The Place for Pedicle Screws in Scoliosis Surgery: A Two Year Follow-Up
Andrew G. King, M.D.,
ChB, FRACS,
Tara E. Mills, B.S.;
Jason E. Smith, B.S.,
Norman B. Chutkan, M.D.
New Orleans, LA, USA
PURPOSE:
A retrospective review was undertaken to compare the efficacy
of pedicle screw constructs to the standard hook constructs in
the treatment of idiopathic scoliosis.
SIGNIFICANCE:
Data from this study will aid in determining which construct
offers better correction and better maintenance of the correction
after two years, in addition the paper sought to identify any
complications or related to the use of pedicle screws.
METHODS:
Fifty–four patients with idiopathic scoliosis underwent
posterior spinal fusion between 1992–1997. Pedicle screws
were used only as the caudal anchors in thirty–four cases
(Group 1). Hook constructs were used in 20 cases (Group 2). The
primary method of surgical correction for both groups was cantilever
bend and transverse approximation. Both groups were similar with
regard to age, preoperative Cobb and tilt angles. Radiographic
analysis was performed measuring pre, immediate post–op
and two–year follow–up Cobb angles, tilt angle, coronal
balance and sagittal balance. All data underwent statistical
analysis utilizing student t–test with p£0.05 as the
standard to assess significance.
RESULTS:
Percent correction of the primary Cobb angles immediately post–op
was 71.4% for the screws (N=34) and 64.8% for the hooks (N=20).
The percent correction at 2 year follow–up was 62.2% for
screws and 58.2% for hooks. The primary tilt angle was measured
preoperatively and compared to the tilt angle measured from the
LIV to the sacrum postoperatively. The preoperative tilt angle
for the screw patients was 29 degrees (N=28) and 28.6 degrees
(N=17) for the hook patients. At two–year follow–up
the measurement of the LIV to the sacrum was 6 degrees for Group
1 and 8 degrees for Group 2. No significant difference was demonstrated
in comparing tilt angles between the screw patients and the hook
patients. No complications arose that were specific to the placement
of the pedicle screws. Five patients were later diagnosed with
pseudoarthrosis, three in Group 1 and two in Group 2. The three
cases in Group 1 had a pseudoarthrosis cephalic to the caudal
anchor while the 2 cases in Group 2 were sited at the most caudal
level instrumented. All pseudoarthroses were surgically repaired.
CONCLUSION:
Cantilever bend and translational mechanics are effective in
correcting scoliosis and can be carried out using screws of hook
caudal anchors. No significant differences were demonstrated
between the two groups when comparing Cobb angles of tilt angles.
Neither intra–operative nor postoperative complications
occurred from the use of either hooks or pedicle screws. In this
series, the pedicle screws did show a greater percent correction
of the primary Cobb angle and of the tilt angle, but the difference
was not statistically significant.
** The FDA has not cleared a drug and/or medical device for the
use described in this presentation. (i.e., the drug or medical
device is being discussed in an “off–label" use).