Pelvis registration instrument and method

1 . A pelvis registration apparatus comprising:

a body having a distal end and a proximal end, the body extending along a longitudinal axis; and

an engagement assembly coupled to the distal end of the body and comprising three or more contact points, wherein the contact points are:

selectively movable radially with respect to the longitudinal axis to position the contact points at a desired distance relative to a centerline of the body; and

selectively movable about the body to position the contact points at desired circumferential locations relative to one another:

wherein:

the engagement assembly comprises a plurality of leg linkages coupled to the body, each leg linkage providing one or more of the contact points, the leg linkages each comprising a leg member having a proximal end and an opposite, distal end;

the proximal ends of the leg members are pivotably coupled to the body about a pivot axis perpendicular to the longitudinal axis to position the distal ends of the leg members at the desired distance;

the leg linkages are rotatable about the body to selectively position the leg assemblies at desired circumferential locations;

each leg linkage further comprises a support member having a proximal end pivotably coupled to the body and a distal end pivotably coupled to an intermediate portion of the leg member; and

the body comprises an outer shaft and an inner shaft extending within the outer shaft, the proximal ends of the support member are coupled to the inner shaft; and further comprising a handle coupled to the inner shaft and threadingly engaged with the outer shaft, such that rotation of the handle causes the inner shaft to move longitudinally with respect to the outer shaft, movement of the inner shaft causing the support member to move the distal ends of the leg members radially with respect to the body.

2 . The pelvis registration apparatus of claim 1 , further comprising one or more locking mechanisms to restrict movement of the contact points relative to the body.

3 . The pelvis registration apparatus of claim 1 , wherein, for each leg linkage, the contact point is a foot pivotably coupled to the distal end of the leg member.

4 . The pelvis registration apparatus of claim 1 , wherein one of the outer shaft or handle includes sizing gradation indications thereon; and the other of the outer shaft or handle includes a line movable with respect to the sizing gradation indications to indicate sizing distances on which the feet of the leg linkages are disposed.

5 . The pelvis registration apparatus of claim 1 , further comprising a radial lock collar arranged around the body, the radial lock collar slidable with respect to the handle along the longitudinal axis and biased to a locked position preventing rotation of the handle relative to the outer shaft.

6 . The pelvis registration apparatus of claim 1 , wherein each leg linkage further comprises:

a top mount including a bracket having the proximal end of the leg member pivotably mounted thereto and a guide disc extending radially inward from the bracket, the guide disc arranged around the body and fixed with respect to the outer shaft; and

a bottom mount including a bracket having the proximal end of the support member pivotably mounted thereto and a follower disc extending radially inward from the bracket, the follower disc extending around the body and fixed with respect to the outer shaft.

7 . The pelvis registration apparatus of claim 6 , wherein the guide discs and the follower discs of the leg linkages are disposed in a stacked relation to one another along the body.

8 . The pelvis registration apparatus of claim 6 , wherein the bracket of the top mount includes one or more grip recesses for aiding in circumferential leg assembly adjustment.

9 . The pelvis registration apparatus of claim 6 , wherein the outer shaft comprises an extension tip extending distally therefrom around the inner shaft, the guide discs of the leg assemblies being disposed around the extension tip.

10 . The pelvis registration apparatus of claim 9 , further comprising a slider mounted to the extension tip distally of the guide discs, the slider configured to engage the brackets of the top mounts to prevent unwanted circumferential movement thereof.

11 . The pelvis registration apparatus of claim 9 , further comprising a circumferential lock collar arranged around the extension tip and longitudinally movable with respect thereto, the circumferential lock collar slidable with respect to the extension tip along the longitudinal axis and biased to a locked position engaging the top mounts of the leg assemblies and preventing circumferential movement of the leg assemblies relative to the extension tip.

12 . The pelvis registration apparatus of claim 11 , wherein the extension tip further comprises an outwardly extending ring portion, the ring portion configured to provide a stop surface for the circumferential lock collar when manipulated away from the locked position to allow circumferential movement of the leg assemblies.

13 . The pelvis registration apparatus of claim 11 , wherein the extension tip includes angular gradation indications therearound; and each top mount of the leg assemblies includes a pointer or protrusion shiftable along the angular gradation indications when the leg assemblies are manipulated around the body to indicate a circumferential location for each of the contact points.

14 . The pelvis registration apparatus of claim 1 , further comprising a sensor mount coupled to the body, the sensor mount configured to have a sensor removably coupled thereto.

15 . The pelvis registration apparatus of claim 1 , wherein at least one of the body or engagement assembly includes openings extending therethrough to provide access to interior surfaces thereof for cleaning.

16 . A pelvis registration apparatus comprising:

a body having a distal end and a proximal end, the body extending along a longitudinal axis;

an engagement assembly coupled to the distal end of the body and comprising three or more contact points, wherein the contact points are:

selectively movable radially with respect to the longitudinal axis to position the contact points at a desired distance relative to a centerline of the body; and

selectively movable about the body to position the contact points at desired circumferential locations relative to one another; and

acetabulum data from one or more computed tomography scans of a patient, the desired distances relative to the centerline of the body and the desired circumferential locations for the contact points of the engagement assembly being determined based on the acetabulum data.

17 . A system for use in implanting a prosthesis, the system comprising:

a pelvis registration apparatus comprising:

a body having a distal end and a proximal end, the body extending along a longitudinal axis; and

an engagement assembly coupled to the distal end of the body and comprising three or more contact points, wherein the contact points are:

selectively movable radially with respect to the longitudinal axis to position the contact points at a desired distance relative to a centerline of the body; and

selectively movable about the body to position the contact points at desired circumferential locations relative to one another;

a controller; and

first and second position sensors capable of reporting position and orientation data to the controller, the first position sensor being removably coupled to the pelvis registration apparatus and the second position sensor disposed in a fixed, spaced relation relative to the first position sensor, wherein the second position sensor is configured to be coupled to a patient's bony anatomic structure;

wherein the controller is configured to:

receive the position and orientation data from the first and second position sensors; and

calculate angular relationships derived from the position and orientation data.

18 . The system of claim 17 , wherein the bony anatomic structure is the pelvis.

19 . The system of claim 17 , wherein the angular relationships include one or more of angle of inclination or angle of anteversion.

20 . The system of claim 17 , wherein the controller is configured to calculate the angular relationships on demand.

21 . The system of claim 17 , wherein the controller is configured to calculate the angular relationships continuously in real time.