Classification of bone flap resorption after cranioplasty: a proposal for a computed tomography-based scoring system

Area of Science:

• Neurosurgery
• Radiology
• Biomaterials Science

Background:

• Bone flap resorption (BFR) is a frequent complication following autologous cranioplasty.
• A lack of standardized definitions and radiological interpretations hinders consistent BFR assessment.
• This study addresses the need for a uniform method to evaluate radiological BFR findings.

Purpose of the Study:

• To develop and validate an easy-to-use scoring system for standardizing the interpretation of radiological bone flap resorption.
• To establish a clear threshold for defining clinically relevant BFR based on radiological findings.

Main Methods:

• A three-variable scoring system (Extent, Severity, Focus) was developed based on previous literature.
• The scoring system was applied to 45 autologous cranioplasty patients.
• Independent neurosurgeons' assessments of BFR relevance were compared against the developed scoring system.

Main Results:

• A BFR score of 5 or higher was identified as the threshold for relevant BFR (grades II and III).
• Using this threshold, 36.6% of patients exhibited relevant BFR.
• Substantial agreement (κ=0.64) was found between the scoring system and neurosurgeons' relevance assessments.

Conclusions:

• The developed scoring system is easy to use and effectively standardizes BFR assessment.
• Neurosurgical consultation is recommended for cranioplasty cases with grades II and III BFR (score ≥ 5).
• Further validation in independent cohorts is necessary to confirm the general applicability of the scoring system.