Anatomical etiology of "pseudo-sciatica" from superior cluneal nerve entrapment: a laboratory investigation.

OBJECTIVE: The 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 METHODS: SCN 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. RESULTS: Eighty-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. CONCLUSION: The 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.

Prospective study of superior cluneal nerve disorder as a potential cause of low back pain and leg symptoms.

BACKGROUND: Entrapment 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. METHODS: A 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. RESULTS: Of 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. CONCLUSIONS: SCN 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.

Anatomical study of superior cluneal nerve entrapment.

OBJECT: Entrapment of the superior cluneal nerve (SCN) in an osteofibrous tunnel in the space surrounded by the iliac crest and the thoracolumbar fascia is a cause of low-back pain (LBP). Several anatomical and surgical reports describe SCN entrapment as a cause of LBP, and a recent clinical study reported that patients with suspected SCN disorder constitute approximately 10% of the patients suffering from LBP and/or leg symptoms. However, a detailed anatomical study of SCN entrapment is rare. The purpose of this study was to investigate the courses of SCN branches and to ascertain the frequency of SCN entrapment. METHODS: Branches of the SCN were dissected in 109 usable specimens (54 on the right side and 55 on the left side) obtained in 59 formalin-preserved cadavers (average age at death 84.8 years old). All branches were exposed at the points where they perforated the thoracolumbar fascia. The presence or absence of an osteofibrous tunnel was ascertained and, if present, the entrapment of the branches in the tunnel was determined. RESULTS: Of 109 specimens, 61 (56%) had at least 1 branch running through an osteofibrous tunnel. Forty-two medial (39%), 30 intermediate (28%), and 14 lateral (13%) SCN branches passed through such a tunnel. Of these, only 2 medial branches had obvious entrapment in an osteofibrous tunnel. There were several patterns for the SCN course through the tunnel: medial branch only (n = 25), intermediate branch only (n = 11), lateral branch only (n = 4), medial and intermediate branches (n = 11), medial and lateral branches (n = 2), intermediate and lateral branches (n = 4), and all branches (n = 4). CONCLUSIONS: Several anatomical variations of the running patterns of SCN branches were detected. Entrapment was seen only in the medial branches. Although obvious entrapment of the SCN is rare, it may cause LBP.

Optimal arm position for evaluation of spinal sagittal balance.

STUDY DESIGN: Analysis of sagittal vertical axis (SVA) on lateral spine radiographs in healthy normal volunteers. OBJECTIVES: To determine the optimal arm position with the smallest negative shift in SVA. SUMMARY OF BACKGROUND DATA: Radiographic visualization of spinal and pelvic sagittal morphology is difficult with the participant in a relaxed standing position because of interference from the arms. Standing with shoulder flexion (SF) results in a negative shift in SVA. The fists-on-clavicles (FC) position reduces the negative shift in SVA seen in SF, but only by 25%. The best arm position to produce the smallest negative shift in SVA has yet to be determined. METHODS: The SVA was measured using standing lateral radiographs of 21 healthy participants. Five different arm positions were used: relaxed with arms at sides (RLX), arms flexed to 45 degrees (SF), FC, arms folded across the chest (FA), and arms relaxed in front with hands loosely clasped (FHC). Negative shifts in SVA resulting from the SF, FC, FA, and FHC arm positions were compared. RESULTS: The mean SVA with RLX was 2.3±2.0 cm. The other arm positions resulted in a significant negative SVA shift compared with RLX (P<0.001). Mean negative shifts were -5.1±1.6 cm for SF, -3.9±1.5 cm for FC, -3.1±1.1 cm for FA, and -1.8±1.7 cm for FHC. The FC position reduced negative SVA shift seen in the SF arm position by 24%, FA by 39%, and FHC by 65%. The FHC position resulted in a significantly reduced SVA negative shift (P<0.001) compared with the FC, FA, and SF positions. CONCLUSION: FHC that produced the least negative shift in SVA, is the best arm position for SVA measurement.