S2-Alar-Iliac Screws are Associated with Lower Rate of Symptomatic Screw Prominence than Iliac Screws: Radiographic Analysis of Minimal Distance from Screw Head to Skin.
BACKGROUND
In sacropelvic fixation, the iliac screw technique offers biomechanically strong constructs, but its disadvantages include screw prominence, wound dehiscence, and postoperative pain secondary to the high profile nature. To overcome this drawback, S2-alar-iliac (S2AI) screws were developed as an alternative technique for sacropelvic fixation. This study aimed to compare the S2AI screw technique with the iliac screw technique in terms of postoperative symptomatic screw prominence.


METHODS
A retrospective review of the records of sacropelvic fusion procedures performed at a single institution between October 2010 and January 2015 identified 32 patients with 72 iliac screws and 68 patients with 148 S2AI screws, and clinical and radiographic data were collected. If a patient had wound dehiscence and/or tenderness in the buttock immediately overlying a pelvic screw head postoperatively, it was defined as symptomatic screw prominence. The minimal distance from screw head to skin (MDSS) on postoperative computed tomography scans was measured for each patient to clarify the relationship between symptomatic screw prominence and MDSS.


RESULTS
Mean follow-up period was 22.0 months. There was significantly more symptomatic pelvic screw prominence in the iliac screw group (11.1% vs. 1.4%, P = 0.002). MDSS ≤23 mm was the strongest predictor of symptomatic pelvic screw prominence, which yielded sensitivity of 100%, specificity of 94.1%, positive predictive value of 47.6%, and negative predictive value of 100%.


CONCLUSIONS
The use of the S2AI screw technique resulted in a reduced rate of symptomatic screw prominence. MDSS ≤23 mm was the strongest predictor of symptomatic screw prominence.
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Wataru
W
Ishida
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Electronic address: belder4@jhmi.edu.
Benjamin D
BD
Elder
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Christina
C
Holmes
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
C Rory
CR
Goodwin
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Sheng-Fu L
SF
Lo
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Thomas A
TA
Kosztowski
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Ali
A
Bydon
Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA.
Ziya L
ZL
Gokaslan
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Jean-Paul
JP
Wolinsky
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Daniel M
DM
Sciubba
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Timothy F
TF
Witham
D001863:Bone Screws / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007085:Ilium / Q000000981:diagnostic imaging / Q000601:surgery*; D022125:Lacerations / Q000000981:diagnostic imaging / Q000453:epidemiology*; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000453:epidemiology*; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012867:Skin / Q000000981:diagnostic imaging / Q000293:injuries*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000706:statistics & numerical data*; D016896:Treatment Outcome
Iliac screw; Lumbosacropelvic fixation; Pelvic screw; Reoperation; S2-alar-iliac screw; Sacroiliac joint pain; Screw prominence