In-vivo-Untersuchung zur Degradation von Poly-(D,L-)Laktid- und Poly-(L-Laktid-co-Glykolid)-Osteosynthesematerial

Remodelling of mandibular condylar head after fixation of fractures with ultrasound activated resorbable pins: A retrospective case series

The aim of this study was to assess whether the resorption of poly-lactic acid pins, used for condylar head fracture fixation, adversely affect remodelling of the condylar head. A retrospective review of patients was performed that underwent ORIF of CHF with ultrasound activated resorbable poly-lactic acid pins and had CT/CBCT scans of the condyle at least 18 months after surgery, at which point the fixation material was expected to be resorbed. We reviewed the size, shape and position of the condylar head and compared this to the normal side and compared this to the results of conservative management and ORIF with titanium screws in the literature. Most patients had condylar heads normally positioned and shaped, with minimal bone changes. The position of the condyle in the fossa, its shape and bone changes compare favourably with previous studies on CHF managed conservatively or with titanium screw fixation. There was no radiographic evidence of the pins after 18 months. In conclusion, ultrasound activated resorbable pins can provide suitable fixation for ORIF of condylar head fractures, avoiding the need for screw removal, and there was no evidence that the resorption process adversely affected the remodelling of the condylar head.

Biocompatibility and degradation comparisons of four biodegradable copolymeric osteosynthesis systems used in maxillofacial surgery: A goat model with four years follow-up

Applying biodegradable osteosyntheses avoids the disadvantages of titanium osteosyntheses. However, foreign-body reactions remain a major concern and evidence of complete resorption is lacking. This study compared the physico-chemical properties, histological response and radiographs of four copolymeric biodegradable osteosynthesis systems in a goat model with 48-months follow-up. The systems were implanted subperiosteally in both tibia and radius of 12 Dutch White goats. The BioSorb FX [poly(70LLA-co-30DLLA)], Inion CPS [poly([70–78.5]LLA-co-[16–24]DLLA-co-4TMC)], SonicWeld Rx [poly(DLLA)], LactoSorb [poly(82LLA-co-18GA)] systems and a negative control were randomly implanted in each extremity. Samples were assessed at 6-, 12-, 18-, 24-, 36-, and 48-month follow-up. Surface topography was performed using scanning electron microscopy (SEM). Differential scanning calorimetry and gel permeation chromatography were performed on initial and explanted samples. Histological sections were systematically assessed by two blinded researchers using (polarized) light microscopy, SEM and energy-dispersive X-ray analysis. The SonicWeld Rx system was amorphous while the others were semi-crystalline. Foreign-body reactions were not observed during the complete follow-up. The SonicWeld Rx and LactoSorb systems reached bone percentages of negative controls after 18 months while the BioSorb Fx and Inion CPS systems reached these levels after 36 months. The SonicWeld Rx system showed the most predictable degradation profile. All the biodegradable systems were safe to use and well-tolerated (i.e., complete implant replacement by bone, no clinical or histological foreign body reactions, no [sterile] abscess formation, no re-interventions needed), but nanoscale residual polymeric fragments were observed at every system's assessment.

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Foreign-body reactions are a major concern of biodegradable osteosyntheses.

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Amorphous poly(DLLA) showed the most predictable degradation profile.

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Nanoscale residual polymeric fragments could still be observed after 4 years.

From rigid bone plate fixation to stable dynamic osteosynthesis in mandibular and craniomaxillo-facial surgery: Historical evolution of concepts and technical developments

Historically, extensive observation of limb fracture healing led to a consensus that only complete rigid immobilization could guarantee recovery. This agreement was arrived at because for a long time progress in treatment was driven by clinicians and did not stem from the application of biological research. The clinical approach was based on immobilization of the fracture by rigid osteosynthesis plates and bicortical screws. Subsequently, after extrapolation of the ideas of Lane, the concept of rigid compressive osteosynthesis rapidly gained in acceptance. It was not until the second half of the 20th century that maxillofacial surgeons concluded that the principles of osteosynthesis should be based on biomechanical studies and not only on clinical observation. The concept of stable dynamic osteosynthesis stems from basic research. This paper traces the evolution of concepts in maxillofacial osteosynthesis.

Novel ultrasound assisted suture anchor system using the BoneWelding® technology yields a comparable primary stability in osteopenic and healthy human humeri as a benchmark anchor

Introduction

The aim of this biomechanical study was to evaluate the primary stability of the SportWelding® Sombrero 3.6 mm suture anchor system in osteopenic and healthy cadaveric humeri.

Methods

The Sombrero® and BioCorkscrew® anchors were deployed in 8 osteopenic and 4 healthy cadaver humeri after the bone mineral density (BMD) measurements of the 32 specimens. Both anchors were loaded with a USP Nr. 2 FiberWire® suture. An established cyclic testing protocol was performed. The maximum failure load (Fmax), the system displacement and the modes of failure were recorded.

Results

The F_max and system displacement of the Sombrero® in osteopenic and healthy humeri was equivalent to the Bio-Corkscrew® benchmark anchor; there were no significant differences in the maximum failure loads and system displacement values. Only anchor and suture dislocations were observed; suture ruptures did not occur.

Conclusion

This study shows that the Sombrero® yields similar maximum failure loads and system displacement values as the established Bio-Corkscrew® benchmark anchor. The primary stability of the Sombrero® and Bio-Corkscrew® seems to be independent of the bone mineral quality. This relatively small-sized polymer anchor is independent of the BMD and may be an alternative to established suture anchors in rotator cuff repair.

Biomaterial shell bending with 3D-printed templates in vertical and alveolar ridge augmentation: a technical note

OBJECTIVES

Alveolar ridge and vertical augmentations are challenging procedures in dental implantology. Even material blocks with an interconnecting porous system are never completely resorbed. Shell techniques combined with autologous bone chips are therefore the gold standard. Using biopolymers for these techniques is well documented. We applied three-dimensional (3-D) techniques to create an individualized bending model for the adjustment of a plane biopolymer membrane made of polylactide.

STUDY DESIGN

Two cases with a vertical alveolar ridge defect in the maxilla were chosen. The cone beam computed tomography data were processed with a 3-D slicer and the Autodesk Meshmixer to generate data about the desired augmentation result. STL data were used to print a bending model. A 0.2-mm poly-D, L-lactic acid membrane (KLS Matin Inc., Tuttlingen, Germany) was bended accordingly and placed into the defect via a tunnel approach in both cases. A mesh graft of autologous bone chips and hydroxylapatite material was augmented beneath the shell, which was fixed with osteosynthesis screws.

RESULTS

The operative procedure was fast and without peri- or postoperative complications or complaints. The panoramic x-ray showed correct fitting of the material in the location. Bone quality at the time of implant placement was type II, resulting in good primary stability.

CONCLUSIONS

A custom-made 3-D model for bending confectioned biomaterial pieces is an appropriate method for individualized adjustment in shell techniques. The advantages over direct printing of the biomaterial shell and products on the market, such as the Xyoss shell (Reoss Inc., Germany), include cost-efficiency and avoidance of regulatory issues.

Efficacy and Safety of Biodegradable Osteofixation Devices in Oral and Maxillofacial Surgery: a Systematic Review

The use of osteofixation devices should be evidence-based if uncomplicated bone healing is to be achieved. Numerous studies describe and claim the advantages of biodegradable over titanium devices as a bone fixation method. Here, we systematically review the available literature to determine the clinical efficacy and safety of biodegradable devices compared with titanium devices in oral and maxillofacial surgery. In addition, related general aspects of bone surgery are discussed. We conducted a highly sensitive search in the databases of MEDLINE (1966–2005), EMBASE (1989–2005), and CENTRAL (1800–2005) to identify eligible studies. Eligible studies were independently evaluated by two assessors using a quality assessment scale. The study selection procedure revealed four methodologically ‘acceptable’ articles. Owing to the different outcome measures used in the studies, it was impossible to perform a meta-analysis. Therefore, the major effects regarding the stability and morbidity of fracture fixation using titanium and biodegradable fixation systems were qualitatively described. Any firm conclusions regarding the fixation of traumatically fractured bone segments cannot be drawn, due to the lack of controlled clinical trials. Regarding the fixation of bone segments in orthognathic surgery, only a few controlled clinical studies are available. There does not appear to be a significant short-term difference between titanium and biodegradable fixation systems regarding stability and morbidity. However, definite conclusions, especially with respect to the long-term performance of biodegradable fixation devices used in maxillofacial surgery, cannot be drawn. Abbreviations: CENTRAL, Cochrane Central Register of Controlled Trials; MeSH, Medical Subject Heading; VAS, Visual Analogue Scale; and W, weight.

Patient-specific biodegradable implant in pediatric craniofacial surgery

Surgical correction of premature fusion of calvarial sutures involving the fronto-orbital region can be challenging due to the demanding three-dimensional (3D) anatomy. If fronto-orbital advancement (FOA) is necessary, surgery is typically performed using resorbable plates and screws that are bent manually intraoperatively. A new approach using individually manufactured resorbable implants (KLS Martin Group, Tuttlingen, Germany) is presented in the current paper. Preoperative CT scan data were processed in iPlan (ver. 3.0.5; Brainlab, Feldkirchen, Germany) to generate a 3D reconstruction. Virtual osteotomies and simulation of the ideal outer contour with reassembled bony segments were performed. Digital planning was transferred with a cutting guide, and an individually manufactured resorbable implant was used for rigid fixation. A resorbable patient-specific implant (Resorb X-PSI) allows precise surgery for FOA in craniosynostosis using a complete digital workflow and should be considered superior to manually bent resorbable plates.

Bone Regeneration after Treatment with Covering Materials Composed of Flax Fibers and Biodegradable Plastics: A Histological Study in Rats

The aim of this study was to examine the osteogenic potential of new flax covering materials. Bone defects were created on the skull of forty rats. Materials of pure PLA and PCL and their composites with flax fibers, genetically modified producing PHB (PLA-transgen, PCL-transgen) and unmodified (PLA-wt, PCL-wt), were inserted. The skulls were harvested after four weeks and subjected to histological examination. The percentage of bone regeneration by using PLA was less pronounced than after usage of pure PCL in comparison with controls. After treatment with PCL-transgen, a large amount of new formed bone could be found. In contrast, PCL-wt decreased significantly the bone regeneration, compared to the other tested groups. The bone covers made of pure PLA had substantially less influence on bone regeneration and the bone healing proceeded with a lot of connective tissue, whereas PLA-transgen and PLA-wt showed nearly comparable amount of new formed bone. Regarding the histological data, the hypothesis could be proposed that PCL and its composites have contributed to a higher quantity of the regenerated bone, compared to PLA. The histological studies showed comparable bone regeneration processes after treatment with tested covering materials, as well as in the untreated bone lesions.

Evaluation of the Fatigue Performance and Degradability of Resorbable PLDLLA-TMC Osteofixations

The fatigue performance of explanted in-situ degraded osteofixations/osteosyntheses, fabricated from poly (70L-lactide-co-24DL-lactide-6-trimethylane-carbonate or PLDLLA-TMC) copolymer was compared to that of virgin products. The fatigue test was performed on 21 explants retrieved from 12 women and 6 men; 16-46 years by a custom-designed three-point bend apparatus using a staircase method and a specified failure criterion (an increase of the deflection of the specimen > 1 mm) with run-out designated as “no failure” after 150,000 loading cycles. While all the virgin products showed run-out at 38N, all of the specimens fabricated from explants failed at this load level. For the explant specimens, although there was a trend of decreased failure load with increased in-situ time, this decrease was pronounced after 4 months in-situ, however, not yet statistically significant, while a 6-month in-situ explant had significantly less failure load. Three and four month in-situ explants had highly significant differences in failure load between measurements close and distant to the osteotomy line: p=0.0017 (the region of maximum load in-situ). In the virgin products, there were only traces of melt joining and cooling, left from a stage in the manufacturing process. For the implants retrieved after 4.5 months in-situ, the fracture surfaces showed signs of degradation of the implants, possibly caused by hydrolysis, and for those retrieved after 9 months in-situ, there were cracks and pores. Thus, the morphological results are consistent with those obtained in the fatigue test. The present results suggest that resorbable osteofixations fabricated from PLDLLA-TMC are stable enough to allow loading of the healing bone and degrade reliably

Intramedullary fixation in digital replantation using bioabsorbable poly-DL-lactic acid rods

PURPOSE

To evaluate bioabsorbable poly-DL-lactic acid (PDLLA) intramedullary rods for fracture fixation of amputated digits.

METHODS

From October 2005 to October 2007, we used bioabsorbable rods made of PDLLA as intramedullary fixation in osteosynthesis procedures in 9 cases of digital replantation. Four cases involved the middle phalanx and 5 the proximal phalanx. The amputation level was diaphyseal in all cases. All patients were followed up from 6 months to 2 years, with an average of 13 months.

RESULTS

All fractures healed in 6 to 8 weeks. There were no infections. There was no evidence of hardware failure at 4 weeks after surgery. According to the Tamai et al criteria, the results were excellent in 8 cases and good in 1.

CONCLUSIONS

Using bioabsorbable PDLLA rods for intramedullary fixation can be an effective technique for replantation with fractures through the proximal or middle phalanges. Bioabsorbable rods can provide rigid stable fixation, which allows early mobilization.

Cochlear implant fixation using resorbable mesh

In this article we describe a new method of cochlear implant receiver-stimulator fixation using a resorbable poly (D,L) lactic acid mesh. We conducted a retrospective case review at a tertiary referral center; 10 pediatric and 4 adult patients had undergone cochlear implantation during the period from February to October 2008. Resorbable poly (D,L) lactic acid mesh and pins were used for fixation of the cochlear implant receiver stimulator. The receiver stimulator was assessed for stability/migration, and the scalp flap/incision were evaluated for allergic reactions, infections, and healing problems. With an average follow-up of 17.2 months, no patients had migration of the receiver stimulator, and there was no evidence of infection, wound dehiscence, or allergic reaction. Early results indicate that fixation of a cochlear implant receiver stimulator using resorbable mesh is well tolerated and provides good stability without device migration. Resorbable mesh fixation of the receiver stimulator is a reasonable alternative technique for cochlear implantation.

Resorbable screws for fixation of autologous bone grafts

The aim of this study was to evaluate the suitability of resorbable screws made of poly (D.L-lactide) acid (PDLLA) for fixation of autologous bone grafts related to graft regeneration and osseointegration of dental implants. In eight edentulous patients suffering from insufficient retention of their upper denture related to a severely resorbed maxilla, the floor of both maxillary sinus and width of the alveolar crest were augmented with an autologous bone graft from the iliac crest. Randomly, the bone graft used to augment the alveolar crest was fixed with two titanium screws on one side and two resorbable screws on the other side (split-mouth design). Three months after the reconstruction, a bone biopsy was taken with a trephine including one resorbable screw (N = 8). Subsequently, six implants were placed in the left and right posterior maxilla. Six months later, at the abutment connection, a bone biopsy was taken including the other resorbable screw (N = 8). The biopsies were processed for light microscopic examination. In addition, clinical parameters were scored. Wound healing was uneventful. Clinically no difference in wound healing was observed between sides treated with either a resorbable or titanium screw. No implants were lost. Six months after implantation, implant retained overdentures could be fabricated in all patients. All patients functioned well with their overdentures (follow-up 22.2 +/- 4.3 months). Three as well as 9 months after insertion (remnants of), the resorbable screws were still visible after reflecting the mucoperiosteum. Histological examination confirmed that a considerable quantity of remnants of the resorbable screws was still present, although areas with some fragmentation of the PDLLA were also observed. The screws were separated by a fibrous tissue layer containing many giant cells from the bone. Particles of PDLLA were observed within these giant cells. This study revealed that resorbable screws made of PDLLA can be used for fixation of bone grafts. The bulk of the PDLLA material is still present after 9 months.

Maxillary and mandibular osteosyntheses with PLGA and P(L/DL)LA implants: a 5-year inpatient biocompatibility and degradation experience

BACKGROUND

This study consists of a 5-year experience with 413 maxillary and mandibular resorbable plate osteosyntheses focusing on clinically apparent foreign body reaction (i.e., swelling, osteolyses, and fistulation), indirect implant degradation (i.e., palpability and radiographic reossification), and direct implant degradation (i.e., molecular weight and crystallinity of explants).

METHODS

Eighty fracture and reconstruction cases (32 female and 48 male patients, aged 1 to 83 years) were osteofixated with poly(L-lactide-co-glycolide) (PLGA) copolymer (n = 20) (139 PLGA osteosyntheses) or poly(L-lactide-co-DL-lactide) [P(L/DL)LA] (n = 60) [274 P(L/DL)LA osteosyntheses]. Local revisions (n = 30) were performed during secondary operations at 3, 6, 12, 18, or 24 months. Average clinical and radiographic follow-up lasted 29 months (range, 6 to 63 months).

RESULTS

Five patients (6 percent) had apparent foreign body reactions, whereas 75 (94 percent) did not. One P(L/DL)LA mild reaction was effectively treated with cold packs and analgesics, one PLGA and three P(L/DL)LA medium severe reactions were treated with curettage, and one local osteolysis disappeared at 6 months. Implant palpability lasted 12 (PLGA) or 24 months [P(L/DL)LA]. The difference was significant (p < 0.000001). Burr holes reossified at 24 (PLGA) and 36 months [P(L/DL)LA] (p < 0.05). The 85:15 PLGA explants' initial 44,600 molecular weight decreased to 11,000 at 6 months; and scarce powdering granular residuals, too small for molecular weight assessment, were encountered at 12 months. The 70:30 P(L/DL)LA initial molecular weight of 45,000 decreased to 25,000 at 6 months and 8,000 at 18 months and to similar granules at 24 months (p < 0.02). Histology showed macrophages, giant cells, lymphocyte infiltration, little granulocytic infiltration, and minimal bleeding residuals.

CONCLUSIONS

Both copolymers showed reliable biocompatibility and disintegration. Overall, 6 percent clinically apparent foreign body reactions were controlled conservatively and by local curettage; 85:15 PLGA degraded within 12 months and 70:30 P(L/DL)LA within 24 months, leaving powdering residual granules. Burr holes reossified 12 months later.

In-patient versus in vitro degradation of P(L/DL)LA and PLGA

To assess and compare degradation rates, poly(70L-lactide-co-30DL-lactide) [P(L/DL)LA] and poly(85L-lactide-co-15-glycolide) (PLGA) copolymer degradation were studied in patients (maxillofacial region) and in vitro. Five patients of a total of 20 with 85:15 PLGA osteosyntheses, and 15 of a total of 60 with 70:30 P(L/DL)LA osteosyntheses, (10 females and 10 males, 26-55 years; mean, 33 years) underwent explantations after 3, 6, 9, 12, 18, and 24 months. Identical resorbables immersed in physiological buffer solution at 37 degrees C were compared at identical intervals. P(L/DL)LA's initial average molecular weight of 45,000 decreased to 25,000 in patients (and to 21,000 in vitro) after 6 months, and to 8000 in patients after 18 months. PLGA's average molecular weight decreased from 44,600 to 22,000 after 3 months in patients and in vitro, and to 11,000 in patients and 1300 in vitro at 6 months. In-patient and in vitro glass-transition temperatures decreased from approximately 60 degrees C to 50 degrees C over 18 months. Crystallinity in explants was < or = 4% in P(L/DL)LA throughout testing, and 16% and 30% in PLGA at 6 and 12 months, respectively. Both copolymers decomposed reliably in patients: 85:15 PLGA within 12 months and 70:30 P(L/DL)LA within 24 months on average (p < 0.005), leaving only extremely small granules that powder upon finger touch. In vitro rates were significantly faster (p < 0.005). Crystallinity associated with foreign-body reactions was minor and did not inhibit decomposition.

Resorbable poly(D,L)lactide plates and screws for osteosynthesis of condylar neck fractures in sheep

We made osteotomies in the condylar neck in 12 adult sheep to simulate fractures, and joined the two ends with 2 poly(D,L)lactide (PDLLA) plates and 8 PDLLA screws 2mm in diameter. The animals were killed after 2, 6, and 12 months and bony healing was assessed macroscopically and histologically. The plates and screws remained intact and there was no displacement of the bony ends. The degrading plates, which were still visible in the specimens after 6 months, had been replaced by bone. At 12 months the PDLLA had been resorbed with no foreign body reaction and no resorption of underlying bone. The articular discs showed no signs of degeneration.