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Home Forums General Ergonomics Topics Lateral Epicondylitis and Forearm Pronation

This topic contains 26 replies, has 7 voices, and was last updated by  vino 16 years, 7 months ago.

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  • #41553

    admin
    Keymaster

    Hello, David and Tom (and other interested parties…),

    I would like to add a point of clarity in discussing neutral/natural wrist postures. It appears there is some confusion of terms between wrist posture and forearm posture. Wrist posture is concerned primarily with the anatomical motions of flexion, extension, ulnar deviation and radial deviation. Forearm posture is concerned with rotation down the axis of the two forearm bones, commonly referred to as supination (palm up) and pronation (palm down). When the palm is supinated, the ulna and radius bones of the forearm are parallel. When the palm is pronated, the radius rotates/crosses over the ulna.

    For clarity, I would suggest when discussing wrist postures, limit the discussion to flexion, extension, ulnar deviation and radial deviation. When discussing the relative position of the palm (up or down or somewhere in between), refer to this as forearm posture.

    Regarding the degrees of motion that define “neutral” wrist posture, I find it best to have a person hang their arm at rest down by their side. You will note their is a slight amount of wrist extension, perhaps 10 to 15 degrees. I don’t have the exact references with me, but I recall research on intercarpal pressure indicating that these pressures are lowest between approximately 20 degrees of flexion and 20 degrees of extension (a 40 degree arc of motion). Grip and pinch strengths are also strongest in this range. Conveniently, this “arm at rest by the side” posture also describes neutral forearm posture.

    David, I used to hold my mouse like you, with the ulnar side of my palm on the desk. After two days of very mouse-intensive graphics work, I developed a good case of ulnar nerve compression as I was resting right on it for at least 10 hours a day.

    Respectfully,

    #41549

    admin
    Keymaster

    First of all, my apologies to David for making such an issue of this; his contributions to the list serve are always a rich and valuable source of information.

    The point that I’m trying to make is that as a group we often use terms such as ‘straight wrist”, “natural posture”, and “contact pressure” loosely and that it leads to a great deal of confusion, particularly when working with designers and other non-ergonomists.

    The consumers for our services keep asking pesky questions like “is this posture more natural than that one?”; “what if I only do it once?”; “How straight is straight?”; “how much contact pressure is too much?”; “How much forearm rotation is too much?”. My experience has been that they expect a quantifiable answer rather than an expert opinion as experts often differ. There is certainly some utility to be able to say that “posture A is better than posture B”, but the rub comes when we’re asked to draw a line of demarcation between A and B.

    It is our job to formulate answers to these questions. To do that we first need to offer clear definitions and then apply scientific method to refine them.

    To illustrate, let me offer the followiing thought experiment. As per a recent post in this thread; a natural wrist posture for keyboarding and mousing might be defined by (1) support to the outer edge of the hand, and (2) the thumb is higher than the other fingers. Consider the following.

    Posture 1. The hand is palm down on a flat surface, digits 2-5 on the surface and the outer edge of the hand supported. The thumb is elevated so that it is higher than the other digits.

    Posture 2. The hand is resting on its outer edge, perpendicular to the flat surface so that the thumb is higher than the other digits.

    Posture 3. The hand is resting on its outer edge, but is nearly fully supinated. The thumb is higher than the other digits.

    Posture 4. The hand is resting on its outer edge, but is nearly fully pronated. The thumb is higher than the other digits.

    I would certainly find some of these postures less than natural.

    You can see the shadings that follow. For example, one might argue that we should add “palm facing down” to the criteria, and that postures 2 and 3 should then be excluded as the palm doesn’t face down. Now suppose that for posture 2 the angle of the hand to the surface is 89 degrees instead of 90. Clearly the palm now faces down.

    Finally, just to make things interesting, don’t we tell people to avoid postural fixity (using a single posture)? If so, what postures or range of postures are acceptable?

    Best regards,

    Tom Albin

    #41557

    [private user]
    Participant

    James:

    Thank you for the enlightening description of the forearm response to hand position. I’m often trying to visualize forearm motion when the upper extremity is moving through its complete range of motion, ROM. Your clear description is one I will save, and refer to.

    thank again,

    Bev Burke RN CMA CIE

    #41559

    admin
    Keymaster

    Dear James,

    I have been holding my right wrist in a “natural” position for years when doing mouse work and I have never had any problems. However, I do take frequent rest breaks while I do my my two-forefinger typing. I guess that the problem with multi-factorial syndromes is that you have to control ALL of risk factors.

    Do we really want to make these discussions so academic? I have been trying to avoid that by using “Plain English” as much as possible.

    If we do wish to make the discussion more academic I suggest we use the terminologies of the best-known authors in this area of the literature. I prefer the definitions used by Hsiao & Keyserling and those of Nakaseko, Grandjean, Hunting & Gierer. These are the definitions that I used in my masters treatise (I would refer you to the copy on the Goldtouch website but sadly it seems to be closing down in a most untimely fashion!)

    For the sake of clarity it might be worthwhile to point out that is customary to describe supination and pronation of the arm and wrist jointly in the manner described and illustrated by Hsiao and colleagues (1991). They have also provided an illustration of flexion and extension of the hand. (See parts k and n of figure A2 in that paper.)

    Ulnar deviation of the hand and adduction of forearm were defined in the manner described by Nakaseko and colleagues (1985). (See figure is figure 9 in the paper in that paper.)

    I hope that is helpful for those of you who wish to do some literature searching!

    Regards,

    David.

    References

    #41560

    admin
    Keymaster

    The following information is worth every penny paid for it:

    At the gym (high force, low repetition), “neutral” forearm posture is very important in minimizing pain related to my left medial epicondylitis.

    At work (low force, high repetition) I have some right wrist extensor pain just below the lateral epicondyle. It is exacerbated by wrist extension (dorsiflexion) induced by mouse grip and especially by small mouse movement toward the body with wrist “planted” on the work surface (involving dorsiflexion – and other muscle activation too complex to describe here).

    As I rotate my forearm from “neutral” to pronation while using a mouse, dorsiflexion increases, as does discomfort. Whether we focus on pronation or dorsiflexion, awkward postures tend to lead to trouble. Why not eliminate all of them – at least for part of the workday?

    When working with clients I will often simply suggest trying a different input device – one that is different enough to allow injured tissues some rest. I also spend a significant amount of time showing (and helping the client practice) ways to reduce mouse/pointer usage.

    It’s a low-tech strategy, but the results are good.

    I’m David Wolff, and I approved this message.

    #41561

    ttilbury
    Participant

    Dear all,

    As some terminology is not universal, it appears, could I summarise the information as follows:

    The initial question was regarding research on lateral epicondylitis and forearm pronation – but in a very specific circumstance known to most of us – ie forearm pronation using a keyboard and mouse.

    When discussing ‘neutral posture’ for the wrist and forearm, James made a number of contributions, but I think the ‘key’ point is that for most therapists and medical professionals (who evaluate range of motion so much that they could be considered ‘experts’) we acknowledge that there will be differences in wrist position and forearm position depending on whether the elbow is flexed or extended. James made an excellent point about evaluating wrist position in standing, with the arm hanging down by the side, which illustrates that there will be differences based on whether the elbow is flexed or extended.

    As David pointed out, using a keyboard and mouse is ‘functionally’ going to involve pronation of the forearm (in the majority of cases) and as I would like to reinforce in the case of keyboard use – elbow flexion. From a ‘functional’ perspective, this will always mean that certain soft tissues such as muscles and nerves may be close to their ‘stretched’ position, and some closer to their ‘compressed’ position. This also follows for the joints, etc – ie some will be close to their limit of range. James pointed out that when mousing, the most likely action causing an effect on the lateral epicondyle is the ulnar/radial deviation movement demonstrated by many ‘mouse’ users.

    James has described some of the adaptations that he has seen in mouse users. The postures and positions tend to follow a general pattern of elbow flexion/forearm pronation/wrist extension and ulnar deviation (please note that wrist extension appears to be a more commonly accepted term than dorsiflexion from my reading). In the real world, there will be a range of ‘actual’ positions which vary from the “90- 100 degrees elbow flexion, 80 degrees to full pronation, 10-15 degrees wrist extension” which I am nominating as a description of those illustrated in the usual “guides for workstation setup”. Unfortunately in research, because of the limited numbers of subjects, and the need to ‘measure’ activity of muscles etc, some of these adaptations can tend to be incompletely described.

    In observation, I have seen a combination of postures and positions in mouse usage, in some cases elbow extension, forearm pronation and wrist extension – depending on if the user is performing primarily mouse work. In both extremes, and those elbow/forearm/wrist postures in between – most times the only way the mouse can be manipulated is by using wrist ulnar/radial deviation. Depending on the design of the input device, the need to brace or stabilise the dominant/mousing arm with a fixed posture will dictate the adaptation of other joints and soft tissues around that area. James and David have already mentioned their experiences in trying to adapt, and what tissues were affected.

    Bret pointed out that we must not forget about the joints and postures above and below – which physiotherapists in most countries have drummed into them! Beverly rightly mentioned the influence of other factors on devlopment of a number of musculoskeletal conditions.

    Finally, although David has suggested some research articles, practioners should at least evaluate that the research has some functional relevance to the task that they are interested in. Although our NOHSC guide gives an illustration of ‘neutral/natural’ position of the wrist, it would be difficult as Tom has pointed out, to get some agreement and understanding with non health professionals. I would suggest that if ergonomists cannot agree on what terminology ( and possibly specific ‘numbers’ or ranges of ‘numbers’ to describe postures adopted and what is better (or do we mean closer to what evidence indicates is better or less hazardous?) then we have little hope of gaining influence over designers and others. This discussion has certainly been good to illustrate that many of us are coming to ergonomics with very different levels of understanding (interpretation) on functional anatomy, range of motion, task analysis, etc – and that lack of common ground makes it difficult to communicate with non-ergonomists!

    #41562

    admin
    Keymaster

    Trudy,

    I suspect that the fundamental problem with the terminology here is that many terms in gross anatomy relate to the position of a corpse that has been laid out for dissection (on its back with its arms by its side and the hands place palm upwards). Not only does this position not correlate well to the functional positions of the limbs it introduces unrealistic conventions like hands in lying flat and inert.

    I would like to suggest that a certain amount of dorsiflexion (backward bending) of the hand is actually more normal. Try this little experiment; clasp your hands in front of and then place them on a desktop in front of you, then unclasp them and allow them to fall into a natural position you. When I do this my hands remain slightly dorsiflexed

    #41597

    vino
    Participant

    1. And what to think about a vertical mouse? I’ve always been very sceptical about such “gadgets”, but the results of a 3 year follow-up study seem pretty convincing. After 6 months of using a vertical mouse (type Renaissance/Anir), the VDU workers experienced less pain at the neck, shoulders, fore-arm, wrist and hand. This decrease in pain (measured with a visual analogue scale) remained after 3 years.

    2. Another study points out that this kind of mouse also results in a more neutral position of the wrist (so less extension and ulnar deviation), with less muscle activity of the wrist extensors. However, the productivity and preference were still in favor of a traditional mouse (because the users were not accostumed to?).

    References:

    1. A

    #38377

    Pronator
    Participant

    We have seen a lot of lateral & medial epicondylitis associated with TOS. Certainly sustained forearm pronation would activate wrist extensors as the hand is held in position against gravity, but the activity may also provoke compression of the cervicothoracic junction, compromising neurovascular function. This is my first post here – I’d love to hear what you find out regarding research!

    #38380

    admin
    Keymaster

    Hello.

    I write right and mouse left. Mousing left is convenient to free up the right to jot notes, etc. Regardless of side, I’ve found that for myself I need to take regular stretching breaks for both hands (mousing, writing, typing). I also stretch my arms, especially shoulders, and neck & upper back. I’m taking online classes for my doctorate in physical therapy and am having to practice what I preach, so to speak. Prevention is a key and primary issue in dealing with overuse problems, such as lateral epicondylitis. I currently have a patient in treatment for this. It has taken almost 4 weeks of exercise/stretches, work modification and pacing of use, and modalities (adding ionto seemed to get it knocked out faster) to get her painfree at work and home. Patience can be a virtue.

    Monique Brownlee PT, DPT student

    #38381

    admin
    Keymaster

    Would you actually use shockwave therapy on someone? I’ve read some on it, sounds almost too good to be true. I also observed a demonstration (on a horse) and just didn’t leave convinced that I would actually do that to a human or animal. Just curious.

    Monique Brownlee PT, DPT student

    #38393

    [private user]
    Participant

    Hello, Monique, sorry to answere you this late, but I just happende to read your mail.

    As for your question, – and because I am no “torturist”: Yes, I would try Radial Shockwave Therapy 2-6 times, based upon my own experiences and those of a wide range of therapists around the world. Lateral epicondylitis seems to respond fairly quickly to this treatment.

    May be you should have a look at http://www.ismst.com/congresses , then look at “abstracts”, – or you could try http://www.ems-medical.com (www.ems-medical.ch) + http://www.wigero.de

    Goog luck!

    best regards

    Roald D

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