Abstract:
A dual speed medical procedure power tool includes first and second gear sets. The first and second gear sets may be engaged and disengaged, selectively, to provide a first speed for a high-speed, low-torque drilling function and a second speed for a low-speed, high-torque reaming function.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is related to and claims priority to U.S. Provisional Application No. 62/168,834 filed on May 31, 2015. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates generally to single use or limited use power tools and more particularly to external components that can be removed for cleaning when a tool is being cleaned, reconditioned, sterilized and deployed for re-use. 
         [0003]    Important factors for any surgical instrument include sterility, cost of acquisition, maintenance, and reliability during use in the surgical suite. Each of these factors can have a significant impact on the cost of medical care for both the patient and the provider. 
         [0004]    In recent years, there has been significant focus on the ever increasing cost of medical care. These cost increases have led to skyrocketing insurance premiums, reduced coverage, reduced reimbursements, increased fees for services, severe reductions in the services for some patient groups by some providers, and unfortunately an apparent increase in infections and medical mishaps. 
         [0005]    In an effort to reduce costs and improve profitability, both service providers and medical device suppliers are continuously looking for ways to streamline procedures, reduce time, cost, and risk from their products and services without reducing the quality of the products or services they provide to their customers. One area to benefit from these savings and improvements has been in the orthopedic surgical field through the use of high precision, battery powered surgical instrumentation. In the late 1960&#39;s and early 1970&#39;s battery operated drills were bulky, ill-balanced and required multiple batteries to perform some surgeries due to the limited energy storage capacity and poor efficiency of the electric motors. 
         [0006]    Since then, manufacturers have attempted to make batteries more efficient with higher energy storage capacity, reduced size, and improved rechargeable lifespans. Likewise, motor housings such as saw and drill bodies have become more ergonomic, balanced, lightweight and energy efficient. As with many standard hand tools having multiple moving components, instrument manufacturers have reduced weight by utilizing lighter materials such as plastic housings, and gears, and put weight-reducing apertures in what were previously solid housings. In some cases, standard mountings for attachments have been replaced with modular fittings, allowing for greater interchangeability and component selections. Additionally, manufacturers have attempted to improve electrical components by upgrading them with more modern components wherever possible. 
         [0007]    All of these improvements in equipment have improved efficiencies, costs and quality in some areas while at the same time increasing costs for acquisition, maintenance and increasing patient risks in other ways that were not previously seen or predicted. Often times cost, quality and risk can be inversely proportional to one another. One example of the increased cost and reduced patient risk is seen in the cleaning and maintenance of instruments. 
         [0008]    Recent published reports suggest that many of the surgical instruments used in operations were not being cleaned and/or sterilized appropriately in the very hospital facilities that were established and tasked for that purpose. In numerous reports, following cleaning and sterilization, it was noted that upon closer secondary inspection, the inside of small diameter cannulas and intricate mini-components of arthroscopic shavers that are used for many of today&#39;s minimally invasive procedures, contained human tissue and bone fragments from previous surgeries. In other cases, modular components of drills and saws such as chucks, drill bits and blades were found to have similar debris or pieces of cleaning brushes and/or bristles embedded in or on them. These investigations have demonstrated that in most cases the instruments were not cleaned according to manufacturer&#39;s specifications which has likely led to many documented cases of serious, multiple, serial infections for subsequent patients. A pilot program conducted by the Centers for Medicare and Medicaid Services (Schaefer et al., 2010; JAMA 2010; 303(22): 2273-2279) inspected 1500 outpatient surgery centers and found that 28% had been cited for infectious control deficiencies associated with equipment cleaning and sterilization. The costs to the patients and the hospitals in both expense and liability to deal with these infections can be and has been staggering. 
         [0009]    In other cases, critical battery-operated, motorized tools such as drills or bone saws have ceased to function due to dead batteries that no longer maintain their capacity to hold a charge, or due to internal part failure, often attributable to overuse or lack of proper maintenance. The resultant downtime in the operating suite is extremely costly, as the procedure step must be put on hold while replacement or substitute tools are obtained. Wait times may often exceed 20-30 minutes, resulting in additional anesthesia exposure for the patient, additional operating room time (charged to the patient) and potential delays to other procedures where the replacement or substitute equipment had been scheduled for use in a later procedure. Recent estimates (2005) establish the average cost of operating room time to range between $62/min. (range $21.80-$133.12) depending on the procedure. These figures did not include extra resources provided by the hospital for special, non-routine situations which often occur during standard procedures, and did not include the surgeon and anesthesia provider fees, (anesthesia fees are estimated to be $4/min; range $2.20-$6.10). 
         [0010]    Hospitals and instrument manufacturers are continuously attempting to find improved ways to reduce risk associated with infection in general, and more recently, specifically from improperly cleaned instruments. One approach has been to use more disposable, single-use instruments such as drills, saw blades and plastic cannulas. Additionally, many laparoscopic devices, such as surgical staplers and trocars, are designed as single use items that are intended to be immediately disposed of after use. Unfortunately, at today&#39;s acquisition costs, the total cost of ownership and benefits are not always clear for high-use battery-operated, motorized instruments such as saws, drills and reamers used in orthopedic procedures and the idea of disposable powered instruments has not been readily embraced. 
         [0011]    A recent trend in the medical community is the reprocessing of single use medical instruments, by parties other than the original equipment manufacturer, instead of discarding them after use. During reprocessing, the medical instruments are disassembled, cleaned and sterilized. They are then reassembled for future use. However, because the medical instruments reprocessed for further use are specifically provided for use during a single procedure, the performance of the medical instruments tends to decline after reprocessing, because the components making up the medical instrument are not adapted for multiple uses and will degrade in performance when used beyond their intended life span. For example, reprocessing of the cutting devices on trocars is intended to extend these devices beyond their intended mission life, but often results in duller cutting edges on the blades because neither the materials used nor the reprocessing method can restore the device to the original manufacturing specifications. A greater force, therefore, is needed to make an initial incision, causing more trauma to the patient. In addition, the use of greater force increases the potential for error during the surgical procedure. 
         [0012]    Most hospitals and surgery centers buy high-use, reusable motorized, pneumatic, wired or battery operated, orthopedic surgical equipment and are expected to clean, sterilize, and maintain them internally within the hospital. Unfortunately, the technicians hired to perform this work are typically not qualified or trained to perform this work adequately for the many varieties of powered instruments used. Further, manufacturers rarely provide the hospital/client with the training or diagnostic equipment necessary to evaluate or test the equipment. Often times the hospital employees responsible for cleaning and maintenance are not technicians at all, being paid slightly more than minimum wage, working at a fast pace to merely wash, count, and reload instruments into their appropriate system trays and flash sterilize them as quickly as possible, in an effort to keep the equipment in rotation in the hospital operating rooms, where higher throughput dictates profitability for the hospital or surgery center. 
         [0013]    As a result of high throughput requirements, general maintenance is rarely done and preventative monitoring and maintenance is almost never done on this type of equipment. Hospital budgets for internal maintenance of equipment are generally geared toward high-end, multi-million dollar capital equipment such as x-ray and radiological equipment. It is generally assumed that it is faster, simpler, and more economical for the hospital to wait for hand-held instruments, such as drills, saws and reamers to fail, then, send them back to the manufacturer for repair or replacement. Additionally, it would be beneficial to provide single use or limited use surgical power tools that have two sets of gears, one of which can be engaged while the other is not and vice versa, to enable dual speed operation depending on the location of an external control lever 
       SUMMARY 
       [0014]    Accordingly, one embodiment comprises a dual speed medical procedure power tool wherein first and second gear sets are selectively engageable for performing mutually exclusive drilling and reaming speeds. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view illustrating an embodiment of a medical procedure power tool. 
           [0016]      FIG. 2  is a partial cut-away side view illustrating an embodiment of a medical procedure power tool having a gear set in a first speed position. 
           [0017]      FIG. 3  is the partial cut-away view of  FIG. 2  illustrating the gear set in a second speed position. 
           [0018]      FIG. 4  is a perspective exploded view illustrating a gear set capable of axial motion on a shaft and transfer of rotational energy to the shaft. 
           [0019]      FIG. 5  is an alternate perspective view of the gear set of  FIG. 4 . 
           [0020]      FIG. 6  is a partial view illustrating an embodiment of a drilling attachment for use with a medical procedure power tool. 
           [0021]      FIG. 7  is a partial view illustrating an embodiment of a reaming attachment for use with a medical procedure power tool. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    A medical procedure power tool  10  is illustrated in  FIG. 1  and includes an integrated housing  12  having a power and attachment portion  14 , a handle portion  16  and a battery-housing portion  18 . The power and attachment portion  14  contains an electric motor, discussed below, and a chuck  19  for securing various attachments to the tool  10 . The handle portion  16  includes a trigger  20 , and the battery-housing portion  18  defines a battery compartment  22 . The housing  12  is preferably formed of a synthetic material. A battery in compartment  22  may be either rechargeable or disposable. 
         [0023]    More specifically, in  FIGS. 2 and 3 , a medical procedure power tool  410  includes a housing  412  having a motor  414  and a motor output shaft  416 . A plurality of gear clusters, discussed below, are provided to power a tool output shaft  418 , and a chuck  419 , at a selected speed for either a reaming or drilling operation. The tool  410  has a manually operable sliding speed selector knob  420  protruding from housing  412  and movable from a first or forward position  420   a,    FIG. 3 , to a second or rearward position  420   b,    FIG. 2 . A speed selector fork  422  is connected to move with selector knob  420 . The fork  422  engages a receiver  424  mounted on power tool output shaft  418 , see also  FIGS. 4 and 5 . The receiver  424  and a pair of gears, discussed below, are slidably mounted on the tool output shaft  418 . 
         [0024]    The motor  414 ,  FIG. 3 , provides rotational output via the motor output shaft  416  and through a sequential cluster of gears  426 ,  428 ,  430 ,  432 ,  434 ,  436  to rotationally drive a first or driving gear set including gears  438  and  440  mounted to rotate with a shaft  442 . Depending on the position of speed selector knob  420 , one of the gears  438  and  440  is positioned to drive a second or driven gear set including gears  444  and  446  mounted to rotate with the shaft  418 . However, the gears  444  and  446  are slidably mounted on shaft  418 , and simultaneously are mounted to rotate shaft  418  as further discussed below. 
         [0025]    In operation, when it is desired to perform a drilling operation, which is a high-speed, low-torque operation, the selector knob  420  is positioned rearward,  FIG. 2 , thus causing the speed selector fork  422  to simultaneously move (or slide) the receiver  424  and both gears  444  and  446  rearward on shaft  418 . As a result, gear  446  meshes with gear  440  and shaft  418  is rotated at the high-speed, low-torque drill setting. When it is desired to perform a reaming operation, which is a low-speed, high-torque operation, the selector knob is positioned forward,  FIG. 3 , causing the speed selector fork  422  to simultaneously move (or slide) the receiver  424  and both gears  444  and  446  forward on shaft  418 . As a result, gear  444  meshes with gear  438  and shaft  418  is rotated at the low-speed, high-torque reaming setting.  FIG. 6  illustrates an attachment  470  for use with power tool  410  to accomplish a drilling operation, and  FIG. 7  illustrates an attachment  472  for use with power tool  410  to accomplish a reaming operation. Attachments  470  and  472  are bidirectionally rotatable. 
         [0026]    Gears  444  and  446  are enabled to slide on shaft  418  and also transfer rotational energy to shaft  418  and chuck  419  due to a key and keyway connection, see  FIGS. 4 and 5 . The gears  444 ,  446  and the receiver  424  have a continuous keyway  450 , which engages a key  452  mounted on shaft  418 . A groove  454  in shaft  418  receives a ring  456 ,  FIGS. 2 and 3 , which limits rearward sliding movement of gears  444 ,  446  and receiver  424  on shaft  418 . 
         [0027]    As a result of the foregoing, a dual speed medical procedure power tool  410  is provided. The power tool  410  comprises a housing  412  including a motor  414  providing a rotational output  416  to a first gear set having a first driving gear  438  and a second driving gear  440 , the first and second driving gears rotating with a first shaft  442 . A second gear set in the housing rotates with, and is axially movable on, a second shaft  418 , the second gear set including a first driven gear  444  and a second driven gear  446 , the first and second driven gears  444 ,  446  being selectively axially movable into and out of engagement, respectively, with the first and second driving gears  438 ,  440 . A speed selector  420  is mounted on the housing  412  and is connected to move the axially movable gears,  444 ,  446  from a first position, wherein the first driving gear  438  engages the first driven gear  444 , to a second position wherein the second driving gear  440  engages the second driven gear  446 , whereby mutually exclusive drilling and reaming speeds are selected. It should be apparent that the same variable speed result could be achieved in an alternate embodiment, wherein a pair of driving gears could be axially positionable to engage a pair of axially stationary driven gears, which is opposite of the gear arrangement as illustrated above. 
         [0028]    Although illustrative embodiments have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure and in some instances; some features of the embodiments may be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the embodiments disclosed herein.