BACKGROUND

 

 

Malignant tumors of the foot present a significant and formidable challenge to the orthopaedic oncologist due to the foot's unique function and anatomic peculiarities.

 

Both bone and soft tissue contribute to the structure and function of the foot. Furthermore, the foot is composed of compact compartments that are interconnected by nerves and vascular structures. Complete resection (wide local excision) of osseous structures of the foot is difficult because of the interruption of these complex anatomic relationships, which afford stability to the foot, in addition to the interconnected compartments. Malignant tumors of bone are rare in the foot and rarer still in locations distal to the

metatarsophalangeal joints.5,9,12,14,17,18 Many of these tumors are treated with amputations.

 

FIG 1A shows all anatomic sites, FIG 1B shows the distribution of malignant and benign cases, and FIG 1C

shows the distribution of all types of surgical procedures.

 

In the senior author's experience of foot and ankle tumors in 153 cases, 31 amputations were performed (see FIG 1C). Fortunately, tumors distal to the metatarsophalangeal joint can be treated by amputation through the metatarsophalangeal joint with minimal disruption to function. The only exception is the first ray, which typically bears 50% of the weight with toe-off during each gait cycle. Therefore, preservation of as much proximal phalanx as possible is important to optimize this important structure.

 

ANATOMY

 

The foot is uniquely adapted for bipedal motion and as such is essentially a tripod. The tripod is basically formed by the first ray, the fifth ray, and the calcaneus and is supported by the osseous configuration of bones in the midfoot that form a Roman arch, which in and of itself is inherently stable.

 

These bones are supported by ligamentous structures as well as tendons that help preserve the arch and support foot function. For this reason, resections of the first and fifth rays typically result in significant alterations in function, especially the first ray. The resulting forces after resection of the first ray result in transfer to the lesser metatarsals, which are ill adapted to structurally support the weight of the body, resulting in transfer metatarsalgia.

 

These structural alterations can be mitigated in part by the judicious use of orthotics, such as a medial heel wedge to transfer the forces farther lateral or the use of a metatarsal bar, which will more evenly distribute the weight across the lesser metatarsals. Resection of the fifth ray is relatively easily compensated for by creating an orthosis that transfers the forces medially; thus, a lateral heel wedge is beneficial.

 

Resection of the middle rays results in insignificant loss of function and acceptable cosmesis. The only net result is narrowing of the forefoot, which can be easily compensated for with shoe modifications.

 

The Lisfranc joint is the tarsometatarsal joint. An amputation at this level will preserve the dorsiflexors and

plantarflexors. These amputation levels are highly functional with minor shoe-wear modifications and forefoot fillers. If the metatarsal bases can be preserved using a transmetatarsal amputation, the functional outcome is improved.

 

The Chopart joint is also known as the transverse tarsal joint. It includes the talonavicular and calcaneocuboid joints. An amputation at this level preserves the plantarflexors but sacrifices the dorsiflexors, often resulting in an equinus contracture due to unopposed action of the Achilles tendon.

 

 

To circumvent this problem, the tibialis anterior is used. It is detached from the tarsal navicular with a cuff of soft tissue, preferably periosteum. A drill hole is made through the neck and head of the talus in an oblique fashion from dorsolateral to plantar medial. The tendon is then routed through this bone tunnel and sewn to itself or soft tissue as it exits through the tunnel. This repair may be augmented with bone anchors placed near the dorsal opening of the tunnel. The residual foot is maintained in maximal dorsiflexion (FIG 2).

 

The advantage of a Chopart amputation over a Syme amputation is the maintenance of hindfoot height. This is an end-bearing residual limb and the patient can negotiate short distances without modified shoe wear or prosthetic fitting.

 

INDICATIONS

 

Tumors involving the toe or metatarsal bone are rare. Primary tumors affecting the foot, including osteosarcomas, have a low incidence.2,4,14 Metastatic tumors of the foot are also rare.9,20 The most common sites of primary tumors which metastasize to the foot are lung, kidney, and colon.9

Ray Resections

 

The indications for ray resections are tumors involving the toe or metatarsal bone. Benign tumors make up the majority of these lesions.12

 

P.403

 

 

 

FIG 1 • A. All anatomic sites of tumors of the foot and ankle (n = 153). B. Distribution of malignant and benign tumors of the foot and ankle (n = 153). C. Distribution of surgical procedures for tumors of the foot and ankle (n = 153).

Lisfranc

 

Extensive tumor involving the first and second interspaces in adjacent metatarsals or multiple metatarsals (FIG 3)

Chopart

 

Tumors extending to the tarsometatarsal joint with soft tissue extension. FIG 4 shows the pathology specimen after wide resection of a chondrosarcoma involving multiple small bones of the foot.

 

FIG 2 • Good dorsiflexion function after Chopart amputation.

 

 

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with tumors of the metatarsals complain of pain with an associated mass. The mass may be small and chronic. It may be first noticed after a minor injury. The patient may have difficulty with weight-bearing activities, including walking and standing. Shoe wear, particularly fashionable shoes, may be limited.

 

Physical examination (Table 1) often shows a tender mass localized to the toe, metatarsal, or midfoot. There may be associated swelling. If a sensory nerve overlies the mass, there may be paresthesias. If the mass is large, there may be loss of motion or discomfort with active range of motion of the foot and ankle.

 

IMAGING AND OTHER STAGING STUDIES

 

Preoperative studies include standing plain radiographs of the foot, including anteroposterior, lateral, and oblique views. If there is involvement of the ankle joint, anteroposterior and mortise views of the ipsilateral ankle are obtained as well.

 

 

Magnetic resonance imaging (MRI) is important to evaluate the amount of involvement of the metatarsals to determine the level of amputation (FIG 5). It also shows the extent

 

of soft tissue tumors and may be helpful in distinguishing benign from malignant tumors.19

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FIG 3 • Synovial sarcoma involving the forefoot. A. This patient's radiographs showed radiodensity surrounding the second metatarsal, a typical radiographic appearance of a synovial sarcoma. B,C. MRIs show extensive soft tissue mass. The patient was treated with a Chopart amputation.

 

SURGICAL MANAGEMENT

 

The goal of the surgical procedure is to remove the tumor with adequate margins.

 

 

FIG 6 illustrates a case of osteosarcoma of the calcaneus. Osteosarcoma is usually treated with wide resection, but in this case, the tumor was confined to the calcaneus. The patient had a good response to adjuvant chemotherapy, with 100% tumor necrosis and was treated with the only calcaneal prosthesis reported in the world.

 

A long plantar flap is important for a sturdy end-bearing stump.

 

 

 

 

The quality of the tissue is more important than the quantity.1 The bony edges should be smooth and beveled if possible. Myodesis is helpful to pad the end of the stump.

 

Reconstruction of the anterior tibialis tendon insertion into the neck of the talus in the Chopart amputation will help prevent an equinus contracture.

 

 

 

FIG 4 • Chondrosarcoma can spread to involve multiple sites. This photograph shows the pathology specimen after a below-knee amputation of a chondrosarcoma involving multiple small bones of the foot.

 

Preoperative Planning

 

Preoperative planning is crucial for a good outcome. The preoperative radiographs, computed tomography (CT), and MRI studies are important to determine the amount of tumor involvement (FIG 7). They also show

the extent of soft tissue tumors and may be helpful in distinguishing benign from malignant tumors.19 The results of the biopsy will determine the level of amputation.

 

The level of amputation is an important part of preoperative planning. The length of the residual stump is as important as the quality of soft tissue. There must be adequate padding of skin, subcutaneous fat, muscle, and tendons to cover the end of the bones.

 

Table 1 Physical Examination Methods

Examination Technique

Significance

Inspection

Evaluate the lower extremity with the

patient undressed from the knees.

Examination of both extremities allows for

comparison to identify abnormalities.

Palpation

Gentle and deep palpation of the

mass or area of pain

Evaluates tenderness of the mass;

evaluates whether the mass is mobile or fixed

Range of

motion

Observe passive and active range of

motion of the foot and ankle.

Identifies joint involvement with tumor

Vascular

examination

Palpate dorsalis pedis and posterior

tibia arteries.

Evaluates vascularity of the extremity and

whether there is tumor involvement

 

Neurologic

examination

Evaluate motor strength and

sensation to light touch.

Evaluates involvement of muscles and

sensory nerves

 

 

 

P.405

 

 

 

 

FIG 5 • Chondrosarcoma of the calcaneus. A,B. MRI shows extension into the soft tissue. It was treated with cryosurgery but recurred and a below-knee amputation was performed. C,D. Unicameral bone cyst (UBC) of the calcaneus. The radiograph shows the typical expansile appearance of the UBC. The CT scan shows greater bony detail. The lesion was treated with curettage, graft, and PMMA.

 

 

 

FIG 6 • Osteosarcoma is an aggressive malignant tumor that has been reported to occur in the calcaneus. Osteosarcoma is usually treated with wide resection, but in this case, the tumor was confined to the calcaneus. The patient had a good response to adjuvant chemotherapy, with 100% tumor necrosis, and was treated with the only calcaneal prosthesis reported in the world. A. The lateral radiograph shows the expansile tumor. B. The bone scan shows isolated involvement. C,D. At 10 years postoperatively, the patient was tumor-free and enjoyed working and normal activities.

 

 

P.406

 

 

 

FIG 7 • A. Benign tumors can show cortical thickening, mimicking a stress fracture. In this case, it was a benign lesion of the second metatarsal. B. Clinical photograph shows increased space between the metatarsals from the mass. C. MRI shows the amount of soft tissue involvement. D,E. Pigmented villonodular synovitis (PVNS) is usually treated with simple excision. This case localized to the plantar aspect of the first metatarsal head. Clinical photographs show the mass. F. MRI shows soft tissue involvement. G. Intraoperative photograph shows tumor resection.

 

Positioning

 

The patient is placed supine on the operating table.

 

A thigh tourniquet is placed over adequate padding, such as Webril.

 

A bump may be placed proximal to the sciatic notch on the ipsilateral hip to limit external rotation of the extremity during the procedure.

 

Approach

 

The surgical approach is planned preoperatively. It is important to maintain as much plantar skin as possible because this skin is thicker and has specialized columns of plantar fat for weight bearing.

 

Ray resections are performed through a longitudinal dorsal incision in line with the involved metatarsal.

 

Lisfranc and transmetatarsal amputations are performed through a midfoot incision, with a long plantar flap. This is the same approach with the Chopart amputation. The plantar skin is thicker and has specialized columns of plantar fat to provide for a weight-bearing stump.

 

 

P.407

 

 

TECHNIQUES

• Ray Resection

  In performing a ray resection, an incision is made longitudinally and dorsally in line with the involved metatarsal. At the metatarsophalangeal joint, the incision is carried plantarly in a curvilinear fashion around the joint (TECH FIG 1).

  This tissue is then used to reconstruct the resulting web space between the adjacent digits.

  The sensory nerves are identified just beneath the skin and are pulled distally and transected sharply with a scalpel. The extensor tendon is also transected sharply at and proximally near the tarsometatarsal joint.

  The common digital nerve is identified along with the vascular bundle. If they are involved or closely adherent to the tumor pseudocapsule, they are ligated proximally. The lumbrical and interosseous muscles are transected proximally, exposing the base of the metatarsal. It is preferable to preserve the base of the metatarsal if possible because this does not cause any disruption in the arch formed by the tarsal-metatarsal articulation.

  An oscillating saw is used to transect the metatarsal, or the metatarsal is disarticulated at the tarsometatarsal joint and elevated. The resection then is performed from proximal to distal. The flexor tendon is identified and transected. The entire metatarsal is then excised along with the adjacent soft tissue (lumbricals, intrinsics, and flexor extensor tendons). The dissection is then carried distally and plantarward. The capsular structures of the metatarsophalangeal joint are then separated from the underlying dermis and the ray is removed.

  A suture is placed through the capsular structures of the adjacent metatarsal heads. Pressure is then applied to the tibial and fibular aspect of the foot to close the defect between the adjacent metatarsals, and a 0 nonabsorbable suture is used to anchor the capsular structures between the adjacent metatarsals to bring the metatarsals together and narrow the defect between the adjacent rays. A small drain is placed in the defect and brought out through a separate puncture wound distally. The subcutaneous tissue is then closed with 3-0 absorbable sutures placed in interrupted fashion. The skin is closed with 4-0 nylon sutures placed in interrupted fashion.

   

   

   

  TECH FIG 1 • A. Skin incision location in a metatarsal ray resection. B. Dorsal incision. C. Plantar incision. D. The plantar flap is longer and is brought dorsally to cover the bony end of the stump.

   

   

  A bulky dressing is applied, maintaining even compression across the foot and compressing the adjacent metatarsals to decrease tension on the capsular stitch maintaining the metatarsal heads in close proximity. If the flexor or extensor tendons are not involved with tumor, they can be woven through the metatarsal heads to create a sling to anchor the metatarsal heads in close proximity and maintain the close space between the metatarsal heads.

  First Ray Resection with Reconstruction with Autogenous Fibular Graft

   

  Under epidural anesthesia, an incision is made over the first metatarsal. Anterior and posterior fasciocutaneous flaps are made extending to the level of the second metatarsal anterior and posterior. The proximal limb of the incision extends beyond the metatarsal cuneiform joint and the distal incision extends to the web space.

   

  Resection consists of the planes between the first and second metatarsals following the bone in the second metatarsal through the metatarsal cuneiform joint and posteriorly and around the first metatarsal the flexor longus muscle tendon. The distal metatarsal is osteotomized at the condyles and proximally just distal to the joint. The tumor mass is removed; the anterior tibial tendon, peroneal tendons, and anterior tibial vessels are preserved.

   

  Reconstruction is performed with a fibular graft from the midshaft of the fibula of the ipsilateral limb. This is placed within the defect, measuring about 8 cm between the cuneiform and the metatarsal head.

  Fixation is achieved with two small cortical interfragmentary screws proximally and distally. The hallux is maintained in neutral position.

   

  Corticocancellous bone graft is placed around the base and the distal osteotomy sites with fibrin glue for

  hemostasis and

   

  P.408

  to promote healing. The fibular bone graft is taken through a separate incision with separate instruments in the midportion of the fibula on the same side between the peroneus longus and the soleus interval.

  The muscles are retracted, and the intermuscular septum is released with the cutting electrocautery. An oscillating saw is used to remove 8 to 10 cm of the fibula. The wound is then irrigated, and the peroneal muscles are repaired. A drain is used.

  Metatarsophalangeal Joint Amputation

   

  A longer plantar flap is planned. The incision is carried out at the level of the metatarsophalangeal joint on the dorsum of the foot.

   

  Sharp dissection is used to expose the joint, and the capsule, ligaments, and tendons are cut at that level. The vessels are cauterized.

   

  The plantar flap is brought over the dorsal aspect and nylon suture is used to repair the skin.

• Transmetatarsal Amputation

   

  A transverse incision is made either at the middle or proximal third of the metatarsals, extending through skin into the subcutaneous tissue (TECH FIG 2A).

   

  The cutaneous branches of the terminal portions of the peroneal nerve are identified. Traction is applied, pulling the nerve distally. The nerve is transected sharply to allow it to retract proximally.

   

  The terminal branch of the dorsalis pedis is preserved, if possible, to maintain continuity of the anastomosis with the posterior tibial terminal arterial branch, thus maintaining the dorsalis pedis contribution of arterial flow through the arch.

   

  The extensor tendons are placed on a stretch, and this is best accomplished by flexing the forefoot and sharply dividing the tendons at the level of the skin incision, allowing the tendons to retract proximally.

   

  A beveled cut is made in the metatarsal heads by angling an oscillating saw 30 degrees from the perpendicular with the foot placed in neutral position on the operating table. A plantar flap is then fashioned by extending the incision through the skin approximately 45 degrees from the transverse dorsal incision obliquely across the medial and lateral foot to the level of approximately the metatarsal heads and then transversely across the skin just proximal to the metatarsal heads (TECH FIG 2B).

   

   

   

  TECH FIG 2 • Surgical technique for transmetatarsal amputation. A. Dorsal and plantar skin incisions. B.

  Bone cuts are made with a sagittal saw.

   

   

  The sensory nerve to the first ray is identified, traction is placed, and the nerve is transected sharply. The terminal branches in the medial plantar nerve are identified as well, placed on stretch, and sharply divided. The terminal branches of the medial plantar artery are identified, ligated, and divided.

   

  The superficial and deep flexor tendons are placed on stretch by dorsiflexing the forefoot through the metatarsal osteotomies and sharply dividing them, allowing them to retract proximally. No attempt is made to suture the extensor tendons to the flexor tendons.

   

  P.409

   

  If there is a significant plantar extension of the tumor, a long plantar flap cannot be used. In this case, a fish-mouth configuration is preferable. To achieve this, equal dorsal and plantar flaps are constructed and the same operation is carried out as indicated earlier.

   

  The tourniquet is deflated and meticulous hemostasis is obtained. Excessive use of cautery to obtain hemostasis is discouraged to limit dysvascularity of the plantar flap.

   

  The plantar flap is brought up and myodesed to the residual metatarsals or tarsal bones. Alternatively, the plantar fascia can be sewn into the periosteum overlying the residual metatarsal heads or capsular structures in and around the tarsal bones.

   

  The skin is closed with 4-0 nylon sutures. A Penrose drain is placed deep to the flap and brought out either medially or laterally through the incision.

• Lisfranc Amputation

   

  A transverse incision is made either at the middle or proximal third of the metatarsals, extending through

  skin into the subcutaneous tissue.

   

  The cutaneous branches of the terminal portions of the peroneal nerve are identified. Traction is applied, pulling the nerve distally. The nerve is transected sharply to allow it to retract proximally.

   

  The terminal branch of the dorsalis pedis artery is ligated and divided as it enters the first dorsal interspace and courses in the plantar fascia.

   

  The extensor tendons are placed on a stretch; this is best accomplished by flexing the forefoot and sharply dividing the tendons at the level of the skin incision, allowing the tendons to retract proximally.

   

  The Lisfranc joint is disarticulated sharply. A plantar flap is fashioned by extending the incision through the skin approximately 45 degrees from the transverse dorsal incision obliquely across the medial and lateral foot to the level of the distal metatarsals (TECH FIG 3A).

   

  The sensory nerve to the first ray is identified, traction is placed, and the nerve is transected sharply. The terminal branches in the medial plantar nerve are identified, placed on stretch, and sharply divided.

   

   

   

  TECH FIG 3 • Surgical technique for Lisfranc amputation. A. Skin incisions are made on the dorsal and plantar aspects of the foot, and the metatarsals are dissected and removed. The plantar skin flap is longer. B. Wound closure with sutures.

   

   

  The terminal branches of the medial plantar artery are identified, ligated, and divided. The superficial and deep flexor tendons are placed on stretch by dorsiflexing the forefoot through the Lisfranc joint and sharply dividing them, allowing them to retract proximally. No attempt is made to suture the extensor tendons to the flexor tendons.

   

  If there is a significant plantar extension of the tumor, a long plantar flap cannot be used. In this case, a fish-mouth configuration is preferable. To achieve this, equal dorsal and plantar flaps are constructed and the same operation is carried out as indicated earlier.

   

  The tourniquet is deflated and meticulous hemostasis is obtained. Excessive use of cautery to obtain hemostasis is discouraged to limit dysvascularity of the plantar flap.

   

  The plantar flap is brought up and myodesed to the tarsal bones. Alternatively, the plantar fascia can be sewn into the periosteum overlying the capsular structures in and around the tarsal bones.

   

   

  The skin is closed with 4-0 nylon sutures (TECH FIG 3B), and a small drain is placed deep to the flap and brought out either medially or laterally through the incision.

   

• Chopart Amputation

P.410

 

The Chopart amputation is performed through a transverse incision that is dorsally based at or just distal to the talonavicular joint (TECH FIG 4A).

 

The dorsalis pedis artery and accompanying nerve are identified. The dorsalis pedis artery is ligated and divided, and the sensory nerve is placed on stretch and transected sharply, allowing it to retract proximally.

 

The capsule of the talonavicular joint is circumferentially divided, along with release of the posterior tibial tendon. This tendon is tagged for later use as it is brought through the interosseous membrane and reattached to the neck of the talus with suture anchors or through a hole drilled in the talus as described earlier.

 

An alternative solution is to place the posterior tibial tendon through the interosseous membrane with the medial half of the Achilles tendon. The Achilles tendon is then suture- anchored to the neck of the talus and used to augment the tibialis anterior or posterior tibial tendon. Achilles lengthening is also a helpful technique because it reduces the stress on the tibialis anterior. The Achilles tendon is not necessary for normal ambulation due to the lack of forefoot.

 

A long plantar flap is preferred, but if the tumor extends into the plantar base and soft tissues, a fish-mouth incision is made with equal length dorsal and plantar flaps.

 

To help prevent equinus contracture, the tibialis anterior is detached from the tarsal navicular with a cuff of soft tissue, preferably periosteum. A drill hole is made through the neck and head of the talus in an oblique fashion from dorsolateral to plantar medial. The tendon is then routed through this bone tunnel and sewn to itself or soft tissue as it exits through the tunnel (TECH FIG 4B). This repair may be augmented with bone anchors placed near the dorsal opening of the tunnel.

 

The residual foot is maintained in maximal dorsiflexion during this repair. TECH FIG 4C shows the position of the ankle after the amputation and reconstruction of the tibialis anterior into the talus. Several additional procedures are required for a functional Chopart amputation. Contracture prevention is critical and ensured through transfer of the extensor tendons to the dorsum of the foot and lengthening of the

Achilles tendon.7

 

 

 

TECH FIG 4 • Surgical technique for Chopart amputation. A. Skin incisions with dorsal and plantar flaps. Bones are dissected and removed. B. Attachment of tibialis anterior tendon into the neck of the talus through drill holes. Wound closure with sutures. C. Chopart amputation has a poor reputation because equinus contracture develops in many patients. With transfer of the tibialis anterior to the neck of the talus, this problem can be avoided. This patient also had a bupivacaine catheter placed for postoperative pain control.

 

 

The posterior tibial tendon and the flexor hallucis longus and brevis tendons are divided; the tendons are allowed to retract proximally unless the posterior tibial tendon is used to augment the dorsiflexion repair.

 

The plantar branch of the posterior tibial artery is located, ligated, and divided. The flaps are maintained with sufficient soft tissue to keep them as thick as possible to prevent devitalization of the skin.

 

If the head of the talus is prominent, a portion of this bone can be removed in a beveled fashion by using an oscillating saw and angling the blade 30 degrees from distal proximal to plantar distal. The calcaneocuboid articulation is generally divided, but if part of the cuboid can be maintained, this is preferable. Contouring the distal talus and calcaneus will help to decrease the size of the stump, and this will help with prosthetic fitting.

 

The repair of the plantar soft tissue to the dorsal soft tissue is tenuous as there is no stout tissue dorsally to anchor the plantar flap. For this reason, a myodesis is preferred; it is performed by drilling holes in the distal talus and residual cuboid and anchoring the plantar fascia to the dorsal residual bone with 0 nonabsorbable suture. The subcutaneous tissue is approximated with 3-0 absorbable sutures and the skin repaired with 4-0 nylon suture.

 

The residual foot must be maintained in as much dorsiflexion as possible. To help achieve this, a rigid

dressing is applied by binding the residual foot from a proximal-plantar to distal-dorsal direction and applying gentle but firm compression on the residual foot. This rigid dressing is applied and extended up to the proximal leg, maintaining the residual foot and ankle in a maximally dorsiflexed position to protect the repair.

 

P.411

• Curettage and Cryosurgery of the Calcaneus

  Curettage

   

  A sciatic nerve catheter is used for intraoperative and postoperative pain control. General anesthesia is used for the procedure. The patient is placed into the lateral decubitus position with the affected side up. A tourniquet is placed on the upper thigh.

   

  After sterile surgical preparation and draping, an L-shaped incision is made from the tip of the fibula posteriorly and anterior to the Achilles tendon. The incision is parallel to the fibula, extending distally and making a curve at the border between the dorsal and plantar skin of the calcaneus laterally.

   

  The initial skin is incised using the scalpel and dissection is carried down through the subcutaneous tissue. The incision and approach are inferior to the peroneal tendons, which remain safely superior to the dorsal fasciocutaneous flap. The sural nerve is also more superior and away from the operative field. The lateral wall of the calcaneus is exposed.

   

  A corticotomy is made using a drill to open the lateral wall of the calcaneus. The tumor is opened, which allows for the curettage. Large curettes are used to remove the obvious tumor material. This is followed by inspecting and burring the edges of the remaining calcaneal wall.

   

  Once the resection is completed, the cavity is irrigated to again inspect the cavity for remaining tumor.

  Cryosurgery

   

  The tourniquet is inflated to 350 mm Hg.

   

  Gelfoam is used to line the skin edges and subcutaneous tissue around the wound site. The retractors are placed over the Gelfoam, and laparoscopic tape sponges are placed around the skin to cover the skin.

   

  The foot is placed into a basin of warm water to try to keep the foot warm to prevent any problems that the decreased temperature from the cryosurgery may cause in the uninvolved portions of the foot.

   

  Normal saline is poured into the tumor cavity.

   

  Endocare cryosurgery probes are prepared on the back table. Ice balls are formed and noted at the tip of each of the probes. Three- and 5-mm probes are used for the cryosurgery. The cryoprobes are placed into the tumor cavity and left in to complete a 10-minute cycle.

   

   

  The skin is monitored for necrosis, and warm saline is used to keep the skin warm and supple. The cavity is allowed to thaw and the tourniquet is deflated.

  Reconstruction

   

  The reconstruction portion of the procedure consists of an allograft cancellous bone block from the bone tissue bank that is cut and contoured and placed against the subchondral surface adjacent to the subtalar joint.

   

  Two small Rush rods are cut, contoured, and placed within the calcaneus to extend from the subtalar joint, abutting and holding the allograft in place.

   

  Polymethylmethacrylate (PMMA) is mixed with 1 g vancomycin on the back table and prepared by hand mixing. This is placed into the tumor cavity to fill the cavity, completing the reconstruction.

   

  The midfoot and forefoot are taken through gentle range of motion to ensure normal movement of these joints and to make sure that there was no iatrogenic extrusion of cement, which could compromise the motion of these joints.

  The calcaneus is gently axially loaded with hand pressure to ensure that the reconstructed calcaneus moves as a single unit.

  A drain is placed, and the wound is closed in layers. A plaster splint is used.

• Syme Amputation

The incision extends from the anterior aspect of the lateral malleolus to the anterior aspect of the medial malleolus, continuing to the plantar skin. The incision at the plantar flap is made to the level of the calcaneocuboid joint. The soft tissues, including tendons, are incised and allowed to retract; the neurovascular bundle is identified and ligated. The talus and calcaneus are dissected sharply and removed.

The surgeon must be cautious at the point of the Achilles tendon insertion site: The skin is thin and adherent and must be protected.

The flares of the malleoli are removed with a sagittal saw. The plantar fat pad is fixed to the end of the stump with nonabsorbable sutures into drill holes of the distal tibia and fibula.

A drain is placed and the wound closed in layers; 3-0 nylon suture is used to repair the skin. A well-padded soft dressing is applied.

 

 

P.412

 

PEARLS AND PITFALLS

Indications

• A careful and complete history and physical examination are essential. Preoperative studies are necessary to plan the

resection and reconstruction.

Surgical incision

• A long plantar flap results in a better end-bearing stump. The natural cascade of metatarsal lengths should be

maintained.

Wound healing

complications

• Local wound care with dressings and oral antibiotics are usually sufficient to allow for healing.

Deep infection

• Parenteral antibiotics and surgical débridement may be necessary to treat deep infections. Early diagnosis and

treatment can affect outcome.

Contractures

• Postoperative splinting can help prevent contractures. Once a contracture occurs, it is treated with stretching if mild.

Serial casting may be needed.

Painful stump

• The end of the bones should be contoured to be smooth. A rasp is effective. Adequate soft tissue coverage will help

prevent bony prominence, which may become symptomatic.

 

 

POSTOPERATIVE CARE

 

Postoperative pain control will allow early mobilization of the patient. Wound healing without complications and prevention of contractures, particularly equinus contractures, are vital.1

 

After a ray resection, the patient is placed in a well-padded splint. Crutches are used until the sutures are removed. The patient may begin range-of-motion exercises and weight bearing as tolerated.

 

Toe amputation patients may ambulate in a postoperative shoe immediately. The sutures are removed at 2 to

3 weeks. A wide comfort shoe is worn and activities are progressed as tolerated.

 

For the Lisfranc and transmetatarsal amputations, a rigid postoperative dressing is used. The wound is dressed with nonadherent dressing gauze. A gauze roll is used to bind the residual foot. Cotton padding is then placed in strips from the hindfoot to the forefoot from plantar to dorsal in an attempt to reduce the tension on the suture line. The heel is well padded with cotton padding, and then a plaster cast is applied. The cotton padding may have elastic in it for built-in stretch. The plaster is also applied from proximal and plantar to distal and dorsal to reduce the tension on the suture line. The plaster application should be firm but not tight. It should be placed in closed-toe fashion and should extend up to the proximal leg, maintaining the residual foot in the neutral position to a slightly dorsiflexed position.

 

 

This initial dressing is changed after 3 to 5 days and the Penrose drain is removed with the first dressing change. A similar plaster is applied for an additional 2 weeks. At the time of plaster removal, the sutures are removed. The patient is given a prescription for a shoe filler.

 

After 2.5 weeks, the patient's foot is placed in a bucklewedge shoe for an additional 3 to 4 weeks. After that, shoe wear and progressive ambulation are encouraged.

 

After a Chopart amputation, the cast is removed after 5 days and the drain is removed. A second dressing and cast are applied for about 3 weeks. The second cast is removed and the sutures are removed at the end of the 3 weeks. A third cast is applied and maintained for 6 to 8 weeks. After the final cast is removed, the patient begins physical therapy to begin range of motion, in particular dorsiflexion and plantarflexion excursion of the residual foot. A prosthetic measurement is taken.

 

OUTCOMES

After a toe amputation at the level of the metatarsophalangeal joint, full preoperative function is regained. A cosmetic toe prosthesis may be used if the patient desires one, but it has no functional purpose.

Ray resection outcomes depend on the number of rays amputated and whether the first ray is involved. A ray resection of the second, third, fourth, or fifth metatarsal does not need shoe modification with a molded insert or filler. Generally, ordinary store-bought shoes that are wide and have adequate cushioning are worn.

A first ray resection affects the remaining foot function because of loss of the windlass mechanism. Reconstruction of the first ray would prevent this problem (FIG 8).

Removal of two central rays will leave a narrower foot and shoe-wear problems.

Patients with a metatarsal ray or transmetatarsal amputation have better outcomes than patients with a Syme amputation.8

Patients with a Lisfranc, transmetatarsal, or Chopart amputation have good overall function compared with patients with a Syme amputation.1,13,16 However, patients with an equinus contracture after a Chopart amputation have inferior results.8,10

 

 

 

 

FIG 8 • This patient had a recurrent giant cell tumor of the first metatarsal that was treated successfully with a fibular strut graft. This lateral radiograph shows the healed graft 7 years postoperatively.

 

 

P.413

 

A Chopart amputation in a young patient is inferior in function to a Syme amputation due to the lack of ability to replace forefoot function when the space between the floor and the plantar surface is reduced significantly in a Chopart amputation.

 

The Chopart procedure provides an excellent level of amputation for a patient with limited activities and goals.1 The main advantage to this level is that little is lost between the distal end of the residual limb and the floor. This allows ease of ambulation without the need for a prosthetic device.15

 

For persons requiring short trips to the bathroom in the middle of the night or stability for transfers, the Chopart level is perfect. Unfortunately, the lack of anatomic structure and minimal distance from the plantar surface to the floor makes the Chopart amputation a poor choice for the active amputee.

 

Ambulation is achieved with a foot spacer. For the Chopart stump, a clamshell type of prosthesis allows good weight-bearing function and restores the effective foot length.6

 

 

Generally, patients are able to ambulate 3 months after amputation using a simple shoe prosthesis.16 Gait analysis shows that abnormality and asymmetry of ground-reaction forces were less with a greater preserved stump length.11

 

 

COMPLICATIONS

Wound healing complications are treated with local wound care, elevation, and non-weight bearing. Oral antibiotics may be indicated. If there is skin flap necrosis, débridement with a skin graft may be

 

necessary.3

Superficial infection is often resolved with a short course of oral antibiotics.

Deep infection may require immediate operative débridement of devitalized tissue. Parenteral antibiotics are important to treat this limb-threatening problem. At the time of the débridement, a bone culture should be ordered to help determine the appropriate antibiotic.

Equinus contracture is most easily treated by prevention. However, stretching with a therapist may be helpful. Serial casting may be required to correct the deformity.

 

 

REFERENCES

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2. Bugnone AN, Temple HT, Pitcher JD. Low-grade central osteosarcoma of the foot and ankle: radiographic and pathologic features in two patients: case report and literature review. Foot Ankle Int 2005;26:494-500.

    

    

3. Chang BB, Bock DE, Jacobs RL, et al. Increased limb salvage by the use of unconventional foot amputations. J Vasc Surg 1994;19:341-349.

    

    

4. Choong PF, Qureshi AA, Sim FH, et al. Osteosarcoma of the foot: a review of 52 patients at the Mayo Clinic. Acta Orthop Scand 1999;70:361-364.

    

    

5. Chou LB, Malawer MM. Analysis of surgical treatment of 33 foot and ankle tumors. Foot Ankle Int 1994;15:175-181.

    

    

6. Dillon MP, Barker TM. Can partial foot prostheses effectively restore foot length? Prosthet Orthot Int 2006;30:17-23.

    

    

7. Garbalosa JC, Cavanagh PR, Wu G, et al. Foot function in diabetic patients after partial amputation. Foot Ankle Int 1996;17:43-48.

    

    

8. Greene WB, Cary JM. Partial foot amputations in children: a comparison of the several types with the Syme amputation. J Bone Joint Surg Am 1982;64A:438-443.

    

    

9. Hattrup SJ, Amadio PC, Sim FH, et al. Metastatic tumors of the foot and ankle. Foot Ankle 1988;8:243-247.

    

    

10. Heim M. A new orthotic device for Chopart amputees. Orthop Rev 1994;23:249-252.

     

     

11. Hirsch G, McBride ME, Murray DD, et al. Chopart prosthesis and semirigid foot orthosis in traumatic forefoot amputation: comparative gait analysis. Am J Phys Med Rehabil 1996;75:283-291.

     

     

12. Kirby EJ, Shereff MJ, Lewis MM. Soft-tissue tumors and tumor-like lesions of the foot: an analysis of eighty-three cases. J Bone Joint Surg Am 1989;71A:621-626.

     

     

13. Millstein SG, McCowan SA, Hunter GA. Traumatic partial foot amputations in adults: a long-term review. J Bone Joint Surg Br 1988;70B:251-254.

     

     

14. Murari TM, Callaghan JJ, Berrey BH Jr, et al. Primary benign and malignant osseous neoplasms of the foot. Foot Ankle 1989;10:68-80.

     

     

15. Philbin TM, Leyes M, Sferra JJ, et al. Orthotic and prosthetic devices in partial foot amputations. Foot Ankle Clin 2001;6:215-228.

     

     

16. Roach JJ, Deutsch A, McFarlane DS. Resurrection of the amputations of Lisfranc and Chopart for diabetic gangrene. Arch Surg 1987;122:931-934.

     

     

17. Seale KS, Lange TA, Monson D, et al. Soft tissue tumors of the foot and ankle. Foot Ankle 1988;9:19-27.

     

     

18. Sundberg SB, Carlson WO, Johnson KA. Metastatic lesions of the foot and ankle. Foot Ankle 1982;3:167-169.

     

     

19. Wetzel LH, Levine E. Soft-tissue tumors of the foot: value of MR imaging for specific diagnosis. AJR Am J Roentgenol 1990;155:1025-1030.

     

     

20. Wu KK, Guise ER. Metastatic tumors of the foot. South Med J 1978;71:807-812.