Risk Of Proximal Junctional Failure Research Articles

Comparative Analysis of Hounsfield Units and Vertebral Bone Quality Scores for Predicting Proximal Junctional Failure in Female Adult Spinal Deformity Patients Undergoing Planned 2-Stage Corrective Surgery with Lateral Lumbar Interbody Fusion

This study aimed to evaluate the utility of computed tomography (CT)-based Hounsfield units (HUs) and magnetic resonance imaging-based Vertebral Bone Quality (VBQ) scores as alternatives to dual-energy x-ray absorptiometry for predicting the risk of proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD) undergoing 2-stage corrective surgery with lateral lumbar interbody fusion (LLIF). The study included 53 female patients with ASD who underwent 2-stage corrective surgery with LLIF from January 2016 to April 2022 with a minimum follow-up of 1year. CT and magnetic resonance imaging scans were evaluated for their correlation with PJF. Of the 53 patients (mean age 70.2years), 14 had PJF. Patients with PJF had significantly lower HU values at the upper instrumented vertebra (UIV) (113.0±29.4 vs. 141.1±41.5, P=0.036) and L4 (113.4±59.5 vs. 160.0±64.9, P=0.026) than those without PJF. However, there was no difference in VBQ scores between the 2 groups. PJF correlated with HU values at UIV and L4 but not with VBQ scores. Patients with PJF also had significantly different pre- and postoperative thoracic kyphosis, postoperative pelvic tilt, pelvic incidence minus lumbar lordosis, and proximal junctional angle compared to those without PJF. The findings suggest that measuring HU values at UIV or L4 by CT may be useful for predicting the risk of PJF in female ASD patients undergoing 2-stage corrective surgery with LLIF. Therefore, CT-based HUs should be considered in ASD surgery planning to reduce the risk of PJF.

Optimization of Spinal Reconstructions for Thoracolumbar Burst Fractures to Prevent Proximal Junctional Complications: A Finite Element Study.

The management strategies of thoracolumbar (TL) burst fractures include posterior, anterior, and combined approaches. However, the rigid constructs pose a risk of proximal junctional failure. In this study, we aim to systemically evaluate the biomechanical performance of different TL reconstruction constructs using finite element analysis. Furthermore, we investigate the motion and the stress on the proximal junctional level adjacent to the constructs. We used a T10-L3 finite element model and simulated L1 burst fracture. Reconstruction with posterior instrumentation (PI) alone (U2L2 and U1L1+(intermediate screw) and three-column spinal reconstruction (TCSR) constructs (U1L1+PMMA and U1L1+Cage) were compared. Long-segment PI resulted in greater global motion reduction compared to constructs with short-segment PI. TCSR constructs provided better stabilization in L1 compared to PI alone. Decreased intradiscal and intravertebral pressure in the proximal level were observed in U1L1+IS, U1L1+PMMA, and U1L1+Cage compared to U2L2. The stress and strain energy of the pedicle screws decreased when anterior reconstruction was performed in addition to PI. We showed that TCSR with anterior reconstruction and SSPI provided sufficient immobilization while offering additional advantages in the preservation of physiological motion, the decreased burden on the proximal junctional level, and lower risk of implant failure.

Sublaminar Tethers Significantly Reduce the Risk of Proximal Junctional Failure in Surgery for Severe Adult Spinal Deformity: A Propensity Score-matched Analysis.

This was a retrospective case series of prospectively collected data. The present study first described the effect of sublaminar tethering (SLT) on proximal junctional failure (PJF) in adult spinal deformity (ASD) surgery. PJF is a devastating complication following ASD surgery. Teriparatide administration and spinous process tethering have been reported as alternatives for the prevention of PJF, but a clinically effective prevention strategy is still a matter of debate. We used data from an ASD database that included 381 patients with ASD (minimum 2-y follow-up). Among them, the data of patients who had a severe sagittal deformity and had surgery from the lower thoracic spine (T9-T11) to the pelvis were extracted and propensity score matched by age, sex, body mass index, bone mineral density, curve type, sagittal alignment, and fused level to clarify whether SLT prevented the development of PJF [SLT vs. control (CTR); age: 67±7 vs. 66±8 y, T-score: -1.4±0.7 vs. -1.3±0.6, body mass index: 22±4 vs. 22±5 kg/m2, C7 sagittal vertical axis (C7SVA): 12±7 vs. 11±5 cm, pelvic incidence-lumbar lordosis (PI-LL): 51±22 vs. 49±21 degrees, pelvic tilt (PT): 36±10 vs. 34±10 degrees, level fused: 11±2 vs. 11±2]. Sixty-four patients were matched into 32 pairs and compared in terms of the postoperative alignment and frequency of PJF. Two years postoperatively, C7SVA and PT were significantly larger in the CTR group, while no significant difference in PI-LL was found (C7SVA: 3±3 vs. 6±4 cm, P<0.01, PT: 16±6 vs. 24±9 degrees, P<0.01, PI-LL: 7±9 vs. 11±11 degrees, P=0.22). The proximal junctional angle was significantly greater in the CTR group (proximal junctional kyphosis: 8±8 vs. 17±13 degrees, P<0.01). The incidence of PJF was significantly lower in the SLT group (3% vs. 25%, P=0.03), with an odds ratio of 0.1 (95% confidence interval: 0.0-0.8, P=0.03). In the propensity score-matched cohort, the incidence of PJF was significantly lower in the SLT group. SLT is a promising procedure that may reduce the risk of PJF in severe ASD surgery.

Caudally directed upper-instrumented vertebra pedicle screws associated with minimized risk of proximal junctional failure in patients with long posterior spinal fusion for adult spinal deformity

BACKGROUND CONTEXTIt is unknown whether upper instrumented vertebra (UIV) pedicle screw trajectory and UIV screw-rod angle are associated with development of proximal junctional kyphosis (PJK) and/or proximal junctional failure (PJF). PURPOSETo determine whether (1) the cranial-caudal trajectory of UIV pedicle screws and (2) UIV screw-vertebra angle are associated with PJK and/or PJF after long posterior spinal fusion in patients with adult spinal deformity (ASD). STUDY DESIGN/SETTINGRetrospective review. PATIENT SAMPLEWe included 96 patients with ASD who underwent fusion from T9–T12 to the pelvis (>5 vertebrae fused) between 2008 and 2015. OUTCOME MEASURESPedicle screw trajectory was measured as the UIV pedicle screw–vertebra angle (UIV-PVA), which is the mean of the two angles between the UIV superior endplate and both UIV pedicle screws. (Positive values indicate screws angled cranially; negative values indicate screws angled caudally.) We measured UIV rod-vertebra angle (UIV-RVA) between the rod at the point of screw attachment and the UIV superior endplate. METHODSDuring ≥2-year follow-up, 38 patients developed PJK, and 28 developed PJF. Mean (± standard deviation) UIV-PVA was −0.9° ± 6.0°. Mean UIV-RVA was 87° ± 5.2°. We examined the development of PJK and PJF using a UIV-PVA/UIV-RVA cutoff of 3° identified by a receiver operating characteristic curve, while controlling for osteoporosis, age, sex, and preoperative thoracic kyphosis. RESULTSPatients with UIV-PVA ≥3° had significantly greater odds of developing PJK (odds ratio 2.7; 95% confidence interval: 1.0–7.1) and PJF (odds ratio 3.6; 95% confidence interval: 1.3–10) compared with patients with UIV-PVA <3°. UIV-RVA was not significantly associated with development of PJK or PJF. CONCLUSIONSIn long thoracic fusion to the pelvis for ASD, UIV-PVA ≥3° was associated with 2.7-fold greater odds of PJK and 3.6-fold greater odds of PJF compared with UIV-PVA <3°. UIV-RVA was not associated with PJK or PJF. LEVEL OF EVIDENCEIII

Accuracy of Rod Contouring to Desired Angles With and Without a Template: Implications for Achieving Desired Spinal Alignment and Outcomes.

Biomechanical Study. The search for optimal spinal alignment has led to the development of sophisticated formulas and software for preoperative planning. However, preoperative plans are not always appropriately executed since rod contouring during surgery is often subjective and estimated by the surgeon. We aimed to assess whether rods contoured to specific angles with a French rod bender using a template guide will be more accurate than rods contoured without a template. Ten experienced spine surgeons were requested to contour two 125 × 5.5 mm Ti64 rods to 40°, 60° and 80° without templates and then 2 more rods using 2D metallic templates with the same angles. Rod angles were then measured for accuracy and compared. Average angles for rods bent without a template to 40°, 60° and 80° were 60.2°, 78.9° and 97.5°, respectively. Without a template, rods were overbent by a mean of 18.9°. When using templates of 40°, 60° and 80°, mean bend angles were 41.5°, 59.1° and 78.7°, respectively, with an average underbend of 0.2°. Differences between the template and non-template groups for each target angle were all significant (p < 0.001). Without the template, surgeons tend to overbend rods compared to the desired angle, while surgeons improved markedly with a template guide. This tendency to overbend could have significant impact on patient outcomes and risk of proximal junctional failure and warrants further research to better enable surgeons to more accurately execute preoperative alignment plans.

Should Thoracolumbar Junction Be Always Avoided as Upper Instrumented Vertebra in Long Instrumented Fusion for Adult Spinal Deformity?: Risk Factor Analysis for Proximal Junctional Failure.

Retrospective study. The aim of this study was to investigate the risk factors for proximal junctional failure (PJF) following long instrumented fusion stopping at thoracolumbar junction (TLJ) in adult spinal deformity (ASD) and to determine which cases are suitable for TLJ stop without increasing the risk for PJF. PJF following long fusion for ASD is a well-recognized complication that negatively affects clinical outcomes. Generally, the uppermost instrumented vertebra (UIV) at the TLJ is associated with the risk of PJF. Little is known about the risk factors for PJF in case with the UIV at TLJ. Radiographic and clinical data of 63 consecutive patients who underwent instrumented fusion from sacrum to TLJ (T11, T12, and L1) for the treatment of ASD with a minimum 2-year follow-up were analyzed to identify the risk factors for PJF, which was defined as proximal junctional angle (PJA) ≥20°, fracture at UIV or UIV+1, failure of UIV fixation, myelopathy, or 'need for proximal extension of fusion. During the average follow-up duration of 51.7 months, PJF developed in 23 patients (36.5%) at a mean of 9.3 months after surgery. Multivariate analysis revealed that age >70 years (odds ratio [OR]: 1.119), osteoporosis (OR: 4.459), and preoperative kyphotic PJA (OR: 1.138) were significant risk factors for the development of PJF. No PJF occurred in 14 patients lacking any risk factors. The last follow-up clinical results were significantly inferior in the PJF group than in the non-PJF group in terms of Oswestry Disability Index and Scoliosis Research Society-22 score. Age >70 years, osteoporosis, and PJA greater 0° were identified as significant risk factors for PJF. Therefore, the TLJ level can be considered as UIV selectively for patients younger than 70 years without osteoporosis and with lordotic preoperative PJA. 3.

P29. Caudally directed upper-instrumented vertebra pedicle screws minimize the risk of proximal junctional failure in patients with long posterior spinal fusion for adult spinal deformity

BACKGROUND CONTEXT Proximal junctional kyphosis (PJK) and Proximal Junctional Failure (PJF) are significant complications following Adult Spinal Deformity (ASD) surgery. Orientation of the Upper Instrumented Vertebra (UIV) pedicle screw has not been studied as a potential risk factor for PJK/PJF. PURPOSE To demonstrate the association between UIV pedicle screw cranial-caudal trajectory and the development of both PJK and PJF in ASD patients with thoracolumbar fusion to the pelvis. STUDY DESIGN/SETTING Retrospective case series. PATIENT SAMPLE A total of 96 ASD patients (>5 levels fused) were identified from a multiprovider academic institution with fusion from T8-T12 to pelvis and 2-year follow-up. OUTCOME MEASURES Our primary outcomes were the development of PJK, defined as a proximal junction sagittal Cobb angle ≥10° and proximal junction sagittal Cobb angle ≥10° higher than preoperative measurement; and PJF, defined as revision surgery for PJK. METHODS We defined a novel measurement of the UIV Screw Angle (UIVSA) as the mean of the angles between the UIV superior endplate and each UIV pedicle screw using intraoperative sagittal radiographs. A screw pointed cranially was measured as (+) UIVSA and a screw pointed caudally was measured as (-)UIVSA. A threshold UIVSA of +3° was determined by the maximum likelihood of PJK using the area under a Receiver Operating Curve. Using binary logistic regression, we examined the development of PJK and PJF in patients with UIVSA above and below +3°, while controlling for preoperative TK, osteoporosis and age. RESULTS Ninety-six patients were studied with 2-year follow up. Mean age was 62 ± 11 years, 68% female. Mean follow-up was 4.6 ± 2.3 years. Patients had the following mean preoperative radiographic parameters: SVA: 10.7 ± 8.7 cm; TK: 33 ± 16°; Coronal Cobb 31 ± 17°. Mean UIVSA was -0.9° ± 6.0° (range -12.99° to 11.93°). 38 (40%) of patients had PJK at any time point and 28 (29%) went on to develop PJF. Patients with UIVSA greater than +3° had significantly greater odds of developing both PJK (OR 2.7 95% CI: 1.3, 7.0) and PJF (OR 3.6 95% CI: 1.3, 10.0). Screw-rod angle was not significantly associated with development of PJK/PJF, p>0.05. CONCLUSIONS In surgically treated ASD patients with lower thoracic fusion to the sacrum, a UIVSA of greater than +3° is associated with 2.7 times greater odds of PJK and 3.6 times greater odds of PJF. Pedicle screws at the UIV should be directed caudally in ASD patients and thoracolumbar fusion to the pelvis to minimize the risk of proximal junctional failure. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

What Factors Predict the Risk of Proximal Junctional Failure in the Long Term, Demographic, Surgical, or Radiographic?: Results From a Time-dependent ROC Curve.

Retrospective review of prospective multicenter database. To identify an optimal set of factors predicting the risk of proximal junctional failure (PJF) while taking the time dependency of PJF and those factors into account. Surgical correction of adult spinal deformity (ASD) can be complex and therefore, may come with high revision rates due to PJF. Seven hundred sixty-three operative ASD patients with a minimum of 1-year follow-up were included. PJF was defined as any type of proximal junctional kyphosis (PJK) requiring revision surgery. Time-dependent ROC curves were estimated with corresponding Cox proportional hazard models. The predictive abilities of demographic, surgical, radiographic parameters, and their possible combinations were assessed sequentially. The area under the curve (AUC) was used to evaluate models' performance. PJF occurred in 42 patients (6%), with a median time to revision of approximately 1 year. Larger preoperative pelvic tilt (PT) (hazard ratio [HR]=1.044, P = 0.034) significantly increased the risk of PJF. With respect to changes in the radiographic parameters at 6-week postsurgery, larger differences in pelvic incidence-lumbar lordosis (PI-LL) mismatch (HR = 0.924, P = 0.002) decreased risk of PJF. The combination of demographic, surgical, and radiographic parameters has the best predictive ability for the occurrence of PJF (AUC = 0.863), followed by demographic along with radiographic parameters (AUC = 0.859). Both models' predictive ability was preserved over time. Over correction increased the risk of PJF. Radiographic along with demographic parameters have shown the approximately equivalent predictive ability for PJF over time as with the addition of surgical parameters. Radiographic rather than surgical factors may be of particular importance in predicting the development of PJF over time. These results set the groundwork for risk stratification and corresponding prophylactic interventions for patients undergoing ASD surgery. 4.

Saturday, September 29, 2018 10:30 am–12:00 pm Applying Deformity Concepts in Your Practice

BACKGROUND CONTEXT Proximal junctional failure (PJF) is a serious complication following ASD surgery. Patients undergoing caudal extension of fusion and spinal realignment may be at decreased risk of PJF if there is a new upper instrumented vertebra (UIV). PURPOSE To determine if patients with an existing instrumentation constructs undergoing distal extension of fusion have decreased rates of PJF. STUDY DESIGN/SETTING Retrospective cohort study with propensity matching of prospectively collected multicenter patient data. PATIENT SAMPLE A total of 754 adult spinal deformity patients. OUTCOME MEASURES Proximal junctional failure. METHODS Prospective multicenter cohort of 754 adult patients undergoing thoracolumbar fusion for ASD were analyzed. A total of 41 patients undergoing distal extension of or osteotomy through prior fusion with an unchanged UIV were identified. PJF was defined as either proximal junction (PJ) angle ≥ 28.0° and Δ PJ angle ≥21.6°) or by listhesis. Propensity score matching was performed for unaltered UIV patients and new UIV patients for age, BMI, number of levels fused, UIV, frailty score, ΔSVA, Δ PI-LL and ΔTPA and were compared for rates of PJF. RESULTS Patients with an unaltered UIV had a 0% rate of radiographic PJF, compared to 13.8% of those with a new UIV (p=.012). Mean time to PJF was 11.2 months (range: 0.5-33.7). Prior to propensity matching, unaltered UIV patients had worse sagittal malalignment with a higher PI-LL (27.0 vs. 16.6; p=.003), and SVA (90.6 mm vs. 68.5 mm; p=.073) and underwent larger sagittal alignment correction (ΔSVA −55.6 mm vs. -43.1 mm; p=.049). After propensity matching, all radiographic and demographic parameters were similar (p>.05), and PJF rates remained lower in the unaltered UIV patients compared to the new UIV patients (0% vs. 8.5%; p=.009) CONCLUSIONS Despite worse preoperative sagittal deformity and larger operative correction, patients undergoing distal extension of fusion with unaltered upper instrumented vertebra (UIV) experienced a 0% rate of proximal junctional failure, compared to 13.8% of ASD patients undergoing surgery with a new UIV (p=.01), This study suggests that the etiology of PJF includes acute soft tissue trauma and lack of adjacent segment bony remodeling as contributing factors. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Low Bone-Mineral Density Is a Significant Risk for Proximal Junctional Failure After Surgical Correction of Adult Spinal Deformity: A Propensity Score-Matched Analysis.

A propensity-matched comparison of risk factors for proximal junctional failure (PJF), which is a symptomatic proximal junctional kyphosis developing after corrective surgery for adult spinal deformity (ASD). To elucidate the role of bone strength for developing PJF. PJF, a devastating complication of corrective surgery for ASD, often recurs even after revision surgery. Most studies of risk factors for PJF are retrospective and have a selection bias in surgical strategy, making it difficult to identify modifiable PJF risk factors. We conducted propensity-matched comparisons of 113 surgically treated ASD patients who were followed for at least 2 years, to elucidate whether low bone-mineral density (BMD) was a true risk factor for PJF in a uniform population from a multicenter database. Patients were grouped as having mildly low to normal BMD (M group; T-score≧ - 1.5) or significantly low BMD (S group; T-score < -1.5), and were propensity-matched for age, upper and lower instrumented vertebrae, history of spine surgery, and Schwab-Scoliosis Research Society (SRS) ASD classification. PJF was defined as a ≥20° increase from the baseline proximal junction angle with a concomitant deterioration of at least one SRS-Schwab sagittal modifier grade, or any type of proximal junctional kyphosis requiring revision. PJF developed in 22 of 113 patients (19%). There were 48 propensity-matched patients in the M and S groups (24 in each) with similar parameters for age, body mass index, number of vertebrae involved, C7SVA, pelvic incidence - LL, and SRS-Schwab type. In this propensity-matched population, the incidence of PJF was significantly higher in the S group (33% vs. 8%, P < 0.01, odds ratio 6.4, 95% CI: 1.2-32.3). Low BMD was a significant risk factor for PJF in this propensity-matched cohort (odds ratio 6.4). Surgeons should consider prophylactic treatments when correcting ASD in patients with low BMD. 3.

T9 versus T10 as the upper instrumented vertebra for correction of adult deformity—rationale and recommendations

Background ContextAdult spinal deformity correction sometimes involves long posterior pedicle screw constructs extending from the lumbosacral spine to the thoracic vertebra. As fusion obliterates motion and places supraphysiological stress on adjacent spinal segments, it is crucial to ascertain the ideal upper instrumented vertebra (UIV) to minimize risk of proximal junctional failure (PJF). The T10 vertebra is often chosen to allow bridging of the thoracolumbar junction into the immobile thoracic vertebrae on the basis that it is the lowest immobile thoracic vertebra strut by the rib cage. PurposeThis study aimed to characterize the range of motion (ROM) of each vertebral segment from T7 to S1 to determine if T10 is truly the lowest immobile thoracic vertebra. Study Design/SettingThis is a prospective, comparative study. Patient SampleSeventy-nine adults (mean age of 45.4 years) presenting with low back pain or lower limb radiculopathy or both, without previous spinal intervention, metastases, fractures, infection, or congenital deformities of the spine, were included in the study. Outcome MeasuresA ROM >5° across two vertebral segments as determined by the Cobb method from radiographs. MethodsLumbar flexion-extension and neutral erect radiographs were obtained in randomized order using a slot scanner. Segmental ROM was measured from T7–T8 to L5–S1 and analyzed for significant differences using t tests. Age, gender, radiographical indices such as standard spinopelvic parameters, sagittal vertical axis (SVA), C7–T12 SVA, T1 slope, thoracic kyphosis (TK), and lumbar lordosis (LL) were studied via multivariate analysis to identify predictive factors for >5° change in ROM at the various segmental levels. There were no sources of funding and no conflicts of interest associated with this study. ResultsIn the thoracolumbar spine, significant decreases in ROM when compared with the adjacent caudad segment occurs up to T9–T10, with mean total ROM of 1.98±1.47° (p<.001) seen in T9–T10, 2.19±1.67° (p<.001) in T10–T11, and 3.92±3.21°(p<.001) in T11–T12. The total ROM of T8–T9 (2.53±1.79°) was not significantly different from that of T9–T10 (p=.261). At the thoracolumbar junction, absence of scoliosis (OR 11.37, p=.020), high pelvic incidence (OR 1.14, p=.046), and low T1 slope (OR 1.45, p=.030) were predictive of ROM >5°. ConclusionsLumbar spine flexion-extension ROM decreases as it approaches the thoracolumbar junction. T10 is indeed the lowest immobile thoracic vertebra strut by the rib cage, and the last significant decrease in ROM is observed at T9–T10, in relation to T10–T11. However, because this also implies that a UIV of T10 would mean there is only one level of fixation above the relatively mobile segment, while respecting other factors that influence UIV selection, we propose the T9 vertebra as a more ideal UIV to fulfill the biomechanical concept of bridge fixation. However, this decision should still be taken on a case-by-case basis.

Biomechanical effects of fusion levels on the risk of proximal junctional failure and kyphosis in lumbar spinal fusion surgery

BackgroundSpinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear. MethodsA finite element model of the thoracolumbar spine was used. Nine fusion models with pedicle screw systems implanted at the L2–L3, L3–L4, L4–L5, L5–S1, L2–L4, L3–L5, L4–S1, L2–L5, and L3–S1 levels were developed based on the respective surgical protocols. The developed models simulated flexion–extension using hybrid testing protocol. FindingsWhen spinal fusion was performed at more distal levels, particularly at the L5–S1 level, the following biomechanical properties increased during flexion–extension: range of motion, stress on the annulus fibrosus fibers and vertebra at the adjacent motion segment, and the magnitude of axial forces on the pedicle screw at the uppermost instrumented vertebra. InterpretationsThe results of this study demonstrate that more distal fusion levels, particularly in spinal fusion including the L5–S1 level, lead to greater increases in the risk of proximal junctional kyphosis and failure, as evidenced by larger ranges of motion, higher stresses on fibers of the annulus fibrosus and vertebra at the adjacent segment, and higher axial forces on the screw at the uppermost instrumented vertebra in flexion–extension. Therefore, fusion levels should be carefully selected to avoid proximal junctional kyphosis and failure.