MSD | ergovet

The Ergonomics of Postures and Positions

On this site I’ve written a lot about “good” vs “bad” ergonomics, but what exactly makes certain postures and positions “good” or “bad” ergonomically?

The answer has to do with stress and strain. The concepts in this post are codified in an ergonomics scoring system called RULA, or Rapid Upper Limb Assessment. Here is a link to the original peer-reviewed article that introduced RULA. The RULA assessment may look technical and daunting, but here are the basic concepts that it is based upon.

Reducing musculoskeletal strain and effort

Different body postures result in different musculoskeletal strains. When we’re looking for “good ergonomics,” it means we are looking for postures and positions that reduce musculoskeletal strain and effort.

When we talk about whole body postures and head and neck postures, the excess strain we want to avoid usually comes from our musculoskeletal system’s work against the force of gravity.

When we’re talking about hand and wrist postures, the excess strain has more to do with the forces of the work we’re doing on our joints and muscles, and the strain of working at the extremes of our joints’ ranges of motion.

Postures in which the bony columns of our skeletons are aligned require less work (and less fatigue and strain) than postures in which the bony supports are out of alignment. In the illustrations below, the upright surgeon’s stance functions like a stack of boxes balanced atop one another. Minimal muscular effort is needed to hold this posture. On the other hand, the surgeon who is bending as she works must exert muscular effort to hold her body in this posture.

Here, the upright surgeon’s stance functions like a stack of boxes balanced atop one another. Minimal muscular effort is needed to hold this posture.

This surgeon is bending as they work and must exert muscular effort to hold their body in this posture. As you can see, the stack of boxes is off balance and would topple without muscular effort.

Twisted Postures

Twisted body postures add additional strain to the musculoskeletal system. Reaching across the body or resting one leg during surgeries can put particular strain on the muscles of the lower back.

Occasional or intermittent twisting is unlikely to cause a problem, but repeated or ongoing twisted postures will likely lead to strain and discomfort.

amala twist standing — Twisting may be the result of reaching across the body. When twisting occurs repeatedly, this results in musculoskeletal strain

amala resting leg back — Twisting may also be the result of resting a leg during surgery, especially if always on the same side of the body.

Arm and Shoulder Positions

Arm and shoulder positioning also affects muscular strain.

Allow your arms to remain relaxed near your sides and avoid raising your shoulders. Raising your shoulders and arms relies on muscular work by the trapezius, the deltoids, and other muscles. This muscular work can lead to tension, pain, and fatigue in the neck and upper back. For some people, tension in the neck can be a trigger for migraine headaches.

elbows out amala — Holding the elbows out and raising the shoulders during surgery takes extra musculoskeletal effort.

elbows at sides amala — Elbows near the sides and shoulders lowered requires less effort and will lead to less strain on neck and back.

Head and Neck Positions

Most spay-neuter veterinarians work with some degree of forward bend to the neck, but it is important to minimize the degree of head and neck bend whenever possible. In a neutral head position (above left), the weight of the head is supported by the spinal column with little muscular effort. If the head is bent forward or to the side, the muscles of the neck and upper back engage to help support the weight of the head, potentially leading to fatigue, strain, and pain.

There is usually little need to side-bend or turn the head during surgery. These postures are likely to be intermittent and transient when they do occur.

Wrist Positions

Wrist and forearm positions during surgery are dynamic. As you manipulate tissues and suture during surgery, your forearms, wrists, and hands will go through a range of movements. However, strain, discomfort, and even damage can occur if you regularly use extreme wrist positions.

Extreme wrist positions including flexion, extension, and lateral deviation have potentially serious effects:

constriction of blood supply to the hand
compression of the carpal tunnel resulting in pressure on the median nerve within the carpal tunnel
constriction, compression, and irritation of tendons and tendon sheaths, especially during movement

These factors may result in pain, inflammation and eventually tendinitis or tenosynovitis, and may contribute to carpal tunnel symptoms.

Pronation and Supination

Pronation and supination refer to the rotation or twisting of the forearm. Some forearm rotation is expected while performing surgery, but repeated and extreme rotation is unnecessary and potentially harmful.

Repeated rotation, especially with a bent wrist, can lead to pain and irritation around the elbow and can eventually lead to epicondylitis or “tennis elbow” or “golfer’s elbow.”

Good instrument handling techniques should not require forearm rotation range of more than 80-100 degrees (about 1/4 turn) while suturing.

Conclusion

Even though what’s in this post may seem simple and obvious, these concepts are the basis for understanding the “why” behind a wide variety of ergonomics recommendations. I hope these images and descriptions help you picture the forces and strains that affect your body regardless of the work that you are doing.

Stretches and Strength Exercises for Surgeons

Recently, I’ve been catching up on some journal reading and came across an ergonomics article in an online plastic surgery journal that I wanted to share.

We feel your pain

The article, Stretching and Strength Training to Improve Postural Ergonomics and Endurance in the Operating Room, offers all the usual warnings about musculoskeletal discomfort among surgeons as a result of surgical postures. It seems that the areas of pain are similar to those in spay neuter veterinarians. Many of the surgeon postures described in the article are also common in veterinary surgeons. And many of the solutions they suggest, like adjusting the table height or sitting for surgery, are the same as we have discussed previously.

Screen Shot 2022 04 10 At 4.08.55 PM 1024x996 — Painful body areas in the study of surgeons. Look familiar? Neck, back, and shoulders are common areas for spay neuter vets to experience pain as well.

Stretches for Surgeons

What I liked about the article, though, was that it published a supplemental set of videos of one of the authors’ consultations with a physical therapist. The physical therapist offers exercises and stretches to counteract common surgical postures. The videos are available along with the article (and are slow to load, but be patient). Video 1, video 2, and video 3 are all recordings of this consultation, while the final video shows the surgeon by himself, performing each of the exercises from the consultation in the first 3 videos. The final video goes too fast for viewers to follow along while doing the exercises themselves so works better as a reference than as an accompaniment to exercise.

These videos offer something specific that I hadn’t seen before and that I have wished I could share with others: stretches and exercises targeted for surgeons. (Maybe this exists somewhere but I haven’t come across it yet). I’m curious to try some and if they help relieve some neck/shoulder/upper back tension.

It would be even more exciting if the study had actually tested the stretches and exercises to determine if the surgeons were more comfortable or more flexible after using them for a time. But they didn’t, so as it is we’re left with recommendations based off the physical therapists’ “standard practice algorithms” for addressing the surgeons’ complaints.

Limitations

The study had other limitations besides not having tested the exercises on surgeons. The study design isn’t optimal: the sample size is limited, and the authors didn’t use a validated musculoskeletal discomfort questionnaire. The participants’ surgical posture self-assessment was also problematic. After watching a 2-minute video, the participants were asked to judge deficiencies in their own surgical posture based on their ability to complete the stretches and range of motion activities in the video. They didn’t have the chance to view video of themselves at work or to have any assessment by an ergonomist or physical therapist, so I’m skeptical of that measure’s validity.

Despite the article’s shortcomings as a scientific study, I think that the exercises suggested in the videos could be a good resource or starting point for surgeons experiencing discomfort and for those trying to avoid it. Let me know if any of these work for you, or if there are any other exercises or stretches that work better.

Meanwhile

Today we had the chance to fire up the Hartland Community Oven which was built in our town during the pandemic. Tina was on the oven committee (she helped build it, too) so she has been through several firings in 2020 and 2021, but this is only my second time baking in the oven. Despite a sometimes windy, sleety afternoon, we spent a few hours out there baking different things as the oven went from really hot to only sort of hot. Everything looks and tastes great and I think I’m done cooking for the week! (well, maybe).

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Lifting and Carrying

Let’s start with some ergonomics fundamentals: lifting and carrying. This post shares some basic concepts that we’ll be able to apply later to specific veterinary activities like lifting and carrying dogs.

This will be the first in a series of posts about ergonomics in the veterinary clinic–and everywhere else. It’s been a long pandemic, but in the past half-year I’ve had a couple of opportunities to talk about veterinary tasks aside from surgery. Today’s slushy snowstorm seems like a good time to share some of the illustrations and ideas from these presentations.

March “snowstorm” with Spaymobile in background

Lifting and Carrying: the fundamentals

First, what are the characteristics of a lifting task that can make it more or less hazardous?

Weight of load
Distance of your hands from your lower back
Height of lift (From floor or from above knee height? How high do you need to lift?)
Twisting and side bending
Working in a restricted space
Good grip, or irregular, bulky, floppy, unpredictable load
Flooring condition (dry, clean, good condition, or wet or uneven)
Communication and coordination when lifting as a team

Hold Box Near Waist — Carrying an object close to the body and near waist height

For our lifting and carrying example, we’ll use the ubiquitous brown cardboard box. In the first illustration, the lifter is carrying a box near her body and near waist height. This puts the object close to her center of mass and puts the least amount of strain on her body. It makes intuitive sense to us that she would carry the box this way instead of carrying it with her arms extended, far away from her body and her center of mass.

In this next set of illustrations, it looks a bit strange to carry the box with extended arms. But when the worker is carrying a larger box of the same weight, she is essentially doing just that– carrying the weight further from her center of mass and putting more strain on her back. A bulky object’s center of mass is further from the worker’s center of mass, meaning that even if this object is the same weight as the first box, it puts more strain on the worker’s back. The increased strain is due to the leverage created by the weight’s greater distance from the worker’s core.

Hold Box Far — While carrying a box far from the body looks strange, it’s the same strain as carrying a big box of the same weight.

Hold Big Box Low — While carrying a box far from the body looks strange, it’s the same strain as carrying a big box of the same weight.

(Want to learn more about how lifting strain increases depending on the size, shape, and weight of the object and the height of the lift? Check out the NIOSH Lifting Equation.)

Another circumstance where the worker might be holding an object far from her center of mass is when obstructions in the environment require her to do so. Removing objects that obstruct work areas (such as boxes obstructing a countertop) may seem obvious but it can also be the “low hanging fruit” when making ergonomic improvements.

Place Box On Counter Obstruct — In the first illustration, the worker has to extend her arms to place the object on the counter. In the second, the obstructions are removed and she can place the object without extending her arms as far.

Place Box On Counter No Obstruct — In the first illustration, the worker has to extend her arms to place the object on the counter. In the second, the obstructions are removed and she can place the object without extending her arms as far.

Yet another reason for carrying a weight far from one’s body because it the load is smelly, damp, messy, or covered in some bodily fluid– but the same principles apply. If it’s a soiled but lightweight cat carrier, it makes sense to hold it at arm’s length on the way to the wash area. But if it’s a whole load of smelly laundry or a patient covered in pee, using a protective barrier (plastic bag or clean towel) and holding the weight close to the body is a better choice because it allows for a more secure hold and less strain on the lower back.

Lift Box Low Shelf — Lifting below the knees or above the shoulders adds additional strain.

Lift Box High Shelf — Lifting below the knees or above the shoulders adds additional strain.

Lifting or placing objects below the knees or above the shoulders also adds additional strain on the worker’s body. Low placement may put strain on knees and lower back, while high placement can strain shoulders and arms (and introduce the risk of the object falling). Heavy items that need to be lifted and carried (cases of wet food; trays of instrument packs) should be near waist level to reduce the strain of lifting them. Lightweight objects can be placed on high shelves, with the bottom shelves reserved for heavier objects that will be transported with mechanical help like a wheeled cart or items that are used less often.

Big Box Hand Truck Back Side — A worker uses a hand truck/ a dolly/ a trolley/ a two-wheeled cart to transport a large box. (Nomenclature for this device varies a lot as you can hear in this link )

Mechanical help can be an excellent way to reduce strain when transporting objects. Gurneys, hand trucks, carts, and other devices bear the weight of the load, freeing the worker from the heavy lift.

Next time we’ll talk about the ergonomics of lifting and carrying dogs– stay tuned!

Surgical Ergonomics: Movement and Posture

In order to find pictures to demonstrate surgical posture, I went again to Google images to find some pictures of spaying and neutering, and came across several with surgeons in what appeared to be uncomfortable and ergonomically risky postures. Here are a couple of photos that I found:

https://images.app.goo.gl/7Fhew62NGyxoGRe96

https://images.app.goo.gl/QmP7Mmq6uqSUKyGh7

Both of these pictures show trainee surgeons leaning over their patients with about a 90 degree neck angle, bent waists, and elevated shoulders. We can’t know if these surgeons are using their bodies in this way because of the way their surgery room is set up, or because of habit, apprehension, or unawareness of their posture– or all of the above. Maybe these are brief positions during the surgery – but if these postures are sustained through a surgery day, these individuals are likely to experience some pain as a result.

In small animal surgery, we can achieve a fairly neutral posture except for our neck position. A neutral neck position would involve flexion of less than 10 degrees, but for a surgeon it is often 20-30 degrees. In this picture, I have a neck angle approaching 40 degrees.

It may not be possible to avoid extreme neck flexion in this work, and the important thing will be getting out of this posture between surgeries to allow those muscles to release and stretch. Turning your neck to each side, rolling your head, extending your neck, and shrugging your shoulders are all ways to release the tension in the muscles around your neck.

Other surgical postures to watch out for can be twisted or asymmetrical postures. If a surgeon maintains an asymmetrical or twisted posture, that can lead to uneven muscle use and strain and discomfort at the end of the day.

However, varying position during the surgery day is a good thing. If this surgeon balances the twist in one direction over time with a twist in the other direction, then she may not experience strain from the posture.

In this case, this surgeon might be more comfortable with a foot stool to rest her foot on, rather than using her weight-bearing foot as a footrest.

Another important thing you can do for yourself is to move during the surgery day. Between surgeries, take a few seconds to change your position. Roll your neck and shoulders, stretch. walk a few steps.

A study on human surgeons (abstract here) showed that taking a 20 second break every 20 minutes can increase your comfort and decrease fatigue after a day of surgery, and it can sustain your surgical performance and accuracy better through the surgery day. (If you can get access to the article, it’s a fun read not just for the scientific finding but also for the authors’ wry humor).

We are fortunate in spay neuter that we have short-enough surgery times that we can use the end of each surgery as a cue to move a little. We aren’t doing hours-long surgeries where we would need to set an alarm to remind us to move (although if you are someone who does long-duration surgeries, setting an alarm could be a good way to remind yourself to take your 20-second stretch break). So take a moment when you switch from one surgery to the next, to break the muscular tension that you hold during surgery.

We don’t necessarily think of or talk about spay neuter surgery as a sport or an activity that requires physical fitness or work hardening, but it does. As you do this work, your ligaments adapt, if you give them the recovery time they need between use.

Ligaments adapt to exercise and use by increasing size, strength, and collagen content (given adequate rest and recovery time between uses)
Surgeons in regular work may have greater resilience due to this tissue adaptation
New HQHVSN surgeons (or those returning from an extended break such as a maternity leave) will not have the ligament strength and may be at greater risk for hand/ wrist injury and discomfort.
Consider having a lighter schedule for new/ returning surgeons to allow their bodies to become conditioned to the work. Gradual increases in work hours, rather than starting off with a full-time schedule, may be more likely to lead to well-adapted ligaments rather than injury and strain.

For a much more in-depth discussion of ligament physiology, check out Ligaments: A source of musculoskeletal disorders. If this link isn’t available (it is not from the original publisher’s site), you can find other versions posted on Google Scholar.

Solomonow M. Ligaments: a source of musculoskeletal disorders. Journal of bodywork and movement therapies 2009;13:136-154.

Finally, physical activity outside of work is important to reducing physical discomfort while at work.

Physical activity outside of work is known to be associated with lower prevalence of pain
Surgeons who are physically active experience less fatigue due to work
For people experiencing low back pain, maintaining daily activities as much as possible is associated with quicker recovery from symptoms
Staying physically fit, maintaining friendships outside of work, eating well, and maintaining a work-life balance are all ways to reduce work-related musculoskeletal discomfort and stress.

There are not specific activities or exercises that research says are “best” – and it will likely vary between individuals– the key is simply being active and moving.

I hope this series of posts about surgical ergonomics has given you some ideas of how you might improve your own comfort during surgery. Remember that taking videos or photos of yourself during surgery can be a great way to understand what you are doing with your body, and to start to make improvements.

Let me know what works and what doesn’t work for you, and make comments with questions and with your own experiences of surgical ergonomics.

Surgical Ergonomics: Pain in HQHVSN vets

So… is there even a problem? Is ergonomics and pain something we need to spend time thinking about in spay-neuter veterinarians?

In order to figure this out, in 2011 I designed an online survey and collected responses from veterinarians who currently or previously perform spay and neuter surgeries at least 4 hours a week. I asked about hand and body pain, and whether that pain affected their work or activities, whether the pain was related to spay/neuter, and whether they had ever had to miss work because of the pain. I also asked about interventions that they had tried in their surgery day as well as outside of surgery, and about job stress and their satisfaction at work.

Here you can see the profile of the 219 people who responded to the survey.

As you can see, there is quite a range in experience and workload, but overall from what I have seen, this population is pretty representative of the population of people working in the spay neuter field.

When I looked at the prevalence of pain, I found that 99% of the vets in this survey had experienced some musculoskeletal discomfort in the past month. 98% had body pain, and just over ¾ had hand or wrist pain. While this sounds really alarming, other surveys of veterinarians in a variety of practice areas have shown nearly as high prevalence of discomfort.

There is a lot of variability in the severity of discomfort that people experience, and the number of body regions that were uncomfortable. Some veterinarians had worked full time for many years in spay neuter with relatively little discomfort, and others are uncomfortable with a much lighter workload.

This diagram shows the body regions where spay neuter veterinarians most commonly experience discomfort. As you can see, the low back, neck, and shoulders are the most likely to be uncomfortable.

Low back pain is common in humans, and so the high proportion of vets reporting low back pain in the past month is actually in line with other surveys of people.

However, the rate of neck, shoulder, and upper back pain is about 40% higher than what is reported in other surveys of veterinarians. The only surveys where I have seen these high rates of neck pain are in human surgeons.

This diagram shows the areas of the hands and wrists where spay neuter veterinarians most commonly experience discomfort.

The right thumb and wrist are the most commonly painful areas– this was true of the lefties that answered as well as the right handed vets.

One big question this research was trying to answer was “what are the workplace factors that contribute to pain?”

Of the work factors, hours per week in surgery (TIME) had the greatest relative importance in predicting total pain score, followed by years in spay neuter (CAREER). Number of surgeries (LOAD) and surgeries per hour (SPEED) were the least important predictors of pain:

TIME > CAREER > SATISFACTION > LOAD > SPEED

However, these workplace factors only explained a small amount of the pain score. Most of the differences would have to be explained by individual variability, genetics, activities outside of work, and other factors that we may not even think about.

Many studies in many fields have shown that people who have higher job stress or lower job satisfaction experience more work-related pain. In this study, nearly every measure of discomfort increased as people had higher stress and lower satisfaction.

We can’t say from this survey that this is a direct cause-and-effect process, although other studies have suggested that it can be. It may be best to think about pain, stress and low job satisfaction as a cycle that feeds on itself.

So as you’re trying to solve ergonomics problems in your workplace, take the time to consider that working on psychosocial issues may actually improve peoples’ physical comfort as well.

This is a basic summary of my study Prevalence and Risk Factors Associated with Musculoskeletal Discomfort in Spay and Neuter Veterinarians. If you are interested in more details and analysis, you can download and read the entire study here http://www.mdpi.com/2076-2615/3/1/85.

In my next post, I’ll talk about some basic things that spay neuter veterinarians can do to improve their physical ergonomics when they set up their surgical space.