News Column

Patent Issued for Hollow Curved Superelastic Medical Needle and Method

June 23, 2014

By a News Reporter-Staff News Editor at Clinical Oncology Week -- From Alexandria, Virginia, NewsRx journalists report that a patent by the inventors Pakter, Robert L. (Tucson, AZ); Morris, Edward J. (Bloomington, IN), filed on November 8, 2011, was published online on June 10, 2014 (see also Cook Medical Technologies LLC).

The patent's assignee for patent number 8747359 is Cook Medical Technologies LLC (Bloomington, IN).

News editors obtained the following quote from the background information supplied by the inventors: "Medical procedures involving the vertebrae are typically complicated because of the preciseness required to avoid both neural damage and injury to major blood vessels, as well as the indirect path that is usually required to access the treatment site.

"This is certainly the case when performing a vertebroplasty, a procedure whereby bone cement, most commonly methyl methacrylate, is injected into a vertebral body to provide stabilization and/or pain relief in selected patients having a spinal condition such as osteolytic metastasis and myeioma, painful or aggressive hemangiome (benign lesions of the spine), or painful osteoporotic vertebral collapse.

"Standard treatment practice depends on the region of the spine being treated. For the cervical vertebrae, anterolateral access is used with a 15 gauge needle. The large vessels adjacent to the vertebra are laterally manipulated by the radiologist to provide an access site between the vessels and the pharyngolarynx. An upward access route is required because the needle must be introduced below the mandible.

"When accessing the thoracic or lumbar vertebrae, typically a large 10 gauge needle is used following a transpedicular or posterolateral approach. The transpedicular route is preferred to avoid spinal nerve injury and to decrease the probability of the cement leaking into tissues adjacent to the vertebral body.

"To obtain complete fill of a damaged vertebral body, it is often required that a second transpedicular access be made from the opposite side. A single infusion usually cannot fill the entire target area because the needle tip cannot be redirected from the original plane of entry. Continued infusion of cement from the first access site will usually not result in an adequate infusion due to the tendency of the material to set before it fills all of the affected area, thereby becoming a baffle to itself. Furthermore, the thick density of the marrow and structures, such as veins, usually acts to impede free flow of the cement within the vertebral body.

"Another concern during the procedure is accidental puncture of the these veins. Because vertebral veins lead directly to the lungs, there is a significant risk of pulmonary embolism if cement is accidentally introduced therein.

"The inability to adequately maneuver the needle cannula tip within a body or around structures is a major limitation of the straight needle. Additional needle sticks to complete a medical procedure result in discomfort to the patient and additional risk of leakage and other complications.

"To sufficiently access a vertebral body for complete infusion of cement, the needle tip must be capable of being deflected at significantly large angles from the original axis. This would require that the needle have a distal bend so that the needle could be rotated to selectively direct the material.

"Rigid curved needles are well known for suturing applications; however, adding anything more than a slight bend to an infusion needle limits its access path and ability to deeply penetrate tissue, especially bone. For example, a rigid curved needle is unsuitable for use in a vertebroplasty procedure where the needle cannula must be driven through the bone and deep into the vertebral body using a relatively straight approach and maintained in place to avoid additional damage to the entry site. While the initial needle access must be done with a straight needle of sufficient strength to penetrate bone, the ideal approach would be to direct a lateral infusion of cement following needle penetration, and then to withdraw the needle along its original path.

"Accomplishing this is problematic. The tissue density and resistance of the tissue to penetration at the treatment site can require that the inner infusion member be nearly as stiff as the outer piercing cannula. A certain degree of needle rigidity is required in order to be able to maneuver the needle and accurately direct flow of material.

"While stainless steel needles having a slight distal bend are known, the amount of needle curvature necessary to provide adequate lateral infusion is not possible--the needle plasticly deforms once inside the outer restraining cannula and hence is unable to return resiliently to its preformed shape. Thus, a second needle access would still be required to provide adequate filling.

"Other medical procedures present similar problems when a single straight needle is used. One example is tumor ablation where percutaneous ethanol injection is used to treat carcinoma of the liver and kidney. Originally introduced as a palliative treatment for inoperable hepatocellular carcinoma of the liver, ethanol injection has now been shown to have curative potential comparable to resection in many patients, especially for smaller tumors.

"Practice has been to inject ethanol directly into masses using a straight needle and to allow the ethanol to infuse from one or more side holes into the tissue. The problem is that the infusion may not penetrate any deeper than the needle tract; thus portions of the tumor are not effectively treated. It is desirable to provide a device for more effective infusion of ethanol into the tumor mass."

As a supplement to the background information on this patent, NewsRx correspondents also obtained the inventors' summary information for this patent: "The foregoing problems are solved and a technical advance is achieved in an infusion needle made of rigid superelastic material and having at least one performed bend along the distal portion of its length. The needle is used as an inner cannula coaxially with a second hollow cannula for restraining the inner needle cannula in a substantially straight orientation during percutaneous introduction to the target site, whereby the inner needle cannula is deployed to resiliently return to its preformed configuration.

"The ability of the preformed inner needle cannula to deflect laterally upon exiting the outer cannula allows the inner needle cannula to infuse or aspirate material at multiple points within different planes in the body as the inner infusion needle rotates about its longitudinal axis. This helps to reduce or eliminate the need for additional 'sticks' with the outer cannula; it also allows the operator to make an entry from one direction, then to deploy the curved inner cannula to reach a site that cannot be accessed directly, such as where another structure lies along the access path, thereby blocking the target site.

"The preferred material for the inner cannula is a superelastic, shape memory alloy such as sold under the trademark Nitinol (Ni--Ti); however, there are other non Ni Ti alloys that may be used. A Nitinol alloy is desirably selected that has properties whereby the temperature at which the martensitic to austenitic phase change occurs is lower than the working temperature of the device (i.e. room temperature).

"As described in U.S. Pat. No. 5,597,378, incorporated herein by reference, a permanent bend may be heat set in a superelastic Nitinol cannula by maintaining the cannula in the desired final shape while subjecting it to a prescribed high temperature for a specific time period. The resulting cannula can be elastically manipulated far beyond the point at which stainless steel or other metals would experience plastic deformation. Nitinol and other superelastic materials when sufficiently deformed undergo a local phase change at the point of stress to what is called 'stress-induced martensite' (SIM). When the stress is released, the material resiliently returns to the austenitic state.

"A second method of imparting a permanent bend to the needle material is by a process commonly known as 'cold working.' Cold working involves mechanically overstressing or overbending the superelastic cannula. The material within the bending region undergoes a localized phase shift from austenite to martensite and does not fully return to its original shape. In the case of the cold-worked cannula, the result is a permanent curve about the bending zone which has been locked in to at least a partial martensitic crystalline state.

"In contrast, when heat treating is used, the entire heat-annealed cannula is in a austenitic condition, even in the curved region, and is only temporarily transformed to martensite under sufficient bending stresses. Therefore, the flexural properties of the annealed cannula vary little across its length.

"Conversely, the bend of a cold-worked cannula, which contains martensite, has increased resistance to deformation and therefore holds its shape better than the more flexible bend of the pure austenitic cannula This increased rigidity can be an advantage for certain clinical applications.

"In one aspect of the invention, an introducer trocar or stylet is used with either the outer or inner needle cannula, depending on the luminate size of the needle, to facilitate access to tissue and/or prevent coring tissue into the distal tip of the needle device. The infusion needle or inner cannula is introduced through the outer cannula after access has been established and the trocar or stylet is removed.

"Depending on the size of the cannulas, the degree of the preformed bend, or the method used to form the bend, the inner cannula or needle may slightly deform the outer cannula as the preformed bend present in the inner needle or cannula is constrained within the outer cannula. As a result, the outer cannula may be deflected a few degrees from its normal longitudinal axis at a point corresponding to the bend of the inner cannula. As the inner cannula is deployed from the outer cannula, the inner cannula deflects laterally until the entire region of the bend is unsheathed. The distal opening of the inner cannula is oriented at a large angle (preferably within the range of from the original longitudinal axis when the inner needle is fully deployed.

"The ability of the inner cannula to deflect at a significant angle from the original longitudinal axis has great utility in a number of applications where straight access is required followed by redirection of the distal opening. This deflection permits access to a different site without the necessity of withdrawing and reintroducing the needle.

"A primary example of such a procedure is vertebroplasty in which infusion of the stabilizing cement with a straight needle often requires a second stick to provide complete filling to stabilize the vertebral body while avoiding damage to delicate structures such as veins. As with the standard single-needle procedure involving the thoracic or lumbar regions of the spine, a transpedicular approach is normally used whereby the larger outer needle cannula, such as a coaxial Jamshldi-type needle, is introduced into the damaged or diseased vertebral body. The outer needle includes an inner introducer trocar which is then replaced with a inner curved needle for infusion of the cement.

"The ability of the curved needle to deflect laterally and rotate to reach multiple planes gives it a significant advantages over straight needles which have a limited range of movement. Because of this additional range of movement, the curved needle can usually complete the vertebroplasty procedure with a single access of the vertebral body. This avoids additional discomfort and risks to the patient, which include complications from leakage of cement or inadvertent infusion into non-target areas.

"In addition to using the coaxial needle for infusion of cement as above, the device can also be adapted for aspirating material or serving as a conduit for the introduction of other devices. The apparatus may be used for a percutaneous corpectomy, a procedure which involves fusion and decompression of two or more vertebrae by first aspirating tissue from the damaged vertebral bodies, then introducing a prosthesis having a carbon fiber composite cage packed with bone graft material to serve as scaffolding for the affected vertebrae. Once the cage is properly positioned, methyl methacrylate or another suitable material is infused into the vertebral bodies to secure the prosthesis. The percutaneous corpectamy offers less trauma, and with the reinforcement cage, provides superior rigidity over a conventional corpectomy utilizing bone graft material alone.

"In another aspect of the invention, the coaxial needle can be adapted for paraspinal use to inject medicaments within the neural canal or epidural space as part of management and/or diagnosis of pain. Preferably, the outer cannula has a tip adapted for piercing soft tissue. This outer needle cannula, preferably about twenty-one (21) gauge, is introduced percutaneously parallel to the spinal column along with an internal stylet with matched bevel to prevent coring tissue into the distal opening. The stylet is removed and the curved needle, about twenty-five (25) gauge, is inserted into the outer cannula. The needle assembly is then maneuvered to contact a nerve root during a diagnostic procedure to help recreate pain symptoms of the patient. The inner infusion needle also includes a stylet which is situated within the passageway of the needle as it is directed to the target site. The stylet is then removed from the infusion needle and medicaments, commonly steroids such as celestone (injected with lidocaine), kenalog, or methylprednisone are introduced to the treatment site. The inner needle is then withdrawn into the outer sheathing cannula and both are withdrawn from the patient.

"Another use of the smaller gauge paraspinal needle is for diskography which consists of injecting a contrast agent (preferably nonionic contrast media) directly into the patient's disk to delineate the extent of any malformation or injury to the vertebral body.

"Yet another aspect of the invention solves the problem of infusion of ethanol into a tumor mass by utilizing a plurality of curved needle cannulae deployed within an cannula introduced into the tumor where the curved needle cannulae radiate outward into an umbrella-shaped configuration. Infusion can take place at multiple points within the tumor to provide wider dispersion of the ethanol. Following treatment, the curved needle cannulae are withdrawn into the cannula and the device is removed from the patient.

"In a related aspect, one or more needle cannulae are located proximal to the distal end of the infusion needle. These proximally-located cannulae allow infusion of medicaments at different points along the length of the device. By having multiple sets of needles arranged in the umbrella configuration, the volume of tissue treated is increased. The coaxial outer cannula includes a plurality of side apertures that allow the proximally-located needle cannulae to deploy after the infusion needle is placed at the desired location in the body and the outer cannula is withdrawn. An outer sheath over the coaxial outer cannula selectively exposes the side apertures to permit the appropriate alignment of needle cannulae and apertures when there are multiple rows of each.

"The invention has applicability in any clinical situation where a straight approach is dictated and there is a need to avoid an obstructing structure (a large vessel, bowel loop, etc.) in the entry path, or the need to redirect the approach to a more lateral pathway to infuse medicaments or aspirate, such as to drain an abscess.

"In addition to infusion or aspiration, the invention can provide a conduit for introducing and/or directing the path of other medical devices within the body such as radio-frequency ablation catheters or wire guides. This would allow a straight approach to a critical juncture whereafter the curved infusion needle can be deployed to precisely proceed to the desired anatomical site, especially in situations such as a luminal bifurcation or when access to an ostium is required.

"Another use of the invention is to place the infusion needle in a bronchoscope or colonoscope which can serve as the outer constraining device. Under visualization, the inner needle then can be directed to perform a biopsy or other type of procedure."

For additional information on this patent, see: Pakter, Robert L.; Morris, Edward J.. Hollow Curved Superelastic Medical Needle and Method. U.S. Patent Number 8747359, filed November 8, 2011, and published online on June 10, 2014. Patent URL:

Keywords for this news article include: Alcohols, Technology, Bone Research, Ethanolamines, Pulmonary Embolism, Risk and Prevention.

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Source: Clinical Oncology Week

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