Reduced occurrence of primary rod fracture after adult spinal deformity surgery with accessory supplemental rods: retrospective analysis of 114 patients with minimum 2-year follow-up

Abstract

OBJECTIVE Rod fracture (RF) after adult spinal deformity (ASD) surgery is reported in approximately 6.8%–33% of patients and is associated with loss of deformity correction and higher reoperation rates. The authors’ objective was to determine the effect of accessory supplemental rod (ASR) placement on postoperative occurrence of primary RF after ASD surgery. METHODS This retrospective analysis examined patients who underwent ASD surgery between 2014 and 2017 by the senior authors. Inclusion criteria were age > 18 years, ≥ 5 instrumented levels including sacropelvic fixation, and diagnosis of ASD, which was defined as the presence of pelvic tilt ≥ 25°, sagittal vertical axis ≥ 5 cm, thoracic kyphosis ≥ 60°, coronal Cobb angle ≥ 20°, or pelvic incidence to lumbar lordosis mismatch ≥ 10°. The primary focus was patients with a minimum 2-year follow-up. RESULTS Of 148 patients who otherwise met the inclusion criteria, 114 (77.0%) achieved minimum 2-year follow-up and were included (68.4% were women, mean age 67.9 years, average body mass index 30.4 kg/m2). Sixty-two (54.4%) patients were treated with traditional dual-rod construct (DRC), and 52 (45.6%) were treated with ASR. Overall, the mean number of levels fused was 11.7, 79.8% of patients underwent Smith-Petersen osteotomy (SPO), 19.3% underwent pedicle subtraction osteotomy (PSO), and 66.7% underwent transforaminal lumbar interbody fusion (TLIF). Significantly more patients in the DRC cohort underwent SPO (88.7% of the DRC cohort vs 69.2% of the ASR cohort, p = 0.010) and TLIF (77.4% of the DRC cohort vs 53.8% of the ASR cohort, p = 0.0001). Patients treated with ASR had greater baseline sagittal malalignment (12.0 vs 8.6 cm, p = 0.014) than patients treated with DRC, and more patients in the ASR cohort underwent PSO (40.3% vs 1.6%, p < 0.0001). Among the 114 patients who completed follow-up, postoperative occurrence of RF was reported in 16 (14.0%) patients, with mean ± SD time to RF of 27.5 ± 11.8 months. There was significantly greater occurrence of RF among patients who underwent DRC compared with those who underwent ASR (21.0% vs 5.8%, p = 0.012) at comparable mean follow-up (38.4 vs 34.9 months, p = 0.072). Multivariate analysis demonstrated that ASR had a significant protective effect against RF (OR 0.231, 95% CI 0.051–0.770, p = 0.029). CONCLUSIONS This study demonstrated a statistically significant decrease in the occurrence of RF among ASD patients treated with ASR, despite greater baseline deformity and higher rate of PSO. These findings suggest that ASR placement may provide benefit to patients who undergo ASD surgery.

Long-term Morbidity in Patients After Surgical Correction of Adult Spinal Deformity

“…Outcomes after ASD corrective surgery is variable, with complications occurring commonly in complex deformity correction cases 21–23 . Encouraging results have previously been published in the literature on outcomes of ASD corrective surgery, but these have generally been relegated to the short term 24–26 . Here, we present the clinical experience with ASD surgery among contributors to a single-center database, with surveillance of complications and need for reoperation maintained to 5Y after the index procedure.…”

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

“…Substantial rates ranging from 23.7% to 56.0% have been reported by previous cohort studies ( Guler et al, 2015 ; Hallager et al, 2017 ; Eastlack et al, 2022 ). Among the implant failure, rod fracture (RF) was the most common complication, and 28.0%–81.3% of RF occurred at lumbosacral rods ( Devlin et al, 1991 ; Lertudomphonwanit et al, 2018 ; Rabinovich et al, 2021 ). The culprits of RF were pseudarthrosis and the increasing fatigue cracks under external stress ( Yamanaka et al, 2015 ; Sardi et al, 2022 ).…”

“…The culprits of RF were pseudarthrosis and the increasing fatigue cracks under external stress (Yamanaka et al, 2015;Sardi et al, 2022). We reviewed and synthesised the data of all published clinical studies comparing the mechanical complication rate between two-rod construct and multirod construct, and a significantly lower Frontiers in Bioengineering and Biotechnology frontiersin.org incidence of pseudarthrosis (14.2% vs. 35.0%) and RF (15.8% vs. 32.9%) was detected in patients undergoing multirod construct (Hyun et al, 2014;Han et al, 2017;Merrill et al, 2017;Guevara-Villazón et al, 2020;Yamato et al, 2020;Bourghli et al, 2021;Dinizo et al, 2021;Lamas et al, 2021;Rabinovich et al, 2021;Lyu et al, 2022). There are two options to anchor the distal end of accessory rods, including domino connectors and multiple pelvic screws.…”

Systematic review and meta-analysis for the impact of rod materials and sizes in the surgical treatment of adult spine deformity

“…The other meta-analysis did not evaluate rod characteristics associated with rod fracture; however, patient factors found to be associated with rod fracture included advanced age, higher body mass index, previous spine surgery, pedicle subtraction osteotomy, a larger preoperative pelvic tilt, and a larger preoperative thoracic kyphosis [13]. Efforts to reduce the incidence of rod fracture have been made, including the use of CoCr rods and multi-rod constructs; [12][13][14][15][16][17][18]; however, rod fracture continues to be a significant concern with the currently available rod treatment options and constructs [13]. Hence, there is a need for rods with improved fatigue performance so that breakage and, potentially pseudarthrosis, may be minimized.…”

“…Spinal fixation rods are an important component of pedicle screw fixation systems and may play a significant role in the overall surgical outcomes and in the likelihood of complications [12]. Surgeons require rod options that resist rod fracture and breakage and that deliver the optimal alignment and treatment approach to meet the needs of each patient [12][13][14][15][16][17][18]. It is important to gain a better understanding of the rod-specific factors that may contribute to successful surgical and safety outcomes in ASD patients.…”