Minimally invasive surgical access device

A minimally invasive surgical access device that allows access to a pathology being treated while significantly reducing the risk of damaging anatomical structures proximate the pathology. The access device includes a base portion having a central bore extending therethrough, and retractor blades pivotably mounted to the base portion. An insertion handle is coupled to the base portion to thread the retractor blades into the patient. The insertion handle is removed from the base portion, and a core hollow screw is threaded into the base portion to separate the retractor blades to gain access to the pathology through the hollow screw.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a minimally invasive access device for a surgical procedure and, more particularly, to a minimally invasive access device for spinal surgery, where the device includes retractor blades and an access tube, where the access tube is threaded into the retractor blades to cause them to separate, which provides a corridor for accessing a surgical pathology.

2. Discussion of the Related Art

Traditional surgical approaches for the human body involve the dissection of supporting structures, such as muscle, ligaments and/or bone, to access and expose the pathology being treated. These structures are usually vital to the long term health and function of the body. Typically, these structures are not involved in a disease process, but frequently need to be removed or dissected in order to gain visualization of the pathology.

In the case of spinal disorders, the supporting muscle and ligaments of the spine are removed to expose the underlying bony part of the spine where the pathology is typically located. These supporting structures are not causing the patient any discomfort or pain, however, because the surgeon must be able to visualize the surgical operation, they need to be removed or detached. For example, in the treatment of a lumbar disk herniation or stenosis, the muscle and ligaments are dissected from the spine to expose the lamina of the spine, sometimes over many levels of the spine. In performing spinal fusion and instrumentation, extensive muscle and ligamentous detachment may be performed. As a result, these tissues never return to their normal anatomical position, which is disrupted in the surgical process, weakening their function and strength. Also, the patient may experience significant pain and discomfort resulting in longer hospital stays and recoveries. The long term health of the spine can also be affected because these supporting structures are not able to perform their function normally. This can result in further pain and discomfort, and can even lead to additional surgeries.

A frequently encountered problem is transitional syndrome whereby the nerves adjacent to an open fusion and instrumentation become compressed. The treatment is often an additional surgery with extension of the fusion and instrumentation. This may in-part be due to the initial fusion procedure dissecting supporting muscles and ligaments creating an iatrogenic instability that leads to adjacent level stenosis. In addition, large open procedures often result in extensive scar formation that can lead to conditions such as arachnoiditis and failed back syndrome. These patients suffer significant and debilitating pain which is often refractory to additional surgery. Many can no longer work or conduct normal activities of daily living.

In an attempt to preserve normal anatomical structures during spine surgery, minimally invasive surgical procedures have been devised. One such procedure involves the use of a series of muscle dilators that spread open the muscle fibers of the spine to create a pathway to the spine. A Kirschner (K) wire (a thin metal wire) is initially introduced through a small incision and directed towards the spinal pathology. The position of the K-wire is visualized by a fluoroscopic imaging system to identify its location. An initial narrow diameter muscle dilator is passed over the K-wire, and the K-wire is removed and subsequent larger muscle dilators are continually passed. When the opening is large enough, an access tube or retractor is positioned around the last muscle dilator through which the surgery is performed. The inner sequential muscle dilators are then removed allowing the surgeon to operate through the tubular retractor. The retractors come in a variety of lengths and diameters for different patients and procedures.

Unfortunately, a number of complications have occurred using the previously described system. The K-wire is very thin and sharp and can be easily passed to deep and into the spinal cord or injure a nerve root or large blood vessel. Additionally considerable downward force is required to pass the muscle dilators towards the spine. Incidences have occurred in which the dilators are passed into the spinal canal resulting in neural injury and paralysis. The muscle dilators also tend to be pushed upward out of the wound requiring multiple repositioning during placement, each time placing the neural structures at risk. This is especially true for large muscular individuals. Lastly, multiple, sequentially larger dilators are used causing considerable patient risk with placement of each muscle dilator. Therefore, it is desirable to improve the known minimally invasive surgical access devices.

SUMMARY OF THE INVENTION

In accordance with the teachings of the present invention, a minimally invasive surgical access device is disclosed that allows access to a pathology being treated while significantly reducing the risk of damaging anatomical structures proximate the pathology. The access device includes a base portion having a bore extending therethrough. Retractor blades including inner and outer threads are pivotably mounted to the base portion. An insertion handle having an elongated body is attached to and extends through the bore in the base portion, and includes tabs for holding the retractor blades together in a conical orientation. The insertion handle is used to thread the retractor blades into the soft tissue of the patient towards the pathology. When the retractor blades are in place, the insertion handle is removed from the base portion, and a core hollow screw having a threaded outer portion is inserted through the opening of the base portion. An access handle is attached to the core hollow screw and is used to rotate the core hollow screw so that the threaded portion of the core hollow screw and the internal threads of the retractor blades interact to separate the retractor blades and expose the pathology through an internal bore in the core hollow screw.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following discussion of the embodiments of the invention directed to a minimally invasive surgical access device is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, the access device of the invention has particular application for minimally invasive spinal surgical procedures. However, as will be appreciated by those skilled in the art, the access device of the invention will have application for other types of minimally invasive surgeries.

FIGS. 1-10show various views of various components of a minimally invasive surgical access device assembly10, according to an embodiment of the present invention. The various components of the assembly10can be fabricated and assembled by any suitable technique, such as molding, stamping, welding, etc., and can be made of any suitable material, such as aluminum, steel, radio-lucent carbon/graphite composites, etc.

As shown inFIGS. 1 and 2, the access device assembly10includes a round base portion12having a central bore14extending therethrough. Three small holes16are symmetrically disposed around the central bore14and also extend through the base portion12. A mounting ring18is positioned around an outer edge of the base portion12, and is clamped thereto by a bolt20. The mounting ring18includes an extended portion28, where the bolt20is threaded through a tab36across a gap into the extended portion28to rigidly mount the mounting ring18to the base portion12. The extended portion28includes a threaded opening38that accepts a securing bolt of a holding arm (not shown). As would be well understood to those skilled in the art and more apparent from the discussion below, when the access device assembly10is being used in a surgical procedure, it needs to be rigidly mounted to a supporting structure, such as the operating table.

Three symmetrical retractor blades22,24and26are pivotably mounted to the base portion12. The retractor blade22includes an upper tab30, the retractor blade24includes an upper tab32and the retractor blade26includes an upper tab34. The tabs30,32and34each have a bore extending therethrough. The base portion12includes a rod (not shown) extending across an opening in the base portion12in which each of the tabs30,32and34is positioned. Thus, the retractor blades22-26are free to pivot on their independent rods. The retractor blades22-26have an inner thread and an outer thread for reasons that will become apparent from the discussion below. The internal and external threads of the retractor blades22-26need not be continuous between the blades22-26, but can be in other embodiments. Further, when the retractor blades22-26are in their unpivoted position, the retractor blades22-26form a conical shape having a pointed end opposite to the base portion12.

As will be appreciated by those skilled in the art, a conical shape for the retractor blades22-26is non-limiting in that the retractor blades22-26can form other shapes, such as a parabolic swept section, concave and convex orientations, stepped linear sections, a spiral, etc. Further, the cone can be unitary or broken up into multiple components along its axis. Further, the cone shape can be a canculated cone to allow it to follow a K-wire to the pathology. In this embodiment, there are three retractor blades. However, it other embodiments there may be more retractor blades within the scope of the present invention.

As shown inFIG. 3, the access device assembly10also includes an insertion handle40having a support portion42and a conical bottom portion44. In one embodiment, the insertion handle40can be a single piece unit made from a suitable material, such as aluminum. Three cylindrical pins46extend down from the support portion42and are configured to be inserted into the holes16in the base portion12. Further, the conical portion44is dimensioned to fit within the retractor blades22-26when the retractor blades22-26are in their unpivoted position.

FIG. 4is a perspective view of the insertion handle40attached to the base portion12. The conical portion44includes three extending tabs48that are configured to be positioned within openings50between the retractor blades22-26at an upper location proximate the base portion12.FIG. 5is a blown-up view at this location of the assembly10. The tabs48include a pair of fingers52that are inserted within notches54in two adjacent retractor blades22-26so that when the insertion handle40is positioned in the base portion12, the retractor blades22-26are held in place and prevented from pivoting.

When the access handle40is positioned in the base portion12, the pointed end of the retractor blades22-26are positioned over the pathology on the patient's skin. The handle40is rotated to thread the retractor blades22-26into the patient towards the pathology. The pins46in the support portion42prevent the handle40from being rotated relative to the base portion12. Once the retractor blades22-26are fully inserted into the patient to the desired depth, the handle40can be removed from the base portion12by merely pulling up on it. The retractor blades22-26are unique in allowing for a single pass or access towards the spine, and once positioned and opened, to expose the spinal pathology while minimizing muscle or ligamentous resection. The screw type outer conical design allows for a controlled approach since the driving force to advance the retractor blades22-26toward the spine is a turning motion, not a downward forced motion. The rate of advancement of the tip of the retractor blades22-26is controlled at all times by the rate of rotation of the insertion handle40. This significantly improves the safety of the assembly10for accessing the pathology.

FIG. 6is a front view of a core hollow screw60that is part of the assembly10. The core hollow screw60includes an outer threaded portion62at a bottom of the core hollow screw60that aligns with the inner threads of the retractor blades22-26. A top edge of the core hollow screw60includes four symmetrically disposed cut-outs64.

FIG. 7is a front view of an access handle70including an elongated rod72and an end portion74having symmetrically disposed pins76.FIG. 8is a front view of the access handle70mounted to the core hollow screw60where the end portion74is positioned within an internal bore80of the core hollow screw60and the pins76are positioned within the cut-outs64.

When the insertion handle40is removed from the base portion12after the retractor blades22-26are threaded into the patient, the surgeon will attach the access handle to the core hollow screw60and then position the threaded portion62of the core hollow screw60into the central bore14of the base portion12. When the surgeon rotates the access handle70to turn the core hollow screw60, the threaded portion62of the core hollow screw60and the retractor blades22-26interact to cause the core hollow screw60to be threaded downward, which causes the retractor blades22-26to pivot and separate.

FIG. 9is a perspective view of the access device assembly10, where the screw tube60has been threaded into the retractor blades22-26. The distance that the core hollow screw60is inserted into the retractor blades22-26would depend on the surgical procedure being performed and the pathology being treated. Once the core hollow screw60is threaded into the retractor blades22-26to the proper distance, the handle70is removed from the core hollow screw60, by pulling up on it. The internal bore80of the core hollow screw60is used to gain access to the pathology to perform the surgical procedure.FIG. 10is a top view of the base portion12with the core hollow screw60in place showing the internal bore80through which the surgical procedure is performed. Different size access device assemblies including different diameter and length core hollow screws can be provided for treating different pathologies.

The discussion of the access device assembly10above has particular application for minimally invasive spinal surgery where the retractor blades are threaded through the patient's tissue towards the pathology. In alternate embodiments, the retractor blades22-26can be self-drilling through facia, muscle and soft tissue. Further, the retractor blades22-26may be able to be drilled into bone or cartilage to provide for nail entry portals, cranial access ports, bone compaction to prepare an ACL tunnel, tendon repair tunnel preparation, suture anchor, etc. The bone cutting version could have a cutting flute instead of the external threads on the retractor blades22-26.