Absorbable collagen implants and encircling elements in retinal detachment surgery.
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Absorption↗
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Impact of the use of absorbable fracture fixation implants on consumption of hospital resources and economic costs.
Within a 6-year period (1984-1989) absorbable pins, rods, and screws made of polyglycolide, polylactide, or lactide-glycolide copolymer were used in the internal fixation of 881 fractures, 73.1% of which were displaced malleolar fractures of the ankle. During the last 3 years the patients treated using absorbable fracture fixation constituted 19.6% of all fracture patients managed by internal fixation at the department. The number of hardware removal procedures avoided during the 6-year period as a result of the use of the absorbable implants was estimated at approximately 700. By determining all direct and indirect costs associated with internal fracture fixation and the influence of the percentage of hardware removal, a cost coefficient was calculated for certain fracture types when treated using absorbable versus metallic internal fixation. In bimalleolar fractures, an optimal indication for absorbable fixation, the coefficient was 1.04 (cost of absorbable fixation 4% higher than that of metallic fixation) if the removal percentage with metallic fixation was zero and 0.91 (cost of absorbable fixation 9% lower than that of metallic fixation) if the removal percentage was 100%. The breakeven point was a removal rate of 31%.
Absorption↗
Bone regeneration with recombinant human bone morphogenetic protein-2 (rhBMP-2) using absorbable collagen sponges (ACS): influence of processing on ACS characteristics and formulation.
The effects of variability in three parameters (mass, cross-linking with CH2O, and EtO sterilization) of three surgically implantable absorbable collagen sponges (ACS) were studied. Sponges soaked with recombinant human bone morphogenetic protein-2 (rhBMP-2) solution were analyzed for pH, conductivity, and rhBMP-2 precipitation. A method using trinitrobenzenesulfonic acid was developed to quantify the free amino groups of the collagen sponge. With up to 240 min exposure to CH2O, the amount of free amino groups was reduced to 80%. In comparison, the denaturation temperature as determined by differential scanning calorimetry (DSC) after the sponges were soaked with phosphate-buffered saline, increased from 48 to 55 degrees C, indicating stronger interactions due to cross-linking. Subsequent sterilization with EtO caused a marked decrease in the amount of free amino groups (approximately 33% of nonsterilized controls) independent of previous CH2O treatment. However, the denaturation temperature was on average 5 degrees C lower in sterilized sponges than in nonsterilized material. In contrast to CH2O exposure, the strong reaction with EtO appeared to weaken the collagen structure. Resistance of the sponge to collagenase correlated with the degree of collagen cross-linking but was slightly reduced by sterilization. In addition, the pH of ACS soaked with water was substantially increased by sterilization. Protein precipitation was a function of pH and salt concentration but there was no effect due to collagen alone. Results indicated that ACS weight has to be limited to avoid rhBMP-2 precipitation.
Absorbable Implants↗
Effects of bacterial infection on absorbable vascular ligating clips.
Electron microscopic observations of two implanted absorbable clips, Absolok and Lactomer, infected with Escherichia coli and Streptococcus faecalis, were carried out. An overgrowth of bacteria was observed over the entire surface of the clips. The mating surfaces of the Lactomer clips and the locking mechanisms of both types of clip were more heavily infected--that is, provided better support for bacterial growth--than other areas of the clips in the initial postimplantation period. However, with longer periods (up to seven days), the initial bacterial deposits developed into a thick, plaquelike layer. This layer appeared to restrict access to the surfaces such that the infected clips degraded at a much slower rate than did the noninfected clips, particularly Lactomer clips, on which little morphologic change was detectable seven days after implantation.
Animals↗
[The use of bioresorbable implants (Biofix) in surgery. The indications, technic and initial clinical results].
Carrying out osteosyntheses with absorbable implants is a dream cherished by traumatologists for a long time. The absorbable rods available on the medical market comply within narrow ranges with the necessary conditions with regard to stability, absorption time and biocompatibility. In our clinical department 38 osteosyntheses with Biofix rods were performed. The complication rate amounted to 13%-5 abacterial disturbances of wound healing and secretions. The indications assured so far are limited to refixation of chondral and osteochondral fragments as well as the fixation of cortical-cancellous bone grafts.
Absorption↗
Bioresorbable implants: applications in orthopaedic surgery.
There are several new and potential uses for absorbable implants. Some will provide exciting options in the future. Ongoing animal and clinical studies will help focus future areas of development.
Adult↗
Guided bone regeneration for dehiscence and fenestration defects on implants using an absorbable polymer barrier.
BACKGROUND: Guided bone regeneration (GBR) using a non-absorbable barrier has provided clinicians the ability to place implants in sites compromised by insufficient bone, including immediate extraction sites. Recent evidence suggests that successful GBR outcomes may be possible using bioabsorbable polymer barriers. METHODS: This report presents a case series of 9 patients with 8 fenestration and 3 dehiscence defects on implants consecutively treated with GBR. A bioabsorbable polymer barrier of poly(DL-lactide) was used in conjunction with a composite graft of freeze-dried bone allograft (FDBA)/demineralized freeze-dried bone allograft (DFDBA) mixed in a ratio of 1:1. Second-stage surgeries were performed at 4 to 8.5 months (5. 7 months average) post-placement. Biopsy material from 2 sites was obtained while exposing the implant for healing abutment connection. RESULTS: Ten of the 11 defects (90.9%) achieved complete coverage of the osseous defects. Histologic evaluations revealed the formation of viable bone, frequently in close amalgamation with residual graft particles. CONCLUSION: These case reports suggest that a poly(DL-lactide) polymer can be used as a physical barrier with a composite bone replacement graft to achieve successful GBR results of dehiscence/fenestration defects when placing implants.
Absorbable Implants↗
Six bioabsorbable polymers: in vitro acute toxicity of accumulated degradation products.
Bioabsorbable polymer implants may provide a viable alternative to metal implants for internal fracture fixation. One of the potential difficulties with absorbable implants is the possible toxicity of the polymeric degradation products especially if they accumulate and become concentrated. Accordingly, material evaluation must involve dose-response toxicity data as well as mechanical properties and degradation rates. In this study the toxicity and rates of degradation for six polymers were determined, along with the toxicity of their degradation product components. The polymers studied were poly(glycolic acid) (PGA), two samples of poly(L-lactic acid) (PLA) having different molecular weights, poly(ortho ester) (POE), poly(epsilon-caprolactone) (PCL), and poly(hydroxy butyrate valerate) (5% valerate) (PHBV). Polymeric specimens were incubated at 37 degrees C in 0.05 M Tris buffer (pH 7.4 at 37 degrees C) and sterile deionized water. The solutions were not changed during the incubation intervals, providing a worst-case model of the effects of accumulation of degradation products. The pH and acute toxicity of the incubation solutions and the mass loss and logarithmic viscosity number of the polymer samples were measured at 10 days, 4, 8, 12, and 16 weeks. Toxicity was measured using a bioluminescent bacteria, acute toxicity assay system. The acute toxicity of pure PGA, PLA, POE, and PCL degradation product components was also determined. Degradation products for PHBV were not tested. PGA incubation solutions were toxic at 10 days and at all following intervals. The lower molecular weight PLA incubation solutions were not toxic in buffer but were toxic by 4 weeks in water.(ABSTRACT TRUNCATED AT 250 WORDS)
Biodegradation, Environmental↗
[Resorbable implants and their use exemplified by fracture of the head of the radius].
First a short survey of the variety of experiments concerning absorbable implants is given. The result of those experiments, especially with large implants are still quite unsatisfactory. For small osteosynthesis the development of Polydioxanon-Pins seems to open new perspectives of therapy. Also some selected indications in the field of hand surgery as well as maxillary surgery are mentioned. Promising characteristics of PDS-Pins, such as gentle application, complete absorbability, no late infections and no removal of metal plates, made us implant these pins in eight patients aged 35 to 58 suffering from radial head fractures (type Ib and Ic according to Vogt). Early functional treatment showed very good results. Two exemplary cases are illustrated.
Female↗
Assessment of osteogenic potential of the natural origin bioceramics implanted into the human infrabony periodontal defects.
The osteogenic potential of natural origin bioceramics implanted in human periodontal infrabony defects was investigated Histologic and electron-microscopic analyses of implants 3 and 4.5 months after implantation were used for the estimation of osteogenic potential. Results show that the bioceramics of natural origin with a microstructure and canalicular system of the natural bone has a strong osteogenic potential. Results of histologic and electron-microscopic analyses, performed four and half months after implantation, show that new bone has been formed in the places of absorbed or partially absorbed implant granules as also in the pores of implant granules. Histological structure of the newly-formed bone correspond to the structure of the matured lamellated bone.
Biocompatible Materials↗
Restoration of tissue components after insertion of absorbable fracture fixation devices of polyglycolide through the articular surface: an experimental study in the distal rabbit femur.
Absorbable implants for fracture fixation do not require a secondary removal procedure, a fact that could make them particularly suitable for intra-articular fixation, provided the degree of regeneration of the articular surface is acceptable. To determine the restoration pattern in distal rabbit femurs after the intra-articular insertion of absorbable fixation devices, polyglycolide pins and screws were implanted through the articular surface of the intercondylar portion of the bone in adult animals. The polymer was known to have a degradation time of approximately 20 weeks. At follow-up times of 3-48 weeks, the restoration of the tissue components was examined histomorphometrically and microradiographically. The intact contralateral femur served as an internal control. The first signs of degradation of the implants were seen at 6 weeks. The mean fractional osteoid formation surface of the bone trabeculae within the sample fields showed significantly increased values until 6 weeks but thereafter approached the level of the control femur. In the 36-week and 48-week specimens, the polyglycolide had been absorbed and the intra-articular entrance of the implant channel had become filled either with firm whitish tissue resembling mature articular cartilage or with soft undifferentiated mesenchymal tissue only. Good restoration of the trabecular bone architecture corresponding to the original subchondral bone was a prerequisite for the regeneration of the articular cartilage. The causes of the dichotomous pattern of restoration could not be identified, but possibly it represented a normal biologic variation.(ABSTRACT TRUNCATED AT 250 WORDS)
Absorption↗
Biodegradable implants as intramedullary nails. A survey of recent studies and an introduction to their use.
The high stiffness of metallic implants often requires a removal of the implant through a second operation, after fracture healing has occurred, to prevent disuse osteoporosis from occurring. An absorbable implant, lending sufficient strength and stiffness for support of the fracture during the healing period, would then gradually decay, and shift acting forces over to the healing bone. This paper presents a background to the development of such an implant of self-reinforced polylactic acid, and some recent results from different studies using these rod shaped implants for intramedullary nailing of both experimental and clinical fractures on animals. A short description of the operational technique for use of these implants is also given.
Animals↗
Retinal circulatory changes after scleral buckling procedures.
The noninvasive laser Doppler technique was used to study retinal circulatory characteristics in five patients who underwent uncomplicated scleral buckling procedures. In each patient, the systolic/diastolic variation of the red blood cell speed in the retinal arteries (flow pulsatility ratio) was lower in the eye that had received an intrascleral implant and an encircling band than in the fellow eye. In one patient, an increase in flow pulsatility ratio accompanied an increase in retinal blood flow after removal of the scleral buckling elements. In another patient, the flow pulsatility ratio in the eye that had received a solid implant and an encircling band was less than the ratio in the fellow eye that had received an absorbable implant alone. Our results indicated that reduced retinal blood flow may be common after scleral buckling procedures, and may be a significant factor in otherwise inexplicable postoperative complications.
Adult↗
Swelling of collagen intracanalicular implants.
BACKGROUND: Absorbable intracanalicular collagen implants are used to attempt to determine if permanent closure of the tear drainage system will diminish or alleviate the signs and symptoms of dryness. The rate of swelling of the collagen implants was measured in vitro in this study. METHODS: Collagen implants were submersed in saline, Refresh Plus artificial tears or Tobrex antibiotic solution on a hanging drop microscope slide. The diameter of the collagen rod was measured over time using videotaping and image processing. RESULTS: The 0.3- and 0.4-mm diameter collagen implants swelled approximately 55% to 65% in Unisol 4 Preservative Free saline and Refresh Plus artificial tear solution, with the majority of the swelling occurring over the first 30 minutes. The 0.4-mm diameter implants took slightly longer to reach the fully swollen state than did the 0.3-mm implants. They swelled somewhat less in Tobrex Ophthalmic Solution. CONCLUSIONS: Collagen implants swell approximately 60%, with the majority of the swelling occurring in the first 30 minutes. Thus, it will take approximately 30 minutes after insertion of the implants for the full occlusive effect to occur.
Anti-Bacterial Agents↗
Enhanced activity of lysosomal beta-galactosidase after silicone implantation: an experimental study in rats.
Biologic consequences of silicone implantation may include changes in host connective tissue metabolism. Lysosomal beta-galactosidase (beta-GAL) activity, which is a sensitive marker of fibrotic diseases and may be a useful marker of collagen turnover, was examined in the serum of rats with implanted silicones. No significant difference in spectrofluorometrically determined enzyme activity was demonstrated in rats subjected to dorsal submuscular pocket dissection without implantation and corresponding nonoperative controls. Rats with implanted solid silicone elastomer or free polydimethylsiloxane gel (both components obtained from mammary implant) revealed enhanced activity of serum beta-GAL. Higher enzyme activity was observed in animals with implanted silicone gel with a peak level of 2.73 +/- 0.08 pmol/30 min/ml 16 weeks after implantation. Increased collagen deposition and capsular thickness was demonstrated around implanted gel material as compared with that around elastomer shell. Animals with implanted absorbable and nonabsorbable materials, polyglactin and Teflon (polytetrafluoroethylene), respectively, after initial increase of beta-GAL activity demonstrated enzyme activity within the normal range. Findings indicate that there is enhanced lysosomal beta-GAL activity after silicone implantation in rats. Clinical relevance and its possible significance as a predictor or indicator of local or systemic fibrosis after silicone implantation seems worthy of further investigation.
Animals↗
Defining the heating characteristics of ferromagnetic implants using calorimetry.
The induction heating of small, cylindrical ferromagnetic implants for localized tumors is currently under investigation. These thermal rods are implanted within a lesion in 1 cm(2) arrays and subsequently exposed to an externally applied alternating magnetic field. Implants absorb energy from the field and transfer it as heat to the surrounding tissue. To achieve a uniform temperature rise throughout the tissue volume and to account for any field-rod misalignment, 400 mW of power per implant is used as the design specification. The temperature to necrose cells must be greater than 46 degrees C. A calorimeter was constructed to confirm that the rod power output specification is satisfied at temperatures adequate for inducing cell death. The rods were designed to undergo a ferromagnetic to paramagnetic transition at temperatures of 55 degrees C, 60 degrees C, 65 degrees C, and 70 degrees C; this transition produces rods that are temperature self-regulating. Calorimetric results demonstrated that 55 degrees C, 60 degrees C, 65 degrees C, and 70 degrees C rods provided 400 mW at 47-51 degrees C, 51-53.5 degrees C, 57 degrees C, and 62.5-63.5 degrees C, respectively. Thermal rods provide sufficient power output at the temperatures necessary to cause thermal ablation of tumors. The higher-temperature rods give a greater margin to ensure that necrotizing temperatures can be achieved throughout the rod array even with minor misalignment.
Algorithms↗
Thermodifferential analysis of ceramic implants.
Ceramic pelletes (in Al2O3 92% and in calcium aluminate) implanted into the muscles of rabbits for varying periods of time, and samples of similar material, not implanted but mixed with organic substances, have been analyzed by means of thermal differential analysis (TDA). Which hydrated calcium aluminates are formed from implants after contract with the tissue fluid, has been established. It has also been ascertained that the ceramic implants absorb organic substances from the tissue fluid, which, from a first evaluation, seem to be composed of simple molecules. The results of this initial inquiry have provided positive indications of the utility of TDA to assist in elucidating the phenomena that occur between implant and tissue.
Absorption↗
An in vivo analysis of an elliptical dental implant design.
The interface attachment strength and histology of an elliptical hydroxylapatite-coated (HA) endosseous dental implant were compared with those of an otherwise identical cylindrical dental implant. The implant designs were tested in two canine in vivo models: healed mandibular extraction sites and the femoral unicortical plug. The implants were evaluated 15 weeks post-implantation. The elliptical geometry of the dental implant was not found significantly to enhance axial pull-out strength or torsional implant-bone interface attachment in either in vivo model. The cylindrical implant absorbed more energy to failure in both the mandible and the femur; however, the difference was not statistically significant. Differences in the interface shear attachment strength between the two models (mandible and femur) were statistically significant when the maximum load to failure was normalized by the actual bone contact surface area. In all cases, femoral values were significantly greater. Examination of HA-coating thickness revealed uniform coatings on both implant types which were well maintained in vivo. Mechanical failure occurred primarily at the metal substrate-HA interface in each type of implant in both models. The amounts of bone apposition to both implants in both models were identical. Coating break-up and inflammatory response to the particulate debris were minimal.
Analysis of Variance↗