Comparison of the long-term clinical performance of a biodegradable and a titanium fixation system in maxillofacial surgery: A multicenter randomized controlled trial

BACKGROUND

Biodegradable fixation systems could reduce or eliminate problems associated with titanium removal of implants in a second operation.

AIM

The aim of this study was to compare the long-term (i.e. >5 years postoperatively) clinical performance of a titanium and a biodegradable system in oral and maxillofacial surgery.

MATERIALS AND METHODS

The present multicenter Randomized Controlled Trial (RCT) was performed in four hospitals in the Netherlands. Patients treated with a bilateral sagittal split osteotomy (BSSO) and/or a Le Fort-I osteotomy, and those treated for fractures of the mandible, maxilla, or zygoma were included from December 2006 to July 2009. The patients were randomly assigned to either a titanium (KLS Martin) or a biodegradable group (Inion CPS).

RESULTS

After >5 years postoperatively, plate removal was performed in 22 of the 134 (16.4%) patients treated with titanium and in 23 of the 87 (26.4%) patients treated with the biodegradable system (P = 0.036, hazard ratio (HR) biodegradable (95% CI) = 2.0 (1.05-3.8), HR titanium = 1). Occlusion, VAS pain scores, and MFIQ showed good and (almost) pain free mandibular function in both groups.

CONCLUSION

In conclusion, the performance of the Inion CPS biodegradable system was inferior compared to the KLS Martin titanium system regarding plate/screws removal in the abovementioned surgical procedures.

TRIAL REGISTRATION

http://controlled-trials.com ISRCTN44212338.

Comparative animal study on hard tissue integration and bone formation of different Nobel Biocare implants

Dental implantation aims at optimal and long-term hard tissue integration. Beside primary stability, loading time and other factors, e.g. the surface of the endosteal part of the implant, is a matter of special importance. In this animal trial, hard tissue integration of two different implant types was studied using radiological, histological and histomorphometric analysis. Two different implants with an oxidized surface (TiUnite; Nobel Biocare AB, Goteborg, Sweden, NobelReplace Tapered Groovy 4.3 x 10 mm and Replace Select Tapered 4.3 x 10 mm) were inserted into the right and left mandibles of 10 German domestic pigs between canine and premolar and immediately provided with a ceramic crown. The primary implant stability was determined using resonance frequency analysis. After 70 days, the test animals were killed and specimens were collected for histological and histomorphometric examination. All implants showed good primary stability after surgery. Histological and histomorphometrical analysis revealed no significant differences in the bone apposition. The immediate loading of the different implant types don't have any negative effects on the bone apposition in the period of 70 days. The long-term effects of immediate loading of these types of implant requires further studies.

Fracture of Ni-Ti superelastic alloy under sustained tensile load in physiological saline solution containing hydrogen peroxide

The fracture of Ni-Ti superelastic alloy has been investigated by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide (0.15M NaCl + 0.3M H(2)O(2)). The fracture always occurs when the applied stress exceeds the critical stress for martensite transformation. In contrast, under a low applied stress, the fracture does not always occur within 1000 h. The fracture is probably mainly caused by localized corrosion associated with the preferential dissolution of nickel ions. In 0.3M H(2)O(2) solution without NaCl, the fracture does not occur even under a high applied stress. The results of the present study imply that one reason for the fracture of the Ni-Ti superelastic alloy in vivo is localized corrosion due to the synergistic effects of hydrogen peroxide and sodium chloride under applied stress.

Anterior cervical fusion with interbody titanium cage containing surgical bone site graft: our institution's experience in 103 consecutive cases of degenerative spondylosis

The objective of this study is to evaluate whether anterior cervical fusion performed using BAK-C cage is a safe and effective method in the treatment of degenerative cervical disorders. Between 1998 and 2001, a consecutive series of 103 patients underwent anterior cervical fusion with titanium cage for cervical radiculopathy and/or spondylotic myelopathy. All the patients underwent single-level surgery. The mean follow-up period was 4.8 years. Results were evaluated on the basis of Nurick scale, JOA classification, patient satisfaction, fusion status, and degree of cervical lordosis. Patients are seen postoperatively at 2, 12 months, and annually. At the last follow-up the patient satisfaction rate was excellent in 83% of the patients, good in 12%, fair in 3%, and poor in 1%. A solid fusion was achieved in 98.9% of the patients. Preoperative lordosis was maintained in 93.8% of the patients and increased in 6.2%. This study suggests that BAK-C system filled with autologous bone graft for anterior cervical fusion is a safe and effective method, with a good rate of fusion, very high rate of patient satisfaction, and satisfactory clinical outcome.

Interspinous process devices in the lumbar spine

A growing number of interspinous process devices have been introduced to the lumbar spine implant market. Implant designs vary from static spacers to dynamized devices. Furthermore, they are composed of a range of different materials including bone allograft, titanium, polyetheretherketone, and elastomeric compounds. The common link between them is the mechanical goal of distracting the spinous processes to affect the intervertebral relationship. In contrast, the purported clinical goals are more variable, ranging from treatment of degenerative spinal stenosis, discogenic low back pain, facet syndrome, disk herniations, and instability. Though some clinical data exist for some of these devices, defining the indications for these minimally invasive procedures will be crucial. Indications should emerge from thoughtful consideration of data from randomized controlled studies.

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs

This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following manufacturers: (1) Morelli®, (2) Abzil®, (3) TP Orthodontics® and (4) American Orthodontics®. The specimens were extended to twice their original length and stored in artificial saliva at 37°C. Initial force was measured by means of an Instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. The results revealed that the elastomeric chains delivered a mean initial force of 347 g for Morelli®, 351 g for American Orthodontics®, 402 g for Abzil®, and 404 g for TP Orthodontics®. The NiTi closed coil springs generated a mean initial force of 196 g for American Orthodontics®, 208 g for TP Orthodontics®, 216 g for Abzil®, and 223 g for Morelli®. The mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for TP Orthodontics®, 48.1% for American Orthodontics®, 65.4% for Morelli®, and 71.6% for Abzil®. After 28 days, the NiTi closed coil springs presented a mean percentage of force decay of 22.6% for American Orthodontics®, 29.8% for Abzil®, 30.6% for Morelli®, and 45.8% for TP Orthodontics®. At the end of the study, significant differences were observed between the elastomeric chains and the NiTi closed coil springs. The results indicated that the studied NiTi closed coil springs are more adequate for dental movement than the elastomeric chains.

Titanium versus stainless steel for anterior spinal fusions: an analysis of rod stress as a predictor of rod breakage during physiologic loading in a bovine model

STUDY DESIGN

In vitro biomechanical evaluation of rod stress during physiologic loading of anterior scoliosis instrumentation.

OBJECTIVES

To determine effects of material properties and rod diameter on rod stresses in anterior scoliosis instrumentation.

SUMMARY OF BACKGROUND DATA

Relationships between instrumentation dimensions, materials, and potential rod failure in anterior scoliosis instrumentation remain unclear.

METHODS

Eighteen immature bovine spines were randomized to 3 groups: 1) 4.0-mm stainless steel, 2) 5.0-mm stainless steel, and 3) 4.75-mm titanium alloy. Spines underwent physiologic tests in flexion-extension, lateral bending, and torsion. Rod surface strains were converted to rod stress and normalized to each material's yield stress. Construct stiffness and the normalized rod stresses were compared with a one-way ANOVA (P < 0.05).

RESULTS

The 4.0-mm steel and 4.75-mm titanium construct stiffness was similar across all tests. The 5.0-mm steel system was significantly stiffer than 4.0-mm steel (lateral bending/torsion) and 4.75-mm titanium (torsion/flexion) constructs. Rod surface stress was significantly lower for the 4.75-mm titanium rod compared with 4.0-mm and 5.0-mm steel rods for all tests.

CONCLUSIONS

The percentage of yield stress was lowest for the 4.75-mm Ti rod for all tests due to titanium's greater yield stress. This suggests the 4.75-mm rod has a lower fatigue failure risk than either steel construct.

Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA

The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using (45)Sc(p, n)(45)Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 degrees to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres.

Characterisation of kilo electron volt neutron fluence standard with the 45Sc(p,n)45Ti reaction at NMIJ

We are developing a national standard of a monoenergetic kilo electron volt neutron field with the (45)Sc(p,n)(45)Ti resonance reaction. A wide resonance yields 27.4 keV neutrons at 0 degrees with respect to the proton beam. The proton energy was precisely determined in the measurement of the relative neutron yield as a function of the proton energy from the threshold energy to 2.942 MeV. Absolute measurement of the monoenergetic neutron fluence was performed using a (3)He proportional counter. Relative measurement was also carried out using a Bonner sphere calibrated at our 144 keV standard neutron field. Calibration factors were obtained between the count of a neutron monitor and the neutron fluence. A silicon-surface barrier detector with a (6)LiF foil converter was also being developed for the neutron fluence measurement. Successful results were obtained in the tests in the 144 keV standard neutron field.

Hydroxyapatite dip coated and uncoated titanium poly-axial pedicle screws: an in vivo bovine model

STUDY DESIGN

A 1-year-old calf was implanted with titanium pedicle screws either uncoated (n = 7) or coated with hydroxyapatite (n = 7) by the dipping method on the pedicles of vertebrae (t10-l3).

OBJECTIVE

To evaluate biomechanical and histomorphologic responses to titanium pedicle screws uncoated and coated with hydroxyapatite.

SUMMARY OF BACKGROUND DATA

Failure of fixation caused by loosening of pedicle screws is a problem in spinal surgery. Enhancement of the fixation ability of screws by coating with biocompatible materials may improve prognosis of surgery.

METHODS

The calf was euthanized 4 months after implantation for determination of insertion and extraction torques for screws, and histologic and scanning electron microscopic examinations of areas screw embedded.

RESULTS

Insertion torques did not differ by the kind of screws (99 +/- 5.7 Ncm). However, extraction torques for screws coated with hydroxyapatite were higher than for screws uncoated (249 vs. 133 Ncm, P < 0.01). As compared with uncoated screws, implanted areas for hydroxyapatite-coated screws were denser, had more cracks, and provided better bonding. Fibrous tissue and new bone formation were observed around the areas of uncoated and hydroxyapatite-coated screws embedded, respectively.

CONCLUSIONS

Hydroxyapatite coating of titanium pedicle screws by the dipping method improved fixation and vertebral bone-implant interface, suggesting a decreased risk of a screw-loosening problem.

An evaluation of the quality of root fillings in mandibular incisors and maxillary and mandibular canines using different methodologies

OBJECTIVES

To evaluate the quality of root fillings in mandibular incisors and maxillary and mandibular canines using different methodologies of evaluation, namely radiographs, the fluid transport test and the percentage of gutta-percha (PGP), and to determine if a correlation occurs between the results of the different methodologies used.

METHODS

One group of mandibular incisors with oval canals (n=20) and one group of maxillary and mandibular canines (n=20) were instrumented and obturated by cold lateral compaction using AH 26 as the sealer. The filled roots were bucco-lingually and mesio-distally radiographed. Using a scoring system, the quality of each root filling was radiographically evaluated, the higher the score the poorer the quality. Fluid transport along the root filling was then measured using a fluid transportation device. Each root was horizontally sectioned 4 and 6mm from the apex. Images of the cross-sections were taken, using a microscope and a digital camera. Images were scanned into a PC as TIFF images. Using a KS 100 Imaging system the canal area and the gutta-percha filled areas were measured. The percentage of gutta-percha filled areas was calculated.

RESULTS

Considering the radiographic scores of the two different projections together the score was significantly higher for the mandibular incisors than for the canines (P=0.039). The radiographic score was significantly higher for the mesio-distal radiograph in comparison with the bucco-lingual radiograph (P=0.0001), for the canines as well as the incisors. Using only the bucco-lingual radiograph there was no significant difference between the mandibular incisors and the canines (P=0.992). The mandibular incisors displayed significantly more fluid transport than the canines (P=0.049). A significantly greater percentage of gutta-percha filled areas was found in the cross-sections of canines as compared to the cross-sections of mandibular incisors (P=0.000001). The correlation between the radiographic score of the mesio-distal radiograph and the PGP 4 and 6mm was significant (P=0.013). There was no significant correlation between the FT and the radiograph or the FT and the PGP.

CONCLUSIONS

The quality of the root fillings in oval canal-mandibular incisors may be compromised.

Biomechanical comparison of stainless steel and titanium nails for fixation of simulated femoral fractures

Flexible intramedullary nails are commonly used to treat femoral fractures in children. This study evaluated the biomechanical differences between stainless steel and titanium nails when securing transverse and comminuted fractures in a synthetic femur model. Retrograde flexible stainless steel and titanium nails placed in a divergent "C" pattern were mechanically tested, and axial rotation and compression stiffness were analyzed with a two-way ANOVA. Rotational stability was significantly greater for titanium nails than stainless steel nails for both fracture patterns. Axial compression stiffness was significantly greater for titanium nails than stainless steel nails for both fracture patterns. There was no statistical difference between materials for axial "failure" load that produced 5 mm of shortening. Titanium intramedullary nails were more stable than stainless steel nails in torsion and axial compression. Both materials stabilized simulated fractures at levels beyond physiologic non-weight-bearing loads without permanent deformation.

The memory properties of cold-worked titanium rods in scoliosis constructs

STUDY DESIGN

Time series monitoring changes in titanium and stainless steel rod curvature kept at a constant temperature of 37 C as a function of time.

OBJECTIVES

To assess the possibility of loss of curvature in titanium rods after scoliosis surgery.

SUMMARY OF BACKGROUND DATA

Titanium rods have gained use in scoliosis surgery due to their excellent biocompatibility, while allowing medical personnel to obtain undistorted magnetic resonance imaging scans following surgery. However, the impression of several clinicians has been that when screw pullout and/or loss of sagittal balance occurs, it may be due to the rods losing some of their curvature.

METHODS

Five 6-mm rods of differing compositions and lengths (titanium 300 and 100 mm, stainless steel 300 and 100 mm, prebent titanium 85 mm) were bent at room temperature with a 3-point rod bender, then placed in an incubator at 37 C. Digital photographs were taken every 2 weeks and analyzed to extract the radius of curvature of each rod.

RESULTS

The Ti rods had a significantly decreasing curvature with time. The prebent Ti and stainless steel rods did not exhibit significant change in curvature.

CONCLUSIONS

Titanium rods bent at room temperature and then exposed to body temperature over time tend to exhibit "metal memory"; they gradually revert to their original shape. This may result in loss of sagittal balance and/or proximal screw pullout.

Restpartikelfreie raue Oberflächen nach Stahldrahtkornstrahlen in der Hüftendoprothetik / Residual particle free rough surfaces after rough blasting with steel grit in total hip arthroplasty

INTRODUCTION

Several shot peening and grit blasting techniques are used to modify the surface in the production of hip endoprostheses. A number of publications in maxillo- facial- surgery and orthopedic surgery demonstrated significant contamination on alumina blasted surfaces. Latest research studies suspected an association between surface contamination and early failure of endoprostheses associated with third body wear. Additionally, the European standard EN 12010 requires surfaces free of residual particles. The aim of this study is to evaluate the effects of rough blasting using steel grit followed by a pH dependent cleaning procedures with regard to complying with EN 12010.

MATERIAL AND METHOD

Ti6Al7Nb rods were rough blasted 1 time using steel grit ("Stahldrahtkorn", hardness: 56 HRC; R+K Draht GmbH, Leisnig). All blasting procedures were carried out with a special grit blasting device with direct pressure. One Ti6Al7Nb rod each was grit blasted with 3 and 4 bar pressure and 10 rods with 5 bar pressure. Surface roughness was measured by means of Mitutoyo- Surftest 301 three times before and after grit blasting. The mean value was calculated. A field emission scanning electron microscopy (SEM, LEO 1525) was used for the detection of residual particles on the surface of the rods with a backscattered electron detector.

RESULTS

By rough blasting using steel grit a mean roughness of 54,9 microm and a maximum roughness of 61,4 microm could be achieved. The surface of all rods showed a considerable contamination with steel particles after grit blasting. After the a pH- dependent cleaning procedure a residual particle free surface was detected in all samples.

DISCUSSION

The European standard EN 12010 can be fulfilled using rough blasting with steel grit followed by a pH dependent cleaning procedure.

Weld characteristics of orthodontic archwire materials

Welding attachments to archwires can produce change in their physical as well as mechanical properties. This study evaluated three archwire alloy materials-stainless steel, Beta titanium, and Timolium for their weld characteristics. The study was divided into tensile-shear test using instron universal testing machine, surface evaluation with the help of scanning electron microscope, and metallographic examination with optical microscope. Six specimens were used for evaluation of each parameter. Increased strength in tensile-shear test and smooth surface and characteristic nugget formation in scanning and optical micrographs, respectively, clearly indicated superior weld characteristics for Beta titanium alloys when compared with the other two archwire alloys. Stainless steel was found to be intermediate in nature, whereas Timolium exhibited poor weld characteristics.

Reconstruction of a large post-traumatic cranial defect with a customized titanium plaque

The treatment of serious cranial defects has always been a fascinating and controversial issue for craniofacial surgeons and in the last years many solutions have been proposed. One of the most effective method is a personalized titanium plaque prepared by processing anatomical data obtained with a CAT of the patient. A case of wide cranial defect on the left fronto-parietal region in a 56-year-old man treated with a personalized titanium plaque obtained by processing the data of a spiral CAT of the skull is described. No complications were observed in the postoperative course and follow-up after 6 moths showed that the patient was in good general condition.

Titanium cages in the surgical treatment of severe vertebral osteomyelitis

The role of spinal implants in the presence of infection is critically discussed. In this study 20 patients with destructive vertebral osteomyelitis were surgically treated with one-stage posterior instrumentation and fusion and anterior debridement, decompression and anterior column reconstruction using an expandable titanium cage filled with morsellised autologous bone graft. The patients' records and radiographs were retrospectively analysed and follow-up clinical and radiographic data obtained. At a mean follow-up of 23 months (range 12-56 months) all cages were radiographically fused and all infections eradicated. There were no cases of cage dislocation, migration or subsidence. Local kyphosis was corrected from 9.2 degrees (range -20 degrees to 64 degrees ) by 9.4 degrees to -0.2 degrees (range -32 degrees to 40 degrees ) postoperatively and lost 0.9 degrees during follow-up. All five patients with preoperative neurological deficits improved to Frankel score D or E. Patient-perceived disability caused by back pain averaged 7.9 (range 0-22) in the Roland-Morris score at follow-up. In cases of vertebral osteomyelitis with severe anterior column destruction the use of titanium cages in combination with posterior instrumentation is effective and safe and offers a good alternative to structural bone grafts. Further follow-up is necessary to confirm these early results.

Surface hardening by anodizing and heat treatments of Ti6Al4V alloys for articular prostheses

This paper presents a study of the surface hardening of Ti6Al4V alloy produced by electrochemical anodizing and by different heat treatments, in addition to studying the annealing of the martensitic structure. Results of the combination of both methods produce hardening over 1300 HV and an important improvement on the tribological behaviour. These values could improve wear resistance of this alloy in applications like articular prostheses.

Titanium applications in dentistry

BACKGROUND

The ADA Council on Scientific Affairs outlines the status of titanium and titanium alloys used in dentistry and provides its recommendations concerning their use in clinical practice.

CONCLUSIONS

Titanium and titanium alloys, based on their physical and chemical properties, appear to be especially suitable for dental implants and prostheses. For the construction of endosseous implant devices, titanium and its alloys have become well-accepted and can be considered the materials of choice.

CLINICAL IMPLICATIONS

For crown and bridge prostheses, dentists can consider titanium and its alloys as viable options to more traditional noble and base metal alloys, but careful selection of processing methods and laboratory skill are necessary to ensure success.

Bone histomorphometric evaluation of a clinically fused titanium tumour cage in a child

An intervertebral titanium tumour cage was implanted in a 2-year-old-girl after T11 spondylectomy due to Ewing sarcoma. After 2-years' follow-up without evidence of recurrence, the titanium cage was explanted to correct spinal deformity and to allow normal spinal growth development. Radiological follow-up and surgical exploration at the time of retrieval suggested fusion of the segment. Histologic evaluation, however, demonstrated ingrowth of trabecular bone, but without bridging trabecular bone. The distance between the opposing bone fronts measured 1.5 mm and the viable bone volume (BV/TV) within the cage was 36%. Histologic evaluation demonstrated that bone formation was still an ongoing process in the fusion zone 2 years after implantation.

Pedicle screws with high electrical resistance: a potential source of error with stimulus-evoked EMG

STUDY DESIGN

Clinically relevant aspects of pedicle screws were subjected to electrical resistance testing.

OBJECTIVES

To catalog commonly used pedicle screws in terms of electrical resistance, and to determine whether polyaxial-type pedicle screws have the potential to create a high-resistance circuit during stimulus-evoked electromyographic testing.

SUMMARY OF BACKGROUND DATA

Although stimulus-evoked electromyography is commonly used to confirm the accuracy of pedicle screw placement, no studies have documented the electrical resistance of commonly used pedicle screws.

METHODS

Resistance measurements were obtained from eight pedicle screw varieties (5 screws of each type) across the screw shank and between the shank and regions of the screw that would be clinically accessible to stimulus-evoked electromyographic testing with a screw implanted in a pedicle. To determine measurement variability, resistance was measured three times at each site and with the crown of the polyaxial-type screw in three random positions.

RESULTS

Resistance across the screw shank ranged from 0 to 36.4 ohms, whereas resistance across the length of the monoaxial-type screws ranged from 0.1 to 31.8 ohms. Resistance between the hexagonal port and shank of polyaxial-type screws ranged from 0 to 25 ohms. In contrast, resistance between the mobile crown and shank of polyaxial-type screws varied widely, ranging from 0.1 ohms to an open circuit (no electrical conduction). Polyaxial-type screws demonstrated an open circuit in 28 of 75 measurements (37%) and a high-resistance circuit (exceeding 1000 ohms) in 5 of 75 measurements (7%).

CONCLUSIONS

Polyaxial-type pedicle screws have the potential for high electrical resistance between the mobile crown and shank, and therefore may fail to demonstrate an electromyographic response during stimulus-evoked electromyographic testing in the setting of a pedicle breech. To avoid false-negative stimulus-evoked electromyographic testing, the cathode stimulator probe should be applied to the hexagonal port or directly to the screw shank, and not to the mobile crown.

Initial contact angle measurements on variously treated dental/medical titanium materials

The cell attachment to bioapplicable titanium surfaces is an important parameter in the area of clinical implant dentistry and medicine. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues contacting the implants. In this study, three titanium materials (commercially pure titanium - CPT -, Ti-6Al-4V, and TiNi) were treated mechanically, chemically, mechano-chemically, and thermally to produce concave surfaces with varying roughness. Using four media (distilled water, 1% NaCl aqueous solution, a suspension of human neutrophils, and a suspension of the MG-63 osteoblast-like cells), the initial contact angles were measured. Six readings (three drops each measured by two observers) were collected for each material and for each medium. The interclass correlation coefficients were used for the group comparisons. A one-way analysis of variance (ANOVA) and Tukey's HSD (honestly significant difference) statistical analyses were employed. It was found, for CPT, that (1) statistically, there were no significant differences among four media in contact angles, (2) the contact angle increased linearly with average roughness when the angles were higher than 45 degrees, and (3) the contact angle decreased linearly with roughness when the angle was less than 45 degrees.

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.

Failures of pin removal after in situ pinning of slipped capital femoral epiphyses: a comparison of different pin types

We reviewed 75 pin retrievals after in situ pinning of 35 children with slipped capital femoral epiphysis (SCFE). Four types of pins were used. Ten pins in 8 hips could not be removed because of pin breakage or stripping. Our failure rate was significantly related to pin type and size (p less than 0.039). As compared with the expected values using the chi-square method of analysis, the noncannulated large steel pins and cannulated steel pin groups had fewer failures (p less than 0.001) as compared with the cannulated titanium and noncannulated small steel pin groups. We now avoid using cannulated titanium or noncannulated small pins in treatment of SCFE.

Three-dimensional motion analysis with Synex. Comparative biomechanical test series with a new vertebral body replacement for the thoracolumbar spine

The authors present a new implant for vertebral body replacement in the thoracic and lumbar spine. Synex is a titanium implant designated for reconstruction of the anterior column in injury, post-traumatic kyphosis or tumour of the thoracolumbar spine and must be supplemented by a stabilizing implant. After positioning, the implant is distracted in situ, thus ensuring best contact with adjacent end-plates and three-dimensional (3D) stability, and minimizing the possibility of secondary dislocation or loss of correction. We compared the effectiveness of the Synex implant with that of the "Harms cage" (MOSS) in combination with two alternative stabilizing instrumentations: the USS and Ventrofix. In a 3D spinal loading simulator, we determined the bisegmental (T12-L2) neutral zone (NZ), elastic zone (EZ), and range of motion (ROM) of 12 human cadaveric spines. After corpectomy of L1, we tested the four possible combinations of stabilizing instrumentation and vertebral replacement implant: USS/Synex, USS/MOSS, Ventrofix/Synex, Ventrofix/MOSS. We analysed the differences between each of the instrumentations as well as differences compared to the intact spine. Comparing the two stabilizing implants, a significantly higher stability was achieved with the USS for flexion, extension, and lateral bending, regardless of whether Synex or MOSS was used as vertebral body replacement. No differences were observed for axial rotation. In addition, no implant combination was able to restore the rotational stability of the intact spine. Comparing the vertebral body replacing implants, significantly higher stability was noted with Synex in combination with USS for extension, lateral bending, and axial rotation. No differences between Synex and MOSS were observed in combination with Ventrofix. Posterior fixation was found to offer superior stability compared to anterior fixation. Synex was at least comparable to MOSS for suspensory replacement of the vertebral body in the thoracolumbar spine. The increased biomechanical stability demonstrated for Synex suggests that a more rigid construction would also be achieved in vivo. When using MOSS in combination with posterior stabilization, the induction of intervertebral compression via the posterior fixator is recommended. This surgical step was not necessary with Synex.

Plate fixation of prostheses after segmental resection for bone tumours

This study investigated the concept of using plates to attach endoprostheses to bone after segmental resection for bone tumours in an animal model. Titanium alloy plates integrated with the prosthesis and coated with hydroxyapatite were attached to bone by screws. This type of uncemented fixation relied on the induction of periosteal bone formation into and around the plates to secure the implant to bone. Two, three, and six-slotted plate designs were investigated. On retrieval, each plate was securely fixed by new bone. Bone apposition on the external surface of the plates occurred through a combination of periosteal bone production, invasion of bone through slots in the plate, and bone growth over the ends of the plates. Most plates became incorporated into a remodelled cortex. Higher bone turnover rates (microm day(-1)) were seen in bone in the slots of the plate compared with normal cortical bone turnover (p < 0.05). Significantly higher rates of turnover were measured beneath slotted parts of the plates compared with regions below the unslotted parts (p < 0.05). The cross-sectional area of bone surrounding the six-plate implant design was significantly higher than that of the three-plate (p < 0.05) and two-plate (p < 0.05) designs. In addition, significantly more bone formed adjacent to the six-plated implant design compared with that in the contralateral limb (p = 0.002). However, no significant difference was found when the total cortical area around the three-plated design was compared with that of the contralateral limb (p = 0.63). In contrast, significantly less bone was measured adjacent to the two-plate design than in the untreated limb (p = 0.001). Image analysis also demonstrated increased cortical porosity adjacent to the six-plate design compared with the three-plate (p = 0.004) and two-plate (p < 0.05) designs. Finite element analysis demonstrated that the six and three-plate designs increased the second moment of area compared with that in the left tibia (p = 0.003 and 0.066, respectively). However, the attachment of the more flexible two-plate design did not significantly increase the second moment of area compared with that in the contralateral limb (p = 0.235). It was concluded that due to both mechanical and biological effects, the hydroxyapatite-coated plate designs generated new bone that enhanced fixation and encouraged plate integration into the load-bearing structure of the cortex. This method of fixation may be an alternative to the use of intramedullary cemented stems in patients requiring bone tumour implants and may be the only way to preserve the joint in difficult cases where only short segments of bone remain.

Sliding wear studies of selected nitride coatings and their potential for long-term use in orthopaedic applications

In the area of orthopaedic implants, particularly total hip joint replacements, a metal-plastic combination is still the most popular choice consisting of a femoral head fabricated from 316L stainless steel, Ti alloy or Co-Cr alloy in contact with an ultra-high molecular weight polyethylene (UHMWPD) acetabular cup. It is recently considered that wear of the UHMWPE cup is of major concern. Generation of the wear debris can have adverse effects on the body, both localized and systemic. It is envisaged that wear of the prosthetic components, particularly those fabricated from UHMWPE can be reduced through the use of surface coatings. The aim of this investigation was to deposit a selection of refractory element nitride-based coatings (TiN, TiA1N, ZrN) onto 316L stainless steel substrates, using physical vapour deposition (PVD) technology and to study their sliding wear behaviour in contact with both UHMWPE and 316L stainless steel pins, using a pin-on-plate testing rig. Tests were conducted in Ringers solution and Ringers solution plus bone cement particles. The volume of material removed from the pins served as an indication of their wear behaviour. Wear mechanisms were identified using scanning electron microscopy. The results of these findings and the potential for these coatings to be used in orthopaedic applications are discussed.

Finite element analysis of anterior cervical spine interbody fusion

The present study investigated the external and the internal biomechanical responses of anterior cervical discectomy coupled with fusion. Five different types of interbody fusion materials were used: titanium core, titanium cage, tricortical iliac crest, tantalum core, and tantalum cage. Two different types of surgical procedures were analyzed: Smith-Robinson and Bailey-Badgley. A validated three-dimensional anatomically accurate finite element model of the human cervical spine was used in the study. The finite element model was exercised in compression, flexion, extension, and lateral bending for the intact case and for the two surgical procedures with five implant materials. The external response in terms of the stiffness and angular rotation, and the internal response in terms of the disc and the vertebral stresses were determined. The Smith-Robinson technique resulted in the highest increase in external response under all modes of loading for all implant materials. In contrast, the Bailey-Badgley technique produced a higher increase in the disc and the vertebral body stresses than the Smith-Robinson technique. As experimental human cadaver tests can only determine the external response of the non-fused spine simulating immediate post-operative structure, the present finite element studies assist in the understanding of biomechanics of interbody fusion by delineating the changes in the extrinsic and intrinsic characteristics of the cervical spine components due to surgery.

New titanium alloys for biomaterials: a study of mechanical and corrosion properties and cytotoxicity

Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.

Fracture analysis of cast pure Ti and Ti-6Al-4V alloy for dental use

The fracture behavior of cast two types of pure Ti and Ti-6Al-4V alloy was understood by acoustic emission (AE) analysis during a fracture toughness test. Specimens for test were cast by the lost wax method using a specially designed Ti casting machine of pressure-different method for dental use. A fatigue crack was inserted from the machined notch tip into the body of a specimen in the range of 0.45-0.55 a/W. Acoustic emission signals released during the fracture toughness test were detected by two sensors attached to both ends of the specimen. Then the signals were recorded and analysed by the PAC 3000/3104 system. From the early stage of the fracture toughness test, AE signals started to be released in all types of specimens tested. A reaction layer with the investment materials of about 50-100 microns was thought to be the result of the AE release from an early stage of the fracture toughness test. A microfracture behavior of the cast pure Ti and Ti alloys was proposed based on the results obtained from the AE releasing pattern and fracture surface findings.

Biodegradable and titanium plating in experimental craniotomies: a radiographic follow-up study

Plain film radiography and computed tomography (CT) were evaluated in assessing the consolidation of experimental craniotomy lines covered with titanium miniplates or biodegradable self-reinforced poly-L-lactide (SR-PLLA) plates. Two sagittal (2.3-2.5 mm wide and 22 mm long) symmetrical craniotomy lines were made in the skulls of eight young sheep. One craniotomy line was covered with a biodegradable SR-PLLA plate and the other with a titanium miniplate. Both plates were fixed with four titanium miniscrews. Consolidation of the osteotomies was studied using plain film radiography and CT 6, 12, 20, and 52 weeks postoperatively. Microradiography and histology were used for reference. Plain film was not reliable in assessing osseous consolidation because false-positive results were obtained in three osteotomies. Osseous consolidation was more reliably assessed by CT, which showed consolidation on the SR-PLLA side within 20 weeks, whereas none of the titanium-plated lines was consolidated by 52 weeks. Superior consolidation under the resorbable plate was confirmed in histology and microradiography. The radiolucent SR-PLLA plates did not interfere with CT, whereas the titanium plates caused minor CT artifacts.

The prevention of prosthetic infection using a cross-linked albumin coating in a rabbit model

We evaluated the effects of a serum protein coating on prosthetic infection in 29 adult male rabbits divided into three groups: control, albumin-coated and uncoated. We used 34 grit-blasted, commercially pure titanium implants. Eleven were coated with cross-linked albumin. All the implants were exposed to a suspension of Staphylococcus epidermidis before implantation. Our findings showed that albumin-coated implants had a much lower infection rate (27%) than the uncoated implants (62%). This may be a useful method of reducing the infection of prostheses.

A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns

The in vitro marginal fit of three all-ceramic crown systems (In-Ceram, Procera, and IPS Empress) was compared. All crown systems were significantly different from each other at P = 0.05. In-Ceram exhibited the greatest marginal discrepancy (161 microns), followed by Procera (83 microns), and IPS Empress (63 microns). There were no significant differences among the various stages of the crown fabrication: core fabrication, porcelain veneering, and glazing. The facial and lingual margins exhibited significantly larger marginal discrepancies than the mesial and distal margins.

Improved fixation of porous-coated versus grit-blasted surface texture of hydroxyapatite-coated implants in dogs

We inserted, in 8 dogs, implants with either porous-coated or grit-blasted titanium surface and coated with hydroxyapatite (HA) into trabecular bone in the proximal humerus, using a 1 mm gap model. After 25 weeks, push-out tests showed that energy absorption for porous-coated implants was twice that of grit-blasted implants, whereas shear stiffness was reduced by one fifth, indicating a stronger fixation of porous-coated implants. Macroscopically, all grit-blasted implants had delamination of the HA coating, whereas porous implants failed mostly at the HA-tissue interface. Porous-coated implants had 47% bone ingrowth and grit-blasted implants 70% (p = 0.02), however, no difference in absolute surface area was found. Part of the HA coating was resorbed during the implantation period as regards volume and thickness. HA coverage was more reduced on porous-coated than on grit-blasted implants (p = 0.01). No foreign-body reaction or osteolysis was seen. An important finding was that one fifth of the surface with complete resorption of HA coating was replaced by newly formed bone.

Cora rotary pump for implantable left ventricular assist device: biomaterial aspects

Our group is developing a left ventricular assist device based on the principle of the Maillard-Wankel rotative compressor: it is a rotary, not centrifugal, pump that produces a pulsatile flow. Stringent requirements have been defined for construction materials. They must be light, yet sufficiently hard and rigid, and able to be machined with high precision. The friction coefficient must be low and the wear resistance high. The materials must be chemically inert and not deformable. Also, the materials must be biocompatible, and the blood contacting surface must be hemocompatible. We assessed the materials in terms of physiochemistry, mechanics, and tribology to select the best for hemocompatibility (determined by studies of protein adsorption; platelet, leukocyte, and red cell retention; and hemolysis, among other measurements) and biocompatibility (determined by measurement of complement activation and toxicity, among other criteria). Of the materials tested, for short- and middle-term assistance, we chose titanium alloy (Ti6Al4V) and alumina ceramic (Al2O3) and for long-term and permanent use, composite materials (TiN coating on graphite). We saw that the polishing process of the substrate must be improved. For the future, the best coating material would be diamond-like carbon (DLC) or crystalline diamond coating.

Development of a titanium alloy suitable for an optimized coating with hydroxyapatite

By means of the metallurgical method of alloying, the thermal expansion coefficient of commercially pure titanium was adapted to that of hydroxyapatite (HA) in order to produce a tailored composite material with a maximum adhesion strength of HA to the metallic material. The alloying element chosen was manganese, which is an important trace element in the human organism. With the alloy TiMn6 a good compromise concerning the expansion coefficient, the mechanical properties and the biocompatible behaviour was found. With this alloy coatings with an extremely high adhesion strength could be produced, especially when the sol-gel process was used for HA precipitation. In addition, these layers fulfil the requirements of favourable thin coatings according to theoretical considerations.

Synthesis of bioactive coatings on Ti substrates using glass enamel

Bioactive coatings on titanium can be prepared by dispersing hydroxyapatite particles into a borosilicate glass enamel doped with TiO2. Adhesion of the coating is obtained when the titanium substrate has been preoxidized before enameling in such a way as to form a continuous TiO2-layer. Adhesion results from the diffusion of this TiO2-layer into the liquid glass during enameling. The evolution of the diffusion zone was followed by scanning electron microscopy and electron probe microanalysis. Adhesion disappears after a critical time of firing which corresponds to the completion of the dissolution of the TiO2-layer by the glass. The borosilicate glass wets the hydroxyapatite particles and adheres strongly to them after cooling.

[Application of titanium-nitride coatings in dentistry]

Titanium and its alloys are increasingly important in dentistry. Thin titanium-nitride (Ti-N) coatings improve the properties of metallic material for industrial purposes. Recently Ti-N coatings have been advocated in dentistry. In a survey of literature aspects of biological, mechanical and corrosive behaviour are assessed. Moreover, specific problems for clinical application are indicated. It is concluded that as long as the integrity of the Ti-N coating is not guaranteed under critical conditions one should be cautious with its clinical application. By no means it can be used for improvement of deficient dental alloys.

Evaluations of catalysts for wet oxidation waste management in CELSS

A wet oxidation is considered to be one of the most effective methods of waste processing and recycling in CELSS (Controlled Ecological Life Support System). The first test using rabbit waste as raw material was conducted under a decomposition temperature of 280 degrees C for 30 minutes and an initial pure oxygen pressure of 4.9 MPa (50 kgf/cm2) before heating, and the following results were obtained. The value of COD (Chemical Oxygen Demand) was reduced 82.5% by the wet oxidation. And also the Kjeldahl nitrogen concentration was decreased 98.8%. However, the organic carbon compound in the residual solution was almost acetic acid and ammonia was produced. In order to activate the oxidation more strongly, the second tests using catalysts such as Pd, Ru and Ru+Rh were conducted. As the results of these tests, the effectiveness of catalysts for oxidizing raw material was shown as follows: COD and the Kjeldahl nitrogen values were drastically decreased 99.65% and 99.88%, respectively. Furthermore, the quantity of acetic acid and ammonia were reduced considerably. On the other hand, nitrate was showed a value 30 times as much as without catalytic oxidation.

Laparoscopic clips. Evaluation of absorbable and titanium with regard to hemostasis and tissue reactivity

Advanced laparoscopic techniques require laparoscopic means of providing hemostasis. We tested the hemostatic ability of laparoscopic surgical clips and their tissue reactivity as assessed by adhesion formation in an animal model. Twenty-six New Zealand white rabbits were randomized at laparotomy to one of three treatment groups: titanium surgical clips, absorbable surgical clips (both applied with a laparoscopic clip applicator) and chromic sutures of equal mass. Either the right fallopian tube was transected, with clips or sutures applied proximally and distally to control bleeding, or the clips or sutures were applied 5 mm apart and the tube transected. A clip or suture of the same material was placed on the midportion of the left fallopian tube. Necropsy was performed at 42 days, and each clip/suture site was scored for adhesions. All the materials were easily applied and effective in achieving hemostasis. The adhesion scores tended to be lower with the absorbable clips; however, there were no statistically significant differences between the groups. Laparoscopic clips are effective in providing hemostasis, are easily applied and cause no more adhesion formation than do conventional suture materials.

An analysis of the changes in the surfaces of metallic femoral components in hip prostheses. A study of 60 prostheses removed after 1-20 years

A study of 60 femoral prosthetic components removed after 1-20 years allowed us to study the behaviour of the metallic surface in real life conditions. Changes were observed exclusively in cemented prostheses. They consisted of corrosion phenomena characteristic of the components of steel EN 58 J and 316 S, and wear phenomena secondary to mobilisation. The latter were observed in steel components as well as in those in Co-Cr alloy. The areas of corrosion in the steel prostheses were characteristically distributed, indicating a combination of causal factors, including an insufficient capacity of passivation of the metal and the particular situation of the cement-to-metal interface.