The Effect of Spinopelvic Parameters on the Development of Proximal Junctional Kyphosis in Early Onset: Mean 4.5-Year Follow-up.

BACKGROUND: Proximal junctional kyphosis (PJK) is a major complication after posterior spinal surgery. It is diagnosed radiographically based on a proximal junctional angle (PJA) and clinically when proximal extension is required. We hypothesized that abnormal spinopelvic alignment will increase the risk of PJK in children with early-onset scoliosis (EOS).

METHODS: A retrospective study of 135 children with EOS from 2 registries, who were treated with distraction-based implants. Etiologies included 54 congenital, 10 neuromuscular, 37 syndromic, 32 idiopathic, and 2 unknown. A total of 89 rib-based and 46 spine-based surgeries were performed at a mean age of 5.3±2.83 years. On sagittal radiographs, spinopelvic parameters were measured preoperatively and at last follow-up: scoliosis angle (Cobb method, CA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope and PJA. Radiographic PJK was defined as PJA≥10 degrees and PJA≥10 degrees greater than preoperative measurement. The requirement for the proximal extension of the upper instrumented vertebrae was considered a proximal junctional failure (PJF). Analysis of risk factors for the development of PJK and PJF was performed.

RESULTS: At final follow-up (mean: 4.5±2.6 y), CA decreased (P<0.005), LL (P=0.029), and PI (P<0.005) increased, whereas PI-LL (pelvic incidence minus lumbar lordosis) did not change (P=0.706). Overall, 38% of children developed radiographic PJK and 18% developed PJF. Preoperative TK>50 degrees was a risk factor for the development of radiographic PJK (relative risk: 1.67, P=0.04). Children with high postoperative CA [hazard ratio (HR): 1.03, P=0.015], postoperative PT≥30 degrees (HR: 2.77, P=0.043), PI-LL>20 degrees (HR: 2.92, P=0.034), as well as greater preoperative to postoperative changes in PT (HR: 1.05, P=0.004), PI (HR: 1.06, P=0.0004) and PI-LL (HR: 1.03, P=0.013) were more likely to develop PJF. Children with rib-based constructs were less likely to develop radiographic PJK compared with children with spine-based distraction constructs (31% vs. 54%, respectively, P=0.038).

CONCLUSIONS: In EOS patients undergoing growth-friendly surgery for EOS, preoperative TK>50 degrees was associated with increased risk for radiographic PJK. Postoperative PI-LL>20 degrees, PT≥30 degrees, and overcorrection of PT and PI-LL increased risk for PJF. Rib-based distraction construct decreased the risk for radiographic PJK in contrast with the spine-based constructs.

LEVEL OF EVIDENCE: Level III.