Research

Reliability and development of a new classification of lumbosacral spondylolisthesis

Jean-Marc Mac-Thiong^1,2,3* , Hubert Labelle^1,3* , Stefan Parent^1,2,3* , Michael Timothy Hresko^4* , Vedat Deviren^5* , Mark Weidenbaum^6* and members of the Spinal Deformity Study Group

¹  Department of Surgery, University of Montreal, Montreal, Canada

²  Division of Orthopedic Surgery, Hôpital du Sacré-Coeur, Montreal, Canada

³  Division of Orthopedic Surgery, CHU Sainte-Justine, Montreal, Canada

⁴  Department of Orthopaedic Surgery, Boston Children Hospital, Harvard University, USA

⁵  Department of Orthopaedic Surgery, San Francisco General Hospital, UCSF, SF, USA

⁶  Department of Orthopaedic Surgery, Columbia University, New York Presbyterian Hospital, NY, USA

author email corresponding author email* Contributed equally

Scoliosis 2008, 3:19doi:10.1186/1748-7161-3-19

Published:	10 December 2008

Abstract

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.

Conclusion

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.