Surgical instrument and method
An adjustable spacer instrument, kit of parts and surgical methods of use in a knee arthroplasty procedure are described. The adjustable spacer comprises a first member having a substantially planar upper surface and a second member having a substantially planar lower surface. An angular adjustment mechanism is interposed between the first member and the second member, and is operable to adjust the degree of tilt between the upper surface and the lower surface. A releasable lock is provided which can maintain the degree of tilt. The spacer instrument can be used with the knee in extension or flexion to allow various cuts or re-cuts to be made to the tibia or femur while the ligaments are in balance or to balance the ligaments.
1. A method for carrying out a knee arthroplasty procedure, comprising:
resecting the proximal part of the tibia or the distal part of the femur to produce a substantially flat bone surface;
placing an adjustable spacer instrument having an upper surface and a lower surface on the flat bone surface in a gap between the tibia and the femur;
operating the adjustable spacer instrument to vary the degree of tilt between the upper surface and the lower surface; and
assessing the balance of ligaments of the knee;
wherein operating the adjustable spacer instrument includes rotating the upper surface relative to the lower surface of the adjustable spacer instrument about an axis extending in a superior-inferior direction to vary the degree of tilt.
2. The method of claim 1 , and further comprising:
attaching a cutting block having a cutting guide to the adjustable spacer instrument, wherein the cutting guide is parallel to the upper or lower surface of the adjustable spacer; and
using the cutting guide to resect at least part of the proximal part of the tibia or the distal part of the femur not already resected.
3. The method of claim 2 , wherein the knee is in extension when the cutting guide is used to resect at least part of the proximal part of the tibia or the distal part of the femur.
4. The method of claim 1 , wherein both the proximal part of the tibia and the distal part of the femur are resected to produce substantially flat bone surfaces, and further comprising:
attaching a cutting block having a cutting guide to the adjustable spacer instrument, wherein the cutting guide is parallel to the upper or lower surface of the adjustable spacer; and
using the cutting guide to re-cut the already resected proximal part of the tibia or the distal part of femur.
5. The method of claim 4 , wherein the knee is in extension when the cutting guide is used to re-cut the already resected proximal part of the tibia or the distal part of femur.
6. The method of claim 1 , wherein the knee is in extension when assessing the balance of ligaments of the knee.
7. The method of claim 1 , wherein the knee is in flexion when assessing the balance of ligaments of the knee.
8. The method of claim 7 , wherein the proximal part of the tibia is resected and wherein operating the adjustable spacer instrument also rotates the femur relative to the tibia.
9. The method of claim 8 , and further comprising:
attaching a cutting block having a cutting guide to the adjustable spacer instrument, wherein the cutting guide is parallel to the lower surface of the adjustable spacer; and
using the cutting guide to resect an anterior part and/or a posterior part of the femur.