Midfoot Amputations

Bryan Van Dyke, DO

Maria Romano McGann, DO

Bryan Witt, DO

Terrence M. Philbin, DO

Dr. Philbin or an immediate family member has received royalties from Arthrex, Inc., Biomet, Crossroads, Paragon 28, and Wright Medical Technology, Inc.; is a member of a speakers’ bureau or has made paid presentations on behalf of Arthrex, Inc., Crossroads, DJ Orthopaedics, Medline, Tissue Tech, and Zimmer Biomet; serves as a paid consultant to or is an employee of Artelon, Arthrex, Inc., Crossroads, DJ Orthopaedics, Medline, Tissue Tech, and Zimmer Biomet; has stock or stock options held in Tissue Tech; has received research or institutional support from Biomimetic and DJ Orthopaedics; and serves as a board member, owner, officer, or committee member of the American Osteopathic Academy of Orthopedics. None of the following authors or any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter: Dr. Van Dyke, Dr. McGann, and Dr. Witt.

INTRODUCTION

For patients, amputations are often feared as a disfiguring failure of treatment or as a last resort for life over limb type situations. However, with appropriate discussion, amputation can be offered as a more predictable and direct route to begin healing.¹^,²^,³ Advances in vascular interventions, surgical techniques, and prosthetic devices have initiated a reemergence of partial foot amputations¹^,² (Figure 1). Pedal amputations can result in increased function, better cosmesis, improved lifestyle, and decreased energy consumption as compared with transtibial amputations.² Among the midfoot amputations, the most commonly performed is the transmetatarsal amputation. However, the Lisfranc and Chopart amputations are also considered viable options.⁴

FIGURE 1 Illustration depicts levels of partial foot amputation.

In the United States, there are approximately 1.7 million people living with an amputation.⁵ Moreover, an average of 133,235 amputations are performed yearly in the United States.⁵ The vast majority of amputations (82%) are due to vascular conditions and are increasing in incidence.⁵ Traumatic and congenital deformity amputations are the second and third most common causes of amputations, respectively.⁵ Lower limb amputations account for 97% of all dysvascular amputations.⁵ Over 50% of all lower extremity amputations are either transfemoral or transtibial; pedal amputations constitute 31% of lower extremity amputations.⁵

The transmetatarsal amputation was described by McKittrick in 1949 as a surgical option to treat pedal infections associated with diabetes mellitus.¹^,²^,⁶ The procedure
involves a resection of the metatarsal bones at the midshaft level. This amputation is a midfoot alternative to the standard transtibial amputation and generally has a lower mortality rate, results in less energy expenditure with ambulation, and provides a distal weight-bearing stump.¹^,² Approximately 10,000 transmetatarsal amputations are performed yearly in the United States.¹^,²

The Lisfranc amputation was developed in the 1800s by Jacques Lisfranc de St. Martin, a French surgeon and gynecologist during the Napoleonic Wars.¹^,⁴ Lisfranc described this midfoot amputation as a disarticulation between the metatarsals and tarsal bones.⁴ The amputation was developed for a soldier that suffered a dysvascular foot with infection after a fall from a horse where his foot remained caught in the stirrup. Fractures and dislocations about the tarsometatarsal joint are now also referred to as Lisfranc injuries.

The Chopart amputation was described by Francois Chopart, a French surgeon in the late 1700s. This amputation is performed at a more proximal level in comparison to the Lisfranc and transmetatarsal amputations.⁴ The Chopart amputation involves disarticulating the transverse tarsal joint which includes the talonavicular and calcaneocuboid joints¹^,²^,⁴ (Figure 2). Owing to its proximal location, the Chopart amputation is more prone to postoperative deformity if tendon forces are not balanced with tendon transfers at the time of the amputation.

FIGURE 2 Illustration shows the Chopart amputation. A, Lateral view of incision. B, Dorsal view of incision. C and D, Dorsal and plantar flaps after resection of the distal foot. E, Transfer of the anterior tibialis tendon to the talar neck and transfer of the peroneus brevis tendon to the anterior calcaneus. F, Appearance of completed amputation after skin closure.

PATIENT SELECTION

Indications

The ideal amputation is at a level that will provide predictable wound healing while still maintaining the highest functional outcome for the patient. Typically the amputation level is dictated in part by the quality of the distal tissues. The primary indication for a midfoot amputation is extensive soft-tissue compromise of the forefoot that does not allow for a more distal amputation.¹^,⁴^,⁷ These soft-tissue complications can be due to a variety of medical or traumatic events, including a traumatic nonsalvageable forefoot injury (Figure 3), diabetes mellitus, chronic forefoot ulceration, Charcot neuroarthropathy, frostbite, peripheral vascular disease, bony neoplasm, osteomyelitis, soft-tissue infection, failed prior surgery, and intractable pain.²^,⁷^,⁸^,⁹

Contraindications

Midfoot amputations are contraindicated in patients with vascular insufficiency at the level of the proposed amputation.³^,⁴^,⁶^,⁷^,⁸ Inadequate perfusion to the amputated stump leads to poor wound healing which may necessitate a revision amputation at a more proximal level.³^,⁴^,⁶^,⁷^,⁸ In addition, patients receiving a pedal amputation secondary to infection require an amputation that is proximal to the active site of infection.³^,⁷ Amputating below the level of infection may necessitate future surgery to completely
eradicate the infection.³^,⁷ Furthermore, nonambulatory patients, especially those being considered for a Chopart or Lisfranc amputation, should undergo a more proximal transtibial amputation, as it does not significantly change the functional outcome.⁴. Also, those patients who have any type of revascularization procedure to the lower extremity ideally should wait at least 72 hours before proceeding with a pedal amputation.⁷

FIGURE 3 Photograph depicts a traumatic nonsalvageable forefoot injury. (Courtesy of Christopher Hyer, DPM, FACFAS, Orthopedic Foot and Ankle Center, Westerville, OH.)

PREOPERATIVE EVALUATION

Laboratory and Diagnostic Tests

The preoperative management of a patient undergoing pedal amputation often requires a multitude of laboratory and diagnostic tests. The underlying pathologic reason for amputation, whether traumatic, infectious, or vascular, will guide the surgeon’s decision making with regard to preoperative planning. A multidisciplinary team approach, including representatives from internal medicine, cardiology, nephrology, vascular surgery, and wound management, among other healthcare professionals, is paramount for the most appropriate care of the pedal amputation patient.¹^,⁸^,¹⁰^,¹¹

Prior to a midfoot amputation, preoperative laboratory testing is completed, including an assessment of immune and nutritional status.¹^,⁴^,¹⁰^,¹¹ A complete blood count with differential is obtained to help determine the presence or absence of an acute infection.¹¹ A white blood cell count greater than 12,000 and increased polymorphonuclear leukocytes may indicate an infectious process.⁸^,¹¹ The erythrocyte sedimentation rate and C-reactive protein level are nonspecific markers of inflammation.¹¹ These tests aid in the diagnosis of an infectious process such as osteomyelitis.¹¹ Moreover, the total lymphocyte count is used to determine the potential for wound healing.¹¹ A level greater than 1,500 is considered immunocompetent and is associated with a better healing prognosis.¹^,⁶^,⁹^,¹⁰^,¹¹ Hemoglobin and hematocrit levels are assessed for the presence of anemia.¹¹ Low hemoglobin and hematocrit levels are associated with poor tissue oxygenation and healing capacity.⁹^,¹¹ Furthermore, serum albumin and protein levels are assessed preoperatively to determine the patient’s healing capacity.¹^,¹¹ A serum albumin level greater than 3.0 g/dL and protein level greater than 6.0 g/dL are associated with improved wound healing.¹^,⁶^,⁸^,¹⁰^,¹¹

A comprehensive vascular examination is imperative for all patients undergoing a pedal amputation.⁴^,¹⁰^,¹¹ It is extremely important to assess the perfusion of the affected lower extremity to determine the appropriate level of amputation and healing capacity.¹⁰^,¹¹ The vascular examination begins with assessing the peripheral pulses, including the dorsalis pedis and the posterior tibial arteries.¹⁰^,¹¹ In addition, capillary refill is assessed to determine digital perfusion. Furthermore, the patient’s skin should be examined for atrophic changes as well as hair loss about the foot.¹⁰^,¹¹ Nonpalpable peripheral pulses, sluggish capillary refill, atrophic skin changes, and loss of hair should trigger further vascular examination.¹⁰^,¹¹

Noninvasive vascular studies, such as the ankle-brachial index (ABI), can help determine the appropriate level of amputation and the postoperative healing potential.¹^,⁶^,¹⁰^,¹¹ An ABI less than 0.9 may indicate impaired peripheral vasculature. An ABI greater than 0.5 is associated with better potential for distal stump healing.¹^,²^,⁶^,⁸^,¹⁰ However, the ABI can be falsely normal in patients with noncompressible blood vessels from calcification.¹⁰^,¹¹ High suspicion and more invasive testing are indicated in these individuals. The arterial Doppler ultrasonography examination with waveforms is useful in determining arterial occlusive disease.¹⁰^,¹¹ A monophasic waveform indicates arterial occlusive disease, whereas a triphasic waveform represents vascular patency.¹⁰^,¹¹ Transcutaneous oxygen pressures have the highest predictive value for determining the level of ischemia and the potential for wound healing.¹^,⁴^,⁶^,¹⁰^,¹¹^,¹² A pressure less than 30 mm Hg is an indicator of limb ischemia and poor wound healing capacity.¹^,²^,⁶^,⁸^,¹⁰^,¹¹^,¹² Patients with abnormal noninvasive vascular studies are candidates for an invasive examination of the affected lower extremity vasculature.¹⁰^,¹¹

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