Orthopedic management of Diabetic foot
Surgical management of the diabetic foot plays an integral role in the prevention and management of limb-threatening complications for people with diabetes. It should be understood at the outset that early intervention provides the best chance of surgical cure and limb salvage.
The goal is to preserve a functional plantigrade foot, and to prevent major amputation.
Surgery of the diabetic foot will be stratiﬁed into three broad categories including:
- Elective surgical procedures
- Prophylactic surgical procedures
- Emergent (emergency) surgical procedures.
Elective surgical procedures
Elective surgery includes procedures that are advantageous to the patient but not urgent. For example, correction of a painful bunion or hammer toe in a stage 1 patient (with protective pain sensation, adequate perfusion and well controlled diabetes) is considered elective.
Prophylactic surgical procedures
Prophylactic surgery includes procedures which are necessary to prevent further compromise of the foot: for example, a patient with chronic recurrent ulceration beneath the hallux, who has a limitation of motion at the 1st metatarsophalangeal joint. The pathomechanical aetiology of this lesion, in an insensate patient, is hallux limitus or rigidus. Unless this condition is corrected the ulcer will never be completely resolved.
Emergent surgical procedures
Emergent surgery includes conditions that require immediate surgical intervention. These patients generally present to the Emergency Room/Casualty department with serious foot infections. It is important to emphasize that signs of systemic toxicity are not always present and clinical ﬁndings may be subtle. Patients may or may not be febrile and may or may not have an elevated white blood cell count; however, their diabetes is most often out of control. Depending upon the presentation, surgical treatment may include: incision and drainage of pus, exploration of wounds, debridement of necrotic soft tissue and bone, revascularization and local amputation of the foot.
Principles of surgical management include:
- Prompt detection and intervention
- Preoperative medical work-up and clearance for surgery
- Medical management of diabetes and comorbid conditions
- Targeted antibiotic coverage of infection
- Vascular work-up
- Wound care and dressings
- Postsurgical surveillance
- Podiatric care, footwear and orthoses.
GOALS OF DIABETIC FOOT SURGERY
- Establish dependent drainage
- Remove bacteria-laden necrotic soft tissues
- Remove infected/necrotic bone
- Correct deformity
- Reduce risk of ulceration or amputation
- Restore stability and alignment
- Preserve function
- Achieve a cosmetically acceptable result
- Prevent major amputation of the leg.
Hammer toe correction
Patients with diabetes often develop one or more digital contractures. Flexion contracture of the toes develops as a result of biomechanical imbalance between the long ﬂexor and extensor tendons to the toe. The intrinsic muscles of the foot, the interossei and lumbricales, function to stabilize the toes on the weightbearing surface. Weakness of these muscles, secondary to motor neuropathy, results in the development of hammer toes and, in some cases, claw toes.
A hammer toe is characterized by hyperextension of the toe at the metatarsophalangeal joint, and ﬂexion contracture of the toe at the proximal interphalangeal joint. The resulting deformity, like a swan’s neck, results in retro-grade force on the metatarsal head, causing increased plantar pressure, metatarsalgia, callus formation and eventually ulceration. Friction and pressure caused by the shoe on a prominent proximal interphalangeal joint results in the development of a corn and, eventually, an ulcer. Pressure at the tip of the ﬂexed toe may result in a distal corn and eventually an ulcer.
Claw toes are characterized by ﬂexion contracture at both the proximal interphalangeal joint and distal interphalangeal joint.
Mallet toe is a digital deformity characterized by ﬂexion at the distal joint. Risk of ulceration is associated with each of these three digital deformities, at the tips of the toes and over the prominent interphalangeal joints.
Proximal interphalangeal joint arthroplasty
Proximal interphalangeal joint arthroplasty is indicated for correction of rigidly contracted hammer toes with or without ulceration at the tip of the toe, or over the prominent proximal interphalangeal joint.
- The procedure is performed in the operating theatre under local anaesthesia and sedation, with an ankle tourniquet for haemostasis.
- If an ulcer or corn is present over the proximal interphalangeal joint, it is excised,using two converging semi-elliptical incisions. The incisions are carried down to the subcutaneous tissue and the ulcer is excised.
- The extensor tendon is exposed and transected at the level of the interphalangeal joint. The tendon is retracted proximally, exposing the head and neck of the proximal phalanx.
- The medial and lateral collateral ligaments are freed using scalpel with a No. 15 blade. The head of the proximal phalanx is then transected at the surgicalneck using double action bone-cutting forceps or a power saw. The bone is examined for evidence of osteomyelitis which, if present, would dictate removal of additional bone.
- The extensor tendon is then repaired with absorbable sutures at the level of the proximal interphalangeal joint. If there is evidence of extension of the toe at the metatarsophalangeal joint, then the extensor tendon can be lengthened or transected, followed by a dorsal transverse metatarsophalangeal capsulotomy.
- In the presence of infection the wound should be packed open, with a return to the operating theatre for delayed primary closure within a week. For clean wounds, the skin is closed with 5– 0 nylon simple interrupted sutures.
- The use of a 0.45 Kirschner wire, placed across the joint, is optional. When used to maintain the corrected position of the toe, the wire is placed in a retrograde fashion, from the proximal interphalangeal joint, out through the tip of the toe. It is then driven back into the proximal phalanx. It is wise to reserve the use of internal ﬁxation for clean, elective cases.
Dressings and postoperative care
Dressings consist of non-adherent ﬁne mesh gauze (petrolatum, 3% Xeroform and a dry sterile gauze bandage with the toe splinted in its corrected position. A surgical shoe is dispensed and the patient is able to ambulate as tolerated. The ﬁrst postoperative dressing change is within 1 week. Sutures are removed in 10–14 days, and if a Kirschner wire was used it is removed at 3 weeks. The patient is able to return to a roomy shoe with a broad toe box after 3–6 weeks, as oedema resolves.
Mallet toe correction distal interphalangeal joint arthroplasty
Mallet toe correction is indicated for lesions that develop at the tip of the toe. In the presence of mallet toe deformity the tip of the toe is traumatized with every step that the patient takes. The initial lesion is a callus, which eventually progresses to a preulcerative lesion (haemorrhage within the callus) and then to a full thickness ulcer that may probe to bone.
- The procedure is performed in the operating theatre under local anaesthesia, with a Penrose drain applied as a tourniquet at the base of the toe. No tourniquet is used if there is a question of vascular compromise.
- Two semielliptical incisions are made in a transverse manner over the distal interphalangeal joint of the toe. The incisions are carried down through the skin, the extensor tendon and joint capsule, and these structures are removed.
- The interphalangeal joint is identiﬁed and the collateral ligaments are severed using a No15 mini-blade. The blade is kept close to bone at all times. The distal aspect of the middle phalanx is transected with a power saw or with bone-cutting forceps.
- It may be necessary to release the long ﬂexor tendon, and this can be done through the same dorsal incision. The deformity is reduced and the dorsal capsule and skin are repaired in the usual fashion. In the absence of ulceration or infection, the corrected position of the toe is maintained by placing a 0.45 Kirschner wire .
Hallux limitus/rigidus with plantar ulceration of the hallux
Limited joint mobility of the 1st metatarsophalangeal joint, with decreased range of dorsiﬂexion, results in ele- vated plantar pressure beneath the hallux. Repetitive moderate stress on the skin is observed clinically by the formation of a callus beneath (or plantar medial to) the hallux interphalangeal joint . Haemorrhage within the callus represents a preulcerative condition that requires regular debridement and footwear modiﬁcation. The natural history for hallux interphalangeal joint,lesions is for the preulcerative condition to progress to a full-thickness ulcer and eventually to amputation. Although local wound care and off-loading of the foot may result in healing of the ulcer, this outcome is short-lived. The ulcer inevitably recurs and becomes a chronic non-healing wound.
Keller resectional arthroplasty of the 1st metatarsophalangeal joint
- This procedure can be performed under regional ankle block anaesthesia, with an ankle tourniquet.
- A dorsal longitudinal incision is made over the 1st metatarsophalangeal joint just medial to the extensor hallucis longus tendon. The incision starts at the neck of the proximal phalanx and extends ∼2 cm proximal to the metatarsal Skin hooks are used to retract the skin edges, small bleeders are clamped and electrocoagulated, and the incision is then carried deep through the capsule down to bone.
- Subperiosteal dissection is carried out over the proximal phalanx. The joint capsule is reﬂected, allowing direct visualization of the metatarsophalangeal joint. The collateral ligaments are cut using No. 15 blade and the proximal one-quarter to one-third of the proximal phalanx is transected, perpendicular to the long axis of the phalanx, with a power saw. The bone is grasped with a bone clamp and the intrinsic muscle attachments, for the ﬂexor hallucis brevis and the adductor hallucis, are carefully freed using a blade. Care must be taken to avoid cutting the ﬂexor hallucis longus tendon.
- The wound is irrigated with normal sterile saline and a piece of Gelfoamsponge (haemostatic absorbable gelatin) is placed in the void created by removal of the phalangeal base. The joint capsule is closed with 3–0 absorbable sutures in a simple interrupted fashion. If possible, the capsule should be purse stringed, interposing soft tissue between the metatarsal head and the phalangeal base. The skin is closed with a 4–0 absorbable suture in a running subcuticular fashion and Steri-Strips are placed across the incision. The use of one or two Kirschner wires to maintain the hallux position is at the surgeon’s discretion.
Sesamoidectomy is indicated for the treatment of a discrete intractable lesion, beneath the 1st metatarsal head,that fails to heal or remain healed with a conservative approach to treatment (local wound care, total-contact casting or attempts to off-load the forefoot with orthoses and custom footwear). Sesamoidectomy is also indicated for the curative treatment of osteomyelitis of the sesamoid bone. This procedure is appropriate for the treatment of neuropathic patients with evidence of increased plantar pressure beneath the 1st metatarsal head. Weightbearing radiographs taken with a radio-opaque open circle marker placed over the ulcer will conﬁrm the relationship between an enlarged or arthritic sesamoid bone and the plantar lesion. There may also be evidence of a plantar ﬂexed 1st metatarsal associated with a cavus foot deformity. Excision of the tibial sesamoid, ﬁbular sesamoid or both sesamoids may be indicated.
Surgical approach to the tibial sesamoid can be either medial or plantar. A low medial longitudinal incision is centred over the 1st metatarsophalangeal joint between the dorsal and plantar cutaneous nerves to the hallux. This incision is deepened to the level of the joint capsule and the capsule is incised in the same plane. The tibial (medial) sesamoid is visualized within the joint capsule beneath the metatarsal head. The capsule is grasped with a clamp and the sesamoid is shelled out with a No. 15 scalpel blade. The ﬁbular (lateral) sesamoid is more difﬁcult to reach through a medial incision, and may be more accessible from a dorsal longitudinal approach, over the ﬁrst webspace. This is a reasonable approach if the sesamoid is located in the intermetatarsal space. A plantar approach is indicated for excision of the ulcer, and allows for direct visualization of both sesamoid bones.
Dressings and postoperative care
The decision to close the wound primarily or to pack it open will vary with each case. Infected or contaminated wounds should be packed open, and either allowed to heal by secondary intention or brought back to the operating theatre for delayed wound closure. Dressings consist of a dry sterile compression gauze bandage with the hallux splinted in its proper alignment. The patient is instructed to rest at home, remain non-weightbearing and elevate his feet for 48 hours. If the wound was packed open, the dressing is changed on the ﬁrst or second postoperative day. If possible, arrangements should be made for a visiting nurse to perform the necessary daily dressing changes. The patient is then allowed limited protected weightbearing in a walking brace. The ﬁrst postoperative visit is scheduled within 1 week with weekly visits scheduled until the wound is healed. Once healed, the patient will require therapeutic shoes and insoles.
Lesser metatarsal osteotomy
Dorsiﬂexory metatarsal osteotomies are performed for the treatment of lesser metatarsalgia, most often for intractable plantar keratoses (IPKs), when non-surgical methods have failed. These procedures are controversial and are often plagued by postoperative complications such as transfer lesions, non-union or malunion, and ﬂoating toes. Infection and screw failure have also been reported. Caution should be exercised when considering these procedures for neuropathic individuals. Metatarsal osteotomy is not advised in the presence of infection or full-thickness ulceration beneath the metatarsal head.
The Weil osteotomy
The Weil shortening osteotomy is a distal lesser metatarsal procedure, designed to shorten one or more of the central metatarsals (2nd, 3rd and sometimes the 4th) without elevating or depressing the metatarsal head. The head moves proximal to the existing plantar callus, and decompresses the metatarsophalangeal joint. The procedure should be reserved for cases that fail conservative treatment, and only used in cases where the affected metatarsals are comparatively long. Complications are similar to those associated with other metatarsal osteotomies.
The procedure is performed in the operating theatre under local anaesthesia with an ankle tourniquet. A dorsal longitudinal incision is made over the metatarsophalangeal joint and then deepened to the joint capsule.
The capsule is dissected between the extensor digitorum longus and the extensor digitorum brevis. The capsule is reﬂected, allowing for release of the collateral ligaments. Two small Hohmann retractors are inserted under the metatarsal neck to provide sufﬁcient exposure to the metatarsal head.
The toe is plantar ﬂexed and the osteotomy is performed with a long, thin sagittal saw blade. The osteotomy cut begins at the distal dorsal edge of the articular cartilage and is directed proximally, oblique to the metatarsal shaft, and as parallel as possible to the sole of the foot.
The distal fragment is displaced proximally, 3–5 mm, and ﬁxed with a single self-drilling, self-tapping partially threaded 2.0 mm screw. The screw is directed from dorsal-proximal to plantar-distal. The bone peak is then resected with a rongeur and smoothed with a burr.
The joint capsule is closed with 3–0 absorbable sutures and the skin is closed with 4–0 absorbable subcuticular sutures, or nylon simple interrupted sutures.
Metatarsal head resection
Resection of a single metatarsal head is indicated for one of the following reasons, when non-surgical methods fail to achieve the desired result:
- For removal of infected bone, in the case of chronic osteomyelitis
- For decompression of a plantar ulcer, as an alternative to metatarsal osteotomy, to facilitate wound healing
- For deformity of the 5th metatarsal with painful callus on the plantar or lateral aspect of the metatarsal head.
Resection of the metatarsal head can be performed through a dorsal incision over the metatarsophalangeal joint, or in the presence of a deep plantar ulcer, the ulcer and the metatarsal head can both be excised through a plantar approach.
Fifth metatarsal head resection
This procedure is well suited for older sedentary individuals, and for patients with osteopaenia or osteomyelitis of the metatarsal head, where a transpositional osteotomy is not appropriate. Although transfer lesions (callus or ulcer) have been reported to occur beneath adjacent metatarsal heads, following metatarsal head resections, this is not a frequent problem with 5th metatarsal head resections.
Fifth metatarsal head resection is performed under local anaesthesia with IV sedation. An ankle tourniquet is used for haemostasis.
A 4 cm dorsal longitudinal incision is made over the 5th metatarsophalangeal joint and shaft, just lateral to the extensor digitorum longus tendon. The incision is carried down to fascia, the skin edges are retracted, and the incision is then continued through joint capsule and deep to the periosteum.
The joint is visualized, collateral ligaments are cut with a Beaver mini-blade and the metatarsal is cut in an oblique manner, at the surgical neck, from distal-medial to proximal-lateral. The metatarsal head is removed, and the wound is irrigated. Gelfoam is placed in the void, and the capsule is closed with 3–0 absorbable sutures in a simple interrupted fashion. The skin is closed with 4–0 nylon sutures, in a simple interrupted and horizontal mattress fashion.
Achilles tendon lengthening
Increased pressure on the plantar aspect of the forefoot has been shown to be associated with limited joint mobility and with equinus deformity of the ankle. In the presence of peripheral neuropathy, elevated pressure beneath one or more metatarsal heads can result in the development of ulceration. Ankle equinus may also contribute to the development of Charcot’s osteoarthropathy withcollapse of the mid-foot or avulsion fracture of the posterior process of the calcaneus. Armstrong and coworkers, at the University of Texas Health Science Centre at San Antonio, reported on a study to determine the degree to which pressure on the plantar aspect of the forefoot is reduced following percutaneous lengthening of the Achilles tendon in high-risk subjects with diabetes. They demonstrated that peak plantar forefoot pressures were reduced by approximately 27% following percutaneous Achilles tendon lengthening. These authors suggest that lengthening of the Achilles tendon, in high-risk patients with diabetes, may decrease the likelihood of ulceration and may increase the efﬁcacy of pressure-reduction modalities such as casts or braces. In fact, this procedure facilitates the healing of recalcitrant forefoot plantar ulcers.
Percutaneous Achilles tendon lengthening triple hemisection
This procedure is indicated for correction of mild to moderate gastrocnemius-soleus ankle equinus. Three hemisections of the tendon are performed, two medial and one lateral. The distance between the hemisections is determined by the overall size of the tendon and the amount of lengthening desired. An alternative procedure, attributed to Hoke, incorporates two posterior and one anterior hemisections of the Achilles tendon, and is performed in the frontal plane through a medial approach.
The patient is placed in a prone position on the operating room table. Local anaesthesia is inﬁltrated just above the Achilles tendon on the back of the leg. A tourniquet is not required for this procedure. The surgeon stands at the end of the operating table facing the foot, which hangs over the end of the table.
The plantar surface of the foot is placed against the abdomen of the surgeon and gently dorsiﬂexed while palpating the Achilles tendon. A skin marker is used to deﬁne the borders of the tendon, from its insertion into the calcaneus, to its proximal myotendinous junction. The proposed cuts in the tendon are drawn on the skin. These marks help the surgeon to remember the direction of the cuts.
The distal cut is made 1.0–2.5 cm superior to the tendon’s insertion into the calcaneal tuberosity. A No 10 blade is introduced through the skin and tendon in a perpendicular manner, bisecting the tendon. The tendon is then lifted away from the leg, and the blade turned medially.
Hemisection of the tendon is accomplished by gently working the blade against the tendon until its ﬁbres are completely cut. When satisfactorily performed a gap can be palpated in the tendon. Avoid forcefully pushing the blade against the tendon as this may result in tenotomy, with rapid loss of resistance, followed by uncontrolled movement of the blade and subsequent laceration of the skin or the surgeon’s ﬁnger.
This procedure is repeated in the opposite direction, 2.5–4.0 cm more proximally, and then again 2.5–4.0 cm more proximal to the second cut. The foot is then ﬁrmly dorsiﬂexed to an angle greater than 90°, generally 5° above neutral . Overcorrection should be avoided, as this may lead to rupture of the tendon or a calcaneus deformity.
The stab wounds are generally so small that they do not require sutures. However,if desired, a single interrupted 5–0 nylon suture can be used.
Dressings and postoperative care
Dressings consist of non-adherent ﬁne mesh gauze(petrolatum, 3% Xeroform), and dry sterile gauze dressing. A well-padded plaster splint is applied to immobilize the foot and ankle, and to maintain the ankle in approximately 5° of dorsiﬂexion. At the ﬁrst dressing change, the patient is placed in either a short-leg walking cast or a walking brace for 6 weeks.
Partial calcanectomy is indicated for the surgical management of large non-healing wounds located over the heel,with or without osteomyelitis. These wounds are typically chronic decubitus ulcers located on the posterior aspectof the heel, or neuropathic ulcers on the plantar surface of the heel. Regardless of the aetiology, heel ulcers are often unresponsive to conservative therapy and are frustrating to treat. Partial calcanectomy is a viable alternative to below-knee amputation for these patients, provided that they have adequate distal perfusion. The procedure eradicates infection and achieves wound closure and limb preservation.
The procedure is performed under spinal anaesthesia using a thigh tourniquet for haemostasis. The patient is placed in a prone position on the operating theatre table.
Two converging semi-elliptical incisions are made surrounding the ulcer. The incisions are carried deep to bone, and the ulcer is completely excised. The incision is extended proximally, to expose the posterior aspect of the calcaneus, and deepened to the fascia overlying the Achilles tendon . A No. 15 blade is used to transect thetendon at its insertion on the posterior tubercle of the heel. The tendon is dissected free, grasped with an Allis clamp and reﬂected out of the wound. Dissection is then directed close to bone, exposing the body of the calcaneus.
the posterior aspect of the heel is resected, using a sagittal saw, in a plane entering the posterior superior aspect of the calcaneus and exiting plantarly at the insertion of the plantar fascia. The wound is thoroughly irrigated using 2 L of normal sterile saline solution containing an antibiotic. Three drill
holes are then made in the posterosuperior aspect of the calcaneus, for reattachment of the Achilles tendon, using 0 Ethibond non-absorbable sutures. A tube low suction drain was inserted, exiting through the lateral aspect of the heel. The deep tissues were closed with 2–0 absorbable sutures. The skin was closed using a combination of 3–0 nylon vertical and horizontal mattress sutures,and simple interrupted sutures. (Cautionainfected wounds should be packed open and allowed to heal by secondary intention, or brought back to the operating theatre for delayed wound closure.)
Dressings and postoperative care
Dressings consist of non-adherent ﬁne mesh gauze (petrolatum, 3% Xeroform , placed on the suture line, a bulky gauze ﬂuff dressing and additional padding for protection of the heel and lateral border of the foot. Dressings are held in place by gauze bandage. A well-padded plaster splint is applied to immobilize the foot and ankle. Drains are generally removed after 48 hours. Moderate bleeding from the cut cancellous bone is to be expected, especially over the ﬁrst 12–24 hours, and dressings may need to be reinforced with additional absorbent material. After 7 days, a well-padded short-leg non-weightbearing cast is applied. The cast is changed at 2-week intervals for inspection of the wounds. Sutures are left in place for 3–4 weeks. Once the skin is healed, the patient is placed in a walking brace for 4 weeks and is then allowed to ambulate in a therapeutic shoe with an ankle–foot orthosis (AFO).
AMPUTATIONS OF THE FOOT
Amputations of the foot can be divided into emergent and non-emergent procedures. Non-emergency amputations allow some ﬂexibility in the creation of skin ﬂaps, selection of level and wound closure. These cases generally include neuropathic feet that are structurally or functionally impaired, with satisfactory circulation and controlled infection. They are characterized by moderate to severe forefoot deformities with associated chronic non-healing wounds that are recalcitrant to conservative medical and surgical management. In some cases, the presenting deformities are the residuals of prior infection, tissue necrosis and chronic non-healing wounds. Emergent amputations include those performed for gangrene, severe soft tissue infection, osteomyelitis, peripheral vascular disease, tumours or trauma. The main consideration in determining the level of amputation in these cases is the extent of healthy tissue. When infection is the primary issue, an open or guillotine amputation may be necessary. In most cases, adequacy of blood supply to the foot ultimately determines the level at which successful amputation can be performed. Although non-invasive laboratory methods have been proposed for evaluating wound healing potential, clinical experience and judgement are most often relied upon.
Preoperative physical examination should include a quantitative assessment of ankle joint dorsiﬂexion. Contracture of the Achilles tendon is generally more apparent prior to amputation of the forefoot, and suggests the need for tendon lengthening at the time of amputation. The procedure is performed as necessary, in the presence of equinus or excessive spasticity. In many cases equinovarus deformity is a complication of Lisfranc and Chopart amputations. A longitudinal open procedure or percutaneous approach can be utilized according to the surgeon’s preference.
Wound healing criteria for amputation surgery
Measurements of TcPo2 are useful to accurately predict the presence of critical vascular disease and the success of major or minor amputations. TcPo2 levels ≥ 30 mmHg bode well for healing of a forefoot amputation, and are more accurate predictors than a palpable pedal pulse.
TcPo2 levels < 30 mmHg indicate signiﬁcant vascular disease and foreshadow wound healing failure and amputation. These patients require well-timed vascular surgery consultation, arteriography and revascularization.Toe pressures, measured by photoplethysmography, are helpful to predict the healing potential of primary forefoot amputations. Other preoperative criteria for wound healing include: an ankle–brachial index > 0.50, serum albumin >3.0 g/dL, serum protein > 6.0 g/dL and total lymphocyte count > 1500. Patients should be medically stable, with diabetes and infection under control.
Partial digital amputation of the hallux
Distal amputation of the hallux, sometimes referred to as a terminal Syme’s amputation, is indicated for lesions of the distal toe or nail bed, e.g. osteomyelitis of the distal phalangeal tuft, ulceration of the nail bed or tumour. Theprocedure employs either resection of the tuft of the distal phalanx or disarticulation of the toe at the interphalangeal joint. This procedure preserves acceptable length and function of the hallux. A similar surgical approach can be modiﬁed for the lesser toes.
The procedure for amputation through the hallux interphalangeal joint is performed in the operating theatre under local anaesthesia and sedation, with a Penrose drain applied as a tourniquet around the base of the great toe. A long plantar and short dorsal skin ﬂap is fashioned. The transverse dorsal skin incision is made, proximal to the posterior nail fold, at the level of the interphalangeal joint. The incision extends from medial to lateral and is then directed distally around the end of the toe, to form a long plantar ﬂap. The toe is disarticulated at the interphalangeal joint and all tissues are excised (nail plate, nail bed, nail matrix and distal phalanx). A long plantar ﬂap is fashioned (trimmed to ﬁt), and sutured without tension to the short dorsal ﬂap with 4–0 nylon simple interrupted sutures. If the toe is infected at the time of surgery, the wound should be left open or very loosely approximated. The patient can then be brought back to the operating theatre for delayed wound closure when the infection is resolved.
A ray resection consists of excision of a toe and its corresponding metatarsal. The most frequent complication of a ray resection is transfer ulceration. The overall success rate for ray amputations is low; however, there is reasonable success with resection of a central ray (2nd or 3rd), or 5th ray. Amputation of the hallux and 1st metatarsal frequently results in imbalance of the medial column of the foot with a poor functional outcome. Therefore, it is very important to preserve 1st metatarsal shaft length whenever possible.
Amputation of the 5th ray alone is indicated when infection and necrosis involve the 5th toe and/or the skin over the metatarsophalangeal joint. This can develop in neuroischaemic patients from unremitting pressure, caused by a tight shoe or bandage, over the lateral aspect of the 5th metatarsal head. In neuropathic individuals, repetitive moderate stress on the skin beneath a prominent 5th metatarsal head will eventually result in callus formation, ulceration and infection. The primary objective of this procedure is to achieve adequate resection of the infected or necrotic tissues, in order to create a wound that can be closed without tension. The conﬁguration of the skin incision is determined by the extent of the infected necrotic tissues to be excised. Whenever possible, the 5th metatarsal base should be preserved together with its muscle attachments for the peroneus brevis and tertius. This is important for the prevention of varus deformity of the foot. Varus deformity occurs when inversion of the foot is left unopposed. Following ray resection, part or all of the incision may be left open, with the patient returning to the operating theatre for delayed primary closure. Ray resections are sometimes performed as an initial incision and drainage procedure to control infection prior to a more deﬁnitive amputation.
Transmetatarsal and mid-foot amputations
Amputations through the forefoot and mid-foot include the transmetatarsal, Lisfranc and Chopart amputations. The Lisfranc amputation is performed at the tarsometatarsal joints and the Chopart amputation is performed at the mid-tarsal joints . Mid-foot amputations frequently develop equinovarus deformity, which requires Achilles tendon lengthening or tenotomy. When preoperative criteria are met, healing occurs in > 80% of transmetatarsal and mid-foot amputations.
Transmetatarsal amputation Indications
- Gangrene of one or more toes, without entering on to the foot
- Stabilized infection or open wound involving the distal portion of the foot
- An infected lesion in a neuropathic foot
- Moderate to severe forefoot deformity.
Careful preoperative preparation is necessary with drainage of infection, culture-directed antibiotics and daily wound care.
The patient is placed in a supine position with the foot and lower half of the leg prepped and draped in the usual manner. Bony landmarks are identiﬁed for the 1st and 5th metatarsal heads and bases. The desired level of bone resection is determined, e.g. mid-shaft level, and then using a skin marker a line is drawn across the dorsum of the foot from mid-shaft of the 1st metatarsal to mid-shaft of the 5th metatarsal. Lines are then extended distally, along the 1st and 5th metatarsal shafts, to the bases of the hallux and 5th toe, and then curved across the plantar skin just proximal to the sulcus of the toes. This approach will create a short dorsal and long plantar ﬂap.
Starting anteromedially at the 1st metatarsal shaft, the knife is held perpendicular to the skin and an incision is made through the skin, across the dorsum of the foot, ending at the previously determined level on the 5th metatarsal shaft. The dorsal incision is deepened to expose the long extensor tendons. Vessels are identiﬁed,ligated or electrocoagulated. The incision is then carried down to bone. Prior to transection of the metatarsals, an osteotome or key elevator is directed distally away from the dorsal skin incision, to reﬂect the soft tissues and periosteum. The dorsal ﬂap should not be undermined.Incisions are then carried distally toward the toes and then across the plantar aspect of the foot, developing a long, thick myocutaneous ﬂap. The plantar ﬂap is retracted using rake retractors. It is important to keep the dissection close to the metatarsal shafts, thereby creating a thick viable plantar ﬂap. The plantar ﬂap is reﬂected proximally to the intended level of bone resection. The metatarsal bones are then cut transversely, with a power saw, at the level of the dorsal skin ﬂap. The cuts are angled slightly from dorsal-distal to plantar-proximal. The 1st and 5th metatarsals are bevelled medially and laterally to prevent focal points of pressure. The distal foot is grasped securely with a small bone clamp, and then removed by sharp dissection.
The plantar ﬂap is inspected, and debrided as necessary. Exposed ﬂexor tendons should be grasped without tension and excised. Antibiotic solution is used to irrigate the wound. The plantar ﬂap is then brought up over the resected metatarsals and approximated with the dorsal ﬂap. If the plantar ﬂap is too long, redundant skin should be remodelled. The ﬂap should be carefully marked with a skin marker and excess skin removed. Accurate trimming of the skin is accomplished by placing several Allis tissue forceps on the edge of the skin to be excised. The surgical assistant holds the forceps with gentle tension, and a fresh blade is used to trim the excess skin. Placing a malleable retractor beneath the plantar ﬂap, while it rests on the dorsum of the foot, provides a ﬁrm supporting surface to cut on.
The tourniquet is deﬂated prior to wound closure, and bleeders are ligated or coagulated. Some oozing of blood from the transected bone marrow and from muscle is to be expected. The skin ﬂaps are approximated without tension and secured with a few simple interrupted, subcutaneous 3–0 absorbable sutures. A drain is placed in the wound, exiting the skin on the dorsolateral aspect of the foot. Skin ﬂaps are carefully positioned and secured with 4–0 nylon sutures in a simple interrupted fashion, or with stainless steel staples.
Amputations through the mid-foot
Lisfranc and Chopart amputations are frequently complicated by the development of equinus deformity. Equinovarus deformity is associated with Lisfranc disarticulation.Amputation at the tarsometatarsal joints appears to be the most proximal level that allows for satisfactory function of the foot. For surgery to work at this level, care must be taken to preserve the base of the 5th metatarsal with its tendinous attachments, for eversion of the foot. The Achilles tendon should be lengthened, as necessary. Chopart’s mid-tarsal joint amputation has the advantage of producing less limb shortening than a Syme’s procedure because the talus and calcaneus are retained. However, complications are commonly reported with the Chopart amputation. Severe equinus deformity develops due to loss of the tibialis anterior, long extensor and peroneal tendons, with resultant failure to balance the force of the triceps surae. The resulting foot is short with a very small weightbearing surface, and is at increased risk of further breakdown. Some authors advise reattachment of the tibialis anterior to the talus to prevent equinus deformity of the hindfoot.
The patient is placed in a supine position with the foot and lower half of the leg prepared and draped in the usual manner. This procedure is performed in a manner similar to the transmetatarsal amputation, with the development of a longer plantar ﬂap and short dorsal ﬂap. The dorsal skin incision is made just distal to the 1st metatarso-cuneiform joint and carried across the dorsum of the foot, ending just distal to the 5th metatarsal base. Occasionally it may be necessary to develop a longer dorsal ﬂap to compensate for devitalized plantar skin. The medial and lateral incisions are carried distally along the metatarsal shafts to the necks of the metatarsals and then curved plantarly across the ball of the foot. The plantar ﬂap is developed to the intended level of disarticulation. The 1st metatarsal base is disarticulated from the medial cuneiform. Using a power saw, and working from medial to lateral, the 2nd metatarsal is transected at the level of the 1st and 3rd cuneiforms, leaving its base intact in the intercuneiform mortise. The 3rd and 4th metatarsals are then disarticulated, followed by transection of the 5th metatarsal, just distal to its base. Although the 5th metatarsal base will leave a prominence of bone, this generally does not cause a problem. Wound closure is performed in the same manner as described above for a transmetatarsal amputation.
The incision for a Chopart amputation starts medially, at the level just proximal to the navicular tuberosity and extends over the dorsum of the foot to a point midway between the 5th metatarsal base and the lateral malleolus. Medial and lateral incisions are then carried distally, over the 1st and 5th metatarsal shafts. At mid-shaft, the incision is curved down across the sole to fashion a plantar ﬂap. The plantar ﬂap is developed in a careful manner,using rakes for retraction, to the level of the mid-tarsal joint. The ligaments around the talonavicular and calcaneocuboid joints are divided. A suture is placed in the end of the tendon of the tibialis anterior. Soft tissue attachments are sharply dissected free from the foot, and it is disarticulated from the rearfoot. A drill hole is made in the talus for attachment of the tibialis anterior. The plantar ﬂap is trimmed to size. Tourniquet is released and bleeders ligated or electrocoagulated. The skin ﬂaps are then approximated, over a drain. The Achilles tendon is tenotomized. Standard dressings and splints are applied as for a transmetatarsal amputation.