The capsule's contribution to total hip construct stability – A finite element analysis

Abstract

Instability is a significant concern in total hip arthroplasty, particularly when there is structural compromise of the capsule due to pre-existing pathology or due to necessities of surgical approach. An experimentally grounded fiber-direction-based finite element model of the hip capsule was developed, and was integrated with an established three-dimensional model of impingement/dislocation. Model validity was established by close similarity to results from a cadaveric experiment in a servohydraulic hip simulator. Parametric computational runs explored effects of graded levels of capsule thickness, of regional detachment from the capsule’s femoral or acetabular insertions, of surgical incisions of capsule substance, and of capsule defect repairs. Depending strongly upon the specific site, localized capsule defects caused varying degrees of construct stability compromise, with several specific situations involving over 60% decrement in dislocation resistance. Construct stability was returned substantially toward intact-capsule levels following well conceived repairs, although the suture sites involved were often at substantial risk of failure. These parametric model results underscore the importance of retaining or robustly repairing capsular structures in total hip arthroplasty, in order to maximize overall construct stability.

Dual-mobility or Constrained Liners Are More Effective Than Preoperative Bariatric Surgery in Prevention of THA Dislocation

“…The higher dislocation rate in women with obesity than in men with obesity can be explained by distribution of adipose tissues [22] (with gynoid obesity as opposed to android obesity). Recently, Elkins et al [10,11] demonstrated that morbid obesity may increase dislocation because of thigh soft tissue impingement. This is in concordance with our study that demonstrates that the effect of obesity on dislocation may be underestimated without adjustment for hip and thigh circumference.…”

“…However, in these patients with obesity, it is not known whether the risk is only in the early postoperative period or if the risk persists several years after surgery. Biomechanical studies [10,11,31] have shown that the periprosthetic soft tissues, especially large thighs, can act as moment arms (soft tissue impingement or thigh impingement) during adduction to create a laterally directed force on the femoral component and dislocation (Fig. 1).…”

Do Obesity and/or Stripe Wear Increase Ceramic Liner Fracture Risk? An XFEM Analysis

“…These stresses were then subsequently passed to a separate XFEM submodel of the liner, allowing for fracture initiation and propagation to be simulated. A previously developed and physically validated [12] FE model of the overall THA construct was used for the global analysis. The computational zoning for the global model had been optimized for bearing contact and edge-loading [9] and had been validated by comparison with a corresponding Hertzian analytical contact stress solution reported by Sanders and Brannon [32].…”

Development and initial evaluation of a finite element model of the pediatric craniocervical junction

“…The FEM method is very powerful and has been widely used in the field of biomechanics to evaluate complex structures, including the adult CCJ. 1,5,8,[11][12][13][14][15][16]20,21,27,34 Several factors must be considered to apply the FEM method correctly. Spine models include complicated 3D geometry, nonlinear and/or inhomogeneous material properties, and complex boundary and loading conditions.…”