Patella resection drill and prosthesis implantation device

A patella resection and replacement device comprising a pliers-like clamp for gripping and holding the patella, the clamp having a spring biased hinge bolt. A specially designed drill guide may be snapped into place and removed from the hinge bolt without releasing the patella during surgery. Similarly, a specially designed patella button presser may be snapped into place and removed from the hinge bolt. Without the necessity of releasing, re-gripping and re-orienting the patella during the process, the time for the operation is greatly reduced.

The present invention is directed to a pliers-like device for performing 
surgery on the patella, commonly known as the knee cap. Specifically, the 
device is a patella resection and replacement clamp for holding the 
patella while removing the damaged articulating surface and replacement 
thereof with a prosthesis, also known as a patella button. 
BACKGROUND OF THE INVENTION 
The patella is a sesamoid of lens shaped bone which slides in a groove 
between the condyles of the femur. Its function is to increase the 
efficiency of the quadriceps muscle by shifting the line of action of the 
muscle's pull forward. As the knee articulates, the muscles and tendons 
force the patella toward the condyles of the femur. Consequently, there is 
considerable relative motion between the patella and the other bones 
comprising the knee joint. 
Because of aging, disease or sporting activities, the articulating surfaces 
of the knee may degrade. To treat certain pathologies, it has become 
common to surgically remove the condyles and replace these structures with 
prosthetic implants. By the same processes, the articulating surfaces of 
the patella may also be replaced. Because of the tendons connected to the 
patella, it is generally advisable to replace only the articulating 
surface. A patella button made of ultra high molecular weight polyethylene 
with an articulating surface, with or without a metal base plate has been 
used to replace the posterior or interior side of the patella, adjacent 
the femoral condyles. To implant such a prosthesis, the posterior surface 
of the patella is resected to produce a flat surface on which the 
prosthesis can be mounted. 
The process of cutting, drilling and replacing the damaged surface of a 
patella is complex, awkward and time consuming. The process requires three 
separate basic steps: 
1) Resecting or removing the damaged posterior articulating surface of the 
patella; 
2) providing means in the resected patella for receiving the prosthesis; 
and 
3) attaching the prosthesis to the resected and prepared patella. 
To accomplish these three steps, several separate devices are employed. 
These include a device for firmly holding the patella to expose its 
posterior surface; a saw; a saw guide to control the portion of the 
patella that is to be removed; a drill to provide means to attach the 
implant securely; a drill guide to control the placement and depth of the 
means for attaching the prosthetic implant; and a device to insert the 
prosthesis and press the prosthesis into place. This latter device ensures 
that the attachment of the prosthesis with the resectioned patella is 
secure. 
Devices for such a process have been developed and described. In 
particular, clamp-like patella resection and replacement devices have been 
described in U.S. Pat. Nos. 4,633,862; 5,002,547; 5,108,401; 5,129,908; 
5,147,365; 5,542,947; 5,716,360; and 5,716,362. 
U.S. Pat. No. 4,633,862 described two clamps: one to resection and drill 
holes in the patella and one to insert and press the prosthesis into 
place. Tongue members were provided on the first clamp for controlling the 
depth for resection of the patella. After which, the patella was released 
for the mounting of a drill guide onto the clamp. The drilled patella was 
again released, and a second clamp provided with a plunger was used to 
insert, press and cement the prosthesis to the cut patella. 
The clamps that are in use or known are quite bulky and awkward to use. 
Moreover, at each step of the process, the patella must be released for 
the detachment and installation of the various implements, such as the saw 
guide and the drill guide, and the use of the second clamp for the 
implanting the prosthesis. These maneuvers necessitate the re-positioning 
and re-orientation of the patella at each of the step of the process. For 
this reason, the process for resection and replacement of a patella is not 
efficient. 
U.S. Pat. No. 5,002,547, disclosed a total of 14 different devices for 
surgery of the knee. Among which, a clamp with separately mountable 
modular patella resection guide, drill guide and prosthesis attachment was 
shown. The prong members of the clamp were provided with a quick 
disconnect mechanism for attaching separately a resection guide, a drill 
guide and a prosthesis presser. Because of the need to mount the resection 
guide, the drill guide and the prosthesis presser on the prong members of 
the clamp, it is still necessary to re-position and re-orient the patella 
with the clamp at each step. 
A pliers-like device with jaw members for holding a patella securely for 
resection is described in U.S. Pat. No. 5,108,401. The device was provided 
with an elevator member to engage the anterior surface of the patella held 
at a predetermined distance between the elevator member and the jaws 
members to ensure that the cut is made at an appropriate thickness. There 
is no description of a drill guide or a presser for securing the patella 
prosthesis to the resected patella. This means that additional implements 
would be needed for drilling the patella and for implanting the 
prosthesis. 
U.S. Pat. No. 5,129,908 disclosed a clamp for holding and reaming a patella 
to provide a centrally raised portion for fixation of a prosthesis. The 
clamp was provided with a C-like jaw member and an L-shaped jaw member. 
The C-shaped jaw member has a spiked platform for engaging and holding the 
anterior surface of the patella with a reamer guide detachably connected 
to a plunger mounted on another arm of the C-shaped jaw member. The 
distance of the reamer guide from the platform was adjustable to 
accommodate patellas of different sizes. In this device, a reamer is used 
to remove a portion of the posterior surface of the patella in a rotary 
manner. The position of a reamer guide controls the depth to which the cut 
is made. The '908 patent further disclosed a drill guide added to the 
reamer guide. The Petersen '908 patent does not include presser clamp or 
device for the implantation of a prosthesis. 
U.S. Pat. No. 5,147,365 also disclosed a pliers-like device for clamping 
and guiding a sagittal saw for the resection of a pre-determined portion 
of the patella. A rotating, calibrated stylus measures the position of the 
patella with respect to the integral sagittal saw. Capture slots are 
provided in each of the jaw members through which the sagittal saw may be 
mounted. The stylus and a draw bar served as a saw guide. The stylus and 
draw bar assembly comprised a scale bushing which fits through bores 
provided at the fulcrum of the clamp. The stylus arm carried a scale post, 
which could be adjusted vertically. This enables the surgeon to determine 
the precise amount of the patella, which is to be removed. There is no 
disclosure of a drill guide or a prosthesis presser. 
U.S. Pat. No. 5,542,947 disclosed a clamp with a resection guide and stylus 
for the patella. The clamp was provided with a pair of tooth-edged jaw 
members for holding the patella. A plurality of calibrated and marked 
slots located at different fixed predetermined heights above the resection 
level is integrally formed on the jaw members. Each slot was provided with 
a saw blade insertion guide and a removably attachable stylus. The stylus 
is employed to select the slot for setting the resection depth. After the 
slot was selected and the saw blade inserted, the stylus may be detached 
to provide more visibility for the surgeon. The clamp was provided with a 
spring biased pivot to maintain the jaw members in a closed position and 
an adjustable locking means on the handles to lock the relative position 
of the jaw members. There is no disclosure of a drill guiding clamp nor a 
prosthesis presser clamp. 
U.S. Pat. No. 5,716,360 described an instrument to resection a patella into 
different shapes: oval, tri-oval, or elliptical to receive a patella 
prosthesis of like shape. The patented device was a clamp with up-and-down 
jaw members for gripping the patella firmly for resection. It is clear 
that the resection instrument described in the '360 patent device is 
different from the present invention. 
U.S. Pat. No. 5,716,362 described a patella-milling instrument having a 
base member with a handle assembly. A clamping element was slidably 
mounted on the base component. The support arm of a milling tool was 
slidably mounted on a post extending perpendicularly from the base member. 
The driving motor for the milling tool is mounted at the end of the arm to 
rotate the milling tool, or move it up and down. The '362 patent does not 
describe a clamp that is useful for drilling holes in the resected patella 
nor for pressing the patella prosthesis to engage with the resected 
patella. 
The problems encountered in connection with the use of existing devices, 
generally known as "patella clamps" are several. 
Many of the existing devices for patella replacement surgery are in the 
form of plier-like clamps. The clamp is used to securely hold the patella 
during surgery. The clamp is provided with a saw guide to ensure that the 
depth of the resection is appropriate and the resulting cut surface is 
even. After the damaged articulating posterior portion of the patella is 
removed, holes are drilled into the resectioned patella to receive the 
posts provided on the patella button. To ensure that the size and depth of 
the drill hole is appropriate, another clamp is provided with a drill 
guide or a drill guide attachable to the clamp jaw members is used. 
The use of another clamp or the attachment of a drill guide to a clamp jaw 
member of a patella resection and replacement device requires the release 
and re-clamping of the patella. After the holes are drilled, the patella 
button or prosthesis is placed against the resectioned surface of the 
patella with its posts engaging the holes drilled into the resectioned 
patella. The prosthesis is pressed against the patella to ensure a tight 
fit of the posts into the drilled holes and to cement the surface of the 
prosthesis to the cut patella. In this step, the patella is again released 
from the clamp and a patella clamping or pressing device ("the prosthesis 
presser") is used. The release and re-clamping of the patella means that 
the position of the patella needs to be re-oriented at the beginning of 
each step of the operation. 
Furthermore, most of the existing patella clamps are rather large and 
bulky. When in use, the device blocks the surgeon's view and prevents 
physical access to the joint. This is a particularly acute problem when 
the patella prosthesis is being cemented and pressed into the resected 
patella. The surgeon must wait until the prosthesis is cemented into place 
before continuing with the operation, thereby causing delay. Moreover, 
some of the existing patella presser clamps are provided with rather long 
handles to improve the mechanical advantage. However, this increases the 
risks of fracturing the patella during the operation, a very undesirable 
occurrence. 
OBJECTIVES OF THE INVENTION 
It is an objective of the present invention to provide a device for the 
resection, drilling and replacement of a patella which is simpler, less 
cumbersome, easier to use and does not block the surgeon's view during the 
operation. 
It is a further objective of the present invention to provide a pliers-like 
device with snap in means for resection, drill and prosthesis replacement 
without the need for releasing the patella at each step of the process. 
It is also another objective of the invention to provide a combination 
patella resection and replacement device without the need for using 
multiple implements. 
SUMMARY OF THE INVENTION 
The present invention provides a pliers-like device for the resection and 
implantation of a patella button prosthesis comprising: 
a) a top and a bottom combination prong and handle members with a fulcrum 
therebetween and having a posterior and anterior surface, the prong and 
handle members being pivotably mounted in relation with one another at the 
fulcrum with a hinge bolt, said hinge bolt extending through holes at the 
fulcrum and having a rotatably adjustable knob thereon to maintain a set 
distance from the posterior surface of the top prong and handle member; 
b) means along the inner edges of the prong members for firmly holding the 
periphery of a patella, with the posterior surfaces of the prong members 
defining the plane along which the patella is to be resected; 
c) a locking device at the ends of the handle members opposite the prong 
members to enable locking of the prong members to maintain a firm hold 
around the periphery of the patella; 
d) a tongue member attached to a prong member near the fulcrum of the 
device and positioned between the prong members and at a predetermined 
distance from the anterior surface of the prong members for engaging the 
anterior surface of the patella thereby controlling the depth to which the 
patella is to be resected; 
e) a drill guide consisting of a member having holes therethrough with an 
attached slotted member, the slot being of a suitable width and thickness 
to be slidably insertable between and removable from the knob of the hinge 
bolt and the posterior surface of the top handle member and to fit snuggly 
around the post of the hinge bolt; and 
f) a patella button presser consisting of an S-shaped bar having at one end 
a slotted tongue member and at the opposite end a hole with a bolt 
inserted therethrough with means to control the up-and-down movement of 
the bolt through the hole, the tip of the bolt having a platen movably 
mounted thereon, the platen having a concave surface for engaging the 
convex surface of the patella button, and said patella button presser 
being slidably insertable between and removable from the hinged bolt knob 
and the posterior surface of the top handle member.

DETAILED DESCRIPTION OF THE INVENTION 
A preferred embodiment of the patella resection and replacement device of 
the present invention is shown in FIGS. 1-5. 
The device of the present invention is a pliers-like clamp having a pair of 
combination prong (12,14) and handle (11,13) members pivotally mounted 
with a hinge bolt, preferably spring-biased, (15) in relation with one 
another. One of the prong and handle member is mounted on top and the 
other prong and handle member is mounted on the bottom. FIG. 1 shows the 
posterior side of the clamp device. 
The inner edges of the prong members (12,14) are provided with means to 
securely hold the periphery of the patella. The means may be in the form 
of tines spaced apart at the edge (19) as shown in FIG. 1. The number of 
tines may be varied as needed. Alternatively, the inner edges of the prong 
members may be provided with a saw-toothed edge (23) to provide the 
desired hold. The distance between the prong members are generally 
maintained in an open position by hinge means installed with the hinge 
bolt. 
Locking means is provided at the handle end to maintain a desired distance 
between the prong members. An example of the locking means is a rachet 
mounted at the end of the handle members as shown in FIGS. 1 & 2. A leaf 
spring (17) is attached fixedly to handle (13) by means of a press-fit pin 
or welding. The rachet consists of a leaf spring biased saw-toothed plate 
(16) mounted at the end of one handle member engaging a sharp indented 
edge at the end of the other handle member (11). The device is normally 
held in an open position by the hinge bolt, which is preferably 
spring-biased. 
As the handle of the device is compressed the distance between the prong 
members is reduced, the engagement of the indented edge at the end of one 
handle member with a tooth on the saw-toothed plate mounted on the other 
handle member locks the position of the device. By pulling on the end of 
the saw-toothed plate, the locking means is released. The leaf spring (17) 
for holding the saw-toothed plate is welded to the bottom handle member 
(13) and together with bolt (22) maintains the saw-toothed plate at an 
angle, preferably less than 90.degree., to the handle member (13). 
A tongue member (21) is attached fixedly by welding means or a bolt (20) to 
a prong member (12) at a site near the fulcrum of the device and 
maintained midway between the prong members (12,14) at a predetermined 
distance from the anterior surface of the prong members. The distance of 
the tongue member (21) from the surfaces of the prong members determines 
the depth to which the patella is resected. 
In operation, the patella is held firmly in place with the tines or the 
teeth on the prong members around the periphery of the patella. Squeezing 
the handle members until the patella is securely held locks the position 
of the clamp. The patella is then turned 180.degree. with the clamp to 
expose its posterior surface. With the anterior surface of the patella 
abutting the tongue member, the side of a sagittal saw is held firmly 
against the posterior surfaces of the prong members to provide a planar 
smooth and even surface as a saw guide when removing a portion of the 
posterior of the patella. The depth of the cut is controlled by the 
distance of the tongue member from the plane of the prong members. 
After the patella is resected, a drill guide (30) is inserted between the 
hinged bolt pivotally holding the pair of prong and handle members. It is 
to be noted that there is no need to release and re-orient the patella in 
order to insert the drill guide. The drill guide comprises a member (32), 
preferably circular or trifoliated as shown in FIGS. 3 and 4, having 
apertures (33) spaced thereon for guiding the placement of the drill holes 
and a slotted tongue member (31). The drill guide is of sufficient 
thickness to control the depth of the drill hole and be slidably 
insertable between the knob of the hinge bolt and the surface of the prong 
and handle member. The slotted tongue is of sufficient width to fit 
snuggly around the post (24) of the hinge bolt (15). The drill guide is 
positioned over the cut surface of the patella (100) and the knob (15) is 
adjusted to securely hold the drill guide (30) in place. The holes are 
drilled into the resected patella (100) to correspond to the post 
positions provided on the patella button (200). Generally, commercially 
available patella buttons are provided with a central post or three posts 
spaced around the center. 
After the holes are drilled, the drill guide is removed from the hinge 
bolt, without releasing the patella. The patella button (200), with a 
coating of cement over its flat surface and post(s), is placed over the 
resected patella (100) with the position of its post(s) inserted into the 
hole(s) made. The patella button presser (50) is inserted between the 
hinge bolt knob (15) and the surface of the clamp (10). The bolt (52) of 
the patella button presser is positioned over the patella button (200). 
The patella button presser (50) comprises an S-shaped bar (51) and a platen 
(54) swivably attached at the bottom tip of a bolt (52) mounted through a 
hole at one end of the S-shaped bar. The phrase "swivably attached", means 
that the platen is attached to the bottom tip of the bolt in such a manner 
that the platen can swivel and tilt. The bolt is provided with means to 
control its up-and-down movement through the hole. One way of controlling 
the up-and-down movement is by means of a threaded bolt mated to a 
threaded hole at one end of the S-shaped bar. At the other end of the 
S-shaped bar is provided with a slotted tongue similar to that of the 
drill guide. The bottom tip of the bolt (52) is provided with a cavity. If 
the bolt is threaded, the distance between the threaded portion (53) and 
the bottom of the threaded bolt is preferably more than the thickness of 
the S-shaped bar. 
The platen comprises a round disc preferably made of an autoclavable 
thermoplastic resin such as polyacetal, available as DELRIN.RTM. (E.I. du 
Pont de Nemours, Inc.) with a central post (55). The post on the platen 
(55) is swivably attached to the cavity at the bottom tip of the bolt, the 
edges of the post being rounded. The post is rotatably held to the rim 
around the cavity by a press fit pin (56). The platen can swivel and tilt 
at an angle of approximately +/-5.degree. as shown in FIGS. 7A and 7B. 
This feature enables the platen to align itself with the patella button. 
Alternatively, the cavity at the bottom tip of the bolt is provided with a 
rim around the perimeter thereof. The central post (55) of the platen is 
topped with a knob (57). The knob snap-fits into the cavity of the bolt 
and is held in place by the rim around the perimeter of the cavity. The 
sides of the central post are curved to enable the platen to swivel and 
tilt in the cavity. Once the platen is attached, it is preferable that it 
cannot be removed from the tip of the bolt. The surface of the platen (54) 
is concave to provide close contact with the convex posterior surface of 
the patella button (200). By turning the knob on the threaded bolt, the 
post(s) of the patella button is gently pushed into the hole(s) in the 
resected patella and the flat surfaces of the patella button and the 
resected patella abut each other intimately. See FIGS. 11 and 12. After 
the cement has set, the patella button presser can then be removed from 
the clamp; the locking means released and the patella gently positioned 
into the condyles of the femur. 
As described in detail above, the clamp device of the present invention is 
simpler in construction. It is made of surgical steel optionally with a 
thermoplastic resin such as DELRIN.RTM., a polyacetal, and can be 
autoclaved at a temperature of about 121.degree. C. without being 
deformed. The most important feature of the present invention is that the 
resection, drilling and replacement of the process can be made by clamping 
the patella, turning it around to expose the posterior surface in one 
maneuver. There is no need to release the patella after every single step 
in order to proceed to the next step. By designing and structuring the 
clamp to accept the drill guide and the patella button presser and 
designing the drill guide and the patella button presser in such manner to 
allow these implements to be snapped into place easily. With the clamp of 
the present invention, there is much less maneuvering of the patella 
during the entire patella resection and replacement process. It is to be 
noted that the exposed patella with the blood and body fluids is quite 
slippery. Thus, to re-clamp and re-invert the patella takes quite a bit of 
time. By avoiding the multiple times when the patella has to be released, 
re-clamped and re-oriented during the surgical process, the time needed 
for the process using the clamp of the present invention is much reduced, 
a very important consideration for both the surgeon and the patient. 
The above is a description of the preferred embodiments of the patella 
resection and replacement device of the present invention. Variations and 
modifications of the preferred embodiments may be made without departing 
from the spirit of the present invention. The above is an illustration of 
the invention and is not intended to limit the scope thereof.