Listhesis and Spinopelvic Inclination of Upper Instrumented Vertebra Region and the Implications on Proximal Junctional Kyphosis

Retrospective analysis of prospective data. Evaluate the impact of radiographic and morphologic configuration of the uppermost instrumented vertebrae (UIV) region on proximal junctional kyphosis (PJK) rates. Literature is limited on evaluation of the preoperative landing zone (UIV-1 to UIV +2 levels) and its impact on development of PJK. Adult ASD patients with native baseline thoracolumbar junction, postoperative UIV between T9 and T12 and LIV extending to pelvis, and two-year follow-up available were included. Landing zone was assessed on radiographs for Meyerding grade listhesis and posterior translation angle by 2 spine surgeons. Comparative analyses were performed on demographics, radiographic parameters, and PJK rates across patients with/without landing zone listhesis and above/below 15&#xb0; UIV spinopelvic inclination (UIV SPi). Multivariable regression, accounting for listhesis, UIV SPi, PJK prophylaxis, age, osteoporosis, radiographic UIV quality (bridging osteophytes/degenerative disc disease), and change in PI-LL and SVA, was used to identify independent predictors of PJK. Among 244 patients, mean age was 64.41 years, 73.0% were females, mean CCI was 1.97. In total, 30% had preoperative landing zone listhesis and 42% had posterior translation (41% with baseline posterior translation and 59% with iatrogenic translation). Listhesis patients had similar baseline and two-year radiographic alignment but higher two-year PJK rates (32.9% vs . 20.5%, P = 0.04). UIV SPi >15&#xb0; patients also had higher PJK (37.5% vs . 14.2%, P < 0.01) and PJK reoperation (16.3% vs . 5.8%, P = 0.01) rates. Patients with both listhesis and UIV SPi >15&#xb0; had the highest PJK (45.5%, P = 0.03) and PJK reoperation (21.1%, P = 0.18) rates. Multivariable regression (R 2 = 0.33) identified landing zone listhesis (coeff = 1.0, P = 0.01) and UIV SPi (coeff = -0.22, P < 0.001) to be predictive of PJK. Preoperative listhesis and postoperative posterior translation are independent predictors of two-year PJK. These findings highlight the importance of meticulous selection of the UIV landing zone, with particular emphasis on preoperative listhesis and spinopelvic inclination. Level IV.