# Patent

## Title
Expandable proximal reamer

## Abstract

A kit for reaming a portion of a long bone cavity for use in implanting a joint prosthesis, the reamers for cooperation with portions of an orthopaedic implant component. The kit includes a distal reamer for reaming a distal portion of the long bone and a proximal reamer for reaming a proximal portion of the long bone. The kit further includes a pilot shaft for insertion into a reamed distal portion and attachment to the proximal reamer during the reaming of the proximal portion. At least one of the distal reamer, proximal reamer, and pilot shaft is expandable, such that the at least one of the distal reamer, proximal reamer, and pilot shaft includes an expandable body adapted to adjust between a plurality of diameters.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a divisional application of U.S. patent application Ser. No. 11/743,325 entitled “EXPANDABLE PROXIMAL REAMER”, which is incorporated by reference herein in its entirety.


TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to the field of orthopaedics, and more particularly, to an implant for use in arthroplasty.
BACKGROUND OF THE INVENTION
Patients who suffer from the pain and immobility caused by osteoarthritis and rheumatoid arthritis have an option of joint replacement surgery. Joint replacement surgery is quite common and enables many individuals to function properly when it would not be otherwise possible to do so. Artificial joints are usually comprised of metal, ceramic and/or plastic components that are fixed to existing bone.
Such joint replacement surgery is otherwise known as joint arthroplasty. Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged joint is replaced with a prosthetic joint. In a typical total joint arthroplasty, the ends or distal portions of the bones adjacent to the joint are resected or a portion of the distal part of the bone is removed and the artificial joint is secured thereto.
There are known to exist many designs and methods for manufacturing implantable articles, such as bone prostheses. Such bone prostheses include components of artificial joints such as elbows, hips, knees and shoulders.
Currently in total hip arthroplasty, a major critical concern is the instability of the joint. Instability is associated with dislocation. Dislocation is particularly a problem in total hip arthroplasty.
Factors related to dislocation include surgical technique, implant design, implant positioning and patient related factors. In total hip arthroplasty, implant systems address this concern by offering a series of products with a range of lateral offsets, neck offsets, head offsets and leg lengths. The combination of these four factors affects the laxity of the soft tissue. By optimizing the biomechanics, the surgeon can provide a patient a stable hip that is more resistant to dislocation.
In order to accommodate the range of patient arthropathy metrics, a wide range of hip implant geometries are currently manufactured by DePuy Orthopaedics, Inc., the assignee of the current application, and by other companies. In particular, the 5-ROM® total hip systems offered by DePuy Orthopaedics, Inc. may include up to six neck offsets per stem diameter, six head lengths and one leg length adjustment. The combination of all these biomechanic options is rather complex.
Anteversion of a total hip system is closely linked to the stability of the joint. Improper anteversion can lead to dislocation and patient dissatisfaction. Anteversion control is important in all hip stems. However, it is a more challenging issue with the advent of stems with additional modularity.
The prior art has provided for some addressing of the anteversion problem. For example, the current S-ROM® stems have laser markings on the medial stem and the proximal sleeve. This marking enables the surgeon to measure relative alignment between these components. Since the sleeve has infinite anteversion, it is not necessarily oriented relative to a bony landmark that can be used to define anteversion. In fact, the current sleeves are sometimes oriented with the spout pointing directly laterally into the remaining available bone.
When a primary or index total joint arthroplasty fails, a revision procedure is performed in which the index devices (some or all) are removed. Quite often the remaining bone is significantly compromised compared to a primary hip procedure. Significant bone loss is observed, often with a lack of bone landmarks typically used for alignment.
In a common step in the surgical procedure known as total hip arthroplasty, a trial or substitute stem is first implanted into the patient. The trial is utilized to verify the selected size and shape of the implant in situ on the patient and the patient is subjected to what is known as a trial reduction. This trial reduction represents moving the joint, including the trial implant through selected typical motions for that joint. Current hip instruments provide a series of trials of different sizes to help the surgeon assess the fit and position of the implant. Trials, which are also known as provisionals, allow the surgeon to perform a trial reduction to assess the suitability of the implant and the implant's stability prior to final implant selection. In order to reduce inventory costs and complexity, many trialing systems are modular. For example, in the ExcelTM Instrument System, a product of DePuy Orthopaedics, Inc., there is a series of broaches and a series of neck trials that can be mixed and matched to represent the full range of implants. There is a single fixed relationship between a broach and a neck trial, because these trials represent a system of monolithic stem implants.
Likewise, in the current S-ROME instrument systems provided by DePuy Orthopaedics, Inc., there are neck trials, proximal body trials, distal stem trials, head trials and sleeve trials. By combining all of these components, the implant is represented. Since the S-ROM® stem is modular and includes a stem and a sleeve, the angular relationship or relative anteversion between the neck and the sleeve is independent and represented by teeth mating between the neck and the proximal body trial. The proximal body trial has fixed transverse bolts that are keyed to the sleeve in the trialing for straight, primary stems. The long stem trials do not have the transverse bolts and are thus not rotationally stable during trial reduction and therefore are not always used by the surgeon.
With the introduction of additional implant modularity, the need for independent positioning of the distal stem, proximal body and any sleeve that comprise the implants is required. Currently, modular stems for one replacement may come with up to thirty four different sleeve geometries, requiring up to seven different reamer attachments and corresponding pilot shafts to prepare the cone region of the sleeve.
While the prior art has attempted to reduce the steps in surgical techniques and improve the ability to precisely remove bone to prepare the bone for receiving a proximal component, the need remains for a system and apparatus to reduce the number of components required to perform hip arthoplasty.
The present invention is directed to alleviate at least some of the problems with the prior art.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, a reamer for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamer is for cooperation with a portion of an orthopaedic implant component and includes an expandable body that is adapted to adjust between a plurality of diameters. A plurality of cutting edges extending outwardly from the body is also included. The edges are adapted for cooperation with bone, such that the cutting edges expand as the expandable body expands.
According to another embodiment of the present invention, a method for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamer is used in cooperation with a portion of an orthopaedic implant component. The method includes reaming a distal portion of the long bone using a distal reamer as well as reaming a proximal portion of the long bone using a proximal reamer. At least one of the distal reamer and proximal reamer is an expandable reamer, such that one of the distal reamer and proximal reamer includes an expandable body adapted to adjust between a plurality of diameters.
According to yet another embodiment of the present invention, a kit for reaming a portion of a long bone cavity for use in implanting a joint prosthesis is provided. The reamers are used in cooperation with portions of an orthopaedic implant component. The kit includes a distal reamer for reaming a distal portion of the long bone, a proximal reamer for reaming a proximal portion of the long bone, and a pilot shaft for insertion into a reamed distal portion and attachment to the proximal reamer during the reaming of the proximal portion. At least one of the distal reamer, proximal reamer, and pilot shaft is expandable, such that one of the distal reamer, proximal reamer, and pilot shaft includes an expandable body adapted to adjust between a plurality of diameters.



BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in connection with the accompanying drawings, in which:
FIG. 1 is a plan view of a distal reamer in position in a long bone for preparing a bone canal for receiving a long bone prosthetic stem;
FIG. 2 is a plan view of an expandable distal reamer according to one embodiment of the present invention;
FIG. 2a is a plan view of the expandable distal reamer of FIG. 2 in an expanded position, including a view of the internal components of the reamer;
FIG. 3 is a plan view of a proximal reamer in position in a long bone for preparing a bone canal for receiving a long bone prosthetic stem;
FIG. 4 is a plan view of an expandable proximal reamer according to one embodiment of the present invention;
FIG. 4a is a plan view of the expandable proximal reamer of FIG. 4 in an expanded position, including a view of the internal components of the reamer;
FIG. 5 is a plan view of an expandable pilot shaft according to another embodiment of the present invention.
FIG. 5a is a plan view of the expandable pilot shaft of FIG. 5, including a view of the internal components of the shaft.
FIG. 6 is a plan view of an expandable proximal reamer according to another embodiment of the present invention.
FIG. 7 is a plan view of an expandable proximal reamer according to yet another embodiment of the present invention.
FIG. 7a is a plan view of the expandable proximal reamer of FIG. 7 in an expanded state.
FIG. 8 is a flow chart illustrating a method of using an expandable reamer according to one embodiment of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention and the advantages thereof are best understood by referring to the following descriptions and drawings, wherein like numerals are used for like and corresponding parts of the drawings.
Referring now to FIG. 1 a long bone or femur 2 for use with the present invention is shown. The femur 2 includes an intermedullary canal 4 into which the prosthesis of the present invention may be inserted. The femur 2 is resected along resection line 6 by, for example, a power tool, for example, a saw. The resecting of the long bone or femur 2 exposes the intermedullary canal 4 of femur 2. A distal or cylindrical reamer 8 that may be a standard commercially available reamer is positioned in the intermedullary canal 4 of the long bone 2 to form cavity 10 for receiving an orthopedic joint implant. The distal reamer 8 includes a plurality of longitudinally extending channels, or flutes 12 which are used to remove bone and other biological matter from the intermedullary canal 4 to form the cavity 10. The distal reamer 8 may be rotated by use of a connector 14 positioned on the distal reamer 8. The connector 14 may be any standard connector for example a Hudson or an A-O connector. The connector 14 is used to connect to a power tool 15 for rotating the distal reamer 8. The power tool 15 may be any standard power tool. It should be appreciated that the distal reamer 8 may be rotated through the use of the connector 14 by a hand tool for example a “T” shaped handle.
The diameter “D” of the distal reamer 8 is determined by the size of the distal stem (not shown) that is to be implanted into the femur 2. Because of variances in human anatomy, there are numerous sizes of distal stems that can be implanted. Therefore, there are numerous sizes of reamers 8 that can also be used. The large number of reamers 8 can increase production and manufacturing costs, as well as create problems during the surgery should the doctor select the wrong size distal reamer 8 to be used.
Turning now to FIG. 2, an embodiment of an expandable distal reamer 8a is shown. Because the distal reamer 8a is expandable, the diameter Da of the distal reamer 8a is variable, unlike the fixed diameters of the prior art distal reamers.
As shown in FIG. 2, the expandable distal reamer 8a includes a proximal portion 16 and a distal cutting portion 17. The proximal portion 16 includes at least two gears 18, 20 that are in contact with each other such that when the gear 18 is rotated, the gear 20 also rotates. Similar to the distal reamer 8 of FIG. 1, the expandable distal reamer 8a includes flutes 12a. The flutes 12a expand outwardly from the reamer 8a when the gears 18, 20 are activated. The reamer 8a also includes a plurality of slits, or cuts, 22a, 22b around its circumference. Such slits 22a, 22b allow the diameter Da of the expandable distal reamer 8a to enlarge when the gears 18, 20 are rotated.
The gear 18 may be activated by inserting a chuck (not shown) into a hole 24 of the proximal portion 16 and then rotating the chuck. Alternatively, a gauge 25 (FIG. 2a) may be inserted into the hole 24 until it engages the gear 18 and rotated a desired amount. The gauge 25 may include markers 27 (FIG. 2a) to allow the user to know when to stop rotating the gauge. Any other known method for activating a gear may also be utilized.
Once the gears 18, 20 are activated, the gear 20 forces a cone 26 down through the proximal portion 16 into the distal cutting portion 17. As the cone 26 moves downwardly, the cone's increasing diameter forces the distal cutting portion 17 to become enlarged. As stated above, the reamer 8a includes slits 22a, 22b. These slits 22a, 22b allow the distal portion 17 to expand as the cone 26 pushes further into the distal portion 17. Therefore, the diameter Da of the reamer 8a also increases.
In FIG. 2a, the gauge 25 is shown inserted into the top of the expandable distal reamer 8a and the distal reamer 8a is shown in an expanded position, having a radius Db. When the gauge 25 is inserted, it engages the gear 18. The gauge 25 may include markings 27 that correlate to the size of the diameter Da of the expandable distal reamer 8a. In other words, if the surgeon or other healthcare professional rotates the gauge 25 a particular amount, the marking 27 indicates that the rotation correlates to a particular diameter Da of the expandable distal reamer 8a. Furthermore, as the gauge 25 is rotated, the slits 22a, 22b enlarge as shown in FIG. 2a, creating the larger diameter Db.
As shown in FIGS. 2 and 2a, the diameter Da of the expandable distal reamer 8a may be enlarged through mechanical means such as gears 18, 20. However, other devices, such as pneumatic or hydraulic mechanisms could also be used to adjust the diameter Da of the expandable distal reamer 8a. In addition, other mechanical devices, such as cross-bars and/or levers could be used to increase the diameter Da of the expandable distal reamer 8a. 
After the distal region of the femur 2 is reamed, the proximal portion must then be reamed. As shown in FIG. 3, a conical or proximal reamer 30 is used to form cavity 10 for receiving an orthopedic joint implant. The proximal reamer 30 includes a plurality of longitudinally extending channels or flutes 32 which are used to remove bone and other biological matter from the femur 2 to form a cavity 33 having a cone-shape, with a diameter varying between a diameter d1 to d2, which is the same shape and diameter range of the cone-shaped proximal reamer 30. The proximal reamer 30 may be rotated by use of a connector 34 positioned on the proximal reamer 30. The connector 34 may be any standard connector for example a Hudson or an A-O connector. The connector 34 is used to connect to a power tool 35 for rotating the proximal reamer 30. The power tool 35 may be any standard power tool. It should be appreciated that the proximal reamer 30 may be rotated through the use of the connector 34 by a hand tool for example a “T” shaped handle. The proximal reamer 30 is coupled to a pilot shaft 36 that fits into the reamed cavity 10. The pilot shaft 36 ensures that the proximal reamer 30 goes into the canal and reams straight.
Turning now to FIG. 4, an expandable proximal reamer 30a according to one embodiment of the present invention is illustrated. Because the proximal reamer 30a is expandable, the diameters da1-da2 of the proximal reamer 30a are variable, unlike the fixed diameters of the prior art proximal reamers.
Similar to the distal reamer 8a shown in FIGS. 2 and 2a above, the proximal reamer includes a proximal portion 37 and a distal cutting portion 38. The proximal portion 37 includes at least two gears 39, 40 that are in contact with each other such that when the gear 39 is rotated, the gear 40 also rotates. Similar to the proximal reamer 30 of FIG. 3, the expandable proximal reamer 30a includes flutes 32a. The flutes 32a expand outwardly from the reamer 30a when the gears 39, 40 are activated. The reamer 30a also includes a plurality of slits, or cuts, 42a, 42b, around its circumference. Such slits 42a, 42b, allow the diameters da1 and da2 of the expandable proximal reamer 30a to enlarge when the gears 39, 40 are rotated.
The gear 18 may be activated by inserting a chuck (not shown) into a hole 43 of the proximal portion 16 and then rotating the chuck. Alternatively, a gauge 44 (FIG. 4a) may be inserted into the hole 43 until it engages the gear 39 and rotated a desired amount. The gauge 44 may include markers 46 (FIG. 4a) to allow the user to know when to stop rotating the gauge. Any other known method for activating a gear may also be utilized.
Once the gears 39, 40 are activated, the gear 40 forces a cone 48 down through the proximal portion 37 into the distal cutting portion 38. As the cone 48 moves downwardly, the cone's increasing diameter forces the distal cutting portion 38 to become enlarged. As stated above, the reamer 30a includes slits 42a, 42b. These slits 42a, 42b allow the distal portion 38 to expand as the cone 48 pushes further into the distal portion 38. Therefore, the diameters d1a and d1b of the proximal reamer 30a also increase.
In FIG. 4a, the gauge 44 is shown inserted into the top of the expandable proximal reamer 30a and the reamer is shown in an expanded position having diameters db1 and db2 that are greater than the diameters da1 and da2. The gauge 44 may include markings 46 that correlate to the size of the diameters da1 and da2 of the expandable proximal reamer 30a. In other words, if the surgeon or other healthcare professional rotates the gauge 44 a particular amount, the marking 46 indicates that the rotation correlates to particular diameters da1 and da2 of the expandable proximal reamer 30a. Furthermore, as the gauge 44 is rotated, the slits 42a, 42b enlarge as shown in FIG. 4a, creating the larger diameters db1 and db2. In this embodiment, because of the conical shape of the reamer 30a, as the gears 39, 40 are rotated, the diameter da1 increases more relative to the diameter da2. In other words, proximal portion 37 is expanded more relative to the distal portion 38.
As shown in FIGS. 4 and 4a, the diameters da1 and da2 of the expandable proximal reamer 30a may be enlarged through mechanical means such as gears 39, 40. However, other devices, such as pneumatic or hydraulic mechanisms could also be used to adjust the diameters da1 and da2 of the expandable proximal reamer 30a. In addition, other mechanical devices, such as cross-bars and/or levers could be used to increase the diameters da1 and da2 of the expandable proximal reamer 30a. 
Turning now to FIGS. 5 and 5a, an alternative embodiment of a pilot shaft 50 is shown. As discussed above, a pilot shaft is attached to the proximal reamer to ensure that the reamer properly extends downwardly into the canal. Also as discussed above, because the distal reamer 8 may come in various sizes, the pilot shaft must also come in a variety of sizes. Therefore, to cut-down on manufacturing costs and to reduce the possibility of confusion in the operating, in one embodiment of the present invention, the pilot shaft 50 is also adjustable. As shown in FIG. 5, the pilot shaft 50 includes a proximal portion 52, a distal portion 54 and a central portion 56. The central portion 56 includes a sleeve 58 that engages two threaded screws 60, 62. As the sleeve 58 is rotated, the threaded screws 60, 62 are pushed into openings 64, 66 in the proximal and distal portions 52, 54. The proximal and distal portions 52, 54 each include slits 68, 70 that open as the threaded screws 60, 62 are pushed into the openings 64, 66 (as shown in FIG. 5b). Thus, the operator is able to adjust the diameter of the pilot shaft 50 to match the diameter of the reamed canal 10. In the embodiments illustrated in FIGS. 5 and 5a, the pilot shaft 50 is adjusted from having a diameter of Dc to Dd. As shown in FIGS. 5 and 5a, the pilot shaft 50 also includes a connectable mechanism such as a threaded portion 72 for attachment to the expandable proximal reamer 30a. Alternatively, the threaded portion 72 may also attach to a miller shell or a proximal body trial (not shown).
Turning now to FIG. 6, an alternative embodiment of an expandable proximal reamer 80 is illustrated. In this embodiment, the expandable proximal reamer 80 includes an upper conical recess 82. A threaded expansion rod 84 has a threaded end 86 and is inserted into the upper conical recess 82. As the threaded expansion rod 84 is advanced through the upper conical recess 82, the expandable reamer 80 is widened through the use of a slit 88. The user may thus adjust the diameters of the expandable reamer 80.
As shown in FIG. 6, the threaded expansion rod 84 may include a gauge 90, allowing the user to determine the diameter of the reamer 80. Also, the rod 84 may include upper and lower support rods 92, 94 that extend into the reamer 80 to keep the reamer 80 and the rod 84 rigid during use. Either or both of the support rods may also be used in connection with any of the embodiments discussed above.
In all of the embodiments discussed above, whether for distal reamers, proximal reamers, or pilot shafts, the various gauges and/or markings may also include preset stops that correspond to certain sizes. Such preset stops would make it easier for a user to accurately stop adjusting at the correct diameter. The preset stops may be fashioned out of notches in a thread or any other known mechanism.
Turning now to FIG. 7, another embodiment of an expandable proximal reamer 100 is illustrated. In this embodiment, the proximal reamer 100 includes a screw 102 that extends outwardly from the proximal reamer 100. The screw 102 has a threaded portion 104a that is threadably engaged with threaded portions 104b, 104c of supports 105. The supports 105 provide the reamer 100 with support during cutting, enabling the reamer 100 to expand, yet still maintain its strength and rigidity.
As a user rotates the screw 102, the threads 104a cause the threaded portions 140b, 104c to also rotate. The threaded portions 104b, 104c are also threadably engaged with a thread 104d, such that when the threaded portions 104b, 104c are rotated, the threaded portion 104d also rotates. The threaded portion 104d is coupled to a cone 106, such that as the threaded portion 104d rotates, the cone 106 moves in a downward direction 112 (FIG. 7a), causing the proximal reamer 100 to expand outwardly in the direction indicated by arrows 114. This also causes the supports 105 to move outwardly in directions 110 as shown in FIG. 7a. 
As shown in FIGS. 7 and 7a, the proximal reamer 100 is coupled to a pilot shaft 108, such that as the cone 106 moves downwardly, the pilot shaft 108 may also expand in an outward direction as indicated by arrows 114 (FIG. 7a).
Turning now to FIG. 8, a method for utilizing the expandable reamers is shown. At step s200, the femur is resected. Next, the user selects the distal reamer to be used at step s202. If an expandable distal reamer is to be used, then at step s202, the user then adjusts the diameter of the distal reamer as described above. At step s204, the distal reamer is inserted and the distal portion of the long bone is reamed (step s206). Next, at step s208, the proximal reamer is selected. If the proximal reamer is an adjustable reamer, the user will adjust the proximal reamer to the appropriate diameter. If the proximal reamer is not adjustable, then the user must select a proximal reamer with an appropriate diameter from a set of reamers. Next, at step s210, the pilot shaft is selected or adjusted as necessary. At steps 212, the proximal reamer is attached to a pilot shaft. The proximal reamer and shaft are inserted into the proximal portion of the long bone and the reamed distal portion, respectively at step 214. The proximal portion is then reamed at step s216. The rest of the reaming and implantation process is then completed in any of the ways customary and known in the prior art. It should be noted that although in this example, both the proximal reamer and the distal reamer were expandable, that in some embodiments, only one of the reamers may be expandable. Also, while some embodiments refer to an adjustable pilot shaft, in other embodiments, the pilot shafts of the prior art may be attached to the proximal reamers.
In some embodiments of the present invention, a kit for reaming the long bone is provided, including distal reamers, proximal reamers, and pilot shafts. The kit includes at least one reamer that is an expandable reamer. In some embodiments, both the distal reamer and the proximal reamers will be expandable. In other embodiments, only one of the types of reamer will be expandable. In some embodiments, the pilot shaft may also be expandable.
According to some embodiments of the present invention, the expandable reamers may be able to expand to all sizes required for that type of reamer. In other embodiments, the expandable reamers may only expand through a range, and a plurality of reamers may still be required. For example, if the expandable reamer is a proximal reamer, a kit may include three expandable proximal reamers. Each expandable proximal reamer in such a kit has a diameter that is variable within a range.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

## Claims

1. A kit for reaming a portion of a long bone cavity for use in implanting a joint prosthesis, using a plurality of reamers for cooperation with portions of an orthopaedic implant component, the kit comprising:
a distal reamer for reaming a distal portion of the long bone;
a proximal reamer for reaming a proximal portion of the long bone; and
a pilot shaft for insertion into a reamed distal portion and attachment to the proximal reamer during the reaming of the proximal portion;
wherein at least one of the distal reamer, proximal reamer, and pilot shaft is expandable, such that the at least one of the distal reamer, proximal reamer, and pilot shaft includes an expandable body and the expandable body includes at least one gear and a cone, the gear engaging the cone, such that as the gear is rotated, the cone's increasing diameter forces the body to expand;
wherein the expandable body includes an outer sleeve coupled to a pair of threaded screws, such that when the sleeve is rotated, the threaded screws extend into the expandable body, increasing the diameter of the pilot shaft.

2. The kit of claim 1, wherein the expandable body includes longitudinal channels, such that the longitudinal channels enlarge when the expandable body is expanded.

3. The kit of claim 1, wherein each of the distal reamer, proximal reamer, and pilot shaft is expandable such that each of the distal reamer, proximal reamer, and pilot shaft includes an expandable body and the expandable body includes at least one gear and a cone, the gear engaging the cone, such that as the gear is rotated, the cone's increasing diameter forces the body to expand.

4. The kit of claim 1, wherein the distal reamer is expandable and includes a plurality of cutting edges and each of the plurality of cutting edges extend longitudinally along the body of the reamer.

5. The kit of claim 4, wherein the plurality of cutting edges of the distal reamer are equally spaced apart.

6. The kit of claim 4, wherein the plurality of cutting edges of the distal reamer extend out radially as the actuator rod is turned in the one direction.