Background and rationale

Low back pain (LBP) is among the most prevalent musculoskeletal disorders; further, it is a major cause of activity limitation and disability, which imposes a substantial socioeconomic burden [1]. Most acute episodes of LBP subsequently improve; however, a considerable proportion of cases progress to non-acute or chronic LBP [2], which represents a major challenge in modern medicine. Conservative treatments include pharmacologic, physical, and injection therapies; however, they often have limited long-term effectiveness and may involve adverse effects. Accordingly, there is increasing demand for more effective and safer non-pharmacologic treatments [3].

There has been increasing interest in manual therapy as a crucial non-pharmacologic treatment for patients with non-acute and chronic LBP. Manual therapy includes spinal manipulation, joint mobilization, and soft tissue techniques; further, it has demonstrated beneficial effects in patients with chronic LBP [4,5]. Specifically, manual therapy has been shown to restore abnormal joint motion, relieve tension in surrounding muscles, and induce neurophysiological changes contributing to therapeutic effects [6,7].

Chuna manual therapy is a traditional Korean modality in which doctors use their hands, body, or auxiliary tools to push or pull the patient’s spine, joints, and muscles for correction of structural and functional problems. It has demonstrated clinical effectiveness and safety; further it is covered under the Korean national health insurance system for spinal disorders [8,9]. Specifically, Chuna manual therapy acts along meridian pathways to correct structural malpositions and exert therapeutic effects across various diseases, especially through pain reduction and functional improvement in musculoskeletal disorders [8,10].

In Chuna manual therapy, the diagnosis is based on both symptoms and the underlying structural cause of pain. Korean medicine doctors diagnose spinal malposition using palpation and radiographic imaging, followed by application of the appropriate Chuna manual therapy. In Chuna medicine, radiograph-based diagnosis has higher inter-rater and intra-rater agreement and diagnostic efficiency than palpation alone [11]. Additionally, quantitative radiographic angle measurements have been applied to determine malposition targets for Chuna manual therapy [12]. However, there remains limited clinical evidence regarding whether radiograph-based malposition diagnosis contributes to treatment effectiveness and functional improvement. Accordingly, this study will aim to evaluate the superiority and safety of a treatment intervention based on radiograph-based Chuna diagnosis.

Objectives

The primary study objective is to evaluate the clinical effectiveness and safety of Chuna manual therapy guided by radiograph-based malposition diagnosis. We hypothesize that, among patients with non-acute LBP who demonstrate spinal malposition on plain radiographs, the addition of Chuna manual therapy to usual care (physical therapy, exercise, and lifestyle guidance) will yield superior pain reduction and functional improvement compared with usual care alone.

Trial design

This will be a multicenter, two-arm, parallel-group, assessor-blind, randomized controlled trial. Patients with non-acute LBP for ≥3 weeks will undergo standardized L-spine standing anteroposterior and lateral radiography to determine the presence or absence of malposition based on the Chuna manual therapy diagnostic criteria [12,13] (S1 Checklist). Inter-rater reliability of the radiograph-based malposition diagnosis has been previously evaluated using the same diagnostic criteria and trained assessors [11,12]. Because the assessors involved in the prior reliability study will continue to participate in the present trial, an additional formal inter-rater reliability assessment has not been planned. Participants who have malposition and meet the relevant criteria will be randomly assigned in a 1:1 ratio to the usual care plus Chuna manual therapy intervention group (Group I) or the usual care intervention group (Group II). The study period will comprise screening, a 4-week treatment period, and an 8-week follow-up period. This protocol has been developed in accordance with the SPIRIT guidelines, and the schedule of enrolment, interventions, and assessments is summarized in the SPIRIT schedule (Table 1). The anticipated flow of participants through screening, randomization, allocation, follow-up, and analysis is illustrated in the CONSORT flow diagram (Fig 1).

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Table 1. SPIRIT schedule.

https://doi.org/10.1371/journal.pone.0347321.t001

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Fig 1. Flow chart of the study CONSORT Flow Diagram.

https://doi.org/10.1371/journal.pone.0347321.g001

Protocol version and identifier: Version 1.1, dated June 04, 2025; Protocol ID: Chuna-RCT-V1.0.

Ethical considerations

1. • This study will be conducted in accordance with the ethical principles of the Declaration of Helsinki and Korean Good Clinical Practice. The protocol has been reviewed and approved by the Institutional Review Board of each participating institution: Catholic Kwandong University International St. Mary’s Hospital (IRB No. IS25EIMI0027; approval date: 12 May 2025) and Wonkwang University Korean Medicine Hospital (IRB No. 2025−06; approval date: 1 October 2025). All participants will be fully informed about the study purpose, procedures, potential risks and benefits, and written informed consent will be obtained before any study-related procedures are performed.
2. • Participants who require evaluation or treatment for worsening low back pain or trial-related adverse effects during or after trial completion will receive appropriate care at the study institutions in accordance with institutional policies. Participants may return for assessment at any time per the investigator’s instruction to monitor for delayed adverse events.
3. • Medical expenses for injuries or harms considered related to trial participation will be covered in accordance with the trial insurance contract and institutional policies. Procedures for reporting, evaluating, and compensating trial-related harms will follow the terms of the insurance and applicable regulations.

Participants, interventions, and outcomes

Eligibility criteria

Inclusion criteria:

• Adults aged 19–70 years
• Patients with non-acute LBP for ≥ 3 weeks with an average Numeric Rating Scale (NRS) score ≥4 over the past week
• Patients with a radiograph-based diagnosis of malposition
• Participants who voluntarily provided written informed consent

Exclusion criteria:

1. • Patients diagnosed with serious specific conditions that may cause LBP, including spinal tumor metastasis, acute fracture or dislocation, or moderate-to-severe scoliosis
2. • Patients with structural abnormalities of the lumbar spine (e.g., sacralization or lumbarization), a history of osteoporosis, or suspected fracture
3. • Patients who have undergone lumbar surgery within the past 3 months
4. • Patients with other chronic diseases that may interfere with treatment effects or result interpretation (including chronic renal failure)
5. • Patients with progressive neurologic deficits or severe neurologic symptoms, including cauda equina syndrome
6. • Patients with internal fixation or stabilizing devices from previous lumbar surgery
7. • Patients with contraindications to interferential current therapy (ICT), including cancer-related pain or implanted pacemaker
8. • Patients currently taking steroids, immunosuppressants, psychiatric medications, or other medications that could affect study outcomes
9. • Patients who have received Chuna manual therapy, strong opioid analgesics, anesthetic drugs, or other invasive treatments (including acupuncture or injections) within the past week
10. • Patients who have undergone lumbar nerve block procedures within the past 2 months
11. • Patients who are pregnant, breastfeeding, or planning pregnancy
12. • Patients expected to undergo surgery, procedures, or treatments that may influence outcome assessment during the 4-week intervention period
13. • Individuals considered inappropriate for trial participation at the discretion of the investigators

Discontinuation and withdrawal criteria

1. • Participants are not allowed to take the following medications during the study period:
   1. ◦ Strong opioid analgesics or local anesthetics outside the study clinician’s prescription. However, non-steroidal anti-inflammatory drugs, muscle relaxants, and other medications prescribed as needed may be permitted based on the clinician’s judgment(See Concomitant care and rescue medication below)
   2. ◦ Any other medication considered by the study clinician to pose a risk to the patient or influence the study outcomes
2. • Participants who request discontinuation of the intervention or withdraw their consent to trial participation
3. • Occurrence of a serious adverse event that is considered by the investigator as sufficient grounds for discontinuation
4. • Identification of a major protocol violation during the trial, including a newly discovered violation of inclusion or exclusion criteria
5. • Participants who fail to attend at least 5 of the 8 scheduled treatment sessions
6. • Any other circumstance considered by the principal investigator or study clinician as sufficient grounds for trial discontinuation

Early treatment criteria

• If a participant’s symptoms improve during the trial and they request discontinuation, with the study clinician determining that further intervention is unnecessary. Participants who are terminated early for this reason will not be classified as discontinuation or dropout cases and will be considered fully compliant with treatment.

Interventions

Control group (Group II: usual care intervention)

Participants in the control group will only receive usual care. Usual care will comprise ICT, exercise guidance, and lifestyle education, which will be provided twice per week for 4 weeks. This group will not receive Chuna manual therapy.

Rescue medication

From the screening visit onward, if intolerable pain occurs, the study investigator may allow the use of non-opioid rescue medications—specifically limited Non-steroidal anti-inflammatory drugs (NSAIDs) and skeletal muscle relaxants—while opioid analgesics and anesthetics are prohibited. To reduce adverse effects associated with rescue medication, gastroprotective agents may be co-administered. Whenever rescue medication is taken, the date and dose must be recorded in the Case Report Form (CRF)

Permitted classes of rescue medication Skeletal muscle relaxants, Anticonvulsants, NSAIDs, non-opioid analgesics, Agents for neuropathic pain, Antidepressants, Antipyretics, Weak opioids, Gastroprotective agents

Outcomes

Sample size calculation

The sample size for this study was calculated based on Cohen’s effect size derived from previously reported results [17]. In the prior study, the LBP NRS scores in the experimental and control groups were 3.02 ± 1.72 and 1.36 ± 1.75 (p < 0.001), respectively. Based on these values, the calculated effect size (Cohen’s d) was 0.96. Using a two-tailed test with a significance level (α) of 0.05 and 80 percent power (β), the following formula was applied: Here, Zα/2 is 1.96 for a two-tailed test at α = 0.05, and Zβ is 0.84 for 80 percent power. Based on this calculation, a minimum of 18 participants per group would be required. Anticipating a dropout rate of 20%, the final sample size was set at 23 participants per group, yielding a total of 46 participants.

Recruitment

Participants will be recruited through advertisements approved by the Institutional Review Boards (IRBs) of each center. Recruitment notices will be posted on bulletin boards and in outpatient clinics within each center.

Randomization and blinding

Data collection and management

All data will be recorded in electronic Case Report Forms. Regular monitoring will be conducted to verify data accuracy and completeness. Data management will comply with IRB policies and regulatory requirements. All data will be anonymized to protect personal information.

Statistical methods

Primary analyses will follow the intention-to-treat principle using the full analysis set (FAS), defined as all randomized participants with at least one post-baseline efficacy assessment and analyzed according to assigned groups. The per-protocol set (PPS), defined as participants without major protocol deviations who complete the primary endpoint, will be used for supportive analyses. The safety set will include all participants who receive ≥1 session of the allocated intervention.

Demographic and baseline characteristics will be summarized using descriptive statistics. Continuous variables will be presented as mean ± standard deviation or median and interquartile range depending on the normality of data distribution. Categorical variables will be presented as frequency and percentage. Between-group comparisons of continuous variables will be performed using the independent t test or Wilcoxon rank sum test. Between-group comparisons of categorical variables will be conducted using the chi-square test or Fisher’s exact test. The full analysis set will be the primary analysis population, while the per protocol set will be used as a supportive analysis.

All statistical tests will be two-tailed with a significance level of 5%; further, two-sided 95% confidence intervals will be presented. The primary efficacy outcome will be the change in the LBP NRS score from baseline. Within-group comparisons will be performed using the paired t test or Wilcoxon signed rank test. Between-group comparisons will be performed using an analysis of covariance model, with the baseline NRS score as a covariate. Here, we will report the least square mean difference, 95% confidence interval, and p-value.

Secondary efficacy outcomes will include changes in the NRS score for leg pain, ODI, EQ-5D, and RMDQ from baseline. These will be analyzed using the same approach as the primary outcome. Exploratory effectiveness outcomes include the rate of additional invasive procedures or surgery and the rate of early treatment termination. Between-group comparisons for proportions will be conducted using the chi-square test or Fisher’s exact test. Between-group comparisons of the rescue medication type and frequency will be performed using the independent t test or Wilcoxon signed rank test. Treatment responders will be defined as participants with a ≥ 2 reduction in the NRS score from baseline, which represents the minimal clinically important difference. Appropriate post hoc analyses will be conducted based on the responder group.

Primary analyses will use the FAS, with PPS analyses as supportive. For continuous outcomes in the FAS, missing data will be handled using a mixed model for repeated measures (MMRM), which uses all available repeated-measures data without ad hoc imputation. The primary analysis will be conducted under the missing-at-random (MAR) assumption, while non-continuous outcomes will be analyzed without imputation. Sensitivity analyses will include complete-case analyses and responder analyses to assess robustness; responders are defined a priori as participants with a ≥ 2-point reduction in LBP NRS from baseline. In addition, sensitivity analyses under alternative missing-data assumptions (e.g., multiple imputation with delta adjustment) will be performed to assess the robustness to potential departures from the MAR assumption.

Safety evaluation will include descriptive statistics for the number of adverse events, number of participants experiencing adverse events, severity, and causality; additionally, non-parametric methods may be applied if necessary. Statistical analyses for this study will be performed after study completion. An interim analysis is not planned for this study

Trial status

This manuscript is based on protocol version 1.1, dated June 04, 2025. Participant recruitment began on August 26, 2025 and the trial is currently ongoing. Study interventions are being delivered according to the protocol, but no data have yet been analyzed. Recruitment and follow-up are expected to be completed by approximately June 30, 2026.

Core significance of this study: evaluation of the clinical validity of diagnostic concepts

The diagnostic concept of “radiographic malposition” investigated in this study should be interpreted within the biopsychosocial (BPS) model, which is widely used in contemporary low back pain management. While previous clinical studies have primarily focused on the overall effectiveness of Chuna manual therapy [17], the clinical validity of the underlying diagnostic concepts used in manual medicine remains controversial [18].

The study aimed not to replace existing clinical guidelines but provide complementary data that may enhance therapeutic precision by quantifying radiographic alignment features using objective criteria, which are often not addressed in detail by standard protocols. We propose that “malposition” should be viewed not as a fixed pathological deformity, but as a potential biomechanical marker reflecting the patient’s structural stress that may help inform standardized decisions about the direction and intensity of Chuna interventions.

By visualizing and quantifying individual biomechanical imbalances through objective digital markers, this study seeks to strengthen the assessment within the “biological” domain of the BPS model by incorporating quantifiable biomechanical measures. This approach is particularly significant given that recent guidelines often caution against over-interpreting static structural deviations due to their sometimes weak correlation with subjective clinical symptoms [19]. Ultimately, by observing the correlation between structural alignment changes and subjective clinical improvement (NRS), we aim to explore how structural alignment changes relate to clinical improvement and provide complementary evidence to support the scientific basis of Chuna manual therapy within an integrated pain management context.

Efforts to ensure objectivity through standardized procedures

Another strength of this study is the active use of SOPs to improve reliability. In the diagnostic process, standardized radiographic positioning and diagnostic methods based on prior research and expert consensus will be applied. Similarly, standardized Chuna techniques based on the malposition type have been pre-specified in the protocol. By applying SOPs for both diagnosis and treatment, this will minimize bias and maximize reproducibility, which is a common challenge in clinical research regarding manual therapies. These procedures are expected to serve as foundational data for developing clinical guidelines and education in Chuna manual therapy.

Clinical implications and future directions

The findings of this study will highlight the potential of “personalized manual therapy” for LBP. Rather than applying uniform treatment to all patients, individualized treatment effects will be verified based on radiograph-based subgroup classification, which may improve both patient satisfaction and adherence. Furthermore, by adopting a practical clinical research model in which Chuna manual therapy is provided as an add-on to clinically validated usual care, our findings may serve as key clinical evidence for expanding the scope of health insurance coverage for Chuna manual therapy from treatment to diagnostic application.

Limitations

Despite these strengths, this study has inherent limitations. First, this study was designed as a pragmatic trial to evaluate the “add-on” effectiveness of Chuna manual therapy in a real-world clinical setting. Consequently, we did not employ a sham control group, which may introduce performance bias or expectation effects on the primary outcome, the NRS score. Consequently, non-specific effects (e.g., additional time, physical touch, and patient–provider interaction) cannot be fully separated from the specific effects of Chuna manual therapy. Establishing a validated “inactive” sham for manual therapy is technically challenging, and in the South Korean medical context—where Chuna manual therapy is a highly familiar, insurance-covered treatment—an imperfect sham could lead to unintentional unblinding and high dropout rates. To mitigate these inherent limitations of a pragmatic design, we incorporated objective radiographic markers (radiographic malposition) as key secondary outcomes. Unlike self-reported pain scores, these structural spinal alignments are less susceptible to placebo effects, providing more reliable evidence regarding the specific therapeutic mechanisms of Chuna manual therapy. Second, the relatively short intervention (4 weeks) and follow-up (8 weeks) periods may be insufficient for evaluating long-term effects. Third, although standardized positioning will be used to minimize error, radiographs represent only a static structural alignment and may not fully reflect three-dimensional spinal configuration or dynamic functional aspects. Fourth, although Chuna manual therapy can be applied to the spine and extremities in clinical practice, this study is limited to the lumbar spine; therefore, it will not evaluate the full diagnostic or therapeutic scope of Chuna manual therapy. Lastly, the protocol involves three radiographic assessments to monitor structural changes, which is more frequent than that in routine clinical practice for low back pain. While this frequency was necessary to investigate the therapeutic mechanisms of Chuna manual therapy, it presents a practical burden and potential ethical considerations regarding cumulative radiation exposure. Future studies should consider optimizing the number of imaging sessions or exploring low-dose protocols to balance diagnostic need with patient safety.

Quality control and data monitoring

To enhance study quality, independent monitoring will be conducted by the Clinical Trial Center of Kyung Hee University Korean Medicine Hospital, which is independent from the study institutions and research team. Throughout the study period, the CRO will oversee management of all trial-related files (case report forms, informed consent forms, adverse event reports) and perform regular monitoring to ensure compliance with the study protocol.

Trial registration and protocol access

This study was publicly registered before initiation through the Clinical Research Information Service (CRIS) of the Korea Disease Control and Prevention Agency (https://cris.nih.go.kr/) to ensure transparency and prevent publication bias (Registration number: KCT0011042). The registered protocol is accessible to the public through the CRIS website. Any major protocol amendments during the study will be approved by the IRB and updated in CRIS.

Dissemination

The study results will be submitted for publication in peer-reviewed academic journals and presented at national and international academic conferences.