Reliability and development of a new classification of lumbosacral spondylolisthesis.
BACKGROUND
A classification of lumbosacral spondylolisthesis has been proposed recently. This classification describes eight distinct types of spondylolisthesis based on the slip grade, the degree of dysplasia, and the sagittal sacro-pelvic balance. The objectives of this study are to assess the reliability of this classification and to propose a new and refined classification.


METHODS
Standing posteroanterior and lateral radiographs of the spine and pelvis of 40 subjects (22 low-grade, 18 high-grade) with lumbosacral spondylolisthesis were reviewed twice by six spine surgeons. Each radiograph was classified based on the slip grade, the degree of dysplasia, and the sagittal sacro-pelvic balance. No measurements from the radiographs were allowed. Intra- and inter-observer reliability was assessed using kappa coefficients. A refined classification is proposed based on the reliability study.


RESULTS
All eight types of spondylolisthesis described in the original classification were identified. Overall intra- and inter-observer agreement was respectively 76.7% (kappa: 0.72) and 57.0% (kappa: 0.49). The specific intra-observer agreement was 97.1% (kappa: 0.94), 85.0% (kappa: 0.69) and 88.8% (kappa: 0.85) with respect to the slip grade, the degree of dysplasia, and the sacro-pelvic balance, respectively. The specific inter-observer agreement was 95.2% (kappa: 0.90), 72.2% (kappa: 0.43) and 77.2% (kappa: 0.69) with respect to the slip grade, the degree of dysplasia, and the sacro-pelvic balance, respectively.


CONCLUSIONS
This study confirmed that surgeons can classify radiographic findings into all eight types of spondylolisthesis. The intra-observer reliability was substantial, while the inter-observer reliability was moderate mainly due to the difficulty in distinguishing between low- and high-dysplasia. A refined classification excluding the assessment of dysplasia, while incorporating the assessment of the slip grade, sacro-pelvic balance and global spino-pelvic balance is proposed, and now includes five types of lumbosacral spondylolisthesis.
Mac-Thiong
Jean-Marc
JM
Department of Surgery, University of Montreal, Montreal, Canada.|Division of Orthopedic Surgery, Hôpital du Sacré-Coeur, Montreal, Canada.|Division of Orthopedic Surgery, CHU Sainte-Justine, Montreal, Canada.
Labelle
Hubert
H
Department of Surgery, University of Montreal, Montreal, Canada.|Division of Orthopedic Surgery, CHU Sainte-Justine, Montreal, Canada.
Parent
Stefan
S
Department of Surgery, University of Montreal, Montreal, Canada.|Division of Orthopedic Surgery, Hôpital du Sacré-Coeur, Montreal, Canada.|Division of Orthopedic Surgery, CHU Sainte-Justine, Montreal, Canada.
Hresko
Michael Timothy
MT
Department of Orthopaedic Surgery, Boston Children Hospital, Harvard University, USA.
Deviren
Vedat
V
Department of Orthopaedic Surgery, San Francisco General Hospital, UCSF, SF, USA.
Weidenbaum
Mark
M
Department of Orthopaedic Surgery, Columbia University, New York Presbyterian Hospital, NY, USA.