The ApiFix System is a new idea in spinal curve correction. It was developed in Israel and has been used in Europe since 2012. It is designed to correct certain types of moderate scoliosis, mostly single curves. The ApiFix procedure allows the patient to keep most¹ of their spine flexibility while improving the curve. The surgery to put it in is much less complex than the usual surgery to treat a spinal curve. The time in the hospital and recovery period at home are shorter. Because it is a new device, we do not yet know how it will perform long term.

The device is placed on the inside part of the curve. It is attached to the spine with two screws at the top and a single screw at the bottom of the device. It usually covers five to seven levels of the spine. The device has a ratchet mechanism that is meant to gradually stretch and straighten the spine from the inside of the curve. This also aims to let the back grow without curving again. The amount of improvement in the curve is usually less than with a spine fusion.

The initial reports of the ApiFix device for treating scoliosis were written by the inventor^{2, 3} and were encouraging. A 2021 study from a different center showed some concerning results. Half of their patients had problems and needed more surgery.⁴ That study included only early generation implants. The current system may have fixed these problems, but that is not yet proven.

Use of the ApiFix device has not been reported in adults. As of the end of 2021, about 650 surgeries have been done in the world. Some patients are over 8 years out from surgery. The ApiFix System was approved in the U.S. as a Humanitarian Use Device. Its use in the United Stated began in June 2020. Longer follow-up of the current generation device is needed before it can be widely accepted.

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References

1. Holewijn RM, de Kleuver M, et. al. A novel spinal implant for fusionless scoliosis correction: a biomechanical analysis of the motion preserving properties of a posterior periapical concave distraction device. Global Spine Journal 2017; 7(5):400-409.
2. Floman Y, Burnei G, et. al. Surgical management of moderate adolescent idiopathic scoliosis with ApiFix®: a short peri-apical fixation followed by post-operative curve reduction with exercises. Scoliosis 2015; 10:4.
3. Floman Y, El-Hawary R, et al. Vertebral growth modulation by posterior dynamic deformity correction device in skeletally immature patients with moderate adolescent idiopathic scoliosis. Spine Deformity 2021; 9(1):148-153.
4. Stadhouder A, Holewijn RM, et. al. High failure rates of unilateral posterior peri-apical distraction device(ApiFix) for fusionless treatment of adolescent idiopathic scoliosis. J Bone Joint Surg 2021 Oct 6; 109(19):1834-1843.

Minimally Invasive Surgery (MIS) is the concept of performing a standard surgery through a smaller incision. It has been used in many different types of surgery with some encouraging results. An example is when treating an appendicitis. Years ago, a general surgeon would remove the appendix through a five-centimeter (two-inch) incision. Today, this is done through a couple of one-centimeter cuts with the use of a special tool called a scope. Patients often can go home one day after surgery compared to three or four days in the past.

Over the last two decades, methods have been developed to perform Minimally Invasive Spine Surgery (MISS). This has become a common approach for adults with arthritis of the spine. The MISS approach works well for this problem because only a short part of the spine needs treating. Similarly, this approach works well in spine fractures. MISS may result in less bleeding, lower risk of infection, less pain after surgery, and a quicker recovery.

Special tools and implants are required to be able to perform MISS. These tools together with computer guidance enables MISS to be performed through several small incisions. The goal is still to achieve a spinal fusion. Scoliosis and kyphosis surgery, for both adults and adolescents, often involves a longer section of the spine. This makes MISS more challenging. In recent years, some surgeons have been able to perform MISS for these longer surgeries. Early results are mixed with less bleeding but no improvement in recovery or pain. Long-term results of this approach need to become available before we know how it compares to current surgeries.

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References

1. de Bodman C, Ansorge A, et. al. Clinical and radiological outcome of minimal invasive surgery for adolescent idiopathic scoliosis at a minimum two years’ follow-up. Bone Joint J 2020 Apr;102-B(4):506-512.
2. Si G, Li T, et.al. Minimally invasive surgery versus standard posterior approach for Lenke Type 1-4 adolescent idiopathic scoliosis: a multicenter, retrospective study. Eur Spine J 2021 Mar;30(3):706-713.
3. Yang JH, Chang DG, et. al. Safety and effectiveness of minimally invasive scoliosis surgery for adolescent idiopathic scoliosis: a retrospective case series of 84 patients. Eur Spine J. 2020 Apr;29(4):761-769.
4. Tarpada SP, Morris MT. Minimally invasive surgery in the treatment of adolescent idiopathic scoliosis: A literature review and meta-analysis. J Orthop. 2016 Oct 24;14(1):19-22.

Navigation and robotics are two closely connected technologies. They are becoming more common in scoliosis surgery. Navigation allows a spine surgeon the precisely identify parts of a patient’s anatomy relative to a computer model. Robotics builds on this by helping a surgeon perform a surgery planned out on a computer model.

A critical step in spine surgery is the insertion of implants. Navigation can help with that step. To straighten a scoliosis, the surgeon places screws in the spine. These are then attached to corrective rods. They are placed within a narrow column of bone in the spine and must be placed very precisely to prevent complications. Most surgeons place these by understanding the anatomy and experience. The placement is then confirmed with x-rays. No surgeon is 100 percent successful at placing these screws. Navigation offers the potential to make surgeons more exact.

Navigation for the spine works in a similar way to the navigation app on your phone. Your phone (computer) understands where you are relative to a computer map. Spine navigation uses three-dimensional imaging such as a CAT scan to model the spine. An image guidance system is then used with the scan to help the surgeon. This allows the surgeon to see on a computer screen how the intended plan fits the spine. The result is improved precision. Most studies confirm better accuracy when navigating screws. The down side includes increased cost, the added radiation of a CAT scan, and longer operative times.¹

Robots bring up memories of Arnold Schwarzenegger in the Terminator. The idea of using robots in spine surgery may seem like science fiction. On more careful thought, we realize that our world is filled with robots. They are designed to make our lives easier or better in some way. Some simple robots have jobs like vacuuming the floor. Others can be very complex, performing tasks like helping to build a car. Others handle shipping products from mega-warehouses. Since the 1980s, scientists have been developing ways to use robotics in surgery.

Robots have been very successful in manufacturing. They have more precision, improved endurance, better speed, greater consistency, and reduced cost. Can these advantages carry over to the area of surgery? Robotic surgery has shown promise in several areas. They are commonly used in heart surgery, bladder surgery, and general surgery. They allow these surgeries to be done with a minimally invasive approach. This means a very small cut is used. Robots have also been used in joint replacement surgery and shown improved precision.

Many patients worry that a robot will be performing their surgery. This is not the case. The surgeon is doing the surgery using the robot as an aide. The robot is an extension of the surgeon’s hands. Current systems use a robot in different ways:

• Supervisory – The surgeon plans the surgery and the robot performs certain parts of the surgery under control of the surgeon.
• Tele-surgical – The surgeon performs the surgery at a computer console. The robot mimics the movements of the surgeon’s hands. The console is typically in the operating room. This is a little like a video game.

There are currently several robots approved for spine surgery. They have mostly been used in adults for fusion of the spine. Studies done so far show that robots probably are slightly more precise than humans. Robots add to the cost, slow down surgery and have equal long term patient results.² At this point, efforts to use robotics in adolescent scoliosis have been few.

Robotic systems for surgery have come a long way over the last thirty years. They show promise for the more precise insertion of pedicle screws. There are still questions about increased cost, long term patient outcomes, x-ray exposure, and total surgical time. Once these are resolved, robotic scoliosis surgery may become more common.

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References:

1. Baldwin KD, Kadiyala M, Talwar D, Sankar WN, Flynn JJ, Anari JB. Does intraoperative CT navigation increase the accuracy of pedicle screw placement in pediatric spinal deformity surgery? A systematic review and meta-analysis. Spine Deformity (2022) 10(1):19-29.
2. Tovar MA, Dowlati E, Zhao DY, Khan Z, Pasko KBD, Sandhu FA, Voyadzis JM. Robot-assisted and augmented reality-assisted spinal instrumentation: a systematic review and meta-analysis of screw accuracy and outcomes over the last decade. J Neurosurg Spine (2022) Feb 25:1-16, published online ahead of print.

Surgery for severe scoliosis has improved dramatically over the last 50 years. With modern treatment, patients can expect to spend just a few days in the hospital. Their curves can be corrected about 70% or more. Within a few months, they can return to all their normal activities. There is only a small chance of needing another surgery. Despite these successes, scoliosis surgery does not give a normal spine.

Standard scoliosis surgery is a spinal fusion. This is where the spine is permanently stiffened in a straighter position. This way the curve cannot return. The results of this treatment have been very good even 20 or more years after surgery. Still, we have concerns about our patients having a stiff spine. This may make it hard for some to return to all their earlier activities. If the fusion includes much of the lower part of the spine, we are concerned that the stiffness will wear out this part of the spine more quickly and result in arthritis.

The ideal surgery for severe scoliosis would be one that straightens the spine without causing stiffness or degrading over time. Vertebral body tethering (VBT) was conceived to help the spine straighten with growth. It is based on a tried and true concept within pediatric orthopedics - that of guided growth. If a child has crooked legs, we can insert a device over the growth plate on the bowed side. This acts to limit growth. Any growth on the opposite side, will slowly straighten the leg.

Spinal growth can be controlled in a similar way by VBT. Growth on the outside of a scoliosis curve is slowed by placing a tether. This tether is flexible and allows the spine to move. The inside part of the curve can grow more easily and gradually straighten out the curve. This type of correction requires that the spine continue to grow.

In 2019, the U.S. Food and Drug Administration (FDA) approved the first tethering device for the spine for use in humans. Metal bone screws are placed into the spine. A flexible cord is attached to these screws and acts as a tether. A group of 57 patients was followed for over 4 years. Seven patients (12%) needed a second surgery. Two patients had spinal fusion surgery. Twelve patients had overcorrection where the spine curved opposite to the original curve. Only six needed more surgery for overcorrection.¹

We are still learning which patients do best with tethering. Patients should still be growing. If a patient is too young (and has too much growth left) when tethered, their curve may overcorrect. This can make a new curve going the opposite direction. If they are too old, the curve may not correct enough. There should be a “sweet spot” that avoids both these problems. It is hard to know when a child is the perfect age. Doctors use x-rays of the hands to tell how mature a patient is, but this method is not perfect.

The FDA says VBT is for growing patients with very flexible, thoracic curves measuring between 30 and 65 degrees. The patient should have failed or was unable to tolerate bracing. There is not much data on tethering for lumbar curves. Based on this, only a small percentage of patients are good candidates for VBT. Many questions remain about how VBT will hold up over time. Because the spine can still move after VBT, the tether could eventually break. In addition, the long-term effect of tethering on the spine is not known. The screws could come loose. The discs may also degenerate more quickly over time. The longest study of VBT was only four years past surgery and showed about half with a broken tether. This resulted in 40 percent having another surgery.²

We are not sure whether VBT will have a role in treating adults with scoliosis. A tether could theoretically work in adults but this effect would be much less powerful than the effect in a growing patient. So far, there have been no published reports about the safety or benefit of spine tethering in adults. Any use of tethers for scoliosis correction in adults is considered experimental and without FDA approval in the United States.

Summary (in children with a scoliosis):

• Spinal fusion gives much better correction
• Spinal fusion has less complications
• Spinal fusion has less chance of needing another surgery
• Spinal fusion has a long record of success
• VBT has faster early recovery
• VBT retains more flexibility

The risks and benefits of VBT should be discussed carefully with your physician. VBT should only be considered when standard nonoperative treatments do not work.

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References:

1. Samdani AF, Pahys JM, Ames RJ, Grewal H, Pelletier GJ, Hwang SW, and Betz RR. Prospective follow-up report on anterior vertebral body tethering for idiopathic scoliosis: interim results from an FDA IDE study. J Bone Joint Surg Am (2021) 103(17):1611-1619.
2. Newton PO, Kluck DG, Saito W, Yaszay B, Bartley CE, and Bastrom TP. Anterior spinal growth tethering for skeletally immature patients with scoliosis: a retrospective look two to four years postoperatively. J Bone Joint Surg Am (2018) 100(19):1691-1697.

The Scoliosis Research Society recognizes that the FDA regulatory policies are specific to the United States. Every member nation of the SRS has its own regulatory agency whose policies may differ from those of the FDA