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Orthopaedic Surgery

Innovative Techniques in Spine Surgery

Spine surgery is one of the most rapidly evolving fields in orthopaedics. New techniques have revolutionized the post-operative course of patients, curtailing post-operative pain and accelerating a return to normal function. Video-assisted thoracoscopic surgery (VATS) is one of these promising techniques. Surgeons have performed thoracoscopic surgery (using cameras to operate within the chest cavity) for over 80 years. In the early 1990s spine surgeons began applying thoracoscopic techniques to correct spine deformities including scoliosis. Since then, VATS has become a new powerful tool in the surgeons armamentarium. (1, 5, 7) At the Morgan Stanley Childrens Hospital of New York we are optimizing the use of this tool to benefit our patients.

Surgeons use two main approaches to correct scoliosis curves:

• The anterior approach: Vertebrae are visualized and fused from the front through a chest wall opening.
• The posterior approach: Vertebrae are visualized and fused from the back through a midline back incision.

Each approach can incorporate:

• Fusion: eliminating the vertebrae growth plates and connecting them with bone bridges so that they will not bend or curve as the patient grows.
• Release: removing the intervertebral discs and ablating the joints between the vertebrae to free up the spine.
• Instrumentation: placing laminar hooks or inserting screws through the vertebral pedicles and connecting them with a rod to straighten the curve.

Traditionally, the anterior open approach has required a full thoracotomy (chest wall opening) to access the thoracic vertebrae. The approach, though effective, does leave a significant chest wall scar. With the advent of VATS, surgeons strived to obviate the need for the large incision and leave the patient with only the small incisions from the VATS camera and tool portholes. Currently, we employ the technique to successfully perform anterior fusion with instrumentation and can also combine it with a conventional posterior approach.

Thoracoscopic Spine Surgery

During the thoracoscopic procedure, the anesthesiologist placed a breathing tube in the patient that has a double lumen (one lumen in each lung bronchus) in order to control the inflation of each lung independently. Using this tube, the anesthesiologist collapses one lung to allow the surgeon access and workspace within the chest. The surgeon then cuts several small skin incisions along the side of the chest wall that will serve as portholes for a fiber-optic camera and surgical instruments. The camera magnifies and makes the structures inside the chest easier to identify.

During the procedure, fluoroscopy (live X-ray imaging) is used to orient the surgeons to the vertebral levels that are being fused. Once the surgeon identifies the thoracic spine, vertebral discs are removed (release), bone-graft is added to fuse the vertebrae together and instrumentation (screws and rods) are placed. The bone graft can be harvested from the patient herself (e.g. a piece of rib) or from prepared bone graft material such as demineralized bone matrix. In our experience, children do well with either type. After the operation, the patient usually wears a brace for about three months.

Thoracoscopic surgery is most helpful for patients who require a release of the anterior thoracic spine. Instrumentation can also be added to the procedure.

Anterior release is typically indicated in:

• Severe or rigid scoliosis and kyphosis: Removal of anterior vertebral disks and anterior spinal ligaments increases the flexibility of the spine and facilitates a better correction of the curve.
• Young patients: Because they have much growth left, young children are at risk for developing a post-operative crankshaft phenomenon. This phenomenon results from continued growth of the anterior spine after fusing the posterior spine only. Ablating the anterior vertebral growth plates during VATS prevents this from happening.

Indications for VATS with instrumentation (rods and screws) include:

• A single thoracic curve with either no or a very mild lumbar curvature that does not cross the midline.
• Curves that are relatively supple and present in young patients.
• Low thoracic curves (below vertebral level T5).

Contraindications for thoracoscopic spine surgery include:

• Patients with curves larger than 90: These curves result in a small chest cavity that makes VATS difficult.
• Small children: Children have to be large enough to handle a double lumen breathing tube, and have adequate lung function to tolerate single lung ventilation.
• Patients with scarring in the chest cavity: (History of previous chest cavity surgery, emphysema or severe pneumonia) This makes thoracoscopic surgery difficult.
• Certain patients with neuromuscular disease: These patients are more likely to suffer from osteopenia (thin, brittle bones) be on seizure medications, both of which are predisposing factors for more bleeding. Excessive bleeding obstructs the thoracoscopic camera view, making the surgery very difficult. Open procedures should be considered for these patients.

Contraindications for thoracoscopic instrumentation include:

• Curves above vertebral level T5 or below L2 are technically very difficult to instrument thoracoscopically.
• Male patients with severe, rigid curves: VATS uses smaller rods than in open surgery. This makes the rods more prone to break or loosen, especially in the rigid curves seen in male patients.

Many studies have overwhelmingly shown that thoracoscopic spine surgery anterior release and fusion is safe and effective, at least within a two year follow-up period. In fact, it is at least as effective as the open procedure. Long-term results are not yet available.

Ultimately, success with VATS can only improve with time, experience and a motivated, thorascopically trained team of surgeons, anesthesiologists, nurses and surgical technicians. The pediatric orthopaedic surgery team at the Morgan Stanley Children's Hospital has been and continues to be at the forefront of VATS development and is among the best trained in the procedure.

Advantages of Thoracoscopic Surgery over the Open Approach

Thoracoscopic surgery can be preferable to the open approach for several reasons. One, it spares the chest wall muscles, decreasing postoperative pain, improving cosmetic results and hastening a return to normal function. Two, it leaves smaller skin incisions, which are more aesthetically appealing and which should decrease the risks of wound infection. Three, it should lead to a shorter stay in the hospital and less pain for the patient. VATS does not add any time in the hospital for a child who has also had a simultaneous posterior fusion. Furthermore, studies are beginning to show that VATS leads to a shorter hospital stay than the open approach. This is exactly what we have seen in our experience.

Potential Complications of Thoracoscopic Spine Surgery

There are also drawbacks to the thoracoscopic approach. The one major drawback is that we do not have the long-term follow up data or large studies to truly know how well the procedure works and what the complication rates are.

Open thoracotomy and thoracoscopic spine surgery share some of the same potential complications. These include:

• Pulmonary complications
• Urine tract infections.
• Injury to blood vessels leading to blood loss.
• Injury Injury to lymphatics leading to lymphatic fluid in the chest cavity (chyothorax).
• Injury to nerves and spinal cord.
• Pleural scarring/ lung damage: However, some studies have shown that the thoracoscopic approach results in better pulmonary function than the open approach.

Other complications are associated uniquely with the thoracoscopic approach. These include:

• Intercostal neuralgia: Nerves located around the ribs are injured by the portal placements.
• Tension pneumothorax (lung collapse) can occur if the guiding pin for the screws injures the lung. This is treatable with careful monitoring.
• Complications of anesthesia: Related to single lung ventilation.
• Hardware problems: The screws on the upper vertebrae may come out.
• Pseudoarthrosis (failure of the bone to fuse) has also been reported.

With proper monitoring, most complications are reversible and treatable. In addition, occasionally, cases that are attempted thoracoscopically may need to be converted into open approaches. Reasons for this are difficulty ventilating with in just one lung, unknown scarring and excessive bleeding.

Future Developments with Thorascopic Spine Surgery

Recent technological advances, including new tools for controlling bleeding and more refined instruments have improved the thoracoscopic procedure. For example, soon we will have instruments that can remove disk fragments while still remaining in the chest cavity. The instrumentation rods and screws are always being modified to give better results. Development and approval of better bone graft material is being actively researched. For example, bone morphogenic proteins, contained in bone marrow, accelerate bone formation. By using these proteins, it may be possible to improve fusion rates without using an autogenous bone graft (a rib from the patient). This would decrease both the invasiveness and duration of the procedure, since there would be no need to harvest bone from the patient.

Ultimately, thoracoscopic gene therapy may play a role in anterior fusion by decreasing the amount of dissection necessary. Technologies to assist the surgeon, such as voice-activated robotics to guide the camera, special "virtual" glasses with inbuilt monitors and three-dimensional video assistance, may be further developed and refined.

Conclusion

Thoracoscopic anterior spinal surgery is a relatively new treatment. The surgery team at the Morgan Stanley Children's Hospital boasts considerable experience and success with this minimally invasive approach to anterior release of the thoracic spine. In experienced hands, it is a safe, effective treatment option for a sub-group of patients. With time and further experience, we will learn more about additional uses of minimally invasive spine surgery, including thoracoscopic instrumentation, in an effort to provide patients with the best options for the treatment of scoliosis.

References

1. Newton PO, Shea KG, Granlund KF. Defining the Pediatric Spinal Thorascopy Learning Curve Sixty-Five Consecutive Cases. Spine 2000; 25(8):1028-35.
2. Regan JJ. Point of View. Spine 2000; 25(8):1028-35.
3. Roush TF, Crawford AH, Berlin RE, Wolf RK. Tension Pneumothorax as a Complication of Video-Assisted Thorascopic Surgery for Anterioir Correction of Idiopathic Scoliosis in an Adolescent Female. Spine 2001; 26(4): 448-50.
4. Newton PO, Wenger Dr, Mubarak SJ, Meyer RS. Anterior Release and Fusion in Pediatric Spinal Deformity A Comparison of Early Outcome and Cost of Thoracoscopic and Open Thoracotomy Approaches. Spine 1997; 22(12):1398-1406.
5. Crawford AH, Wall EJ, Wolf RK. Video-Assisted Thoracoscopy. Orthopedic Clinics of North America 1999; 30(3):367-385.
6. McAfee PC, Regan JR, Zdeblick T, Zuckerman J, Picetti GD, Heim S, Geis WP, Fedder IL. The Incidence of Complications in Endoscopic Anterior Thoracolumbar Spinal Reconstructive Surgery A Prospective Multicenter Study Comprising the First 100 Consecutive Cases. Spine 1995; 20(14):1624-32.
7. Huntington CF, Murrell WD, Betz RR, Cole BA, Clements DH 3rd, Balsara RK. Comparison of Thoracoscopic and Open Thoracic Discectomy in a Live Ovine Model for Anterior Spinal Fusion. Spine 1998; 23(15):1699-702.
8. Graham EJ, Lenke LG, Lowe TG, Betz RR, Bridwell KH, Kong Y, Blanke K. Prospective Pulmonary Function Evaluation Following Open Thoracotomy for Anterior Spinal Fusion in Adolescent Idiopathic Scoliosis. Spine 2000; 25(18):2319-25.
9. Furrer M, Rechsteiner R, Eigenmann V, Signer C, Althaus U, Ris HB. Thoracotomy and thocoscopy: Postoperative Pulmonary Function, Pain and Chest Wall Complaints. Eur. J Cardiothorac Surg 1997; 12(1):82-7.
10. Kaseda S, Aoki T, Hangai N, Shimizu K. Better Pulmonary Function and Prognosis with Video-Assisted Thoracic Surgery than with Thoracotomy. Ann Thorac Surg 2000; 70(5):1644-6.
11. McDonnell MF, Glassman SD, Dimar JR 2nd, Puno RM, Johnson JR. Perioperative Complications of Anterior Procedures on the Spine. J Bone Surg Am 1996; 78(6):839-47.
12. Sucate DJ, Hedequist D, Pierce B, Zhang H, Colby S, OBrien S, Welch RD. rh BMP-Induced Anterior Spinal Fusion in a Thoracoscopically Instrumented Animal Model. Presented at Pediatric Orthopaedic Society of North America (POSNA), Annual Meeting 2001, May 1-5. Paper No. 26.
13. Riew KD, Lou J, Wright NM, Cheng S.-L, Bae T, Aviolo LV. Thoracoscopic Intradiscal Spine Fusion Using Gene Therapy. Scoliosis Research Society 35th Annual Meeting, Oct 18-21, 2000. Paper No. 72.
14. Newton PO, Lee SS, Mahar AT, Farnsworth CL, Weinstein C. Comparison of Autograft Vs. Demineralized Allograft in Anterior Thoracoscopically Instrumented Scoliosis Fusions A Caprine Model. Scoliosis Research Society 35th Annual Meeting, Oct 18-21, 2000. Paper No. 71.
15. Betz RR, Lenke LG, Clements DH, Newton PO. Thoracoscopic Versus Open Thoracotomy Correction by Anterior Instrumentation for the Treatment of Thoracic Adolescent Idiopathic Scoliosis. Scoliosis Research Society 35th Annual Meeting, Oct 18-21, 2000. Exhibit #18.
16. Knapp DR. VATS, An Initial Learning Curve and Reasons for Conversion to Thoracotomy. Scoliosis Research Society 35th Annual Meeting, Oct 18-21, 2000. Exhibit #63.
17. Picetti GD, Bueff HU. Endoscopic Instrumentation, Correction and Fusion of Thoracic Curves in Idiopathic Adolescent. Scoliosis. Research Society 35th Annual Meeting, Oct 18-21, 2000. Paper #54.
18. Arlet V. Anterior Thoracoscopic Spine Release in Deformity Surgery: A Meta-Analysis and Review. Eur Spine J 2000 Suppl 1:S17-23.
19. Early SD, Newton PO, Wenger DR and Mubarak SJ. The Results of Anterior Thoracoscopic Spine Surgery in Children Under Thirty Kilograms. Scoliosis. Research Society 36th Annual Meeting, Oct 18-21, 2001. Paper #60.

Growing Rods

For some children in the 3-8 year-old age range, a device known as a "growing rod" may be utilized. In this type of treatment a metal rod attached to the spine is periodically lengthened by a simple procedure. This correction without fusing the spine minimizes any stunting of growth that can occur with fusion. Several other types of experimental surgical treatments are currently under investigation and have shown promising results, including those performed by our pediatric orthopaedic group here at Columbia. One procedure, called an anterior epiphysiodesis, is designed to limit the growth of the spine in the region of the instrumentation, so that the existing curve does not worsen and new curves not emerge. Artificial ligaments, attached to one side of the spine, may be effective in stabilizing the spine over time and are also being investigated. Because of the stability and effectiveness of the devices used in spine operations today, patients are usually able to walk the day following their surgery, and hospital stays are generally under 1 week. The majority of children return to school within four weeks and can often return to full activity within a year, though contact sports are not recommended.

The Titanium Rib

The spine center at NewYork-Presbyterian Morgan Stanley Children's Hospital is unique in New York in offering this new and exciting treatment for the infant or child with thoracic insufficiency syndrome. Thoracic Insufficiency Syndrome has been defined as the inability of the chest to support normal breathing or lung growth. If the chest cannot grow normally, the child's lungs cannot grow and life threatening breathing problems may develop. The VEPTR has been designed to allow the rib cage to grow while controlling spinal deformity without fusion of the spine. Before this technique was developed, there was no effective treatment for the combination of chest wall deformity and scoliosis that created problems with lung growth and pulmonary function.

Some testing is required before the surgery, including X-rays. The children will require a CT scan and an MRI. Pulmonary function evaluation and consultation with pediatric pulmonology is also required. All of our patients are part of a clinical research protocol that allow us to track and measure the outcome of the surgery and thus to insure the best possible results.

The surgery is performed under general anesthesia with the child on his or her side. The incision is seen in the illustration. The ribs are exposed and are separated allowing correction of the rib cage. One or two of the VEPTR devices are placed depending on the extent and type of deformity. On some occasions, the devices are attached to the spine and to the ribs. The initial procedure requires admission to the hospital for three to five days. The child is treated in the pediatric intensive care unit until the staff is confident that she is healthy enough to be moved to the regular floor.

In the postoperative period there is no casting or bracing necessary and regular activities are not limited. To keep the rib cage growing, the VEPTR must be lengthened every 4 to 6 months. The lengthening surgeries are generally performed as outpatient surgery and only a small portion of the incision is used to perform the lengthening.

In this special group of children, the VEPTR technique offers real promise in preventing the late sequelae of inadequate growth of the chest wall and thus inadequate growth of the lung and subsequent breathing problems.