Botulinum Toxin A for Chronic Exertional Compartment Syndrome Evaluated With Shear Wave Elastography: A Case Report

Effect of interstitial fluid pressure on shear wave elastography: an experimental and computational study

Objective. An elevated interstitial fluid pressure (IFP) can lead to strain-induced stiffening of poroelastic biological tissues. As shear wave elastography (SWE) measures functional tissue stiffness based on the propagation speed of acoustically induced shear waves, the shear wave velocity (SWV) can be used as an indirect measurement of the IFP. The underlying biomechanical principle for this stiffening behavior with pressurization is however not well understood, and we therefore studied how IFP affects SWV through SWE experiments and numerical modeling.Approach. For model set-up and verification, SWE experiments were performed while dynamically modulating IFP in a chicken breast. To identify the confounding factors of the SWV-IFP relationship, we manipulated the material model (linear poroelastic versus porohyperelastic), deformation assumptions (geometric linearity versus nonlinearity), and boundary conditions (constrained versus unconstrained) in a finite element model mimicking the SWE experiments.Main results. The experiments demonstrated a statistically significant positive correlation between the SWV and IFP. The model was able to reproduce a similar SWV-IFP relationship by considering an unconstrained porohyperelastic tissue. Material nonlinearity was identified as the primary factor contributing to this relationship, whereas geometric nonlinearity played a smaller role. The experiments also highlighted the importance of the dynamic nature of the pressurization procedure, as indicated by a different observed SWV-IFP for pressure buildup and relaxation, but its clinical relevance needs to be further investigated.Significance. The developed model provides an adaptable framework for SWE of poroelastic tissues and paves the way towards non-invasive measurements of IFP.

Review of Reliable and Valid Noninvasive Tools for the Diagnosis of Chronic Exertional Compartment Syndrome

Background

Currently, invasive dynamic intracompartmental pressure (ICP) measurements are considered the gold standard for diagnosis of chronic exertional compartment syndrome (CECS). During recent years, different noninvasive imaging modalities have been presented as a possible replacement for ICP measurement.

Purpose

To provide an overview of the current state of evidence and possibilities regarding noninvasive diagnostic methods for CECS.

Study Design

Scoping review; Level of evidence, 4.

Methods

The PubMed (MEDLINE) and Embase databases were searched using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Full-text articles were included if they reported on noninvasive diagnostic methods for CECS, included ≥5 patients with CECS, and were published between 1994 and 2022. Articles not written in English were excluded. Systematic reviews, letters to the editor, and case reports were not eligible for inclusion. Out of 961 articles identified in the initial search, 25 studies (N = 1257 participants) were included. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-Comparative (QUADAS-C) tool for comparative studies and the QUADAS-2 tool for noncomparative studies. Narrative synthesis was used to present results.

Results

The level of evidence for the 25 studies ranged from 2 to 4. Four studies were classified as having a low risk of bias, 21 studies were classified as being at risk of bias. The following noninvasive diagnostic tools for CECS were reported: magnetic resonance imaging/diffusion tensor imaging (n = 8), near-infrared spectroscopy (n = 6), electromyography (n = 4), single-photon emission computed tomography (n = 5), ultrasound (n = 2), myotonometry (n=1) and predictive clinical model (n = 1). There was insufficient evidence in the literature to support the use of any of these noninvasive diagnostic tools as a gold standard for CECS.

Conclusion

Despite the need to replace the controversial use of ICP for the diagnosis of CECS, our review indicated a lack of validity on all discussed noninvasive diagnostic tools as a replacement.