Oluwatobi O Onafowokan, Mohammad Daher, Renaud Lafage, Virginie Lafage, Justin S Smith, D Kojo Hamilton, Max R Fisher, Bassel G Diebo, Alan H Daniels, Robert Eastlack, Gregory Mundis, Breton G Line, Pierce Nunley, Neel Anand, Themistocles Protopsaltis, David O Okonkwo, Khaled M Kebaish, Justin K Scheer, Praveen V Mummaneni, Dean Chou, Han Jo Kim, Richard Hostin, Munish Gupta, Douglas Burton, Christopher P Ames, Frank Schwab, Christopher I Shaffrey, Shay Bess, Lawrence Lenke, Peter G Passias
There is notable variation in how ASD patients compensate as the severity of their deformity progresses. There is also variation in how these patterns are altered postoperatively.
OBJECTIVE: Adult spinal deformity (ASD) surgery patients maintain upright posture by using numerous compensatory mechanisms. The distribution of this compensation throughout the skeleton has not been fully investigated.
METHODS: Patients with lumbar deformity curves undergoing fusion from T10 to the pelvis were included. Groups were stratified by Scoliosis Research Society (SRS)-Schwab sagittal deformity severity (mild, moderate, and severe). Compensation was determined based on the published values of asymptomatic individuals by Bao et al. (2018), with patients outside 1 standard deviation of the mean values deemed to be compensating. Adequate deformity correction was determined based on matching published sagittal age-adjusted score (SAAS) criteria. Means comparisons tests assessed differences between cohorts at each time point.
RESULTS: In total, 379 ASD patients were included (mean age 66.7 ± 10.2 years, body mass index 28.4 ± 5.4 kg/m2, Charlson Comorbidity Index 1.20 ± 1.73). In total, 23.8% of patients had mild deformity, 19.2% moderate, and 57% severe. The severe deformity cohort generally demonstrated the highest rates of compensation across all regions at different time points. At baseline, the severe and moderate cohorts demonstrated predominantly lower limb-dominant compensation, with the highest frequencies of compensation seen at the knee and pelvis. In the mild cohort, knee compensation was relieved by 1 year when adequate correction was achieved. For the moderate cohort, hip and pelvic compensation were relieved first, with knee compensatory relief occurring by 2 years. For the severe cohort, pelvic compensation was relieved first, with global lower limb and thoracic compensation subsequently occurring.
CONCLUSIONS: There is notable variation in how ASD patients compensate as the severity of their deformity progresses. There is also variation in how these patterns are altered postoperatively.