Elsevier

World Neurosurgery

Volume 104, August 2017, Pages 669-673
World Neurosurgery

Original Article
The Subcostal Nerve During Lateral Approaches to the Lumbar Spine: An Anatomical Study with Relevance for Injury Avoidance and Postoperative Complications Such as Abdominal Wall Hernia

https://doi.org/10.1016/j.wneu.2017.05.055Get rights and content

Background

Lateral approaches to the spine are increasing in popularity. However, details of the innervation pattern of the abdominal oblique muscles with the initial dissection have not been well studied.

Methods

Ten adult fresh-frozen cadavers (20 sides) were placed in the lateral position. On each side, the region in which transpsoas approaches are performed, between the iliac crest and the 12th rib, was dissected. The nerves, their course, and their muscular supply were studied.

Results

The subcostal nerve is the predominant nerve supply for the anterolateral abdominal muscle innervation. It is larger and has a wider field of distribution and more branches (8 on average) compared with the L1 (4 on average) and 11th intercostal nerves (2 on average 2). The proximal 6–10 cm of each nerve has few if any branches. The subcostal nerve is often (75%) located up to 5 cm inferior to the 12th rib in its initial course. The area of least concentration (“safe zone”) is located at an approximate midpoint between the lower edge of the 12th rib and the superior-most aspect of the iliac crest. A previously undescribed branch of the subcostal nerve was found traveling posterior to the quadratus lumborum and joining the remaining subcostal nerve in an anastomosis at or near the lateral position.

Conclusions

Knowledge of the innervation and nerve dominance patterns might help decrease postoperative complications such as sensory deficits or abdominal wall hernias. The subcostal nerve is the dominant nerve in both size and innervation of the oblique muscles in the lateral position, transpsoas approach.

Introduction

There has been a recent increase in minimally invasive spine surgery. One approach used is the lateral transpsoas approach, refined by Ozgur et al. in 2006.1 Intraoperative monitoring is used when accessing the space between the 12th rib and the iliac crest. Lumbar lateral interbody fusion procedures have gained popularity owing to several advantages, including low blood loss, preservation of the posterior musculature and ligamentous chain, and the ability to perform an extensive discectomy and placement of a large intervertebral graft across the apophyseal ring, leading to indirect decompression.2 As the use of lateral transpsoas approaches continues to increase, it is important for surgeons to be aware of procedural complications, such as postoperative nerve palsies.3

The corridor used to gain access to the retroperitoneal space during the lateral transpsoas approach lies between the 12th rib and the iliac crest, which is supplied primarily by the 11th intercostal and subcostal nerves, with lesser contributions from the 10th intercostal nerve and L1 nerve.4 Minimal access lateral spine exposure involves di2ssection through the abdominal musculature in addition to possible resection of the rib. However, details of the innervation pattern of the abdominal oblique muscles with the initial dissection for this procedure have not been well studied, particularly in relation to lateral abdominal hernias (Figure 1).

Most of the literature on iatrogenic abdominal wall pseudohernias resulting from lateral approaches has been derived from renal and thoracic approaches, where the visible defect may lead to emotional discomfort.5, 6, 7 Therefore, we conducted an anatomical study to study the innervation of the abdominal oblique musculature through a lateral transpsoas approach. We hypothesized that the 12th intercostal nerve provides most of the branches and is the dominant nerve for innervating the lateral abdominal wall between the iliac crest and 12th rib (i.e., the window for lateral approaches to the lumbar spine) in contrast to T11 and L1. Recognition of the most common innervation pattern should guide the surgeon in planning the safest possible surgical corridor and dissection technique.

Section snippets

Methods

Dissection of the lateral abdomen was performed on 10 adult fresh-frozen cadavers (20 sides), 5 males and 5 females, aged 77–92 years at the time of death. On each side, the region between the iliac crest and 12th rib was dissected, with close attention given to the nerves in this region, particularly to their course and muscular supply at the lateral position where transpsoas approaches are performed. The overlying skin, subcutaneous tissues, latissimus dorsi, and associated thoracolumbar

Results

In the lateral position, the subcostal nerve was found to be the predominant nerve in terms of abdominal oblique muscle innervation. It was the largest (average diameter, 6 mm) nerve in this region and had a wider field of distribution with more branches (8 on average) compared with the L1 (4 on average) and 11th intercostal nerves (2 on average) (Figures 2 and 3). L2 contributed only small branches to the lateral abdominal wall musculature on 2 sides. The average diameter of the L1 and L2

Discussion

The intercostal nerves are composed of 4 branches: muscular, collateral, lateral cutaneous, and anterior cutaneous. The collateral branch arises at the angle of the ribs and supplies the intercostal muscles and the parietal pleura as it courses closely with the subcostal vessels.8 The subcostal nerve, which we identified as the dominant nerve in the incision for a lateral transpsoas approach, travels with the subcostal vein and the artery in the inferior aspect of the 12th rib. Whereas the

Conclusion

Knowledge of the specific innervation and nerve dominance pattern for the lateral approach to the spine might help decrease postoperative complications, such as sensory deficits or abdominal wall hernias. The subcostal nerve is the dominant nerve in terms of both size and innervation of the oblique muscles in the lateral position approach.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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