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PubMed1994

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↗
PubMed1989

[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↗
PubMedDate not supplied

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↗
PubMed1994

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↗
PubMed1992

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↗
PubMed1983

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↗
PubMed2006

High rate of fusion in sheep cervical spines following anterior interbody surgery with absorbable and nonabsorbable implant devices.

STUDY DESIGN: Fourteen sheep were fused using anterior interbody implants at C2-C3 and C4-C5 and followed for 6 months. OBJECTIVE: To evaluate the effect of absorbable and nonabsorbable implants on fusion rate, cage migration, and implant integrity. SUMMARY OF BACKGROUND DATA: Despite the high clinical success rate with metallic plates and interbody grafting, complications such as dysphagia, imaging artifacts, and revision difficulties exist. Less permanent and lower profile implants could minimize these problems. METHODS: Four treatments were studied: 1) carbon fiber-reinforced polymer (CFRP) cage alone, 2) CFRP cage with an absorbable tension band, 3) absorbable cage with an absorbable tension band, and 4) absorbable cage with a titanium plate. Fusion was assessed using radiographs, biomechanical testing, and micro-CT analysis. RESULTS: Treatments with the CFRP cage alone had the lowest fusion rate at 3 months (2/6) and 6 months (4/6). The CFRP cage with the absorbable strap treatments had 5/6 fusions at 6 months. The absorbable cage with absorbable strap also had 5/6 fusions, but two of the cages fractured. The absorbable cage with titanium plate had 5/6 fusions, but the one partial fusion was attributed to poor screw and plate placement. CONCLUSION: Using both absorbable and nonabsorbable implants, high fusion rates were achieved in the challenging sheep cervical spine model. However, the absorbable cages were not able to withstand the mechanical forces during the 6-month survival period.

Absorbable Implants↗
PubMed1997

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↗
PubMed2005

Oestradiol-17beta responsiveness, plasma LH profiles, pituitary LH and FSH concentrations in long-term ovariectomised Holstein cows at 24 h, 48 h and 21 days following treatment with an absorbable GnRH agonist implant.

Non-lactating OVX Holstein cows (N = 34) were used to investigate the effect of s.c. placement of an absorbable GnRH agonist implant (Ovuplant; deslorelin 2.1mg, Peptech Animal Health, Australia) on the relationship of plasma LH, oestradiol responsiveness and pituitary LH content. On the day of implant insertion (Day 0), one group (OVU-48h; N = 5) received Ovuplant and had blood samples collected at hourly intervals to characterize the LH response, while a second group (CON-48 h; N = 5) remained untreated and acted as controls. Blood samples were collected every 10 min over 6 h from CON-48 h and OVU-48 h, at 24 h post-implant insertion. These cows were then slaughtered at 48 h post-implant insertion and their pituitaries recovered. Another group received Ovuplant (OVU-21d+E2; N = 10) or were left untreated (CON-21d+E2) and 21 days later were injected i.m. with 0.5 mg 17beta-E2. Blood samples were collected every 10 min for 4 h on the day before E2 injection to characterize LH pulse frequency and amplitude. Beginning 14 h later, blood samples were collected hourly for 12 h to characterize the expected LH surge. These cows were slaughtered and their pituitary glands recovered and assayed for LH and FSH content. Peak plasma LH concentrations (59 +/- 19 ng/ml) were measured after 30 min of Ovuplant insertion. They had returned to pre-treatment levels by 7 h. By 24 h post-implant insertion, OVU-48 h plasma LH profiles were characterized by reduced LH pulse frequency (0.23 +/- 0.09 pulses/h versus 0.75 +/- 0.26 pulses/h; OVU-48 h versus CON-48 h; P < 0.05). The cows that received Ovuplant had lower LH pulse amplitude, LH pulse frequency and mean LH concentrations after 20 days. Injection of 0.5 mg 17beta-E2 induced an LH surge in every one of the control cows with their peak concentrations measured 18 h post injection. No increase in LH was detected in any Ovuplant treated cows. Pituitary FSH content was reduced in Ovuplant treated cows after 48 h, but not that of LH. In conclusion, absorbable deslorelin implants induced a substantial but temporary release of LH, but even 21 days later their LH profiles were characterized by marked suppression of pulsatile LH and an absence of response to E2. These results suggest the implant has prolonged biological activity.

Absorption↗
PubMed2003

Conversion from trabeculectomy to deep sclerectomy. Prospective study of the first 44 cases.

PURPOSE: To evaluate the outcomes of conversion from trabeculectomy to deep sclerectomy with placement of a drainage implant. SETTING: Department of Ophthalmology, Hospital of Buskerud, Drammen, Norway. METHODS: Deep sclerectomy was performed in 41 patients (44 eyes) from November 1999 to January 2002. An absorbable implant (AquaFlow((R)), Staar Surgical) and a nonabsorbable implant (T.Flux((R)), IOLTech Laboratories) were used in 75% and 25% of eyes, respectively. Patients with open-angle glaucoma who needed filtering surgery were enrolled consecutively in a prospective study. Patients with 2 or more previous filtering surgeries or neovascular glaucoma were excluded, as were children. Of the original 48 eyes, accidental perforation of the trabeculo-Descemet's membrane occurred in 8.3%; these eyes were excluded from the study. The severity of optic nerve damage was considered in the decision to start therapy. An intraocular pressure (IOP) above 22 mm Hg was always treated. RESULTS: After a mean follow-up of 12.9 months +/- 7.1 (SD), 61.4% of eyes were controlled without therapy. When eyes with previous surgery were excluded, the rate increased to 66.7% after a mean follow-up of 13.8 +/- 7.2 months. The mean IOP preoperatively and after 12 months was 27.9 +/- 6.9 mm Hg and 14.6 +/- 3.5 mm Hg, respectively (P<.001). The mean number of medications decreased from 3.4 +/- 1.0 preoperatively to 0.6 +/- 1.1 12 months postoperatively (P<.001). A reoperation was required in 2 cases (4.5%). There were no complications related to hypotony or other significant complications. CONCLUSIONS: This study shows that conversion from trabeculectomy to deep sclerectomy with placement of an implant is safe. The postoperative IOP reduction was acceptable, and no significant complications occurred.

Adult↗
PubMed2005

A comparison of human and porcine acellular dermal tissues in the subcutaneous space of a rat model.

The study compared the host response to a human and a porcine acellular dermal tissue implanted in the subcutaneous space of a rat model. The human and porcine acellular grafts were surgically implanted in the subcutaneous tissue of rats (5 rats/group) and the materials were evaluated at 7, 15, 30, 60 and 180 postoperative days (PO). The histological immune response was quantified using a digital image analysis system, which evaluated the number of vessels present in the implants and in the surrounding soft tissue, the area of inflammatory cell infiltration in the grafts, the width of the capsular formation present around the tissues and the area of implants absorbed. The data were submitted to statistical analysis. Light microscopy showed mononuclear cellular infiltration, the presence of a capsular formation surrounding the grafts and the presence of vacuolar structures (optically "empty spaces") inside the implants. The image analysis comparing both materials showed significant inflammatory cells in the human graft at 15 and 30 PO, thicker capsular formation in the porcine tissue at 60 PO, increased number of vessels inside the implants and in the surrounding tissues in the porcine graft and a similar absorption pattern in both materials at 180 PO. The histological findings showed that both tissues were well-tolerated when implanted in the subcutaneous tissue of rats, allowing us to consider the porcine acellular dermal graft as a provisional alternative material for reconstructive plastic surgery.

Analysis of Variance↗
PubMed1993

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↗
PubMed2000

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↗
PubMed1975

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↗
PubMed2004

Transtibial tubercle fixation without hardware for anterior cruciate ligament and posterior cruciate ligament reconstruction: A new technique.

Tibial fixation with implants for both anterior and posterior cruciate ligament reconstructions (ACLR and PCLR) can be associated with a wide variety of problems. Common problems encountered include graft-tunnel mismatch when using grafts with bone blocks, graft damage or poor graft fixation using metal or absorbable implants, painful retained hardware requiring removal, and hardware interference during revision surgery. A new technique is presented using transosseous graft suture passage across the tibial tubercle followed by knot tying over a bone bridge. The technique provides a quick, simple, safe, and reproducible alternative for primary or supplemental tibial graft fixation without hardware in ACLR and PCLR.

Anterior Cruciate Ligament↗
PubMed1993

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↗