Defining and measuring objective and subjective spinal stiffness : a scoping review

Abstract

OBJECTIVE: To examine and identify the breadth of definitions and measures of objective and subjective spinal stiffness in the literature, with a focus on clinical implications and research opportunities.

DATA SOURCES: Eligible peer-reviewed studies were identified using PubMed, Ebsco health, and Scopus electronic databases.

DATA EXTRACTION: Following the 6-step framework by Arksey and O’Malley1 and based on the eligibility criteria, studies that reported definitions and measures of spinal stiffness were collected using a data abstraction form and classified into four themes; biomechanical, surgical, pathophysiological and segmental spinal assessment. Fifteen categories to identify similarities and differences between studies were generated.

DATA SYNTHESIS: Among 2121 records that were identified, 333 met the eligibility criteria. There were 299 subjective and objective measures (124 subjective;175 objective measures) and 60 indicators of spinal stiffness. The majority of studies (n = 72%) did not define stiffness and there is no consensus regarding a standardised definition of stiffness in the reviewed literature.

CONCLUSION: This review highlights the breadth of objective and subjective measures that are both clinically and methodologically diverse. There was marked variation in the definitions reported in studies. There were no definitions of stiffness provided alongside self-reported or patient-reported outcome measures. Stiffness is a clinically important symptom that may indicate the presence of underlying pathophysiology/disease which has implications for patients’ health outcomes. An important distinction should be made between the patient’s subjective reports of stiffness and this may differ from objective clinical assessments.