Περίληψη:
Study Design. Comparative 3-dimensional biomechanical testing.
Objective. To compare 5 fixation techniques, 3 using screws or screw and
plates and 2 spinal, used for stabilization of complete unilateral
sacroiliac dislocation in composite models.
Summary of Background Data. Harrington compression rods have been used
for posterior iliosacral stabilization. Recently, the use of compact
spinal instrumentation has been introduced for stabilization of
iliosacral joint separation to achieve immediate and permanent
stability, allowing early mobilization. To the authors’ knowledge, no
comparative mechanical studies between commonly used internal fixation
techniques and contemporary spinal instrumentation have been performed.
Methods. Fifteen identical composite models of the left hemipelvis and
sacrum were used to simulate consistently the “worst-case scenario”
of complete unilateral sacroiliac dislocation. Subgroups of 3 models
each were used to apply 5 (A - E) alternative fixation iliosacral joint
fixation techniques: 1 multiaxial 7.5-mm Cotrel-Dubousset screw inserted
in the posterior superior iliac spine and connected with a long
Cotrel-Dubousset horizontal rod with 6.5 mm multiaxial Cotrel-Dubousset
screws inserted bilaterally in the S1 pedicles (technique A); 1
multiaxial 7.5 mm Cotrel-Dubousset titanium pedicle screw inserted in
the posterior superior iliac spine and connected with a short horizontal
Cotrel-Dubousset-rod to a 6.5 mm multiaxial Cotrel-Dubousset-screw
inserted to the ipsilateral S1 pedicle (technique B); 1, 6.5 mm
cancellous AO-screw (technique C); 2, 6.5 mm cancellous AO screws
(technique D); and 2 dynamic stainless steel compression plates
(technique E) placed anteriorly. Constructs were biomechanically tested.
The ilium was unilaterally rigidly fixed, the sacrum was put horizontal
in the mediolateral direction with a forward tilt of 30 degrees (close
to physiologic conditions) in the sagittal plane, and a vertical
quasi-static compressive load ranging from 0 to 500 N was applied on
theendplate of S1, reproducing a “worst case” loading scenario.
Construct stiffness, frontal plus sagittal kinematics, and iliosacral
joint gap size for all 5 techniques were measured.
Results. The construct stiffness (N/mm +/- standard deviation) ranged
for model: A, 121 +/- 18; B, 78 +/- 10; C, 168 +/- 13; D, 193 +/- 42;
and E, 145 +/- 4. All other parameters exhibited minor variations
between the different techniques of fixation: at the 400 N load level,
the maximum iliosacral gap globally ranged 0.9 +/- 2.8 mm, the maximum
mediolateral sacral tilt ranged 1.3 +/- 2.4, and the maximum
anteroposterior sacral tilt ranged 0.6 +/- 3.0.
Conclusions. The iliosacral fixation with 2 6.5 mm AO-cancellous screws
for complete sacroiliac dislocation demonstrated the highest stiffness
and the short spinal instrumentation the poorest stiffness. All other
fixation techniques could be generally considered of equivalent
stability value.
Συγγραφείς:
Korovessis, Panagiotis G.
Magnissalis, Evangelos A.
Deligianni,
Despina
