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Achieving Optimal Offloading After A Chopart Amputation

Given the challenges of post-op ambulation after a Chopart amputation, these authors review key factors that are essential to amputation and limb salvage planning, discuss common complications after proximal amputations, and explore the role of orthotic and prosthetic management in facilitating improved outcomes.

The risk factors for patients who may require a proximal foot amputation are extensive and are best categorized as traumatic versus non-traumatic causes. In all cases, salvage attempts must include a comprehensive evaluation, which takes into consideration a multitude of patient-related parameters that aim to identify postoperative short and long-term function.

In today’s medical practice, most surgeons will proceed with a more proximal limb amputation given the questionable durability of a Chopart or Syme’s amputation. There are those who propose that preservation of limb length is a key component to long-term lower extremity outcomes. For example, Schade and colleagues explain that one should consider a proximal foot amputation first given the amputation’s potential benefits of limb length preservation as well as decreased energy expenditure, cardiac demand and mortality rates.1

For patients who suffer a traumatic injury, it is important to consider the patient’s age and the degree of pre-injury functional/ambulation status. For example, children suffering a traumatic injury may benefit from a Chopart amputation rather than a transmetatarsal amputation as children will continue to grow and therefore will require multiple subsequent surgeries if they retain their metatarsals.2 Secondly, more active patients may benefit from a below-knee amputation and subsequent fitting with an appropriate prosthetic as they would likely progress better in terms of functionality after rehabilitation rather than with a shortened foot.

In considering a proximal foot amputation, particularly a Chopart or Syme’s amputation, it is more beneficial to consider a Chopart amputation first over a Syme’s amputation. If a Chopart amputation results in additional need for surgical resection, authors recommend progressing to a major proximal amputation given that a Syme’s amputation results in an acquired limb length discrepancy.3 Therefore, a proximal foot amputation such as a Chopart is the final level of amputation for functional limb salvage before considering a major proximal amputation despite written evidence of more proximal foot amputation procedures.3

For the purposes of this discussion, we exclude the discussion of the transmetatarsal and Lisfranc amputations as one can easily accommodate these with the use of forefoot fillers that are well tolerated by patients in terms of postoperative offloading and long-term ambulatory shoe gear modifications.

Essential Factors For Formulating A Limb Salvage Plan

The prerequisite notion is that the physician has performed a comprehensive evaluation and reached an accurate consensus regarding the need for a midfoot amputation. Certainly, there are a plethora of patients for whom one may employ limb salvage modalities, as deemed necessary, that incorporate the plastic surgery reconstructive ladder. After making the clinical decision to proceed with a proximal foot amputation, one should evaluate concurrent use of these modalities that may be required to improve clinical outcomes. This evaluation should always include the discussion for a major lower extremity amputation. These notions are beyond the scope of this discussion but are certainly worth mentioning.

Important questions to answer about any attempt at limb salvage include glycemic control, body mass index, ambulatory status, distal vascular runoff and, of course, a goal-oriented discussion regarding postoperative expectations in the short- and long-term. Other considerations include contralateral lower extremity pathology, evaluation for low cardiac function, history of stroke with impairment as well as the patient’s daily routine. These factors may play a role in guiding the clinical decision between a proximal foot amputation and major lower extremity amputation.

The key in all cases is to ensure a multidisciplinary team approach to the pre- and postoperative evaluations. These often include subspecialties such as endocrinology, podiatric surgery, vascular surgery, plastic surgery, physical therapy, and a certified orthotist, prosthetist and/or dual-certified prosthetist-orthotists (CPOs). Efficient communication among all involved specialties and with the patient is critical for an efficacious plan of treatment and care. It is vital to include a discussion regarding how the patient will navigate the space as well as what kind of shoe gear, orthotic or prosthetic offloading modality he or she will require.

We have found patients with the triad of diabetes—those with neuropathy, a history of ulceration and/or previous amputations—and those with compromised distal vascular perfusion are at the highest risk for non-traumatic proximal foot amputations. For the purposes of this topic, we will only focus on proximal foot amputations. However, it is important to note that these patients are high risk for amputations at all levels including major proximal lower extremity amputations.

A predominance of patients who undergo surgical intervention will fall under two major subcategories: urgent versus non-urgent surgery. Acute needs are typically related to soft tissue and osseous infections as well as ischemic necrosis. In many cases, ischemia and infection are not exclusive. Patients suffering from infectious and ischemic processes will generally also have comorbidities such as diabetes along with an associated predilection for an increased chance of complications, requiring a more extensive approach to determining the best level of functionality for the patient. Unfortunately, these patients are at higher risk for complications and the need for further amputation in many cases. Accordingly, surgeons must consider a postoperative offloading plan in their decision tree. Orthoses and prosthetic devices must impart a protective aspect to mitigate the risk of further breakdown at the amputation site.

Pertinent Offloading Pearls With Proximal Amputations

After committing to a proximal foot amputation, one must factor several elements into the surgical algorithm in order to increase the rate of postoperative healing and decrease the risk of postoperative complications. In patients who undergo distal foot amputations such as transmetatarsal or Lisfranc amputations, a percutaneous Hoke tendo-Achilles lengthening procedure is a helpful, low-risk adjunct procedure that reduces pressure at the distal foot.

With proximal foot amputations, however, the first step in offloading begins with an Achilles tenectomy. In this case, rather than preserving and lengthening the tendon, an open surgical procedure ensures resection of approximately 1 cm to 1.5 cm of tendon. This is an essential step with surgical consideration not only to decrease forefoot loading but also to provide a positive impact on fall risk and post-op ambulation with prevention of equinus contracture.2 The most commonly reported complication with a Chopart amputation is distal ulceration secondary to equinovarus contracture.1 This is ultimately due to the patient’s inability to push off during the gait cycle with an unstable subtalar joint, resulting in compensatory changes more proximally.4

Postoperative offloading is no different than any other pedal surgery. Healing in the complex medical patient is often delayed. One should provide ample time on a case-by-case basis to ensure complete surgical site healing prior to a transition to weightbearing. Once the entire soft tissue envelope has completely healed, a new evaluation of the surgical limb is warranted. This is also the point when full weightbearing rehabilitation and physical therapy are crucial for healing in order to preserve biomechanical function for the patient.

A common complication is some degree of equinus contracture despite intraoperative intervention due to the shortened forefoot lever arm. For example, despite an Achilles tenotomy and tendon transfers, there is still a risk of foot deformity, limb length discrepancy, genu recurvatum and contralateral hip and back pain, all of which may require subsequent surgery in an already high-risk patient.2

During postoperative recovery, which is usually prolonged in the complex medical host, patients can develop unexpected changes in the degree of muscle atrophy in the ipsilateral and contralateral lower leg compartments. This can result in positional changes at the level of the foot, which must be accommodated in order to prevent new lesion formation. An unstable subtalar joint may also result in excessive anterior weightbearing with skin breakdown. Generally, this is more pronounced with distal foot amputations. Heel valgus and varus deformities are difficult to address, and one should note these changes as they could lead to hindfoot/ankle Charcot osteoarthropathy in those with peripheral neuropathy. Counsel patients preoperatively on the prospect that any future surgical intervention increases risk for major proximal lower extremity amputation.

For those amputation patients who have biomechanically-induced changes, accommodation is preferable over surgical correction in the immediate postoperative period. Bracing and shoe gear for proximal foot amputations have progressed tremendously over the recent decades. At this time, a highly rigid, high-profile prosthesis within shoe gear helps prevent further movement of the remaining joint and thus prevents contracture, deformity and ultimate skin breakdown.4

As patients become more mobile, undergo rehabilitation and have physical therapy, some of these changes can become quiescent. For those patients who may have persistent biomechanically-induced changes, further surgery may be required and one should do this prior to the development of full-thickness ulcerations. Due to the elective nature of these procedures, medical and cardiac optimization can be rate-limiting, but one should aggressively pursue optimization. In these cases, evaluate the patient’s offloading device to ascertain if the device is contributory to the newly formed ulceration or high pressure area. Of note, sometimes these ulcers are not strictly on the plantar weightbearing surface.

What You Should Know About Orthotic And Prosthetic Considerations

Up to this point, the entire perioperative goal has revolved around providing the patient with a functional limb. In other words, the goal is allowing the patient to continue with independent ambulation with the least long-term morbidity. Most patients who have undergone a proximal foot amputation such as a Chopart amputation for non-traumatic reasons have benefitted from preservation of the limb as long as they maintained use of a lifelong, high-profile brace to prevent further skin breakdown secondary to contracture or deformity.

During the postoperative period, most clinicians will not evaluate or cast a patient for custom ankle foot orthosis until the patient has completely healed. In such cases, there is a lag time in which the patient has healed but cannot return to regular shoes. This is a critical period when patient adherence and routine surveillance are important to prevent immediate postoperative complications. Sometimes the time from an orthotic order to patient use for accommodative shoe gear can be months. It is imperative that during this time period, the patient remain in an offloading device such as a controlled ankle motion (CAM) boot or DH Offloading Walker (Ossur). Since physicians should emphasize mobility and rehabilitation, unless there are other contraindications to ambulation, one should encourage patients toward transitioning from offloading to protected ambulation until the proper orthotic becomes available. During that time frame, patients must be diligent about daily self-monitoring.

Considerations during the patient’s course of rehabilitation in relation to protected offloading include emphasis on non-ambulatory skills. Such parameters include improving strength, balance and proprioception. As the patient progresses, the emphasis can shift toward ambulatory skills. Such parameters can include improving walking distance, stair climbing and other similar functional goals. Assess each patient individually and the time frame for therapy is best allotted after evaluation by a certified physical therapist.

Once the patient heals and progresses to high-profile bracing and accommodative shoe gear, there are several options to ensure that the patient gains his or her highest functional mobility with the least compromise in gait efficiency. Do not undervalue the roles of the certified or licensed pedorthist, certified orthotist and the certified prosthetist in the prevention of complications in these patients. Once the patient is ready to progress to accommodative footwear, there should be a subsequent evaluation by a clinician who can advise on appropriate bracing and shoe gear not only to prevent further complications but also to increase functional mobility.5 Other studies using high-profile bracing showed limited ankle joint range of motion.6,7
 

Case Study: When A Patient Presents With An Open TMA And Exposed Bone But No Active Infection

A 58-year-old African-American man with a past medical history of insulin-dependent diabetes, hypertension, peripheral arterial disease and chronic kidney disease presented for a third opinion for a left foot salvage attempt. The patient presented to our service for evaluation of a left foot that required a transmetatarsal amputation secondary to necrotizing infection. The patient’s previous physician told him he would need a below-knee amputation and discharged him for further treatment.

Upon presentation to our service, the patient had an open transmetatarsal amputation in the left foot with exposed bone and extensive soft tissue loss, but without active infection. Upon the patient’s admittance to the hospital, vascular surgeons performed endovascular angioplasty to optimize lower extremity perfusion to the foot. The initial operative plan was to excise nonviable tissue, assess tissue quality and obtain bone biopsies.

After several surgical debridements, we performed a proximal foot amputation along with an Achilles tenotomy. The patient did require long-term antibiotics, hyperbaric oxygen therapy and aggressive physical therapy. Once he healed, the patient used a custom ankle foot orthosis (AFO), which provided stability at the ankle. The orthosis is affixed to a shoe with accommodative insoles to allow ambulation and prevent falls.

In Search Of The Optimal Ortho-Prosthesis

With any level of amputation, we attempt to design, fabricate and fit the individual modality to achieve the most functional and comfortable ortho-prosthesis as possible for the patient. Success depends on trial and error, and requires a great deal of creativity and willingness from the multidisciplinary team and, most importantly, the patient, who will require the device for many years until another device is medically necessary.

We present two unique approaches here with a more traditional standard carbon AFO with anterior struts and a total contact custom-molded socket foot bed design with tri-lamination soft interface materials readily available and incorporated throughout the orthotic and prosthetic industry. This design is much lighter and easier to design and fabricate to achieve the goals of reduced friction, pressure and shear forces during weightbearing, ambulation and the required changes of direction we all experience throughout the day. As we stated previously, the challenges of having a solid lever from the short transmetatarsal, Lisfranc and/or Chopart amputation levels are well known throughout the medical community. Maintaining the full anatomical support length still available leaves no “real estate” to allow for a symmetrical leg length to match up to the sound side, especially if one adds too much dynamic support material (i.e. carbon fiber) to the device.

Therefore, we present a more unique approach of the “Crone-Toe” option. We worked with an established prosthetics manufacturer, Hanger Clinic, to allow us to use the mechanical articulated toe section only and incorporated that into a carbon fiber total contact laminated socket. We carefully aligned and bonded one half portion of the prosthetic foot to simulate the metatarsal articulation and toe break function of the anatomical foot during trial fittings. The actual metatarsal toe-break articulation is the main difference in this design with an option of nine different dorsiflexion bumpers to customize the dynamic resistance. The primary anterior full lever support works similarly to the AFO with custom toe filler but the support of the posterior door allows for increased loading and therefore a more dynamic and aggressive ambulation, which is required for the world-class cyclist for whom we designed this device.

The Crone-Toe allows for increased dynamic articulation of the ankle joint and more natural function and movement along with realigning the required calcaneal angle. The modality’s open posterior design promotes greater expansion of the gastrocnemius muscle group.

There will always be pros and cons to any design. However, these two options are considerations for further discussion and research of future options and desired advancements for this very functional and desired result for many of our patients and surgeons who are well versed in limb salvage and seeking more functional outcomes for the end users.

Dr. Gulati is a first-year resident in podiatric surgery at the MedStar Washington Hospital Center in Washington, D.C.

Dr. Elmarsafi is an Attending Surgeon in podiatric surgery at the MedStar Washington Hospital Center in Washington, D.C.

Mr. Crone is the Clinical Director of Prosthetics at Hanger Clinic in Austin, Texas.

Dr. Steinberg is a Professor in the Department of Plastic Surgery at the MedStar Washington Hospital Center in Washington, DC. He is a Fellow and Past President of the American College of Foot and Ankle Surgeons.

References
1.     Schade VL, Roukis TS, Yan JL. Factors associated with successful Chopart amputation in patients with diabetes: a systematic review. Foot Ankle Specialist. 2010; 3(5):278-284.
2.     Baima J, Trovato M, Hopkins M, Delateur B. Achieving functional ambulation in a patient with Chopart amputation. Am J Phys Med Rehabil. 2008; 87(6):0894-9115.
3.     Faglia E, Clerici G, Frykberg R, et al. Outcomes of Chopart amputation in a tertiary referral diabetic foot clinic: data from a consecutive series of 83 hospitalized patients. J Foot Ankle Surg. 2016; 55(2):230-234.
4.     Burger H, Erzar D, Maver T, Olensenk A, Cikajlo I, Matjacic Z. Biomechanics of walking with silicone prosthesis after mid tarsal (Chopart) disarticulation. Clinical Biomechanics. 2016; 24(6):510-516.
5.     Janisse DJ, Janisse EJ. Shoes, orthoses, and prosthesis for partial foot amputation and diabetic foot infection. Foot Ankle Clin. 2010; 15(3):509-523.
6.     Dillon MP, Barker TM. Preservation of residual foot length in partial foot amputation: a biomechanical analysis. Foot Ankle Int. 2006; 27(2):110–116.
7.     Dillon MP, Barker TM. Can partial foot prostheses effectively restore foot length? Prosthet Orthot Int. 2006; 30(1):17–23.

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By Amar Gulati, DPM, Tammer Elmarsafi, DPM, MBBCh, Charles Crone, CP, and John Steinberg, DPM, FACFAS
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