A final muscle stabilization technique, tenodesis, is very secure but frequently anatomically impossible. Tenodesis involves the firm distal attachment of the severed tendon down to the bone, and is the most physiologic and effective means of muscle stabilization. It is possible only when the muscle belly itself is not transected and the tendon is intact. Tenodesis is most commonly used in disarticulations, and is the primary method in knee disarticulations in which the patellar tendon is secured to the origin of the cruciate ligaments on the distal femur. Whenever anatomical circumstances permit, distal attachment of the muscles, tendon, fascia or aponeurosis directly to the bone should be performed.

To optimize effective residual limb muscle activity, the muscle should be stabilized under near physiologic tension. Correct muscle tension varies from case to case, and the primary determinants of appropriate tension level remain somewhat amorphous. There is no set of hard and fast rules. Studied clinical judgement and adherence to the principles of muscle tension provide the best results. Determining correct muscle tension in an amputation is similar to determining the tension of tendon transfers in the hand or foot. In general, most surgeons err on the side of too lax rather than too tight. Unfortunately, it is entirely possible that when stabilizing muscle groups the surgeon can apply excessive or unbalanced tension, causing sever pain to the patient. One example of accidental implementation of excessive tension occurs if a surgeon advances the quadriceps under too far, a scenario that leads to hip-flexion contracture. Though it is difficult to establish a solid set of guidelines when performing muscle stabilization, stabilization is an essential element of amputation surgery and the reconstructive process.

The Nerves
The management of sectioned nerves remains a controversial aspect of amputation surgery. The free end of a divided nerve heals by forming a neuroma. This intertwined mass of scar and nerve tissue can be painful to pressure, stretching and other types of physical manipulation. Even when completely undisturbed, electrical potentials may arise within the mass, causing negative local and distant sensory and motor phenomena. These sensations can be bothersome and painful to the amputee. While numerous techniques have been devised in order to minimize neuroma formation, none have proven uniformly successful. Some methods have included cauterizing the nerve ends using chemicals or heat, burying the nerve in bone, encasing the nerve in impervious material, ligating the nerve or injecting the nerve with a variety of chemicals. Other methods include sewing the sectioned nerves to other nerves or sewing them back onto themselves, thereby creating a nerve loop. Others methods entail simply dividing the nerve and allowing it to retract.

Since neuroma formation is to some degree inevitable, the generally accepted management procedure is drawing the nerve distally, sectioning it and allowing it to retract away from areas of pressure, scarring and pulsating vessels. Ligation of a nerve is indicated if the nerve is likely to bleed, as is the case with the sciatic nerve. When a nerve is severed in the amputation process, the surgeon’s goal is to position the nerve ending in a well-cushioned soft tissue site away from the incision and any scar tissue. There it will not be irritated by traction, pressure from the prosthetic socket or any other potential sources of contact.

Neuromas in very scarred and adherent areas are the most symptomatic. When working in these areas the surgeon should apply moderate tension to the nerve and section it cleanly, allowing it to retract away from the site of amputation and into the proximal soft tissues. This circumvents the distal end of the nerve scarring to the surgical site where traction and pressure are more likely. Traction on the nerve at the time of sectioning should not be excessive, as too much tension can lead to proximal pain and neuropathy. As with the conservation of muscle tissue in the residual limb, the surgeon’s goal is to retain and employ as much of the useful remaining nerve function. Care should be taken to avoid disturbing the nerve fibers enervating the remaining limb structures, particularly those enervating the muscles and skin.

The theory that proximity between nerves and blood vessels causes symptoms is undergoing renewed interest. When a nerve is unintentionally ligated together with a pulsing vessel a situation may result in which the nerve endings sense the vessel’s cadence and become a source of throbbing and pain. In the transtibial amputation, the two most common nerves ligated with a vessel are the deep peroneal nerve and the tibial nerve. This happens if the deep peroneal nerve is not separated off the anterior tibial vessels, or the tibial nerve is not separated off the posterior tibial vessels. At revision surgery, the separation and division of the nerve away from the re-ligatated vessels can relieve the throbbing. Extra caution concerning the nerves should always be exercised in the high-level upper extremity amputations. Unfortunately, particularly in surgeries involving the brachial plexus, nerves are often accidentally included in the ligatures with the axillary vessels.

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