AUTHOR=Yang Peng , Liu Qi , Lin Tianye , Aikebaier Aobulikasimu , Jiang Luoyong , Sun Weichao , Zhang Qingwen , Bai Xueling , Sun Wei 

TITLE=Mechanical upside of PAO mainstream fixations: co-simulation based on early postoperative gait characteristics of DDH patients

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2023.1171040

DOI=10.3389/fbioe.2023.1171040

ISSN=2296-4185

ABSTRACT=Purpose: To investigate the early postoperative gait characteristics of patients who have undergone periacetabular osteotomy (PAO) and to predict the biomechanical performance of two commonly used PAO fixation methods: iliac screws (IS) and transverse screws (TS). Methods: 12 unilateral Developmental dysplasia of the hip (DDH) patients (mean age 27.81±4.64 years, 42% male) scheduled to undergo PAO surgery were included in this study. Their preoperative CT images, pre-and postoperative gait data were used to create subject-specific musculoskeletal models, and completing the inverse dynamics analysis (IDA). Two patients with typical gait characteristics were selected using clustering analysis, and their IDA data were incorporated into finite element (FE) models of the IS and TS fixations. Failure simulation was performed by applying iterative steps with increasing gait load to predict yield load. Stress results and yield loads were calculated for each FE model at different phases of the gait cycle. Results: Postoperative gait showed improvement compared to preoperative gait, but remained inferior to that of healthy individuals. Postoperative gait was characterized by lower hip range of motion, lower peri-ilium muscle forces, particularly in the abductors, and a sharper initial peak and flatter second peak of hip joint reaction force. Finite element analysis (FEA) showed a trend of increasing stress during the 2nd-4th phases of the gait cycle, with lower stress levels in other phases. At high stress gait phases, mean stress of maximum 𝑝̅ 100 differed significantly between IS and TS (p <0.05) and between coupled and uncoupled muscle forces (p <0.05). Failure analysis predicted a slightly larger yield load for TS configurations (6.21*BW) compared to IS (6.16*BW), but both were well above the gait load. Coupled and uncoupled groups showed similar results, but uncoupled groups had lower yield loads (5.9*BW). Conclusions: PAO early postoperative gait shows a normalized trend, but abnormalities persist. IS and TS are both capable of resisting mechanical strain failure, with no significant mechanical advantage found for transverse screw fixation during PAO early postoperative gait. Additionally, it is important to note that the TS may have a higher risk of cyclic fatigue failure due to the localized greater stress concentration.