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. 2021 Sep;18(3):457-463.
doi: 10.14245/ns.2142182.091. Epub 2021 Apr 12.

The Incidence of Adding-On or Distal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Treated by Anterior Spinal Fusion to L3 Was Significantly Higher Than by Posterior Spinal Fusion to L3

Seung-Jae Hyun  1 , Lawrence G Lenke  2 , Yongjung Kim  3 , Keith H Bridwell  4 , Meghan Cerpa  2 , Kathy M Blanke  4
Affiliations

The Incidence of Adding-On or Distal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Treated by Anterior Spinal Fusion to L3 Was Significantly Higher Than by Posterior Spinal Fusion to L3

Seung-Jae Hyun et al. Neurospine. 2021 Sep.

Abstract

Objective: To compare and identify risk factors for distal adding-on (AO) or distal junctional kyphosis (DJK) in adolescent idiopathic scoliosis (AIS) treated by anterior- (ASF) and posterior spinal fusion (PSF) to L3.

Methods: AIS patients undergoing ASF versus PSF to L3 from 2000-2010 were analyzed. Distal AO and DJK were deemed poor radiographic results. New stable (SV) and neutral vertebra (NV) scores were defined for this study. The total stability (TS) score was the sum of the SV and NV scores.

Results: Twenty of 42 (ASF group: 47.6%) and 8 of 72 patients (PSF group: 11.1%) showed poor radiographic outcome. Fused vertebrae, correction rate of main curve, coronal reduction rate of L3 were significantly higher in PSF group. Multiple logistic regression results indicated that preoperative SV-3 at L3 in standing and side benders (odds ratio [OR], 2.7 and 3.7, respectively), TS score -5, -6 at L3 (OR, 4.9), rigid disc at L3-4 (OR, 3.7), lowest instrumented vertebra (LIV) rotation > 15° (OR, 3.3), LIV deviation > 2 cm from center sacral vertical line (OR, 3.1) and ASF (OR, 13.4; p < 0.001) were independent predictive factors. There was significant improvement of the Scoliosis Research Society (SRS)-22 average scores only in PSF group. Furthermore, the ultimate scores of PSF group were significantly superior to ASF group.

Conclusion: The prevalence of AO or DJK at ultimate follow-up for AIS with LIV at L3 was significantly higher in ASF group. Ultimate SRS-22 scores were significantly better in PSF group.

Keywords: Adding-on; Adolescent idiopathic scoliosis; Anterior spinal fusion; Distal junctional kyphosis; Lowest instrumented vertebra; Posterior spinal fusion.

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Conflict of interest statement

Dr. Lenke shares numerous patents with Medtronic (unpaid). He is a consultant for DePuy Synthes Spine, K2M, Medtronic (monies donated to a charitable foundation). He receives substantial royalties from Medtronic and modest royalties from Quality Medical Publishing. Dr. Lenke also receives or has received reimbursement related to meetings/courses from AOSpine, BroadWater, DePuy Synthes Spine, K2M, Medtronic, Scoliosis Research Society, Seattle Science Foundation, Stryker Spine, The Spinal Research Foundation. Except for that, the other authors have nothing to disclose.

Figures

Fig. 1.
Fig. 1.
An example of radiographic measurement for deviation of the center of the L3 from the center sacral vertical line, distal junctional discal angulation at L3–4 in the coronal or sagittal plane.
Fig. 2.
Fig. 2.
An example of radiographic evaluation for gravity, rotational and total stability scoring system. Gravity stability score (new stable vertebra [SV] was defined for this study: SV-1, CSVL is passing between medial borders of pedicles of the LIV; SV-2, CSVL touching body of LIV; SV-3, CSVL does not touch LIV body), rotational stability score (neutral vertebra [NV]: vertebra without rotation; NV-1, 1 vertebra proximal to NV; NV-2, 2 vertebra proximal to NV; NV-3, 3 vertebra proximal to NV), and total stability score (summation of gravity and rotational stability score). CSVL, center sacral vertical line; LIV, lower instrumented vertebra; TS, total stability.
Fig. 3.
Fig. 3.
An example of radiographic outcomes of patients having similar Lenke 6CN curve and same Risser grade following posterior spinal fusion and anterior spinal fusion to L3. Two-year postoperative plain films with good- (left) and poor radiographic outcome (right) showing 3.14-cm deviation of the center of the L3 from the center sacral vertical line in the coronal plane.
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