Durable Polymer Versus Biodegradable Polymer Drug-Eluting Stents After Percutaneous Coronary Intervention in Patients with Acute Coronary Syndrome: The HOST-REDUCE-POLYTECH-ACS Trial.

BACKGROUND: Large-scale randomized comparison of drug-eluting stents (DES) based on durable polymer versus biodegradable polymer technology is currently insufficient in patients with acute coronary syndrome (ACS). The present study aimed to prove the noninferiority of the durable polymer DES (DP-DES) compared with the biodegradable polymer DES (BP-DES) in such patients. METHODS: The HOST-REDUCE-POLYTECH-ACS (Harmonizing Optimal Strategy for Treatment of Coronary Artery Diseases-Comparison of Reduction of Prasugrel Dose or Polymer Technology in ACS Patients) trial is an investigator-initiated, randomized, open-label, adjudicator-blinded, multicenter, noninferiority trial comparing the efficacy and safety of DP-DES and BP-DES in patients with ACS. The primary end point was a patient-oriented composite outcome (a composite of all-cause death, nonfatal myocardial infarction, and any repeat revascularization) at 12 months. The key secondary end point was device-oriented composite outcome (a composite of cardiac death, target-vessel myocardial infarction, or target lesion revascularization) at 12 months. RESULTS: A total of 3413 patients were randomized to receive the DP-DES (1713 patients) and BP-DES (1700 patients). At 12 months, patient-oriented composite outcome occurred in 5.2% in the DP-DES group and 6.4% in the BP-DES group (absolute risk difference, -1.2%; Pnoninferiority<0.001). The key secondary end point, device-oriented composite outcome, occurred less frequently in the DP-DES group (DP-DES vs BP-DES, 2.6% vs 3.9%; hazard ratio, 0.67 [95% CI, 0.46-0.98]; P=0.038), mostly because of a reduction in target lesion revascularization. The rate of spontaneous nonfatal myocardial infarction and stent thrombosis were extremely low, with no significant difference between the 2 groups (0.6% versus 0.8%; P=0.513 and 0.1% versus 0.4%; P=0.174, respectively). CONCLUSIONS: In ACS patients receiving percutaneous coronary intervention, DP-DES was noninferior to BP-DES with regard to patient-oriented composite outcomes at 12 months after index percutaneous coronary intervention. Registration: URL: https://wwwclinicaltrials.gov; Unique identifier: NCT02193971.

Balloons and Stents and Scaffolds: Preclinical Evaluation of Interventional Devices for Occlusive Arterial Disease.

Atherosclerosis places a significant burden on humankind; it is the leading cause of mortality globally, and for those living with atherosclerosis, it can significantly impact quality of life. Fortunately, treatment advances have effectively reduced the morbidity and mortality related to atherosclerosis, with one such modality being percutaneous intervention (PCI) to open occluded arteries. Over the 40-year history of PCI, preclinical models have played a critical role in demonstrating proof of concept, characterizing the in vivo behavior (pharmacokinetics, degradation) and providing a reasonable assurance of biologic safety of interventional devices before entering into clinical trials. Further, preclinical models may provide insight into the potential efficacy of these devices with the appropriate study design and end points. While several species have been used in the evaluation of interventional devices, the porcine model has been the principal model used in the evaluation of safety of devices for both coronary and endovascular treatments. This article reviews the fundamentals of permanent stents, transient scaffolds, and drug-coated balloons and the models, objectives, and methods used in their preclinical evaluation.

Serial Optical Coherence Tomography at Baseline, 7 Days, and 1, 3, 6 and 12 Months After Bioresorbable Scaffold Implantation in a Growing Porcine Model.

BACKGROUND: Little is known about serial changes in lumen and device dimensions after bioresorbable scaffold implantation in a growing animal model. Methods and Results: ABSORB (n=14) or bare metal stents (ICROS amg [Abbott Vascular, Santa Clara, CA, USA], Winsen-Luhe, Germany; n=15) were implanted in the coronary arteries of domestic swine (a hybrid of Finnish-Norwegian Landrace swine) weighing 30-35 kg. Angiography and optical coherence tomography (OCT) were performed immediately after implantation and repeated at 7 days, 1, 3, 6 and 12 months after the index procedure. One month after implantation, mean lumen area decreased relative to baseline in both groups (relative area change from baseline, -41.4±15.6% for ABSORB vs. -20.9±18.6% for ICROS) while mean device area decreased only in the ABSORB group (relative area change: -11.1±9.4% vs. +0.14±7.95%, respectively). At 12 months, mean lumen area increased relative to baseline in both groups (relative area change from baseline, +55.6±22.4% vs. +32.3±83.6%, respectively) in accordance with the swine growth weighing up to 260-300 kg. Mean device area in the ICROS group remained stable whereas that in the ABSORB group began to increase between 3 and 6 months along with the vessel growth (relative area change: +107.8±25.7% vs. +0.14±7.95%). CONCLUSIONS: In the growing porcine model, ABSORB was associated with greater extent of recoil 1 month after implantation compared with ICROS but demonstrated substantial adaptability to vessel growth in late phase.

Histopathological Evaluation of Orthopedic Medical Devices: The State-of-the-art in Animal Models, Imaging, and Histomorphometry Techniques.

Orthopedic medical devices are continuously evolving for the latest clinical indications in craniomaxillofacial, spine, trauma, joint arthroplasty, sports medicine, and soft tissue regeneration fields, with a variety of materials from new metallic alloys and ceramics to composite polymers, bioresorbables, or surface-treated implants. There is great need for qualified medical device pathologists to evaluate these next generation biomaterials, with improved biocompatibility and bioactivity for orthopedic applications, and a broad range of knowledge is required to stay abreast of this ever-changing field. Orthopedic implants require specialized imaging and processing techniques to fully evaluate the bone-implant interface, and the pathologist plays an important role in determining the proper combination of histologic processing and staining for quality slide production based on research and development trials and validation. Additionally, histomorphometry is an essential part of the analysis to quantify tissue integration and residual biomaterials. In this article, an overview of orthopedic implants and animal models, as well as pertinent insights for tissue collection, imaging, processing, and slide generation will be provided with a special focus on histopathology and histomorphometry evaluation.

Pathology of Bioabsorbable Implants in Preclinical Studies.

Bioabsorbable implants can be advantageous for certain surgical tissue bioengineering applications and implant-assisted tissue repair. They offer the obvious benefits of nonpermanence and eventual restoration of the native tissue's biomechanical and immunological properties, while providing a structural scaffold for healing and a route for additional therapies (i.e., drug elution). They present unique developmental, imaging, and histopathological challenges in the conduct of preclinical animal studies and in interpretation of pathology data. The bioabsorption process is typically associated with a gradual decline (over months to years) in structural strength and integrity and may also be associated with cellular responses such as phagocytosis that may confound interpretation of efficacy and safety end points. Additionally, as these implants bioabsorb, they become increasingly difficult to isolate histologically and thus imaging modalities such as microCT become very valuable to determine the original location of the implants and to assess the remodeling response in tandem with histopathology. In this article, we will review different types of bioabsorbable implants and commonly used bioabsorbable materials; additionally, we will address some of the most common challenges and pitfalls confronting histologists and pathologists in collecting, handling, imaging, preparing tissues through histology, evaluating, and interpreting study data associated with bioabsorbable implants.

Report of an ESC-EAPCI Task Force on the evaluation and use of bioresorbable scaffolds for percutaneous coronary intervention: executive summary.

A previous Task Force of the European Society of Cardiology (ESC) and European Association of Percutaneous Cardiovascular Interventions (EAPCI) provided a report on recommendations for the non-clinical and clinical evaluation of coronary stents. Following dialogue with the European Commission, the Task Force was asked to prepare an additional report on the class of devices known as bioresorbable scaffolds (BRS). Five BRS have CE-mark approval for use in Europe. Only one device-the Absorb bioresorbable vascular scaffold-has published randomized clinical trial data and this data show inferior outcomes to conventional drug-eluting stents (DES) at 2-3 years. For this reason, at present BRS should not be preferred to conventional DES in clinical practice. The Task Force recommends that new BRS devices should undergo systematic non-clinical testing according to standardized criteria prior to evaluation in clinical studies. A clinical evaluation plan should include data from a medium sized, randomized trial against DES powered for a surrogate end point of clinical efficacy. Manufacturers of successful devices receive CE-mark approval for use and must have an approved plan for a large-scale randomized clinical trial with planned long-term follow-up.

Comparison of clinical outcomes of coronary artery stent implantation in patients with end-stage chronic kidney disease including hemodialysis for three everolimus eluting (EES) stent designs: Bioresorbable polymer-EES, platinum chromium-EES, and cobalt chrome-EES.

BACKGROUNDS: New-generation bioresorbable polymer-everolimus eluting stents (BP-EES) are available. This study aimed to compare the clinical outcomes for BP-EES compared to more established stent designs, namely the platinum chromium-EES (PtCr-EES) and cobalt chrome-EES(CoCr-EES) in patients with the end-stage chronic kidney disease (CKD) including hemodialysis (HD). METHODS: One-hundred-forty-one consecutive stents (BP-EES [n = 44], PtCr-EES [n = 45], and CoCr-EES [n = 52]) were implanted in 104 patients with CKD. All patients underwent a follow-up coronary angiography at 12 months after implantation. End-stage CKD was defined as an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2 , or the need for HD. The following outcome variables were compared among the three stent groups after implantation and the 12-month follow-up: target lesion revascularization (TLR), stent thrombosis (ST), and major adverse cardiac event (MACE). Minimal stent diameter (MSD) and %diameter-stenosis (%DS) were measured using quantitative coronary angiography. RESULTS: The overall rate of TLR and MACE was 14.6% and 30.8%, respectively, with no incidence of ST. Immediately after implantation, the MSD (P = 0.22) and %DS (P = 0.42) were equivalent among the three groups. However, at the 12-month follow-up, a tendency towards higher TLR was observed for the BP-EES group (22.7%) compared with the PtCr-EES (8.8%) and CoCr-EES (9.6%) groups (P = 0.07). Late loss in lumen diameter was also significantly greater for the BP-EES (0.51 ± 0.64 mm) group than either the PtCr-EES (0.20 ± 0.61 mm) and CoCr-EES (0.25 ± 0.70 mm) groups (P = 0.03). CONCLUSIONS: BP-EES might increase the risk of in-stent restenosis in patients with end-stage of CKD or the need for HD.

Expert Consensus on Absorbable Advanced Suspension Technology for Facial Tissue Repositioning and Volume Enhancement.

BACKGROUND: Signs of facial aging include wrinkles, loss of subcutaneous volume, decreased tone, texture, and sagging of the skin. The objective of this review is to determine whether facial suspension absorbable sutures are a safe and effective modality for facial rejuvenation.

METHOD: A group of US plastic surgeons and dermatologists who practice medical aesthetics convened to review evidence obtained from literature searches and to reach a consensus on clinical practice guidelines for the use of facial absorbable suspension sutures.

RESULTS: Currently, there are different types of lifting sutures available. Absorbable, facial suspension sutures allow for superior repositioning of tissue along a vector line together with the added benefit of volumization of the area. These benefits are for patients who have moderate facial aging and require treatment beyond the use of injectable products only.

CONCLUSIONS: Treatment with absorbable facial suspension sutures, when performed properly, is associated with minor and infrequent complications and offers a beneficial clinical alternative to traditional facial rejuvenation techniques.

J Drugs Dermatol. 2017;16(7):661-666.

Edge Vascular Response After Resorption of the Everolimus-Eluting Bioresorbable Vascular Scaffold　- A 5-Year Serial Optical Coherence Tomography Study.

BACKGROUND: The edge vascular response (EVR) has been linked to important prognostic implications in patients treated with permanent metallic stents. We aimed to investigate the relationship of EVR with the geometric changes in the everolimus-eluting bioresorbable scaffold using serial optical coherence tomography (OCT) analysis. METHODS AND RESULTS: In the first-in-man ABSORB trial, 28 patients (29 lesions) underwent serial OCT at 4 different time points (Cohort B1: post-procedure, 6, 24, and 60 months [n=13]; Cohort B2: post-procedure, 12, 36, and 60 months [n=15]) following implantation of the scaffold. In Cohort B1, there was no significant luminal change at the distal or proximal edge segment throughout the entire follow-up. In contrast, there was a significant reduction of the lumen flow area (LFA) of the scaffold between post-procedure and 6 months (-1.03±0.49 mm(2)[P<0.001]), whereas between 6 and 60 months the LFA remained stable (+0.31±1.00 mm(2)[P=0.293]). In Cohort B2, there was a significant luminal reduction of the proximal edge between post-procedure and 12 months (-0.57±0.74 mm(2)[P=0.017]), whereas the lumen area remained stable (-0.26±1.22 mm(2)[P=0.462]) between 12 and 60 months. The scaffold LFA showed a change similar to that observed in Cohort B1. CONCLUSIONS: Our study demonstrated a reduction in the scaffold luminal area in the absence of major EVR, suggesting that the physiological continuity of the lumen contour is restored long term. (Circ J 2016; 80: 1131-1141).

New generation coronary stent technology--is the future biodegradable?

A new generation of drug eluting coronary stents are undergoing clinical trial evaluation and being introduced into clinical practice. These technologies comprise a broad range of innovations and include non-polymeric stents, biodegradable polymer coated stents and fully biodegradable scaffolds. The new devices are designed to improve long-term safety and efficacy and overcome limitations associated with a durable polymer and a persistent metallic stent scaffold. At the present time, none have demonstrated convincing superiority over current second generation drug eluting stents and large, long-term randomised controlled trials are required.

Treatment of a canine carotid artery aneurysm model with a biodegradable nanofiber-covered stent: a prospective pilot study.

AIM: To evaluate the use of a biodegradable nanofiber-covered stent (BDNCS) in the treatment of a canine carotid artery aneurysm. MATERIALS AND METHODS: Seventeen beagle dogs, each with one lateral saccular aneurysm created using a venous pouch, were selected to test the BDNCS. The BDNCS consists of three parts: A bare stent, a biodegradable nanofiber membrane, and a balloon catheter. The bare stent was sculpted by a laser from a cobalt chromium superalloy, and the biodegradable nanofiber membrane was constructed from polylactic acid (PLA) and polycaprolactone [PCL, P (LLA-CL)] by the electro-spinning method. The biodegradable nanofiber stent was premounted on a balloon catheter to form a BDNCS. Angiographic assessments were categorized as complete or incomplete occlusion. Data regarding technical success, initial and final angiographic results, mortality and morbidity were collected, and follow-up was performed at 1 and 3 months after the procedure. RESULTS: BDNCS placement was successful in 17 canines with 17 aneurysms. The initial angiographies showed that a complete occlusion was achieved in 13 canines (76.5%) and an incomplete occlusion in 4 (23.5%). One canine died 1 week later. The angiographies obtained at 3-month follow-up exhibited complete occlusion in 14 canines (87.5%) and an incomplete occlusion in 2 canines, with mild in-stent stenosis in 5 canines. CONCLUSIONS: Our results suggest that BDNCS may be a feasible approach for aneurysm occlusion, although the occurrence of mild in-stent stenosis was relatively high. Longer-term follow-up investigations are needed to validate these findings.

Osteolysis following resorbable poly-L-lactide-co-D, L-lactide PLIF cage use: a review of cases.

STUDY DESIGN: Report of case series. OBJECTIVE: To report a problem with bioabsorbable poly-L-lactide-co-D, L-lactide, PLDLLA, posterior lumbar instrumented fusion (PLIF) cage implants. SUMMARY OF BACKGROUND DATA: Synthetic bioabsorbable implants have recently been introduced to spinal surgery and their indications and applications are still being explored. There is evidence that the use of bioabsorbable cages may be of benefit in interbody spinal fusion. METHODS: We present a case series of nine patients who have undergone PLIF with bioabsorbable cages in the lumbar spine. RESULTS: At follow-up over at least 1 year, four of these patients were found to have osteolysis around the implant on CT scanning. One of these patients underwent an operation to remove the cage and histology sent during surgery suggested that the implant had caused the bone loss and there was no evidence of infection. Another patient had ongoing pain in relation to the lysis, while the other two patients with lysis remained asymptomatic. CONCLUSIONS: PLDLLA cage, which has high osteolytic nature, is considered not suitable as a fusion cage.

Biodegradable polymer drug-eluting stents versus durable polymer drug-eluting stents for percutaneous coronary intervention: a contemporary registry-based analysis.

AIMS: We aimed to compare the long-term outcomes of patients undergoing percutaneous coronary intervention (PCI) with biodegradable polymer drug-eluting stents (BP-DES) versus durable polymer drug-eluting stents (DP-DES). METHODS AND RESULTS: Among 11 517 PCIs with second-generation DES performed in our institution between 2007 and 2019, we identified 8042 procedures performed using DP-DES and 3475 using BP-DES. The primary outcome was target lesion failure, the composite target lesion revascularization (TLR), target vessel myocardial infarction and death. Propensity score matching was used to create a well-balanced cohort. Mean follow-up was 4.8 years. Of the 3413 matched pairs, 21% were females, and the mean age was 66 years. At 1 year, the primary outcome occurred in 8.3% patients versus 7.1% (P = 0.07), and TLR rate was 3% versus 2% (P = 0.006) in patients with DP-DES and BP-DES respectively. Within 5 years, the primary outcome occurred in 23.1% versus 23.4% (P = 0.44), and the rate of TLR was 7.2% versus 6.5% (P = 0.07) in patients with DP-DES and BP-DES, respectively. CONCLUSION: Similar rates of the composite outcome were observed throughout the entire follow-up. Target lesion revascularization rates were lower in the BP-DES group at 1-year but equalized within 5 years.

Predictors and outcomes of acute recoil after ultrathin bioresorbable polymer sirolimus-eluting stents implantation: an intravascular ultrasound in native coronary arteries.

BACKGROUND: Ultrathin bioresorbable polymer sirolimus-eluting stents (BP-SESs) may easily lead to acute recoil. This study investigated acute recoil after BP-SES implantation on the basis of intravascular ultrasound (IVUS). METHODS: We enrolled 40 consecutive stents. Absolute acute recoil by quantitative coronary angiography was defined as the difference between the mean diameter of the last inflated balloon (X) and mean lumen diameter of the BP-SES immediately after balloon deflation (Y). Percent (%) acute recoil was defined as (X-Y)×100/X. IVUS was performed within the culprit lesion. Plaque eccentricity, % plaque burden and calcification grade score were assessed using IVUS. Calcification grade was scored on the basis of quadrants. On the basis of the median acute recoil value of 5.0%, the stents were divided into two groups: low (LAR, n = 20) and high % acute recoil (HAR, n = 20). RESULTS: Mean % acute recoil was 5.8 ± 5.3%. Plaque eccentricity, % plaque burden and stent/artery ratio were significantly higher in the HAR group than in the LAR group. Significant differences in % acute recoil were not observed regarding the types of stent diameter. In multivariate logistic regression and multiple linear regression analysis, plaque eccentricity and % plaque burden in the culprit plaque were significant positive predictors for the occurrence of % acute recoil. No significant differences, including clinical outcomes, were found between both groups at follow-up. CONCLUSION: Acute recoil of BP-SESs may be influenced by an eccentric plaque with a large burden, which did not affect long-term outcomes. However, the present study might suggest the proper strategy (e.g. a more exhaustive plaque preparation) before BP-SES implantation in a case with these IVUS characteristics.

Radiation and ethylene oxide terminal sterilization experiences with drug eluting stent products.

Radiation and ethylene oxide terminal sterilization are the two most frequently used processes in the medical device industry to render product within the final sterile barrier package free from viable microorganisms. They are efficacious, safe, and efficient approaches to the manufacture of sterile product. Terminal sterilization is routinely applied to a wide variety of commodity healthcare products (drapes, gowns, etc.) and implantable medical devices (bare metal stents, heart valves, vessel closure devices, etc.) along with products used during implantation procedures (catheters, guidewires, etc.). Terminal sterilization is also routinely used for processing combination products where devices, drugs, and/or biologics are combined on a single product. High patient safety, robust standards, routine process controls, and low-cost manufacturing are appealing aspects of terminal sterilization. As the field of combination products continues to expand and evolve, opportunity exists to expand the application of terminal sterilization to new combination products. Material compatibility challenges must be overcome to realize these opportunities. This article introduces the reader to terminal sterilization concepts, technologies, and the related standards that span different industries (pharmaceutical, medical device, biopharmaceuticals, etc.) and provides guidance on the application of these technologies. Guidance and examples of the application of terminal sterilization are discussed using experiences with drug eluting stents and bioresorbable vascular restoration devices. The examples provide insight into selecting the sterilization method, developing the process around it, and finally qualifying/validating the product in preparation for regulatory approval and commercialization. Future activities, including new sterilization technologies, are briefly discussed.

Efficacy and Safety of Bioabsorbable Bone Hemostatic Agent in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial.

Although a bioabsorbable bone hemostatic agent (BBHA) was developed approximately 20 years ago to overcome the shortcomings of conventional bone wax, its bleeding control capacity has not yet been studied. This study was aimed at investigating the efficacy and safety of BBHA in total knee arthroplasty (TKA). Sixty-two patients who underwent unilateral primary TKA for knee osteoarthritis were included and randomized to the control or BBHA group. Before releasing the tourniquet, BBHA was applied on the bone-cut surface that was not covered by implants. The primary variable was the drainage volume during the postoperative period. The secondary outcomes were total estimated blood loss (EBL), hemoglobin level, hematocrit level, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, range of motion (ROM), pain visual analog scale (VAS) score, and rate of complications. There were no significant differences in drainage volume or EBL between the 2 groups. Hemoglobin and hematocrit levels were higher in the BBHA group during the 4-week postoperative period; however, the intergroup differences were not significant. The ESR, CRP, ROM, and pain VAS scores in the BBHA group were not significantly different from the corresponding values in the control group. No specific complications were observed. Although BBHA was found to be safe without complications, it did not decrease bleeding after TKA in general cases. Further studies are necessary to evaluate the efficacy of BBHA in patients with coagulation problems.

Biodegradation of porous calcium phosphate scaffolds in an ectopic bone formation model studied by X-ray computed microtomograph.

Three types of ceramic scaffolds with different composition and structure [namely synthetic 100% hydroxyapatite (HA; Engipore), synthetic calcium phosphate multiphase biomaterial containing 67% silicon stabilized tricalcium phosphate (Si-TCP; Skelite) and natural bone mineral derived scaffolds (Bio-oss)] were seeded with mesenchymal stem cells (MSC) and ectopically implanted for 8 and 16 weeks in immunodeficient mice. X-ray synchrotron radiation microtomography was used to derive 3D structural information on the same scaffolds both before and after implantation. Meaningful images and morphometric parameters such as scaffold and bone volume fraction, mean thickness and thickness distribution of the different phases as a function of the implantation time, were obtained. The used imaging algorithms allowed a direct comparison and registration of the 3D structure before and after implantation of the same sub-volume of a given scaffold. In this way it was possible to directly monitor the tissue engineered bone growth and the complete or partial degradation of the scaffold. Further, the detailed kinetics studies on Skelite scaffolds implanted for different length of times from 3 days to 24 weeks, revealed in the X-ray absorption histograms two separate peaks associated to HA and TCP. It was therefore possible to observe that the progressive degradation of the Skelite scaffolds was mainly due to the resorption of TCP. The different saturation times in the tissue engineered bone growth and in the TCP resorption confirmed that the bone growth was not limited the scaffold regions that were resorbed but continued in the inward direction with respect to the pore surface.

Tensile strength and adhesion formation of mesh fixation systems used in laparoscopic incisional hernia repair.

BACKGROUND: Mesh tearoff from the tissue is the most common reason for hernia recurrence after hernia surgery involving the use of a synthetic mesh. Various fixation systems were critically compared in terms of their retention strength and the formation of adhesions. METHODS: In a prospective study with 25 Sprague-Dawley rats, two pieces of Parietex composite meshes measuring 2 x 3 cm were fixed intraperitoneally in a paramedian location. The randomized mesh fixation groups included transfascial fixed suture, ProTack, AbsorbaTack, and I-Clip. Of the 25 rats, 12 were killed and analyzed 1 week after implantation, with the remaining 13 rats killed and analyzed after 2 months. Adhesions observed at the time of mesh removal were measured according to an adhesion scoring system, and the fixation strengths of the individual fixation systems were tested. Additionally, the foreign body reaction to the mesh and fixation systems was measured as well as their potential degradation. RESULTS: After 1 week, the retention strength of transfascial fixed suture was significantly higher (8.7 N/cm(2)) than that of ProTack (5.6 N/cm(2)) or AbsorbaTack (5.7 N/cm(2)). After 2 months, the retention strength had increased to 13.2 N/cm(2) in the transfascial fixed suture group, which was significantly higher than in the ProTack (9.7 N/cm(2)) or AbsorbaTack (8.7 N/cm(2)) groups. In contrast, the mesh could be fixed with the I-Clip only in 56% of the cases, and then achieved rather poor retention strength. Adhesion was significantly greater in the ProTack group than in any of the other groups (p < 0.001). At 2 months, scanning electron microscopy showed only marginal degradation of the absorbable elements. CONCLUSIONS: Suture fixation led to satisfactory attachment of the prosthesis. Additional widespread anchorage of the mesh was achieved with ProTack or AbsorbaTack. The feasibility and retention strength of the I-Clip were poor.

Biomechanical testing of two devices for internal fixation of fractured ribs.

BACKGROUND: An intramedullary screw (Portland Orthopaedics, St. Clair, MI) and Inion (Tampere, Finland) Orthopaedic Trauma Plating System (OTPS) mesh for use for internal fixation of fractured ribs have not previously undergone biomechanical testing. The aim of this study is to compare the biomechanics of intact ribs undergoing four-point bending to the biomechanics of fractured ribs fixed with each of the two devices to determine which device provides superior fixation. STUDY: Thirty fresh-frozen porcine ribs (ribs 6-8) were submitted to four-point bending to failure, at a rate of 2.5 mm/min, to determine stiffness and force at failure. The ribs were then randomized to receive fixation with either Inion OTPS mesh or an intramedullary screw. The fixated ribs were again submitted to four-point bending to failure. RESULTS: Ribs fixated with OTPS mesh were significantly stiffer and failed at a significantly higher load than ribs fixated with intramedullary screws (p = 0.0001). Ribs fixated with OTPS mesh were less stiff than intact ribs but failed at a similar force to intact ribs. CONCLUSION: The Inion OTPS mesh system provides superior fixation of fractured ribs compared with an intramedullary screw when tested with four-point bending. The OTPS mesh system also has the added advantage of being absorbable. The intramedullary screw needs to undergo modification and further testing before use in humans. Future studies should focus on more physiologic methods of loading.

Mode of failure of rib fixation with absorbable plates: a clinical and numerical modeling study.

BACKGROUND: Rib fractures as a result of trauma are a relatively common injury. There is an increasing interest in the operative stabilization of these injuries. Absorbable fixation plates are an option for improved rib fracture treatment. The aim of this study was to review our plating failures and to create a numerical model of muscle forces on fractured ribs to identify the mechanism by which these rib fixations have failed. METHODS: Thirteen patients who had 58 ribs fixed with absorbable prostheses were reviewed. Finite element modeling was used to simulate the fixation of a lateral rib fracture using an absorbable plate and screw system. Internal pressure, intercostal forces, and appropriate displacement and rotational constraints were enforced at the rib ends. RESULTS: Ten rib fixation failures were noted in the clinical series. The modeling results showed that stresses on the plate differ during inspiration and expiration. Failure to use the two central screws resulted in higher stresses on the plating system. During inspiration simulations, the screws on both rib parts are active in keeping the rib and plate surfaces unseparated. However, during expiration, there is a greater stress on the screws on the posterior part of the broken rib, and separation of the plate from the rib seems to be more likely to occur at this site. CONCLUSIONS: This study indicates that the likely mode of failure of this absorbable plating system occurs on the posterior part of the rib, which correlates with the clinical failures seen.