Expansion and fixation properties of a new braided biodegradable urethral stent: an experimental study in the rabbit

PURPOSE: Biodegradable spiral urethral stents have been used with favorable results combined with thermal treatments of the prostate and for recurrent urethral strictures but the configuration of the helical spiral is not ideal. We developed a new tubular mesh configuration for the biodegradable urethral stent and evaluated its expansion and locking properties in the rabbit urethra. MATERIALS AND METHODS: The stents were made of self-reinforced polylactic acid polymer (Bionx Implants, Ltd., Tampere, Finland) blended with BaSO (Alfa Chem, New York, New York) to achieve radiopacity. Two braiding patterns, that is 1 over 1 and 2 over 2 + 1, were used to produce a tubular mesh structure. Stainless steel stents (pattern 1 over 1) served as controls. The stents were inserted into the posterior urethra of 27 male rabbits. The animals were sacrificed after 1 week, 1 and 6 months, respectively. X-rays were done immediately after stent insertion and at sacrifice. Longitudinal movement and expansion were assessed on the x-rays.(4) RESULTS: All stents maintained position in the urethra without fixation. Macroscopic disorientation of the structure of the 2 over 2 + 1 braided self-reinforced polylactic acid polymer stents began before 1 month, while 1 over 1 braided stents retained their construction. At 6 months 3 of 6 biodegradable stents were degraded. Average longitudinal movement was 2 mm. (range 1 to 3) in the 1 over 1 self-reinforced polylactic acid polymer group, 2 mm. (range 0 to 7) in the 2 over 2 + 1 polylactic acid group and 3 mm. (range 3 to 3) in controls at 1 month. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. The expansion properties of the 2 braiding models tested in this study sufficed to fix the stents in situ in the prostatic urethra. However, the 1 over 1 braiding pattern was superior to the 2 over 2 + 1 pattern, in that it retained its macroscopic construction until the degradation of single self-reinforced polylactic acid polymer fibers.     

Urethral substitution using autologous lingual mucosal grafts: an experimental study

OBJECTIVE

To investigate the feasibility of urethral substitution using free lingual mucosa grafts (LMGs) in a dog model.

MATERIALS AND METHODS

The study included 10 female mongrel dogs in which a 4 × 1 cm² section of urethral mucosa was excised. The defect was immediately repaired with a size‐matched free LMG harvested from the inferior lateral surface of the tongue. A 12 F urethral catheter was kept inside the urethra for a mean of 7 days. At 3 months after the procedure, the patency of the urethra was assessed by both insertion of a 12 F catheter and by retrograde urethrography. Dogs were killed, the grafted areas excised, and evaluated by gross and histopathological examination.

RESULTS

All dogs survived the procedure and there were no tongue complications. One of the 10 dogs developed a slight urethral stricture near the proximal anastomosis. The remaining nine dogs voided spontaneously with no difficulty. Retrograde urethrography showed that no strictures or fistulas had formed. The LMGs shortened by 9.5% after surgery, from a mean (sd ) of 4 (0.13) to 3.62 (0.11) cm (statistically significant, P < 0.05). Histological examination showed that the LMGs were well‐incorporated into the urethral walls and covered by a keratinized squamous epithelium. Neovascularization was evident beneath the grafts.

CONCLUSION

We successfully developed an dog model for free LMGs and showed the feasibility of this approach for urethral substitution.     

Comparison of clinical outcomes between intravascular ultrasound‐guided and angiography‐guided drug‐eluting stent implantation: A meta‐analysis of randomised control trials and systematic review

This systematic review was designed to evaluate the overall efficacy of angiography‐guided drug‐eluting stent (DES) implantation vs intravascular ultrasound‐guided (IVUS) implantation for percutaneous coronary intervention. The electronic databases CENTRAL, PubMed, Cochrane, and EMBASE were searched for systematic reviews to investigate angiography‐guided and IVUS‐guided DES implantation. We measured the following six parameters in each patient: cardiovascular death, stent thrombosis, target lesion revascularisation (TLR), myocardial infarction (MI), major adverse cardiac events (MACEs), and all‐cause death. Twelve studies involving 6268 subjects were included, with 2984 receiving IVUS‐guided DES implantation and 3284 using angiography‐guided DES implantation. With regard to MACEs, TLR, MI, cardiovascular death, and all‐cause death, the IVUS‐guided DES implantation group had remarkably improved clinical outcomes. However, there was no significant statistical difference in stent thrombosis between the two groups. Dramatic decrease in MACEs through IVUS guidance was presented by trial sequential analysis. Remarkably improved clinical outcomes, including MACEs, cardiovascular death, all‐cause death, and TLR, were identified through IVUS‐guided DES implantation in comparison with angiography‐guided DES implantation. Nonetheless, the effect on stent thrombosis and MI required further confirmation. In this meta‐analysis, eligible randomised clinical trials were warranted to verify the findings and to determine the beneficial effect of IVUS guidance for patients.     

Biodegradable urethral stents seeded with autologous urethral epithelial cells in the treatment of post‐traumatic urethral stricture: a feasibility study in a rabbit model

OBJECTIVE

To evaluate the adhesion and growth of rabbit urethral epithelial cells (UECs) on a biodegradable unbraided mesh urethral stent, and to assess the feasibility and effect of the cell‐seeded urethral stent for treating post‐traumatic urethral stricture (PTUS) in a rabbit model.

MATERIALS AND METHODS

Rabbit UECs were collected by biopsy from adult rabbit urethra and seeded onto the outer layer of a mesh biodegradable urethral stent. The growth of UECs in cell‐scaffolds was assessed by scanning electron microscopy, immunohistochemical and fluorescence staining. In all, 32 male New Zealand rabbits were used, with either PTUS or uninjured, as a control group. Cell‐seeded stents were implanted into the rabbits strictured urethra. The histological and immunohistochemical findings were assessed after death at 1, 2, 8, 12 and 24 weeks, respectively. The reconstruction and function were evaluated by urethroscopy and retrograde urethrography.

RESULTS

The cultured UECs adhered to the stent and grew well. Immunohistochemistry showed that the cells were stained positively for cytokeratin. At 4 weeks, vs 2 weeks, the thickness of the papillary projections of the epithelium decreased and inflammatory cell infiltration diminished. At 24 weeks the injured urethra was completely covered by integrated regeneration of three to five layers of urothelium. There was no evidence of voiding difficulty, stricture recurrence or other complications.

CONCLUSIONS

The unbraided mesh biodegradable urethral stent with autologous UECs seemed to be feasible for treating PTUS in the rabbit urethra, and provides a hopeful avenue for clinical application allowing reconstruction of PTUS.     

Urethroplasty for urethral strictures: Quality assessment of an in‐home algorithm

Objectives: To evaluate the outcome of different techniques of urethroplasty and to assess the quality of an in‐home algorithm. Methods: Two hundred fifty‐two male patients underwent urethroplasty. Mean patient's age was 48 years (range 1–85 years). Data were analyzed for the failure rate of the different techniques of urethroplasty. An additional analysis was done based on an in‐home algorithm. Results: Median follow up was 37 months (range: 6–92 months). Global failure rate was 14.9%, with an individual failure rate of 11.7%, 16.0%, 20.7% and 20.8% for anastomotic repair, free graft urethroplasty, pedicled flap urethroplasty and combined urethroplasty, respectively. In free graft urethroplasty, results were significantly worse when extrapreputial skin was used. Anastomotic repair was the principle technique for short strictures (83.3%), at the bulbar and posterior urethra (respectively 50.8 and 100%). Free graft urethroplasty was mainly used for 3–10 cm strictures (58.6%). Anastomotic repair and free graft urethroplasty were more used in case of no previous interventions or after urethrotomy/dilation. Pedicled flap urethroplasty was the main technique at the penile urethra (40.7%). Combined urethroplasty was necessary in 41 and 47.1% in the treatment of, respectively, >10 cm or panurethral/multifocal anterior urethral strictures and was the most important technique in these circumstances. Two‐stage urethroplasty or perineostomy were only used in 2% as first‐line treatment but were already used in 14.9% after failed urethroplasty. Conclusion: Urethroplasty has good results at intermediate follow up. Different types of techniques must be used for different types of strictures.     

The use of triclosan eluting stents effectively reduces ureteral stent symptoms: a prospective randomized trial

Study Type – Therapy (RCT) Level of Evidence 1b What's known on the subject? and What does the study add? Infection, encrustation and ureteral‐stent‐related symptoms (USRS) including pain, urgency and frequency are all major problems associated with stent use. No current ureteral stent or exogenously applied therapy adequately deals with these problems and antibiotic use is ineffective once a bacterial biofilm forms on the device. Triclosan is a broad spectrum antibacterial agent widely used in numerous healthcare products and has been previously shown to reduce inflammation on the skin and in the oral cavity. This study tested a triclosan‐impregnated ureteral stent for its ability to reduce infection, encrustation and USRS. This study shows that while a triclosan‐impregnated ureteral stent cannot reduce infection rates alone compared with antibiotic use, the stent can reduce several USRS including pain during indwelling. This study suggests that the triclosan eluting stent may have a role in treating patients, perhaps in combination with standard antibiotic therapy.

OBJECTIVE

• ? To evaluate the capacity of triclosan‐loaded ureteral stents to reduce stent‐associated bacterial attachment, biofilm formation and encrustation, thereby potentially reducing infection development and other device‐related sequelae.

PATIENTS AND METHODS

• ? Twenty subjects requiring short‐term stenting (7–15 days) were randomized to receive either a Percuflex Plus® non‐eluting stent (control) or a Triumph® triclosan eluting stent.
• ? Control‐stented subjects received 3 days of levofloxacin prophylaxis (500 mg once daily) while Triumph®‐stented subjects did not.
• ? All subjects were assessed for positive urine and stent cultures, stent biofilm development and encrustation.
• ? Following device removal, each subject completed an analogue‐scale symptom assessment questionnaire.

RESULTS

• ? Ureteral stenting was performed after nine ureteroscopic and one extracorporeal shock wave lithotripsy procedure in the control group and eight ureteroscopic and two shock wave lithotripsy procedures in the triclosan group.
• ? No significant differences were observed for culture, biofilm and encrustation between the two groups.
• ? Subjects in the triclosan group reported significant reductions in lower flank pain scores during activity (58.1% reduction, P= 0.017) and urination (42.6%, P= 0.041), abdominal pain during activity (42.1%, P= 0.042) and urethral pain during urination (31.7%, P= 0.049).

CONCLUSIONS

• ? In this study, the use of the Triumph® triclosan eluting stent had no marked impact on biofilm formation, encrustation or infection development in short‐term stented patients.
• ? The Triumph® device led to significant reductions in several common ureteral‐stent‐related symptoms, supporting its use in this patient population.

     

Application of paclitaxel-eluting metal mesh stents within the pig ureter: an experimental study

OBJECTIVE: The purpose of the present study is to compare the standard bare metal stents (BMS) with the Paclitaxel-Drug Eluting Stent (DES) in the ureter of a pig model. MATERIALS AND METHODS: We report on an experimental study with ten female pigs weighing between 25 and 30 kg. The stents were randomly placed in either the right or left ureter in each of 10 study animals, for a total of 20 stented ureters. Ten ureters were stented with an R-Stent (Orbus Medical Technologies, Hoevelaken Netherlands), and ten with a Paclitaxel-Eluting Coronary Stent (Boston Scientific, Natick, MA, USA). Patency was measured by radiograph of the nephrostomy tract, intravenous urography and virtual endoscopy at 24 hours and 21 days after the initial procedure, respectively. RESULTS: Free flow of urine through the stents into the bladder was documented in all stented ureters 24 hours after stent insertion by radiograph of the nephrostomy tract. At the 21 day follow-up examination, 5 R-Stents were found to be completely occluded and two partially stenosed, whereas no occluded stent was detected in the Paclitaxel-DES group. Pathology examination of the stents at 21 days follow-up showed that the obstructed R-Stents generated severe inflammation with metaplasia of the urothelium. The Paclitaxel-Eluting MS generated a mild inflammatory response within the ureteral lumen at the site of the stent, without hindering ureteral patency. R-stents proved to develop more hyperplasia compared to the Paclitaxel-Eluting MS. CONCLUSIONS: Paclitaxel-DES, when compared with the standard R- Stent BMS, generated less inflammation and/or hyperplasia of the surrounding tissues, thus maintaining ureteral patency. Long-term animal trials are required to further validate our results.     

A new biodegradable braided self-expandable PLGA prostatic stent: an experimental study in the rabbit

PURPOSE: The biodegradable PLGA (a copolymer of L-lactide and glycolide) urethral stent with a spiral configuration has been used clinically for the prevention of postoperative urinary retention after different types of thermal therapy for benign prostatic hyperplasia. A new braiding pattern for this stent has recently been developed by our group. The aim here was to investigate the in situ degradation and biocompatibility of the new braided stent in the rabbit urethra. MATERIALS AND METHODS: PLGA stents with a one-over-one braiding pattern and steel stents served as controls that were inserted into the posterior urethras of 24 male rabbits using a special delivery instrument. The animals were sacrificed after 1 week, 1 month, 2 months, or 4 months, and light microscopy and histologic analyses were performed. RESULTS: The delivery instrument worked well and cystoscopy was not needed in the insertion process. The braided PLGA stents degraded smoothly in 1 to 2 months. The metallic stents induced more epithelial hyperplasia and epithelial changes than the biodegradable stents at all time points analyzed. These differences increased during follow-up. CONCLUSION: The degradation process was well controlled and the biodegradable stents were more biocompatible than the metallic stents. The new stent can be inserted into the posterior urethra without cystoscopic aid.     

Does a previous end‐to‐end urethroplasty alter the results of redo end‐to‐end urethroplasty in patients with traumatic posterior urethral strictures?

Objectives: To evaluate the success rate of redo anastomotic urethroplasty and to compare it with primary anastomotic urethroplasty. Methods: We compared 52 patients with post‐traumatic posterior urethral strictures (group 1, mean age 24.6 years, range 10–62) who had undergone redo urethroplasty with 66 patients (group 2, mean age 22.6, range 6–71) who had undergone primary anastomotic urethroplasty. Mean stricture length was 2.0 cm (1–4.5) and 2.5 cm (1.5–6), respectively. All of the patients in group 1 had a stricture located at the bulboprostatic anastomotic site. In group 2, 43 (65.2%) had a bulbomembranous stricture and 23 (34.8%) had a prostatomembranous stricture. Results: Mean operative time was 140 (100–240) and 90 min (75–200) in group 1 and 2, respectively. Mean blood loss was 180 (80–900) and 125 mL (50–700), respectively. Mean hospital stay was comparable (6.6 days vs 5.5 days) between the two groups. Mean follow up was 54 months (10–144) for group 1 and 62 months (12–122) for group 2. Corporal separation, inferior pubectomy, a transpubic approach and urethral rerouting were required in 22 (42.3%) and 12 (18.2%), 7 (13.5%) and 3 (4.5%), 12 (23%) and 5 (7.6%), 2 (3.8%) and nil patients in group 1 and 2, respectively. An excellent or acceptable outcome was achieved in 42 (80.8%) and 57 (86.4%), 8 (15.4%) and 7 (10.6%) patients, respectively. Two patients in each group failed. Conclusions: Previously failed end‐to‐end urethroplasty does not alter the success rate of redo end‐to‐end urethroplasty.     

Laser resistance of expandable metal stents in interventional bronchoscopy: an experimental evaluation

BACKGROUND AND OBJECTIVE: Nd-YAG non-contact laser therapy is used to eliminate recurrent tumor tissue within airway stents. This study was performed to determine maximum exposure time until the stent wire is destroyed as well as exposure time necessary to deliberately fracture the wire mesh. STUDY DESIGN/MATERIALS AND METHODS: Strecker stents, Wallstents, and Nitinol Accuflex stents were implanted into pig bronchi. Then Nd-YAG laser light was directed to the stent wires at different power levels. Portions of the stent surrounded by bronchial tissue as well as bare wires were investigated. RESULTS: The Strecker stent and the Wallstent revealed a considerably higher laser resistance than did the Nitinol Accuflex stent. At 15 W, minimum exposure time until wire destruction was 4.6 and 6.3 s for the Strecker stent and the Wallstent respectively. In contrast, the Nitinol Accuflex stent tolerated only 1.7 s. CONCLUSIONS: Laser therapy with bronchial wire stents can be carried out at low power levels. It should, however, be avoided in the case of Nitinol Accuflex stents due to their low heat tolerance.     

Biocompatibility and implantation properties of 2 differently braided, biodegradable, self-reinforced polylactic acid urethral stents: an experimental study in the rabbit

PURPOSE: Biodegradable urethral stents have been in clinical use for more than 10 years. To solve the problems connected with the helical spiral configuration of the stents used to date we developed a new tubular mesh configuration and evaluated the biocompatibility properties and degradation time of 2 differently braided stents in the rabbit urethra. MATERIALS AND METHODS: The biodegradable, self-expanding stents were made of self-reinforced polylactic acid polymer blended with BaSO4 (Alfa Chem, Kings Point, New York). Two braiding patterns, namely a diamond 1/1 and a regular 2/2 + 1 (Prodesco, Perkasie, Pennsylvania), were used to produce a tubular mesh configuration. Stainless steel stents with 1/1 braiding served as controls. The stents were inserted into the posterior urethra of 36 male rabbits. The animals were sacrificed after 1 week, 1 month, 6 months or 12 months. Light microscopy and scanning electron microscopy analyses were done. RESULTS: Tissue reactions to operative trauma were seen in all specimens at week 1. The changes gradually abated in the biodegradable stent groups, whereas chronic inflammatory changes and fibrosis were increasingly seen with metallic stents after 6 months. Epithelial hyperplasia increased with time for all stent types and materials. As expected, stent fragmentation started at 6 months. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. However, the braided configuration of the stent with a decreased mass of material does not prevent the development of epithelial hyperplasia. The biodegradable, self-expanding, braided stents functioned well in the rabbit urethra and are suitable for clinical studies.     

Biocompatibility properties of a new braided biodegradable urethral stent: a comparison with a biodegradable spiral and a braided metallic stent in the rabbit urethra

OBJECTIVE: To compare the biocompatibility properties of a new braided biodegradable self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent to the former spiral biodegradable SR-PLLA stent and the stainless steel stent in a rabbit model. MATERIALS AND METHODS: In all, 54 male New Zealand White rabbits were anaesthetized and stents inserted into the prostatic urethra, three of each kind for each sample time. The rabbits were killed after 1, 3, 6, 9, 12 or 15 months and light microscopy and scanning electron microscopy used to analyse the effects. RESULTS: The disintegration of the braided SR-PLLA stent was more closely controlled than that of the spiral SR-PLLA stent. The metallic stent induced epithelial hyperplasia and polyposis earlier than the biodegradable stents, and in these rabbits the polyposis disappeared after the disintegration process. There were no differences in the histological analyses between the biodegradable stents, whereas the metallic stents caused the strongest inflammatory reactions. CONCLUSIONS: The braided SR-PLLA urethral stent functioned well in the rabbit urethra and clinical studies are already planned.