Iliac vein variation in the sacral promontory on three-dimensional computed tomography angiography: a prospective observational study before laparoscopic sacrocolpopexy.

INTRODUCTION AND HYPOTHESIS: Venous injury may occur during exposure of the anterior longitudinal ligament at the anterior sacral promontory (SP). We aimed to quantitatively measure the extent of the vascular window (VW) in front of the SP in patients with internal iliac vein (IIV) variations using preoperative three-dimensional computed tomography angiography (3DCTA). We hypothesized that patients with IIV variations would have a narrow VW. METHODS: This prospective observational study included patients scheduled for laparoscopic sacrocolpopexy (LSC) between July 2022 and April 2023 who underwent preoperative 3DCTA. The primary endpoint was the VW measurement in the standard and variant IIV groups using 3DCTA before LSC. The secondary endpoint was the difference between the two IIV groups adjusted for age, body mass index, hypertension, and diabetes using an analysis of covariance (ANCOVA) model. Multiple regression analysis was performed to analyze the effect of factors on the distance from the SP to great vascular bifurcations. RESULTS: There were 20 cases of IIV variation (20.2%). VW was 28.8 ± 12.4 mm in the variant group and 39.6 ± 12.6 mm in the standard group (p = 0.001). In the ANCOVA model, IIV variations affected VW (coefficient, -11.8; 95% confidence interval [CI], -18.4 to -5.08, p < 0.001). Multivariate analysis revealed that the aorta-SP distance decreased with age (coefficient, -0.44; 95% CI, -0.77 to -0.11, p = 0.009). CONCLUSIONS: One in five women has a vascular variant at the SP that restricts the "safe" zone of fixation to < 3 cm.

Left Distal Transradial Approach for the Treatment of a Sacral Extradural Arteriovenous Fistula: A Technical Note and Literature Review.

BACKGROUND: Sacral extradural arteriovenous fistula (SEAVF) is relatively rare, and its etiology is unknown. They are mostly fed by the lateral sacral artery (LSA). For endovascular treatment, both the stability of the guiding catheter and accessibility of the microcatheter to the fistula, distal to the LSA are required for sufficient embolization of the fistulous point. Cannulation of these vessels requires either crossover at the aortic bifurcation or retrograde cannulation using the transfemoral approach. However, atherosclerotic femoral and tortuous aortoiliac vessels can make the procedure technically difficult. Although the right transradial approach (TRA) can reduce this difficulty by straightening the access route, a potential risk remains for cerebral embolism because it passes the aortic arch. Herein, we present a case of successful embolization of a SEAVF using a left distal TRA. METHODS: We report a case of a 47-year-old man with SEAVF treated with embolization using a left distal TRA. Lumbar spinal angiography showed a SEAVF with an intradural vein through the epidural venous plexus fed by the left LSA. A 6-French guiding sheath was cannulated into the internal iliac artery via the descending aorta using the left distal TRA. A microcatheter could be advanced into the extradural venous plexus over the fistula point from the intermediate catheter placed at the LSA. Embolization with coils and n-butyl cyanoacrylate was successfully performed. RESULTS: The SEAVF completely disappeared on neuroimaging, and the patient gradually recovered. CONCLUSIONS: Left distal TRA could be a useful, safe, and less invasive option for the embolization of SEAVF, especially for patients with high-risk factors for aortogenic embolism or puncture site complications.

The fibrinogen levels on admission is a predictive marker of the contrast extravasation on enhanced computed tomography in sacral fracture.

ABSTRACT: Sacral fracture is the most frequent posterior injury among unstable pelvic ring fractures and is prone to massive hemorrhage and hemodynamic instability. Contrast extravasation (CE) on computed tomography (CT) is widely used as an indicator of significant arterial bleeding. However, while CE is effective to detect significant arterial bleeding but negative result cannot completely rule out massive bleeding. Therefore, additional factors help to compensate CE for the prediction of early hemodynamically unstable condition.We evaluated the risk factors that predict CE on enhanced computed CT in patients with sacral fractures. Patients were classified into 2 groups: CE positive on enhanced CT of the pelvis [CE(+)] and CE negative [CE(-)]. We compared age, sex, injury severity score (ISS), systolic blood pressure (sBP), type of sacral fracture based on Denis classification, platelet (PLT), base excess, lactate, prothrombin time-international normalized ratio, hemoglobin (Hb), activated partial thromboplastin time, D-dimer, and fibrinogen between the 2 groups.A total of 82 patients were treated for sacral fracture, of whom 69 patients were enrolled. There were 17 patients (10 men and 7 women) in CE(+) and 52 patients (28 men and 24 women) in CE(-). Age, ISS, and blood transfusion within 24 hours were significantly higher in the CE(+) group than in the CE(-) group (P = .023, P < .001, P < .001). sBP, Hb, PLT, fibrinogen were significantly lower in the CE(+) group than in the CE(-) group (P < .001, P < .001, P < .001, P < .001). D-dimer and lactate were higher in the CE(+) group than in the CE(-) group (P = .036, P < .001) with significant differences. On multivariate analysis, the level of fibrinogen was an independent predictor of CE(+). The area under the curve value for fibrinogen was 0.88, and the optimal cut-off value for prediction was 199 mg/dL.The fibrinogen levels on admission can predict contrast extravasation on enhanced CT in patients with sacral fractures. The optimal cut-off value of fibrinogen for CE(+) prediction in sacral fracture was 199 mg/dL. The use of fibrinogen to predict CE(+) could lead to prompt and effective treatment of active arterial hemorrhage in sacral fracture.

Endovascular treatment of a sacral dural arteriovenous fistula.

Spinal dural arteriovenous fistula (SDAVF) is a rare pathological communication between arterial and venous vessels within the spinal dural sheath. Clinical presentation includes progressive spinal cord symptoms including gait difficulty, sensory disturbances, changes in bowel or bladder function, and sexual dysfunction. These fistulas are most often present in the thoracolumbar region. Diagnoses of SDVAFs are commonly missed, possibly due to the low index of suspicion, non-specific symptoms and challenging imaging. In this case report, we describe a rare presentation of a sacral SDAVF which was detected by collective efforts between endovascular neurosurgery and interventional radiology. We outline the diagnostic and imaging challenges we faced to discover the fistula. In particular, mechanical pump injection instead of hand injection during angiography was required to reveal the fistula. Following identification, the fistula was successfully treated endovascularly by using onyx (ethylene vinyl alcohol glue), a less invasive alternative to surgical intervention.

Effects of cycle periods and pressure amplitudes of alternating pressure on sacral skin blood flow responses.

BACKGROUND: There are no guidelines on selecting alternating pressure (AP) configurations on increasing sacral skin blood flow (SBF). AIM: The specific aims were to compare different cycle periods and pressure amplitudes of AP on sacral SBF responses in healthy people to establish the efficacy and safety of the protocols. METHODS: Two studies were tested, including the cycle period study (8 2.5-min vs 4 5-min protocols) and the pressure amplitude study (75/5 vs 65/15 mmHg protocols). Sacral SBF was measured using laser Doppler flowmetry (LDF) in 20 participants. AP loads were randomly applied using an indenter through the rigid LDF probe. Each protocol included a 10-min baseline, 20-min AP and 10-min recovery periods. A 30-min washout period was provided. The SBF response was normalized to the baseline SBF of each condition of each participant. RESULTS: For the cycle period study, the 4 5-min cycle protocol partially restored more SBF than the 8 2.5-min cycle protocol at the low-pressure phase (0.87 ± 0.04 vs 0.71 ± 0.03, p < 0.05) and at the high-pressure phase (0.25 ± 0.03 vs 0.19 ± 0.03, p < 0.05). For the pressure amplitude study, the 75/5 mmHg protocol partially restored more sacral SBF than the 65/15 mmHg protocol at the low-pressure phase (0.87 ± 0.1 vs 0.25 ± 0.03, p < 0.05) but not at the high-pressure phase (0.23 ± 0.02 vs 0.21 ± 0.02, non-significant). CONCLUSION: This study demonstrated that 1) a cycle period of 5 min was better than 2.5 min and 2) a pressure amplitude of 75/5 mmHg was better than 65/15 mmHg. The finding provides insights for selecting the AP configurations for increasing SBF.

The Shunt Point of the Sacral Dural Arteriovenous Fistula: A Case Report and Literature Review.

BACKGROUND: The occurrence of sacral dural arteriovenous fistula (dAVF) is rare. The detailed vascular architecture of sacral dAVF, including 3-dimensional (3D) angiographic images with operative findings, has not been evaluated compared with that of the thoracic and lumbar levels. We report a case of sacral dAVF with 3D angiographic examination and operative findings, with a literature review. CASE DESCRIPTION: A 60-year-old man presented with progressive urinary incontinence and gait disturbance. A sacral dAVF was detected at the S1-2 level. The shunt point was at the medial side of the line between the intermediate sacral crest and the most medial point of the L5 pedicle circle at the anterior posterior view of the angiography; we defined this type as the medial type. After embolization, latent inflow arteries were visualized ipsilaterally and contralaterally. During surgery, because of dAVF recurrence, a vascular tangle was found on the dura. The surgical interruption of the draining vein improved the patient's symptoms. From the literature review, 92% of cases had medial-type shunt point. It is possible for sacral dAVF to have multiple inflow arteries originating ipsilaterally or bilaterally, and a venous pouch. CONCLUSIONS: The shunt point of sacral dAVF tended to be located medially, not in the sacral foramen. Sacral dAVF has unique angioarchitecture. The differentiation of dAVF from epidural arteriovenous fistula may not be easy in some cases of sacral lesions. Therefore, further studies with a larger number of patients focused on the detailed vascular architecture are needed.

Republished: Transradial approach in the treatment of a sacral dural arteriovenous fistula: a technical note.

Sacral dural arteriovenous fistulas (SDAVFs) are rare, constituting no more than 10% of all spinal dural fistulas. They are most commonly fed by the lateral sacral artery (LSA), a branch of the internal iliac artery (IIA). Catheterization of this vessel requires either a crossover at the aortic bifurcation in cases of right femoral access or retrograde catheterization from the ipsilateral common femoral artery. We present the case of a 79-year-old man with tethered cord syndrome and a symptomatic SDAVF fed by two feeders from the left LSA. Spinal diagnostic angiography was made exceptionally challenging by an aorto-bi-iliac endograft, and selective catheterization of the left IIA was not possible. The patient could not undergo surgery due to multiple comorbidities, therefore embolization was considered the best approach. The procedure was carried out through a transradial access (TRA) with Onyx and n-butyl cyanoacrylate. The SDAVF was successfully treated and the patient made a full neurological recovery.

Transradial approach in the treatment of a sacral dural arteriovenous fistula: a technical note.

Sacral dural arteriovenous fistulas (SDAVFs) are rare, constituting no more than 10% of all spinal dural fistulas. They are most commonly fed by the lateral sacral artery (LSA), a branch of the internal iliac artery (IIA). Catheterization of this vessel requires either a crossover at the aortic bifurcation in cases of right femoral access or retrograde catheterization from the ipsilateral common femoral artery. We present the case of a 79-year-old man with tethered cord syndrome and a symptomatic SDAVF fed by two feeders from the left LSA. Spinal diagnostic angiography was made exceptionally challenging by an aorto-bi-iliac endograft, and selective catheterization of the left IIA was not possible. The patient could not undergo surgery due to multiple comorbidities, therefore embolization was considered the best approach. The procedure was carried out through a transradial access (TRA) with Onyx and n-butyl cyanoacrylate. The SDAVF was successfully treated and the patient made a full neurological recovery.

Anterior robotic approach in en-bloc sacrectomy: a preliminary experience.

En-bloc sacrectomy is a highly demanding surgical procedure necessary to obtain wide margin in sacral tumor. The double approach, anterior and posterior approach, is usually preferred for tumors extending proximally to S3 level where iliac internal vessels are at a higher risk for damage during posterior surgery. It can be justified also in selected cases to decrease the risk of posterior approach as in local recurrence or in patients who already underwent laparotomy. Our intent was to apply robotic-assisted techniques for performing anterior preparatory approach for sacrectomy surgery. Between December 2010 and December 2014, three cases of sacrectomies were performed in a previous robotic-assisted preparatory approach to separate the rectum from the tumor. Dissections were successfully performed in all cases close to the pelvic floor. The surgeon was able to position a Gore-Tex spacer between the anterior tumor surface and the rectum in all cases. The anterior dissections were performed with a perfect control of bleeding. No complications related to the anterior approach were reported. Robot-assisted surgery can be considered a valid and minimally invasive technique which allows a safe anterior dissection of the pelvic structures dividing tumors from surrounding tissues. It allows to place a spacer to protect organs during posterior sacral resection performed on the same day or at a later time. Further experiences are advocated to evaluate its efficiency in sacral tumors of greater size.

Presentation and outcomes of patients with thoracic and lumbosacral spinal epidural arteriovenous fistulas: a systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Thoracolumbar and sacral spinal epidural arteriovenous fistulas (SEDAVFs) are an increasingly recognized form of spinal vascular malformation. The purpose of this study was to perform a systematic review of the demographics, clinical presentation and treatment results of thoracolumbar SEDAVFs. MATERIALS AND METHODS: Pubmed, Scopus and Web of Science databases were searched from January 2000 to January 2018 for articles on treatment of SEDAVFs. Pooled data of individual patients were analyzed for demographic and clinical features of SEDAVFs as well as treatment outcomes. RESULTS: There were 125 patients from 11 studies included. Mean age was 63.5 years. There was a male sex predilection (69.6%). Sensory symptoms including pain or numbness were the most frequently presenting symptoms. Fistula location was the lumbosacral spine in 79.2% and the thoracic spine in 20.8%. Involvement of intradural venous drainage was more common than extradural venous drainage only (89.6% vs 10.4%). Of the 123 treated patients, endovascular therapy was performed in 67.5% of patients, microsurgery in 23.6%, and combined treatment in 8.9%. The overall complete obliteration rate was 83.5% and did not differ between groups. Clinical symptoms improved in 70.7% of patients, were stable in 25%, and worsened in 1.7% with no difference between treatment modalities. CONCLUSIONS: Thoracic and lumbosacral SEDAVFs often present with symptoms secondary to congestive myelopathy or compressive symptoms. Both endovascular and microsurgical treatments were associated with high obliteration rates and good clinical outcomes.

Laparoscopic Division of Median Sacral Artery and Dissection of Types III and IV Sacrococcygeal Teratomas to Decrease Intraoperative Hemorrhagic Complications: Case Series and Review of the Literature.

INTRODUCTION: Sacrococcygeal teratoma (SCT) is the most common teratoma presenting at birth. Life-threatening bleeding is a major complication during tumor excision in children. In this study we demonstrate our technique for laparoscopic division of median sacral artery (MSA) during dissection of SCT in 2 pediatric patients as a safe technique to minimize risk of hemorrhage. METHODS: Two female infants diagnosed with types III and IV SCTs underwent preoperative evaluation in the postnatal period. The first patient was an 18-month-old girl who presented with metastatic type IV teratoma, resected after neoadjuvant therapy, and the second patient was a 6-day-old girl with prenatal diagnosis of cystic type III teratoma. Using laparoscopy in both patients, the presacral space was reached by opening the peritoneal reflection with blunt dissection and the MSA was identified. Then it was carefully isolated and divided with 3 or 5 mm sealing device. The pelvic components of the tumors were partially dissected using laparoscopy. The first patient's tumor resection was completed using a posterior sagittal approach and the second patient required a standard Chevron incision. Along with the description of our technique, a review of the current literature for the management of SCT and MSA was performed. RESULTS: Both patients underwent successful laparoscopic division of the MSA and resection of the SCTs without complications. CONCLUSION: Laparoscopic MSA division before SCT excision offers a safe approach that can reduce the risk of hemorrhage during surgery.

Fetal median sacral artery anatomy study by micro-CT imaging.

PURPOSE: The median sacral artery (MSA) is the termination of the dorsal aorta, which undergoes a complex regression and remodeling process during embryo and fetal development. The MSA contributes to the pelvic vascularization and may be injured during pelvic surgery. The embryological steps of MSA development, anastomosis formation and anatomical variations are linked, but not fully understood. METHODS: The pelvic vascularization and more precisely the MSA of a human fetus at 22 weeks of gestation (GW) were studied using micro-CT imaging. Image treatment included arterial segmentations and 3D visualization. RESULTS: At 22 GW, the MSA was a well-developed straight artery in front of the sacrum and was longer than the abdominal aorta. Anastomoses between the MSA and the internal pudendal arteries and the superior rectal artery were detected. No evidence was found for the existence of a coccygeal glomus with arteriovenous anastomosis. CONCLUSIONS: Micro-CT imaging and 3D visualization helped us understand the MSA central role in pelvic vascularization through the ilio-aortic anastomotic system. It is essential to know this anastomotic network to treat pathological conditions, such as sacrococcygeal teratomas and parasitic ischiopagus twins (for instance, fetus in fetu and twin-reversed arterial perfusion sequence).

Awareness of middle sacral artery pathway: A cadaveric study of the presacral area.

PURPOSE: To assess the anatomic path of the middle sacral artery (MSA) at the presacral area and its relationship to the spinal midline during an axial lumbar interbody fusion (AxiaLif) approach. METHODS: Fifty human cadavers (25 males, 25 females) were used in this study. A transabdominal approach was used to expose the anterior aspect of the L5/S1 intervertebral disc and the presacral space. We measured the size and distance from the spinal midline at the following positions: (a) middle of the L5/S1 disc level, (b) 1 cm below the sacral promontory (SP), and (c) 2 cm below the SP. Each parameter was measured three times by two observers, and the mean value analyzed. RESULTS: The MSA was present and originated from the left common iliac artery in all cadavers with a mean width of 2.14 mm. The position of the MSA in relation to the midline was most commonly on the left side (LS, 56%) followed by the right side (RS, 34%) and midline (ML, 10%). In the LS group, the distance from the midline is relatively constant in the three measured positions with a mean value of (a) 1.78 mm (range, 0-8.17 mm), (b) 2.08 mm (range, 0-7.10 mm), and (c) 2.06 mm (range, 0-9.76 mm). In the RS group, the distance from the midline increased from cephalad to caudad, with a mean value of (a) 1.44 mm (range, 0-9.64 mm), (b) 2.19 mm (range, 0-9.95 mm), and (c) 2.92 mm (range, 0-10.03 mm). CONCLUSIONS: Our study found the presacral anatomic path of the MSA was most commonly at the left of midline. In addition, the right-sided MSA variant had increasing distance from the midline along its anatomic path from cephalad to caudad. Our findings suggest an AxiaLif approach at the left of midline may place the MSA at greatest risk.

The middle rectal artery arising from the lateral sacral artery.

A middle rectal artery arising from the lateral sacral artery (MRAls) in the right pelvis of a 99-year-old male was observed. Although variations of the origin of the middle rectal artery have been reported on many occasions, there are few descriptions of the trajectory in the literature. In our case, the MRAls branched from the lateral sacral artery on the sacral surface close to the third sacral sympathetic ganglion and immediately penetrated the third sacral splanchnic nerve and the parasympathetic pelvic splanchnic nerve from the ventral ramus of the forth sacral nerve. The MRAls entered in the lateral wall of the rectal ampulla without giving off a prostatic branch. Preservation of the pelvic autonomic nerves are crucial in rectal cancer excision to preserve the autonomic functions. The close topography of the MRAls to the origin of the fine autonomic nerves should be noted.

Efficacy of rectus muscle fragment welding in the control of presacral venous bleeding.

BACKGROUND: The incidence of presacral venous bleeding during rectal resection is low, but this complication can be severe and even lethal. Occasionally, the traditional methods - such as pelvic gauze packing and the use of metallic thumbtacks - are not effective. When combined with their complications and difficulties, these failures have resulted in numerous creative procedures with which to control this complication. In 1994, the indirect electrocoagulation method, which is performed via a fragment of the rectus abdominis muscle of the abdomen, was introduced to control presacral venous bleeding. METHODS: From January 2002 to December 2015, five of 872 patients with rectal cancer and one patient with rectal metastasis of gastric cancer developed presacral venous bleeding, and this technique was used in every case. RESULTS: Haemostasis was permanent in all cases. There were no complications such as infection or rebleeding. CONCLUSION: In our experience, indirect electrocoagulation via a fragment of the rectus abdominis muscle of the abdomen is a rapid, easily executed and effective method for controlling presacral venous bleeding during rectal resection.

Sacral dural arteriovenous fistulas: a diagnostic and therapeutic challenge - single-centre experience of 13 cases and review of the literature.

BACKGROUND: Sacral dural arteriovenous fistulas (DAVFs) are rare vascular abnormalities of the spine characterised by slowly progressive symptoms that can mimic different myelopathy disorders. OBJECT: To report our single Institution experience with sacral DAVFs. METHODS: We retrospectively reviewed the clinical records of patients admitted from 1 January 2006 to 31 December 2016 with a diagnosis of sacral DAVFs, treated by endovascular embolisation or surgical clipping. Clinical presentation, imaging characteristics, treatment results and follow-up were analysed. RESULTS: We identify 13 patients with sacral DAVFs supplied by lateral sacral arteries. Clinical presentation was characterised by different degrees of motor weakness and sphincter disturbances. In all patients, spinal MRI showed spinal cord hyperintensities with enhancement and prominent perimedullary vessels. Selective internal iliac angiography was mandatory to identify the exact location of the fistula. A complete embolisation was achieved in eight patients performing a single endovascular embolisation and in three patients performing a single surgical disconnection: two patients required combined procedures. Follow-up imaging showed a complete resolution of the spinal cord hyperintensities in 81% of patients and a reduction of the intramedullary enhancement in 91%. Gait improvement was observed in 73% of patients, while remaining stable in 27%. Sphincter disturbances improved in 36% of patients and remained stable in 64%. CONCLUSION: Awareness of sacral location of DAVFs is critical because standard spinal angiography will not identify sacral supplies, unless internal iliac arteries are properly examined. In our experience, the endovascular treatment show results comparable to surgery when the fistula point is correctly disconnected.

A Case of Common Peroneal Nerve Palsy Associated with Internal Iliac Artery Embolization by Using N-butyl-2-cyanoacrylate (NBCA).

A 64-year-old man was scheduled to undergo endovascular aneurysm repair for an abdominal aortic aneurysm (AAA). Since preoperative computed tomography showed an AAA with common iliac artery and internal iliac artery (IIA) aneurysms, IIA embolization was scheduled. Embolization using a coil was supposed to be performed; however, the lateral sacral artery could not be selected. For this reason, IIA embolization using N-butyl-2-cyanoacrylate (NBCA) was undertaken. During embolization, the median sacral artery was unexpectedly embolized through the lateral sacral artery. The patient complained of drop foot just after embolization; he was diagnosed with iatrogenic common peroneal nerve palsy. We have learned that sciatic nerve palsy can occur in cases of embolization with a liquid NBCA-Lipiodol mixture to the lateral or sacral median artery.

Sacral epidural arteriovenous fistulas: imitators of spinal dural arteriovenous fistulas with different pathologic anatomy: report of three cases and review of the literature.

BACKGROUND: Sacral epidural arteriovenous fistulas (eAVFs) are rare and often misdiagnosed because of the incongruence between the thoracic level of clinical deficits and the sacral location of the offending pathology. Failure to diagnose this lesion delays treatment, resulting in prolonged venous hypertension in the cord, progressive neurological deterioration, and decreased chances of recovery. METHODS: A single-institution case series and the published literature were reviewed. RESULTS: Three patients had sacral eAVFs are located in the ventral epidural space with outflow connections to radicular veins that arterialized spinal cord veins, all presenting with thoracic myelopathy, venous engorgement, and delayed diagnosis. All eAVFs were occluded completely with radiographic and clinical improvement. CONCLUSIONS: Sacral eAVF pathophysiology, namely venous hypertension and compromised spinal cord circulation, is exactly the same as dural AVFs, as is their treatment: the interruption of outflow by occlusion of the draining vein, which effectively eliminates venous hypertension, without occlusion of the actual fistula itself. Epidural exposure of sacral eAVFs is not necessary, whereas complete intradural occlusion of their radicular drainage is. Draining radicular veins intermingle with the nerve roots and their occasional multiplicity makes them more difficult to identify intraoperatively.

The blood supply to the sacrotuberous ligament.

Knowledge of the vascular supply associated with the sacrotuberous ligament is incomplete, and at most attributed to a single coccygeal branch. Our aim was to investigate the sacrotuberous ligament vasculature with a focus on its origin and distribution. We dissected 21 hemipelvises (10 male and 11 female). The gluteus maximus was reflected medially, and a special emphasis was placed on the dissection of the vascular and neuronal structures. All specimens exhibited several (1-4) coccygeal arteries branching from the inferior gluteal artery penetrating the sacrotuberous ligament along its length. Seven specimens demonstrated the superior gluteal artery supplying sacral branches to the proximal superior border of the sacrotuberous ligament. Our study highlights several branches from a variety of origins as the supply to sacrotuberous ligament unlike previous reports stating only one vessel. Our results implicate surgical procedures in and around the area of the gluteal region such as decompressive procedures of the pudendal nerve, as it travels between the sacrotuberous and sacrospinous ligaments.

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

OBJECTIVE 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.