Reference marker stability in computer aided orthopedic surgery: a biomechanical study in artificial bone and...

Area of Science:

• Orthopaedic Surgery
• Biomedical Engineering
• Surgical Navigation Systems

Background:

• Accurate computer-assisted orthopaedic surgery relies on rigid fixation of Reference Marker (RM) systems.
• RM system shifts can cause significant registration errors and navigation inaccuracies.
• Limited data exists on the comparative stability of different RM systems.

Purpose of the Study:

• To evaluate and compare the rotational stability of three commonly used Reference Marker (RM) systems.
• To determine the influence of anatomical site and fixation type on RM stability.

Main Methods:

• Tested rotational stability of Schanz' screw (RM A), RM B, and RM C systems.
• Utilized 130 Synbones and 15 cadavers with a specialized testing device.
• Assessed peak torque in various anatomical locations, including femoral shaft, distal femur, tibial shaft, proximal tibia, anterior superior iliac spine, iliac crest, and talus.

Main Results:

• RM C exhibited the highest stability (mean peak torque 5.60 Nm), followed by RM B (2.53 Nm) and RM A (0.77 Nm) in Synbone tests (p<0.01).
• Stability order by anatomical site: femoral shaft > distal femur > tibial shaft > proximal tibia > anterior superior iliac spine > iliac crest > talus.
• Bicortical fixation was more stable than unicortical fixation in the femur (p<0.01) but not the tibia (p=0.22). Cadaver results mirrored Synbone findings.

Conclusions:

• Reference Marker (RM) system stability is critical for accurate computer-navigated surgery.
• Surgeons should consider the relative stability of RM systems and the anatomical site of placement.
• Bicortical fixation generally offers superior stability compared to unicortical fixation.