Patients who require transtibial amputation can be grouped into nonischemic or dysvascular causes. Nonischemic indications generally include trauma, tumor, infection, or congenital deformities. These patients are typically younger and healthier, with fewer comorbid conditions. Patients with dysvascular limbs likely have additional comorbidities that need to be assessed before surgical intervention. Successful wound healing in the setting of vascular compromise can be dramatically improved through appropriate surgical technique using a long posterior flap as described by Burgess et al.^3,4 A recent Cochrane Database analysis demonstrated no significant differences between a variety of incisions to include skew flap, sagittal flap, and long posterior techniques.⁵

When possible, preoperative assessment of healing potential should be performed. Ideally, patients undergoing a transtibial amputation should have an ankle-brachial index greater than 0.5, transcutaneous oxygen saturation on room air greater than 20 to 30 mm Hg, an albumin level greater than 2.5 g/dL, and an absolute lymphocyte count greater than 1,500 per µL.⁶

Patients with vascular compromise who are not in extremis but require amputation should undergo optimization before limb removal at a transtibial level or consideration of amputation at a higher level. In the setting of trauma, initial limb salvage affords a dialogue with the patient and possibly their family regarding expectations and outcomes and affords opportunity for the patient to participate in the decision-making process. This is not a contraindication, per se, rather a delay to include the patient in decisions. An insensate foot is not considered a reliable indicator of function and therefore is not an indication for amputation.¹¹ Finally, ascending infection proximal to the knee is a contraindication for this level.

The patient is positioned in the supine with a bump under the buttocks to position the patella in a direct anterior position. A well-padded thigh tourniquet is often placed, however exsanguination should not be performed with malignancy or active infection. The ideal length of the residual limb is at least 12 cm distal to the knee joint line, and at least 25 cm above the plantar heel pad at a level where sufficient gastrocnemius muscle can effectively serve as padding by way of a myodesis. The positioning below the knee allows optimal residual lever arm, while the position from the floor allows for optimum prosthesis components and adequate distal padding.

A standard posterior flap, as described by Burgess, is drawn circumferentially. The transverse skin incision should be 1 to 2 cm below the proposed tibial transection line and should extend from 1 cm posterior to the posterior medial border of the tibia laterally to the fibula. The handle of a hemostat can be used to outline a curve at each border medially and laterally (Figure 1). The incision extends distally in longitudinal fashion following the posterior medial border of the tibia medially, posterior to the fibula laterally, and is carried completely around the posterior aspect of the distal calf. The length of this flap should be roughly twice that of the transverse arm or twice the diameter of the calf. Additional skin can later be resected. In certain trauma situations the extended posterior flap has been described as being emplaced onto the anterior tibial fascia proximal to the tibial bevel. Tisi and Than⁵ performed a detailed Cochrane review of various skin incisions and noted no difference in wound healing, but the ability to wear a prosthesis appears to be optimal when the scar is not over the weight-bearing end of the residual limb.

Following the circumferential skin marking of anticipated incision, the limb is exsanguinated and the tourniquet elevated and the entire skin incision performed down to the fascia. If an osteoperiosteal flap is to be raised, care should be taken on the anteromedial border to preserve the tibial periosteum, tibial periosteum proximally, which in bone bridge cases should be separately elevated. Following complete skin and fascial incision, the anterior and lateral muscular compartments are transected. It is helpful to carry out the transection proximally into the anterior and lateral compartments as these compartments add nothing to a myodesis and often add tension to the fascia and skin in wound closure. The anterior tibial artery is identified before transection and is doubly ligated. The deep and superficial peroneal nerves can be identified and injected before transection with 1% lidocaine. Similarly, on the medial side the saphenous vein is identified and ligated and the saphenous nerve is transected following injection. It is equally important to perform traction neurectomy for the sural remnant in the posterior flap so as to avoid incisional neuromata.¹³

Subperiosteal dissection around the posterior tibia using a Cobb elevator enables exposure of the intermuscular septum, the tibial shaft, and the fibula. This tibial shaft bone cut can be made by a oscillating saw or Gigli saw with care taken to ensure perpendicular cut in both the AP and lateral plane. One can avoid splintering a posterior bone spike by ensuring support of the foot during the cut. Next the fibula is cut no more than 1 cm proximal to the tibia and performed in a contoured position from proximal lateral to distal medial. Sharp bone edges can be rounded using a hand rasp or power saw. An anterior bevel is essential for prosthesis comfort, and deserves additional comments. If a bevel is begun within the medullary canal, later reabsorption of the bone can result in two medial and lateral prominent points and therefore the bevel should be clearly outside the medullary canal and fully intracortical (Figure 2). This bevel is made at a 30° to 45° angle, with care taken to preserve the proximal periosteum for myodesis or myoplasty.

Following tibial and fibular osteotomies, a long amputation knife is best used to optimize the contour of the gastrocnemius fascia. This knife, using long
sweeping strokes, permits resection of the posterior tibial muscle; transection of the neurovascular bundle distal to the bone ends; and a tapered resection of the soleus followed by transection of the gastrocnemius fascia at the most distal aspect. Completing a circumferential skin incision initially prevents inadvertent buttonhole or irregular skin edges. The foot is passed off the field and attention is turned to the neurovascular bundle. Proximal dissection and removal of the posterior tibialis muscle belly permit exposure of the tibial neurovascular bundle where the artery is doubly tied with a suture ligature and the veins are separately ligated. The tibial nerve is separately dissected from the vessels to prevent pulsatile irritation. This nerve is similarly injected proximally and gentle traction neurotomy, or more advanced nerve management technique as discussed in later chapters, is performed above the level of the tibial bone cut. At this point the tourniquet should be released, hemostasis can be fully obtained, and an assessment of the gastrocnemius fascia for myodesis or myoplasty performed.

When a myodesis is performed, it is best to avoid a central core style of suture as these can create sterile abscesses. A large #5 braided suture is used to perform a Krackow style locking stitch with four strands.¹⁴ A 2 to 3 mm drill bit is used when creating a formal myodesis and the drill hole should be proximal to the bevel to facilitate complete coverage of the distal tibia (Figure 3). If a myoplasty is performed, the terminal end of the gastrocnemius fascia is simply secured to the anterior tibial periosteum and fascia; it is worth noting that, because the gastrocnemius-soleus complex is not stabilized to a truly dynamic, opposing muscle group, this technique of myoplasty technically is a form of myodesis. Even in vascular patients, security of the gastrocnemius over the distal tibial cut is important for future prostheses wear. Following meticulous hemostasis, myodesis is secured and fascial closure is performed in layers. While the decision for draining is individual, there is little scientific evidence to support routine placement of drains. Meticulous hemostasis before closure is the best practice for avoiding postoperative hematomas or wound healing problems. The skin is closed in layers, and the dressing of choice applied. A postoperative splint protecting the distal residual limb prevents wound complications in postoperative falls. There is some risk for the patient to forget in the early phases and depend on the now-absent limb. Falls on the residual limb can be devastating.