Enhancing diagnosis and treatment of superior cluneal nerve entrapment: cadaveric, clinical, and ultrasonographic insights

Abstract

Objectives: Low back pain is a prevalent public health issue caused by superior cluneal nerve (SCN) entrapment. This study aimed to explore the course of SCN branches, cross-sectional area (CSA) of the nerves, and effects of ultrasound-guided SCN hydrodissection.

Methods: SCN distance relative to the posterior superior iliac spines was measured and compared with ultrasound findings in asymptomatic volunteers. The CSA of the SCN, pressure-pain threshold, and pain measurements were obtained from asymptomatic controls and patients with SCN entrapment at various time points after hydrodissection (with 1 mL of 50% dextrose, 4 mL of 1% lidocaine, and 5 mL of 1% normal saline) in the short-axis view.

Results: Twenty sides of 10 formalin-fixed cadavers were dissected. The SCN locations on the iliac crest did not differ from the ultrasound findings in 30 asymptomatic volunteers. The average CSA of the SCN across different branches and sites ranged between 4.69-5.67 mm2 and did not vary across different segments/branches or pain statuses. Initial treatment success was observed in 77.7% (n = 28) of 36 patients receiving hydrodissection due to SCN entrapment. A group with initial treatment success experienced symptom recurrence in 25% (n = 7) of cases, and those with recurrent pain had a higher prevalence of scoliosis than those without symptom recurrence.

Conclusions: Ultrasonography effectively localizes SCN branches on the iliac crest, whereby increased nerve CSA is not useful for diagnosis. Most patients benefit from ultrasound-guided dextrose hydrodissection; however, those with scoliosis may experience symptom recurrence and whether structured rehabilitation can reduce recurrence post-injection should be considered as one perspective in future research. Trial registration ClinicalTrials.gov (NCT04478344). Registered on 20 July 2020, https://ichgcp.net/clinical-trials-registry/NCT04478344?cond=Superior+Cluneal+Nerve&cntry=TW&draw=2&rank=1 . Critical relevance statement Ultrasound imaging accurately locates SCN branches on the iliac crest, while enlargement of the CSA is not useful in diagnosing SCN entrapment; however, approximately 80% of SCN entrapment cases respond positively to ultrasound-guided dextrose hydrodissection.

Keywords: Dextrose; Hydro-dissection; Low back pain; Neuropathy; Sonography.

Conflict of interest statement

No conflicts of interest have been reported by the authors or by any individual in control of the content of this article.

© 2023. The Author(s).

Figures

Fig. 1

Flow diagram of the cadaveric study (track 1), human volunteer study (track 2) and clinical trial (track 3) of ultrasound (US) guided injection for the superior cluneal nerves (SCN). PSIS, posterior superior iliac spine; CSA, cross-sectional area; PTT, pain pressure threshold; VAS, visual analogue scale of pain; ODI, Oswestry Disability Index

Fig. 2

A A, B, C and D inside the squares correspond to probe positioning for the subgraphs of A, B, C and D for scanning of the superior cluneal nerves (yellow lines and black arrowheads). B The probe is placed in the horizontal plane over the posterior superior iliac spine (PSIS) and (C) is then relocated more cranially to see the medial branch of the superior cluneal nerve embedded underneath the thoracolumbar fascia (white dashed line). D Moving the probe more cranially, the superior cluneal nerve is seen over the erector spinae muscle. E Shifting the probe more laterally, the three branches of the superior clunear nerve are identified along the posterior iliac crest (PIC). F Ultrasound guided hydrodissection is performed for the superior cluneal nerves using the in-plane, medial-to-lateral approach. MU, multifidus; GMAX, gluteus maximus; LO, longissimus; IC, iliocostalis; arrows, needle trajectory

Fig. 3

A The medial branch of the superior cluneal nerve was stained by methylene blue following ultrasound guided injection on the cadavers. B The distance between the superior cluneal nerves over the iliac crest (white dots) and the posterior superior iliac spine (green dot) was measured along the horizontal and vertical axes (dashed lines)

Fig. 4

The mean value and 95% confidence interval of the distance between the superior cluneal nerves over the iliac crest and the posterior superior iliac spine on the (A) horizontal and (B) vertical axes. C., cadaver; V., asymptomatic volunteers; Rt., right; Lt., left; M., medial branch; I., intermediate branch; L., lateral branch; X., horizontal axis; Y., vertical axis

Fig. 5

A Visual analogue scale of pain and (B) Oswestry Disability Index at baseline, post-injection 1st and 3rd months for each group. Group 1, who did not respond to the initial treatment; Group 2, who initially responded to treatment but experienced symptom recurrence; and Group 3, who responded well to treatment and did not experience symptom recurrence