Selection of Distal Fusion Level for Lenke 5 Curve

Abstract

Study Design. A retrospective analysis. Objective. To evaluate whether the rotation of the presumed lower instrumented vertebra (LIV) on baseline convex side-bending (SB) radiographs leads to distal adding-on in Lenke 5C adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data. In Lenke 1A patients, derotation of the presumed LIV on baseline bending films is important owing to the association between LIV rotation and postoperative distal adding-on. However, the relationship between distal adding-on and derotation of the presumed LIV in Lenke 5C patients remains unknown. Methods. Eighty-five Lenke 5C patients with a minimum of 2-year follow-up for posterior fusion were enrolled. L3 was selected as the LIV in all patients. Patients were divided into the presumed LIV derotation (DR group) and nonderotation (NDR group) groups according to derotation of the presumed LIV on SB films. Radiographic parameters, including Cobb angle, coronal balance, lower disc angle of LIV, LIV tilt, and LIV translation, were measured pre- and postoperatively. Results. Distal adding-on occurred in 16 patients (18.8%) at the final follow-up: 2 patients (10%) in the DR group and 14 patients (21.5%) in the NDR group (P = 0.248). Distal adding-on incidence was not greatly reduced with derotation of the presumed LIV on SB films at baseline. In the NDR group, the immediately postoperative lower disc angle of the LIV, LIV tilt, and LIV translation were significantly smaller in patients without than in those with distal adding-on (all P < 0.05). Logistic regression analysis revealed that the immediately postoperative LIV tilt and LIV translation were significant predictors of distal adding-on. Conclusion. Derotation of the presumed LIV on SB films may hint less risk of distal adding-on in Lenke 5C patients. Nevertheless, horizontalization of the LIV and minimizing LIV translation during correction could reduce the risk of distal adding-on despite the presence of LIV rotation at baseline. Level of Evidence: 4

Transient fixation of L4 vertebra preserves lumbar motion and function in Lenke Type 5C and 6C scoliosis

“…The former group satisfied two of the three criteria for transient L4 fixation in this study. Similarly, Shu et al 11 reported worse results with a LIV tilting angle of 11.0 ± 3.5° in patients with adding-on phenomenon than the group without adding-on phenomenon with LIV (L3) in Lenke Type 5C scoliosis. In this study, the final LIV (L3) tilting angle was 4.7 ± 2.2°.…”

“…Despite advances in scoliosis surgeries, there is still a major controversy regarding the distal fusion level for idiopathic scoliosis surgery 5,[7][8][9][10][11][12][13][14] . A 40-year follow-up study by Lander et al 12 indicated that there was a higher risk of additional surgery and poorer functional outcome after L4 or below L4 fixation in idiopathic scoliosis surgery.…”

“…However, it was inferior to 65% (7.2 ± 6.8/21.1 ± 11.1 mm) when L4 was fixed. Recently, Shu et al 11 reported a coronal balance correction ratio of 22% in a distal adding-on group when the LIV presented L3 in Lenke Type 5C scoliosis; however, it was 57% in patients not exhibiting adding-on phenomenon 19 . Considering results from previous studies, we could assume that the transient L4 fixation might correct coronal balance effectively even without fusion up to the L4 and might lower the potential for adding-on phenomenon.…”

Posterior-only correction surgery for idiopathic scoliosis Lenke type 5c: differences of strategies and outcomes between adult patients and adolescent patients

“…First, lower end vertebra is not far from CSVL. Shu found that horizontalization of the LIV and minimizing LIV translation during correction could reduce the risk of distal adding-on [ 18 ]. In a meta-analysis, Yang evaluated the incidence, characteristics, and risk factors for "adding-on", and demonstrated that lowest instrumented vertebra (LIV)-center Sacral Vertical Line (CSVL) and deviation of LIV + 1 were found to be significantly associated with "adding-on" [ 19 ].…”

“…Second, lower end vertebra should be well derotated. Shu also demonstrated that derotation of the presumed LIV on SB films may hint less risk of distal adding-on in Lenke 5c patients [ 18 ]. In another word, well derotation could reduce the incidence of adding-on.…”