Minimally Invasive Transforaminal Lumbar Interbody Fusion

Introduction

Traditional transforaminal lumbar interbody fusion (TLIF) is performed through a large midline open incision on the back. With this approach the surgeon must dissect and retract the paraspinal musculature in order to access the target level/s. This can lead to significant intraoperative blood loss, postoperative pain, muscle impairment, and longer hospital stays. With the integration of minimally invasive surgical techniques to the field of spine surgery, a TLIF can now be performed with much smaller incision sizes and minimal disruption to adjacent tissues ( Fig. 155.1 ). Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) offers a safe and effective alternative to the conventional midline open approach. The technique is extremely versatile and allows treatment of a variety of conditions including degenerative disc disease, spondylolisthesis with and without lumbar stenosis, and scoliosis. The posterior approach permits direct decompression of the neural elements, allows collection of local autograft bone for fusion material, and promotes arthrodesis by placing bone graft material in the interspace between adjacent vertebrae ( Fig. 155.2 ). Comparative studies have shown the superiority of MI-TLIF to the similar open technique. This can be attributed to the ability of this technique to preserve normal anatomical structures while achieving equivalent or superior clinical outcomes compared to the open approach.

Patient Selection and Surgical Indications

Indications for MI-TLIF include: degenerative disc disease, spondylolisthesis with or without stenosis, instability due to trauma or tumors, discogenic pain disorder, stabilization after osteotomy, pars interarticularis defect, stabilization of degenerative discs or recurrent disc herniations, and scoliosis correction and stabilization. These conditions are known to produce refractory chronic back pain disorders and can be considered as indications for spinal fusion. Additionally, MI-TLIF is designed to replace the disc space with bone graft material to treat: isthmic spondylolisthesis (grade 1 to 4), junctional degeneration adjacent to a fusion mass, recurrent disc herniations with significant back pain, terminal end of long fusion constructs requiring interbody fusion, degenerative scoliosis, and postlaminectomy spondylolisthesis ( Fig. 155.3 ). These conditions can often result in foraminal stenosis causing compression of the exiting nerve root. Restoration of disc height, sagittal alignment, and foraminal circumference can be all be achieved using the MI-TLIF approach.

Patients with osteoporosis, bleeding disorders, and active infection can be considered as relative contraindications. However, since the MI-TLIF procedure is performed with minimal tissue destruction and blood loss, these patients can also be treated using this technique when surgical intervention is indicated. In a retrospective cohort study of 74 obese patients (21 open and 53 MI-TLIF), patients who underwent MI-TLIF achieved similar clinical benefit compared with their counterparts in the open group. However, they experienced clinically and statistically significant improvement in both pain and function after undergoing MI-TLIF, as well as faster time to ambulation and quicker recovery due to the tissue-sparing nature of the approach. In addition, MI-TLIF is not associated with increased risk of developing perioperative complications in overweight or obese patients, suggesting a potential advantage in this subset of patients. Further contraindications include arachnoiditis, extensive epidural scarring, and conjoined nerve roots, which may prevent access to the disc space. However, we have treated a number of these types of patients with excellent long-term clinical outcomes.

Patients with multiple medical comorbidities tend to achieve good to excellent results after MI-TLIF. This was demonstrated based on a retrospective analysis we conducted on 74 patients with degenerative or isthmic spondylolisthesis who underwent MI-TLIF between November 2011 and August 2013. The most frequent comorbidities present in this series were hypertension, obesity, and diabetes mellitus type 2 ( Table 155.1 ). The average preoperative visual analogue score (VAS) reduced from 7 to 3.5. The preoperative Oswestry Disability Index (ODI) decreased from 45.5% to 37%. This illustrates the efficacy and safety of the MI-TLIF technique in patients with one or more comorbidities.

Preoperative Planning

As in all surgical disciplines, a thorough understanding of the surgical anatomy involved in MI-TLIF is crucial for maximal patient benefit and complication avoidance. Therefore, careful preoperative evaluation including thorough physical examination is performed. Radiographic workup typically includes plain X-rays with anteroposterior (AP) and lateral flexion and extension views. Magnetic resonance imaging (MRI) of the lumbar spine is performed ( Fig. 155.4 ). In redo operations with hardware in place or patients with significant scoliosis, computed tomography (CT) with myelogram may be helpful to better visualize the patient’s pathology. In those patients with no clear neurological compression, discography with post-discography CT is useful in determining the possible source of the patient’s chronic back pain.

Decompression Alone Versus Decompression With MI-TLIF

Determining the most appropriate surgical approach is critical to improving patient outcomes and satisfaction while providing focused treatment and avoiding unnecessary surgical time and intervention. We conducted a retrospective analysis of facet anatomy in a large series of patients and demonstrated that facet length could assist in identifying optimal surgical approach. Those patients found to have lumbar stenosis and facet lengths (i.e., length of superior and inferior facets) similar to nonpathological segments could be treated with decompression alone. In patients with elongated facets and stenosis, decompression in combination with MI-TLIF provided excellent patient outcomes and reduced the incidence of subsequent surgical intervention. Conversely, the surface area of the facet complex in patients with elongated facets was also greater than nonpathological segments. Elongation of the facet complex occurs frequently in patients with spondylolisthesis: the subluxation of one vertebra relative to another over an extended period of time (i.e., years) results in facet elongation. The MI-TLIF procedure allows for solid stabilization of the segment, as well as restoration of disc and foraminal height, and thus facilitates fusion and improves patient outcomes by stabilizing the spinal segment, and preventing recurrence of stenosis and further subluxation of the vertebrae ( Fig. 155.5 ).

Surgical Technique