Rotatable cutting instrument

A surgical instrument includes a first member having an inner surface defining a first passageway. A second member is disposable within the first passageway and movable relative to the first member. The second member defines a longitudinal axis and extends between a first end and a second end configured to engage tissue. The second end includes a first surface configured for a non-penetrating engagement with the tissue and a second surface including at least two spaced apart cutting members extending axially from the first surface. The cutting members are rotatable to excise a portion of the tissue.

TECHNICAL FIELD

The present disclosure generally relates to medical devices for the treatment of musculoskeletal disorders, and more particularly to a surgical system for tissue removal and a method for treating a spine.

BACKGROUND

Spinal stenosis typically occurs when the spinal cord, cauda equina and/or nerve root(s) are impinged by one or more tissues in the spine, such as a buckled or thickened ligamentum flavum. Impingement of neural and/or neurovascular tissue in the spine by a buckled or thickened ligamentum flavum may cause pain, numbness and/or loss of strength or mobility in one or both of a patient's lower limbs and/or of the patient's back.

In lumbar spinal stenosis (LSS), the space around the spinal cord becomes narrow, thus compressing the spinal cord and the nerve roots. This causes back pain with neurogenic claudication, i.e., pain, numbness, or weakness in the legs that worsens with standing or walking and is alleviated with sitting or leaning forward. Compression of neural elements generally occurs as a result of hypertrophied facet or ligamentum flavum hypertrophy. LSS is one of the most common reasons for back surgery and the most common reason for lumbar spine surgery in adults over 65 years of age. Patients suffering from spinal stenosis are typically first treated with conservative approaches such as exercise therapy, analgesics, anti-inflammatory medications, and epidural steroid injections. When these conservative treatment options fail and symptoms are severe, surgery may be required to remove impinging tissue and decompress the impinged nerve tissue.

Decompressive laminectomy, a well-known treatment for LSS, unroofs the spinal canal by resectioning posterior spinal elements, such as the ligamentum flavum and/or the facet adjacent to the lumbar nerve roots. Wide muscular dissection and retraction is needed to achieve adequate surgical visualization. The extensive resection and injury to the posterior spine and supporting muscles can lead to instability with significant morbidity, both post-operatively and longer-term. Spinal fusion may be required to reduce the resultant instability. Laminectomy may be used for extensive multi-level decompression.

Standard methods of cutting tissue may include using a scalpel and scissors or electrosurgical procedures using radio frequency energy. Electrosurgical procedures and techniques using radio frequency energy are currently used since they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities.

Minimally invasive procedures in nerve and/or soft tissue such as the spine or the breast, however, are difficult to perform using standard scissors and scalpel. Furthermore, in a closed environment, radio frequency current dissipates into the surrounding tissue causing a decreased ability to achieve a current at the cutting electrode of sufficiently high density to initiate a cut. To overcome this problem, high power settings are often required to initiate the cut which often is painful and increases thermal damage to the tissue whether using a standard or a custom electrosurgical generator.

Another problem associated with cutting tissue is the control of bleeding. Radio frequency energy controls bleeding by coagulating small blood vessels. Another method of controlling bleeding is through the use of heat. For example, some commercially available scalpels use direct heat to control bleeding. However, while the bleeding is generally controlled, the cutting of tissue is often slower than with radio frequency energy and the knife edge readily dulls. Other commercially available scalpels use ultrasonic energy generally at 50 kHz to heat the tissue so as to coagulate severed blood vessels but cut slower than a standard electrosurgical electrode and are costly as a custom ultrasonic generator is required.

A further disadvantage of using radio frequency energy is the generation of smoke. The smoke is malodorous and can contain airborne viral particles that may be infectious. Furthermore, the smoke often obscures visualization of the procedure. When the smoke becomes too dense, the procedure is delayed until the smoke is released through one of the trocar ports and after enough carbon dioxide gas has re-insufflated the abdominal cavity. This unnecessarily prolongs the operative time.

Radiofrequency (RF) energy is used in a wide range of surgical procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. Conventional monopolar high frequency electrosurgical devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a “cutting effect” along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site. This collateral tissue damage often causes indiscriminate destruction of tissue, resulting in the loss of the proper function of the tissue. In addition, the device does not remove any tissue directly, but rather depends on destroying a zone of tissue and allowing the body to eventually remove the destroyed tissue.

Present electrosurgical techniques used for tissue ablation may suffer from an inability to provide the ability for fine dissection of soft tissue. The distal end of electrosurgical devices is wide and flat, creating a relatively wide area of volumetric tissue removal and making fine dissections along tissue planes more difficult to achieve because of the lack of precision provided by the current tip geometries.

In addition, identification of the plane is more difficult because the large ablated area and overall size of the device tip obscures the physician's view of the surgical field. The inability to provide for fine dissection of soft tissue is a significant disadvantage in using electrosurgical techniques for tissue ablation, particularly in arthroscopic, otolaryngological, and spinal procedures.

Traditional monopolar RF systems can provide fine dissection capabilities of soft tissue, but may also cause a high level of collateral thermal damage. Further, these devices may suffer from an inability to control the depth of necrosis in the tissue being treated. The high heat intensity generated by these systems causes burning and charring of the surrounding tissue, leading to increased pain and slower recovery of the remaining tissue. Further, the desire for an electrosurgical device to provide for fine dissection of soft tissue may compromise the ability to provide consistent ablative cutting without significant collateral damage while allowing for concomitant hemostasis and good coagulation of the remaining tissue.

Further, the health care practitioner may have difficulty positioning the tip of the device in the optimal location to get an optimal and consistent clinical result. This may also result in unwanted necrosis of adjacent tissue, which can lead to clinical adverse events including subsequent repair of the necrotic tissue.

Accordingly, there is a need for devices and methods to provide efficient severing or cutting of nerve and/or soft tissue that can be used during a procedure, such as, for example, open decompression. Further, there is also a need for devices and methods that provide fine dissection capabilities of nerve and/or soft tissue. Devices and methods that do not cause a high level of collateral thermal damage and allow for the control of necrosis in the tissue being treated are also needed. Devices and methods that provide efficient, controlled and safe debulking of tissue would also be beneficial.

SUMMARY

In one embodiment, a surgical instrument is provided. The surgical instrument comprises a first member including an inner surface defining a first passageway. A second member is disposable within the first passageway and movable relative to the first member. The second member defines a longitudinal axis and extends between a first end and a second end configured to engage tissue. The second end includes a first surface configured for a non-penetrating engagement with the tissue and a second surface including at least two spaced apart cutting members extending axially from the first surface. The cutting members are rotatable to excise a portion of the tissue. Systems and methods are provided.

In one embodiment, a surgical instrument is provided. The surgical instrument comprises a cannula including an inner surface defining a passageway. A tubular shaft is disposable within the passageway and axially translatable relative to the cannula. The shaft defines a longitudinal axis and extends between a first end and a second end configured to engage a ligamentum flavum. The second end includes a distal face configured for a non-penetrating engagement with the ligamentum flavum and at least two spaced apart cutting blades extending axially from the distal face. The blades each include a tip configured to axially pierce the ligamentum flavum and the blades are rotatable relative to the cannula to excise a portion of the ligamentum flavum.

In one embodiment, a surgical instrument is provided. The surgical instrument comprises a first member including an inner surface defining a first passageway. A second member is disposable within the first passageway and movable relative to the first member. The second member defines a longitudinal axis and extends between a first end and a second end configured to engage a ligamentum flavum. The second end includes a distal face configured for a non-penetrating engagement with the ligamentum flavum and a second surface including at least two spaced apart cutting blades extending axially from the distal face. The cutting blades are rotatable to excise a portion of the ligamentum flavum. A third member is disposable within the first passageway and movable relative to the first member. The third member extends between a first end and a second end configured to penetrate laminae and form a cavity therein.

DETAILED DESCRIPTION

The exemplary embodiments of a surgical system are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a surgical system for tissue removal and a method for treating a spine. In some embodiments, the surgical system and method are employed using minimally invasive surgical techniques to achieve permanent lumbar decompression by removing a ligamentum flavum.

In one embodiment, the surgical system of the present disclosure is employed for resecting a ligamentum flavum to achieve lumbar decompression and avoids damaging dura mater. In some embodiments, the surgical system includes a cannula inserted adjacent a surgical site and tissue. A partial laminectomy can be performed using a circular ultrasonic bone saw or a trephine. In some embodiments, components of the surgical system create a circular access hole through the lamina to access the ligamentum flavum from a posterior approach. In some embodiments, the surgical system includes a cutter that is rotatable and punches through the ligamentum flavum but does not damage the dura. In some embodiments, upon disposal of the cutter through the ligamentum flavum, the cutter is rotated. The cutter includes blades having knife edges that cut an excised portion of the tissue, which comprises a circular hole in the ligamentum flavum. In some embodiments, the surgical system includes suction or other devices to remove the excised portion.

In one embodiment, the surgical system includes a rotating cutter that punches safely through the ligamentum flavum with a blunt point and/or a rounded shape. In some embodiments, the cutter is configured to not harm the dura and is self-limiting in depth because of the geometry of the circular cutter. In one embodiment, the cutter includes tips comprising knives. In some embodiments, the cutter is connected to an electrosurgical device to employ RF to core the ligamentum flavum.

The following discussion includes a description of a surgical system including a surgical instrument, related components and methods of employing the surgical system in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. Reference will now be made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning now toFIGS. 1-3, there is illustrated components of a surgical system10including a surgical instrument12.

System10includes a surgical instrument12. Instrument12includes a first member, such as, for example a cannula14. Cannula14includes an inner surface16defining a first passageway18. Passageway18has a circular cross section configuration having a uniform diameter along the length of cannula14. It is contemplated that passageway18has alternate cross section configurations, such as, for example, oval, oblong, triangular, square, hexagonal, polygonal, irregular, uniform, non-uniform and/or tapered. Cannula14has an outer diameter of approximately 10 mm and an inner diameter of approximately 5-8 mm. It is contemplated that cannula14has various inner and outer diameters according to a particular application. Passageway18is sized and dimensioned for disposal of a second member. Cannula14has an outer surface that is smooth or even to prevent injury to the anatomy of a patient, such as, for example, soft tissue, when instrument12is inserted through an incision and delivered to the surgical site. It is contemplated that all or only a portion of the outer surface of cannula14may have various surface configurations, such as, for example, rough, threaded, arcuate, undulating, porous, semi-porous, dimpled, polished and/or textured, to enhance fixation of cannula14with tissue. Cannula14is made of stainless steel. It is contemplated that cannula14is made of any combination of suitable materials provided in the present disclosure.

Instrument12includes a second member, such as, for example, a shaft20. Shaft20has a tubular configuration along its length. It is contemplated that shaft20has various shapes, such as, for example, oval, oblong, triangular, square, hexagonal, polygonal, irregular, uniform, non-uniform and/or tapered. Shaft20is disposable within first passageway18and movable or axially translatable relative to cannula14. Shaft20includes an inner surface38that defines a second passageway40. Second passageway40is connected to a suction source42in a configuration to draw an excised portion of ligamentum flavum LF through second passageway40. Shaft20has an opening at its distal end having a circular cross section configuration. It is envisioned that the opening may have alternate cross section configurations, such as, for example, oval, oblong, triangular, square, hexagonal, polygonal, irregular, uniform, non-uniform and/or tapered. As suction source42is actuated, a vacuum or suction is produced at the opening such that excised tissue is drawn out of the surgical site through passageway40of shaft20.

Shaft20defines a longitudinal axis L1 and extends between a first end22and a second end24. First end22is in fluid communication with suction source42. End22of cutting member includes a drive portion (not shown) configured to rotate shaft20in the direction shown by arrow B and/or the direction shown by arrow BB. It is envisioned that the drive portion may be configured to engage an actuator, such as, for example, a surgical instrument, powered drill, hand drill, driver or other tool to rotate shaft20, in the direction shown by arrow B and/or the direction shown by arrow BB. In one embodiment, drive portion has a hexagonal cross sectional configuration and is configured to engage a correspondingly shaped portion of the actuator. It is envisioned that the drive portion may include a square, triangular, polygonal, star or hexalobe cross sectional configuration configured engage a correspondingly shaped portion of the actuator.

Second end24is configured to engage soft tissue, such as, for example, ligamentum flavum LF. Second end24has a tubular configuration having a diameter of approximately 2 mm to 6 mm. It is contemplated that second end24has various configurations, such as, for example, those alternatives described herein. Second end24includes a first surface26configured for non-penetrating engagement with the ligamentum flavum LF and a second surface28configured for penetrating engagement with the ligamentum flavum LF.

First surface26includes a distal face30defined by the circumferential edge of shaft20. Distal face30is planar so as to not cut tissue. Second surface28includes at least two spaced apart cutting members32extending axially along longitudinal axis L1 from distal face30. Members34are blunt to push through the relatively taught ligamentum flavum and simultaneously protect the dura mater by not being sharp to penetrate it. Adjacent to members34are members36which are sharpened blades to cut ligamentum flavum with rotational motion.

Each cutting member32includes a blunt distal tip34configured to axially pierce the ligamentum flavum LF and not the dura of the spinal cord SC. In one embodiment, distal tip34is rounded. In one embodiment, distal tip34is shaped similarly to that of a Tuohy needle tip. The blunt distal tip34is specifically designed so as to be an atraumatic tip. That is, the blunt distal tip34is specifically designed so as to prevent or minimalize damage to tissue as the device is used in situ. The blunt distal tip34can have different configurations such as circular, oval, arcuate, trapezoidal with rounded corners or any other configuration that would not damage tissue as the device is used in situ. The surface of the blunt distal tip34is non-abrasive so that it slides across tissue as the device is moved about at the surgical site and does not damage adjacent tissue.

Each cutting member32has a cutting blade36extending between distal face30and a portion of cutting member32proximal to distal tip34. Cutting blades36are oriented in the circumferential plane of shaft20. It is contemplated that blades36have various surface configurations, such as, for example, serrated, linear, straight, curved, convex, concave, continuous, intermittent, even, uneven and combinations thereof to facilitate cutting tissue.

Instrument12includes a third member, such as, for example, a bone cutter46disposable within first passageway18of cannula14and movable relative to cannula14. Bone cutter46extends between a first end48and a second end50configured to penetrate laminae and form a cavity therein. In one embodiment, second end50includes an ultrasonic circular bone saw52. In one embodiment, second end50includes a trephine52.

In assembly, operation and use, system10is employed with a surgical procedure, such as, for example, a treatment of lumbar spinal stenosis. It is contemplated that one or all of the components of system10can be delivered or implanted as a pre-assembled device or can be assembled in situ. System10may be completely or partially revised, removed or replaced. It is envisioned that system10may also be used to treat other affected portions of the patient, such as, for example, a calcaneus bone, bones of the feet or hands, bones of the spine, bones of the arms and legs, etc.

In use, to treat lumbar spinal stenosis, the medical practitioner obtains access to a surgical site in any appropriate manner, such as through the skin, or through an incision and retraction of tissues. In one embodiment, a drill is employed to remove bone tissue to provide access to a repair site. It is envisioned that system10can be used in any existing surgical method or technique including open surgery, mini-open surgery, minimally invasive surgery and percutaneous surgical implantation. Once access to the surgical site is obtained, the particular surgical procedure can be performed for treating the injury or disorder. The configuration and dimension of system10is determined according to the configuration, dimension and location of a selected section of nerves and the requirements of a particular application.

An incision is made in the body of a patient and a cutting instrument (not shown) creates a surgical pathway for positioning of components of system10. A preparation instrument (not shown) can be employed to prepare tissue surfaces, as well as for aspiration and irrigation of a surgical region according to the requirements of a particular surgical application.

Cannula14is positioned within the surgical pathway creating a working pathway to a lamina L of a vertebra V. Bone cutter46is axially translated through passageway18of cannula14such that bone cutter46engages lamina L. Bone cutter46is then activated to rotate relative to lamina L. In one embodiment, ultrasonic bone saw52is activated to perform a partial laminectomy to create a circular access hole through lamina L to access ligamentum flavum LF. In one embodiment, a partial laminectomy is performed by rotating trephine52to create a circular access hole through lamina L to access ligamentum flavum LF. After the access hole is created in lamina L, bone cutter46is withdrawn from cannula14. Shaft20is then axially translated through passageway18of cannula14until distal tip34of cutting members32makes contact with ligamentum flavum LF. The practitioner then punctures through ligamentum flavum LF with the cutting members32using a downward motion until he or she feels an absence of resistance and distal face30is engaged with ligamentum flavum LF preventing further downward movement of cutting members32. Once cutting members32have punctured through ligamentum flavum LF, the drive portion of end22is then activated by an activator, such as, for example, an electric motor to rotate cutting blades36in direction BB to excise a portion of ligamentum flavum LF. Cutting blades36rotate at least 180 degrees about longitudinal axis L1 forming a bore in ligamentum flavum LF. Suction source42is then activated to draw the excised portion through second passageway40out of the surgical site.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplification of the various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. The embodiments above can also be modified so that some features of one embodiment are used with the features of another embodiment. One skilled in the art may find variations of these preferred embodiments, which, nevertheless, fall within the spirit of the present invention, whose scope is defined by the claims set forth below. It is envisioned that system10may comprise various instruments including the configuration of the present disclosure, such as, for example, inserters, extenders, reducers, spreaders, distractors, blades, retractors, clamps, forceps, elevators and drills, which may be alternately sized and dimensioned, and arranged as a kit, according to the requirements of a particular application.

The components of system10can be made of radiolucent materials such as polymers. Radiomarkers may be included for identification under x-ray, fluoroscopy, CT or other imaging techniques. It is envisioned that the use of microsurgical and image guided technologies may be employed to access, view and repair spinal deterioration or damage, with the aid of system10.