Conventional gamma sterilization could induce substantial oxidative degradation during subsequent storage of the PE component in air and during their use in vivo. This oxidative degradation may induce high wear rates, delamination and/or gross fracture of the affected PE component. An improved understanding of the effects of cross-linking and oxidation on ultra high molecular weight polyethylene (UHMWPE) has lead to the common use of oxygen-protected packing during radiation sterilization and shelf storage. More recently, methods to deliberately highly cross link UHMWPE while reducing the material's potential to oxidize have been develop in the form of highly cross linked UHMWPE. We reviewed the manufacturing, sterilization, cross linking methods and clinical results of the new polyethylene.
Aluminum Hydroxide ; Arthroplasty ; Carbonates ; Hip ; Molecular Weight ; Polyethylene ; Polyethylenes ; Sterilization

STUDY DESIGN: This is a mechanical study. OBJECTIVES: We wanted to investigate the mechanical properties of newly developed dual growing rods for obtaining approval for their clinical application. SUMMARY OF LITERATURE REVIEW: The current expandable spinal implant system appears effective for controlling progressive early onset scoliosis, and it allows for spinal growth and improving lung development. MATERIALS AND METHODS: We investigate the yield load and ultimate load during compression, tension and torsion of the growing rods and the conventional rods assembly using UHMWPE blocks, and the diameter of the rods was 6.0 mm and they expanded 5cm long. We also performed a fatigue test with growing rods, and the diameter of which was 6.0 mm and it expanded 2.5cm long. The guideline for the American Society for Testing Materials was followed during the entire mechanical test. With the growing rods and conventional rods, we tested for each mechanical property7 times with the new rods and blocks. RESULTS: The yield load of the growing rods and conventional rods were 845.2+/-18.2 (N) and 812.9+/-29.9 (N), respectively, and the ultimate load of the growing rods and conventional rods were 961.9+/-31.1 (N) and 914.9+/-25.6 (N), respectively, when compression force was applied. The yield load and ultimate load of the growing rods were statistically higher than those of the conventional rods (p<0.05). The ultimate load of the growing rods and conventional rods were 3281.7+/-41.5 (N) and 3678.5+/-447.9 (N), respectively when tension force was applied. The ultimate load was similar for both types of rods (p>0.05). The yield loads of the growing rods and conventional rods were 11.56+/-0.59 (Nm) and 12.46+/-0.71 (Nm), respectively, the ultimate loads of the growing rods and conventional rods were 16.97+/-0.94 (Nm) and 17.42+/-2.66 (Nm) during the torsion, respectively. The yield load and ultimate load of the growing rods were statistically lower than that of the conventional rods (p<0.05). CONCLUSIONS: The newly developed growing rods have a higher yield load and ultimate load under compression, a similar ultimate load under tension and a lower yield load and ultimate load under torsion. The differences of the yield load and ultimate load under torsion were minimal, and so the growing rods and conventional rods have similar mechanical properties.
Fatigue ; Lung ; Polyethylenes ; Scoliosis

OBJECTIVE: Medpor porous polyethylene was used to reconstruct small bone defects (gaps and burr holes) along a craniotomy bone flap. The feasibility and cosmetic results were evaluated. METHODS: Medpor Craniotomy Gap Wedges, V and T, were designed. The V implant is a 10 cm-long wedge strip, the cross section of which is an isosceles triangle with a 4 mm-long base, making it suitable for gaps less than 4 mm after trimming. Meanwhile, the Medpor T wedge includes a 10 mm-wide thin plate on the top surface of the Medpor V Wedge, making it suitable for gaps wider than 4 mm and burr holes. Sixty-eight pterional craniotomies and 39 superciliary approaches were performed using the implants, and the operative results were evaluated with respect to the cosmetic results and pain or tenderness related to the cranial flap. RESULTS: The small bone defects were eliminated with less than 10 minutes additional operative time. In a physical examination, there were no considerable cosmetic problems regarding to the cranial bone defects, such as a linear depression or dimple in the forehead, anterior temporal hollow, preauricular depression, and parietal burr hole defect. Plus, no patient suffered from any infectious complications. CONCLUSION: The Medpor Craniotomy Gap Wedge is technically easy to work with for reconstructing small bone defects, such as the bone gaps and burr holes created by a craniotomy, and produces excellent cosmetic results.
Benzeneacetamides ; Cosmetics ; Craniotomy ; Depression ; Forehead ; Humans ; Operative Time ; Physical Examination ; Piperidones ; Polyethylene ; Polyethylenes

PURPOSE: The purpose of this study is to evaluate the effect of change in tibial posterior slope on contact force and ligament stress using finite element analysis. MATERIALS AND METHODS: A 3-dimensional finite element model for total knee arthroplasty was developed by using a computed tomography scan. For validation, the tibial translations were compared with previous studies. The finite element analysis was conducted under the standard gait cycle, and contact force on ultra-high molecular weight polyethylene (UHMWPE) and stresses on lateral and medial collateral ligaments were evaluated. RESULTS: The tibial translations showed similarity with previous studies. As the tibial posterior slope angle increases, the contact stress area increased and was well distributed, and the contact force on UHMWPE decreased overall. However, the maximum contact force in the case for 10degrees case was greater than those for others. The stresses on ligaments were the greatest and smallest in 0degrees and 10degrees cases, respectively. CONCLUSIONS: The higher tibial posterior slope angle leads to the lower contact stress and more extensive stress distribution overall in posterior-stabilized total knee arthroscopy. However, it does not absolutely mean the smallest contact force. The stresses on ligaments increased with respect to the smaller tibial posterior slope angle.
Arthroplasty ; Arthroscopy ; Collateral Ligaments ; Finite Element Analysis ; Gait ; Knee ; Ligaments ; Molecular Weight ; Polyethylene ; Polyethylenes ; Translations

Enophthalmos means displacement of the globe into the bony orbit backward, and usually downward. In post-traumatic enophthalmos, the mechanisms that determine the globe position can be the enlargement of the orbital cavity, the herniation of orbital fat into the maxillary sinus, fat atrophy, loss of ligament support, and scar contracture. It can be reconstructed through several approaches such as transconjunctival, canthotomy, lower eye lid, coronal approach, and by using bone, cartilage, and alloplastic materials. The authors report a case of postoperative enophthalmos reconstructed through subciliary and transnasal endoscopic approaches using porous polyethylene with embedded titanium.
Atrophy ; Cartilage ; Cicatrix ; Contracture ; Displacement (Psychology) ; Endoscopes ; Enophthalmos ; Eye ; Humans ; Ligaments ; Maxillary Sinus ; Orbit ; Polyethylene ; Polyethylenes ; Titanium

PURPOSE: Augmentation rhinoplasty using alloplastic materials is a relatively common procedure among Asians. Silicon, expanded polytetrafluoroethylene (Gore-tex(R)), and porous high density polyethylene (Medpor(R)) are most frequently used materials. This study was conducted to analyze revisional rhinoplasty cases with alloplastic materials, and to investigate the usage of alloplastic materials and their complications. We also reviewed complications caused by various materials used in plastic surgery while operating rhinoplasty. MATERIALS AND METHODS: We report 581 cases of complications rhinoplasty with alloplastic implants and review of the literature available to offer plastic surgeons an overview on alloplastic implant-related complications. RESULTS: Among a total 581 revisional rhinoplasty cases reviewed, the alloplastic materials used were silicone implants in 376, Gore-tex(R) in 183, and Medpor(R) in 22 cases. Revision cases and complications differed according to each alloplastic implant. CONCLUSION: Optimal alloplastic implants should be used in nasal structure by taking into account the properties of the materials for the goal of minimizing their complications and revision rates. A thorough understanding of the mechanism involved in alloplastic material interaction and wound healing is the top priority in successfully overcoming alloplastic-related complications.
Asian Continental Ancestry Group ; *Biocompatible Materials/adverse effects ; Humans ; Polyethylene ; Polyethylenes ; *Polytetrafluoroethylene ; Postoperative Complications ; Prosthesis Implantation/*methods ; Rhinoplasty/*methods ; Silicones ; Treatment Outcome

OBJECTIVES: Evaluation of a new material, high-density porous polyethylene (HDPP), which is covered with fascia lata, for experimental nasal septal perforation closure. METHODS: Twenty New Zealand albino rabbits were included and divided into study and control groups. A lateral incision was made from the lateral aspect of the left nares to the incisura nasomaxillaris. After exposure of the cavum nasi, the nasal mucoperichondrium was elevated bilaterally. A full-thickness 0.5x0.5-cm perforation was created over the septum nasi with a No. 11 surgical blade. A fascia lata graft was used for the study group. The HDPP was covered with fascia lata and placed under the elevated mucosa. HDPP without a fascial covering was used in the control group. Four months after the procedure, magnetic resonance imaging was performed to evaluate resorption of the material. The animals were sacrificed, and the nasal septum was completely removed. Macroscopic and histopathological examinations were performed on the nasal septum. RESULTS: All rabbits had survived after the 4-month period. Macroscopically, nine of 10 (90%) perforations were closed in the fascia lata-covered HDPP group. Histopathological examination of these nine rabbits revealed that the continuity of cartilage was disturbed in the perforation areas. Granulation tissue was inverted in areas in which the cartilage continuity was disturbed. The HDPP had remained intact at the edge of the perforation. In the HDPP group, six of 10 implants were still perforated (60%) and four (40%) were closed. The fascia lata-covered HDPP implant had a significantly higher perforation closure rate than that of the HDPP implant alone (P<0.05). CONCLUSION: In cases of septal perforation, it is better to cover the HDPP implant with fascia lata. This covered implant can be used for the repair of nasal septal perforations. HDPP implants are easy to work with and avoid the increased operative time and morbidity associated with harvesting autografts.
Animals ; Cartilage ; Fascia ; Fascia Lata ; Granulation Tissue ; Magnetic Resonance Imaging ; Mucous Membrane ; Nasal Septal Perforation ; Nasal Septum ; New Zealand ; Operative Time ; Polyethylene ; Polyethylenes ; Pyridones ; Rabbits ; Transplants

OBJECTIVETo investigate if the Ribbond polyethylene fiber has the effect of reinforcing polymethyl methacylate.

METHODS28 specimens were fabricated and divided into 3 groups: group of chemical-cured PMMA, group of chemical-cured PMMA reinforced by stainless steel wire and group of chemical-cured PMMA reinforced by Ribbond polyethylene fiber. A three-point bending test was used to measure the flexural strength and flexural modulus of specimens. Then the data were analyzed with a one-way analysis of variance.

RESULTSThe flexural strength of chemical-cured PMMA group was (51.383 +/- 2.761) MPa, the flexural modulus was (1791.2 +/- 113.760) MPa; The flexural strength of stainless steel wire reinforced group was (58.725 +/- 1.218) MPa, the flexural modulus was (2092.76 +/- 120.28) MPa; The flexural strength of Ribbond polyethylene fiber reinforced group was (80.975 +/- 2.58) MPa, the flexural modulus was (2866.53 +/- 107.51) MPa. The one-way analysis of variance showed that the results were significant (P < 0.001). Newman-Keuls method showed that the differences among all groups were significant (P < 0.05).

CONCLUSIONThe Ribbond polyethylene fiber can raise the flexural strength and flexural modulu of polymethyl methacylate.

Dental Bonding ; Dental Materials ; chemistry ; Dental Stress Analysis ; Materials Testing ; Polyethylene ; chemistry ; Polyethylenes ; chemistry ; Polymethyl Methacrylate ; chemistry ; Stress, Mechanical ; Tensile Strength

OBJECTIVE: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. METHODS: Roots of human mandibular central incisors were covered with silicone, mimicking the periodontal ligament, and embedded in polymethylmethacrylate. The specimens (N = 50), with two teeth each, were randomly divided into five groups (n = 10/group) according to the retainer materials: (1) Interlig (E-glass), (2) everStick Ortho (E-glass), (3) DentaPreg Splint (S2-glass), (4) Ribbond (polyethylene), and (5) Quad Cat wire (stainless steel). After the recommended adhesive procedures, the retainers were bonded to the teeth by using flowable composite resin (Tetric Flow). The teeth were subjected to 10,00,000 cyclic loads (8 Hz, 3 - 100 N, 45degrees angle, under 37 +/- 3degrees C water) at their incisoproximal contact, and debonding forces were measured with a universal testing machine (1 mm/min crosshead speed). Failure sites were examined under a stereomicroscope (x40 magnification). Data were analyzed by one-way analysis of variance. RESULTS: All the specimens survived the cyclic loading. Their mean debonding forces were not significantly different (p > 0.05). The DentaPreg Splint group (80%) showed the highest incidence of complete adhesive debonding, followed by the Interlig group (60%). The everStick Ortho group (80%) presented predominantly partial adhesive debonding. The Quad Cat wire group (50%) presented overlying composite detachment. CONCLUSIONS: Cyclic loading did not cause debonding. The retainers presented similar debonding forces but different failure types. Braided stainless steel wire retainers presented the most repairable failure type.
Adenine ; Adhesives ; Animals ; Carbamates ; Cats ; Collodion ; Composite Resins ; Deoxycytidine ; Drug Combinations ; Fatigue ; Humans ; Incidence ; Incisor ; Organophosphonates ; Periodontal Ligament ; Polyethylene ; Polyethylenes ; Polymethyl Methacrylate ; Quinolones ; Recurrence ; Retention (Psychology) ; Silicones ; Splints ; Stainless Steel ; Thiazoles ; Tooth ; Elvitegravir, Cobicistat, Emtricitabine, Tenofovir Disoproxil Fumarate Drug Combination

OBJECTIVETo develop a chitosan (CH)/polyethylene glycols succinate acid (PEG-SA)-mediated mitomycin C (MMC) delivery system and investigate its drug release characteristics in vitro and its effect against scar tissue adhesion in vivo.

METHODSMitomycin C loading in the composite CH/PEG-SA/MMC films was determined using ultraviolet. The freeze-dried films were dispersed in 1 ml PBS (pH7.4) and mitomycin C release in vitro was determined according to the mitomycin C concentration-UV value standard curve. The influence of the film structure on the drug release was evaluated. The drug delivery system was then implanted in SD rats, and 4 weeks later, immunohistochemical and histological examinations were carried out to assess the therapeutic effect on epidural scar tissue.

RESULTSThe linear regression equation of the mitomycin C concentration-UV value standard curve was y=0.593x(3)-2.563x(2)+25.944x-0.236 (R(2)=1.000). The film demonstrated good drug delivery capability, and 20 mg of the samples in PBS showed a peak mitomycin C release after 12 days of 14.9616 microg/ml, which was higher than the ID(50) of mitomycin C (10.4713 microg/l) to the fibroblasts. On days 18 and 32, another two drug release peaks occurred (14.4824 microg/ml and 11.4092 microg/ml, respectively), followed by maintenance of slow release. Till day 60, the accumulative mitomycin release reached 0.1793 microg/ml, and the loaded drug was ultimately completely released. Significant differences were noted in the hydroxyproline content in the scar tissues of different groups (F=12.085, P=0.000), and the CH/PEG-SA/MMC DDS reduced the amount of scar tissue and promoted its orderly alignment to control potential scar hyperplasia that may compress the spinal cord and nerve roots.

CONCLUSIONThe composite film for drug delivery possesses good flexibility and mechanical properties and allows sustained drug release of mitomycin C to prevent epidural scar tissue adhesion following lumbar laminectomy.

Animals ; Chitosan ; chemistry ; Drug Delivery Systems ; Intervertebral Disc ; drug effects ; physiopathology ; surgery ; Mitomycin ; administration & dosage ; chemistry ; Polyethylene Glycols ; chemistry ; Polyethylenes ; chemistry ; Rats ; Rats, Sprague-Dawley ; Succinates ; chemistry ; Tissue Adhesions ; prevention & control