Injury of ~(125)Ⅰ seeds implants to trachea and esophagus of rabbits

Objective To evaluate the impact of 1125 seeds para-tracheal braehytherapy on regional tissue injury in rab-bit models. Methods 42 rabbits were randomized into 7 groups. Group 1 to 6 belong to study groups (in which 1,4,5 and 6 belong to "dose gradient" subgroup, while 2,3 and 4 to "chronologic" subgroup) , while the last group acts as negative con-trol. The activity of seeds in study group were 0.3 mCi in group 1, 0.5 mCi in group 2 to 5, 0.7 mCi in group 5, and 0.9mCi in group 6. False seeds (0 mCi) were used for the negative control. 4 seeds with equal dosage were implanted between trachea and esophagus in each rabbit under general anesthesia. Seeds arrangement was made according to Paris principle. For the tissue injury evaluation, group 2 was sacrificed by the end of first month post-operatively, group 3 at the end of the second month, and group 4 end of the third month. The rest of rabbits were also sacrificed at the end of the third month. Pieces of adjacent e-sophagus and trachea were sampled from each rabbit. Tissue injury features such as inflammation, edema, congestion or fibrosis as evaluated histologically. Results All rabbits were healthy during study period except 5. Histological analysis revealed that trachea samples from all groups had lymphocytas and plasma cells infiltration as signs of chronic inflammation, hut fibrosis was nut clearly visible. There were no differences between study and control groups with respect to inflammation, edema and con-gestion scores. But in groups which received the highest doses of radiation or sacrificed at 60 d showed more eosinophil infiltra-tion and epithelum degeneration, and statistical significance was reached between these groups and control. Esophageal samples had less histological changes compared with trachea. Conclusion Para-tracheal implantation of ~(125)Ⅰ seeds with therapeutic or higher dosage only induce minor and reversible damage to the regional tissue. This implies that ~(125)Ⅰ implants adjacent to trachea or esophagus are clinically safe.     

Injury of ~(125)Ⅰ seeds implants to trachea and esophagus of rabbits

Objective To evaluate the impact of 1125 seeds para-tracheal braehytherapy on regional tissue injury in rab-bit models. Methods 42 rabbits were randomized into 7 groups. Group 1 to 6 belong to study groups (in which 1,4,5 and 6 belong to "dose gradient" subgroup, while 2,3 and 4 to "chronologic" subgroup) , while the last group acts as negative con-trol. The activity of seeds in study group were 0.3 mCi in group 1, 0.5 mCi in group 2 to 5, 0.7 mCi in group 5, and 0.9mCi in group 6. False seeds (0 mCi) were used for the negative control. 4 seeds with equal dosage were implanted between trachea and esophagus in each rabbit under general anesthesia. Seeds arrangement was made according to Paris principle. For the tissue injury evaluation, group 2 was sacrificed by the end of first month post-operatively, group 3 at the end of the second month, and group 4 end of the third month. The rest of rabbits were also sacrificed at the end of the third month. Pieces of adjacent e-sophagus and trachea were sampled from each rabbit. Tissue injury features such as inflammation, edema, congestion or fibrosis as evaluated histologically. Results All rabbits were healthy during study period except 5. Histological analysis revealed that trachea samples from all groups had lymphocytas and plasma cells infiltration as signs of chronic inflammation, hut fibrosis was nut clearly visible. There were no differences between study and control groups with respect to inflammation, edema and con-gestion scores. But in groups which received the highest doses of radiation or sacrificed at 60 d showed more eosinophil infiltra-tion and epithelum degeneration, and statistical significance was reached between these groups and control. Esophageal samples had less histological changes compared with trachea. Conclusion Para-tracheal implantation of ~(125)Ⅰ seeds with therapeutic or higher dosage only induce minor and reversible damage to the regional tissue. This implies that ~(125)Ⅰ implants adjacent to trachea or esophagus are clinically safe.     

Alkaline biodegradable implants for osteoporotic bone defects—importance of microenvironment pH

Summary

Change of microenvironment pH by biodegradable implants may ameliorate unbalanced osteoporotic bone remodeling. The present work demonstrated that a weak alkaline condition stimulated osteoblasts differentiation while suppressed osteoclast generation. In vivo, implants with an alkaline microenvironment pH (monitored by a pH microelectrode) exhibited a promising healing effect for the repair of osteoporotic bone defects.

Introduction

Under osteoporotic conditions, the response of the bone microenvironment to an endosseous implant is significantly impaired, and this substantially increases the risk of fracture, non-union and aseptic implant loosening. Acid-base equilibrium is an important factor influencing bone cell behaviour. The present purpose was to study the effect of a series of alkaline biodegradable implant materials on regeneration of osteoporotic bone defect, monitoring the microenvironment pH (μe-pH) over time.

Methods

The proliferation and differentiation potential of osteoporotic rat bone marrow stromal cells and RAW 264.7 cells were examined under various pH conditions. Ovariectomized rat bone defects were filled with specific biodegradable materials, and μe-pH was measured by pH microelectrode. New osteoid and tartrate-resistant acid phosphatase-positive osteoclast-like cells were examined by Goldner’s trichrome and TRAP staining, respectively. The intermediate layer between implants and new bone were studied using energy-dispersive X-ray spectroscopy (EDX) linear scanning.

Results

In vitro, weak alkaline conditions stimulated osteoporotic rat bone marrow stromal cells (oBMSC) differentiation, while inhibiting the formation of osteoclasts. In vivo, μe-pH differs from that of the homogeneous peripheral blood and exhibits variations over time particular to each material. Higher initial μe-pH was associated with more new bone formation, late response of TRAP-positive osteoclast-like cells and the development of an intermediate ‘apatitic’ layer in vivo. EDX suggested that residual material may influence μe-pH even 9 weeks post-surgery.

Conclusion

The pH microelectrode is suitable for in vivo μe-pH detection. Alkaline biodegradable materials generate an in vivo microenvironmental pH which is higher than the normal physiological value and show promising healing effects in the context of osteoporotic bone defects.

     

Errors of computer-assisted migration analysis in conventional radiographs of femoral hip implants – an experimental study

Several methods have been described in the literature in order to analyze migration of femoral hip implants in conventional radiographs. However, no measurements were done regarding the potential errors inherent in such unstandardized radiographs of daily routine. In order to quantify this lack of reproducibility, we carried out experimental examinations with radiographs of a hip revision prosthesis, where different variables of technical X-ray conditions and femoral positions were changed. All radiographs were analyzed with a computer-assisted processing system by different procedures. At first, the radiographs were calibrated geometrically. Then, particular reference distances between defined points of the implant and cortical bone structures were analyzed quantitatively. The error of the axial migration analysis was up to 11.11 mm concerning different femoral positions, up to 8.29 mm in the case of different source-to-film distances and up to 2.21 mm due to different lateral localizations of the central X-ray focus. Significant errors for the migration analysis in the transverse and rotational planes were only found under conditions of varying the femoral position, and not under different technical X-ray conditions. From these experimental results, we derived the following criteria to minimize failure in a quantitative radiographic migration analysis: (1) the patient’s leg has to be placed into an antirotation device to ensure identical object position; (2) the same source-to-film distance has to be used; (3) the central X-ray focus has to be localized on the center of the film-cassette; (4) film-screen systems should be of the same type and size; (5) the object has to be placed in the same position as in previous radiographs. As a conclusion, only if these standardization criteria are respected in the daily routine of conventional radiographs will an effective and meaningful use of migration analysis systems be possible to prove or to exclude mechanical failure of femoral hip implants in prospective longitudinal follow-up series. Received: 19 May 1998     

Should the galvanic combination of titanium and stainless steel surgical implants be avoided?

It is recommended that one should not combine different metals in orthopaedic devices. The least noble metal in such a galvanic coupling is more likely to corrode. However, some studies have failed to show increased corrosion when titanium and stainless steel are combined. The aim of this study was to determine the fretting corrosion of the contact areas between screws and plates made of these dissimilar metals used for internal fixation of bone fractures. The plates were fixed to a bone-simulating material and subjected to tensile and compressive forces in both human serum and Hank's solution. The outcome variables included in the analyses were weight loss, and release of Ti, Cr, Ni and Mo to the different media. Results from the multiple combinations were subjected to multivariate statistics. Principal component analysis visualised our findings and allowed classification of similar samples and separation of discrepant groups of samples. We found a significant effect of the test medium, but no dramatic effect due to mixing of metals. The titanium screws and plates corroded more in serum than in saline, while the opposite was true for stainless steel. Combination of dissimilar screws and plates did not cause higher weight loss or metal release than the single-material constructions, indicating comparable clinical safety.     

Correction of Poland’s syndrome in a male with solid chest wall implants

In the past, breast implantation for men was limited to transsexuals. Recently, more men have requested an adequate chest wall symmetry and an increase of chest size, particularly in the area of the pectoralis major muscle. This has lead to the development of pectoralis implants. This paper describes the surgical technique and possible complications of the correction of the chest wall deformity in Poland’s syndrome with solid silicone implants. These implants can either be custom made, using a moulage technique, or can be obtained as pre-fabricated, manufactured implants, which can be modified on the operating table. This method, with the appropriate indications, gives good predictable long term results. Received: 24 March 1998 / Accepted: 17 November 1998     

Did we push dental ceramics too far? A brief history of ceramic dental implants

Humankind has developed and used ceramics throughout history. It currently has widespread industrial applications. Dental ceramics are used for fabricating highly esthetic prosthetic denture teeth, crowns, and inlays. However, ceramic's biocompatibility and compressive strength are offset by its hardness and brittleness. Nonetheless, a single crystal sapphire aluminum oxide endosseous implant was developed in 1972 as an alternative to metal. It was more esthetic than its metallic counterparts and was eventually produced in a variety of shapes and sizes. Clinical studies demonstrated its excellent soft and hard tissue biocompatibility, yet the range of problems included fractures during surgery, fractures after loading, mobility, infection, pain, bone loss, and lack of osseointegration. Ultimately, single crystal sapphire implants fell into irredeemable disfavor because of its poor impact strength, and dentists and surgeons eventually turned to other implant materials. However, bioactive ceramic coatings on metal implants have kept ceramics as a key component in dental implantology.     

Are triglyceride breast implants really biocompatible?

A case of augmentation mammaplasty with triglyceride implants is presented. Histological examination of the capsules 3 years postimplantation showed retained, irregular, refractile yellow-brown fragments embedded in granulomatous tissue.     

Compressive osseointegration promotes viable bone at the endoprosthetic interface: retrieval study of Compress® implants

The Compress implant (Biomet, Warsaw, IN) is an innovative device developed to enable massive endoprosthetic fixation through the application of compressive forces at the bone-implant interface. This design provides immediate, stable anchorage and helps to avoid the long-term complication of aseptic loosening secondary to stress shielding and particle-induced osteolysis seen in conventional, stemmed megaprostheses. The purpose of our study was to evaluate the in vivo biological effects of the high compressive forces attained. Twelve consecutive Compress patients undergoing revision surgery for infection, periprosthetic fracture, or local tumour recurrence were reviewed in order to exclude the possibility of osteonecrosis at the prosthetic interface. Compressive forces ranged from 400-800 lb. Duration of implantation averaged 3.3 years (range 0.4-12.2 years). Two patients with infection demonstrated loosening at the bone-prosthetic interface; otherwise, there was no radiographic evidence of prosthetic failure in any of the patients. No patient demonstrated histological evidence of osteonecrosis. In fact, new woven bone and other findings consistent with viable bone were noted in all of the retrieved specimens.     

Internal fixation on the lower cervical spine – biomechanics and clinical practice of procedures and implants

The decision to opt for a particular internal fixation procedure of a traumatized unstable lower cervical spine should be based on analysis and implementation of scientific and clinical data on the biomechanics of the intact, the unstable and the implant-fixed spine. The following recommendations for surgical stabilization of the lower cervical spine seem, therefore, to be justified. Firstly, the surgical procedure should be to bring about decompression, realignment, and stability. Secondly, the anterior approach should be the primary and preferred one. With regard to surgical and positioning technique, this access clearly involves fewer problems than the posterior approach; if required, unrestricted additional cord decompression can take place; implant fixation is technically simple, and the fusion is under direct compression, thus allowing optimal fusion healing. The awareness of instability and type of implant permits functional therapy, above all for the paraplegic patient. Thirdly, for traumatic conditions, posterior methods should be reserved for exceptional indications. The restriction to this approach is that the anterior column must be intact and a multi-segmental fixation must be used. Posterior fixation seems, therefore, to be more appropriate for degenerative, rheumatoid or tumorous instabilities than for traumatic instabilities. The cerclage wire technique depends on intact osseous posterior elements, while after laminectomy only implants fixed with screws can create safe stability. The disadvantages of the posterior access for the proprioception of the cervical muscles and the subjective symptoms of the patient are known and must be taken into account. Fourthly, combined techniques are indicated for highly unstable or particularly complex injuries. On the cervicothoracic junction, or in cases of Bechterew's disease, the decision is justifiably made in favor of this technique, which can be performed as a one-stage or two-stage operation. Finally, whenever possible, selection of the implant should take into account the foreseeable developments in diagnostic procedures, and therefore, in view of the modern imaging techniques likely to be used in any follow-up examinations required later, the implant chosen should be made of titanium.     

The bovine bone protein lyophilisate Colloss improves fixation of allografted implants—an experimental study in dogs

Background?Impacted morselized bone allograft is a well-established way of giving joint arthroplasties additional support in situations where there is insufficient bone stock. For long-term survival of the implant, early implant fixation is important. We hypothesized that Col-loss, a bone protein lyophilisate, might improve early implant fixation of allografted implants.

Method?We inserted 4 porous-coated Ti implants in the distal femurs of 16 dogs. All implants were surrounded by a 2.5-mm gap, which was impacted with morselized allograft with or without Colloss. In each dog, the implants were treated with no Collos or low-, middle- or high-dose (0, 10, 20 and 40 mg) Colloss per cm³ allograft. The observation time was 4 weeks.

Results?Mechanical implant fixation was improved for all 3 groups with Colloss-treated implants (p < 0.05). The best anchorage was seen in the middle-dose group, where fixation was improved by 100%. We saw a dramatic reduction in fibrous tissue on the surface of the Colloss-treated implants (p < 0.001). The Colloss groups showed increased ongrowth of new bone (p < 0.01) and accelerated gap remodeling (p < 0.05).

Interpretation?Colloss can improve early osseointegration and fixation of allografted implants.     

Smooth or textured implants: what to select?

Envelope structure has evolved since the seventies. Indeed, low-bleed implants allow an important reduction of capsular contracture for silicone filled implants. Later, textured implants permit an additional reduction of capsular contracture, especially when positioned in a retroglandular pocket. Whereas many studies confirm these findings, the interest of textured implants in the retromuscular plane is not really clear, even if some authors recommend it. Due to the need of a tissular anchorage, anatomical implants are not manufactured with smooth envelopes.