T Välimaa

Publications (26)75.79 Total impact

• Article: A bioabsorbable self-expandable, self-reinforced poly-L-lactic acid urethral stent for recurrent urethral strictures: long-term results.

  T Isotalo, M Talja, T Välimaa, P Törmälä, T L J Tammela
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  ABSTRACT: Biodegradable urethral stents have been used clinically for some years mainly in order to prevent postoperative urinary retention after minimally invasive thermotreatment of benign prostatic hyperplasia. We previously reported a 15-month-follow-up pilot study of a bioabsorbable self-expandable, self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent in combination with optical urethrotomy in the treatment of recurrent urethral strictures. The present aim was to evaluate the long-term results of this new treatment modality. A series of 22 patients with severe urethral strictures (mean number of earlier urethrotomies 2.5) were involved. An SR-PLLA spiral stent with a bioabsorption time of 10 to 12 months was inserted into the urethra at the stricture site immediately after optical urethrotomy. Uroflowmetry, measurement of postvoiding residual urine, urine culture, and urethroscopy were performed preoperatively and at 1 and 3 months and then every 3 months up to 12 months, with subsequent follow-up visits every 6 months. The mean follow-up was 46 months. The treatment was successful in 8 of the 22 patients (36%). Six recurrences were found within the stented area and 15 outside. Patients with failure have since been treated with several urethrotomies and repeat self-dilatations or free skin urethroplasties. The results of the use of a bioabsorbable SR-PLLA urethral stent for the treatment of recurrent strictures were encouraging. Without this additional therapy, the recurrence rate of strictures might have been much higher. The main problem was sudden collapse of the stent, possibly induced by outer compression. A new generation of bioabsorbable stents is already under development.
  Journal of Endourology 01/2003; 16(10):759-62. · 1.85 Impact Factor
• Article: Viscoelastic memory and self-expansion of self-reinforced bioabsorbable stents.

  T Välimaa, S Laaksovirta, T L J Tammela, P Laippala, M Talja, T Isotalo, A Pétas, K Tarri, P Törmälä
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  ABSTRACT: The possibility to decide the speed and rate of expansion of stents is of great clinical importance by reason of the varying requirements for different indications to use stents. Self-reinforced bioabsorbable stents can be made self-expanding owing to the viscoelastic memory of the material. Stents are stable at room temperature and expansion occurs at body temperature. The level at which the expansion stops depends on the material, crystallinity, initial diameter of spira and annealing temperature. The expansion rate can be estimated by logarithmic equation, if material, draw ratio and diameter of stent wire are constant. This is, however, possible only if processing parameters are constant. Based on the present results annealing temperature and expansion time were seen to be directly proportional to the expansion rate of the stent.
  Biomaterials 10/2002; 23(17):3575-82. · 7.40 Impact Factor
• Article: Expansion and bioabsorption of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent.

  S Laaksovirta, M Talja, T Välimaa, T Isotalo, P Törmälä, T L Tammela
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  ABSTRACT: Self-reinforced bioabsorbable stents can be made self-expanding due to the viscoelastic memory of the oriented bioabsorbable materials. A new self-expandable self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80:20 stent was developed to prevent postoperative urinary retention after procedures that induced prostatic edema. In in vitro experiments the expansion rate has been up to 100% during the first few hours at body temperature. We investigated the expansion rate and biodegradation of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent in vivo in the prostatic urethra. A total of 39 men, 52 to 84 years old, with lower urinary tract symptoms due to benign prostatic enlargement underwent interstitial laser coagulation of the prostate. A self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was inserted into the prostatic urethra at the end of the operation. The stent lumen diameter was 4.5 mm. The location and diameter of the lumen and degradation of the stent were studied with transrectal ultrasound at 1, 2, 4 and 6 months postoperatively. At 6 months patients underwent cystoscopy. All except 1 patient voided on postoperative day 1. Mean lumen diameter was 7.4 mm. (range 6.2 to 8.2) at 1 month and 7.2 mm (range 6.2 to 7.5) at 2 months. At 4 months the stent was degraded into small pieces. No pieces of stent were found in the prostatic urethra on ultrasound or cystoscopy at 6 months. However, a portion of the spiral stent was found at the bottom of the bladder in 2 patients. The speed and expansion rate of the self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was sufficient to lock the stent in place and ensure voiding in cases of edema induced bladder outlet obstruction. Strength retention greater than 2 months was long enough to avoid later impairments of voiding.
  The Journal of Urology 10/2001; 166(3):919-22. · 3.75 Impact Factor
• Article: A double-blind, randomized, placebo-controlled pilot study to investigate the effects of finasteride combined with a biodegradable self-reinforced poly L-lactic acid spiral stent in patients with urinary retention caused by bladder outlet obstruction from benign prostatic hyperplasia.

  T Isotalo, M Talja, P Hellström, I Perttilä, T Välimaa, P Törmälä, T L Tammela
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  ABSTRACT: To assess whether patients in acute urinary retention from benign prostatic enlargement can be treated with a combined therapy comprising finasteride and a bioabsorbable self-reinforced poly L-lactic acid (SR-PLLA) urethral stent. Fifty-five patients in acute urinary retention were treated as outpatients; they had a suprapubic catheter inserted and the SR-PLLA stent placed cystoscopically. After 2 weeks the patients were randomized to receive either finasteride 5 mg daily or placebo. They were assessed at baseline and at 6, 12 and 18 months for maximum urinary flow rate, prostate volume and serum prostate-specific antigen (PSA). Nineteen patients completed the study while 36 discontinued. There was a statistically significant increase in the mean maximum flow rate, and a statistically significant decrease in the prostatic volume and serum PSA in the finasteride group. The same number of patients discontinued in both groups; the major reason for discontinuation was insufficient therapeutic response. The major problems were discontinuation of treatment because the response to therapy was insufficient, and uncontrolled breakdown of the spiral stent. To solve these problems, new configurations of bioabsorbable stents are needed.
  BJU International 08/2001; 88(1):30-4. · 2.84 Impact Factor
• Article: A double‐blind, randomized, placebo‐controlled pilot study to investigate the effects of finasteride combined with a biodegradable self‐reinforced poly l‐lactic acid spiral stent in patients with urinary retention caused by bladder outlet obstruction from benign prostatic hyperplasia

  T. Isotalo, M. Talja, P. Hellström, I. Perttilä, T. Välimaa, P. Törmälä, T.L.J. Tammela
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  ABSTRACT: Objective To assess whether patients in acute urinary retention from benign prostatic enlargement can be treated with a combined therapy comprising finasteride and a bioabsorbable self-reinforced poly l-lactic acid (SR-PLLA) urethral stent.Patients and methods Fifty-five patients in acute urinary retention were treated as outpatients; they had a suprapubic catheter inserted and the SR-PLLA stent placed cystoscopically. After 2 weeks the patients were randomized to receive either finasteride 5 mg daily or placebo. They were assessed at baseline and at 6, 12 and 18 months for maximum urinary flow rate, prostate volume and serum prostate-specific antigen (PSA).Results Nineteen patients completed the study while 36 discontinued. There was a statistically significant increase in the mean maximum flow rate, and a statistically significant decrease in the prostatic volume and serum PSA in the finasteride group. The same number of patients discontinued in both groups; the major reason for discontinuation was insufficient therapeutic response.Conclusions The major problems were discontinuation of treatment because the response to therapy was insufficient, and uncontrolled breakdown of the spiral stent. To solve these problems, new configurations of bioabsorbable stents are needed.
  BJU International 06/2001; 88(1):30 - 34. · 2.84 Impact Factor
• Article: Biocompatibility of silver nitrate and ofloxacine coated bioabsorbable SR-PLLA rods.

  M Multanen, M Talja, T L Tammela, J Seppälä, T Välimaa, K Järvi, P Törmälä
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  ABSTRACT: The purpose of this study was to evaluate the biocompatibility of silver nitrate and ofloxacine coatings of bioresorbable self-reinforced poly-L-lactic acid (SR-PLLA) rods. SR-PLLA rods coated with pure poly(caprolactone-co-L-lactide) or blended with silver nitrate (10, 5 or 2 weight-%) or ofloxacine (5 or 2 weight-%) were implanted in the dorsal muscles of 25 male rabbits. Tissue reactions caused by implantation trauma were seen 1 week after implantation. The positive control and 10 w-% silver nitrate coating showed the most marked reactions 1 month after implantation. Only sparse reactions were seen 6 months after implantation. Tissue reactions were scored semi-quantitatively. As a result of this study, we concluded that silver nitrate or ofloxacine coatings up to five w-% did not alter the good biocompatibility of SR-PLLA essentially. The method may lead to the possibility of preventing bacterial adhesion to urological stents during insertion.
  Urological Research 05/2001; 29(2):113-7. · 1.23 Impact Factor
• Article: Bacterial adherence to ofloxacin-blended polylactone-coated self-reinforced L-lactic acid polymer urological stents.

  M Multanen, M Talja, S Hallanvuo, A Siitonen, T Välimaa, T L Tammela, J Seppälä, P Törmälä
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  ABSTRACT: To determine whether ofloxacin coating has any effect on bacterial adherence to bioresorbable self-reinforced L-lactic acid polymer (SR-PLLA) urological stents. MATERIALS ANS METHODS: SR-PLLA stents were coated with epsilon-caprolactone/L-lactide copolymer blended with ofloxacin at three different concentrations of ofloxacin (0.5, 2 and 5% w/w). The adherence of five bacterial strains (Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis and two strains of Escherichia coli) to the coated SR-PLLA stents was analysed. Uncoated stent pieces were used as controls. The effect of ofloxacin coating on bacterial growth in the microenvironment of the stent pieces was also analysed. Ofloxacin coating prevented bacterial adherence to SR-PLLA stent material; this effect correlated significantly with the ofloxacin concentration of the caprolactone coating. Ofloxacin coating reduced the amount of bacteria in the microenvironment of the stent, but because of natural resistance, ofloxacin coating had little effect on E. faecalis. Except for E. faecalis, ofloxacin coating may reduce stent-associated infections. However, further studies are needed to confirm its biocompatibility and efficacy in clinical use.
  BJU International 01/2001; 86(9):966-9. · 2.84 Impact Factor
• Article: Bacterial adherence to ofloxacin‐blended polylactone‐coated self‐reinforced l‐lactic acid polymer urological stents

  M. Multanen, M. Talja, S. Hallanvuo, A. Siitonen, T. Välimaa, T.L.J. Tammela, J. Seppälä, P. Törmälä
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  ABSTRACT: Objective To determine whether ofloxacin coating has any effect on bacterial adherence to bioresorbable self-reinforced l-lactic acid polymer (SR-PLLA) urological stents.Materials and methods SR-PLLA stents were coated with ε-caprolactone/l-lactide copolymer blended with ofloxacin at three different concentrations of ofloxacin (0.5, 2 and 5% w/w). The adherence of five bacterial strains (Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis and two strains of Escherichia coli) to the coated SR-PLLA stents was analysed. Uncoated stent pieces were used as controls. The effect of ofloxacin coating on bacterial growth in the microenvironment of the stent pieces was also analysed.Results Ofloxacin coating prevented bacterial adherence to SR-PLLA stent material; this effect correlated significantly with the ofloxacin concentration of the caprolactone coating. Ofloxacin coating reduced the amount of bacteria in the microenvironment of the stent, but because of natural resistance, ofloxacin coating had little effect on E. faecalis.Conclusion Except for E. faecalis, ofloxacin coating may reduce stent-associated infections. However, further studies are needed to confirm its biocompatibility and efficacy in clinical use.
  BJU International 11/2000; 86(9):966 - 969. · 2.84 Impact Factor
• Article: Bacterial adherence to silver nitrate coated poly-L-lactic acid urological stents in vitro.

  M Multanen, M Talja, S Hallanvuo, A Siitonen, T Välimaa, T L Tammela, J Seppälä, P Törmälä
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  ABSTRACT: The purpose of this study was to see whether it is possible to prevent bacterial adherence to bioabsorbable self-reinforced L-lactic acid polymer (SR-PLLA) urological stents. The SR-PLLA stents were coated with silver nitrate blended epsilon-caprolactone/L-lactide copolymer. The adherence of five bacterial strains (Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis and two strains of Escherichia coli) to coated and non-coated SR-PLLA wires were tested. It was found that silver nitrate coating prevented the adherence of bacteria (except E. faecalis) to SR-PLLA stents. The preventive effect correlated with the silver nitrate concentration. It was also found that silver nitrate coating reduced the amount of bacteria in ambient urine. In conclusion, silver nitrate coating may reduce stent-associated bacterial infections by preventing the adherence of bacteria. Further studies are needed to confirm its efficacy and safety in clinical practice.
  Urological Research 11/2000; 28(5):327-31. · 1.23 Impact Factor
• Article: The morphological, in situ effects of a self-reinforced bioabsorbable polylactide (SR-PLA 96) ureteric stent; an experimental study.

  J Lumiaho, A Heino, T Pietiläinen, M Ala-Opas, M Talja, T Välimaa, P Törmälä
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  ABSTRACT: The present study was done to evaluate the biocompatibility of a new biodegradable double helical spiral self-reinforced poly-L, D-lactide copolymer (L/D ratio 96/4, SR-PLA96) ureteric stent. In sixteen dogs, the right ureter was cut transversally, sutured and stented with a 50 mm. long SR-PLA 96 stent. In eight dogs, left ureter was similarly operated and stented with a double-J pigtail stent (C-Flex, Cook Urological Inc.), while eight remaining ureters served as plain controls. Urine was analyzed for signs of infection. The dogs were terminated at 6, 12 and 24 weeks postoperatively and the ureters dissected to find persistent SR-PLA 96 particles or local ureteric changes. Histologic samples were taken at three levels of dissected ureters in contact with the stent. C-Flex and SR-PLA 96 materials were well tolerated. Both of these induced only minimal ureteral wall edema, epithelial hyperplasia, epithelial destruction and inflammatory cell reaction. In SR-PLA 96 stented ureters the tissue reaction subsided after the degradation of the device. SR-PLA 96 spiral stent is regarded highly compatible and SR-PLA 96 might be a suitable material for a partial ureteric stent. Biodegradation of a SR-PLA 96 stent makes stent removal unnecessary.
  The Journal of Urology 11/2000; 164(4):1360-3. · 3.75 Impact Factor
• Article: A randomised study to evaluate the efficacy of a biodegradable stent in the prevention of postoperative urinary retention after interstitial laser coagulation of the prostate.

  A Pétas, T Isotalo, M Talja, T L Tammela, T Välimaa, P Törmälä
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  ABSTRACT: Interstitial laser coagulation (ILC) of the prostate induces necrosis, oedema and increased risk for postoperative urinary retention. The present randomized study was carried out to investigate the feasibility and efficacy of a biodegradable self-reinforced polyglycolic acid (SR-PGA) stent in preventing postoperative urinary retention and the need for prolonged catheterization after ILC treatment. 35 males with benign prostatic enlargement (BPE) entered the study: 21 in the ILC + stent group and 14 in the ILC group without a stent. A suprapubic catheter was inserted for all patients and ILC was performed. The SR-PGA stent was inserted immediately after laser therapy in the stent group and kept open until the next morning when it was closed and the patient started trying to void. The suprapubic catheter was removed after voiding had started and the urinary bladder emptied adequately. In the ILC + stent group voiding started on the first postoperative day in 17 patients and on the second day in 2 patients. Voiding was delayed in 2 cases: in 1 case due to inadequate length of the stent and in the other as a result of the stent placement being too proximal. There was 1 case of urinary retention due to early degradation of the stent. In the ILC-only group voiding started on average 6.1 days postoperatively. At 1 month follow-up, the mean peak urinary flow rate had increased significantly in the ILC + stent group (p < 0.05) but not in the ILC-only group (p = 0.26). Improvements in symptom scores were significant in both groups (p < 0.005) but in terms of the mean peak urinary flow rates at 6 months follow-up the improvement was significant only in the stent group (p < 0.05). The use of a SR-PGA stent enabled early voiding and is safe and effective in the treatment of postoperative urinary retention after ILC. The 3-4 week degradation time of the SR-PGA stent was too short for some patients. There is still a need for further development work to improve the stents and larger controlled studies to show the true value of biodegradable stents in the treatment of BPE.
  Scandinavian Journal of Urology and Nephrology 09/2000; 34(4):262-6. · 0.99 Impact Factor
• Article: A new biodegradable stent for the pancreaticojejunal anastomosis after pancreaticoduodenal resection: in vitro examination and pilot experiences in humans.

  M Parviainen, J Sand, A Harmoinen, H Kainulainen, T Välimaa, P Törmälä, I Nordback
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  ABSTRACT: We sought to develop a biodegradable pancreatic stent that could be easily placed at operation into the human pancreatic duct and the degradation of which could be easily followed up. Spiral-shaped, gamma-sterilized stents were manufactured of 0.4-mm polylactide wire in which there was added 23 weight-% barium sulfate. The biodegradability of the stents was studied in vitro at two different pH values, the first resembling that of pancreatic juice and the other that of bile. The effects of enzymoactivity in the test solution and the composition of the stents (with or without barium addition) also were tested. These kinds of stents have been experimented with in two pilot patients. Degradation of the stents occurred from 24 to 52 weeks of incubation. Alkaline milieu together with the presence of pancreatic enzyme made the stents degrade twice as fast as when either alkaline milieu or enzyme was present. In the milieu resembling pancreatic juice, barium sulfate had no effect on the degradation time. Neither of the pilot patients had any postoperative complications. Biodegradable, x-ray-positive stents degrade faster in pancreatic than in biliary milieu. Their safety and efficacy in human pancreaticojejunal anastomoses need further study.
  Pancreas 08/2000; 21(1):14-21. · 2.39 Impact Factor
• Article: A pilot study of a bioabsorbable self-reinforced poly L-lactic acid urethral stent combined with finasteride in the treatment of acute urinary retention from benign prostatic enlargement.

  T Isotalo, M Talja, T Välimaa, P Törmälä, T L Tammela
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  ABSTRACT: To assess whether patients with acute urinary retention from benign prostatic enlargement can be treated with a combined therapy comprising a bioabsorbable self-reinforced poly L-lactic acid (SR-PLLA) urethral stent and finasteride. Eleven men in acute urinary retention were treated as outpatients; they had a suprapubic catheter inserted and the SR-PLLA stent placed cystoscopically. The patients were allowed to attempt to void spontaneously after 2 days. All patients started to void spontaneously within 2 weeks. There was a steady improvement in urinary flow rates up to 9 months, followed by a slight impairment after the bioabsorption of the stent. During the mean (range) follow-up of 24 (23-26) months only three patients required surgical treatment. The bioabsorbable SR-PLLA stent combined with finasteride therapy provides a promising new alternative in the treatment of acute urinary retention, especially in patients unfit for surgical therapy. Larger, placebo-controlled studies are needed to establish the efficacy of this combined therapy.
  BJU International 02/2000; 85(1):83-6. · 2.84 Impact Factor
• Article: Biocompatibility testing of a new bioabsorbable X-ray positive SR-PLA 96/4 urethral stent.

  T Isotalo, E Alarakkola, M Talja, T L Tammela, T Välimaa, P Törmälä
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  ABSTRACT: Recently a first X-ray-positive bioabsorbable urethral stent was developed by our group. The stent is made from self-reinforced poly-L,D-lactic acid (SR-PLA 96/4) blended with barium sulfate. The aim of this study was to evaluate the biocompatibility properties of the new stent materials. Rods made from pure SR-PLA 96/4 and SR-PLA 96/4 blended with barium sulfate were inserted into the dorsal muscles of a rabbit. Rods made from latex and silicone were used as positive and negative controls. To evaluate the long-term effect of BASO4 after the bioabsorption of the polymer, fast degrading SR-PGA (self-reinforced polyglycolic acid) and SR-PLA + BASO4 rods were used as controls. Urethral stents made from SR-PLA 96/4 and X-ray-positive SR-PLA 96/4 stents were inserted cystoscopically into the rabbit urethra. Metal stents were used as controls. The animals were sacrificed after 1 week, 1 month or 6 months. In the muscle implantation samples acute tissue reactions due to operative trauma were seen in all specimens at 1 week. After 6 months chronic inflammatory changes and foreign body reaction were seen only in the positive controls. The stent worked well in the rabbit urethra, its biocompatibility was good and there was less encrustation than in the metal stents. This first X-ray-positive bioabsorbable urethral stent showed no toxic tissue effects.
  The Journal of Urology 12/1999; 162(5):1764-7. · 3.75 Impact Factor
• Article: New bioabsorbable polylactide ureteral stent in the treatment of ureteral lesions: an experimental study.

  J Lumiaho, A Heino, V Tunninen, M Ala-Opas, M Talja, T Välimaa, P Törmälä
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  ABSTRACT: To evaluate the suitability of a new biodegradable double-helical spiral self-reinforced poly-L,D-lactide copolymer (SR-PLA 96; L/D ratio 96/4) stent as a device for ureteral stenting in respect to changes in kidney function during the biodegradation process. Sixteen dogs were used as experimental animals and were subdivided into two groups of eight. In Group A, both ureters were cut transversally, sutured, and stented. The right ureter was stented using an SR-PLA 96 stent, whereas a double-J C-Flex stent was used on the left side. Cystotomy was performed at 6 weeks to remove the double-J stents. In Group B, the right ureter of each dog was cut and stented in similar manner using an SR-PLA 96 stent, whereas the left ureters served as untreated controls, and cystotomy was not performed. Serum creatinine and nitrogen values were measured, urine was analyzed for signs of infection, and renal function was evaluated by urography and renography examinations preoperatively and at 6, 12, and 24 weeks postoperatively, at which time points, the dogs were euthanized and the ureters dissected to find persistent SR-PLA 96 particles and macroscopic local changes. There were no urinary tract infections found during the study. In the SR-PLA 96-stented ureters, obstructive hydronephrosis and stricture formation were observed in two cases (11%), with distal displacement of the SR-PLA 96 stent in another case (5.5%). In two additional renal units, a temporary prolongation in the kidney washout time was observed at 6-week renogram examinations. In the C-Flex-stented ureters, temporary changes in renography studies were observed in three cases (37.5%) at 6 weeks. Kidney washout times were protracted at 6 weeks in the pigtail-stented ureters in Group A as a sign of a pressure rise in the renal pelvis secondary to the direct connection between the renal pelvis and bladder, whereas pressure remained normal in SR-PLA 96-stented ureters. In Group B, renal function remained normal after ureteral repair in SR-PLA 96-stented ureters compared with the controls. The double-helical apical stent design offers some advantages over a double-J design. The risk of pressure-induced kidney damage is lowered, because there is no direct connection between the bladder and renal pelvis, and the risk of upper urinary tract infections is reduced. The biodegradation of the device necessitates the removal of the stent. These preliminary results suggest that a biodegradable SR-PLA 96 stent with more effective expansion capacity can be used for stenting after a ureteral repair.
  Journal of Endourology 04/1999; 13(2):107-12. · 1.85 Impact Factor
• Article: A bioabsorbable self-expandable, self-reinforced poly-l-lactic acid urethral stent for recurrent urethral strictures: a preliminary report.

  T Isotalo, T L Tammela, M Talja, T Välimaa, P Törmälä
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  ABSTRACT: We studied whether a new bioabsorbable self-expandable, self-retaining and self-reinforced poly-l-lactic acid double spiral stent is able to prevent the edges of a cut recurrent urethral stricture from adhering together and the scar from shrinking, thus obviating stricture recurrence. A bioabsorbable spiral stent was inserted into the stricture site in the urethra immediately after optical urethrotomy in 22 patients with recurrent urethral stricture. Uroflowmetry, measurement of residual urine volume, urine culture and urethroscopy were performed before and 1, 3, 6 and 12 months after optical urethrotomy. All 22 patients voided freely on day 1 or 2 after urethrotomy. The stent slipped partially proximal to the stricture and had to be changed in only 1 patient. The stent was totally epithelialized in all but 1 patient at 6 months and had degraded in all at 12 months. The improvement in flow rate was maintained during followup except in 10 patients with stricture recurrence, which was outside the stent area usually close to the external sphincter in 7 and in the stent area in 3. All recurrences were treated with repeat optical urethrotomy and a new stent was inserted. Urinary infections developed in 2 patients and were successfully treated with oral antibiotics. The self-expandable self-reinforced poly-l-lactic acid double spiral stent is a promising new method in the treatment of recurrent urethral strictures. There is no need to remove the device and no foreign material remains in the urethra. However, longer followup and controlled studies are needed to evaluate all benefits and side effects of this new treatment modality.
  The Journal of Urology 01/1999; 160(6 Pt 1):2033-6. · 3.75 Impact Factor
• Article: Effects of biodegradable self-reinforced polyglycolic acid, poly-DL-lactic acid and stainless-steel spiral stents on uroepithelium after Nd:YAG laser irradiation of the canine prostate.

  A Pétas, P Kärkkäinen, M Talja, K Taari, M Laato, T Välimaa, P Törmälä
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  ABSTRACT: To evaluate the safety and tissue effects on canine uroepithelium and prostate of biodegradable self-reinforced polyglycolic acid (SR-PGA) and self-reinforced poly-DL-lactic acid (SR-PLA) spiral stents compared to stainless-steel (SS) spiral stents. Twenty-five dogs (median body weight 12 kg) underwent a one-stage midline laparotomy and cystotomy. A side-firing Nd:YAG laser fibre was placed in the prostatic urethra antegradely and laser power applied at a setting of 20 W for 10 s in each side lobe, followed by dilatation to 4 mm diameter and insertion of a spiral stent. Dogs were randomized to receive an SR-PGA, SR-PLA or SS stent and no catheter was placed post-operatively. The dogs were killed after a follow-up of 1, 3 or 6 months and the bladder, prostate and urethra removed. Routine histological sections were prepared from the bladder, prostate, the proximal urethra immediately below the prostate and the distal urethra. Histological examination showed a mild to moderate foreign-body reaction and an acute inflammatory reaction after 1 month in the SR-PGA and the SR-PLA groups. The tissue effect was minimal in the SR-PGA group after 6 and 12 months. The SS stent group had more fibrosis, chronic inflammation and oedema at all follow-up assessments. There were erosions of the epithelium with subepithelial oedema in the animals with the SS stent. No dysplasia was detected and some remnants of the suture material were evident in the area of the cystotomy closure. There was one stricture at the apex of prostate in the SR-PGA group at 3 months in one re-operated dog. The histopathological changes in tissues caused by SR-PGA and SR-PLA stents were generally minor and decreased during the follow-up. The biocompatibility of SR-PGA and SR-PLA stents was good when combined with Nd:YAG laser treatment of the prostate.
  British Journal of Urology 01/1998; 80(6):903-7.
• Article: Bioabsorbable and biodegradable stents in urology.

  M Talja, T Välimaa, T Tammela, A Petas, P Törmälä
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  ABSTRACT: Since the early 1970s, bioabsorbable polymers have been used increasingly as suture and device materials. Bioabsorbable materials are high-molecular-weight polymers of polylactide (PLA; poly[lactic acid]) or polyglycolide (PGA; poly[glycolic acid]). The mechanical properties of self-reinforced (SR) devices (SR-PGA, SR-PLLA, and SR-PLA96 spiral stents) are acquired by special processing methods from polymer materials. As a result, the spiral stent has an expansion property of up to 70% of its original outer diameter, 50% of which may occur in 30 minutes. The stent may also have variable degradation properties in different parts of the device. The use of bioabsorbable devices in urology is novel. Today, SR-PGA spirals (Biofix) to be used for the prostatic urethra are commercially available but with restrictions. Their indications are the prevention of urinary retention after thermal therapy of prostatic hyperplasia, temporary treatment of urinary retention in patients waiting for surgery, and the early-phase resolution of bladder outlet obstruction in patients waiting for the effect of medical therapy. Stents can be also used to observe the effects of prostatic surgery on bladder function. The SR-PLLA and SR-PLA96 spiral stents are still under development for use in the anterior urethra, prostatic urethra, and ureters. Further experimental and controlled clinical studies are needed to find out the suitability of bioabsorbable devices in urology. Many efforts have been made to discover the best possible materials, models, coating materials, and additives of bioabsorbable stents in urology.
  Journal of Endourology 01/1998; 11(6):391-7. · 1.85 Impact Factor
• Article: The biodegradable self-reinforced poly-DL-lactic acid spiral stent compared with a suprapubic catheter in the treatment of post-operative urinary retention after visual laser ablation of the prostate.

  A Pétas, M Talja, T L Tammela, K Taari, T Välimaa, P Törmälä
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  ABSTRACT: To evaluate the efficacy and safety of a biodegradable self-reinforced poly-DL-lactic acid (SR-PLA) spiral stent compared with a suprapubic catheter after visual laser ablation of the prostate (VLAP) in a randomized study. The study comprised 45 patients (mean age 67.6 years, range 52-81) with bladder outlet obstruction caused by benign prostatic hyperplasia who received either a SR-PLA stent (22 patients) and a suprapubic catheter, or a suprapubic catheter only (23 patients) after undergoing VLAP. The suprapubic catheter was removed when voiding started. The response to VLAP and the effect of the stent or catheter were assessed using symptom scores, peak flow rate (Qmax), post-void residual volume (PVR), stent degradation, infection and outcome. Voiding started on the first or second day after treatment in 18 (median one day) of 22 patients with a spiral stent and in eight (median 6 days) of 23 patients with only the suprapubic catheter. The mean degradation time of the SR-PLA stent was 6 months; spiral fragments were found in the prostatic urethra or the urinary bladder in 20 of the patients on cystoscopy. Improvements in patient-weighted symptom score, mean Qmax and PVR were significant in both groups at the 6 month follow-up. The infection rate increased with the duration of suprapubic catheterization, from 25% (0-3 days) to 44% (> 3 days). Stones were seen in two stented patients during the follow-up. The SR-PLA spiral stent is safe and effective for the treatment of post-operative urinary retention after laser therapy. The degradation time of the stent was unnecessarily long compared with the duration of prostatic swelling and tissue sloughing after laser therapy. The infection rate depends on the duration of suprapubic catheterization.
  British Journal of Urology 09/1997; 80(3):439-43.
• Article: The biodegradable self‐reinforced poly‐dl‐lactic acid spiral stent compared with a suprapubic catheter in the treatment of post‐operative urinary retention after visual laser ablation of the prostate

  A. PÉTAS, M. TALJA, T.L.J. TAMMELA, K. TAARI, T. VÄLIMAA, P. TÖRMÄLÄ
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  ABSTRACT: Objective To evaluate the efficacy and safety of a biodegradable self-reinforced poly-dl-lactic acid (SR-PLA) spiral stent compared with a suprapubic catheter after visual laser ablation of the prostate (VLAP) in a randomized study.Patients and methods The study comprised 45 patients (mean age 67.6 years, range 52–81) with bladder outlet obstruction caused by benign prostatic hyperplasia who received either a SR-PLA stent (22 patients) and a suprapubic catheter, or a suprapubic catheter only (23 patients) after undergoing VLAP. The suprapubic catheter was removed when voiding started. The response to VLAP and the effect of the stent or catheter were assessed using symptom scores, peak flow rate (Qmax ), post-void residual volume (PVR), stent degradation, infection and outcome.Results Voiding started on the first or second day after treatment in 18 (median one day) of 22 patients with a spiral stent and in eight (median 6 days) of 23 patients with only the suprapubic catheter. The mean degradation time of the SR-PLA stent was 6 months; spiral fragments were found in the prostatic urethra or the urinary bladder in 20 of the patients on cystoscopy. Improvements in patient-weighted symptom score, mean Qmax and PVR were significant in both groups at the 6 month follow-up. The infection rate increased with the duration of suprapubic catheterization, from 25% (0–3 days) to 44% (>3 days). Stones were seen in two stented patients during the follow-up.Conclusion The SR-PLA spiral stent is safe and effective for the treatment of post-operative urinary retention after laser therapy. The degradation time of the stent was unnecessarily long compared with the duration of prostatic swelling and tissue sloughing after laser therapy. The infection rate depends on the duration of suprapubic catheterization.
  BJU International 08/1997; 80(3):439 - 443. · 2.84 Impact Factor