Unilateral versus bilateral iliac screws for spinopelvic fixation: are two screws better than one?
OBJECTIVE
Long-segment spinal instrumentation ending at the sacrum places substantial biomechanical stress on sacral screws. Iliac (pelvic) screws relieve some of this stress by supplementing the caudal fixation. It remains an open question whether there is any clinically significant difference in sacropelvic fixation with bilateral versus unilateral iliac screws. The primary purpose of this study was to compare clinical and radiographic complications in the use of bilateral versus unilateral iliac screw fixation.


METHODS
The authors retrospectively reviewed 102 consecutive spinal fixation cases that extended to the pelvis at a single institution (University of California, San Francisco) in the period from 2005 to 2012 performed by the senior authors. Charts were reviewed for the following complications: reoperation, L5-S1 pseudarthrosis, sacral insufficiency fracture, hardware prominence, iliac screw loosening, and infection. The t-test, Pearson chi-square test, and Fisher exact test were used to determine statistical significance.


RESULTS
The mean follow-up was 31 months. Thirty cases were excluded: 12 for inadequate follow-up, 15 for lack of L5-S1 interbody fusion, and 3 for preoperative osteomyelitis. The mean age among the 72 remaining cases was 62 years (range 39-79 years). Forty-six patients underwent unilateral and 26 bilateral iliac screw fixation. Forty-one percent (n = 19) of the unilateral cases and 50% (n = 13) of the bilateral cases were treated with reoperation (p = 0.48). In addition, 13% (n = 6) of the unilateral and 19% (n = 5) of the bilateral cases developed L5-S1 pseudarthrosis (p = 0.51). There were no sacral insufficiency fractures. Thirteen percent (n = 6) of the unilateral and 7.7% (n = 2) of the bilateral cases developed postoperative infection (p = 0.70).


CONCLUSIONS
In a retrospective single-institution study, single versus dual pelvic screws led to comparable rates of reoperation, iliac screw removal, postoperative infection, pseudarthrosis, and sacral insufficiency fractures. For spinopelvic fixation, placing bilateral (vs unilateral) pelvic screws produced no added clinical benefit in most cases.
Departments of Neurological Surgery and.
Rajiv
R
Saigal
Darryl
D
Lau
Rishi
R
Wadhwa
Hai
H
Le
Morsi
M
Khashan
Sigurd
S
Berven
Dean
D
Chou
Praveen V
PV
Mummaneni
D000328:Adult; D000368:Aged; D001863:Bone Screws; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008875:Middle Aged; D011542:Pseudarthrosis / Q000601:surgery; D012086:Reoperation; D012189:Retrospective Studies; D016103:Spinal Fractures / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation