Novel Method Using Baseline Normalization and Area Under the Curve to Evaluate Differences in Outcome Between Treatment Groups and Application to Patients With Cervical Spondylotic Myelopathy Undergoing Anterior Versus Posterior Surgery.
METHODS
Retrospective review of a prospective database.


OBJECTIVE
To describe a novel method that uses baseline normalization and area under the curve (AUC) to compare surgical outcomes between patients surgically treated anteriorly versus posteriorly for cervical spondylotic myelopathy (CSM).


BACKGROUND
It is important to control for baseline characteristics, especially disease severity, when evaluating differences in outcomes between 2 treatment groups. However, current methods of reporting outcomes are limited perhaps diminish the health impact of the entire postoperative recovery experience.


METHODS
In the prospective, multicenter AO Spine North America CSM database, 147 patients had complete modified Japanese Orthopaedic Association (mJOA) data at baseline and at 6-, 12-, and 24-months postoperatively and were either treated anteriorly (n = 94) or posteriorly (n = 53). Each patient's follow-up mJOA scores were normalized by dividing them by the patient's baseline value. A graph was then plotted with the time point on the x-axis and the normalized score or "recovery index" on the y-axis. The AUC was calculated and then compared between the anterior and posterior surgical approach groups.


RESULTS
The non-normalized recovery profile of the anterior group was better than that of the posterior group, as the patients treated anteriorly had less functional impairment at baseline. After normalization, patients in the anterior and posterior group had similar recovery indices and AUCs at 6-months following surgery. At 24-months, patients treated posteriorly had a significantly higher recovery index (1.32) and a larger AUC (16.3) than those treated anteriorly (1.11, 14.5, P = 0.004 and P = 0.006, respectively).


CONCLUSIONS
This is the first study to apply AUC analysis to patients with CSM. In surgical patients with CSM, those treated anteriorly achieved a higher mJOA score at all time points than those treated posteriorly. The recovery indices, however, were not significantly different between approach groups at 6 months.


METHODS
3.
*Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY†Department of Neurosurgery, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada‡Department of Neurosurgery, University of Virginia Health System, Charlottesville, VA§Department of Neurosurgery, University of Kansas, Kansas City, KS¶Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL||Department of Orthopaedic Surgery, University of Washington, Seattle, WA#Department of Health Services, University of Washington, Seattle, WA**Division of Neurosurgery, Toronto Western Hospital, Toronto, Canada††Department of Orthopaedics, Emory University, Atlanta, GA‡‡Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA.
Shian
S
Liu
Lindsay
L
Tetreault
Michael G
MG
Fehlings
Vincent
V
Challier
Justin S
JS
Smith
Christopher I
CI
Shaffrey
Paul M
PM
Arnold
Justin K
JK
Scheer
Jens R
JR
Chapman
Branko
B
Kopjar
Themistocles S
TS
Protopsaltis
Virginie
V
Lafage
Frank
F
Schwab
Eric M
EM
Massicotte
Sangwook T
ST
Yoon
Christopher P
CP
Ames
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000706:statistics & numerical data*; D011788:Quality of Life; D012189:Retrospective Studies; D055009:Spondylosis / Q000453:epidemiology* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome