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11 Articles in Volume 12, Issue #10
An Anti-inflammatory Diet For Pain Patients
Focus on the Foot
How to Use Adrenocorticotropin As a Biomarker in Pain Management
Iatrogenic Nerve Injury Following Dry Needling For Foot Pain: Case Challenge
Methamphetamine Urine Toxicology: An In-depth Review
Musculoskeletal Ultrasound: A Primer for Primary Care
November 2012 Letters to the Editor
Off-label Use of Pain Treatment No Longer Covered by Insurance
Proper Disposal of Fentanyl Patches: What Patients Need to Know
The Next Barriers to Care: Your Local Pharmacy
Why Podiatric Medicine Must Embrace Pain Management

Iatrogenic Nerve Injury Following Dry Needling For Foot Pain: Case Challenge

Editor’s Note: Needling for Pain Relief

One of the most ancient treatments for pain has been sticking a needle into the painful site. Last year, the “Iceman” was discovered in the Northern Italian Alps. He was thawed out after spending several thousand years in ice, and needle puncture wounds were found over his joints. (For those of you who didn’t see the pictures and story, it appeared in the November 2011 issue of National Geographic Magazine.)

Today, there is a resurgence of interest in sticking needles into pain sites. The term “dry” needling means there are no anesthetics or corticosteroids to accompany the injection, and this article describes what may happen if a “dry” needle hits an unanesthetized nerve.

Interestingly, most advocates of needling avoid discussing why a dry needle may relieve pain. The answer primarily centers around the work of Dr. Luigi Galvani, who in the late 1700s found that injured nerves “leak” electricity. This phenomenon is known as the “current of injury.” In his book, The Body Electric: Electromagnetism and the Foundation of Life, Robert Becker, MD, the father of the bone stimulator, and Gary Selden found that a needle placed in an acupressure point attracted “electricity” and “shorted out” the area, providing local anesthesia. Needles consist of polished steel, which is made from the positively charged element—iron. When a positively charged metal is injected into a pain site that is collecting electricity from damaged nerves, it will attract negatively charged electrons. The result is less pain and tissue spasm around the pain site. With a little luck, this procedure can even be curative and, at worst, provide a little pain relief until electricity again accumulates in the pain site.

Case

A 48-year-old man reported left plantar heel/foot pain. His symptoms began 20 years ago while playing basketball. At the initial onset of plantar heel pain, he reported burning and tearing pain when first getting out of bed in the mornings, which would typically resolve during the day and between basketball sessions, but which was always present and most intense after playing basketball. Since then, the symptoms have continued on and off for months at a time. The plantar heel pain returned in January 2010 after jogging up a small incline approximately 10 times over a 3-week period. The patient reported he was exercising in “poor quality running shoes” to get in shape. These symptoms have continued since that time without spontaneous resolution.

In the United States, the incidence of heel pain is approximately 10%, ranging from 8% to 15%, accounting for 11% to 15% of healthcare provider service visits.1-4 In adults, plantar fasciitis is the most common source of heel pain.3,4 When pain is associated with foot and ankle conditions, it results in disturbances in gait and difficulties in balance.5 In fact, older adults suffering from plantar heel pain are at higher risk for falls.5 Heel pain is considered to be a self-limiting condition that often takes between 6 to 18 months to spontaneously resolve.3,6 In fact, 80% of plantar heel pain cases spontaneously resolve in 12 months.3

Table 1. Risk Factors for Plantar Foot Pain

Etiology of Plantar Heel Pain
The plantar fascia consists of three bands: the central, medial, and lateral. The medial and lateral bands originate off the abductor hallucis and the abductor digiti minimi, which may play a role in the etiology or at least a potential role in treatment.2 The thick and fibrous connective tissue of the plantar fascia performs a twofold purpose—a static support of the longitudinal arch and a dynamic shock absorption for the foot and lower leg.2,3,6 Present research has identified many possible risk factors for planter heel pain (Table 1).3,6-8

Travell and Simons have suggested that myofascial trigger points (MTrPs)—hyperirritable spots with hard hypersensitive palpable nodules located in taut bands within the muscles that can cause predictable patterns of pain spontaneously or when manually compressed—in lower extremity muscles are involved in plantar heel pain.9 When stimulated, MTrPs found in the gastrocnemius, soleus, and tibialis posterior muscles refer pain to the plantar heel and may play a part in the development of plantar heel pain symptoms. Site specific musculature that may have pain-causing MTrPs include the abductor hallucis, flexor digitorum brevis, and quadratus plantae (QP) musculature.9

Treatment Options
Invasive and non-invasive management strategies for plantar heel pain vary greatly and lack consensus. Table 2 highlights various non-surgical options for treating plantar heel pain.1-6 Acupuncture has been proposed as a treatment option, but acupuncture studies vary in needle placement, sometimes using acupoints at the symptomatic site and sometimes at distal acupoints traditionally used for general pain control.3,10 Traditional acupuncture theory has not specified a particular acupoint for treating heel pain.10

Healthcare providers in Europe have performed dry needling for many years. Dry needling is an invasive procedure in which an acupuncture needle is inserted into the skin and muscle.11,12 Although the pathophysiology and mechanism of action are not completely understood, the knowledge base regarding dry needling is growing for musculoskeletal and myofacial pain conditions.11,13-18 Adverse events include local soreness, bruising, bleeding, pain, and, rarely, pneumothorax. However, the literature supports the safety of this procedure when performed by a trained clinician.13,19

In research studies, needling procedures for MTrPs have been efficacious.13,20 However, Cotchett et al performed a systematic review of the effectiveness of MTrP dry needling and injections associated with plantar heel pain. They found limited evidence, with methodological inadequacies.21

Dry needling is not intended to be a stand-alone treatment procedure. Rather, it is used as an adjunct to standard orthopedic manual physical therapy services, including soft tissue mobilization, joint mobilization/manipulation, and therapeutic exercises. At this time, there is no established dosage for dry needling application. The needle can be inserted and remain in place from seconds to minutes. It can remain stationary, be pistoned up and down, or twirled or spun clockwise and/or counterclockwise. Various electrical stimulation devices can be attached to the needle in some form or fashion to electrically stimulate the targeted muscle. The needle can be inserted superficially (superficial dry needling) to a depth just before penetration of the actual MTrP or it can be inserted deeply (deep dry needling) directly into the MTrP.

Current Case: Medical History
The patient’s past medical history included extensive knee surgeries bilaterally, as well as a history of low back pain. The surgical history of the patient's right knee included arthroscopic debridement in 1984, anterior cruciate ligament (ACL) repair with patellar tendon and calcium excision at graft donor site in 1994, and meniscal resection in March 2009. The surgical history of the left knee included ACL repair with hamstring graft in 1998, arthroscopic debridement in 1999, followed by a Maquet procedure several months later in 1999. The patient reported intermittent low back pain in the late 1980s and 1990s, and worsening of symptoms in 2000, culminating in left lower extremity radiating pain with numbness and tingling that lasted 5 to 6 months. The pain and numbness gradually resolved without intervention. Currently, he reports rare incidences of localized stiffness and low back pain. The referring physician did not provide any objective diagnostic findings, such as high-resolution ultrasound imaging of the fascia, needed to truly document whether there was fasciopathy, and there were no electrodiagnostic findings despite the long history of back symptoms.

Table 2. Treatment Options for Plantar Foot Pain

Testing Results
The patient was recruited for dry needling treatment at a local hospital and signed informed consent. The patient was initially seen on April 25, 2011, for assessment and dry needling treatment with follow-up assessment sessions on May 9, 2011, and July 17, 2011. No other interventions or life changes were recommended or prescribed for the patient. The data and examination items were chosen primarily based on the clinical practice guidelines regarding heel pain–plantar fasciitis.22

The patient reported intermittent pain in the left plantar heel just distal to the medial tubercle of the calcaneus that varied in intensity from 0 to 4 out of 10 points on the numeric pain rating scale (NPRS), with pain worse in the mornings. First-step pain was reported at 3 to 4 on the NPRS. He completed the Foot and Ankle Ability Measure (FAAM) and the Lower Extremity Functional Scale (LEFS) perceived disability index scales. Objective data included pressure pain threshold (PPT) testing and handheld dynamometer muscle function assessment. On the FAAM he scored a 100 on a 0 to 100 scale and on the LEFS he scored an 80 on a 0 to 80 scale, resulting in no perceived level of disability from his present condition despite the reported symptoms. It is unknown why the patient’s perceived level of disability is absent in the presence of obvious plantar heel symptoms.

Results of PPT algometry range-of-motion testing and muscle function assessment are shown in Tables 3 to 5. PPT findings revealed significant differences in readings taken over the muscle bellies of flexor hallucis brevis (FHB) and QP. Active range of motion (AROM) and passive range of motion (PROM) found that great toe (1st ray) extension was bilaterally symmetrical at 70°, but there was a marked limitation in left ankle dorsiflexion compared to right ankle dorsiflexion, which also was relatively limited. Unilateral close-chain toe raises measured functional muscle strength. The patient completed 20 of 20 repetitions on the right side without complaint. During the repetitions on the left, the patient reported initial pain during the first few and stated the repetitions were more difficult and fatiguing. Dynamometer muscle function measurement findings were not markedly dramatic but demonstrated slight impairment in left ankle muscle strength. Palpation failed to reveal active or latent trigger points in the lower leg musculature bilaterally. There were no taut bands that resulted in local twitch responses or that reproduced the patient’s primary plantar heel pain.

Tables 3-5 Iatrogenic Nerve Injury Following Dry Needling for Foot Pain

Local tenderness was identified in the plantar aspect of the feet bilaterally just distal to the medial tubercle of the calcaneus that was more evident in the left foot. This spot on the left heel was identified by the patient as the location of symptoms but palpation did not reproduce the same types of pain. The clinician speculated that the muscular source of the patient’s condition was coming from the QP muscle and not the flexor digitorum brevis (FDB) based on the site of tenderness, the absence of pain referral distally during palpation, and the absence of vague distal pain in the plantar foot that could be attributed to other muscles. General arch tenderness was noted; however, a muscular source for the pain could not be identified exclusively due to the fact that there were no initial reports of distally referred symptoms and no provocation of more distal plantar referred symptoms during palpation. General medial plantar arch tenderness was attributed to non-contractile soft tissues, based on the overly pronated foot position of the patient when weight bearing.

Treatment
The clinician performed a single session of dry needling to the patient’s left foot. He chose this protocol to study the potential subjective and objective effects from one dry needling treatment session. The patient was placed prone with the foot over the edge of the table and a “J” 0.30 x 50 mm gauge needle was inserted on the plantar surface. The initial dry needling procedure, placed approximately 1 cm distal to the medial tuberosity of the calcaneus, was assumed to strike a nerve as it sent immediate shock-like symptoms in both the medial and lateral aspects of the foot (Figure 1). The needle was immediately withdrawn. Based on the patient’s reported symptoms, it was surmised that somehow the junction area of the medial and lateral plantar nerves was struck. If this were the case, then the anatomy of this structure for this patient would be considered abnormal. Unfortunately, these new electric-like symptoms persisted so the patient was asked to wait prior to a second attempt.

The new discomfort continued to persist and was described as similar to hitting one’s ulnar nerve at the “funny” bone region but resulted in more of a noxious result that initially prevented an immediate second attempt at dry needling. A second attempt (Figure 2) was made later that day and the “J” 0.30 x 50 mm gauge needle was reinserted with the patient lying on his side using a medial approach, which did not result in electric-like symptoms. Rather, it reproduced the typical deep dull ache symptoms and was reportedly “very” intense but lasted only a few seconds. The needle was not rotated, but merely placed for response, with a few piston-type motions of the needle in the QP muscle after the initial response.

The procedure, from needle insertion to removal, took approximately 5 seconds. The patient’s subjective response to the second dry needling procedure was an immediate decrease in symptoms in his primary pain region. The patient did not have a palpable MTrP but did elicit symptom provocation (pain reproduction and referred pain) and local twitch response (LTR) from the second needle application. This is a key occurrence for positive treatment outcomes following the trigger point hypotheses model.23 However, the lingering effects of the new symptoms directly related to the first dry needling procedure remained evident and were still described as electric-like sensations.

To the author’s knowledge, the persistence of the nerve-like symptoms is very interesting because it has not been documented in the literature. In a personal communication, Edo Zylstra, PT, MS, OCS, IMSp, the CEO and the lead instructor of Kinetacore Physical Therapy Education, which teaches dry needling courses throughout the United States, stated that in his experience, needle strikes to healthy nerves typically result in similar intense nerve-like reports that last only a few moments; however, sensitized nerves may have a more robust response, as in this case.24

Over the next few days, the patient’s primary plantar heel pain steadily decreased, but the nerve-like symptoms persisted as the dominant aggravating factor. The patient was assessed for the second time on May 9, 2011. Perceived disability ratings from FAAM and LEFS were taken, and again resulted in 0% perceived disability rating. Since this was the second time these ratings were evaluated and resulted in no perceived disability, they were discontinued at this time and were not reassessed. The patient reported his primary plantar heel pain was now more intermittent ranging from 0 to 3 on the NPRS, with first-step pain as 0. However, the nerve-like pain was described as 5 to 6 on the NPRS. PPT was more equal between the left and right foot (Table 3).

Left ankle dorsiflexion AROM and PROM significantly improved toward the ranges of the right ankle. Right ankle dorsiflexion AROM and PROM also improved without any direct or indirect intervention. Foot dynamometer muscle strength also improved bilaterally, but the left measurements remained more limited than the non-involved ankle/foot (Table 5). The patient’s first ray extension at the MTP joint remained at 70° and this reading was not measured after this session. The patient’s primary plantar heel pain complaint had decreased with significant objective changes in PPT, ROM, and muscle function. However, the new nerve-like symptoms from the acupuncture needle striking the nerve bundle of the left foot dominated the subjective discomfort reports.

The patient was assessed for a final time on July 17, 2011. The patient stated that both his nerve-like pain and his plantar heel pain were abolished. Both pains had been resolved for approximately 6 weeks prior to this date. The patient reported he had not experienced first-step pain for approximately 3 weeks. PPT data readings for QP displayed a significantly higher tolerance. Left AROM/PROM gains were maintained. Muscle function dynamometer gains were slightly improved with foot inversion (posterior tibialis) exhibiting the largest discrepancy between the left and right foot.

The patient was contacted in mid-January 2012 via telephone, approximately 6 months after his last assessment session. The patient continued to report that his primary plantar heel pain symptoms, his first-step pain, and the nerve-like pain resulting from the inadvertent initial dry needling attempt remained abolished.

Trigger Point Etiology
A primary theoretical model for the etiology of MTrPs is the integrated hypothesis of the trigger point model. It theorizes that an MTrP is a complex phenomenon with biochemical, biomechanical, and neurophysiological components creating symptoms within the sensory, autonomic, and motor systems. Normal electrical activity within muscle tissue at rest should be relatively silent. Taut bands tend to have spontaneous electrical activity (SEA) and, therefore, exhibit endplate noise when examined by electromyography (EMG). Several factors are speculated to contribute to the presence of SEA. One of these factors involves an excess of acetylcholine (ACh) in the neuromuscular junction. The tension from the MTrP on the integrins (cellular proteins that bind connective tissue) perpetuates the ACh release cycle. These factors contribute to spontaneous ACh release in the absence of direct α-motor neuron activity.25,26 Shah et al found that an MTrP can be acidic without direct damage of the muscle tissue and yet exhibit hyperalgesia.15

Figure 1 and Figure 2 - Dry Needling Approaches

Pain, or nociception, from MTrPs may affect the dorsal horn and central nervous system (CNS), resulting in neuroplastic alterations. MTrPs’ biochemical milieu, or cellular inflammatory factors, activates muscle nociceptors. If this nociception is sustained from an injured site (peripheral sensitization), it can result in changes at the dorsal horn (central sensitization)—a form of neuroplasticity—and lead to hyperalgesia (an abnormal increase in pain perception) and allodynia (pain to a non-noxious stimuli). Thus, perpetuated taut bands result in local ischemia and hypoxia, again increasing ACh. The resulting acidic pH of the muscle further excites muscle nociception. The acidic pH of the tissues adds to the central sensitization process.15 The combination of these factors results in exaggerated pain response, decreased pain thresholds, and increased physical pain field presentation.14,25,26

Dry needling may interrupt the biochemical, biomechanical, and neurophysiological pathways by changing the tension in the connective tissue and resetting sarcomere length. This may reduce SEA by disrupting spontaneous ACh release. The mechanical effect of the needle may also result in electrical polarization of muscle and connective tissue. This mechanotransduction enables tissue remodeling to occur, normalizing the electrical activity of the tissues.27 It is proposed that this connective tissue remodeling and nervous system plasticity results in a removal of the nociceptive factors and reversal of the neuroplastic changes.26 Studies on rabbit MTrPs have shown almost an instantaneous chemical normalization and SEA reduction in the neuromuscular junction with the elicitation of an LTR.27

Despite this information, the exact cause and nature of MTrPs remains ill defined.28 The direct mechanical stimulation (irritant) caused by dry needling may result in connective tissue remodeling and neuroplasticity, which then interrupts the pathogenic mechanism of MTrPs,14-16 thus producing a positive clinical effect.

Summary
This case study provides anecdotal evidence demonstrating significant subjective and objective changes in the patient’s plantar fasciitis over 2 to 3 months after a single dry needling session. The resolution of symptoms was maintained until follow up, approximately 6 months later. It is unclear at this point whether the patient’s condition merely improved due to time, placebo effect, or as a direct result of the dry needling session. However, if it was due to a spontaneous resolution, the absence of a cycle of plantar heel pain episodes is not consistent with the patient’s prior history of exacerbations. In the literature, spontaneous resolution occurs within 6 to 18 months.3,6 This patient had complete resolution of all his symptoms (primary heel pain, adverse response nerve-like symptoms, and first-step pain) within 10 weeks (2 ½ months) of eliciting the patient’s primary pain complaints and LTR during the dry needling treatment session. This is a key component in positive treatment outcomes following the trigger point hypotheses model23 and suggests a causal relationship to the dry needling intervention. It is unknown whether this patient would have progressed more rapidly with multiple needling treatment sessions.

It is also unclear how the inadvertent nerve strike impacted the patient’s overall presentation and recovery. It may have exacerbated and extended the patient’s time to recovery or it could have facilitated the recovery process and may have been the primary catalyst that resulted in this patient’s significant subjective and objective improvements. It can be theorized in conjunction with the trigger point hypotheses model that the iatrogenic nerve injury from the needle strike may have affected the biochemical milieu surrounding the nerve, resulting in noxious afferent stimulation to the dorsal horn and higher CNS centers, imprinting a hyperalgesia to that region lasting longer than what is expected for such an occurrence. It is possible that the area around the nerve tissue and the nerve tissue itself was already experiencing sensitization (peripheral and central sensitization) from the nociception from the plantar fascia. In other words, the tissues in the plantar heel were highly sensitized. At present, there is no dry needling treatment method in which one directly strikes nerve tissue as the primary target of intervention. Instead, the most pervasive dry needling technique is based on the trigger point model, in which a needle is inserted into the muscle/MTrP, as in this case study. What is important is the implication of the length of time adverse event symptoms may persist after an iatrogenic nerve injury, especially when the nerve already is sensitized. What is clear is the fact that the patient had drastic improvement in all measured data markers leading to complete resolution of his primary heel pain and the adverse nerve-like symptoms in 6 weeks of the dry needling session.

Last updated on: December 5, 2012
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