[Archives of Physical Medicine and Rehabilitation 2019;100:1042-9]
In the last years of his life my dad had a pressure sore which was largely resistant to any form of treatment. As those of you who are regular readers will know I am a member of the American Congress of Rehabilitation Medicine and through my membership I have access to the Archives: this article interested me both because of the close family connection and my day job as a catastrophic injury lawyer regularly dealing with individuals who have suffered a spinal cord injury [SCI]. Pressure injury remains the most common secondary complication after spinal cord injury: and at its worst it can be incredibly debilitating.
The aim of the study was to investigate the intersection between pressure injury history, muscle composition, and tissue health responses under physiologically relevant loading conditions for individuals with SCI: in other words let's look at how people sit down and what makes good rear cushioning.
38 participants were enrolled into the study.
It stands to reason that adequate tissue resilience is required for tissue to be maintained under applied loads. For the full time wheelchair user this means maintaining pelvic region tissue health whilst seated. Traditional techniques to mitigate pressure injury risk focus on reducing applied pressures and decreasing the duration of loading. The purpose of pressure relief is to maintain adequate skin and skeletal muscle perfusion by the recovery of blood flow through the local vessels. It does, however, remain unclear how frequently an individual with SCI needs to weight shift in order to avoid tissue damage.
Let's consider the physiology: after SCI the level and extent of the injury influence the amount of disuse muscle atrophy that occurs in the paralysed muscles. Dystrophic-type muscle changes occur within the lean muscle tissue leading to it being replaced by adipose tissue, specifically intramuscular adipose tissue (IMAT).
Within the high-risk population clinicians have observed that some individuals with SCI never develop pressure injuries whereas others have repeated episodes of tissue breakdown.
However one person's gluteal muscle composition is not the same as another… Detailed analysis of composition can provide insight into hidden tissue health factors impacting personalised risk status. The primary hypothesis under investigation was that gluteal muscle composition impacts tissue resilience under physiologically relevant loading conditions, specifically sitting.
The current study confirms that interface pressure (i.e. a pressure map) alone is an inadequate measure of pressure or injury risk. CT muscle imaging can, however, reveal abnormalities in muscle composition and provide insight into hidden factors that affect tissue health. Some individuals with SCI had their gluteal muscle almost entirely replaced by IMAT. The study also found that muscle composition continues to change over time even for individuals with long-standing SCI.
The relative intramuscular composition of fat and muscle affects tissue resilience. High levels of IMAT reduce the overall micro-vascularity thereby decreasing the basal tissue blood flow.
A key to personalising pressure and risk status may be provided by monitoring changes in muscle quality soft tissue composition and function. Changes in composition, particularly IMAT, may increased pressure injury risk. Individuals with more than 15% gluteal IMAT were statistically more likely to have a history of severe recurrent pressure injuries.
Interface pressure mapping alone provides a limited indication of risk. Soft tissue composition and functional responses under physiological loads can provide a key to personalised risk status referral for persons with SCI. IMAT may provide the missing key to defining safe sitting durations and safe interface pressure thresholds. Don't just look left and right: look behind you as well…
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For more information please contact Ian Slater, Partner DD 0161 603 5066 M 07798 700494