ORIGINAL ARTICLE Changes in the Thickness and Stiffness of Plantar Soft Tissues in People With Diabetic Peripheral Neuropathy Jia-Hui Sun, MPhil, Benson K. Cheng, PhD, Yong-Ping Zheng, PhD, Yan-Ping Huang, MPhil, Jenny Y. Leung, MBBS, Gladys L. Cheing, PhD ABSTRACT. Sun J-H, Cheng BK, Zheng Y-P, Huang Y-P, Leung JY, Cheing GL. Changes in the thickness and stiffness of plantar soft tissues in people with diabetic peripheral neu- ropathy. Arch Phys Med Rehabil 2011;92:1484-9. Objective: To compare the thickness and stiffness of plantar soft tissues between people with diabetic peripheral neuropathy (DPN) and healthy subjects. Design: Cross-sectional study. Setting: University research laboratory. Participants: Subjects with DPN (n=70 [35 men, 35 women]; mean age  SD, 65.48.6y) and healthy control subjects (n=54 [12 men, 42 women]; mean age  SD, 57.96.1y) were recruited. Interventions: Not applicable. Main Outcome Measures: The thickness and stiffness of the plantar soft tissues were measured by the tissue ultrasound palpation system over the pulp of the big toe (BT), first meta- tarsal head (MTH), second MTH, and the heel. Results: No significant difference in the thickness of the plantar soft tissues was found in any measurement site between the diabetic group and control group. The plantar soft tissues of the DPN group were significantly stiffer than those of the control group at the BT (85.29kPa vs 50.49kPa), first MTH (96.29kPa vs 62.05kPa), second MTH (84.77kPa vs 52.93kPa), and the heel (65.62kPa vs 44.95kPa) (all P.01). Conclusions: People with DPN tend to have stiffer plantar tissues than do healthy control subjects. The stiffer plantar soft tissues may reduce the cushioning effects of the foot during walking for people with DPN. Key Words: Biomechanics; Diabetes mellitus; Elasticity; Foot; Rehabilitation; Ultrasonography. © 2011 by the American Congress of Rehabilitation Medicine L OWER LIMB COMPLICATIONS in people with diabetes are common and can influence the quality of life of these patients and the extent to which they will make use of the health care system. Diabetic peripheral neuropathy (DPN) is one of the most common diabetic complications, occurring in up to 50% of people with diabetes, 1 and it can be an important predisposing factor leading to foot ulcers. 2 Foot ulceration is one of the major causes of hospitalization for people with diabetes. Fifty percent of all nontraumatic lower limb amputa- tions were performed because of diabetic complications. 3 Therefore, early identification of people who are at risk for developing foot ulcerations is essential for preventing compli- cations from diabetes. A change in the thickness and stiffness of the plantar soft tissues, together with peripheral neuropathy, 4 high plantar foot pressure, 5 previous foot trauma, or foot deformities, 4 could be a possible risk factor for diabetic foot ulcerations. Recent technical advancements make it possible to quantitatively as- sess the thickness and stiffness of plantar soft tissues. The thickness of plantar tissues reflects morphologic changes in soft tissues, whereas their stiffness reflects the major mechanical property of soft tissues. The thickness and stiffness of plantar soft tissues of healthy subjects have been investigated in pre- vious studies using ultrasonography. 6,7 Previous work on the diabetic foot has examined the thick- ness of different tissues such as the plantar fascia 8 or the plantar fat pads. 9 D’Ambrogi et al 8 found an increase in both the thickness of the plantar fascia and the vertical forces under the metatarsal head (MTH) in people with diabetes (who may or may not have neuropathy). They demonstrated a positive correlation between the thickness of plantar soft tissues and the vertical forces under the MTH (r=.52). As compared with a healthy control group, Bus et al 9 showed that the fat pads in the plantar tissues of DPN subjects with toe deformities were significantly thinner under the MTHs but thicker under the phalanges. They postulated that this alteration in fat pad thick- ness could be due to the distal movement of fat pads caused by toe deformities. Most of these studies tested on the individual layer of the plantar tissues. However, the total plantar soft tissue thickness is composed of various layers of tissues in- cluding the plantar skin, fat pads, fascia, and muscle. This total thickness of plantar soft tissues should be considered as a whole when it serves as the cushion for optimizing load- bearing during ambulation. Very few studies have examined the total thickness of the plantar soft tissues at various sites of the sole in subjects with DPN. It is unclear whether the total thickness of the entire plantar tissue is altered in DPN subjects, or whether such a change only occurs in specific locations of the foot. Stiffness indicates the perceived hardness or elasticity of the material when a compression force is applied. The presence of stiffer structures in a diabetic subject’s foot reduces the ability of the foot to disperse forces over a From the Departments of Rehabilitation Sciences (Sun, Cheng, Cheing) and Health Technology and Informatics (Zheng, Huang), The Hong Kong Polytechnic Univer- sity, Hong Kong; and Department of Integrated Medical Services, Ruttonjee Hospital, Hong Kong (Leung), China. Supported by a General Research Fund provided by Research Grants Council in Hong Kong (PolyU 5131/06E). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organi- zation with which the authors are associated. Reprint requests to Gladys L. Cheing, PhD, Dept of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China, e-mail: gladys.cheing@inet.polyu.edu.hk. 0003-9993/11/9209-01093$36.00/0 doi:10.1016/j.apmr.2011.03.015 List of Abbreviations BT big toe DPN diabetic peripheral neuropathy MTH metatarsal head SWMF Semmes-Weinstein monofilament 1484 Arch Phys Med Rehabil Vol 92, September 2011