Combining Engineering Precision with Clinical Relevance: A Novel Dual Framework for Assessing Pedicle Screw Accuracy...

Area of Science:

• Spine Surgery
• Surgical Accuracy Metrics
• Biomedical Engineering

Background:

• Accurate pedicle screw placement is crucial in spine surgery to prevent complications like neurological injury and ensure construct stability.
• Existing methods for assessing screw placement accuracy have limitations in providing direct, quantitative, and clinically actionable feedback.
• Malpositioned pedicle screws can lead to severe patient harm and compromise surgical outcomes.

Purpose of the Study:

• To develop and validate a dual quantitative framework for assessing pedicle screw placement accuracy.
• To combine coaxiality (trajectory alignment) and pedicle wall distance (dpw, minimal distance to cortex) into a novel assessment tool.
• To compare these metrics between senior surgeons and residents to evaluate the impact of surgical experience.

Main Methods:

• Eight operators performed 240 pedicle screw insertions on synthetic spine models using freehand, CBCT-assisted, and navigation-assisted techniques.
• Predefined trajectories were compared to actual screw positions using sub-millimetric precision digitization.
• Coaxiality, dpw, and various error metrics were computed; dpw was validated against established CBCT-based classifications (Gertzbein, Heary).

Main Results:

• Coaxiality demonstrated robustness as an engineering metric, correlating significantly with entry point, target point, and orientation angle errors.
• The pedicle wall distance (dpw) metric showed near-perfect agreement with CBCT grading (Kappa=0.86), offering interpretable, millimetric feedback and detecting breaches missed by qualitative assessments.
• While senior surgeons showed minor advantages in target point and orientation errors, dpw and entry point errors did not significantly differ between experience levels.

Conclusions:

• The developed dual-metric framework, combining coaxiality and dpw, effectively bridges engineering principles with intraoperative clinical applicability.
• Coaxiality is suitable for reproducible research, while dpw provides actionable surgical feedback, enhancing the evaluation of pedicle screw placement.
• This quantitative framework offers a standardized method for assessing screw accuracy, potentially improving surgical safety, training, and patient outcomes.