Elly Trepman, M.D.
Section of Orthopaedic Surgery,
Department of Surgery, University of Manitoba,
Winnipeg, MB

Foot reconstruction may be indicated to accelerate wound healing. Large wounds that heal with granulation and secondary intention may be debilitating, in part, because healing may require many months of dressing changes and clinic visits. In some instances, it may be more effective and efficient to aggressively debride infected and necrotic tissue, repeatedly if necessary, and then consider delayed primary closure over drains when the wound appears clean and granulating.

Ulcers: Non-infected and Infected
Acute ulcers may be managed with local wound care and off-loading, including total contact casting.² If infection is present, debridement of the ulcer may be required. A bony prominence may cause recurrence of an ulcer that had healed with off-loading and in this case ostectomy may be required to prevent further recurrence.

Chronic ulcers do not heal because of three potential factors: 1) ongoing mechanical pressure, 2) vascular compromise, or 3) infection. Therefore, if an ulcer fails to heal in reasonable period of time (generally, approximately 3 months), further evaluation and treatment may be indicated to address these factors.

Surgical treatment includes aggressive debridement of infected and necrotic wounds until healthy perfused tissue is exposed. The ulcer wound is left open and dressed to allow granulation and secondary healing. Antibiotic selection is based on operative cultures of deep tissue. Excision of bony prominence and correction of deformity may be done to relieve pressure. If a plantarflexion contracture is present, Achilles tendon lengthening may be considered to reduce forefoot plantar pressure. Rotational muscle flaps, free tissue transfer, and skin grafting may be indicated for large wounds.

Special situations may require unique approaches to solve a specific mechanical problem that may contribute to poor wound healing. In the forefoot, a refractory ulcer under the first metatarsal sesamoid bones may require sesamoidectomy (partial or complete), first metatarsal dorsiflexion osteotomy, or first metatarsophalangeal joint arthrodesis.¹ If both sesamoids are excised, a first metatarsophalangeal joint arthrodesis may prevent a cock-up toe deformity. Ulcers under the lesser metatarsal heads may be managed with extensor tenotomy, metatarsophalangeal joint capsulotomy, and Duvries metatarsal condylectomy, which preserves weight bearing function of the metatarsal head,¹ or metatarsal head resection with claw toe correction (PIP Duvries condylectomy). For recurrent or multiple forefoot ulcers, options include a Hoffman procedure (excision of all lesser metatarsal heads), ray amputation, or transmetatarsal amputation.¹ Forefoot debridement is done either through the ulcer if exposure is adequate, or through a separate incision on the dorsal, medial, or lateral aspects of the foot, leaving the ulcer open to heal secondarily.¹

Midfoot ulcers may occur at the plantar or medial prominence of a rocker bottom foot resulting from a tarsometatarsal (Lisfranc) Charcot dislocation or medial navicular prominence from a talonavicular (Chopart) Charcot dislocation. In some instances, resection of the bony prominence may be adequate. If recurrent ulceration and osteomyelitis is likely, the potential risks of reconstructive osteotomy and arthrodesis may be favorably compared with those of failed ostectomy.³

Ulcers on the lateral border of the foot may be caused by a prominence at the base or head of the fifth metatarsal. These ulcers may be refractory to local resection of the bony prominence because of an associated varus hindfoot deformity.¹ In these cases, triple arthrodesis,¹ Dwyer calcaneal lateral closing wedge osteotomy, or if flexible, peroneus longus tendon transfer to the dorsolateral cuboid (F. Duerksen, Personal communication, 2001) may reduce the lateral foot pressure and allow healing of the ulcer.

Treatment of ulcers of the hindfoot and ankle may be extremely difficult. The soft tissues are thin, potentially increasing susceptibility to ulceration and early osteomyelitis. Marked instability and deformity from Charcot arthropathy may cause direct external pressure of the malleoli or talar head against shoes or braces, or skin tension over a bony prominence. If the ulcer is likely to recur after successful debridement and immobilization, realignment osteotomy and arthrodesis may be required.⁴ Amputation is another option. Refractory heel ulcers may respond well to partial calcanectomy if the vascular and nutritional parameters reflect adequate healing potential,⁵ but full-time use of an ankle foot orthosis is required because the posterior calcaneal tuberosity and Achilles tendon insertion are ablated.⁵

Abscess and Osteomyelitis
Diabetic foot infections are frequently polymicrobial. The patient may have poor glucose control and impaired leukocyte function. When surgical debridement is done, aerobic and anerobic cultures of tissue (biopsy or curettage) are submitted from deep in the wound; simple wound swab may be an unreliable indicator of deep organisms because of superficial colonization with outside organisms.

Foot salvage of the infected diabetic foot may require aggressive debridement and revascularization. Preoperative treatment with intravenous antibiotics for a period of time may reduce the surrounding cellulitis, facilitate the surgical procedure, and improve operative success.⁶ Abscesses may quickly spread along tissue planes such as the plantar fascia or tendon sheaths, and a long incision may be necessary to adequately drain the infection. Osteomyelitis is managed with resection of infected bone, debridement of surrounding soft tissues, and antibiotics. The surgical wound is left open, and subsequent dressing changes may stimulate granulation tissue and wound healing. Some episodes of osteomyelitis may be treated with antibiotic therapy alone.7

Amputations
If amputation is required, an attempt may be made to preserve part of the foot. A higher amputation level (from ankle disarticulation to transfemoral amputation) increases morbidity including increased energy of walking and associated strain on the heart that may already be compromised by arteriosclerotic disease. Mortality after lower extremity amputation is approximately 11-41% within 1 year. However, early identification of the foot that cannot be salvaged is desirable to minimize treatment morbidity and costs of attempting to save a non-viable foot.

Indications for amputation include acute, life-threatening, rapidly progressive infection such as gas gangrene or necrotizing fasciitis; chronic ulceration or infection that persists despite other treatment; gangrene; or severe, uncontrollable deformity or instability that precludes fitting in footwear or brace. Adequate vascularity is required to permit healing of the amputation stump.

Amputation of the toe at the metatarsophalangeal joint may be complicated by adduction or abduction deformity of the remaining toes. Partial toe amputation retains the base of the proximal phalanx, which may function as a spacer for adjacent toes and limit adduction or abduction toe deformity. Furthermore, preserving the insertion of the plantar fascia to the base of the proximal phalanx retains the weight bearing function of the plantar fascia in stabilizing the arch via the windlass effect. However, some authors favour disarticulation of the metatarsophalangeal joint instead of a partial toe amputation.⁸ Toe amputation is not likely to heal in the absence of palpable pulses without revascularization.⁹ Preoperative transcutaneous oxygen tension may be more useful than ankle blood pressure in predicting successful healing of amputations below the knee.¹⁰

A single ray amputation may be functional.⁸ First ray amputation may be complicated by poor balance and increased pressure under the lesser metatarsal heads, leading to ulceration.⁸ Removal of more than one ray is better tolerated on the lateral border of the foot than along the medial or central forefoot.⁸

The quality of the result after a partial foot (transmetatarsal, Lisfranc, or Chopart) amputation is not necessarily related directly to the length of the stump.¹¹ Factors that contribute to successful partial foot amputation include the presence of normal, healthy, full-thickness skin covering the stump and mobility of remaining joints.¹¹ A stiff stump covered by abnormal skin such as scar tissue or skin graft may be less likely to endure the mechanical stresses of weight bearing and shoe friction.¹¹

Transmetatarsal amputation, with retention of the metatarsal bases, may provide a functional residual limb. The metatarsal stumps are beveled and smoothed to avoid bony prominence. If equinus contracture is present, Achilles tendon lengthening may be required to decrease the potential for stump problems.⁸ The Lisfranc amputation maintains active ankle dorsiflexion and may give good functional results.¹²

The Chopart amputation may be complicated by equinus contracture and stump breakdown because of unopposed pull of the gastrocsoleus.¹² Achilles tenotomy, with or without reattachment of the tibialis anterior and extensor tendons to the dorsum of the talus and calcaneus, may prevent an equinus deformity after Chopart amputation.^8,12

The Syme amputation is an ankle disarticulation with resection of the medial and lateral malleoli.¹³ Removal of the malleoli provides a broad weight bearing area for the end-bearing stump.¹³ The plane of the malleolar resection is made parallel to the ground when the patient is standing.¹³ The stump enables partial weight bearing on the specialized plantar heel pad with a longer residual limb than with a transtibial amputation. An intact and viable plantar heel pad is required for successful healing and durability of the stump.¹³

In the Pirigoff amputation, ankle disarticulation, talectomy, and malleolar resection is done with dorsiflexion and arthrodesis of part of the posterior calcaneus to the tibia, resulting in a longer residual limb than with the Syme procedure.^8,13,14 The Boyd amputation retains most of the calcaneus in neutral position but otherwise is similar to the Pirigoff amputation.

Below knee (transtibial) amputation is required when foot salvage is unsuccessful. A stump length of 6-7 inches (15-17.5 cm) enables prosthetic fitting, avoiding the problems of a stump that is too short or long.⁸ The flaps are rounded to avoid prominent side flaps (so-called "dog ears"), resulting in a tapered stump that facilitates prosthetic fitting.⁸ Knee disarticulation amputation with trimming of the femoral condyles and patellofemoral arthrodesis may provide a conical stump with a large area for end-bearing, and may be a functional alternative to above knee (transfemoral) amputation in some patients.¹⁵

Acute Fracture and Charcot Arthropathy
Treatment of acute fracture in the foot and ankle may be similar in principle in diabetic and non-diabetic patients, with some exceptions. If surgical treatment of the fracture is indicated based on the fracture pattern, preoperative assessment of adequate arterial supply is advised to predict potential for surgical wound healing. The presence of neuropathy may increase the risk of fixation failure or displacement of apparently stable fractures; therefore, more secure methods of fixation and prolonged non-weight bearing immobilization (i.e. twice the duration used in the non-neuropathic patient) may be used.¹ Furthermore, the fracture may be the presenting sign of Charcot arthropathy, and the patient may require more frequent observation and cast changes until the fracture appears healed, followed by prolonged protection with shoes or orthoses.

Until recently, surgical treatment for Charcot arthropathy had been limited to the stage of reconstruction-consolidation (Eichenholtz Stage III).¹ Ostectomy is indicated to prevent or treat ulcerations resulting from a bony prominence.¹⁶ Osteotomy and arthrodesis is done for severe deformity and instability to improve potential for the fitting of shoes and braces.¹⁷

Recent work suggests that reduction and arthrodesis of the Charcot foot in earlier stages (Stage I, development-fragmentation; Stage II, coalescence)¹ may preserve function and prevent ulceration with reasonable surgical risks.^3,18 This topic is reviewed in another article in this supplement.

Conclusion
Ulceration, infection, ischemia, and Charcot arthropathy may place the diabetic foot and ankle at risk for amputation. If nonoperative treatment is unlikely to resolve the active problem, a surgical approach may improve the potential for functional limb salvage.

References

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2. Myerson, M., Papa, J., Eaton, K., Wilson, K.: The total-contact cast for management of neuropathic plantar ulceration of the foot. J. Bone Joint Surg., 74-A: 261-269, 1992.
3. Schon, L.C., Easley, M.E., Weinfeld, S.B.: Charcot neuroarthropathy of the foot and ankle. Clin. Orthop. Rel. Res., 349: 116-131, 1998.
4. Johnson, J.E.: Operative treatment of neuropathic arthropathy of the foot and ankle. J. Bone Joint Surg., 80-A: 1700-1709, 1998.
5. Smith, D.G., Stuck, R.M., Ketner, L., Sage, R.M., Pinzur, M.S.: Partial calcanectomy for the treatment of large ulcerations of the heel and calcaneal osteomyelitis. J. Bone Joint Surg., 74-A: 571-576, 1992.
6. Goodman, J., Bessman, A.N., Teget, B., Wagner, W.: Risk factors in local surgical procedures for diabetic gangrene. Surg. Gynecol. Obstet., 143: 587-591, 1976.
7. Embil, J.M.: The Management of Diabetic Foot Osteomyelitis. Diabetic Foot 3: 76-84, 2000.
8. Brodsky, J.W.: Amputations of the foot and ankle. In M. J. Coughlin and R. A. Mann (eds.), Surgery of the foot and ankle, seventh edition, chapter 22. St. Louis, Mosby, 1999, pp. 970-995.
9. Hunter, G.A.: Results of minor foot amputations for ischemia of the lower extremity in diabetics and nondiabetics. Can. J. Surg., 18: 273-276, 1975.
10. Wyss, C.R., Harrington, R.M., Burgess, E.M., Matsen, F.A.: Transcutaneous oxygen tension as a predictor of success after an amputation. J. Bone Joint Surg., 70-A: 203-207, 1988
11. Harris, W.R., Silverstein, E.A.: Partial amputations of the foot: a follow-up study. Can. J. Surg., 7: 6-11, 1964.
12. Chang, B.B., Bock, D.E.M., Jacobs, R.L., Darling, R.C., Leather, R.P., Shah, D.M.: Increased limb salvage by the use of unconventional foot amputations. J. Vasc. Surg., 19: 341-349, 1994.
13. Harris, R.I.: Syme's amputation - the technique essential to secure a satisfactory end-bearing stump. Can. J. Surg., 6:456-469, 1963 and 7:53-63, 1964,
14. Nakhgevany, K.B., Rhoads, J.E.: Ankle-level amputation. Surgery, 95: 549-552, 1984
15. Duerksen, F., Rogalsky, R.J., Cochrane, I.W.: Knee disarticulation with intercondylar patellofemoral arthrodesis. Clin. Orthop. Rel. Res., 256: 50-57, 1990.
16. Brodsky, J.W., Rouse, A.M.: Exostectomy for symptomatic bony prominences in diabetic Charcot feet. Clin. Orthop. Rel. Res., 296: 21-26, 1993.
17. Pinzur, M.S.: Benchmark analysis of diabetic patients with neuropathic (Charcot) foot deformity. Foot Ankle Intl., 20: 564-567, 1999.
18. Stone, N.C., Daniels, T.R.: Midfoot and hindfoot arthrodeses in diabetic Charcot arthropathy. Can. J. Surg., 43: 449-455, 2000.