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

Abstract

Gait modifications in acetabular dysplasia patients may influence cartilage contact stress patterns within the hip joint, with serious implications for clinical outcomes and the risk of developing osteoarthritis. The objective of this study was to understand how the gait pattern used to load computational models of dysplastic hips influences computed joint mechanics. Three-dimensional pre- and post-operative hip models of thirty patients previously treated for hip dysplasia with periacetabular osteotomy (PAO) were developed for performing discrete element analysis (DEA). Using DEA, contact stress patterns were calculated for each pre- and post-operative hip model when loaded with an instrumented total hip, a dysplastic, a matched control, and a normal gait pattern. DEA models loaded with the dysplastic and matched control gait patterns had significantly higher (p = 0.012 and p < 0.001) average pre-operative maximum contact stress than models loaded with the normal gait. Models loaded with the dysplastic and matched control gait patterns had nearly significantly higher (p = 0.051) and significantly higher (p = 0.008) average pre-operative contact stress, respectively, than models loaded with the instrumented hip gait. Following PAO, the average maximum contact stress for DEA models loaded with the dysplastic and matched control patterns decreased, which was significantly different (p < 0.001) from observed increases in maximum contact stress calculated when utilizing the instrumented hip and normal gait patterns. The correlation between change in DEA-computed maximum contact stress and the change in radiographic measurements of lateral center-edge angle were greatest (R = 0.330) when utilizing the dysplastic gait pattern. These results indicate that utilizing a dysplastic gait pattern to load DEA models may be a crucial element to capturing contact stress patterns most representative of this patient population.

Subject-specific geometry affects acetabular contact pressure during gait more than subject-specific loading patterns

“…Higher subject-specific loading in S1 increased contact area, while in S2 it increased contact pressure. Although the importance of taking the aberrant gait pattern of dysplasia patients into account when considering contact mechanics has already been reported (Thomas-Aitken et al 2018), the present study indicates that individual gait pattern of healthy subjects is also important. Together, these results highlight complex interplay between geometry, loading and kinematics and their effect on contact mechanics.…”

“…To the best of our knowledge, only one recent study employed subject-specific boundary conditions, calculated using musculoskeletal models, when considering hip cartilage contact mechanics (Ng et al 2017). Another study used an average dysplastic, but not subject-specific, gait pattern, which altered hip contact stress patterns compared to using a generic gait pattern (Thomas-Aitken et al 2018).…”

Effects of Hip Abductor Strengthening on Musculoskeletal Loading in Hip Dysplasia Patients after Total Hip Replacement

“…Unfortunately, no similar studies are available on hip contact and muscle forces after THR in DDH patients, indeed this is the first study that analyzed the musculoskeletal loads during gait in DDH patients after THR. Previous research focused on dysplastic hips [32,33] or in patients operated on periacetabular osteotomy [34,35]. Sørensen et al [35] reported a normal hip muscle function during walking after 12 month periacetabular osteotomy, and found that joint force magnitude continued to be higher than normal, justifying this finding with the need for joint structures of a longer time to heal than muscles, with a residual pain alleviating strategy.…”

The Femoral Head “Divot” Sign: A Useful Arthroscopic Sign of Hip Microinstability

“…Previous biomechanical studies have shown reduction in contact stresses of the hip joint in patients undergoing PAO and transfer of the load to more medial areas of the acetabulum and femoral head. 26,30 The reduced loads laterally as well as the change in the orientation of the acetabulum likely reduce the continued engagement and edge-loading of the divot lesion.…”