Chapter 9A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Elbow Disarticulation and Transhumeral Amputation: Surgical Principles
John A. McAuliffe, M.D.
The vast majority of amputations through the humerus or elbow joint result from trauma. As with other types of injury, young males represent a major proportion of these amputees, which makes early functional rehabilitation critical. Tumor control remains the next most important reason for amputation at these levels despite recent advances in oncologic surgery favoring limb salvage procedures. Elbow disarticulation may be the level of choice for lesions of the forearm requiring radical surgical margins if the resultant cosmetic limitations are acceptable. Unlike the lower limb, vascular disorders account for fewer than 5% of upper limb amputations and are equally likely to occur in children and young adults due to entities such as fulminating purpura, the inflammatory vasculitides, and particularly Buerger's disease.
An important subset of trauma patients in whom secondary amputation is frequently a consideration are those with unreconstructable brachial plexus injuries. For a full discussion of this problem, the reader is referred to Chapter 12A.
Replantation of traumatically amputated limbs is now a clinical reality. The superior potential for neurologic recovery in children makes them candidates for these procedures with injury at almost any level. Reports of transhumeral replantation in adults are still relatively few in number. Useful elbow control in these patients seems fairly predictable, while return of function to the wrist and hand is unusual and limited at best. While the functional gain of converting these patients to transradial (below-elbow) prosthetic wearers is significant,the potential psychological turmoil inherent in suggesting transradial amputation following successful transhumeral replantation is very real. Such "segmental replantation" is just one example of unconventional use of portions of an amputated limb that would otherwise be discarded in the form of microvascular free-tissue transfer. Major limb replantation entails significant metabolic disturbance and risk and requires scrupulous medical management. The caveat that such a procedure must result in a limb of more functional benefit than a prosthesis must always be borne in mind.
Rigid postoperative dressings can be of value at these levels of amputation, with beneficial effects on wound management, residual-limb shrinkage, and pain control, as well as making immediate postoperative prosthetic fitting possible. Rigid dressings are, however, not of such proven benefit for upper-limb amputees to have gained the level of acceptance that they enjoy in the lower limb. Many feel them to be an unnecessary complication and expense and cite frequently encountered difficulties with suspension. Early prosthetic fitting, within 30 days, remains the single most important variable affecting the success of prosthetic rehabilitation and seems to be as effective as immediate postsurgical fitting in producing this effect. Training is usually begun by using a conventional body-powered prosthesis, with the decision regarding final prosthetic prescription made later. The use of electrically powered prostheses, although they are more costly and fragile, is associated with increased prosthetic acceptance in the transhumeral (above-elbow) amputee, particularly those with shorter residual limbs.
Amputation should generally be performed at the most distal level compatible with the disease process that will allow for adequate padding and wound closure with healthy skin. Elbow disarticulation remains controversial even though it provides improved suspension capabilities and rotational stability of the prosthesis because the adult amputee is limited to cable controls and relatively weak external hinges. In addition, the full humeral length in the case of disarticulation precludes the use of a myoelectric elbow. Disarticulation is clearly the level of choice, however, for juvenile amputees.The high incidence of bony overgrowth requiring stump revision in the case of transhumeral amputation in the child is avoided, while it can be anticipated that slowed humeral growth will result in a humeral length at maturity equivalent to a transhumeral level. Supracondylar amputations should take into account that internal elbow mechanisms occupy approximately 4 to 6 cm of length. Although functionally equivalent to shoulder disarticulation, amputation through the surgical neck of the humerus has the significant cosmetic benefit of leaving shoulder width and axillary borders intact, which makes prosthetic suspension somewhat easier when compared with shoulder disarticulation.High transhumeral amputations also provide more stable electromyographic sites for the myoelectric wearer and improved range of motion for body-powered function. It must be recognized that the deltoid tuberosity is the most proximal level at which shoulder joint control is effective.
Equal anterior and posterior flaps are the norm; however, unconventional flaps should be used whenever necessary to preserve residual-limb length. The ultimate position of the scar is not critical with modern total-contact sockets. Be aware that the skin in the region of the medial epicondyle is thin and wears poorly; therefore, a long medial flap is the least desirable. Although preservation of length is important, remember that a bulbous or flabby stump produced by overzeal-ous preservation of soft tissues is a functional impediment in or out of a prosthesis.
Muscle and Tendon
Myoplasty of the flexor and extensor musculotendinous units not only provides coverage and control of the stump but is also an important adjunct to maintaining shoulder control inasmuch as several of these motors cross this joint. Myodesis (suture of muscle to bone) is seldom necessary, save for possible reinsertion of the deltoid at very proximal levels to enhance myoelectric control. It has been suggested that a portion of the forearm extensor musculature be reflected as a flap over the distal end of the humerus and affixed in the region of the medial epicondyle in the case of disarticulation; however, this is not of proven benefit and is to be avoided when attempting oncologic control of forearm lesions by radical margins. Pectoralis cineplasty has in the past been performed to provide control of elbow locking mechanisms; however, this technique has been made obsolete by the development of practical myoelectric prostheses.
None of the myriad of physical and chemical techniques described to lessen the likelihood of symptomatic neuromas are particularly effective or to be recommended. Neuroma formation is the normal and expected consequence of nerve division, and the goal is to locate the cut nerve end away from areas of contact and cicatrix so that it will be asymptomatic. Nerves should be gently withdrawn from the wound, sharply divided, and allowed to retract under cover of proximal soft tissue. It has been suggested that because of their close proximity, the median and ulnar nerves be divided in such fashion that their stumps do not come to lie at the same level, although this is not of proven benefit.
Use of a pneumatic tourniquet greatly facilitates more distal amputations. As has often been emphasized, exsanguination of the distal portion of the limb should not be performed in cases of tumor or infection, and the tourniquet should always be deflated and careful hemostasis achieved prior to wound closure. Tourniquet deflation also allows for proper muscle tensioning. Major vascular structures are doubly ligated proximally, and cautery alone should not be relied upon to control larger collaterals. Postoperative wound drainage is essential to prevent hematoma formation and delayed wound healing, which can adversely affect early prosthetic training.
Bone and Joints
During elbow disarticulation, epicondylar prominences may be reduced medially and laterally to prevent areas of pressure concentration within the socket. This must, however, be done conservatively to avoid negating the inherent suspension and rotational control value of elbow disarticulation. The articular cartilage is left undisturbed. Transhumeral amputations should be performed with minimal periosteal stripping to prevent the occurrence of ring sequestra or bony spurs. If myodesis is performed, care should be taken not to devitalize a large segment of bone. Rough edges should be removed with a file or rongeur, although beveling of the bone is unnecessary. The wound should be thoroughly irrigated following bone contouring. A technique of angulation osteotomy of the humerus to provide rotational control for long transhumeral amputees is described in Chapter 36A and may be of value in selected patients.
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Chapter 9A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles