Abstract: The invention provides systems, devices, and methods for the delivery, deployment, and positioning of magnetic compression devices at a desired site so as to improve the accuracy of anastomoses creation between tissues, organs, or the like.

Abstract: A delivery system for delivering and deploying an implantable medical device is presented that includes a delivery member having a flexible distal portion. The deliver member can include a proximal hypotube, a flexible coil extending distally from the proximal hypotube, a compressible distal hypotube extending distally from the flexible coil, a sleeve extending along the flexible coil, and a loop wire. The loop wire can be effective to inhibit longitudinal elongation of the flexible coil. The sleeve can be effective to inhibit radial expansion of the flexible coil.

Abstract: An introducer sheath is provided to facilitate placement of two or more catheters in a patient's vasculature. The introducer sheath includes at least one internal partition thereby providing at least two lumens and the at least one internal partition is made of an elastic material. The internal partition may be made of materials such as polyurethane, silicone, or thermoplastic polymer. The internal partition may also have an expandable fold. The wall of the sheath may also have an expandable fold. An exemplary procedure where an introducer sheath of the present invention may be used is percutaneous coronary intervention on chronic total occlusion in a coronary artery. The introducer sheath of the present invention may also be used to deliver an implant mounted on a catheter.

Abstract: Devices, systems, and methods for treating vascular defects are disclosed herein. One aspect of the present technology, for example, is directed toward an occlusive device comprising a coil having a proximal end, a distal end, and a longitudinal axis extending therebetween. The coil may be formed of an elongated member wound about the longitudinal axis of the coil in a series of contiguous loops, wherein each of the loops extend around the longitudinal axis between a first end and a second end. The second end may be disposed at generally the same angular position as the first end about to the longitudinal axis of the coil. The elongated member may undulate along its longitudinal axis between the first and second ends of at least some of the individual loops.

Abstract: Devices, systems, and methods for treating vascular defects are disclosed herein. One aspect of the present technology, for example, is directed toward an occlusive device having a distal end, a proximal end, and a longitudinal axis extending therebetween. The occlusive device may comprise an elongated member wound about the longitudinal axis to form a series of loops, wherein along at least some of the loops, the elongated member includes a first peak and a second peak axially offset from the first peak, the first peak being axially between the second peak and the proximal end. The first peak may be convex towards the distal end, and the second peak may be convex towards the proximal end.

Abstract: An embodiment provides a method for normalizing cardiac venous return, including: inserting percutaneously a calibrated balloon catheter through a femoral vein; advancing the calibrated balloon catheter to the inferior vena cava; and placing a balloon portion of the calibrated balloon catheter at a location before the drainage point of the hepatic vein. Other aspects are described and claimed.

Abstract: A hemostatic device is provided to stop bleeding at a puncture site on the wrist of a patient, the device comprising a transparent flexible band to be wrapped at the site where the bleeding is to be stopped, a curved frame having an inner peripheral side and possessing a first curved portion in its first half and a second curved portion in its second half, a first balloon provided on the inner peripheral side in the first half of the curved frame and a second balloon provided on the inner peripheral side in the second half of the curved frame. The bleeding from a first artery is stopped by compressing the first artery at the puncture site using inflation of the first balloon and the blood flow in the first artery is increased by compression of a second artery using inflation of the second balloon.

Abstract: A sheathed blade assembly for minimizing or preventing contact between the moving interior blade and the exterior sheath. The assembly includes an exterior sheath having a first portion and second portion with an inner lumen therebetween, an interior blade movable within the inner lumen of the exterior sheath, a first pocket within a first surface of the interior blade, and a first ball bearing within the first pocket. The first ball bearing creates a clearance amount between the first surface of the interior blade and the first portion of the exterior sheath. The assembly may also include a second pocket within a second surface of the interior blade for a second ball bearing. The second ball bearing creates a clearance amount between the second surface of the interior blade and the second portion of the exterior sheath. The second pocket is in a staggered configuration relative to the first pocket.

Abstract: This disclosure relates to reaming assemblies and methods for repairing bone defects. The reaming assemblies disclosed herein may be utilized for removing bone prior to positioning a graft and/or implant at a surgical site.

Abstract: A rotatable surgical instrument and method includes an outer tubular member and an inner tubular member contained, at least in part, within the outer tubular member and configured to rotate relative to the outer tubular member, the inner tubular member and outer tubular member forming a gap therebetween. A distal tip is coupled to and configured to rotate with the inner tubular member. Bearings, each positioned in the gap and encircling the inner tubular member, are configured to maintain a separation between the outer tubular member and the inner tubular member. A spacer is positioned within the gap and between two of the bearings, wherein the spacer is configured to maintain a spacing between the bearings.

Abstract: A rotatable surgical instrument, system, and method includes an outer tubular member and an inner tubular member contained, at least in part, within the outer tubular member and configured to rotate relative to the outer tubular member. A distal tip is coupled to and configured to rotate with the inner tubular member, the distal tip forming a channel around a portion of the distal tip. A bearing is rotatably positioned within the channel, wherein the channel inhibits radial and axial movement of the bearing, with respect to the distal tip, along a major axis of the outer tubular member and inner tubular member, and wherein the bearing is configured to inhibit deflection of the distal tip from the major axis.

Abstract: A guided punch is disclosed. The guided punch generally comprises a strike cap comprising a strike surface, a punch comprising a distal cutting edge, and a guide rod. The strike cap defines a first cavity therein. The punch defines a second cavity therein in communication with the first cavity. The guide rod is located within the first and second cavities and extends a predetermined distance beyond the distal cutting edge of the punch. The strike cap and the punch are moveable relative to the guide rod.

Abstract: The present disclosure in one aspect provides an adjustable depth drill guide comprising a trigger assembly further comprising a trigger and a primary actuating element and a telescopic rotational assembly which abuts the primary actuating element and further comprises an intermediate actuating element. The drill guide described herein allows a surgeon to adjust the depth of the drill guide using only one hand while in-situ.

Abstract: A surgical tool for use with a drill bit to prevent skiving at an implant insertion site on a bone includes a cannulated sleeve having a distal end defining a burr surface. The distal end may be detachable from a body of the cannulated sleeve. The tool may be used with more than one distal end, each of the distal ends defining a burr surface having a different cutting surface from the others. The tool may form a system that includes the drill bit.

Abstract: This invention relates to a positioning template used to determine correct cutting planes and angles and drilling positions during surgical procedures, and more particularly, but not exclusively, to a femoral cutting template (10) used in the preparation of a femoral condyle during a unicondylar knee arthroplasty (UKA). The femoral cutting template (10) comprises attachment means (12) for releasably attaching the template to a tibiofemoral spacer shim (50), provided between a proximal tibia and a femoral condyle. The template further comprises a main body (14) defining first and second guide apertures (16,18) for guiding first and second tools respectively. The first and second tools are used for creating first and second receiving formations (206,208), in the femoral condyle, which are created for receiving first and second parts of a femoral component forming part of an unicondylar knee prosthesis.

Abstract: A tissue specimen retrieval device includes a first shaft and a second shaft telescopically movable relative to the first shaft. The second shaft supports an end effector assembly at a distal end thereof. The end effector assembly includes a tissue specimen bag supported by a first bag arm and a second bag arm. The first and second bag arms open the tissue specimen bag when the second shaft is in the deployed position. An insertion cap extends outwardly from the tissue specimen bag. The insertion cap retains the first and second bag arms at distal ends thereof. The insertion cap includes a release mechanism. The release mechanism releases the first and second bag arms from the insertion cap upon retraction of the second shaft from the deployed position.

Abstract: Various embodiments of the systems, methods and devices are provided comprising angioplasty to break up calcification or other tissue in occlusive areas within a blood vessel. The various embodiments disclosed comprise pressure pulse periods designed to break up calcified occlusive material through a cyclically stretching of the vessel walls without damaging the vessel wall tissue.

Abstract: A device having a hub assembly and a lever coupled with the hub assembly is provided. The device includes a sheath coupled with the lever and extending from the hub assembly. The sheath has a surgical elevator with a surgical elevator edge along with a hypotube having an access hole. The device has a shaver blade assembly with an outer shaft having an outer blade and an inner blade within the outer blade. The outer shaft has a stop and an access hole near the outer and inner blades. The sheath partially surrounds the outer shaft and the lever moves between a first position and a second position. In the first position, the surgical elevator edge abuts the outer shaft stop and the outer shaft access hole aligns with the hypotube access hole. In the second position, the surgical elevator edge is spaced apart from the outer shaft stop.

Abstract: A skin grafting system having a handheld device, a cartridge, and a device shield. The handheld device includes a device housing forming an interior that secures a drive system. The cartridge includes a plurality of hollow microneedles surrounded by a peripheral housing and is configured to be operated by the drive system to extend and retract past the peripheral housing into a subject to harvest tissue during a skin grafting process. The device shield is formed of a polymer extending from an interior opening to an exterior edge, the interior opening sized to extend about the peripheral housing to positon the exterior edge over the device housing to control ingress of fluids into the interior of the device housing from fluid about the peripheral housing of the cartridge during the skin grafting process performed using the skin grafting system.

Abstract: Systems, instruments, and methods for minimally invasive procedures including one or more of fractional resection, fractional lipectomy, fractional skin grafting, fractional scar revision, and/or fractional tattoo removal are described. Embodiments include instrumentation comprising a scalpet assembly coupled to a carrier, and the scalpet assembly includes a scalpet array. The scalpet array includes one or more scalpets configured for fractional resection, fractional lipectomy, fractional skin grafting, fractional scar revision, and/or fractional tattoo removal. The system includes a vacuum component coupled to the scalpet assembly and configured to evacuate tissue from the a site. The carrier is configured to control application of a rotational force and/or a vacuum force to the scalpet assembly.

Abstract: A tissue removal device, and methods of using the same, are described. An exemplary detachable, handheld tissue removal device comprises a hand piece and a blade assembly removably attachable to the hand piece. The blade assembly includes a rotatable resection member driven to rotate and surgically remove tissue from a target tissue site, and a coupling assembly including a locking member to detachably couple the blade assembly to the hand piece and operatively enable or disable the rotation of the blade assembly relative to the hand piece. The rotation of the blade assembly causes a change in rotating angle of the blade assembly. The coupling assembly can secure the rotating angle of the blade assembly during the tissue resection procedure.

Abstract: A reciprocating drive system for a surgical instrument can include a housing defining a central axis. An inner surface of the housing can define a plurality of helical threads extending along the housing. The reciprocating drive system can include a shaft member defining a motive coupler configured to receive torque from a motive source to rotate the shaft member, and a first follower engaged with, and extending radially outward from, the shaft member, and configured to correspondingly engage the plurality of helical threads, such that rotation of the shaft member translates the shaft member laterally along the central axis.

Abstract: An arthroscopic surgical device including: a body with a proximal end, a distal end, and a body longitudinal axis extending between the proximal end and the distal end; the body including: an elongated sheath arranged along a sheath longitudinal axis, the sheath including: a sheath flexible portion; and a lumen running longitudinally through the sheath; an elongated spine arranged along a spine longitudinal axis, the spine connected to the sheath, the spine including a spine joint; wherein the spine is rigid in a direction of elongation of the spine; wherein the sheath longitudinal axis and the spine longitudinal axis are aligned, for at least a portion of a sheath longitudinal length, wherein the flexible portion axially overlaps with the spine joint, bending the spine joint thereby bending the flexible portion.

Abstract: A tissue resecting device includes an end effector assembly including a proximal hub housing and a cutting member extending distally from the proximal hub housing, and a handpiece assembly. The handpiece assembly includes a handle housing, a drive casing extending distally from the handle housing, a drive rotor extending through and distally from the drive casing, and a seal ring disposed about the drive rotor. In an at-rest position, the seal ring is sealingly engaged between the drive casing and the drive rotor to inhibit fluid ingress into the annular space. Upon engagement of the end effector assembly with the handpiece assembly, a portion of the proximal hub housing is configured to urge the seal ring from the at-rest position to a displaced position wherein the seal ring is displaced from the drive rotor to reduce friction therebetween upon rotation of the drive rotor relative to the drive casing.

Abstract: Various example embodiments described herein are directed to articulating surgical instruments for treating tissue comprising an end effector and a shaft extending proximally from the end effector along a longitudinal axis. In certain embodiments, the shaft comprises a plurality of transverse spacer members as well as first and second rotatable members extending through at least a portion of the plurality of transverse spacer members. The first and second rotatable members may both be biased away from the longitudinal axis such that their respective directions of bias vary with rotation of the first rotatable member. When the respective directions of bias of the first and second rotatable members oppose one another, the shaft may be substantially straight. When the respective directions of bias of the first and second rotatable members are aligned with one another, the shaft may articulate away from the longitudinal axis in the direction of the alignment.

Abstract: Disclosed is a method of controlling a modular battery powered handheld surgical instrument. The surgical instrument including a battery, a user input sensor, a controller, a radio frequency (RF) drive circuit, an ultrasonic transducer, ultrasonic transducer drive circuit, and an end effector. The end effector including an electrode electrically coupled to RF drive circuit, an ultrasonic blade acoustically coupled to the ultrasonic transducer, and a sensor to measure tissue parameters. The method includes applying an RF current drive signal to the electrode by the RF drive circuit; applying an ultrasonic drive signal to the ultrasonic transducer by the ultrasonic transducer drive circuit to acoustically excite the ultrasonic blade; controlling intensity, wave shape, and/or frequency of the RF current drive signal and the ultrasonic drive signal on a sensed measure of a tissue or user parameter.

Abstract: A medical device is disclosed for cutting substances inside a body lumen. The medical device includes: a rotatable tubular drive shaft; a treatment member arranged on a distal side of the drive shaft; a device handle configured to locate the drive shaft; a guide cover located in the device handle and disposed to cover the drive shaft; an outer sheath disposed to cover the guide cover and located in a housing of the device handle; a first sealing member located proximal to a proximal end of the outer sheath and proximal to a fluid connection, the fluid connection configured to supply a saline solution into the outer sheath on the guide cover; and a drainage tube located proximal to the outer sheath and the first sealing member, the drainage tube being located in the housing of the device handle, and the drainage tube is fixed with respect to the housing.

Abstract: Disclosed herein is a rotary embolectomy device. The device includes a rotatable bit which contacts a blood clot within a cannula, thereby disintegrating the clot. The clot can be removed by means of suction, complete disintegration, or a collecting basket.

Abstract: Devices for removing implanted objects from body vessels are provided. A device includes a sheath assembly having a cutting tip. The cutting tip includes a cutting surface that is adapted to cut tissue coupled to an implanted object as the cutting tip rotates. The sheath assembly further includes an outer shield carried outside of the cutting tip. The outer shield includes a distal opening, and the outer shield is translatable relative to the cutting tip from a first position to a second position and vice versa. In the first position the cutting surface of the cutting tip is disposed within the outer shield, and in the second position the cutting tip extends through the distal opening and the cutting surface is at least partially disposed outside of the outer shield.

Abstract: A seal assembly for use with an access apparatus includes an integral filter and evacuation port for filtering of fluids, e.g., smoke, from an operating site and removing contaminants and/or odor from the fluids for release of the filtered fluids into the ambient atmosphere. The seal assembly may be a separate subassembly or component which is releasably couplable to the access apparatus or may be integral with the access apparatus. The seal assembly defines its own flow path independent of the insufflation mechanism of the cannula assembly, and is capable of filtering fluids even in the presence of a surgical object positioned within the cannula assembly.

Abstract: A uterine manipulator can include a shaft including a first end, a second end, and a channel along an axis of the shaft, a handle coupled to the first end of the shaft, and a triangular balloon coupled to the second end of the shaft. The triangular balloon can be configured to inflate upon insertion into a vagina via a fluid injected into the channel of the shaft.

Abstract: A bone fixation clamp includes a first clamp assembly, a second clamp assembly, an inner locking member, and an outer locking assembly. The first and second clamp assemblies are transitionable between open and closed configurations. The inner locking member is transitionable between a locked position and an unlocked position. In the locked position the inner locking member engages the first clamp assembly substantially preventing the first clamp assembly from transitioning from the closed configuration to the open configuration. The outer locking assembly is transitionable between a locked position and an unlocked position. In the locked position the outer locking assembly engages the first clamp assembly and the second clamp assembly substantially preventing both the first clamp assembly from transitioning from the closed configuration to the open configuration and the second clamp assembly from transitioning from the closed configuration to the open configuration.

Abstract: A method for percutaneous fixation of a humeral head fracture and a related external fixation device, the method comprising the steps of: inserting two oblique wires through the cortical bone of the humerus shaft, said oblique wires being substantially oblique with respect to the humeral axis and crossing the surgical neck toward the humeral head; inserting two proximal transverse wires through the cortical bone of the humerus, said proximal transverse wires being substantially perpendicular with respect to the humeral axis and being inserted into the humeral head; inserting two distal transverse wires through the cortical bone of the humerus, said distal transverse wires being substantially perpendicular with respect to the humeral axis and being inserted into the humeral shaft; connecting the oblique wires, the proximal transverse wires and the distal transverse wires to a common external fixator frame.

Abstract: Kits and systems are disclosed that include one or more segments of elastically deformable membrane in combination with one or more external fixation members and optionally in combination with one or more tension protector pads. Also disclosed are methods of use of the kits and systems in methods that involve stretching the elastically deformable membrane and applying the stretched membrane to the skin of a patient, and releasing the tension on the membrane, thus causing compression of the skin to which the membrane is applied. The method may further include the optional steps of inserting one or more external fixation members through the membrane/skin combination and into a bone segment, applying a distraction force to the one or more external fixation members, and separating at least a portion of the membrane so as to release a portion of the tension in the skin at a rate that is similar to a rate at which the distraction force is applied.

Abstract: An external adjustment device includes at least one permanent magnet configured for rotation about an axis with a first handle extending linearly at a first end of the device and a second handle at a second end of the device, the second handle extending in a direction substantially off axis to the first handle. The external adjustment device further includes a motor mounted inside the first handle and a first button located in the proximity to one of the first handle or the second handle, the first button configured to be operated by the thumb of a hand that grips the one of the first handle or second handle. The first button is configured to actuate the motor causing the at least one permanent magnet to rotate about the axis in a first direction.

Abstract: Bone anchor assemblies are disclosed herein that can provide for improved fixation as compared with traditional bone anchor assemblies. An exemplary assembly can include a bracket or wing that extends down from the receiver member. The distal portion of the wing can define a bone anchor opening through which one or more auxiliary bone anchors can be disposed to augment the fixation of the assembly's primary bone anchor. A distal surface of the distal portion of the wing can be obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction. A distal surface of the distal portion of the wing can be obliquely angled relative to the proximal-distal axis of the spanning portion to face one of a medial direction or a lateral direction. Surgical methods using the bone anchor assemblies described herein are also disclosed.

Abstract: The present disclosure includes a polyaxial bone fixation element for use in spinal fixation to interconnect a longitudinal spinal rod with a patient's vertebra. The polyaxial bone fixation element preferably includes a bone anchor, a collet, a body, and a locking cap. The polyaxial bone fixation element preferably enables in-situ assembly. That is, the polyaxial bone fixation element is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body. Accordingly, the polyaxial bone fixation element enables a surgeon to implant the bone anchor without the body to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the body can be snapped-onto the bone anchor. The bone anchor preferably also includes a second tool interface so that a surgical instrument can be directly coupled to the bone anchor.

Abstract: A bone hook apparatus is provided that includes a base, a rod receptacle disposed on a proximal side of the base, a first hook distally extending from the base and oriented in a first direction, and a second hook distally extending from the base and oriented in a second direction opposing the first direction, the first hook and second hook together configured to receive the bone.

Abstract: Interspinous process implants are disclosed. Also disclosed are systems and kits including such implants, methods of inserting such implants, and methods of alleviating pain or discomfort associated with the spinal column.

Abstract: This disclosure describes example embodiments of rod reduction instrumentation and other rod and vertebrae manipulation instruments. The rod reducers can be used during the installation of a rod based surgical fixation system to help urge the rod into the fixation anchors. The reducers described provide various configurations delivering large reduction distance capabilities, strong controlled reduction coupled with an ability to quickly advance the reducer if desired, and reduction of bulk through the surgical corridor.

Abstract: An interfragmentary guide and plate system is described.

Abstract: The invention relates to an implant (1) for osteosynthesis, comprising a securing region (3) that has a plurality of holes (2) for receiving securing means, and two projections (4) which extend away, at least partially curved, from said securing region (3), wherein at least one one of the two projections (4) takes the form of a snap-on lug (5) that can snap onto a bone segment (7, 8) of a mammal bone (6); the invention also relates to an implant kit comprising such an implant (1).

Abstract: A surgical guide used in computer-aided orthognathic or similar bone surgery, the guide being structured to properly locate the osteotomy marking members and implant fixation screw-receiving holes on the bone surfaces of the patient, and/or the cutting of the osteotomy or the drilling of implant fixation screw-receiving holes. The guide has a bone-conforming member and a dental-interface member connected by a bridging member, the inner surfaces of the bone-conforming member and the dental interface member conforming to the topographical surfaces of the patient's bone and teeth. The dental-interface member abuts the front and sides of the teeth. A similarly designed fixation implant may also be provided.

Abstract: A bone repair device includes a plate having a pathway and a flexible structure. The plate includes opposing top and bottom surfaces and a first side extending between the top and the bottom surfaces. The flexible structure is directly attached to and extends from the first side of the plate. In operation, the bone repair device is placed around and over a plurality of bone parts. The plate is secured to the plurality of bone parts with a cable inserted through the pathway and wrapped around the bone parts.

Abstract: Tether tensioning instruments, such as instruments used to tension and/or lock a tether about a spinal feature to assist in spinal fixation, and related methods and systems. In some embodiments, the instrument may comprise a handle, a tensioner base coupled with the handle, at least a portion thereof being movably coupled to the handle, and a tether coupling member coupled with the tensioner base and configured to fixedly engage a tether. The instrument may further comprise a tensioner tip movably coupled with the tensioner base, wherein at least a portion of the tensioner base is biased away from the tensioner tip, and wherein the instrument is configured to allow for step-wise movement of the tensioner tip away from the tensioner base to increase tension between the tether and an element of the spinal fixation system.

Abstract: Implant delivery systems for delivering sheet-like implants include a delivery shaft, an implant expander, a sheath, and a sheet-like implant. In some embodiments, the delivery shaft has a proximal end and a distal end. The implant expander is mounted to the distal end of the delivery shaft. The implant expander includes a central portion and a plurality of leg portions radiating from the central portion. The implant expander is evertable between an unstressed configuration in which a distal surface of the implant expander defines a concave surface, and a first compact configuration in which the distal surface of the implant expander defines a convex surface. The implant expander has a first lateral extent when the implant expander is free to assume the unstressed configuration. The sheath defines a lumen having a lumen diameter. At least a portion of the delivery shaft is slidably disposed in the lumen.

Abstract: The present application discloses devices that ablate human tissue. The device comprises a catheter with a shaft through which an ablative agent can travel, a liquid reservoir and a heating component, which may comprise a length of coiled tubing contained within a heating element, wherein activation of said heating element causes said coiled tubing to increase from a first temperature to a second temperature and wherein the increase causes a conversion of liquid within the coiled tubing to vapor, a reusable cord connecting the outlet of the reservoir to the inlet of the heating component, and a single use cord connecting a pressure-resistant inlet port of a vapor based ablation device to the outlet of the heating component.

Abstract: Ablation devices, more specifically needle injectors configured to deliver flowable thermal treatment media into an interface with tissue and that can provide a single dose of ablative energy.

Abstract: An energy application apparatus applies energy to an object. An energy application unit applies energy to the object, wherein the energy application unit is adapted to use electrical current for applying the energy. A current measuring unit measures the electrical current used by the energy application unit and provides a signal being indicative of whether the energy is applied to the object based on the measured electrical current. The signal can be used by, for instance, a monitoring unit and/or a display unit for using and/or indicating the information whether energy is actually applied or not, without requiring a direct communication between the energy application unit and the monitoring unit and/or the display unit.

Abstract: The electrosurgical systems and corresponding methods of the present disclosure involve an electrosurgical generator, sensing circuitry, and a controller. The electrosurgical generator includes a radio frequency (RF) output stage that supplies power to tissue. The sensing circuitry measures impedance of tissue. The controller controls the power supplied from the RF output stage to track a nonlinear power curve until the power supplied from the RF output stage has reached a predetermined peak power of the nonlinear power curve. The controller further determines whether a tissue reaction has occurred based on impedance measured by the sensing circuitry and controls the power supplied from the RF output stage during a cooling phase if the controller determines that a tissue reaction has occurred. The controller may further control the power supplied from the RF output stage to track a linear power curve.