Total Sacrectomy

Successful en bloc resection of the sacrum and lumbopelvic reconstruction requires a thorough understanding of the anatomy of the region and the functional and biomechanical consequences of such an operation. The primary blood supply to the sacrum is from ventral vascular structures, including the median sacral artery, a branch of the aorta, and the lateral sacral arteries, which are branches of the internal iliac vessels. In addition, the rectum, bladder, ureters, and iliac vessels are located ventral to the sacrum. Dorsally, within the sacral canal, the dural sac terminates at S2. Total sacrectomy requires sectioning of all sacral roots caudal to L5; therefore, watertight closure of the thecal sac should be ensured to prevent cerebrospinal fluid (CSF) leakage or pseudomeningocele formation.

We usually categorize sacral resections into midline and lateral resections, with the latter reserved for lesions such as chondrosarcoma of the sacral joint. Midline resections are further classified into four groups based on the levels of nerve root sacrifice, which include low sacral amputation (S4 and below), middle sacral amputation (S3 and below), high sacral amputation (bilateral S2 and below), and total sacrectomy (bilateral S1 and below). ¹ Bilateral preservation of the L5 nerve roots is necessary for subsequent satisfactory ambulation. In our series, 66.7% of patients with high or total sacrectomy had no difficulty in ambulation, and 33.3% were able to walk with the help of external support, whereas all of the patients with low or middle sacrectomy had no motor deficits after the operations. ² Because bilateral preservation of the S2 nerve roots and above is needed for satisfactory bowel/bladder control and sexual function, high sacral amputation and total sacrectomy result in loss of voluntary control of bowel or bladder and loss of genital sensation and function (inability to obtain an erection), whereas in our series, 62.5% of patients with a middle sacral amputation had intact bladder function and 71.4% had intact bowel function at 1 year postoperatively, and 91.7% of patients with a low sacral amputation had intact bladder function and bowel function. ² In most patients, however, bowel dysfunction can be successfully managed by bowel training, maintenance of formed stool, and periodic use of laxatives and enemas, whereas bladder dysfunction requires intermittent catheterization.

The bony sacrum itself has no inherent stability. Posterior ligamentous structures, particularly the sacroiliac ligaments, provide the pelvic ring with most of its stability. Whereas removal of the sacrum caudal to the middle-S1 level, along with preservation of the sacroiliac ligaments, does not require additional stabilization for walking, total sacrectomy results in the dissociation of the lumbar spine from the pelvis and destabilizes the pelvic ring. Thus, reconstruction of the lumbopelvic region after total sacrectomy should not only provide a union between the lumbar vertebrae and the remaining iliac wings bilaterally but should also reestablish the pelvic ring and, therefore, pelvic stability.

48.2 Patient Selection

This operation is most suitable for patients who have locally invasive sacral tumors such as sarcomas, chondrosarcomas, or chordomas. It may also be suitable for patients with locally invasive rectal or cervical carcinoma for whom there is no evidence of metastatic disease and who are otherwise in good medical condition. Total sacrectomy is an extensive surgical procedure with a significant amount of blood loss; therefore, it is usually recommended for patients who are young and otherwise healthy and should be performed with caution on those who are older and have serious medical problems such as respiratory compromise, coronary artery disease, or heart failure. When considering surgery for some tumors involving this area, one should also take into account the high likelihood that radiation therapy has already been administered and that limited sacral procedures have been attempted before the patient’s referral to a cancer center. In some patients, these modalities may arrest tumor progression for a limited time, but in most patients, the disease eventually recurs, with progressive neurologic decline.

A computed tomographically (CT)-guided needle biopsy should be obtained in any patient undergoing an en bloc resection. The biopsy site and needle tract should be planned in such a way that this area can be included in the specimen during radical excision. In most patients, plain X-rays, vascular imaging, CT scans, and magnetic resonance imaging (MRI) studies should be obtained before surgery. Plain X-rays demonstrate the alignment of the spinal column and the extent of bony disruption in the sacrum. MRI is the best method for showing the extent of soft tissue involvement and the relationship to other nearby structures such as the rectum and neural elements ( ▶ Fig. 48.1). CT scanning is best at demonstrating the quality of the bone and the bony destruction.

Fig. 48.1 (a) Three-dimensional reconstruction of preoperative computed tomography with contrast revealed the tumor in the lumbosacral area of the spine with highly vascular components extending from S1 to S5. None of the major vasculature was involved, which was a good indication for a posterior-only approach. (Reproduced with permission from Neurosurgery 2008;63[ONS Suppl 1]:ONS117–ONS122.) (b) Preoperative magnetic resonance imaging showing a chordoma involving the sacrum arising from the S2–3 junction. Laterally this tumor involved the right sacroiliac joint. This patient complained of intractable local pain and bilateral sciatica as well as worsening bowel and bladder dysfunction; a two-staged approach was performed. (Reproduced with permission from Neurosurgical Operative Atlas 2007;7:11–20.)

To determine which surgical approach is appropriate, namely, posterior-only approach or anterior-posterior two-staged approach, the aforementioned preoperative assessments should be taken into consideration ( ▶ Fig. 48.1). The advantage of a two-staged approach is to gain secured access to the rectum and iliac vessels, but one of the shortcomings is the additional risk of complications associated with laparotomy and longer hospital course given the time between the first and second stages of the procedure. Therefore, our institution has preferentially extended the indications for posterior-only approach and selected posterior-only approaches whenever feasible. Indications for an anterior–posterior operation are if the patient has had significant radiation in the past, if there is rectal involvement, or if a myocutaneous rectus flap is needed to close a soft tissue defect.

The potential risks are related mainly to the extent of the surgical procedure, the amount of blood loss, and the danger to nearby structures. The colon, given its proximity to the sacrum, is frequently adherent to the tumor and is at risk for injury during the surgical procedure. The internal and external iliac vessels, aorta, and inferior vena cava also can be injured. The internal iliac vessels are ligated during the operation; yet injury to the external iliac vessels can potentially result in loss of the limb. The risk of wound dehiscence or healing complications is a concern, especially in those who receive radiation treatment or have had previous abdominal operations before the final procedure. Therefore, consultation with plastic surgeons before total sacrectomy is important, and a vascularized wound closure using a flap with a vascularized pedicle or a free flap should be planned in advance.

48.3 Preoperative Preparation

Because there is a risk of injuring the colon and rectum during the operation, the patient should have a full bowel preparation before the procedure. We usually use prophylactic antibiotics such as second-generation cephalosporins preoperatively and in the immediate postoperative period. No specific antibiotic regimen is otherwise needed, and no other special medications are required.

48.4 Operative Procedure

48.4.1 Anesthetic Technique

Good vascular access is needed, and central venous pressure monitoring is almost always required because of the amount of blood loss potentially encountered during the operation. Large-bore intravenous catheters are also necessary to administer a large volume of fluids and blood. The anesthetic agents are of a standard type. A spinal block is usually not considered because, after the sacrectomy, the lower end of the sacral canal will be open, and, therefore, the anesthetic agent will not remain in the epidural space. Hypotension is not deliberately induced. A spinal drain is used if there is any concern about a CSF leak during the surgical procedure, but it is not routinely placed.

48.4.2 Monitoring

Continuous electromyography monitoring is used routinely during the surgical procedure to preserve motor functions, especially L4 and L5 nerve roots and sacral roots if sacral root preservation is planned.

48.4.3 Draping

No special draping is needed with either approach. Before draping for the posterior-only approach and the posterior stage of the two-staged procedure, the rectum is irrigated with half concentrated Betadine (Purdue Pharma LP, Stamford, Connecticut), and the anus is usually sutured. The coccyx is included in the draped operative field because the dissection extends down to structures near the coccyx.

48.4.4 Posterior-Only Approach

The patient is positioned prone in the Kraske position. To prevent facial pressure ulcers ( ▶ Fig. 48.2 a), a Mayfield clamp (Integra LifeSciences Corporation, Cincinnati, Ohio) is routinely used for head fixation ( ▶ Fig. 48.2 b). ³ A midline incision is performed from the L2–3 spinous process through the level of the coccyx. The lumbosacral fascia is identified, and the dissection is carried laterally over the lumbosacral fascia to both iliac crests. Self-retaining retractors are placed, and the gluteus maximus and medius muscles are mobilized and preserved so that they can be subsequently used as pedicle flaps. The sacrum is completely exposed, along with the lateral edge of the sacral wall caudally and the sciatic notches bilaterally. The posterior iliac crests are exposed bilaterally, in addition to the facet joints and spinous and transverse processes from L3 to L5 ( ▶ Fig. 48.3 a). Subsequently, an L5 laminectomy and bilateral L5–S1 foraminotomies are performed, and the L5 and S1 nerve roots are visualized bilaterally. Usually at this point, the tumor extending into the sacral vertebral body can be recognized. Using a high-speed diamond bur, lateral iliac osteotomies are performed ( ▶ Fig. 48.3 b), and the entire course of the L5 nerve roots from the thecal sac to the sciatic notch are exposed and mobilized. The thecal sac is transected and closed using a double-layered suture closure with a 5–0 Prolene running suture (Ethicon, Inc., Somerville, New Jersey) or double ligated using 0-silk ties in a watertight fashion. After closure of the thecal sac, it is possible to see the entire dorsal aspect of the L5–S1 disk space, and the diskectomy is completed. A no. 3 Penfield dissector is used to protect the iliac vessels and middle sacral artery and vein as the sacrum is disconnected ventrally. A disk-space distractor is positioned within the L5–S1 disk space, and the sacrum is simultaneously lifted by using bone hooks to obtain the adequate ventral surgical views, which are critical for preserving ventral vasculature and rectum. The anterior and lateral sacral artery and vein are identified and ligated. The internal iliac artery and vein, which are potential sources of massive blood loss intraoperatively, are ligated and divided ( ▶ Fig. 48.4). Subsequently, the mesorectum is mobilized from the ventral surface of the sacrum and tumor, usually using Kittner dissectors.

Fig. 48.2 (a) Facial pressure ulcer intraoperatively acquired via prone positioning on a face pillow. Ecchymosis that developed over the bony prominence of the chin is seen. (b) Patient undergoing Kraske positioning for total sacrectomy with Mayfield clamp fixation of the head. (Reproduced with permission from J Neurosurg Spine 2011;14:85–87.)

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