Gelatin as an absorbable implant in scleral buckling procedures. A preliminary report.
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Absorption↗
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Effect of annealing temperature on the degradation of reinforcing fibers for absorbable implants.
Calcium phosphate fibers designed for reinforcement of bioabsorbable fracture fixation devices were evaluated for their properties upon annealing. The composition of these fibers were 54% PO4, 27% Ca, 12% ZnO, 2.5% NaPO3, and 4.5% Fe2O3, and they were either not annealed, annealed at 250 degrees C, or annealed at 420 degrees C. Chemical degradation, mass loss, and morphology upon degradation were studied. Chemical degradation was performed in Tris-buffered HCl, while mass loss and morphologic studies were performed in both physiologic and nonphysiologic solutions. The results showed that degradation rates for fibers were inversely proportional to the annealing temperature. Mass loss analysis of fibers immersed in the two physiologic solutions (calf serum and simulated body fluid) revealed little change in fiber diameter up to 60 days. Morphologic examination revealed little change in fibers immersed in the two physiologic solutions until 60 days, after which thin shells were found to be peeling off the outer coating of the fiber. Samples in tris-buffered HCl revealed a dramatic difference in mode of degradation among the three fibers. Fibers not annealed and those annealed at lower temperatures underwent a delaminating type of degradation that appeared to destroy the overall integrity of the fiber, whereas fibers annealed at 420 degrees C underwent crater-like deterioration in which the overall alignment of the fiber remained intact. It is therefore concluded that annealing fibers at higher temperatures also undergo a mode of degradation that allows them to maintain their structural integrity. Although annealing fibers close to glass transition temperature may produce an initially weaker fiber, chemical and physical degradation occur much slower, making these fibers most suitable for reinforcement of biodegradable implants.
Absorption↗
Full thickness resection of radiation-induced ulcers of the chest wall: reconstruction with absorbable implants, pedicled omentoplasty, and split skin graft.
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Adult↗
Absorbable implants for the fixation of fractures.
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Absorption↗
Faltin lecture 1989. Absorbable implants in the fixation of fractures.
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Adolescent↗
[Osteosynthesis using absorbable implants].
Authors report on one case of malleolar synthesis with the use of biodegradable implants. The advantages of the resorbing osteosynthesis materials and the possible complications are described.
Adult↗
Bone mineral density in fractures treated with absorbable or metallic implants.
Absorbable fixation devices have been clinically used in the fracture treatment for over ten years. No studies have been published where bone mineral density has been measured after bone consolidation comparing absorbable and metallic fixation. In this study the bone mineral density was measured after operative ankle fracture treatment with absorbable self-reinforced polyglycolic acid (SR-PGA) screws (14 patients) or with absorbable self-reinforced polylactic acid (SR-PLLA) screws (eight patients) compared with metallic fixation (17 patients). The overall results were radiologically good in every group. A statistically significant difference in the bone mineral density (BMD) was found only in the distal tibial metaphysis between SR-PGA screw and metallic fixation. The BMD increased in the distal tibia after SR-PGA screw fixation by an average 18.3%. The average change of BMD in the distal tibia after SR-PLLA screw fixation decreased by 6.4% while after metallic fixation the average change of MBD decreased by 18.6%. Bone mineral density measurements in the present study may indicate osteogenetic capacity of polyglycolide implants in the bone after fracture or osteotomy fixation. On the other hand, metallic implants showed negative effects to the bone.
Adult↗
Processing and characterization of absorbable polylactide polymers for use in surgical implants.
Absorbable fibers of linear poly-alpha-hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly(L-lactide) (PLLA) fibers may degrade too slowly for optimal function. Polymers produced by copolymerization of L-lactide with varying amounts of D-lactide may offer an alternative choice for absorbable fiber based implants. Poly(L/D-lactide) stereocopolymers with L/D lactide molar ratios of 95/5, 90/10, and 85/15 were considered. Melt-spun/hot-drawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x-ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37 degrees C. Fabrication was reproducible and results indicated that tensile strength, modulus, an birefringence all increased with increasing draw ratio up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide stereocopolymer fibers when compared to reported values for PGA and PLLA fibers, suggests these materials may be useful in absorbable surgical implants for tissue repair and regeneration.
Biocompatible Materials↗
Comparison of in vitro hydrolysis, subcutaneous and intramedullary implantation to evaluate the strength retention of absorbable osteosynthesis implants.
To evaluate the behaviour of mechanical properties of absorbable osteosynthesis implants in vivo, the strength retention of self-reinforced polyglycolide rods in distilled water at 37 degrees C in the subcutis and femoral medullary cavity of the rabbit was investigated. The self-reinforced polyglycolide rods lost their strength significantly faster in vivo than in vitro. The strength loss of the self-reinforced polyglycolide rods was only slightly faster in the medullary cavity than in the subcutis. As the removal of the implants from the medullary cavity became difficult 5-6 wk after implantation, it is suggested that subcutaneous implantation would be a suitable method to evaluate the strength retention of absorbable osteosynthesis implants.
Animals↗
Variations in occlusal forces with a resilient internal implant shock absorber.
The importance of an internal shock absorber for implant prostheses has concerned many, primarily because the efficacy of a shock absorber to reduce stress has not been demonstrated in vivo. This study examined 15 subjects with unilateral distal extension single implant abutments attached to a single natural tooth abutment to assess the effect of a shock-absorbing element within the implant on occlusal force levels. Occlusal forces and bilateral occlusal similarity were examined using specially adapted research software for the T-Scan occlusal analysis system. The results indicate that there is a significant difference (P less than 0.011) between occlusal forces using an internal shock absorber (18 N) and a titanium internal element (30 N).
Adult↗
Properties and applications of Bioplast, an absorbable surgical implant material from fibrin.
Bioplast is the only commercially available absorbable implant material. Compression moulded from fibrin, it is a yellowish, translucent and flexible material which is thermally stable below 170 degrees C. Its mechanical strength depends on glycerol content. Crosslinking with formaldehyde reduces swelling and digestibility. Bioplant is non-antigenic and capable of being absorbed by polymorphonuclear digestive action. The non-toxic metabolites are eliminated via the kidneys while the site is invaded by host tissue. Clinical applications are mentioned.
Biocompatible Materials↗
Effectiveness of operative treatment of internal orbital wall fracture with polydioxanone implant.
Many implants, some made from teflon or silicone, have been used for internal orbital wall reconstruction. Late complications relating to use of such implants have been reported. In this prospective study a polydioxanone (PDS) implant absorbable in vivo was used for internal orbital wall reconstruction. Follow-up involved clinical examination, magnetic resonance imaging (MRI) and computerized tomography (CT). Clinical examinations were undertaken before operation and up to 36 weeks postoperatively. Sixteen consecutive patients (10 pure blow-out fractures, six with associated zygomatic fracture) took part in the study. Prevalences of diplopia, proptosis and enophthalmus were recorded during each follow-up examination. This study revealed no muscle entrapment within the fracture line. Although CT results confirmed bone growth in the internal orbital wall, shape was unsatisfactory, and orbital volume was not reduced. MRI revealed thick scar formations in six cases (37.5%), fibrotic sinuses filled with air or gas in three cases (19%) and a fibrotic sinus with fluid around the PDS in one case (6%). Our results suggest that use of PDS in reconstructing the internal orbital wall is inadvisable.
Absorbable Implants↗
Absorbable devices in the fixation of fractures.
Totally absorbable internal fracture fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at our department in 1984. A total of 2,500 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibers of same polymer) absorbable alpha-hydroxy polyesters between November 5, 1984, and January 12, 1994. The devices used included cylindrical rods or pins, screws, tacks, plugs, and wires. The most common indication for the use of absorbable implants was displaced malleolar fracture of the ankle. Transphyseal fixation with small-diameter polyglycolide pins was used in children. The postoperative clinical course was uneventful in over 90% of the patients. The complications included bacterial wound infection in 3.6% and failure of fixation in 3.7%. In one-fifth of these cases, however, reoperation was not necessary. The occurrence of noninfectious foreign-body reactions 2 to 3 months postoperatively has been observed in 2.3% of the patients operated in the last years with polyglcolide implants but in none of the patients with polylactide implants. This inflammatory tissue response often required aspiration with a needle or small incision but did not influence the ultimate functional or radiologic result of treatment. Owing to the biodegradability of these internal fixation devices, over 1,000 implant removal procedures were avoided during the 9-year period under review, allowing medical personnel at these facilities to focus on other procedures. Avoidance of removal procedures results in financial benefits and psychological advantages. The benefits of absorbable implants for war surgery are the same as for civilian life. Absorbable implants can also be used in open fractures and infection operations.
Absorption↗
Arthroscopic bankart repair: experience with an absorbable, transfixing implant.
The use of arthroscopic means to address shoulder instability has provided a technically advantageous way to approach Bankart lesions while posing complex questions regarding the specific indications for such an intervention. A successful outcome with arthroscopic Bankart repair is a function of proper surgical indication and patient selection. Several authors have evaluated the causes of failure and reasons for success with the Suretac device. The development of a bioabsorbable repair device at the authors' institution was precipitated by a desire to address and repair Bankart lesions arthroscopically while avoiding the frequent complications associated with the metal staple and the transglenoid suture technique. The Suretac represents the first generation of bioabsorbable transfixing devices. The initial objectives of the Suretac device were to adequately and dynamically tension soft tissue to bone, while providing a bioabsorption profile that mirrored the native healing response. The Suretac device is an appropriate surgical tool for arthroscopically repairing Bankart lesions in a carefully selected patient population.
Absorbable Implants↗
Scanning electron microscopy study including maceration techniques of an absorbable alloplastic implant designed for the reconstruction of ventral abdominal wall defects.
The interposition of synthetic material represents the most generally acknowledged method for achieving a tension-free surgical repair of major abdominal wall defects. As permanent materials are frequently associated with severe complications (rejection, peritonitis, enterocutaneous fistula, erosive invasion into the intestine), a newly designed absorbable prosthetic (polydioxanone, PDS) has been developed. The ellipsoid implant is composed of a knitted envelope and a filling of loosely arranged filaments. Interpositioning of the implant into an artificial circular abdominal wall defect was carried out on 30 Wistar rats. Explantation was performed 21 days post implantationem (p.i.), 42 days p.i. and 180 days p.i. The aim of the study was to evaluate the use of scanning electron microscopy (SEM) combined with maceration techniques (2 N NaOH for 1, 3 and 5 days) for a spatial assessment of the interactions between the implanted material and the ingrowing tissue components. Application of 2 N NaOH caused the complete dissolution of the PDS-material and a concomitant gradual disappearance of cellular and amorphous tissue components, thereby unmasking the remaining collageneous network. SEM of non-macerated specimens demonstrated that 21 days p.i. the entire implant has been filled with connective tissue components. Additionally, the ventral and dorsal surfaces of the implant were covered by a collageneous layer (neo-fascia). 21 days p.i. the PDS-filaments had developed minor clefts, which increased in number and depth 42 days p.i., and were transformed into small remnants 180 days p.i. Alkali treatment revealed the three-dimensional arrangement of collagen fibers, which ensheathed the PDS-filaments and formed interconnecting networks between them. At the ventral portion of the implant the fibrous network was more elaborate and densely distributed. 180 days p.i. the implant has been transformed into a membranous structure (neo-membrane) composed of the ventral and dorsal neofascia, remnants of PDS-filaments and a continuous connective tissue layer containing wave-like collagenous structures. Whereas 21 and 42 days p.i. no herniation was observed, 130 days p.i. the implant began to bulge out of the ventral abdominal wall. It is therefore concluded that inspite of the advantages of absorbable materials, longer resorption times may be required to allow a sufficient consolidation of the ingrowing connective tissue to resist the tensile forces of the abdominal muscle coat. SEM combined with 2N NaOH maceration proved to be a usefull tool in addition to conventional histological techniques for a three-dimensional assessment of fibrous connective tissue components ingrowing into alloplastic implants.
Abdominal Muscles↗
Neomembranes: a concept review with special reference to self-reinforced polyglycolide membranes.
Absorbable implants are being increasingly used in various fields of medicine. Important materials for these applications include the polyesters polylactide and polyglycolide. Following implantation of any absorbable device there occurs a proliferation of fibrous tissue, which along with material from the degrading implant forms a composite membranous structure-a neomembrane. Neomembranes can be exploited in guiding tissue regeneration. Success in this respect has been achieved in treatment of bone defects, nerve defects, and periodontal ligaments. Future research may ultimately permit taking advantage of neomembranes in the reconstruction of more complex organs such as the liver. Gaining an understanding of implant characteristics and implant-tissue interaction is essential for further progress in this area.
Animals↗
Operative treatment of displaced intra-articular fractures of the calcaneus using absorbable internal fixation: a prospective study of twenty-five fractures.
OBJECTIVE: To document the use of absorbable implants in the operative treatment of displaced intra-articular fractures of the calcaneus. DESIGN: Prospective clinical study. SETTING: Level one trauma center, university hospital. PATIENTS: Twenty-five displaced intra-articular calcaneal fractures in twenty-one patients. INTERVENTION: The fractures were reduced operatively and fixed with absorbable self-reinforced polyglycolide rods. MAIN OUTCOME MEASUREMENTS: Reduction, healing, and stability of fixation were assessed on radiographs. The functional result was scored using the method of Crosby and Fitzgibbons. Patient satisfaction was recorded. RESULTS: The mean Böhler angle was -12 degrees (standard deviation 22 degrees) preoperatively and 20 degrees (standard deviation 13 degrees) postoperatively. After a two-year follow-up, seven patients had excellent, five good, three fair, and six poor functional results. Subjectively, fifteen patients were satisfied and six were dissatisfied. Twelve patients returned to work within one year, three were unemployed, two were retired prior to the accident, and four were unable to work because of the calcaneal fracture. The postoperative Böhler angle and later the appearance or absence of posttraumatic subtalar arthritis were significant prognostic factors. CONCLUSIONS: Results with absorbable implants are similar to those with other operative methods. Advantages include the absence of secondary procedures for implant removal and undisturbed computed tomography scans postoperatively.
Absorbable Implants↗
Ultrasonically implanted PLA suture anchors are stable in osteopenic bone.
We compared the in vitro pullout strengths of a metallic screw-type suture anchor (5-mm Corkscrew) and a new ultrasonically implanted absorbable pin from cadaveric humeral heads with different bone densities. They were assessed quantitatively using microcomputed tomography. Pullout tests were done at four standardized sites and then correlated with the local bone density. The mean pullout strengths for the 5-mm Corkscrew and the 3.5-mm polylactic pin were similar in weak bone (76 +/- 24 N versus 104 +/- 46 N), intermediate quality bone (194 +/- 81 N versus 218 +/- 76 N), and strong bone (349 +/- 127 N versus 325 +/- 100 N). Pullout strength correlated with bone density for both implants (r = 0.76 and r = 0.86 for the Corkscrew and polylactic pin, respectively). The ultrasonically implanted absorbable 3.5-mm polylactic pin achieved equal pullout strength in weak bone as the larger 5-mm titanium Corkscrew. Bone density is highly variable in humeral heads and influenced the pullout strength of both implants.
Absorbable Implants↗