PHYSICA ZUK SURGICAL TECHNIQUE
Rationale
RATIONALE The basic goals of unicompartmental knee arthroplasty are to improve limb function and to reduce pain. The development of instruments specifically designed to be used through a smaller exposure has had a significant impact on the effort to minimize disruption of the surrounding soft tissue during the procedure. Limb alignment is described by the mechanical axis of the lower extremity, which is a straight line running from the centre of the femoral head to the center of the ankle. When the center of the knee lies on this mechanical axis, the knee is said to be in neutral alignment. Unicompartmental knee disease typically reduces the joint space in the affected compartment, causing a malalignment of the joint. Full correction of the malalignment would return the knee to neutral alignment. (Fig. 1) The alignment goals for unicompartmental knee arthroplasty differ from those that are customary in an osteotomy where overcorrection is desirable to displace the weight bearing forces away from the diseased compartment. In contrast, when adjusting limb alignment in a unicompartmental procedure, it is particularly important to strive for slight under correction of the mechanical alignment to avoid overload in the contralateral compartment and heighten the potential for opposite compartment cartilaginous breakdown. Studies of unicompartmental procedures have shown that slight under correction of the limb alignment correlates to long-term survivorship. 1
Mechanical Axis
Transverse Axis
Figure 1
PHYSICA ZUK Surgical Technique 5
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