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The influence of the degradation process on the PLA/TCP locking bolt thread strength as a part of intramedullary locking nail system

Gryń K., Szaraniec B., Ziąbka M., Morawska-Chochół A., Chłopek J.

Engineering of Biomaterials

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2012

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Vol. 15, no. 116-117 spec. iss.

148

EN

Intramedullary nailing has received increased attention for the treatment of distal femoral fractures. There are many types of nailing systems commonly used. Among them there is locked intramedullary nailing, which combines closed nailing with a special locking piece (bolt), which expands distal part of a nail and anchoring it when a central screw is tightened. Compared to other interlocking nail systems it is very effective and not so invasive way of fractured long bone treatment. However, it is not perfect and has one major disadvantage related to material (metal) and necessity of removing all parts of the system after the bone is recovered. The biggest issue is connected with the locking piece removal. That is why there was a need to find a material for this piece which is biodegradable and strong enough to maintain its mechanical function at the same time. Poly-L-lactide (PLA) is nowadays one of the most used bioabsorbable materials. Unfortunately, this polymer may not meet some application requirements due to inadequate mechanical properties and its degradation characteristics. One of the easiest ways to overcome these obstacles is to introduce an inorganic phase into the polymer matrix to create a composite. In this article a production method of a biodegradable composite (PLA/TCP, 90/10) locking piece of an interlocking intramedullary nail called "OLIVE" and the influence of degradation process in simulated physiological conditions (H2O, PBS) on its mechanical properties is shown. Main stress was placed on the inner thread strength to discover how it changes with time. A special device for mechanical testing machine imitating working conditions was fabricated. 148 Based on SEM observations, pH and electric conductivity monitoring after 14 days no degradation was found. However, mechanical testing shown, that after incubation for such period of time the material was more ductile. Instead of cracking, what was observed for not incubated samples, they changed their shape during the testing process. Nevertheless, it didn't radically influence on the inner thread strength and didn't change mechanical function of the olive. No inner thread destruction was discovered contrary to a metallic screws which in all cases were broken. Preliminary results indicate that proposed composite and an implant made of this material might be used as a locking piece in a locked intramedullary nailing system.

2

Nowe semikrystaliczne bioresorbowalne materiały z pamięcią kształtu

Smola A., Dobrzyński P., Pastusiak M., Sobota M., Kasperczyk J.

Engineering of Biomaterials

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2009

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Vol. 12, no. 89-91

82--87

PL

W procesie terpolimeryzacji cyklicznych monomerów glikolidu, L-laktydu i trimetylenowęglanu (TMC), w obecności niskotoksycznego acetylacetonianu cyrkonu (IV) lub Zn(C2H5)(OC2H5) jako inicjatora, otrzymano z dobrą wydajnością bioresorbowalne trójpolimery wykazujące własność pamięci kształtu. W zależności od zastosowanej metody syntezy (jednostopniowa terpolimeryzacja w stopie, dwustopniowa terpolimeryzacja w stopie, terpolimeryzacja glikolidu, laktydu i wcześniej syntezowanego oligomeru TMC) czy w zależności od rodzaju zastosowanego inicjatora uzyskano terpolimery o zbliżonym składzie lecz o różnorodnej budowie łańcucha polimerowego, a co jest z tym związane o rożnej morfologii - od materiałów całkowicie amorficznych po materiały o dużym stopniu krystaliczności. Przedstawiono podstawowe własności otrzymanych polimerów, w tym zachowanie pamięci kształtu.

EN

On the course of the therpolymerization process of glycolide, L-lactide and trimethylene carbonate (TMC) cyclic monomers, using low-toxic zirconium (IV) acetylacetonate or Zn(C2H5)(OC2H5) as initiator, bioresorbable terpolymers characterized with shape memory properties were efficiently obtained. Depending on the preferred method of synthesis (single-stage terpolymerization in bulk, two-stage terpolymerization in bulk, terpolymerization of glycolide, lactide and previously synthesized TMC oligomer) or the type of the used initiator, we achieved to obtain terpolymers with similar composition but with varied polymer chain microstructure and consequently different morphology – from wholly amorphous to characterized with high degree of crystallinity. Elementary properties of the obtained polymers, including the shape-memory ability, are described herewith.

3

Combinatorial discovery approaches accelerate the development of bioresorbable medical implants

Kohn J.

Engineering of Biomaterials

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2009

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Vol. 12, no. 89-91

258--259

4

Zastosowanie spektroskopii w podczerwieni do badań polimerów z pamięcią kształtu

Kaczmarczyk B., Dobrzyński P., Kasperczyk J., Bero M.

Engineering of Biomaterials

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2007

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Vol. 10, no. 63-64

51-54

PL

W pracy zaprezentowano wyniki badań nad wykazującymi właściwości pamięci kształtu bioresorbowalnymi terpolimerami laktyd/glikolid/trimetylenowęglan. Celem wyjaśnienia charakteru występujących w tych terpolimerach oddziaływań, decydujących o istnieniu ich zdolności do zapamiętywania kształtu, zastosowano do badań metodę spektroskopii w podczerwieni i drugie pochodne widm.

EN

This work presents results of the study of bioresorbable lactide/glycolide/trimethylene carbonate terpolymers exhibiting the shape memory properties. Infrared spectroscopy and second derivative spectra were used to explain the character of appearing at terpolymers interactions, which determine the possibility of existence the shape memory ability of these terpolymers.

5

High-strength bioresorbable polyactide fibres-production and processing

Schlegel U., Glarner M., Gogolewski S.

Inżynieria Biomateriałów

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2004

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R. 7, nr 37

9-10

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Evaluation of the effect of transphyseal bioabsorbable screws on growth of rabbit femur

Waris E., Kelly C. P., Andrus L., Waris T., Jackson I. T., Ashammakhi N.

Inżynieria Biomateriałów

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2004

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R. 7, nr 37

20-20

EN

A self-reinforced bioabsorbable poly-L-lactide/polyglycolide (SR-PLGA) 80/20 screw 2.0 mm in diameter was implanted in a transphyseal location across the distal growth plate of the right femur in 24 immature rabbits. Radiological evaluation revealed a mean shortening of 3.1 mm at 3 weeks (p=0.050), 11.1 mm at 6 weeks (p=0.001), 9.3 mm at 24 weeks (p=0.011), 9.0 mm at 48 weeks (p=0.009) and 12.6 mm at 72 weeks (p=0.002) compared with the intact contralateral femur. Growth retardation continued for 6 weeks postoperatively (3 versus 6 weeks, p=0.003), after which the bones grew normally up to 72 weeks (p=0.6). The duration of temporary growth retardation correlated with that of strength retention of the SR-PLGA 80/20 copolymer. These findings suggest that SR-PLGA 80/20 screws can be applied in transphyseal bone fixation. The use of bioabsorbable screws for temporary epiphyseodesis seems attractive but requires further study.