Patient‐specific finite element analysis of chronic contact stress exposure after intraarticular fracture of the tibial plafond

Abstract

The role of altered contact mechanics in the pathogenesis of posttraumatic osteoarthritis (PTOA) following intraarticular fracture remains poorly understood. One proposed etiology is that residual incongruities lead to altered joint contact stresses that, over time, predispose to PTOA. Prevailing joint contact stresses following surgical fracture reduction were quantified in this study using patientspecific contact finite element (FE) analysis. FE models were created for 11 ankle pairs from tibial plafond fracture patients. Both (reduced) fractured ankles and their intact contralaterals were modeled. A sequence of 13 loading instances was used to simulate the stance phase of gait. Contact stresses were summed across loadings in the simulation, weighted by resident time in the gait cycle. This chronic exposure measure, a metric of degeneration propensity, was then compared between intact and fractured ankle pairs. Intact ankles had lower peak contact stress exposures that were more uniform and centrally located. The series-average peak contact stress elevation for fractured ankles was 38% (p ¼ 0.0015; peak elevation was 82%). Fractured ankles had less area with low contact stress exposure than intact ankles and a greater area with high exposure. Chronic contact stress overexposures (stresses exceeding a damage threshold) ranged from near zero to a high of 18 times the matched intact value. The patient-specific FE models represent substantial progress toward elucidating the relationship between altered contact stresses and the outcome of patients treated for intraarticular fractures. ß

Objective Structured Assessments of Technical Skills (OSATS) Does Not Assess the Quality of the Surgical Result Effectively

“…The reduction was first directly assessed by measuring the 3-D deviations of the reduced articular surfaces from their intact positions. To understand the impact of these surface deviations on the ankle contact mechanics, a second analysis method assessed contact stresses predicted in the fracture-reduced configuration using previously established computational stress analysis methods [7,9].…”

“…2B). The method was validated in previous work examining the relationship between contact stress and eventual posttraumatic osteoarthritis development in tibial plafond fractures [1,7,9]. Each of the 3-D models from the fracture reduction exercise was run through a 13-pose flexion-extension arc representing the stance phase of gait.…”

Extrinsic Muscle Forces Affect Ankle Loading Before and After Total Ankle Arthroplasty

“…All these factors are hypothesized to alter the loading pattern in the joint [1,6], which is theorized to affect the genesis and progression of degenerative joint diseases [1,6,7]. Several studies have evaluated the effect of tibial fracture [1,14], joint instability [23], and ligament injury and repair [20] on joint contact stresses and related it to the development of OA. However, the effective contribution of the muscles on the load distribution in the ankle during gait has not been fully explored.…”

FE analysis of stress and displacements occurring in the bony chain of leg

“…These structures also maintain the integrity and stability of the ankle mortise and are important for balance loading of the foot through the fibula. Li and Anderson, 16 carried on an FE analyses included several provisional loading steps (to bring the joint into a seated apposition as governed by the articular surfaces), followed by 13 steps spanning the stance phase of gait. Prevailing joint contact stresses following surgical fracture reduction were quantified in this study using patient specific contact finite element (FE) analysis.…”