A surgical implant system comprising: a bone fastener which comprises an inner member configured for penetrating a sacrum, and an outer member including a head configured to engage an outer non-articular surface of an ilium, wherein the inner member includes an inner surface defining a first socket interface, and the head of the outer member includes an inner surface defining a second socket interface, wherein the inner member includes an outer surface comprising a distal threaded portion and a proximal threaded portion, and the outer member comprises a shaft with an internal threaded portion, and wherein the inner member is threadably engageable with and axially translatable relative to the outer member by engagement of the proximal threaded portion with the internal threaded portion; and a surgical instrument comprising: a first member defining a longitudinal axis (a) and including a drive interface which comprises a first surface defining a first drive interface and a second surface defining a second drive interface, the first drive interface being engageable with the first socket interface of the bone fastener to rotate the inner member of the bone fastener for fixation with the sacrum and the second drive interface being simultaneously engageable with the second socket interface of the bone fastener to rotate the outer member of the bone fastener with the inner member of the bone fastener; and a second member including a drive interface engageable with the second socket interface of the bone fastener to rotate the outer member independent of the inner member and to axially translate the inner member relative to the outer member such that the outer member engages an outer non-articular surface of an ilium to draw separated articular surfaces of the sacrum and the ilium into fixation. a bone fastener which comprises an inner member configured for penetrating a sacrum, and an outer member including a head configured to engage an outer non-articular surface of an ilium, wherein the inner member includes an inner surface defining a first socket interface, and the head of the outer member includes an inner surface defining a second socket interface, wherein the inner member includes an outer surface comprising a distal threaded portion and a proximal threaded portion, and the outer member comprises a shaft with an internal threaded portion, and wherein the inner member is threadably engageable with and axially translatable relative to the outer member by engagement of the proximal threaded portion with the internal threaded portion; and a surgical instrument comprising: a first member defining a longitudinal axis (a) and including a drive interface which comprises a first surface defining a first drive interface and a second surface defining a second drive interface, the first drive interface being engageable with the first socket interface of the bone fastener to rotate the inner member of the bone fastener for fixation with the sacrum and the second drive interface being simultaneously engageable with the second socket interface of the bone fastener to rotate the outer member of the bone fastener with the inner member of the bone fastener; and a second member including a drive interface engageable with the second socket interface of the bone fastener to rotate the outer member independent of the inner member and to axially translate the inner member relative to the outer member such that the outer member engages an outer non-articular surface of an ilium to draw separated articular surfaces of the sacrum and the ilium into fixation. a first member defining a longitudinal axis (a) and including a drive interface which comprises a first surface defining a first drive interface and a second surface defining a second drive interface, the first drive interface being engageable with the first socket interface of the bone fastener to rotate the inner member of the bone fastener for fixation with the sacrum and the second drive interface being simultaneously engageable with the second socket interface of the bone fastener to rotate the outer member of the bone fastener with the inner member of the bone fastener; and a second member including a drive interface engageable with the second socket interface of the bone fastener to rotate the outer member independent of the inner member and to axially translate the inner member relative to the outer member such that the outer member engages an outer non-articular surface of an ilium to draw separated articular surfaces of the sacrum and the ilium into fixation.