Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multicenter review of incidence, failure mechanisms, and risk factors

Abstract

OBJECTIVE There are few prior reports of acute pelvic instrumentation failure in spinal deformity surgery. The objective of this study was to determine if a previously identified mechanism and rate of pelvic fixation failure were present across multiple institutions, and to determine risk factors for these types of failures. METHODS Thirteen academic medical centers performed a retrospective review of 18 months of consecutive adult spinal fusions extending 3 or more levels, which included new pelvic screws at the time of surgery. Acute pelvic fixation failure was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS Failure occurred in 37 (5%) of 779 cases and consisted of either slippage of the rods or displacement of the set screws from the screw tulip head (17 cases), screw shaft fracture (9 cases), screw loosening (9 cases), and/or resultant kyphotic fracture of the sacrum (6 cases). Revision strategies involved new pelvic fixation and/or multiple rod constructs. Six patients (16%) who underwent revision with fewer than 4 rods to the pelvis sustained a second acute failure, but no secondary failures occurred when at least 4 rods were used. In the univariate analysis, the magnitude of surgical correction was higher in the failure cohort (higher preoperative T1-pelvic angle [T1PA], presence of a 3-column osteotomy; p < 0.05). Uncorrected postoperative deformity increased failure risk (pelvic incidence–lumbar lordosis mismatch > 10°, higher postoperative T1PA; p < 0.05). Use of pelvic screws less than 8.5 mm in diameter also increased the likelihood of failure (p < 0.05). In the multivariate analysis, a larger preoperative global deformity as measured by T1PA was associated with failure, male patients were more likely to experience failure than female patients, and there was a strong association with implant manufacturer (p < 0.05). Anterior column support with an L5–S1 interbody fusion was protective against failure (p < 0.05). CONCLUSIONS Acute catastrophic failures involved large-magnitude surgical corrections and likely resulted from high mechanical strain on the pelvic instrumentation. Patients with large corrections may benefit from anterior structural support placed at the most caudal motion segment and multiple rods connecting to more than 2 pelvic fixation points. If failure occurs, salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

Multiple Points of Pelvic Fixation

“…At our institution, we identified a 5% acute pelvic fixation failure rate over an 18-month period 10 . In a subsequent multicenter retrospective series, a similar 5% acute pelvic fixation failure rate was also reported 11 . In response to these findings, our institution changed its pelvic fixation strategies to incorporate multiple points of pelvic fixation.…”

Sacropelvic Fixation for Adult Deformity Surgery Comparing Iliac Screw and Sacral 2 Alar-Iliac Screw Fixation: Systematic Review and Updated Meta-Analysis

“…A recent multicenter study found a slightly higher rate of screw failure with IS than that with S2AI in the univari-ate analysis, with no significant difference in the multivariate analysis. 19 Another recent multicenter study found higher loosening rate of pelvic screw in the S2AI group than that in the IS group and higher rod fracture rate in the IS group than that in the S2AI group. 18 In a study by Cho et al, 34 involving 45 cases, the S2AI had a higher failure rate than the IS (35% vs. 12%).…”

“…14,24 In this meta-analysis, we pooled data from 10 cohort studies comparing the IS and S2AI fixation techniques in adult patients. 11,13,14,18,19,[24][25][26][27][28] Analysis of the outcomes based on the implant failure showed that the pooled proportion of patients with implant failure was not statistically different between the 2 techniques: 21.9% with IS and 18.9% with S2AI, respectively (p= 0.59). However, analysis based on revision, screw prominence, and wound complications showed that the pooled proportion of patients with each complication was higher in the IS group than that in the S2AI group (revision, IS: 21.0% vs. S2AI: 8.5%, p= 0.02; screw prominence, IS: 9.6% vs. S2AI: 0.0%, p< 0.01; wound complications, IS: 31.7% vs. S2AI: 3.9%, p < 0.01).…”

“…Finally, a total of 10 studies were included in this meta-analysis. 11,13,14,18,19,[24][25][26][27][28] The detailed selection process is illustrated in Fig. 1.…”

“…[15][16][17] As pelvic fixation techniques have become more popular in recent years, several multicenter studies with large numbers of patients have been conducted. 18,19 The objective of the current study was to perform a meta-analysis comparing IS and S2AI fixation techniques in patients with adult deformities, with a focus on postoperative outcomes, considering recent multicenter studies with large numbers of patients.…”