nitinol and Ureteral-Calculi

Advances in ureteroscope and stone basket design have catapulted ureteroscopy to the forefront of surgical stone management; however, persistent problems such as stone migration continue to challenge urologists. The Escape nitinol stone retrieval basket (Boston Scientific, Natick, MA) is a stone basket designed to capture calculi and facilitate simultaneous laser lithotripsy in situ. We report our initial experience with the Escape basket for the management of urinary calculi and compare the use of this device with other methods of optimizing ureteroscopic stone management.. A prospective evaluation of 23 patients undergoing ureteroscopic holmium:yttrium-aluminum-garnet laser lithotripsy of urinary calculi was performed at two institutions by two surgeons (R.M. and G.M.P). The Escape basket was used to prevent retrograde ureteral stone migration or to facilitate fragmentation and extraction of large renal calculi. Patient demographics and perioperative parameters were assessed.. Twenty-three patients (16 men, 7 women), with a mean age of 55.5 years (range 33-74 yrs) were treated for renal (n = 9) or ureteral (n = 14) calculi. The mean stone diameter was 1.4 cm (range 0.4-2.5 cm), mean fragmentation time was 44.1 minutes (range 10-75 min), and mean energy used was 3.1 kJ (range 0.4-10.6 kJ). No complications were encountered. Eighty-seven percent (20/23) of patients were rendered completely stone free after ureteroscopic laser lithotripsy using the Escape basket. Of the three patients with residual calculi, one patient with a 2.5-cm renal calculus had residual fragments larger than 3 mm, and two patients with large renal calculi had residual fragments smaller than 3 mm.. The Escape basket appears to be safe and effective in preventing stone migration and facilitating ureteroscopic laser lithotripsy and stone extraction.

Topics: Adult; Aged; Alloys; Female; Humans; Kidney Calculi; Lithotripsy, Laser; Male; Middle Aged; Pilot Projects; Treatment Outcome; Ureteral Calculi

This study aimed to compare the simultaneous use of two devices versus a single device through a single working channel in flexible ureteroscopy using a ureteral access sheath for single ureteral stones.. In a bench study, the time to (i) set laser fiber, (ii) exchange laser fiber and nitinol basket through working channel, and (iii) pull out the device from working channel were measured 10 times in each step. In a clinical study, 156 patients who underwent flexible ureteroscopy with a ureteral access sheath for a ureteral stone in middle and upper ureter between April 2019 and November 2021 were assessed. One device was used at a time for 79 patients (S-Group) and two were simultaneously used for 77 (D-Group). Surgical outcomes and complications were compared.. In the bench study, the mean time to change from laser fiber to basket and from basket to laser fiber through the working channel were 26.1 ± 3.7 s and 23.6 ± 2.0 s (p = 0.084), respectively, which were significantly longer than the laser setup time (p < 0.001). In the clinical study, although the stone-free rate was not significantly different between the groups (S-Group 89.8%, D-Group 93.5%; p = 0.412), the median operation time was significantly shorter (p < 0.001) and the rate of postoperative stenting was significantly lower (p = 0.002) in the D-Group. There were no significant between-group differences in intra- and post-operative complications.. The simultaneous use of two devices through a single working channel is safe and could help save the time needed to exchange the laser fiber and nitinol basket.

Topics: Alloys; Humans; Male; Retrospective Studies; Ureter; Ureteral Calculi; Ureteroscopes; Ureteroscopy

We have developed the Peralta Stone Extraction System to increase the safety of ureteral stone extraction. The device combines a nitinol stone basket and low-pressure balloon into a single device. After visualization, the stone is captured in the tipless nitinol basket and enveloped by a low-pressure balloon. We tested the performance of device prototypes in a porcine model using stone mimics with diameters ranging from 4.2 to 6.2 mm. Stones extracted with the device required less force when compared with stones in a standard ureteral stone basket. The force reduction was most pronounced for stones greater than 4.2 mm in diameter, and when traversing a ureteral stenosis model. In conclusion, a combination stone basket and balloon device may provide a new and safer way to extract ureteral stones.

Topics: Alloys; Animals; Dilatation; Humans; Hysteroscopes; Male; Swine; Ureteral Calculi; Ureteral Obstruction; Ureteroscopy

Intraoperative assessment of stone size is crucial for the successful and safe extraction of stones. The first automatically fixating measuring stone basket prototype showed a mismatch between the steel spring and the nitinol basket; therefore, to improve this prototype, the steel spring was replaced with a nitinol spring and a modified scale was implemented on the basket handle for accurate intraoperative stone size measurement.. The proposed tipped basket was composed of nitinol. A standard handle with a spring-supported self-closing mechanism (2.5 F, Urotech. The material difference between the basket and the spring was eliminated. The measuring scale ranged from 2 mm (green) through 5 mm (yellow) to 8 mm (red), and the scale was nonlinear because of the nonlinear relationship between the diameter of the stone and the distance marked on the scale.. The proposed automatically fixating stone basket with a nitinol spring has the potential to improve the safety and effectiveness of endourological stone retrieval. Further validation of this new scale and basket should follow.

Topics: Alloys; Humans; Ureteral Calculi; Ureteroscopy

Complications after endoscopic retrieval of kidney and ureter stones are obviously related to the size of the stones as well as the experience of the surgeon and other factors. During the procedure it is sometimes difficult for surgeons to estimate stone size and therefore give prognostic advises. The visual perception of the stone size depends on the shape, colour, distance to the renoscope and dilatation of the ureter. This is the so-called binding problem, because shape, color and direction of motion are processed separately by different population of optical neurons. In order to establish a better prognostic ratio, especially for less experienced surgeons we established an intraoperative semi-quantitative measurement of the stone size supported by a stone basket.. We modified the tipped nitinol stone baskets from the company Urotech with diameters of 2.5, 3.0 and 4 Ch. The handle of this basket has a spring mechanism, which automatically closes the basket and provides a predefined fixation force of the stones within the basket. On the handle we established a non-linear scale in mm by grabbing standardized balls or standardized screws.. The scales are nonlinear because of the nonlinear relation between the diameter of the stone and the distance of the slider. Also the scales differ in between the basket size, because of the different strain conditions due to the different wire sizes and materials or the spring and basket.. This scale could be an important orientation for a surgeon during endourological procedures to estimate stone sizes. It could be used also for the documentation of the size of fragments after an endourologic lithotripsy and could help in the decision for or against an extraction. Finally it could be very interesting for other disciplines like gastroenterology. The scale should be validated in further clinical trials.

Topics: Alloys; Equipment Design; Humans; Kidney Calculi; Size Perception; Ureteral Calculi; Ureteroscopy

We developed a prototype magnetic tool for ureteroscopic extraction of magnetized stone particles. We compared its efficiency for retrieving magnetized calcium oxalate monohydrate stone particles with that of a conventional nitinol basket from the pelvi-collecting system of a bench top ureteroscopic simulator.. Iron oxide microparticles were successfully bound to 1 to 1.5, 1.5 to 2 and 2 to 2.5 mm human calcium oxalate monohydrate stones. Several coated fragments of each size were implanted in the collecting system of a bench top ureteroscopic simulator. Five-minute timed stone extraction trials were performed for each fragment size using a back loaded 8Fr magnetic tool mounted on a 0.038-inch guidewire or a conventional basket. The median number of fragments retrieved per timed trial was compared for the magnetic tool vs the basket using the Mann-Whitney U test.. For 1 to 1.5 mm fragments the median number retrieved within 5 minutes was significantly higher for the prototype magnetic tool than for the nitinol basket (9.5 vs 3.5, p = 0.03). For 1.5 to 2 mm fragments the magnetic tool was more efficient but the difference in the number of fragments retrieved was not statistically significant (9.5 vs 4.5, p = 0.19). For 2 to 2.5 mm fragments there was no difference between the instruments in the number retrieved (6 per group, p = 1.0).. The prototype magnetic tool improved the efficiency of retrieving stone particles rendered paramagnetic that were less than 2 mm but showed no advantage for larger fragments. This system has the potential to decrease the number of small retained fragments after ureteroscopic lithotripsy.

Topics: Alloys; Calcium Oxalate; Computer Simulation; Electron Spin Resonance Spectroscopy; Equipment Design; Ferric Compounds; Humans; In Vitro Techniques; Magnetics; Models, Anatomic; Particle Size; Ureteral Calculi; Ureteroscopy

To evaluate the radial dilation force and basket opening dynamics of three small (<1.5F) stone baskets.. Boston Scientific OptiFlex (1.3F), Cook N-Circle Nitinol Tipless Stone Extractor (1.5F), and Sacred Heart Medical Halo (1.5F) baskets were tested for radial dilation force in 10 repetitions using a floating block atop a stationary block secured to a digital scale. The floating block, attached to a plastic frame and base, pressed down on the scale to measure the radial dilation of the open basket while being passed through the cylindrical opening between the blocks. These same baskets were tested in triplicate for basket width in 0.5- to 2-mm length increments using a mechanical caliper under optical light microscope visualization to evaluate the linearity of basket opening and length at which target basket width (5 mm) was reached.. The Sacred Heart Medical Halo had the best radial dilation (2.97 ± 0.22 g), followed by the Cook N-Circle (1.29 ± 0.04 g), and finally Boston Scientific OptiFlex (1.19 ± 0.12 g). The N-Circle was the only basket to exhibit linear opening, while the Halo exhibited an exponential curve. The OptiFlex exhibited a polynomial curve, with linear opening across the midrange of the basket length. From these curve equations, the target basket width (5 mm) was calculated. The N-Circle and the OptiFlex reached the target basket width at a basket length of 9.4 mm and 9.6 mm, respectively. The Halo reached the target basket width at a basket length of 11.5 mm.. The radial dilation force differs significantly among commercial baskets and may affect ureteral stone extraction. Linear basket opening may provide the physician more control in stone retrieval.

Topics: Alloys; Humans; Mechanical Phenomena; Surgical Instruments; Ureteral Calculi

Retropulsion of ureteral stones during laser lithotripsy may result in difficult and incomplete stone fragmentation. The Stone Cone nitinol urological retrieval coil and the NTrap nitinol ureteral occlusion device have been introduced into clinical practice to possibly limit stone retropulsion and enhance the efficiency of holmium laser (Convergent Laser Technologies, Alameda, California) stone fragmentation.. A total of 360 BegoStone Plus phantom stones (Bego USA, Smithfield, Rhode Island) of similar mass and weight were divided into 3 groups, including control, Stone Cone and NTrap. The groups were further subdivided according to fiber size (200 or 400 microm) and pulse width (350 or 700 microsec). These stones were placed in a horizontal pipette 12 mm in diameter, submerged in normal saline and disintegrated at laser settings of 1 J and 10 Hz continuously applied for 300 seconds. Retropulsion in cm and fragmentation efficiency with mass loss in mg were measured after treatment.. The 2 devices were effective for preventing retropulsion. In the control group the mean +/- SD retropulsion distance using a 350-microsec pulse width with the 200 and 400 microm fibers was 18.4 +/- 5.9 and 14.1 +/- 4.6 cm, while it was 6.2 +/- 2.6 and 5.6 +/- 2.4, respectively, using the 700-microsec pulse width. There was a statistically significant higher loss of stone weight in the Stone Cone and NTrap experimental groups than in the control group (p <0.0001). However, there was no difference between the 2 experimental groups across all groups (p = 0.32).. The Stone Cone and NTrap eliminated retropulsion and equally improved fragmentation efficiency. The maximum efficiency of fragmentation was seen using the 200 microm fiber at a 700-microsec pulse width.

Topics: Alloys; Holmium; In Vitro Techniques; Lithotripsy, Laser; Surgical Instruments; Ureter; Ureteral Calculi; Ureteroscopy

Stents are used abundantly to maintain ureteral patency. The majority are plastic tubes that adjust easily to upper urinary-tract motion. Recently, a coiled-wire lumenless stent was introduced (ZebraStent, Neo Medical, Munich, Germany) to facilitate expulsion of stone fragments after lithotripsy. Its metal core is composed of Nitinol, with the soft J ends being of titanium. The thin shape considerably increases the extraluminal space. The ZebraStent stretches the ureter and also provides a surface for the fragments to glide along. In our 18-month experience with the ZebraStent, two of them fractured along the shaft. We sought to learn whether this complication resulted from a defect in stent design or from material fatigue secondary to constant movement.. Our model is powered by an electric motor that produces a constant displacement similar to stent movements in vivo. The whole ZebraStent is embedded in a 37 degrees C waterbath to simulate physiological conditions within the ureter. We used an average displacement of 16 mm. The average frequency of ventilatory-cycle simulation was 20 times that in vivo, allowing us to collect data in a shorter time.. All 10 stents broke within the proximal Nitinol shaft at the equivalent of 4 to 6 months (125-179 days).. Our preliminary results show that all stents break after the equivalent of 4 or more months. The fact that this occurs in the homogenous proximal Nitinol shaft rather than at the welding point between the shaft and the titanium curl implies that breakage is secondary to material fatigue and not design error. Extensive testing is under way to confirm material fatigue as the cause of breakage. We hope to determine a safe dwelling time for these stents, which at the moment should not exceed 3 months.

Topics: Alloys; Feasibility Studies; Humans; Materials Testing; Models, Anatomic; Prosthesis Design; Prosthesis Implantation; Stents; Stress, Mechanical; Titanium; Ureteral Calculi; Ureteral Obstruction

To compare stone retrieval and release from seven basket designs in vitro.. We tested two tipped and one tipless NCompass models, three other tipless Nitinol designs (NCircle, Sur-Catch, and Dimension), and the Segura Hemisphere for their ability to retrieve and release single beads 8, 6, 5.6, and 5 mm diameter and multiple beads 3.6 mm diameter in both a ureteral and a caliceal model in three separate attempts.. In the ureteral model, all baskets were successful in retrieving all sizes of single beads. With multiple 3.6-mm beads, only the NCompass and Dimension designs were able to retrieve at least two of three beads in all attempts. With the exception of the Segura Hemisphere, all designs were successful in releasing all bead sizes. In the caliceal model, only the NCircle, Dimension, and tipless NCompass models were able to retrieve all bead sizes in 100% of the trials. The tipped NCompass and Hemisphere designs were unable to retrieve any beads in this model. The Sur-Catch basket was successful in the retrieval of large beads only. The Dimension articulating design was the only basket able to release all bead sizes in all attempts. The tipless NCompass basket did not release any of the beads once engaged.. Nitinol basket designs show excellent retrieval and release capabilities in the in-vitro ureteral model. The articulating Nitinol basket has the best stone-releasing capability of all baskets tested.

Topics: Alloys; Equipment Design; Humans; Kidney Calculi; Kidney Calices; Models, Biological; Surgical Instruments; Ureteral Calculi

The use of stone baskets for repositioning of stones or removal of fragment in conjunction with ureterorenoscopy has become widespread. We tested the performance of the ACMI Sur-Catch NT, Bard Dimension, Boston Scientific Zero-tip, and Cook N-Circle in a pig kidney model of flexible ureterorenoscopy.. Opening characteristics of the basket were measured with mechanical calipers at 1-mm increments and compared with published reports to ensure the tested baskets were representative. Pig kidneys were placed in a basin and the ureters secured with a suture to a weight for stability. Flexible renoscopy was performed using a 16F flexible cystonephroscope. An 8-mm calculus was placed in the lower pole. Using each of four designs, the time necessary to grasp the stone, time to release the stone, and total time to move a stone from the lower-pole calix to the upper-pole were recorded. Total time experiments were repeated six times with each basket by three surgeons for a total of 18 attempts, and catch-and-release experiments were repeated six times by four surgeons for a total of 24 attempts per basket.. The Sur-Catch was significantly slower for catch and release (P < 0.001) and total time; P < 0.05) compared with all other baskets. There were no differences between the other baskets in either catch, release, or total times. There was no difference between surgeons (P < 0.0634) or between attempts one through six (P = 0.538).. Baskets with added complexity of the wire configurations (Sur-Catch) or a deflectable-wire mechanism (Dimension) offer no advantages and may slow capture and release of stones.

Topics: Alloys; Animals; In Vitro Techniques; Swine; Time Factors; Ureteral Calculi

A serious problem during calculus retrieval is the inability to release a stone from the basket. We evaluated a variety of basket designs to address this issue in two in-vitro models.. Four baskets--a modified, flat-wire, a double-helical, and two tipless Nitinol models (a passive and an articulating type)--were evaluated. The ability to retrieve and release beads of 4, 6, 8, 10, 12, and 14 mm diameter was compared in both a ureteral and a caliceal model.. In the ureteral model, all baskets were successful in retrieving all sizes of beads as long as the bead was smaller than the measured basket diameter. Only the articulating (all sizes) and larger non-articulating Nitinol models were able to release each of the bead sizes once engaged. The double-helical basket (larger size only) was able to release only the 4- and 6-mm beads after retrieval. For the 10- and 12-mm beads, the respective articulating Nitinol baskets could liberate the bead only when the articulating mechanism was used. In the caliceal model, the flat-wire and double-helical baskets were unsuccessful in all attempts at retrieval. The larger non-articulating Nitinol model was successful for beads >8 mm but had difficulty retrieving those smaller. Only the articulating Nitinol models were able to engage and release each of the beads.. From these in-vitro studies, it is apparent that the Nitinol basket designs have the best retrieval capabilities. The ability to articulate the basket improves release of a stone once engaged.

Topics: Alloys; Equipment Design; Humans; Lithotripsy; Ureteral Calculi

We designed a device to minimize ureteral stone migration during intracorporeal lithotripsy, decrease the likelihood of stone and/or basket entrapment, and extract whole stones and fragments.. Nitinol and stainless steel wires were configured into expandable tapered cones, which were placed cephalad to in vitro and in vivo concretions, and used to trap and extract stones as well as other test material. Safety features were evaluated by measuring the release of ball bearings and the tension needed to unwind the coils of the cone, which were greater than 4 mm. in diameter. We treated 4 patients with ureteral calculi using the Stone Conedagger to prevent migration and extract fragments.. The cone-shaped devices expanded to occlude the test devices and human ureters, and prevented stone migration. They extracted whole concretions and fragments greater than 1.5 mm. The cone-shaped basket released a 5.5 mm. ball bearing at an average 0.127 pounds of tension when pulled through a 5 mm. plastic orifice. Coils greater than 4 mm. in diameter were straightened at a tension of 0.10 to 0.14 pounds. Stone migration during intracorporeal lithotripsy was prevented in the 4 patients with ureteral calculi, in whom large and small fragments were safely extracted.. The Stone Cone may be placed via a ureteral catheter and opened cephalad to a ureteral stone to prevent stone migration during intracorporeal lithotripsy. It may extract whole stones and fragments greater than 1.5 mm. It is designed, so that its coils greater than 4 mm. in diameter release concretions too wide for the ureter or ureteral orifice after approximately 0.127 pounds of tension are applied. Because of these features, the Stone Cone represents a new generation of basketry appropriate to the era of ureteroscopy and intracorporeal lithotripsy. It is worthy of further clinical study.

Topics: Alloys; Biomechanical Phenomena; Equipment Design; Female; Humans; In Vitro Techniques; Lithotripsy; Male; Pilot Projects; Stainless Steel; Tensile Strength; Ureteral Calculi

The Browne Pneumatic Impactor (BPI; Browne Medical Systems, Minneapolis, MN) is a new mechanical lithotripter that relies on a pneumatically driven metal probe. It can be employed through both rigid and actively deflectable flexible endoscopes. Prior in vivo studies have shown excellent fragmentation of hard human calculi while employing the BPI with active endoscope deflection of as much as 45 degrees. In this study, we set out to define the efficiency of stone fragmentation with active endoscope deflection and to quantify the extent of retrograde stone migration that is often noted when mechanical lithotripters are employed. Pressure transducer testing of the BPI revealed an inverse relation between increased deflection of the endoscope and transduced voltage. Calculus fragmentation tests showed that as the endoscope was actively deflected to 90 degrees, the BPI still was able to fragment human calcium oxalate monohydrate calculi into extractable fragments with as few as six pulses. The maximum active endoscope deflection was 95 degrees with the 0.020-inch Nitinol probe passed through the working channel. At this deflection, the BPI was able to fragment an 8 mm pure calcium oxalate monohydrate calculus into two fragments after 14 pulses. Retrograde migration was evaluated by employing the BPI in a simulated ureter in a waterbath. The travel distance of a 5-mm 5-g calculus with one pulse averaged 12.2 mm (range 1-44 mm). Smaller, less dense calculi travelled farther. A rebound effect was occasionally noted, and this was associated with an off-center delivery. In conclusion, the BPI is an efficient mechanical lithotrite able to fragment hard human calculi when employed with active endoscope deflection of as much as 95 degrees. Delivered energy decreased with active endoscope deflection, but this change did not prevent fragmentation. Retrograde migration was an important variable more notable with smaller calculi.

Topics: Alloys; Endoscopy; Humans; Lithotripsy; Ureteral Calculi