The Myths and Facts of Trigger Point Dry Needling
What is dry needling? In the recent years, dry needling is becoming a more popular as a physiotherapy treatment modality and we want to shed some light to how we see dry needling. Dry needling as a name came from differentiating itself from “wet needling” which injections are. Dry needling does not insert any solution or injection – hence “dry”. In particular; the form of dry needling we want to discuss is trigger point dry needling in physiotherapy, and not acupuncture.
What is a trigger point?
First, we must discuss about what a trigger point is. A trigger point is can be defined as a taut band of hardened muscle that is tender and produce local and referred pain along with other symptoms. Once this trigger point is located and a firm pressure is applied, if it reproduces some of the person’s symptoms, it is called an active trigger point, while if it produces symptoms that the person is not familiar with, it is called a latent trigger point. It is theorised that trigger points can be activated by a variety of stimuli including poor posture, overuse, over training, muscle imbalance or as a result of another pathology.
Myofascial Pain Syndrome caused by trigger points mimic a lot of musculoskeletal problems and other problems. Myofascial trigger points can cause sensory, motor and autonomic symptoms e.g. pins and needles. Diagnosis of the trigger point relies on the palpation or needle insertion by the clinician to find the taut band of muscle that produces symptoms.
Research on myofascial trigger points are around but some say is insufficient. Current research suggests (Shah & Gilliams 2008) that trigger points are related to biochemical changes. When a sample was taken out of a muscle that is palpated to have a trigger point is compared to a normal muscle, the chemical composition is different (substance P and CGRP). When treated until the tension was reduced/deactivated, the chemical composition was rechecked, and the chemical composition had returned to that of a normal muscle. Deactivating the trigger point can be done in several ways: trigger point release/therapy, massage, myofascial release, or dry needling. However, the treatment has to be done to the point the symptom/tension/trigger point is reduced and this usually takes several repetitions.
Working the Trigger Point
Let’s take massage for example. Although going through the trigger point once is likely to aggravate it a bit, as you keep going through it the tension/trigger point will be reduced. If you went through it only once, it is unlikely to make a change and therefore would unlikely to give improved clinical outcomes. If you massage it several times and the tension/trigger point is unchanged, by the same principle, you are unlikely to give an improved clinical outcome – that trigger point is not responding to your massage. This is similar to other manual therapy that many manual therapists are familiar with: if you do a mobilisation on the spinal segment once and leave it still at its original level of pain and stiffness, you probably did not change anything. The clinical outcomes are best improved when you do a mobilisation on the spinal segment and then the pain/stiffness starts at 4/10 then goes to 3/10, then reduces all the way to 0-1/10.
Trigger point dry needling by GEMt follows the same principle; when the needle has hit a trigger point you would get a twitch response – the aim is to “twitch it out” from say a 5/10 twitch, then 4/10, 2/10, to a 1/10 or 0/10 twitch. If you’ve twitched it only once (5/10), and leave it, you may not make much of a clinical difference.
Trigger Point Models
There are several models that guide how to dry needle.
The Travell and Simon’s Model maps out common trigger points and their most common referral patterns; which may differ from person to person. The model proposes then that if you are able to address (deactivate) the trigger point, you should have improved symptoms and function. It also addresses how there can be a primary trigger point can then affect other muscles causing secondary trigger points and this guides on where to needle. This largely guides symptoms and muscles approach.
The Chan Gunn Intra-muscular Stimulation (IMS) model approaches dry needling differently. Rather than a “find the trigger point and needle it” approach, they group muscles based on which segment of the spine innervates it. Also, rather than finding a specific trigger point, all they ask for is to provide a noxious stimulus on a muscle and other muscles innervated by that segment would be affected as well. Note that the noxious stimulus does not need to be a trigger point, but a trigger point dry needling can be that noxious stimulus to affect other muscles innervated by that segment, including the contralateral side (opposite side).
But How Does It Work?
Now comes the question that everyone has been waiting for: How does it work? As discussed, there are some evidence to suggest that the trigger point dry needling causes biochemical changes. There are even models on how you should dry needle (Trigger Point Model and IMS). None of them so far have revealed to us what the needle actually does. Essentially, there remains a debate on the mechanisms, but some that have been discussed are:
· Mechanical effects: Needling may mechanically disrupt the dysfunctional motor end plates in muscles and/or cause sufficient mechanical stress to disentangle myosin filaments so that the muscles (sarcomere) will resume to its normal resting length.
· Blood flow effects: Sustained muscle contraction such as a trigger point may cause local ischaemia and hypoxia. Some studies suggest needling may increase blood flow and oxygenation which normalizes this.
· Neurophysiological effects: As discussed prior, Shah et al showed there is a biochemical difference between an active trigger point and latent trigger points or normal tissue with regards to substance P and CGRP and were lowered after local twitch response were illicited. The proposed mechanism for this change was via peripheral opioid analgesia which inhibits the pain pathway.
· Cervical sensitisation: The hyperstimulation using a dry needle may stimulate both nerve A delta fibres and C-Fibres which affects pain processing. Some also suggested dry needling may have effects only on segmental inhibition (spine levels) via Gate Control (pain mechanism).
· Radiculopathic model: Gunn who also proposes the IMS model believes that there could be neuropathic sensitivity making muscle fibres overreact to normal inputs resulting the mechanical effects of muscle shortening according to their segmental levels.
As you may have noticed, every proposed mechanism is a “maybe”. This simply means we don’t have enough research yet to conclusively explain how dry needling mechanism works. Some studies have shown effects, but not conclusive mechanisms. There are even models on how you can dry needle. For the most part, dry needling, trigger points and their effects have been documented, but still lacking in research: “we know it works to some extent in a particular capacity, we don’t know how or why.” This may put some people off from having dry needling done – and that is fine enough. However, for those of you who want to try and if dry needling is indicated for you as recommended by a clinician, hopefully this gives some insight before you decide on whether you want a dry needling or not. As always, when in doubt, ask your health professional for further information.