The first installment of this two-part article, published in the November issue of LER, discussed offloading strategies for healing difficult diabetic ulcers. This second installment addresses preventing  recurrence and management of Charcot foot and foot amputations.

by Robert J. Snyder, DPM, FACFAS, CWS, and Karen K. Lanier, CPed

Once the wound is healed, maintaining closure is imperative. Recurring ulceration is usually due to non-compliance with prescription shoe wear. A lack of protective shoe gear is the most common cause of ulcer recurrence.³⁶ A study undertaken by Helm et al³⁷ revealed a recurrence rate of 19.4% out of 102 patients. Myerson et al¹³ postulated a recurrence rate of 31% out of 71 patients.

Research has documented poor compliance with footwear and other offloading devices in patients at risk for diabetic foot ulcers.^65-67 Studies have also shown that ulcer recurrence rates are higher in patients with poor compliance, suggesting that compliance with offloading devices has a preventive effect. A Centers for Disease Control study determined that diabetics with proper shoe protection had only a 20% recurrence, while those without had an 80% recurrence.³⁸ Similarly, another study found that patients who reported using protective footwear for more than 60% of the day had recurrence rates that were less than half those of patients who reported wearing their footwear less often.⁶⁸

Preventing recidivism

The following modalities can be utilized to prevent recidivism.

Custom molded shoes. Prescription shoes accommodate, stabilize, and support deformities and limit inappropriate motion of joints. These measures can decrease inflammation and pain and reduce pressure on the foot.³² Molded shoes are individually constructed over a modified positive model of the individual’s foot. The molded shoe should be deep enough to accommodate a removable insole. The federal government, through the Medicare “Therapeutic Shoe Bill,” recognizes the benefit of special shoes and insoles made for diabetic patients.⁴⁰

Depth shoes. These shoes provide additional vertical depth of 3/16 to 1/2 inch. Wide shank depth shoes give additional width in the girth (instep).

Depth wide shank shoes. This shoe is 1/4-inch deeper than regular depth shoes and will accommodate up to a 1/2-inch inlay.

Moldable shoes. The entire lining of this shoe is constructed of 1/8-inch foam and is covered with a seamless fabric. This shoe is moldable (when heated) and can accommodate many different deformities by using a “ball and ring” device.

Full contact orthoses/total contact inserts (TCI). Special insoles reduce foot pressures by as much as 50%.^40,69,70 These devices are molded over a positive model or directly to the patient’s foot with appropriate posting. This modality is made of material that may accommodate the deformity, and/or alters lower extremity biomechanics. A full-contact orthosis requires shoes of sufficient depth.

Steel shanks and extended shanks. Steel bars are used with the rocker sole to reduce metatarsophalangeal extension or provide better biomechanics for the transmetatarsal amputee.

SACH heel and other heel modifications. The insertion of a SACH heel to the rear midsole of a patient’s shoe acts as an extrinsic shock absorber. This device is constructed of a high-density material with give and is inserted to prevent wear while absorbing shock and immediately rebounding for the next heel strike. SACH heels often are used in conjunction with short leg braces and can replace some of the lost rotational movement of the limb on the foot when such torque is lost due to fusion or trauma.⁴¹ This device also can stabilize the foot after partial calcanectomy.

Wedging is frequently used for stabilizing a flexible deformity in a corrected position or in accommodating a fixed deformity. A medial wedge is indicated in extreme pronation, and a lateral wedge can be used for ankle instability or a varus heel deformity. Wedges can be placed between the upper and the sole or directly on the bottom of sole. Heel and sole flaring often are used for support. This type of modification provides medial lateral stability to the foot on the side to which it is applied. Flaring is often united with wedging for maximal effect (see Figure 4).

Rocker bottoms. Rocker-sole shoes are one of the most commonly prescribed shoe modifications^42,43 and are associated with significant reductions in plantar pressure.⁷¹ They represent exterior additions to the outsole that taper off at the distal tip and may taper off to the posterior edge of the heel, creating changes in biomechanical function. In general, rocker soles are custom made for each patient; six basic types of rocker soles can be identified based on the variation of position and the degree of the rocker angle (see Figure 5).

1.  Mild rocker sole — The most widely used and most basic of the rocker soles has a mild angle at both the heel and the toe. This type of rocker sole can relieve metatarsal pressure and may assist gait by increasing propulsion and reducing energy expended when walking. It is appropriate for the foot that is not at risk and typically found on athletic walking shoes.

2.  Heel-to-toe rocker sole — Shaped with a more severe angle at both the heel and the toe, the heel-to-toe rocker is extended to provide greater propulsion at toe off. This causes a decrease in heel strike and reduces the need for full range of ankle motion. The modality is appropriate for a fixed claw toe, rigid hammertoe, midfoot amputation, calcaneal ulcers, or for the patient who has undergone triple arthrodesis.

3.  Toe-only rocker sole — The purpose of a toe-only rocker sole is to increase weight bearing behind the metatarsal heads, provide stability at midstance, and reduce the need for toe dorsiflexion. It is useful for hallux rigidus, hammertoes, and metatarsal ulcers associated with diabetes.

4.  Severe angle rocker sole — This type of sole also has a rocker angle only at the toe; however, the angle is much more severe than that found on the toe-only rocker sole. This device eliminates the weight-bearing forces at the metatarsal heads and anterior to them and is most often used for extreme relief of diabetic ulcers at the metatarsal heads.

5.  Negative heel rocker sole — Shaped with a rocker angle at the toe and a negative heel, this type of rocker sole results in the patient’s heel being at the same height or lower than the ball of the foot when the patient is standing. The negative heel rocker sole accommodates a foot that is fixed in dorsiflexion and/or relieves forefoot pressure by shifting it to the hind foot and midfoot. The negative heel rocker sole should be used with caution because the patient’s inability to attain the appropriate ankle dorsiflexion may cause discomfort and ultimately increase pressure on the problem area.

6.  Double rocker sole — This is a mild rocker sole with a section removed in the midfoot area; thereby giving the appearance of two rocker soles — one at the hind foot and one at the forefoot (two areas of midstance). Because the thinnest area of the double rocker sole is at the midfoot, it is used to relieve a specific midfoot problem area, such as the Charcot foot deformity associated with diabetes.

Charcot Foot (Osteoarthropathy)

The etiology of Charcot foot (see Figure 6) is multifactorial and based on neuropathy and metabolic processes.⁴⁴ Neuropathic arthropathy may be defined as a relatively painless, progressive, and degenerative condition of single and multiple joints caused by underlying neurological deficits.⁴⁵ Additional neurovascular theory postulates that increased peripheral blood flow due to autonomic neuropathy leads to a hyperemic bone resorption.⁴⁶ Other predisposing factors may include renal transplantation, immunosuppressive therapy, impaired cartilage growth, and nonenzymatic glycosolation.⁴⁵ Sadly, these deformities can result in major limb amputation.⁴⁷

Eichenholtz⁴⁸ described the stages of bone and joint destruction followed by fracture healing and remodeling. This temporal classification is based on the characteristic clinical and radiographic changes that occur with neuropathic joint destruction and fracture over time; progression occurs from the acute phase (dissolution) through the healing phase (coalescence) to the resolution phase. The resulting foot deformities cause difficulty with shoe fit and significantly increase the propensity toward ulceration in high-pressure areas.⁴⁹ Almost all patients with these deformities will ultimately require specialized footwear with custom total-contact inserts or custom bracing. Surgery for these conditions is predicated on the goal that restoration of stability and alignment of the foot and ankle will make appropriate shoe wear and bracing possible.⁵⁰ Foot ulcers in association with significant neuropathic deformity are usually treated with many modalities, ranging from total-contact casts, CROW boots, AFOs, PTB devices, and removable prefabricated walking braces to custom molded insoles, bracing, and shoes. The type of appliance used is predicated on the Eichenholtz stage of development.

Eichenholtz stages.

Stage I (Dissolution). Radiologically, regional bone demineralization with periarticular fragmentation and joint disarticulation is present. Clinically, acute inflammation, swelling, erythema, and heat are evident. This early stage is easily mistaken for infection or thrombophlebitis.⁵¹ Treatment is nonweight-bearing and usually consists of a total contact cast, BAFO, CROW boot, or a removable prefabricated walking brace. One study of 34 feet revealed that treatment averaged 8.4 months. However, follow-up could continue for 35 months or more.⁵² As treatment progresses, care must be taken to gradually wean the patient from nonweight-bearing to partial and then full weight-bearing along with the help of assistive devices; these include appropriate and professionally guided use of crutches, walkers, or canes.⁵³

Stage II (Coalescence). Radiologically, absorption of bone debris in the soft tissues is evident, along with organization and early healing of fracture fragments and periosteal new bone formation. Clinically, a decrease in inflammation with less fluctuance can be noted as well as increased stability of fracture segments. A study of 43 feet in this classification³⁰ revealed that immobilization lasted an average of 6.4 months in 34 of the feet and follow-up averaged 16.4 months.

Stage III (Resolution). Radiologically, a smoothing of large bone fragment edges is present, along with sclerosis and bony/fibrous ankylosis. Clinically, permanent enlargement of the foot and ankle, fixed deformity, minimal swelling, and normalization of temperature are evident. A study of 60 feet in this category³⁰ required follow-up for 22.1 months. Treatment consisted of custom-molded shoes and insoles unless ulceration dictated otherwise. No immobilization was required in this group because of the healed nature of the process. Anderson et al²¹ recommends an extra-depth shoe coupled with a cushioned insert attached to a double-upright calf-lacing brace with a fixed ankle joint and rigid rocker sole. The shoe may need a wide shank or a more rigid rocker if the midfoot or hindfoot areas are involved. The patient also should be fitted with knee-high compression hose. An AFO or CROW can be used as an alternative.

Pedorthic Management of Amputations of the Foot

Partial amputations of the foot are becoming more frequent when compared with transtibial or trans-femoral amputations because retained length results in better function and lower energy expenditure.^54,55 The goal of surgery is to achieve the most distal level of amputation that will heal. These procedures should result in a stable shoeable or braceable residual limb that allows for maximum rehabilitation.⁵⁶ The practitioner should strive to provide a comfortable, safe, stable, and supportive device that is easy to use and adjust.^30,57 Function of the amputated part should be stable enough so as not to cause breakdown of the contralateral limb.

Conclusion

Lower extremity wounds in the diabetic population represent a challenge to the clinician. Treatment is multifocal and includes debridement, infection control, offloading, the use of protective and active dressings, revascularization, and patient education. Offloading is imperative if foot pressures are to be reduced, healing is to progress, and ulcer prevention is to be a realistic goal.

Using footwear as a means of attempting to heal open wounds is rarely desirable. However, once healing has occurred, utilizing shoe gear, insoles, and shoe modifications to maintain closure is imperative. This is also true of Charcot foot and amputations of the foot and ankle.

This written and pictorial compendium of modalities and algorithm of care was compiled to aid the clinician in choosing appropriate devices for individual conditions and to update knowledge of available modalities and resources. Constant technological improvements require clinicians to be diligent in seeking additional information on improvements and enhancements when prescribing offloading devices.

Robert J. Snyder DPM, FACFAS, CWS, and is a faculty physician at the Wound Healing Center, University Hospital, Tamarac, FL, and a faculty physician and director of wound management education at the Wound Healing Center, Northwest Medical Center, Margate, FL. Karen K. Lanier, CPed, is CEO of Branier Orthopedic Custom Molded Shoes in Sebring FL.

This two-part series is reprinted with permission from: Snyder RJ, Lanier KK. Offloading difficult wounds and conditions in the diabetic patient. Ostomy Wound Management 2002;48(1):22-35. The text has been edited to reflect new developments since the original publication date.

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Additional Resources

Valmassy RL. Clinical Biomechanics of the Lower Extremities. St. Louis: Mosby Yearbook; 1996:365–366.

Armstrong DG, Abu-Rumman PL, Nixon, BP, Boulton, AJM. Continuous activity monitoring with persons at high risk for diabetis-related extremity amputation. J Am Podiatr Med Assoc. 2001;91(9):451–455.