Abstract: An instrument for use in cartilage removal comprises an elongate body having a first end and a longitudinal axis having a longitudinal direction. A cartilage removal portion is coupled to the elongate body at the first end. The cartilage removal portion includes a plurality of serrated blades substantially perpendicular to the longitudinal axis and adapted for removing material while moving in the longitudinal direction. Each serrated blade has a centroid located along the longitudinal axis.

Abstract: A reamer attachment system for attaching a reamer to a robotic arm comprises a reaming guide comprising a guide shaft and a collar attached to the guide shaft, a reamer shaft extending through the collar to articulate against the collar, and a reamer lock couplable to the reamer shaft to engage the collar and prevent axial displacement of the reamer shaft relative to the collar while permitting the reamer shaft to articulate against the collar. A method for collaborative reaming of a bone between a surgical robot and a surgeon comprises positioning a reamer guide at a location in a coordinate system for the surgical robot system using a robotic arm of the surgical robot, coupling a reamer to the reamer guide such that a reamer axis passes through the location, constraining movement of the reamer along the reamer axis, and pivoting the reamer at the location to remove bone.

Abstract: A glenoid component for coupling to a scapula of a subject includes a body. The body includes an articulation surface adapted to articulate with a humeral component, and the body further includes a distal surface adapted to face the glenoid of the scapula. The distal surface includes a base surface portion adapted to face a first portion of the glenoid. The distal surface further includes an augmented surface portion adapted to face a second portion of the glenoid. The base surface portion and the augmented surface portion define an obtuse angle therebetween.

Abstract: A cannulated retrograde reamer configured to be disposed over a guidewire that is adjustable to create tunnels of multiple different diameters. The cannulated retrograde reamer substantially reduces the risk of tunnel malposition and/or misalignment, and can be adjusted to create a range of tunnel diameters, thereby allowing inventory levels to be reduced for a surgical case.

Abstract: A system, method and/or reamer driver device is provided having a domed external surface and a domed internal surface being concentric to the domed external surface thereby defining a hollow dome or section thereof. At least one cutting tooth is disposed on the hollow dome or section thereof. The cross-sectional thickness T measured substantially perpendicular to the crest of the at least one tooth is greater than the radial distance t between the external and internal domed surfaces. The hollow dome or section thereof is made using an injection molding process or a 3D printing process.

Abstract: An acetabular cup removal device and method. The removal device can include a mounting ring attachable to an acetabular cup, a rotor rotatably coupled to the mounting ring and rotatable about a first axis, an arm pivotably coupled to the rotor and pivotable about a second axis orthogonal to the first axis, an oscillator assembly slidably disposed in a first slit of the arm, and a blade slidably disposed in a second slit of the arm. A rotation of the oscillator assembly causes an oscillation of the blade within the second slit. The removal method includes coupling the device to an acetabular cup, positioning the arm and blade at an initial location, oscillating the blade so as to perform a cut, repositioning the arm at a subsequent adjacent location, repeating the repositioning and oscillating steps until a 360° circumference is cut around the acetabular cup, and removing the acetabular cup.

Abstract: Reamer instruments and related methods are disclosed for use in preparing bone, such as a glenoid bone surface, to receive an implant requiring one of two or more possible surface geometries. Described reamer instruments can have a modular or multi-component design. A minimal number of components can be particular to a particular required geometry, which can allow assembly and use of reamer instruments of the present disclosure to be flexible, intuitive, and efficient. In some embodiments, a disposable reamer head assembly can be driven by a disposable drive tip through a pin-on-pin connection. The remaining components of the reamer instrument can be sterilized and re-used. To prepare bone for a half-wedge implant, a half-wedge housing can be coupled to a reamer instrument handle and a depth stop can be coupled to the housing to achieve the required geometry. Alternatively, a full-wedge housing can be coupled to the instrument handle.

Abstract: A system can form a pilot hole to secure a securable element, such as an acetabular cup. A saddle can removably attach to the securable element. The saddle can confine a translator and allow the translator to move along a translator axis between a first translator position and a second translator position. A punch element can be movably coupled to the saddle and the translator such that when the saddle is removably attached to the securable element, moving the translator from the first translator position toward the second translator position can advance a tip of the punch element from the saddle through the securable element along a punch axis that is angled with respect to the translator axis. An impaction stem can be coupled to the translator by a joint, such as a ball-and-socket joint, and can impart motion to the translator.

Abstract: A reamer attachment system for attaching a reamer to a robotic arm comprises a reaming guide comprising a guide shaft and a collar attached to the guide shaft, a reamer shaft extending through the collar to articulate against the collar, and a reamer lock couplable to the reamer shaft to engage the collar and prevent axial displacement of the reamer shaft relative to the collar while permitting the reamer shaft to articulate against the collar. A method for collaborative reaming of a bone between a surgical robot and a surgeon comprises positioning a reamer guide at a location in a coordinate system for the surgical robot system using a robotic arm of the surgical robot, coupling a reamer to the reamer guide such that a reamer axis passes through the location, constraining movement of the reamer along the reamer axis, and pivoting the reamer at the location to remove bone.

Abstract: Methods of implanting a prosthesis to repair a joint include displacing a first bone from the joint formed by an intersection between the first bone and a second bone. An end portion of the first bone is resected to define a resected end. A concavity is formed into the resected end using a shaping tool. The bone is compacted to form a support layer lining the concavity. The prosthesis is implanted in the concavity against the support layer without attaching the prosthesis to the support layer. The joint is reformed with the prosthesis such that the prosthesis remains unattached to the support layer and the first and second bones articulate about the prosthesis.

Abstract: A cannulated retrograde reamer is adjustable to create tunnels of multiple different diameters. The cannulated retrograde reamer has a first tubular shaft and a second tubular shaft disposed about the first tubular shaft. A cutting member is pivotably coupled to the distal end of the first tubular shaft. The distal end of the second tubular shaft is configured to engage and disengage the proximal end of the cutting member by the rotation and axial movement of the second tubular shaft relative to the first tubular shaft to open and close the cutting member. The cannulated retrograde reamer substantially reduces the risk of tunnel malposition and/or misalignment, and can be adjusted to create a range of tunnel diameters, thereby allowing inventory levels to be reduced for a surgical case.

Abstract: The present invention relates to a dental drill (10) formed of titanium or a titanium alloy having a hardness greater than pure titanium, said drill extending along a central axis (A) from a proximal end (14) to a distal end (16). The drill comprises a shank (12) arranged in a proximal end region of the drill (10) and extending along the central axis (A), a flute portion (20) arranged distally to and running coaxially with the shank (12), said flute portion (20) comprising two or more flutes (22a, 22b, 22c) extending along the flute portion (20) and being interposed by lands (24a, 24b, 24c), the flute portion further comprising a central solid web and a drill tip (26) directly adjoining the distal end (28) of the flute portion (20) and comprising two or more flanks (25a, 25b, 25c) which taper radially inwardly from the distal end of each land in the distal direction toward the central axis (A), each flank (25a, 25b, 25c) comprising a cutting edge (30a, 30b, 30c).

Abstract: A system and method for improving installation of a prosthesis. Devices include prosthesis installation tools, prosthesis assembly tools, site preparation systems, and improved power tools used in implant site preparation, the tools including a secondary motion that preferably includes an ultrasonic vibration.

Abstract: Tools for cutting bone, specifically cutting a hemispherical cavity in bone. Preferably, tools including an adaptor device configured to provide independent control of the cutting orientation.

Abstract: A system, method and/or reamer driver device provides a fully closed tube which prevents the invasion of debris and minimizes abrasion of soft tissue during use. The reamer device includes a minimum number of component assemblies, so as to permit easy replacement and minimize wear.

Abstract: Disclosed herein are a system and method for attaching an implant, such as an acetabular cup, to an adapter connector without requiring rotation of the connector or the implant, to allow for easy connection, manipulation, and insertion of the implant into a patient. An adapter connector or adapter inserter can include a collet and a collet spreader. The collet can include an exterior surface and an interior surface. The exterior surface can define a protuberance sized to engage an indentation in an adapter. The interior surface can define a collet cavity. The collet spreader can be located at least partially within the collet cavity. The collet spreader can include a flared surface and an engagement surface. The flared surface can be located at a first end of the collet spreader and arranged to engage the interior surface of the collet so as to cause the collet to expand.

Abstract: An orthopedic instrument in the form of an acetabular cup extractor system for reliably and efficiently extracting an acetabular cup implant from an acetabulum. The system includes a handle assembly, an extractor attachable to a distal end of the handle, and a dome guide assembly having a hemi-spherical dome for engaging the extractor and a centering body extending distally from the hemi-spherical dome for engaging an acetabular implant. The extractor includes a curved, concave guide and a curved blade. The curved, concave guide is sized and shaped to substantially matingly engage with and cover a substantial portion of the hemi-spherical dome. As a result of such an arrangement, a uniform cut is achieved by the curved blade thereby resulting in a minimum of bone being extracted from the acetabulum around the acetabular cup implant during a surgical procedure.

Abstract: A device is provided, including a cutting rib, the cutting rib including an arcuate portion having an outer sharp edge and a centralizer configured to receive the cutting rib through a radial slot, the radial slot forming a gap with the cutting rib. The arcuate portion of the cutting rib is formed into a profile that follows a surface of the centralizer, the outer sharp edge of the arcuate portion of the cutting rib has a wavy profile that forms a tunnel in the gap between the centralizer and the cutting rib, and the outer sharp edge of the arcuate portion of the cutting rib protrudes outwardly from the surface of the centralizer. A method for using the device to cut bone in a surgical configuration is also provided.

Abstract: A system, method and/or reamer driver device is provided having a domed external surface and a domed internal surface being concentric to the domed external surface thereby defining a hollow dome. At least one cutting tooth is disposed on the hollow dome. The cross-sectional thickness T measured substantially perpendicular to the crest of the at least one tooth is greater than the radial distance t between the external and internal domed surfaces.

Abstract: A reaming instrument includes a reamer head having a cutting face rotatable about a cutting face axis and a drive shaft operably connected to the cutting face at a point spaced radially outwardly from the cutting face axis.

Abstract: A method of total hip arthroplasty using a direct anterior approach to prepare an acetabulum of a patient for implantation of an acetabular cup implant, the method including providing a positioning instrument, forming a main incision substantially over the acetabulum, the main incision having a length of about the size the acetabular shell to be implanted, placing the positioning instrument in the main incision such that the shell of the positioning instrument rests in said acetabulum of the patient, and using a guide bore of the instrument to locate and form a portal incision, the portal incision communicating with the main incision. A cannula is inserted through the portal incision, such that a proximal end of the cannula extends from the portal incision and a distal end of the cannula is adjacent to and in communication with the acetabulum and main incision. The cannula is used to prepare the acetabulum and implant the final implant.

Abstract: Described herein are examples of adjustable orthopedic reamer heads and methods for preparing a bone to receive an implant. The adjustable reamer heads and methods can include changing a cutting characteristic such as the size of an adjustable reamer head. In an illustrative example of an adjustable reamer head, the reamer head can include a housing, an actuator and a plurality of cutting elements. The plurality of cutting elements can be retained by the housing and can be operably coupled to the actuator. The plurality of cutting elements can include a first size cutting element and a second size cutting element. When the actuator is actuated, the first size cutting element and the second size cutting element can move relative to one another to change from a first cutting size to a second cutting size.

Abstract: A milling head for a milling tool for prosthetic surgery operations and a milling tool comprising said milling head.

Abstract: A surgical instrument assembly includes a metallic hemispherical component and a driver component removably coupled to the hemispherical component. The metallic hemispherical component has a convex outer surface configured to engage a patient's natural acetabulum, a concave inner surface positioned opposite the outer surface and defining a cavity in the hemispherical component, a plurality of cutting teeth extending outwardly from the outer surface, and a plurality of apertures defined in the inner surface. The driver component has a shank and a plurality of ribs secured to, and extending outwardly from, the shank. Each rib has a tab that is received in a corresponding aperture of the hemispherical component to secure the driver component to the hemispherical component.

Abstract: Illustrative methods and systems for customizing a pre-manufactured acetabular shell to a specific patient are described herein. An illustrative method can include positioning a provisional shell at an acetabulum of the patient, the provisional shell having a plurality of selectable openings. The method further including marking, based on the assessing of the bone, a patient-matched hole location on a provisional liner that corresponds to one of the plurality of selectable openings in the provisional shell. With the provisional liner marked, the method can further include removing the provisional liner from the provisional shell and positioning the provisional liner in the pre-manufactured acetabular shell that is to be implanted in the patient. Using the provisional liner as a guide, the method can include forming a hole in the acetabular shell corresponding to the marked patient-matched hole location on the provisional liner.

Abstract: The invention provides a surgical tool driver having a proximal end having a coupling and a distal end comprising a surgical tool connector having a release sleeve for disconnecting the surgical tool. The surgical tool connector further includes a locking member having a locking head adapted for coupling with at least one surgical tool. The locking member is slidingly disposed and at least substantially enclosed within the center of the driver and closely interfaces therewith so as to minimize seams, gaps or openings. The locking member has an axial range of motion which assures that between an unlock and lock position, the locking head is embedded in the driver in the unlock position and then extends axially outwardly, in snug juxtaposition with the driver, to a lock position which is capable of locking a surgical tool to the tool driver in a manner so as to avoid the exposure of a significant seam, gap or opening during activation and so helping prevent debris and/or bone chips from entering the driver.

Abstract: An orthopedic bone cutter for cutting bone and tissue is described. The cutting device comprises a plurality of radially extending struts that form a frame to which a base is connected thereto. Each of the struts that form the frame comprise sidewalls having left and right sidewall portions that are positioned at an angular relationship with respect to a primary strut sidewall portion. A plurality of cutting teeth reside along each of the struts have a tissue cutting surface that is raised above the exterior strut surface. The base of the orthopedic bone cutter may comprise a cross bar or bar and boss interface which secure bone cutter to a drive shaft.

Abstract: A system (200) and method (600) for identifying cutting tools for use during a surgical procedure are described. For example, the system includes a cutting tool assembly (210) including a shaft (212) having a cutting element (214) and at least one identifying feature (216) that uniquely corresponds to the cutting element. The system further includes a drive assembly (220) including a reference pin (224), a motor (230) mechanically connected to the drive assembly, a control unit (240) configured to activate the motor to move the cutting tool assembly such that the reference pin engages with the at least one identifying feature, a sensor system (226) configured to determine positioning information related to the reference pin when the reference pin engages the at least one identifying feature, and a computing unit (250) configured to receive the positioning information from the sensor system and identify the cutting element based upon the position information.

Abstract: A spherical reamer comprises a cutting element having a support member and at least one circumference cutting member built on it. The cutting member can be characterized by edge configuration, geometric parameters or further by positional parameters, respectively. All variations of the parameters above lead various types of the cutting elements and methods of including self- assembling and/or “One Size Cutting Element for Assembling Several Size of Reamers” in order to assembling either reusable or disposable reamer.

Abstract: A device is provided, including a cutting rib, the cutting rib including an arcuate portion having an outer sharp edge and a centralizer configured to receive the cutting rib through a radial slot, the radial slot forming a gap with the cutting rib. The arcuate portion of the cutting rib is formed into a profile that follows a surface of the centralizer, the outer sharp edge of the arcuate portion of the cutting rib has a wavy profile that forms a tunnel in the gap between the centralizer and the cutting rib, and the outer sharp edge of the arcuate portion of the cutting rib protrudes outwardly from the surface of the centralizer. A method for using the device to cut bone in a surgical configuration is also provided.

Abstract: An acetabular cup remover with a blade for removing tissue adjacent an acetabular cup. The blade is oscillated against an arcuate section of tissue. Once a section of tissue is cut, an indexing assembly rotates the blade. The blade is again oscillated to cut a new arcuate section of tissue.

Abstract: Implementations described and claimed herein provide an arthroplasty system and methods for positioning an acetabular cup implant. In one implementation, the system includes a shape-match hip guide having a patient specific mating region that is a negative of the surface contour of the inside surface of the patient's acetabular cup, and a directional rod that extends generally along the axis of the patient's femoral head and femoral neck. They system can additionally include an outrigger or silo device to aid in the alignment of surgical tools for preparing and implanting of the prosthetic acetabular cup in the patient's acetabular cup. Related methods are also disclosed herein for generating a shape-match guide and implanting an acetabular cup with the guide.

Abstract: Methods and apparatus for preparing at least a hemispherical surface with a desired dimension have been disclosed. The method includes at least two steps: a primary cutting mode for mostly reaming a lower portion of the target site, which enveloped area from the pole to intermediate latitude and a finishing cutting mode for reaming either an upper portion or an entire area of the site by less number of times of rotation, respectively. The intermediate latitude locates between the pole and the equator of hemisphere.

Abstract: An orthopedic driver includes a drivetrain having a driven end and a second end opposite the driven end, the drivetrain defining a first axis; an instrument connector rotatably coupled to the second end of the drivetrain and defining a second axis angled relative to the first axis; an angling bushing associated with the instrument connector; and a housing having a straight portion covering at least a portion of the drivetrain and an angled portion connected to the straight portion, the angled portion interacting with the angling bushing to hold the instrument connector angled relative to the drivetrain.

Abstract: A system for creating a patient-specific instrument model for chondral graft plugging comprises a bone model generator for producing a bone/cartilage model of an articular region of a bone from images thereof. A defect geometry identifier identifies a graft geometry from a defect region of said bone/cartilage model. A donor locator locates an autograft at a donor site or identifies an allograft from a database, using said bone/cartilage model and the graft geometry. A patient-specific instrument model generator creates a model of a graft-plugging patient-specific instrument from said bone/cartilage model, and the graft geometry, the graft-plugging patient-specific instrument model comprising a bone/cartilage interface surface shaped as a function of the bone/cartilage model for the at least one graft-plugging patient-specific instrument to be selectively positioned on the bone/cartilage to pose the autograft or the allograft at the defect region.

Abstract: An instrument for preparing an acetabulum. The instrument includes a handle having a reamer coupling feature and a trial coupling feature. The instrument further includes an acetabular reamer having an outer cutting surface and an inner concave surface having an apex. The acetabular reamer has a first handle coupling feature located at the apex adapted to couple to the reamer coupling feature of the handle. A trial having an outer convex surface having an apex is also included. The outer convex surface adapted to fit inside the inner concave surface of the acetabular reamer. The trial has a second handle coupling feature located at the apex of the outer convex surface adapted to couple to the trial coupling feature of the handle.

Abstract: A system and method for allowing any surgeon, including those surgeons who perform a fewer number of a replacement procedure as compared to a more experienced surgeon who performs a greater number of procedures, to provide an improved likelihood of a favorable outcome approaching, if not exceeding, a likelihood of a favorable outcome as performed by a very experienced surgeon with the replacement procedure.

Abstract: An orthopedic bone cutter for cutting bone and tissue is described. The cutting device comprises a support frame having a plurality of radially extending struts to which a cutting shell is removably connected thereto. The frame serves as a universal support structure that provides added mechanical support and stability to which various embodiments of cutting shells may be connected thereto. The bone cutter of the present invention is designed such that the cutting shell may comprise a variety of embodiments that enable the removal of bone and tissue. Embodiments of the cutting shell may comprise at least a partially hemispherical shape in which a plurality of cutting surfaces may extend. In addition, the cutting shell may comprise a plurality of removal cutting blade inserts that are received within slots that extend through the shell thickness.

Abstract: Apparatus and methods for preparing a bone socket, such as the glenoid of the scapula, to receive a prosthetic component. The apparatus is an orthopedic instrument (reamer) used for the preparation of bone surface for the insertion of an implant. The reamer includes an elongate shaft, a connecting system (for example, a quick connect system), and a cutting head having a specific configuration, i.e., in the shape of a Nautilus shell having a logarithmic spiral. The cutting head is provided with a plurality of spokes that have different radii or lengths (that confer a non-constant non-uniform radius to the overall cutting head).

Abstract: The present invention provides a surgical reamer (10), surgical reamer system, and kit including a surgical reamer. The surgical reamer has a domed shell (12) extending from the apex to the rim (13), a rotation axis (17), cutting teeth (14) disposed around the domed shell wherein a first connecting bar (15) having a first longitudinal axis and a first diameter is located on the inside surface of the domed shell, with its first longitudinal axis and a first diameter is located on the inside surface of the domed shell, with its first longitudinal axis being adjacent or closely adjacent to the rim and in which a second connecting bar (16) having a second longitudinal axis and a second diameter is located on the inside surface of the domed shell and spaced apart from the first connecting bar.

Abstract: Surgical systems and tools are disclosed including a surgical tool that has a shroud and a drive mechanism. The drive mechanism can have a distal end configured to connect to a surgical cutting instrument. The shroud can be configured to be disposed adjacent the distal end of the drive mechanism and can be adapted to be disposed between the drive mechanism and tissue of a patient.

Abstract: A tool and method for locating a proper position for a portal incision for hip arthroplasty, the tool being a tubular body having a first portion defining a first axis, a second portion defining a second axis non-parallel to the first axis, the second portion having a directional tool and a lead coaxially aligned, wherein when the tubular body is placed adjacent to an acetabulum with the directional tool aimed at the acetabulum and perpendicular to a plane of the face of the acetabulum, the lead points to location on the skin that would be the proper location for the portal incision. The lead may have a blunt tip, a cutting instrument, or an opening through which a flexible tool can be inserted to forge a path towards the proper location for the portal incision.

Abstract: A surgical device includes a housing, a cannula, a driving handle, and a cutting blade. The housing defines a hole in which the cannula that defines a passageway extending from a distal end to a proximal end is disposed. The driving handle is movably coupled to the housing and includes a driving rod slidably received within the passageway. The cutting blade is disposed within the passageway of the cannula and includes a distal end coupled to the distal end of the cannula, a proximal end configured to engage a distal end of the driving rod, and a reversibly deformable blade region disposed between the distal and proximal ends of the cutting blade. The deformable blade region is sized and configured to be received within at least one slot defined by the cannula and bends and straightens in response to movement of the driving handle relative to the housing.

Abstract: An acetabular reaming system is disclosed of the type having a driver and a tool held together by a quick-release coupling mechanism. The tool (10) has a hollow body (12) defining a domed shape with a rotational axis (14), an apex (16) aligned with the axis (14) and a hemispherical wall (18) extending from the apex (16) to an equatorial rim (20) spaced 90 degrees from the axis (14). The rim (20) has an edge (22) visible to the user that indicates the position of the tool (10) relative to the bone. A first plurality of cutting sites (24) is arrayed along the body (12) and a second plurality of cutting sites (28) is arrayed circumferentially along the edge (22). Preferably, the first plurality of cutting sites (24) present raised first teeth (30, 130, 230, 330) having a profile selected from continuous squared (30), continuous rounded (130), discontinuous squared (230) and tongued (330) profiles.

Abstract: An orthopaedic surgical instrument comprising an internal support about which a plastic substrate is disposed, and which includes exposed cutting surfaces relative to the plastic substrate. The surgical instrument may have a generally hemispherical shape and the internal support may comprise a non-planar shim. In particular embodiments the shim includes multiple interconnected limbs with multiple holes or slots disposed in the limbs and with the holes or slots including the cutting surfaces.

Abstract: An adapter for a surgical reamer driver having one of a crossbar and a crossbridge reamer driver. The adapter includes a base having an interface for connecting with one of the crossbar and crossbridge reamer drivers. The adapter further includes at least one recess on the opposite end of the base opening in an axial direction. The recess is configured to receive a reamer of a style unlike the given style interface. A pair of hooks or tabs resiliently hold the reamer in place in the recesses.

Abstract: An orthopedic instrument for installing a new reverse hip prosthesis, particularly the acetabular cup thereof, wherein the cup can be affixed to the pelvis with or without screws. The acetabular cup is releasably attached to the instrument and the instrument is used to position the cup in the pelvis. Optional screw guides are provided in the instrument in case the surgeon wishes to use screws to affix the cup to the pelvis.

Abstract: The present invention includes a measurement/assessment technique based upon a collection of angular and distance measurements taken with respect to x-ray visible osteo-anatomical artifacts to arrive at accurate and easily reproducible component placement. In the context of hip arthroplasty surgery the method of the present invention involves determinations, from two different two-dimensional views, of the angles and distances from osteo-anatomical artifacts, to allow a surgeon to approach a hip resurfacing operation with the distance and angular measurements to be translated into actual markings and device settings to be able to accurately ream the femoral head structure, position and affix the femoral cap and acetabular cup components in accordance with the pre-determined distance and angular measurements.

Abstract: A disposable reamer designed to improve bone and tissue removal efficiency is described. The reamer device comprises a reamer body shell, a series of reamer blades and a reamer shaft interface. The reamer body shell has a hemispherical structure having a concave interior surface and a convex outer surface. The series of reamer blades have a cutting portion comprised of a series of discrete cutting edges that is bent at an angle from the planar portion of the blade. The reamer blades are positioned along the curved concave interior surface of the hemispherical shell or along the curved convex outer surface of the shell. The reamer blades are positioned along the hemispherical shell such that their leading edges lie parallel to and tangent a bisecting plane.

Abstract: An instrument for removing tissue from a bone to create a cavity consists of an approximately spherical body having cutting formations in its external surface for cutting a bone. The body has a connector by which it can be connected to a drive by which it can be rotated about an axis, and a recess at the pole, opposite the connector. When the instrument is applied to the surface of a bone and is rotated about its axis, bone is cut as a result of the action of the formations against the bone, and a circular region of bone adjacent to the polar recess in the body remains generally intact.