersaturated calcium phosphate solution, which is clinically useful due to the immersion temperature. After percutaneous implantation in a proximal tibial metaphysis for four weeks in rabbits (n = 20), the Ti pin coated with the Ap layer showed significantly increased extraction torque compared with that of an uncoated Ti screw even with partial osteomyelitis present, owing to dense bone formation on the Ap layer in the cortical and medullary cavity regions. When the infection status was changed from “no osteomyelitis” to “partial osteomyelitis,” the extraction torque in the Ap group with “partial osteomyelitis” was almost identical to that for “no osteomyelitis” cases. These results suggest that the Ap layer formed by the room temperature process could effectively improve the fixation strength of the Ti pin for external fixation clinically even with partial osteomyelitis present.

In Vivo Performance and Structural Relaxation of Biodegradable Bone Implants Made from MgZnCa Bulk Metallic Glasses

AbstractA study of Mg‐based bulk metallic glasses (BMGs) as biodegradable bone implants is presented. The implantation site can affect performance, so the BMGs were evaluated in vivo in rat femurs using µ‐CT scans at various times for more than 90 days. Estimates of H2 evolution correlate well with previous in vitro studies and bone–implant contact is similar to that for Ti pins. One potential drawback of Mg‐based BMGs in this application is embrittlement due to structural relaxation. Here, relaxation at 20 and 37 °C is examined, and an increase in the characteristic relaxation time, from 10 to 30 days at 20 °C, is observed as Zn increases from 29 to 32 at.%, correlating with dramatically reduced hydrogen evolution.

Emerging ideas: can erythromycin reduce the risk of aseptic loosening?

Persistent inflammatory reaction to wear debris causes periprosthetic osteolysis and loosening. Some authors have advocated pharmaceutical approaches to reduce the inflammatory reaction. Erythromycin has antiinflammatory effects independent of its antimicrobial properties. Although oral erythromycin reportedly inhibits periprosthetic tissue inflammation in patients with aseptic loosening, long-term systematic erythromycin treatment is not recommended owing to its side effects. Therefore, it would be advantageous to restrict erythromycin delivery to the inflammatory periprosthetic tissue without causing side effects. Erythromycin eluted from hydroxyapatite-coated titanium (Ti) pins inhibits periprosthetic tissue inflammation and osteolysis. We propose restricting erythromycin delivery to the inflammatory periprosthetic site. A previously described rat model of ultrahigh molecular weight polyethylene (UHMWPE) particle-induced periprosthetic tissue inflammation and osteolysis will be used to test the effect of local delivery of erythromycin via Peri-Apatite(TM)-coated Ti implants. The outcome measures will include bone ingrowth (μCT), implant stability (pullout test), and histologic analysis of periprosthetic tissues. Pharmacologic intervention aimed at slowing, preventing, or reversing the aseptic loosening process would represent an advance in the management of joint replacement. Erythromycin may be appropriate for prophylactically treating patients who have repeated revision surgery and/or show early signs of progressive osteolysis after arthroplasty.

Efficacy of periprosthetic erythromycin delivery for wear debris-induced inflammation and osteolysis

We have reported that oral erythromycin (EM) inhibits periprosthetic tissue inflammation in a group of patients with aseptic loosening. The purpose of this study was to assess the efficacy of local, periprosthetic EM delivery in a rat model. Uncoated Ti pins were press-fit into the right tibia of fourteen Sprague-Dawley rats following an intramedullar injection of UHMWPE (ultra high molecular weight polyethylene) particles. Revision surgeries were performed 2 months after the primary surgery. EM was applied to the Peri-Apatite™ (PA) layer of the titanium (Ti) pins. The previously implanted Ti pins were withdrawn and replaced with Ti pins coated either with (n = 7) or without (n = 7) EM. The rats were killed 1 month after "revision surgery". The EM efficacy was evaluated by (MicroCT) μCT and histology. μCT analysis showed that bone volume percentage (BV/TV) was significantly higher in the EM-treated group compared to the untreated group (p < 0.05). Histological analysis showed that EM treatment inhibits UHMWPE particle-induced periprosthetic tissue inflammation compared to the untreated group. This study demonstrated that periprosthetic EM delivery reduced periprosthetic inflammation and improved the quality of surrounding bone.

The development of binary Mg–Ca alloys for use as biodegradable materials within bone

Binary Mg–Ca alloys with various Ca contents were fabricated under different working conditions. X-ray diffraction (XRD) analysis and optical microscopy observations showed that Mg– xCa ( x = 1–3 wt%) alloys were composed of two phases, α(Mg) and Mg 2Ca. The results of tensile tests and in vitro corrosion tests indicated that the mechanical properties could be adjusted by controlling the Ca content and processing treatment. The yield strength (YS), ultimate tensile strength (UTS) and elongation decreased with increasing Ca content. The UTS and elongation of as-cast Mg–1Ca alloy (71.38 ± 3.01 MPa and 1.87 ± 0.14%) were largely improved after hot rolling (166.7 ± 3.01 MPa and 3 ± 0.78%) and hot extrusion (239.63 ± 7.21 MPa and 10.63 ± 0.64%). The in vitro corrosion test in simulated body fluid (SBF) indicated that the microstructure and working history of Mg– xCa alloys strongly affected their corrosion behaviors. An increasing content of Mg 2Ca phase led to a higher corrosion rate whereas hot rolling and hot extrusion could reduce it. The cytotoxicity evaluation using L-929 cells revealed that Mg–1Ca alloy did not induce toxicity to cells, and the viability of cells for Mg–1Ca alloy extraction medium was better than that of control. Moreover, Mg–1Ca alloy pins, with commercial pure Ti pins as control, were implanted into the left and right rabbit femoral shafts, respectively, and observed for 1, 2 and 3 months. High activity of osteoblast and osteocytes were observed around the Mg–1Ca alloy pins as shown by hematoxylin and eosin stained tissue sections. Radiographic examination revealed that the Mg–1Ca alloy pins gradually degraded in vivo within 90 days and the newly formed bone was clearly seen at month 3. Both the in vitro and in vivo corrosion suggested that a mixture of Mg(OH) 2 and hydroxyapatite formed on the surface of Mg–1Ca alloy with the extension of immersion/implantation time. In addition, no significant difference ( p > 0.05) of serum magnesium was detected at different degradation stages. All these results revealed that Mg–1Ca alloy had the acceptable biocompatibility as a new kind of biodegradable implant material. Based on the above results, a solid alloy/liquid solution interface model was also proposed to interpret the biocorrosion process and the associated hydroxyapatite mineralization.

An in Vivo Experimental Comparison of Stainless Steel and Titanium Schanz Screws for External Fixation.

To compare the clinical benefits of stainless steel (SS) to titanium (Ti) on reducing pin track irritation/infection and pin loosening during external fracture fixation. A tibial gap osteotomy was created in 17 sheep and stabilized with four Schanz screws of either SS or Ti and an external fixation frame. Over the 12 week observation period, pin loosening was assessed by grading the radiolucency around the pins and measuring the extraction torque on pin removal at sacrifice. Irritation/infection was assessed with weekly clinical pin track grading. A histological analysis of the tissue adjacent to the pin site was made to assess biocompatibility. A statistically non-significant trend for less bone resorption around Ti pins was found during the early observation period. However, at sacrifice, there was no difference between the two materials. Also, there was no difference in the extraction torque, and there was similar remodeling and apposition of the bone around the pins. A statistically non-significant trend for more infection about SS pins at sacrifice was found. Histology showed a slightly higher prevalence of reactionary cells in SS samples, but was otherwise not much different than around Ti pins. There is no clinically relevant substantial advantage in using either SS or Ti pins on reducing pin loosening or pin track irritation/infection.

Dry sliding behaviour of non-hydrogenated DLC coatings against Al, Cu and Ti in ambient air and argon

Magnetron sputtered non-hydrogenated diamond-like carbon (DLC) coatings were tested against Al, Cu and Ti pins using a vacuum pin-on-disc tribometer. The objective was to investigate the effect of counterface material on the tribological behaviour of the non-hydrogenated DLC coatings in air (29% RH) and an inert atmosphere (argon). In argon, a significant amount of adhesion and material transfer occurred from the Al and Ti pins to the DLC coating surfaces, increasing the coefficient of friction (COF) and inflicting severe damage to the coatings. Wear and material transfer between DLC coating and Cu were negligible in argon. Compared to the tests in argon, the tribological performance of DLC coatings against Al and Ti significantly improved in ambient air. In contrast, the wear rate of DLC coatings against Cu was higher in ambient air and its COF was similar under both conditions. In ambient air, carbonaceous layers were generated on Al and Ti but not on Cu. The adsorption of water vapour on the DLC coating surface and the formation of an easy-to-shear carbonaceous material at the sliding interface reduced the COFs and wear rates of non-hydrogenated DLC coatings in air with humidity.

Anodic Plasma Chemical Treatment of Titanium Schanz Screws Reduces Pin Loosening

This study was designed to assess the benefits of a new Anodic Plasma Chemical calcium-phosphate (APC-CaP) surface treatment on reducing pin track infection and pin loosening in comparison to anodized titanium (Ti) during external fracture fixation. A tibial midshaft, transverse, 6-mm gap osteotomy was created in 17 adult female Swiss alpine sheep. The tibia was stabilized with an external fixator and 4 Schanz screws of Ti or APC-CaP-treated Ti. The sheep were examined during a 12-week observation period. Infection was assessed with weekly clinical pin track grading and microbiologic assessment at sacrifice. Pin loosening was assessed by grading for radiolucency on biweekly radiographs and by measuring extraction torque on pin removal. In vivo bending stiffness measurements were performed to determine gap healing. A qualitative histologic assessment of the tissue adjacent to pin sites was also performed. A trend (P = 0.056) for less infection around APC-CaP pins was found at 6 weeks, but the strength of this difference diminished with time. Significantly more radiolucency was found around Ti pins after 8 (P = 0.011) and 12 (P < 0.001) weeks. At all pin sites, the extraction torque for APC-CaP pins was higher than for Ti pins (P = 0.007). No difference in the progression of gap healing was found. Histology showed bone growth at the implant surface in the form of distance osteogenesis for Ti and contact osteogenesis for APC-CaP. This study has shown that the APC-CaP surface improves the clinical performance of Ti pins with respect to pin loosening and pin track infection.