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

View More View Less
  • 1 Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia; and
  • | 2 Departments of Neurological Surgery and
  • | 3 Orthopedic Surgery, Duke University Medical Center, Durham, North Carolina
Free access

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.

ABBREVIATIONS

ASD = adult spinal deformity; ASR = accessory supplemental rod; DRC = dual-rod construct; EBL = estimated blood loss; LL = lumbar lordosis; PI = pelvic incidence; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; RF = rod fracture; SPO = Smith-Petersen osteotomy; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLIF = transforaminal lumbar interbody fusion.

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.

ABBREVIATIONS

ASD = adult spinal deformity; ASR = accessory supplemental rod; DRC = dual-rod construct; EBL = estimated blood loss; LL = lumbar lordosis; PI = pelvic incidence; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; RF = rod fracture; SPO = Smith-Petersen osteotomy; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLIF = transforaminal lumbar interbody fusion.

In Brief

The present study evaluated the effect of accessory supplemental rod (ASR) implantation on postoperative occurrence of primary rod fracture (RF) in 114 patients who underwent long-segment spinal instrumentation for adult spinal deformity. Patients treated with ASR were 76.9% less likely to experience RF than patients managed with dual-rod construct. The statistically significant improvement in RF rates among patients treated with ASR suggests a potential benefit to using this technique to prevent RF.

Adult spinal deformity (ASD) is an increasingly prevalent medical condition with considerable adverse effects on health-related quality of life.1–4 In the United States alone, the prevalence of ASD is reportedly 32%–68% among the population aged 65 years and older, with a projected incidence of more than 60 million individuals within this age group diagnosed with some form of ASD by 2050.5 Data acquired from the National (Nationwide) Inpatient Sample have demonstrated that the total number of surgical procedures performed for ASD has more than doubled in the last decade,6 and that surgical intervention has been rapidly utilized to meet the increasing prevalence of this condition within the older population.5,7

Studies have shown that appropriate restoration of spinal alignment can lead to significant improvements in reported pain and disability.4,8,9 However, ASD surgery is associated with high complication rates.7,10–14 Commonly reported complications include instrumentation failures such as rod fracture (RF), which is reported by 6.8%–33% of patients and can lead to loss of deformity correction and reoperation.15–18 The etiology of RF may be due to increased instrumentation fatigue in the setting of pseudarthrosis and increased biomechanical loads.19,20 Reports have shown that segmental pedicle screw fixation with traditional dual-rod construct (DRC) and sacropelvic fixation is susceptible to increased risk of fatigue failure and shearing due to the unfavorable biomechanics of the long lever arms that generate robust forces across the lumbosacral junction.21,22 Therefore, multiple-rod configurations (e.g., accessory supplemental rod [ASR], satellite rod, kickstand rod) have been proposed to reduce this complication by conferring increased biomechanical stability and resistance to implant fatigue.20,23,24

Use of multiple-rod constructs with ASR has been considered a possible alternative technique that confers significantly improved biomechanical stability for spinal fixation, thereby minimizing susceptibility to implant failure and symptomatic pseudarthrosis25 when compared with standard DRC.20,26,27 However, the paucity of relevant clinical data and studies documenting the efficacy, complication rates, and outcomes associated with this technique has limited its widespread consideration as an alternative. Improved understanding of the clinical effects of ASR for the treatment of ASD may prove valuable for patient counseling and surgical planning. The objective of this study was to investigate the use of ASR as part of multiple-rod constructs and to determine its impact on postoperative occurrence of primary RF after ASD surgery. We hypothesized that use of ASR in multiple-rod constructs would likely reduce postoperative RF in patients who were surgically treated with long-segment spinal instrumentation for ASD.

Methods

Patient Population

We reviewed a single-center database of consecutive patients (age > 18 years) who underwent operative treatment of ASD by the senior authors at the University of Virginia Health System between 2014 and 2017. For this study, ASD was defined on the basis of the presence of at least one of the following characteristics: pelvic tilt (PT) ≥ 25°, sagittal vertical axis (SVA) ≥ 5 cm, thoracic kyphosis (TK) ≥ 60°, coronal Cobb angle ≥ 20°, and pelvic incidence (PI) to lumbar lordosis (LL) mismatch ≥ 10°. Other study inclusion criteria included 1) index surgery with ≥ 5 instrumented levels including sacropelvic fixation, 2) complete radiographic data assessed by using full-length standing scoliosis radiographs (36-inch-long cassettes), and 3) a minimum 2-year follow-up.

Cohorts were selected on the basis of each case by the senior operating surgeon. Patients who were at higher risk for RF, such as those with osteopenia/osteoporosis and greater baseline deformity, and those who required multilevel Smith-Petersen osteotomies (SPOs) and greater deformity correction, were likely chosen for treatment with ASR.14,17,19,28 To our knowledge, the medical records and examination findings of these patients did not indicate any other significant changes in technique, including those related to anesthesia and postoperative care, that could have accounted for outcome differences between cohorts. The present study was approved by the University of Virginia institutional review board.

Data Collection and Radiographic Assessment

Data on patient demographic and clinical characteristics, including information on index operations, radiographic outcomes, and complications, were obtained from patient medical records. Demographic and clinical variables included sex, age at time of index operation, BMI, history of osteopenia/osteoporosis, and etiology of adult scoliosis (i.e., adult idiopathic scoliosis, de novo degenerative adult scoliosis, and iatrogenic scoliosis) or other ASD (i.e., kyphoscoliosis, proximal junctional kyphosis/failure, or flatback syndrome). Index surgery–related variables included number of levels fused, type and number of osteotomies performed, type and level of interbody fusions performed, total estimated blood loss (EBL), operative duration, length of hospital stay, and adjunctive techniques used to reduce complications. The recorded surgical strategies used to reduce complications included application of junctional tethers, intraoperative tranexamic acid, and local intrawound vancomycin powder.

We evaluated all preoperative, early postoperative (approximately 6 weeks after index surgery), and final postoperative standing posteroanterior and lateral long-cassette radiographs (13 × 46 inches) that showed the cervical spine to pelvis of all patients. The coronal Cobb angle was measured by assessing the degree of curvature between the most tilted vertebra below and above the apex of the curve. Radiographic sagittal-plane variables included degree of TK (Cobb angle between superior T4 endplate and inferior T12 endplate), LL (Cobb angle between superior T12 endplate and inferior S1 endplate), PT, PI, PI-LL mismatch, and C7–S1 SVA.

Surgical Technique

After unsuccessful treatment with conservative management, each patient elected to proceed with surgical intervention. The patient was placed prone, in a mild reverse Trendelenburg position with all pressure points padded. After complete exposure, posterior instrumentation was placed, including pedicle screws and iliac bolts, by using standard techniques. Temporary distraction rods were placed during completion of all necessary osteotomy or transforaminal lumbar interbody fusion (TLIF) procedures. SPO was performed as part of the TLIF procedure at L3–4, L4–5, and L5–S1. Appropriate rods are then selected and contoured appropriately for fixation and deformity correction. All patients in this cohort received off-label use of bone morphogenetic protein at the lowest effective dosage via collagen sponges for posterior thoracolumbar arthrodesis. Wounds were drained per standard institutional protocol.29

For patients treated with ASR, side-to-side connectors were placed at the appropriate location, as defined by the senior operating surgeons, for attachment of ASR and to increase immediate biomechanical stability of the instrumentation. A subgroup of patients was treated with unilateral ASR spanning multilevel SPOs; another subset of these patients was treated with bilateral ASR, and when possible, bilateral rods were staggered to distribute stress across the construct and to maximally reduce rod strain. This offset conformation of bilateral ASR constructs further distributes tension across the areas of instrumentation that are subject to the greatest degree of mechanical stress, thereby reducing risk of instrumentation failure at these levels. Patients treated with pedicle subtraction osteotomy (PSO) underwent placement of ASRs spanning the PSO site.30 These three conformations are shown in Fig. 1. In all patients, ASRs—rather than satellite rods, which are affixed posteriorly, medially, or laterally with dual-headed screws immediately adjacent to the PSO level—were applied by using side-to-side connectors.31,32

FIG. 1.
FIG. 1.

Radiographs obtained from patients who underwent surgical treatment with ASR. A: A patient treated with unilateral ASRs spanning multiple SPOs. B: Bilateral ASRs spanning multiple SPOs in a staggered conformation. C: A patient treated with bilateral ASRs spanning across an L4 PSO site.

Detection of RF and Primary Outcomes

Patients underwent routine postoperative imaging at approximately 6 weeks, 3–4 months, 6 months, 1 year, and 2 years. If patients experienced symptomatic RF, further imaging with CT was performed to determine the etiology of pain and any associated symptoms. For patients with radiographic evidence of RF who underwent revision surgery for repeat arthrodesis and rod replacement, RF was confirmed intraoperatively.

Data and Statistical Analysis

Data are presented as the mean ± SD for continuous variables and as number (percent) for categorical variables. Differences in demographic characteristics, radiographic parameters, and various surgical characteristics between the cohort of patients treated with DRC and the cohort treated with ASR were assessed by using the chi-square test for categorical variables and the univariate independent-samples t-test for continuous variables. Further analyses were conducted with binary logistic regression, when appropriate, to assess for additional factors associated with the occurrence of primary RF. Covariates that were significant in univariate analysis were selected for inclusion in multivariate analysis, as well as those reported in the literature as related to the outcome of interest.14,19 All tests were 2-tailed, for which p values < 0.05 were considered statistically significant. All statistical analysis was performed by using RStudio (version 1.2.5019, RStudio, Inc.).

Results

Patient Population and Surgical Characteristics

Of 148 patients who otherwise met the inclusion criteria, 114 (77.0%) achieved minimum 2-year follow-up and were included in this study (mean follow-up 36.8 months). Most (68.4%) patients were women. The mean age at surgery was 67.9 years, and the average BMI was 30.4 kg/m2 (i.e., obese). The cohort comprised 28 (24.6%), 69 (60.5%), and 17 (14.9%) patients with adult idiopathic scoliosis, de novo degenerative adult scoliosis, and iatrogenic scoliosis, respectively. A total of 24 (21.1%) patients had a history of osteopenia or osteoporosis recorded in their medical record, and most of these patients had received treatment. Other demographic data are presented in Table 1.

TABLE 1.

Summary of demographic characteristics and surgical data of 114 patients treated for ASD between 2014 and 2017

VariableAll Patients (n = 114)DRC (n = 62)ASR (n = 52)p Value*
Age, yrs67.9 ± 7.567.6 ± 8.468.2 ± 6.30.664
Female sex78 (68.4)43 (69.4)35 (67.3)0.815
BMI, kg/m230.4 ± 5.730.3 ± 5.530.6 ± 6.00.730
ASA physical status classification score3 (2–3)3 (2–3)3 (2–3)0.857
Osteopenia/osteoporosis24 (21.1)11 (17.7)13 (25.0)0.343
Scoliosis diagnosis
 Idiopathic28 (24.6)17 (27.4)11 (19.2)0.439
 De novo degenerative69 (60.5)37 (59.7)32 (61.5)0.366
 Iatrogenic17 (14.9)8 (12.9)9 (17.3)0.511
Upper instrumented vertebra
 T2–432 (28.1)13 (21.0)19 (36.5)0.065
 T9–1182 (71.9)49 (79.0)33 (63.5)0.065
Levels fused11.7 ± 3.011.2 ± 2.712.4 ± 3.30.050
SPO91 (79.8)55 (88.7)36 (69.2) 0.010
 0–129 (25.4)7 (11.3)22 (42.3)0.121
 2–463 (55.2)41 (66.2)22 (42.3)0.091
 5–920 (17.5)12 (19.4)8 (15.4)0.818
 ≥102 (1.7)2 (3.2)0 (0.0)0.191
PSO/VCR22 (19.3)1 (1.6)21 (40.3)<0.0001
TLIF76 (66.7)48 (77.4)28 (53.8)0.0001
 L3–47 (6.1)5 (8.1)2 (3.8)0.350
 L4–559 (51.2)38 (61.3)21 (40.3)0.026
 L5–S170 (61.4)44 (71.0)26 (50.0)0.022
Technique to reduce complications
 Junctional tether92 (80.7)54 (87.1)38 (73.1)0.170
 Intraop tranexamic acid91 (79.8)49 (79.0)42 (80.8)0.818
 Local intrawound vancomycin powder109 (95.6)61 (98.4)48 (92.3)0.114
Total EBL, L2.2 ± 1.42.1 ± 1.32.3 ± 1.60.634
Op duration, hr5.6 ± 1.45.5 ± 1.35.6 ± 1.50.743
Length of hospital stay, days7.6 ± 2.97.4 ± 3.17.9 ± 2.50.419
Discharged to rehabilitation center83 (72.8)43 (69.4)40 (76.9)0.366
Follow-up, mos36.8 ± 10.438.4 ± 11.034.9 ± 9.40.072

ASA = American Society of Anesthesiologists; VCR = vertebral column resection.

Values are expressed as number (percent) of patients or mean ± SD. Boldface type indicates statistical significance (p < 0.05).

Comparison between groups with and without ASR.

Overall, 62 (54.4%) patients were treated with DRC, and 52 (45.6%) were treated with ASR. All patients underwent sacropelvic fixation, with the upper instrumented vertebra in the lower thoracic spine at T9–11 (71.9% of patients) or upper thoracic spine at T2–4 (28.1%) and a mean ± SD instrumented fusion length of 11.7 ± 3.0 levels. The mean ± SD operative duration was 5.6 ± 1.4 hours, and the mean ± SD total EBL was 2.2 ± 1.4 L. There was no apparent significant disadvantage of using multiple-rod technique with respect to EBL or operative time. Surgical techniques implemented to reduce complications included application of junctional tethers (n = 92 [80.7%]), intraoperative tranexamic acid (n = 91 [79.8%]), and local intrawound vancomycin powder (n = 109 [95.6%]).

Radiographic Outcome Measurements

Preoperative baseline, early postoperative (most commonly 6 weeks after surgery), and final postoperative changes in the sagittal-plane radiographic parameters of the patients who met the inclusion criteria are summarized in Table 2.

TABLE 2.

Comparison of preoperative and postoperative radiographic parameters of 114 patients with ASD who were surgically treated

Sagittal-Plane ParameterDRCASRp Value*
TK, °
 Baseline43.3 ± 17.440.9 ± 18.60.335
 Immediately postop53.7 ± 12.647.6 ± 11.60.005
 Change after surgery10.4 ± 15.17.0 ± 18.20.289
p value<0.00010.008
 Final55.8 ± 11.149.3 ± 11.60.003
LL, °
 Baseline30.3 ± 20.325.4 ± 18.90.182
 Immediately postop49.5 ± 10.145.6 ± 12.60.074
 Change after surgery19.1 ± 18.220.1 ± 18.60.768
p value<0.0001<0.0001
 Final50.2 ± 9.646.0 ± 10.40.026
PI-LL mismatch, °
 Baseline26.8 ± 19.229.1 ± 20.90.541
 Immediately postop7.4 ± 12.79.0 ± 13.00.509
 Change after surgery−19.4 ± 18.4−20.1 ± 18.70.837
p value<0.0001<0.0001
 Final6.5 ± 13.18.2 ± 13.10.491
PT, °
 Baseline30.0 ± 9.630.1 ± 9.80.948
 Immediately postop26.7 ± 8.626.3 ± 7.10.770
 Change after surgery−3.3 ± 10.2−3.8 ± 8.30.752
p value0.0130.002
 Final26.2 ± 8.726.7 ± 7.50.767
SVA, cm
 Baseline8.6 ± 5.612.0 ± 8.60.014
 Immediately postop4.2 ± 7.15.0 ± 4.90.480
 Change after surgery−4.3 ± 8.4−7.0 ± 7.50.075
p value0.0001<0.0001
 Final4.9 ± 4.45.2 ± 4.40.696
PI, °
 Baseline57.2 ± 12.254.5 ± 12.60.265
 Immediately postop56.9 ± 12.354.5 ± 12.10.315
 Change after surgery−0.3 ± 1.50.007 ± 3.70.576
p value0.1200.990
 Final56.7 ± 12.554.2 ± 11.80.265

Values are presented as mean ± SD unless indicated otherwise. Boldface type indicates statistical significance (p < 0.05).

Comparison between groups with and without ASR. Determined with the 2-tailed Student t-test.

Overall LL improved by 19.1° ± 18.2° (30.3° ± 20.3° at baseline vs 49.5° ± 10.1° immediately postoperatively, p < 0.0001) in patients treated with DRC and by 20.1° ± 18.6° (25.4° ± 18.9° at baseline vs 45.6° ± 12.6° immediately postoperatively, p < 0.0001) in patients with treated with ASR. PT decreased by 3.3° ± 10.2° (30.0° ± 9.6° at baseline vs 26.7° ± 8.6° immediately postoperatively, p = 0.013) in patients treated with DRC and by 3.8° ± 8.3° (30.1° ± 9.8° at baseline vs 26.3° ± 7.1° immediately postoperatively, p = 0.002) in patients treated with ASR. PI-LL mismatch decreased by 19.4° ± 18.4° (26.8° ± 19.2° at baseline vs 7.4° ± 12.7° immediately postoperatively, p < 0.0001) in patients treated with DRC and by 20.1° ± 18.7° (29.1° ± 20.9° at baseline vs 9.0° ± 13.0° immediately postoperatively, p < 0.0001) in patients treated with ASR. TK increased by 10.4° ± 15.1° (43.3° ± 17.4° at baseline vs 53.7° ± 12.6° immediately postoperatively, p < 0.0001) among patients treated with DRC and by 7.0° ± 18.2° (40.9° ± 18.6° at baseline vs 47.6° ± 11.6° immediately postoperatively, p = 0.008) among those treated with ASR. SVA improved by 4.3 cm ± 8.4 cm (8.6 cm ± 5.6 cm at baseline vs 4.2 cm ± 7.1 cm immediately postoperatively, p = 0.0001) among patients treated with DRC and by 7.0 cm ± 7.5 cm (12.0 cm ± 8.6 cm at baseline vs 5.0 cm ± 4.9 cm immediately postoperatively, p < 0.0001) among those treated with ASR. All surgical corrections were maintained at final follow-up.

Baseline Differences Between the DRC and Multiple-Rod Construct Subgroups

Significantly more patients in the DRC cohort underwent TLIF (77.4% of patients vs 53.8% of those in the ASR cohort, p = 0.0001) and SPO (88.7% vs 69.2% of those in the ASR cohort, p = 0.010). Significantly more patients in the ASR cohort underwent PSO (40.3% vs 1.6% of patients in the DRC cohort, p < 0.0001).

Patients treated with ASR had significantly greater baseline malalignment (12.0 cm ± 8.6 cm) than those treated with DRC (8.6 cm ± 5.6 cm, p = 0.014) (Table 2).

Rod Composition, Fracture Location, and Revision for RF

Among the 114 patients who completed 2-year follow-up, radiographic imaging revealed evidence of RF in 16 (14.0%) patients. There was a significantly greater incidence of RF among those treated with DRC than among those treated with ASR (21.0% vs 5.8%, p = 0.012) (Table 3), and the mean follow-up duration of these patients was comparable to that of the patients treated with ASR (38.4 months for the DRC cohort vs 34.9 months for the ASR cohort, p = 0.072) (Table 1). After stratification of patients according to early (≤ 6 weeks) and delayed (> 6 weeks) RF, there remained a significantly greater incidence of RF among patients treated with DRC after 6 weeks (19.5% vs 3.8%, p = 0.012) (Table 4).

TABLE 3.

Rates of complications associated with ASD surgery in 114 patients with minimum 2-year follow-up

Complication CategoryEarly (≤6 wks)Delayed (>6 wks)All Patients
DRC (n = 62)ARS (n = 52)Total (n = 114)p Value*DRC (n = 62)ASR (n = 52)Total (n = 114)p Value*
Implant2 (3.2)1 (1.9)3 (2.6)0.66512 (19.4)2 (3.8)14 (12.3)0.01217 (14.9)
 Rod breakage1 (1.6)1 (1.9)2 (1.8)0.90012 (19.4)§2 (3.8)14 (12.3)§0.01216 (14.0)
 Screw nerve impingement1 (1.6)0 (0.0)1 (0.9)0.3580 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
Neurological2 (3.2)1 (1.9)3 (2.6)0.6651 (1.6)4 (7.7)5 (4.4)0.1148 (7.0)
 Radiculopathy0 (0.0)0 (0.0)0 (0.0)>0.991 (1.6)2 (3.8)3 (2.6)0.4583 (2.6)
 Motor deficit2 (3.2)0 (0.0)2 (1.8)0.1910 (0.0)2 (3.8)2 (1.8)0.1194 (3.5)
 Mental status change0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
Op8 (12.9)7 (13.5)15 (13.2)0.9300 (0.0)0 (0.0)0 (0.0)>0.9915 (13.2)
 Dural tear8 (12.9)7 (13.5)15 (13.2)0.9300 (0.0)0 (0.0)0 (0.0)>0.9915 (13.2)
Radiographic0 (0.0)0 (0.0)0 (0.0)>0.998 (12.9)3 (5.8)11 (9.6)0.19911 (9.6)
 Proximal junctional kyphosis0 (0.0)0 (0.0)0 (0.0)>0.996 (9.7)3 (5.8)9 (7.9)0.4419 (7.9)
 Adjacent-segment disease0 (0.0)0 (0.0)0 (0.0)>0.992 (3.2)0 (0.0)2 (1.8)0.1912 (1.8)
Infection2 (3.2)1 (1.9)3 (2.6)0.6650 (0.0)0 (0.0)0 (0.0)>0.993 (2.6)
 Deep wound infection2 (3.2)0 (0.0)2 (1.8)0.1910 (0.0)0 (0.0)0 (0.0)>0.992 (1.8)
 Urinary tract infection0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
Wound1 (1.6)0 (0.0)1 (0.9)0.3580 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
 Dehiscence1 (1.6)0 (0.0)1 (0.9)0.3580 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
Gastrointestinal8 (12.9)5 (9.6)13 (11.4)0.5820 (0.0)0 (0.0)0 (0.0)>0.9913 (11.4)
 Ileus6 (9.7)3 (5.8)9 (7.9)0.4410 (0.0)0 (0.0)0 (0.0)>0.999 (7.9)
 Abdominal distension2 (3.2)2 (3.8)4 (3.5)0.8580 (0.0)0 (0.0)0 (0.0)>0.994 (3.5)
Cardiopulmonary0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
 Pulmonary embolism0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
Vascular0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)
 Febrile nonhemolytic transfusion reaction0 (0.0)1 (1.9)1 (0.9)0.2730 (0.0)0 (0.0)0 (0.0)>0.991 (0.9)

Values are shown as number (percent) unless indicated otherwise. Boldface type indicates statistical significance (p < 0.05).

Comparison of groups with and without ASR.

One patient required reoperation.

Two patients required reoperation.

Seven patients required reoperation.

Infection was excluded.

TABLE 4.

Rates of RF among patients treated with DRC and ASR

Type of RFDRC (n = 62)ASR (n = 52)p Value
Total*13 (21.0)3 (5.8)0.012
 Early (≤6 wks)1 (1.6)1 (1.9)0.900
 Delayed (>6 wks)12 (19.4)2 (3.8)0.012
Unilat9 (69.2)2 (66.7)0.931
Bilat4 (30.8)1 (33.3)0.931

Values are expressed as number (percent) of patients. Boldface type indicates statistical significance (p < 0.05).

The average ± SD time to RF was 27.5 ± 11.8 months.

One patient required reoperation.

Seven patients required reoperation.

Among patients with RF, the rod was 6.0-mm-diameter cobalt chromium (n = 7), 5.5-mm-diameter cobalt chromium (n = 3), and 5.5- to 6.5-mm-diameter tapered cobalt chromium (n = 6) (Fig. 2A). The majority of RFs occurred at the lumbar spine or thoracolumbar junction (n = 12 [75.0%]) (Fig. 2A). Figure 2A also shows individual cases of symptomatic RF and interbody graft position. Examples of RFs in patients who underwent spinal fixation with DRC and ASR are shown in Fig. 3A–B and 3C–D, respectively.

FIG. 2.
FIG. 2.

A: Rod composition, rod diameter, and location of RFs detected in 16 adult patients treated surgically for ASD. The vertical axis shows the spinal levels from the thoracic spine through the ilium. Each vertically oriented bar indicates the level of fusion for each patient. For patients treated with ASR, the level of additional instrumentation relative to RF location is indicated in red (patients 14–16). Rod composition, including cobalt chromium (CC) and tapered cobalt chromium (CCt) and diameter (5.5–6.0 mm), is indicated along the top of the figure. Asterisks indicate patients who presented with symptomatic RF; RF was incidentally detected in other patients. B: Graphical depiction of time to RF from date of surgery, in months, for each patient who sustained an RF. The mean ± SD time to RF was 27.5 ± 11.8 months. Figure is available in color online only.

FIG. 3.
FIG. 3.

A and B: Example of RFs in a patient treated with DRC. The patient underwent instrumented arthrodesis from T10 to the ilium with T12–L1 through L5–S1 SPOs. Two SPOs were performed as part of L4–5 and L5–S1 TLIF. RFs occurred on the right side at the L5–S1 level and on the left side at the L4–5 level (red arrows). C and D: Example of an RF in a patient treated with ASR. The patient underwent T4 to iliac instrumentation and fusion with L4–5 and L5–S1 TLIF and multiple SPOs for correction of thoracolumbar kyphoscoliosis. RF occurred at the L4–5 level on the left side (red arrow). Figure is available in color online only.

At last follow-up, 9 of 16 (56.3%) patients with RF had undergone reoperation for repeat arthrodesis and rod replacement. All these patients presented with symptomatic RF and reported symptoms such as low-back pain and radiculopathy. Incidental RF was identified on routine imaging in 7 (43.8%) of 16 patients with RF; none of these patients reported clinical symptoms. Diagnosis of RF in these patients was made according to findings on routine radiographic imaging (Fig. 3). Average time to RF was 27.5 months from date of index surgery among the patients with RF. The time to RF of each patient is shown in Fig. 2B.

At last follow-up, 9 of 16 (56.3%) patients with RF had undergone reoperation for repeat arthrodesis and rod replacement. All these patients presented with symptomatic RF and reported symptoms such as low-back pain and radiculopathy. Incidental RF was identified on routine imaging in 7 (43.8%) of 16 patients with RF; none of these patients reported clinical symptoms. Diagnosis of RF in these patients was made according to findings on routine radiographic imaging (Fig. 3). Average time to RF was 27.5 months from date of index surgery among the patients with RF. The time to RF of each patient is shown in Fig. 2B.

Of 34 patients without 2-year minimum follow-up, 11 (32.4%) were treated with DRC and 23 (67.6%) were treated with ASR. Among those treated with DRC, 1 (9.1%) patient had RF. There was no case of reported RF among the patients treated with ASR. At the time of data collection, 3 of these patients had not received any follow-up after 6 months, 11 had not received any follow-up after 1 year, and 31 had not received follow-up after 18 months.

Multivariate Analysis

The covariates selected for inclusion in the multivariable logistic regression models included use of ASR, baseline SVA, total change in SVA after index surgery, and treatment with PSO (Table 5). Use of ASR was protective against postoperative RF in this patient cohort; patients with ASR were 76.9% less likely to have RF than patients treated with traditional DRC (OR 0.231, 95% CI 0.051–0.770, p = 0.029). No other selected covariates were significantly associated with postoperative RF.

TABLE 5.

Risk of RF with respect to selected covariates

CovariateOR (95% CI)p Value
ASR0.231 (0.051–0.770)0.029
Baseline SVA0.968 (0.889–1.043)0.430
SVA change after surgery1.015 (0.949–1.081)0.648
Treatment w/ PSO0.244 (0.013–1.317)0.185

Boldface type indicates statistical significance (p < 0.05).

Summary of Complications

The most common intraoperative complication was durotomy in 15 (13.2%) patients; all cases were repaired primarily. No durotomies resulted in postoperative CSF leak. Early postoperative complications included deep wound infection (n = 2 [1.8%]; 1 patient required reoperation), urinary tract infection (n = 1 [0.9%]), wound dehiscence (n = 1 [0.9%]), ileus (n = 9 [7.9%]), abdominal distention (n = 4 [3.8%]), pulmonary embolism (n = 1 [0.9%]), febrile nonhemolytic transfusion reaction (n = 1 [0.9%]), motor deficit (n = 2 [1.8%]), screw nerve impingement requiring reoperation (n = 1 [0.9%]), and postoperative delirium (n = 1 [0.9%]).

Delayed complications included radiculopathy (n = 3 [2.6%]), motor deficit (n = 2 [1.8%]), and radiographic evidence of proximal junctional kyphosis (n = 9 [7.9%]) and adjacent-segment disease (n = 2 [1.8%]). Table 3 summarizes the complications reported associated with the index operations.

Discussion

The objective of the present study was to determine the effect of ASR implantation on postoperative occurrence of primary RF in patients with ASD. This study provides a retrospective single-center analysis of RF rates among adult patients surgically treated for spinal deformity with DRC or multiple-rod construct with ASR. Previous studies have demonstrated high incidence rates of RF (approximately 6.8%–32.7%) after surgical treatment of ASD with long-segment pedicle screw fixation and DRC.15–19,28,33

The present study revealed that the overall rate of RF in patients with minimum of 2 years of radiographic follow-up was 14.0% (n = 16), which is consistent with previous findings.15–19,28,33 Further analysis indicated significantly increased incidence of RF among patients treated with DRC (n = 13 [21.0%]) compared with those treated with ASR (n = 3 [5.8%]). No additional factors were significantly associated with RF on multivariate analysis (Table 5). Of 16 patients diagnosed with RF at final follow-up, 9 (56.3%) presented with symptomatic RF and reported symptoms such as pain and radiculopathy. All these patients underwent reoperation, primarily for repeat arthrodesis and replacement of fractured instrumentation. The remaining patients presented with asymptomatic RF, but none required reoperation. This finding is consistent with those of the 2018 study by Yamato et al.,34 which determined that nonoperative care is indicated for patients with asymptomatic RF. The results of our study provide a valuable addition to the current scope of clinical knowledge regarding the comparative resistance of these two techniques to biomechanical fatigue, because these results are derived from the examination of 114 patients diagnosed with ASD.

Other authors have cited high rates of RF across the lumbosacral junction or adjacent levels, with rates as high as 77%.35,36 The findings of the present study are consistent with these reported rates because 13 (81.3%) of 16 RFs were found between L4 and S1.

With respect to the operative characteristics, there were no significant differences in total EBL, operative duration, length of hospital stay, or postoperative discharge to rehabilitation centers between the two cohorts, indicating that ASR may provide a comparable alternative technique; this would be consistent with the findings of the 2017 study conducted by Merrill et al.20 Several risk factors have been identified as contributors to increased primary rod strain in patients who undergo ASD correction, including fusion construct crossing two junctions,21 pelvic fixation, and increased baseline imbalance.17

PSO allows for marked correction of severe sagittal malalignment and fixed sagittal deformity in patients with ASD,37,38 as well as for approximately 20°–45° of lordosis.39 Notwithstanding the evidence supporting the structural benefits of treatment with PSO, the classic PSO technique is reportedly associated with substantiated complications, particularly RF and instrumentation failure, due to severe angulation that decreases fatigue resistance in instrumentation.4,39,40 Although significantly more patients in the ASR cohort underwent PSO (21 [40.3%] patients vs 1 [1.6%] patient in the DRC cohort, p < 0.0001)—indicating that patients were selected for treatment with ASR by institutional protocol and likely required a greater degree of sagittal correction than those treated with DRC—multivariate analysis revealed no significant association between PSO and RF among these patients. No additional risk factors were identified on multivariate analysis.

To reduce selection bias in this study, we conducted a subanalysis of the RF rates between the patients who did not undergo PSO in the DCR cohort and those in the ASR cohort. Further analysis revealed that 13 (21.3%) of 61 patients in the DRC cohort and 2 (6.5%) of 31 patients in the ASR cohort sustained an RF by the time of data collection. Although the effect of ASR on RF rates in this subanalysis was not statistically significant (13 [21.3%] patients had RF in the DCR cohort vs 2 [6.5%] in the ASR cohort, p = 0.068), the data still demonstrate an approximate 15% decrease in the rate of RF among patients treated with ASR.

Prior reports have demonstrated the potential benefits of multiple-rod construct implantation to prevent subsequent primary instrumentation failure in patients who undergo long-segment spinal fusion. In a 2013 study, Wang et al.27 conducted an in vitro biomechanical spine study, wherein 4-rod techniques conferred greater stability during lumbosacral fixation for long-segment fusion. In an in vitro study by La Barbera et al.41 on human cadaveric spine segments, biomechanical flexibility tests demonstrated that the addition of ASR with or without cages significantly reduced primary rod strain. Although the biomechanical implications of multiple-rod constructs have been recorded,26,27,39,41,42 studies in the literature delineating comparative clinical outcomes between patients treated with multiple-rod construct versus those treated with DRC are sparse. Merrill et al.20 examined the clinical effects of multiple-rod construct on stability and fusion rates within the lumbosacral junction in a cohort of 31 patients, providing results supporting increased mechanical stability due to multiple-rod constructs. To our knowledge, the 2017 study by Merrill and colleagues provided the first retrospective review of clinical patient outcomes after treatment with DRC versus multiple-rod construct for correction of ASD. Later studies further supported the protective effects of 4-rod configurations in preventing RF among patients treated with PSO.43 The present study confirmed their findings and significantly expands the available clinical data that suggest treatment of ASD with multiple-rod constructs may be a compelling alternative to conventional DRC. Given the limitations discussed in the next section, further investigation is necessary to expand upon the results of the aforementioned studies. Nevertheless, the present study contributes to the currently available literature on adult scoliosis and provides additional surgical data for future studies.

Limitations

The present study must be considered in light of its limitations. The nature of retrospective analysis introduces unique challenges and inherent biases, thereby diminishing the quality of data owing to the lack of prospective randomization and information bias within medical records.

Loss to follow-up has been raised as a concerning limitation that threatens the internal validity of data derived from cohort studies.44 In the present study, 77% of patients received 2-year minimum follow-up. However, we evaluated the data of the remaining 34 patients who did not meet the minimum follow-up criteria to account for loss of data. At the time of data collection, approximately 9.1% of patients treated with DRC presented with RF, and there were no reported cases of RF among the patients treated with ASR. These findings are consistent with data suggesting that use of ASR reduces the occurrence of postoperative RF in patients treated with long-segment spinal instrumentation for ASD. It is also possible that use of ASR simply delays instrumentation failure if solid bony fusion is not achieved. Further research may benefit from the collection of data on fusion rates among patients who sustained RF. Early RF has been associated with increased rates of pseudarthrosis, whereas delayed RF is commonly associated with instrumentation fatigue secondary to pseudarthrosis.18,45 In the present study, CT was not routinely ordered postoperatively because primarily only those patients with symptomatic RF underwent further imaging. RF was often identified and confirmed intraoperatively or with postoperative full-length scoliosis radiographs.

Another limitation is selection bias due to the lack of random assignment of the patients into the two treatment cohorts. Patient selection, surgical technique and approach, and postoperative management were directed by physicians at a single center. From 2014 to 2017, the senior operating surgeons performed both DRC and ASR techniques, rendering it difficult to fully elucidate the temporal effect of knowledge and technique improvement in a retrospective study. However, there was no significant difference in the proportion of patients treated with either DRC or ASR before December 2015 (54.8% vs 46.2%, p = 0.356), which is the median date of this study, indicating that it is unlikely that varying surgical technique preferences over time introduced additional bias. Patients were selected for surgical intervention on the basis of an institutional protocol, and the ASR technique was likely chosen for patients at higher risk for postoperative RF (as evidenced by their greater baseline SVA values and rate of PSO).

Although a single-center study design allows for decreased variability in patient selection, surgical technique, and postoperative management protocol, thus reducing potential for confounding bias, this design introduces inherent selection bias that may otherwise be reduced in a prospective multicenter randomized controlled trial with multiple surgeons. The overall impact of this study could be improved by including multiple surgeons across various centers to mitigate bias introduced by the individual preferences of the physician responsible for patient care and treatment. Until prospective multicenter studies with larger randomized cohorts of patients are conducted, this study may serve as an additional source of information for surgeons seeking to correct severe cases of ASD. To our knowledge, this is the largest comparative analysis of consecutive patients treated with DRC versus those treated with ASR for ASD with 2-year minimum follow-up.

Conclusions

In this single-center retrospective analysis of the incidence of RF in patients diagnosed with ASD, patients treated with ASR had significantly reduced rates of RF when compared with those of a similar cohort of patients treated with traditional DRC. ASR was associated with reduced RF despite its utilization in patients with worse baseline deformity who underwent more PSO procedures. This study contributes to the literature on surgical techniques for ASD, expands the current knowledge base and available clinical data for comparison of rates of complications between patients with ASD who receive multiple-rod construct and those who receive DRC for long-segment pedicle screw fixation, and indicates the potential benefit of using ASR to prevent RF.

Disclosures

Dr. Smith is a consultant for and receives royalties from Zimmer Biomet and NuVasive; is a consultant for and receives study group research grants from DePuy Synthes; is a consultant for Stryker, Cerapedics, and Carlsmed; owns stock in Alphatec; receives fellowship funding and research support from AO Spine; receives fellowship funding from the Neurosurgery Research and Education Foundation; receives research funding from ISSGF and NuVasive; and receives royalties from Thieme. Dr. Shaffrey is a consultant for NuVasive, Medtronic, Globus, and SI Bone; owns stock in NuVasive; holds patents with NuVasive, Medtronic, and Zimmer Biomet; and receives royalties from NuVasive and Medtronic.

Author Contributions

Conception and design: Smith, Rabinovich, Buell, Shaffrey. Acquisition of data: Smith, Rabinovich, Buell, Wang. Analysis and interpretation of data: Smith, Rabinovich, Buell. Drafting the article: Smith, Rabinovich, Buell. Critically revising the article: Smith, Rabinovich, Buell, Shaffrey. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Smith. Statistical analysis: Rabinovich, Buell. Study supervision: Smith, Buell.

References

  • 1

    Diebo BG, Shah NV, Boachie-Adjei O, et al. Adult spinal deformity. Lancet. 2019;394(10193):160172.

  • 2

    Buell TJ, Chen C-J, Nguyen JH, et al. Surgical correction of severe adult lumbar scoliosis (major curves ≥ 75°): retrospective analysis with minimum 2-year follow-up. J Neurosurg Spine. 2019;31(4):114.

    • Search Google Scholar
    • Export Citation
  • 3

    Lafage V, Smith JS, Bess S, et al. Sagittal spino-pelvic alignment failures following three column thoracic osteotomy for adult spinal deformity. Eur Spine J. 2012;21(4):698704.

    • Search Google Scholar
    • Export Citation
  • 4

    Smith JS, Shaffrey CI, Glassman SD, et al. Risk-benefit assessment of surgery for adult scoliosis: an analysis based on patient age. Spine (Phila Pa 1976). 2011;36(10):817824.

    • Search Google Scholar
    • Export Citation
  • 5

    Ames CP, Scheer JK, Lafage V, et al. Adult spinal deformity: epidemiology, health impact, evaluation, and management. Spine Deform. 2016;4(4):310322.

    • Search Google Scholar
    • Export Citation
  • 6

    Pellisé F, Vila-Casademunt A, Ferrer M, et al. Impact on health related quality of life of adult spinal deformity (ASD) compared with other chronic conditions. Eur Spine J. 2015;24(1):311.

    • Search Google Scholar
    • Export Citation
  • 7

    Daubs MD, Lenke LG, Cheh G, et al. Adult spinal deformity surgery: complications and outcomes in patients over age 60. Spine (Phila Pa 1976). 2007;32(20):22382244.

    • Search Google Scholar
    • Export Citation
  • 8

    Lippman CR, Spence CA, Youssef AS, Cahill DW. Correction of adult scoliosis via a posterior-only approach. Neurosurg Focus. 2003;14(1):e5.

    • Search Google Scholar
    • Export Citation
  • 9

    Oskouian RJ Jr, Shaffrey CI. Degenerative lumbar scoliosis. Neurosurg Clin N Am. 2006;17(3):299315, vii.

  • 10

    Zanirato A, Damilano M, Formica M, et al. Complications in adult spine deformity surgery: a systematic review of the recent literature with reporting of aggregated incidences. Eur Spine J. 2018;27(9):22722284.

    • Search Google Scholar
    • Export Citation
  • 11

    Baron EM, Albert TJ. Medical complications of surgical treatment of adult spinal deformity and how to avoid them. Spine (Phila Pa 1976). 2006;31(19)(suppl):S106S118.

    • Search Google Scholar
    • Export Citation
  • 12

    Slone RM, MacMillan M, Montgomery WJ. Spinal fixation. Part 3. Complications of spinal instrumentation. Radiographics. 1993;13(4):797816.

    • Search Google Scholar
    • Export Citation
  • 13

    Schwab FJ, Hawkinson N, Lafage V, et al. Risk factors for major peri-operative complications in adult spinal deformity surgery: a multi-center review of 953 consecutive patients. Eur Spine J. 2012;21(12):26032610.

    • Search Google Scholar
    • Export Citation
  • 14

    Smith JS, Klineberg E, Lafage V, et al. Prospective multicenter assessment of perioperative and minimum 2-year postoperative complication rates associated with adult spinal deformity surgery. J Neurosurg Spine. 2016;25(1):114.

    • Search Google Scholar
    • Export Citation
  • 15

    Hamilton DK, Buza JA III, Passias P, et al. The fate of patients with adult spinal deformity incurring rod fracture after thoracolumbar fusion. World Neurosurg. 2017;106:905911.

    • Search Google Scholar
    • Export Citation
  • 16

    Smith JS, Shaffrey CI, Klineberg E, et al. Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up. J Neurosurg Spine. 2017;27(4):444457.

    • Search Google Scholar
    • Export Citation
  • 17

    Barton C, Noshchenko A, Patel V, et al. Risk factors for rod fracture after posterior correction of adult spinal deformity with osteotomy: a retrospective case-series. Scoliosis. 2015;10(1):30.

    • Search Google Scholar
    • Export Citation
  • 18

    Smith JS, Shaffrey CI, Ames CP, et al. Assessment of symptomatic rod fracture after posterior instrumented fusion for adult spinal deformity. Neurosurgery. 2012;71(4):862867.

    • Search Google Scholar
    • Export Citation
  • 19

    Daniels AH, DePasse JM, Durand W, et al. Rod fracture after apparently solid radiographic fusion in adult spinal deformity patients. World Neurosurg. 2018;117:e530e537.

    • Search Google Scholar
    • Export Citation
  • 20

    Merrill RK, Kim JS, Leven DM, et al. Multi-rod constructs can prevent rod breakage and pseudarthrosis at the lumbosacral junction in adult spinal deformity. Global Spine J. 2017;7(6):514520.

    • Search Google Scholar
    • Export Citation
  • 21

    Edwards CC II, Bridwell KH, Patel A, et al. Long adult deformity fusions to L5 and the sacrum. A matched cohort analysis. Spine (Phila Pa 1976). 2004;29(18):19962005.

    • Search Google Scholar
    • Export Citation
  • 22

    Emami A, Deviren V, Berven S, et al. Outcome and complications of long fusions to the sacrum in adult spine deformity: Luque-Galveston, combined iliac and sacral screws, and sacral fixation. Spine (Phila Pa 1976). 2002;27(7):776786.

    • Search Google Scholar
    • Export Citation
  • 23

    Buell TJ, Buchholz AL, Mazur MD, et al. Kickstand rod technique for correcting coronal imbalance in adult scoliosis: 2-dimensional operative video. Oper Neurosurg (Hagerstown). 2020;19(2):E163E164.

    • Search Google Scholar
    • Export Citation
  • 24

    Jager ZS, İnceoğlu S, Palmer D, et al. Preventing instrumentation failure in three-column spinal osteotomy: biomechanical analysis of rod configuration. Spine Deform. 2016;4(1):39.

    • Search Google Scholar
    • Export Citation
  • 25

    Hyun S-J, Lenke LG, Kim Y-C, et al. Comparison of standard 2-rod constructs to multiple-rod constructs for fixation across 3-column spinal osteotomies. Spine (Phila Pa 1976). 2014;39(22):18991904.

    • Search Google Scholar
    • Export Citation
  • 26

    Kelly BP, Shen FH, Schwab JS, et al. Biomechanical testing of a novel four-rod technique for lumbo-pelvic reconstruction. Spine (Phila Pa 1976). 2008;33(13):E400E406.

    • Search Google Scholar
    • Export Citation
  • 27

    Wang T, Liu H, Zheng Z, et al. Biomechanical effect of 4-rod technique on lumbosacral fixation: an in vitro human cadaveric investigation. Spine (Phila Pa 1976). 2013;38(15):E925E929.

    • Search Google Scholar
    • Export Citation
  • 28

    Akazawa T, Kotani T, Sakuma T, et al. Rod fracture after long construct fusion for spinal deformity: clinical and radiographic risk factors. J Orthop Sci. 2013;18(6):926931.

    • Search Google Scholar
    • Export Citation
  • 29

    Saulle D, Fu K-MG, Shaffrey CI, Smith JS. Multiple-day drainage when using bone morphogenic protein for long-segment thoracolumbar fusions is associated with low rates of wound complications. World Neurosurg. 2013;80(1-2):204207.

    • Search Google Scholar
    • Export Citation
  • 30

    Buell TJ, Nguyen JH, Mazur MD, et al. Radiographic outcome and complications after single-level lumbar extended pedicle subtraction osteotomy for fixed sagittal malalignment: a retrospective analysis of 55 adult spinal deformity patients with a minimum 2-year follow-up. J Neurosurg Spine. 2018;30(2):242252.

    • Search Google Scholar
    • Export Citation
  • 31

    Zhu ZZ, Chen X, Qiu Y, et al. Adding satellite rods to standard two-rod construct with the use of duet screws: an effective technique to improve surgical outcomes and preventing proximal junctional kyphosis in posterior-only correction of Scheuermann kyphosis. Spine (Phila Pa 1976). 2018;43(13):E758E765.

    • Search Google Scholar
    • Export Citation
  • 32

    Smith JS, Shaffrey CI, Bess S, et al. Recent and emerging advances in spinal deformity. Neurosurgery. 2017;80(3S):S70S85.

  • 33

    Wang H, Guo J, Wang S, et al. Instrumentation failure after posterior vertebral column resection in adult spinal deformity. Spine (Phila Pa 1976). 2017;42(7):471478.

    • Search Google Scholar
    • Export Citation
  • 34

    Yamato Y, Hasegawa T, Kobayashi S, et al. Treatment strategy for rod fractures following corrective fusion surgery in adult spinal deformity depends on symptoms and local alignment change. J Neurosurg Spine. 2018;29(1):5967.

    • Search Google Scholar
    • Export Citation
  • 35

    Jung JM, Hyun SJ, Kim KJ, Jahng TA. Rod fracture after multiple-rod constructs for adult spinal deformity. J Neurosurg Spine. 2020;32(3):407414.

    • Search Google Scholar
    • Export Citation
  • 36

    Devlin VJ, Boachie-Adjei O, Bradford DS, et al. Treatment of adult spinal deformity with fusion to the sacrum using CD instrumentation. J Spinal Disord. 1991;4(1):114.

    • Search Google Scholar
    • Export Citation
  • 37

    Berjano P, Aebi M. Pedicle subtraction osteotomies (PSO) in the lumbar spine for sagittal deformities. Eur Spine J. 2015;24(1)(suppl 1):S49S57.

    • Search Google Scholar
    • Export Citation
  • 38

    Bridwell KH, Lewis SJ, Lenke LG, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance. J Bone Joint Surg Am. 2003;85(3):454463.

    • Search Google Scholar
    • Export Citation
  • 39

    Januszewski J, Beckman JM, Harris JE, et al. Biomechanical study of rod stress after pedicle subtraction osteotomy versus anterior column reconstruction: a finite element study. Surg Neurol Int. 2017;8:207.

    • Search Google Scholar
    • Export Citation
  • 40

    Hyun SJ, Rhim SC. Clinical outcomes and complications after pedicle subtraction osteotomy for fixed sagittal imbalance patients: a long-term follow-up data. J Korean Neurosurg Soc. 2010;47(2):95101.

    • Search Google Scholar
    • Export Citation
  • 41

    La Barbera L, Brayda-Bruno M, Liebsch C, et al. Biomechanical advantages of supplemental accessory and satellite rods with and without interbody cages implantation for the stabilization of pedicle subtraction osteotomy. Eur Spine J. 2018;27(9):23572366.

    • Search Google Scholar
    • Export Citation
  • 42

    Luca A, Ottardi C, Sasso M, et al. Instrumentation failure following pedicle subtraction osteotomy: the role of rod material, diameter, and multi-rod constructs. Eur Spine J. 2017;26(3):764770.

    • Search Google Scholar
    • Export Citation
  • 43

    Gupta S, Eksi MS, Ames CP, et al. A novel 4-rod technique offers potential to reduce rod breakage and pseudarthrosis in pedicle subtraction osteotomies for adult spinal deformity correction. Oper Neurosurg (Hagerstown). 2018;14(4):449456.

    • Search Google Scholar
    • Export Citation
  • 44

    Howe CJ, Cole SR, Lau B, et al. Selection bias due to loss to follow up in cohort studies. Epidemiology. 2016;27(1):9197.

  • 45

    Charosky S, Guigui P, Blamoutier A, et al. Complications and risk factors of primary adult scoliosis surgery: a multicenter study of 306 patients. Spine (Phila Pa 1976). 2012;37(8):693700.

    • Search Google Scholar
    • Export Citation

Illustration from Rothrock et al. (pp 535–545). Copyright Roberto Suazo. Published with permission.

  • View in gallery

    Radiographs obtained from patients who underwent surgical treatment with ASR. A: A patient treated with unilateral ASRs spanning multiple SPOs. B: Bilateral ASRs spanning multiple SPOs in a staggered conformation. C: A patient treated with bilateral ASRs spanning across an L4 PSO site.

  • View in gallery

    A: Rod composition, rod diameter, and location of RFs detected in 16 adult patients treated surgically for ASD. The vertical axis shows the spinal levels from the thoracic spine through the ilium. Each vertically oriented bar indicates the level of fusion for each patient. For patients treated with ASR, the level of additional instrumentation relative to RF location is indicated in red (patients 14–16). Rod composition, including cobalt chromium (CC) and tapered cobalt chromium (CCt) and diameter (5.5–6.0 mm), is indicated along the top of the figure. Asterisks indicate patients who presented with symptomatic RF; RF was incidentally detected in other patients. B: Graphical depiction of time to RF from date of surgery, in months, for each patient who sustained an RF. The mean ± SD time to RF was 27.5 ± 11.8 months. Figure is available in color online only.

  • View in gallery

    A and B: Example of RFs in a patient treated with DRC. The patient underwent instrumented arthrodesis from T10 to the ilium with T12–L1 through L5–S1 SPOs. Two SPOs were performed as part of L4–5 and L5–S1 TLIF. RFs occurred on the right side at the L5–S1 level and on the left side at the L4–5 level (red arrows). C and D: Example of an RF in a patient treated with ASR. The patient underwent T4 to iliac instrumentation and fusion with L4–5 and L5–S1 TLIF and multiple SPOs for correction of thoracolumbar kyphoscoliosis. RF occurred at the L4–5 level on the left side (red arrow). Figure is available in color online only.

  • 1

    Diebo BG, Shah NV, Boachie-Adjei O, et al. Adult spinal deformity. Lancet. 2019;394(10193):160172.

  • 2

    Buell TJ, Chen C-J, Nguyen JH, et al. Surgical correction of severe adult lumbar scoliosis (major curves ≥ 75°): retrospective analysis with minimum 2-year follow-up. J Neurosurg Spine. 2019;31(4):114.

    • Search Google Scholar
    • Export Citation
  • 3

    Lafage V, Smith JS, Bess S, et al. Sagittal spino-pelvic alignment failures following three column thoracic osteotomy for adult spinal deformity. Eur Spine J. 2012;21(4):698704.

    • Search Google Scholar
    • Export Citation
  • 4

    Smith JS, Shaffrey CI, Glassman SD, et al. Risk-benefit assessment of surgery for adult scoliosis: an analysis based on patient age. Spine (Phila Pa 1976). 2011;36(10):817824.

    • Search Google Scholar
    • Export Citation
  • 5

    Ames CP, Scheer JK, Lafage V, et al. Adult spinal deformity: epidemiology, health impact, evaluation, and management. Spine Deform. 2016;4(4):310322.

    • Search Google Scholar
    • Export Citation
  • 6

    Pellisé F, Vila-Casademunt A, Ferrer M, et al. Impact on health related quality of life of adult spinal deformity (ASD) compared with other chronic conditions. Eur Spine J. 2015;24(1):311.

    • Search Google Scholar
    • Export Citation
  • 7

    Daubs MD, Lenke LG, Cheh G, et al. Adult spinal deformity surgery: complications and outcomes in patients over age 60. Spine (Phila Pa 1976). 2007;32(20):22382244.

    • Search Google Scholar
    • Export Citation
  • 8

    Lippman CR, Spence CA, Youssef AS, Cahill DW. Correction of adult scoliosis via a posterior-only approach. Neurosurg Focus. 2003;14(1):e5.

    • Search Google Scholar
    • Export Citation
  • 9

    Oskouian RJ Jr, Shaffrey CI. Degenerative lumbar scoliosis. Neurosurg Clin N Am. 2006;17(3):299315, vii.

  • 10

    Zanirato A, Damilano M, Formica M, et al. Complications in adult spine deformity surgery: a systematic review of the recent literature with reporting of aggregated incidences. Eur Spine J. 2018;27(9):22722284.

    • Search Google Scholar
    • Export Citation
  • 11

    Baron EM, Albert TJ. Medical complications of surgical treatment of adult spinal deformity and how to avoid them. Spine (Phila Pa 1976). 2006;31(19)(suppl):S106S118.

    • Search Google Scholar
    • Export Citation
  • 12

    Slone RM, MacMillan M, Montgomery WJ. Spinal fixation. Part 3. Complications of spinal instrumentation. Radiographics. 1993;13(4):797816.

    • Search Google Scholar
    • Export Citation
  • 13

    Schwab FJ, Hawkinson N, Lafage V, et al. Risk factors for major peri-operative complications in adult spinal deformity surgery: a multi-center review of 953 consecutive patients. Eur Spine J. 2012;21(12):26032610.

    • Search Google Scholar
    • Export Citation
  • 14

    Smith JS, Klineberg E, Lafage V, et al. Prospective multicenter assessment of perioperative and minimum 2-year postoperative complication rates associated with adult spinal deformity surgery. J Neurosurg Spine. 2016;25(1):114.

    • Search Google Scholar
    • Export Citation
  • 15

    Hamilton DK, Buza JA III, Passias P, et al. The fate of patients with adult spinal deformity incurring rod fracture after thoracolumbar fusion. World Neurosurg. 2017;106:905911.

    • Search Google Scholar
    • Export Citation
  • 16

    Smith JS, Shaffrey CI, Klineberg E, et al. Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up. J Neurosurg Spine. 2017;27(4):444457.

    • Search Google Scholar
    • Export Citation
  • 17

    Barton C, Noshchenko A, Patel V, et al. Risk factors for rod fracture after posterior correction of adult spinal deformity with osteotomy: a retrospective case-series. Scoliosis. 2015;10(1):30.

    • Search Google Scholar
    • Export Citation
  • 18

    Smith JS, Shaffrey CI, Ames CP, et al. Assessment of symptomatic rod fracture after posterior instrumented fusion for adult spinal deformity. Neurosurgery. 2012;71(4):862867.

    • Search Google Scholar
    • Export Citation
  • 19

    Daniels AH, DePasse JM, Durand W, et al. Rod fracture after apparently solid radiographic fusion in adult spinal deformity patients. World Neurosurg. 2018;117:e530e537.

    • Search Google Scholar
    • Export Citation
  • 20

    Merrill RK, Kim JS, Leven DM, et al. Multi-rod constructs can prevent rod breakage and pseudarthrosis at the lumbosacral junction in adult spinal deformity. Global Spine J. 2017;7(6):514520.

    • Search Google Scholar
    • Export Citation
  • 21

    Edwards CC II, Bridwell KH, Patel A, et al. Long adult deformity fusions to L5 and the sacrum. A matched cohort analysis. Spine (Phila Pa 1976). 2004;29(18):19962005.

    • Search Google Scholar
    • Export Citation
  • 22

    Emami A, Deviren V, Berven S, et al. Outcome and complications of long fusions to the sacrum in adult spine deformity: Luque-Galveston, combined iliac and sacral screws, and sacral fixation. Spine (Phila Pa 1976). 2002;27(7):776786.

    • Search Google Scholar
    • Export Citation
  • 23

    Buell TJ, Buchholz AL, Mazur MD, et al. Kickstand rod technique for correcting coronal imbalance in adult scoliosis: 2-dimensional operative video. Oper Neurosurg (Hagerstown). 2020;19(2):E163E164.

    • Search Google Scholar
    • Export Citation
  • 24

    Jager ZS, İnceoğlu S, Palmer D, et al. Preventing instrumentation failure in three-column spinal osteotomy: biomechanical analysis of rod configuration. Spine Deform. 2016;4(1):39.

    • Search Google Scholar
    • Export Citation
  • 25

    Hyun S-J, Lenke LG, Kim Y-C, et al. Comparison of standard 2-rod constructs to multiple-rod constructs for fixation across 3-column spinal osteotomies. Spine (Phila Pa 1976). 2014;39(22):18991904.

    • Search Google Scholar
    • Export Citation
  • 26

    Kelly BP, Shen FH, Schwab JS, et al. Biomechanical testing of a novel four-rod technique for lumbo-pelvic reconstruction. Spine (Phila Pa 1976). 2008;33(13):E400E406.

    • Search Google Scholar
    • Export Citation
  • 27

    Wang T, Liu H, Zheng Z, et al. Biomechanical effect of 4-rod technique on lumbosacral fixation: an in vitro human cadaveric investigation. Spine (Phila Pa 1976). 2013;38(15):E925E929.

    • Search Google Scholar
    • Export Citation
  • 28

    Akazawa T, Kotani T, Sakuma T, et al. Rod fracture after long construct fusion for spinal deformity: clinical and radiographic risk factors. J Orthop Sci. 2013;18(6):926931.

    • Search Google Scholar
    • Export Citation
  • 29

    Saulle D, Fu K-MG, Shaffrey CI, Smith JS. Multiple-day drainage when using bone morphogenic protein for long-segment thoracolumbar fusions is associated with low rates of wound complications. World Neurosurg. 2013;80(1-2):204207.

    • Search Google Scholar
    • Export Citation
  • 30

    Buell TJ, Nguyen JH, Mazur MD, et al. Radiographic outcome and complications after single-level lumbar extended pedicle subtraction osteotomy for fixed sagittal malalignment: a retrospective analysis of 55 adult spinal deformity patients with a minimum 2-year follow-up. J Neurosurg Spine. 2018;30(2):242252.

    • Search Google Scholar
    • Export Citation
  • 31

    Zhu ZZ, Chen X, Qiu Y, et al. Adding satellite rods to standard two-rod construct with the use of duet screws: an effective technique to improve surgical outcomes and preventing proximal junctional kyphosis in posterior-only correction of Scheuermann kyphosis. Spine (Phila Pa 1976). 2018;43(13):E758E765.

    • Search Google Scholar
    • Export Citation
  • 32

    Smith JS, Shaffrey CI, Bess S, et al. Recent and emerging advances in spinal deformity. Neurosurgery. 2017;80(3S):S70S85.

  • 33

    Wang H, Guo J, Wang S, et al. Instrumentation failure after posterior vertebral column resection in adult spinal deformity. Spine (Phila Pa 1976). 2017;42(7):471478.

    • Search Google Scholar
    • Export Citation
  • 34

    Yamato Y, Hasegawa T, Kobayashi S, et al. Treatment strategy for rod fractures following corrective fusion surgery in adult spinal deformity depends on symptoms and local alignment change. J Neurosurg Spine. 2018;29(1):5967.

    • Search Google Scholar
    • Export Citation
  • 35

    Jung JM, Hyun SJ, Kim KJ, Jahng TA. Rod fracture after multiple-rod constructs for adult spinal deformity. J Neurosurg Spine. 2020;32(3):407414.

    • Search Google Scholar
    • Export Citation
  • 36

    Devlin VJ, Boachie-Adjei O, Bradford DS, et al. Treatment of adult spinal deformity with fusion to the sacrum using CD instrumentation. J Spinal Disord. 1991;4(1):114.

    • Search Google Scholar
    • Export Citation
  • 37

    Berjano P, Aebi M. Pedicle subtraction osteotomies (PSO) in the lumbar spine for sagittal deformities. Eur Spine J. 2015;24(1)(suppl 1):S49S57.

    • Search Google Scholar
    • Export Citation
  • 38

    Bridwell KH, Lewis SJ, Lenke LG, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance. J Bone Joint Surg Am. 2003;85(3):454463.

    • Search Google Scholar
    • Export Citation
  • 39

    Januszewski J, Beckman JM, Harris JE, et al. Biomechanical study of rod stress after pedicle subtraction osteotomy versus anterior column reconstruction: a finite element study. Surg Neurol Int. 2017;8:207.

    • Search Google Scholar
    • Export Citation
  • 40

    Hyun SJ, Rhim SC. Clinical outcomes and complications after pedicle subtraction osteotomy for fixed sagittal imbalance patients: a long-term follow-up data. J Korean Neurosurg Soc. 2010;47(2):95101.

    • Search Google Scholar
    • Export Citation
  • 41

    La Barbera L, Brayda-Bruno M, Liebsch C, et al. Biomechanical advantages of supplemental accessory and satellite rods with and without interbody cages implantation for the stabilization of pedicle subtraction osteotomy. Eur Spine J. 2018;27(9):23572366.

    • Search Google Scholar
    • Export Citation
  • 42

    Luca A, Ottardi C, Sasso M, et al. Instrumentation failure following pedicle subtraction osteotomy: the role of rod material, diameter, and multi-rod constructs. Eur Spine J. 2017;26(3):764770.

    • Search Google Scholar
    • Export Citation
  • 43

    Gupta S, Eksi MS, Ames CP, et al. A novel 4-rod technique offers potential to reduce rod breakage and pseudarthrosis in pedicle subtraction osteotomies for adult spinal deformity correction. Oper Neurosurg (Hagerstown). 2018;14(4):449456.

    • Search Google Scholar
    • Export Citation
  • 44

    Howe CJ, Cole SR, Lau B, et al. Selection bias due to loss to follow up in cohort studies. Epidemiology. 2016;27(1):9197.

  • 45

    Charosky S, Guigui P, Blamoutier A, et al. Complications and risk factors of primary adult scoliosis surgery: a multicenter study of 306 patients. Spine (Phila Pa 1976). 2012;37(8):693700.

    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 58 58 58
PDF Downloads 67 67 67
EPUB Downloads 0 0 0