Idiopathic Scoliosis: Surgical Results
Surgical Technique for Anterior Thoracoscopic Correction of Idiopathic Scoliosis: Chapter 8
All patients underwent successful endoscopic instrumentation; none were converted to and open procedure. The levels instrumented were from T2 to T12, average number of levels were 7 with a range of 6 to 9. Blood loss averaged 267cc with a range of 100cc to 700cc, no patient received a transfusion. Chest tubes were removed on average postoperative day 2.3 with a range of 1-5 days.
Hospital stay averaged 2.9 days with a range of 2-7 days. Curve correction averaged 50.2%, with a range of 37.5 to 91%. The average curve correction for the last ten cases was 68.6%. Operative time averaged 6 hours and 6 minutes for the first 30 cases with a range of 2 hours and 50 minutes to 8 hours and 30 minutes. The operative time for the last 10 cases was under 4 hours. Patients with hypokyhosis average 20.7 degrees of correction with a range of 11 to 32 degrees. There were a total of 9 nonunions. The first 15 patients had the bone graft substitute Grafton for their fusion. Of these 15 patients 8 went on to nonunion. The next 35 patients underwent rib graft harvesting for their fusion and one developed a non-union. Post operatively all patients were off all pain medication at the first postoperative visit. Children were back to school between 2 and 4 weeks.
There were a total of 14 complications. One patient had a screw pull out of the superior screw. There were three patients with transient chest wall numbness. Five of the patients developed post operative mucus plugs. Two patients developed plug separation from the screws. One patient required wound revision. Two of the Grafton non-union patients have fractured their rods.
The development of the endoscopic technique of instrumentation correction and fusion has been an evolution and the technique has undergone several modifications since the first few cases. Early in the series the bone graft substitute Grafton was used as the grafting material, which led to an unacceptable rate of nonunion, of which one of the two patients with a rod fracture will undergo revision surgery. Since the rib graft has been used as bone grafting material there has been only one of 35 cases with a nonunion. The key to successful fusion is a total discectomy and complete endplate removal, and autogenous bone graft. Bone graft substitutes and allograft should not be used.
Many of the initial cases had poor placement of the screws. Several of these screws were not bicortical. They were not well seated against the veterbral body, thus were standing proud. Many of the most superior screws in the construct were placed at an angle into the vertebral body. The case of the superior screw pullout had a combination of these factors.
The screw was not bicortical, it stood very proud off of the vertebral body, and was placed at an angle into the vertebral body.
Early in this series we struggled somewhat with the portal placement. In attempting to perform complete discectomies and an instrumented fusion it is critical to have the portals placed accurately. If the portals are not appropriately placed then the portal sites are levered against the ribs, and a significant amount of pressure and trauma can be caused to the intercostal nuerovascular bundle. When this occurs patients will complain of dysethesias of the anterior chest wall postoperatively, this can last from weeks up to 6 months. As we have improved our portal placement we have not seen any further transient chest wall numbness or need for wound revision.
The most common complication has been the development of mucus plugs in the ventilated lung. During the surgery the ventilated lung becomes hyperemic and increases its secretions, pooling will also occur secondary to the dependant position of the lung over the course of the surgery. The secretions will eventually become organized and form a mucus plug. To avoid this complication our anesthesiologist will fiber optically suction the ventilated lung prior to extubation.
Since we have suctioned prior to extubation we have not had any further mucus plugs. The curve correction in the early part of the series was not acceptable. This was a direct result of our inability to adequately compress the construct. We have gone through several different designs of compressors and multiple modifications of the current compressor in an attempt to reproducibly be able to compress the construct. Another cause of poor correction in some of the early cases was fusing to short. It is mandatory to fuse the Cobb angles; fusing short to save time will lead to a poor result. Since we have attained the ability to endoscopically compress our average curve correction of 68.6% of our last 10 cases is acceptable.
The operative time of the first cases was excessive for multiple reasons. The initial cases were performed with only a few primitive instruments, the technique had yet to be fully developed. As our experience increased and the instrumentation improved the operating time has decreased. The discectomy continues to be the rate-limiting step. We are currently working on several disc removal systems. The goal is a rapid complete discectomy, which is sage to use via an endoscopic approach. This continues to be the most critical part of the procedure, if the disc is not completely removed than a nonunion will follow and a failure will result.
This initial study is an evaluation of a new technique with very early results. These results show trends of promise for a new technique in evolution, as surgical times continue to decrease, and acceptable fusion rates, as well as the ability to obtain and maintain acceptable curve correction occur. In addition there is shortened hospitalization, decreased rehabilitation time and decreased pain. This technique warrants continued evaluation and follow up. This technique however is new, technically very demanding and has a steep learning curve; one should be adept at endoscopic discetomy and fusion before starting this endeavor.