Coating of titanium implants with type-I collagen.

PURPOSE: Type-I collagen, the major structural protein in bone, has beneficial properties regarding bone regeneration. Little is known about the potential effects of collagen coating on orthopedic implants. METHODS: 3 to 6 microg/cm2 of lyophilized type-I collagen was absorbed on titanium rods. Six coated and uncoated pins of 0.9 mm diameter were inserted into the tibia of adult male Wistar rats for 1, 2, 4, 7, 14, and 28 days. Specimens were embedded in methacrylate-based Technovit 9100N resin. From one portion cutting and grinding sections were obtained. The implant was removed from the other half that was depolymerized, sectioned, and mounted for immunohistochemistry. RESULTS: At day 4, the interface around the collagen-coated implants displayed a granulation tissue with higher numbers of cathepsin D-positive mononucleated cells compared to the uncoated implants (p<0.05). Active osteoblasts, reactive for osteopontin, were increased around the collagen-coated pins at day 4 and 7 (p<0.01). After 28 days of implantation, direct bone contact averaged 74.9% around the collagen-coated implants and 62.1% around uncoated implants (NS). The amount of newly formed bone averaged 76.3% around the collagen-coated pins and 67.8% around the uncoated pins (NS). The histomorphometric findings were confirmed by SRmicroCT in two specimens. CONCLUSIONS: The earlier observation of mononuclear phagocytozing cells and the earlier and higher expression of bone-specific matrix proteins suggest an increased early bone remodeling around titanium pins through collagen coating. A tendency towards increased bone formation was observed around the coated implants.     

Bone ingrowths to press-fit and loose-fit implants: comparisons between titanium and hydroxyapatite

The aim of this study was to investigate whether the coating of titanium (Ti) implants with hydroxyapatite (HA) might create a better fixation when titanium implants are implanted into a gap. In each of 16 rats, the medullary cavity of both femurs was entered by an awl from the trochanteric area. With steel burrs it was successively reamed to a diameter of 1.5 mm. In a random manner the proximal part of the cavity in half of the bones was reamed once again to a diameter of 2.0 mm. Nails with a diameter of 1.5 mm and a length of 34 mm were then inserted into the medullary cavity of these bones with press fit at the distal half and a gap to the bone in the proximal half. In the remaining bones the whole medullary canal was reamed to a diameter of 2.0 mm, and nails with a diameter of 2.0 mm and a length of 34 mm were introduced. In all cases, either a pure Ti nail or a Ti nail entirely plasma sprayed with HA was used in a random manner. The surface roughness of the pure Ti was characterized by Ra 2.6 microm and Rt 22 microm. Ra of HA was 7.5 microm and Rt 52 microm. At sacrifice after 16 weeks, both femurs were dissected free from soft tissues and then immersed in fixative. A specimen slice of about 5 mm in thickness was prepared from the subtrochanteric region with a water-cooled band saw. Sample preparation for undecalcified tissue followed the internal guidelines at the laboratories of the Department of Biomaterials/Handicap Research. Generally, bone contact to the nails with HA coating was more predictable than was bone contact to the Ti nails. But due to rather large variations in bone contact between the samples, statistical analyses revealed non-significant differences between the 4 groups (p = 0.083). There were no significant differences between Ti and HA coated nails of 2.0 mm (p = 0.633), nor between Ti and HA coated nails of 1.5 mm (p = 0.924). The pooled values for the 2.0 mm nails showed significantly higher bone bonding contact than the pooled values of the 1.5 mm nails (p = 0.011). Our results, then, indicate that bone bonding contact to implants with a loose fit insertion is less predictable than in press fit insertion, and HA coating seemed to be more predictable than pure Ti. However, due to large variations between the samples, the differences did not reach significant levels.     

Osseointegration of polyethylene implants coated with titanium and biomimetically or electrochemically deposited hydroxyapatite in a rabbit model

Purpose

The aim of this study was to evaluate the osseointegration of a new coating directly deposited on PE at room temperature.

Methods

Thirty-six (36) male New Zealand rabbits were randomly assigned to receive one out of three types of implants: two tested implants, i.e. PE implant coated with TiPVD and biomimetic HA (biomimetic), PE implant coated with TiPVD and electrolytic HA (electrolytic), and positive control made of massive microrough titanium coated with plasma sprayed HA (TiHAPS). Osseointegration was evaluated by histomorphometry (bone tissue in contact [BIC]), mineralized bone area [MBA]) and mechanical testing (push-out test, interfacial shear strength [ISS]) at six and 12 weeks in the distal femurs.

Results

For BIC there were no differences between the groups at six (p = 0.98) and 12 weeks (p = 0.13). For MBA, no statistically significant difference was measured between groups at six (p = 0.52) and 12 weeks (p = 0.57). At six weeks, interfacial shear strength (ISS) was significantly higher (p = 0.01) for TiHAPs implants compared to biomimetic and electrolytic implants. This difference was not significant at 12 weeks (p = 0.92).

Conclusion

The osseointegration of biomimetic and electrolytic implants was equivalent to a positive control at 12 weeks.     

The effect of hydroxyapatite coating on bone growth into porous titanium alloy implants

In rabbits and goats, test implants with a porous surface of two layers of Tl-6A;-4V beads were examined at intervals for bond strength with bone. Half of the implants were coated with hydroxyapatite by plasma spray. The bonding strength with bone in the coated specimens was about four times greater than that of the uncoated specimens at two weeks, and twice as strong at six weeks. Twelve weeks after implantation, the strengths were similar. The hydroxyapatite coating of the beads provided earlier and stronger fixation.     

Effects of hydroxyapatite tricalcium phosphate coating and intracancellous placement on bone ingrowth in titanium fibermetal implants

The purpose of this study was to compare the host—bone response to hydroxyapatite/tricalcium phosphate (HA/TCP)-coated and noncoated titanium fibermetal implants placed in a load-sharing cancellous bone environment of the distal femurs of rabbits. The influence of implantation site was also investigated by comparing these intracancellous implants with intramedullary implants evaluated in a previous study. Three parameters were measured: percentage implant perimeter surface length in contact with new bone, percentage internal fibermetal surface length in contact with ingrown bone, and percentage of available pore space filled with bone. The HA/TCP coating significantly accelerated and increased bone ongrowth, new bone formation on the perimeter and internal surface of the implants. This effect was evident as early as 2 weeks after implantation. In contrast, there was no difference between HA/TCP-coated and noncoated implants in the bone ingrowth parameter, percentage of available pore space filled with bone, or pull-out strength. Scanning electron microscopy in the backscatter mode demonstrated that new bone formed directly onto the HA/TCP-coated fibers and did not usually form directly on noncoated fibers. Analysis of fluorochrome labeling revealed that bone formation in weeks 1 through 4 was primarily woven and there-after lamellar. Compared with intramedullary placement, intracancellous placement significantly accelerated the apposition of bone to the perimeter and internal surface of HA/TCP-coated implants and both accelerated and increased bone ingrowth as a percentage of available pore volume. These data show that the host response to titanium fibermetal implants is influenced both by HA/TCP coating and by the implantation site.     

Lumbar spine interbody fusion with reinforced hydroxyapatite implants

Summary Porous coralline and synthetic hydroxyapatite blocks reinforced with either self-reinforced polyactide or polyglycolide were implanted into 15 lumbar intervertebral disc spaces in five minipigs in order to determine whether they could provide an osteoconductive bridge for interbody fusion. Histological examination and radiological analysis with plain films, computed tomography and magnetic resonance imaging were carried out. The osteoconductive properties were promising; creeping bone formation could be observed, although no complete fusion had been achieved at 24 weeks.     

Osseointegration of titanium implants

Forty-eight screws, six double cylindrical implants and six T-plates were inserted into the tibia or femur of 6 dogs. Two titanium screws were inserted into the proximal tibia of 5 patients to anchor a titanium mould. The implants were removed en bloc with adjacent bone tissue after 3 to 14 months. They were sectioned using a technique that allowed analysis of the intact tissue-to-metal specimens. Osseointegration, defined as a direct bone-to-implant contact without interposed soft tissue, was confirmed in all screw-shaped implants while the cylindres had only partial bone contact as did the T-plates. We conclude that osseointegrated implants may be applicable in joint reconstruction for arthrosis or rheumatoid arthritis.     

Osseointegration of titanium implants

Forty-eight screws, six double cylindrical implants and six T-plates were inserted into the tibia or femur of 6 dogs. Two titanium screws were inserted into the proximal tibia of 5 patients to anchor a titanium mould. The implants were removed en bloc with adjacent bone tissue after 3 to 14 months. They were sectioned using a technique that allowed analysis of the intact tissue-to-metal specimens. Osseointegration, defined as a direct bone-to-implant contact without interposed soft tissue, was confirmed in all screw-shaped implants while the cylindres had only partial bone contact as did the T-plates. We conclude that osseointegrated implants may be applicable in joint reconstruction for arthrosis or rheumatoid arthritis.     

A new technique for cranioplasty with L-shaped titanium plates and combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite)

OBJECTIVE: The use of hydroxyapatite-based ceramics for cranioplasties has recently increased in Japan, because of the good cosmetic outcomes, biocompatibility, strength, osteoconductive properties, and lack of risk of disease transmission associated with these materials. However, miniplate fixation has not been possible for ceramic implants. We describe a new technique for miniplate fixation of ceramic implants. METHODS: Combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite; NGK Spark Plug Co., Aichi, Japan) were used for cranioplasties. A slot and a pair of holes were cut in each Ceratite implant, for use as a fixation unit. We have also developed a new L-shaped titanium plate (HOMS Engineering Inc., Nagano, Japan) that fits into the fixation unit. We first insert an L-shaped titanium plate through the slot from the back surface of the Ceratite implant. We then bend the plate outward at the front surface of the Ceratite implant and fix it to the cranium of the patient with titanium screws. The Ceratite implant is usually firmly fixed to the cranium of the patient with three L-shaped titanium plates. RESULTS: Using L-shaped titanium plates and Ceratite implants, we successfully performed cranioplasties for seven patients with cranial defects resulting from external decompression craniotomies. The Ceratite implant exactly fit the bone window for each patient. Surgical maneuvers were simple and easy for all patients, permitting shorter operating times. All Ceratite implants were firmly fixed, and no postoperative infections have occurred. CONCLUSION: Our new technique for cranioplasty is simple and allows rigid fixation of Ceratite implants.     

Osteoplastic laminectomy using hydroxyapatite ceramic implants

Cervical osteoplastic laminectomy using ceramic or apatite beads as implants was performed in 31 patients with symptomatic cervical bony canal stenosis. Patients with degenerative changes such as osteochondrosis or disc herniation are included in this study but those with spinal cord tumor, arachnoid cyst or ossification of the posterior longitudinal ligament are not. Initially foraminotomies were performed at the C5-8 levels in an attempt at preventing worsening of radicular signs caused by posterior displacement of the cord and resultant tethering effect on the nerve root. Connecting the medial borders of the foraminotomies, laminae were removed in a single piece. A small suboccipital craniectomy and C1-2 laminectomy were added when necessary. Laminae were replaced maintaining an increased anteroposterior diameter of the bony canal, by means of interposition of apatite or ceramic beads of appropriate size between the cut surfaces of the laminae. Results were excellent in 13 (42%), good in 10 (32%), fair in 4 (13%), no change in 2 (6.5%) and worse in 2 (6.5%). Literature on the osteoplastic laminectomy (laminoplasty) for cervical canal stenosis was reviewed and the advantage of the present method was briefly discussed.     

Innovative antimicrobial coating of titanium implants with iodine

BackgroundPostoperative infection associated with implants remains a serious complication in orthopedic surgery. Several biomaterial surface treatments have been proposed as a means of reducing the incidence of implant-associated infections. In this study, a clinical trial was performed using an iodine-supported titanium that suppresses the microbial activities.MethodsA total of 222 patients with postoperative infection or compromised status were treated using iodine-supported titanium implants. The mean age of the patients was 49.4 years (range 5–85 years). One hundred twenty-seven patients were male and 95 were female. In 158 patients, iodine-supported implants were used to prevent infection, such as compromised hosts and conditions, and in 64 patients to treat active infection. White blood cell (WBCs) and C-reactive protein (CRP) levels were measured pre- and postoperatively in all patients. To confirm whether iodine from the implant affected physiological functions, thyroid hormone levels in the blood were examined. Both examinations were conducted sequentially for a year. Radiological evaluations were performed regularly after the operation. The chronological changes of the iodine amount were evaluated using half pins removed after completion of external fixation.ResultsThe mean follow-up period was 18.4 months (range 3–44 months). Acute infection developed in three tumor cases among the 158 patients on preventive therapy. All three recovered without removal of the implants. Infection was cured in all 64 patients with infection. Median WBC levels were in the normal range, and median CRP levels returned to <0.5 within 4 weeks after surgery. Abnormalities of thyroid gland function were not detected. None of the patients experienced loosening of the implants. There were two patients with mechanical implant failure, which was treated by re-implantation. Excellent bone ingrowth and ongrowth were found around all hip and tumor prostheses. One year later, the amount of iodine on external fixation pins remained about 20–30 %.ConclusionsIodine-supported titanium implants can be very effective for preventing and treating infections after orthopedic surgery. Cytotoxicity and adverse effects were not detected.     

Reconstruction of the ossicular chain with titanium implants

OBJECTIVES: Since 1994 more than 1300 titanium implants have been used to reconstruct the ossicular chain of the middle ear for chronic otitis media. Two different types of implants were used. First, a total and a partial implant of fixed length, available in numerous different lengths. And second, a total and partial implant that has an adjustable length. The implants are commercially available from 2 different companies. Patients were followed for a postoperative term from 6 to 72 months. METHODS: A wide variety of patients aged 5 to 82 years received a tympanoplasty type III. Those patients whose ossicular chain had been reconstructed with titanium implants since 1994 were evaluated. As implants from one company are fixed in length; implants of a second company are trimmable in length. All prostheses are lightweight and made of pure titanium, fitting most anatomical situations. RESULTS: Earlier results already showed a very low complication rate. Extrusions occurred only in cases of middle ear atalectasis with resorption of interposed cartilage (<1%). No adverse reaction to the prostheses could be seen, even in histologic reviews. An average air-bone gap less than 20 dB(A) for all calculated frequencies of 0.5, 1, 2, and 4 kHz was achieved for 76% of cases; 43% of cases showed a calculated air-bone gap of less than 10 dB(A), only 10% higher than 30 dB(A). CONCLUSION: All implants used offer the proven benefits of titanium, namely high biocompatibility and high stability at a very low complication rate with excellent hearing results for the patients. Titanium implants can highly be recommended to reconstruct the ossicular chain of the middle ear.     

羟基磷灰石眼台植入术后并发症及其处理

目的:预防及治疗羟基磷灰石眼台植入术后的并发症,提高手术成功率。方法:实施羟基磷灰石眼台植入术者216例,共发生9种并发症,并给予对症治疗。结果:我院216例实施羟基磷灰石眼台植入术患者,25例发生术后并发症;同时处理外院眼台植入术后并发症者15例,经再次手术均治愈。结论:在羟基磷灰石眼台植入术中采取相应的措施可以减少术后并发症的发生,正确处理术后并发症可以达到治愈的效果。     

Postmortem comparative analysis of titanium and hydroxyapatite porous-coated femoral implants retrieved from the same patient: A case study

The results of bilateral postmortem analysis of titanium and plasma-sprayed hydroxyapatite (HA) porous-coated femoral components of the same Anatomic Porous Replacement design retrieved from a 35-year-old female donor are reported. Analysis was conducted using backscattered electron imaging, histology, and radiographic techniques. The appositional bone index, percent bone ingrowth, and mineral content were measured for both implants. The results showed a 177% higher appositional bone index (P=.014) for the HA porous-coated Anatomic Porous Replacement component compared to the titanium Anatomic Porous Replacement component. Backscattered electron analysis showed 50% more bone in the HA porous-coated implant (P=.028). The mineral content analysis demonstrated that the bone ingrown into the HA porous-coated device was 23% less mineralized (P=.016). The data from this case study suggested that plasma-sprayed HA porous-coated implants may assist in increasing the amount of bone ingrowth and skeletal attachment in total hip arthroplasties.     

Comparison of porous-coated titanium femoral stems with and without hydroxyapatite coating

BACKGROUND: The purpose of this prospective, randomized study was to evaluate the clinical and radiographic results associated with proximally porous-coated titanium stems that were identical in geometry but differed with regard to proximal surface treatment (with or without hydroxyapatite coating). METHODS: A prospective, randomized study was performed to evaluate fifty patients (100 hips) who had undergone sequential bilateral primary total hip replacement. A proximally porous-coated titanium stem with hydroxyapatite coating was implanted on one side and a proximally porous-coated titanium stem without hydroxyapatite coating was implanted on the other side during the same operative setting in all fifty patients. A cementless acetabular component made of titanium was used in all hips. There were thirty-six men and fourteen women; the mean age at the time of the operation was 45.3 years. The mean duration of follow-up was 6.6 years. Clinical and radiographic evaluations were performed preoperatively; at six weeks; at three, six, and twelve months; and yearly thereafter. RESULTS: The Harris hip scores in the hydroxyapatite-coated group (mean, 94 points) and non-hydroxyapatite-coated group (mean, 92 points) were similar at the final follow-up examination. The prevalence of transient pain in the thigh was 4% in each group. No acetabular or femoral component demonstrated aseptic loosening. Bone-remodeling patterns, including calcar atrophy, were similar in the two groups. No acetabular or femoral osteolysis was seen. CONCLUSIONS: At a mean of 6.6 years postoperatively, the clinical and radiographic results associated with proximally porous-coated femoral prostheses with identical geometries that differed only with regard to the presence or absence of hydroxyapatite coating were similar.     

Influence of humate on calcium hydroxyapatite implants

Summary Implanted bovine apatite is highly osteoconductive, since it serves the host tissue as a guide-line for the deposition of newly developing bone tissue. It is well tolerated, but it showed no signs of being resorbed during the course of the experiment. Previous impregnation of the bovine hydroxyapatite with a low molecular humate substance obviously encourages its resorption. This is most easily explained by the known ability of humate to induce the activation of leucocytes. The occasional over-resorption of the apatite is dependent (1) upon the preparation of the implant (granulate) and (2) the local concentration of the humate. Future research is being directed towards the production of a satisfactorily usable form of humate and apatite and the investigation of its HIV blocking action on heterologous cancellous bone.     

Allergic potential of titanium implants

AIM: The aim of this investigation is to evaluate the allergic potential of titanium and titanium alloys for surgical implant applications. MATERIALS AND METHODS: Discs cut from rods supplied by five different titanium suppliers in several diameters were investigated. The samples were cp-Titanium as well as Ti6Al4 V and Ti6Al7Nb, 6 mm thick with a diameter of between 6 and 60 mm. The material was checked by optical spectral analysis. RESULTS: In all samples except iodidtitanium, a Nickel content of 0.012-0,034 wt% could be detected. CONCLUSION: The low nickel content in the implant material results from the production process. The nickel atoms are in solid solution in the titanium lattice. Nickel allergic patients may develop hypersensitivity reactions even due to this low nickel content. Hence, this reaction may be falsely attributed to the titanium material itself. Measurements of ion concentration in the body are helpful for quantifying the maximum content of nickel in titanium materials for surgical implant applications. In addition, technical questions related to the production of nickel free titanium materials for allergic patients have to be solved.     

Comparison of the early healing course of porous titanium with hydroxyapatite-coated porous titanium hip implants: clinical considerations for the use of hydroxyapatite coating in total hip replacement

The role of hydroxyapatite (HA) coating in the fixation of human total joint prostheses remains to be established. Results of animal studies have been favorable, showing very rapid bone formation with a corresponding increase in bone-implant bond strength. In addition, the quantity of bone may be increased. This study compared identical porous titanium primary total hip implants with and without HA in similar patient populations. All of these patients were healthy and reliable, and had optimal bone geometry and bone quality for cementless fixation. The purpose of the study was to contrast the sequence of events, in the first year after surgery, between the two implant groups to identify the contribution of HA to early patient function and early radiographic appearance of the prosthesis. No significant clinical difference could be demonstrated between the two groups at 1 year from surgery. However, the HA group progressed more rapidly when comparing clinical scores at 6 months (P = .0058), and appeared to demonstrate more rapid bone remodeling at 6 months on the femoral side, although this observation did not quite make statistical significance (P = .0618). There was no difference between the acetabular components during the course of this study.     

Sinuscopy in patients with titanium implants in the nose and sinuses

Foreign bodies in the nose and sinuses can cause chronic infections. Long titanium fixtures through the maxilla to the zygomatic bone were followed up with a sinuscope in 14 patients after more than one year. There were no signs of infection or inflammation in the mucosa around the fixtures.     

A prospective randomized study comparing electrochemically deposited hydroxyapatite and plasma-sprayed hydroxyapatite on titanium stems

Background and purpose

Plasma-sprayed hydroxyapatite (HA) is a successful coating for fixation of uncemented femoral stems. There may be alternative coatings with advantages in bone remodeling and transport of bone-active substances. We investigated whether an electrochemically deposited hydroxyapatite, Bonemaster (BM), might be a safe alternative in total hip arthroplasty. Our hypothesis was that the new coating would not be inferior to the conventional one.

Patients and methods

50 patients (55 hips) were included. The stem was tapered and porous-coated proximally. On top of the porous coating was either HA or BM. Patients were evaluated postoperatively and after 3, 6, 12, and 24 months to measure fixation by radiostereometric analysis (RSA), bone mineral density by dual-energy X-ray absorptiometry (DXA), and conventional radiography. Clinical evaluation was performed with Harris hip score and Oxford hip score, both preoperatively and after 2 years.

Results

After 2 years, the stems had subsided 0.25 (HA) and 0.28 (BM) mm and there were no statistically significant differences between the groups in any direction, regarding both migration and rotation. The BM group retained significantly more bone than the HA group in Gruen zone 1 during the first 2 years. The Harris and Oxford hip scores were similar in both groups.

Interpretation

Electrochemically deposited hydroxyapatite on an uncemented stem does not appear to be inferior to plasma-sprayed HA regarding clinical and radiological results, bone remodeling, and micromotion after 2 years follow-up.Aseptic loosening is the most frequent complication of total hip arthroplasty (THA) (Havelin et al. 2000). The long-term survival is thought to depend partly on bone loss or osteolysis in the proximal femur after insertion. Plasma-sprayed hydroxyapatite (HA) coatings appear to give effective fixation in the femur (Hallan et al. 2007). Alternative coatings may, however, influence bone remodeling around the prosthesis and may function as a carrier of bone-active substances.Bonemaster (BM) (Bonemaster is a registered trademark of Biomet Europe) is an electrochemically deposited hydroxyapatite (EDHA) coating (Rößler et al. 2002). This technique makes it possible to add biological substrates such as antibiotics or adhesion peptides to the coating and still keep the coating very thin compared to plasma-sprayed HA.The thickness of a hydroxyapatite coating is a compromise between the mechanical properties and dissolution of the coating. A thinner coating minimizes the potential of particle shedding during insertion. Fewer particles in the joint mean less third-body wear and less periprosthetic osteolysis (Peters et al. 1992, Shanbhag et al. 1994, Campbell et al. 1995, McKellop et al. 1995). Thinner coatings also lower the risk of HA delamination and preserve the porosity of the underlying metallic coating of the implant. The irregular implant surface increases the surface area, providing a greater contact and ingrowth area (Sewing et al. 2002). EDHA, as in Bonemaster, forms a needle-like porous structure (Rößler et al. 2001) and enhances early-stage fixation between implant and bone (Ban et al. 1997).We designed a prospective randomized trial to compare conventional plasma-sprayed HA with electrochemically deposited HA after insertion of an uncemented femoral stem. This is the first clinical trial with the Bonemaster coating. We hypothesized that implants with Bonemaster would achieve the same degree of stability and bone remodeling, and the same clinical outcome as implants with traditionally plasma-sprayed HA.