Interrater reliability of the modified prone instability test for lumbar segmental instability in individuals with mechanical low back pain

ABSTRACT

Objective

The purpose of this study was to establish the interrater reliability of measures obtained with a novel Modified Prone Instability Test (mPIT), which, like the original Prone Instability Test (PIT), is proposed to identify lumbar segmental instability. The mPIT has clinical feasibility advantages to the PIT, but its psychometric properties are yet to be determined.

Design

Repeated measures (test-retest) design, methods study

Methods

The mPIT was administered by two blinded testers, an orthopedic physical therapy resident with < 1 year experience and board-certified orthopedic specialist physical therapist with >25 years’ experience. Procedures were administered at an outpatient physical therapy clinic of a tertiary Medical Center. Participants included 50 adults (≥18 years old) with mechanical low back pain and no radicular (below the knee) symptoms (mean age 50.7 years, 66% female, 76% reported previous episodes of low back pain). Interrater reliability was measured via Fleiss’ kappa coefficient.

Results

Assessments of the mPIT had moderate interrater agreement (κ = .579 [95% CI = .302 to .856], p < .001.)

Conclusion

Measures obtained using the mPIT demonstrated moderate interrater reliability between a new graduate and an experienced clinician, which aligns with several studies examining interrater reliability of the original PIT. Further study examining comparative validation of the mPIT with other lumbar instability measures is warranted.

KEYWORDS:

• Low back pain
• instability
• reproducibility of results
• reliability
• prone instability test

Acknowledgements

The authors would like to acknowledge Dr. Megan Erlandson, PT, DPT, OCS, Dr. Blake Robinson, PT, DPT, OCS, and Dr. Leah Wurm, PT, DPT, SCS for assistance with data collection and direction of the participants. Additionally, we would like to thank Dr. Karli Kerzman, PT, DPT, Dr. Kathleen Michaels, PT, DPT, and Dr. Elora Koepcke, PT, DPT for critical reviews of the study proposal, participation in the technical editing of the manuscript, and figure production.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/10669817.2024.2352934.

Additional information

Funding

Funding provided by the Mayo Clinic Physical Medicine and Rehabilitation Department at Mayo Clinic, under Grant #21-006546.

Notes on contributors

Ellen R. Larkin

Ellen R. Larkin, PT, DPT, OCS, graduated from the Mayo Clinic School of Health Sciences Program in Physical Therapy in 2020 and completed the Mayo Clinic Orthopaedic Physical Therapy Residency in 2022. She is a full-time orthopaedic physical therapist in at M Health Fairview in Fridley, MN. Her research interests include clinical utility of diagnostic testing in low back pain, biopsychosocial factors related to musculoskelatal pain, and diagnosis and interventions in shoulder pain for the overhead athlete.

Darren Q. Calley

Darren Q. Calley, PT, DScPT, OCS, is the Program Director of the Mayo Clinic Physical Therapy Residency Programs and Assistant Professor of Physical Therapy in the Mayo Clinic College of Medicine and Science in Rochester, MN. He has 28 years of clinical experience specializing in orthopaedic physical therapy, with primary research interests in clinical & residency education, musculoskeletal examination & interventions, and biopsychosocial factors related to musculoskeletal pain.

John H. Hollman

John H. Hollman, PT, PhD, is Program Director of the Program in Physical Therapy and Associate Dean for Academic Affairs in the Mayo Clinic School of Health Sciences, and Professor of Physical Therapy in the Mayo Clinic College of Medicine and Science in Rochester, MN. He has been a physical therapist for 30 years and earned a PhD in Biomechanics, with specific expertise in kinematics and kinesiologic electromyography. His primary research interests include gait dynamics and lower extremity biomechanics.