Noninvasively adjustable suture anchors

In one embodiment, an adjustable implant system includes a bone anchor having first and second ends, a bone engagement surface adjacent the first end, and a housing extending between the first and second ends. The adjustable implant system can further include a non-invasively actuatable driving element within the housing and coupled to an adjustment component configured to couple to a flexible elongate tension member which is capable of engaging a patient's soft tissue (e.g., rotator cuff or ACL). Non-invasive actuation of the driving element can cause the adjustment component to change the amount of tension on the flexible elongate tension member and consequently on the patient's soft tissue. The adjustable implant system can include an external adjustment device configured to be placed on or adjacent the patient's skin and comprising at least one energy transferring component configured to energize/actuate the driving element inside the housing of the adjustable implant.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention generally relates to medical devices for attaching soft tissue to bone.

2. Description of the Related Art

In many common surgical techniques, soft tissue (muscle, tendon, ligament) is secured to the bone using a variety of types of tissue anchors. In most of these surgeries, it is important that that the connection between the soft tissue and the bone remain consistent, without significant degradation after surgery and recovery, both short term and long term. One common method of securing soft tissue to bone is with a suture anchor, which is sutured or otherwise attached to the particular portion of soft tissue and then anchored to the bone. The anchoring to the bone may be achieved by a threaded screw, or several other types of securement.

One of the common complications of many of these surgical techniques is for the connection between the soft tissue and the bone to degrade. For example, the healing of the tissue may cause the tensile force at which the soft tissue is secured to the bone to increase or decrease. Also, the length of the connection may increase or decrease, creating such effects as too much joint motion, too little joint motion, hyperextension, and of course fatigue and pain. Laxity of a suture is a common occurrence, and can increase the variance in the final tension in the connection of the soft tissue to the bone.

Rotator cuff injury is one of the most common ailments of the shoulder. The rotator cuff is a group of muscles and tendons that stabilize the shoulder joint. Many of the injuries to the rotator cuff are able to be treated without surgery, for example, certain cases of tendonitis and other traumatic injuries. Often, the injury to the rotator cuff involves the tearing of the tendons that attach one or more of the rotator cuff muscles to the humerus (upper arm) bone. Active patients who have substantial or complete tears of one of more portions of the rotator cuff are often treated by rotator cuff surgery. Rotator cuff tears are sometimes classified as small (<1 cm), medium (1 cm to 3 cm), large (3 cm to 5 cm), and massive (>5 cm). They are also characterized by shape, such as transverse, L-shaped, linear, crescent, and triangular. Rotator cuff surgery may be performed as an open surgery, a mini-open surgery (wherein the deltoid muscle need not be detached during surgery), or an arthroscopic surgery. Many different suture techniques are used, each attempting to improve upon strength, stability, safety and procedural speed and invasiveness. In certain groups of patients, postoperative stiffness develops. This may happen in more than 8% of patient under the age of 50, and in more than 15% of patients who also have either calcific tendonitis or adhesive capsulitis. Many patients with postoperative stiffness choose to undergo subsequent arthrosopic procedures to remove or remodel scar tissue. Re-tears are also somewhat common after the recovery following the initial rotator cuff surgery, with reported rates between 4% to 26%.

Anterior cruciate ligament (ACL) injury is common in athletes in a variety of sports, especially in contact sports, with the ACL. ACL reconstruction surgery is often performed after tear or rupture of the ACL, and usually includes the removal of the damaged ligament and replacement with a graft. The graft may be an autograft (a portion of the patient's own patellar tendon or hamstring) or an allograft (cadaveric patellar tendon, anterior tibialis tendon, or Achilles tendon). This surgery is commonly performed arthroscopically, with the graft inserted into tunnels created in the tibia and femur, and then secured to these bones with tissue anchors. Post-recovery, some ACL reconstruction patients have persistent loss in range of motion, in either flexion or extension, which may be due to imprecise placement of the graft during the initial surgery or the healing process itself. A classification system has been proposed that includes four different grades: Type 1: less than a 10° loss of extension with normal flexion, Type 2: more than a 10° loss of extension with normal flexion, Type 3: more than a 10° loss of extension with a flexion deficit of greater than 25°, and Type 4: more than a 20° loss of extension with a flexion deficit greater than 30°. Some of these patients are able to improve through rehabilitation, but others require an additional surgical procedure.

Despite the wide variety of available devices for anchoring soft tissue (e.g. tendon) to bone, there remains a need for an implant which can be adjusted post-operatively to increase or decrease tension without the need for additional surgical intervention.

SUMMARY OF THE INVENTION

In a first embodiment of the invention, an adjustable implant system includes a bone anchor having a first end and a second end, and including a bone engagement surface adjacent the first end, the bone anchor further comprising a housing extending between the first end and the second end. The adjustable implant system further includes a driving element carried within the housing and configured for non-invasive actuation, wherein the driving element is coupled to an adjustment component, the adjustment component configured for coupling to a flexible elongate tension member capable of engaging soft tissue of a patient, wherein non-invasive actuation of the driving element causes the adjustment component to change the amount of tension on the flexible elongate tension member. The adjustable implant system further includes an external adjustment device comprising at least one energy transferring component and configured to be placed on or adjacent the skin of the patient, and wherein the at least one energy transferring component of the external adjustment device is configured to energize the driving element inside the housing of the adjustable implant.

In another embodiment of the invention, a method of treating a patient includes the steps of providing a tensioning device having a connector for connection to soft tissue, and a drive for drawing the connector in the direction of the tensioning device, inserting the tensioning device into a bone, and connecting the connector to soft tissue, wherein the tensioning device is configured to draw the connector in the direction of the tensioning device in response to a wireless signal.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1illustrates an anatomical view of a human shoulder10, which includes the following bones: scapula28, clavicle26and humerus18The glenohumeral joint42(or shoulder joint) is an articulation between the scapula28and the head20of the humerus18, the head20visible in a cross-sectional view inFIG. 2. The acromion32is a bony process on the scapula28which articulates with the clavicle26at the acromioclavicular joint30. There is very little interface between the humerus18and the scapula28in the glenohumeral joint42making it the most mobile joint in the human body. The rotator cuff46is a group of muscles and their respective tendons which serve to stabilize the shoulder10, including the supraspinatus36, infraspinatus (not visible inFIG. 1), subscapularis38, and teres minor40. All four of these muscles arise from different portions of the scapula28and attach via their respective tendons to either the greater tubercle12of the humerus18, which is lateral to the humeral head20or the lesser tubercle (not shown). Also shown inFIG. 1is the bursa34, a fluid-filled sac which cushions the bones, muscles and tendons of the glenohumeral joint42. Additionally, the biceps muscle44is show for perspective purposes.

A simplified cross-sectional view of the shoulder10is shown inFIG. 2, with an embodiment of an adjustable suture anchor100implanted within the shoulder10. The adjustable suture anchor100has a first end102and a second end104, the second end104configured for insertion through cancellous bone24and the first end102configured for securing in the cortical bone22of the humerus18. InFIG. 3detail of the second end104shows a tapered thread106and a tapered tip108, which can aid in driving the adjustable suture anchor100through the humerus18. Alternatively, an initial hole may be reamed in the cortical bone22and cancellous bone24to aid in the insertion of the adjustable suture anchor100. A housing110extends between the first end102and second end104of the adjustable suture anchor100. At the first end102, a threaded portion112is provided which allows a secure interface with the cortical bone22. The threaded portion112may be of a single major diameter (for example with a minor diameter that increases towards the first end), or the major diameter may vary from smaller to larger as it approaches the first end102. The threaded portion112may be provided with cutting threads, in order to better create the interface with the cortical bone22. A keyed cavity114is provided in the first end102for interfacing with a driving tool. The shapes of both the driving tool and the keyed cavity114may be hexagonal, cross-shaped, star-shaped or a number of other keyed shapes that allow a maximal torque in securing the adjustable suture anchor100into the humerus18.

A simplified rotator cuff46is represented inFIG. 2by a muscle14and its tendon16, in cross-section. In this embodiment of the adjustable suture anchor100, a suture116is secured to the tendon16through at least one puncture118. The suture116is held in place with one or more knots120, which may comprise a number of different knot types. Any of the possible suturing techniques are envisioned, including: single-row technique, double-row techniques, diamond, mattress double anchor, or modified mattress double anchor.

The adjustable suture anchor100contains within its housing110an adjustable component122having an eyelet124. The eyelet124is configured for securing an end of the suture116. As shown inFIG. 4, the adjustable suture anchor100is supplied with a threading tool126, which can be used to aid the placement of the suture116through the eyelet124of the adjustable component122. The suture116is looped through or tied to a hook128in the threading tool126, and then the threading tool126is pulled from gripping structure130at the opposite end of the threading tool126from the hook128. The suture116is pulled through the eyelet124of the adjustable component122and tied or otherwise secured in place. The suture116is tied with the desired amount of tension.

The adjustable component122of the adjustable suture anchor100further includes a shaft132and a base134at the opposite end of the shaft132from the eyelet124. The adjustable component122is configured to be axially movable within a longitudinal cavity136of the housing110. Fins138are slidable within longitudinal grooves140in the longitudinal cavity136of the housing110, thus inhibiting the rotation of the adjustable component122in relation to the housing110. The hollow magnet142is radially poled, and is bonded within a threaded magnet housing144. The threaded magnet housing144threadingly engages an internal thread146of the housing110. A thrust bearing148is disposed between the base134of the adjustable component122and a first end150of the threaded magnet housing144. If it is desired during or particularly after surgery to tighten the tension on the suture116, a moving magnetic field is applied externally to the patient in a first rotational direction A, causing the hollow magnet142and threaded magnet housing144to spin in a second rotational direction B. Because it is secured to the hollow magnet142, the threaded magnet housing144therefore turns within the internal thread146of the housing110, actuating it in a first axial direction C. As the first end150of the threaded magnet housing144pushes against the thrust bearing148and the base134of the adjustable component122, the adjustable component122is moved in the first axial direction C. This shortens the effective length of the suture116, and thus increases its tensile force, which is the force it applies to the tendon16. This ability to adjust the tension on the suture16non-invasively on an awake, mobile patient, make it possible to assure the ideal state of the shoulder10during the healing process. To isolate the longitudinal cavity136of the housing (and its contents) from body fluids, a seal152is carried near the first end102of the adjustable suture anchor100. The suture116is able to move within this seal152(o-ring or slit diaphragm) without causing any significant material to enter the longitudinal cavity136. If the tension on the suture116is higher than desired, a moving magnetic field is applied externally to the patient in a rotational direction D (opposite A), causing the hollow magnet142and threaded magnet housing144to spin in a rotational direction E (opposite B). This moves the adjustable component in an axial direction F (opposite C). The tension on the suture116is thus lowered.

Turning now toFIG. 5, a different embodiment of an adjustable suture anchor200is depicted in its implanted configuration within the humerus18. The adjustable suture anchor200has a first end202and a second end204. As seen in more detail inFIG. 6, the second end204includes a tapered tip208, to aid in insertion through the cancellous bone24. A pilot hole may be drilled through the cortical bone24and the cancellous bone24, and an additional pocket23may be drilled, into which the tapered tip208may reside, for increased stability. A threaded portion212is provided adjacent the first end202of the adjustable suture anchor200for engaging with the cortical bone24. A keyed outer surface215, having for example a hexagonal shape, is provided for tightening the adjustable suture anchor into humerus18. In this embodiment, suture216extends from a longitudinal cavity236within a housing210of the adjustable suture anchor. The suture216is partially wound on a spool222, which is rotatable within the longitudinal cavity236. The suture216can slide through a seal252, which protects the longitudinal cavity236from body fluids. The first end202of the adjustable suture anchor200includes a radiused surface213, which allows the suture216to be slid over it without fraying. A rotatable cylindrical radially-poled magnet241bonded within a magnet housing243having a pin245. The magnet housing243is constrained axially within the longitudinal cavity236. The pin245turns within a radial bearing247. The magnet housing243connects to a first planetary gear stage249, which connects to a second planetary gear stage251. The second planetary gear stage251is coupled to the spool222by a pin253. After implanting the adjustable suture anchor200into the humerus18, the suture216is pulled partially out of the longitudinal cavity236and secured to a tendon16via a puncture118. The suture is tied in a knot120so that it is at the desired amount of tension.

If at a later time, for example after surgery, the tension on the suture216is higher than desired, a moving magnetic field is applied externally to the patient in a first rotational direction, causing the magnet241to be turned, and thus the first and second planetary gear stages249,251and spool222. Because of the gear reduction from the first and second planetary gear stages249,251, the spool222is turned at a slower rotational speed than the magnet241, allowing precision adjustment of the tension in the suture216. The gearing also allows the desired tension to be achievable without an undesirably large applied moving magnetic field, for example a field that is above International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for current density in body tissues and fluids, for example 0.04 Amperes/m2or less. As the spool222is turned the suture216is pulled into the longitudinal cavity236through the seal252, tightening the tension in the suture216, and thus on the tendon16. A stepped post255is secured to the first end202of the adjustable suture anchor200. A thrust bearing248and the spool222are both carried on a small diameter portion257of the stepped post255. When the suture216is in tension, the spool222is forced against the thrust bearing248, which in turn is forced against the edge of a large diameter portion259of the stepped post255, thus minimizing the rotational resistance of the spool222. The suture216passes through a guide loop261to aid its takeup onto the spool222. In both the adjustable suture anchor100and adjustable suture anchor200, a pulley may be carried by the first end102,202to serve the function of the radiused surface213, both in keeping the suture116,216from fraying, and in changing the direction of the of the suture116,216which is in tension.

A different embodiment of an adjustable suture anchor300is depicted inFIGS. 7 and 8. In this embodiment, a loop of suture316extends from the tendon16in an external portion370and an internal portion372. A tunnel374through which the suture316can slide is made in the tendon16, so that the length of the loop of suture316which extends from point A to point B to point C, can be adjusted, thus adjusting the tension with which the suture316holds the tendon16. A pad376of biocompatible material is placed underneath the suture316to minimize damage to the tendon as the suture316slides over it. A first end302of the adjustable suture anchor300includes a threaded portion312and an external circumferential groove378, around which external portion370of suture316can be wrapped and/or tied. A second end304of the adjustable suture anchor300has a tapered tip308, which may be used as described in the prior embodiments. Within the longitudinal cavity336of the housing310of the adjustable suture anchor300, a cylindrical, radially poled magnet341is bonded within a magnet housing343, which is secured to a rotating shaft380. The magnet housing343and shaft380are rotatably held between a radial bearing347and a thrust bearing348. A spool322is secured to the shaft380so that rotation of magnet341causes rotation of the shaft. A spacer384is disposed between the spool322and the magnet341and secured to the housing310. A seal or diaphragm352is carried within an aperture382in the lateral wall of the housing310, allowing the internal portion372of the loop of suture316to move in and out of the housing310of the adjustable suture anchor300, with the contents of the longitudinal cavity336remaining protected from body fluids.

During implantation, two pilot holes are drilled through which through the cortical bone22and cancellous bone24, a first hole50extending from point C towards point A. The first hole may even be extended to create an additional pocket23. A second hole48extends from point B towards (and just past) point A. A grasper tool is placed through hole48, and a suture insertion tool inserts the end of the external portion370of the suture316through hole50. The grasper tool grasps the suture316and pulls it out through hole48. The adjustable suture anchor is then inserted and secured inside hole50, tightening it with a driving tool inserted into a keyed cavity314. The housing may be oriented so that the aperture382extends in a direction towards hole48. The external portion370of the suture316is now placed through the tunnel374in the tendon16, and then wrapped and/or tied around the external circumferential groove378, thus closing the loop in the suture316. To adjust the tension of the suture316, a moving magnetic field is applied externally to the patient in a first rotational direction, causing the magnet341to turn and the spool322to tighten the tension in the suture316. The moving magnetic field may be applied in an opposite rotational direction in order to loosen the tension in the suture316.

FIGS. 9 and 10illustrate an external adjustment device478configured for applying a moving magnetic field to allow for non-invasive adjustment of the adjustable suture anchor100,200,300by turning the magnet142,241,341within the adjustable suture anchor100,200,300.FIG. 9illustrates the internal components of the external adjustment device478, and for clear reference, shows a simplified version338of the magnet142,241,341of the adjustable suture anchor100,200,300, without the rest of the assembly. The internal working components of the external adjustment device478may, in certain embodiments, be similar to that described in U.S. Patent Application Publication No. 2012/0004494. A motor480with a gear box482outputs to a motor gear484. The motor gear484engages and turns a central (idler) gear486, which has the appropriate number of teeth to turn first and second magnet gears488,490at identical rotational speeds. First and second magnets492,494turn in unison with the first and second magnet gears488,490, respectively. Each magnet492,494is held within a respective magnet cup496(shown partially). An exemplary rotational speed is 60 RPM or less. This speed range may be desired in order to limit the amount of current density induced in the body tissue and fluids, to meet international guidelines or standards. As seen inFIG. 9, the south pole498of the first magnet492is oriented the same as the north pole404of the second magnet494, and likewise, the first magnet492has its north pole400oriented the same as the south pole402of the second magnet494. As these two magnets492,494turn synchronously together, they apply a complementary and additive moving magnetic field to the radially-poled, magnet338, having a north pole406and a south pole408. Magnets having multiple north poles (for example, two) and multiple south poles (for example, two) are also contemplated in each of the devices. As the two magnets492,494turn in a first rotational direction410(e.g., counter-clockwise), the magnetic coupling causes the magnet338to turn in a second, opposite rotational direction412(e.g., clockwise). The rotational direction of the motor480is controlled by buttons414,416. One or more circuit boards418contain control circuitry for both sensing rotation of the magnets492,494and controlling the rotation of the magnets492,494.

FIG. 10shows the external adjustment device478for use with an adjustable suture anchor100,200,300placed in the humerus. The external adjustment device478has a first handle424attached to a housing444for carrying or for steadying the external adjustment device478, for example, steadying it against a shoulder10, as inFIG. 10, or against a knee, in the case of an adjustable anchor for anterior cruciate ligament attachment. The external adjustment device478includes a control panel including a display (not shown). Control circuitry contained on circuit boards418may be used by the surgeon to store important information related to the specific aspects of each particular patient. The external adjustment device478may be able to receive and transfer information via an SD card or USB device, or by wireless input. An additional feature is a camera at the portion of the external adjustment device478that is placed over the skin. For example, the camera may be located between the first magnet492and the second magnet494. The skin directly over the implanted magnet338may be marked with indelible ink. A live image from the camera is then displayed on the display448of the control panel446, allowing the user to place the first and second magnets492,494directly over the area marked on the skin. Crosshairs can be overlayed on the display over the live image, allowing the user to align the mark on the skin between the crosshairs, and thus optimally place the external adjustment device478.

FIG. 11illustrates an alternative geometry for creating a hole62at the greater tubercule12of the humerus18. An adjustable suture anchor500having an adjustable component522is implanted in the hole62and is capable of adjusting the tension in a suture516, which is attached to a tendon16of a rotator cuff46. The hole62is parallel the axis of the humerus18, and thus allows for a longer length adjustable suture anchor500. This makes possible an adjustable suture anchor500with more planetary gear sets and allow allows for a greater range of adjustability (length, tension).

Though the adjustable suture anchors100,200,300,500as described are adapted for attaching the tendon of the rotator cuff to the humerus, it is conceived that similar suture anchors would be useful for adjusting other soft tissue attachments to bone. Some examples include the anterior cruciate ligament (ACL) in one or both of its attachment point to the bone (femur and/or tibia).FIG. 12shows a configuration for an adjustable suture anchor600for adjusting the tension in a graft690for replacing the ACL (for example a portion of the patellar tendon). The graft690is secured in a femoral tunnel686in a femur678with a traditional tissue anchor684. The tissue anchor684may be metallic, or may be of a resorbable material. The adjustable suture anchor600is anchored to bone inside a tibial tunnel688created in a tibia680. An adjustable component682within the adjustable suture anchor600adjusts the tension in a suture616which is attached to the graft690. The diameter of the tissue anchor684may be less than about 14 mm, or preferably less than about 12 mm. The length of the femoral tunnel686may be on the order of about 25 mm to about 35 mm.

An alternative ligament for which the adjustable suture anchors100,200,300,500,600may be used is the medial collateral ligament (MCL) whose attachment points are the femur678and tibia680. The lateral collateral ligament (LCL), whose attachment points are the femur678and fibula676, may also be adjustably attached by a modified embodiment of the adjustable suture anchor100,200,300,500,600. Other tendons and ligaments which may benefit from the adjustability of the adjustable suture anchors100,200,300,500,600include the talo-fibular ligament, the tibial tendon, and the Achilles tendon. Typical ranges of the length of adjustment for the tendon and ligament applications discussed may be typically on the order of less than about 2 cm, or in some embodiments less than about 1 cm.

Other indications for an adjustable connection between soft tissue and bone which may benefit from embodiments of the adjustable suture anchors100,200,300,500,600include adjustable slings attached to the pubic bone, for urinary stress incontinence.

Magnet materials may include rare earth magnets, including Neodymium-Iron-Boron. Rigid components of the adjustable suture anchor may be made from titanium, titanium allows, or other biocompatible materials. In some cases, polyether ether ketone (PEEK) may be an appropriate material. In some cases, at least some components may comprise bioabsorbable materials.

On any of the embodiments presented, it is envisioned that a unidirectional version may be constructed. For example, a ratcheting wheel that allows stepped increases in in the rotational direction which increases the tension on the suture, but does not allow the opposite rotational direction to occur. In addition, any of the embodiments may or may not use gearing, for example to increase the deliverable for or increase the precision.

In addition to a threaded screw attachment to the bone, the bone anchor may comprise an interference fit, for example a tack, a bone adhesive interface, or a staple. Additionally pronged, flanged, snagging, barbed, spiked, tabbed or curved anchors may be secured to the bone. Often, multiple anchors are attached in the same patient.

Though magnetic actuating adjustable implants are presented, other non-invasive systems are considered to be within the scope of the adjustable suture anchors described. For example, the adjustable component may be driven by any of a variety of alternative drives such as an implanted motor which may be powered via inductive coupling, internal battery, or hard wired connection via leads that extend percutaneously but may be detached from the implant and removed following a post-surgical adjustment. The adjustable component may instead be driven by an ultrasonically actuated motor, such as a piezoelectric motor manufactured by Actuated Medical of Bellefonte, Pa. The adjustable component may also be driven by a subcutaneous hydraulic or pneumatic pump which pressurizes fluid through a valve when pressure is placed on the skin of the patient, over the pump interface. The adjustable component may also be driven by an implantable shape-memory driven actuator.

The adjustable suture anchors100,200,300,500,600may be configured so that the magnets and magnet housings may be removed from the adjustable suture anchor assembly, using a small minimally invasive incision, leaving the remained of the adjustable suture anchor100,200,300,500,600in place. For example, if magnetic resonance imaging is prescribed for the patient, the magnet may be temporarily or permanently removed, to allow imaging of the implant area.