Anterior and Posterior Decompression and Stabilization in Patients with Metastatic Disease Using the Transpedicular Approach

54 Anterior and Posterior Decompression and Stabilization in Patients With Metastatic Disease Using the Transpedicular Approach

Fintan J. Shannon and Patrick J. Boland

Goals of Surgical Treatment

1. A single posterior incision

2. Three-column tumor decompression

3. Durable immediate fixation

Diagnosis

The diagnosis of metastatic disease to the spine is made from the history, physical examination, radiographic studies, and histologic examination. Plain radiographs, isotope bone scan, and computed tomography are all used, but magnetic resonance imaging (MRI) is the established gold standard. Preoperative evaluation of the entire spine is essential to (1) provide detailed assessment of the offending lesion, and (2) to detect and quantify the degree of tumor involvement in adjacent levels. Positron emission topography (PET) scans may be valuable in distinguishing osteoporotic fractures from those due to tumor.

Angiography and embolization should be done preoperatively in patients with suspected vascular tumors (e.g., myeloma, renal cell, thyroid and some sarcomas). Surgery should be performed within 48 hours of embolization.

Indications for Surgery

1. Failed radiotherapy or history of radiotherapy to spinal cord tolerance

2. Radioresistant tumors (e.g., renal, melanoma)

3. Patient with expected survival more than 2 months

4. Circumferential bony disease with or without spinal cord compression (Fig. 54–1)

5. High-grade spinal cord compression from epidural disease

6. Disease involving the vertebral body and one/both pedicles with or without posterior disease

7. Extensive unresectable paraspinal mass (precluding anterior vertebral body access)

8. Any medical contraindication to an anterior/transcavitary approach

a. Compromised pulmonary function

b. Concurrent medical illness

c. Previous anterior surgery

d. Previous radiation to abdomen/thorax

Contraindications

1. Isolated anterior epidural tumor

2. Disease confined to vertebral body only

3. Primary resectable bone tumors

Advantages

1. The entire procedure can be performed through a single posterior incision.

2. Allows excellent circumferential access for decompression of spinal cord and nerve roots.

3. Circumferential stabilization is achieved.

4. Immediate postoperative mobilization without orthosis.

5. Significant pain relief.

6. Low risk of postoperative morbidity; eliminates the morbidity of thoracotomy/anterior abdominal surgery.

Disadvantages

1. Anterior dura not well visualized.

2. Anterior visualization and instrumentation is more difficult when compared with an anterior approach.

3. Anterior bleeding can be more difficult to control.

Procedure

Setup and Approach

Following induction of general anesthesia, the patient is turned from the supine to the prone position. Bolsters should be placed along each side of the patient extending from the axilla to the anterior superior iliac spine. With this arrangement, the anterior chest and abdominal walls should clear the table and be able to expand. The table is tilted so that the patient lies in a mild Trendelenburg position. Alternatively, the patient may be placed in the knee-chest position. The head is placed in a Mayfield pin fixation device.

The gluteal cleft and the C7-T1 spinous processes mark the midline, and typically all spinous processes are palpable between these levels. The level of interest is confirmed by using the 12th rib to identify T12 and then counting up or down as appropriate. The L4 spinous process is located on the same axial plane as the iliac crest, which is easily palpable laterally. Intraoperative x-ray confirmation may be carried out if necessary. A posterior midline incision centered over the affected level is made long enough to expose the entire length to be instrumented (Fig. 54–2).

If a posterior soft tissue tumor mass is present, sharp dissection is used outside the mass, prior to its excision with the posterior bony elements. During the stripping of paraspinous muscles from the spinous process and laminae, care must be taken to avoid inadvertently plunging through the vertebral lamina, which may be deficient owing to tumor destruction.

Tumor Decompression

1. The posterior bone work is initiated by removing the spinous process of the involved vertebra with a rongeur.

2. Following clear identification of the affected lamina, transverse process, and pars, the posterolateral aspect of the tumor mass is then removed in piecemeal fashion.

3. A high-speed bur is used to thin the lamina to a cortical shell prior to its excision with a rongeur. The ligamentum flavum and posterior epidural tumor is then removed with tenotomy scissors. It is necessary to resect one half of the laminae above and below the resected tumor level to gain access to the cranial and caudal vertebral discs (Fig. 54–3).

4. Bilateral facetectomies are accomplished using the burr, and each tumor-laden pedicle can be gently curetted from inside outward, collapsing it in on itself once the core is removed. If a pedicle is disease free, the high-speed bur is used to remove its cancellous core and preserve the medial cortical margin (Fig. 54–4).

Only gold members can continue reading. Log In or Register to continue