Preventing Distal Junctional Kyphosis by Applying the Stable Sagittal Vertebra Concept to Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis

Costs of revision operations for distal junctional kyphosis following thoracic posterior spinal fusion for adolescent idiopathic scoliosis

PURPOSE

To assess direct costs and risks associated with revision operations for distal junctional kyphosis/failure (DJK) following thoracic posterior spinal instrumented fusions (TPSF) for adolescent idiopathic scoliosis (AIS).

METHODS

Children who underwent TPSF for AIS by a single surgeon (2014-2020) were reviewed. Inclusion criteria were minimum follow-up of 2 years, thoracolumbar posterior instrumented fusion with a lower instrumented vertebra (LIV) cranial to L2. Patients who developed DJK requiring revision operations were identified and compared with those who did not develop DJK.

RESULTS

Seventy-nine children were included for analysis. Of these, 6.3% developed DJK. Average time to revision was 20.8 ± 16.2 months. Comparing index operations, children who developed DJK had significantly greater BMIs, significantly lower thoracic kyphosis postoperatively, greater post-operative lumbar Cobb angles, and significantly more LIVs cranial to the sagittal stable vertebrae (SSV), despite having statistically similar pre-operative coronal and sagittal alignment parameters and operative details compared with non-DJK patients. Revision operations for DJK, when compared with index operations, involved significantly fewer levels, longer operative times, greater blood loss, and longer hospital lengths of stay. These factors resulted in significantly greater direct costs for revision operations for DJK ($76,883 v. $46,595; p < 0.01).

CONCLUSIONS

In this single-center experience, risk factors for development of DJK were greater BMI, lower post-operative thoracic kyphosis, and LIV cranial to SSV. As revision operations for DJK were significantly more costly than index operations, all efforts should be aimed at strategies to prevent DJK in the AIS population.

Distal Junctional Failures in Degenerative Thoracolumbar Hyperkyphosis

OBJECTIVE

Degenerative thoracolumbar hyperkyphosis (DTH) is a disease that negatively affects individual health and requires surgical intervention, yet the ideal surgical approach and complications, especially distal junctional failures (DJF), remain poorly understood. This study aims to investigate DJF in DTH and to identify the risk factors for DJF so that we can improve surgical decision-making, and advance our knowledge in the field of spinal surgery to enhance patient outcomes.

METHODS

This study retrospectively reviewed 78 cases (late osteoporotic vertebral compression fracture [OVCF], 51; Scheuermann's kyphosis [SK], 17; and degenerative disc diseases [DDD], 10) who underwent corrective surgery in our institute from 2008 to 2019. Clinical outcomes were assessed using health-related quality of life (HRQOL) measures, including the visual analogue scale (VAS) scores for back and leg pain, the Oswestry disability index (ODI), and the Japanese Orthopaedic Association (JOA) scoring system. Multiple radiographic parameters, such as global kyphosis (GK) and thoracolumbar kyphosis (TLK), were assessed to determine radiographic outcomes. Multivariate logistic regression analysis was employed to identify the risk factors associated with DJF.

RESULTS

HRQOL improved, and GK, TLK decreased at the final follow-up, with a correction rate of 67.7% and 68.5%, respectively. DJF was found in 13 of 78 cases (16.7%), two cases had wedging in the disc (L3-4) below the instrumentation, one case had a fracture of the lowest instrumented vertebrae (LIV), one case had osteoporotic fracture below the fixation, nine cases had pull-out or loosening of the screws at the LIV and three cases (23.1%) required revision surgery. The DJF group had older age, lower computed tomography Hounsfield unit (CT HU), longer follow-up, more blood loss, greater preoperative sagittal vertical axis (SVA), and poorer postoperative JOA and VAS scores (back). The change in TLK level was larger in the non-DJF group. Post-sagittal stable vertebrae (SSV) moved cranially compared with pre-SSV.

CONCLUSION

Age, CT HU, length of follow-up, estimated blood loss, and preoperative SVA were independent risk factors for DJF. We recommend fixation of the two vertebrae below the apex vertebrae for DTH to minimize surgical trauma.

[Translated article] How do I plan adolescent idiopathic scoliosis surgery? Systematization of a preoperative planning method

Preoperative planning is essential in adolescent idiopathic scoliosis (AIS) surgery to determine the fusion levels and to perform the procedure with greater precision and diligence. However, the protocolized performance of such planning is not as widespread among specialists in training. The aim of this article is to describe in detail the preoperative planning method for AIS used in a specialised paediatric and adolescent spine unit of a referral centre, as well as the logistics and the tactics, supported a free semi-automatic digital measurement and planning software. Three representative cases of different vertebral deformities, treated by posterior spinal fusion after preoperative planning according to the method, are shown. This method is highly suitable for the trainee surgeon as it combines the advantages of traditional and modern methods, and is simple, low-cost, accessible, reproducible and with an educational character.

How do I plan adolescent idiopathic scoliosis surgery? Systematization of a preoperative planning method

Preoperative planning is essential in adolescent idiopathic scoliosis (AIS) surgery to determine the fusion levels and to perform the procedure with greater precision and diligence. However, the protocolized performance of such planning is not as widespread among specialists in training. The aim of this article is to describe in detail the preoperative planning method for AIS used in a specialized pediatric and adolescent spine unit of a referral center, as well as the logistics and the tactics, supported a free semi-automatic digital measurement and planning software. Three representative cases of different vertebral deformities, treated by posterior spinal fusion after preoperative planning according to the method, are shown. This method is highly suitable for the trainee surgeon as it combines the advantages of traditional and modern methods, and is simple, low cost, accessible, reproducible and with an educational character.

Lowest Instrumented Vertebra at L3 Versus L4 in Posterior Fusion for Moderate Lenke 5C Type Adolescent Idiopathic Scoliosis: A Case-Match Radiological Study

OBJECTIVE

To compare the radiological outcomes in Lenke 5C type patients whose lowest instrumented vertebra (LIV) was L3 or L4 in a case-match study.

METHODS

We conducted a retrospective case-match study and included 82 patients in the study. Radiological results before surgery, after surgery, and at last follow-up were recorded and analyzed in the L3 and L4 groups.

RESULTS

After matching the age, Risser's sign, sex, and main Cobb, 41 pairs of patients were enrolled in our study. The total fusion segments in the L3 group (median [interquartile range]: 5.0 [6.0-5.0]) were shorter than those in the L4 group (6.0 [6.5-6.0]). The main curve was significantly corrected after surgery in both groups, and was comparable at the last followup between groups. In addition, according to the results of Fisher precision probability test, there was no significant difference of coronal or sagittal imbalance between the 2 groups at the 2-year follow-up.

CONCLUSION

The correction in coronal and sagittal planes in L3 group and L4 group remains similar. On account of more motion segments, L3 could be an ideal choice as LIV in moderate Lenke 5C type AIS. Long-term follow-up is needed to evaluate the effect of larger compensatory lumbar-sacral curve when stopping at L3.

Risk Factors for Distal Junctional Problems Following Long Instrumented Fusion for Degenerative Lumbar Scoliosis: Are they Related to the Paraspinal Muscles

PURPOSE

Although the incidence of distal junctional problems (DJPs) following long construct-based treatment for degenerative lumbar scoliosis (DLS) is lower, affected patients are more likely to require revision surgery when they occur. So the aim of this study is to identify risk factors associated with DJPs to avoid its occurrence by at least 1-year follow-up.

METHODS

A total of 182 DLS patients undergoing long instrumented fusion surgery (≥4 levels) between February 2011 and March 2022 were retrospectively analyzed. Patients were placed into the DJP group if a DJP occurred at the final follow-up; patients without mechanical complications were matched 1:2 according to age, sex and BMI as the control group. Patient characteristics, surgical variables, radiographic parameters, lumbar muscularity and fatty degeneration were analyzed statistically. The statistical differences in the results between the two groups (p values <0.05) and other variables selected by experts were entered into a multivariate logistic regression model, and the forwards likelihood ratio method was used to analyze the independent risk factors for DJPs.

RESULTS

Twenty-four (13.2%) patients suffered a DJP in the postoperative period and the reoperation rate was 8.8%. On univariate analysis, the lowest instrumented vertebra (LIV) CT value (p = 0.042); instrumented levels (p = 0.030); preoperative coronal vertical axis (CVA) (p = 0.046), thoracolumbar kyphosis (TLK) (p = 0.006), L4-S1 lordosis (p = 0.013), sacral slop (SS) (p = 0.030), pelvic tilt (PT) classification (p = 0.004), and sagittal vertical axis (SVA) (p = 0.021); TLK correction (p = 0.049); post-operative CVA (p = 0.029); Overall, There was no significant difference in the paraspinal muscle parameters between the two groups. On multivariate analysis, instrumented levels (OR = 1.595; p = 0.035), preoperative SVA (OR = 1.016; p = 0.022) and preoperative PT (OR = 0.873; p = 0.001) were identified as significant independent risk factors for DJP.

CONCLUSION

Longer instrumented levels, a greater preoperative SVA and a smaller PT were found to be strongly associated with the presence of DJPs in patients treated for DLS. The degeneration of the paraspinal muscles may not be related to the occurrence of DJPs. For DLS patients, the occurrence of DJP can be reduced by selecting reasonable fusion segments and evaluating the patient's sagittal balance and spino-pelvic parameters before operation.

Risk factors for distal junctional kyphosis after posterior spinal surgery in adolescent idiopathic scoliosis: a meta-analysis

Introduction

Distal junctional kyphosis (DJK) is a serious complication after posterior spinal surgery in managing adolescent idiopathic scoliosis (AIS). Our study aims to investigate the predictors of DJK in AIS patients.

Methods

We searched the English databases of PubMed, Embase, and the Cochrane Library for clinical research studies on AIS. To identify the risk factors for DJK, we collected demographic data, such as age, gender, and body mass index (BMI), and sagittal parameters, including preoperative pelvic tilt (PT), sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), distal junctional angle (DJA), lowest instrumented vertebrae (LIV) relative to sagittal stable vertebrae (SSV), and postoperative DJA. Data were analyzed by RevMan (5.3 version) and STATA (12.0 version).

Results

Finally, six included articles (1,240 patients) showed 9% (98 of 1,240 patients) of patients suffering from DJK. Our findings indicated that preoperative TK [p = 0.007, OR = 0.35, 95% CI (0.10, 0.61)], TLK [p < 0.0001, OR = 5.99, 95% CI (3.33, 8.65)], and postoperative DJA [p = 0.002, OR = 0.56, 95% CI (0.21, 0.91)] in the DJK group were markedly higher than those in the non-DJK group. Moreover, patients with LIV above SSV [p < 0.0001, OR = 7.95, 95% CI (4.16, 15.22)] were more likely to develop DJK. No discernible difference was found in age, sex, BMI, preoperative PT, SVA, LL, or DJA between the two groups.

Conclusions

Regarding the AIS patients, factors such as higher preoperative TK and TLK, higher postoperative DJA, and LIV above the SSV were related to an increased rate of DJK.

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.

Optimal lowest instrumented vertebra selection with consideration of coronal and sagittal planes to prevent distal junctional complications in patients with Lenke type 1A and 2A adolescent idiopathic scoliosis

PURPOSE

Postoperative distal adding-on and distal junctional kyphosis are major distal junctional complications after selective thoracic fusion in patients with adolescent idiopathic scoliosis (AIS). This study aimed to investigate the incidence of distal adding-on and distal junctional kyphosis and evaluate the validity of our selection criteria for the lowest instrumented vertebra (LIV) in patients with Lenke type 1A and 2A AIS.

METHODS

We retrospectively analyzed the data of patients with Lenke type 1A and 2A AIS, who underwent posterior fusion surgery. LIV selection included the followings: (1) stable vertebra on traction film, (2) disc space neutralization below the LIV on the side-bending film, and (3) lordotic disc below the LIV on the lateral film. Radiographic parameters and the revised 22-item Scoliosis Research Society Questionnaire (SRS-22r) were evaluated. The incidence of postoperative distal adding-on and distal junctional kyphosis was also investigated.

RESULTS

Ninety patients (83 women and 7 men; 64 with type 1A and 26 with type 2A) were included. After the operation, each curve and the SRS-22r of self-image, mental health, and subtotal domains were significantly improved. Distal adding-on occurred in three patients (3.3%, one in type 1A and two in type 2A) at 2 years postoperatively. No patients exhibited distal junctional kyphosis.

CONCLUSIONS

Our LIV selection criteria could reduce the incidence of postoperative distal adding-on and distal junctional kyphosis in patients with Lenke type 1A and 2A AIS.

LEVEL OF EVIDENCE

Level IV.

Distal junctional kyphosis in adult cervical deformity patients: where does it occur?

PURPOSE

To evaluate the impact of the lowest instrumented vertebra (LIV) on Distal Junctional kyphosis (DJK) incidence in adult cervical deformity (ACD) surgery.

METHODS

Prospectively collected data from ACD patients undergoing posterior or anterior-posterior reconstruction at 13 US sites was reviewed up to 2-years postoperatively (n = 140). Data was stratified into five groups by level of LIV: C6-C7, T1-T2, T3-Apex, Apex-T10, and T11-L2. DJK was defined as a kyphotic increase > 10° in Cobb angle from LIV to LIV-1. Analysis included DJK-free survival, covariate-controlled cox regression, and DJK incidence at 1-year follow-up.

RESULTS

25/27 cases of DJK developed within 1-year post-op. In patients with a minimum follow-up of 1-year (n = 102), the incidence of DJK by level of LIV was: C6-7 (3/12, 25.00%), T1-T2 (3/29, 10.34%), T3-Apex (7/41, 17.07%), Apex-T10 (8/11, 72.73%), and T11-L2 (4/8, 50.00%) (p < 0.001). DJK incidence was significantly lower in the T1-T2 LIV group (adjusted residual = -2.13), and significantly higher in the Apex-T10 LIV group (adjusted residual = 3.91). In covariate-controlled regression using the T11-L2 LIV group as reference, LIV selected at the T1-T2 level (HR = 0.054, p = 0.008) or T3-Apex level (HR = 0.081, p = 0.010) was associated with significantly lower risk of DJK. However, there was no difference in DJK risk when LIV was selected at the C6-C7 level (HR = 0.239, p = 0.214).

CONCLUSION

DJK risk is lower when the LIV is at the upper thoracic segment than the lower cervical segment. DJK incidence is highest with LIV level in the lower thoracic or thoracolumbar junction.

Updated Criteria for Fusion Level Selection in Adolescent Idiopathic Scoliosis Including Use of Three-Dimensional Analysis

The development of new technologies and an enhanced understanding of the three-dimensional deformity in adolescent idiopathic scoliosis has led to advances in surgical management of adolescent idiopathic scoliosis. Posterior spinal approaches with pedicle screw constructs are now standard of care because they allow for powerful rotation maneuvers with three-column deformity correction. Selective fusion of the main curve while allowing for spontaneous correction of compensatory curves should be attempted whenever possible in the interest of limiting fusion size and preserving spinal mobility. Recent research provides updated criteria to determine optimal candidates for selective fusion. These criteria must be weighed against patient goals and patient-specific factors to limit complications and maximize chances of successful deformity correction.

Thoracic posterior spinal instrumented fusion vs. thoracic anterior spinal tethering for adolescent idiopathic scoliosis with a minimum of 2-year follow-up: a cost comparison of index and revision operations

PURPOSE

To compare direct costs of index and revision operations of thoracic posterior spinal instrumented fusion (TPSIF) and thoracic anterior spinal tethering (TAST) for adolescent idiopathic thoracic scoliosis in children.

METHODS

Children (ages 11-18 years) who underwent TPSIF and TAST (2/2013-9/2019) were reviewed. Follow-up < 2 years and cervical instrumentation and/or instrumentation of a lumbar level at L3 or below were exclusion criteria. Patient demographics, radiographic curve magnitude, index operations and postoperative data, as well as indications for revisions/readmissions were collected. Direct costs were identified and compared for index and revision operations during follow-up.

RESULTS

One hundred and four patients were included (TPSIF: 78; TAST: 25). TAST procedures were performed in children significantly younger and for smaller curve magnitudes. They had significantly fewer levels instrumented, shorter operating room (OR) times, and less estimated blood loss (EBL). After operation, a significantly higher percentage of TAST were admitted to ICU. Hospital length of stay (LOS) was similar between groups. Index operations' average direct costs were significantly higher for TAST than TPSIF ($52,947 v. $46,641; p = 0.02). Major cost drivers for both groups were implants, OR services, post-anesthesia care unit (PACU), and room/board. Revisions following TAST were more frequent than for TPSIF (36 v. 11.5%). Majority of TPSIF revisions were for junctional deformity. Curve progression and overcorrection were most common reason for TAST revisions. Average direct costs for revisions/readmissions were similar between groups (TPSIF: $28,485 v. TAST: $27,590; p = 0.46).

CONCLUSIONS

Index operations' average direct costs were statistically similar between TPSIF and TAST for adolescent idiopathic scoliosis. Major cost drivers were implants, OR services, PACU, and room/board. TAST index operations' direct costs and associated direct costs for implants and room/board were significantly higher, while their anesthesia and OR services were significantly lower than TPSIF. TAST revisions were for overcorrection and curve progression, while TPSIF revisions were most commonly for junctional deformity. Overall average direct costs for revisions were similar despite revision rates being higher for TAST.

LEVEL OF EVIDENCE

III.

Surgical Level Selection in Adolescent Idiopathic Scoliosis: An Evidence-Based Approach

The selection of fusion levels in the treatment of adolescent idiopathic scoliosis remains complex. The goals of surgery are to minimize the risk of future progression and optimize spinal balance while fusing the least number of levels necessary. Several classifications, rules, and algorithms exist to guide decision making, although these have previously not been easily referenced in a study. This review aims to provide an evidence-based approach of selecting fusion levels that balances the expert opinion of the authors with the current literature.

The Sagittal Plane in Spinal Fusion for Adolescent Idiopathic Scoliosis

Sagittal balance is widely recognized as the primary determinant of optimal outcomes in adult spinal deformity. In adolescent idiopathic scoliosis (AIS), coronal correction risks being obtained at the expense of sagittal malalignment after posterior spinal fusion. Apical lordosis, often underestimated on two-dimensional imaging, is the primary deforming factor in AIS. Failure to restore thoracic kyphosis and lumbar lordosis during posterior spinal fusion contributes to problematic early surgical complications, including proximal or distal junctional kyphosis and failure. Although adolescent patients often compensate for sagittal imbalance in the short-term and mid-term, late sequelae of iatrogenic sagittal imbalance include flatback syndrome, disk degeneration, cervical kyphosis, and late decompensation. Objective criteria using spinopelvic parameters and preoperative three-dimensional planning can guide sagittal plane correction during PSF for AIS. Technical caveats can help avoid sagittal plane complications, including instrumentation level selection, anchor type, and anatomic protection of adjacent levels. Other surgical techniques to optimize restoration of thoracic kyphosis include higher implant density, stiffer rod material, Ponte osteotomies, and deformity correction technique.

Risk factors for the development of DJK in AIS patients undergoing posterior spinal instrumentation and fusion

PURPOSE

Typically, selection of lowest instrumented vertebra (LIV) in Adolescent Idiopathic Scoliosis (AIS) is based on the coronal radiograph; however, increasing evidence suggests that fusions proximal to the stable sagittal vertebrae (SSV) on the lateral radiograph can result in distal junctional kyphosis (DJK). The purpose of this study is to compare rates of DJK in patients with AIS that have a discordance between the Lowest Touched Vertebra (LTV) and the SSV and to identify risk factors for developing DJK.

METHODS

Patients with AIS Lenke type 1, 2 and 3 curves treated with a posterior spinal fusion were separated into two groups. Group 1 had SSV that was proximal to the LTV whereas group 2 had SSV that was distal to the LTV. Comparisons were made for patients that were fused to the SSV(a), LTV(b) or between(c). Distal junctional angle (DJA) > 5° and increasing kyphosis at the end of the fusion construct were evaluated as risk factors for DJK.

RESULTS

The rate of DJK was 0.0% in group 1a, 1b, and 1c compared to 4.3%, 18.5% and 10.0% in groups 2a, 2b and 2c, respectively(p < 0.001). The rate of DJK was 22.9% when the distal junctional angle(DJA) > 5° versus 1.4% when the DJA < 5°(p < 0.001).

CONCLUSION

There was a low risk for progression of DJK when the SSV was proximal to the LTV, however, those with SSV distal to the LTV represent a high-risk group. Importantly, the development of DJK occurred almost exclusively in patients with LIV at the thoracolumbar junction which demonstrates that surgeons need to be cautious when ending fusions at T11, T12, and L1 in patients at high risk for DJK. Furthermore, having a distal junctional angle 5° or greater increased the risk of developing DJK by roughly 16-fold. At a minimum of 5-year follow-up, the development of DJK did not appear to adversely impact SRS outcomes or revision rates.

The impact of the lower instrumented level on outcomes in cervical deformity surgery

Background:

The lower instrumented vertebrae (LIVs) in cervical deformity (CD) constructs may have varying effects on patient outcomes that are still poorly understood.

Objective:

The objective of the study is to compare outcomes in CD patients undergoing instrumented correction according to the relation of LIV with primary driver (PD).

Methods:

Patients who met radiographic criteria for CD were included in the study. Patients were stratified by PD of deformity: cervical (C) through AMES classification (TS-CL >20 or cervical sagittal vertical axis >40) and thoracic (T) through hyper/hypokyphosis (TK) from T4-T12 (60 < TK < 40). Patients were further stratified by LIV in relation to curve apex (above/below). Univariate and multivariate analyses identified group differences in postoperative health-related quality-of-life and distal junctional kyphosis (DJK) (>10° LIV and LIV + 2) rate up to 1 year.

Results:

Sixty-two patients were analyzed. Twenty-one patients had a C-PD and 41 had a T-PD by definition. 100% of C-PDs had LIVs below CL apex, while 9.2% of T-PDs had LIVs below (caudal) to TK apex and 90.8% had LIVs above TK apex. By 1 year, C patients trended lower Neck Disability Index (NDI) (21.9 vs. 29.0, P = 0.245), lower numeric rating scales neck pain (4.2 vs. 5.1, P = 0.358), and significantly higher EuroQol five-dimensional questionnaire Visual Analog Scale (69.2 vs. 52.4, P = 0.040). When T patients with LIVs below TK apex were excluded, remaining T patients with LIV above apex had significantly higher 1-year NDI than C patients (37.5 vs. 21.9, P = .05). T patients also trended higher rates of postoperative DJK than C (19.5% vs. 4.8%, P = 0.119).

Conclusions:

Stopping before apex was more common in patients with a primary thoracic driver (T) and associated with deleterious effects. Primary cervical driver (C) tended to have LIVs inclusive of CL apex with lower rates of DJK.

Distal Junctional Kyphosis after Posterior Spinal Fusion in Lenke 1 and 2 Adolescent Idiopathic Scoliosis-Exploring Detailed Features of the Sagittal Stable Vertebra Concept

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To investigate the factors contributing to the development of postoperative distal junctional kyphosis (DJK) in adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF) with lowest instrumented vertebrae (LIV) at or above L1.

METHODS

Patients with Lenke type 1 or 2 curves who underwent PSF with LIV at or above L1 with a minimum follow-up of 2 years were evaluated. The primary outcome measure was the occurrence of postoperative DJK. Radiographic parameters of sagittal alignment and inclusion/exclusion of sagittal stable vertebra (SSV) in PSF were analyzed to determine their associations with the occurrence of postoperative DJK.

RESULTS

Overall, 122 patients (mean age: 15.1 ± 3.2 years) were included. The overall incidence of postoperative DJK was 6.6%. DJK was observed in 19.0% (8/42) of patients whose SSV was not included in PSF and not in patients with SSV included in PSF (n = 80). In the SSV-excluded group, univariate analysis found two significant risk factors for DJK: postoperative thoracic kyphosis (TK, T5-12) and postoperative thoracolumbar kyphosis (TLK, T11-L2). The ROC curve revealed that postoperative TK ≥ 25° and TLK ≥ 10° best predicted the occurrence of postoperative DJK in the SSV-excluded group. The incidence was significantly higher in cases with postoperative TK ≥ 25° or TLK ≥ 10° (7/13 = 53.8%) than in those with postoperative TK < 25° and TLK < 10° (1/29 = 3.4%).

CONCLUSIONS

The current study revealed that postoperative TK ≥ 25° or postoperative TLK ≥ 10° with SSV excluded from PSF were related to DJK after PSF for Lenke type 1 and type 2 AIS. When the SSV is intended to be spared from PSF to save more motion segments, TK and TLK should be carefully evaluated and attained in a lesser magnitude (TK < 25°, TLK < 10°) after surgery.

Including the stable sagittal vertebra in the fusion for adolescent idiopathic scoliosis reduces the risk of distal junctional kyphosis in Lenke 1-3 B and C curves

PURPOSE

The selection of lowest instrumented vertebra (LIV) in adolescent idiopathic scoliosis (AIS) is determined by coronal and sagittal plane indicators. Failure to properly select the LIV can lead to suboptimal outcomes and the need for revision surgery. A subset of patients have discordant coronal last touched vertebra (cLTV) and stable sagittal vertebra (SSV) which complicates the choice of LIV. The purpose of this study is to report the incidence of discordant cLTV and SSV when choosing LIV and investigate the association between length of fusion and patient-reported outcomes (PROs) and distal junctional kyphosis (DJK).

METHODS

This retrospective multicenter cohort study included AIS patients with discordant pre-operative cLTV and SSV. Patients fused only to include the proximal cLTV were compared to patients fused to include the distal SSV. Primary outcomes included DJK and PROs measured by SRS-22.

RESULTS

Eight hundred and fifty-six patients were identified of which 114 (13.3%) had discordant SSV and cLTV. The DJK incidence was 7.7% and 45.5% in patients fused to include the SSV versus short of the SSV, respectively. Lenke Modifier type B and C patients with fusions short of the SSV had a 9.2 times increased risk of developing DJK at 2 years compared to patients with fusions including the SSV (95% CI 2.8, 29.7; p < 0.001). However, patients with fusions short of the SSV and no evidence of DJK were 9.2 times more likely to have improvement in the SRS-22 pain domain compared to patients with fusions including the distal SSV (95% CI 1.1, 77.4; p = 0.042) CONCLUSION: Patients fused short of the SSV are at significant risk for the development of DJK at 2 years post-operatively. However, patients with shorter fusions were more likely to have an improvement in their pain as measured by patient-reported outcomes than patients with longer fusions.

Spinal balance and lumbar curve stability after selective thoracic fusion in idiopathic scoliosis

PURPOSE

Selective thoracic fusion (STF) for double curve patterns in idiopathic scoliosis is an attractive treatment option. However, short-term coronal decompensation and truncal imbalance are known findings. Previous studies with hook constructs showed that eventually balance is achieved via an increase in lumbar curve magnitude, as the lumbosacral obliquity did not change following surgery. Our aim is to investigate patients with idiopathic curves who underwent STF using all-pedicle screw constructs to determine if the uninstrumented lumbar curve and lumbosacral obliquity responded in the same manner as was previously reported with all-hook constructs.

METHODS

102 consecutive patients with Lenke 1B, 1C or 3C curves who underwent STF using all-screw constructs at a single institution were included in this study. Radiographic assessment was performed, and patient reported outcomes were obtained. Subgroup analyses were performed based on preoperative thoracic: lumbar curve ratio as well as lumbar curve magnitude.

RESULTS

Overall, the patients showed statistically significant improvement in both trunk shift and L4-pelvis obliquity at final follow-up. The uninstrumented lumbar curves trended toward improvement over time, but did not reach statistical significance (p = 0.107). SRS-30 scores were statistically significantly improved in multiple domains.

CONCLUSION

Selective thoracic fusion is an excellent treatment option in most double curve patterns. Balance in the coronal plane is predictably achieved at 2-year follow-up. The lumbosacral obliquity improves more with screw technology than was previously found with hook constructs; therefore, the improvement in balance over time does not depend upon an increase in the uninstrumented lumbar curve.

LEVEL OF EVIDENCE

IV.

Predictive Probability of the Global Alignment and Proportion Score for the Development of Mechanical Failure Following Adult Spinal Deformity Surgery in Asian Patients

STUDY DESIGN

This is a multicenter retrospective review of 257 surgically treated consecutive ASD patients who had a minimum of five fused segments, completed a 2-year follow-up (53 ± 19 yrs, females: 236 [92%]).

OBJECTIVE

This study aimed to validate the predictive probability of the GAP score in an Asian ASD patient cohort.

SUMMARY OF BACKGROUND DATA

The GAP score is a recently established risk stratification model for MF following ASD surgery. However, the predictive ability of the GAP score is not well studied. This study aimed to validate the predictive probability of the GAP score in an Asian ASD patient cohort.

METHODS

Comparisons of the immediate postoperative GAP scores between MF the and MF-free groups were performed. We evaluated the discriminative ability of the GAP score based on the area under the receiver operating characteristic curve (AUROC). The Cuzick test was performed to determine whether there is a trend between the GAP score and the incidence of MF or revision surgery. Univariate logistic regression analyses were performed to explore the associations between the GAP score and the incidence of MF or revision surgery.

RESULTS

No difference was observed in the GAP score between the MF and MF-free groups (MF vs. MF-free; GAP: 5.9 ± 3.3 vs. 5.2 ± 2.7, P = 0.07). The Cuzick analysis showed no trend between the GAP score and the risk for MF or revision surgery. Likewise, the MF rate was not correlated with the GAP score, as shown by the ROC curve (AUC of 0.56 [95% CI 0.48-0.63], P = 0.124). Univariate logistic regression confirmed no associations between the GAP score and the incidence of MF or revision surgery (MF; moderately disproportioned [MD]: OR: 0.6 [95% CI: 0.3-1.2], P = 0.17, severely disproportioned [SD]: OR: 1.2 [95% CI: 0.6-2.3], P = 0.69, revision surgery; MD: OR: 0.8 [95% CI: 0.2-2.8], P = 0.71, SD: OR: 1.2 [95% CI: 0.9-8.7], P = 0.08).

CONCLUSION

In this multicenter study, in an Asian ASD patient cohort, the GAP score was not associated with the incidence of MF or revision surgery. Additional studies on the predictive ability of the GAP score in different patient cohorts are warranted.Level of Evidence: 3.

Risk Factors Associated With Failure to Reach Minimal Clinically Important Difference After Correction Surgery in Patients With Degenerative Lumbar Scoliosis

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to evaluate the factors affecting health-related quality of life (HRQOL) after surgery in patients with degenerative lumbar scoliosis (DLS) by minimum clinically important difference (MCID).

SUMMARY OF BACKGROUND DATA

MCID has been introduced in the adult spinal deformity to quantify the absolute minimum change that can be considered a success. There are limited data available to identify factors affecting reaching MCID after DLS surgery.

METHODS

This study reviewed a cohort of 123 DLS patients after correction surgery and with a minimum 2-year follow-up (FU). Inclusion criteria included age ≥40 and minimum five vertebrae fused and the availability of Scoliosis Research Society (SRS)-22 scores and radiographic data at baseline (BL) and FU. Using a multivariate analysis, two groups were compared to identify possible risk factors: those who reached MCID in the all four SRS domains (N = 65) at the last FU and those who missed MCID (N = 58).

RESULTS

At baseline, patients differed significantly from matched normative data in all SRS-22 domains. The baseline HRQOL was comparable in reached MCID and missed MCID group patients (P > 0.05). The HRQOL scores at FU were significantly higher than those at baseline. Of 123 included patients, 77.2% (N = 95), 72.4% (N = 89), 76.4% (N = 94), and 89.4% (N = 110) reached MCID in SRS pain, activity, appearance, and mental domain, respectively. Pelvic incidence (PI) >55°, lumbar lordosis (LL) loss >4.65°, coronal imbalance at FU, sagittal vertical axis (SVA) at FU >80 mm, and presence of proximal junctional kyphosis (PJK) and distal junctional problem (DJP) had negative effects on the recovery process.

CONCLUSION

Factors affecting reaching MCID after surgery for DLS were higher PI, LL loss, coronal imbalance, severe sagittal imbalance, and the occurrence of PJK and DJP.

LEVEL OF EVIDENCE

4.

Variability in stable sagittal vertebra (SSV) during full-length biplanar xrays can affect the choice of fusion levels in patients with adolescent idiopathic scoliosis (AIS)

PURPOSE

Surgical planning for Adolescent Idiopathic Scoliosis (AIS) relies on the coronal and sagittal plane to determine the lowest instrumented vertebra (LIV). Failure to include the stable sagittal vertebra (SSV) within the construct can increase the incidence of postoperative distal junctional kyphosis (DJK). The purpose of this study is to assess the variability of SSV within patients and to identify positional parameters that may lead to its change.

METHODS

This is a case-control study of AIS patients with changes in SSV throughout serial radiographs. Radiographic sagittal parameters and hand positioning for the patients with changes in SSV were compared to patients with stable SSV. Additionally, a subgroup analysis was conducted to compare the positional parameters of only the patients with changes in SSV.

RESULTS

46 patients with a mean age of 15 ± 1.8 years old at the time of surgery were included in this study. 33/76 (43.4%) image pairs were found to have a change in SSV. Positional parameters associated with the more distally measured SSV were found to have a more negative sagittal vertebral axis (p = 0.001), more positive pelvic shift (p = 0.023), and more negative Global Sagittal Axis (p = 0.001) when compared to the more proximally measured SSV.

CONCLUSION

Significant variability exists in the determination of SSV in AIS patients undergoing serial radiographs. Positional parameters associated with the proximal and distally measured SSV also have variability which indicates that posture has a significant impact on this measure. Surgeons need to be aware of SSV variability during preoperative planning and must consider multiple parameters for the determination of LIV.

LEVEL OF EVIDENCE

3.

Selecting the "Touched Vertebra" as the Lowest Instrumented Vertebra in Patients with Lenke Type-1 and 2 Curves: Radiographic Results After a Minimum 5-Year Follow-up

BACKGROUND

The selection of the lowest instrumented vertebra (LIV) in patients with adolescent idiopathic scoliosis (AIS) is still controversial. Although multiple radiographic methods have been proposed, there is no universally accepted guideline for appropriate selection of the LIV. We developed a simple and reproducible method for selection of the LIV in patients with Lenke type-1 (main thoracic) and 2 (double thoracic) curves and investigated its effectiveness in producing optimal positioning of the LIV at 5 years of follow-up.

METHODS

The radiographs for 299 patients with Lenke type-1 or 2 AIS curves that were included in a multicenter database were evaluated after a minimum duration of follow-up of 5 years. The "touched vertebra" (TV) was selected on preoperative radiographs by 2 independent examiners. The LIV on postoperative radiographs was compared with the preoperative TV. The final LIV position in relation to the center sacral vertical line (CSVL) was assessed. The CSVL-LIV distance and coronal balance in patients who had fusion to the TV were compared with those in patients who had fusion cephalad and caudad to the TV. The sagittal plane was also reviewed.

RESULTS

In 86.6% of patients, the LIV was selected at or immediately adjacent to the TV. Among patients with an "A" lumbar modifier, those who had fusion cephalad to the TV had a significantly greater CSVL-LIV distance than those who had fusion to the TV (p = 0.006) or caudad to the TV (p = 0.002). In the groups with "B" (p = 0.424) and "C" (p = 0.326) lumbar modifiers, there were no differences among the TV groups.

CONCLUSIONS

We recommend the TV rule as a third modifier in the Lenke AIS classification system. Selecting the TV as the LIV in patients with Lenke type-1 and 2 curves provides acceptable positioning of the LIV at long-term follow-up. The position of the LIV was not different when fusion was performed caudad to the TV but came at the expense of fewer motion segments. Patients with lumbar modifier "A" who had fusion cephalad to the TV had greater translation of the LIV, putting these patients at risk for poor long-term outcomes.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Fusions ending above the sagittal stable vertebrae in adolescent idiopathic scoliosis: does it matter?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To validate whether fusions that end proximal to the sagittal stable vertebrae are at risk for developing distal junctional kyphosis in adolescent idiopathic scoliosis.

BACKGROUND

Posterior spinal fusion is routinely used for the treatment of patients with adolescent idiopathic scoliosis. Fusions that end in either the lower thoracic or upper lumbar spine have the advantage of preserving motion segments. However, fusions ending proximal to the sagittal stable vertebrae has been shown to be at higher risk for developing distal junctional kyphosis.

METHODS

A multi-center database of prospectively enrolled subjects was queried for patients with adolescent idiopathic scoliosis that had Lenke type 1, 2 and 3 curves treated with posterior pedicle screw instrumentation. PA (posterior-anterior) and lateral full-length scoliosis films were obtained on each patient. PA radiographs were viewed to determine the coronal deformity and lateral radiographs to determine the sagittal deformity. Distal junctional kyphosis was defined as a greater than 10° increase in segmental kyphosis between the LIV and the LIV + 1 vertebra.

RESULTS

346 patients were included with 85% being female and mean age of cohort 14.2 [Formula: see text] 2.08 years. At 5 years postoperatively, there was significant difference occurrence of distal junctional kyphosis dependent on whether the LIV relative to SSV with only 2.2% of fusions below the SSV developing DJK compared to 6.5% for fusions ending at the SSV and 15% for fusions with LIV above the SSV (p < 0.001). There was no statistical difference in revision rates based on the relationship of LIV to SSV.

CONCLUSION

There is an increased risk for development of DJK in patients with AIS treated with posterior fusion where the LIV was chosen proximal to the SSV.

LEVEL EVIDENCE

Level III.

Fusions ending at the thoracolumbar junction in adolescent idiopathic scoliosis: comparison of lower instrumented vertebrae

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To compare clinical outcomes and radiographic parameters between patients treated with a posterior spinal fusion that had a lower instrumented vertebra at T11, T12, and L1.

BACKGROUND

Posterior instrumented fusions are well established for treating patients with adolescent idiopathic scoliosis (AIS). Fusions limited to the thoracic spine can adequately correct a spinal deformity while preserving lumbar segmental mobility. However, fusions that end at the thoracolumbar junction have been proposed to cause adjacent segment complications. Studies comparing outcomes between patients who were treated with fusions that end at the thoracolumbar junction with varying LIVs are limited.

METHODS

A multicenter database was queried for patients with AIS that had Lenke Type 1 and 2 curves treated with a fusion that had an LIV at T11, T12, or L1. Coronal curve magnitude, degree of junctional kyphosis, C7-central sacral line, thoracic apical translation, and sagittal stable vertebrae were measured. Clinical and functional outcomes were assessed using the Scoliosis Research Society-22 (SRS-22) questionnaire and lumbar flexibility testing.

RESULTS

The lower instrumented level was below the sagittal stable vertebrae in 22.7%, 40%, and 66.2% of patients in the LIV-T11, T12, and L1 groups, respectively (p < 0.001). The 5-year postoperative lumbar curve magnitudes were 20.3°, 16.3°, and 14.0° for T11, T12, and L1-LIV, respectively (p < 0.001). No patients in the T11 group (0%), two patients in the T12 group (2.5%), and one patient in the L1 (0.8%) group developed distal junctional kyphosis (p = 0.5). The 5-year postoperative total SRS-22 scores were 4.21, 4.50, and 4.38 (p = 0.029). Lumbar flexion decreased by 0.78 cm in the T11-LIV group, increased by 0.01 cm in the T12-LIV group, and decreased by 0.15 cm in the L1-LIV group (p = 0.434).

CONCLUSION

There was no significant difference in SRS-22 scores, development of distal junctional kyphosis or loss of lumbar mobility between patients treated with a spinal fusion that had an LIV at T11, T12, or L1.

LEVEL OF EVIDENCE

Level III.

Restoring sagittal and frontal balance following posterior instrumented fusion

Correction techniques for adolescent idiopathic scoliosis have evolved over the years as the understanding of the disease and the implant technology advanced. Utilization of the modern implant systems, along with the appropriate corrective maneuvers and selection of the appropriate levels of instrumentation, improves the outcomes after surgical treatment of adolescent idiopathic scoliosis. Coronal and sagittal balance are important predictors for successful posterior spine fusion. Many corrective methods have been developed to address the multiple facets of the spinal deformity and curve types. Treating surgeons should familiarize themselves with all of the techniques, their utility, and appropriate usage in different deformity settings. A literature review is provided with the best evidence available to achieve optimal deformity correction to help guide treating physicians.

Comparison Between Stable Sagittal Vertebra and First Lordotic Vertebra Instrumentation for Prevention of Distal Junctional Kyphosis in Scheuermann Disease: Systematic Review and Meta-analysis

STUDY DESIGN

This study was a systematic review and meta-analysis.

OBJECTIVES

To compare stable sagittal vertebra (SSV) and first lordotic vertebra (FLV) instrumentation for prevention of distal junctional kyphosis (DJK) in Scheuermann disease.

SUMMARY OF BACKGROUND DATA

The SSV has been increasingly chosen as the lowest instrumented vertebra to prevent DJK, and some studies have provided supportive results. However, other studies demonstrate that lowest instrumented vertebra located in the FLV has similar DJK incidence with the benefit of saving levels.

MATERIALS AND METHODS

Electronic searches of PubMed, Embase, the Cochrane Database, and Web of Science were performed. Radiographic parameters, incidence of DJK, and revision surgery rates were compared between SSV and FLV groups. The odds ratio (OR) was used to identify differences between the groups and P<0.05 was considered statistically significant.

RESULTS

Four studies with a total of 173 patients were included. There were no differences between the SSV and FLV groups in most radiographic parameters. The incidence of DJK among 173 patients was 20.8% (36/173). The SSV group demonstrated a significantly lower DJK rate than the FLV group (OR, 0.11; 95% confidence interval, 0.04-0.30; P<0.0001; I=39%). In this study, 5.9% (5/85) of the SSV group and 43.6% (24/55) of the FLV group developed DJK; 27.8% (10/36) who developed DJK underwent revision surgery, including 25.0% (6/24) in the FLV group and 40.0% (2/5) in the SSV group. The revision surgery rate was lower in the FLV group than in the SSV group, with no statistical difference (OR, 3.27; 95% confidence interval, 0.26-41.73; P=0.36; I=0%).

CONCLUSIONS

The overall DJK rate in Scheuermann disease was 20.8%, and 27.8% of DJK patients needed revision surgery. A distal fusion level including the SSV demonstrated a significantly lower DJK rate.

Distal Junctional Failure Following Pediatric Spinal Fusion

BACKGROUND

Adjacent segment pathology is a known complication after spinal fusion, but little has been reported on junctional failure. A series of adolescent patients presented with acute distal junctional failure (DJF). We sought to determine any common features of these patients to develop a prevention strategy.

METHODS

A retrospective review was conducted of pediatric patients who developed DJF after instrumented spinal fusion performed at 2 institutions from 1999 to 2013. Patients with proximal junctional failure or junctional kyphosis without failure were excluded.

RESULTS

Fifteen subjects were identified with mean follow-up of 38 months. Distal failure occurred a mean of 60 days after index surgery, with history of minor trauma in 4 patients. Failures included 3-column Chance fracture (11) or instrumentation failure (4). Thirteen patients presented with back pain and/or acute kyphosis, whereas 2 asymptomatic patients presented with healed fractures. Two patients also developed new onset of severe lower extremity neurological deficit after fracture, which improved but never resolved after revision. A total of 13/15 subjects required revision surgery, typically within 1 week. Complications associated with revision surgery were encountered in 8 patients (62%). Major complications that required return to the operating room included 2 deep infections, 2 instrumentation failures, and dense lower extremity paralysis that improved after medial screw revision and decompression. At final follow-up, 10 patients are asymptomatic, 2 have persistent neurological deficit, 2 have chronic pain, and 1 has altered gait with gait aid requirement.

CONCLUSIONS

This study analyzes a heterogenous cohort of spinal fusion patients who developed DJF from 3-column Chance fracture or instrumentation failure. Revision surgery is typically required, but has a high complication rate and can result in severe neurological deficit, highlighting the morbidity of this complication. It is unclear whether level of the lowest instrumented vertebra contributes to DJF. Increased awareness of junctional failure in children may prompt additional studies to further characterize risk factors and preventative strategies.

LEVEL OF EVIDENCE

Level IV-study-type case series.