Prophylactic foot surgery in the diabetic patient
Catanzariti, Alan R
MANY PRACTITIONERS WHO TREAT PATIENTS with diabetes are reluctant to recommend or perform surgery to correct sometimes simple structural abnormalities of the foot. However, the practitioner must weigh the risks and benefits and consider the multiple factors affecting outcome. Avoiding surgery when foot abnormalities are in their early stages can result in more destructive and debilitating ablative surgery later. The role of prophylactic or elective surgery in treating the diabetic foot remains controversial. Nonetheless, the presumed prohibition against any and all surgical procedures involving the diabetic foot is unwarranted.1
Although there is no apparent universally accepted classification for elective surgery in the diabetic patient, several useful categories previously have been described. Corey divides elective surgery into 3 categories: prophylactic, reconstruction, and traumatic.2 Deformities or nonemergent foot surgery in the diabetic patient, as described by Frykberg, also suggest 3 general categories of surgery: ablative, curative, and prophylactic or reconstructive.3 Most medical literature, however, has concentrated on surgical management of ulcers, infections, and vascular derangements; there are sparse references on the indications for prophylactic or reconstructive surgery. Banks recommends that surgical intervention be considered for 4 distinct reasons, not all of which may be truly elective: incision and drainage, biopsy, exostectomy, and reconstruction.4 Despite the relative lack of emphasis on surgical management in the diabetic patient prior to ulceration or infection, it seems unreasonable to withhold justifiable surgical procedures until more advanced and debilitating conditions develop.
Indications and Contraindications
The literature varies on the correct timing and appropriate indications for performing prophylactic surgery. Reasonable indications include failure of conservative treatment to prevent or heal ulceration and treatment of healed ulcers that are stabilized but prone to further breakdown.3 In addition, recurrence of severe callosities, inability to relieve pressure with conservative means, and high-risk areas that are not amenable to shoe therapy or bracing are mentioned as indications for prophylactic surgery.5 Surgical management of foot deformity after limb revascularization also may be indicated to prevent further ulceration or deformity. Patients with lesions who have a history of minor infection and have reconstructible deformity also are candidates for elective surgery.
Described contraindications include patients with advanced symptomatic neuropathy. Gudas believes that patients with active Charcot arthropathy and limbs with inadequate vascularity to heal surgical incisions have a poor prognosis with elective surgery.6 It also is prudent to avoid elective clean surgery when infected tissue is being debrided.
Goals of Surgery
The goals of prophylactic or elective diabetic foot surgery are: (1) prevention of recurrent ulceration; (2) reduction of pressure, primarily over bony prominences; and (3) prevention of more serious or debilitating consequences in an at-risk foot.3,7 Preserving function, while also obtaining a plantigrade foot, should be paramount. Furthermore, it is a reasonable goal to create a foot that can be accommodated in a custom-made shoe or appliance, or an ankle-foot orthosis or brace in cases in which previous ablative surgery has resulted in a high-risk, ulcer-prone extremity. These goals can be achieved through a comprehensive treatment plan that includes contributions from foot and ankle surgeons, pedorthotists, vascular surgeons, diabetologists, nutritionists, plastic surgeons, and other practitioners involved in caring for these patients.
The patient’s overall medical condition must be assessed before proceeding with elective surgery. Evaluation of the patient should proceed with a team approach involving all specialties interested in caring for patients with diabetes mellitus. This typically entails examinations by the internist or endocrinologist primarily responsible for the patient’s glucose control. Depending on physical findings and medical history, a more detailed evaluation of the patient’s vascular, neurologic, nutritional, or bacterial status may be warranted. A careful systematic evaluation of the patient’s lower extremity is a vital component of the overall preoperative assessment.
Vascular disease is a well-known complication of diabetes mellitus. Elective surgery in the diabetic patient should not be performed prior to evaluation of the lower arterial supply in the involved extremity. Examination should include a detailed physical examination and use of noninvasive modalities, including toe pressures, pulsed volume recordings, and transcutaneous oxygen tensions. In certain situations, invasive vascular testing may be necessary. In patients with a questionable vascular status, evaluation in conjunction with a vascular surgeon and certified vascular laboratory is imperative.
Neuropathy, vascular disease, infection, and deformity are the 4 major contributors to the development of diabetic foot lesions. The most common cause of all types of diabetic foot problems is symmetrical polyneuropathy. There are essentially 3 forms of diabetic symmetrical polyneuropathy that should be considered: sensory, autonomic, and motor neuropathy. Of these, sensory alterations seem to be most common.
Sensory neuropathy appears to be the primary cause of most unrecognized injuries in the diabetic patient. Sensory impairment may be responsible for ulcers, fractures, or dislocations. Patients frequently present with decreased sensation in a stocking-type distribution below the knee. Assessments of light touch, sharp/ dull, and two-point discrimination are performed. Semmes-Weinstein monofilaments may be used to estimate protective threshold. These monofilaments are currently the most widely recommended methods of measuring sensory function in the diabetic.1 It has been proposed that patients who can feel the 5.07 monofilament have a sufficient level of sensation to avoid neuropathic ulceration.
Autonomic neuropathy may manifest as loss of normal sweating and skin temperature regulation, predisposing the patient to dry, scaly, and stiff skin. Noncompliance of the skin may predispose the diabetic to cracks and fissures. Additionally, autonomic neuropathy may result in diabetic neuropathy and subsequent foot deformity.
Motor neuropathy manifests as a dysfunction of intrinsic musculature, contributing to pedal deformities. Included in the evaluation of motor neuropathy should be a gait analysis and complete muscle testing and grading.
Deformity evaluation is an important part of a preoperative assessment. Diabetic ulcerations usually result from a combination of insensitivity and the pressure of a bony protuberance against the skin. Patients without neuropathy usually do not ulcerate because their pain threshold remains intact and protects them from excessive pressure. Those with neuropathy typically do not ulcerate in the areas of the foot where there is no bony prominence unless there is underlying ischemia. The most common deformities in the diabetic patient are those of the forefoot. Reconstructive procedures should be contemplated in patients predisposed to ulcerations because of structural or biomechanical abnormalities. The development of structural deformities in the diabetic patient places the foot at risk for the dangers of ulceration and infection (Figures 1a, b, and c).
Careful preoperative evaluation and planning should be instituted prior to deterning whether surgical or nonsurgical means would be best suited for the patient at risk. It is not possible to establish absolute criteria for the selection of the diabetic patient most suitable for surgical intervention. Each patient should be evaluated based on the degree of deformity, history of ulcerations, general physical condition, and impairment of glucose control. Withholding surgical management of high-risk deformities in the well-controlled diabetic patient may place the foot at undue risk for future deterioration. Failure to remove the source of the lesion is more dangerous than the judicious use of surgery to correct a deformity and relieve bony pressure.
Nutritional evaluation is important prior to any type of elective surgical procedure in the diabetic patient. Studies have shown that impaired healing may occur in patients with a poor nutritional status. A serum albumin level less than 3.5 gm/dL and a total lymphocyte count of less than 1,500 cells per cubic millimeter have been accepted as evidence of pre-existing malnutrition. Another simple nutritional index indicating nutritional adequacy for healing is total protein level greater than 6.2 gm/dL.8
In addition to nutritional requirements, endocrine factors must be considered, the most important of which is good control of blood glucose levels. Adequate control of glucose has been felt to significantly improve the diabetic patient’s ability to heal a wound. Hyperglycemia may have deleterious effects on the immune system, including delayed wound closure, delayed contraction, and defects in chemotaxis and granulocyte activity, as well as interference in collagen synthesis and erythrocyte function.9 A useful laboratory test indicating longterm glucose control is the glycosylated hemoglobin (HbA,C). This test indicates the blood glucose control over the preceding 120 days. The normal HbA,C may differ, depending on the laboratory, but a goal of 7.5% corresponds to a glucose value of 150 mg/dL in preoperative patients. Surgery may be delayed for several weeks to regain control of the glucose level in diabetics whose HbA,C is greater than 9%.2 Adequate glucose control between 100 and 250 mg/dL has been established by The American College of Surgeons as “within surgical zone.” Failure of the patient to comply with long-term glucose control should result in the postponement of elective surgical procedures. One obvious exception would include the diabetic foot with acute infection, in which the patient’s blood glucose level may be elevated.
The use of anesthesia in diabetic patients is ultimately the decision of the anesthesia team. Modes of anesthesia used to treat diabetic patients include general anesthesia with inhalation agents or spinal, epidural, or regional anesthesia with or without intravenous sedation. Historically, morbidity and mortality associated with high-risk diabetes mellitus patients and lower-extremity surgery under general or spinal anesthesia have exceeded 20%.10 However, with a thorough understanding of the unique demands of these patients, prudent preoperative management, and judicious use of anesthesia, these complications can be contained.
Manifestations of diabetes mellitus that directly affect anesthesia include autonomic dysfunction, renal insufficiency, coronary artery disease with silent myocardial infarction, and hypertension. Gastroparesis is a well-known complication of autonomic neuropathy, and to reduce the risk of regurgitation or aspiration, preoperative histamine^sub 2^ antagonists or rapid sequence induction may be necessary.11
Because spinal, epidural, and regional blocks have no clinically significant effects on carbohydrate metabolism, the use of local anesthetic block in prophylactic foot surgery is preferred.12 Such a block may include ankle, ray, and digital nerve blocks. Previous concerns about injecting a local anesthetic into an infected or ischemic extremity for fear of precipitating local tissue necrosis are without confirmation. Furthermore, Kaufman showed no complications related specifically to the use of a local anesthetic in over 127 foot and ankle procedures that included open and closed amputations and neuropathic ulcer debridements.10 He concluded that local nerve blocks are the optimal anesthesia in the management of ischemic and diabetic foot disorders with no measured risk of gangrene or infection.10 Others also advocate the use of local anesthesia over general inhalation agents in the surgical management of the diabetic foot with no documented deleterious effects on wound healing.3,7,13
Types of Prophylactic Surgery
Nail surgery. The management of ingrown nails, subungual exostosis, and paronychia is vital to the overall care of a patient (Figure 2).
Digital surgery. Surgical management of deformities includes procedures such as arthroplasty, arthrodesis with or without fixation, flexor or extensor tenotomies, flexor tendon transfer, and distal Symes amputation. Tenotomy for a flexible mallet toe deformity (Figure 3) is acceptable, as is a terminal Symes amputation in the face of chronic digital ulceration.
Lesser metatarsal surgery. Options for lesser metatarsal surgery include metatarsal head resection, ray resection, ostectomy, longitudinal segmental resections, and metatarsal neck or base osteotomy (Figures 4a, b, and c).
Panmetatarsal head resection. This type of resection has been developed for management of the diabetic foot as an alternative to transmetatarsal amputation. The procedure is indicated when chronic recurrent forefoot ulceration that has failed multiple metatarsal osteotomies or resection or when there is a high likelihood that a transfer ulcer will occur (Figures 5a and b).
First-ray surgery. Prophylactic firstray surgery may include first metatarsal osteotomy, sesamoidectomy, hallux abducto valgus repair, and hallux rigidous surgery (Figures 6a and b).
Tendo Achilles lengthening. There are primarily 2 indications for lengthening the Achilles tendon in the diabetic foot: an adjunct to surgical management of diabetic neuroarthropathy primarily affecting the midfoot and hindfoot, and recurrent plantar ulcerations following transmetatarsal amputation.
Exostectomy for ulcerations associated with Charcot deformity. Plantar ulcerations commonly occur secondary to Charcot deformity. The architectural disruption of the joints and the osseous collapse in the diabetic foot with neuroarthropathy is well recognized. This foot type concentrates enormous amounts of pressure in isolated areas, which may result in ulcerations. In those patients who fail nonoperative therapy, exostectomy may be a satisfactory procedure (Figures 7a, b, c, and d).
Arthrodesis stabilization for Charcot deformity. Arthrodesis for stabilization of a Charcot deformity may be divided into midfoot procedures and hindfoot procedures. If exostectomy fails or is inappropriate, then arthrodesis procedure may be considered as a means of limb salvage (Figures 8a, b, and c).
Fifth metatarsal base ulcers. Ulcers directly over the fifth metatarsal base are usually the result of an uncompensated varus deformity. These ulcers have a poor prognosis and are very difficult to heal with nonoperative care. A triple arthrodesis may be indicated for recurrent ulcerations that have failed nonoperative care or exostectomy and that predispose the patient to the possibility of osteomyelitis.
Soft tissue coverage. This type of surgery may be necessary for closure of a soft tissue envelope, which often is the case when there is significant soft tissue destruction. Some patients may require simple soft tissue maneuver to fill the defect, while others may require more sophisticated plastic surgical technique (Figures 9a and b).
Subtotal calcanectomy. This procedure is indicated for diabetic patients with recurrent ulcers of the heel that may place them at risk for below-the-knee amputation. Subtotal calcanectomy requires resection of the major portion of the calcaneus, but it does not prevent the patient from bearing weight on the foot. This procedure may be a reliable and predictable alternative to below-the-knee amputation.
The preoperative and perioperative evaluation of diabetic foot pathologies has been discussed. The effects of vascular and neuropathic alterations in such cases can be devastating. Only through understanding of the underlying mechanisms that contribute to the diabetic foot can progressive, appropriate care be rendered.
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Alan R. Catanzariti. DPMs is Director of Podiatric Residency Training at The Western Pennsylvania Hospital, Pittsburgh, PA. This paper is based on his lecture at the 13th Annual Clinical Symposium on Wound Care, October 8 to 11998, in Atlanta, GA.
Copyright Springhouse Corporation Jul/Aug 1999
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