Thoracoscopic Approaches to Deformity Correction [2]

38 Thoracoscopic Approaches to Deformity Correction [2]

Rudolph J. Schrot and George D. Picetti III

38.1 Introduction

This chapter presents the thoracoscopic approach to deformity correction in a progressive manner, each part building on the techniques of the previous part.

38.2 Thoracoscopic-Assisted Arthrodesis for Posterior Deformity Correction

38.2.1 Indications

• Rigid scoliotic curves with Cobb angles greater than 75° and with less than 50° of lateral bending on anteroposterior radiographs 1

• Lesser curves in immature patients at risk for differential anteroposterior (AP) growth after posterior arthrodesis (“crankshaft phenomenon”)

38.2.2 Case Presentation

The patient was a 7-year-old female (20.4 kg) with progressive, severe postlaminectomy kyphosis after resection of a spinal cord anaplastic astrocytoma (Fig. 38.1a). The patient underwent T1–L1 Ponte osteotomies, pedicle screw instrumentation, deformity correction, and fusion (Fig. 38.1b).

Pseudarthrosis resulted in implant failure, with rod fractures and re-creation of the kyphotic deformity (Fig. 38.1c).

The patient underwent redo posterior exploration of the fusion, hardware removal, and redo deformity correction and fusion from T4 to T8 with iliac crest bone graft (Fig. 38.1d).

38.2.3 Preoperative Plan

• It was determined that, due to the prior laminectomies, the patient lacked adequate posterior fusion surface and was at high risk for repeat pseudarthrosis. Therefore, anterior diskectomies and fusion with autologous rib graft were planned.

Fig. 38.1 (a,b) A 7-year-old female developed progressive postlaminectomy kyphosis after resection of a spinal cord astrocytoma at ages 2 and 3. (c,d) A postoperative X-ray shows the deformity correction at age 6. (e,f) A follow-up X-ray revealed hardware failure and loss of correction. (g,h) Redo posterior surgery was performed.

Fig. 38.2 The patient is in the direct left lateral decubitus position. The arms and hips are taped onto the operating table to maintain this position throughout the procedure.

Fig. 38.3 The projection of the intervertebral disks is marked on the skin.

• A minimally invasive thoracoscopic approach was selected to minimize blood loss and recovery time, and to optimize cosmesis, shoulder girdle function, and pulmonary function.

38.2.4 Position and Anesthesia

• Selective intubation of the left bronchus with a single-lumen endotracheal tube was achieved. The patient was placed in a direct lateral decubitus position with the right side up. An arterial line was placed. The pelvis was protected with a lead apron (Fig. 38.2).

• AP C-arm fluoroscopy was used to mark the projection of the intervertebral disks on the skin. In this case, the scapula and shoulder girdle could be mobilized superiorly for access to T4–T5. Three portal sites were planned at T4 and T8, with an additional site at T10 for the inflatable lung retractor (Fig. 38.3).

• Two video monitors were positioned at the head of the bed 180° apart to afford an endoscopic view to both the surgeon and the assistant holding the endoscope. The surgeon was positioned posterior to the patient, and the assistant stood anterior to the patient.

38.2.5 Thoracoscopic Access (Video 38.1)

• After preparation of the skin and draping, a skin incision is made at T7–T8 and carried through the subcutaneous tissue over the superior surface of T8 to avoid the neurovascular bundle along the inferior surface. A 5-mm portal was inserted.

• The 30° endoscope was inserted into the pleural cavity.

• Under direct endoscopic vision, a second portal for the working channel was placed at T4 and a final portal was placed at T10 to accommodate the lung retractor.

• The lung retractor was placed and inflated and manipulated to afford a view of the anterolateral pleural angle between the thoracic spine and rib heads.

• Instruments and suction were exchanged through the working channel at T4 as needed.

38.2.6 Pleural Dissection

• After the level was confirmed fluoroscopically, the parietal pleura was incised longitudinally with electrocautery, starting at the disk and then along the length of the spine requiring diskectomies and fusion. A hook electrocautery was placed on the pleura overlying the intervertebral disk, and a pleural opening was made. The pleura was elevated off the spine and incised. This maneuver allowed for incision of the pleura along the spine segments to be fused and avoided injury to the segmental vessels.

• The pleura was further dissected anteriorly from the anterior longitudinal ligament and posteriorly from the rib heads.

38.2.7 Rib Head Resection and Diskectomies

• Partial resection of the rib head was performed with osteotomes and rongeurs to gain access to the posterior part of the disk. This maneuver is not required in older patients.

• The intervertebral disk annulus was incised with electrocautery. A complete diskectomy was performed using specialized curets and rongeurs to expose the chondral end plates. The removal of the disk and annulus extended anteriorly to the anterior longitudinal ligament and posteriorly to just behind the remaining rib head.

• In cases performed for anterior release prior to posterior fusion, the anterior longitudinal ligament is thinned so that it can no longer limit spinal mobility but still provides structural support to contain the bone graft.

• The chondral end plates were removed, and the bony end plates were rasped to a homogenous bleeding surface. The disk space was packed with Surgicel for hemostasis.

• The working channel and endoscopic port were interchanged as needed to provide optimal access to the disk spaces.

Fig. 38.4 The disk spaces are filled with morcellized autologous bone graft harvested from the rib resection. The chest tube can be seen superiorly.

38.2.8 Bone Graft Harvest

• Attention is directed to rib graft harvest. In this case, because the patient was young, a complete rib block could be resected with expected regrowth.

• A proximal section of the T8 rib was dissected subperiostially and circumferentially to avoid the neurovascular bundle.

• The rib was cut with an endoscopic rib cutter.

• A second rib graft was harvested at T6 after skipping the T7 rib. It is crucial to skip levels when harvesting rib grafts to avoid a flail chest.

• The rib grafts were milled to produce morcellized autologous bone graft.

• For bone graft harvest in older patients, a perpendicular cut using the endoscopic rib cutter is made in the superior aspect of the rib at the anterior and posterior extent of the rib dissection. The cuts are connected with a straight osteotome, thus removing the superior portion of the rib. This technique maintains the integrity of the rib and protects the intercostal nerve.

38.2.9 Arthrodesis

• After the Surgicel was removed from each disk space, the endoscopic bone funnel and plunger were used to pack morcellized local autologous bone graft into each of the disk spaces (Fig. 38.4).

• The disk was partially filled, then a small tamp was used to push the graft to the opposite side to ensure complete filling of the space.

• After the disk space was filled, more graft was placed over the space and the adjoining area where the periosteum had been elevated for improved fusion surface.

38.2.10 Closure

• The chest cavity was irrigated, and the lung retractor was removed. The lung was allowed to re-inflate.

• The portals were removed. A 20-French chest tube was placed out of the opening from the inferior portal.

• The portals were closed in layers with absorbable suture. A 2–0 nylon purse-string suture was placed around the chest tube exit site. Steri-Strips (Nexcare), Xeroform gauze, and sterile dressings were placed. The chest tube was attached to suction.

38.2.11 Results

• Intraoperative blood loss was 30 mL. There were no intra-operative or perioperative complications. The chest tube was removed on postoperative day 1, and the patient was discharged home in stable condition on postoperative day 2.

38.2.12 Notes

• Although fully posterior deformity corrections and fusions are more common with the advent of fourth-generation spinal instrumentation, in this case a lack of posterior fusion surface resulted in failure of the initial treatment with posterior fusion and necessitated an anterior arthrodesis.

• Endoscopic transthoracic diskectomy and fusion provided a minimally invasive option that resulted in minimal blood loss and a short hospital stay.

• The procedure was feasible even in a patient weighing less than 30 kg. A double-lumen endotracheal tube was not required.

• For young patients with low Risser stage, anterior diskectomy and fusion reduce the risk of the crankshaft phenomenon from expansion of the anterior growth plates.

• The key to successful fusion is a total diskectomy and complete removal of the end plate.

• A retrospective comparison review (Level III evidence) showed that Scheuermann’s kyphosis was more effectively treated through a completely posterior approach.²

38.3 Fully Endoscopic, Completely Transthoracic Deformity Correction

38.3.1 Indications

Progressive primary idiopathic thoracic scoliosis (Lenke type 1 and 2 curves).³

38.3.2 Position and Anesthesia

• Positioning and anesthesia are as for the thoracoscopic-assisted arthrodesis for posterior deformity correction described above.

• Double-lumen intubation is used in adults and children weighing more than 45 kg. Children weighing less than 40 to 45 kg require selective intubation of the ventilated lung.

• Intraoperative somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring is established.

• The patient is placed in the lateral decubitus position with the concave side of the scoliotic curve down. The C-arm is used to mark the portal sites, spanning the inferior and superior ends of the Cobb angle. The portal placement must account for spinal rotation as determined with C-arm fluoroscopy. Three to five incisions are planned, depending on the number of levels to be instrumented (Fig. 38.5).