The development of the Functional Capacity Index

Area of Science:

• Traumatology and Rehabilitation Medicine
• Biostatistics and Health Outcomes Research

Background:

• The Abbreviated Injury Scale (AIS) is widely used but does not directly quantify functional capacity post-injury.
• Existing scales like the Injury Impairment Scale (IIS) have limitations in reflecting long-term functional deficits.

Purpose of the Study:

• To develop and validate the Functional Capacity Index (FCI) as a measure of expected functional capacity one year after injury.
• To compare the FCI with the Abbreviated Injury Scale (AIS) and Injury Impairment Scale (IIS).

Main Methods:

• The FCI was developed through expert consensus on functional dimensions and validated by correlating scores with patient-reported outcomes and clinical assessments.
• A panel defined 10 functional dimensions and capacity levels.
• Clinical experts assigned FCI scores to AIS '90 injury descriptions.

Main Results:

• The FCI demonstrated conceptual integrity, with most injuries receiving low or zero scores, indicating minimal expected long-term impairment.
• In a cohort of 301 lower extremity fracture patients, FCI scores showed a modest correlation with observed impairment levels at one year.
• The FCI appeared to offer better discrimination of functional levels compared to AIS and IIS.

Conclusions:

• The FCI represents a novel, AIS-based approach to quantifying expected functional outcomes after traumatic injuries.
• Further empirical validation across diverse injury types and settings is recommended before widespread clinical adoption.