Influence of the Fluoroscopy Setting towards the Patient When Identifying the MPFL Insertion Point

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Femoral tunnel malposition in medial patellofemoral ligament (MPFL) reconstruction is a leading cause of revision surgery.
• Incorrect tunnel placement can alter graft length and increase patellofemoral joint pressure.

Purpose of the Study:

• To investigate if intraoperative fluoroscopy positioning affects femoral tunnel accuracy in MPFL reconstruction.
• To evaluate the impact of image receptor distance and direction on determining the correct femoral origin of the MPFL.

Main Methods:

• 3D-printed femurs from CT scans were used to simulate MPFL reconstruction.
• True-lateral fluoroscopies were performed at different image receptor distances (25 cm and 5 cm) and directions (lateral-to-medial and medial-to-lateral).
• MPFL femoral origin points were determined using the Schöttle et al. method and compared across different fluoroscopic setups.

Main Results:

• Determining the MPFL origin in a 5 cm medial-to-lateral view resulted in a significant distal and posterior shift (5.3 mm) when checked in a 25 cm lateral-to-medial view.
• Conversely, determining the origin in the 25 cm lateral-to-medial view and rechecking in the 5 cm medial-to-lateral view caused an anterior and proximal shift (4.8 mm).
• Variations in femur positioning (distal, proximal, superior, inferior) did not significantly influence the results.

Conclusions:

• Fluoroscopy positioning is critical for accurate femoral tunnel placement in MPFL reconstruction.
• Surgeons must consider the fluoroscopy's position relative to the image receptor, not just a true-lateral view, to avoid MPFL graft malposition.
• Attention to fluoroscopic angulation is crucial for successful MPFL reconstruction outcomes.