Determination of the width of the presacral space on magnetic resonance imaging

Determination of the width of the presacral space on magnetic resonance imaging among adults in south-western Nigeria

BACKGROUND

The presacral space is a clinically relevant potential space and contents may give rise to a variety of benign and malignant conditions, hence the need for detailed knowledge of its dimensions.

PURPOSE

To determine the width of the presacral space and existing variations among adults in south-western Nigeria using a magnetic resonance imaging (MRI) technique.

MATERIAL AND METHODS

A total of 369 consenting adults were included in the study. Measurements of the presacral space were then made electronically by consensus of two radiologists. Values derived were recorded and subjected to analyses of variance.

RESULTS

The mean normal widths of the presacral space in men and women were 11.7 mm and 11.1 mm at the S1 level, 11.7 mm and 10.35 mm at the S2 level, and 12.3 mm and 9.7 mm at the S3 level, respectively. Measurements of the presacral space width were significantly larger in the male population. Variations in the dimensions due to age greater than 40 years, male sex, and increasing body mass index (BMI) were also noted.

CONCLUSION

This study provides baseline dimensions under more physiological conditions and gives more accurate information about the true width of the space in Nigerian adults. Variations due to age, sex, and BMI may also be considered while interpreting abnormal values.

Paracoccygeal Transsacral Approach: A Rare Approach for Axial Lumbosacral Interbody Fusion

Lumbosacral interbody fusion is a mainstay of surgical treatment for degenerative spinal pathologies causing chronic pain and functional impairment. However, the optimal technique for this procedure remains controversial. Well-established open approaches, including anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF), have historically been the standard of practice. A recent paradigm shift in spinal surgery has led to the investigation of minimally invasive approaches to mitigate tissue damage without compromising outcomes. This extensive review aims to examine current clinical and biomechanical evidence on the paracoccygeal transsacral approach to an axial lumbosacral interbody fusion. Since this technique was first described in 2004, accumulating evidence suggests it results in high fusion rates, consistent improvements in pain and function, reduced perioperative morbidity, and low rates of complication. Although early clinical outcomes have been promising, there is a paucity of comparative data investigating outcomes of the paracoccygeal transsacral approach to traditional alternatives and other minimally invasive techniques. Here, we summarize current evidence and discuss pertinent topics for the spinal surgeon considering this novel approach, including indications, advantages, relevant anatomy, contraindications, and technical considerations.

Rectocutaneous fistula and nonunion after TranS1 axial lumbar interbody fusion L5–S1 fixation

The authors report a case of rectal injury, rectocutaneous fistula, and pseudarthrosis after a TranS1 axial lumbar interbody fusion (AxiaLIF) L5–S1 fixation. The TranS1 AxiaLIF procedure is a percutaneous minimally invasive approach to transsacral fusion of the L4–S1 vertebral levels. It is gaining popularity due to the ease of access to the sacrum through the presacral space, which is relatively free from intraabdominal and neurovascular structures.

This 35-year-old man had undergone the procedure for the treatment of degenerative disc disease. The patient subsequently presented with fever, syncope, and foul-smelling gas and bloody drainage from the surgical site. A CT fistulagram and flexible sigmoidoscopy showed evidence of rectocutaneous fistula, which was managed with intravenous antibiotic therapy and bowel rest with total parenteral nutrition. Subsequent studies performed 6 months postoperatively revealed evidence of pseudarthrosis. The patient's rectocutaneous fistula symptoms gradually subsided, but his preoperative back pain recurred prompting a revision of his L5–S1 spinal fusion.

The relevant anatomy of the approach for axial lumbar interbody fusion

STUDY DESIGN

Prospective trial.

OBJECTIVE

To perform a precise anatomical study of the presacral space and to examine the approach safety of AxiaLIF (axial lumbar interbody fusion) in an anatomical aspect.

SUMMARY OF BACKGROUND DATA

AxiaLIF is a novel, minimally invasive surgery. Though there were a few clinical reports on its safety, AxiaLIF is less used in current practice because of the unfamiliarity of surgeons with the regional anatomy of presacral space. METHODS.: Sixteen adult cadaveric pelvic specimens were divided along the median sagittal plane. The presacral fascial structures, the rectosacral fascia, and the pelvic splanchnic nerves were dissected and measured. In the simulated operation, a blunt guide pin was inserted bilaterally to determine the relation of the guide pin's path with important anatomic structures. Mean distances with 95% confidence intervals (CIs) were calculated.

RESULTS

The results showed that the fascial structures of the presacral space were divided into 5 layers, and the pelvic splanchnic nerves limited the dissection of the lower rectum, the mean length of which was 2.2 cm (1.9-2.5 cm). In the simulated operation, the mean minimum distance from the guide pin to the pelvic splanchnic nerves was 0.8 cm (0.4-1.2 cm), and the mean vertical distance to the S3-S4 junction was 1.5 cm (1.2-1.7 cm).

CONCLUSION

Our study suggests that the approach for AxiaLIF is risky and requires further modification. We should choose the accurate surgical plane when performing the presacral approach.

Minimally invasive trans-sacral approach to L5-S1 interbody fusion: Preliminary results from 1 center and review of the literature

BACKGROUND

Lumbar interbody fusion has long been used for the treatment of painful degenerative spinal conditions. The anterior approach is not feasible in some patients, and the posterior approach is associated with a risk of neural complications and possibly muscle injury. A trans-sacral technique was developed that allows access to the L5-S1 disc space. The purposes of this study were to investigate the clinical outcome of trans-sacral interbody fusion in a consecutive series of patients from 1 center and to perform a comprehensive review of the literature on this procedure.

METHODS

A literature search using PubMed was performed to identify articles published on trans-sacral axial lumbar interbody fusion (AxiaLIF). Articles reviewed included biomechanical testing, feasibility of the technique, and clinical results. The data from our center were collected retrospectively from charts for the consecutive series, beginning with the first case, of all patients undergoing fusion using the AxiaLIF technique. In most cases, posterior instrumentation was also used. A total of 41 patients with at least 6 months' follow-up were included (mean follow-up, 22.2 months). The primary clinical outcome measures were visual analog scales separately assessing back and leg pain and the Oswestry Disability Index. Radiographic assessment of fusion was also performed.

RESULTS

In the group of 28 patients undergoing single-level AxiaLIF combined with posterior fusion, the visual analog scale scores assessing back and leg pain and mean Oswestry Disability Index scores improved significantly (P < .01). In the remaining 13 patients, back pain improved significantly with a trend for improvement in leg pain. Reoperation occurred in 19.5% of patients; in half of these, reoperation was not related to the anterior procedure.

CONCLUSIONS

A review of the literature found that the AxiaLIF technique was similar to other fusion techniques with respect to biomechanical properties and produced acceptable clinical outcomes, although results varied among studies.

CLINICAL RELEVANCE

The AxiaLIF approach allows access to the L5-S1 interspace without violating the annulus or longitudinal ligaments and with minimal risk to dorsal neural elements. It may be a viable alternative to other approaches to interbody fusion at the L5-S1 level. It is important that the patients be selected carefully and surgeons are familiar with the presacral anatomy and the surgical approach.

AxiaLIF system: minimally invasive device for presacral lumbar interbody spinal fusion

Lumbar fusion is commonly performed to alleviate chronic low back and leg pain secondary to disc degeneration, spondylolisthesis with or without concomitant lumbar spinal stenosis, or chronic lumbar instability. However, the risk of iatrogenic injury during traditional anterior, posterior, and transforaminal open fusion surgery is significant. The axial lumbar interbody fusion (AxiaLIF) system is a minimally invasive fusion device that accesses the lumbar (L4–S1) intervertebral disc spaces via a reproducible presacral approach that avoids critical neurovascular and musculoligamentous structures. Since the AxiaLIF system received marketing clearance from the US Food and Drug Administration in 2004, clinical studies of this device have reported high fusion rates without implant subsidence, significant improvements in pain and function, and low complication rates. This paper describes the design and approach of this lumbar fusion system, details the indications for use, and summarizes the clinical experience with the AxiaLIF system to date.

High rectal injury during trans-1 axial lumbar interbody fusion L5-S1 fixation: a case report

STUDY DESIGN

A case report.

OBJECTIVE

To report a case of high rectal injury during trans-1 axial Lumbar Interbody Fusion (axiaLIF) L5-S1 fixation.

SUMMARY OF BACKGROUND DATA

Trans-1 axiaLIF procedure is gaining in popularity for L5-S1 fusion due to the ease of access to the sacrum through the presacral space. Normally, the midline of the sacrum at S1-S2 is relatively free from neurovascular and intra-abdominal structures, making this level a safe entry point for the axiaLIF procedure. We report a case of high rectal injury during Trans-1 axiaLIF L5-S1 procedure due to altered intra-abdominal anatomy as a result of multifactorial adhesions formation.

METHODS

A 44-year-old female patient with a history of previous anterior and posterior spinal surgeries, pelvic inflammatory disease, and non-disclosed previous diverticulitis, developed a high rectal injury during Trans-1 axiaLIF L5-S1 fixation.

RESULTS

After Trans-1 axiaLIF L5-S1, the patient presented with an episode of melena and hypogastric pain with nausea and vomiting. A computed tomography (CT) scan of the abdomen with intravenous and oral contrast showed presacral soft tissue fluid density with fat stranding and extraluminal rectal contrast and gas with some areas of soft tissue enhancement compatible with probable high rectal perforation. Patient's symptoms gradually subsided during a period of 6 months with aid from a temporary diverting ileostomy and a course of i.v. antibiotics. No spine implants were removed.

CONCLUSION

We report a case of high rectal injury during Trans-1 axiaLIF L5-S1 fixation and strongly advice that patients who are candidates for this surgery and have any risk factors for intra-abdominal adhesion formation, undergo a pelvic CT with rectal contrast before the surgery to evaluate for any signs of altered rectal-sacral anatomy.

The presacral space and its impact on sacral neuromodulator implantation

PURPOSE

We describe the presacral space and its potential impact on sacral neuromodulator implantation and bowel injury.

MATERIALS AND METHODS

Parasagittal images containing bilateral sacral foramina (S2-S4) were examined on 45 pelvic magnetic resonance images. Images were excluded from analysis if they were poor quality or had any history causing distortion of normal anatomy. We measured the natural angle between the foramina and the dorsal skin to approximate the needle angulation during neuromodulator electrode placement. Using these angles we measured the distance from the skin to any bowel (D1), the skin to the dorsal sacrum (D2) and then calculated the distance from the dorsal sacrum to any bowel (D3).

RESULTS

Mean subject age was 45 years (range 19 to 78) and body mass index was 27.9 kg/m(2) (range 18.6 to 56.2). At S3 the mean foraminal angle and D3 were 46 +/- 8.4 degrees and 27.4 +/- 11.7 mm, respectively. Increasing age was moderately correlated to widening D3 at each foramina (r = 0.3, Pearson's p <0.05). Body mass index did not consistently vary with D3 at any foramina.

CONCLUSIONS

Our measurements suggest that the presacral space can be expected to be approximately 27 mm at the level of S3 where the neuromodulator electrode is implanted. It is possible to encounter bowel while performing this implantation using standard techniques and equipment. We recommend the standard use of fluoroscopy during placement.

Anatomy of the percutaneous presacral space for a novel fusion technique

OBJECTIVES

Lumbar fusion has been widely used to treat unstable spinal disorders. Methods are evolving from open procedures to less invasive methods to avoid soft tissue trauma. Recently, a soft tissue sparing method to access the axial lumbosacral spine has been developed. It is crucial to determine structures potentially at risk for injury during this fusion technique. The anatomy of the presacral space and safety of the paracoccygeal approach were evaluated through cadaveric dissection and radiographic studies. The objective was to evaluate the safety of a paracoccygeal approach to the axial lumbosacral spine and determine structures that could potentially be injured.

METHODS

The paracoccygeal approach was performed on two cadavers, followed by dissection. Distances from the midline trajectory of the approach to surrounding vascular structures were determined. Similar distances were also measured on computed tomography (CT) and magnetic resonance imaging (MRI) of 12 patients, as well as CT images of two additional patients. A "safe zone" was determined using the sagittal length of the presacral space and the distance between the most medial internal iliac vessel on the right and left, respectively.

RESULTS

The coronal safe zone averaged 6.9 and 6.0 cm on MRI and CT, respectively. The mean distance from the anterior sacral margin to the rectum at the S3-S4 level was 1.2 and 1.3 cm on MRI and CT, respectively.

CONCLUSION

In this study, we defined the "coronal safe zone" within the presacral space. This "safe zone" may guide surgeons when utilizing the percutaneous paracoccygeal approach.

Definition and delineation of the clinical target volume for rectal cancer

PURPOSE

Optimization of radiation techniques to maximize local tumor control and to minimize small bowel toxicity in locally advanced rectal cancer requires proper definition and delineation guidelines for the clinical target volume (CTV). The purpose of this investigation was to analyze reported data on the predominant locations and frequency of local recurrences and lymph node involvement in rectal cancer, to propose a definition of the CTV for rectal cancer and guidelines for its delineation.

METHODS AND MATERIALS

Seven reports were analyzed to assess the incidence and predominant location of local recurrences in rectal cancer. The distribution of lymphatic spread was analyzed in another 10 reports to record the relative frequency and location of metastatic lymph nodes in rectal cancer, according to the stage and level of the primary tumor.

RESULTS

The mesorectal, posterior, and inferior pelvic subsites are most at risk for local recurrences, whereas lymphatic tumor spread occurs mainly in three directions: upward into the inferior mesenteric nodes; lateral into the internal iliac lymph nodes; and, in a few cases, downward into the external iliac and inguinal lymph nodes. The risk for recurrence or lymph node involvement is related to the stage and the level of the primary lesion.

CONCLUSION

Based on a review of articles reporting on the incidence and predominant location of local recurrences and the distribution of lymphatic spread in rectal cancer, we defined guidelines for CTV delineation including the pelvic subsites and lymph node groups at risk for microscopic involvement. We propose to include the primary tumor, the mesorectal subsite, and the posterior pelvic subsite in the CTV in all patients. Moreover, the lateral lymph nodes are at high risk for microscopic involvement and should also be added in the CTV.

A novel minimally invasive presacral approach and instrumentation technique for anterior L5-S1 intervertebral discectomy and fusion: technical description and case presentations

OBJECT

The authors describe a new paracoccygeal approach to the L5-S1 junction for interbody fusion with transsacral instrumentation. The purpose of this technical note is to demonstrate a novel surgical approach, technique, and instrumentation system for the treatment of L5-S1 instability in degenerative disc disease and spondylolisthesis.

METHODS

This technical note highlights the AxiaLif (TranS1) transsacral system as an alternative method to transforaminal lumbar interbody fusion or posterior lumbar interbody fusion. Via a novel presacral approach corridor, a truly percutaneous L5-S1 discectomy, interbody distraction, and fixation are achieved, and retroperitoneal viscera and dorsal neural elements are avoided. Percutaneous pedicle screw fixation is then used to provide additional stabilization at the treated level.

CONCLUSIONS

This novel technique of interbody distraction and fusion via a truly percutaneous approach corridor allows for circumferential treatment of the lower lumbar segments with minimal risk to the anterior organs and dorsal neural elements.