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PubMed2001

[Reconstruction of the acetabulum during replacement of the aseptically loosened polyethylene cup].

THE PURPOSE OF THE STUDY: The aim of the study was to verify the method after Slooff in our modification, i.e. "a cemented cup--cancellous bone grafts--a metal net" for the revision surgery of aseptic loosening of cemented polyethylene acetabular cup in combined defects of acetabulum. MATERIAL: The followed-up group of 52 patients (36 women and 16 men), average age of 65 years (age range, 50-81 years) with aseptic loosened cemented polyethylene Poldi cups included 52 operated on hip joints. The average interval between the primary implantation and the revision surgery was 9 years (2-21 years). METHOD: We reconstructed acetabulum with combined bone defects (AAOS III Degree--as a result of aseptic loosening and migration of cemented acetabular cups) by means of cancellous bone allografts, a shaped Howmedica metal net, Simplex bone cement and a polyethylene cup. RESULTS: Average follow-up was 36 months (range, 14-49 months). Clinical evaluation of the group was performed after Harris Hip Score averaging 80 points. Radiological evaluation focused on the density and presence of bridging trabeculae between the grafts and the host bone. Positive finding was in 46 patients, i.e. 90%. Further, we evaluated migration of the cup after Conn. In 4 patients (7.7%) it was less than 2 mm and in 3 patients (5.7%) it was greater than 5 mm. Reconstruction failed in 1 patient (1.9%). Radiolucent line was found in the zone between the host bone and bone grafts only in III zone after De Lee and Charnley in 8 cases (15.3%), in zones I and II it was not encountered in any of the patients in the group. One case required another revision surgery in which Burch-Schneider ring, bone allografts and Müller cemented cup were used for the reconstruction. In two patients of this group there developed a phlebographically verified phlebothrombosis without signs of embolism into pulmonary artery. In two cases there occurred a superficial inflammation of the wound which subsided before the removal of the suture. No deep infection of the wound was encountered. Particular ossifications were assessed after Brooker. Type I occurred in 7 cases and Type II in 1 patient. DISCUSSION: At present several methods are used for the reconstruction of acetabulum and their choice is limited by the extent of the bone loss. For cavitary defects it is possible to use the combination of bone grafts with cementless cups. In segmental and combined defects the situation is more complicated and it can be solved by the application of a solid bone graft. In case the solid bone graft assumed greater load, the situation logically resulted in the fatigue fracture of screws and failure of the whole reconstruction prior to the bone graft-host bone osteointegration. In cementless cups and solid bone grafts the situation is slightly more favourable. If there is a timely biological (secondary) osteointegration of the cup the reconstruction has a chance to survive. The timeliness of biological (secondary) osteointegration is significantly influenced also by the quality of the applied bone graft and a good contact of the bone graft and the host bone and the surface of the cementless cup. Our method of the reconstruction of acetabulum by means of cancellous bone grafts, metal net and cemented cup allows a relatively good primary stability of the cup. Due to its partial elasticity the metal net does not prevent transmission of forces on the bone grafts which are placed under the net. As a result there occurs a faster union of bone grafts with the host bone. CONCLUSION: The method of cemented cup--cancellous bone grafts--metal net after Slooff is in our modification one of the accepted options of the reconstruction of acetabulum. Its benefit is the possibility of early weight bearing of the limb operated on. The stress on the bone grafts under an elastic construction conduces to a relatively fast good secondary osteointegration. The method can be recommended for II and III Degrees of acetabular bone loss according to AAOS classification. Of no less importance is also the economic aspect of the whole reconstruction.

Acetabulum↗
PubMed2001

[A rare case of extensive bilateral polyethylene granuloma after knee replacement].

The authors present a case of bilateral loosening of total knee arthroplasty as a result of polyethylene (PE) wear. Five and seven years after TKA the patient developed a polyethylene granuloma leading to extensive bone defects under the implant. Finally it resulted in pathological fracture of medial condyle of tibia. A revision PFC stabilized prosthesis was used for reimplantation. Bone defects were filled in by bone grafts from the bone bank. Authors point out the issues of PE wear. In the discussion they list various factors (time, indication, material, design and the factor of individual response of the organism) which may play an important role in the incidence of PE wear. The incidence of polyethylene granuloma in TKA is still a rare complication, however, it is necessary to take this issue into account as the number of such cases will undoubtedly grow.

Aged↗
PubMed1979

Conglutinin binding polyethylene glycol precipitation assay for immune complexes.

An assay for circulating immune complexes is described which uses radiolabelled bovine conglutinin as ligand and polyethylene glycol precipitation as the technique for separating bound ligands. The technique is simple to perform and gives good sensitivity detecting artificial immune complexes. Its use in detecting complexes in systemic lupus erythematosus and Burkitt's lymphoma is described and it is compared with the Clq binding assay also performed with polyethylene glycol. It is suggested that the simultaneous performance of polyethylene glycol assays using radiolabelled Clq and radiolabelled conglutinin may be an advantageous method for screening sera for the presence of immune complexes.

Animals↗
PubMed2001

[Porous polyethylene (Medpor) orbital implant. Prospective study of 75 primary implantations].

PURPOSE: To examine the incidence of orbital complications in patients who underwent primary placement of a porous polyethylene implant (Medpor) after enucleation. MATERIAL AND METHOD: Prospective non randomized case series of 75 consecutive patients in whom a porous polyethylene (PP) spherical implant wrapped with homologous sclera was implanted after enucleation. RESULTS: The mean age at the time of enucleation was 42.7 years (range, 1.4 to 80 years). The histopathological diagnoses after enucleation included uveal melanoma in 28 patients, retinoblastoma in 11 patients, phthisis bulbi in 23 patients, neovascular glaucoma in 5 patients, endophthalmitis in 3 patients, ruptured traumatic globe in 2 patients, microphthalmos in two patients, and medulloepithelioma in one patient. Thirty-four patients (45%) had had prior ocular surgery. The prosthesis was fitted after a mean interval of 4.5 weeks (range, 3 to 10 weeks). After a mean follow-up of 20 months (range, 3 to 33 months), there was one case (1%) of conjunctival dehiscence with material exposure secondary to massive postoperative orbital hemorrhage 2 weeks after enucleation. There was no case of orbital cellulitis, implant extrusion, or significant inflammatory response. No PP implant was drilled for peg placement. DISCUSSION-CONCLUSIONS: The anteriorly wrapped porous polyethylene orbital (Medpor) sphere appears to be well tolerated by all age groups with no major complication in primary implantation after enucleation.

Adolescent↗
PubMed2002

[Paralytic ectropion correction with porous polyethylene spacer by subciliar external approach].

PURPOSE: To evaluate the efficacy of porous polyethylene spacer in paralytic ectropion. METHODS: Nine eyes of 8 patients (5 male and 3 female, medium age 55.6 S.D. 11.2 years) with paralytic ectropion were operated. All of them presented a scleral show of more than 3 mm, exposure queratopathy and epiphora grade III-IV in Munk scale. A tarsal strip procedure, internal cathoplasty and porous polyethylene spacer sutured to the inferior border of the tarsal plate and over the palpebral retractors by subciliar external approach were performed. RESULTS: The mean followup time was 9.8 S.D. 4.3 months. The scleral show, exposure queratopathy and epiphora improved in all patients. There were two extrusions of the synthetic material, with removal of the implant in one of them. In these two cases a long lasting facial palsy with miocutaneous atrophy was the cause of the ectropion. CONCLUSIONS: Porous polyethylene speacer is a good alternative for paralytic ectropion treatment. This technique decreases the risk of infectious disease transmission as in homologous grafts and the need of a second surgical procedure as in autologous grafts.

Adult↗
PubMed1976

Nonchromatographic radioimmunoassay of unconjugated estriol in plasma, with polyethylene glycol as precipitant.

We describe a rapid, reliable radioimmunoassay for unconjugated estriol in plasma. Polyethylene glycol (Carbowax 6000) is used to separate antibody-bound and free steroid. The assay is sensitive (25 pg for standards), precise, and accurate. At high and low concentrations of estriol, intra-assay coefficients of variation were 7.1% and 7.6%, respectively, and inter-assay coefficients of variation were 7.2% and 10.0 %, respectively. Free [3H] estriol is not precipitated by polyethylene glycol. This radioimmunoassay of estriol, with a highly specific antiserum and with polyethylene glycol as the antibody precipitant, is a reliable one-day assay that is practical both for the clinical laboratory and the obstetrician.

Analysis of Variance↗
PubMed2002

Screening of stabilized crosslinked polyethylene using a novel wear tester.

A novel pin-on-disk type wear tester is described allowing a rapid screening of different types of polyethylene under both unidirectional and multidirectional sliding motion. The wear of four polyethylene materials sliding against a roughened CoCrMo alloy was evaluated: a non-irradiated UHMWPE, a UHMWPE irradiated with a dose of 25 kGy in air, and two types of crosslinked UHMWPE (100 kGy, air), which were subjected to a stabilization heat treatment in nitrogen at 155 degrees C for 72 hours (XLPE I) and in water at 130 degrees C for 72 hours (XLPE II), respectively.Under multidirectional sliding conditions both types of XLPE exhibited significantly less wear with respect to the 25 kGy irradiated UHMWPE and the non-irradiated UHMWPE, even under the rough counterface conditions applied. Under unidirectional sliding motion both types of XLPE exhibited the highest wear of all materials tested, because the orientation hardening effect acting under linear lubricated condition is less pronounced for crosslinked polyethylene.

Dose-Response Relationship, Radiation↗
PubMed2003

Dissociation of the S-ROM metal-backed polyethylene acetabular liner--a case report and literature review.

The authors report a case of early failure of a total hip arthroplasty with dissociation of the polyethylene liner of an S-ROM Oblong Cup*, which presented as a dislocation. Initial closed reduction of the dislocation was not possible. Open exploration of the hip revealed that the modular Poly Dial* polyethylene acetabular liner had become dislodged from the acetabular cup. The liner was revised and a stable reduction of the hip was achieved. To our knowledge, no previous case of dissociation of the polyethylene liner from the S-ROM Oblong acetabular component has been reported. A review of the literature with other relevant cases is presented.

Acetabulum↗
PubMedDate not supplied

Neostigmine and polyethylene glycol electrolyte solution for the therapy of acute hepatic encephalopathy with liver cirrhosis and ascites.

We treated a 75-year-old man who had non-B and non-C, and Child's class C liver cirrhosis and acute hepatic encephalopathy with neostigmine and polyethylene glycol electrolyte solution. He received repeated transcatheter artrial embolization and percutaneous ethanol injection combination therapy for multiple hepatocellular carcinomas, which controlled his disease for 25 months from the first treatment. He was admitted in a state of hepatic coma after being found unresponsive at his home. With the consent of the patient's family, we gave him 1.0 mg of neostigmine intramuscularly to improve his peristaltic movement, and 2 L of polyethylene glycol electrolyte solution through a nasogastric tube for 4 hours to reduce the production and absorption of gut-derived toxins of nitrogenous compounds. Using these treatments, the blood ammonia level decreased to the normal range within 8 hours, and the coma disappeared after 2 days. We suggest that a combination approach of neostigmime and polyethylene glycol electrolyte solution may be one of the most effective treatments for acute hepatic encephalopathy associated with liver cirrhosis and ascites.

Carcinoma, Hepatocellular↗
PubMed2003

Effect of alumina femoral heads on polyethylene wear in cemented total hip arthroplasty. Old versus current alumina.

We examined the behaviour of alumina ceramic heads in 156 cemented total hip arthroplasties, at a minimum follow-up of eight years. They were divided into three groups according to the size of the femoral head; 22, 26, and 28 mm. We measured polyethylene wear radiologically using a computer-aided technique. The linear wear rate of polyethylene sockets for the 28 mm heads was high (0.156 mm/year), whereas those for the 22 and 26 mm heads were relatively low (0.090 and 0.098 mm/year, respectively). Moreover, the surface roughness data of retrieved femoral heads clearly showed maintenance of an excellent surface finish of the current alumina. We conclude that the alumina ceramic femoral heads currently used are associated with a reduced rate of polyethylene wear.

Adult↗
PubMed2003

[Using porous polyethylene sheets in late surgical intervention for orbital blowout fractures].

OBJECTIVE: To evaluate the efficacy of using porous polyethylene sheets as orbital implants in late surgical intervention for orbital blowout fractures (BOF). METHODS: CT scan and 3-D reconstruction were used for the diagnosis of BOF. Hertel exophthalmometer was used for the measurement of enophthalmos. Lancaster test was used for examination of diplopia. Porous polyethylene sheets were used for the repair of orbital defects and the correction of orbital volume expansion on 42 patients with enophthalmos of BOF. The time of surgeries perform was from one month to two years post-injury, and the average duration was six months. The mean follow up time was 7 months. RESULTS: Enophthalmos of BOF was corrected in 32 of 42 cases and improved in the rest 10 patients. Twenty-five of 42 patients had diplopia preoperatively. The diplopia disappeared in 5 patients and improved in 10 patients postoperatively. The rest 10 patients had no significant change. Preoperatively 19 of 42 patients had restriction of ductions. Postoperatively, the limited ductions were recovered in 7 cases, improved in 4 cases and no change in 8 cases. No patient had infection and dislocation of implants. CONCLUSIONS: Porous polyethylene sheets are safe and effective when used for orbital reconstruction.

Female↗
PubMed2004

[Three-dimensional orthotopic tissue reconstruction with a free, prefabricated high-density porous polyethylene implant flap].

BACKGROUND: We investigated the appropriateness of the implant to be used in free-tissue transfers in a rabbit model in which a full-thickness skin graft was wrapped around a prefabricated high-density porous polyethylene implant. METHODS: In ten New Zealand white rabbits, high-density porous polyethylene implants (Medpor), 10x15x3 mm in size, were bilaterally placed and anchored underneath the superficial inferior epigastric artery and vein pedicle under anesthesia. The flaps were prefabricated through vascular induction. Eight weeks later, the flaps were wrapped by a full-thickness postauricular skin graft, following orthotopic transplantation. Two weeks after grafting, full-thickness biopsy samples were obtained from the distal one-third of the implants and stained with hematoxylin-eosin and Masson trichrome for histologic examination. RESULTS: Graft compliance was observed in all the implants. Histologic sections showed rich fibro-neovascular tissue, neovascularization, and development of connective tissue cells. There were very few polymorphonuclear cells. No signs of inflammation were observed. CONCLUSION: Prefabrication of the high-density porous polyethylene implant under the superficial inferior epigastric artery and vein results in sufficient conditions for its use in free transfers.

Animals↗
PubMed2003

Loading of the acetabulum by polyethylene and all-ceramic inserts in metal-backed acetabular cups.

Both static and dynamic loads were applied to metal-backed acetabular cups with ceramic or polyethylene inserts and the resulting load transmissions at a simulated bone interface were determined. Perfect fit and under-sized and over-sized cavities were prepared in simulated bone substrates, lined with Fuji pressure sensitive film, and acetabular cups inserted with physiological loads. The magnitude and location of contact forces between the cup and bone were measured. These cups were then subjected to a controlled impact load and the intensity and frequency of the loads transmitted to the substrate were determined. The results suggest that a polyethylene backing for ceramics is not necessary as there were no major differences in the static and dynamic stresses transmitted to the cup-bone interface with all polyethylene or ceramic inserts.

Acetabulum↗
PubMed2003

Comparative studies of global migration levels of recycled vs virgin polyethylene for packing and storage of milk.

The use of Low-density polyethylene (LDPE) is increased for packaging and storage of food, milk etc. Virgin polyethylene is safe due to non-toxic, inertness and insoluble in milk. It is a replacement of conventional bottle packing of milk. Detection of contamination of milk contact of LDPE film in which milk was packed is being done by global migration method. LDPE films developed by well known technique i.e. Blown film extrusion technique, containing different ratio of virgin-recycled polyethylene materials as well as additives such antioxidants, filler, colourant etc. The impact of above LDPE films on the quality of milk was studied by global migration testing. After analyzing the observed results, it is found that the values of global migration increase with increase in percentage of recycled granules and percentage and type of additives in the film.

Animals↗
PubMedDate not supplied

Management of porous polyethylene implant exposure in patients with retinoblastoma following enucleation.

BACKGROUND AND OBJECTIVE: To report the features and the management of porous polyethylene implant exposure in patients with retinoblastoma following enucleation. PATIENTS AND METHODS: The medical records of 33 patients (33 sockets) following enucleation and porous polyethylene implantation for retinoblastoma were reviewed. RESULTS: The mean age at enucleation was 24 months (range, 2 to 85 months). The exposure rate was 33% (11 cases), and the mean time from enucleation to exposure was 15 months (range, 7 to 29 months). One case was resolved only by supportive management, and the remaining 10 were successfully treated with a scleral patch graft and maintained well during a mean follow-up of 15 months after surgical repair. There was no statistical evidence that age, gender, implant size, or chemotherapy had an effect on implant exposure. CONCLUSIONS: Porous polyethylene implant exposure does not seem to be resolved by conservative management. We recommend early surgical management, such as scleral patch graft, as opposed to supportive management.

Antineoplastic Agents↗
PubMed2005

Short-term survival analysis of the all-polyethylene tibial component in total knee arthroplasty.

OBJECTIVE: To report the clinical and radiological results of 24 total knee arthroplasty in which all-polyethylene tibial components were used. METHODS: Between December 2000 and December 2002, 24 cemented total knee arthroplasty in 21 patients were performed using all-polyethylene tibial components. The mean age of the 21 patients (9 men and 12 women) at operation was 55 years, ranging 48-61 years. The mean preoperative hospital for special surgery (HSS) score was 40.2 (range, 36-43). The diagnoses were degenerative osteoarthritis in 15 patients, rheumatoid arthritis in 5 and traumatic arthritis in 1. All the operations were performed by the same surgeon group and there were unilateral operations in 18 patients and bilateral operations in 3. RESULTS: Eighteen patients were followed up with a follow-up rate of 85.7%. The mean follow-up is 2.5 years (range, 1-3 years) and mean postoperative HSS scores was 87.5 (range, 83-89). Among them, 18 were excellent, 3 good, 3 poor and none was fair (the results of three lost patients were classified as poor). Of those reviewed, the prosthesis was all in situ and no revision occurred. Radiological assessment of these patients revealed 4 (16.67%) tibial components with radiolucent lines (mean width < or = 2 mm) distributed mainly in zone 1 and zone 4. None of these knees was symptomatic. CONCLUSIONS: The result of total knee arthroplasty using all-polyethylene tibial components is encouraging. The operative techniques are similar to those in arthroplasty using metal-backed tibial component.

Arthritis↗
PubMed2006

Mechanical response of polyethylene tibial component using compression loading contact test: experimental and finite element analysis.

An experimental apparatus has been developed to study the mechanical response of Total Knee Replacement (TKR) prosthesis under compression loading test (Tibial HDPE component and femoral Vitallium component). Analysis of experimental results indicates that the load-displacement curve depends on the initial contact location. The position of this curve varies between two curves of lower and higher stiffness. Experimental compression loading curve for femoral part resting on flat HDPE is located between the extreme curves. This result allows us to model load-displacement curve of TKR prosthesis under compression loading using femoral component resting on flat polyethylene surface. For simple contact geometry of spherical cap on flat HDPE specimen, Hertz elastic theory can be used to describe the load displacement curve for loads under 635 N. This value corresponds to the load which induces plastic flow of polyethylene. In the case of femoral component on flat HDPE specimen, Hertz elastic theory can be considered for loads under 800 N. Finite element 2D is also used to model the compression load displacement curve for femoral component resting on flat HDPE specimen. The finite element results are similar to the Hertz elastic theory analysis for compression loading under 1200 N. Damage of tibial component can be related to the critical load which induces plastic flow of polyethylene. This load depends on the contact geometry and can be estimated with the Hertz elastic theory.

Compressive Strength↗
PubMed1991

Simplified procedure for transient transformation of plant protoplasts using polyethylene glycol treatment.

A modification of the polyethylene glycol-mediated transformation procedure which eliminates the manual polyethylene glycol dilution step is presented. A transformation mixture of protoplasts, DNA and polyethylene glycol was plated directly onto agarose blocks after incubation. The procedure was simple and fast, thereby suitable for screening the gene activity of large numbers of plasmid constructions. It has been tested for both maize and rice protoplasts.

DNA, Recombinant↗