Sagittal spino-pelvic alignment failures following three column thoracic osteotomy for adult spinal deformity

Abstract

Purpose: Three column thoracic osteotomy (TCTO) is effective to correct rigid thoracic deformities, however, reasons for residual postoperative spinal deformity are poorly defined. Our objective was to evaluate risk factors for poor spino-pelvic alignment (SPA) following TCTO for adult spinal deformity (ASD).

Methods: Multicenter, retrospective radiographic analysis of ASD patients treated with TCTO. Radiographic measures included: correction at the osteotomy site, thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence (PI). Final SVA and PT were assessed to determine if ideal SPA (SVA < 4 cm, PT < 25°) was achieved. Differences between the ideal (IDEAL) and failed (FAIL) SPA groups were evaluated.

Results: A total of 41 consecutive ASD patients treated with TCTO were evaluated. TCTO significantly decreased TK, maximum coronal Cobb angle, SVA and PT (P < 0.05). Ideal SPA was achieved in 32 (78%) and failed in 9 (22%) patients. The IDEAL and FAIL groups had similar total fusion levels and similar focal, SVA and PT correction (P > 0.05). FAIL group had larger pre- and post-operative SVA, PT and PI and a smaller LL than IDEAL (P < 0.05).

Conclusions: Poor SPA occurred in 22% of TCTO patients despite similar operative procedures and deformity correction as patients in the IDEAL group. Greater pre-operative PT and SVA predicted failed post-operative SPA. Alternative or additional correction procedures should be considered when planning TCTO for patients with large sagittal global malalignment, otherwise patients are at risk for suboptimal correction and poor outcomes.

Figures

Fig. 1

Method used to calculate degree of sagittal correction at the osteotomy site. The difference between the two angles, α1 and α2, reflects the degree of focal sagittal correction. The degree of coronal correction at the osteotomy site was determined using a similar approach based on antero-posterior imaging

Fig. 2

Definition of sagittal spino-pelvic parameters, including thoracic kyphosis, lumbar lordosis, and sagittal vertical axis (SVA) in (a), and T1 spino-pelvic inclination (T1-SPI) and T9 spino-pelvic inclination (T9-SPI) in (b). Circle in bottom right corner of b depicts the femoral head. (Reprinted with permission from: Schwab F, et al. Gravity line analysis in adult volunteers. Spine 31(25):E959–E967, 2006)

Fig. 3

Definition of pelvic parameters, including sacral slope (SS), pelvic incidence (PI), and pelvic tilt (PT), based on the center of the femoral head (dark, solid circle) and the sacrum. (Reprinted with permission from: Schwab F, et al. Gravity line analysis in adult volunteers. Spine 31(25):E959–E967, 2006)

Fig. 4

Distribution of 43 TCTO procedures performed in 41 adults for treatment of spinal deformity

Fig. 5

Pre- (a) and post-operative (b) full length sagittal radiographs of a patient with fixed thoracic kyphosis with good post-operative spino-pelvic alignment following thoracic pedicle subtraction osteotomy (TPSO). Pre- (c) and post-operative (d) full length sagittal radiographs of a patient with fixed thoracic kyphosis with poor post-operative spino-pelvic alignment following TPSO. Note the substantial positive sagittal malalignment, high pelvic tilt, and relative lack of lumbar lordosis for the patient in (c). Vertical line is the C7 plumb line. Circles represent femoral heads