Transhumeral Prosthesis

Functional Levels Above the Elbow

Amputations above the elbow may be classified in three basic functional levels. This system of classification is based on the anatomy that provides the primary control.  Note:  There is no standard classification system… it may depend on length of limb or based on the body function.

I. Elbow Disarticulation: Primary control of the prosthesis is by the humerus. Typically, the remaining anatomy includes the humeral condyles (elbow disarticulation). The oval shape of the distal end provides rotational control and stability of the prosthesis. Flatten in the AP to capture the anatomy of condyles.

• Trimlines = proximal trimlines are distal to shoulder do not need to cross the deltopectoral groove
  • o The humerus controls motions of flexion, extension, rotation and abduction, but are dependent on the fit of the socket
  • o Proximal portion should never impede glenohumeral ROM
• For limbs 95-100% of arm length, a single wall socket is used.
• The available ROM and lower placement of the base plate allows the individual to capture ample excursion to operate the prosthetic elbow and TD.

II. Standard Transverse Humeral Limb Loss: Primary control of the prosthesis is by the humerus assisted by the shoulder girdle. The remaining anatomy is above the humeral condyles (long transhumeral). The prosthesis is secured to the shoulder girdle providing an A-P compressive force between the deltopectoral groove posteriorly over the scapula.

• Trimlines extend higher and the posterior stabilizer may extend to the lateral border of the scapula to gain rotational control and stability.
  • o The humerus provides flexion, extension and abduction stability, but is dependent on the fit of the socket
  • o The shoulder girdle provides rotational stability
• Control motions should be measured to aid in the type of socket design and harnessing system to achieve maximum function.

III. Short humerus: Primary control of the prosthesis is by the shoulder girdle assisted by a short humerus. The remaining anatomy is from the deltoid insertion to the axillary level (short transhumeral). Prosthesis operation is dependent on bilateral shoulder girdles motions

• Trimlines: 1) anteriorly include approximately 25mm of deltopectoral groove; 2) posteriorly approximately 25mm of lateral border of the scapula; and 3) May superiorly extend to the acromioclavicular joint
  • o Shoulder girdle provides flexion, extension, abduction and rotational stability
  • o The trimlines limit shoulder movement in all three planes
• Prosthesis operation is dependent on bilateral shoulder girdle motions.
• Pre-positioning of the prosthesis is limited.