Date Published: June 15, 2018
Publisher: Public Library of Science
Author(s): Troy Morrison, Sara Jones, Ryan S. Causby, Kerry Thoirs, Rayaz A Malik.
Diabetes mellitus (DM) is associated with hyperglycaemia and advanced glycosylation end-products. In the foot, the consequences of chronic or uncontrolled diabetes are micro and macrovascular disease, neuropathy, reduced joint mobility and structural and soft tissue changes that increase the risk of ulcer development and amputation. Diabetes foot assessment currently includes a comprehensive history, neurological and vascular assessments and examination focussed on dermatological and musculoskeletal abnormalities. Whilst these assessments are helpful for predicting ulceration risk, direct identifiers that enable early therapeutic intervention are lacking. The intention of this review was to ascertain if B-mode ultrasound could be clinically applied to identify structural change in the diabetic foot and be utilised as an early predictor of ulceration risk.
Primary databases and grey literature sources were systematically searched. Selection criteria were that the study included a diabetic sample and used B-mode ultrasound to assess soft tissue structures of the foot (plantar skin, plantar fat pad or intrinsic muscles).
Fifteen studies were identified for inclusion (combined diabetic sample of 773). Ultrasound demonstrated reductions in tissue thickness in diabetics compared to non-diabetics under first (p = 0.01) and second (p = 0.03) metatarsal heads, but not the third (p = 0.24). Statistical heterogeneity was high for ultrasound thickness measures under metatarsal heads four/five (I2 65%, 81%) and very high for plantar skin (I2 98%), heel pad (I2 76%) and intrinsic muscles (I2 91%, 81%). Extensor digitorum brevis (EDB) ultrasound measures were significantly thinner in diabetics for all dimension measures compared to healthy controls except one study, which reported no significant differences in EDB thickness.
No direct evidence was found to indicate B-mode ultrasound measures can predict soft tissue changes in the plantar foot in diabetes, although low level studies indicate ultrasound has the potential to identify structural change. Clinical, methodological and statistical heterogeneity limit result applicability. This review highlights the need for robust prospective longitudinal research to examine the predictive validity of this method.
Diabetes mellitus (DM) is a chronic metabolic disease that is predicted to impact over 640 million people by the year 2040 . People with DM are at increased risk of developing diabetes-related foot complications with the risk of ulcer development reported at 15–25% [2, 3]. Up to 20% of diabetics with foot ulcers require amputation .
Using PRISMA guidelines , a PICOS (participants, intervention, comparison, outcome and study) search strategy was developed (S1 Fig) to identify and review studies that used high resolution ultrasound to image the soft tissues of the plantar foot in people with DM.
There is merit in investigating the value of ultrasound measurements of the plantar soft tissues as a predictor of diabetes-related change as its low cost, low risk, portability, non-invasiveness and accessibility would suit community screening programs. We identified fifteen studies that compared dimensional ultrasound measurements of the soft tissue of the foot between diabetic and non-diabetic participants, and between different groups of diabetic participants including those with and without peripheral neuropathy or foot ulceration. A range of plantar foot structures were investigated including the skin, heel pad, forefoot and intrinsic muscles. While some studies demonstrated that ultrasound identified structural changes in the soft tissues of the diabetic foot compared to a non-diabetic foot, the study designs are not strong enough to suggest these changes are either causal or predictive of diabetes-related foot complications.
This review has not revealed direct evidence to support the use of high resolution (B-mode) ultrasound to identify soft tissue changes of the foot as a cause or predictor of diabetes-related complications in the foot. However, the finding that dimensions of soft tissues under the first and second metatarsal heads and the EDB muscles are reduced in diabetic people compared to healthy people, and is further reduced in people with more chronic diabetes, suggests that standardised and reproducible ultrasound measurement techniques may have a role in identifying causal or predictive changes and which could be tested with quality prospective cohort studies.