Postoperative trunk shift in Lenke 1 and 2 curves: how common is it? and analysis of risk factors

Abstract

The goal of surgical treatment for adolescent idiopathic scoliosis (AIS) is to achieve a solid fusion in a balanced spine. While many previous studies analyzed coronal balance, there is a paucity of studies that comment on postoperative trunk shift, which has shown to have impact on clinical outcome. The purpose of this retrospective, multicenter data analysis was to analyze the incidence of postoperative trunk shift in patients with surgical treatment for AIS. We conducted a retrospective, multicenter data analysis of 1,555 patients with AIS. Patients with a Lenke type 1 or 2 curve pattern and a minimum follow-up of 24 months after surgery were included. A >2 cm deviation of the trunk in relation to the pelvis was considered positive trunk shift. A subanalysis was performed to identify potential risk factors for trunk shift. 273 patients meeting the inclusion criteria were analyzed. While the preoperative prevalence of trunk shift was surgically reduced from 29.3 to 13.6%, 24 patients (8.8%) with postoperative trunk shift had not had preoperative trunk shift, and the trunk shift was considered iatrogenic. Undercorrection of the lumbar curve was identified as potential risk factor, whereas thoracic correction, coronal balance, angulation and translation of the lowest instrumented vertebra did not seem to influence postoperative trunk shift. Iatrogenic postoperative trunk shift has an incidence of 8.8% in the surgical treatment of AIS.

Fig. 1

Schematic description for measuring trunk shift. A horizontal line is drawn through the apex of the thoracic curve. The endpoints of this line represent the truncal margin (A, B). The bisecting perpendicular line represents the vertical trunk reference line (VTRL, dashed). Trunk shift is defined as a distance greater than 2 cm between the VTRL and the center sacral vertical line (CSVL). The VTRL differs from the C7 plumb line (C7P, dotted) that is used to measure coronal balance (distance between CSVL and C7P)