Implant system for bone fixation
An implant system for use in orthopaedic surgery for fixation of bone includes an intramedullary nail and a coupling member. The intramedullary nail includes a proximal portion defining a longitudinal axis. The proximal portion includes an axial bore defining an axis substantially parallel to the longitudinal axis of the proximal portion and a transverse bore configured to receive a bone fastener. The coupling member includes a through hole and is movably arranged within the axial bore of the proximal portion. Further, the coupling member includes a drive portion and a bone fastener engagement portion. The drive portion is in one variant non-rotatably coupled to the bone fastener engagement portion. The bone fastener engagement portion is configured to engage the bone fastener penetrating the transverse bore. In one variant the engagement is realized via an extended contact region.
1. A method of fracture fixation of a bone comprising the steps of:
inserting a guide wire into a marrow cavity of the bone;
inserting a cannulated intramedullary nail over the guide wire into the marrow cavity of the bone, wherein the intramedullary nail comprises a proximal portion defining a longitudinal axis, wherein the proximal portion includes an axial bore defining an axis substantially parallel to the longitudinal axis of the proximal portion and a transverse bore configured to receive a bone fastener; and a coupling member with a through hole movably arranged within the axial bore of the proximal portion of the intramedullary nail, the coupling member including a drive portion and a bone fastener engagement portion, wherein the drive portion and the bone fastener engagement portion each have a proximal extent and a distal extent, the distal extent of the bone fastener engagement portion defining a planar surface perpendicular to a central axis of the coupling member, the bone fastener engagement portion having a rounded edge intersecting the planar surface, the rounded edge defining a convex curvature, wherein the through hole extends through the bone fastener engagement portion and drive portion and through the proximal and distal extents thereof, the drive portion is non-rotatably coupled to the bone fastener engagement portion, and the guide wire extends through the drive portion and bone fastener engagement portion via the through hole after the cannulated intramedullary nail is inserted into the marrow cavity;
removing the guide wire;
inserting a bone fastener through the transverse bore of the intramedullary nail into the bone for stabilization of the bone fracture, the bone fastener having a longitudinal groove in an exterior thereof, the longitudinal groove defining a concave curvature complementary to the convex curvature of the rounded edge of the bone fastener engagement portion; and
driving the coupling member so that the rounded edge is received within the longitudinal groove for producing an engagement of the bone fastener engagement portion with the bone fastener penetrating the transverse bore of the intramedullary nail, thereby preventing rotation of the bone fastener.
2. The method of claim 1 , wherein only a portion of the rounded edge is received within the longitudinal groove.
3. The method of claim 1 , wherein the rounded edge is curved in a sagittal plane, the central axis of the coupling member lying in the sagittal plane.
4. A method of fracture fixation of a bone comprising the steps of:
inserting a guide wire into a marrow cavity of the bone;
inserting a cannulated intramedullary nail over the guide wire into the marrow cavity of the bone, wherein the intramedullary nail comprises a proximal portion defining a longitudinal axis, wherein the proximal portion includes an axial bore defining an axis substantially parallel to the longitudinal axis of the proximal portion and a transverse bore configured to receive a bone fastener; and a coupling member with a through hole movably arranged within the axial bore of the proximal portion of the intramedullary nail, the coupling member including a drive portion and a bone fastener engagement portion, wherein the through hole extends through the bone fastener engagement portion and drive portion, the bone fastener engagement portion includes a planar surface facing a distal direction and is perpendicular to a central axis of the coupling member, and a rounded edge intersecting the planar surface and configured to engage a bone fastener penetrating the transverse bore, and the guide wire extends through the drive portion and bone fastener engagement portion via the through hole after the cannulated intramedullary nail is inserted into the marrow cavity;
removing the guide wire;
inserting a bone fastener having a longitudinal groove through the transverse bore of the intramedullary nail into bone for stabilization of the bone fracture; and
driving the coupling member so that the rounded edge is eccentrically received within the longitudinal groove for producing an engagement of the bone fastener engagement portion with the bone fastener penetrating the transverse bore of the intramedullary nail via the rounded edge, thereby preventing rotation of the bone fastener.
5. The method of claim 4 , wherein the longitudinal groove is defined by a rounded inner surface of the screw, the rounded inner surface having a substantially equal curvature to that of the rounded edge of the bone fastener engagement portion.
6. The method of claim 4 , wherein the rounded edge is curved in a sagittal plane, the central axis of the coupling member lying in the sagittal plane.