Impact of Needle Diameter on Long-Term Dry Needling Treatment of Chronic Lumbar Myofascial Pain Syndrome

Lumbar myofascial pain syndrome (LMPS) is one of the leading causes of chronic pain, affecting approximately 95% of people with persistent pain disorders. Characterized by the presence of trigger points in muscles, fasciae, and tendinous insertions, this condition causes significant local pain and functional limitation. Dry needling has emerged as a promising therapy, based on the mechanical inactivation of trigger points through needle insertion without medications. This randomized controlled trial investigated a clinically relevant question: does needle diameter influence the therapeutic efficacy of dry needling?

The researchers recruited 48 patients with chronic LMPS (duration greater than 12 months) at the General Hospital of the Chinese People's Liberation Army, randomly dividing them into three groups. Group A received treatment with 0.25 mm diameter needles (traditional acupuncture needles), Group B with 0.5 mm needles, and Group C with special 0.9 mm needles. All participants had pain scores between 5 and 10 on the Visual Analog Scale (VAS) and underwent a single treatment session with 20 needles directed at the most sensitive lumbar trigger points. The protocol followed strict double-blinding criteria, with independent evaluators responsible for measurements before and after treatment.

Assessments were performed at baseline, 7 days, 1 month, and 3 months after treatment, using both the VAS and the SF-36 (Short Form Health Survey) questionnaire to measure health-related quality of life. The results revealed important findings about the relationship between needle diameter and therapeutic efficacy. All three groups demonstrated significant pain improvement over time, confirming the overall efficacy of dry needling in chronic LMPS. However, important differences emerged in the temporal analysis.

Groups A and B (0.25 mm and 0.5 mm needles) showed consistent improvement from the first 7 days, remaining stable through 3 months. Group C (0.9 mm needles) presented a different pattern: minimal improvement in the first week, followed by progressive and significant pain reduction at one and three months. At 3-month follow-up, Group C demonstrated statistically significant superiority over Group B (P = 0.047), with mean VAS scores of 2.16 versus 4.05, respectively. This finding suggests that thicker needles produce superior long-term therapeutic benefits, possibly due to greater mechanical inactivation of trigger points and stimulation of tissue repair processes.

The SF-36 analysis partially corroborated these results, showing improvement in quality of life across all groups, although without significant differences between them at 3 months. This finding may reflect the more comprehensive nature of the SF-36 questionnaire, which may be less sensitive to specific changes in pain intensity. A crucial aspect investigated was treatment tolerability. As expected, larger-diameter needles caused significantly more pain during the procedure (4.72 points on the VAS versus 1.37-1.45 in the other groups).

This difference directly impacted initial patient acceptance: only 33.3% of Group C patients were willing to repeat the treatment immediately after the session, compared with 87.5% and 100% in groups A and B, respectively. Interestingly, acceptance in Group C increased progressively throughout follow-up, reaching 80% at 3 months, likely reflecting recognition of the superior therapeutic benefits. The proposed mechanisms to explain the greater efficacy of thicker needles include: more complete inactivation of trigger points due to greater rigidity and targeting precision, more intense stimulation for activation of descending pain inhibition pathways, greater controlled tissue damage promoting more robust repair processes, and possible stimulation of local neovascularization. Study limitations include the absence of a control group (placebo or conventional treatment), a relatively small sample, specific focus on low back pain (limiting generalization), and evaluation of only three needle diameters.

Future studies should explore other diameters, different anatomical locations, and direct comparisons with other therapeutic modalities.