Comparative Biomechanical Study of Screw Fixation Techniques in Periacetabular Osteotomy

Abstract

Periacetabular osteotomy (PAO) is a common surgical treatment for developmental dysplasia of the hip. To obtain the optimal method of fixation during PAO, different screw fixation techniques have been proposed for stabilizing the acetabular fragment. This study assesses the biomechanical performance of two popular 3-screw fixation techniques: iliac (IS) and transverse (IT) configurations, through finite element simulations. Additionally, different 2-screw combinations are simulated to investigate the biomechanical significance of each screw of the fixation configurations. The study findings show that yield load of the pelvic bone subject to gait loading for IT configuration is on average 7% higher compared to that of the IS. Although the yield load of the IT is predicted to be slightly higher, no significant difference in bone stiffness and displacement of the acetabular fragment are found between two configurations. Simulation results, therefore, do not demonstrate a significant biomechanical advantage of the IT configuration over the IS. Furthermore, the biomechanical comparison between the 2-screw combinations of IS and IT fixations demonstrates that the most anterior screw in IS, located at the iliac crest, and the most medial screw in the IT are the most critical elements in providing sufficient stability and support for acetabular fragment.

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

“…During the surgery, intraoperative osteotomy requires internal fixation to maintain stabilization of the acetabular fragment. The IS and TS internal fixation techniques are the mainstream approaches used in PAO, and various clinical and mechanical studies, ranging from in vitro experiments to simulations, have been reported ( Babis et al, 2002 ; Yassir et al, 2005 ; Mechlenburg et al, 2007 ; Widmer et al, 2010 ; Bakhtiarinejad et al, 2021 ; Leopold et al, 2021 ). However, those mechanical research studies were limited due to the lack of realistic gait simulation, and muscle force that should contribute to the deformation and stress of the bone was not represented in models, leading to underreported FE results ( Chen et al, 2019 ).…”

Postoperative stability following a triple pelvic osteotomy is affected by implant configuration: a finite element analysis

“…The FE method has been proven to be useful for postoperative modeling of different orthopedic applications and has been used to evaluate different fixation methods for PAO [ 20 , 27 , 28 ]. Despite TPO being a mainstay of advanced surgical treatment of multiple conditions, FE analysis has, to our knowledge, not previously been applied to evaluate the stability of different implant constructs.…”

“…Although the study demonstrated the comparison of different fixation systems, the modeling had its limitations. Similar to other established finite element models of the pelvis [ 28 ], the implant screws were simplified as homogeneous with isotropic materials. Furthermore, a constant cortical thickness and homogeneous and isotropic material properties were assigned to the pelvis bone.…”

“…Furthermore, a constant cortical thickness and homogeneous and isotropic material properties were assigned to the pelvis bone. This is a simplification compared to some other models in the literature that include a non-homogeneous distribution of trabecular bone properties [ 28 , 32 , 33 ]. However, since the aim of this study was to compare the biomechanical performance of different implant configurations in identical conditions, and not to study the stress–strain state of the bone or the contact stress of the osteotomy, this simplification was justified.…”

Comparative Finite Element Analysis of Fixation Techniques for APC II Open-Book Injuries of the Pelvis

“…Similar to other established finite element models of the pelvis [60], the implant screws were simplified as cylindrical solids with no threads to avoid singularities at sharp edges or notches with a very small radius. However, since the aim of this study is to compare the biomechanical performance of different fixation techniques and identical simplifications are applied, it is unlikely that modeling of the threads would change the outcome.…”