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Novel Therapeutic Approach for Tibial Nerve Entrapment in Chronic Heel Pain Diagnosed as Plantar Fasciitis: A Case Report
Korean J Sports Med 2023;41:241-245
Published online December 1, 2023;  https://doi.org/10.5763/kjsm.2023.41.4.241
© 2023 The Korean Society of Sports Medicine.

Cheol-Jung Yang1, Jeong Won Seong2, Dongrak Kwon3, Yuntae Kim4

1Department of Orthopedic Surgery, Borntouch Orthopaedic Clinic, Seoul, 2Department of Family Medicine, Sarang Clinic, Jinju, 3Department of Rehabilitation Medicine, Catholic University of Daegu School of Medicine, Daegu, 4Department of Rehabilitation Medicine, Soonchunhyang University Cheonan Hospital, Cheonan, Korea
Correspondence to: Yuntae Kim
Department of Rehabilitation Medicine, Hansarang Clinic, 8 Ilbong-ro, Dongnam-gu, Cheonan 31184, Korea
Tel: +82-41-573-5595, Fax: +82-41-573-9986
E-mail: simon108@naver.com
*Current affiliation: Department of Rehabilitation Medicine, Hansarang Clinic, Cheonan, Korea.
Received August 25, 2023; Revised September 11, 2023; Accepted September 25, 2023.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
Plantar heel pain is common in sports medicine and orthopedics; it is usually diagnosed as plantar fasciitis. We report the case of a 43-year-old healthy man with chronic pain over the right heel for 5 years. He was diagnosed with plantar fasciitis and received conservative treatment. Surgery was recommended for the intractable pain, which he refused. He had tenderness in the medial calcaneal tubercle region and midportion of soleus muscle near the tendinous arch. At a tibial nerve entrapment point (NEP) over the tender soleus, 4-mL isotonic saline was injected at presentation and 1, 3, and 6 weeks later. The pain improved significantly. He had no adverse effects or aggravation of symptoms at 6 months later. The injection therapy at NEP of the soleus can be considered in chronic unhealed plantar heel pain, including plantar fasciitis, to release the entrapped tibial nerve.
Keywords : Tibial nerve, Nerve Entrapment, Plantar fasciitis, Soleus muscle
Introduction

Plantar heel pain is a common orthopedic problem with a reported prevalence of 4% in adult Americans1. Plantar heel pain may be caused by plantar fasciitis, calcaneal fracture, plantar fascia rupture, heel fat pad atrophy, or neural involvement (tibial, lateral plantar, medial calcaneal, or medial plantar nerve). In plantar heel pain, plantar fasciitis is the most common diagnosis with a reported prevalence of 1.1% in adult Americans2.

Unhealed chronic plantar heel pain diagnosed as plantar fasciitis is often caused by nerve entrapment syndrome; entrapment of the plantar or calcaneal nerves originating from the tibial nerve could cause heel pain3. The classic concept of nerve entrapment can cause not only symptoms of nerve irritation but also weakness and atrophy4. Many patients often complain of discomfort without abnormal findings on electromyography. Functional nerve entrapment is possible at the site of the nerve passing through the muscle or connective tissues. We labeled the aforementioned concept as a nerve entrapment point (NEP). Based on clinical experience, we know that NEP may cause various pain symptoms.

The tendinous arch of the soleus muscle can act as NEP of the tibial nerve. This nerve can be functionally entrapped in the tendinous arch of the soleus with excessive tension. Herein, we report a case of intractable heel pain that was diagnosed as plantar fasciitis and was successfully treated with four injections of isotonic saline into the soleus. Chronic heel pain was improved by applying the concept of NEP to resolve the entrapment of the tibial nerve.

The patient provided written informed consent for the publication of this case report and the accompanying images. This case study was approved by the Institutional Review Board of the Armed Forces Medical Command in Seongnam, South Korea (No. AFMC-18-IRB-066).

Case Report

A 43-year-old healthy man (180 cm, 75 kg) with right inferior heel pain for 5 years visited the orthopedic outpatient department of The Armed Forces Daejeon Hospital. He was a soldier who often ran and climbed mountains as a part of his training. His heel pain aggravated when taking the first barefoot steps in the morning. Physical examination revealed a normal ankle range of motion with tenderness in the medial calcaneal tubercle region. Plain lateral foot radiograph shows no abnormal findings, such as heel spur and calcaneal stress fracture (Fig. 1). He was diagnosed with plantar fasciitis 5 years ago at an orthopedic clinic and had been receiving conservative treatments, such as nonsteroidal anti-inflammatory drugs, physical therapy, extracorporeal shock-wave treatment, and custom-made orthotic shoes. However, there was no improvement in the pain, and surgery was recommended. He refused surgery and continued with conservative treatment since then.

Fig. 1. Plain lateral foot radiograph shows no abnormal findings, such as heel spur and calcaneal stress fracture.

In addition to the pain with the first barefoot steps in the morning, he complained of burning pain in his heel area at rest. Physical examination revealed tenderness at the right medial calcaneal tubercle region, and compared with the opposite side, there was severe tenderness over the medial flexor retinaculum and the midportion of soleus muscle. Although the patient has been treated for plantar fasciitis for a long time, it has not improved, and the current pattern of pain is resting neuralgia, so the authors decided to approach the possibility of entrapping tibial nerve. The tender regions of the medial flexor retinaculum and medial calcaneal tubercle corresponded with the entrapment point of the medial calcaneal nerve5, and the tendinous arch of the soleus muscle corresponded with the location of the tibial nerve3,6. Ultra-sonography revealed no abnormalities that could result in tibial nerve entrapment in the medial ankle. Therefore, we hypothesized that the tenderness point of the soleus was tibial NEP and the entrapped tibial nerve at the tendinous arch of the soleus stimulated the medial calcaneal nerve originating from the tibial nerve, which caused the chronic heel pain7. He was subsequently diagnosed with tibial nerve entrapment syndrome within the soleus.

As a therapeutic intervention, to release the tibial NEP within the soleus, 4 mL of isotonic saline was injected using a 23-gauge syringe at approximately the midportion of the soleus—the most tender region of the soleus—under ultrasound guidance (EPIQ 5; Philips Diagnostic Ultrasound System and Transducers) (Fig. 2). The injection was repeated at 1, 3, and 6 weeks after the first injection.

Fig. 2. Ultrasound-guided injection into the midportion of the soleus muscle, which was most tender. (A) Ultrasonography confirmed that the needle was within the soleus (arrow, 23-gauge needle). (B) The flow of the injected isotonic saline within the soleus was confirmed by color Doppler ultrasonography. G, gastrocnemius; S, soleus; A, aponeurosis.

Functional outcomes were measured using the Foot and Ankle Ability Measure–activities of daily living subscale (FAAM-A), numeric pain rating scale (NPRS), and percent pain intensity difference (PPID). The parameters were assessed before each injection; first, as a baseline measure and at each subsequent visit to evaluate the effects of the previous injection. The final outcome was measured 6 months after the first injection. While evaluating the outcomes, the patient was requested to report any adverse effects at each visit.

Before the first injection, the baseline FAAM-A, NPRS, and PPID scores were 52, 7, and 100 points, respectively. A week after the first injection, those scores improved to 65, 4, and 60 points, respectively, and further improved to 78, 0, and 10 points, respectively, 6 months after the first injection (Fig. 3). He had no adverse effects or aggravation of symptoms at follow-up 6 months later. At 6 months after the first injection, the patient reported comfort without wearing the custom-made orthotic shoes and slight pain after mountain climbing. He was satisfied with the outcome of the treatment.

Fig. 3. Foot and Ankle Ability Measure–activities of daily living subscale (FAAM-A) and numeric pain rating scale (NPRS) scores improved by 13 and 3 points, respectively, 1 week after the first injection, and 26 and 7 points, respectively, at 6 months after the first injection. Both outcomes surpassed their respective minimal clinically important differences and were maintained at 6 months after the first injection. Subjective measures of percent pain intensity difference (PPID) also improved after the injections. FAAM-A (0–84, higher is better), NPRS (0–10, lower is better), and PPID (0–100, lower is better). *Outcome measurements performed before the injection.
Discussion

The present report is meaningful because it describes the case of intractable heel pain for 5 years in a healthy adult male who was diagnosed with plantar fasciitis and was successfully treated with four injections of isotonic saline into the soleus. The cause of the pain was treated by using the concept of NEP to release tibial nerve entrapment.

Seong7 defined NEP as a point at which a muscle physically compresses a nerve and, thereby, causes pain in the nerve-innervated region. When a muscle repeatedly suffers microtrauma, it becomes tense and tender, and entraps or compresses the adjacent vasa nervorum, thereby, causing focal ischemia7,8. This may lead to membrane hyperexcitability9. A hyperexcited nerve can produce abnormal excitation signals, resulting in a variety of pain. In this case, the tibial nerve could be entrapped in the tendinous arch of the soleus, and the entrapped tibial nerve could have stimulated the distal nerve branch and caused neural pain in the plantar regions of the medial calcaneal nerve7,8. Therefore, to improve the heel pain, releasing the tension within the soleus in which NEP had formed is necessary. The injection therapy involves an intramuscular injection of diluted lidocaine or isotonic saline into the pain-causing muscles. This allows access to the treatment points that address excessive tension of muscles and may ultimately resolve the excitability of the specific nerves entrapped by muscles10.

In the presented case, the plantar heel pain significantly improved after four injections of isotonic saline into NEP of the soleus. The functional outcomes of FAAM-A and NPRS improved by 13 and 3 points and 26 and 7 points at 1 week and 6 months, respectively, after the first injection of isotonic saline. FAAM-A is a valid measure of physical function in plantar fasciitis and a minimal clinically important difference (MCID) of 8 points has been reported to be significant. NPRS is a reliable and generalizable measure of pain intensity with a reported MCID of 2 points. PPID is a subjective assessment of the patient’s responses that is used to calculate the percent decrease in pain with respect to the baseline. The present measurement outcomes of FAAM-A and NPRS surpassed their respective MCIDs and were maintained at 6 months after the first injection. Subjective measures of PPID had also meaningfully improved after the injections.

In addition to plantar fasciitis, plantar heel pain can be caused by several other conditions, such as calcaneal fracture, plantar fascia rupture, heel fat pad atrophy, and neural origin pain3,6. When a patient complains of nerve symptoms, the nerve is usually believed to be compressed by some structures5,11,12, such as bony protrusions or ganglia; thus, in cases like this, surgical treatment is usually recommended to resect the structural cause. However, when there are no particular structural causes of nerve compression identified on radiologic studies, the muscle should be suspected to compress the adjacent nerve7. In plantar heel pain, the possible causes are stimulated medial calcaneal, medial plantar, and lateral plantar nerves originating from an entrapped tibial nerve3,6.

Some studies have reported that injecting isotonic saline into muscles for pain reduction in the control group is just as effective and is not statistically inferior to the interventions in the experimental group—platelet-rich plasma injections in chronic rotator cuff tear, lidocaine injection in fibromyalgia, autologous blood and corticosteroid injections in lateral epicondylitis, and prolotherapy injections in chronic low-back pain13-16. In these studies, pain improvement following injection of isotonic saline was considered a placebo effect13-16. However, we only used isotonic saline to release NEP without using other commonly used chemical agents such as lidocaine or steroids. Regardless of the solution used, the excitability of the nerves is reduced following the injection as the compression of the vasa nervorum is relieved. Furthermore, isotonic saline is safer and more easily available than other chemical agents14,15. Several studies have also focused on the calf muscles to alleviate heel pain with manual therapy or stretching of the calf muscles17,18. However, to our knowledge, this is the first report of treatment of chronic heel pain by resolving NEP formed in the soleus.

There are several limitations to this report. First, this report included the clinical findings of only one patient. Second, NEP injection treatment was not compared with other treatments. Nevertheless, the fact that chronic pain of more than 5 years improved significantly with only a few injections suggests the importance of the concept of NEP in the treatment of pain.

This case report highlights releasing NEP in the soleus should be considered for chronic heel pain, including plantar fasciitis, especially when conservative treatment has failed. Excessive tension in the soleus muscle causes entrapment of the tibial nerve near the tendinous arch, which can irritate the medial calcaneal branch of ankle. Patients usually complain of the most severe tenderness at the central point within the muscle, and simple injection therapy into this area has a fundamental recovery effect.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Acknowledgments

The authors thank Ms. Hye-Sun Han for her invaluable technical assistance and contributions to the graphic design. This work was supported by the TongSa (Association of Pain and Function Analysis) Research Fund.

Author Contributions

Conceptualization: CJY, JWS. Funding acquisition: YK. Writing–original draft: CJY. Writing–review & editing: YK, DK.

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