The Otto Bock MOVOHOOK 2GRIP (part number 10A80) got here today after I had documented previous model build / design problems related to cable control, standard aluminium and steel hook. I love the new hook and it seems like it does all I ask that cable control-hook-combo to do. The MOVOHOOK 2GRIP will be in any new Otto Bock catalog - but right now it's brand spanking new.
A demo page that allows for some functional comparison to other prostheses such as the iLimb has been placed here.
Here are the features. The images are high quality; right-mouse-click and view them separately for full graphic information.
1. Optimal relative angle, length and shape of claw
The claw is bent not straight but towards the radius or where the thumb was. The amount of bending is less than Otto Bock's standard steel hook (10A60) but more than their steel hook mod. 58 (10A63).It is thus optimal for both typing and grasping - whereas both other hooks felt too extreme.
The claw opens rather wide - the ends go out to 4 inches.
3. Cable attachment
The cable attachment provides bending-free action. The ball can be snapped out of the bearing if necessary.
Here is a video showing smooth cable action:
00:00 to 00:05 - This hook opens huge and wide. Watch the cable ball mount - no bending any more.
00:11 to 00:17 - Cable mounted perfectly well, no bending to be seen here.
00:20 to 00:30 - Top view into the metal notch that holds the ball end that is clamped to the cable.
00:30 to 00:40 - Bottom view. No cable bending.
This video also shows the Otto Bock hook spring setting for light and heavy loads, as well as the ease with which the cable can be popped in and out of the bearing:
00:00 - 00:55 Cable action: ball bearing makes bending and cable fray highly unlikely.
00:58 - 01:01 Switch spring to "heavy load" position.
01:01 - 01:04 Heavy action!! Full force.
01:04 - 01:05 Demonstrates how fast you go back to easy loads. No rubber mounting required.
01:19 - 01:23 I pop the cable out of the hinge.
01:24 - 01:31 I pop it back in. That's all there is to it.
Another problem of both Hosmer and Otto Bock hooks was the joint coming lose. In this revised model, the hook contains a fork-type joint with an axis; this type of joint is far more stable and better suited for this type of strain. This effectively remedies earlier problems of instability, causing the hook ends to become imprecise and unaligned.
Problems after over 6 months
The hook exhibited significant wiggle in the joint.
Problems after a few years
The issue of bimanual heavy work in context of prosthetic arm usage / design / build is discussed in this article in depth: