Levels Of Upper Extremity Prosthetics
Each amputee with upper limb loss or limb difference presents a unique residual limb, with amputation levels that range from partial finger to shoulder levels.
Each amputee with upper limb loss or limb difference presents a unique residual limb, with amputation levels that range from partial finger to shoulder levels. Each level requires a distinct prosthetic arm to be fitted, as per the needs of the amputee.
- Partial Hand - Transcarpal
- Wrist Disarticulation
- Elbow Disarticulation
- Shoulder Disarticulation
- Forequarter Amputation
With digital amputations, the amputation and involved finger location are important. Thumb amputations are the most debilitating due to the functional importance of the thumb in opposition and prehension. When amputation is carried out, efforts should focus on the preservation of length, sensation, and mobility. Patients receiving thumb amputations or amputations at or distal to the interphalangeal joint experience loss of dexterity, but very often, retain good overall function. Another type of digital amputation is ray amputations that are characterized by the surgical elimination of the complete digit and a part or the full corresponding metacarpal bone.
Transcarpal Amputations – Partial Hand
Partial hand or transcarpal amputations retain wrist flexion and extension and allow the amputee to easily perform activities. It commonly occurs due to trauma and infections.
Wrist disarticulation is the surgical separation of the wrist and hand from the arm where the radius and ulna are separated from the carpals. It retains virtually the full range of wrist elbow and pronation. Wrist disarticulations provide a long lever arm for a lifting of the terminal device loads, with good sensation and proprioception. The triangular fibrocartilage (TFCC) on the ulnar aspect, along with the distal radio-ulnar joints should be retained to preserve some amount of forearm pronation-supination. The bony, protruding surfaces of the radius and ulna must be smoothed to make it easy and comfortable for fitting the prosthetic arm.
Transradial amputations can be done at different points along the forearm, that extends from just below the elbow joint up to the wrist joint. Limb loss below this level can be caused by trauma, disease, or be a limb difference that is present from birth. Preserving some amount of forearm length is significant since it helps in pronating and supinating the upper limb. The prosthetic arm fitment at the transradial level requires the preservation of at least 4cm of ulnar bone length. An added benefit of transradial amputations is that they provide ample space for fitting prosthetic components.
An elbow disarticulation is the surgical separation of the forearm from the upper arm at the elbow joint, whereby the radius and ulna are separated from the humerus. The forearm and hand are then removed from the body. The Elbow disarticulation technique maintains a patient’s ability to rotate the humerus. This motion can provide an additional means of control to a prosthetic arm. The presence of the humeral condyles in these techniques provide an appropriate base for the suspension of the prosthesis. Elbow disarticulation is a controversial technique despite its advantages such as improved suspension and prosthetic stability because the adult amputee is limited to cable control.
Transhumeral amputations are performed at any point on the arm, starting from just above the elbow to just below the shoulder joint. Surgeons prefer to amputate the arm 4 cm proximal to the elbow joint to obtain enough space for the fitment of prosthetic elbow mechanisms at equal length to the elbow joint on the sound side.
Amputating at the level of the insertion of the pectoralis major muscle, or above it, up to the level of the humeral neck, results in a residual limb that functions as a shoulder disarticulation amputation as it restricts humeral rotation and only provides contouring to fit the prosthetic arm.
Shoulder disarticulation is the surgical separation of the shoulder joint, quite similar to transhumeral amputation. After the head of the humerus and the joint are disarticulated, the uncovered muscles help to fill the gaps in the glenoid cavity, and flaps are designed in a way that allows for prosthetic fitment.
Forequarter (Interscapulothoracic) Amputations
Forequarter amputation is the removal of the entire upper limb and shoulder joint from the thoracic wall and the scapula. This complex technique is often indicated in patients with malignant tumors that invade tissues or trauma in the shoulder.