Avoiding abdominal flank bulge after anterolateral approaches to the thoracolumbar spine: cadaveric study and electrophysiological investigation

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The thoracolumbar junction is frequently accessed through an anterolateral approach with the incision and muscle dissection extending from the lower thoracic region to the lateral border of the rectus abdominis muscle. This approach is frequently associated with the subsequent development of an unsightly and uncomfortable relaxation of the ipsilateral abdominal wall, or flank bulge, caused by denervation injury to the intercostal nerves. However, the etiology of this complication is not widely recognized by spine surgeons. The object of this study was to better define the relevant anatomy and innervation of the anterolateral abdominal wall musculature.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors performed 32 cadaveric dissections and 6 intraoperative electromyography (EMG) evaluations.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The cadaveric dissection studies and intraoperative EMG evaluations provided detailed anatomy of the anterolateral abdominal wall and its innervation. Cadaveric dissections revealed that the most significant intercostal nerve contributions to the anterolateral abdominal wall arise from T11 and T12. Electrophysiological confirmation of these findings was accomplished through intraoperative stimulation in 6 patients undergoing anterolateral retroperitoneal approaches to the thoracolumbar junction. The authors confirmed T11 and T12 innervation of the anterolateral abdominal wall musculature by direct intraoperative EMG recording in all 6 patients.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The authors classified the 3 potential zones of injury that can be affected during an anterolateral approach to the thoracolumbar junction. Modifications to the operative technique are suggested to avoid the complication of flank bulge. The most significant intercostal nerve contributions to the anterolateral abdominal wall arise from T11 and T12.</jats:p></jats:sec>

Cutaneous Sensory Block Area, Muscle-Relaxing Effect, and Block Duration of the Transversus Abdominis Plane Block

“…This finding is supported by an anatomical study of the innervation of the lateral abdominal wall in cadavers demonstrating that the 3 lateral muscle layers EO, IO, and TA are primarily innervated by branches from T12 and L1. 15 The clinical effect of this relaxation is still unknown, but muscle relaxation may be part of the pain-relieving effects reported in clinical studies. Pain originating from deeper structures than the skin may play an important role.…”

Abdominal Bulge After Retroperitoneal Dissection

“…14 In cadaveric dissections and intraoperative electromyography studies, T11 and T12 were found to be responsible for abdominal wall innervation in 81% to 97% of patients. 15 Clinical reports have given support to anatomical studies, as preservation of T11 and T12 through electromyography monitoring results in preservation of the abdominal musculature postoperatively. 15 Furthermore, reports of temporary, reversible lateral abdominal bulge after infiltration of local anesthetic into the transversus abdominus plane block 16,17 and bulge after postherpetic neuralgia occurring in the T11 and T12 dermatomal distributions further support the importance of the T11 and T12 nerves in anterolateral abdominal wall innervation.…”

“…15 Clinical reports have given support to anatomical studies, as preservation of T11 and T12 through electromyography monitoring results in preservation of the abdominal musculature postoperatively. 15 Furthermore, reports of temporary, reversible lateral abdominal bulge after infiltration of local anesthetic into the transversus abdominus plane block 16,17 and bulge after postherpetic neuralgia occurring in the T11 and T12 dermatomal distributions further support the importance of the T11 and T12 nerves in anterolateral abdominal wall innervation. 18 Standard flank incisions result in postoperative bulge rates up to 57%, 5 and demonstrate greater volumetric bulge, paresthesia, and numbness.…”

“…19 Reported risk factors for abdominal bulge include comorbid renal disease or cancer, incision length is greater than 15 cm or body mass index greater than 23 kg/m 2 . 2,5 Although limited data to support the following recommendations is available, surgeons have reported the following surgical techniques to reduce iatrogenic flank bulge after retroperitoneal dissection: minimize incision length, 5 direct identification and preservation of intercostal nerves, careful suture placement to avoid nerve strangulation, 15 incision placement superior to the line between the tip of the 12th rib and umbilicus, 14,20 anterior paramedian incision, 2 and limit incisions from entering the intercostal space. 6 Current techniques of abdominal wall reconstruction using fascial fixation of mesh demonstrate high recurrence rates, up to 100%, 10,12 due to failure to address attenuation of the denervated abdominal wall.…”

Flank bulge following supracostal percutaneous nephrolithotomy: a report of 2 cases.

“…14,15 Flank bulge due to laxity of the anterolateral abdominal musculature may be caused by damage to intercostal nerves. 14 In a cadaveric and electrophysiological study, Fahim and colleagues showed that the most significant intercostal nerve contributions to the anterolateral wall came from the T11 and T12 nerves.…”