OBJECTIVE Proximal junctional kyphosis (PJK) remains problematic following multilevel instrumented spine surgery. Previous biomechanical studies indicate that providing less rigid fixation at the ...cranial aspect of a long posterior instrumented construct, via transition rods or hooks at the upper instrumented vertebra (UIV), may provide a gradual transition to normal motion and prevent PJK. The purpose of this study was to evaluate the ability of posterior anchored polyethylene tethers to distribute proximal motion segment stiffness in long instrumented spine constructs. METHODS A finite element model of a T7-L5 spine segment was created to evaluate range of motion (ROM), intradiscal pressure, pedicle screw loads, and forces in the posterior ligament complex within and adjacent to the proximal terminus of an instrumented spine construct. Six models were tested: 1) intact spine; 2) bilateral, segmental pedicle screws (PS) at all levels from T-11 through L-5; 3) bilateral pedicle screws from T-12 to L-5 and transverse process hooks (TPH) at T-11 (the UIV); 4) pedicle screws from T-11 to L5 and 1-level tethers from T-10 to T-11 (TE-UIV+1); 5) pedicle screws from T-11 to L-5 and 2-level tethers from T-9 to T-11 (TE-UIV+2); and 6) pedicle screws and 3-level tethers from T-8 to T-11 (TE-UIV+3). RESULTS Proximal-segment range of motion (ROM) for the PS construct increased from 16% at UIV-1 to 91% at UIV. Proximal-segment ROM for the TPH construct increased from 27% at UIV-1 to 92% at UIV. Posterior tether constructs distributed ROM at the UIV and cranial adjacent segments most effectively; ROM for TE-UIV+1 was 14% of the intact model at UIV-1, 76% at UIV, and 98% at UIV+1. ROM for TE-UIV+2 was 10% at UIV-1, 51% at UIV, 69% at UIV+1, and 97% at UIV+2. ROM for TE-UIV+3 was 7% at UIV-1, 33% at UIV, 45% at UIV+1, and 64% at UIV+2. Proximal segment intradiscal pressures, pedicle screw loads, and ligament forces in the posterior ligament complex were progressively reduced with increasing number of posterior tethers used. CONCLUSIONS Finite element analysis of long instrumented spine constructs demonstrated that posterior tethers created a more gradual transition in ROM and adjacent-segment stress from the instrumented to the noninstrumented spine compared with all PS and TPH constructs. Posterior tethers may limit the biomechanical risk factor for PJK; however, further clinical research is needed to evaluate clinical efficacy.
Retrospective review of a prospective, multicenter database.
The purpose of this study was to assess whether elderly patients undergoing scoliosis surgery had an incidence of complications and ...improvement in outcome measures comparable with younger patients.
Complications increase with age for adults undergoing scoliosis surgery, but whether this impacts the outcomes of older patients is largely unknown.
This is a retrospective review of a prospective, multicenter spinal deformity database. Patients complete the Oswestry Disability Index (ODI), SF-12, Scoliosis Research Society-22 (SRS-22), and numerical rating scale (NRS; 0-10) for back and leg pain. Inclusion criteria included age 25 to 85 years, scoliosis (Cobb ≥ 30°), plan for scoliosis surgery, and 2-year follow-up.
Two hundred six of 453 patients (45%) completed 2-year follow-up, which is distributed among age groups as follows: 25 to 44 (n = 47), 45 to 64 (n = 121), and 65 to 85 (n = 38) years. The percentages of patients with 2-year follow-up by age group were as follows: 25 to 44 (45%), 45 to 64 (48%), and 65 to 85 (40%) years. These groups had perioperative complication rates of 17%, 42%, and 71%, respectively (P < 0.001). At baseline, elderly patients (65-85 years) had greater disability (ODI, P = 0.001), worse health status (SF-12 physical component score (PCS), P < 0.001), and more severe back and leg pain (NRS, P = 0.04 and P = 0.01, respectively) than younger patients. Mean SRS-22 did not differ significantly at baseline. Within each age group, at 2-year follow-up there were significant improvements in ODI (P ≤ 0.004), SRS-22 (P ≤ 0.001), back pain (P < 0.001), and leg pain (P ≤ 0.04). SF-12 PCS did not improve significantly for patients aged 25 to 44 years but did among those aged 45 to 64 (P < 0.001) and 65 to 85 years (P = 0.001). Improvement in ODI and leg pain NRS were significantly greater among elderly patients (P = 0.003, P = 0.02, respectively), and there were trends for greater improvements in SF-12 PCS (P = 0.07), SRS-22 (P = 0.048), and back pain NRS (P = 0.06) among elderly patients, when compared with younger patients.
Collectively, these data demonstrate the potential benefits of surgical treatment for adult scoliosis and suggest that the elderly, despite facing the greatest risk of complications, may stand to gain a disproportionately greater improvement in disability and pain with surgery.
Given that the pelvis is the pedestal on which the spine lies, its morphology has been observed to be associated with specific sagittal spinal shapes and should therefore be taken into account when ...dealing with pathologic conditions of the spine. However, the exact relationship between the pelvic morphology and lumbar lordosis still remains poorly defined. We hypothesized that the shape of the lumbar lordosis and its relationship with the pelvis could be described using anatomic parameters, independently of posture.
(1) What is the variation of lumbar segmental lordosis in an asymptomatic adult population? (2) Is there an association between increasing magnitude of pelvic incidence (PI) and segmental lordosis? (3) How does the position of the apex of lordosis change with increasing magnitude of PI value?
This retrospective study used data drawn from a longitudinally maintained database; between March 2014 and January 2015, 119 asymptomatic volunteers between 18 and 79 years old were enrolled in the study. Mean age was 51 years; there were 81 women and 38 men. Both segmental and cumulative lordosis were measured and used to describe the shape of the lumbar spine. We defined cumulative lordosis as the angle between L1 and S1, proximal lordosis as the angle between L1 and the superior endplate of L4, and distal lordosis as the angle between the superior endplates of L4 and S1. PI is defined as the angle between the line passing through the center of the femoral head and the center of the sacral endplate and a line perpendicular to the sacral endplate. Pearson's correlation was performed to analyze the relationship among PI, proximal and distal lordosis. Stratification by PI was performed (low, < 45°; average, 45°-60°; and high, > 60°) and the proportions of distal and proximal lordosis were then compared using an analysis of variance test.
In the whole cohort, proximal lordosis accounted for 38% of total lordosis, whereas distal lordosis accounted for 62%. PI revealed a positive correlation with proximal lordosis (r = 0.546; p < 0.001). However, there was no correlation with distal lordosis (r = 0.087; p = 0.346). Stratification by PI showed that proximal lordosis increased across PI groups (16.6° ± 10 versus 21.6° ± 9 versus 30.1° ± 9; p < 0.001), whereas distal lordosis remained relatively constant (34.8° ± 8 versus 36.7° ± 7 versus 35.9° ± 10; p = 0.581). Apex position was overall more proximal as PI increased (r = -0.199; p = 0.034).
Our study demonstrated that PI influences only the proximal part of the lordosis, but not the distal part in an asymptomatic adult population. The proximal part of the lumbar spine had the most variability across individuals and appeared to accommodate to pelvic morphology (incidence). Further studies using a larger cohort size are encouraged not only to refine this relationship, but also to investigate the effect of restoration of normal lordotic shape of the lumbar spine on the functional outcomes after spinal fusion.
Our findings may be useful for surgical planning in an era of patient-specific care. The findings suggest that surgeons should aim for a patient-specific lumbar shape rather than simple global lordosis matched to the PI.
STUDY DESIGN.Narrative review.
OBJECTIVE.To provide a comprehensive narrative review of cervical alignment parameters, the methods for quantifying cervical alignment, normal cervical alignment ...values, and how alignment is associated with cervical deformity and myelopathy with discussions of health-related quality of life.
SUMMARY OF BACKGROUND DATA.Indications for surgery to correct cervical alignment are not well-defined and there is no set standard to address the amount of correction to be achieved. In addition, classifications of cervical deformity have yet to be fully established and treatment options defined and clarified.
METHODS.A survey of the cervical spine literature was conducted.
RESULTS.New normative cervical alignment values from an asymptomatic volunteer population are introduced, updated methods for quantifying cervical alignment are discussed, and describing the relationship between cervical alignment, disability, and myelopathy are outlined. Specifically, methods used to quantify cervical alignment include cervical lordosis, cervical sagittal vertical axis, and horizontal gaze with the chin-brow vertical angle. Updated methods include T1 slope. Evidence from a few recent studies suggests correlations between radiographical parameters in the cervical spine and health-related quality of life. Analysis of the cervical regional alignment with respect to overall spinal pelvic alignment is emerging and critical. Cervical myelopthay and sagittal alignment of the cervical spine are closely related as cervical deformity can lead to spinal cord compression and tension.
CONCLUSION.Cervical deformity correction should take on a comprehensive approach in assessing global cervical-pelvic relationships and the radiographical parameters that effect health-related quality of life scores are not well-defined. Cervical alignment may be important in assessment and treatment of cervical myelopathy. Future work should concentrate on correlation of cervical alignment parameters to disability scores and myelopathy outcomes.Statement 1Cervical sagittal alignment (cervical SVA and kyphosis) is related to thoracolumbar spinal pelvic alignment and to T1 slope.Statement 2When significant deformity is clinically or radiographically suspected, regional cervical and relative global spinal alignment should be evaluated preoperatively via standing 3-foot scoliosis X-rays for appropriate operative planning.Statement 3Cervical sagittal alignment (C2-C7 SVA) is correlated to regional disability, general health scores and to myelopathy severity.Statement 4When performing decompressive surgery for CSM, consideration should be given to correction of cervical kyphosis and cervical sagittal imbalance (C2-C7 SVA) when present.
Previous forceplate studies analyzing the impact of sagittal-plane spinal deformity on pelvic parameters have demonstrated the compensatory mechanisms of pelvis translation in addition to rotation. ...However, the mechanisms recruited for this pelvic rotation were not assessed. This study aims to analyze the relationship between spinopelvic and lower-extremity parameters and clarify the role of pelvic translation.
This is a retrospective study of patients with spinal deformity and full-body EOS images. Patients with only stenosis or low-back pain were excluded. Patients were grouped according to T-1 spinopelvic inclination (T1SPi): sagittal forward (forward, > 0.5°), neutral (-6.3° to 0.5°), or backward (< -6.3°). Pelvic translation was quantified by pelvic shift (sagittal offset between the posterosuperior corner of the sacrum and anterior cortex of the distal tibia), hip extension was measured using the sacrofemoral angle (SFA; the angle formed by the middle of the sacral endplate and the bicoxofemoral axis and the line between the bicoxofemoral axis and the femoral axis), and chin-brow vertical angle (CBVA). Univariate and multivariate analyses were used to compare the parameters and correlation with the Oswestry Disability Index (ODI).
In total, 336 patients (71% female; mean age 57 years; mean body mass index 27 kg/m(2)) had mean T1SPi values of -8.8°, -3.5°, and 5.9° in the backward, neutral, and forward groups, respectively. There were significant differences in the lower-extremity and spinopelvic parameters between T1SPi groups. The backward group had a normal lumbar lordosis (LL), negative SVA and pelvic shift, and the largest hip extension. Forward patients had a small LL and an increased SVA, with a large pelvic shift creating compensatory knee flexion. Significant correlations existed between lower-limb parameter and pelvic shift, pelvic tilt, T-1 pelvic angle, T1SPi, and sagittal vertical axis (0.3 < r < 0.8; p < 0.001). ODI was significantly correlated with knee flexion and pelvic shift.
This is the first study to describe full-body alignment in a large population of patients with spinal pathologies. Furthermore, patients categorized based on T1SPi were found to have significant differences in the pelvic shift and lower-limb compensatory mechanisms. Correlations between lower-limb angles, pelvic shift, and ODI were identified. These differences in compensatory mechanisms should be considered when evaluating and planning surgical intervention for adult patients with spinal deformity.
Abstract
BACKGROUND:
Improved understanding of rod fracture (RF) in adult spinal deformity could be valuable for implant design, surgical planning, and patient counseling.
OBJECTIVE:
To evaluate ...symptomatic RF after posterior instrumented fusion for adult spinal deformity.
METHODS:
A multicenter, retrospective review of RF in adult spinal deformity was performed. Inclusion criteria were spinal deformity, age older than 18 years, and more than 5 levels posterior instrumented fusion. Rod failures were divided into early (⩽12 months) and late (>12 months).
RESULTS:
Of 442 patients, 6.8% had symptomatic RF. RF rates were 8.6% for titanium alloy, 7.4% for stainless steel, and 2.7% for cobalt chromium. RF incidence after pedicle subtraction osteotomy (PSO) was 15.8%. Among patients with a PSO and RF, 89% had RF at or adjacent to the PSO. Mean time to early RF (63%) was 6.4 months (range, 2-12 months). Mean time to late RF (37%) was 31.8 months (range, 14-73 months). The majority of RFs after PSO (71%) were early (mean, 10 months). Among RF cases, mean sagittal vertical axis improved from preoperative (163 mm) to postoperative (76.9 mm) measures (P < .001); however, 16 had postoperative malalignment (sagittal vertical axis >50 mm; mean, 109 mm).
CONCLUSION:
Symptomatic RF occurred in 6.8% of adult spinal deformity cases and in 15.8% of PSO patients. The rate of RF was lower with cobalt chromium than with titanium alloy or stainless steel. Early failure was most common after PSO and favored the PSO site, suggesting that RF may be caused by stress at the PSO site. Postoperative sagittal malalignment may increase the risk of RF.
Retrospective case-control series.
The purpose of this study is to determine whether perioperative complications alter subsequent clinical outcome measures in adult spinal deformity surgery.
...Increasingly, the benefit of surgical intervention is being evaluated based on patient reported outcomes and standardized health related quality of life (HRQOL) measures. As improvement or deterioration in HRQOL scores becomes a standard for clinical evaluation in adult spinal deformity, the correlation between HRQOL outcome scores and historic benchmarks, such as curve correction, sagittal balance, fusion healing, or the occurrence of a complication, must be clarified.
This study analyzes a prospective multicenter data base for adult spinal deformity. Patients with major, minor, and no complications were matched using a logistic regression technique producing 46 patients in each group. Standardized outcome measures at baseline and at 1 year postop were compared.
Forty-seven major complications were reported in 46 patients. Sixty-two minor complications were noted in 46 patients. Comparison between the 3 complication groups revealed that 1-year postoperative outcome measures were not statistically different for the Scoliosis Research Society Outcomes Instrument, Medical Outcomes Short Form-36 (SF-12), Oswestry Disability Index, or Numerical Pain Scales. The only significant interaction was in the rate of change from preop to 1-year postop for the SF-12 general health subscale. For the group with major complications, SF-12 general health deteriorated by 2.1 points from preop to 1-year postop. During the same period, the group with minor complications experienced an improvement of 4.2 points and the group with no complications experienced an improvement of 1.5 points.
This study suggests that risk for minor complications may be a less substantial obstacle than previously assumed for surgical treatment in adult spinal deformity. In contrast, major complications were reported in approximately 10% of cases and adversely affected outcome as evidenced by the deterioration in SF-12 general health scores at 1 year after surgery.
Retrospective review of a multicenter database of consecutive patients undergoing 3-column osteotomy for treatment of adult spinal deformity (ASD).
To rigorously develop a T1 pelvic angle (TPA) ...categorization paradigm and use it to assess the surgical management of patients with ASD.
TPA, the angle between the hips-T1 line and hips-S1 endplate line, is a novel spinopelvic parameter that assesses the combined effect of a loss of lordosis on trunk inclination and pelvic retroversion.
A prospective, multicenter database of consecutive patients with ASD was queried to identify the severe deformity threshold and meaningful change values for TPA by correlation with Oswestry Disability Index. A separate multicenter, consecutive, retrospective database of patients with ASD treated with single lumbar 3-column osteotomy was then analyzed at baseline, 3-month, and 1-year follow-up. Subjects were classified into well-aligned or poorly aligned groups at 3 months on the basis of TPA. Patients "deteriorated" if they lost more than 1 meaningful change in TPA between 3 months and 1 year and had TPA more than deformity threshold at 1 year.
The severe deformity threshold for TPA was 20° (Oswestry Disability Index > 40) and the meaningful change was 4.1° (Oswestry Disability Index change = 15). Review of the 3-column osteotomy database identified 179 patients with preoperative severe deformity; 63 were well-aligned (TPA < 15.9°) and 73 were poorly aligned (TPA > 20°) at 3-month follow-up. This newly developed TPA categorization mechanism grouped patients in a manner comparable with the Scoliosis Research Society-Schwab Classification. Subjects who were well-aligned at 3 months had less severe baseline deformity, but received more correction, than poorly aligned subjects. Four well-aligned patients and 13 poorly aligned patients deteriorated between 3 months and 1 year after surgery.
TPA accounts for sagittal vertical axis and pelvic tilt and shows great promise as a classification tool. Longitudinal analysis demonstrated undercorrection among patients with more severe preoperative deformity. We propose a surgical target of 10° for TPA.
4.
STUDY DESIGN.Retrospective analysis of prospectively-collected, multicenter adult spinal deformity (ASD) databases.
OBJECTIVE.To predict the likelihood of reaching minimum clinically important ...differences in patient-reported outcomes after ASD surgery.
SUMMARY OF BACKGROUND DATA.ASD surgeries are costly procedures that do not always provide the desired benefit. In some series only 50% of patients achieve minimum clinically important differences in patient-reported outcomes (PROs). Predictive modeling may be useful in shared-decision making and surgical planning processes. The goal of this study was to model the probability of achieving minimum clinically important differences change in PROs at 1 and 2 years after surgery.
METHODS.Two prospective observational ASD cohorts were queried. Patients with Scoliosis Research Society-22, Oswestry Disability Index , and Short Form-36 data at preoperative baseline and at 1 and 2 years after surgery were included. Seventy-five variables were used in the training of the models including demographics, baseline PROs, and modifiable surgical parameters. Eight predictive algorithms were trained at four-time horizonspreoperative or postoperative baseline to 1 year and preoperative or postoperative baseline to 2 years. External validation was accomplished via an 80%/20% random split. Five-fold cross validation within the training sample was performed. Precision was measured as the mean average error (MAE) and R values.
RESULTS.Five hundred seventy patients were included in the analysis. Models with the lowest MAE were selected; R values ranged from 20% to 45% and MAE ranged from 8% to 15% depending upon the predicted outcome. Patients with worse preoperative baseline PROs achieved the greatest mean improvements. Surgeon and site were not important components of the models, explaining little variance in the predicted 1- and 2-year PROs.
CONCLUSION.We present an accurate and consistent way of predicting the probability for achieving clinically relevant improvement after ASD surgery in the largest-to-date prospective operative multicenter cohort with 2-year follow-up. This study has significant clinical implications for shared decision making, surgical planning, and postoperative counseling.Level of Evidence4
Improved understanding of rod fracture (RF) following adult spinal deformity (ASD) surgery could prove valuable for surgical planning, patient counseling, and implant design. The objective of this ...study was to prospectively assess the rates of and risk factors for RF following surgery for ASD.
This was a prospective, multicenter, consecutive series. Inclusion criteria were ASD, age > 18 years, ≥5 levels posterior instrumented fusion, baseline full-length standing spine radiographs, and either development of RF or full-length standing spine radiographs obtained at least 1 year after surgery that demonstrated lack of RF. ASD was defined as presence of at least one of the following: coronal Cobb angle ≥20°, sagittal vertical axis (SVA) ≥5 cm, pelvic tilt (PT) ≥25°, and thoracic kyphosis ≥60°.
Of 287 patients who otherwise met inclusion criteria, 200 (70%) either demonstrated RF or had radiographic imaging obtained at a minimum of 1 year after surgery showing lack of RF. The patients' mean age was 54.8 ± 15.8 years; 81% were women; 10% were smokers; the mean body mass index (BMI) was 27.1 ± 6.5; the mean number of levels fused was 12.0 ± 3.8; and 50 patients (25%) had a pedicle subtraction osteotomy (PSO). The rod material was cobalt chromium (CC) in 53%, stainless steel (SS), in 26%, or titanium alloy (TA) in 21% of cases; the rod diameters were 5.5 mm (in 68% of cases), 6.0 mm (in 13%), or 6.35 mm (in 19%). RF occurred in 18 cases (9.0%) at a mean of 14.7 months (range 3-27 months); patients without RF had a mean follow-up of 19 months (range 12-24 months). Patients with RF were older (62.3 vs 54.1 years, p = 0.036), had greater BMI (30.6 vs 26.7, p = 0.019), had greater baseline sagittal malalignment (SVA 11.8 vs 5.0 cm, p = 0.001; PT 29.1° vs 21.9°, p = 0.016; and pelvic incidence PI-lumbar lordosis LL mismatch 29.6° vs 12.0°, p = 0.002), and had greater sagittal alignment correction following surgery (SVA reduction by 9.6 vs 2.8 cm, p < 0.001; and PI-LL mismatch reduction by 26.3° vs 10.9°, p = 0.003). RF occurred in 22.0% of patients with PSO (10 of the 11 fractures occurred adjacent to the PSO level), with rates ranging from 10.0% to 31.6% across centers. CC rods were used in 68% of PSO cases, including all with RF. Smoking, levels fused, and rod diameter did not differ significantly between patients with and without RF (p > 0.05). In cases including a PSO, the rate of RF was significantly higher with CC rods than with TA or SS rods (33% vs 0%, p = 0.010). On multivariate analysis, only PSO was associated with RF (p = 0.001, OR 5.76, 95% CI 2.01-15.8).
Rod fracture occurred in 9.0% of ASD patients and in 22.0% of PSO patients with a minimum of 1-year follow-up. With further follow-up these rates would likely be even higher. There was a substantial range in the rate of RF with PSO across centers, suggesting potential variations in technique that warrant future investigation. Due to higher rates of RF with PSO, alternative instrumentation strategies should be considered for these cases.
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