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PubMed1990

Mechanical properties of biodegradable polymers and composites proposed for internal fixation of bone.

The mechanical properties of biodegradable polymers and composites proposed for use in internal fixation (in place of stainless steel) are crucial to the performance of devices made from them for support of healing bone. To assess the reported range of properties and degradation rates, we searched and reviewed papers and abstracts published in English from 1980 through 1988. Mechanical property data were found for poly(lactic acid), poly(glycolic acid), poly(epsilon-caprolactone), polydioxanone, poly(ortho ester), poly(ethylene oxide), and/or their copolymers. Reports of composites based on several of these materials, reinforced with nondegradable and degradable fibers, were also found. The largest group of studies involved poly(lactic acid). Mechanical test methods varied widely, and studies of the degradation of mechanical properties were performed under a variety of conditions, mostly in vitro rather than in vivo. Compared to annealed stainless steel, unreinforced biodegradable polymers were initially up to 36% as strong in tension and 54% in bending, but only about 3% as stiff in either test mode. With fiber reinforcement, reported highest initial strengths exceeded that of stainless steel. Stiffness reached 62% of stainless steel with nondegradable carbon fibers, 15% with degradable inorganic fibers, but only 5% with degradable polymeric fibers. The slowest-degrading unreinforced biodegradable polymers were poly(L-lactic acid) and poly(ortho ester). Biodegradable composites with carbon or inorganic fibers generally lost strength rapidly, with a slower loss of stiffness, suggesting the difficulty of fiber-matrix coupling in these systems. The strength of composites reinforced with (lower modulus) degradable polymeric fibers decreased more slowly. Low implant stiffness might be expected to allow too much bone motion for satisfactory healing. However, unreinforced or degradable polymeric fiber reinforced materials have been used successfully clinically. The key has been careful selection of applications, plus use of designs and fixation methods distinctly different from those appropriate for stainless steel devices.

Biocompatible Materials↗
PubMed2002

Biomaterial implants induce the inflammation marker CRP at the site of implantation.

Following implantation of biomaterial patches into the gastrointestinal tract, we analyzed the host's response towards the foreign material. Asymmetric patches of polydioxanone covered Vicryl or poly-3-hydroxybutyrate were sutured onto the rat stomach. Tissue samples were generated at distinct time intervals after surgery, and RNA profiles were compared by Differential Display. RT-PCR analysis of gene candidates that seemed differentially expressed showed that vitamin D binding protein mRNA was induced in stomach tissue after implantation of the biomaterial patches. In parallel, the amount of C-reactive protein mRNA was found to be increased transiently as well. Implants induce a tissue response that is specific for a given material.

Absorbable Implants↗
PubMed2001

Resorbable polymer fibers for ligament augmentation.

Resorbable augmentation devices for cruciate ligament surgery have been developed to temporarily protect healing tendon grafts or sutured ligaments against high tensile loads during the postoperative healing period. Materials available at present [e.g., polydioxanone (PDS)] show a half-life tensile strength of only 4-6 weeks, whereas the process of revitalization and recovering of the transplanted tendon graft can take up to 12 months. Therefore, a device that provides gradually decreasing mechanical properties with a half-time strength of at least 6 months would be desirable. In order to obtain a suitable material, we investigated the degradation kinetics of a variety of different resorbable fibers made of poly(L-lactide) and poly(L-lactide-co-glycolide). The fiber materials differed in processing and treatment parameters like thermal posttreatment, irradiation, and fiber diameter. The fibers were degraded in vitro and were tested for mechanical properties and molecular weight at various time points up to 72 weeks. The half-time strength of the materials ranged between 5 and 64 weeks, depending on their treatment parameters. In contrast, the stiffness did not decrease adequately. However, an augmentation stiffness that does not change much versus time could not provide a gradual increase in graft load, which is important to stimulate the orientation of the collagenous tissue. Therefore, design of an augmentation construct braided out of more than one quickly degrading fiber materials is suggested. After the breakdown of the faster-degrading fiber components the stiffness would automatically decrease by the diminution of the load-carrying fiber volume.

Absorbable Implants↗
PubMed1990

A histomorphological study on self-reinforced polyglycolide (SR-PGA) osteosynthesis implants coated with slowly absorbable polymers.

A total of 150 osteotomies of rabbits' distal femur were fixed with absorbable self-reinforced polyglycolide (SR-PGA) rods coated with slowly absorbable polymers. In order to reduce the degradation rate of the SR-PGA construction rods were coated with n-butyl-2-cyanoacrylate, polydioxanone (PDS), poly-beta-hydroxybutyrate (PHBA), or poly-l-lactide (PLLA). Biocompatibility and the rate of biodegradation were evaluated in histological, histomorphometric, microradiographic, and oxytetracycline labeling studies. PDS, PHBA, and PLLA coatings showed good biocompatibility although there were scattered fluid accumulations around the rod in each group. Cyanoacrylate coating seemed to inhibit cartilage regeneration and cause the formation of considerable amount of connective tissue around the implant. The PGA core of the rod had totally degraded in 24 to 36 weeks in each coating group. Cyanoacrylate and PDS coatings were not detectable after 6 weeks while PHBA and PLLA coatings were still observed after 48 weeks. There were five (14%) non-unions in the cyanoacrylate coating group, one (3%) in the PHBA coating group caused by a purulent infection and none in the PDS and PLLA coating groups.

Absorption↗
PubMed2006

Biological response to a new composite polymer augmentation device used for cruciate ligament reconstruction.

A resorbable composite augmentation cord braided of poly(L-lactide) and poly(L-lactide-co-glycolide) fibers was designed for the temporary protection of repaired cruciate ligaments. This study examined the biocompatibility of the new device and the influence of augmentation duration on ligament healing in a sheep model. The anterior cruciate ligament (ACL) was cut close to the femoral insertion and reinserted with sutures. The repaired ACLs were augmented with the slowly degrading new composite cord and alternatively with a faster degrading polydioxanone cord (PDS). A tendon graft group (gold standard) served as control. Histological evaluation and biomechanical testing were performed after 6 months. The composite cord showed no signs of degradation, whereas the PDS was intra-articularly resorbed. Both devices showed only minor foreign body reactions, proving their good biocompatibility. However, 9 of 11 composite cords had ruptured too early because of fatigue at the bone tunnel entrances. All operated knees were less stable than the nonoperated collateral joints. Knees equipped with the composite cord showed the largest anterior instabilities, whereas the PDS-augmented group exhibited in some cases knee instabilities comparable with that of the tendon group. A positive effect of a longer mechanical protection by a slowly degrading augmentation could not yet be shown. The fatigue strength of the device still needs improvement.

Animals↗
PubMed2005

Safety of donor right hepatectomy without abdominal drainage: a prospective evaluation in 100 consecutive liver donors.

Although the role of routine abdominal drainage after liver resection for tumors has been questioned, abdominal drainage after donor right hepatectomy for live donor liver transplantation (LDLT) has been a routine practice in most transplant centers. The present study aimed to evaluate the safety of the procedure without abdominal drainage. A prospective study was performed on 100 consecutive liver donors who underwent right hepatectomy for LDLT from July 2000 to September 2003. Biliary anatomy was carefully studied with intraoperative cholangiography using fluoroscopy. The middle hepatic vein was included in the graft in all except 1 patient. Parenchymal transection was performed using an ultrasonic dissector. The right hepatic duct was transected at the hilum and the stump was closed with 6-O polydioxanone continuous suture. Absence of bile leakage was confirmed with methylene blue solution instilled through the cystic duct stump. The abdomen was closed after careful hemostasis without drainage in all donors. The median age of the donors was 36 years (range 18-56 years). Median operative blood loss and operating time were 350 mL (range 42-1,400 mL) and 7.5 hours (range 5.2-10.7 hours), respectively. None of the donors required any blood or blood product transfusion. There was no operative mortality. The median postoperative hospital stay was 8 days (range 5-30 days). Postoperative morbidity occurred in 19 patients (19%), most of which were minor complications. No donor experienced bile leakage, intraabdominal bleeding, or collection. None required surgical, radiologic, or endoscopic intervention for postoperative complications, except for 1 donor who developed late biliary stricture that required endoscopic dilatation. All donors were well with a median follow-up of 32 months (range 11-50 months). In conclusion, with detailed study of the biliary anatomy and meticulous surgical technique, donor right hepatectomy can be safely performed without abdominal drainage. Abdominal drainage is not a mandatory procedure after donor hepatectomy in LDLT.

Abdomen↗
PubMed1994

Mechanical comparison of 10 suture materials before and after in vivo incubation.

The material properties of ten 2-O suture materials were evaluated tensiometrically at time = 0 and again after 6 weeks incubation in rats. All suture material was incubated and tested without knots. Specialized machinery was used with a custom securing apparatus to pull suture material apart at constant speed. Stress-strain curves were derived, and from these strength, toughness, strain at rupture, and elastic modulus were determined. Sutures tested included Vicryl [poly(glycolide-lactide)], Dexon (polyglycolic acid), Ethibond (polyester), silk, plain gut, chromic gut, Maxon (polyglyconate), PDS (polydioxanone), nylon, and Prolene (polypropylene). Elastic modulus was greatest for braided, least for monofilament, and intermediate for gut sutures, regardless of chemical composition (ANOVA, P = 0.0001). Strength, strain, and toughness decreased in all of the sutures over time in vivo with the exception of braided polyester (Ethibond), which remained stable. Silk demonstrated the least strength and toughness while PDS and Maxon were the strongest and toughest at time = 0. Vicryl, Dexon, and gut sutures were absorbed to the point that they could not be tested after 6 weeks in vivo. Performance tables are provided for all sutures.

Animals↗
PubMed1995

Biodegradable implants in traumatology: a review on the state-of-the-art.

Up to now the internal fixation of fractured bones and joints has been managed by metal implants. There are certain associated disadvantages: the mechanical properties of the metals are stronger than those of cortical bone ("stress-protection"); the removal of the implants requires a second operation; an increasing number of patients are confronted with problems of sensitivity to metal components of the implants, especially nickel. About 40 different biodegradable polymers, copolymers and composites have been developed as substitutes for metal implants in internal fracture fixation. The early experimental and clinical results demonstrate their limitations. From the current point of view, it is not possible to transfer the designs and assembling principles of metal implants in orthopaedic surgery to biodegradable polymers. The attempt to simply mimic metal implants in polymers is condemned to fail from the very beginning. This is a review of the literature and of our first 100 patients operated on using implants made of self-reinforced polyglycolide acid and polydioxanone. The main difficulty with the material is the loss of stiffness in a time interval which is not long enough to guarantee bone healing. The development of a sterile sinus over the site of implantation is a problem also reported by other groups. Certain additives have to be inserted into the polymers to make them visible on conventional X-radiographs. Despite these drawbacks, however, there are indications for the isolated or adjuvant implantation of biodegradable materials. They could be employed in the treatment of osteochondral fractures and other defined injuries. The available literature on these indications will be discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Distribution and localization of cells and collagens in the proliferated intima of arterially implanted autovein grafts.

We examined the microscopic features and distribution of collagens in the hyperplastic intima of arterially implanted autovein bypass grafts under conditions of a reduced blood flow with a poor distal outflow. Vascular anastomosis was made using 7-0 nonabsorbable polypropylene sutures (PP group), or absorbable polydioxanone sutures (PDS group). On the contralateral limb, an autovein bypass graft was performed under normal flow conditions (NF group). The thickness of the intima in the NF group was approximately 50 microm throughout the duration of the study, while in the PP and PDS groups, intimal hyperplasia progressed to 290+/-112 microm and 267+/-123 microm, respectively, at 13 months after grafting. Collagen accumulated significantly in both the PP and PDS groups; types IV and V collagen in particular increased considerably in the deep layer. Regardless of the suture materials, the progression of intimal hyperplasia was considered to be closely related to the poor distal outflow to be and caused by the proliferation of myofibroblasts and active production of collagen. The increase in types IV and V collagen, particularly in the deep layer of the hyperplastic intima, was due to development of numerous vasa vasora in this region.

Anastomosis, Surgical↗
PubMed1985

Vascular evolution of single-layer end-on colonic anastomosis. A microangiographic study of 180 anastomoses in the rat from two to 180 days.

One hundred eighty left colonic single-layer end-on anastomoses performed on 90 rats by microsurgical techniques, using polydioxanone monofilament absorbable sutures, were examined histopathologically and microangiographically at nine different times, from two to 180 days. There was no anastomotic leakage. The vascular state after suturing and the evolution of the neovascularization are described. The neovascularization appeared to follow the same process of evolution as tissue restoration. It began early, was greatest on the seventh day, and diminished thereafter. When granulation tissue was narrow, the anastomoses were barely hypervascular, the neovascularization assured by submucosal plexus. A voluminous granulation tissue was hypervascular, had a slower evolution, and neovascularization was then assured above all by the peritoneal formations adherent to the suture.

Animals↗
PubMed2002

[Development of new, biodegradable implants].

The advantage of biodegradable implants is that they do degrade after they have fulfilled their function. Therefore, a second operation for removing metal implants is not necessary. Additionally, the healing process may be stimulated by the successive loss of the mechanical properties of the implant during degradation, corresponding with the increasing loading on the healing tissue. The most important materials are polylactide, polyglycolide and their copolymers, and polydioxanone. The mechanical properties of these polymers were improved by special fabrication techniques. Nevertheless, the materials have disadvantages relating to their stiffness and relaxation behavior. Therefore, their use has to be restricted to nearly unloaded situations. The degradation behavior of the materials can be controlled by the production of copolymers and by the molecular weight of the polymers. The degradation behavior cannot be predicted exactly in vivo, as it is influenced not only by the chemistry and the implant design but also by the localization of the implant in the tissue. In general, the biocompatibility of the polymers used today is good and the observed complication rate is very low. Osteolytic reactions, which can sometimes be observed, have no clinical consequences in most instances. The clinical applications comprise resorbable pins and screws for the fixation of small bony fragments, interference screws for the surgery of the anterior cruciate ligament, resorbable augmentation devices for ligaments and tendons, resorbable membranes for guided bone regeneration in maxillofacial surgery, and a lot more. Future developments are expected in the field of tissue engineering and drug release.

Absorbable Implants↗
PubMed1997

[4-fragment fractures of the proximal humerus. Alternative strategies for surgical treatment].

The operative treatment of dislocated fractures of the proximal humerus has been evolving in recent years. Replacement using endoprostheses often results in only moderate functional outcome, and with the high risk of aseptic necrosis with ORIF, new methods of minimally invasive stabilisation have been developed. These methods reduce the opening of the fracture site to a minimum and thereby limit the risk of iatrogenic damage to local vascularity and the rotator cuff. This study reviewed 18 patients operated on with minimal osteosynthesis for dislocated four-part fractures of the proximal humerus from March 1991 to October 1994. Only tension band wiring with resorbable cords from woven polydioxanone was applied. After an average follow-up of 26 months (20-37 months), 72% (n = 13) of the four-part fractures were rated as good and very good results according to the Neer Score. In 16.7%, a complete head necrosis occurred, requiring a prosthetic replacement. Two patients with partial necrosis (11.1%) had a good functional outcome. With regard to these results, we recommend head-preserving tension band wiring with resorbable cords and preservation of the articular surface. At the present time the procedure seems comparable with prosthetic replacement in respect of shoulder function.

Adult↗
PubMed1999

[Growth behavior of chondrocytes on various biomaterials].

Chondrocytes can be cultured on different three-dimensional culture systems suitable for transplantation to enhance the repair of localized cartilage defects. Articular cartilage chondrocytes from adult rabbit knees and from bovine calf metacarpophalangeal joints were isolated by enzymatic digestion and cultured in a monolayer system to amplify cell count. After amplification the cells were seeded on different biocompatible materials. We investigated two types of bioresorbable polymer fleece matrices (a composite fleece of polydioxanon and polyglactin and a resorbable poly-L-lactic acid fleece) and lyophilized dura as a biological carrier. On all three types of transport media the phenotypic and morphological appearance of cultured chondrocytes could be observed. The production of glycosaminoglycans was revealed by Alcian blue staining and immunohistochemical detection of Chondroitin-4 and 6-sulfate in the created constructs. The material properties of the carriers allow for transplantation of the artificial cartilage-like products into full thickness articular cartilage defects and could therefore improve the minor intrinsic healing capacity of cartilage tissue. Bioartificial cartilage may become a future perspective in the treatment options of orthopaedic and plastic surgery.

Animals↗
PubMedDate not supplied

External rhinoplasty for the Arabian nose: a columellar scar analysis.

This study aimed to evaluate columellar scar problems after external rhinoplasty in the Arabian population, and to analyze the technical factors that help prevent such problems and maximize the scar cosmesis. The investigation was conducted in university and private practice settings of the author in Alexandria, Egypt. A total of 600 Arab patients who underwent external rhinoplasty were included in the study. All the patients underwent surgery using the external rhinoplasty approach, in which bilateral alar marginal incisions were connected by an inverted V-shaped transcolumellar incision. At completion of the procedure, a two-layer closure of the columellar incision was performed. At a minimum of 1 year postoperatively, the columellar scar was evaluated subjectively by means of a patient questionnaire, and objectively by clinical examination and comparison of the close-up pre- and postoperative basal view photographs. Objectively, anything less than a barely visible, leveled, thin, linear scar was considered unsatisfactory. Subjectively, 95.5% of the patients rated the scar as unnoticeable, 3% as noticeable but acceptable, and 1.5% as unacceptable. Objectively, the scar was unsatisfactory in 7% of the cases. This was because of scar widening with or without depression (5%), hyperpigmentation (1.5%), and columellar rim notching (0.5%). The use of a deep 6/0 polydioxanon (PDS) suture significantly decreased the incidence of scar widening (p < 0.005).The columellar incision can be used safely in the Arab population regardless of their thick, dark, and oily skin. Technical factors that contributed to the favorable outcome of the columellar scar included proper planning of location and design of the incision used, precise execution, meticulous multilayered closure, and good postoperative care.

Adolescent↗
PubMed2005

Cell-based treatment of osteochondral defects in the rabbit knee with natural and synthetic matrices: cellular seeding determines the outcome.

INTRODUCTION: Matrix-associated transplantation of cartilage constructs is an appealing method in cartilage repair. Three different matrices seeded with allogenic chondrocytes were compared in an osteochondral defect model in the rabbit. An investigation was conducted to identify the best matrix for cell-based treatment of osteochondral defects in the rabbit knee joint. MATERIALS AND METHODS: Osteochondral defects (diameter 3 mm) were created in the trochlea and the femoral condyles of 33 New Zealand White rabbits, which were then treated with bioartificial cartilage constructs. The cartilage constructs were created in vitro using three different resorbable carrier materials (two fleece matrices: one of PLLA, and one composite of polydioxanon/ polyglactin, as well as one consisting of lyophilized dura) cultured with isolated allogenic chondrocytes. The defects were evaluated macroscopically, by histological and immunhistological techniques, and by scanning electron microscopy after 6 weeks, 6 months, and 12 months. The chondrocyte-seeded constructs were compared to defects treated with carrier material alone as well as to untreated control defects. RESULTS: There was a significant improvement in defect repair quality in the transport materials, which were cultured with chondrocytes prior to implantation (P < 0.0005). No significant differences were observed between the three carrier matrices, and no significant differences were seen between the unseeded matrices and the untreated control defects. CONCLUSION: There is no difference in the outcome between the three tested matrices in the treatment of osteochondral defects in the rabbit knee. The results of this in vitro experiment are promising and with refinement may lead to useful clinical therapies.

Animals↗
PubMed2003

Laparoscopic resection of type I choledochal cyst.

Type I choledochal cyst is a rare saccular or fusiform congenital dilatation of the extrahepatic biliary tract. It is usually treated by laparotomy at which the cyst is completely excised and a Roux-en-Y hepaticojejunostomy is performed to establish biliary enteric drainage. We report the laparoscopic excision and hepaticoduodenostomy of type I choledochal cyst in two girls aged 1 and 3 years. The entire procedure was performed laparoscopically using needlescopic instruments. A 7-mm telescope port was inserted at the umbilicus, a 3-mm port in the right upper quadrant, and a 6-mm port in left upper quadrant. An additional 3-mm fan-shaped liver retractor was passed through the abdominal wall without a trocar. The gallbladder and choledochal cyst was dissected and removed en bloc. The lower end of the common bile duct was closed with 5-0 polydioxanone. The duodenum was anastomosed to the common hepatic duct below the confluence of the right and left hepatic ducts. There were no intraoperative complications, and the children were asymptomatic with no episodes of cholangitis at 6 months follow-up. Pediatric surgeons trained in advanced laparoscopic techniques including intracorporeal suturing can perform laparoscopic repair of choledochal cyst safely.

Anastomosis, Surgical↗
PubMed2006

Evaluation of new prosthetic meshes for ventral hernia repair.

BACKGROUND: In hernia repair, particularly laparoscopic hernia repair, direct contact between mesh and abdominal organs cannot always be avoided. Several mesh materials and composite meshes have been developed to decrease subsequent adhesion formation. Recently, new meshes have been introduced. In an experimental rat study, their value was established and compared with that of meshes already available on the market. METHODS: In 200 rats, eight different meshes were placed intraperitoneally and in direct contact with abdominal viscera. The following meshes were tested: polypropylene (Prolene), e-PTFE (Dualmesh), polypropylene- polyglecaprone composite (Ultrapro), titanium-polypropylene composite (Timesh), polypropylene with carboxymethylcellulose-sodium hyaluronate coating (Sepramesh), polyester with collagen-polyethylene glycol-glycerol coating (Parietex Composite), polypropylene-polydioxanone composite with oxidized cellulose coating (Proceed), and bovine pericardium (Tutomesh). At 7 and then at 30 days postoperatively, adhesion formation, mesh incorporation, tensile strength, shrinkage, and infection were scored by two independent observers. RESULTS: Parietex Composite, Sepramesh, and Tutomesh resulted in decreased surface coverage with adhesions, whereas Prolene, Dualmesh, Ultrapro, Timesh, and Proceed resulted in increased adhesion coverage. Parietex Composite, Prolene, Ultrapro, and Sepramesh resulted in the most mesh incorporation. Dualmesh and Tutomesh resulted in significantly increased shrinkage. There were no differences in mesh infection. Parietex Composite and Dualmesh resulted in a moderate inflammatory reaction, as compared with the mild reaction the other meshes exhibited. CONCLUSION: Parietex Composite and Sepramesh combine minimal adhesion formation with maximum mesh incorporation and tensile strength. The authors recommend the use of these meshes for hernia repair in which direct contact with the abdominal viscera cannot be avoided.

Animals↗
PubMed2006

Tissue reaction and surface morphology of absorbable sutures after in vivo exposure.

Tissue reaction to suture materials depends mainly on how the polymer they are composed of interacts with the tissues. There are few in vivo studies evaluating the suture material modifications resulting from its interaction with tissues. This paper aimed to study rat subcutaneous tissue reaction to irradiated polyglactin 910, polydioxanone, poliglecaprone 25 and chromic gut and its correlation with the ultra-structural alterations the materials undergo. The histological alterations were studied on the 1st, 2nd, 3rd, 7th and 14th day after suture implantations. In these periods, the materials were removed from the tissues and their surfaces were analyzed by scanning electron microscopy. Irradiated polyglactin 910 stimulated the formation of multinucleated giant cells and its filaments underwent cleavage and dissolution. In potydioxanone, a few inflammatory cells and scar fibrosis was observed, and triangular cracks appeared on its surface. Around the poliglecaprone 25, a diffused infiltration of a few mononuclear cells and fibrosis was recorded and formation of craters was observed on its surface. Chromic gut induced necrosis and granulation tissue and underwent dissolution in the tissues during the studied periods. In this study, it was observed that suture materials induced differentiated tissue reactions and morphologic surface changes, suggesting that indications should be individualized.

Animals↗