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PubMed2003

Chondral injury after arthroscopic meniscal repair using bioabsorbable Mitek Rapidloc meniscal fixation.

Arthroscopic meniscal repair is a commonly performed procedure in clinical practice. With improvements in bioabsorbable implants, all-inside techniques have increased in popularity. The Mitek RapidLoc meniscal fixation implant may be used to fix reparable meniscal tears arthroscopically without requiring an additional incision. We report 2 potential complications associated with this implant: chondral injury causing femoral grooving and recurrent meniscal tear 4 months after initial surgery.

Absorbable Implants↗
PubMed2002

Self-reinforced bioabsorbable versus metallic fixation systems for metacarpal and phalangeal fractures: a biomechanical study.

Bioabsorbable fixation devices offer a useful option to treat small bone fractures of the hand if the prerequisite of reliable and stable osteofixation is met. We compared the stabilities of various bioabsorbable fixation devices with metallic fixation devices by using an oblique osteotomy model in radial to ulnar orientation. The 1.5-mm, self-reinforced, poly-L-lactide (SR-PLLA) pins provided fixation rigidity comparable with 1.5-mm K-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 K-wires. The 2.0-mm, self-reinforced, poly-L/DL-lactide (SR-P(L/DL)LA) 70/30 screws provided rigidity comparable with that of 1.5-mm K-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 show that by using ultra-high strength self-reinforced implants adequate fixation stability for hand fracture fixation can be achieved.

Absorbable Implants↗
PubMed2006

The effect of rhBMP-2 around endosseous implants with and without membranes in the canine model.

BACKGROUND: Bone morphogenetic protein (BMP) is a potent differentiating agent for cells of the osteoblastic lineage. It has been used in the oral cavity under a variety of indications and with different carriers. However, the optimal carrier for each indication is not known. This study examined a synthetic bioabsorbable carrier for BMP used in osseous defects around dental implants in the canine mandible. METHODS: Twelve canines had their mandibular four premolars and first molar teeth extracted bilaterally. After 5 months, four implants were placed with standardized circumferential defects around the coronal 4 mm of each implant. One-half of the defects received a polylactide/glycolide (PLGA) polymer carrier with or without recombinant human BMP-2 (rhBMP-2), and the other half received a collagen carrier with or without rhBMP-2. Additionally, one-half of the implants were covered with a non-resorbable (expanded polytetrafluoroethylene [ePTFE]) membrane to exclude soft tissues. Animals were sacrificed either 4 or 12 weeks later. Histomorphometric analysis included the percentage of new bone contact with the implant, the area of new bone, and the percentage of defect fill. This article describes results with the PLGA carrier. RESULTS: All implants demonstrated clinical and radiographic success with the amount of new bone formed dependent on the time and presence/absence of rhBMP-2 and presence/absence of a membrane. The percentage of bone-to-implant contact was greater with rhBMP-2, and after 12 weeks of healing, there was approximately one-third of the implant contacting bone in the defect site. After 4 weeks, the presence of a membrane appeared to slow new bone area formation. The percentage of fill in membrane-treated sites with rhBMP-2 rose from 24% fill to 42% after 4 and 12 weeks, respectively. Without rhBMP-2, the percentage of fill was 14% rising to 36% fill, respectively. CONCLUSIONS: After 4 weeks, the rhBMP-2-treated sites had a significantly higher percentage of contact, more new bone area, and higher percentage of defect fill than the sites without rhBMP-2. After 12 weeks, there was no significant difference in sites with or without rhBMP-2 regarding percentage of contact, new bone area, or percentage of defect fill. In regard to these three outcomes, comparing the results with this carrier to the results reported earlier with a collagen carrier in this study, only the area of new bone was significantly different with the collagen carrier resulting in greater bone than the PLGA carrier. Thus, the PLGA carrier for rhBMP-2 significantly stimulated bone formation around dental implants in this model after 1 month but not after 3 months of healing. The use of this growth factor and carrier combination appears to stimulate early bone healing events around the implants but not quite to the same degree as a collagen carrier.

Absorbable Implants↗
PubMed2002

Comparison of surgical outcomes between small collagen and chromic catgut implants in deep sclerectomy.

In deep sclerectomy, collagen implant has been used to maintain space under the scleral flap. However, the effect of other implants has not been studied. In this retrospective study, we compared surgical outcomes between small collagen and chromic catgut used as implants in deep sclerectomy. Deep sclerectomy was performed on 23 patients (25 eyes) who either had an open angle and a high intraocular pressure (IOP) (> 22 mmHg) in spite of receiving the maximal tolerable medical treatment, or who were intolerant to medications. Our study consisted of 14 patients (15 eyes) in the small collagen group and 8 (9 eyes) in the chromic catgut group. The mean follow-up period was 8.6 +/- 3.3 months in the small collagen group and 4.4 +/- 1.2 months in the chromic catgut group. The mean preoperative IOP was not significantly different between the two groups. The complete success rate of the small collagen group was significantly better than that of the chromic catgut group at the final follow-up when data were analyzed using the Kaplan-Meier survival curve (87% versus 30%; P = .01). As for the qualified success rate, the small collagen group showed significantly better results at the final follow-up (93% versus 80%; P = .046). The mean number of postoperative medications was significantly lower in the small collagen group (0.26 versus 1.10; P < .05). These results confirmed that the use of small collagen implant in deep sclerectomy produced a higher success rate and a lowered need for postoperative medication compared to the use of chromic catgut implant. Because equal sized implants were used, the difference in biochemical properties, particularly the severity of inflammation caused by the implant, is presumed to be the cause of the different surgical outcomes.

Absorbable Implants↗
PubMed2002

Biomaterial implants induce the inflammation marker CRP at the site of implantation.

Following implantation of biomaterial patches into the gastrointestinal tract, we analyzed the host's response towards the foreign material. Asymmetric patches of polydioxanone covered Vicryl or poly-3-hydroxybutyrate were sutured onto the rat stomach. Tissue samples were generated at distinct time intervals after surgery, and RNA profiles were compared by Differential Display. RT-PCR analysis of gene candidates that seemed differentially expressed showed that vitamin D binding protein mRNA was induced in stomach tissue after implantation of the biomaterial patches. In parallel, the amount of C-reactive protein mRNA was found to be increased transiently as well. Implants induce a tissue response that is specific for a given material.

Absorbable Implants↗
PubMed2005

Comparison of implantation and cytotoxicity testing for initially toxic biomaterials.

To evaluate the predictive value of cytotoxicity testing, the present study compares the in vivo tissue responses to in vitro cytotoxicity before and after implantation. Material toxicity was caused by addition of the toxic substance Zincdiethyldithiocarbamate (ZDEC) that is used as a standard for in vitro cytotoxicity testing. Polyurethane discs with the addition of 0.5% or 1% ZDEC as well as nontoxic discs were inserted in the abdominal wall of rats for 1 day up to 6 weeks. After explantation the foreign body response was analyzed immunohistochemically. An in vitro reanalysis of the explanted reference materials (RMs) revealed remaining high concentrations of toxic compounds after 1-week implantation, whereas no toxicity was seen after 6 weeks implantation. This was reflected in the foreign body response where a significantly thicker capsule and more inflammatory cells were seen at 1 week for the toxic implants. Over time, with decreasing toxicity, these differences disappeared. Test samples that only were subjected to in vitro extraction with water did not elute toxic compounds to the same extent as the in vivo conditions. It is concluded that many clinically useful implant materials may be unnecessarily rejected due to the results of in vitro tests.

Absorbable Implants↗
PubMed2005

Bioresorbable polymers: heading for a new generation of spinal cages.

The use of polymer-based bioresorbable materials is now expanding to the realm of spinal interbody fusion. Bioresorbable polymers have important advantages over metals, because they are temporary, much less stiff, and radiolucent. Most promising is a group of alpha-polyesters, in particular polylactide acids (PLAs). Their biocompatibility is excellent, and they have sufficient stiffness and strength to provide initial and intermediate-term stability required for bone healing. However, polylactides have characteristics that make them vulnerable to complications if not properly controlled. Degradation rate strongly depends on polymer type, impurities, manufacturing process, sterilization, device size, and the local environment. The fact that larger implants degrade faster is contra-intuitive, and should be considered in the design process. Also optimal surgical techniques, such as careful bone bed preparation, are required for a successful application of these materials. The purpose of this paper is to highlight the specific properties of these bioresorbable polymers and to discuss their potential and limitations. This is illustrated with early preclinical and clinical data.Bioresorbable cage technology is just emerging: their time-engineered degradation characteristics allow controlled dynamization in interbody applications, facilitating spinal fusion. Their radiolucency improves image assessment of fusion healing. Acceptance and use of bioresorbable implants may increase as further research and clinical studies report on their safety, efficacy, and proper usage.

Absorbable Implants↗
PubMed2006

Application of polylactides in spinal cages: studies in a goat model.

Spinal cages are currently made of non-resorbable materials, but they only have a temporary function: after fusion, resorption is desirable both from a biological and mechanical point of view. We studied different polylactides in stand-alone condition in a goat model. Cages were made of 100% poly(L-lactic acid) (PLLA) or 70/30 poly(L/DL-Lactic acid) (PLDLLA); titanium served as control. After six months, all titanium cages showed non-unions comparable to that observed in a clinical retrieval, thus showing validity of the goat model. PLLA cages maintained their mechanical integrity for six months, enough to allow fusion. After that, the material resorbed within 48 months without adverse tissue reactions. Bone formation was faster in PLDLLA cages, but these already failed within three months, thus losing their stabilising function: 50% ended in pseudo-arthrosis. Additional internal fixation provided enough stability for fusion (83%). Biocompatibility of both PLLA and PLDLLA was excellent. The long-term results show that PLLA cages can be used for stand-alone interbody fusion, and that PLLA is an improvement over titanium in terms of fusion rate. PLDLLA showed enhanced bone formation, but also earlier failure of the implant. Chances for spinal fusion were better with additional internal fixation.

Absorbable Implants↗
PubMed2005

Bioabsorbable fixation in foot and ankle.

Bioabsorbable implants are playing an increasing role in the surgical management of foot and ankle pathologies. Current technology allows implants to have acceptably comparable strength and pull-out characteristics to metallic implants. The advantages include elimination of secondary surgeries, biodegradability of implants placed across mobile articular surfaces, as well as acceptable biocompatibility and resorption properties to limit historical complication concerns.

Absorbable Implants↗
PubMed2004

Prevention and treatment of experimental osteomyelitis in dogs with ciprofloxacin-loaded crosslinked high amylose starch implants.

Crosslinked high amylose starch (CLHAS) matrix was used as a biodegradable drug delivery implant for the prevention and treatment of osteomyelitis. Thirty-two dogs underwent the femoral insertion of a screw inoculated with Staphylococcus aureus and were then randomly assigned to four groups: (A) prevention with ciprofloxacin-CLHAS implants, (B) surgical debridement (positive control), (C) surgical debridement and oral ciprofloxacin treatment and (D) surgical debridement and treatment with ciprofloxacin-CLHAS implants. At week 4 the osteomyelitis was confirmed, the infected site debrided and respective treatments initiated for groups B, C and D. Radiographs, macroscopic evaluations, bacterial cultures and histopathological examinations were used to evaluate the femora at week 10. Femora from preventive group A were almost normal. Dogs of both ciprofloxacin treatment groups C and D showed better bone healing, less periosteal reaction and less screw mobility than dogs from group B. Eradication of infection was observed at proximal/distal sites in B: 25%/12%, C: 37%/62% and D: 62%/75%. Both ciprofloxacin treated groups improved radiographically from week 4 to week 10. Periosteal and marrow neutrophilic and lymphoplasmocytic infiltrations were less severe in groups C and D versus group B. These data suggest that biodegradable ciprofloxacin-CLHAS implants are a safe and efficient modality for the prevention and treatment of osteomyelitis.

Absorbable Implants↗
PubMed2003

Enhancing effect of poly(L-lactide) on the differentiation of mouse osteoblast-like MC3T3-E1 cells.

Poly(L-lactide) (PLLA) has bioabsorbability and biocompatibility, and it is used as biodegradable screws, pins and plates for internal bone fixation. The purpose of this study was to clarify the effects of low molecular weight (Mw) PLLA on the proliferation and differentiation of mouse osteoblast-like MC3T3-E1 cells. MC3T3-E1 cells were cultured with the concentration of 5-50 microg/ml of PLLA with weight average Mw of 5000 (PLLA-5k) and 10,000 (PLLA-10k) for 2 weeks using the micromass culture. Both PLLAs did not affect the proliferation of MC3T3-E1 cells. However, the calcifications of MC3T3-E1 cells were stimulated with increasing the concentration of the PLLAs. Then PLLA-5k increased the calcification of MC3T3-E1 cells more than PLLA-10k. Additionally, both PLLAs increased the alkaline phosphatase (ALP) activity and calcium content of MC3T3-E1 cells up to the similar level to the calcification. These results indicated that low Mw PLLA enhanced the differentiation of MC3T3-E1 cells with no effect on the proliferation. Moreover, it was suggested that the increase of the ALP activity was a key step to stimulate the calcification of MC3T3-E1 cells. The osteoconductivity of implanted PLLA would be based on the enhancing effect of low Mw PLLA on the differentiation of the osteoblasts.

3T3 Cells↗
PubMed2000

Bone augmentation by onlay implant using recombinant human BMP-2 and collagen on adult rat skull without periosteum.

The purpose of this study was to determine whether bone augmentation could be obtained by the composite of recombinant human bone morphogenetic protein-2 (rhBMP-2) and bioabsorbable atelocollagen when the periosteum was resected, and to compare the efficacy of the rhBMP-2/collagen implant and the collagen alone implant. The onlay implant was inserted into the space between the elevated galea aponeurotica and the skull without the periosteum of 10-month-old rats. The rhBMP-2/collagen implant resulted in osteoblasts differentiation under the galea at 1 week and active bone formation without a prior formation of cartilage. At 4 weeks, the bony trabeculae were interconnected and connected directly with the compact bone of the skull. Histomorphometric analysis at 4 weeks demonstrated that the rhBMP-2/collagen implant showed 92.5% in the volume of bone tissue, whereas the collagen alone showed 0%. The implanted collagen was gradually replaced by bone tissue in the presence of rhBMP-2. Our present results indicate that rhBMP-2 stimulates undifferentiated mesenchymal cells in the galea overlying the implant to proliferate and differentiate directly into osteoblasts on the carrier collagen fibers. The collagen matrix was stably placed on the skull and suitable as a substitute for rhBMP-2. The rhBMP-2/collagen onlay implant might be clinically applicable for bone augmentation even under the condition without the periosteum.

Absorbable Implants↗
PubMed2000

Bone bonding ability of a new biodegradable composite for internal fixation of bone fractures.

Hydroxyapatite particles and poly(L-lactide) composites for internal fixation of bone fractures have been developed based on the hypothesis that incorporation of hydroxyapatite particles in a poly(L-lactide) matrix might enhance bone bonding. This study evaluated the bone bonding ability of these biodegradable composites. Two types of hydroxyapatite and poly(L-lactide) composite were used in this study: calcined hydroxyapatite/poly(L-lactide) and uncalcined hydroxyapatite/poly(L-lactide). Rectangular plates (2 x 10 x 15 mm) of each composite or poly(L-lactide) were implanted into the metaphysis of the tibiae of 33 male rabbits, and the failure load was measured by conducting a detaching test 8, 16, and 25 weeks after implantation. The failure loads of calcined hydroxyapatite/poly(L-lactide), uncalcined hydroxyapatite/poly(L-lactide), and poly(L-lactide), respectively, were 13.60, 13.95, and 0.46 N at 8 weeks; 29.84, 24.09, and 2.86 N at 16 weeks; and 25.50, 29.67, and 2.43 N at 25 weeks. Histologic observation revealed that the composites formed direct contact with the bone. The results in this study indicate that the composites improved the strength of the interface between bone and plate. This improved interfacial strength lead to a substantial decrease in the frequency of implant loosening in the treatment of fractured bones by internal fixation.

Absorbable Implants↗
PubMed2001

Surgical therapy of peri-implant disease: a 3-year follow-up study of cases treated with 3 different techniques of bone regeneration.

BACKGROUND: Advanced peri-implant intrabony defects require comprehensive surgical treatment regimens different from periodontal therapy strategies. The purpose of this longitudinal trial was to evaluate the peri-implant outcomes following guided bone regeneration with 3 treatment protocols. METHODS: In 25 patients, 41 peri-implant defects with supporting bone loss >50% of the implant length were treated with flap surgery plus autogenous bone grafts alone (FG) (controls, n = 12) plus non-resorbable (FGM) (test 1, n = 20) or bioabsorbable barriers (FGRM) (test 2, n = 9) and supportive antimicrobial therapy. Following submerged healing, the membranes were removed (FGM), and the peri-implant probing depths (PD), probing bone levels (BL), mobility scores (PT), and intrabony defect height (DH) were radiographically evaluated at baseline, 6 months, and 1 and 3 years post-therapy. RESULTS: Non-surgical/anti-infective therapy resulted in a limited improvement of PD scores after 6 months. At the 3-year visit, surgical treatment revealed significant changes from baseline for the controls and both of the test groups for PD: 5.1 +/- 2.7 mm (FG), 5.4 +/- 3.0 mm (FGM), and 2.6 +/- 1.6 mm (FGRM), and for BL: 3.2 +/- 2.4 mm (FG), 3.4 +/- 2.4 mm (FGM), and 2.3 +/- 1.6 mm (FGRM), Mann-Whitney test, P < or = 0.05. The changes for DH and PT were significant only for FG- and FGM-treated subjects. The overall improvement for FGRM-treated patients during the 3-year observation was less marked. However, the differences between the 3 surgical treatment protocols did not affect the treatment outcomes after 3 years. CONCLUSIONS: Autogenous bone grafting is an appropriate treatment regimen to augment open crater-formed peri-implant defects. Although certain clinical situations require an additional fixation of barrier membranes, their routine application should be approached with caution.

Absorbable Implants↗
PubMed2005

A comparison between enamel matrix derivative and a bioabsorbable membrane to enhance healing around transmucosal immediate post-extraction implants.

BACKGROUND: This clinical report compares the use of an enamel matrix derivative (EMD) and bioabsorbable barrier membrane to enhance healing following the immediate placement of transmucosal implants into extraction sockets. METHODS: Thirty-two adult patients scheduled for tooth replacement with dental implants agreed to participate. Following the insertion of a transmucosal implant into the extraction site, the subjects were assigned to one of two treatment alternatives of the remaining bone defects around the implants: 1) the residual bone defects were filled with EMD (EMD group) or 2) the residual bone defects were covered with a bioabsorbable membrane (membrane group). Flaps were then coronally positioned around implant cover screws. Patients followed weekly maintenance recalls for the first 6 weeks and then monthly recalls until the final prosthetic restoration was completed (after 6 months). The treatment outcome was evaluated after 12 months by the use of clinical variables. The null hypothesis of no treatment group differences was tested by the use of analysis of variance (ANOVA). RESULTS: At a 12-month follow-up, all of the implants were completely osseointegrated and successfully functioning, showing a success rate of 100%. The membrane group showed a significantly lower mean probing attachment level than the EMD group at proximal (0.60 mm, standard deviation (SD) 0.37 versus 1.19 mm, SD 1.10), buccal (0.80 mm, SD 0.79 versus 1.77 mm, SD 1.16), and lingual sites (0.44 mm, SD 0.52 versus 1.48 mm, SD 1.46). The difference was statistically significant at all sites (P < 0.05). With respect to the position of the soft tissue margin around the implant shoulder, the membrane group showed a consistently higher value than the EMD group at, respectively, proximal (1.30 mm, SD 2.37 versus 1.16 mm, SD 1.0), buccal (0.90 mm, SD 1.29 versus 0.22 mm, SD 1.47), and lingual sites (1.12 mm, SD 1.10 versus 0.55 mm, SD 1.42). CONCLUSIONS: The membrane group obtained more favorable results in terms of both the probing attachment level and peri-implant position of soft tissues compared to the EMD group. The use of a bioabsorbable membrane around immediately placed transmucosal implants enhanced soft and hard tissue healing and might be an advisable treatment choice particularly in areas with high esthetic demands.

Absorbable Implants↗
PubMed2005

Nerve regeneration across a 2-cm gap in the rat median nerve using a resorbable nerve conduit filled with Schwann cells.

OBJECT: In a rat model, nerve regeneration was evaluated across a 2-cm defect in the median nerve by using a resorbable artificial nerve conduit. The aim of this study was to develop an artificial, biocompatible nerve guide to induce regeneration in the peripheral nervous system. METHODS: The authors compared a nerve conduit of trimethylenecarbonate-co-epsilon-caprolactone (TMC/CL) filled with autologous Schwann cells with both an empty hollow conduit and an autologous nerve graft. Animals that did not undergo surgery served as the control group. Nerve regeneration was evaluated with the grasping test, histological analysis of the nerve, muscle weight analysis (flexor digitorum superficialis muscle), and electrophysiological examination. After an observation period of 9 months, regeneration occurred only in animals that had received an autologous graft or a Schwann cell containing nerve conduit. No signs of regeneration were found in animals supplied with the empty conduit. CONCLUSIONS: Results of this study reveal the important role of Schwann cells in the regeneration process across a 2-cm defect in the rat median nerve. Furthermore, Schwann cell-filled nerve conduits induced functional recovery, as demonstrated in the grasping test, that was comparable with that of the autologous graft 9 months after implantation.

Absorbable Implants↗
PubMed2004

Deproteinized bovine bone and biodegradable barrier membranes to support healing following immediate placement of transmucosal implants: a short-term controlled clinical trial.

This 6-month clinical study evaluated the use of a porous bone mineral matrix xenograft (Bio-Oss) as an adjunct to a biodegradable barrier membrane (Bio-Gide) to support healing following the immediate placement of transmucosal implants into extraction sockets. Twenty adult patients scheduled for tooth replacement with dental implants were accepted for participation. Following implant placement into the extraction site, subjects were assigned to one of two treatment alternatives for the remaining bone defect around the implant: (1) Bio-Oss + Bio-Gide membrane (test); or (2) Bio-Gide membrane (control). The treatment outcome was evaluated after 6 months by the use of clinical and radiographic variables. The null hypothesis of no treatment group differences was tested by ANOVA. At 6 months, the radiographic bone level remained unchanged compared to baseline in the test and control groups. No differences were observed between test and control groups in terms of mean probing attachment level. At proximal sites, the soft tissue margin was located 2.6 mm more coronal than the shoulder of the implant in the test group, compared to 1.3 mm in the control group. The corresponding figures for the lingual aspect were 2.3 mm and 1.1 mm, respectively, and at buccal sites 2.1 mm and 0.9 mm, respectively. The use of deproteinized bovine bone mineral as a membrane support at immediately placed transmucosal implants may offer an advantage in areas with high esthetic demands in terms of soft tissue support.

Absorbable Implants↗