Bone fixation system for sacroiliac joint and related methods

A bone fixation system for compression of a sacroiliac joint defined between a sacrum and an iliac bone, the bone fixation system comprising:

• a sacrum anchor that is elongate along a first central axis, the sacrum anchor having a proximal end, a distal end spaced from the proximal end along the first central axis, an external thread portion, an internal channel defined by an inner surface, the inner surface including an internal thread portion within the internal channel opposite the external thread portion, wherein the external thread portion is aligned with the internal thread portion along a radial direction that is substantially perpendicular to the first central axis;
• and
• a compression anchor configured for implantation through a bore in the iliac bone into engagement with the sacrum anchor, the compression anchor including a head having iliac-bone-engaging threads, a shaft that is elongate along a second central axis and that extends relative to the head, a cannulation that extends from the head to a distal end of the shaft, and an outer thread portion along part of the shaft, wherein the outer thread portion of the compression anchor is configured to threadably engage the internal thread portion of the sacrum anchor,
• wherein the external thread portion includes a plurality of external thread peaks and a first pitch that extends between first and second peaks of the plurality of external thread peaks, wherein the internal thread portion includes a plurality of internal thread peaks and a second pitch that extends between first and second peaks of the plurality of internal thread peaks, wherein the first pitch is greater than the second pitch,
• wherein rotation of the compression anchor about the second central axis draws the head of the compression anchor closer to or further away from the sacrum anchor when the outer thread portion of the compression anchor is threadably engaged with the internal thread portion of the sacrum anchor.