Bioabsorbable Materials Research Articles

Étude de la corrélation entre le coût réel d’une intervention et ses modes de facturation en France : exemple de l’ablation de matériel d’ostéosynthèse de mandibule

economic cost is a timely topic which will have to be taken in consideration more and more for determining the appropriate indication for surgical procedures. "Health has no price, but it has a cost" is a common proverb urging us to think in terms real cost of a surgical procedure. The purpose of this study is to estimate the real cost of a usual and frequent intervention: removal of osteosynthesis material in mandibular fractures. Real cost was compared with the cost charged by the French health insurance fund. this retrospective study collected all the interventions concerning material removal after mandibular fractures performed in our department during 2002. The following parameters were retained: the number of consultations, the duration of occupation of the surgical unit and the recovery room, the list of materials and products used, the cost of the medical staffs and cleaning agents, the duration of hospitalization, other administrative loads and expenses. a series of 30 patients was found, each patient had had three consultations, the average duration of hospitalization was 36 hours, the time of occupation of the surgical unit was 100 minutes and occupation of the recovery room was 2 hours. The total real cost of this intervention was 510 Euros, the cost estimated by the health insurance fund was 110 Euros and the cost of hospitalisation charged was 997 Euros. these results show us the real cost of this intervention and the cost estimated by the French health insurance fund. It is highly noteworthy that the cost estimates were totally inadequate. This study leads to a discussion concerning a more global approach to the cost-benefit ratio of such an intervention as well as the indication for bioabsorbable material compared with titanium in facial traumatology.

Type III fracture of the tibial tubercle with avulsion of the tibialis anterior muscle in the adolescent male athlete

Introduction: Type III fracture of the tibial tubercle by Watson–Jones, or type IIIa injury according to John Ogden’s classification has been well described and its management is now well codified in standard orthopaedic textbooks. Materials and methods: The authors present a case of type III fracture of the tibial tubercle associated with an avulsion of the tibialis anterior muscle. Results: We demonstrated the effectiveness of bioabsorbable material for fixing the fracture preventing the need for removal of metalware, and that the anterior tibialis muscle had been stripped by the injury. Conclusion: A displaced type III fracture of the tibial tubercle may have an associated with avulsion of the tibialis anterior muscle, particularly in adolescent athletes. Prompt recognition and appropriate surgical treatment can give an excellent outcome.

Biliary and pancreatic stents.

The use of biliary and pancreatic stents has increased significantly during the last 2 decades because of improvements in available endoscopes and endoscopic accessories, as well as better techniques. The number of endoscopists who can successfully complete these demanding procedures has also increased, as have the indications for stent therapy in biliary and pancreatic diseases. Stents are now made in various shapes and configurations from different types of polymers (plastics), various expandable metallic alloys, and bioabsorbable materials. Most of the available data relate to plastic and metallic stents for biliary tract disease; the data for pancreatic disease are fewer and involve a smaller number of patients. This article reviews the most recent available data concerning biliary and pancreatic stents and discusses possible future developments. It does not attempt to cover all data reported in biliopancreatic stent therapy.

Synthesis of poly(L-lactide) end-capped with lactose residue.

The synthesis of poly(L-lactide) (polyLA) end-capped with lactose residue was studied from the standpoint of development of a new bioabsorbable material. After the hydroxyl group of t-butoxycarbonyl(Boc)-aminoethanol was converted to Boc-aminoethanol-OK by using potassium/naphthalene, L-lactide was polymerized in tetrahydrofuran using Boc-aminoethanol-OK as an initiator at room temperature to prepare polyLA-NHBoc. Subsequently, the removal of the Boc group in terminal Boc-aminoethanol residue was performed by treatment of formic acid to obtain the amino group end-capped polyLA (polyLA-NH(2)) as a reactive polyLA derivative. The coupling reactions of lactose with polyLA-NH(2) were investigated by two methods; the synthetic method through reductive amination of lactose with polyLA-NH(2) in the presence of sodium cyanoborohydride as a reducing agent did not give high degree of substitution of end-capped lactose residue per polyLA molecule, whereas the synthetic method through the ester interchange reaction of lactonolactone with polyLA-NH(2) gave Lac-polyLA perfectly end-capped with lactose residue.

Spotlight on naturally absorbable osteofixation devices.

The practice of using implants is growing day by day, and more foreign materials are being inserted for various indications. The field of implantology thus deserves intensive research and careful evaluation of results. Solutions to overcome current problems and risks are necessary. It has taken a long time to arrive at where we are now. Bioabsorbable devices were explored in the 1960s for surgical bone fixation. Failures were followed by changes in ways of thinking and innovations. Improvements in the strength properties and biocompatibility were achieved. Bioabsorbable polymeric materials such as high-molecular-weight polymers were used and also reinforced with other material or, more recently, by self-reinforcement to produce small yet strong devices. New generations of implants include those that contain bioactive substances such as antibiotics and growth factors. Developments in bioabsorbable materials continue to accommodate the new way of thinking brought about by the emergence of the field of tissue engineering. Surgeons, conversely, are also inventing new surgical techniques and methods to exploit the plastic and bioabsorbability properties of these materials for the better future of our patients. Such a multidisciplinary approach that involves surgeons and materials scientists should help to find solutions to the current limitations of these devices.

Use of triethylcitrate plasticizer in the production of poly-L-lactic acid implants with different degradation times.

Bioabsorbable materials have been widely used in the repair of damaged tissue as well as in the controlled release of drugs and as a supports for cultured cells. The degradation time of poly-L-(lactic acid) (PLLA) may be controlled by altering the polymer porosity through the addition of the plasticizer triethylcitrate. This in turn influences the extent cellular infiltration. In this study, we examined the degradation of PLLA membranes containing different concentrations of plasticizer. PLLA discs were implanted subcutaneouly in rats and withdrawn 2, 14 and 60 days after implantation. The samples were processed for light microscopy and scanning electron microscopy (SEM). Polymer degradation was proportional to the concentration of plasticizer, indicating that triethylcitrate could affect the degradation time of the implants, without damaging the polymer biocompatibility.

Effect of Bioabsorbable Osseous Fixation Materials on Dura Mater and Brain Tissue

Bioabsorbable materials are frequently used in pediatric cranial surgery, but the effects of these materials on neural tissue are not known. The authors assessed the histologic alterations to dura mater and brain tissue associated with bioabsorbable plates. Fifteen Sprague-Dawley rats were given sham cranial surgery; an additional 30 underwent placement of 8 x 8-mm polylactic acid/poly-glycolic acid plates. The rats were assessed weekly for neurologic or behavioral changes suggesting neural damage. A portion of each group was killed at 3, 6, and 12 months for histologic analysis of cranium, dura mater, and brain tissue by standard hematoxylin and eosin stain. None of the animals showed any behavioral changes or neurologic deficits. The plates were gradually hydrolyzed over the study period, and all had disappeared by 12 months. The histologic examination showed fibrous encapsulation around the plates, accompanied by foreign body giant cell reaction and calcification. Focal gliosis, where evident, was mild and confined primarily to the superficial cortex of the brain beneath the plate. The infiltration of the dura mater and underlying brain parenchyma was negligible. In conclusion, the neurologic and histologic effect of bioabsorbable plates on neural tissue may be considered negligible in the early postoperative period.

309 残留応力を利用した生体吸収性材料の吸収速度コントロールに関する研究

It is necessary to control of absorption time of drug capsule made of bio-absorbable material in drug delivery system (DDS), in order to release the drug concentrated at an affected part. Drug capsule with non-uniform thickness is useful to control the absorption time because capsule break and drug release occur at a thinnest part of the capsule. Mechanical stress occurred in bio-absorbable material also affect to its absorption ratio, so it is possible to control the absorption time by varying residual stress value if residual stress is given for the drug capsule of DDS. We investigated effect of the non-uniform shape and residual stress to the absorption time in two-dimensional ring made of bio-absorbable material. Variable cross-sectional ring with residual stress was made of PLLA, and absorption examination was carried out in HCOOH solution. From the results, possibility of control absorption time of drug capsule in DDS was considered.

Repair of facial nerve with alginate sponge without suturing: an experimental study in cats.

A bioabsorbable material, alginate, was used to repair a defect in the facial nerve. In five cats a 5-mm gap was created in the dorsal ramus of the facial nerve on one side selected at random, which was repaired by implantation of alginate sponge without suturing. In the control group, two cats had a similar nerve injury but without implantation of alginate. Behavioural, electrophysiological, and histological examinations were made over a period of 16 weeks postoperatively. Movement of the upper eyelids and electrophysiological function were restored 12 weeks postoperatively, and many myelinated axons were observed both in the gap of facial nerve and its branches 16 weeks after operation, whereas no alginate residue was detected remaining within gap. In the control group, no movement or electrophysiological restoration was recorded, and there were few regenerated axons accompanied by a large amount of scar tissue. The nerve repaired with alginate showed remarkable regeneration. These results suggest that alginate is a promising material for facial nerve repair, and sutureless repair with alginate is a possible option for treating defects in the facial nerve.

Strength retention properties of self-reinforced poly l-lactide (SR-PLLA) sutures compared with polyglyconate (Maxon R) and polydioxanone (PDS) sutures. An in vitro study

Recent developments in manufacturing techniques have led to the development of strong bioabsorbable materials such as self-reinforced poly l-lactide (SR-PLLA) sutures. The aim of the study was to investigate the mechanical properties of SR-PLLA sutures in comparison with polyglyconate (Maxon R) and polydioxanone (PDS) sutures in vitro. Sutures made of SR-PLLA (0.3, 0.5 and 0.7 mm ∅), Maxon R (0.3 and 0.5 mm ∅) and PDS (0.3 and 0.5 mm ∅) were studied by immersion in phosphate-buffered distilled water (pH 7.4) at 37°C for 40 weeks. The breaking force of straight sutures and suture knots was measured. Tensile strength and percentage elongation were calculated. Means, standard deviations, differences between means, and confidence intervals for differences between means were evaluated. SR-PLLA, PDS and Maxon R sutures of 0.3 and 0.5 mm ∅ were of comparable initial tensile strength. Initial knot tensile strength values were lower than those of their counterpart straight sutures. Maxon R sutures had lost their tensile strength by 12 weeks; PDS sutures by 20 weeks. SR-PLLA sutures of 0.3 mm ∅ had a strength of 161.6 MPa and those of 0.5 mm ∅ had a strength of 134 MPa at 40 weeks. The highest percentage elongation of straight sutures (62.8% and 62%) was exhibited by PDS; the lowest by SR-PLLA (35.6% and 35%). In loop tests, PDS showed the highest percentage elongation (43.7% and 58.1%) and SR-PLLA had the lowest values (19.7% and 33%). SR-PLLA sutures had the most prolonged strength retention in vitro, but the lowest elongation (elasticity). Compared with straight sutures, knots had lower tensile strength and elongation values. SR-PLLA sutures can be applied to the closure of wounds that need prolonged support, such as bone.

Bioabsorbable implants in orthopaedics: new developments and clinical applications.

The use of bioabsorbable implants in orthopaedic surgical procedures is becoming more frequent. Advances in polymer science have allowed the production of implants with the mechanical strength necessary for such procedures. Bioabsorbable materials have been utilized for the fixation of fractures as well as for soft-tissue fixation. These implants offer the advantages of gradual load transfer to the healing tissue, reduced need for hardware removal, and radiolucency, which facilitates postoperative radiographic evaluation. Reported complications with the use of these materials include sterile sinus tract formation, osteolysis, synovitis, and hypertrophic fibrous encapsulation. Further study is required to determine the clinical situations in which these materials are of most benefit.

EXPANSION AND BIOABSORPTION OF THE SELF-REINFORCED LACTIC AND GLYCOLIC ACID COPOLYMER PROSTATIC SPIRAL STENT

Self-reinforced bioabsorbable stents can be made self-expanding due to the viscoelastic memory of the oriented bioabsorbable materials. A new self-expandable self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80:20 stent was developed to prevent postoperative urinary retention after procedures that induced prostatic edema. In in vitro experiments the expansion rate has been up to 100% during the first few hours at body temperature. We investigated the expansion rate and biodegradation of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent in vivo in the prostatic urethra. A total of 39 men, 52 to 84 years old, with lower urinary tract symptoms due to benign prostatic enlargement underwent interstitial laser coagulation of the prostate. A self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was inserted into the prostatic urethra at the end of the operation. The stent lumen diameter was 4.5 mm. The location and diameter of the lumen and degradation of the stent were studied with transrectal ultrasound at 1, 2, 4 and 6 months postoperatively. At 6 months patients underwent cystoscopy. All except 1 patient voided on postoperative day 1. Mean lumen diameter was 7.4 mm. (range 6.2 to 8.2) at 1 month and 7.2 mm (range 6.2 to 7.5) at 2 months. At 4 months the stent was degraded into small pieces. No pieces of stent were found in the prostatic urethra on ultrasound or cystoscopy at 6 months. However, a portion of the spiral stent was found at the bottom of the bladder in 2 patients. The speed and expansion rate of the self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was sufficient to lock the stent in place and ensure voiding in cases of edema induced bladder outlet obstruction. Strength retention greater than 2 months was long enough to avoid later impairments of voiding.

Bone tunnel remodeling at the site of biodegradable interference screws used for anterior cruciate ligament reconstruction: 5-year follow-up

Purpose: The purpose of this prospective study was to review, using expanded clinical-assessment tools, the long-term results of the local effects of a bioabsorbable interference screw (copolymer 85/15 D,L lactide/glycolide) in anterior cruciate ligament (ACL) reconstruction. Type of Study: This prospective study was initiated in May 1993. The inclusion criteria for patient selection included rupture of the ACL in athletic patients without involvement of the collateral ligaments, arthroscopic ACL reconstruction using middle third of the ligamentum patella, and magnetic resonance imaging (MRI) and plain radiographic examinations of the knee joint during follow-up. Materials: Between May 1993 and October 1994, 32 patients were enlisted in the study; 48 patients did not fit the inclusion criteria. There were 25 men 7 women. The average age was 29.1 years (range, 19 to 50 years). There were 21 right knees and 11 left knees. The follow-up examinations were performed by an independent examiner. There were 28 patients available for follow-up at a medium of 5.2 years (range, 4.1 to 6.4 years). The evaluation included various testing systems (i.e., OAK, IKDC, Lysholm) as well as MRI and plain radiographic studies to investigate the longevity of the implant and potential adverse effects of this new bioabsorbable material. Results: The clinical results were good. The OAK score (Orthopädische Arbeitsgruppe Knie) showed 93% excellent and good results, and 7% fair results. The IKDC and Lysholm scores were 92% and 96% good and excellent results, respectively. MRI showed bone remodeling and new bone formations at the site of the implant in the femoral as well as in the tibial bone tunnel at follow-up. No cystic or osteolytic changes where seen on MRI or plain radiographs. Conclusions: This study showed the correlation between histology and MRI: there was minimal surgical-site edema, minimal reaction to this material, and complete replacement by new bone formation of the previous site of this implant. At 5 years, this bioabsorbable interference screw appeared clinically safe and effective for fixation of bone blocks during ACL reconstruction and MRI showed complete absorption and replacement with new bone.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 6 (July-August), 2001: pp 597–602

F-0914 生体吸収性膜を用いた骨組織の再建(S44-1 生体材料研究の新展開(1))(S44 生体材料研究の新展開)

Experimental bone regeneration with the aid of bioabsorbable membrane was carried out for the cases of canine mandibular, tibia, and skull. The membrane was made of the composite of the copolymer of L-lactic acid, glycol acid and caprolactone and the inorganic material β-TCP. The experimental bone defects were covered by the membranes and the open spaces for the bone regeneration were realized. After 12 weeks of the operation, complete bone regeneration was observed in the case of mandibular. Partial regeneration in the cases of tibia and skull, in which cases the full regeneration was observed with the additional implantation of the bioabsorbable materials.

Pre-clinical in vivo evaluation of orthopaedic bioabsorbable devices

The presence of bioabsorbable materials in orthopaedics has grown significantly over the past two decades with applications in fracture fixation, bone replacement, cartilage repair, meniscal repair, fixation of ligaments, and drug delivery. Numerous biocompatible, biodegradable polymers are now available for both experimental and clinical use. Not surprisingly, there have been a wealth of studies investigating the biomechanical properties, biocompatibility, degradation characteristics, osteoconductivity, potential toxicity, and histologic effects of various materials. Promising results have been reported in the areas of fracture fixation, ligament repair, and drug delivery. In this article we review the pre-clinical in vivo testing of bioabsorbable devices with particular emphasis on implants used for these applications.

Reconstruction of rabbit Achilles tendon with three bioabsorbable materials: histological and biomechanical studies

This study investigated whether three biodegradable materials, poly–N–acetyl–D–glucosamine (chitin), poly-ε-caprolactone (p-CL), polylactic acid (PLA), and chitin/p-CL composite could be used as scaffold implants in the reconstruction of extra-articular ligaments or tendons. Braided artificial tendons made from these materials were soaked in phosphate-buffered saline or implanted in the subcutaneous tissue of 31 Japanese white rabbits and then subjected to load at failure testing. There was no significant loss of load at failure when chitin tendons were soaked in saline for 26 weeks, but a rapid decrease occurred in vivo. The other two types of tendons showed significant loss of strength after 26 weeks both in vitro and in vivo. Another 111 rabbits were used to assess Achilles tendon reconstruction with the braided tendon implants. The tendon regeneration process was assessed macroscopically, histologically, immunohisto-chemically, and mechanically (maximum load at failure). Chitin showed more rapid degradation than the other materials on histological examination. There was good formation of fibrous tissue composed of type I and type III collagen around the chitin, PLA, and chitin/p-CL fibers in comparison with p-CL fibers, but chitin tendons showed more rapid loss of strength after implantation. Both PLA and the chitin/p-CL composite tendons had good initial strength and showed increased ingrowth of fibrous tissue, suggesting that these materials are promising as artificial tendons.

Bioabsorbable polymer scaffolds for tissue engineering capable of sustained growth factor delivery

Engineering new tissues utilizing cell transplantation on biodegradable polymer matrices is an attractive approach to treat patients suffering from the loss or dysfunction of a number of tissues and organs. The matrices must maintain structural integrity during the process of tissue formation, and promote the vascularization of the developing tissue. A number of molecules (angiogenic factors) have been identified that promote the formation of new vascular beds from endothelial cells present within tissues, and the localized, controlled delivery of these factors from a matrix may allow an enhanced vascularization of engineered tissues. We have developed a gas foaming polymer processing approach that allows the fabrication of three-dimensional porous matrices from bioabsorbable materials (e.g., copolymers of lactide and glycolide [PLG]) without the use of organic solvents or high temperatures. The effects of several processing parameters (e.g., gas type, polymer composition and molecular weight) on the process were studied. Several gases (CO 2, N 2, He) were utilized in the fabrication process, but only CO 2 resulted in the formation of highly porous, structurally intact matrices. Crystalline polymers (polylactide and polyglycolide) did not form porous matrices, while amorphous copolymers (50:50, 75:25, and 85:15 ratio of lactide:glycolide) foamed to yield matrices with porosity up to 95%. The mechanical properties of matrices were also regulated by the choice of PLG composition and molecular weight. Angiogenic factors (e.g., vascular endothelial growth factor) were subsequently incorporated into matrices during the fabrication process, and released in a controlled manner. Importantly, the released growth factor retains over 90% of its bioactivity. In summary, a promising system for the incorporation and delivery of angiogenic factors from three-dimensional, biodegradable polymer matrices has been developed, and the fabrication process allows incorporation under mild conditions.

Mechanical and fracture behavior of a fiber-reinforced bioabsorbable material for orthopaedic applications.

Tensile and fracture tests were conducted on thin panels of a fiber-reinforced bioabsorbable material. The composites were made of polycarbonate matrix and calcium phosphate fibers. Both matrix and fibers were bioabsorbable orthopaedic biomaterials. The fibers were short and randomly distributed. The properties were compared for composites with and without a coating of methane on the fibers. Composites with the methane coating had a higher elastic modulus, a higher proportional limit, but a lower load at failure on pre-cracked panels. Electron microscopy showed that the coating resulted in a better bond between the matrix and the fiber.

Serial Magnetic Resonance Imaging Evaluation of a Bioabsorbable Interference Screw and the Adjacent Bone

Summary: The purpose of this prospective study was to review, using expanded clinical assessment tools, the initial use of a bioabsorbable interference screw (copolymer 85/15 D, L lactide/glycolide) in anterior cruciate ligament (ACL) reconstruction at the Wels Hospital, Austria. The study enlisted 32 patients of whom 28 were available for follow-up at minimum of 2.5 years. Since the implant material was new and the screw would not show on plain film radiographs, the clinical assessment was expanded beyond the usual historical and physical findings. The evaluation included opportunistic knee joint aspiration and repeat magnetic resonance imaging (MRI) studies to investigate the longevity of the implant and potential adverse effects of this new bioabsorbable material. The knee joint aspirations showed no infection. Serial MRIs showed the physical presence of the screw to remain intact for 4 months and disappear in 6 months. The MRIs showed minimal collection of edema around the bone tunnels that resolved by 12 months. There were no symptoms or adverse clinical result correlated with the MRI evidence of edema. There was temporary bone tunnel expansion. The clinical results were good. The OAK-score (Orthopädische Arbeitsgruppe Knie) showed 89.5 % excellent and good results, 7% fair results and 3.5 % poor results. The average score was 90.7 points (range, 63 to 100 points). The knee joint stability measured with the KT-1000 arthrometer showed 93% to have a 3-mm or less difference compared with the unoperated knee. This bioabsorbable interference screw appeared safe and effective for fixation of bone blocks during ACL reconstruction while producing no occult infection or adverse clinical response during the degradation process.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 5 (July-August), 1999: pp 481–488

Bioabsorbable Self-reinforced Poly-l-Lactide, Metallic, and Silicone Stents in the Management of Experimental Tracheal Stenosis

The aim of the present study was to compare, in rabbits, the biocompatibility and suitability of a bioabsorbable spiral stent made of self-reinforced poly-L-lactide (SR-PLLA) in the management of experimental tracheal stenosis with stents made of metal and silicone. Tracheobronchial stenosis, and its management, is still problematic because stenoses are not always amenable to surgical resection and reconstruction, especially concerning anastomotic problems and stenosis after lung transplantation. Stenosis can be handled with stenting, although the ideal stent has yet to be developed; all the stents available have their disadvantages. Because stenting of the airways can be only temporary, stents made of bioabsorbable materials, theoretically, offer benefits. Tracheal stenosis was created in rabbits by the extramucosal resection of cartilaginous arches of the cervical trachea. After a few weeks, the animals were operated on again, and those stenoses that had developed were dilated with a balloon. Stents then were implanted in the area of stenosis to keep the dilated trachea open. All the animals in the group with silicone stents had to be killed because of respiratory difficulties: their stents had a tendency to occlude because of internal encrustation, and they developed a hyperplastic polyp at the ends of the stents. The SR-PLLA and metallic stents were tolerated well, and after follow-up ended the animals were put to death. This experimental study showed that silicone stents had a tendency to occlude and that stents made of metal and of SR-PLLA were well tolerated and can be used in the management of airway stenosis.