Electric Power in Upper Limb Prosthetics The Michigan Experience

SHIRLEY FURGERSONShirley Furgerson is Administrator at the Area Child Amputee Center, 235 Wealthy Street, SE, Grand Rapids, Michigan 49503.

In 1962, Northwestern University and the Area Child Amputee Center collaborated in the development of the first electrically-powered prosthesis. Since that time, the Center has fitted several other types of electrically-powered prosthetic devices to children with severe upper limb loss. This photo-essay documents, historically and chronologically, most of those prostheses tested at the Area Child Amputee Center. A more descriptive discussion of components developed and tested elsewhere is not included.

The first design, developed in 1962, was the Michigan Feeder Arm (Figure 1A ).1,9 It incorporated a four-bar linkage to provide combined supination with wrist flexion for easier feeding. The patient, however, had the option to lock this motion. The prostheses were fitted to children aged three to seven years with diagnoses of bilateral upper amelia or other severe upper limb deficiencies. Two push buttons were located in the shoulder cap for externally-powered elbow flexion and extension, and the terminal device was body-powered (Figure 1B ).

Within four years, the feeder arm principles were incorporated into the Michigan Electric Mark IV Arm (Figure 2A ). The four-bar linkage was retained, but a new hook design was utilized. The hammerhead hook was electrically powered by another pushbutton control in the shoulder cap (Figure 2B ). Center pull allowed the cable to be concealed in the forearm.

In 1971, Colin A. McLauren6 designed the Ontario Crippled Children's Centre (OCCC) Coordinated Arm (Figure 3A ). The model was fitted to a child with complete upper phocomelia on the right side and upper amelia on the left.4 The right phocomelic digits controlled the function of the left prosthesis (Figure 3B ). Two control switches provided terminal device function (open/ close), another switch caused elbow flexion end a fourth switch activated elbow extension.

A form of cam action produced internal shoulder rotation (Figure 3C ). The shoulder was hinged for passive abduction, flexion and extension. By gross trunk movement and momentum, the arm might swing to a level that would accommodate opening a door. Articulated shoulder motion also offered easy in retrieving articles from ground level.

The OCCC electric elbow was combined with the Mark IV hook (Figure 4 ). Although the four-bar linkage was not integrated into these prescriptions, wrist flexion units or swivel spoons offered satisfactory feeding function.

One of the earliest developments of a myoelectrically-controlled prosthesis for children emanated from the University of New Brunswick (UNB) (Figure 5A ). The 1972 design utilized the Otto Buck hand with UNB controls housed in a Muenster socket (Figure 5B ). Another type of myoelectric prosthesis combined the Otto Bock control system with the Swedish hand's (Figure 6 ), to be fitted to children as young as two and a half years of age.

The Michigan electric hook3, developed by Dudley Childress at Northwestern University, used a standard Dorrance 10X hook; a housed motor was added to the stud (Figure 7 ). A pulley-system curd was attached to the "thumb" of the hook. Although superior to the hammerhead hook design for ruse of operation and fine prehension control, it offered only approximately 900 grams (2 pounds) pinch force. The electric hook, in combination with the OCCC elbow, quickly became a standard prescription fur externally-powered upper-limb prostheses.

Another advance in the area of electric external power was the Michigan Feeder Arm II, also developed at Northwestern University (Figures 8A ). The design was patterned on a similar model that was powered by carbon dioxide and developed by D.C. Simpsun.7 The Michigan Feeder Arm II had, as the terminal device, a Michigan hook that could be positioned medially to hold a utensil near the body's midline (Figure 8B). A linear actuator consisting of an electric motor, gear train and drive screw, locate) in the humeral section, flexed the elbow. The hook, mounted on a parallelogram-like forearm, maintained the orientation of the hook fixed During elbow flexion. The flexed wrist and utensil, in conjunction with the forearm linkage, facilitate) lifting foul from table to mouth, without spillage, in one discrete motion. The arm was designed to assist with rating, but it might be use), in sonic measure, fur educational and recreational activities. The system was activate) by a set of three switches operated by shoulder motion. Protraction pushed one switch that extended the arm; retraction of the shoulder against a second switch flexed the arm; and elevation was used to contact the third switch that opened the Michigan hook. An electrical sensor (Hall-effect transducer) Determine) rotation of the drive screw and automatically disengaged the motor current if the elbow stalled During operation. Another circuit turned the hook off if the switch had been left on for more than a specified time period, for example, three seconds. If, by chance, the drive motors stalled (due to inadvertent operation of controls) the energy source was protected from discharge of these circuits. An additional and important-feature was that the Michigan Electric Arm II weighed only 644 grams (1.4 pounds) with hook and battery, approximately one-third the weight of the original Michigan Feeder Arm.

At New York University, where many of the components were field-tested, the electric elbow was redesigned to provide faster operation. In more recent prescriptions, the Michigan electric hook completed the power assembly (Figure 9 ) that is now commercially available.

As stated, the Michigan electric hook produces only limited pinch force. At New York University, William Lembeck5 designed the prehension actuator (PA) that electrically pulls a cable, thereby replacing the body-powered pull with an electrical drive system (Figure 10 ). The PA accepts a voluntary-opening hand or hook of any size. A range of pinch force from between 450 grams to 3600 grams (1-8 pounds) may be obtained depending upon terminal device size anti number of rubber bands or terminal device adjustment.

A myoelectrically-controlled prosthesis developed by the University of New Brunswick10 has been lifted to a child with bilateral upper amelia (Figures 11A , 11B ). For this prescription, a three-state control2 activated by the latissimus dorsi muscle, operates the OCCC elbow. Another three-state control, activated by the trapezius, operates the electric hand.

The prosthetic forearm has been canted to 35 degrees of preflexion for midline access, useful in hand-to-mouth and toilet functions, as well as other activities.

The sophistication of technique and equipment in the past twenty years is encouraging, but increased research, development and applied clinical field-testing is necessary to improve prosthetic function for the juvenile amputee.


  1. Aitken, George T., The Child Amputee: An Overview. Orthop Olin 3:447--172, 1972
  2. Dorcas, D.S., and R.N. Scott, A Three-State Myo-Electric Control. Med and Biol Engin 4:367-371, 1966
  3. Fisher, Anne G., and Dudley Childress. The Michigan Electric I look: A Preliminary Report on a New Electrically Powered hook for Children. Inter-Clin Inform Bull 12:11(1, 1973
  4. Frantz. Charles H., and Ronan O'Rahilly, Congenital Skeletal Limb Deficiencies. J Bone and Joint Surg 43-A:12112-1224, 1961
  5. Lembeck, William. Personal communication
  6. McLaurin, Colin A., The Coordinated Electric Arm. Inter-Clin Inform Bull 11:14-15, 1969
  7. Simpson, D.C., and D.W. Lamb, A System of Powered Prostheses for Severe Bilateral Upper Limb Deficiency. J Bone and Joint Surg 47-B:442-4-t7. 1965
  8. Sorbye, Rolf, Myoclectric Controlled Hand Prostheses in Children. J Rehabil Res I, 1977
  9. Taft C. B., Thomas Grille and Ann Gorton, Evaluation of the Michigan Electric Feeder Arm. Prosthetics and Orthotics, New York University Post-Graduate Medical School. 1967
  10. University of New Brunswick Bio-Engineering Institute, Myoelectric Control of Artificial Limb Manual. University of New Brunswick, 1980