Patient-specific guides for minimally invasive sacroiliac joint fusion revision surgery

• Novel patient-specific guide for minimally invasive SI joint fusion revision surgery. • Guide positioning is based on previously placed implants; no bone seating is required. • Non-parallel implant positioning beyond traditional parallel configuration. • Non-parallel is favorable, especially if there is limited space in the SI joint. • Accuracy was evaluated using 3D positional and angular measurements. Implant loosening or persistent pain after sacroiliac joint fusion or stabilization surgery may require revision surgery. Accurate and safe implant placement in minimally invasive sacroiliac joint fusion (SIJF) revision surgery is challenging due to limited visibility and restricted space for new implants. A patient-specific guide (PSG) allows customization of implant positioning beyond the traditional parallel configuration generally used in SIJF but has only been applied in open procedures requiring bone exposure. This study presents the implementation and evaluation of a novel PSG for minimally invasive SIJF revision surgery in patients with prior SI fusion or stabilization surgery. A retrospective cohort study was conducted to evaluate implant placement accuracy using a novel PSG. The guide design was iteratively refined to enhance rigidity and placement accuracy. Postoperative implant positions were compared to the planned positions using 3D deviation analysis. Furthermore, implant malpositioning and other complications were monitored. Fourteen SIJF revisions were performed, comprising a total of 23 newly placed implants. Implant positioning using PSGs was feasible in all cases, and all implants were placed without malpositioning complications. Accuracy analysis showed a median 3D total positional deviation of 5.3 mm (Q1: 4.8 mm, Q3: 8.3 mm) and a median total 3D angle of 3.7° (Q1: 2.4°, Q3: 5.2°). The study showed that the developed PSG design for use in minimally invasive SIJF revision surgery is feasible with what is considered a clinically acceptable level of accuracy.