Surgical instrument and method of positioning an acetabular prosthetic component

1. An orthopaedic surgical instrument for positioning an acetabular prosthetic component in a patient's surgically-prepared acetabulum, the instrument comprising:

a base including a plurality of mounting legs configured to engage the patient's pelvis,

a first linkage pivotally coupled to the base, the first linkage including a spirit level,

a locking mechanism operable to lock the first linkage in position relative to the base,

a second linkage removably coupled to the first linkage, the second linkage having an alignment axis corresponding to a desired abduction angle and a desired anteversion angle of an acetabular axis of the acetabular prosthetic component, and

a shaft configured to be secured to the acetabular prosthetic component, the shaft having a longitudinal axis that is coincident with the acetabular axis of the acetabular prosthetic component when the acetabular prosthetic component is secured thereto,

wherein the second linkage includes a parallelogram linkage configured to maintain the acetabular axis of the acetabular prosthetic component parallel with the alignment axis of the second linkage, and the parallelogram linkage includes a mount configured to receive the shaft such that the longitudinal axis extends parallel to the alignment axis.

2. The orthopaedic surgical instrument of claim 1 , wherein each mounting leg includes a telescopic shaft and a mounting foot configured to engage the patient's pelvis.

3. The orthopaedic surgical instrument of claim 2 , wherein the mounting feet include a pair of mounting feet configured to engage the patient's anterior superior iliac spines of the patient's pelvis and a pair of mounting feet configured to engage the pubic tubercles of the patient's pelvis.

4. The orthopaedic surgical instrument of claim 1 , wherein the base includes a frame and each mounting leg is pivotally coupled to the frame.

5. The orthopaedic surgical instrument of claim 1 , further comprising a plurality of second linkages, each second linkage having an alignment axis different from the alignment axis of every other second linkage.

6. The orthopaedic surgical instrument of claim 1 , wherein the second linkage includes:

a first adjustment mechanism operable to move a first arm of the second linkage such that the alignment axis corresponds to a second abduction angle, and

a second adjustment mechanism operable to move the first arm such that the alignment axis corresponds to a second anteversion angle.

7. The orthopaedic surgical instrument of claim 1 , wherein:

the base includes a first mount positioned on a medial side of the base and a second mount positioned on a lateral side of the base, the first mount and the second mount being configured to be coupled to the first linkage, and

the first linkage is pivotally coupled to the first mount.

8. An orthopaedic surgical instrument for positioning an acetabular prosthetic component in a patient's surgically-prepared acetabulum, the instrument comprising:

a base configured to engage the patient's pelvis,

a first linkage coupled to the base, the first linkage including a gravity-based indicator,

a locking mechanism operable to lock the first linkage in position relative to the base,

a second linkage coupled to the first linkage, the second linkage having an alignment axis corresponding to a desired abduction angle and a desired anteversion angle of an acetabular axis of the acetabular prosthetic component, and

a shaft configured to be secured to the acetabular prosthetic component, the shaft having a longitudinal axis that is coincident with the acetabular axis of the acetabular prosthetic component when the acetabular prosthetic component is secured thereto,

wherein the second linkage includes a parallelogram linkage configured to maintain the acetabular axis of the acetabular prosthetic component parallel with the alignment axis of the second linkage, and the parallelogram linkage includes a mount configured to receive the shaft such that the longitudinal axis extends parallel to the alignment axis.