BackgroundEntrapment of the superior cluneal nerve (SCN) in an osteofibrous tunnel has been reported as a cause of low back pain (LBP). However, there are few reports on the prevalence of SCN disorder and there are several reports only on favorable outcomes of treatment of SCN disorder on LBP. The purposes of this prospective study were to investigate the prevalence of SCN disorder and to characterize clinical manifestations of this clinical entity.MethodsA total of 834 patients suffering from LBP and/or leg symptoms were enrolled in this study. Diagnostic criteria for suspected SCN disorder were that the maximally tender point was on the posterior iliac crest 70 mm from the midline and that palpation of the tender point reproduced the chief complaint. When patients met both criteria, a nerve block injection was performed. At the initial evaluation, LBP and leg symptoms were assessed by visual analog scale (VAS) score. At 15 min and 1 week after the injection, VAS pain levels were recorded. If insufficient pain decrease or recurrence of pain was observed, injections were repeated weekly up to three times. Surgery was done under microscopy. Operative findings of the SCN and outcomes were recorded.ResultsOf the 834 patients, 113 (14%) met the criteria and were given nerve block injections. Of these, 54 (49%) had leg symptoms. Before injection, the mean VAS score was 68.6 ± 19.2 mm. At 1 week after injection, the mean VAS score significantly decreased to 45.2 ± 28.8 mm (p < 0.05). Ninety-six of the 113 patients (85%) experienced more than a 20 mm decrease of the VAS score following three injections and 77 patients (68%) experienced more than a 50% decrease in the VAS score. Surgery was performed in 19 patients who had intractable symptoms. Complete and almost complete relief of leg symptoms were obtained in five of these surgical patients.ConclusionsSCN disorder is not a rare clinical entity and should be considered as a cause of chronic LBP or leg pain. Approximately 50% of SCN disorder patients had leg symptoms.Electronic supplementary materialThe online version of this article (doi:10.1186/s13018-014-0139-7) contains supplementary material, which is available to authorized users.

ObjectEntrapment of the middle cluneal nerve (MCN) under the long posterior sacroiliac ligament (LPSL) is a possible, and underdiagnosed, cause of low-back and/or leg symptoms. To date, detailed anatomical studies of MCN entrapment are few. The purpose of this study was to ascertain, using cadavers, the relationship between the MCN and LPSL and to investigate MCN entrapment.MethodsA total of 30 hemipelves from 20 cadaveric donors (15 female, 5 male) designated for education or research, were studied by gross anatomical dissection. The age range of the donors at death was 71–101 years with a mean of 88 years. Branches of the MCN were identified under or over the gluteus maximus fascia caudal to the posterior superior iliac spine (PSIS) and traced laterally as far as their finest ramification. Special attention was paid to the relationship between the MCN and LPSL. The distance from the branch of the MCN to the PSIS and to the midline and the diameter of the MCN were measured.ResultsA total of 64 MCN branches were identified in the 30 hemipelves. Of 64 branches, 10 (16%) penetrated the LPSL. The average cephalocaudal distance from the PSIS to where the MCN penetrated the LPSL was 28.5±11.2 mm (9.1–53.7 mm). The distance from the midline was 36.0±6.4 mm (23.5–45.2 mm). The diameter of the MCN branch traversing the LPSL averaged 1.6±0.5 mm (0.5–3.1 mm). Four of the 10 branches penetrating the LPSL had obvious constriction under the ligament.ConclusionThis is the first anatomical study illustrating MCN entrapment. It is likely that MCN entrapment is not a rare clinical entity.

ObjectiveThe superior cluneal nerve (SCN) may become entrapped where it pierces the thoracolumbar fascia over the iliac crest; this can cause low back pain (LBP) and referred pain radiating into the posterior thigh, calf, and occasionally the foot, producing the condition known as “pseudo-sciatica.” Because the SCN was thought to be a cutaneous branch of the lumbar dorsal rami, originating from the dorsal roots of L1–L3, previous anatomical studies failed to explain why SCN causes “pseudo-sciatica”. The purpose of the present anatomical study was to better elucidate the anatomy and improve the understanding of “pseudo-sciatica” from SCN entrapment.Materials and methodsSCN branches were dissected from their origin to termination in subcutaneous tissue in 16 cadavers (5 male and 11 female) with a mean death age of 88 years (range 81–101 years). Special attention was paid to identify SCNs from their emergence from nerve roots and passage through the fascial attachment to the iliac crest.ResultsEighty-one SCN branches were identified originating from T12 to L5 nerve roots with 13 branches passing through the osteofibrous tunnel. These 13 branches originated from L3 (two sides), L4 (six sides), and L5 (five sides). Ten of the 13 branches showed macroscopic entrapment in the tunnel.ConclusionThe majority of SCNs at risk of nerve entrapment originated from the lower lumbar nerve. These anatomical results may explain why patients with SCN entrapment often evince leg pain or tingling that mimics sciatica.

Purpose Lumbar intra-spinal canal stenosis is characterized by leg pain that intensifies during walking and intermittent claudication, while leg pain at rest is a characteristic neurological symptom of lumbar disc herniation. Until now, a correlation between leg pain at rest and symptomatic foraminal stenosis has not been reported. This is a prospective and comparative study of unilateral leg pain from L5 nerve root compression due to spinal canal stenosis to determine clinical characteristics of lumbar foraminal stenosis. Methods Clinical and neurological findings were compared among 38 patients receiving L5-S1 transforaminal lumbar interbody fusion for L5-S1 foraminal stenosis (FS group) and 60 patients receiving L4-5 decompression or/ and fusion for L4-5 intra-spinal canal stenosis (CS group). Results The only significant difference between the FS and CS groups in demographic clinical data was leg pain at rest. The prevalence of leg pain was significantly higher in the FS group compared to the CS group (76 vs. 35 %). The visual analogue scale for leg pain at rest was also significantly higher in the FS group than in the CS group (6.6 ± 3.1 vs. 1.3 ± 1.9). Conclusions Leg pain at rest is characteristic of L5-S1 foraminal stenosis.

A large segmental range of motion in sagittal plane of L5-S1 and posterior instability of L5 are risk factors for symptomatic L5-S1 foraminal stenosis. These dynamic radiological findings support the diagnosis of symptomatic foraminal stenosis.