Palpation: Our Most Reliable Outcome Measure?

In the never-ending search for reliable outcome measures, are we overlooking our most valuable, reliable and repeatable measure – manual palpation? A recent research article made me question the value I placed on this tool, and the ways in which we could increase its usefulness as a repeatable outcome measure for patients.

Manual palpation has been shown to be reliable, repeatable and clinically practical, even when compared to mechanical outcome measures such as pressure algometry or FlexiForce Sensors. The use of a detailed and comprehensive scale increases its accuracy.

We love to look for tools to improve our efficacy, but what if our most effective tool needs only to be effectively measured?

What are we measuring?

When evaluating our patients, we want to measure a few different variables to establish the structures most severely affected, the level of dysfunction or disability affecting our patients, and their response to treatment interventions.

With regard to patient response, we specifically want to be able to objectively measure the following variables:

• pain, reactivity and tone of soft tissue structures
• posture and conformation
• movement and symmetry of the gait
• range of motion and quality of motion of the joints throughout the body
• functionality of the patient

In this article, we focus on the objective ways in which we can assess the first variable – pain, reactivity and tone of soft tissue structures.

Measuring and quantifying pain poses a few challenges or questions when it comes to our patients, including how we can accurately measure or quantify pain in a patient that is unable to verbalise their experience. If we measure the mechanical nociceptive threshold and combine that with the tone and quality of the tissue, is that an accurate representation of pain for the patient?

Until we have a better answer to this question, we will try to quantify pain in our patients as best we can from a combination of behavioural responses, the physical characteristics of the tissue beneath our hands, and our clinical reasoning.

Mechanical nociceptive threshold (MNT) refers to the threshold where a behavioural change or physical response is noted in the patient in response to a mechanical force being applied. The ability to measure this force or pressure allows us to objectively measure an individual’s MNT for a specific point on a soft tissue structure.

What are the tools available to measure?

When measuring MNT, palpation is the go-to for the majority of us in clinical practice on a day-to-day basis. But just how well-validated is palpation in terms of repeatability, reliability and assessment of patient progress? We also don’t think of what we are measuring or assessing as the MNT, and are instead assessing a variety of different factors such as muscle tone and mass, the alignment of fibres, muscle symmetry, hydration of the tissue, mobility of the fascial lines and reactivity of the tissue, along with behavioural cues and responses from our patient.

In the research environment, pressure algometry has been used as a way of simplifying the palpation of a patient and measuring one specific variable: MNT. But how well-validated is this tool in the literature, and how easily does it translate to clinical practice? In addition, if we are still continuing to use palpation to assess the other variables we want to evaluate, how much value does pressure algometry add to our assessment and measurable outcomes? In general, it is an easy-to-use, inexpensive tool in clinical practice.

Let’s compare these two tools in the literature:

From the above we can see varying results for the reliability of both modalities, but more so for palpation. Palpation relies much more heavily on the skill and experience of the individual performing the technique, and is strongly subjective, raising the question: ‘How can we make it more objective?’
Pressure algometry is not perfect either, and shows a lack of consistency in the literature.

Why is objectivity important?

There are multiple benefits to bringing more objectivity into our evaluations and reassessments, with the most important being that we can more accurately assess the progress and response of our patients to treatment interventions, which allows us to be more effective and efficient in the treatment and progression of our patients.

Objective measures also help us to

• communicate and share results with other members of the MDT
• motivate and foster compliance in owners
• participate in research
• present the results of specific cases with our peers and
• evaluate and share the role we played in the care of a patient when things have gone awry.

As an evidence-based profession, Veterinary Rehabilitation needs to ensure that the objective outcome measures we use have been validated, and can be repeated between different practitioners.

Using the right scale

If we use palpation as our primary outcome measure in clinical practice, we need to use a scoring system that will increase the objectivity and which can be applied by different practitioners to yield reliable, repeatable and descriptive results. If we can create a scoring system that can be used by Vetrehabbers around the world, the value will increase exponentially as we can then compare our findings with those of other practitioners.

In the literature, I have come across a few different palpation scoring systems. Most use a scale of 1-3 or mild, moderate, severe. There is still a great deal of subjectivity in this.

Merryfield-Jones et al (2019) used the following scoring system in their research, which yielded excellent interrater reliability:

Conclusion

Using objective outcome measures in our clinical practice does not need to be something that is restrictive, time intensive or expensive. With some intention and small changes to the way we collect data from our evaluations, we can use the tools we already have to collect data that is objective, repeatable, comparable and descriptive.

Resources

• Let’s Get Objective with Pressure Algometry
• Putting a Number on Pain
• Stress and Pain – Is there a Link?
• Equine Myofascial Pain
• The Pain Management Pyramid
• Canine Amputees and Phantom Limb Pain
• The Causes of Equine Back Pain
• Why Your Dog has Back Pain and How Your Vetrehabber Can Help

References

• Bendtsen, L., Jensen, R., Jensen, N.K. & Olesen, J. (1995). Pressure-Controlled Palpation: A New Technique Which Increases the Reliability of Manual Palpation. Sage Journals.
• De Heus, P., Van Oossanen, G., Van Dierendonck, M. & Back, W. (2010). A Pressure Algometer Is a Useful Tool to Objectively Monitor the Effect of Diagnostic Palpation by a Physiotherapist in Warmblood Horses. Journal of Equine Veterinary Science, Volume 30, Issue 6, June 2010, pages 310-321.
• Fingleton, C. Dempsey, L. Smart, K. & Doody, K. (2014). Intraexaminer and Interexaminer Reliability of Manual Palpation and Pressure Algometry of the Lower Limb Nerves in Asymptomatic Subjects. Journal of Manipulative and Physiological Therapeutics.
• Merrifield-Jones, M., Tabor, G. & Williams, J. (2019). Inter- and Intra-Rater Reliability of Soft Tissue Palpation Scoring in the Equine Thoracic Epaxial Region. Journal of Equine Veterinary Science 83 (2019) 102812.