Amputations of the Foot and Ankle

Maria Romano McGann, DO

Bryan Van Dyke, DO

G. Alex Simpson, 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. McGann, Dr. Van Dyke, and Dr. Simpson.

ABSTRACT

Amputations of the foot and ankle are performed for several indications including infection, ischemia, and trauma. Diabetes and peripheral vascular disease often contribute to the development of nonhealing wounds that may necessitate amputation. Lower extremity trauma, both civilian and military, may also lead to amputation both acutely and after failed salvage attempts. Patients undergoing amputation should undergo a thorough evaluation that involves a multidisciplinary team to medically optimize the patient, evaluate for the best level of amputation, and plan for postoperative management. Once a patient is prepared for the procedure, the surgeon must maintain diligence to achieve adequate removal of tissue while maintaining viable tissue where useful. Postoperative muscle balance is important for improving appearance and function. New techniques in amputation surgery continue to develop, and with each advancement, further outcomes studies will help guide surgical decision making.

Introduction

Amputations of the foot and ankle are procedures that have been described for centuries. Amputations can be thought of as a function-restoring procedure, as they are usually indicated once a limb is deemed nonfunctioning or nonviable. In the United States, common reasons for foot and ankle amputations include complications that result from diabetes and vascular disease. More than 60% of nontraumatic lower limb amputations occur in people with diabetes, while only approximately 3% of patients with symptomatic peripheral artery disease require.¹^,² Other reasons for amputation of the foot and ankle include severe trauma, chronic pain infection, congenital abnormality, and malignancy.

Amputations are deemed a reconstructive procedure that will assist the patient in locomotion and sensory feedback.³ Treatment by means of amputation should be considered the first step in a patient’s rehabilitation, not as a failure of treatment.⁴ The goals of all amputations are to heal the wound, avoid further infections, and return a patient to a preamputation ambulatory level. Furthermore, goals include adequate balancing of the remaining muscles to avoid contractures and retain residual limb control.⁵ Amputations of the foot and ankle range from simple phalangeal amputations to those of the midfoot, hindfoot, ankle disarticulations, and transtibial amputations. Those amputations of the midfoot and hindfoot may preserve the ability for ambulation, which may decrease patient morbidity.⁶

A well-organized, multidisciplinary team must care for patients undergoing major amputations. The surgeon performing the amputation must be well versed in the surgical technique, postoperative treatment of patients, and the knowledge of prosthetics and footwear modification.

Preoperative Management

Patients in need of an amputation commonly have medical comorbidities, such as diabetes and vascular disease. A thorough preoperative evaluation of the extremity’s color, temperature, pulses, sensation, and tissue quality should be performed to give the patient the best chance for a good
outcome. Radiographs and advanced imaging studies are ordered to evaluate bony structure and determine the extent of any underlying osteomyelitis. Evaluation should also include their functional ability, social environment, nutritional and immune status, and mental state. Preoperative evaluation, including laboratory and vascular studies can aid in determining the potential wound healing of patients undergoing amputation. Predictors of wound healing include serum albumin level, total lymphocyte count, transcutaneous oxygen pressures, and ankle brachial indices.⁷^,⁸

Every patient must have a good rapport with their medical specialists including an orthopedic surgeon, vascular surgeon, medical doctor, therapists, social worker, physiatrist, and mental health professional. A psychiatric evaluation is an important preoperative tool, as an amputation can be a major life-changing event.⁹

Indications

Vascular Disease and Diabetes

The indications for an amputation are multiple and, in some cases, may be multifactorial, such as in diabetics with vascular disease. In vascular disease alone, high 2-year mortality rate of 40% has been documented.¹⁰ In the foot and ankle, the combination of peripheral vascular disease and diabetes creates an environment of dysvascularity that is prone to infections. These infections can easily spread and cause life-threatening sepsis. High-risk patients, especially African-American diabetic patients residing in low-intensity vascular care regions, represent an important target for systematic efforts to reduce amputation risk.¹¹ Among the general population aged ≥45 years, the incidence of vascular lower extremity amputation at, or proximal to, the transmetatarsal level is eight times higher in diabetic than in nondiabetic individuals. Additionally, one in four amputees may require contralateral amputation and/or reamputation at a higher level.¹² The last decade saw a marked decline in the use of lower extremity amputation in the Medicare population, and among diabetics, an increase in conservative care of diabetic ulcers has occurred.¹³^,¹⁴ However, those diabetic Medicare patients saw an increase in amputations occurring at distal, limb-conserving locations.¹⁵^,¹⁶ Additionally, patients with poorly controlled diabetes were more likely to undergo amputation versus limb salvage.¹⁶^,¹⁷ Complications in diabetics after a primary transtibial amputation or below requiring a readmission is approximately 10%, mostly due to deep infections or wound dehiscence.¹⁸ Limb salvage has been shown to be more of a cost burden compared with amputation in diabetic patients diagnosed with severe Charcot arthropathy.¹⁹

Trauma

Traumatic amputation rates resulting from a mangled extremity have decreased from as high as 20% of patients to less than 10% of patients; however, traditional injury severity scores have been proven to fail in predicting the need for amputation in trauma.²⁰ Despite this relatively low proportion of amputations done following trauma, individuals with a traumatic amputation account for nearly 45% of the estimated 1.6 million living people with an amputation.⁵ Those patients that undergo amputations due to trauma frequently battle complications and other difficulties such as chronic pain and decreased rates of return to work.²¹^,²² In the current age of combat warfare, injury patterns sustained due to blast injuries have increased efforts in military trauma care. United States service men and women have been exposed to an increased amount of complex blast injuries which affects limb tissue availability that, in turn, limits reconstruction efforts.²³^,²⁴ Research has shown that patients undergoing amputation from combat trauma fair better than those undergoing salvage, with increased rates of function and decreased psychological symptoms.²⁵^,²⁶^,²⁷ Those who undergo a delayed amputation after attempted limb salvage achieve similar functional results as those with a more immediate amputation.²⁷ Unfortunately, increased morbidity is associated with the effects of combat warfare.²⁸

Malignancy

Amputation was once the treatment of choice in the management of malignant bone tumors. However, in the current age of increased radiographic modalities, pharmaceutical innovations, and increased surgical skill, surgeons are performing more and more reconstructive surgery.²⁹ If an amputation is deemed the appropriate treatment option, then the primary goal of surgery is to maintain the most appropriate length needed to fully excise the malignancy while diminishing local recurrence and improve overall survival.²⁹

Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) with an unknown etiology, specifically Type I, is a debilitating condition that can affect patients. After a combination of pharmacological and physical therapies, symptoms are difficult to improve, and patients may request elective amputations. Patient who undergo an amputation for CRPS-1 have a 77% rate of residual phantom pain after 1 year with varying amounts of disability ranging from none to very disabling.³⁰ Yet, 95% of CRPS-1 patients who elected to undergo an amputation reported an overall improvement in their lives.³¹

Level of Amputation

The ultimate goal of an amputation is to restore function to the residual limb, all while maintaining the greatest residual limb length in hopes of returning a patient’s maximum function.³² Furthermore, patient mobility and functional independence should be maintained. The level of amputation will affect how much energy is exhausted by the patient, so maintaining length, whenever possible, is important.³²^,³³ The overall length of the residual limb is affected by the preoperative condition of the limb, associated pathology, and general intraoperative findings. Coverage of residual osseous structures is important to prevent tissue breakdown; therefore it is important to maintain thick myocutaneous flap coverage. In instances of blast trauma, the residual tissue available for wound closure greatly affects the level of amputation.³⁴

Amputations may either be through a joint, disarticulation, or through bone, transosseous. Disarticulations are end bearing, in that loads are directly transmitted through the joint surface and metaphyseal bone. Alternatively, transosseous amputations have a smaller residual cross-sectional area, through which the weight is transferred indirectly. In transosseous amputations, load transfer is through the entire limb via a total contact prosthesis.³⁵

In adults, the energy required for ambulation is drastically different depending upon which level of amputation is performed. As the amputation level becomes more proximal, an increased amount of energy is required to ambulate. Alternatively, recent studies have shown that in children having undergone a Syme, transtibial, or bilateral below-the-knee amputation, no increase was documented in their energy cost of walking, no significant gait difference or function, and they walk at similar speeds compared with their peers.³⁶^,³⁷

Types of Amputations

Toe Amputations

Great Toe Amputations

This amputation is indicated in cases where there is pathology of the distal aspect of the hallux or chronic conditions of the nail plate. The benefits of this amputation over a disarticulation of the metatarsal phalangeal joint include maintenance of the plantar flexion mechanism of the first ray. Also, some preservation of the weight-bearing function of the hallux exists, which will decrease the transfer stress of the adjacent rays. When completing this amputation, it is important to save at least 1 cm of the proximal phalangeal base.³⁸

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