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1

Study of complete resorption of self-reinforced polyactide-polyglycolide 80/20 screws in rabbit cranial bone

Tiainen J., Soini Y., Tormala P., Waris T., Ashammakhi N.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

12-12

EN

The aim of this study was to assess tissue reaction to bioabsorbable self-reinforced polyactide/polyglycolide (SR-PLGA) 80/20 miniscrews in rabbit cranial bone. One PLGA screw was implanted on one side and one titanium screw on the other side of the sagittal suture (N=21). Three animals were sacrificed after 2, 4, 8, 16, 24, 54 and 72 weeks. In histological examination the numbers of macrophages, giant cells, active osteoblasts and fibrous tissue layers were assessed and degradation of the bioabsorbable screws was evaluated. After two weeks, macrophages were seen near the heads of both screws. After 4 and 8 weeks, the bioabsrobable screws were surrounded by fibrous tissue. Osteoblastic activity and groups of several giant cells were seen. After 24 weeks, a significant change in the morphology of the PLGA screws has occurred. Osteoblastic activity and the amount of giant cells had decreased. After one year, some PLGA biomaterial was still present. PLGA screws had been replaced by adipose tissue, fibrous tissue and "foamy macrophages" which had PLGA particles inside them. After 11 years, the amount of biomaterial remaining had decreased remarkably. The particles of biomaterial were inside "foamy macrophages". SR-PLGA 80/20 screws are biocompatible and have no clinically manifested complications when used in cranial bone of rabbits. No contraindications as regards their clinical use in craniofacial surgery was found when studied in cranial bone of rabbit.

2

Study of biomechanical properties of self-reinforced bioabsorbable implants for use in small bone fixation in the hand

Waris T., Happonen H., Raatikainen T., Kaarela O., Tormala P., Santavirta S., Konttinen Y. T., Ashammakhi N.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

15-15

EN

Bioabsorbable fixation devices offer a useful option to treat small bone features of the hand, if the prerequisite of reliable and stable osteofixation is met. In a biomechanical study in transversally osteotomized cadaver metacalpal bones, bioabsorbable self-reinforced (SR) poly-L/DL-lactide (P(L/DL)LA) 70/30 and polylactide-polyglycolide (PLGA) 80/20 miniplatings were compared with standard metallic fixation methods. On hundred twelve fresh-frozen metacarpals from humans had three-point bending and torsional loading after transverse osteotomy followed by fixation using seven methods: dorsal and dorsolateral 2.0-mm SR-PLGA plating, dorsal and dorsolateral 2.0-mm SR-P (L/DL)LA plating, dorsal 1.7-mm titanium plating, dorsal 2.3 mm titanium plating, and crossed 1.25-mm Kirschner wires. In apex dorsal and palmar bending, dorsal SR-PLGA and SR-P(L/DL)LA plates provided stability comparable with dorsal titanium 1.7-mm plating. When the bioabsorbable plates were applied dorsolaterally, apex palmar rigidity was increased and apex dorsal rigidity was decreased. Bioabsorbable platings resulted in higher torsional rigidity than 1.7-mm titanium plating. In another biomechanical study on obliquely (radial to ulnar orientation) osteotomized pig metacarpal bones, we compared the stabilities of various bioabsorbable fixation devices with metallic fixation devices. 1.5 mm self-reinforced poly-L-lactide (SR-PLLA) pins provided fixation rigidity comparable with 1.5 mm Kirschenr wires in dorsal and palmar apex bending, whereas in lateral apex bending and in torsion the rigidity was equal to that of 1.25 mm Kirschner wires 2.0 mm SR-P(L/DL)LA screws provided rigidity comparable with that of 1.5 mm Kirschner wires in all testing modes. The bioabsorbable plate considerably enhanced the bending stabilities of the fixation system, but a single interfragmentary screw provided only limited rotational rigidity. The results demonstrate that using ultra-high strength SR implants, adequate fixation stability for hand fracture fixation can be achieved. These findings suggest that bioabsorbable miniplating can be used safely in the clinical stabilization of metacarpal and phalangeal fractures.

3

Resorbable multifunctional antibiotic releasing tacks

Tiainen J., Knuutila K., Veiranto M., Suokas E., Waris T., Tormala P., Kaarela O., Ashammakhi N.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

11-11

EN

The aim of this study was to compare the pullout forces of recently developed bioabsorbable ciprofloxacin-releasing and plain self-reinforced polylactide/polyglycolide (SR-PLGA) 80/20 tacks in human cadaver parietal bones. Parietal bone pieces (approximately 6 x 20 cm) were collected from five human male cadavers (29-77 years of age). Fifty plain SR-PLGA 80/20 tacks (diameter = 2 mm, length = 6,0 mm) and 50 ciprofloxacin-releasing SR-PLGA 80/20 tacks of similar dimensions were applied to drill holes using a special tack-shooter without tapping the drill holes. The force needed to pull the tacks from human parietal cadaver bones was measured using a universal tensile testing machine. The tack pullout speed was 10 mm/min. Means and standard deviations (SDs) were calculated and analyzed using the Student t test (SPSS version 10.0 for Windows). The pullout forces of the ciprofloxacin-releasing and plain tacks were 147 +/- 10.3 N and 141.4 +/- 12.6 N respectively (insignificant difference, P<0.001). The main cause of failure was the breakage of tack barbs (95% in the both cases). Ciprofloxacin-releasing SR-PLGA tacks have a pullout strength similar to corresponding plain conventional SR-PLGA tacks and they can be applied in cranial bone fixation.

4

Report on a new technique for correction of trigonocephaly using bioabsorbable osteofixation tacks and plates and a novel tack-shooter

Serlo W., Ashammakhi N., Lansman S., Tormala P., Waris T.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

14-14

EN

We report on the feasibility of applying bioabsorbable tacks using a new tack-shooter to fix bioabsorbale plates applied endocranially for the correction of three cases of trigonocephaly. Tacks do not require tapping or tightening because they are applied using a tack-shooter directly into drill holes in the bone. Hence, the technique saves valuable operative time. A 1.5 to 2.0-cm broad supraorbital bar (bandeau) was raised and reshaped. The corrected shape was maintained used a Biosorb plate (Bionx Implants Ltd, Tampere, Finland), and tacks were applied on the endocranial side of the bar. The plate extended a few centimeters laterally beyond the edge of the supraorbital bar, and it was fixed with Biosorb miniscrews and/or tacks affixed to the temporal bones. Other molded bone pieces were fixed using Biosorb plates, screws, and/or tacks. The technique of using tacks was easy, and it provided secure osteofixation. Cosmetic results were excellent, and no complications were encountered except for palpability of plate edges on the right side of the skull in one case.

5

Overview of bioabsorbable biomaterials: development of multifunctional osteoconductive drug-releasing hard tissue fixation screws

Ashammakhi N., Veiranto M., Vitanen P., Knuutila K., Suokas E., Tiainen J., Leinonen S., Niemela S.-M., Waris T., Aro H., Törmälä P.

Inżynieria Biomateriałów

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2004

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R. 7, nr 37

42-42

6

Investigation of the effect of ciprofloxacin-releasing bioabsorbable implant on staphylococcus epidermidis attachment and biofilm formation in vitro

Niemela S.-M., Ikaheimo I., Koskela M., Veiranto M., Suokas E., Tormala P., Waris T., Ashammakhi N., Syrjala H.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

13-14

7

In vivo characterization poly-L/D-lactide (PLDLA) 96/4 sutures in the Achilles tendon of rabbits

Kangas J., Palaja A., Leppilahti J., Ryhanen J., Lansman S., Tormala P., Waris T., Ashammakhi N.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

10-11

8

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.

9

Bioasorbable osteofixation used devices in 165 cranial and maxillofacial cases: a multicenter report

Ashammakhi N., Renier D., Arnaud E., Marchac D., Ninkovic M., Donaway D., Jones B., Serlo W., Laurikainen K., Törmälä P., Waris T.

Inżynieria Biomateriałów

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2004

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R. 7, nr 38-42

13-13

EN

Bioasorbable osteofixation devices were developed to avoid problems associated with metals. Bioasorbable devices are mostly made of the polymers polylactide (PLA), polyglycolide (PGA) and their copolymers (PLGA and P(L/DL)LA). Using the technique of self-reinforcement of bioabsorbable materials, it is possible to manufacture osteofixation devices with ultra high strength. Self-reinforced (SR) polyglycolide-co-polylactide (SR-PLGA) 80/20 was selected to make devices (Biosorb TM PDX) for this study because of its favorable degradation characteristics. The aim of this study was to evaluate the efficacy of using SR-PLGA (Biosorb TM) plates and screws in the fixation of osteotomies in craniomaxillofacial (CMF) surgery. In a prospective study, 165 patients (161 children and 4 adults) were operated on in four EU centers (Paris, Innsbruck, London and Oulu) from May 1st, 1998 to January 31st, 2002. Indications included correction of dyssynostotic deformities (n=159), reconstruction of bone defects following trauma (n=2), tumor removal (n=2), and treatment of encephalocoele (n=2). Plates used were 0.8, 1 or 1,2 mm thick and screws has an outer (thread) diameter of 1.5 or 2 mm and a length of 4, 6 or 8 mm. Tacks had an outer diameter of 1.5 or 2 mm and a length of 4 or 6 mm. Intraoperatively the devices were easy to handle and apply and provided stable fixation apart from two cases (7.3%), comprising infection (n=6), bone resorption (n=4), diabetes insipidus (n=1), delayed skin wound healing/skin slough (n=2), and liquorrhea (n=1). Accordingly, SR-PLGA 80/20 (Biosorb) plates and screws can be used safely and with favorable outcome in corrective cranioplasties, especially in infants and young children.