title: Compartment elasticity measured by pressure-related ultrasound to determine patients "at risk" for compartment syndrome: an experimental in vitro study.
abstract: BACKGROUND
  Decision-making in treatment of an acute compartment syndrome is based on clinical assessment, supported by invasive monitoring. Thus, evolving compartment syndrome may require repeated pressure measurements. In suspected cases of potential compartment syndromes clinical assessment alone seems to be unreliable. The objective of this study was to investigate the feasibility of a non-invasive application estimating whole compartmental elasticity by ultrasound, which may improve accuracy of diagnostics.
  
  
  METHODS
  In an in vitro model, using an artificial container simulating dimensions of the human anterior tibial compartment, intra-compartmental pressures (p) were raised subsequently up to 80 mmHg by infusion of saline solution. The compartmental depth (mm) in the cross-section view was measured before and after manual probe compression (100 mmHg) upon the surface resulting in a linear compartmental displacement (∆d). This was repeated at rising compartmental pressures. The resulting displacements were related to the corresponding intra-compartmental pressures simulated in our model. A hypothesized relationship between pressures related compartmental displacement and the elasticity at elevated compartment pressures was investigated.
  
  
  RESULTS
  With rising compartmental pressures, a non-linear, reciprocal proportional relation between the displacement (mm) and the intra-compartmental pressure (mmHg) occurred. The Pearson coefficient showed a high correlation (r(2) = -0.960). The intra-observer reliability value kappa resulted in a statistically high reliability (κ = 0.840). The inter-observer value indicated a fair reliability (κ = 0.640).
  
  
  CONCLUSIONS
  Our model reveals that a strong correlation between compartmental strain displacements assessed by ultrasound and the intra-compartmental pressure changes occurs. Further studies are required to prove whether this assessment is transferable to human muscle tissue. Determining the complete compartmental elasticity by ultrasound enhancement, this application may improve detection of early signs of potential compartment syndrome.
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany ; Department of Orthopaedic Trauma, Sana Klinikum Offenbach am Main, Offenbach am Main, Germany.
authors.forename: Richard Martin
authors.initials: RM
authors.lastname: Sellei
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany.
authors.forename: Simon Johannes
authors.initials: SJ
authors.lastname: Hingmann
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kobbe
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Weber
authors.affiliation: Department of Orthopaedics and Trauma, Queen Alexandra Hospital, Portsmouth, UK.
authors.forename: John Edward
authors.initials: JE
authors.lastname: Grice
authors.affiliation: Helmholtz-Institute for biomedical engineering, Chair of medical engineering, RWTH Aachen University, Aachen, Germany.
authors.forename: Frauke
authors.initials: F
authors.lastname: Zimmerman
authors.affiliation: Helmholtz-Institute for biomedical engineering, Chair of medical engineering, RWTH Aachen University, Aachen, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Jeromin
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Hildebrand
authors.affiliation: Department of Orthopaedic Trauma, Aachen University Medical Center, Aachen, Germany.
authors.forename: Hans-Christoph
authors.initials: HC
authors.lastname: Pape
keywords: Compartment syndrome; Elasticity measurement; Elastography; Intra-compartmental pressure; Non-invasive diagnostic