Robohand 2.0 (powered, 3-D printed hand)

The Robohand has been getting an amazing amount of press in recent months.  I have previously blogged on the topic Previous Prosthetic post with basic information.  Since then, there has been a  Kansas City Star article on the topic.  

As I previously mentioned, I had the opportunity to work with senior engineering students at Washington University, Biomedical Engineering 401.  Together with Lindley Wall (my congenital hand partner) and Valerie Calhoun (occupational/ hand therapist at Shriners Hospital), I met with three students: Kendall Gretsch, Henry Lather, Kranti Peddada.  

Biomedical Engineering Students

We met on several occasions to discuss prosthetics in general, challenges with the Robohand, and other issues.  They brought their engineering expertise and we shared our practical experience with prosthetics and the needs of children.  It was a valuable experience as Kendall, Henry, and Kranti had no prosthetic experience and were able to think about the issues in a very different way.  Needless to say, three smart undergraduate students can solve a lot of problems.

This was a "design", rather than a "build" class but they were able to design AND build a basic prototype of a motorized Robohand prosthetic.  It was judged a success as they won the design competition and received an A+ in the class.  But, they are not done and are planning to fit one of the new prostheses for one or two patients, moving forward.

There are 2 key design differences compared to the Robohand: the motor and the working thumb.  This prosthetic is battery powered and controlled with an accelerometer (like in the iPhone).  The thumb moves with a slightly different trigger (compared to finger motion).   Importantly, the total cost is still inexpensive, less than $150.

Motorized, 3-D printed prosthetic hand

Motorized, 3-D printed prosthetic hand, side view.

Motorized, 3-D printed prosthetic hand, fingers.

Motorized, 3-D printed prosthetic hand, one more view.

Amazing, right?  However the still pictures above simply do not do it justice.  Here are 2 videos to better show its potential.  Watch how the shoulder- motion up/ down- powers the finger motion and then shoulder motion- front/ back- powers thumb motion.  Currently, it has been set to require a good deal of motion to power the prosthetic but that can be easily changed.  When the prosthetic is fit for the particular patient, the specific controls and sensitivity of the controls will be altered for each child!

Video 1

Video 2

Thumb Deformity in Untreated Thumb Hypoplasia

Thumb hypoplasia is a part of the spectrum of radial longitundial deficiency (RLD).  Classically, there are three parts to the small thumb: looseness or laxity at the MCP joint, a tight first webspace, and poor muscles around the thumb.   I have previously written about the small thumb and these key points at Small thumb .

Decisions on how to address the small thumb follow an algorithm or treatment plan.  Most congenital hand surgeons agree with the following basic principles.

1) If the thumb is small, has poor muscle to power movement, and has instability, then the thumb is reconstructed to allow the best long term function.

2) If the thumb is very small, without good muscle and with poor bone development, then pollicization, or making a thumb from the index finger, may be the best option.  This may be a difficult choice for the family but can offer a really great functioning thumb/ hand and also a hand that looks very good.  I have blogged about pollicization on several occasions.
Pollicization 1
Pollicization 2
Pollicization 3

3) The most difficult situation is the "tweener" thumb which seem be too big to remove and replace with a pollicized index finger but still too small or too unstable to expect great function.


An untreated hypoplastic thumb can provide acceptable function in the young child but with tasks that require finer skills and dexterity (i.e., as the child reaches school age and beyond), the thumb may not be able to do its job.  Without a good thumb, hand function will be poor.  Additionally, with time, the thumb may assume a progressive worsening posture as in the case below.  In this patient, the thumb (and really the hand in general) was simply not used for many activities.  The fingers were useful, the thumb not at all.

Thumb deformity with hypoplastic thumb

Thumb deformity with hypoplastic thumb.  Note that there are some thumb muscles but smaller than typical.

Marked thumb deformity with hypoplastic thumb

The thumb cannot serve its normal purpose given the position and deformity.

Note the zig-zag deformity of the thumb.  Both the CMC joint and MCP joints are markedly out of position.

Reconstruction of such a thumb is a real challenge.  The thumb most importantly needs a stable MCP joint and CMC joint.  The distal joint of the thumb has already been fused and so, at most, fusion of either the MCP OR the CMC joint can be considered but not both.  But the thumb also needs a tendon transfer for muscle power.  The other option, given how good the fingers are, is to consider removal of the thumb (which clearly has a large number of serious problems) and pollicization of the index finger.

Charles A. Goldfarb
My Washington University Bio
congenitalhand@wudosis.wustl.edu

Ollier Disease, multiple enchondromas

Ollier Disease is a nonhereditary condition in which the patient develops multiple benign cartilage tumors, or enchondromas.  While isolated enchondromas are not terribly uncommon, Ollier Disease (or multiple tumors) is quite rare.  It has been estimated to occur in less than 1 in 100,000 births.  It is believed to be non- herditary and related to a spontaneous mutation.  The basic underlying issue in Ollier Disease, the multiple benign cartilage tumors, does not seem terribly concerning.  However, there are two reasons why this can be a very difficult condition.

First, and most concerning, there is a "high" risk of malignancy.  Some estimate this to be as high as 25% of patients.  Either the previously discussed benign cartilaginous tumor can become malignant or another tumor may present.   This can include scary things like chondrosarcoma (malignant cartilage tumors) or even brain tumors.  For this reason, patients with Ollier Disease are monitored closely over time.

Ollier Disease is different than Maffucci syndrome which is a related condition in which patients have enchondromas as well as vascular anomalies, hemangiomas.  These are essentially blood vessel masses just below the skin which can lead to skin discoloration.

The second difficult issue is bone dysplasia or bone deformity.  The cartilage growths can lead to abnormal growth in any bone affected.  This can be most difficult to treat if it affects a segment with two bones such as the forearm (with radius and ulna).  In this situation, slower or angled growth of one bone affects the function of the unit.  The challenging task is monitoring and then intervening at the appropriate time to minimize such deformity and functional limitations.

Ollier Disease typically presents at a young age but is typically not noted at birth.  The enchondromas are painless and it is the deformity or the functional limitations (i.e., a lack of forearm rotation) that lead to presentation to the physician.  One side is predominantly affected.  As an upper extremity surgeon, I most commonly encounter and treat enchondromas in the hands or forearm bones.

Here are some images from a recent patient with Ollier Disease.  The diagnosis may not be straightforward but these x-rays are very helpful.

Right hand xray in Ollier Disease.  Not the abnormal appearance of the index finger proximal phalanx.  

Ollier Disease with humerus involvement.

Finally, Ollier Disease affecting the radius.  This concerns me the most as the growth of the radius is already affected and will only likely get worse.

Media

A couple of news stories over the last week have highlighted children at the Shriners Hospital and St Louis Childrens Hospital.  The first child is a Shriners Hospital patient and a part of a great family. Mom and all three children have thumb anomalies, although each individual is a bit different.  We have been able to successfully perform reconstructive surgery for each.  Shriners News Story

The second story is on a 12 year old transferred to St Louis Childrens Hospital from Wichita Kansas after a severe trauma, a near complete amputation of the hand. St Louis Post Dispatch Story

Charles Goldfarb, MD
Washington University Bio Page