Under-contouring of rods: a potential risk factor for proximal junctional kyphosis after posterior correction of Scheuermann kyphosis.

OBJECTIVE: Scheuermann kyphosis (SK) could require surgical treatment in certain situations. A posterior reduction is the most widespread treatment so far, although the development of proximal junctional kyphosis (PJK) is one of the possible complications of this procedure. The contour of the proximal part of the rod could influence the occurrence of PJK in SK patients. The objective of this study was to analyze the impact of the proximal rod contour on the occurrence of a PJK complication in SK patients. METHODS: This retrospective monocentric study was performed in the Nanjing Spine Surgery Department. All eligible patients had undergone posterior correction surgery with pedicle screws only between 2002 and 2017 and had at least 24 months of follow-up. The presence of PJK was quantified on radiographs using the proximal junctional angle (PJA > 10° at the last follow-up). The authors propose a new radiological parameter to measure the angulation of the proximal part of the instrumentation: the proximal contouring rod angle (PCRA) is the angle between the upper endplate of the upper instrumented vertebra (UIV) and the lower endplate of the second vertebra caudal to the UIV. The patients were analyzed according to the presence or absence of PJK. A t-test, receiver operating characteristic (ROC) curve analysis, and logistic regression analysis were performed for statistical analysis. RESULTS: Sixty-two patients treated for SK were included in this study. The mean age was 18.6 ± 8.5 years, and the mean follow-up was 42.5 ± 16.4 months. The mean correction rate of global kyphosis was 46.4% ± 13.7%. At the last follow-up, 17 patients (27.4%) presented with PJK. No significant difference was found between the PJK and non-PJK groups in terms of age and other preoperative variables. A significant difference in the postoperative PCRA was found between the PJK and non-PJK groups (8.2° ± 4.9° vs 15.7° ± 6.6°, respectively; p = 0.001). A postoperative PCRA less than 10.1° predicted a significantly higher risk for PJK (p = 0.002, OR 2.431, 95% CI 1.781-4.133). CONCLUSIONS: Under-contouring of the proximal part of the rods (lower than 10°) is a risk factor for PJK after posterior correction of SK.

The association between lower Hounsfield units of the upper instrumented vertebra and proximal junctional kyphosis in adult spinal deformity surgery with a minimum 2-year follow-up.

OBJECTIVE: Patients undergoing long-segment fusions from the lower thoracic (LT) spine to the sacrum for adult spinal deformity (ASD) correction are at risk for proximal junctional kyphosis (PJK). One mechanism of PJK is fracture of the upper instrumented vertebra (UIV) or higher (UIV+1), which may be related to bone mineral density (BMD). Because Hounsfield units (HUs) on CT correlate with BMD, the authors evaluated whether HU values were correlated with PJK after long fusions for ASD. METHODS: The authors performed a retrospective study of patients older than 50 years who had undergone ASD correction from the LT spine to the sacrum in the period from October 2007 to January 2018 and had a minimum 2-year follow-up. Demographic and spinopelvic parameters were measured. HU values were measured on preoperative CT at the UIV, UIV+1, and UIV+2 (2 levels above the UIV) levels and were assessed for correlations with PJK. RESULTS: The records of 127 patients were reviewed. Fifty-four patients (19 males and 35 females) with a mean age of 64.91 years and mean follow-up of 3.19 years met the study inclusion criteria; there were 29 patients with PJK and 25 patients without. There was no statistically significant difference in demographics or follow-up between these two groups. Neither was there a difference between the groups with regard to postoperative pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), PI minus LL (PI-LL), thoracic kyphosis (TK), or sagittal vertical axis (SVA; all p > 0.05). Postoperative pelvic tilt (p = 0.003) and T1 pelvic angle (p = 0.014) were significantly higher in patients with PJK than in those without. Preoperative HUs at UIV, UIV+1, and UIV+2 were 120.41, 124.52, and 129.28 in the patients with PJK, respectively, and 152.80, 155.96, and 160.00 in the patients without PJK, respectively (p = 0.011, 0.02, and 0.018). Three receiver operating characteristic (ROC) curves for preoperative HU values at the UIV, UIV+1, and UIV+2 as a predictor for PJK were established, with areas under the ROC curve of 0.710 (95% CI 0.574-0.847), 0.679 (95% CI 0.536-0.821), and 0.681 (95% CI 0.539-0.824), respectively. The optimal HU value by Youden index was 104 HU at the UIV (sensitivity 0.840, specificity 0.517), 113 HU at the UIV+1 (sensitivity 0.720, specificity 0.517), and 110 HU at the UIV+2 (sensitivity 0.880, specificity 0.448). CONCLUSIONS: In patients undergoing long-segment fusions from the LT spine to the sacrum for ASD, PJK was associated with lower HU values on CT at the UIV, UIV+1, and UIV+2. The measurement of HU values on preoperative CTs may be a useful adjunct for ASD surgery planning.

Factors affecting approach selection for minimally invasive versus open surgery in the treatment of adult spinal deformity: analysis of a prospective, nonrandomized multicenter study.

OBJECTIVE: Surgical decision-making and planning is a key factor in optimizing outcomes in adult spinal deformity (ASD). Minimally invasive spinal (MIS) strategies for ASD have been increasingly used as an option to decrease postoperative morbidity. This study analyzes factors involved in the selection of either a traditional open approach or a minimally invasive approach to treat ASD in a prospective, nonrandomized multicenter trial. All centers had at least 5 years of experience in minimally invasive techniques for ASD. METHODS: The study enrolled 268 patients, of whom 120 underwent open surgery and 148 underwent MIS surgery. Inclusion criteria included age ≥ 18 years, and at least one of the following criteria: coronal curve (CC) ≥ 20°, sagittal vertical axis (SVA) > 5 cm, pelvic tilt (PT) > 25°, or thoracic kyphosis (TK) > 60°. Surgical approach selection was made at the discretion of the operating surgeon. Preoperative significant differences were included in a multivariate logistic regression analysis to determine odds ratios (ORs) for approach selection. RESULTS: Significant preoperative differences (p < 0.05) between open and MIS groups were noted for age (61.9 vs 66.7 years), numerical rating scale (NRS) back pain score (7.8 vs 7), CC (36° vs 26.1°), PT (26.4° vs 23°), T1 pelvic angle (TPA; 25.8° vs 21.7°), and pelvic incidence-lumbar lordosis (PI-LL; 19.6° vs 14.9°). No significant differences in BMI (29 vs 28.5 kg/m2), NRS leg pain score (5.2 vs 5.7), Oswestry Disability Index (48.4 vs 47.2), Scoliosis Research Society 22-item questionnaire score (2.7 vs 2.8), PI (58.3° vs 57.1°), LL (38.9° vs 42.3°), or SVA (73.8 mm vs 60.3 mm) were found. Multivariate analysis found that age (OR 1.05, p = 0.002), VAS back pain score (OR 1.21, p = 0.016), CC (OR 1.03, p < 0.001), decompression (OR 4.35, p < 0.001), and TPA (OR 1.09, p = 0.023) were significant factors in approach selection. CONCLUSIONS: Increasing age was the primary driver for selecting MIS surgery. Conversely, increasingly severe deformities and the need for open decompression were the main factors influencing the selection of traditional open surgery. As experience with MIS surgery continues to accumulate, future longitudinal evaluation will reveal if more experience, use of specialized treatment algorithms, refinement of techniques, and technology will expand surgeon adoption of MIS techniques for adult spinal deformity.

Complication profile associated with S1 pedicle subtraction osteotomy compared with 3-column osteotomies at other thoracolumbar levels for adult spinal deformity: series of 405 patients with 9 S1 osteotomies.

OBJECTIVE: There is an increased recognition of disproportional lumbar lordosis (LL) and artificially high pelvic incidence (PI) as a cause for positive sagittal imbalance and spinal pelvic mismatch. For such cases, a sacral pedicle subtraction osteotomy (PSO) may be indicated, although its morbidity is not well described. In this study, the authors evaluate the specific complication risks associated with S1 PSO. METHODS: A retrospective review of all adult spinal deformity patients who underwent a 3-column osteotomy (3CO) for thoracolumbar deformity from 2006 to 2019 was performed. Demographic, clinical baseline, and radiographic parameters were recorded. The primary outcome of interest was perioperative complications (surgical, neurological, and medical). Secondary outcomes of interest included case length, blood loss, and length of stay. Multivariate analysis was used to assess the risk of S1 PSO compared with 3CO at other levels. RESULTS: A total of 405 patients underwent 3CO in the following locations: thoracic (n = 55), L1 (n = 25), L2 (n = 29), L3 (n = 141), L4 (n = 129), L5 (n = 17), and S1 (n = 9). After S1 PSO, there were significant improvements in the sagittal vertical axis (14.8 cm vs 6.7 cm, p = 0.004) and PI-LL mismatch (31.7° vs 9.6°, p = 0.025) due to decreased PI (80.3° vs 65.9°, p = 0.006). LL remained unchanged (48.7° vs 57.8°, p = 0.360). The overall complication rate was 27.4%; the surgical, neurological, and medical complication rates were 7.7%, 6.2%, and 20.0%, respectively. S1 PSO was associated with significantly higher rates of overall complications: thoracic (29.1%), L1 (32.0%), L2 (31.0%), L3 (19.9%), L4 (32.6%), L5 (11.8%), and S1 (66.7%) (p = 0.018). Similarly, an S1 PSO was associated with significantly higher rates of surgical (thoracic [9.1%], L1 [4.0%], L2 [6.9%], L3 [5.7%], L4 [10.9%], L5 [5.9%], and S1 [44.4%], p = 0.006) and neurological (thoracic [9.1%], L1 [0.0%], L2 [6.9%], L3 [2.8%], L4 [7.0%], L5 [5.9%], and S1 [44.4%], p < 0.001) complications. On multivariate analysis, S1 PSO was independently associated with higher odds of overall (OR 7.93, p = 0.013), surgical (OR 20.66, p = 0.010), and neurological (OR 14.75, p = 0.007) complications. CONCLUSIONS: S1 PSO is a powerful technique for correction of rigid sagittal imbalance due to an artificially elevated PI in patients with rigid high-grade spondylolisthesis and chronic sacral fractures. However, the technique and intraoperative corrective maneuvers are challenging and associated with high surgical and neurological complications. Additional investigations into the learning curve associated with S1 PSO and complication prevention are needed.

Two different types of postoperative sagittal imbalance after long instrumented fusion to the sacrum for degenerative sagittal imbalance.

OBJECTIVE: Few studies have addressed that dynamic sagittal imbalance can develop distal to the spinal fusion and cause sagittal malalignment, unlike proximal junctional kyphosis (PJK) in the proximal portion. The purpose of this study was to investigate risk factors between the 2 different types of postoperative sagittal imbalance after long fusion to the sacrum for the treatment of degenerative sagittal imbalance (DSI). METHODS: Eighty patients who had undergone surgical correction for DSI were included. Radiographic measurements included spinopelvic parameters on whole-spine plain radiographs and degeneration of paravertebral muscles on MRI. Univariate and multivariate analyses for clinical and radiological factors were conducted for respective risk factors. In subgroup analyses, the 2 different types of postoperative sagittal imbalance were directly compared. RESULTS: Forty patients (50%) developed postoperative sagittal imbalance; of these patients, 22 (55.0%) developed static proximal kyphosis from PJK, and 18 patients (45.0%) developed dynamic sagittal imbalance without PJK. The independent risk factors in proximal kyphosis were greater postoperative pelvic tilt (HR 1.11) and less change in sacral slope (SS) (HR 1.09), whereas there were more fusion levels (HR 3.11), less change in SS (HR 1.28), and less change in thoracic kyphosis (HR 1.26) in dynamic sagittal imbalance. Directly compared with the proximal kyphosis group, dynamic sagittal imbalance was more commonly found in patients who had less correction of sagittal parameters as well as fatty atrophy of the paravertebral muscles. Clinical outcomes in the dynamic sagittal imbalance group were superior to those in the proximal kyphosis group. CONCLUSIONS: Optimal correction of sagittal alignment should be considered in long instrumented fusion for DSI, because insufficient correction might cause one of 2 different types of postoperative sagittal imbalance at different sites of decompression. Dynamic sagittal imbalance compared with proximal kyphosis was significantly associated with less correction of sagittal alignment, in conjunction with more fusion levels and degeneration of the paravertebral muscles.

How does sagittal spinopelvic alignment of lumbar multisegmental spondylolysis differ from monosegmental spondylolysis?

OBJECTIVE: The aim of this study was to investigate sagittal alignment and compensatory mechanisms in patients with monosegmental spondylolysis (mono_lysis) and multisegmental spondylolysis (multi_lysis). METHODS: A total of 453 adult patients treated for symptomatic low-grade spondylolytic spondylolisthesis were retrospectively studied at a single center. Patients were divided into 2 subgroups, the mono_lysis group and the multi_lysis group, based on the number of spondylolysis segments. A total of 158 asymptomatic healthy volunteers were enrolled in this study as the control group. Radiographic parameters measured on standing sagittal radiographs and the ratios of L4-S1 segmental lordosis (SL) to lumbar lordosis (L4-S1 SL/LL) and pelvic tilt to pelvic incidence (PT/PI) were compared between all experimental groups. RESULTS: There were 51 patients (11.3%) with a diagnosis of multi_lysis in the spondylolysis group. When compared with the control group, the spondylolysis group exhibited larger PI (p < 0.001), PT (p < 0.001), LL (p < 0.001), and L4-S1 SL (p = 0.025) and a smaller L4-S1 SL/LL ratio (p < 0.001). When analyzing the specific spondylolysis subgroups, there were no significant differences in PI, but the multi_lysis group had a higher L5 incidence (p = 0.004), PT (p = 0.018), and PT/PI ratio (p = 0.039). The multi_lysis group also had a smaller L4-S1 SL/LL ratio (p = 0.012) and greater sagittal vertical axis (p < 0.001). CONCLUSIONS: A high-PI spinopelvic pattern was involved in the development of spondylolytic spondylolisthesis, and a larger L5 incidence might be associated with the occurrence of consecutive multi_lysis. Unlike patients with mono_lysis, individuals with multi_lysis were characterized by an anterior trunk, insufficiency of L4-S1 SL, and pelvic retroversion.

Association between a prognostic nutritional index less than 50 and the risk of medical complications after adult spinal deformity surgery.

OBJECTIVE: Many complications are likely to occur in patients with malnutrition. The prognostic nutritional index (PNI) is often used when evaluating a patient's nutritional condition. However, no studies have investigated the association between nutritional status and postoperative medical complications or prognosis by using the PNI in the field of spinal surgery. The purpose of this retrospective study was to investigate postoperative medical complications and prognoses of patients who had undergone adult spinal deformity (ASD) surgery, according to their preoperative nutritional status. METHODS: All patients aged ≥ 40 years who had undergone scheduled ASD surgery in the authors' hospital between March 2010 and June 2017 were eligible for study inclusion and were divided into groups according to their PNI (< 50, group L; ≥ 50, group H). Medical complications diagnosed within 30 days postoperatively were evaluated; however, surgical site infection and death were evaluated until 1 and 5 years after surgery, respectively. RESULTS: Among the 285 eligible patients, groups L and H consisted of 118 and 167 patients, whose mean ages were 68.6 and 68.3 years, respectively. There was a significant difference in body mass index (22 vs 24 mg/kg2, respectively, p = 0.000), PNI (46 vs 55, p = 0.000), comorbidity of osteoporosis (50% vs 32%, p = 0.005) and autoimmune disease (13% vs 5%, p = 0.036), medical history of malignant disorder (17% vs 6%, p = 0.007), and medical complications (49% vs 23%, p = 0.000) between groups L and H. Multiple logistic regression analysis suggested that significant risk factors for postoperative medical complications were male sex (p = 0.000, OR 3.5, 95% CI 1.78-6.96), PNI < 50 (p = 0.000, OR 2.9, 95% CI 1.69-4.93), and days to ambulation (p = 0.003, OR 1.1, 95% CI 1.02-1.09). CONCLUSIONS: Medical complication rates are significantly higher in patients with PNI < 50, those with delayed ambulation, and male patients. In malnourished patients scheduled for ASD surgery, improvement of preoperative nutritional status and postoperative early ambulation are important to avoid medical complications.

Impact of knee osteoarthritis on surgical outcomes of lumbar spinal canal stenosis.

OBJECTIVE: Lumbar spinal canal stenosis (LSS) and knee osteoarthritis (KOA), both of which are age-related degenerative diseases, are independently correlated with increased pain and dysfunction of the lower extremities. However, there have been few studies that investigated whether LSS patients with KOA exhibit poor clinical recovery following lumbar spinal surgery. The aim of this study was to elucidate the surgical outcomes of lumbar spinal surgery for LSS patients with KOA using multiple health-related quality of life (HRQOL) parameters. METHODS: A total of 865 consecutive patients who underwent posterior lumbar spinal surgery for LSS were retrospectively reviewed. Baseline characteristics, radiographic parameters, perioperative factors, and multiple HRQOL parameters were analyzed preoperatively and at 1-year follow-up. HRQOL items included the Zurich Claudication Questionnaire, Oswestry Disability Index, Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). The effectiveness of surgical treatment was assessed using the JOABPEQ. The treatment was regarded as effective when it resulted in an increase in postoperative JOABPEQ score by ≥ 20 points compared with preoperative score or achievement of a postoperative score of ≥ 90 points in those with a preoperative score of < 90 points. RESULTS: A total of 32 LSS patients with KOA were identified, and 128 age- and sex-matched LSS patients without KOA were selected as controls. In both groups, all HRQOL parameters markedly improved at the 1-year follow-up. On the SF-36, the postoperative mean score for the role physical domain was significantly lower in the KOA group than in the control group (p = 0.034). The treatment was significantly less "effective" in the social life domain of JOABPEQ in the KOA group than in the control group (p < 0.001). CONCLUSIONS: The surgical outcomes of LSS patients with KOA are favorable, although poorer than those of LSS patients without KOA, particularly in terms of social life and activities. These results indicate that LSS patients with KOA experience difficulty in routine work or ordinary activities due to knee pain or restricted knee ROM even after lumbar spinal surgery. Hence, preoperative KOA status warrants consideration when planning lumbar spinal surgery and estimating surgical outcomes of LSS.

Upper-thoracic versus lower-thoracic upper instrumented vertebra in adult spinal deformity patients undergoing fusion to the pelvis: surgical decision-making and patient outcomes.

OBJECTIVE: Optimal patient selection for upper-thoracic (UT) versus lower-thoracic (LT) fusion during adult spinal deformity (ASD) correction is challenging. Radiographic and clinical outcomes following UT versus LT fusion remain incompletely understood. The purposes of this study were: 1) to evaluate demographic, radiographic, and surgical characteristics associated with choice of UT versus LT fusion endpoint; and 2) to evaluate differences in radiographic, clinical, and health-related quality of life (HRQOL) outcomes following UT versus LT fusion for ASD. METHODS: Retrospective review of a prospectively collected multicenter ASD database was performed. Patients with ASD who underwent fusion from the sacrum/ilium to the LT (T9-L1) or UT (T1-6) spine were compared for demographic, radiographic, and surgical characteristics. Outcomes including proximal junctional kyphosis (PJK), reoperation, rod fracture, pseudarthrosis, overall complications, 2-year change in alignment parameters, and 2-year HRQOL metrics (Lumbar Stiffness Disability Index, Scoliosis Research Society-22r questionnaire, Oswestry Disability Index) were compared after controlling for confounding factors via multivariate analysis. RESULTS: Three hundred three patients (169 LT, 134 UT) were evaluated. Independent predictors of UT fusion included greater thoracic kyphosis (odds ratio [OR] 0.97 per degree, p = 0.0098), greater coronal Cobb angle (OR 1.06 per degree, p < 0.0001), and performance of a 3-column osteotomy (3-CO; OR 2.39, p = 0.0351). While associated with longer operative times (ratio 1.13, p < 0.0001) and greater estimated blood loss (ratio 1.31, p = 0.0018), UT fusions resulted in greater sagittal vertical axis improvement (-59.5 vs -41.0 mm, p = 0.0035) and lower PJK rates (OR 0.49, p = 0.0457). No significant differences in postoperative HRQOL measures, reoperation, or overall complication rates were detected between groups (all p > 0.1). CONCLUSIONS: Greater deformity and need for 3-CO increased the likelihood of UT fusion. Despite longer operative times and greater blood loss, UT fusions resulted in better sagittal correction and lower 2-year PJK rates following surgery for ASD. While continued surveillance is necessary, this information may inform patient counseling and surgical decision-making.

Natural history of the aging spine: a cross-sectional analysis of spinopelvic parameters in the asymptomatic population.

OBJECTIVE: There have been numerous studies demonstrating increased pain and disability when patients' spinopelvic parameters fall outside of certain accepted ranges. However, these values were established based on patients suffering from spinal deformities. It remains unknown how these parameters change over a lifetime in asymptomatic individuals. The goal of this study was to define a range of spinopelvic parameters from asymptomatic individuals. METHODS: Sagittal scoliosis radiographs of 210 asymptomatic patients were evaluated. All measurements were reviewed by 2 trained observers, supervised by a trained clinician. The following parameters and relationships were measured or calculated: cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sagittal vertical axis (SVA), cervical SVA (cSVA), and T1 slope, TK/LL, truncal inclination, pelvic tilt (PT), LL-PI, LL/PI, and T1 slope/PI. Patients were stratified by decade of life, and regression analysis was performed to delineate the relationship between each consecutive age group and the aforementioned parameters. RESULTS: Cervical lordosis (R2 = 0.61), thoracic kyphosis (R2 = 0.84), SVA (R2 = 0.88), cSVA (R2 = 0.51), and T1 slope (R2 = 0.77) all increase with age. Truncal inclination (R2 = 0.36) and T1 slope/CL remain stable over all decades (R2 = 0.01). LL starts greater than PI, but in the 6th decade of life, LL becomes equal to PI and in the 7th decade becomes smaller than PI (R2 = 0.96). The ratio of TK/LL is stable until the 7th decade of life (R2 = 0.81), whereas PT is stable until the 6th decade (R2 = 0.92). CONCLUSIONS: This study further refines the generally accepted LL = PI + 10° by showing that patients under the age of 50 years should have more LL compared to PI, whereas after the 5th decade the relationship is reversed. SVA was not as sensitive across age groups, exhibiting a marked increase only in the 7th decade of life. Given the reliable increase of CL with age, and the stability of T1 slope/CL, this represents another important relationship that should be maintained when performing cervical deformity/fusion surgery. This study has important implications for evaluating adult patients with spinal deformities and for establishing corrective surgical goals.

Proximal fusion constructs in minimally invasive scoliosis surgery are successful without interbody or intertransverse fusion.

OBJECTIVE: Minimally invasive techniques are increasingly used in adult deformity surgery as surgeon familiarity improves and long-term data are published. Concerns raised in such cases include pseudarthrosis at levels where interbody grafts are not utilized. Few previous studies have specifically examined the thoracolumbar component of long surgical constructs, which is commonly instrumented without interbody or intertransverse fusion. METHODS: A retrospective analysis was performed on all patients who underwent hybrid minimally invasive deformity corrections in two academic spine centers over a 9-year period. Inclusion criteria were at least 2 rostral levels instrumented percutaneously, ranging from T8 to L1 as the upper end of the construct. Fusion assessment was made using CT when possible or radiography. Common radiographic parameters and clinical variables were assessed pre- and postoperatively. RESULTS: A total of 36 patients fit the inclusion criteria. Baseline characteristics included a 1:1.8 male/female ratio, average age of 65.7 years, and BMI of 30.2 kg/m2. Follow-up imaging was obtained at a mean of 35.7 months. The average number of levels fused was 7.5, with an average of 3.4 instrumented percutaneously between T8 and L1, representing a total of 120 rostral levels instrumented percutaneously. Fusion assessment was performed using CT in 69 levels and radiography in 51 levels. Among the 120 rostral levels instrumented percutaneously, robust fusion was noted in 25 (20.8%), with 53 (44.2%) exhibiting some evidence of fusion. Pseudarthrosis was noted in 2 rostral segments (1.7%). There were no instances of proximal hardware revision. Eight patients exhibited radiographic proximal junctional kyphosis (PJK; 22.2%), none of whom underwent surgical intervention. CONCLUSIONS: In the present series of adult patients with scoliosis undergoing thoracolumbar deformity correction, rostral segments instrumented percutaneously have a very low rate of pseudarthrosis, with radiographic evidence of bone fusion occurring in more than 60% of patients. The rate of PJK was acceptable and similar to other published series.

Upper instrumented vertebra to the right of the lowest instrumented vertebra as a predictor of an increase in the main thoracic curve after selective posterior fusion for the thoracolumbar/lumbar curve in Lenke type 5C adolescent idiopathic scoliosis: multicenter study on the relationship between fusion area and surgical outcome.

OBJECTIVE: Unfused main thoracic (MT) curvatures occasionally increase after selective thoracolumbar/lumbar (TL/L) fusion. This study sought to identify the predictors of an unacceptable increase in MT curve (UIMT) after selective posterior fusion (SPF) of the TL/L curve in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS). METHODS: Forty-eight consecutive patients (44 females and 4 males, mean age 15.7 ± 2.5 years, range 13-24 years) with Lenke type 5C AIS who underwent SPF of the TL/L curve were analyzed. The novel "Shinshu line" (S-line) was defined as a line connecting the centers of the concave-side pedicles of the upper instrumented vertebra (UIV) and lowest instrumented vertebra (LIV) on preoperative radiographs. The authors established an S-line tilt to the right as S-line positive (S-line+, i.e., the UIV being to the right of the LIV) and compared S-line+ and S-line- groups for thoracic apical vertebral translation (T-AVT) and MT Cobb angle preoperatively, early postoperatively, and at final follow-up. The predictors for T-AVT > 20 mm at final follow-up were evaluated as well. T-AVT > 20 mm was defined as a UIMT. RESULTS: Among the 48 consecutively treated patients, 26 were S-line+ and 22 were S-line-. At preoperative, early postoperative, and final follow-up a minimum of 2 years later, the mean T-AVT was 12.8 mm (range -9.3 to 32.8 mm), 19.6 mm (range -13.0 to 41.0 mm), and 22.8 mm (range -1.9 to 68.7 mm) in the S-line+ group, and 10.8 mm (range -5.1 to 27.3 mm), 16.2 mm (range -11.7 to 42.1 mm), and 11.0 mm (range -6.3 to 26.9 mm) in the S-line- group, respectively. T-AVT in S-line+ patients was significantly larger than that in S-line- patients at the final follow-up. Multivariate analysis revealed S-line+ (odds ratio [OR] 23.8, p = 0.003) and preoperative MT Cobb angle (OR 7.9, p = 0.001) to be predictors of a UIMT. CONCLUSIONS: S-line+ was defined as the UIV being to the right of the LIV. T-AVT in the S-line+ group was significantly larger than in the S-line- group at the final follow-up. S-line+ status and larger preoperative MT Cobb angle were independent predictors of a UIMT after SPF for the TL/L curve in patients with Lenke type 5C AIS. Surgeons should consider changing the UIV and/or LIV in patients exhibiting S-line+ during preoperative planning to avoid a possible increase in MT curve and revision surgery.

Is the apical vertebra the most rotated vertebra in the scoliotic curve?

OBJECTIVE: The aim of this study was to determine if the apical vertebra (AV) in patients with adolescent idiopathic scoliosis (AIS) is the most rotated vertebra in the scoliotic segment. METHODS: A total of 158 patients with AIS (Cobb angle range 20°-101°) underwent biplanar radiography with 3D reconstructions of the spine and calculation of vertebral axial rotations. The type of major curvature was recorded (thoracic, thoracolumbar, or lumbar), and both major and minor curvatures were included. The difference of levels (DL) between the level of maximal vertebral rotation (LMVR) and the AV was calculated as follows: DL = 0 if LMVR and AV were the same, DL = 1 if LMVR was directly above or below the AV, and DL = 2 if LMVR was separated by 1 vertebra or more from the AV. To investigate which factors explained the divergence of the LMVR from the AV, multinomial models were computed. RESULTS: The distribution of the DL was as follows: for major curvatures, 143 were DL = 0, 11 were DL = 1, and 4 were DL = 2; and for minor curvatures, 53 were DL = 0, 9 were DL = 1, and 31 were DL = 2. The determinants of a DL = 2 (compared with DL = 0) were lumbar curvature (compared with thoracic; adjusted OR 0.094, p = 0.001), major curvature (compared with minor; adjusted OR 0.116, p = 0.001), and curvatures with increasing apical vertebral rotation (adjusted OR 0.788, p < 0.001). CONCLUSIONS: This study showed that the AV is the most rotated vertebra in the majority of major curvatures, while in minor curvatures, the most rotated vertebra appears to be the junctional vertebra between major and minor curvatures in a significant proportion of cases.

Preliminary report on the flexible rod technique for prevention of proximal junctional kyphosis following long-segment fusion to the sacrum in adult spinal deformity.

OBJECTIVE: The incidence of proximal junctional kyphosis (PJK) after long-segment fixation in patients with adult spinal deformity (ASD) has been reported to range from 17% to 61.7%. Recent studies have reported using "hybrid" techniques in which semirigid fixation is introduced between the fused and flexible segments at the proximal level to allow a more gradual transition. The authors used these hybrid techniques in a clinical setting and analyzed PJK to evaluate the usefulness of the flexible rod (FR) technique. METHODS: The authors retrospectively selected 77 patients with lumbar degenerative kyphosis (LDK) who underwent sagittal correction and long-segment fixation and had follow-up for > 1 year. An FR was used in 30 of the 77 patients. PJK development and spinal sagittal changes were analyzed in the FR and non-FR groups, and the predictive factors of PJK between a PJK group and a non-PJK group were compared. RESULTS: The patient population comprised 77 patients (75 females and 2 males) with a mean (± SD) follow-up of 32.0 ± 12.7 months (36.7 ± 9.8 months in the non-FR group and 16.8 ± 4.7 months in the FR group) and mean (± SD) age of 71.7 ± 5.1 years. Sagittal balance was well maintained at final follow-up (10.5 and 1.5 mm) in the non-FR and FR groups, respectively. Thoracic kyphosis (TK) and lumbar lordosis (LL) were improved in both groups, without significant differences between the two (p > 0.05). PJK occurred in 28 cases (36.4%) in total, 3 (10%) in the FR and 25 (53.2%) in the non-FR group (p < 0.001). Postoperatively, PJK was observed at an average of 8.9 months in the non-FR group and 1 month in the FR group. No significant differences in the incidence of PJK regarding patient factors or radiological parameters were found between the PJK group and non-PJK group (p > 0.05). However, FR (vs non-FR) and interbody fusion except L5-S1 using oblique lumbar interbody fusion (vs non-oblique lumbar interbody fusion), demonstrated a significantly lower PJK prevalence (p < 0.001 and p = 0.044) among the surgical factors. CONCLUSIONS: PJK was reduced after surgical treatment with the FR in the patients with LDK. Solid long-segment fixation and the use of the FR may become another surgical option for spine surgeons who plan and make decisions regarding spine reconstruction surgery for patients with ASD.

Effect of segmental lordosis on the clinical outcomes of 2-level posterior lumbar interbody fusion for 2-level degenerative lumbar spondylolisthesis.

OBJECTIVE: Although the importance of spinopelvic sagittal balance and its implications for clinical outcomes of spinal fusion surgery have been described, to the authors' knowledge there have been no reports of the relationship between spinopelvic alignment and clinical outcomes for 2-level posterior lumbar interbody fusion (PLIF). The purpose of this study was to elucidate the relationship between clinical outcomes and spinopelvic sagittal parameters after 2-level PLIF for 2-level degenerative spondylolisthesis (DS). METHODS: This study was limited to patients who were treated with 2-level PLIF for 2-level DS at L3-4-5. Between 2005 and 2014, 33 patients who could be followed up for at least 2 years were included in this study. The average age at the time of surgery was 72 years, and the average follow-up period was 5.6 years. Based on clinical assessments, the Japanese Orthopaedic Association (JOA) score and recovery rate were evaluated. The patients were divided into 2 groups based on the recovery rate: the good outcome group (G group; n = 19), with recovery rate ≥ 50%, and the poor outcome group (P group; n = 14) with recovery rate < 50%. Spinopelvic parameters were measured using lateral standing radiographs of the whole spine as follows: sagittal vertical axis (SVA), thoracic kyphosis (TK), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), and segmental lordosis (SL) at L3-4-5. The clinical outcomes and radiological parameters were assessed preoperatively and at the final follow-up. Radiological parameters were compared between the 2 groups. RESULTS: The mean JOA score improved significantly in all patients from 10.8 points before surgery to 19.6 points at the latest follow-up (mean recovery rate 47.7%). For radiological outcomes, no difference was observed from preoperative assessment to final follow-up in any of the spinopelvic parameters except SVA. Although no significant difference between the 2 groups was detected in any of the spinopelvic parameters, there were significant differences in the change in SL and LL (ΔSL 3.7° vs -2.1° and ΔLL 1.2° vs -5.6° for the G and P groups, respectively). In addition, the number of patients in the G group was significantly larger for the patients with ΔSL-plus than those with ΔSL-minus (p = 0.008). CONCLUSIONS: The clinical outcomes of 2-level PLIF for 2-level DS limited at L3-4-5 appeared to be satisfactory. The results indicate that acquisition of increased SL in surgery might lead to better clinical outcomes.

How does the cervical spine respond to hyperkyphosis correction in Scheuermann's disease?

OBJECTIVE: This study aimed to quantify the response of the cervical spine to the surgical correction of Scheuermann's kyphosis (SK) and to postoperative proximal junctional kyphosis (PJK). METHODS: Fifty-nine patients (mean age 14.6 ± 2.3 years) were enrolled in the study: 35 patients in a thoracic SK (T-SK) group and 24 in a thoracolumbar SK (TL-SK) group. The mean follow-up period was 47.2 ± 17.6 months. Radiographic data, PJK-related complications, and patient-reported outcomes were compared between groups. RESULTS: The global kyphosis significantly decreased postoperatively, and similar correction rates were observed between the two groups (mean 47.1% ± 8.6% [T-SK] vs 45.8% ± 9.4% [TL-SK], p = 0.585). The cervical lordosis (CL) in the T-SK group notably decreased from 21.4° ± 13.3° to 13.1° ± 12.4° after surgery and was maintained at 14.9° ± 10.7° at the latest follow-up, whereas in the TL-SK group, CL considerably increased from 7.2° ± 10.7° to 11.7° ± 11.1° after surgery and to 13.8° ± 8.9° at the latest follow-up. PJK was identified in 16 patients (27.1%). Its incidence in the TL-SK group was notably higher than it was in the T-SK group (41.6% [n = 10] vs 17.1% [n = 6], p = 0.037). Compared with non-PJK patients, PJK patients had greater CL and lower pain scores on the Scoliosis Research Society-22 questionnaire (p < 0.05). CONCLUSIONS: Hyperkyphosis correction eventually resulted in reciprocal changes in the cervical spine, with CL notably decreased in the T-SK group but significantly increased in the TL-SK group. Patients developing PJK have increased CL, which seems to have a negative effect on patients' health-related quality of life.

Novel radiographic parameters for the assessment of total body sagittal alignment in adult spinal deformity patients.

OBJECTIVE: In this study, the authors' goal was to develop and validate novel radiographic parameters that better describe total body sagittal alignment (TBSA). METHODS: One hundred sixty-six consecutive operative spinal deformity patients were evaluated using full-body stereoradiographic imaging. Seven TBSA parameters were measured and then correlated to 6 commonly used spinopelvic measurements. TBSA measures consisted of 4 distance measures relating the cranial center of mass (CCOM) to the sacrum, hips, knees, and ankles, and 3 angular measures relating the CCOM to the hips, knees, and ankles. Furthermore, each TBSA parameter was correlated to patient-reported outcome (PRO) scores using the Oswestry Disability Index (ODI) and Scoliosis Research Society-22 (SRS-22) instruments. Thirty patients were randomly selected for inter- and intraobserver reliability testing of the TBSA parameters using intraclass correlation coefficients (ICCs). RESULTS: All TBSA radiographic parameters demonstrated strong linear correlation with the currently accepted primary measure of sagittal balance, the C7 sagittal vertical axis (r = 0.55-0.96, p < 0.001). Moreover, 5 of 7 TBSA measures correlated strongly with ODI and SRS-22 total scores (r = 0.42-0.51, p < 0.001). Inter- and intraobserver reliability for all TBSA measures was good to excellent (interrater ICC = 0.70-0.98, intrarater ICC = 0.77-1.0). CONCLUSIONS: In spine deformity patients, novel TBSA radiographic parameters correlated well with PROs and with currently utilized spinal sagittal measurements. Inter- and intrarater reliability was high for these novel parameters. This is the first study to propose a reliable method for measuring head-to-toe global spinal alignment.

Factors influencing patient satisfaction after adult scoliosis and spinal deformity surgery.

OBJECTIVE: Achieving high patient satisfaction with management is often one of the goals after adult spinal deformity (ASD) surgery. However, literature on associated factors and their correlations with patient satisfaction is limited. The aim of this study was to determine the clinical and radiographic factors independently correlated with patient satisfaction in terms of management at 2 years after surgery. METHODS: A multicenter prospective database of ASD surgery was retrospectively reviewed. The demographics, complications, health-related quality of life (HRQOL) subdomains, and radiographic parameters were examined to determine their correlation coefficients with the Scoliosis Research Society-22 questionnaire (SRS-22R) satisfaction scores at 2 years (Sat-2y score). Subsequently, factors determined to be independently associated with low satisfaction (Sat-2y score ≤ 4.0) were used to construct 2 types of multivariate models: one with 2-year data and the other with improvement (score at 2 years - score at baseline) data. RESULTS: A total of 422 patients who underwent ASD surgery (mean age 53.1 years) were enrolled. All HRQOL subdomains and several coronal and sagittal radiographic parameters had significantly improved 2 years after surgery. The Sat-2y score was strongly correlated with the SRS-22R self-image (SI)/appearance subdomain (r = 0.64), followed by moderate correlation with subdomains related to standing (r = 0.53), body pain (r = 0.49-0.55), and function (r = 0.41-0.55) at 2 years. Conversely, the correlation between radiographic or demographic parameters with Sat-2y score was weak (r < 0.4). Multivariate analysis to eliminate confounding factors revealed that a worse Oswestry Disability Index (ODI) score for standing (≥ 2 points; OR 4.48) and pain intensity (≥ 2 points; OR 2.07), SRS-22R SI/appearance subdomain (< 3 points; OR 2.70) at 2 years, and a greater sagittal vertical axis (SVA) (> 5 cm; OR 2.68) at 2 years were independent related factors for low satisfaction. According to the other model, a lower improvement in ODI for standing (< 30%; OR 2.68), SRS-22R pain (< 50%; OR 3.25) and SI/appearance (< 50%; OR 2.18) subdomains, and an inadequate restoration of the SVA from baseline (< 2 cm; OR 3.16) were associated with low satisfaction. CONCLUSIONS: Self-image, pain, standing difficulty, and sagittal alignment restoration may be useful goals in improving patient satisfaction with management at 2 years after ASD surgery. Surgeons and other medical providers have to take care of these factors to prevent low satisfaction.

Does relocation of the apex after osteotomy affect surgical and clinical outcomes in patients with ankylosing spondylitis and thoracolumbar kyphosis?

OBJECTIVE: Relocation of the apex is often found in patients with ankylosing spondylitis (AS)-associated thoracolumbar/lumbar kyphosis after corrective surgery. This study evaluates the influence of different postoperative apex locations on surgical and clinical outcomes of osteotomy for patients with AS and thoracolumbar kyphosis. METHODS: Sixty-two patients with a mean age of 34.6 ± 9.7 years (range 17-59 years) and a minimum of 2 years of follow-up, who underwent 1-level lumbar pedicle subtraction osteotomy for AS-related thoracolumbar kyphosis, were enrolled in the study, as well as 62 age-matched healthy individuals. Patients were divided into 2 groups according to the postoperative location of the apex (group 1, T8 or above; group 2, T9 or below). Demographic data, radiographic measurements (including 3 postoperative apex-related parameters), and clinical outcomes were compared between the 2 groups preoperatively, postoperatively, and at the last follow-up. Furthermore, a subgroup analysis was performed among patients with a postoperative apex located at T6-11 and postoperatively the entire AS cohort was compared with normal controls regarding the apex location of the thoracic spine. RESULTS: In the majority of the enrolled patients, the apex location changed from T12-L2 preoperatively to T6-9 postoperatively. The sagittal vertical axis (SVA) differed significantly both postoperatively (25.7 vs 59.0 mm, p = 0.001) and at the last follow-up (34.6 vs 59.9 mm, p = 0.003) between the 2 groups, and the patients in group 1 had significantly smaller horizontal distance between the C7-vertical line and the apex (DCA) than the patients in group 2 (67.5 vs 103.7 mm, p = 0.001). Subgroup analysis demonstrated similar results, showing that the patients with a postoperative apex located at T8 or above had an average SVA < 47 mm. Notably, a significant correlation was found between postoperative SVA and DCA (r = 0.642, p = 0.001). Patients who underwent an osteotomy at L3 had limited apex relocation but larger SVA correction than those at L1 or L2. However, no significant difference was found in health-related quality of life between the 2 groups. CONCLUSIONS: AS patients with an apex located at T8 or above after surgery tended to have better SVA correction (within 47 mm) than those who had a more caudally located apical vertebra. For ideal postoperative apex relocation, a higher (closer to or at the preoperative apex) level of osteotomy is more likely to obtain the surgical goal.

Impact of decompression surgery without fusion for lumbar spinal stenosis on sagittal spinopelvic alignment: minimum 2-year follow-up.

OBJECTIVEThe importance of global sagittal alignment is well known. Patients with lumbar spinal stenosis (LSS) generally tend to bend forward to relieve their neurological symptoms, i.e., they have a positive sagittal vertical axis (SVA). We hypothesized that the positive SVA associated with LSS is symptom related and should improve after surgery. However, little is known about the changes in sagittal alignment in LSS patients after decompression surgery. In this study the authors aimed to evaluate midterm radiographical changes in sagittal spinopelvic alignment after decompression surgery for LSS and to determine the factors influencing the improvement in sagittal spinopelvic alignment.METHODSThe authors retrospectively reviewed 89 patients who underwent lumbar decompression without fusion between January 2014 and September 2015 with a minimum follow-up of 2 years. Standing whole-spine radiographs at the preoperative stage and at the final follow-up were examined. We analyzed SVA, lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), thoracolumbar kyphosis (TLK), and thoracic kyphosis (TK).RESULTSLL and TK were significantly increased postoperatively. SVA and PI minus LL (PI-LL) were significantly decreased. There were no significant differences between the preoperative and postoperative PT, PI, SS, or TLK. Twenty-nine patients had preoperative sagittal malalignment with SVA > 50 mm. Thirteen of the 29 patients improved to SVA < 50 mm after decompression surgery. Lower ASA grade, preoperative higher LL, and lower PI-LL were related to patient improvement. A receiver operating characteristic curve for the preoperative PI-LL had an area under the curve value of 0.821, indicating moderate accuracy (p = 0.003). A cutoff value for preoperative PI-LL of 19.2° showed a sensitivity of 93.5% and a specificity of 71.4%.CONCLUSIONSLumbar decompression can lead to a reactive improvement in the lumbar and global sagittal alignment. However, some of the sagittal malalignment in LSS was irreversible. Preoperative PI-LL was a useful predictor to distinguish reversible from irreversible sagittal malalignment.