This study is designed to evaluate a method to improve the treatment of myofascial pain syndrome (MPS), a common condition that causes muscle pain, tenderness, and reduced movement due to the presence of trigger points in muscles.

A commonly used treatment for this condition is the injection of a local anesthetic called lidocaine into these trigger points to relieve pain. However, the pain relief from lidocaine alone may be temporary.

In this study, we are investigating whether adding a small amount of sodium bicarbonate to lidocaine can improve its effectiveness. Sodium bicarbonate may reduce the pain during injection and help the anesthetic work faster and possibly last longer.

Participants in this study will be randomly assigned into one of two groups:

One group will receive lidocaine alone. The other group will receive lidocaine mixed with sodium bicarbonate.

The injection will be performed once into the painful muscle trigger points under sterile conditions.

Pain levels will be assessed using a simple pain scale, and muscle activity will be measured using a non-invasive technique called surface electromyography (sEMG), which records muscle electrical activity. These measurements will be taken before the injection, immediately after, and during follow-up visits.

Participants may experience mild discomfort during or after the injection, but all procedures are routinely used in clinical practice. Safety measures will be in place to manage any possible side effects.

The goal of this study is to determine whether the combined injection provides better pain relief, improves muscle function, and enhances patient comfort compared to lidocaine alone.

Study Overview

This study is a randomized, parallel-group, single-blind clinical trial designed to evaluate the clinical effectiveness of adding sodium bicarbonate to lidocaine in the treatment of myofascial pain syndrome (MPS). The study compares outcomes between lidocaine alone and buffered lidocaine using surface electromyography (sEMG) and pain assessment tools.

Background

Myofascial pain syndrome is a prevalent musculoskeletal disorder characterized by the presence of myofascial trigger points, leading to localized or referred pain, functional limitation, and reduced quality of life. Although trigger point injections with lidocaine are widely used and provide rapid pain relief, their effects are often temporary and may require repeated administration.

Buffered lidocaine, achieved by adding sodium bicarbonate, has been proposed to enhance anesthetic performance by increasing the pH of the solution. This increases the proportion of the non-ionized form of lidocaine, facilitating faster onset of action, improved tissue penetration, and reduced pain during injection. However, its role in managing MPS has not been sufficiently established.

Rationale

There is currently no consensus regarding the optimal injectable solution for trigger point therapy. This study aims to determine whether buffering lidocaine with sodium bicarbonate improves clinical outcomes in terms of pain reduction, patient comfort, and muscle function compared to lidocaine alone.

Objectives

The primary objective is to evaluate the effect of adding sodium bicarbonate to lidocaine on pain reduction in patients with myofascial pain syndrome.

Secondary objectives include:

Assessing pain experienced during injection Evaluating changes in muscle activation patterns and functional recovery Study Design Type: Randomized controlled clinical trial Design: Parallel, two-arm Allocation ratio: 1:1 Blinding: Single-blind (participants blinded) Framework: Superiority Participants

Participants will be recruited from outpatient clinics of the Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Cairo University.

Eligible participants include patients diagnosed with myofascial pain syndrome presenting with active trigger points and moderate to severe pain.

Interventions

Participants will be randomly assigned into two groups:

Control Group: Injection with 2% lidocaine alone Intervention Group: Injection with 2% lidocaine buffered with sodium bicarbonate (8.4%)

The buffered solution will be freshly prepared immediately prior to injection under aseptic conditions.

All injections will be administered into identified trigger points using a standardized technique.

Outcome Measures Primary Outcome

Pain reduction assessed using:

Visual Analog Scale (VAS) Surface electromyography (sEMG) Secondary Outcome Pain during injection (VAS) Tertiary Outcome Changes in muscle activation during voluntary contraction (sEMG)

Assessments will be conducted at baseline, immediately after injection, and at follow-up visits.

Safety Considerations

All procedures will follow strict aseptic protocols. Patients will be monitored immediately after injection for any adverse reactions.

Possible risks include:

Pain at injection site Vasovagal reactions Local tissue injury Rare allergic reactions

Risk mitigation measures include proper injection technique, dose calculation, aspiration before injection, and availability of emergency equipment.

Data Collection and Analysis

Data will be collected using standardized forms and stored securely. Statistical analysis will be performed to compare outcomes between both groups, with significance set at p ≤ 0.05.

Ethical Considerations

The study will be conducted following ethical guidelines and will require approval from the institutional ethics committee. Written informed consent will be obtained from all participants prior to enrollment. Participant confidentiality will be strictly maintained.

Expected Impact

This study aims to provide evidence on whether buffering lidocaine with sodium bicarbonate improves treatment outcomes in myofascial pain syndrome. The findings may help guide clinical practice toward more effective and comfortable treatment options.

Inclusion Criteria:

Patients aged 16 to 70 years Clinical diagnosis of myofascial pain syndrome (MPS) Presence of active myofascial trigger points Pain duration ≥ 3 months Pain intensity ≥ 4 on the Visual Analog Scale (VAS) Trigger points located in accessible muscles No trigger point injection in the affected area within the past 3 months Ability and willingness to provide informed consent Willingness to comply with study procedures and follow-up visits

Exclusion Criteria:

Known allergy or hypersensitivity to lidocaine, sodium bicarbonate, or other amide-type local anesthetics Current use of anticoagulants or presence of bleeding disorders Local or systemic infection at or near the injection site History of fibromyalgia, cancer-related pain, or central pain syndromes Major psychiatric disorders (e.g., schizophrenia, severe depression) Recent trauma or surgery to the neck, shoulder, or back within the past 6 months Use of analgesics (e.g., NSAIDs, opioids) within 5 days prior to injection Severe systemic diseases (e.g., uncontrolled diabetes, liver failure, kidney failure, severe cardiovascular disease)

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This is a single-blind study in which participants are unaware of their group allocation. The operator administering the injection and the outcome assessor are not blinded due to the nature of the intervention and preparation of the buffered solution. Participants are not informed whether they receive lidocaine alone or lidocaine combined with sodium bicarbonate.