The dynamic sagittal balance: Definition of dynamic spino-pelvic parameters using a method based on gait analysis.

Introduction: Evaluation of sagittal balance parameters is a standard assessment before spine surgery. However, these parameters can change during walking. We aimed to describe the behavior of spino-pelvic parameters during walking in healthy subjects.

Material And Methods: Analyses were performed in 60 healthy subjects. spinal sagittal balance parameters were assessed. We performed gait analysis and we used SMART-DX 500® to analyze parameters aimed at defining sagittal balance, including (PTA), (STS), and (TA). We considered rotational and obliquity movements of the pelvis, flexo-extension movements of the hip, trunk, and knees. Analyses were performed in a standing posture and during walking.

Results: PTA-cycle, PTA-stance, PTA-swing, STS-cycle, STS-stance, and STS-swing showed good-to-excellent internal reliability (ICC = 0.867; ICC = 0.700; ICC = 0.817, respectively). The parameters with the lowest variability were radiographic PI (CV = 16.53%), PTA-stance (CV = 9.55%), and PTA-swing (CV = 17.22%). PT was directly related to PTA-cycle (r = 0.534, p = .027). PI was inversely correlated with trunk flexo-extension range of motion (r = -0.654, p = .004) and dynamic PT (r = -0.489, p = .047). LL and SS were directly related to knee flexo-extension (r = 0.505, p = .039; r = 0.493, p = .045, respectively). SVA was correlated with the trunk obliquity in dynamics (r = 0.529, p = .029). PTA-cycle was directly related to trunk obliquity (r = 0.538, p = .049). STS and TA in the three phases of step were related to the kinematic parameters of the pelvis. TA was related to flexo-extension of the hip and knee.

Conclusions: Variations of dynamic spino-pelvic parameters occur during walking and modify sagittal balance from a static to a dynamic condition.