The Elbow and Wrist

Joining together the elbow and wrist requires accommodating a number of different individual joints:

  • Humeroulnar
  • Humeroradial
  • Radioulnar (proximal)
  • Radioulnar (distal)
  • Radiocarpal

Each of these moves relatively quickly, even though there may be a number of individual steps. Let's get started!


Humeroulnar Joint

The ulna tracks around the humeral trochlea in a slight spiral as the elbow flexes and extends. To secure the humerus and the ulna throughout that range of motion, begin by making two passes through the humerus as shown in the photos below:

IMG_20160903_184618.jpg

This will be joined to the ulna through a pair of corresponding holes pictured here. Keep in mind that the tunnel here is close to the joint surface, so make sure you line it up so as not to break the surface with the drill.

IMG_20160903_184823.jpg

Humeroradial Joint

The radius needs to stay flush with the capitulum of the humerus throughout the flexion and extension of the elbow, which can be accomplished with a single bungee cord. Drill holes through the radial head and the capitulum as pictured. Note that in order to allow for movement through a complete range, there is  wide conical opening on the humeral side of the joint.

Note that widening on the capitulum to allow for the bungee cord to move through a larger range


Radioulnar Joints (proximal and distal)

The bones of the forearm need to be joined together to stabilize it while also permitting rotation of the the radius. This can be done with two quick holes drilled at either end. A smaller bungee works for the proximal joint, while a larger bungee is better suited for the distal end. 

the hole is placed to the far edge of the ulna, and through the middle of the radius--though it is difficult to see that from this picture.


Radiocarpal Joint

To create the wrist, drill two holes at the distal radius as shown, and thread a bungee through the gaps between the carpal bones. 


Tying it all together...

The elbow can now by joined together with a pair of bungee cords as the humeroulnar joint, and a single cord at the radioulnar joint. The course of the small bungee cord that holds together the proximal radioulnar joint can also be seen here.


Anatomical Sketches:

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body, Gray's Anatomy, Plate 329, Public Domain