Lumbar Stiffness Disability Index: pilot testing of consistency, reliability, and validity

Area of Science:

• Spine surgery outcomes research
• Patient-reported outcome measures
• Orthopedic biomechanics

Background:

• Surgical arthrodesis aims to reduce pain and deformity by eliminating spinal motion.
• Decreased spinal mobility post-fusion can impair activities of daily living (ADLs) due to stiffness.
• Existing outcome instruments do not capture the impact of spinal stiffness on functional ability.

Purpose of the Study:

• To develop and validate a patient-reported outcome instrument to measure the effect of lumbar stiffness on functional ability after spinal fusion.

Main Methods:

• A 10-item Lumbar Stiffness Disability Index (LSDI) questionnaire was developed.
• The study included 32 lumbar arthrodesis patients (minimum 1 year post-op).
• Internal consistency (Cronbach alpha), retest reliability (ICC), and external validity (correlation with lumbar range of motion) were assessed.

Main Results:

• The LSDI demonstrated high internal consistency (Cronbach alpha=0.89) and retest reliability (ICC=0.87).
• A significant inverse correlation was found between lumbar range of motion and LSDI scores (r=-0.71; p<.001), indicating construct validity.
• The sample comprised 69% women and 31% men, with an average age of 63 years.

Conclusions:

• The LSDI is a reliable and valid tool for assessing functional limitations caused by lumbar stiffness in spinal arthrodesis patients.
• The LSDI can be used in future studies to prospectively evaluate the impact of lumbar stiffness.
• This validated instrument addresses a gap in assessing the functional consequences of spinal fusion stiffness.