Spinal Radiology associated with Redundant Nerve Roots of cauda equina in lumbar spine stenosis

OBJECTIVES

Redundant Nerve Roots (RNR) is a common radiological observation of elongated tortuous appearance of cauda equina nerve roots in sagittal MRI. It is considered a poor prognostic factor, but the associated spinal morphometry remains unfamiliar.

METHODS

A retrospective cohort study was conducted at the Aga Khan University Hospital, Pakistan. Patients, aged 18 or above, undergoing decompressive spinal surgery due to degenerative Lumbar Spinal Canal Stenosis (LSCS) in 2015 were included. Patients were divided in groups as per presence of RNR and assessed for spinal morphometric parameters.

RESULTS

Fifty-two patients, aged 57.52 ± 12.08 years, were enrolled in the study. The patients in RNR group were older than those in non-RNR group (p = 0.023). RNR was significantly associated with sedimentation sign (15 vs 11; p = 0.011), as well as L2/L3 (12 vs 9; p = 0.043) and L3/L4 (18 vs 18; p = 0.034) stenosis. Ligamentum flavum hypertrophy at the most stenotic level was more common in the RNR group (20 vs 19; p = 0.006). The only quantitative parameter statistically associated with RNR was lower ligamentous interfacet distance (5.07 ± 1.95 vs 8.07 ± 4.26 mm; p = 0.010). All other parameters did not contribute to the development of RNR in LSCS patients. The multivariate model revealed significant contribution of age, male sex, ligamentous interfacet distance and disc bulge to develop RNR.

CONCLUSION

Certain spinal morphometric parameters contribute towards RNR formation, which represents higher degree of spinal stenosis. These parameters, along with RNR, should be regularly reported for preoperative consideration of LSCS management.

Comprehensive Anatomic and Morphometric Analyses of Triangular Working Zone for Transforaminal Endoscopic Approach in Lumbar Spine: A Fresh Cadaveric Study

OBJECTIVE

The aim of this study is to provide essential information for endoscopic transforaminal approach by performing morphometric analysis of the triangular working zone (TWZ) in fresh cadavers.

METHODS

Fifteen fresh human cadavers (9 women and 6 men) with no history of spinal surgery were used in this study. Anatomic dissection of 150 foraminal levels were performed. Significant surgical landmarks constructing TWZ were measured bilaterally from L1-2 to L5-S1 on 15 fresh cadavers. The relationship between traversing roots and intervertebral discs was defined.

RESULTS

Base, height, and hypotenuse measurements of TWZ were longer as the level lowered. Mean base height and hypotenuse of TWZ were 12.15 mm, 11.29 mm, and 16.69 mm (L1-2); 17.94 mm, 17.18 mm, and 28.03 mm (L5-S1), respectively. TWZ was triangular shaped at the upper lumbar levels (L1-2, L2-3, and L3-4), and trapezoid at the lower lumbar levels (L4-5 and L5-S1). Going down the levels, the exiting root angle was narrower, the mean exiting angle of the L5 root being 28.23°. All L2 and L3 traversing roots and nearly all L4 traversing roots (86.7%) originated from below the disc level. Forty percent of L5 traversing roots originated above the disc level, and 53.3% originated at the disc level. Most S1 traversing roots originated at the proximal margin of the disc level (80%).

CONCLUSIONS

Our study reveals a detailed morphometric analysis of TWZ. Understanding the foraminal anatomy is crucial for safely performing transforaminal endoscopic surgery. The learning curve of transforaminal surgery can be reduced by garnering knowledge of TWZ anatomy.