First-in-Human Study with Eight Patients Using an Absorbable Vena Cava Filter for the Prevention of Pulmonary Embolism.

PURPOSE: To prospectively evaluate the initial human experience with an absorbable vena cava filter designed for transient protection from pulmonary embolism (PE). MATERIALS AND METHODS: This was a prospective, single-arm, first-in-human study of 8 patients with elevated risk of venous thromboembolism (VTE). Seven absorbable IVC filters (made of polydioxanone that breaks down into H2O and CO2 in 6 mo) were placed prophylactically before orthopedic (n = 5) and gynecologic (n = 2) surgeries, and 1 was placed in a case of deep vein thrombosis. Subjects underwent CT cavography and abdominal radiography before and 5, 11, and 36 weeks after filter placement to assess filter migration, embolization, perforation, and caval thrombosis and/or stenosis. Potential PE was assessed immediately before and 5 weeks after filter placement by pulmonary CT angiography. RESULTS: No symptomatic PE was reported throughout the study or detected at the planned 5-week follow-up. No filter migration was detected based on the fixed location of the radiopaque markers (attached to the stent section of the filter) relative to the vertebral bodies. No filter embolization or caval perforation was detected, and no caval stenosis was observed. Throughout the study, no filter-related adverse events were reported. CONCLUSIONS: Implantation of an absorbable vena cava filter in a limited number of human subjects resulted in 100% clinical success. One planned deployment was aborted as a result of stenotic pelvic veins, resulting in 89% technical success. No PE or filter-related adverse events were observed.

Randomized Controlled Study of an Absorbable Vena Cava Filter in a Porcine Model.

PURPOSE: To compare the safety and efficacy of an absorbable inferior vena cava (IVC) filter and a benchmark IVC filter in a porcine model. MATERIALS AND METHODS: A randomized controlled Good Laboratory Practice study was performed in Domestic Yorkshire cross swine. Sixteen swine were implanted with an absorbable IVC filter (test device; Adient Medical, Pearland, Texas); 8 were implanted with a benchmark metal IVC filter (control device; Cook Medical, Bloomington, Indiana). All animals underwent rotational digital subtraction pulmonary angiography and cavography (anteroposterior and lateral) before filter deployment and 5 and 32 weeks after deployment. Terminal procedures and necropsy were performed at 32 weeks. The IVC, heart, lungs, liver, and kidneys were harvested at necropsy. The reported randomized controlled GLP animal study was conducted at Synchrony Labs, Durham, North Carolina. RESULTS: One animal died early in the test cohort of a recurring hemorrhage at the femoral access site resulting from a filter placement complication. All other animals remained clinically healthy throughout the study. No pulmonary embolism was detected at the 5- and 32-week follow-up visits. The absorbable filter subjects experienced less caval wall perforation (0% vs 100%) and thrombosis (0% vs 75%). The control device routinely perforated the IVC and occasionally produced collateral trauma to adjacent tissues (psoas muscle and aorta). The veins implanted with the absorbable filter were macroscopically indistinguishable from normal adjacent veins at 32 weeks except for the presence of radiopaque markers. Nontarget tissues showed no device-related changes. CONCLUSIONS: Implantation of the absorbable IVC filter in swine proved safe with no pulmonary emboli detected. There was complete to near-complete resorption of the filter polymer by 32 weeks with restoration of the normal appearance and structure of the IVC.

Safety and Efficacy of an Absorbable Filter in the Inferior Vena Cava to Prevent Pulmonary Embolism in Swine.

Purpose To evaluate the immediate and long-term safety as well as thrombus-capturing efficacy for 5 weeks after implantation of an absorbable inferior vena cava (IVC) filter in a swine model. Materials and Methods This study was approved by the institutional animal care and use committee. Eleven absorbable IVC filters made from polydioxanone suture were deployed via a catheter in the IVC of 11 swine. Filters remained in situ for 2 weeks (n = 2), 5 weeks (n = 2), 12 weeks (n = 2), 24 weeks (n = 2), and 32 weeks (n = 3). Autologous thrombus was administered from below the filter in seven swine from 0 to 35 days after filter placement. Fluoroscopy and computed tomography follow-up was performed after filter deployment from weeks 1-6 (weekly), weeks 7-20 (biweekly), and weeks 21-32 (monthly). The infrarenal IVC, lungs, heart, liver, kidneys, and spleen were harvested at necropsy. Continuous variables were evaluated with a Student t test. Results There was no evidence of IVC thrombosis, device migration, caval penetration, or pulmonary embolism. Gross pathologic analysis showed gradual device resorption until 32 weeks after deployment. Histologic assessment demonstrated neointimal hyperplasia around the IVC filter within 2 weeks after IVC filter deployment with residual microscopic fragments of polydioxanone suture within the caval wall at 32 weeks. Each iatrogenic-administered thrombus was successfully captured by the filter until resorbed (range, 1-4 weeks). Conclusion An absorbable IVC filter can be safely deployed in swine and resorbs gradually over the 32-week testing period. The device is effective for the prevention of pulmonary embolism for at least 5 weeks after placement in swine. © RSNA, 2017.

In vitro analysis of polymer candidates for the development of absorbable vascular filters.

PURPOSE: To test absorbable materials as a prelude to development of an absorbable vena cava filter for the prevention of pulmonary embolism (PE). MATERIALS AND METHODS: Three absorbing polymer candidates, poliglecaprone (Monocryl; sizes 4-0 and 1), polyglactin (Vicryl; sizes 4-0 and 1), and polydioxanone (PDSII; sizes 4-0, 2-0, 0, and 1), were fabricated into vascular filters and evaluated in an engineered closed circulation system that replicated human physiologic characteristics. Material performance was determined over a period of 10 weeks via weekly tensile testing, yielding stress-versus-strain parameters. Control samples of the same absorbable polymers were also tested in a static buffer. RESULTS: PDSII (size 2-0) retained 69% strength in circulation versus 86% in control at 6 weeks (P < .0001) and 11% strength in circulation versus 51% in control at 10 weeks (P < .001). It was fully absorbed in circulation by 22 weeks. In contrast, Monocryl and Vicryl absorbed much faster, with Monocryl possessing 6% strength at 2 weeks in circulation and Vicryl reaching 0% strength at 4 weeks. CONCLUSIONS: Polydioxanone appears to be a strong candidate for novel absorbable vascular filters for PE prevention, with sufficient strength retention to catch emboli for at least 6 weeks and sequentially absorb via hydrolysis into CO(2) and H(2)O within 22 weeks.

A comparison of wound closure techniques for total knee arthroplasty.

Four wound closure techniques for total knee arthroplasty were compared in a prospective, randomized, controlled, institutional review board-approved study with 75 subjects. The study compared tissue adhesives, stapling, and suturing with respect to procedure time and cost, together with functional and clinical outcome. Total knee arthroplasty closure time (capsule to cutaneous) favored staples at 26 s/cm, followed by adhesives (45 and 37 s/cm for 2-octyl and n-butyl-2, respectively) and, finally, subcuticular suturing at 54 s/cm (P < .0007). Reduced procedure time translated into intraoperative cost reduction where closure cost per centimeter was $70, $62, $57, and $75 for 2-octyl, n-butyl-2, staples, and sutures, respectively. No significant differences in infection, dehiscence, cosmesis, general health (SF-12v2 (QualityMetric Inc., Lincoln, RI)), and functional and clinical assessments (range of motion, Knee Society knee score, and pain) were observed.

In vivo performance of gold nanoparticle-loaded absorbable inferior vena cava filters in a swine model.

Absorbable inferior vena cava filters (IVCFs) offer a promising alternative to metallic retrievable filters in providing protection against pulmonary embolism (PE) for patients contraindicated for anticoagulant therapy. However, because absorbable filters are not radiopaque, monitoring of the filter using conventional X-ray imaging modalities (e.g. plain film radiographs, computed tomography [CT] and fluoroscopy) during deployment and follow-up is not possible and represents a potential obstacle to widespread clinical integration of the device. Here, we demonstrate that gold nanoparticles (AuNPs) infused into biodegradable filters made up of poly-p-dioxanone (PPDO) may improve device radiopacity without untoward effects on device efficacy and safety, as assessed in swine models for 12 weeks. The absorbable AuNP-infused filters demonstrated significantly improved visualization using CT without affecting tensile strength, in vitro degradation, in vivo resorption, or thrombus-capturing efficacy, as compared to similar non-AuNPs infused resorbable IVCFs. This study presents a significant advancement to the development of imaging enhancers for absorbable IVCFs.

In vitro evaluation of clot capture efficiency of an absorbable vena cava filter.

OBJECTIVE: The purpose of this study was to determine the in vitro clot capture efficiency (CCE) of an investigational absorbable inferior vena cava filter (IVCF) vs the Greenfield IVCF. METHODS: Investigational absorbable and Greenfield filters were challenged with polyacrylamide clot surrogates ranging from 3 × 5 to 10 × 24 mm (diameter × length) in a flow loop simulating the venous system. Filters were challenged with clots until CCE standard error of 5% or less was achieved under binomial statistics. Pressure gradients across the filters were measured for the largest size clot, enabling calculation of forces on the filter. RESULTS: The in vitro CCE of the absorbable IVCF was statistically similar to that of the Greenfield filter for all clot sizes apart from the 3 × 10-mm clot, for which there was statistically significant difference between filter CCEs (absorbable filter, 59%; Greenfield filter, 31%; P = .0001). CCE ranged from an average 32% for the 3 × 5-mm clot to 100% for 7 × 10-mm and larger clots for the absorbable IVCF. Pressure gradient across the absorbable filter with 10 × 24-mm clot averaged 0.14 mm Hg, corresponding to a net force on the filter of 2.1 × 10(-3) N, compared with 0.39 mm Hg or 5.8 × 10(-3) N (P < .001) for the Greenfield filter. CONCLUSIONS: CCE of the absorbable filter was statistically similar to or an improvement on that of the Greenfield stainless steel filter for all clot sizes tested. CCE of the Greenfield filter in this study aligned with data from previous studies. Given the efficacy of the Greenfield filter in attenuating the risk of pulmonary embolism, the current study suggests that the absorbable filter may be a viable candidate for subsequent human testing.

Pilot in vivo study of an absorbable polydioxanone vena cava filter.

OBJECTIVE: The objectives of this study were to evaluate tensile strength retention of polydioxanone as a function of time in a swine venous system and to assess the feasibility of an absorbable inferior vena cava (IVC) filter made from polydioxanone in a pilot swine study. METHODS: Twenty strands (60 cm each) of size 1 polydioxanone absorbable suture (Ethicon, Somerville, NJ) were placed in the central venous system of domestic swine. Strands were harvested at weekly intervals during 10 weeks for tensile strength testing. Results were compared with control samples obtained from an in vitro engineered circulation system containing sodium phosphate buffer solution. Three IVC filters braided from polydioxanone suture were also catheter deployed in three swine to assess absorbable IVC filter feasibility. RESULTS: Polydioxanone retained 82% tensile strength in vitro vs 79% in vivo at 35 days (P > .22), the desired prophylactic duration. For IVC filters made from polydioxanone, technical success of placement was achieved in all three filters deployed (100%). Autologous thrombus deployed inferior to the filter remained trapped in the filter until thrombus resorption, with no evidence of pulmonary emboli on follow-up computed tomography. There were no instances of caval penetration, filter-induced IVC thrombosis, filter migration, or tilt >15 degrees with imaging and clinical follow-up carried out to 32 weeks. CONCLUSIONS: Strength retention of polydioxanone suture placed in the venous system of swine is similar to earlier in vitro studies out to 10 weeks (P > .06 for all weeks) and is more than sufficient (8.20 ± 0.37 kg mean load at break for size 1) to trap thrombus. Pilot animal study suggests that an absorbable polydioxanone IVC filter can be catheter deployed to capture and to hold iatrogenically administered autologous thrombus through resorption.

Improved knee flexion following high-flexion total knee arthroplasty.

BACKGROUND: The application of new techniques and materials in total knee arthroplasty (TKA) continue to be a primary focus in orthopedic surgery. The primary aim of the present study is to evaluate post TKA total range of motion (ROM) among a group of patients who received a gender specific high-flexion design modification implant compared to a control group of patients who received non-gender specific implants. METHODS AND RESULTS: The control group was comprised of 39 TKAs that were recruited pre-operatively and received the non-gender specific implant while the study group consisted of 39 TKAs who received gender specific implants. The study group yielded an improvement in mean post-operative ROM of 21° at 12 months, whereas the mean improvement in ROM among the control group was 11°. Thus, the study group had a 10° increased ROM improvement (91%) over the control group (p = 0.00060). In addition, 100% of the subjects with gender specific high-flexion implants achieved greater or equal ROM post-operatively compared to 82% for the control cohort. Lastly, women who exhibited greater pre-operative ROM and lower body mass index (BMI) were found to benefit the most with the gender specific prosthesis. CONCLUSION: Our study demonstrates that among subjects with a normal BMI, the gender specific high-flexion knee implant is associated with increased ROM as compared to the non-gender specific non-high-flexion implant designs.