**Abstract**

Lumbar stenosis is the most common pathology seen and treated by spine surgeons. It is often seen in the elderly population who frequently have multiple medical co-morbidities. Traditional approaches remove the spinous process and detach paraspinous muscles to achieve adequate canal decompression. This approach can damage the posterior tension band leading to permanent muscle damage, scar tissue formation, iatrogenic flatback syndrome, and increase risk of adjacent segment disease requiring reoperation. Performing lumbar laminectomy in a cost-effective manner is critical in effectively treating patients with lumbar stenosis. This chapter reviews a minimally invasive muscle-sparing approach to treating lumbar stenosis. The technique is performed through a tubular retractor. Direct decompression of the spinal stenosis is achieved while preserving the paraspinous muscle attachments and spinous process. This technique has multiple advantages and can potentially reduce load stress on adjacent levels and subsequent adjacent level pathology leading to further surgical intervention. In addition, the procedure shows how facet fusion is performed using the patient's own locally harvested drilled morselized autograph to achieve bilateral facet fusion. By fusing the facets, we have shown that restenosis at the operative level is less likely to occur. This chapter will review a case series of multilevel lumbar stenosis including clinical outcomes.

**Keywords:** Lumbar stenosis, minimally invasive laminectomy, multilevel stenosis, muscle and bone preservation, autograph posterolateral fusion

### **1. Introduction**

Over the last two decades, minimally invasive spine surgery has undergone a paradigm shift with some procedures garnering increasing favor from the neurosurgical community [1–3]. Outcomes research and an emphasis on improving intra- and post-operative outcomes have increased the importance of selecting techniques that maximize these parameters. The minimally invasive laminectomy for the treatment of spinal stenosis is one such procedure that has gained considerable momentum [2]. Several indications exist for this procedure including

### **Figure 1.**

*A. Sagittal and B. Axial T2 weighted MRI image at the L4-5 level (marked with the green line) showing spinal stenosis caused by hypertrophy of the facets and ligamentum flavum.*

primary or secondary lumbar spinal stenosis. The former is the most frequently diagnosed spinal disorder in the elderly and is a major cause of disability in this population [4].

Lumbar spinal stenosis is defined as a reduced cross-sectional diameter of the vertebral canal, usually resulting in compression of neural structures (**Figure 1**).

There are three types of compression: compression in the central portion of the spinal canal (central stenosis); in the lateral recesses of the canal (lateral recess stenosis); or a combination of stenosis in both regions. Spinal stenosis may be congenital or acquired. Congenital stenosis consists of a group of spine deformities that often present in patients diagnosed with hereditary syndromes (i.e., Achondroplasia). Symptoms of congenital stenosis typically present at a younger age than those of acquired spinal stenosis. Secondary lumbar stenosis presents with a myriad of pathological changes including hypertrophy of the ligamentum flavum, and degeneration of the facet and disc structures [5]. The compression of the central canal often leads to debilitating back pain, radiculopathy, and symptoms of neurogenic claudication, making acquired spinal stenosis one of the most critical factors in the decision for surgical intervention [6]. Lumbar canal stenosis may itself arise as a long-term consequence of sagittal balance abnormalities, spondylolisthesis, and/or degenerative conditions.

### **2. Surgical techniques**

There have been multiple surgical techniques developed to decompress the lumbar spine in patients suffering from lumbar stenosis. The oldest technique is the open lumbar laminectomy, which involves the removal of spinous processes, both laminae and a partial facetectomy. In performing a decompressive laminectomy, the competing forces of adequately decompressing the spine and preventing adjacent segment disease must be balanced. Adjacent segment disease describes the constellation of findings that develop as a result of pathological load forces placed on the spine. The resulting focal tissue hypertrophy and adjacent level stenosis may require additional surgical intervention (**Figure 2**).

*Minimally Invasive Laminectomy for Lumbar Stenosis with Case Series of Patients… DOI: http://dx.doi.org/10.5772/intechopen.105186*

### **Figure 2.**

*A. Sagittal and B. Axial CT myelogram showing traditional laminectomy previously performed with removal of spinous processes and subsequent development of complete myelographic block at the adjacent L4-5 level requiring additional surgical intervention.*

Efforts to preserve midline posterior structures have led to the introduction of minimally invasive techniques to treat degenerative lumbar stenosis. Minimally invasive spine techniques were developed to preserve the normal anatomical integrity of the spine [1, 7–9]. Fessler et al., are credited with developing the currently used technique for performing a minimally invasive laminectomy in the treatment of lumbar stenosis that will be described in this chapter [9]. Over the last several years, various improvements in microscopic visualization techniques [10] have greatly influenced surgical options. These advancements have made it feasible to utilize a unilateral laminectomy to extend instruments to the contralateral side and fully decompress the canal without the long-term spinal instability and risk for additional surgical intervention associated with traditional open procedures.

Minimally invasive laminectomy outcomes studies have confirmed its benefits [1], in patients with and without spondylolisthesis [8]. Several comparative studies have addressed minimally invasive laminectomy vs open laminectomy [11, 12], bilateral decompressive laminectomy vs muscle-sparing interlaminar approach [13], and patient outcomes based on a variety of critical analyses [5, 14, 15]. Further evolution in surgical techniques and technology aims to facilitate the minimally invasive approach [16].

### **3. Indications/contraindications**

### **3.1 Patient selection**

Patients presenting with lumbar stenosis may present with bilateral or unilateral leg pain, weakness, numbness, and/or paresthesias [11]. Many patients suffer from neurogenic claudication, a typical complaint where back or leg pain is aggravated by standing and walking and relieved by sitting, flexing the spine, or lying down. Symptomatic relief with lumbar flexion is often a reliable clinical sign that helps to distinguish neurogenic spinal claudication from vascular claudication. The bicycle test, in which the patient leans forward while riding a stationary bike, can also help

to distinguish the two conditions. The neurological examination can be non-contributory until very late stages of the disease when a fixed motor or sensory deficits become evident. Also important in these patients is the varying degrees of walking impairment progressing over months or years [17]. Sphincter disturbance is a rare, late symptom of this condition and is usually associated with severe compression of the cauda equina, which is sometimes the result of an acute disc herniation superimposed on preexisting spinal stenosis. There are also some classical syndromic descriptions such as footdrop and acute radiculopathy. At some point, the physical examination must be able to rule out hip pathology and sacroiliac joint involvement. Multiple examinations such as Patrick Test, Faber Test, distraction, thigh thrust, compression, and Gaenslen's test are important to make these distinctions [18].

With an increasing incidence of lumbar stenosis, proper patient selection is paramount to achieving good clinical outcomes. Reoperation cases are relatively cumbersome and impose a significant burden on the patient and surgeon. As such reoperations should not be attempted until the spine surgeon has gained considerable experience with minimally invasive laminectomy approaches. In some other conditions, such as morbid obesity, there is an increased working distance from the skin to the spine, thereby increasing the technical difficulty for the surgeon. These cases are best deferred until a high level of experience and comfort with operating through a tubular retractor are achieved.

### **4. Radiographic work-up**

The imaging workup for spinal stenosis usually begins with anteroposterior, lateral, and flexion/extension plain film X-rays, which often reveal degeneration of the anatomic structures manifesting as loss of disc space height, narrowed neural foramina, and hypertrophy of the facet joints. In some patients, dynamic films can potentially reveal instability. Magnetic resonance imaging (MRI) is the study of choice to provide diagnostic images with specific details regarding structure, dimensions, and deformities. Typical findings include degenerative disc disease, ligamentous and facet hypertrophy, and a triangularly shaped "trefoil" spinal canal. The computer tomography myelogram (CT myelogram) study can be particularly useful in patients with degenerative scoliosis, multilevel stenosis, or in cases where prior surgical intervention with instrumentation was performed. In these scenarios, the CT myelogram allows adequate visualization of the stenotic level.

### **5. Electromyographic studies**

Some spinal stenosis patients present with a variety of clinical signs including single or multilevel compression. In those cases, the advantage of requesting additional electrophysiological studies lies in the possibility of confirming compression of individual nerve roots for surgical procedure planning [19].

### **6. Operative set-up and instrumentation**

The minimally invasive lumbar laminectomy is performed in a standard operating room with routinely available equipment. Lateral fluoroscopy is used for confirmation of the correct surgical level. The patient is typically positioned on a Jackson table which allows normal lumbar lordosis and limits abdominal pressure to reduce surgical bleeding.

*Minimally Invasive Laminectomy for Lumbar Stenosis with Case Series of Patients… DOI: http://dx.doi.org/10.5772/intechopen.105186*

**Figure 3.**

*The One-Step-Dilator (Thompson MIS, Salem, NH) has been developed to eliminate the need for guidewire and subsequent muscle dilators. This system allows for a bloodless, muscle-sparing approach to the spine. A., Images of One-Step-Dilator closed and B., expanded to dilate apart muscle tissue. C., Intra-operative image D–E., with fluoroscopic guided approach to the spine by gentle clockwise rotation, F., counterclockwise opening of retractor once on spine, G-H., passing of tubular retractor over dilator, I., and tubular retractor in place for performing the procedure.*

### **7. Incision**

The midline of the spine is palpated and marked. Typically, the skin incision is made a fingerbreadth lateral to the midline if one level is decompressed and no instrumentation is needed. However, for multilevel decompression, percutaneous pedicle screws are often utilized to promote fusion. When pedicle screws are required, the incision is made 3 cm lateral to the midline at the level of stenosis. This allows for adequate access to the canal for decompression and facilitates percutaneous pedicle screw placement. Once the incision is made parallel to the spinous processes, the One-Step-Dilator (Thompson MIS, Salem, NH) is used to approach the spine in a muscle-splitting fashion (**Figure 3**).

### **8. Laminectomy**

The soft tissue on the lamina/facet surface is then removed with monopolar Bovie cautery to the sagittal extent of the tubular retractor. The caudal and rostral edges of the lamina and medial aspects of the facet are exposed. A cutting M8 match-stick burr is used to perform the ipsilateral laminectomy to expose the thickened ligamentum flavum. All drilled bone is collected using the Thompson MIS BoneBac Press, which provides excellent morselized autograft thereafter used to perform a bilateral facet fusion once adequate decompression has been completed. The benefits of morselized autograft bone material include excellent

handling characteristics, adequate softness for remodeling, cost savings, and increased fusion rates [20].

The illustrations below show the steps taken to perform a minimally invasive laminectomy for stenosis. Step one, ipsilateral laminectomy shown in **Figure 4a–d**. Step two, tilt the patient slightly away from the surgeon and wand tubular retractor to expose the base of the spinous process (**Figure 4e**). The spinous process, as well as contralateral lamina, are then undercut with the high-speed burr. The contralateral lamina is undercut to the facet complex. Preservation of the ligament flavum helps protect the dura (**Figure 4f–h**).

Once bony decompression is completed, the ipsilateral ligamentum flavum is removed with an up-biting Kerrison punch. Subsequently, the contralateral ligamentum flavum can be removed. To facilitate the removal of the contralateral ligament flavum, particularly in cases of severe hypertrophy, we used a CO2 laser to facilitate removal along with Kerrison punch, typically number 2 size. In this manner, durotomies are extremely uncommon (**Figure 5**).

### **Figure 4.**

*Illustrations showing a–d, ipsilateral laminectomy with exposure of ligamentum flavum. e, Tilting the table away from the surgeon to perform the contralateral decompression. e–h, undercutting the spinous process and contralateral lamina to achieve bony decompression. (From, An Anatomical Approach to Minimally Invasive Spine Surgery, 2nd edition. Editors MJ Perez-Cruet, RG Fessler, MY Wang, Thieme Publishing Inc, New York, New York, 2019).*

*Minimally Invasive Laminectomy for Lumbar Stenosis with Case Series of Patients… DOI: http://dx.doi.org/10.5772/intechopen.105186*

### **Figure 5.**

*a. Intraoperative photo showing dura after b. Bone decompression is performed by undercutting the spinous process and contralateral lamina with ipsilateral ligamentum flavum removed. c. Steps in removal of the hypertrophied ligamentum flavum include removal of ipsilateral ligamentum flavum followed by removal of the contralateral ligamentum flavum. This can help to reduce the risk of inadvertent durotomies. Removal of the contralateral ligamentum flavum can be aided by the use of a CO2 laser which shrinks the contralateral ligamentum flavum making it easier to remove with a Kerrison punch. (Illustrations from, An Anatomical Approach to Minimally Invasive Spine Surgery, 2nd edition. Editors MJ Perez-Cruet, RG Fessler, MY Wang, Thieme Publishing Inc, New York, New York, 2019).*

### **Figure 6.**

*Intraoperative photograph showing surgeon performing bony decompression with a drill (Stryker TPS, Kalamazoo, MI) using an M8 cutting burr and the collected B. morselized autograft using the BoneBac Press (BoneBac, Salem, NH)*

The morselized autograft collected using the BoneBac press is used with no additional bone graft material needed (**Figure 6**). In-situ fusion of the bilateral decorticated facets is performed to reduce restenosis of the decompressed segment (**Figure 7**).

### **Figure 7.**

*A. Intraoperative photo and B. Illustration showing decortication of the contralateral facet and placement of morselized autograft into the facet complexes bilaterally. C. Illustration and intraoperative photo showing decortication of the ipsilateral facet and placement of surgical site morselized autograft.*

### **Figure 8.**

*Preoperative CT myelogram showing lumbar stenosis. B. Post-operative CT showing decompression by performing ipsilateral laminectomy followed by undercutting the spinous process and contralateral lamina. C. Six-month postoperative coronal and D. Axial CT showing facet fusion and maintenance of spinal canal diameter.*

*Minimally Invasive Laminectomy for Lumbar Stenosis with Case Series of Patients… DOI: http://dx.doi.org/10.5772/intechopen.105186*

### **Figure 9.**

*Illustrative case of patient who presented with neurogenic claudication from four-level lumbar stenosis. a. Sagittal and corresponding axial MRI showing lumbar stenosis at L2-3, L3-L4, L4-L5, and L5-S1 levels. b. Post-operative sagittal and corresponding axial CT showing decompression at each level with postoperative incisions and anteroposterior and lateral x-rays. Note adequate central canal decompression with preservation of the spinous processes.*

In cases of scoliotic deformity of spondylolisthesis (**Figure 8**) or multilevel decompression, (**Figure 9**) percutaneous pedicle screw instrumentation is applied to improve fusion rates.

The collected morselized autograft is then placed via the tubular retractor into the bilaterally decorticated facet complexes to achieve a bilateral posterior facet fusion. Facet fusion reduces the rates of restenosis by stabilizing the segment (**Figure 8**).

With complete hemostasis, the fascia is reapproximated with 2-0 vicryl suture, followed by multilayer subcutaneous closure. Final skin closure is accomplished with the application of Prineo adhesive dressing and Dermabond (Johnson & Johnson). This avoids the need for skin staple or suture removal and leaves a cosmetically pleasing scar.

### **9. Post-operative care**

Post-operatively, the patient is transferred to the floor for recovery. Drainage, if utilized, can usually be removed within 24 hours. Patients are counseled regarding

proper wound care and instructed to return if they have any signs of infection or deterioration in neurological status. The initial follow-up visit is most often scheduled for 2 weeks after surgery and at 3 and 6 months post-operatively. Physical therapy is also initiated as needed, generally beginning 2 weeks after surgery. Most individuals can be sent home the same day of the procedure when they are freely ambulating, tolerate an oral diet, and are able to void spontaneously. Standard information, including universal signs of infection, is conveyed in a regularized form for patient information and record keeping.
