Anatomical differences in patients with lumbosacral transitional vertebrae and implications for minimally invasive spine surgery

Abstract

<jats:sec> <jats:title>OBJECTIVE</jats:title> <jats:p>The objective of this study was to investigate the neurovascular and anatomical differences in patients with lumbosacral transitional vertebrae (LSTV) and the associated risk of neurovascular injury in minimally invasive spine surgery.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>The authors performed a retrospective study of CT and MR images of the lumbar spine obtained at their institution between 2010 and 2014. The following characteristics were evaluated: level of the iliac crest in relation to the L4–5 disc space, union level of the iliac veins and arteries in relation to the L4–5 disc space, distribution of the iliac veins and inferior vena cava according to the different Moro zones (A, I, II, III, IV, P) at the L4–5 disc space, and the location of the psoas muscle at the L4–5 disc space. The findings were compared with findings on images obtained in 28 age- and sex-matched patients without LSTV who underwent imaging studies during the same time period.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>Twenty-eight patients (12 male, 16 female) with LSTV and the required imaging studies were identified; 28 age- and sex-matched patients who had undergone CT and MRI studies of the thoracic and lumbar spine imaging but did not have LSTV were selected for comparison (control group). The mean ages of the patients in the LSTV group and the control group were 52 and 49 years, respectively. The iliac crest was located at a mean distance of 12 mm above the L4–5 disc space in the LSTV group and 4 mm below the L4–5 disc space in the controls. The iliac vein union was located at a mean distance of 8 mm above the L4–5 disc space in the LSTV group and 2.7 mm below the L4–5 disc space in the controls. The iliac artery bifurcation was located at a mean distance of 23 mm above the L4–5 disc space in the LSTV group and 11 mm below the L4–5 disc space in controls. In patients with LSTV, the distribution of iliac vein locations was as follows: Zone A, 7.1%; Zone I only, 78.6%; Zone I encroaching into Zone II, 7.1%; and Zone II only, 7.1%. In the control group, the distribution was as follows: Zone A only, 17.9%; Zone A encroaching into Zone I, 75%; and Zone I only, 7.1%. There were no iliac vessels in Zone II in the control group. The psoas muscle was found to be rising away laterally and anteriorly from the vertebral body more often in patients with LSTV, resulting in the iliac veins being found in the “safe zone” only 14% of the time, greatly increasing the risk of vascular injury.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>In patients with LSTV, the iliac crest is more likely to be above the L4–5 disc space, which increases the technical challenges of a lateral approach. The location of the psoas muscle rising away laterally and ventrally in patients with LSTV compared with controls and with the union of the iliac veins occurring more often above the L4–5 disc space increases the risk for iatrogenic vascular injury at the L4–5 level in this patient population.</jats:p></jats:sec>

Re-examining the Spectrum of Lumbosacral Transitional Dysmorphisms: Quantifying Joint Asymmetries and Evaluating the Anatomy of Screw Fixation Corridors

“…It is rare to find reports that discuss the screw insertion anatomy in the context of the variability of sacral morphology seen in transitional lumbosacral variations. 1,34,35 LSTV anatomy in the setting of sacroiliac joint instrumentations can hardly be overemphasized given the variations presented in the sacral anatomy and the vicinity of vital neurovascular structures along the trajectory of screw placement through the upper osseous corridors in the sacrum. This study presents a detailed report on quantitative assessment of LSTV-related sacral anatomy and, at the same time, identifies and compares differences in dimensions between the normal sacrum and those that are associated with lumbosacral transitional subtypes in context of sacroiliac screw insertion.…”

“…Such numerical identification is required to ascertain visceral position corresponding to a specific vertebral level. [1][2][3][4][5] However, the biomechanical importance LSTV-related alterations at the sacroiliac articular symmetry, facet dimensions, and associated lumbosacral anatomy have been relatively underreported. [6][7][8][9] The 2 classification systems currently available to characterize LSTV focus only at the lumbosacral junction.…”

“…9,14 With the increasing evidence of biomechanical anomalies, the incidence of low back pain and sacroiliac dysfunctions in LSTV, anatomical studies about surgical access at LSTV-associated lumbosacral and sacroiliac regions become important. 1,[15][16][17][18][19][20][21] Accordingly, this study has attempted to (1) elucidate LSTV as a series of morphological changes (the LSTV spectrum) involving sequential exclusion or inclusion of additional vertebral segments into the sacrum; (2) quantify sacral dimensions across this transitional spectrum, comparing parameters within and between LSTV subtypes and normal variants, and (3) quantify sacroiliac screw-placement corridors in LSTV subtypes and the normal variants from a large cohort of sacral specimens.…”

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“…Lumbosacral transitional vertebrae (LSTV) are increasingly recognized as a common anatomical variant associated with altered patterns of degenerative spine changes. 1,2 Due to possible other comorbidities present in the spine, the diagnosis of Bertolotti's syndrome is not straightforward thus making it a diagnosis of exclusion. 3 Patients with symptomatic LSTV, also known as Bertolotti's syndrome, typically present with some combination of unilateral or bilateral symptoms.…”

A Radiographic Measurement of the Anterior Epidural Space at L4–5 Disc Level

“…Over the past few decades, minimally invasive spine surgery (MISS) has become widely used around the world because it is safe, effective, and reproducible. Percutaneous endoscopic transforaminal lumbar discectomy (PELD) is a popular and effective MISS technique used to treat lumbar disease.…”