Implants and implantation techniques for sacroiliac joint fusion
A sacroiliac joint implant includes an implant structure formed from an elongated base member, a forward end structure, an elongated first side member, and an elongated second side member, with an internal support structure extending in an implant plane. A fusion passage is defined in an area between the base member, first side member, and second side member. The fusion passage defines a respective open area through the implant to facilitate bone growth across the sacroiliac joint when the implant is properly implanted in the joint.
1 . An implant for effecting a fusion of an SI joint, the implant including:
(a) a base extending perpendicular to an implant longitudinal axis;
(b) a forward end structure spaced apart from the base along the implant longitudinal axis;
(c) a first side structure extending along a first side longitudinal axis;
(d) a second side structure extending along a second side longitudinal axis wherein the base, the forward end structure, the first side structure, and the second side structure are connected together and are intersected by an implant plane defined by an implant width axis and the implant longitudinal axis, wherein (i) the first side structure, second side structure, and base define a first side facing surface on one side of the implant plane and a second side facing surface on an opposite side of the implant plane, and (ii) the second side facing surface extends at an angle of between 5 and 20 degrees to the first side facing surface in a direction along the implant longitudinal axis from the forward end structure to the base;
(e) an internal support structure located in an area defined by the base, the forward end structure, the first side structure, and the second side structure; and
(f) a fusion passage defined in the area defined between the base, the forward end structure, the first side structure, and the second side structure, the fusion passage extending along a thickness axis perpendicular to the implant plane and defining a respective open area through the implant.
2 . The implant of claim 1 wherein the base forms the base of a triangle, the first side longitudinal axis defines a first lateral side of the triangle, and the second side longitudinal axis defines a second lateral side of the triangle, the triangle lying in the implant plane.
3 . The implant of claim 1 wherein:
(a) the internal support structure includes a first component and a second component;
(b) the first component comprises a first lateral beam extending transverse to the implant width axis along a first lateral beam longitudinal axis from a first lateral beam base end connected to the base to a first lateral beam forward end connected to an intermediate location of the first side structure; and
(c) the second component comprises a second lateral beam extending transverse to the implant width axis along a second lateral beam longitudinal axis from a second lateral beam base end connected to the base to a second lateral beam forward end connected to an intermediate location of the second side structure.
4 . The implant of claim 3 wherein the first lateral beam and the second lateral beam converge in a direction along the implant longitudinal axis from the forward end structure of the implant to the base.
5 . The implant of claim 1 wherein:
(a) the first side structure has a solid transverse cross-section along the entire length thereof from the base to the forward end structure; and
(b) the second side structure has a solid transverse cross-section along the entire length thereof from the base to the forward end structure.
6 . The implant of claim 1 further including:
(a) a locking element having a locking element longitudinal axis;
(b) at least one fixation device receiver formed in the locking element; and
(c) a connector arrangement operable to connect the locking element to the base in a locking position so that the base extends parallel to the locking element longitudinal axis; and
(d) the at least one fixation device receiver is configured to receive a fixation device along a receiver opening extending at an acute angle to the implant plane when the locking element is connected to the base in the locking position.
7 . The implant of claim 6 wherein:
(a) the base includes an elongated channel extending parallel to the implant width axis; and
(b) the locking element includes a projection configured to be received in the elongated channel of the base when the locking element is connected to the base in the locking position.
8 . The implant of claim 6 wherein the connector arrangement includes:
(a) at least one fastener opening through the locking element, the at least one fastener opening extending along an opening longitudinal axis perpendicular to the locking element longitudinal axis;
(b) a fastener shoulder formed in the at least one fastener opening; and
(c) a threaded opening in the base adapted to align with the at least one fastener opening when the locking element is connected to the base in the locking position.
9 . The implant of claim 1 wherein the angle of between 5 and 20 degrees is continuous along the entire extent of the first side structure and second side structure along the implant longitudinal axis.
10 . The implant of claim 1 wherein:
(a) the first side facing surface defines a first side facing surface plane; and
(b) the second side facing surface defines a second side facing surface plane.
11 . The implant of claim 1 further including a first retention feature formed on the first side facing surface and a second retention feature formed on the second side facing surface and wherein:
(a) the first retention feature comprises a number of first side ridges spaced apart along the implant longitudinal axis and extending parallel to the implant width axis; and
(b) the second retention feature comprises a number of second ridges spaced apart along the implant longitudinal axis and extending parallel to the implant width axis.
12 . The implant of claim 1 wherein:
(a) an overall length dimension of the implant along the implant longitudinal axis is approximately 10.0 millimeters to approximately 25.0 millimeters;
(b) an overall width dimension of the implant along the implant width axis is approximately 10.0 millimeters to approximately 30.0 millimeters; and
(c) a thickness of the implant as measured at the widest part thereof in the direction perpendicular to the implant plane is approximately 6.0 millimeters to approximately 14.0 millimeters.
13 . The implant of claim 1 wherein the internal support structure defines a first gap along the first side structure to provide a first additional fusion passage along the thickness axis and further defines a second gap along the second side structure to provide a second additional fusion passage along the thickness axis.
14 . A method for effecting a fusion of an SI joint, the method including:
(a) forming a sacral-side implant receiving surface in the sacral side of the SI joint, the sacral-side implant receiving surface being substantially decorticated;
(b) forming an iliac-side implant receiving surface in the iliac side of the SI joint opposite the sacral-side implant receiving surface, the iliac-side implant receiving surface being substantially decorticated, wherein the sacral-side implant receiving surface and the iliac-side implant receiving surface define an SI joint implant receiving volume for receiving an SI joint implant along a plane of the SI joint implant receiving volume; and
(c) fixing the SI joint implant in the SI joint implant receiving volume in an implanted position in which an implant plane defined by the SI joint implant aligns with the plane of the SI joint implant receiving volume, wherein the SI joint implant includes a first side facing surface on one side of the implant plane and a second side facing surface on an opposite side of the implant plane, the second side facing surface extending at an angle of between 5 and 20 degrees to the first side facing surface in a direction along the implant plane from a forward end structure of the SI joint implant to a base of the SI joint implant, and wherein the SI joint implant includes a fusion passage extending along a thickness axis perpendicular to the implant plane and defining a first opening in the first side facing surface and a second opening in the second side facing surface.
15 . The method of claim 14 wherein fixing the SI joint implant in the implanted position includes:
(a) while the SI joint implant is in the implanted position, attaching a locking element to a base of the SI joint implant; and
(b) placing at least one surgical fastener through a receiver opening of the locking element so as to extend into the sacrum or ilium.
16 . The method of claim 14 wherein the base extends perpendicular to an implant longitudinal axis and wherein the implant plane is defined by the implant longitudinal axis and an implant width axis and wherein the SI joint implant further includes:
(a) a first side structure extending along a first side longitudinal axis;
(b) a second side structure extending along a second side longitudinal axis; and
(c) an internal support structure located in an area defined by the base, the forward end structure, the first side structure, and the second side structure.
17 . The method of claim 16 wherein the base, first side structure, and second side structure are connected together so that the base defines a base of a triangle, the first side longitudinal axis defines a first lateral side of the triangle, and the second side longitudinal axis defines a second lateral side of the triangle.
18 . The method of claim 16 wherein the sacral-side implant receiving surface forms a substantially continuous sacral-side planar shape between a first lateral edge of the sacral-side implant receiving surface and a second lateral edge of the sacral-side implant receiving surface.
19 . The method of claim 16 wherein the iliac-side implant receiving surface forms a substantially continuous iliac-side planar shape between a first lateral edge of the iliac-side implant receiving surface and a second lateral edge of the iliac-side implant receiving surface.
20 . The method of claim 16 wherein the internal support structure defines a first gap along the first side structure to provide a first additional fusion passage along the thickness axis of the SI joint implant and wherein the internal support structure defines a second gap along the second side structure to provide a second additional fusion passage along the thickness axis of the SI joint implant.