Research in Focus: Why Some Pressure Injuries May Be Unpreventable for Individuals With Spinal Cord Injury

  •   August 9, 2019

Full Citation: Lemmer DP, Alvarado N, Henzel K, Richmond MA, McDaniel J, Graebert J, Schwartz K, Sun J, Bogie KM. What Lies Beneath: Why Some Pressure Injuries May Be Unpreventable for Individuals With Spinal Cord Injury. Archives of Physical Medicine and Rehabilitation 2019. 100:1042-1049.

Background

Pressure injury (PrI) is the most common complication secondary to spinal cord injury (SCI). Although commonly thought to be an avoidable condition, the National Pressure Ulcer Advisory Panel now acknowledges that PrI may be unavoidable in some circumstances.

Interventions to prevent PrI in people with SCI typically focus on reducing pressure over bony prominences during sitting and decreasing the duration that pressure is applied. However, some research has indicated the tissue composition of muscle covering bony prominences and the vascularization of the tissue may impact its ability to distribute pressure, maintain tissue health, and avoiding pressure injury. One variable of interest is the extent to which lean muscle has been replaced by intramuscular adipose tissue and how that relates to the incidence or recurrence of PrI as “the muscle quality of paralyzed gluteal muscle varies considerably” between individuals with SCI.

This study compared ischial pressure, tissue vascularity, and gluteal muscle tissue composition (specifically the presence of intramuscular adipose tissue (IMAT)) between individuals with or without a history of PrI.

Methods

  • Repeated measures design
  • Cohort sample
  • 38 participants with complete or incomplete SCI
    • 72% (n=27) of study participants had a history of PrI
  • Exclusion Criteria
    • Open pelvic region PrI at the time of recruitment
    • Presence of systemic disease
    • Known sensitivity to intravenous contrast
  • Tissue health was assessed using interface pressure distribution and transcutaneous oxygen pressure (TcPO2)
    • Interface pressure distribution was assessed using the CONFORMat Pressure Measurement System and a flexible seating interface pressure mat
    • TcPO2 was measured using a Radiometer TCM400 monitor
    • TcPO2 of tissue overlying the ischial tuberosities was assessed with the patient in side-lying position with hips and knees flexed to 90⁰ for 20 minutes, then subsequently in sitting for 20 minutes
  • Computed Tomography (CT) was used to assess tissue volume and composition (proportion of lean muscle, low density muscle and IMAT)
  • Tissue health assessment and pelvic CT scans with contrast we completed at recruitment and repeated annually for up to three years

Findings

  • There was no significant difference in ischial pressure between those with or without a history of PrI.
  • Individuals with a history of PrI were significantly more likely to have a sustained reduction in TcPO2 in the ischial region in sitting.
  • There were significant differences in gluteal muscle composition, specifically the amount of IMAT present, in individuals with a PrI history compared with those with no PrI history.

Pressure and time have long been considered the key factors to address as part of a pressure relief regime. However, as stated by the authors, “IP alone is an inadequate measure of PrI risk. There was no difference between mean ischial pressure values for persons with or without a PrI history... Surface IP be can [sic] similar while internal mechanics change due to higher IMAT which compromises tissue resilience.” The authors go on to state that “higher levels of IMAT reduce the overall micro-vascularity of the affected skeletal muscle, decreasing the basal tissue blood flow…”

“…monitoring changes in muscle quality, soft-tissue composition and function” may help to individualize efforts at PrI prevention.

Limitations

  • 37 of the 38 study participants were male, therefore the generalizability to females with SCI is questioned.
  • The convenience sample of study participants was recruited from a single facility.
    • The cohort included participants with a broad range of injury duration resulting in a heterogeneous sample.
    • Due to recruitment from a single facility, generalizability to the broader SCI population is questioned.
  • Routine use of CT with contrast to assess tissue composition may not be clinically feasible and appropriate due to availability and costs related to CT and concerns regarding radiation exposure.
  • The study identifies a correlation between IMAT and PrI but does not identify a causal relationship or the direction of the causality.
  • Further prospective research involving more robust research design and a larger sample size is required to develop a multivariate predictive model that will inform PrI prevention programs.

Relevance to Physiotherapy practice in Alberta

Prevention of PrI in people with SCI is a fundamental goal due to the many health, quality of life, financial and social costs associated with PrI. Pressure and time do not adequately identify individuals with SCI at risk of PrI. Tissue composition and proportion of IMAT may help to differentiate between those at risk and those not at risk of PrI, aiding efforts to tailor PrI prevention programs to individuals most at risk.

Physiotherapists in Alberta who work with people with SCI should be aware of the limitations of pressure and time to fully explain PrI risk, the potential impact of IMAT on PrI risk and ongoing research related to IMAT and PrI. Physiotherapists working with other individuals at risk of PrI, but without SCI should also be aware of research related to IMAT and PrI due to the potential implications for the individuals they serve.

Disclaimer: The purpose of this summary is to highlight recently published research findings that are not openly accessible. Every effort is made to ensure accuracy and clarity of the summary. Readers are encouraged to review the published article in full for further information.