The development of minimally invasive surgical techniques is a contemporary and rapidly evolving area in orthopaedics. Minimally invasive surgical techniques have led to decreased recovery time, reduced wound-related complications, improved cosmesis, and reduced costs.1,2,3,4 The application of minimally invasive techniques to surgery of the spine is becoming more widespread, and indications for these techniques are expanding.5 At The Children's Hospital, we are using video-assisted thoracoscopic surgical (V.A.T.S.) techniques as an alternative to open thoracotomy for anterior spinal procedures in children and adolescents.

History and Background

           The thoracoscope is a lineal descendant of the cystoscope, an instrument developed by Bozzini in 1806, with which he visualized the urinary bladder using a candle as a light source. Light sources hampered early use of the technique, evolving from a burning mixture of alcohol and turpentine to an early version of the Edison light bulb in 1883.6 Dr. Hans Christian Jacobaeus, a Swedish professor of internal medicine, is credited with the introduction of endoscopic techniques to the management of disorders of the thorax.7 Professor Jacobaeus used the thoracoscope under local anesthesia to cauterize adhesions between the lung and chest wall, allowing the lung to collapse for treatment of pulmonary tuberculosis.8,9 The modern era of thoracoscopy began in 1990 with the addition of fiberoptic light carriers and video projection to standard endoscopic techniques.10 Developments in optics and instrumentation for VATS have led to recent expansion of the indications for thoracoscopic techniques.11

VATS in Pediatric Spinal Deformity

           The application of thoracoscopic techniques to surgery in the pediatric population was first reported by Rodgers and Talbert in 1976 in a review of the treatment of immunocompromised patients with interstitial lung disease.12 Since that report, both the techniques and the indications for thoracoscopy in children have evolved considerably.13 The use of thoracoscopy in anterior release of the spine prior to posterior instrumentation was first reported by Waisman and Saute in 1996, describing their experience with three adolescents with idiopathic scoliosis.14 The thoracoscopic approach has compared favorably to the open thoracotomy in reducing the morbidity of anterior spinal surgery in the treatment of pediatric spinal deformity.15,16

          Anterior access to the thoracic vertebral bodies is often necessary in the treatment of major spine deformities in skeletally immature patients. Anterior release of fixed thoracic deformity facilitates realignment and improves fusion rates.17,18 Vertebral endplate resection is necessary in young patients in order to remove growth potential and prevent the so-called crankshaft deformity which may occur when the vertebral bodies continue to grow after the posterior elements have been fused.19

          Rib resecting thoracotomy in conjunction with an extensive posterior procedure is associated with substantial blood loss and fluid shifts, sometimes necessitating a delay between anterior and posterior procedures.20 Open thoracotomy has been associated with persistent pulmonary compromise21, chronic post-operative pain12, and in children open thoracotomy is a risk factor for major post-operative complications.22

          Thoracoscopic techniques offer a less disfiguring, less painful scar (Figure 1), improved shoulder girdle function, and a more rapid recovery. Animal models have demonstrated similar efficacy of thoracoscopic techniques in increasing flexibility of the spine23, and in promoting intervertebral fusion.24 We are currently studying the clinical efficacy of thoracoscopic anterior release versus open anterior release in increasing flexibility by comparing bending films done intraoperatively before and after release.

           The goals of the thoracoscopic approach to the anterior thoracic spine are to minimize complications associated with the operative exposure without compromising visualization of the spine, or efficacy of techniques.16 Our preliminary experience suggests that video-assisted thoracoscopic techniques can be used safely and effectively in the treatment of pediatric spinal deformities.

Indications/Contraindications

          Video-assisted thoracoscopic surgery is an alternative to open thoracotomy for vertebral body biopsy25, excision of intervertebral discs26, anterior release before scoliosis surgery15, corpectomy27, and anterior spine fusion.16 We have used the anterior approach for thoracoplasty, and we are developing techniques for thoracoscopic internal fixation of the spine.
Contraindications for the VAT approach to the thoracic spine include pre-operative pulmonary function compromise, intolerance of single lung ventilation, and prior pleurodesis.

Details of the Technique

          Equipment required for video-assisted thoracoscopic surgery include a multichip camera with two video screens, a five-millimeter, 0 degree and a ten-millimeter, 30 degree camera, and a set of elongated spinal instruments including an 8-millimeter Cobb, a rongeur, and a curette. An open thoracotomy kit should be readily available in case an open procedure becomes necessary. The anesthesia service induces general endotracheal anesthesia using a double lumen endotracheal tube. For the child less than 40 kilograms or 10 years of age, mainstem bronchial intubation is used to allow passive collapse of the bypassed lung. Arterial lines, central venous access and spinal cord monitoring lines are then applied by the anesthesia and neuro-monitoring services respectively. After the lung on the operative side is collapsed, the patient is shifted to a lateral decubitus position, with the convexity of the curve toward the surgeon. After repositioning the patient, the position of the endotracheal tube should be rechecked, as movement of the double lumen tube is not uncommon.

           The patient is prepped and draped from the level of the axilla to below the iliac crest to allow for open thoracotomy, and possible harvest of autogenous bone graft. Autogenous bone graft may also be harvested from an internal thoracoplasty. The surgeon and first assistant stand on the same side of the operating table, the abdominal side of the patient. A third assistant is necessary because of the need for two-handed control of the orthopaedic instruments, and continual fan retraction of the collapsed lung.

           The first portal is made through a 15-millimeter incision in the midaxillary line at the sixth or seventh intercostal space. To avoid intercostal neuralgia and injury to the central tendon of the diaphragm, a blunt Kelly should be introduced gently over the cephalad portion of the rib. A 10-millimeter plastic trocar is then inserted to maintain an open portal. An initial survey is made with the 5-millimeter, 0-degree camera. Adhesions between visceral pleura and chest wall are taken down with endoshears. Next, the 10-millimeter, 30-degree camera is inserted and additional portals are made under direct vision. Additional portals are made along the midaxillary line, and positioned according to the curvature of the convexity so as to optimize the working angle on the divergent discs. Between four and six thoracic portals are used for spinal deformity cases, all in the mid-axillary line.

          Prior to incising the parietal pleura the levels of the thoracic spine are determined by counting ribs outside and inside the chest wall. Confirmation is then obtained with an anteroposterior radiograph of the thoracic spine taken with a metallic marker in one of the disc spaces. The parietal pleura overlying the affected discs is then incised and the discs are exposed taking care to preserve the segmental vessels over the mid-vertebral bodies. (Figure 2) The annulus fibrosis is then cauterized and the disc space opened. The disc and endplates are excised using a Cobb and a pituitary rongeur, proceeding from the convex to the concave side. As dissection proceeds anteriorly, a grasper is used to elevate and protect the parietal pleura and azygous vein. The anterior annulus and anterior longitudinal ligament are then incised. Morsellized corticocancellous allograft is placed in the intervertebral space through the standard portals, and the parietal pleura may be closed over the disc space using an endoscopic suture device. All instruments and portals are removed, a chest tube is placed through the most inferior portal, and the wounds are closed. The lung is then reexpanded with opening of the endotracheal lumen to the operative side, or withdrawing the lumen from an isolated mainstem. The double lumen endotracheal tube is replaced prior to the posterior procedure.

           At The Children's Hospital, we are developing a retropleural approach to the thoracic spine for use in both open and thoracoscopic surgeries. This approach will serve to minimize intrapleural adhesions post-operatively, and facilitate revision surgeries.

Pitfalls and Complications

           Most surgeons learning thoracoscopic techniques have observed a substantial learning curve. Reports from animal labarotory experience demonstrate intraoperative complications leading to longer operative times, higher estimated blood loss, and increased animal morbidity for novice surgeons.25 A multicenter study reviewing the complications of endoscopic anterior thoracolumbar spinal reconstruction recorded major complications including diaphragmatic laceration, hepatic hemorrhage, common iliac vein laceration, and visceral pleural tears. Minor complications include transient intercostal neuralgias, bone graft donor site infection, and post-operative atelectasis.28

Conclusions

          Video-assisted thoracoscopic surgery is an important and valuable tool for minimizing morbidity in the anterior approach to the pediatric spine. Indications and applications for these techniques continue to evolve with development of new instrumentation systems and the improvement of surgical skills. Our current investigations at The Children's Hospital seek to confirm the efficacy and safety of video-assisted thoracic surgery in the pediatric spine, and to develop new techniques to further minimize morbidity of the anterior approach.

Sigurd Berven, MD is a Resident in the Harvard Combined Orthopaedic Residency Program

M Timothy Hresko, MD is an Attending Surgeon at The Children's Hospital, and Instructor of Orthopaedics at Harvard Medical School

Address correspondence to:
M. Timothy Hresko, MD; Department of Orthopaedics; The Children's Hospital; 300 Longwood Ave.; Boston, MA 02115