Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient.

BACKGROUND: To investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations.

METHOD: Medical records of Lenke 5 AIS patients were reviewed from January 2008 to January 2013, included posteroanterior and lateral full spine X-ray films preoperatively, postoperatively (4-7 days after surgery), and at final follow-up. Demographic data and radiologic parameters were evaluated. Based on the proximal junctional angle (PJA) at final follow-up, those patients were divided into 2 groups: PJK group (n = 35, PJA≧10°), and Non-PJK group (n = 52, PJA<10°). Comparisons analyses between PJK and Non-PJK groups were carried out. Binary logistic Regression analysis was performed to detect the risk factors of PJK at follow-up.

RESULTS: The current study recruited 87 Lenke 5 AIS patients with average follow-up of 4.67 ± 1.17 years. Significant differences between PJK and Non-PJK groups were observed as follows: UIV(P = 0.010), the disruption of junctional ligaments (P < 0.001); preoperative variables [MTC (P = 0.001), TK(P < 0.001), LL (P = 0.017), SVA (P = 0.036), and PJA (P = 0.014)], postoperative variables [TLK(P = 0.004), and PJA (P < 0.001)], and follow-up [SVA (P = 0.014), C-SVA (P < 0.001), and PJA (P0.001). Binary logistic regression showed that the disruption of junctional ligaments, postoperative PJA and UIV (upper instrumented vertebra) at proximal or lower thoracic levels were the main risk factors of PJK [Odds Ratio (OR) = 5.114, 2.345, and 6.212, respectively]. However, the SRS-22 scores did not change significantly in PJK and Non-PJK groups.

CONCLUSION: Greater postoperative PJA, disruption of junctional ligaments, UIV at lower thoracic levels were the main risk factors for PJK in Lenke 5 AIS patients. Recommedation: Preserve junctional ligaments in those individuals with UIV located in the lower thoracic region.