Dorsal spondylodesis in adolescent idiopathic scoliosis: proximal fixation with screws versus claw construct

Surgical treatment of progressive or severe adolescent idiopathic scoliosis
(AIS) often consists of posterior spinal fusion. There is still no consensus on
the preferred instrumentation technique. Recently, the concept of using all
pedicle screw instrumentation has been popularized. Thoracic pedicle screws are
generally believed to give a better correction of coronal Cobb angle and
vertebral rotation, and to have a higher pull-out strength. However, these
studies have poor to fair methodological quality, and at least the clinical
relevance of these findings is not clear. In our hospital we use for years a
proximal hook claw construct with good results. We hypothesize that proximal
fixation of the spondylodesis with a pedicle screw construct gives better
coronal Cobb angle correction with less loss of correction compared to a hook
claw construct.

The main objective is to compare the coronal Cobb angle correction of proximal
hook claw fixation versus proximal pedicle screw fixation after two years of
follow-up. The secondary objectives of the study are: comparison of coronal
Cobb angle correction direct postoperatively, coronal Cobb angle correction
loss after two years, vertebral rotation correction, complication and revision
rate, pulmonary function, postoperative lung volume, cosmetic outcomes, and
subjective questionnaire results in proximal hook claw versus screw fixation,
assessment of the correlation between the extent of scoliosis correction and
the degree of patient satisfaction, and determination of the accuracy rate of
thoracic pedicle screw placement.

Single-blind prospective randomized controlled clinical trial with a follow-up
of two years postoperatively.

Surgical posterior instrumentation and fusion, in accordance with the standard.
There will be randomized between proximal fixation of the instrumentation with
a hook claw construct or with a pedicle screw construct.

Additional to routine treatment are two low dose spirometrically controlled
CT*s (pre- and postoperatively), two clinical photographs of the back (pre- and
postoperatively), one pulmonary function test postoperatively, and three
questionnaires which has to be filled in pre- and postoperatively. Compared to
routine treatment one less conventional radiograph is required because it is
replaced by a CT. It is not known whether proximal hook or screw fixation truly
has more potential disadvantages or risks.