I'm a Neurophysiologist and I don't decide about the surgical methods. I just do IOM procedures during the scolio cases.

MIXED MANEUVER, TRANSLATION, DEROTATION AND INSITU BENDING, SOME COMPRESSION IN LUMBAR CURVES

Surgical correction of AIS is a complex procedure. Per se it is a segmental maneuver including different corrective forces to acheieve a 3D-correction. Usually a combination of distraction, compression and derotation are applied. It is a complex and individualized procedure depending on the type of curves. However, the most used (not favourite) is distraction.

It depends on the type of curves you have. And presence of hypeekyphosis or hypokyphosis , degree of rotation and translation of the curve from midline . I use combination of dertation, translation ,compression and distraction . I agree with my colleagues that it is a complex procedure  as it should be individualize according to the curve and its rigidity and flexibility  

As already is mentioned all depends on the individual who is operated and the deformities that are present. It is, as it is said complex and the need of derotation as well as compression and distraction will be necessary to be used, but of a different degree of application according to the curves.

I agree with my colleague George.

I would divide the principles of correction manoeuvres as follows:

Coronal Plane correction:

1. Compression /distraction

2. Lateral translation

3. Cantilevering of the rod into the screw

4. In-situ rod bending

Sagittal plane correction:

1. Rod contouring to the normal sagittal plane

2. Global rod rotation

Axial plane correction:

1. DVR (Direct vertebral rotation)

2.VCA (vertebral coplanar alignment

It is perhaps important to realise that isolated manoeuvres are rarely performed and depending on the merits of the individual case and the type of device used several combinations are possible and each surgeon has his own strategy to fine tune the correction. Some would chose DVR as the primary manoeuvre and add compression/distraction; other would choose lateral translation as the primary procedure and global rotation as the additional manoeuvre and so on.

I hope I have ben able to help you

Best Regards

KV

Idiopathic scoliosis is a 3-dimension deformity and correction should consider this. First insert your screws, check the flexibility of the curve and size of the curve. If the patient has a flexible curve with small hump, bend the rod with normal sagittal balance, apply it on the screws at its ends and the to other screws with some push by the assistant.

If the curve is semi rigid, do facetectomy, apply the with scoliotic curve and derotate. If there is some residual scoliosis do distraction at concavity and compression at convexity sites.

With rigid curve, you can add some osteotomies. 

Here my experience, only partly published.

With the rediscovered presence of a kyphotic curve at Th10-L2 spine in ALL scoliotic spines in 2003 ( presented in Spine 2008 and confirmed in China ( Ni et al) in 2010, focus was put on the sagittal contour only in the last years of surgical career:

- preplan the extension of the levels to be instrumented.

- Ponte osteotomies at any level, followed by screw placement,  in the lumbar area replaced by partial facetectomy in order to get full extension by compression ( without compromise of the foramen) , every level directly followed by:

-placing screws by the pure anatomic way as learned in France and copied by the Koreans ( for this purpose I used the conical shaft self introducing screws of Stryker France) in always the thickest screw as possible.

- control right placement ( no contact with neural tissue) in the pedicle with a split second of diathermia against any metal device introduced in the pedicle , incl. the final screw

- In neuromuscular scoliosis or severe idiopathic the level for a Pedicle Subtraction Osteotomy was chosen by assessing the longest thoracolumbar laminae and the most central vertebra in the thoracolumbar area on the X.  The shortening power of the PSO is of great importance to get the central cord relaxed. In neuromuscular scoliosis and in all kyphosis the cord is displaced and thight as can be assessed on MRI ( W.Chu et al ) . Roth found this already in the 60theis

- after closing the PSO if done mainly lordotic bend bars are placed and all levels fixed under compression. There is no argument "to restore hypokyphosis into kyphosis" at the thoracic spine if you understand the biomechanic meaning of a pathological kyphosis at the thoracolumbar joint.

Blood loss is an issue, but completely compensated by the impressive physical improvements. The PSO is very rewarding and very good taken by children neuromuscular deformities because the function of the diaphragm is restored to a level, they never had by the a. 30 degrees correction at one level that will pull the sacked diafragm into normal physiologic pre-tension this muscle needs too.

Always used SSEPs and found that relaxing the cord always improved the signals. nI a few cases ( severe kyphosis) disappearance of signals ( sometimes due to too much extension in the neck(!)  occured in the beginning , but restored after closing PSO or in the first 24 hours.

So I stopped cantilevering by S-curved bended bars and uniformed all actions in the same way for any indication.

And by the cruel changes in the Dutch Healthcaresystem with negative impact on the complex spinal surgery performers, I had to stop this too and went on in conseervative and preventive orthopedics in postural problems.

So good luck.