posture | ergovet

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.

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.

Tag: posture

The Ergonomics of Postures and Positions