nitinol and Cadaver

To determine the stability bovine stifles stabilized with nylon or nitinol superelastic prostheses after transection of the cranial cruciate ligament (CCL).. Ex vivo study.. Stifles (n = 15) harvested from adult bovine cadavers.. The stifles were randomly assigned pairwise to a ligament reconstruction technique (n = 5): (1) and (2) Hamilton's technique using a prosthesis made of 24 nitinol strands (0.39 mm) braided at 40°or single 600-lb test nylon implant, and (3) nitinol prosthesis placed in femoral and tibial bone tunnels (bone-to-bone). Craniocaudal tibial translation at ±2000 N was applied to the tibia, and mediolateral angular displacement via measured under torsional tibial loading at ±60 Nm on three occasions: intact CCL, transected, and stabilized. Outcomes were evaluated with a mixed effect linear model for repeated measures.. Bone-to-bone using nitinol was the only repair that decreased tibial translation after CCL transection (p = .001) with a 23% change magnitude compared with intact CCL. Hamilton was the only stabilization reestablishing angular displacement, similar to intact CCL (p = .109 and .134 for nitinol and nylon). Bone-to-bone nitinol stabilization decreased angular displacement after CCL-transection with an 8% change magnitude (p = .040) without returning to normal values.. CCL replacement with nylon did restore joint stability. Nitinol prostheses passed through single femoral and tibial bone tunnels (bone-to-bone) were the only techniques reducing tibial translation.. Bone-to-bone stabilization with a nitinol prosthesis may be considered as an alternative to nylon for CCL replacement in cattle. These results provide evidence to justify clinical evaluation in cattle undergoing CCL replacement.

Topics: Alloys; Animals; Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Biomechanical Phenomena; Cadaver; Cattle; Cattle Diseases; Prostheses and Implants; Stifle; Tibia

The aim of this study was to determine the efficacy of a shape-memory alloy, Nitinol, as a component of an improved stapes prosthesis.. Prospective laboratory and clinical study to develop a Nitinol stapes prosthesis.. Various diameters of Nitinol wire and temperature transition variants were analyzed with regard to ease of deformation, response to heating, and strength. The size and geometry of the closed hook was determined by measurement of 50 incus cadaver bones. Several heat sources for activating the shape memory were evaluated, including electrocautery, lasers, and warm water. Trial surgeries were then performed on human temporal bones in the laboratory. The closure characteristics of the Nitinol loop were studied. Magnetic resonance imaging (MRI) testing at 1.5 Tesla was performed to determine safety during MRI studies. Preliminary human subject trials were then instituted.. In all cases, a low heat condition was ample to activate the shape memory characteristics of the hook and return it to a closed position after it had been opened. Laser power was generally set well below the power needed for removing bone. The Nitinol loop closed snugly around the incus with application to the top of the hook with a low temperature laser setting. Almost any heat source was effective. MRI testing at 1.5 Tesla showed no movement of the prosthesis. Preliminary results in human subjects showed excellent air-bone closure. The Nitinol loop holds uniform contact around the incus.. The Nitinol piston greatly simplifies the stapedectomy procedure by taking the need for a hand operated instrument out of the surgeon's hands. Because of the nature of the Nitinol wire, it can never over-crimp. All these characteristics make the prosthesis advantageous for otosclerosis surgery.

Topics: Alloys; Cadaver; Female; Follow-Up Studies; Humans; Incus; Magnetic Resonance Imaging; Male; Ossicular Prosthesis; Otosclerosis; Prospective Studies; Prosthesis Design; Prosthesis Implantation; Recovery of Function; Risk Assessment; Stapes; Stapes Mobilization; Treatment Outcome

Spinal cord stimulation (SCS) is a common treatment for neuropathic pain. There are 2 main categories of SCS leads: paddle leads and cylindrical leads. Paddle leads have reduced long-term complications and provide better coverage of target dermatomes when compared to cylindrical leads. However, insertion of a paddle lead requires invasive surgery that comes with significantly higher costs and more short-term complications, such as postoperative pain and infection. In contrast, cylindrical leads can be inserted minimally invasively using percutaneous techniques but provide less coverage of targeted dermatomes and have a higher tendency to migrate from intended neuronal targets.. Our objective is to develop a novel improved cylindrical spinal cord stimulation device that can convert into an optimal geometry once exposed to the body's environment after minimally invasive surgery. Such a device would be able to reduce long-term complications, lead migration, and better cover targeted dermatomes.. Biomaterial selection, medical intervention device design with an in-vitro lab-scale test, and cadaveric experimental study.. A shape memory alloy nitinol-based cylindrical lead was designed, and its nitinol core material was processed and geometrically programmed for percutaneous insertion into the epidural space and morphing into an optimal geometry once exposed to the body's environment. Deployment of the nitinol component of the design was tested in the lab and human cadaveric models of the epidural space.. Deployment of the nitinol component of the proposed cylindrical lead was successfully demonstrated in both a lab model of the epidural space and in the epidural space of a human cadaver in a minimally invasive fashion, indicating that a similar component could be used clinically in a full SCS electrode manufactured in a custom final geometry.. The focus of this study was to test the deployment of a novel minimally invasive lead that provides optimal coverage of intended dermatomes using in-vitro methods. Our study does not include in vivo trials. We do not test the electrical components of the design proposed since our design does not make changes to the electrical components of current commercially used cylindrical leads.. The unique shape memory property of nitinol shows promise in allowing cylindrical spinal cord stimulation leads to expand into a more optimal geometry within the epidural space. By having a body temperature-dependent geometry change, nitinol-based cylindrical leads could reduce lead migration, increase dermatomal coverage, and increase electrode density while maintaining the advantages of minimally invasive insertion.

Topics: Alloys; Cadaver; Electrodes, Implanted; Humans; Pain Management; Spinal Cord; Spinal Cord Stimulation

End-stage hallux metatarsophalangeal (MTP) joint arthritis is commonly treated with arthrodesis using stainless steel or titanium implants. These implants provide static compression that is maximal at the time of implant insertion. Alternatively, nitinol staples are capable of dynamic compression. They have most frequently been used for midfoot arthrodesis procedures. However, their biomechanical performance during hallux MTP arthrodesis has not been described.. 8 matched pairs of cadaveric feet (4 female, 4 male) were prepared for hallux MTP arthrodesis using cup and cone reamers. Cadaveric pairs were then instrumented with either (1) a transarticular lag screw and dorsal nitinol staple or (2) orthogonal nitinol staples placed dorsally and medially. Walking in a short leg cast for 6 weeks was simulated by applying 90-N forces at 3 Hz to the plantar proximal phalanx for up to 250 000 cycles. Failure was defined as catastrophic implant failure or plantar gapping beyond 7 mm.. 15 of 16 specimens failed cyclic loading. All 8 specimens fixed with orthogonal staples failed at an average of 37 ± 81 cycles. 7 of 8 specimens fixed with a dorsal staple and crossed screw failed at 14 900 ± 39 000 cycles. Collectively, 5 specimens failed because of bone fracture (1 in orthogonal staples, 4 in staple-screw group) and 10 failed because of excessive gap formation (7 in orthogonal staples, 3 in staple-screw group). The number of cycles to failure was significantly lower (. The tested constructs permit significant motion at the first MTP fusion surface during simulated protected weightbearing. Although multiple in vivo factors should be considered when extrapolating results from this cadaveric study, this motion may result in clinical failure with early postoperative weightbearing protocols.. We report the first biomechanical evaluation of hallux MTP arthrodesis using modern nitinol staples in 2 separate constructs.

Topics: Arthritis; Arthrodesis; Biomechanical Phenomena; Bone Screws; Cadaver; Female; Humans; Male; Metatarsophalangeal Joint

Sudden hearing loss can be treated noninvasively by administering drugs to the middle ear (≈1 ml) via the eustachian tube. The nasopharyngeal cavity requires high dexterity manipulation as it is restricted by the nasal vestibule, and precise drug delivery through the small cavity can allow previously unreachable areas to be reconsidered for localized delivery. Nitinol has shape memory capabilities and can be used for distal actuation accessed from small lumen and a tortuous path. The drug delivery device (DDD) is a soft and needle-sized (2 mm) and comprises of Nitinol, ribbon spring, and a drug delivery tube. By controlling the input voltage to the Nitinol, bending of the device at different angles could be achieved, and the ribbon spring works antagonistically to the Nitinol to revert to the initial position once deactivated. The actuation of the device and its corresponding bending are calculated in vitro and found to have a bending angle ranging between 36.2 and 66.8° for applied voltages of 1.2-2.0 V, with surface temperature of 45.6-154 °C. The DDD is able to actuate 200 cycles with ≈91-76% retention of bending performance, with a temperature increase of ≈8.5-9% when 1.2-2.0 V is applied. Addition of soft insulating material shows ≈34-62% reduction in the surface temperature in the first cycle and ≈37-59% over 200 cycles when actuated at 1.2-2.0 V. The active steering and navigation capabilities of the DDD are demonstrated in simulated environments (based on the eustachian tube dimensions of adult and infant). Preclinical testing in human cadavers is demonstrated and suggests the developed DDD controlled by varying the input voltages for bending, and mechanically varied drug delivery may be a feasible option for localized drug delivery in eustachian tube. Graphical abstract.

Topics: Alloys; Cadaver; Drug Delivery Systems; Female; Humans; Nose; Pilot Projects; Temperature

The integration of a shape memory actuator is a potential mechanism to achieve a consistent perimodiolar position after electrode insertion during cochlear implant surgery. After warming up, and therefore activation of the shape memory effect, the electrode array will change from a straight configuration into a spiral shaped one leading to a final position close to the modiolus. The aim of this study was to investigate whether the integration of an additional thin wire (referred to as an "inlay") made of Nitinol, a well-established shape memory alloy, in a conventional hearing preservation electrode array will affect the insertion behaviour in terms of increased risk of insertion trauma. Six conventional Hybrid-L electrode arrays (Cochlear Ltd., Sydney, Australia) were modified to incorporate a wire inlay made of Nitinol. The diameter of the wires was 100 µm with a tapered tip region. Electrodes were inserted into human temporal bone specimens using a standard surgical approach. After insertion and embedding in epoxy resin, histological sections were prepared to evaluate insertion trauma. Insertion was straightforward and no difficulties were observed. The addition of a shape memory wire, thin but also strong enough to curl the electrode array, does not result in histologically detectable insertion trauma. Atraumatic insertion seems possible.

Topics: Alloys; Cadaver; Cochlear Implantation; Cochlear Implants; Humans; Intraoperative Complications; Prosthesis Design; Temporal Bone

To quantify the deformation behavior of the diseased femoropopliteal segment and assess the change to deformation behavior due to various stent placements.. The length and curvature changes of 6 femoropopliteal segments (the right and left superficial femoral and popliteal arteries) from 3 cadavers were measured in 3-dimensional space based on rotational angiography image data in straight leg and flexed hip/knee (50°/90°) positions before and after placement of nitinol stents of varying type (EverFlex, Misago, and BioMimics 3D) and length (60, 100, and 200 mm) in different locations along the arteries. Three-dimensional centerline data were extracted for the measurements.. All 6 femoropopliteal cadaver segments displayed signs of peripheral artery disease. Hip/knee flexion resulted in vessel shortening and increases in the mean and maximum vessel curvatures in all cases. Location-specific results of the unstented arteries showed that magnitudes of vessel length and curvature change vary as a function of vessel length. The average shortening of the entire femoropopliteal segment due to flexion was observed at 10.7%±0.7%, which was reduced to 8.1%±0.9% after stent deployment. Average and maximum curvatures of the unstented segment increased due to flexion (average: 0.008±0.002 mm. The deformation characteristics of the femoropopliteal segment change in the presence of a stent, with the change to the deformation behavior dependent on stent type, stent length, location, flexibility, and intrinsic centerline curvature.

Topics: Aged; Alloys; Biomechanical Phenomena; Cadaver; Computed Tomography Angiography; Endovascular Procedures; Female; Femoral Artery; Hip Joint; Humans; Knee Joint; Male; Peripheral Arterial Disease; Pliability; Popliteal Artery; Posture; Prosthesis Design; Range of Motion, Articular; Stents

In this study, a new nitinol based fixation device was investigated for use in repairing severed digital flexor tendons. The device, composed of superelastic nitinol, is tubular in shape with inward facing tines for gripping tissue. Its cellular structure was designed such that it has a large effective Poisson's ratio, which facilitates a “finger trap” effect. This allows for reduced tendon compression during a resting state (to permit vascular perfusion) and increased compression during loading (to drive the tines into the tissue for gripping). To test the feasibility of using this device for flexor tendon repair, it was tested on cadaver flexor digitorum profundus tendons. The tendons were excised, cut in the region corresponding to a zone II laceration, and repaired using the device. The device was easy to install and did not prevent the tendon from bending. Constant strain rate tensile testing revealed a mean tensile strength of 57.6 ± 7.7 N, with a force of 53.2 ± 7.8 N at a 2 mm gap. This exceeds the suggested primary repair strength of 45 N, which has been proposed as the necessary strength for enabling early mobilization. Although considerable future studies will be needed to determine the suitability of the new repair device for clinical use, this study demonstrates the feasibility of utilizing a tubular, nitinol repair device for flexor tendon fixation.

Topics: Alloys; Biomechanical Phenomena; Cadaver; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Feasibility Studies; Fingers; Humans; Lacerations; Materials Testing; Stress, Mechanical; Surgical Fixation Devices; Tendon Injuries; Tendons; Tensile Strength

New, stronger suture materials have been introduced for flexor tendon surgery. The advantage of these materials can be lost if the suture loop pulls out from the tendon. The aim of this study was to compare the ability of various locking loops to grip the tendon.. We inserted 4 different standard and 2 experimental locking loops with 200-μm nitinol wire into human cadaveric flexor digitorum profundus tendons. The standard loops were: group 1, cruciate; group 2, Pennington modified Kessler; group 3, cross-stitch; and group 4, Lim-Tsai. The experimental loops were: group 5, a composition of Pennington modified Kessler with a cross-stitch loop; and group 6, a locking Kessler type of loop with a superficial transverse component. We loaded the loops until failure. We recorded the pull-out strength and stiffness and documented failure mechanisms during the pull-out test.. The cruciate loop had the weakest holding capacity, 20 N, which was significantly less than in groups 2 to 6. The cross-stitch loop, Lim-Tsai loop, and modified Kessler loop performed similarly (36 N, 37 N, and 39 N, respectively). The experimental loops had the highest pull-out strength (group 5, 59 N; and group 6, 60 N, both significantly greater than groups 1 to 4). The mode of failure was pull-out for all of the standard loops and 7 of the experimental loops. Of 20 experimental loops, 13 failed by suture rupture.. The 2 experimental loop configurations demonstrated higher pull-out strength and may have advantages when used with newer and stronger suture materials. The number of the locking components in the loops and the way the tension is transmitted to the tendon fibrils explain the results.. The loops presented in this study and that grip the tendon better may be useful with new materials that have high tensile strength.

Topics: Alloys; Cadaver; Fingers; Humans; Materials Testing; Suture Techniques; Sutures; Tendons; Tensile Strength

The use of intravascular stents in the superficial femoral artery (SFA) continues to be controversial due to the potential for compression and fracture in the tortuous physical environment of the adductor canal. The purpose of this study was to (1) characterize the types and ranges of stent distortion theoretically produced by extremity movement and (2) use these ranges as parameters for in vitro long-term fatigue testing of commercially available self-expanding nitinol stents.. Nitinol self-expanding stents were placed in the SFAs of cadavers and lateral view radiographs were obtained with the limb in various degrees of hip and knee flexion. The measured degrees of axial shortening and bending of the stent were estimated by planimetry and used for in vitro fatigue testing, which was undertaken using specially designed equipment. Six different commercially available nitinol self-expanding stents-Protégé EverFlex (EV3, Minneapolis, Minn), S.M.A.R.T. Control (Cordis/Johnson & Johnson, Miami Lakes, Fla), Luminexx (C.R. Bard, Murray Hill, NJ), LifeStent FlexStar (Edwards Lifesciences, Irvine, Calif), and Xceed and Absolute (Abbott Vascular, Santa Clara, Calif)-were mounted in elastic silicone tubing, bathed in phosphate buffered saline at 37 degrees +/- 2 degrees C, and examined for fracture after 10 million cycles of chronic deformation.. For unstented arteries, the distal SFA/proximal popliteal artery exhibited the greatest axial compression (23%) vs the middle SFA (9%) or popliteal artery (14%) at 90 degrees /90 degrees knee/hip flexion. For stented arteries, the popliteal artery exhibited the most axial compression (11%) vs the middle SFA (3%) or distal SFA/proximal popliteal artery (6%) at 90 degrees /90 degrees knee/hip flexion. Axial compression of the stented popliteal artery at 70 degrees /20 degrees knee/hip flexion was 6% with a deflection angle of 33 degrees . These parameters were used for chronic in vitro fatigue testing, which produced a range of responses in commercially available stents. Chronic 5% axial compression resulted in high rates of fracture of Luminexx (80%) and LifeStent FlexStar (50%), with lower fracture rates for Absolute (3%), Protégé EverFlex (0%), and S.M.A.R.T. Control stents (0%). Chronic 48 degrees bending deformation resulted in high rates of fracture in Protégé EverFlex (100%), S.M.A.R.T. Control (100%), and Luminexx stents (100%), with lower rates in Absolute (3%) and LifeStent FlexStar (0%).. Nitinol self-expanding stents undergo both axial and bending deformation when implanted into the superficial femoral and popliteal arteries. Commercially available stents exhibit a variable ability to withstand chronic deformation in vitro, and their response is highly dependent on the type of deformation applied.

Topics: Alloys; Biomechanical Phenomena; Cadaver; Compressive Strength; Female; Femoral Artery; Humans; Male; Popliteal Artery; Prosthesis Failure; Sensitivity and Specificity; Stents; Stress, Mechanical

After osteosynthesis of the proximal humerus by Kirschner wires (K-wire), loosening and secondary loss can occur. This study tested primary fixation of wires made from a shape memory alloy (SMA) Nitinol (NiTi), compared to conventional steel K-wires by pull-out tests. Blocks of cancellous bone were tested with three wire types: NiTi-K-wire with split apex geometry and conventional steel K-wires with and without threads. We found that NiTi-wires can be pulled out of bone more easily than steel wires (P=0.05), even though the former had rougher surfaces. The application of NiTi-wires through bone produced no better stability in comparison to normal steel K-wires, because of triggering the memory effect. Further studies are required to determine if NiTi wires of another appropriate design, surface and localization are superior to conventional wires in the context of this application.

Topics: Alloys; Animals; Biomechanical Phenomena; Bone and Bones; Bone Wires; Cadaver; Cattle; Equipment Design; Fracture Fixation; Microscopy, Electron, Scanning; Models, Animal; Surface Properties

To evaluate the MRI compatibility of 15 different commercially available, new generation, U.S. Food and Drug Administration (FDA)-approved stents suitable for deployment in superficial femoral arteries (SFAs), and to identify the ones that permit MRI to visualize the wall and lumen of stented arteries with sufficient spatial and contrast resolution to quantify restenosis after stent placement.. A total of 13 nitinol stents and two stainless-steel stents were placed in excised cadaveric SFAs and imaged by MRI at 1.5 T ex vivo. The images were evaluated qualitatively for the presence of artifacts and for the effects of the stent on image contrast, and quantitatively for the effect on signal-to-noise ratio (SNR) of the lumen of the artery inside the stent compared to the SNR of the fluid outside the artery. A nitinol stent was placed in the SFA of a 60-year-old man and imaged at 1.5 T in vivo.. Both the vessel wall and the lumen could be visualized in cadaveric SFAs containing either the Absolute nitinol stent, the Dynalink nitinol stent, or the aSpire nitinol-covered stent. Their inside stent/outside stent SNR was 0.7, 0.8, and 0.8, respectively. The other 10 nitinol stents tested obscured the lumen but did not cause major image shape artifacts. Both stainless-steel stents tested, the WallGraft and WallStent, completely obscured the lumen and caused significant distortion of the image shapes. When the Dynalink stent was inserted into a highly stenosed SFA in vivo, the image showed a dark expanded eccentric lumen, circumscribed by a medium intensity band containing the stent.. MRI can be used to visualize both the lumen and wall of SFAs containing selected nitinol stents ex vivo and in vivo. These results suggest that MRI can be used to monitor restenosis in stents placed in the femoral arterial bed.

Topics: Alloys; Artifacts; Cadaver; Femoral Artery; Humans; Magnetic Resonance Angiography; Male; Middle Aged; Recurrence; Stainless Steel; Stents

To determine the efficacy of a covered stent prototype designed for protected carotid angioplasty to reduce cerebral embolization.. The covered stent tested is made of nitinol, coated with a polyurethane membrane (MembraX trade mark; porous size 80 micro m). In a bench-top model (flow-rate 650 ml/min, pulsatile flow [dicrote] 123 Pulses/min, pressure 100/60 mm Hg [mean pressure 80 mmHg]) with inserted human carotid (n = 6) stent implantation was performed (8/32 mm). Passed particles (mg) were determined in the effluent of a 100 micro m filter prior to intervention, after stent deployment and after final dilation (5 mm).. When stenting carotid arteries obtained from human cadavers, the highest rate of particle embolization was measured while crossing the lesion with the delivery device (6,8 mg; for all p < 0,05), embolization after additional balloon angioplasty and particle rates measured in the effluent filter prior covered stent placement were significantly lower (3,8 mg; p < 0,05). Branches of the external carotid artery remained patent in all cases.. The introduced concept of covered stent protected carotid angioplasty with the MembraX trade mark prototype has proven promising results for low cerebral embolization rates ex vivo. Further evaluations using an animal model and a miniaturization of the delivery device are warranted prior to human use.

Topics: Adult; Alloys; Angioplasty, Balloon; Cadaver; Carotid Arteries; Carotid Artery, Common; Carotid Artery, External; Carotid Artery, Internal; Carotid Stenosis; Humans; Intracranial Embolism; Polyurethanes; Stents