Changes in chondrolabral mechanics, coverage, and congruency following peri‐acetabular osteotomy for treatment of acetabular retroversion: A patient‐specific finite element study

Abstract

Using a validated finite element (FE) protocol, we quantified cartilage and labrum mechanics, congruency, and femoral coverage in five male patients before and after they were treated for acetabular retroversion with peri-acetabular osteotomy (PAO). Three-dimensional models of bone, cartilage, and labrum were generated from computed tomography (CT) arthrography images, acquired before and after PAO. Walking, stair-ascent, stair-descent, and rising from a chair were simulated. Cartilage and labrum contact stress, contact area, and femoral coverage were calculated overall and regionally. Mean congruency (average of local congruency values for FE nodes in contact) and peak congruency (most incongruent node in contact) were calculated overall and regionally. Load supported by the labrum was represented as a raw change in the ratio of the applied force transferred through the labrum and percent change following surgery (calculated overall only). Considering all activities, following PAO, mean acetabular cartilage contact stress increased medially, superiorly and posteriorly; peak stress increased medially and posteriorly. Peak labrum stresses decreased overall and superiorly. Acetabular contact area decreased overall and laterally, and increased medially. Labral contact area decreased overall, but not regionally. Load to the labrum decreased. Femoral head coverage increased overall, anterolaterally, and posterolaterally, but decreased anteromedially. Mean congruency indicated the hip became less congruent overall, anteriorly, and posteriorly; peak congruency indicated a less congruent joint posteriorly. Clinical Relevance Medialization of contact and reductions in labral loading following PAO may prevent osteoarthritis, but this procedure increases cartilage stresses, decreases contact area, and makes the hip less congruent, which may overload cartilage.

Joint contact stresses calculated for acetabular dysplasia patients using discrete element analysis are significantly influenced by the applied gait pattern

“…Computational modeling techniques such as finite element analysis (FEA) (Anderson et al, 2010; Harris et al, 2012; Henak et al, 2014; Henak et al, 2011; Knight et al, 2017; Zou et al, 2013) and discrete element analysis (DEA) (Abraham et al, 2013; Armiger et al, 2009; Townsend et al, 2018) have been utilized to predict hip cartilage contact stresses. The majority of these studies have investigated cartilage contact stresses when loading their computational models with walking gait data obtained directly from instrumented total hip implants (Bergmann et al, 2001a).…”

Periacetabular osteotomy with or without arthroscopic management in patients with hip dysplasia: study protocol for a multicenter randomized controlled trial

“…Consequently, adding quantitative T1ρ mapping assessing the hip cartilage condition pre-and post-operatively comparing hip arthroscopy vs. no hip arthroscopy in the setting of a PAO is innovative. This is especially relevant as it has been shown using patient specific finite element modeling [74] that although a PAO favorably alters the joint mechanics at the labral-chondral junction, joint congruency is decreased which could be further impacted if the labral structure is altered with the addition of hip arthroscopy.…”

Diagnosis and Management of Borderline Hip Dysplasia and Acetabular Retroversion

“…81 A recent FEA modeling study of a small number of acetabular retroversion patients found that while PAO served to offload forces passing through the labrum during several activities of daily living and shift contact stress medially and posteriorly within the articular surface of the acetabulum, peak contact stress in these patients actually increased postoperatively. 42 While this finding presently only adds to the controversy of how best to treat individuals with this deformity, it shows the potential for computational modeling to contribute to a better understanding of the effects of different surgical procedures in these unique patient populations.…”

“…Focal overcoverage or under-coverage can often be better visualized on three dimensional (3D) reconstructions of the pelvis CT than on radiographs. Computational methods have been developed based on CT scans to determine potential impingement-free range of motion, [40][41][42] and cross-sectional imaging through the distal femur (CT or MRI) can be used to assess femoral version.…”