Validation of the SRS Adult Deformity Radiographic Classfiication

Purpose: This classification system is designed to provide a radiographic framework for categorizing adults with complex spinal deformities, which will be helpful in predicting treatment strategies.

Methods: Seven primary curve types were developed: 1) Single Thoracic, 2) Double Thoracic, 3) Double Major, 4) Triple Major, 5) Thoracolumbar, 6) Lumbar, and 7) Primary Sagittal Deformity. Three modifiers were developed, which include a Regional Sagittal modifier (upper thoracic, main thoracic, thoracolumbar, and lumbar), a Lumbar Degenerative modifier (degenerative disc disease, listhesis, and fractional lumbosacral curve), and a Global Balance modifier (sagittal and coronal). Erect long AP and Lateral radiographs of 25 adult spinal deformity cases were reviewed by 17 SRS surgeons (including members of the SRS Adult Deformity Committee) for validation of the system and prediction of instrumentation levels based purely on radiographic data.

Results: Kappa scores were calculated for the primary curve type (k=0.64), regional sagittal modifier (k=0.73), degenerative lumbar modifier (k=0.65), global balance modifier (k=0.92), upper instrumented level (k=0.56), and the lower instrumented level (k=0.77). See table 1 for the Kappa value scale.

Summary: Substantial interobserver reliability was noted when classifying complex adult deformities radiographically by SRS surgeons. Clinical modifiers are currently being developed to help further define treatment strategies in adult deformity patients.

Table 1 - Kappa value scale