Technical NoteMinimally Invasive Muscle Sparing Posterior-Only Approach for Lumbar Circumferential Decompression and Stabilization to Treat Spine Metastasis—Technical Report
Introduction
Metastatic disease has a predilection for the skeleton, and in particular the spine, with an estimated 36%–55% of cancer patients developing spine disease 23, 32. There are multiple cancer-specific pathways to the spine, but the principal route is via the valveless venous plexus of Batson (16). After gaining access to this system, tumor cells are thought to enter the internal vertebral plexus to the spine, notably through the basivertebral veins to invade the rich red bone marrow within the vertebral bodies. Indeed, most spinal metastases originate in the posterior vertebral body (1). Thus spinal mechanical instability from decreased anterior and middle column support and compression of neural elements from retropulsed pathologic fracture fragments and tumor are common findings on presentation (7).
Multiple studies have shown the benefit of surgical intervention in managing the pain and neurologic deficits from symptomatic spinal metastases, including patients with incurable disease for which the primary goal of surgery is palliation 11, 21. Due to the spinal instability caused by vertebral body metastases and the associated mechanical pain, successful treatment often requires access to this compartment with adequate resection of tumor-infiltrated vertebral body followed by anterior structural reinforcement with cage insertion. Traditionally, this has been accomplished using an anterior approach with or without a second staged posterior instrumented fixation. In the thoracic spine, a posterior-only approach such as a lateral extracavitary approach may be performed for 360-degree decompression and stabilization with the sacrifice of thoracic spinal nerve roots 9, 24. This is much more difficult in the lumbar spine due to the fact that the lumbar nerve roots have to be preserved given their important role in lower extremity motor function. Although anterior-only approaches for lumbar corpectomy and spinal stabilization have been shown to be effective in instances of traumatic burst fracture or osteoporotic fractures 14, 26, studies have shown that maximal stability is best attained with the addition of a posterior construct (10). Furthermore, anterior approaches have been associated with more intraoperative blood loss, longer operative time, and worse pulmonary function (14).
A posterior approach allows for the placement of a strong pedicle screw stabilization system. Thus vertebral body resection and circumferential fixation via a posterior approach would be ideal. However, this has traditionally been associated with significant muscle dissection, detachment, and devascularization, causing significant surgery-related morbidities including blood loss, pain, infection, and prolonged immobilization and recovery. The subsequent wound healing time required necessitates a delayed initiation of adjuvant chemoradiation therapy, further inhibiting efforts at maximizing tumor control and palliation. Thus a more refined surgical approach is desired.
Minimally invasive spine surgery has seen rapid technologic advancement in recent years. The term minimally invasive has a wide range of meaning, including video-assisted thoracoscopy, mini-open, and solely percutaneous procedures. The fundamental principle of minimally invasive surgery does not reflect the size of the surgical incision or the use of tubular surgical retractors. Rather, it refers to the respect and preservation of the natural tissue architecture, while gaining adequate or even improved access to the surgical pathology using the natural muscle plane. The range of potential applications for minimally invasive spine techniques has seen constant expansion, from simple microdiskectomies to spinal deformity surgery and the resection of both intradural tumors and metastases to the anterior spine 18, 20.
With the advent of transpedicular approaches and expandable cage placement, minimally invasive approaches for vertebral body resection are now feasible. Indeed, several cases of minimally invasive corpectomy for thoracic spine metastases have been reported 18, 25. However, to our knowledge, the present report is the first to report a minimally invasive, muscle-sparing, posterior-only approach for 360-degree lumbar spine decompression, hemicorpectomy, cage placement, and posterior instrumentation and stabilization.
Section snippets
Presentation
The patient is a 59-year-old male with a history of stage III renal cell carcinoma, status post radical left nephrectomy and chemotherapy. He had a known L1 vertebral body metastasis that had been previously irradiated. The patient presented with refractory low back pain that had become progressively more severe and was made worse by sitting up and ambulating. He endorsed chronic mild weakness of his bilateral extensor hallicus longus muscles. His neurologic examination was otherwise
Discussion
Management of metastatic spine disease is an important part of cancer treatments, given its high incidence 23, 32. Most spinal metastases are from lung cancer, followed by breast, prostate, and renal cancer 7, 17. Renal cell carcinoma (RCC), despite accounting for only 2% of all malignancies, has a high incidence of bony including spinal metastases (13). Most spinal tumors metastasize via venous drainage, although they may also infiltrate via direct extension as well: notably lung cancer to the
Conclusions
A minimally invasive muscle-sparing approach for metastases to the load-bearing lumbar spine is a promising surgical technique for patients suffering from mechanical instability and pain associated with lumbar spine metastases. Although such approaches have gained popularity in the thoracic spine, their feasibility in the lumbar spine has been largely unexplored. Lumbar metastases represent a significant proportion of spine tumors. The minimally invasive approach presented herein demonstrates
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