Open and Minimally Invasive Treatment of Cervical Spine Fractures

17 Open and Minimally Invasive Treatment of Cervical Spine Fractures

MIS: Michael Y. Wang and Joanna Gernsback
Open: S. Babak Kalantar and Joseph Paul Letzelter III

17.1 Introduction

Cervical spine trauma is a morbid problem causing potentially debilitating injuries in young patients and the elderly. Cervical spine trauma is associated with high-impact injuries in young patients and low-impact mechanisms in the elderly; hence, it usually occurs in a bimodal distribution. Common causes include motor vehicle accidents, falls, violence, and sports. C1 and C2 fractures are distinct from the fractures that occur in the subaxial spine, and account for 70% of all cervical fractures.1 Gallie described C1–C2 wiring for fractures in 1939,² and the occipitocervical fusion was described in 1969 by Newman and Sweetnam³ as an option for dens fractures. The odontoid screw was described by Böhler⁴ in 1982, as another option for odontoid fractures. C1 lateral mass screws were described in 1994 by Goel and Laheri, for atlantoaxial dislocation,⁵ and in 2001 Harms and Melcher added C2 pars screws.⁶ Transarticular screws were described in 1987 by Grob and Magerl.⁷ In the subaxial cervical spine, unstable fractures include teardrop fractures, jumped facets, and burst fractures associated with significant retropulsion. Treatment of subaxial cervical fractures began with Horlsey⁸ and the simple laminectomy in 1895. Rogers presented spinous process wiring for trauma in 1942.⁹ The anterior cervical discectomy and fusion was presented in 1955 by Smith and Robinson, and Cloward,⁹ with the plate being added in the 1980s. Posterior lateral mass screws were described by Roy-Camille in 1980.⁹ The focus of this chapter is unstable fractures, namely, those that require operative intervention for either internal fixation or decompression of neural elements. Although minimally invasive surgery (MIS) techniques for cervical spine fractures are in their infancy, several have been described. We will present an evidence-based discussion comparing the traditional treatment or “open” surgery for cervical spine fractures with MIS techniques.

17.2 Advantages of Minimally Invasive Surgery

MIS offers decreased operative time and blood loss, which are both beneficial in polytrauma and elderly patients, who may not tolerate longer procedures with significant blood loss. It avoids the necessity of significant muscle dissection, which may decrease postoperative neck pain. It eliminates the need for halos in some trauma patients. The incisions are smaller, meaning lower rates of wound problems and better cosmetic results.

17.3 Advantages of Open Surgery

Open treatment for cervical spine fractures has many potential advantages, which may not only affect the technical ease of performing the procedure but also can potentially result in improved outcomes. The most obvious benefit of open treatment is visualization. Open treatment provides the surgeon with better visualization of the fracture and neural elements not relying on fluoroscopic or indirect visualization of the traumatized segment. This is most important in cases where a discectomy is being performed and visualization of the spinal cord and canal is necessary. Open treatment also carries the benefit of increased fusion rates, which have been reported as high as 100%. Direct access and exposure to potential fusion surfaces both anteriorly and/or posteriorly can allow for more thorough decortication and more volume of bone graft material. Open treatment has also been shown to have high rates of increased stability due to fixation techniques, which add to increasing the likelihood of fusion.

In cases of traumatic spondylolisthesis in the subaxial spine, open treatment provides the benefit of improved access to the disc space in the case of a disc herniation. Access to the disc space also provides visualization of the neural elements, which aids the surgeon in decompression. Flexion-compression injuries approached anteriorly have been shown to restore the canal diameter by 60% compared to only 6% posteriorly. In summary, open treatment of cervical fractures provides better visualization, increased stability, and higher union rates.

17.4 Case Illustration

A 53-year-old homeless man, with a history of diabetes and glaucoma, was brought to the trauma center after falling off a balcony, approximately 8 ft. He was hypotensive and not moving his extremities. He was awake and mildly confused. He had no motor movement or sensation in his extremities. He had weak rectal tone and priapism. A computed tomography (CT) scan of the cervical spine demonstrated a comminuted fracture of the C4 vertebral body, involving the right transverse foramen, jumped facets at C4–C5, and anterolisthesis of C4 on C5 ( Fig. 17.1). The V2 segment was not visualized, suggestive of a vertebral artery injury. Emergent surgical intervention was recommended.

17.5 Surgical Technique in Minimally Invasive Surgery

The patient is brought to the operating room where general endotracheal anesthesia is administered. The patient should be intubated using a fiber optic system. A Foley catheter is inserted, pneumatic compression devices and neurophysiological monitoring leads placed, and an arterial line may be used if indicated. The Mayfield head holder is positioned, and the patient is carefully flipped onto a four-post operating table. All pressure points are padded. Preoperative antibiotics are then administered. The fluoroscopic C-arm is then positioned for lateral fluoroscopy.

Fig. 17.1 (a) Sagittal and (b) axial initial computed tomography images demonstrating comminuted fractures of the C4 vertebral body, involving the right transverse foramen, jumped facets at C4–C5, and anterolisthesis of C4 on C5.

A Steinman pin is inserted through the skin under fluoroscopy to reach the lateral mass. The pin trajectory should be parallel to the facet joint in the sagittal plane, making the skin entry point about three spinal segments below the dislocation. The entry point is midline in the axial plane, so the pin trajectory is in a superolateral direction. A 1.5-cm skin incision is made at the pin entry point. Serial METRx MD tubular dilators (Medtronic, Minneapolis, MN) are inserted to a final diameter of 18 or 22 mm. An 11-blade scalpel can be used to incise the nuchal fascia to facilitate tube placement. A headlight and surgical loupes improve visualization; an operating microscope would be a more cumbersome option.

The lateral mass surface is exposed using monopolar cautery and pituitary rongeurs to remove intervening soft tissue. A curette is used to remove the synovium of the facet joint to be fused, and the facet is packed with autograft bone.

A 14-mm-deep pilot hole is drilled with a 2.4-mm-diameter cancellous drill. The starting point is 1 mm medial to the midpoint of the lateral mass. The trajectory parallels the facet joint, at 20 degrees lateral. The pilot hole is tapped using a 2.43-mm-diameter cancellous tap. The depth is measured, and an appropriate length 3.5-mm-diameter polyaxial screw (Vertex; Medtronic) is placed. A second screw is placed in the adjacent lateral mass. A 3.2-mm-diameter top-loading connecting rod is attached. The rod should be inserted lengthwise into the tubular dilator and advanced superiorly into the upper polyaxial screw head. The tubular retractor is then slightly elevated to allow the inferior aspect of the rod to be inserted into the lower polyaxial screw head. Setscrews are placed to rigidly fix the construct. If a bilateral construct is desired, the process is repeated on the contralateral side. Proper screw placement is confirmed by anteroposterior fluoroscopy prior to skin closure.

17.6 Surgical Technique in Open Surgery

The patient is brought to the operating room and undergoes general endotracheal intubation with fiber optic assistance to avoid excessive cervical extension. Neurophysiologic leads are placed and baselines are recorded after the administration of anesthesia and then again after positioning. A Foley catheter is placed and anesthesia is administered at an arterial line to monitor blood pressure. A Mayfield head holder is applied and the patient is rotated into the prone position on a Stryker frame table. During rotation, light traction should be applied to increase stability.

After prone positioning and establishing neurophysiology baselines, the large C-arm is brought in and a lateral radiograph is obtained to ensure the dissection is carried down at the correct levels. A standard subperiosteal dissection of the posterior cervical spine is then performed down to the C4–C5 vertebrae. Once down to the desired levels, another radiograph is obtained to ensure the correct levels are in view. The lateral masses are then exposed on both vertebrae.

The dislocation is then reduced by grasping the involved spinous processes from C4 and C5 with a towel clip or tenaculum at the spinolaminar junction. The tenaculum or towel clip can be used to apply gentle traction to the caudal vertebrae while at the same time gentle distraction and a kyphotic moment is applied to the cephalad vertebra to disengage the dislocated facets. After the facets are unlocked, axial traction and reduction are performed to reduce the inferior articular processes posterior to the superior articular processes. During the reduction, it is important to have the neurophysiologist be alert for any acute signal changes. If there is an acute signal change, the procedure should be halted.

After the reduction is performed, the quadrilateral posterior surface of the lateral mass is exposed. A high-speed 2-mm burr is used to penetrate the outer cortex of the lateral mass at an entry point 1 mm medial to the center of the posterior surface of the lateral mass. A tap is then used and aimed parallel to the place of the facet joint with 25 degrees of lateral angulation in the axial plane. Prior to placement of screws, a C4 and C5 laminectomy is performed to adequately decompress the spinal cord. Using a high-speed burr, troughs are created at the junction of the lateral mass and lamina bilaterally. Bony resection can be completed with the burr or small Kerrison rongeur. The interspinous ligament and ligamentum flavum at C3–C4 and C5–C6 are resected and the laminae are lifted off and removed. This bone can be morselized and used for bone graft. A polyaxial unicortical screw is then placed into the lateral masses at C4 and C5. If facet or lateral mass fracture is encountered, further fixation points can be obtained at C3 and C6 to enhance stability. Prior to rod placement, the lateral portions of the lateral mass as well as the facet joints are decorticated using a small high-speed burr. Bone graft harvested from the laminectomy and/or iliac crest is morselized and placed posterolaterally. The screw heads are lined up and the rods are inserted and gentle compression across the construct is applied and set screws are placed. Screws are placed in standard fashion at C4 and C5. If there is no soft-tissue injury at the adjacent levels, and adequate biomechanical fixation is obtained, then a one-level fusion can be performed. Compression can be applied across the lateral mass screws to achieve alignment. Proper screw placement is confirmed by anteroposterior fluoroscopy prior to skin closure. The paraspinal muscles are approximated with a loose Vicryl stitch and the fascia is then sutured in watertight fashion using no. 1 or 0 Vicryl suture. A layered closure is completed with skin typically closed with a subcuticular Monocryl suture.

17.7 Discussion of Minimally Invasive Surgery

MIS procedures for the cervical spine are still in their infancy and are associated with a steep learning curve. This means there are not yet many studies in the literature ( Table 17.1 and Table 17.2). With one exception, all data for MIS treatment of cervical spine fractures are level IV; that is, it comes from case reviews or case series. Most of these include fewer than 10 patients, though the endoscopic anterior cervical decompression and fusion (ACDF) series¹⁰ includes 67 patients. As more surgeons begin performing and reporting these procedures, the level of evidence will likely improve.