Chapter 8A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Elizabeth Anne Ouellette, M.D.
In the upper limb, the etiology of 90% of amputations is trauma. This occurs predominantly in the 20- to 40-year-old age group, with males involved four times as frequently as females and the left side affected as often as the right. All other causes of amputation are less common, including peripheral vascular disease, neurologic disorders, malignant tumors, infections, contractures, and congenital deformities. The most common congenital amputation, however, is at the short transradial (below-elbow) level.
With the advent of limb salvage procedures, a malignant tumor no longer automatically leads to an amputation. Microvascular surgical techniques have also aided in the preservation of limbs after trauma. Despite these advances, there are still situations in which amputation is the final outcome.
Amputation levels are now chosen not by the prosthesis, but by the level of injury or involvement by the disease process. If the cause is trauma, there must be adequate debridement of nonviable tissue, but primary amputation closure is contraindicated to prevent infection. Length of the amputation can be preserved by coverage with split grafts over muscle or with free vascularized flaps. Indications for elective shortening of residual limbs are rare. The ultimate goal of amputation surgery is to provide a pain-free residual limb that is functional.
AMPUTATION THROUGH THE CARPUS
The ability to amputate through the carpus allows for the preservation of wrist flexion and extension as well as forearm pronation and supination. The surgical technique is similar to wrist disarticulation. Motor strength can be enhanced by attachment of the wrist flexors and extensors to the remaining carpal bones. The palmar-to-dorsal skin flap ratio should be 2:1 in order to provide coverage of the carpus with durable palmar skin. The movable, sensate, well-padded carpal segment makes this amputation quite useful in "bimanual" activities, even without a prosthesis. Grasp can be provided, however, by a specially designed wrist-driven prosthesis. Although functional, this active prosthesis is not cosmetic. Passive restorations, however, can be quite aesthetic.
Full forearm length preserves pronation and supination and also provides a long lever arm with which to lift the terminal device and its load (Fig 8A-1.,A-C).
Regional anesthesia is ideal. The use of a tourniquet allows for clear identification of tissues and reduces blood loss. Exsanguination by an elastic bandage prior to elevating the tourniquet is indicated except in cases of tumor and infection. In these situations, limb elevation alone is recommended.
Palmar and dorsal flaps in a 2:1 ratio are developed to provide adequate tissue for closure (Fig 8A-2.,A and B). These flaps extend down to deep fascia. Hemostasis should be achieved as these flaps are developed.
The styloid processes need to be contoured enough to create a symmetrical limb for fitting of the prosthesis. The triangular fibrocartilage complex must be preserved because it provides for stability and hence painless motion of the distal radioulnar joint. The dorsal and volar tendons are transected and stabilized under physiologic tension when the vascular supply permits.
Blood vessels may be controlled by coagulation or ligation. The main vessel groups that must be identified are the ulnar, radial, and anterior and posterior interos-sei. The nerves that must be identified are the median, ulnar, posterior interosseous, and radial sensory. These should be cut under moderate tension and allowed to retract proximally into the soft tissues to avoid entrapment in the incisional scar. Specifically, the transected end of the radial sensory nerve should lie beneath the brachioradialis muscle belly in order to protect its neuroma from mechanical trauma during prosthesis use. A minor cosmetic drawback is that the active prosthesis for this level will result in a longer forearm on the prosthetic side.
As long a residual limb as possible should be saved, commensurate with the diagnosis. The longer it is, the stronger the lever arm will be, and the more completely pronation and supination will be preserved (Fig 8A-3.). The prosthesis socket will be more cosmetic when the amputation ends no less than 2 cm proximal to the wrist because there is more room for the prosthetic components. Very short residual limbs, however, may have difficulty tolerating the weight of a myoelectric prosthesis.
The same surgical principles apply to forearm amputations as to wrist disarticulation. The bone is transected after the periosteum has been incised. The bone edges are then carefully smoothed. Myodesis or myoplasty is performed to stabilize the muscle mass, which may be helpful in later myoelectric fitting.
If the amputation must be very proximal, then an ulna 3.8 to 5 cm long is still adequate to preserve the elbow joint. In order to fit this very short residuum with a prosthesis, it may be helpful to detach the biceps and reattach it to the ulna.
A special situation arises when one forearm bone is considerally longer than the other and the longer bone can be covered with an adequate soft-tissue envelope. Rather than decrease prosthetic function by shortening the longer bone, it may be preferable to create a one-bone forearm.
Skin coverage is best achieved by local flaps with care taken to avoid adherence to underlying bone. If skin coverage is a problem, a split graft, free flap, or abdominal flap can be used to obtain coverage and preserve length. Split grafts will require extra care from the patient until the grafts mature but should do well with time. Revision surgery is necessary in approximately one third of transradial amputees. Every effort should be made during revision surgery, however, to preserve even a very short transradial level so long as active range of motion of the elbow will be preserved.
The purpose of this operation is to give an amputee a sensate, active pincer by using the ulna and radius. It is a valuable procedure in patients whose contralateral hand has been lost or severely damaged, as well as for those patients without access to prosthetic limbs, as in some developing nations. It is particularly useful for the blind bilateral transradial amputee since it uses sensation to enhance grasp, something no prosthesis can offer.
The power of the pincer grip is usually 2 to 3 kg with the elbow extended and as high as 8 to 10 kg when the elbow is flexed. The sensation of the tips can approach normal finger sensibility when the operation is performed in children. Adults usually achieve protective sensation and the ability to identify objects. To perform this operation, there must be good skin coverage and muscles in the forearm, so it is usually contraindicated in burn patients (see Chapter 36A).
Because the appearance of the Krukenberg limb may be objectionable in some circumstances, it can be easily fitted with a prosthesis if desired. Myoelectric, body-powered, and passive cosmetic fittings are possible. This will allow the amputee the option of using his Krukenberg limb or prosthesis as the situation dictates.
POSTOPERATIVE IMMEDIATE PROSTHETIC FITTING
Rigid postoperative dressings were initially used in lower-limb amputees. The advantages of a rigid dressing include better control of postsurgical edema and protection of the wound from external trauma. With the addition of prosthetic prehension and suspension components to a rigid postoperative dressing, the patient can begin to use this temporary prosthesis within 1 or 2 days, thus preserving two-handed grasping patterns (Fig 8A-4.).
Elastic bandages may be used if rigid techniques are not feasible. Even pressure must be applied, with care taken to avoid flap necrosis.
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- DeSantolo A: A new approach to the use of the Krukenberg procedure in unilateral wrist amputations, an original functional-cosmetic prosthesis. Bull Hosp Joint Dis Orthop Inst 1984; 44:177-187.
- Louis D: Amputations, in Green DL (ed): Operative Hand Surgery, ed 2. New York, Churchill Livingstone Inc, 1988, pp 61-119.
- Rees MJ, UeGens JJ: Immediate amputation stump coverage with forearm free flaps from the same limb. J Hand Surg [Am] 1988; 13:287-292.
- Sarmiento A, McCollough NC, Williams EM, et al: Immediate post surgical prosthetic fitting in the management of upper extremity amputees. Artif Limbs 1968; 12:14-16.
- Tooms RE: Amputations, in Crenshaw A (ed): Campbell's Operative Orthopaedics, vol 1, ed 7, St Louis, Mosby-Year Book, 1987, pp 597-637.
- Tubiana R: Krukenberg's operation. Orthop Clin North Am 1981; 12:819-826.
- Wood MR, Hunter GA, Millstein SG: The value of stump split grafting following amputation for trauma in the adult upper and lower amputees. Prosthet Orthot Int 1987; 11:71-74.
Chapter 8A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles