Incidence, mechanism, and protective strategies for 2-year pelvic fixation failure after adult spinal deformity surgery with a minimum six-level fusion

Abstract

OBJECTIVE The purpose of this study was to determine the incidence, mechanism, and potential protective strategies for pelvic fixation failure (PFF) within 2 years after adult spinal deformity (ASD) surgery. METHODS Data for ASD patients (age ≥ 18 years, minimum of six instrumented levels) with pelvic fixation (S2-alar-iliac [S2AI] and/or iliac screws) with a minimum 2-year follow-up were consecutively collected (2015–2019). Patients with prior pelvic fixation were excluded. PFF was defined as any revision to pelvic screws, which may include broken rods across the lumbosacral junction requiring revision to pelvic screws, pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws, a broken or loose pelvic screw, or sacral/iliac fracture. Patient information including demographic data and health history (age, sex, BMI, smoking status, American Society of Anesthesiologists score, osteoporosis), operative (total instrumented levels [TIL], three-column osteotomy [3CO], interbody fusion), screw (iliac, S2AI, length, diameter), rod (diameter, kickstand), rod pattern (number crossing lumbopelvic junction, lowest instrumented vertebra [LIV] of accessory rod[s], lateral connectors, dual-headed screws), and pre- and postradiographic (lumbar lordosis, pelvic incidence, pelvic tilt, major Cobb angle, lumbosacral fractional curve, C7 coronal vertical axis [CVA], T1 pelvic angle, C7 sagittal vertical axis) parameters was collected. All rods across the lumbosacral junction were cobalt-chrome. All iliac and S2AI screws were closed-headed tulips. Both univariate and multivariate analyses were performed to determine risk factors for PFF. RESULTS Of 253 patients (mean age 58.9 years, mean TIL 13.6, 3CO 15.8%, L5–S1 interbody 74.7%, mean pelvic screw diameter/length 8.6/87 mm), the 2-year failure rate was 4.3% (n = 11). The mechanisms of failure included broken rods across the lumbosacral junction (n = 4), pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws (n = 3), broken pelvic screw (n = 1), loose pelvic screw (n = 1), sacral/iliac fracture (n = 1), and painful/prominent pelvic screw (n = 1). A higher number of rods crossing the lumbopelvic junction (mean 3.8 no failure vs 2.9 failure, p = 0.009) and accessory rod LIV to S2/ilium (no failure 54.2% vs failure 18.2%, p = 0.003) were protective for failure. Multivariate analysis demonstrated that accessory rod LIV to S2/ilium versus S1 (OR 0.2, p = 0.004) and number of rods crossing the lumbar to pelvis (OR 0.15, p = 0.002) were protective, while worse postoperative CVA (OR 1.5, p = 0.028) was an independent risk factor for failure. CONCLUSIONS The 2-year PFF rate was low relative to what is reported in the literature, despite patients undergoing long fusion constructs for ASD. The number of rods crossing the lumbopelvic junction and accessory rod LIV to S2/ilium relative to S1 alone likely increase construct stiffness. Residual postoperative coronal malalignment should be avoided to reduce PFF.

The “Sandwich” Extended Pedicle Subtraction Osteotomy for the Treatment of Fixed Sagittal Malalignment: Technical Description, Case Series, and Early Results With 2-Year Outcomes

“…The addition of interbody cages also provides anterior column support, serving as a fulcrum for the production of lordosis; its use with multirod constructs increases the overall rigidity across the PSO site. 16,32 To our knowledge, this report is the first clinical investigation to highlight the SE-PSO technique used in patients with ASD with FSM. The preliminary results support further investigations in the use of the SE-PSO technique in select patients with ASD and are in accordance with previously reported clinical observations and biomechanical investigations.…”

“…Different configurations in multirod constructs with adjacent interbody cages were evaluated, 23 with findings suggesting that an increased number of rods crossing the lumbosacral junction were associated with decreased instrumentation failure. 32 Lee et al retrospectively evaluated factors that were associated with reduced mechanical complications in 253 patients who underwent long-fusion deformity correction with pelvic fixation. They found that accessory rods with the lower instrumented vertebrae to S2/ilium vs S1 and the number of rods crossing the lumbopelvic junction were protective factors against instrumentation failure.…”

Biomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery

“…Although SPF indeed reinforces the construct stiffness, 12.0%–46.9% of implant failure rate has been reported by previous studies ( Park et al, 2021b ; Gao et al, 2021 ). To reduce the incidence of mechanical complications, multiple pelvic screws or multirod construct have been applied as an advanced SPF technique ( Uotani et al, 2021 ; Lee et al, 2022a ; Lee et al, 2022b ; Tang et al, 2022 ). The current study revealed that both multiple pelvic screws and multirod construct could increase the mechanical stability of LSJ, reduce strain on the lumbosacral rod, and protect the S1-PS and sacrum.…”

“…Although the application of SPF, the incidence of implant failure is still unsatisfactory, with reported rates ranging from 12.0% to 46.9% ( Park et al, 2021b ; Gao et al, 2021 ). In recent cohort studies, advanced SPF technique by multiple pelvic screws or multirod construct has been recommended following long spinal fusion to stabilize the LSJ further, protect the primary rod and screws, and reduce the persistent motion of SIJ ( Uotani et al, 2021 ; Lee et al, 2022a ; Lee et al, 2022b ). However, there was only one small-size cohort study reporting the application of combining the multiple pelvic screws and multirod construct, without any control groups ( Shen et al, 2018 ).…”

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

“…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.…”