Three-dimensional reconstruction using stereoradiography for evaluating adult spinal deformity: a reproducibility study

In addition to the sagittal alignment, impact of transverse plane parameters (TPP) and rotatory subluxation on patients reported outcomes were highlighted. One of the hypotheses for genesis of degenerative scoliosis is disc degeneration with increased axial vertebral (AVR) and intervertebral rotation (AIR). Therefore, TPP analysis at early stage of the scoliosis seems of particular interest. This study aims at assessing reliability of tridimensional (3D) reconstructions of adult spinal deformity (ASD) patients. Thirty ASD patients underwent biplanar radiographs and were divided into two groups (Cobb angle > 30A degrees or < 30A degrees). Spinal parameters and TPP (apical AVR, AIR of upper and lower level of main curve) were measured. Four operators performed 3D reconstructions twice. Intra and inter-observer reliabilities were analyzed using ISO standard 5725-2, to quantify the global standard deviation of reproducibility (S (R)). Mean Cobb angle was 31A degrees, mean age 55 years (70% of female). Mean values of apical AVR, upper and lower level AIR were, respectively, 16A degrees A +/- 15A degrees, 6A degrees A +/- 6A degrees and 5A degrees A +/- 5A degrees. Spinopelvic parameters S (R) were below 4.5A degrees. For Cobb angle < 30A degrees, S (R) was 7.8A degrees, 9.6A degrees, 4.5A degrees and 4.9A degrees, respectively, for AVR apex, torsion index, upper and lower AIR. Reliability was worse in the group of patients with Cobb angle above 30A degrees. 3D analysis was reliable for Cobb and sagittal parameters. 3D analysis for TPP was reproducible when Cobb is below 30A degrees. However, uncertainty is larger for Cobb above 30A degrees. Nevertheless, 3D reconstructions could help surgeons to anticipate onset of rotatory subluxation while assessing axial rotation evolution for small deformity and choose best delay for surgical treatment.