**3.3 Spinal approach**

### *3.3.1 Incision*

The patient is prone-positioned with appropriate padding, prepping, and draping in sterile surgical fashion. The midline is marked to help orient the surgeon. An

**Figure 3.**

*Intraoperative images showing patient positioned prone on a Jackson table, fluoroscopic unit in place, and pneumatic arm used to holds the tubular retractor for easy repositioning at the press of a button.*

18-gauge spinal needle is used with lateral fluoroscopy to identify the proper level. A 3–3.5 cm incision is made lateral to the midline directly over the disk space in which the MI-TLIF is to be performed. This distance from the midline allows access to the base of the spinous process for adequate minimally invasive laminectomy for direct decompression of the spinal canal. If no decompression is required, the incision is made 3.5 cm distance from the midline. This distance facilitates interbody implant placement within the disk space. After the fascial incision is made parallel to the spinous processes, the one-step-dilator is brought into the operating field (**Figure 4**). With the support of a holder and using fluoroscopic guidance, the dilator is advanced toward the facet in a clockwise fashion. After docking the dilator on the facet, counterclockwise rotation of the handle opens the flanges of the dilator, separating the muscle tissue. A tubular retractor of the appropriate depth is then placed. The procedure is performed under direct microscope visualization through the tubular retractor. The approach is bloodless and obviates the need for K-wires or serial dilation, avoiding the potential complications that can be seen when using these instruments (**Figure 4**).

### *3.3.2 Lumbar exposure and decompression*

After positioning the tubular retractor, the microscope is brought into the surgical field. AP and lateral fluoroscopy can be used to ensure proper retractor placement. Soft tissue is excised to the extent of the facet laterally and the ipsilateral lamina medially, and a high-speed drill and M8 cutting burr are used to drill the lamina. All drilled bone is collected using the BoneBac™ Press (Thompson MIS, Salem, NH). This bone is used for fusion material, avoids graft site morbidity, and if needed, can be combined with other biologic material (**Figure 5**). If significant spinal stenosis coexists, a minimally invasive laminectomy is performed allowing circumferential decompression of the spinal canal. We are strong believers that decompression needs to be addressed before percutaneous screws are placed, as most of the surgical steps are done in a logical stepwise fashion.

*Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Novel Technique… DOI: http://dx.doi.org/10.5772/intechopen.105187*

### **Figure 4.**

*a. Intraoperative images showing the use of one-step-dilator to approach the spine and b. eliminate K-wire and multiple muscle dilators. c. Illustration of the one-step-dilator retractor used to approach the spine in a muscle sparing fashion.*

### **Figure 5.**

*a. Intraoperative view showing the use of microscope. b. Illustration, and c. intraoperative photos showing decompression of lamina with high-speed cutting burr and d. collection of drilled morselized bone graft material e. using the BoneBac™ press.*

### *3.3.3 Interbody fusion*

Upon decompressing the spinal canal, the tubular retractor is repositioned to expose the facet complex. In every case, lateral fluoroscopy is used to confirm the appropriate level. An ipsilateral facetectomy is then completed using a high-speed cutting burr, and an annulotomy is performed to enter the disk space. A series of disk space reamers, curettes, and rongeurs are used to prepare the disk space and vertebral endplates for interbody arthrodesis. Care must be taken to adequately remove the cartilage endplates to improve interbody arthrodesis. Once preparation of the disk space is completed, the implant is selected based on trials. The most commonly used implant size is 7 mm wide by 11 mm or 12 mm tall and 26 mm in length. This size appears to be appropriate in the majority of cases and provides for adequate disk and foraminal height restoration. In many cases, partial reduction of spondylolisthesis occurs with restoration of the disk height. Lateral fluoroscopic images identify the proper location of the implant within the disk space. Once the implant is within the disk space, the tubular retractor is positioned medially to help seat the implant within the center of the disk space. The relatively small width of the implant design and bulleted nose allows for ease of placement within the interbody disk space. The implant is then rotated 90 degrees thus restoring disk space and foraminal height to 11 or 12 mm, respectively. With the implant properly positioned, BoneBac™ TLIF bullets are filled with morselized autograph bone collected during the procedure using the BoneBac™ Press. The bone is then pushed down the handle of the implant to allow filling of the disk space as the bone is pushed out around the implant and contained by the intact annulus fibrosis of the disk. Typically, 10–12 bullets of drilled morselized autograph are used to completely fill the disk space. This process allows for off-loading of the interbody implant while allowing the compression of the morselized autograph to improve fusion rates via Wolff's law. If more bone graft material is needed, the morselized autograph is mixed with additional bone graft material (i.e. allograft, demineralized bone matrix, etc.). Once the disk space is packed with bone graft, the implant is released and deployed into the disk space. The disk space is inspected with a ball-ended probe under microscope visualization to assure that all bone graft material is within the disk space and that adequate direct neural decompression has been achieved. Additionally, bone graft material can be used to reconstruct the resected facet complex allowing for circumferential bone fusion (**Figure 6**). With complete and adequate hemostasis, the tubular retractor is removed allowing the paraspinous muscles to return to their normal anatomical position. Postoperative CT confirms adequate filling of disk space with morselized autograph.

### *3.3.4 Percutaneous pedicle screw instrumentation*

Upon completion of decompression and interbody fusion, the tubular retractor is removed, and the paraspinous muscles are allowed to return to their normal anatomical position. A contralateral incision is made equidistant from the midline, and AP and lateral fluoroscopy are used to target the pedicles for percutaneous pedicle screw fixation. Alternatively, image-guided robotic navigation can be used for this purpose [28, 29]. To avoid parallax distortion on fluoroscopic imaging, the target vertebrae is centered on the image, the endplate is made as one single line, and the spinous process is oriented between the pedicles. Intraoperative electrophysiologic monitoring with EMG is performed (**Figure 6**). To ensure proper positioning after K-wire and pedicle screw placement, these constructs are stimulated with a probe. Stimulation thresholds less than 8 mAmps necessitate repositioning of K-wire and/ or pedicle screw. Typically, percutaneous screws are placed bilaterally and segmentally at each MI-TLIF section to ensure adequate fixation and promote arthrodesis. To reduce radiation exposure, we use the MinRad™ arm (Thompson MIS, Salem, NH) to hold the Jamshidi needle in place. This device also facilitates percutaneous pedicle screw placement by allowing for small adjustments of the pedicle targeting needle, thereby improving pedicle screw placement accuracy (**Figure 7**).

*Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Novel Technique… DOI: http://dx.doi.org/10.5772/intechopen.105187*

### **Figure 6.**

*Preoperative MRI showing A. midline and B. lateral sagittal images of grade 1 spondylolisthesis with severe foraminal stenosis causing patient's symptoms of debilitating back pain. Intraoperative fluoroscopic images showing C. tubular retractor in place, D. placement of 7 wide PEEK implant into the interbody space, E–F. rotation of the implant to restore disk height to 11 mm, G–H. injection of drilled morselized autograph into the disk space, I. deploying implant into the disk space, J. photo showing intraopertive stimulation of K-wires and percutaneous pedicle screws to assure adequate placement, K–L. reduction of the spondylolisthesis using percutaneous pedicle screw reduction methods, and M. final lateral fluoroscopic image using Thompson MIS BoneBac™ TLIF system. Note restoration of disk height, sagittal alignment, and foraminal and canal diameter.*

### **Figure 7.**

If concomitant vertebral subluxation is present, reduction of the spondylolisthesis is attempted to restore sagittal alignment (**Figure 6**). This technique significantly increases the neural foraminal size and central canal diameter while also ensuring sufficient surface area between adjacent vertebrae for arthrodesis (**Figure 8**).

After wound irrigation, a 2–0 vicryl suture is used to close the fascial layer in an interrupted fashion. A subcuticular stitch and skin glue adhesive are used to close the skin. Drainage and wound dressing are generally not required, and the infection rate is negligible. Excellent long-term clinical outcomes using this MI-TLIF technique have been achieved (**Table 1**) [26].

Excellent long-term patient-generated outcome results have been achieved using the MI-TLIF technique described. Source: Quality-of-Life Outcomes With Minimally Invasive Transforaminal Lumbar Interbody Fusion Based on Long-Term Analysis of 304 Consecutive Patients. Mick J. Perez-Cruet, MD, MS, Namath S. Hussain, MD, G. Zachary White, BS, Evan M. Begun, BS, Robert A. Collins, DO, Daniel K. Fahim, MD, Girish K. Hiremath, MD, Fadumo M. Adbi, BS, and Sammy A. Yacob, SPINE Volume 39, Number 3, p E191 - E198, 2014.

Adjacent segment disease over a 5-year postoperative period has been approximately 2% compared to 13.6% in traditional open lumbar arthrodesis series [8, 30].

### *3.3.5 Postoperative care*

Patients typically stay in the hospital for 2–3 days after surgery and ambulate the day after surgery. Postoperative pain is managed initially with IV and oral pain medications and muscle relaxers as needed. Consultation with physical therapist or occupational therapist is arranged before discharge. Patients are discharged with postoperative care guidelines and follow-up plans. The follow-up is performed at

*Intraoperative photo and images of MinRad used to hold pedicle access needle for.*

*Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Novel Technique… DOI: http://dx.doi.org/10.5772/intechopen.105187*

$$\bf{(a)}$$

### **Figure 8.**

*a. Intraoperative lateral fluoroscopic images using unique design of the BoneBacTM TLIF device to reduce grade 1 spondylolisthesis to grade 0 and thus b. restore foraminal height allowing adequate decompression of the exiting nerve root. c. Reduction of multi-segmental spondylolisthesis with percutaneous reduction screws.*


*The values are given as the mean and the standard deviation.*

*SF-36 indicates Short-Form 36.\* Net change and percent improvement from baseline, respectively, are in parenthesis.*

### **Table 1.**

*Long-term results.*

2 weeks, 3 month, 6 month, and 1 year from the day of surgery. Patients are advised to wear a LSO brace when ambulating for the first 3 months postoperatively. Outpatient physical therapy is typically started 2 weeks after surgery, and the patient is taught exercise programs to improve core muscle strength and function.

### *3.3.6 Management of complications*

Our patients tolerate this MI-TLIF procedure exceptionally well. Potential perioperative complications include infection, hematoma, hardware malposition or failure, neurological injury, and cerebrospinal fluid leakage. Perioperative antibiotics, meticulous wound closure, and appropriate dressing changes can prevent wound infections. Proper utilization of fluoroscopic imaging and stimulation of K-wires and pedicle screws minimize the risk of instrumentation malposition and nerve root impingement. A small durotomy can be successfully treated with Gelfoam to cover the defect, followed by fibrin glue, followed by meticulous wound closure using a running locking nylon stitch. Complications can be limited by adequate surgical training and critical patient selection. Most postoperative would infections are superficial and above the fascial plane and can be treated with a week's course of oral antibiotics.

## **4. Clinical series**

Using this technique, the following represents our MI-TLIF clinical series comprised 405 consecutive cases. The clinical characteristics are seen in **Table 2**. The average age of patients in the series was 64 years with most being female (60%). Forty-five percent of patients were classified as obese. The primary condition was treated with spondylolisthesis and spinal stenosis most commonly at the L4–5 level with back pain as the primary complaint. High blood pressure, diabetes, and high cholesterol were the most commonly seen co-morbidities.


**Parameter Patient data** Others 80 (19.9%) **Comorbidity Patient data** Hypertension 95 (23.6%) Diabetes 62 (15.4%) High cholesterol 33 (8.9%) Cardiovascular disease 29 (7.2%) Smoking 33 (8.9%) Urinary incontinence 11 (2.7%) Stroke history 12 (2.9%) Osteoporosis 8 (1.9%) Hypothyroidism 41 (10.2%) Fibromyalgia 10 (2.5%) Cancer 50 (12.4%) Rheumatoid arthritis 11 (2.7%)

*Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Novel Technique… DOI: http://dx.doi.org/10.5772/intechopen.105187*

### **Table 2.**

*Patient characteristics (n = 405).*

## **5. Minimally invasive TLIF series**

Patients had a significant improvement in visual analog scores (VASs), Oswestry Disability Index (ODI), and Short Form-36 (SF36) over the 5-year follow-up period (**Table 3**, **Figure 9**).

ODI: Oswestry Disability Index, VAS: visual analog scale, SF: Short Form, PhF: physical function, RLPh: role limitation due to physical health problem, RLE: role limitation due to emotional health problem.

Complication rates in these series were low with cerebrospinal fluid (CSF) leak/ dural tear experienced in only 0.5% of patients. Fusion rates based on the Bridwell


**Table 3.**

*VAS, ODI, and SF36 (v2) scores (5-year follow-up).*

### **Figure 9.**

*Line graph demonstrating mean VAS of back pain, ODI and SF36 (v2) scores over 5 years follow up time. PhF: Physical function, RLPh: Role limitation due to physical health problem, RLE: Role limitation due to emotional health problem. PO: Post-operative. Op: Operative.*

fusion criteria was extremely high with 97% achieving Grade I (**Table 4**). This was felt to be in large part because of the novel method of injecting the patient's own drilled morselized autograph into the properly prepared disk interspace. With loading of the filled disk space autograph bone material, according to Wolff's law, very high fusion rates can be achieved.


### **Table 4.**

*Postoperative complications and fusion rates %, (n = 405).*

*Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Novel Technique… DOI: http://dx.doi.org/10.5772/intechopen.105187*
