Tibial prosthesis extractor and method for extracting a tibial implant

An extractor for dislodging an implanted tibial prosthesis comprising substantially parallel upper and lower members joined by a yoke, with the lower member comprising a pair of forked blades to insert under the tibial component and the upper member being adapted to receive means for applying upward dislodging force.

BACKGROUND OF THE INVENTION 
The present invention concerns a novel extractor for removing an implanted 
tibial prosthesis, and in particular removal of tibial trays from the 
proximal tibia during surgical revision. 
Current methods used to remove tibial prostheses include using an osteotome 
as a lever by prying under the edge of the tibial tray. This often leads 
to chipping and cracking of the bone stock under the tray. Accordingly, 
there has been a need for a device to remove an implanted tibial 
prosthesis that does not result in these undesired effects. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide an extractor for 
dislodging an implanted tibial prosthesis having a tibial tray and stem, 
comprising substantially parallel upper and lower members joined by a yoke 
at one end; the members are sufficiently spaced by the yoke to admit the 
tibial tray there between; the lower member comprises a pair of forked 
blades for insertion between the tibial tray and the proximal end of the 
tibia, straddling the tibial stem; the upper member is adapted to receive 
means for applying upward dislodging force to the tibial tray in a 
substantially axial alignment with the tibial stem to extract the 
prosthesis from the tibia. The upper member is adapted to attach means for 
applying such dislodging force. 
The extractor is preferably provided with anchoring means for fixed 
securement to the tibial tray while the dislodging force is applied. 
Preferably, the anchoring means is a pointed screw threaded therethrough 
for engaging a plastic insert in the tibial tray. 
The invention also embraces a method of extracting the tibial implant 
having a tibial tray and stem comprising the steps of excising a layer of 
proximal tibial bone, inserting forked means into the space created 
between the tray and proximal tibial surface, straddling the stem, and 
transmitting a dislodging force to the tray through the forked member in a 
direction substantially coaxial with the stem.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of the extractor 202 of the present invention is 
shown in FIG. 1 and comprises substantially paralled upper and lower 
members 2 and 14, respectively connected by a yoke 12. The lower member 14 
has a pair of forked blades 4 and 8, which are adapted for insertion 
between the tibial tray and the proximal end of the tibia, straddling the 
tibial stem. The upper member 2 is adapted to receive means for applying 
upward dislodging force to the prosthesis. In FIG. 1 6 is an internally 
threaded well into which a male threaded means may be inserted to apply 
said dislodging force. Preferably, the extractor has anchoring means 10 
for fixedly securing the extractor to the tibial tray while the dislodging 
force is applied. The anchoring means 10 is, for example, a pointed screw 
threaded therethrough for engaging a plastic insert on the tibial tray. 
FIG. 2 shows the extractor 202 together with means 24 for applying the 
upward dislodging force which is screwed into threaded well 6. The 
dislodging force is applied by moving a sliding weight 16 upwards along 
shaft 18, thereby transmitting an impact shock to the tibial tray which 
dislodges the implanted prostheses. By employing the extractor of the 
present invention the dislodging force is applied in substantially axial 
alignment with the tibial stem, thereby most effectively breaking the 
cement bond between the prosthesis and the bone. 
FIGS. 3 and 4 illustrate the manner in which the extractor 202 is employed 
to remove a tibial prosthesis. Referring to FIG. 3, a layer of proximal 
tibial bone immediately below the tibial tray 26 is excised to create a 
space 28 into which the blades 4 and 8 are inserted so as to straddle the 
tibial stem 30. The threaded screw 10 is tightened against the tibial tray 
26. Upward dislodging force is applied to the upper member to break the 
cement bond between the tibial tray and the proximal bone, thereby 
removing the tibial prosthesis as illustrated by; FIG. 4. 
The prosthesis extractor 202 eliminates many of the problems of previously 
used removal techniques and provides a relatively simple system, yet one 
that applies the necessary impact force to dislodge such prosthesis 
without damage to the bone. 
It is a relatively uncomplicated design, offers easy manipulation and 
sterilization and is adapted for use with existing impact-providing 
devices. 
Further modifications of the invention disclosed herein will occur to 
persons skilled in the art and the invention is not limited to the 
specific embodiments described in the specification. Rather, the scope of 
the present invention is limited only by the appended claims.