Minimally Invasive Spine Surgery

h1 class=”calibre8″>20 Minimally Invasive Spine Surgery

Tyler Atkins and Domagoj Coric

Abstract

Over the past 10 years several authors have published several anatomic feasibility studies, case reports, and small case series regarding minimally invasive spine (MIS) treatment of some specific cervical traumatic injuries. This chapter represents a review of current specific cervical traumatic pathologies that have begun to be treated via MIS techniques and discusses the approaches being utilized. Many of the common upper cervical spine fractures, including odontoid fracture, C2 pars fracture, C2 body fracture, and combined C1–C2 injuries, have been treated with variable anterior and posterior (or combination) MIS techniques as modifications of open approaches, often utilizing intraoperative navigation. In addition to summarizing the published techniques, we have included two simple case examples with imaging. Subaxial cervical fractures can also be treated in select cases with MIS instrumentation such as percutaneous lateral mass or pedicle screws. We summarize these techniques and results currently described in the spine literature. In an era of medicine with much focus on limiting morbidity due to interventions, advancements in instrumentation as well as image guidance is leading to ongoing development of MIS operations. Further utilization and future study of MIS techniques in the cervical spine is likely.

Keywords: minimally invasive, MIS, cervical trauma, fracture, percutaneous, odontoid, C1, C2, subaxial

20.1 Role for Minimally Invasive Surgery in Cervical Trauma

Minimally invasive spine (MIS) techniques have been gaining increasing popularity over the past few decades, with most attention paid to the lumbar spine. This has included treatment of a range of pathologies including traumatic injuries, perhaps most popularly with the use of percutaneous pedicle screw-rod systems for thoracolumbar fractures that do not require open reduction or decompression. MIS cervical techniques have similarly been gaining traction, but certainly less so in regard to instrumentation, with most attention being paid to minimally invasive decompression surgeries for degenerative spine pathology. Within the past 10 years, there have been several published anatomic feasibility studies, case reports, and small case series regarding minimally invasive treatment of some specific cervical traumatic injuries. We will review the common MIS principles among these techniques and discuss specific cervical traumatic pathologies where they may be utilized.

Adopting minimally invasive fixation techniques to the cervical spine comes with slightly more trepidation to the surgeon owing to a higher potential for significant complication and injury. This is due to the complex anatomy of the cervical spine. These anatomic considerations include the relative prominence of the cervical spinal cord, presence of the vertebral arteries, as well as the unique bony anatomy of the high cervical and subaxial spine in regard to these structures.

Despite these risks, some attractive considerations of MIS fixation for cervical injuries include the relatively high prevalence of these types of injuries in the elderly population from ground level falls as well as high-impact trauma. Traditional nonoperative interventions of rigid cervical collars or halo immobilization (which offers a higher rate of immobilization of the higher cervical spine) have a relatively high morbidity in the elderly population and are generally less efficacious and more morbid in this patient population. Similarly, traditional open procedures, such as posterior C1–C2 fusions or high cervical anterior cervical discectomy and fusions (ACDFs), in these patients carry significant morbidity. ¹^,²^,³ The ability to perform a minimally invasive surgery obviating the need for prolonged bracing in this patient population is particularly desirable.

Much of the cervical percutaneous MIS screw technology is derived from the techniques developed for the lumbar spine. The increased popularity and sophistication of intraoperative image-guided navigation systems have facilitated the safety and efficacy of percutaneous placement of cervical instrumentation and the overall adoption of MIS techniques in the cervical spine.

20.2 Injuries Treated by MIS Fixation

20.2.1 Odontoid Fracture

Placement of an odontoid screw via a minimally invasive technique has been investigated with good preliminary results. Although the traditional open technique involves relatively little exposure and soft-tissue dissection, there have been several reports of modifying the procedure to make it even less invasive with decreased morbidity. Wang and associates reported on 19 patients who underwent percutaneous odontoid screw placement for treatment of type II and rostral type III odontoid fractures. ⁴ The overall procedure is quite similar to open odontoid screw placement with only a few differences. The authors report placing the patients in Gardner–Wells tongs with 2 kg of traction. Then, utilizing two c-arms for precise anteroposterior and lateral fluoroscopy to make a 1-cm unilateral horizontal incision at the medial border of the sternocleidomastoid at the C5–C6 level. Dissection is taken to the medial border of the sternocleidomastoid at which point a blunt guide-tube dissector is advanced through the deep tissues to the anterior–superior border of the C2–C3 disc space. A sharp guide wire is placed through the tube once in ideal position, thereafter allowing passing of instruments over the wire in the same sequence as done for open screw placement (drilling, tapping, and screw placement while controlling the guide wire under fluoroscopy). The authors report no surgical complications, specifically no injury to the nonvisualized at-risk visceral and vascular structures of the anterior neck. In this prospective study comparing the percutaneous screw to 23 patients receiving an open operation, they report similar success in fusion with less operating room time and fewer cases of postoperative dysphagia. Images from a similar approach to odontoid screw placement can be seen in ▶ Fig. 20.1, ▶ Fig. 20.2, ▶ Fig. 20.3, and ▶ Fig. 20.4.

$Sagittal reconstruction of cervical spine computed tomography (CT) showing type II odontoid fracture with minimal extension-distraction, ideal for anterior odontoid screw placement.$

Fig. 20.1 Sagittal reconstruction of cervical spine computed tomography (CT) showing type II odontoid fracture with minimal extension-distraction, ideal for anterior odontoid screw placement.

Fig. 20.2 Intraoperative lateral fluoroscopy showing retractor in position in low anterior neck soft tissues, and screw entering C2 body at its inferior border.

Fig. 20.3 Postoperative standing lateral cervical radiograph showing odontoid screw.

Fig. 20.4 Postoperative standing anteroposterior cervical radiograph showing odontoid screw in ideal midline position.

Holly et al describe an alternative minimally invasive approach to fixation of type II odontoid fractures by utilizing dilating tubular retractors and fluoroscopy for a posterior C1–C2 fusion. ⁵ Their report includes five patients with type II odontoid fractures. The patients were all positioned prone in Mayfield pins with a 2 cm incision made bilaterally centered over C2. The authors were able to place C1 lateral mass and C2 pedicle screws with this exposure, as well as decorticate the articular surface, place allograft and demineralized bone, and place an appropriate sized rod on either side. No complications are reported and fusion rates of 100% were noted at an average of 32-months follow-up. Images utilizing intraoperative computed tomography (CT) guidance for a posterior hybrid fusion of anterolisthesed odontoid fracture can be seen in ▶ Fig. 20.5, ▶ Fig. 20.6, and ▶ Fig. 20.7 (one side with C1 and C3 lateral mass screw and other side C1–2 transarticular screw and C4 lateral mass screw).

$Sagittal reconstruction of cervical spine computed tomography (CT) shows nonhealing type II odontoid fracture with minimal anterior displacement. Patient also has anterior and posterior C1 ring fractu$

Fig. 20.5 Sagittal reconstruction of cervical spine computed tomography (CT) shows nonhealing type II odontoid fracture with minimal anterior displacement. Patient also has anterior and posterior C1 ring fractures without displacement. Poor candidate for continued conservative management, also not a candidate for isolated anterior odontoid screw placement.

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