A Guide To Offloading The Diabetic Foot

Start Page: 67

Continuing Education Course #134 September 2005

I am pleased to introduce the latest article, “A Guide To Offloading The Diabetic Foot,” in our CE series. This series, brought to you by the North American Center for Continuing Medical Education (NACCME), consists of regular CE activities that qualify for one continuing education contact hour (.1 CEU). Readers will not be required to pay a processing fee for this course.

When it comes to managing diabetic foot wounds, offloading plays a key role in facilitating healing. With this in mind, Nick Martin, DPM, Tim Oldani, DPM, and Matthew J. Claxton, DPM, offer a thorough review of offloading principles and assess the efficacy of various offloading modalities.

At the end of this article, you’ll find a 10-question exam. Please mark your responses on the enclosed postcard and return it to NACCME. This course will be posted on Podiatry Today’s Web site (www.podiatrytoday.com) roughly one month after the publication date. I hope this CE series contributes to your clinical skills.

Sincerely,

Jeff A. Hall
Executive Editor
Podiatry Today

INSTRUCTIONS: Physicians may receive one continuing education contact hour (.1 CEU) by reading the article on pg. 68 and successfully answering the questions on pg. 74. Use the enclosed card provided to submit your answers or log on to www.podiatrytoday.com and respond via fax to (610) 560-0502.
ACCREDITATION: NACCME is approved by the Council on Podiatric Medical Education as a sponsor of continuing education in podiatric medicine.
DESIGNATION: This activity is approved for 1 continuing education contact hour or .1 CEU.
DISCLOSURE POLICY: All faculty participating in Continuing Education programs sponsored by NACCME are expected to disclose to the audience any real or apparent conflicts of interest related to the content of their presentation.
DISCLOSURE STATEMENTS: Drs. Martin, Oldani and Claxton have disclosed that they have no significant financial relationship with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of their presentation.
GRADING: Answers to the CE exam will be graded by NACCME. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam.
TARGET AUDIENCE: Podiatrists.
RELEASE DATE: September 2005.
EXPIRATION DATE: September 30, 2006.
LEARNING OBJECTIVES: At the conclusion of this activity, participants should be able to:
• discuss biomechanical considerations in selecting appropriate offloading devices;
• explain the concept of total contact pressure relief in offloading plantar foot ulcers;
• assess the benefits and drawbacks of total contact casting (TCC);
• compare and contrast TCC with removable cast walkers and half shoes; and
• discuss the use of insoles and custom devices.

Sponsored by the North American Center for Continuing Medical Education.

Customized ankle foot orthoses (AFOs) are very helpful in special situations in which pressure relief is required but cannot be achieved through simple means.
Here one can see the OrthoWedge Healing Shoe (left) and the HeelWedge Shoe (right). These shoes can be a good choice for facilitating the healing of plantar wounds and are easy to use.
The Active Offloading Walker is quickly becoming the gold standard for pressure offloading due to its ease of use and low peak pressures during ambulation. When one leaves all hexagonal plugs in place, the device works as a multi-density pressure relief i
The Active Offloading Walker is quickly becoming the gold standard for pressure offloading due to its ease of use and low peak pressures during ambulation. The authors cite the device’s one-half inch thickness pressure relief insert. When one leaves all h
In a demonstration of their “pinch test,” the authors say clinicians should examine a patient''s inserts and shoes at each visit to ensure the appropriateness of the offloading materials.
74
Author(s): 
By Nick Martin, DPM, Tim Oldani, DPM, and Matthew J. Claxton, DPM

   Increased plantar foot pressure is a leading cause of ulceration in the diabetic population.1 Healing these ulcers requires adequate blood supply, control of infection, excellent wound care and offloading or pressure redistribution of the ulcerative area.2-16 Out of all these factors, offloading presents a particularly unique challenge in treating chronic wounds. As diabetic foot care has evolved over the years, podiatrists have used numerous approaches including complete bed rest, cutout felt pads and total contact casting to offload these wounds.3,15,17

   However, in order to select an appropriate offloading modality, it is important to be aware of the potential causes of increased plantar pressure in the diabetic foot.

   Ground reactive forces (GRF) impact the plantar foot during weightbearing activities in all ambulatory individuals. The difference in response for diabetic versus non-diabetic individuals is our primary concern as limb salvage specialists. Ground reactive forces can be perpendicular to the foot (known as vertical stress) or they can work parallel to the foot (known as shear stress). When these forces work together in a repetitive fashion, ulcers may form on the plantar foot in people with diabetes due to the inability to appreciate the increased stress on the foot.18

   When people stand, each foot takes on 50 percent of the body weight. However, when people walk, they transfer all of the body weight from one foot to the other.19 During the stance phase of the gait cycle, the entire foot is only on the ground (foot flat) 23 percent of the time.20,21 The heel is in contact with the ground the first 64 percent of the phase while the forefoot is in contact the last 59 percent of the phase. This means all of the body weight is on one heel or one forefoot a significant period of time. This pressure can equal 1.2 to 1.5 times the body weight depending on the walking speed.19

   When a deformity is present, there is increased pressure on the foot. Researchers have shown that diabetes causes a decrease in conduction speed in the tibial and peroneal nerves.22 This correlates to increased lower extremity muscle weakness.22 Muscle weakness may lead to foot deformity and subsequently cause areas of increased pressure.

   Greenman, et. al., have shown that small muscle atrophy occurs in the diabetic foot before clinical peripheral neuropathy is detected.23 Using MRI to look at the cross-sectional anatomy of the foot, they compared the muscle area to total area in non-diabetic controls, diabetic patients without sensory neuropathy and diabetic patients with sensory neuropathy.

   The diabetic group with no sensory neuropathy developed muscle atrophy before clinical sensory loss. Therefore, structural changes may occur with this early muscle weakness before protective sensation becomes diminished. This muscle atrophy may lead to increased plantar foot pressure even in the “low-risk,” sensate diabetic foot. When coupled with the insensate foot, increased pressure patterns typically lead to foot ulceration.

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