Augmented reality for intraoperative verification of surgical template placement

Patient-specific templates (STs) are widely adopted to guide drilling and cutting in orthopaedic procedures. Their intraoperative placement typically relies on visual and tactile assessment, without feedback on positioning accuracy. This work proposes a minimal, low-cost augmented reality (AR) method for intraoperative verification of template placement, designed for the brief and constrained nature of this task.

A miniature camera is rigidly mounted on the surgical template and preoperatively calibrated. During placement, live images are augmented with virtual renderings of the patient's bone model, generated from preoperative CT/MR data and displayed from the same fixed viewpoint. Correct alignment occurs only when the template reaches its planned pose, without requiring tracking systems, registration procedures, or head-mounted displays. Template placement was evaluated on a patient-specific phantom by thirteen participants, with and without AR guidance. Feasibility was further assessed through ex vivo tests on animal tissue involving seven users.

In phantom experiments, AR guidance was associated with improved placement accuracy (mean error 2.23 mm vs. 3.62 mm without AR, p = 0.0093). In ex vivo trials, all AR-guided osteotomy lines remained within ±2 mm of the planned trajectory suggesting experimental feasibility. However, the difference between conditions did not reach statistical significance.

Current literature lacks simple, inexpensive, and workflow-compatible methods for verifying the placement of surgical templates. The proposed approach may provide a simple method for intraoperative visual feedback without tracking hardware or complex AR systems, potentially supporting more consistent template positioning. However, its effectiveness may depend on surgical exposure and anatomical context.