Abstract
Background: Non-healing diabetes-related foot ulcerations (DFUs) continue to precede up to 80% of lower limb amputations, of which those in the high-risk category are disproportionately affected. Despite intensive foot management, they also suffer from high rates of recurrence following an ulcer healing episode. Non-enzymatic glycosylation ensuing from hyperglycaemia, which is a key characteristic of diabetes, results in an excessive accumulation of advanced glycosylation end-products (AGEs) in most human tissues.Recent evidence highlighted that these changes could compromise the structure and function of tendons and soft tissues, making the foot more vulnerable to injury from external biomechanical stresses. As a local biomarker, tissue properties could act as a more sensitive indicator and direct identifier of an individual’s susceptibility to DFU as compared to conventional risk factors. The relationship between external biomechanical stresses and internal soft tissue changes, and how they contribute to DFU development, are also not well understood.
Overall aim: To investigate the role of plantar soft tissue (PST) and Achilles tendon (AT) thickness, stiffness and sonographic abnormalities in people with diabetes with a recently healed DFU.
Methods: To achieve the aims and objectives of this research, a systematic review, a reliability study and a cross-sectional observational study were conducted.
1. Systematic review: Published literature on PST and AT thickness and stiffness in people with and without diabetes were systematically reviewed.
2. Reliability study: The intra- and inter-rater reliability of utilising strain elastography was assessed in the PST and AT in people with diabetes and a recently healed DFU using a GE Logiq S8 ultrasound machine. Cineloops were assessed by a novice and experienced rater to determine the colour scoring, strain index and strain ratio in seven plantar sites and across three AT segments per foot.
3. Cross-sectional study: Key morphological and biomechanical variables of the PST and AT were assessed in 20 people with diabetes and a recently healed DFU. These included: thickness, stiffness and sonographic abnormalities of the PST and AT using grayscale ultrasound and strain elastography with a GE Logiq S8 machine, plantar pressure using a Novel EMED pedography platform and physical activity levels using an activPAL triaxial accelerometer.
Results:
The systematic review found that the PSTs in people with diabetes were significantly stiffer than healthy controls, but no significant differences were found in PST thickness. People with diabetes were also found to have significantly thicker AT than healthy controls, but no significant differences in their AT stiffness. Importantly, it had also identified marked methodological heterogeneities and deficiencies in current literature.
The reliability study found that inter-rater reliability of strain elastography were superior to intra-rater reliability. Colour scoring was the most reliable method, when compared with strain index and strain ratio. The Achilles tendon was also scored more reliably than the PST. The intra-rater reliability of the novice rater was comparable with the experienced rater for most elastographic measures. Importantly, the study also highlighted that, while US-based assessments are widely known to be operator-dependent, subjectivity is also involved in the analysis of elastography cineloops.
This cross-sectional study is the first study to comprehensively report thickness and stiffness outcomes, as well as sonographic features, in plantar sites known to be at high risk of DFUs. However, thickness and stiffness differences between ulcerated and non-ulcerated PST sites, as well as the AT on the ulcerated and non-ulcerated foot, appear broadly modest. By contrast, marked differences were identified in the sonographic characteristics of PST. Additionally, despite generally low physical activity levels observed in participants, peak plantar pressures and cumulative plantar tissue stress were markedly elevated in ulcerated compared to non-ulcerated PST sites. This study highlights that differentiating sonographic features may exist between recently epithelised and non-ulcerated PST sites. It also underscores the importance of offloading at previously ulcerated locations. However, these results ought to be viewed with caution, as the strength of findings are limited by its small sample size and underpowered nature.
Conclusion: Unique differences in soft tissue and biomechanical stresses appear evident between recently epithelised and non-ulcerated plantar sites. However, strain elastography may have limited applications in early DFU prevention due to high operator dependency, poor intra-rater reliability and minimal ability to detect stiffness differences between previously ulcerated and non-ulcerated sites. By contrast, the role of ultrasound in early DFU prevention may be under-utilised as sonographic changes were consistently identified in previously ulcerated sites. Additional robust studies with a larger sample size are required to more fully understand the utility of assessing soft tissue changes in its contributions towards DFU risk.
| Date of Award | 2024 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Sponsors | Carnegie Trust for the Universities of Scotland |
| Supervisor | Ruth Barn (Supervisor), James Woodburn (Supervisor) & Lisa Wright (Supervisor) |