Tissue Oxygen Scanning for Acute Compartment Syndrome (ACS) Diagnosis

PROJECT SUMMARY Acute compartment syndrome (ACS) is a complication of extremity injury caused by increasingly elevated intracompartmental pressure (ICP) that eventually compromises perfusion, causing ischemia of the muscles within the compartment. If this persists longer than 6-8 hours, permanent ischemic damage to the muscle occurs (myofibrosis and ischemic contracture). ACS demands immediate surgical fasciotomy to restore tissue perfusion, yet early ACS diagnosis is problematic because of the current lack of a reliable diagnostic standard. Surgeons rely on clinical judgment and index of suspicion to diagnose and make treatment decisions. Since delayed fasciotomy is the most important factor contributing to poor outcomes; treatment decisions are biased towards early intervention, often leading to unnecessary fasciotomy procedures. Since clinical findings are subjective, measurement of ICP is commonly used despite lack of consensus regarding a threshold for performing fasciotomy Research is needed to identify new methods to diagnose ACS. ICP is the most common objective test used to diagnose ACS, but ICP does not tell the clinician whether the involved muscles are healthy, ischemic, or necrotic, and has poor diagnostic specificity. Current ICP devices provide only a single-point pressure measurement, although it has been shown that ICP varies throughout the compartment. Furthermore, measurement of pressure via a percutaneous needle is subject to sampling and technical error. These factors contribute to uncertainty about the ICP reading and therefore the diagnosis. Here we propose developing a new method to diagnose ACS by measuring a depth profile of tissue oxygen in the affected muscle. A-Scan LLC (Minneapolis, MN) has developed an optical scanning needle probe that scans pO2 along its length without mechanical movement. In this project we will characterize the device performance and then test it in a swine model that replicates the pathophysiology of ACS. Commercially, the market of ACS diagnosis is derived from the fact that ACS is considered in every case of tibia fracture. Considering an annual incidence of 300,000 tibia fractures in the US, the market is estimated at $90 million. This phase I of the project plan will focus on validating the functionality and performance of the probe in a large animal model. In a future phase II extension we plan to significantly advance the process of commercializing the device. It includes optimizing the device design for clinical application, perform testing and device characterization for complying with FDA regulatory requirements and complete an initial request for information (Q-Submission) to the FDA in order to obtain a specific device classification code and a pathway to marketing clearance.