Unicondylar instruments and procedures
Instrumentation and a method for unicompartmental knee replacement procedure are described. The surgical instrumentation may include a unicondylar posterior femoral cutting guide, a unicondylar tibial cutting block assembly and a unicondylar femoral cutting guide. The method may include inserting the unicondylar posterior femoral cutting guide into a joint gap while the knee is in flexion, resecting the posterior femoral condyle of the femur while the knee is in flexion, the surface of the resected posterior femoral condyle defining a reference plane, and setting the position of a unicondylar tibial cutting block on the tibia relative to the reference plane by using the resected surface of the posterior femoral condyle. The unicondylar femoral cutting guide may then be used to make one or more femoral cuts.
1 . Instrumentation for a unicondylar knee replacement procedure, comprising:
a unicondylar posterior femoral cutting guide including a guide body having an anterior guide portion and a guide base, the anterior guide portion and the guide base defining a curved inner surface dimensioned to match a curvature of a condyle of a patient's native femur, the anterior guide portion defines a slot arranged to guide a unicondylar posterior femoral cut to create a resected surface of the patient's femur;
a tibial reference guide; and
a tibial jig,
wherein the tibial reference guide comprises an anterior portion having a curved inner surface, a base extending from the anterior portion and having a flat upper surface defining a reference plane, the flat upper surface being configured to engage the resected surface of the patient's femur, and a coupling mechanism for connecting the tibial reference guide to the tibial jig,
wherein the tibial jig includes a support attachable to a tibia of a patient, an attachment formation for attaching a unicondylar tibial cutting block and a coupling member arranged to connect to the coupling mechanism, and
wherein the tibial reference guide and the tibial jig provide between them a first adjustment mechanism including a housing and an elongate member which is slidable relative to the housing to adjust the separation between the tibial reference guide and the tibial jig in a direction perpendicular to the reference plane when the tibial reference guide and tibial jig are connected together.
2 . Instrumentation as claimed in claim 1 , wherein the anterior portion defines a plurality of apertures there through for receiving respective bone pins to permit fixation of the tibial reference guide to a femur of the patient in use.
3 . Instrumentation as claimed in claim 2 , wherein the plurality of apertures comprises a first aperture, a second aperture and a third aperture, and wherein the first aperture and second aperture are parallel to each other and the third aperture is inclined relative to the first and second apertures.
4 . Instrumentation as claimed in claim 1 , wherein the first adjustment mechanism comprises a releasable lock which is operable to set the position of the elongate member relative to the housing.
5 . Instrumentation as claimed in claim 1 , wherein the housing includes a scale and the elongate member includes an indicium adjacent the scale and arranged to indicate a current separation value for a current position of the elongate member relative to the housing.
6 . Instrumentation as claimed in claim 1 , wherein the first adjustment mechanism is provided as part of the tibial reference guide.
7 . Instrumentation as claimed in claim 6 , wherein the first adjustment mechanism is attached to the base of the tibial reference guide and is positioned to the side of the rest of the tibial reference guide.
8 . Instrumentation as claimed in claim 1 , wherein the tibial reference guide and the tibial jig provide between them a second adjustment mechanism arranged and configured to adjust the varus-valgus angle of the tibial jig relative to the tibial reference guide.
9 . Instrumentation as claimed in claim 1 , wherein the tibial reference guide and the tibial jig provide between them a third adjustment mechanism arranged and configured to adjust the medial-lateral position of the tibial jig relative to the tibial reference guide.
10 . Instrumentation as claimed in claim 1 , wherein the guide base of the unicondylar posterior femoral cutting guide includes an adjustment mechanism having a plurality of gears operable to change the anterior-posterior length of the guide base, the guide base including a portion of the curved inner surface dimensioned to match a curvature of a posterior portion of the condyle of the patient's native femur.