Distal Junctional Kyphosis after Posterior Spinal Fusion in Lenke 1 and 2 Adolescent Idiopathic Scoliosis-Exploring Detailed Features of the Sagittal Stable Vertebra Concept

Abstract

Study Design: A retrospective cohort study. Objective: To investigate the factors contributing to the development of postoperative distal junctional kyphosis (DJK) in adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF) with lowest instrumented vertebrae (LIV) at or above L1. Methods: Patients with Lenke type 1 or 2 curves who underwent PSF with LIV at or above L1 with a minimum follow-up of 2 years were evaluated. The primary outcome measure was the occurrence of postoperative DJK. Radiographic parameters of sagittal alignment and inclusion/exclusion of sagittal stable vertebra (SSV) in PSF were analyzed to determine their associations with the occurrence of postoperative DJK. Results: Overall, 122 patients (mean age: 15.1 ± 3.2 years) were included. The overall incidence of postoperative DJK was 6.6%. DJK was observed in 19.0% (8/42) of patients whose SSV was not included in PSF and not in patients with SSV included in PSF (n = 80). In the SSV-excluded group, univariate analysis found two significant risk factors for DJK: postoperative thoracic kyphosis (TK, T5-12) and postoperative thoracolumbar kyphosis (TLK, T11-L2). The ROC curve revealed that postoperative TK ≥ 25° and TLK ≥ 10° best predicted the occurrence of postoperative DJK in the SSV-excluded group. The incidence was significantly higher in cases with postoperative TK ≥ 25° or TLK ≥ 10° (7/13 = 53.8%) than in those with postoperative TK < 25° and TLK < 10° (1/29 = 3.4%). Conclusions: The current study revealed that postoperative TK ≥ 25° or postoperative TLK ≥ 10° with SSV excluded from PSF were related to DJK after PSF for Lenke type 1 and type 2 AIS. When the SSV is intended to be spared from PSF to save more motion segments, TK and TLK should be carefully evaluated and attained in a lesser magnitude (TK < 25°, TLK < 10°) after surgery.

Risk factors for distal junctional kyphosis after posterior spinal surgery in adolescent idiopathic scoliosis: a meta-analysis

“…Three studies ( 10 , 13 , 14 ) investigated the relationship between preoperative TLK and DJK. The studies had low heterogeneity ( p for heterogeneity = 0.37, I 2 = 0%, Figure 5E ).…”

“…Three studies ( 10 , 12 , 14 ) investigated the relationship between postoperative DJA and DJK. There was no significance in the test for heterogeneity; thus, the studies had low heterogeneity ( p for heterogeneity = 0.59, I 2 = 0%, Figure 7 ).…”

“…Thus, identifying the predictors related to DJK is an urgent need to prevent DJK. Postoperative thoracic kyphosis (TK) ≥25° and thoracolumbar kyphosis (TLK) ≥10° are related to DJK ( 10 ). Segal ( 11 ) demonstrated that the LIV chosen proximal to the sagittal stable vertebra (SSV) was a risk factor for DJK.…”

Is it Possible for Patients with Early Distal Junctional Kyphosis following Adult Cervical Deformity Corrective Surgery to Achieve Similar Outcomes to their Unaffected Counterparts: an Analysis of Recovery Kinetics

“…[7,8] DJK denotes a progression in the degree of kyphosis of the vertebral segment adjacent to the lower instrumented vertebra post-operatively. [9] DJK can lead to considerable morbidity, including pain, imbalance and degenerative disc disease due to increased mechanical stress on adjacent vertebral segments. [10,11] Development of early DJK (within three months post-operatively) is associated with particularly more severe radiographic malalignment and neurologic decline.…”

Cervical Vertebral Bone Quality Score Independently Predicts Distal Junctional Kyphosis After Posterior Cervical Fusion

“…One limitation is the potential occurrence of distal junctional kyphosis (DJK), a complication in which the bottom of the fused segment becomes a hinge point of the spine, collapsing the disk space adjacent to the lowest fused segment and causing the return to a kyphotic curvature of the cervical spine. 8 There is a paucity of data in the literature about DJK as a complication in posterior cervical fusion, and approaches to either identifying or improving the rate of occurrence have been minimal.…”