Discrete element analysis is a valid method for computing joint contact stress in the hip before and after acetabular fracture

Townsend, K; Thomas-Aitken, Holly D.; Rudert, Maximilian; Kern, Andrew M.; Willey, Michael; Anderson, Donald D.; Goetz, Jessica E.

doi:10.1016/j.jbiomech.2017.11.014

Cited by 22 publications

(36 citation statements)

References 47 publications

(70 reference statements)

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“…Peak contact stresses computed using DEA were within an average of 0.5 MPa (range: 0.2-0.8 MPa) of the Tekscan stresses [77]. Correlations between the DEA-computed contact stress distributions and Tekscanmeasured distributions ranged from 0.93-0.99, indicating excellent agreement between the two techniques over the entire contact area [77]. Those results indicated that this custom DEA methodology can accurately predict contact stresses in the hip joint.…”

Section: Previous Work and Rationalementioning

confidence: 68%

“…Contact stresses were physically measured with Tekscan sensors [82] and compared on a point-by-point basis with DEA-calculated stresses. Peak contact stresses computed using DEA were within an average of 0.5 MPa (range: 0.2-0.8 MPa) of the Tekscan stresses [77]. Correlations between the DEA-computed contact stress distributions and Tekscanmeasured distributions ranged from 0.93-0.99, indicating excellent agreement between the two techniques over the entire contact area [77].…”

Section: Previous Work and Rationalementioning

confidence: 80%

“…The distance from this spherical cartilage surface to the subchondral bone varies over the joint surface and produces a non-uniform cartilage thickness, which has been shown by previous studies to be a more realistic cartilage representation [87][88][89][90]. This cartilage generation and smoothing methodology has been validated in cadaveric specimens and produces accurate contact stress computations in the intact hip joint [77]. The realistic cartilage representation and accuracy of the resulting contact stress distributions support the use of this projection and smoothing technique to create the CT-based articular cartilage surfaces for the dysplastic hip models in this work.…”

Section: Purpose Of This Workmentioning

confidence: 98%

“…When a load or displacement is applied to one or all of the bodies in the model, the resulting spring deformation is utilized to solve for the spring forces and the contact stresses between the bodies. The contact stress calculations can be performed using a variety of computational techniques, including the minimum energy principle [75,76] and a Newton-Raphson iterative solver [72,77]. Even though it is a simplified modeling strategy, DEA has been shown to correlate well with FEA results, indicating that it produces accurate stress calculations.…”

Section: Discrete Element Analysismentioning

confidence: 99%

“…To evaluate the accuracy of DEA for contact stress assessment in the hip joint, a validation study was conducted by members of the Orthopaedic Biomechanics Laboratory at the University of Iowa [77]. This study investigated the accuracy of a custom DEA methodology that had previously been validated in the ankle [79] for use in the hip.…”

Section: Previous Work and Rationalementioning

confidence: 99%

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A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint

Thomas¹

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Theses and DissertationsFall 2017 A computational investigation of patient factors contributing to A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint contact stress abnormalities in the dysplastic hip joint ABSTRACT Acetabular dysplasia, a deformity characterized by the presence of a shallow acetabulum inadequately covering the femoral head, alters force transfer through a joint, causing early-onset hip pain and degeneration. Dysplasia is often treated surgically with a periacetabular osteotomy (PAO), which permits multiplanar acetabular reorientation to stabilize the joint and alleviate pain. PAO alters joint mechanics, including contact stress, which can be assessed via computational methods.This work sought to enhance a discrete element analysis (DEA) model for assessment of the dysplastic hip. The primary focus was on understanding how the gait parameters used to load a DEA model affect the computed contact stress. Several additional studies focused on understanding specific anatomic and demographic factors contributing to the contact stress evaluation were also performed.Implementation of a dysplastic gait pattern to load the DEA models resulted in more cases with improved contact stress and clinical measures after PAO, which concurred with clinical findings. Patient demographics and acetabular and femoral geometry all affected the computed contact stress distributions, emphasizing the importance of proper cohort categorization prior to interpretation of DEA-calculated contact stress. These results indicate that accurate modeling of the particular deformity in this cohort likely requires evaluation of both functional and anatomic differences.These studies improve the ability to realistically model and characterize dysplastic hip contact mechanics. DEA is a valuable tool for assessing contact stress in dysplastic joints, which has the potential to improve patient outcomes by guiding clinicians in nonoperative treatment, pre-operative PAO planning, and evaluating intraoperative success. iv PUBLIC ABSTRACTHip dysplasia is a deformity of the pelvic bone that results in a mechanically unstable hip joint. This can be painful and lead to development of arthritis at a young age.Treatment may involve surgery to change how the hip socket is positioned and oriented in the pelvis to improve hip stability and decrease the damaging, painful stresses on the hip socket. Success of this realignment is largely determined by the ability of the surgeon to determine hip function in 3D from 2D X-ray images that can be obtained during surgery.Computational modeling offers the opportunity for analysis of joint mechanical function in 3D, which provides a much more realistic assessment of the mechanical changes after surgery.The purpose of this work was to develop the best method for using a specific type of computational modeling to evaluate changes in the joint mechanics of dysplastic hips before and after corrective surgery. This involved an investigation of mo...

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Section: Previous Work and Rationalementioning

confidence: 68%

Section: Previous Work and Rationalementioning

confidence: 80%

Section: Purpose Of This Workmentioning

confidence: 98%

Section: Discrete Element Analysismentioning

confidence: 99%

Section: Previous Work and Rationalementioning

confidence: 99%

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A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint

Thomas¹

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Chronically elevated contact stress exposure correlates with intra‐articular cartilage degeneration in patients with concurrent acetabular dysplasia and femoroacetabular impingement

Thomas-Aitken

Westermann

Bartschat

et al. 2022

Journal Orthopaedic Research

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Hip dysplasia is known to lead to premature osteoarthritis. Computational models of joint mechanics have documented elevated contact stresses in dysplastic hips, but elevated stress has not been directly associated with regional cartilage degeneration. The purpose of this study was to determine if a relationship exists between elevated contact stress and intra‐articular cartilage damage in patients with symptomatic dysplasia and femoroacetabular impingement. Discrete element analysis was used to compute hip contact stresses during the stance phase of walking gait for 15 patients diagnosed with acetabular dysplasia and femoral head‐neck offset deformity. Contact stresses were summed over the duration of the walking gait cycle and then scaled by patient age to obtain a measure of chronic cartilage contact stress exposure. Linear regression analysis was used to evaluate the relationship between contact stress exposure and cartilage damage in each of six acetabular subregions that had been evaluated arthroscopically for cartilage damage at the time of surgical intervention. A significant correlation (R2 = 0.423, p < 0.001) was identified between chondromalacia grade and chronic stress‐time exposure above both a 1 MPa damage threshold and a 2 MPa‐years accumulated damage threshold. Furthermore, an over‐exposure threshold of 15% regional contact area exceeding the 1 and 2 MPa‐years threshold values resulted in correct identification of cartilage damage in 83.3% (55/66) of the acetabular subregions loaded during gait. These results suggest corrective surgery to alleviate impingement and reduce chronic contact stress exposures below these damage‐inducing thresholds could mitigate further cartilage damage in patients with hip dysplasia.

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Persistently elevated joint contact stress after periacetabular osteotomy is associated with joint failure at minimum 10‐year follow‐up

Aitken,

Goetz,

Glass

et al. 2024

Journal Orthopaedic Research

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Periacetabular osteotomy (PAO) is a common treatment for prearthritic hip dysplasia. The goal of this investigation was to determine if computationally assessed hip contact mechanics are associated with joint failure at minimum 10‐year follow‐up. One hundred patients with hip dysplasia (125 hips) completed patient‐reported outcomes an average of 13.8 years (range 10.0–18.0 years) after PAO. 63/125 hips were classified as having failed: 26 converted to total hip arthroplasty (THA) and 37 with significant disability indicated by modified Harris Hip Score (mHHS) ≤ 70. Differences in discrete element analysis‐computed contact mechanics were compared between (1) preserved and failed hips, (2) preserved hips and hips that failed by THA, and (3) preserved hips and hips that failed by mHHS ≤ 70. Failed hips had significantly higher preoperative contact stress and exposure metrics (p < 0.001–0.009) than preserved hips. Failed hips also had significantly higher postoperative peak contact stress (p = 0.018), higher mean contact stress (p < 0.001), and smaller contact area (p = 0.044). When assessed based on type of failure, hips that failed by THA had significantly higher postoperative contact stress and exposure metrics than preserved hips (p < 0.001–0.020). In hips that failed by mHHS ≤ 70, mean postoperative contact stress exposure was significantly higher compared to preserved hips (p = 0.043). Despite improved radiographic measures of dysplasia after PAO, pathologic joint contact mechanics can persist and predict treatment failure at minimum 10 years after surgery. Operative and nonoperative techniques specifically intended to reduce harmful contact mechanics in dysplastic hips may have the potential to further improve clinical outcomes after PAO.

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Discrete element analysis is a valid method for computing joint contact stress in the hip before and after acetabular fracture

Cited by 22 publications

References 47 publications

A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint

A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint

Chronically elevated contact stress exposure correlates with intra‐articular cartilage degeneration in patients with concurrent acetabular dysplasia and femoroacetabular impingement

Persistently elevated joint contact stress after periacetabular osteotomy is associated with joint failure at minimum 10‐year follow‐up

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