Proximal Junction Kyphosis in Adult Scoliosis. Best Post-Operative Radiological Predictors. Retrospective Cohort Study

Background: Proximal junction kyphosis (PJK) is the post-surgical radiographic event seen in the surgical plane after the fusion of spinal deformity. Unfavorable health outcomes have been reported in symptomatic PJK patients. The purpose of this study was to assess which immediate post-surgical radiographic variable from the four proposed formulae is the best in forecasting the future occurrences of PJK in adult scoliosis after undergoing deformity correction. Methods: : Data for adult scoliosis patients who underwent curve correction were extracted from the hospital database. Pelvic and spinal parameters were measured and calculated to compare four predictive formulae for occurrences of PJK. Formula 1： Restoration of hypothetical values of lumbar lordosis (LL) and thoracic kyphosis (TK) according to pelvic incidence ( PI). Formula 2: evaluation of global sagittal alignment (GSA). Formula 3: Restoration of the apex of LL to its hypothetical position according to the spine shape. Formula 4: evaluation of positive-sum and negative-sum of (LL + TK). Results: : The total number of cases was 52. There were 14 cases of PJK, the incidence of PJK was 26.9% and the mean age for PJK cases was 63.2±5.2. The excellent predictor for occurrences of PJK was formula 3, postsurgical sagittal apexes of lumbar lordosis were located in their hypothetical position in 24 cases, and 12.5% of these cases developed PJK. While sagittal apexes were not located in hypothetical position in 28 patients, 39.3% of patients developed PJK. P =0.03, OR 4.53, (95% CI 1.09-18.9). The second good predictor for occurrences of PJK was formula 2 . GSA > 45 0 versus GSA <45 0 OR= 2.5, (95% CI, 0.67-9.38), P= 0.17. The other two formulae (1 and 4) were not good predictors for occurrences of PJK. Conclusion: Among the proposed formulae for predicting occurrences of PJK, the position of the sagittal apex of lumbar lordosis is an excellent predictor of the development of PJK followed by GSA. Hypothetical values of LL and TK, positive or negative-sum of (LL+TK) are weak predictors for occurrences of PJK. Trial registration: “ retrospective registered ”