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The Minimum Clinically Important Difference of the Modified Japanese Orthopaedic Association Scale in Patients with Degenerative Cervical Myelopathy

Tetreault, Lindsay, BSc*; Nouri, Aria, MD; Kopjar, Branko, MD, PhD; Côté, Pierre, DC, PhD§; Fehlings, Michael G., MD, PhD, FRCSC

doi: 10.1097/BRS.0000000000001127
CERVICAL SPINE
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Study Design. Analysis of the prospective AOSpine CSM-International and North America datasets and survey of AO Spine International.

Objective. This study aims to define the minimum clinically important difference (MCID) of the modified Japanese Orthopaedic Association (mJOA) in patients with degenerative cervical myelopathy (DCM).

Summary of Background Data. The mJOA is the most frequently used clinician-administered tool to assess functional status in patients with DCM. By defining its MCID, clinicians can better evaluate treatment outcomes for this condition.

Methods. Three methods were used to determine the MCID of the mJOA: (1) distribution-based, (2) anchor-based and receiver operating characteristic (ROC) analysis, and (3) professional opinion. Distribution-based methods were used to estimate the MCID by computing the half standard deviation and standard error of measurement. Using anchor-based methods, mJOA at 12 months after surgery was compared between patients who were “slightly improved” on the Neck Disability Index (NDI) and those who were “unchanged.” ROC analysis was performed to compute a discrete integer value for the MCID that yielded the smallest difference between sensitivity and specificity. We repeated anchor-based methods for patients with mild (mJOA: 15–17), moderate (mJOA: 12–14), and severe disease (mJOA <12).

Results. The half standard deviation of the baseline mJOA was 1.36 and the standard error of measurement was 1.21. The difference in mJOA between patients who “slightly improved” on the NDI and “unchanged” patients was 1.11. ROC analysis yielded a value of 2 for the MCID. The survey of 416 spine professionals confirmed these estimates: the mean response was 1.65 ± 0.66. The MCID significantly varied depending on myelopathy severity: ROC analysis yielded a threshold of 1 for mild, 2 for moderate, and 3 for severe patients.

Conclusion. The MCID of the mJOA is estimated to be between 1 and 2 points and varies with myelopathy severity. This knowledge will enable clinicians to identify meaningful functional improvements in DCM patients.

Level of Evidence: N/A

*Institute of Medical Sciences, University of Toronto, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada

Institute of Medical Sciences, University of Toronto, Division of Neurosurgery and Spine Program, Toronto Western Hospital, Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada

University of Washington, Seattle, Washington, USA

§Faculty of Health Sciences, University of Ontario Institute of Technology (UOIT), UOIT-CMCC Centre for the Study of Disability Prevention and Rehabilitation, Toronto, Ontario, Canada

Division of Neural Repair and Regeneration, Department of Neurosurgery, University of Toronto, The Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada.

Address correspondence and reprint requests to Michael G. Fehlings, MD, PhD, FRCSC, Division of Neural Repair and Regeneration, Department of Neurosurgery, University of Toronto, The Toronto Western Hospital, University Health Network, Room 4W-449, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada; E-mail: Michael.Fehlings@uhn.on.ca

Received 9 March, 2015

Revised 4 June, 2015

Accepted 10 August, 2015

The manuscript submitted does not contain information about medical device(s)/drug(s).

AO Spine North America and AO Spine International financially supported data collection for this study.

Relevant financial activities outside the submitted work: consultancy, expert testimony, grants, payment for lectures, travel/accommodations/meeting expenses.

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