Dynamic sagittal alignment and compensation strategies in adult spinal deformity during walking

Abstract

BACKGROUND CONTEXTRadiographic evaluation in adult spinal deformity (ASD) offers no information on spinopelvic alignment and compensation during dynamic conditions. Motion analysis offers the potential to bridge the gap between static radiographic and dynamic alignment measurement, increasing our understanding on how ASD impacts function. PURPOSEThis study aimed to explore the changes in sagittal alignment and compensation strategies in ASD between upright standing and walking, compared to control subjects and within different sagittal alignment groups. Ten patients were measured pre- and six months postoperatively to explore the impact of surgical alignment correction on gait. STUDY DESIGNProspective study. SAMPLE SIZEFull protocol: 58 ASD and 20 controls; Spinal kinematic analysis: 43 ASD and 18 controls; Postoperative analysis: 10 ASD. OUTCOME MEASURESStanding and walking sagittal spinopelvic (thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvis), and lower limb kinematics, spinopelvic changes between standing and walking (∆ ie, difference between mean dynamic and static angle), lower limb kinetics, spatiotemporal parameters, balance (BESTest), patient-reported outcome scores (SRS-22r, ODI, and FES-I) and radiographic parameters. METHODSMotion analysis was used to assess the standing and walking spinopelvic and lower limb kinematics, as well as the lower limb kinetics during walking. All parameters were compared between controls and patients with ASD, divided in three groups based on their sagittal alignment (ASD 1: decompensated sagittal malalignment; ASD 2: compensated sagittal malalignment; ASD 3: scoliosis and normal sagittal alignment). Ten patients were reassessed 6 months after spinal corrective surgery. Continuous kinematic and kinetic data were analyzed through statistical parametric mapping. RESULTSAll patient groups walked with increased forward trunk tilt (∆SVA=41.43 mm, p<.001) in combination with anterior pelvic tilt (∆Pelvis=2.58°, p<.001) compared to standing, as was also observed in controls (∆SVA=37.86 mm, p<.001; ∆Pelvis=1.62°, p=.012). Patients walked with increased SVA, in combination with decreased LL and alterations in lower limb kinematics during terminal stance and initial swing, as well as altered spatiotemporal parameters. Subgroup analysis could link these alterations in gait to sagittal spinopelvic malalignment (ASD 1 and 2). After surgical correction, lower limb kinematics and spatiotemporal parameters during gait were not significantly improved. CONCLUSIONSTo compensate for increased trunk tilt and pelvic anteversion during walking, patients with sagittal malalignment show altered lower limb gait patterns, which have previously been associated with increased risk of falling and secondary lower limb pathology. Since surgical correction of the deformity did not lead to gait improvements, further research on the underlying mechanisms is necessary to improve our understanding of how ASD impacts function.