Anales de la RANM

194 A N A L E S R A N M R E V I S T A F U N D A D A E N 1 8 7 9 THORACOLUMBAR ROTATIONAL KYPHOSIS Pizones J, et al. An RANM. 2022;139(02): 186 - 195 tive (fusion to pelvis) does not. Fusing to the pelvis allows only small deviations from the ideal shape, and forces surgeons to be as accurate as possible in the restoration of the SS. Indeed, most of the mismatches were caused by not achieving an adequate SS in patients with high PI (as they need higher SS values and this failed to be achieved). On the other hand, mismatching in patients with low PI resulted from overcorrecting the SS. Changes in TLK from surgery did not seem to have a direct impact on mechanical complications, although theoretically the TL transition can lead to anchor failure and junctional kyphosis when instru- mentation ends at this transition. No differences in terms of mechanical complications were found between patients instrumented to the upper vs lower thoracic spine. Over one third of our patients had mechanical complications, all of which were associated with older age and instrumentation to pelvis. Pelvic incidence, sagittal plane matching and TLK correction showed no impact on mechanical complications. The difference between this study and others that report a higher rate of mechanical complications in mismatched patients [10, 13] may be due to the fact that patients in this study mainly had coronal deformity and were well aligned pre- and postoperatively in terms of the sagittal plane. Another key factor is age, since patients with AS are usually younger than patients with sagittal disorders, less likely to receive pelvis instrumenta- tion, and have more segments to compensate. Our study as some limitations. Establishing a 20° threshold could be considered as strong evidence of TL transitional kyphosis. The threshold was based on the Lenke classification principles [14], where this degree of transitional kyphosis is considered as a criterion for curve structurality. In addition, not all TL coronal curves exhibit a kyphotic TL transition. This type of transition was found in only one third of our cohort. Therefore, the study results apply only to this specific group of patients. Lastly, although some univariate analyses showed strong associations between some variables and their relation to complications, multivariate analysis later showed confounding associations mainly concerning age and pelvic fixation, so this result should be taken with caution. Despite these limitations, the large sample size of homogeneous patients taken from a multicenter register allows for clear evidence based on robust data. The surgical correction of adult TL scoliosis flattens the TL segment by about 20°, changing the residual transitional kyphosis that readily accommodates to the ideal values dictated by patients’ PI. This surgical correction lengthens the upper lumbar arc by one segment, shifting the inflection point towards a more proximal position. This change in TL kyphosis did not have any direct impact on mechanical complica- tions or final shape matching. The EESG study group receives funding from DePuy-Synthes Spine and Medtronic. All patients signed an informed consent to enter the study. The study was approved by the ethics commit- tees of all recruiting sites. 1. Peloux J du, Fauchet R, Faucon B et al. The plan of choice for the radiologic examination of kyphoscolioses. Rev Chir Orthop reparatrice Appar Mot. 1965; 51: 517-524. 2. Luk KD, Vidyadhara S, Lu DS et al. Coupling between sagittal and frontal plane deformi- ty correction in idiopathic thoracic scoliosis and its relationship with postoperative sa- gittal alignment. Spine. 2010; 35(11): 1158- 1164. doi: 10.1097/BRS.0b013e3181bb49f3 3. Watanabe K, Nakamura T, Iwanami A et al. Vertebral derotation in adolescent idiopathic scoliosis causes hypokyphosis of the thoracic spine. BMC Musculoskelet Disord. 2012; 13: 99. doi: 10.1186/1471-2474-13-99 4. Scemama C, Laouissat F, Abelin-Genevois K et al. Surgical treatment of thoraco-lumbar kyphosis (TLK) associated with low pelvic incidence. Eur Spine J. 2017; 26: 2146-2152. doi: 10.1007/s00586-017-4984-z 5. Berthonnaud E, Dimnet J, Roussouly P et al. Analysis of the sagittal balance of the spine and pelvis using shape and orientation para- meters. J Spinal Disord Tech. 2005; 18: 40-47. doi: 10.1097/01.bsd.0000117542.88865.77 6. Roussouly P, Gollogly S, Berthonnaud E et al. Classification of the normal variation in the sagittal alignment of the human lum- bar spine and pelvis in the standing position. Spine. 2005; 30: 346-353. doi: 10.1097/01. brs.0000152379.54463.65 7. Laouissat F, Sebaaly A, Gehrchen M et al. Clas- sification of normal sagittal spine alignment: Refounding the Roussouly classification. Eur Spine J. 2018; 27(8): 2002-2011. doi: 10.1007/ s00586-017-5111-x 8. Pizones J, Martin MB, Pérez-Grueso FJS et al. Impact of adult scoliosis on Roussouly's sagittal shape classification. Spine. 2019; 44(4): 270-279. doi: 10.1097/ BRS.0000000000002800 9. Pizones J, Moreno-Manzanaro L, Sánchez Pé- rez-Grueso FJ et al. Restoring the ideal Rous- souly sagittal profile in adult scoliosis surgery decreases the risk of mechanical complications. Eur Spine J. 2020; 29(1): 54-62. doi: 10.1007/ s00586-019-06176-x CONCLUSIONS FUNDING ETHICS COMMITTEE BIBLIOGRAPHY