Hip Joint Stresses Due to Cam-Type Femoroacetabular Impingement: A Systematic Review of Finite Element Simulations

Abstract

BackgroundThe cam deformity causes the anterosuperior femoral head to obstruct with the acetabulum, resulting in femoroacetabular impingement (FAI) and elevated risks of early osteoarthritis. Several finite element models have simulated adverse loading conditions due to cam FAI, to better understand the relationship between mechanical stresses and cartilage degeneration. Our purpose was to conduct a systematic review and examine the previous finite element models and simulations that examined hip joint stresses due to cam FAI.MethodsThe systematic review was conducted to identify those finite element studies of cam-type FAI. The review conformed to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and studies that reported hip joint contact pressures or stresses were included in the quantitative synthesis.ResultsNine articles studied FAI morphologies using finite element methods and were included in the qualitative synthesis. Four articles specifically examined contact pressures and stresses due to cam FAI and were included in the quantitative synthesis. The studies demonstrated that cam FAI resulted in substantially elevated contact pressures (median = 10.4 MPa, range = 8.5–12.2 MPa) and von Mises stresses (median 15.5 MPa, range = 15.0–16.0 MPa) at the acetabular cartilage; and elevated maximum-shear stress on the bone (median = 15.2 MPa, range = 14.3–16.0 MPa), in comparison with control hips, during large amplitudes of hip motions. Many studies implemented or adapted idealized, ball-and-cup, parametric models to predict stresses, along with homogeneous bone material properties and in vivo instrumented prostheses loading data.ConclusionThe formulation of a robust subject-specific FE model, to delineate the pathomechanisms of FAI, remains an ongoing challenge. The available literature provides clear insight into the estimated stresses due to the cam deformity and provides an assessment of its risks leading to early joint degeneration.

A novel model for the induction of postnatal murine hip deformity

“…Further, computational studies have demonstrated that acetabular dysplasia patients have higher cartilage contact stresses 11–13 , and increased load transfer to the labrum 14 . Similar modeling studies have shown increased shear stresses to the cartilage of FAI patients 15–17 .…”

Increased Hip Stresses Resulting From a Cam Deformity and Decreased Femoral Neck-Shaft Angle During Level Walking

“…The asymptomatic participants' moderate stresses were higher than the control subjects but were more evenly distributed than the symptomatic models. To our knowledge, no study has investigated hip contact stresses resulting from an asymptomatic cam morphology [36]. In one of the first finite element studies in this area, Chegini and associates [8] examined cartilage stresses using an idealized ball-andsocket model parameterized to various cam and acetabular coverage morphologies, applying instrumented prosthesis loads.…”

“…According to a recent systematic review on finite element simulations of cam FAI [36], there has been limited work pertaining to finite element simulations that examine cam FAI and, moreover, many of the previous studies used idealized hip geometries [8,15] as opposed to models reconstructed from subject-specific imaging data. It has also been demonstrated that subchondral bone density is higher in individuals with a symptomatic or asymptomatic cam morphology [52,53]; however, previous finite element simulations neglected subject-specific bone material properties.…”

Editorial Commentary: When Is It Just a Labral Tear and Not Femoroacetabular Impingement?

“…Because of the associated biological gradient, the more severe the cam deformity, the greater the acetabular cartilage damage. 4,[12][13][14] Combined with the consistent location of the damage on the acetabular side, which has been validated in animal 15 and biomechanical models of joint overload, 16 we can state with some certainty that cam morphology is a cause of cartilage damage.…”