Are insufficient corrections a major factor in distal junctional kyphosis? A simulated analysis of cervical deformity correction using in-construct measurements.

OBJECTIVE: The present study utilized recently developed in-construct measurements in simulations of cervical deformity surgery in order to assess undercorrection and predict distal junctional kyphosis (DJK). METHODS: A retrospective review of a database of operative cervical deformity patients was analyzed for severe DJK and mild DJK. C2-lower instrumented vertebra (LIV) sagittal angle (SA) was measured postoperatively, and the correction was simulated in the preoperative radiograph in order to match the C2-LIV by using the planning software. Linear regression analysis that used C2 pelvic angle (CPA) and pelvic tilt (PT) determined the simulated PT that matched the virtual CPA. Linear regression analysis was used to determine the C2-T1 SA, C2-T4 SA, and C2-T10 SA that corresponded to DJK of 20° and cervical sagittal vertical axis (cSVA) of 40 mm. RESULTS: Sixty-nine cervical deformity patients were included. Severe and mild DJK occurred in 11 (16%) and 22 (32%) patients, respectively; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and mild DJK patients had worse alignment compared to non-DJK patients in terms of cSVA (42.5 mm vs 33.0 mm vs 23.4 mm, p < 0.001) and C2-LIV SVA (68.9 mm vs 57.3 mm vs 36.8 mm, p < 0.001). Linear regression revealed the relationships between in-construct measures (C2-T1 SA, C2-T4 SA, and C2-T10 SA), cSVA, and change in DJK (all R > 0.57, p < 0.001). A cSVA of 40 mm corresponded to C2-T4 SA of 10.4° and C2-T10 SA of 28.0°. A DJK angle change of 10° corresponded to C2-T4 SA of 5.8° and C2-T10 SA of 20.1°. CONCLUSIONS: Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In-construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of cervical deformity correction.

Strategies to Avoid Distal Junctional Pathology.

Distal junctional pathology remains an unsolved issue in spine surgery. Distal junctional pathology can occur on a spectrum from asymptomatic radiographic finding to catastrophic distal construct failure. It is significant to address as postoperative sagittal balance has been shown to be correlated with patient-reported outcomes. Current literature and clinical experience suggest there are techniques that can be implemented regardless of setting to avoid distal junctional pathology. Much of the avoidant strategy relies on understanding the deformity pathology, selection of the lowest instrumented vertebra (LIV), health of the segments caudal to the LIV, and methods of fixation.

Junctional Failures at Both Ends After Long Fusion Arthrodesis Stopping at L5: Incidences and Risk Factors.

OBJECTIVE: Junctional failures after long fusion stopping at L5 can present at both proximal and distal ends. The purpose of this study was to investigate incidences and risk factors of proximal junctional failure (PJF) and distal junctional failure (DJF) after long lumbar instrumented fusion stopping at L5 for adult spinal deformity. METHODS: Sixty-three patients who underwent long fusion surgery stopping at L5 with a minimum follow-up of 3 years were reviewed retrospectively. PJF and DJF were defined as newly developed back pain and/or radiculopathy with corresponding radiographic failures. The incidence and risk factors of each junctional failure were analyzed using a log-rank test and Cox proportional hazards model. RESULTS: Twelve men and 51 women were included in our study. Their mean age was 68.5 ± 7.0 years and the mean follow-up period was 84.5 ± 45.3 months. PJF and DJF occurred in 17 (27%) and 16 patients (25.4%), respectively. PJF and DJF developed at median durations of 32.1 months and 13.3 months, respectively, showing no significant difference between the two. Three patients presented with both PJF and DJF. Risk factors for PJF included lower body mass index, higher preoperative lumbar lordosis, and higher postoperative sagittal vertical axis (SVA) (hazard ratio, 0.570, 1.055, and 1.040, respectively). For DJF, higher preoperative SVA was an independent risk factor (hazard ratio, 1.010). CONCLUSIONS: After long fusion surgery stopping at L5, PJF and DJF occurred at similar rates. Lower body mass index, higher preoperative lumbar lordosis, and higher postoperative SVA were risk factors for PJF. Higher preoperative SVA was an independent risk factor for DJF.

Distal junctional failure after corrective surgery without pelvic fixation for thoracolumbar junctional kyphosis due to osteoporotic vertebral fracture.

BACKGROUND: Thoracolumbar junctional kyphosis (TLJK) due to osteoporotic vertebral fracture (OVF) negatively impacts patients' quality of life. The necessity of pelvic fixation in corrective surgery for TLJK due to OVF remains controversial. This study aimed to: 1) evaluate the surgical outcomes of major corrective surgery for thoracolumbar junctional kyphosis due to osteoporotic vertebral fracture, and 2) identify the risk factors for distal junctional failure to identify potential candidates for pelvic fixation. METHODS: Patients who underwent surgical correction (fixed TLJK>40°, OVF located at T11-L2, the lowermost instrumented vertebra at or above L5) were included. Sagittal vertical axis, pelvic tilt, pelvic incidence, thoracic kyphosis, lumbar lordosis (L1-S1), local kyphosis, and lower lumbar lordosis (L4-S1) were assessed. Proximal and distal junctional kyphosis (P/DJK) and failures (P/DJF) were evaluated. Pre/postoperative spinopelvic parameters were compared between DJF and non-DJF patients. RESULTS: Thirty-one patients (mean age: 72.3 ± 7.9 years) were included. PJK was observed in five patients (16.1%), while DJK in 11 (35.5%). Twelve cases (38.7%) were categorized as failure. Among the patients with PJK, there was only one patient (20%) categorized as PJF and required an additional surgery. Contrary, all of eleven patients with DJK were categorized as DJF, among whom six (54.5%) required additional surgery for pelvic fixation. In comparisons between DJF and non-DJF patients, there was no significant difference in pre/postoperative LK (pre/post, p = 0.725, p = 0.950). However, statistically significant differences were observed in the following preoperative alignment parameters: SVA (p = 0.014), LL (p = 0.001), LLL (p = 0.006), PT (p = 0.003), and PI-LL (p < 0.001). CONCLUSIONS: Spinopelvic parameters, which represent the compensatory function of lumbar hyperlordosis and pelvic retroversion, have notable impacts on surgical outcomes in correction surgery for TLJK due to OVF. Surgeons should consider each patient's compensatory function when choosing a surgical approach.

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

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

Risk factors for L5 pedicle fractures after single-level posterior spinal fusion.

BACKGROUND CONTEXT: Pedicle fractures are a rare but potentially devastating complication of posterior instrumented spinal fusion (PSF). Preoperative awareness of the possible risk factors may help prevent these fractures by modifying the surgical plan. However, the risk factors have not yet been identified. PURPOSE: To determine the preoperative parameters associated with postoperative L5 pedicle fracture after L4/5 PSF. STUDY DESIGN: Case control study. PATIENT SAMPLE: Patients undergoing L4/5 PSF at a single academic institution between 2014 and 2020. OUTCOME MEASURES: Occurrence of postoperative L5 pedicle fracture. METHODS: Of 253 patients (female:male, 145:108) undergoing L4/5 PSF from 2014 to 2020, patients with postoperative L5 pedicle fractures were identified retrospectively as "cases" (n = 8, all female, age: 70 ± 10.7 years). As a control group all remaining patients with a follow-up of more than 12 months were allocated (n = 184, 104 females, age: 64.27 ± 13.00 years). In all but 16 cases, anterior support with transforaminal or posterior interbody fusion was performed. Demographic and clinical data (body mass index (BMI)), surgical factors, and comorbidities) were compared. Radiological assessment of spinopelvic parameters was performed using pre- and postoperative standing lateral radiographs. RESULTS: The overall incidence of L5 pedicle fractures after L4/5 spinal fusion was 3.16%, with a median time from index surgery to diagnosis of 25 days (range, 6-199 days) (75% within the first 32 days postoperatively). Patients with L5 pedicle fractures had higher pelvic incidence (PI) (71° ± 9° vs. 56° ± 11°; p=.001), sacral slope (SS) (45° ± 7° vs. 35° ± 8°; p=.002), L5 slope (30° ± 11° vs. 15° ± 10°, p=.001), L5 incidence (42° ± 14° vs. 26° ± 11°; p= .003), L1-S1 lumbar lordosis (LL) postop (57° ± 10° vs. 45° ± 11°; p=.006), and L4 -S1 LL postop (33° ± 7° vs. 28° ± 7°; p=.049) compared with the control group. Pelvic tilt and PI- LL mismatch were not significantly different. Female gender was a significant risk factor for L5 pedicle fractures (p=.015). BMI (kg/m2) was statistically equal in patients with or without pedicle fractures (28.37 ± 5.96 vs. 28.53 ± 16.32; p=.857). There was no significant difference between the groups for approximative bone mineral density assessment (Hounsfield units; 113 ± 60 vs. 120 ± 43; p=.396) using the L3 trabecular region of interest (ROI) measurement. The correlation analysis demonstrated that most of the identified risk factors except for the postoperative L4-S1 lordosis show significant positive associations among each other. All eight patients in the fracture group underwent revision surgery, and the instrumented fusion was extended to the sacrum, with the addition of sacral-alar-iliac or iliac screws, in six cases. CONCLUSIONS: L5 pedicle fractures occurred in 3% of the patients after single level L4/5 PSF. Risk factors are female gender, higher PI, SS, L5 slope, L5 incidence, and LL postop but not high BMI. These findings can be used for surgical planning and decision of fusion levels.

Acute failure of S2-alar-iliac screw pelvic fixation in adult spinal deformity: novel failure mechanism, case series, and review of the literature.

OBJECTIVE: Pelvic fixation with S2-alar-iliac (S2AI) screws is an established technique in adult deformity surgery. The authors' objective was to report the incidence and risk factors for an underreported acute failure mechanism of S2AI screws. METHODS: The authors retrospectively reviewed a consecutive series of ambulatory adults with fusions extending 3 or more levels, and which included S2AI screws. Acute failure of S2AI screws was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS: Failure occurred in 6 of 125 patients (5%) and consisted of either slippage of the rods or displacement of the set screws from the S2AI tulip head, with resultant kyphotic fracture. All failures occurred within 6 weeks postoperatively. Revision with a minimum of 4 rods connecting to 4 pelvic fixation points was successful. Two of 3 (66%) patients whose revision had less fixation sustained a second failure. Patients who experienced failure were younger (56.5 years vs 65 years, p = 0.03). The magnitude of surgical correction was higher in the failure cohort (number of levels fused, change in lumbar lordosis, change in T1-pelvic angle, and change in coronal C7 vertical axis, each p < 0.05). In the multivariate analysis, younger patient age and change in lumbar lordosis were independently associated with increased failure risk (p < 0.05 for each). There was a trend toward the presence of a transitional S1-2 disc being a risk factor (OR 8.8, 95% CI 0.93-82.6). Failure incidence was the same across implant manufacturers (p = 0.3). CONCLUSIONS: All failures involved large-magnitude correction and resulted from stresses that exceeded the failure loads of the set plugs in the S2AI tulip, with resultant rod displacement and kyphotic fractures. Patients with large corrections may benefit from 4 total S2AI screws at the time of the index surgery, particularly if a transitional segment is present. Salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

Distal Junctional Failure Secondary to Nontraumatic Fracture of Lower Instrumented Vertebra: Our Experience and Review of Literature.

BACKGROUND: Junctional kyphosis (JK) is usually observed in long-level instrumented fusion surgeries. Various contributing factors are proposed, the pre-existing and postoperative spinal imbalance is considered as the single most important factor for the development of JK in adult spinal deformity surgeries. Distal JK (DJK) is seldom reported compared to proximal JK (PJK), and scarce literature exists. METHODS: We report 2 unique cases of distal junctional failure (DJF) with worsening of neurology, secondary to nontraumatic fracture of a lower instrumented vertebra operated for thoracic canal stenosis without deformity. The first case had acute worsening of the Neurology during follow up and on evaluation, the supine CT and MRI scan revealed well decompressed spinal canal, no implant migration to the canal, no screw loosening, or rod failure. Supine sitting radiographs demonstrated DJK with Fracture and the patient underwent extension of fusion till the pelvis with 3-rod construct and interbody fusion, because of the instability at the L1 level.The second case remained neurologically stable for a month and then had an acute onset of back pain, sensory deficit, and urine incontinence. The supine-sitting dynamic radiograph done demonstrated L1 fracture with DJK at D12-L1 levels. The patient was counseled for extension of fusion, which was deferred by the patient. RESULTS: Patients in our series, had an acute worsening of neurological deficit within a month of posterior spinal fixation. Their supine imaging was almost normal, and the diagnosis of DJK with L1 fracture instability was possible only on a supine-sitting dynamic radiograph. Various factors like obesity, TL kyphosis, osteoporosis, etc. can be the attributing factors for the development of DJK CONCLUSION: A high index of suspicion is required for diagnosing nontraumatic fracture in long-level fusion patients with acute neurological worsening. The supine-sitting dynamic radiograph is an important diagnostic tool for DJF in patients having difficulty standing erect. LEVEL OF EVIDENCE: 4. CLINICAL RELEVANCE: Application of sitting and supine dynamic radiographs to diagnose instability in patients unable to stand for flexion and extension radiographs.

Radiographic findings for surgery-related complications after pedicle subtraction osteotomy for thoracolumbar kyphosis in 230 patients with ankylosing spondylitis.

OBJECTIVE: The purpose of this study was to investigate the rate of and the risk factors for surgery-related complications demonstrated on radiography after pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis in patients with ankylosing spondylitis (AS). METHODS: The authors retrospectively reviewed the medical records of 230 consecutive patients with thoracolumbar kyphosis due to AS who had undergone 1-level PSO at a single institution in the period from 2010 to 2017. The causes of surgery-related complications were divided into two types: surgical/technical failure and mechanical failure. RESULTS: The patients consisted of 20 women and 210 men, with an average age of 43.4 years. The average follow-up period was 39.0 months. The preoperative sagittal vertical axis was 18.5 ± 69.3 cm, which improved to 4.9 ± 4.6 cm after PSO. Of the 77 patients (33.5%) who experienced minor or major surgery-related complications, 56 had complications related to surgical/technical failure (overall incidence 24.3%) and 21 had complications related to mechanical failure (overall incidence 9.1%). Fourteen patients (6.1%) underwent reoperation. However, among the 77 patients with complications, the rate of revision surgery was 18.2%. The most common radiological complications were as follows: sagittal translation in 24 patients, coronal imbalance in 20, under-correction in 8, delayed union in 8, and distal junctional failure and kyphosis in 8. The most common causes of reoperation were coronal imbalance in 4 patients, symptomatic malposition of pedicle screws in 3, and distal junctional failure in 3. Delayed union was statistically correlated with posterior sagittal translation (p = 0.007). CONCLUSIONS: PSO can provide acceptable radiographic outcomes for the correction of thoracolumbar kyphosis in patients with AS. However, a high incidence of surgery-related complications related to mechanical failure and surgical technique can develop. Thorough radiographic investigation before and during surgery is needed to determine whether complete ossification occurs along the anterior and posterior longitudinal ligaments of the spine.

Revision surgery in distal junctional kyphosis.

BACKGROUND: Opposed to proximal junctional kyphosis and proximal junctional failure, their distal equivalents, distal junctional kyphosis and failure (DJK/DJF) have received less attention in the literature. The aim of this article is to provide an overview of the problem of DJK-DJF in different clinical scenarios such as adolescent idiopathic scoliosis (AIS), Scheuermann's kyphosis (SK) and adult deformity surgery and to suggest a strategy for prevention and treatment. METHODS: A narrative review of the literature was conducted to identify the best evidence on the risk factors of the problem. RESULTS: DJK/DJF have been described as a complication of AIS, SK and adult spine deformity (ASD). For AIS and SK, the choice of a lower instrumented vertebra more cranial than the sagittal stable vertebra has shown to increase the incidence of DJK and DJF. For ASD, constructs ending with S1 pedicle screws had a higher incidence of DJK/DJF than those ending distally with S1 pedicle plus iliac screws. CONCLUSION: The proposed strategy of treatment includes restoration of normal sagittal alignment, choice of a distal fixation point stable in the sagittal, coronal and transverse planes, balancing the fusion mass over the distal fixation point and providing solid fixation at the distal end of the construct. These slides can be retrieved under Electronic Supplementary Material.

Re-operation After Long-Segment Fusions for Adult Spinal Deformity: The Impact of Extending the Construct Below the Lumbar Spine.

BACKGROUND: Deciding where to end a long-segment fusion for adult spinal deformity (ASD) may be a challenge, particularly in the absence of an abnormality at L5/S1. Some suggest prophylactic extension of the construct to the sacrum and/or ilium (S/I) to protect against distal junctional failure, while others support terminating in the lower lumbar spine to preserve motion. OBJECTIVE: To compare the risk of re-operation after long-segment fusions for ASD that ends at L4 or L5 (L4/5) vs S/I. METHODS: A multicenter database of patients treated for ASD by circumferential minimally invasive surgery or hybrid surgical technique was screened for individuals with long fusions (≥4 vertebral levels) ending at L4 or below and with at least 2 yr of follow-up. Multivariate regression modeling was used to compare surgical morbidity between the L4/5 and S/I groups, and Cox proportional hazard modeling was used to compare risk of re-operation. RESULTS: There were 45 subjects with fusion to L4/5 and 71 to S/I. Over a 32-mo median follow-up, 41 re-operations were performed; 6 were for distal junctional failure. In those with normal or mild degeneration at L5/S1, fusion to S/I afforded no significant change in re-operative risk (hazard ratio = 1.18 [95% confidence interval: 0.53-2.62], P = .682). In those undergoing circumferential minimally invasive surgery correction, fusion to S/I was associated with significantly greater blood loss (499.6 cc, P < .001) and surgical time (97.5 min, P = .04). CONCLUSION: In the setting of a normal or mildly degenerated L5/S1 disc space, fusion to the sacrum/ilium did not significantly change the risk of requiring a re-operation after a long-segment fusion for ASD.

Distal junctional failure secondary to L5 vertebral fracture-a report of two rare cases.

Distal junctional failure (DJF) with fracture at the last instrumented vertebra is a rare occurrence. In this case report, we present two patients with L5 vertebral fracture post-instrumented fusion of the lumbar spine. The first patient is a 78-year-old female who had multi-level degenerative disc disease, spinal stenosis and degenerative scoliosis involving levels T12 to L5. She underwent instrumented posterolateral fusion (PLF) from T12 to L5, and transforaminal lumbar interbody fusion (TLIF) at L2/3 and L4/5. Six months after her operation, she presented with a fracture of the L5 vertebral body necessitating revision of the L5 pedicle screws, with additional TLIF of L5/S1. The second patient is a 71-year-old female who underwent decompression and TLIF of L3/4 and L4/5 for degenerative spondylolisthesis. Six months after the surgery, she developed a fracture of the L5 vertebral body with loosening of the L5 screws. The patient declined revision surgery despite being symptomatic. DJF remains poorly understood as its rare incidence precludes sufficiently powered studies within a single institution. This report aims to contribute to the currently scarce literature on DJF.