212 - Prospective Evaluation of Surgical Planning in Adult Sagittal Realignm...

#212 Prospective Evaluation of Surgical Planning in Adult Sagittal Realignment: Root Cause Analysis Failure

Sagittal Balance

Poster Presented by: S. Liu


B. Moal (1,2)
S. Liu (1)
J. Terran (1)
J. Paul (1)
T. Protopsaltis (1)
F.J. Schwab (1)
V. Lafage (1)

(1) NYU Hospital for Joint Diseases, Orthopaedic Surgery, New York, NY, United States
(2) Arts et Metiers Paris Tech, Laboratory of Biomechanics, Paris, France


Summary: In an attempt to achieve ideal spino-pelvic alignment in operative cases of adult spinal deformity, several preoperative and postoperative parameters need to be considered in the surgical plan. This prospective root cause analysis demonstrated

1) x-ray quality does not permit accurate planning in all cases;

2) planning is not always consistent when using more than 1 method; 3) lumbar lordosis tends to be under-corrected;

3) changes in unfused segments of the thoracic spine are poorly anticipated.

Introduction: In the field of adult spinal deformity surgery, ideal alignment (IA) for surgical treatment has been defined for sagittal alignment (SVA< 40mm, PT< 20 and PI-LL< 10), but published reports highlight high rates of post-operative spino-pelvic malalignment. Collecting surgical planning; pre-, intra-, and post-operative x-rays; the objective of this root cause analysis was to identify the possible reasons contributing to suboptimal postoperative alignment.

Methods: Prospective review of 26 adult patients with realignment procedures. Surgical plans were collected pre-op, defining the expected change in lumbar lordosis (LL) and maximum kyphosis (mTK). Planning was based on a geometrical method as well as a validated formula to predict postoperative SVA and PT. Long Cassette x-rays were obtained intra- and postoperatively. Predicted and actual radiographic measurements were compared.

Results: Radiographs for 20 patients were analyzed due to poor radiographic quality in 6. Comparison of the two planning methods revealed significant differences in the target LL, but no significant difference in mTK or predicted PT and SVA. Due to the magnitude of deformities, 6 geometric and 12 formula plans in 14 patients were predicted to reach IA in all 3 parameters. Compared to the planned correction, intra-operative xrays demonstrated under-correction of LL. Intra-operative x-rays were a good prediction of post-operative LL, but a poor predictor of mTK. Post-operative change in mTK was underestimated with the 2 planning methods. 12 of the 14 patients planned to reach IA in SVA reached this objective; and 6/14 in PT.

Conclusion: Surgical planning and peri-operative assessment of radiographic parameters in cases of sagittal alignment correction are necessary but not sufficient to guarantee ideal alignment goals are met. Predictive methods underestimated the reciprocal change in kyphosis and lumbar lordosis is commonly under-corrected. Target objectives for optimal alignment parameters could not always be met in planning/ execution.