Prospective assessment of the safety and early outcomes of sublaminar band placement for the prevention of proximal junctional kyphosis

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OBJECTIVE

Proximal junctional kyphosis (PJK) can progress to proximal junctional failure (PJF), a widely recognized early and serious complication of multisegment spinal instrumentation for the treatment of adult spinal deformity (ASD). Sublaminar band placement has been suggested as a possible technique to prevent PJK and PJF but carries the theoretical possibility of a paradoxical increase in these complications as a result of the required muscle dissection and posterior ligamentous disruption. In this study, the authors prospectively assess the safety as well as the early clinical and radiological outcomes of sublaminar band insertion at the upper instrumented vertebra (UIV) plus 1 level (UIV+1).

METHODS

Between August 2015 and February 2017, 40 consecutive patients underwent either upper (T2–4) or lower (T8–10) thoracic sublaminar band placement at the UIV+1 during long-segment thoracolumbar arthrodesis surgery. Outcome measures were prospectively collected and uploaded to a web-based REDCap database specifically designed to include demographic, clinical, and radiological data. All patients underwent clinical assessment, as well as radiological assessment with anteroposterior and lateral 36-inch whole-spine standing radiographs both pre- and postoperatively.

RESULTS

Forty patients (24 women and 16 men) were included in this study. Median age at surgery was 64.0 years with an IQR of 57.7–70.0 years. Median follow-up was 12 months (IQR 6–15 months). Three procedure-related complications were noted, including 2 intraoperative cerebrospinal spinal fluid leaks and 1 transient neurological deficit. Median visual analog scale (VAS) scores for back pain significantly improved after surgery (preoperatively: 8.0, IQR 6.0–10.0; 1-year follow-up: 2.0, IQR 0.0–6.0; p = 0.001). Median Oswestry Disability Index (version 2.1a) scores also significantly improved after surgery (preoperatively: 56.0, IQR 45.0–64.0; 1-year follow-up: 46.0, IQR 22.2–54.0; p < 0.001). Sagittal vertical axis (preoperatively: 9.0 cm, IQR 5.3–11.6 cm; final follow-up: 4.7 cm, IQR 2.0–6.6 cm; p < 0.001), pelvic incidence-lumbar lordosis mismatch (24.7°, IQR 11.2°–31.2°; 7.7°, IQR −1.2° to 19.5°; p < 0.001), and pelvic tilt (28.7°, IQR 20.4°–32.6°; 17.1°, IQR 10.8°–25.2°; p < 0.001) were all improved at the final follow-up. While proximal junctional (PJ) Cobb angles increased overall at the final follow-up (preoperatively: 4.2°, IQR 1.9°–7.4°; final follow-up: 8.0°, IQR 5.8°–10.3°; p = 0.002), the significant increase was primarily noted starting at the immediate postoperative time point (7.2°, IQR 4.4°–11.8°; p = 0.001) and not beyond. Three patients (7.5%) developed radiological PJK (mean ΔPJ Cobb 15.5°), while there were no instances of PJF in this cohort.

CONCLUSIONS

Sublaminar band placement at the UIV+1 during long-segment thoracolumbar instrumented arthrodesis is relatively safe and is not associated with an increased rate of PJK. Moreover, no subjects developed PJF. Prospective large-scale and long-term analysis is needed to define the potential benefit of sublaminar bands in reducing the incidence of PJK and PJF following surgery for ASD.

Clinical trial registration no.: NCT02411799 (clinicaltrials.gov)

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; ASD = adult spinal deformity; BMD = bone mineral density; BMI = body mass index; DVT = deep venous thrombosis; LL = lumbar lordosis; MEP = motor evoked potential; ODI = Oswestry Disability Index; PI = pelvic incidence; PJF = proximal junctional failure; PJK = proximal junctional kyphosis; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; REDCap = Research Electronic Data Capture; SPO = Smith-Petersen osteotomy; SRS = Scoliosis Research Society; SS = sacral slope; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis; UIV = upper instrumented vertebra; UIV+1 = UIV plus 1 level; VAS = visual analog scale.

OBJECTIVE

Proximal junctional kyphosis (PJK) can progress to proximal junctional failure (PJF), a widely recognized early and serious complication of multisegment spinal instrumentation for the treatment of adult spinal deformity (ASD). Sublaminar band placement has been suggested as a possible technique to prevent PJK and PJF but carries the theoretical possibility of a paradoxical increase in these complications as a result of the required muscle dissection and posterior ligamentous disruption. In this study, the authors prospectively assess the safety as well as the early clinical and radiological outcomes of sublaminar band insertion at the upper instrumented vertebra (UIV) plus 1 level (UIV+1).

METHODS

Between August 2015 and February 2017, 40 consecutive patients underwent either upper (T2–4) or lower (T8–10) thoracic sublaminar band placement at the UIV+1 during long-segment thoracolumbar arthrodesis surgery. Outcome measures were prospectively collected and uploaded to a web-based REDCap database specifically designed to include demographic, clinical, and radiological data. All patients underwent clinical assessment, as well as radiological assessment with anteroposterior and lateral 36-inch whole-spine standing radiographs both pre- and postoperatively.

RESULTS

Forty patients (24 women and 16 men) were included in this study. Median age at surgery was 64.0 years with an IQR of 57.7–70.0 years. Median follow-up was 12 months (IQR 6–15 months). Three procedure-related complications were noted, including 2 intraoperative cerebrospinal spinal fluid leaks and 1 transient neurological deficit. Median visual analog scale (VAS) scores for back pain significantly improved after surgery (preoperatively: 8.0, IQR 6.0–10.0; 1-year follow-up: 2.0, IQR 0.0–6.0; p = 0.001). Median Oswestry Disability Index (version 2.1a) scores also significantly improved after surgery (preoperatively: 56.0, IQR 45.0–64.0; 1-year follow-up: 46.0, IQR 22.2–54.0; p < 0.001). Sagittal vertical axis (preoperatively: 9.0 cm, IQR 5.3–11.6 cm; final follow-up: 4.7 cm, IQR 2.0–6.6 cm; p < 0.001), pelvic incidence-lumbar lordosis mismatch (24.7°, IQR 11.2°–31.2°; 7.7°, IQR −1.2° to 19.5°; p < 0.001), and pelvic tilt (28.7°, IQR 20.4°–32.6°; 17.1°, IQR 10.8°–25.2°; p < 0.001) were all improved at the final follow-up. While proximal junctional (PJ) Cobb angles increased overall at the final follow-up (preoperatively: 4.2°, IQR 1.9°–7.4°; final follow-up: 8.0°, IQR 5.8°–10.3°; p = 0.002), the significant increase was primarily noted starting at the immediate postoperative time point (7.2°, IQR 4.4°–11.8°; p = 0.001) and not beyond. Three patients (7.5%) developed radiological PJK (mean ΔPJ Cobb 15.5°), while there were no instances of PJF in this cohort.

CONCLUSIONS

Sublaminar band placement at the UIV+1 during long-segment thoracolumbar instrumented arthrodesis is relatively safe and is not associated with an increased rate of PJK. Moreover, no subjects developed PJF. Prospective large-scale and long-term analysis is needed to define the potential benefit of sublaminar bands in reducing the incidence of PJK and PJF following surgery for ASD.

Clinical trial registration no.: NCT02411799 (clinicaltrials.gov)

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; ASD = adult spinal deformity; BMD = bone mineral density; BMI = body mass index; DVT = deep venous thrombosis; LL = lumbar lordosis; MEP = motor evoked potential; ODI = Oswestry Disability Index; PI = pelvic incidence; PJF = proximal junctional failure; PJK = proximal junctional kyphosis; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; REDCap = Research Electronic Data Capture; SPO = Smith-Petersen osteotomy; SRS = Scoliosis Research Society; SS = sacral slope; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis; UIV = upper instrumented vertebra; UIV+1 = UIV plus 1 level; VAS = visual analog scale.

Adult spinal deformity (ASD), including degenerative scoliosis and/or kyphosis, has an estimated prevalence of 68% in the elderly population.47 Deformity correction surgeries for ASD are being performed more frequently as health, functional status, and life expectancy standards improve over time. However, ASD surgeries remain complex and are associated with frequent complications, including proximal junctional kyphosis (PJK),48 which has an incidence of 17%–62%6,17,27,29,37,39,58 with pedicle screw–only constructs and primarily occurs within 3 months postoperatively.30,34,59 Proximal junctional kyphosis is recognized as a harbinger of proximal junctional failure (PJF), a major complication often requiring extensive revision surgery.22,26,51,57 Although various criteria have been designated for PJK, the most accepted definition includes a postoperative proximal junctional (PJ) Cobb angle value of and a relative increase of at least 10° degrees (relative to the preoperative measurement).17

The pathogenesis underlying PJK is probably directly related to the abrupt transition between the rigid fused and the flexible unfused vertebral segments.8,34 The higher incidence of PJK noted in patients with low bone mineral density (BMD) directly supports this theory. A higher incidence of PJK has also been linked to a thoracic kyphosis (TK) Cobb angle > 40° and a postoperative sagittal vertical axis (SVA) difference > 5 cm.37 Recent studies have suggested that facilitating a more gradual transition between the fused and flexible segments with the introduction of semi-rigid fixation at the proximal intervening levels could potentially reduce the incidence of PJK and PJF.7,31,33 Such “hybrid” constructs have included supplementation with PJ hooks, Mersilene tape, and rib anchors.20,31,33,55,60 Vertebroplasty has been studied as a potential prophylactic technique aimed at supplementing the anterior column.14,25,38 Finally, polyester tethers (sublaminar bands) have been suggested as a possible PJK prophylactic technique,3 but to date they have been used primarily in hybrid constructs to address coronal and sagittal deformity correction in adolescent idiopathic scoliosis (AIS).1,23,45 A recent study in AIS patients used proximal sublaminar bands and lamino-laminar claws at the 2 upper instrumented vertebrae (UIVs) and, reassuringly, did not identify an increase in the incidence of PJK despite the associated muscle and PJ ligamentous disruption.16

To assess the feasibility, safety, and potential influence of sublaminar banding on the incidence of PJK and PJF, we prospectively analyzed consecutive ASD patients who underwent long-segment thoracolumbar instrumentation with sublaminar bands inserted at the UIV plus 1 level (UIV+1).

Methods

Patients and Study Design

After obtaining consent, we enrolled patients in an institutional review board–approved protocol designed to prospectively assess those who were undergoing PJ sublaminar band insertion at our center (Prospective Multi-Center Follow-up of Patients Undergoing Instrumented Thoracic and Lumbar Arthrodesis Supplemented by the Implanet Jazz system; clinical trial registration no. NCT02411799; ClinicalTrials.gov database; http://clinicaltrials.gov). A web-based Research Electronic Data Capture (REDCap) database19 was designed to prospectively collect all demographic, clinical, and radiological data. In the current study, we report on 40 consecutively enrolled patients who underwent either upper or lower thoracic band placement in the period between August 2015 and February 2017. Inclusion criteria included an age of 18 years or older at the time of surgery, a diagnosis of ASD (either primary degenerative or postoperative), and at least 3 months of completed follow-up. All patients underwent anteroposterior and lateral 36-inch whole-spine standing radiography studies, whose findings were classified according to the Scoliosis Research Society (SRS)-Schwab ASD system.4 The decision to offer surgery was based on the severity and intractability of a patient’s symptoms (pain and disability), whether an adequate trial of nonoperative measures had been attempted, and the severity of the deformity causing sagittal and/or coronal imbalance with various degrees of canal and/or foraminal stenosis.

All patients underwent a detailed preoperative workup including routine blood investigation, standard whole-spine radiography, lumbar and thoracic MRI, and thoracolumbar CT. Dual-energy x-ray absorptiometry (DEXA) scanning was used to assess bone density. Patients who had low BMD (less than −2.5, 6 patients) received teriparatide injections (Eli Lilly and Co.) for at least 6 weeks before surgery (mean of 8 months). Lower limb venous Doppler scans were obtained in patients who had salient deep venous thrombosis (DVT) risk factors such as prolonged immobilization or restricted ambulatory capacity preoperatively. All patients underwent preoperative inferior vena cava filter placement and received 5000 IU heparin within 1 hour of surgery as prophylaxis against DVT. All patients underwent long-segment fusion and deformity correction extending to either the lower thoracic (T9–11) or upper thoracic (T3–5) levels. The distal extent of fusion was from L-5 to the ilium. The extent of instrumented arthrodesis was based on the severity of the global sagittal imbalance (SVA), the severity of the sagittal/coronal deformities (Cobb angles) and the involved levels, the pelvic incidence-lumbar lordosis (PI-LL) mismatch to be corrected, as well as the levels already fused (for revision cases). All patients underwent long-segment fusions with pedicle screw-rod constructs and an additional anchor at the UIV+1 using a braided polyester sublaminar band (Jazz system, Implanet America) via a posterior approach. Sacro-pelvic fixation was performed using standard iliac or S2-alar screws.

Surgical Technique

Midline posterior exposure of the appropriate spinal levels was performed in all cases. Bilateral hemilaminotomies were performed to widen the interlaminar spaces immediately proximal and distal to the UIV+1 laminas by using a power burr connected to an AM-8 bit and Kerrison rongeurs (Fig. 1). Care was taken to avoid any facet violation. The midline supra- and interspinous ligaments were kept intact. The ligamentum flavum was removed using Kerrison rongeurs until the underlying dura mater was well exposed. After ensuring sufficient hemilaminotomy windows, the 2 bands were sequentially introduced from the inferior to the superior end. Pressure over the dural sac during this maneuver was meticulously avoided. The tips of the bands were curved to prevent inadvertent impingement on the neural elements. At the level of the proximal hemilaminotomies, a nerve hook and/or needle driver was used to gradually deliver the bands out. A sustained push was simultaneously applied with the other hand in a caudocephalad direction. The metal-backed tip of the bands allowed for enhanced maneuverability during this process. Band insertion was performed with motor and sensory neuromonitoring.

FIG. 1.
FIG. 1.

Drawings of the steps involved in the insertion of the sublaminar bands at the UIV+1. A: Hemilaminotomy and widening of the interlaminar space at the superior aspect of the UIV lamina. B: Hemilaminotomy and widening of the interlaminar space at the superior aspect of the UIV+1 laminas. C: Insertion of the band from the inferior hemilaminotomy window. D: Careful retrieval of the band through the superior hemilaminotomy window. E: Posterior, lateral, and axial views of the vertebra showing sublaminar band placement prior to rod attachment. F: Posterior and lateral views of the vertebrae showing the sublaminar bands anchored to the pedicle screw-rod construct. Copyright H. Francis Farhadi. Published with permission.

After applying the sublaminar bands, we inserted pedicle screws at all thoracic, lumbar, and sacral levels as planned preoperatively by using a free-hand technique supplemented with fluoroscopic guidance as needed. Laminectomies, Smith-Petersen osteotomies (SPOs), and pedicle subtraction osteotomies (PSOs) were performed in accordance with the preoperative deformity correction plan. Interbody fusion was performed via anterior, lateral transpsoas, transforaminal, or posterior approaches to provide additional correction in the sagittal and coronal planes. Either titanium or cobalt-chrome rods were positioned, and reduction was achieved using cantilever bending, de-rotation, and in situ bending maneuvers. As a final step, the sublaminar bands were connected to the rods at the UIV level and hand tensioned using a tensioner device. Finally, decortication was performed and bone graft was placed up to the UIV level. All surgeries were performed by the senior spine surgeon (H.F.F.).

Clinical Evaluation

All patients underwent complete general physical examination and detailed spine and neurological examinations preoperatively and at defined postoperative visits. Visual analog scale (VAS), Oswestry Disability Index (ODI) version 2.1a,11–13 and RAND SF-36 scores56 were obtained at baseline (preoperatively) and at each follow-up. Prospective monitoring and recording of complications was undertaken for all enrolled patients. Complications were designated as perioperative (4 weeks or less after surgery) or delayed (more than 4 weeks after surgery) and were subclassified on the basis of the involved system and severity (mild, moderate, severe). All clinical data, including complications, were prospectively uploaded to the web-based REDCap database by the study clinical research coordinator (A.J.M.). Patients underwent regular clinical and radiological follow-up as needed including at 6 weeks, 3 months, 6 months, and 1 year after surgery and annually thereafter.

Radiological Evaluation

Detailed radiological assessments were performed using standard anteroposterior and lateral whole-spine standing radiographs preoperatively and at each postoperative follow-up (starting prior to hospital discharge: “immediate postoperative follow-up”). Using anteroposterior plain-film radiographs, we measured thoracic, thoracolumbar, and lumbar Cobb angles, as described by the SRS-Schwab ASD classification. On lateral plain-film radiographs, SVA, TK (T5–12), thoracolumbar kyphosis (TLK; T10–L2), and LL (L1–S1) Cobb angles, spinopelvic parameters (PI, pelvic tilt [PT], and sacral slope [SS]), PJ Cobb angles (UIV to UIV+2), UIV sagittal tilt (only on postoperative radiographs), and T1 slope were calculated (Fig. 2).

FIG. 2.
FIG. 2.

A: Preoperative 36-inch whole-spine lateral standing radiograph. Line 1, sagittal C-7 plumb line (vertical line dropped from the center of the C-7 vertebral body); line 2, SVA, distance between the sagittal C-7 plumb line and the posterosuperior margin of the S-1 vertebra; TK, angle between superior endplate of T-3 vertebra to inferior endplate of T-12 vertebra; TLK, angle between superior endplate of T-10 vertebra to inferior endplate of L-2 vertebra; LL, angle between superior endplate of L-1 vertebra to superior endplate of S-1 vertebra; SS, angle between superior endplate of S-1 and the horizontal; PT, angle between the line joining the midpoint of the superior endplate of S-1 and the center of the femoral head and the vertical; PI, angle between the line perpendicular to the superior endplate of S-1 and bisecting it and the line joining the midpoint of superior sacral endplate and the center of the femoral heads. B: Lateral postoperative thoracolumbar radiograph showing instrumentation between T-10 and T-12 levels. Proximal junctional (PJ) Cobb angle, angle between inferior endplate of UIV (T-10) and superior endplate of UIV+2 vertebra (T-8); UIV sagittal tilt, angle between the inferior endplate of UIV and the horizontal.

Statistical Analysis

Data were analyzed using SPSS version 24 software (IBM Corp.). Distribution normality was assessed using the Shapiro-Wilk test. Wilcoxon signed-rank tests were used to assess for significant changes between preoperative and postoperative values. A p < 0.05 was considered statistically significant.

Results

Baseline Clinical and Radiological Findings

Forty ASD patients (24 women and 16 men) underwent long-segment thoracolumbar instrumented arthrodesis supplemented with sublaminar bands at the UIV+1 in the period from August 2015 to February 2017. Baseline clinical characteristics of the patients are detailed in Table 1. Median age at surgery was 64.0 (IQR 57.7–70.0 years). Mean and median follow-up was 12 months (IQR 6–15 months). Follow-up was limited to 3 months for 2 patients: the patient in case 18 developed discitis treated with intravenous antibiotics and hardware and sublaminar band removal at 4 months postoperatively, whereas the patient in case 30 died due to unrelated causes at 3.5 months postoperatively. At least 3 months’, 6 months’, and ≥ 1 year’s follow-ups were achieved for 3, 11, and 26 patients, respectively. Eleven patients (27.5%) had a body mass index (BMI) of 30.0–34.9 kg/m2 (obese I), whereas 12 (30.0%) had a BMI ≥ 35.0 kg/m2 (obese II). Twenty-eight patients (70.0%) had a history of prior thoracolumbar spinal surgery. Osteopenia and osteoporosis were found in 8 (20.0%) and 6 (15.0%) patients, respectively. Deformities were classified according to the SRS-Schwab ASD system4 (Table 2). Ten patients (25.0%) had significant combined coronal (greater than 30°) and sagittal deformities. Thirteen (32.5%) and 19 (47.5%) patients had moderate (+) and severe (++) sagittal imbalance (SVA), respectively. Moderate and severe PI-LL mismatches were noted in 8 (20.0%) and 23 (57.5%) patients, respectively.

TABLE 1.

Baseline clinical characteristics in 40 patients who underwent sublaminar band placement

CharacteristicNo.
Median age in yrs64.0 (57.7–70.0)
Sex
 Female24 (60.0)
 Male16 (40.0)
Smoker
 Nonsmoker (>10 yrs)28 (70.0)
 Former smoker (≤10 yrs)8 (20.0)
 Current smoker4 (10.0)
Race
 White38 (95.0)
 Non-white2 (5.0)
BMI
 Median BMI in kg/m2 (range)31.8 (28.2–35.8)
 Normal BMI patients (18.5–24.9 kg/m2)5 (12.5)
 Overweight patients (25.0–29.9 kg/m2)12 (30.0)
 Obese I patients (30.0–34.9 kg/m2)11 (27.5)
 Obese II patients (≥35.0 kg/m2)12 (30.0)
Prior T/L spine surgery
 ≤2 yrs14 (35.0)
 >2 yrs14 (35.0)
Osteopenia/osteoporosis8 (20.0)/6 (15.0)
BMI = body mass index; T/L = thoracic or lumbar.Values expressed as the median (IQR) or as the number (%).
TABLE 2.

Patient profiles: radiological parameters described by the SRS-Schwab classification

ParameterNo. of Patients
PI-LL
 09
 +8
 ++23
SVA
 08
 +13
 ++19
PT
 013
 +15
 ++12
Coronal curve
 Thoracic only (T)0
 TL-lumbar only (L)7
 Double curve (D)3
 No major coronal deformity (N)30
0= nonpathologic; + = moderate; ++ = severe.

Complications

A total of 34 surgery-related complications were recorded in the perioperative period, whereas 5 complications were delayed (identified in 24 of 40 patients overall; Table 3). Of these, 16 complications were graded as mild, 20 as moderate, and 3 as severe. Gastrointestinal (10/34) and neurological (6/34) complications were the 2 most frequent in the perioperative period. Neurological complications in all cases corresponded to postoperative delirium that resolved prior to hospital discharge. Two infectious discitis complications were noted (cases 17 and 18) and were treated with intravenous antibiotics. While the patient in case 17 had full clinical and radiological resolution after 3 months without further intervention, the patient in case 18 underwent hardware and sublaminar band removal at 4 months postoperatively (graded as a delayed and severe complication in Table 3). Three complications were directly related to the study procedure (graded as mild [2 cases] and moderate [1 case]): 2 unintentional durotomies without any further sequelae (cases 6 and 22) and 1 transient neurological deficit (case 22). All 3 complications occurred early in the study period (the fourth and tenth patients in this series). The patient in case 22 had preexisting moderate to severe canal stenosis at the UIV+1 and intraoperatively developed a left-sided unilateral decrease in motor evoked potentials (MEPs) immediately after ipsilateral sublaminar band insertion. He developed left-sided hip flexion weakness postoperatively (Grade 3/5), which completely resolved at the 6-week follow-up (Fig. 3).

TABLE 3.

Prospective evaluation of complications

ComplicationPeriop (≤4 wks)Delayed (>4 wks)Total
MildModerateSevereMildModerateSevereMildModerateSevere% 
Procedure-related2100002107.69%
Cardiopulmonary1100001105.13%
Gastrointestinal37000037025.6%
Infection0100010115.13%
Musculoskeletal13010023012.8%
Neurological24000024015.3%
Op11010121110.3%
Renal1000011015.13%
Vascular3000003007.69%
Wound (excluding infection)0200000205.13%
Total1420020316203
FIG. 3.
FIG. 3.

Case 22. Pre-ASD surgery T2-weighted MR images. A: Midsagittal section showing severe multilevel degeneration and postoperative laminectomy changes at the L2–5 levels. There is a herniated disc at the T9–10 level causing narrowing of the central spinal canal. B: Axial section at the corresponding T9–10 level showing the central herniated disc, slightly eccentric to the left, and associated canal compromise.

Clinical and Radiological Outcomes

Preoperative and postoperative VAS back and leg, ODI, and SF-36 scores are summarized in Table 4. The VAS back score significantly improved after surgery at all time points (preoperatively: 8.0, IQR 6.0–10.0; 1-year follow-up: 2.0, IQR 0.0–6.0; p = 0.001). The VAS leg score significantly improved at the 6-week (preoperatively: 6.0, IQR 2.0–8.0; 6 weeks: 2.0, IQR 0.0–6.0; p = 0.007) and 6-month (2.0, IQR 0.0–6.3; p = 0.045) follow-up intervals but not at the other time points. The ODI scores significantly improved beginning at 3 months postoperatively and throughout the follow-up (preoperatively: 56.0, IQR 45.0–64.0; 1 year: 46.0, IQR 22.2–54.0; p < 0.001). The RAND SF-36 scores (physical functioning, social functioning, and pain measures) improved significantly at various time points following surgery, with all 3 measures improving at the 6-month and the 1-year follow-up.

TABLE 4.

Clinical outcomes in 40 patients who underwent sublaminar band placement

ScalePreop Median (IQR)6 Wks Postop3 Mos Postop6 Mos Postop1 Yr Postop
Median (IQR)p ValueMedian (IQR)p ValueMedian (IQR)p ValueMedian (IQR)p Value  
VAS
 Back8.0 (6.0–10.0)5.0 (2.0–8.0)0.0024.0 (1.8–8.0)<0.0014.0 (2.0–6.0)<0.0012.0 (0.0–6.0)0.001
 Leg6.0 (2.0–8.0)2.0 (0.0–6.0)0.0072.0 (0.0-6.0)0.1082.0 (0.0–6.3)0.0450.5 (0.0–5.0)0.197
ODI56.0 (45.0–64.0)56.0 (44.4–64.0)1.0050.0 (31.1–60.0)0.00344.4 (29.5–52.5)0.00146.0 (22.2–54.0)<0.001
SF-36
 Physical functioning20.0 (5.0–30.0)10.0 (0.0–35.0)0.18620.0 (5.0–40.0)0.44127.5 (19.2–46.3)0.00332.5 (17.5–53.8)0.003
 Social functioning37.5 (12.5–50.0)25.0 (12.5–75.0)0.85050.0 (37.5–75.0)0.26550.0 (37.5–75.0)0.00256.3 (37.5–96.9)0.007
 Pain12.5 (0.0–22.5)22.5 (10.0–36.3)0.03832.5 (22.5–55.0)<0.00133.8 (22.5–48.1)<0.00145.0 (22.5–67.5)<0.001
The p values are based on Wilcoxon signed-rank tests comparing follow-up to preoperative radiographic values.

Preoperative and postoperative radiological measurements are summarized in Table 5. Thoracolumbar kyphosis, LL, PT, and PI-LL mismatch improved significantly after surgery; improvements were found on the immediate postoperative radiographs and were maintained until the last follow-up. While SVA values significantly improved by the final follow-up (preoperatively: 9.0 cm, IQR 5.3–11.6 cm; final follow-up: 4.7 cm, IQR 1.8–6.6 cm; p < 0.001), they were not significantly different on the immediate postoperative radiographs (5.4 cm, IQR 3.0–9.1 cm; p = 0.200).

TABLE 5.

Median pre- and postoperative radiographic measures

MeasurePreop Median (IQR)Immediate PostopFinal FU
Median (IQR)p ValueMedian (IQR)p Value  
T1 slope (°)25.3 (19.1–34.2)27.8 (20.2–32.1)0.74925.7 (20.9–30.4)1.00
TK (°)29.8 (20.5–40.9)38.6 (29.3–46.1)<0.00137.1 (29.9–46.0)<0.001
TLK (°)10.2 (3.9–24.0)4.2 (−2.0 to 7.0)0.0044.2 (2.2–8.0)0.018
LL (°)32.5 (22.2–45.4)46.8 (34.0–54.0)<0.00147.1 (39.0–53.4)<0.001
SVA (cm)9.0 (5.3–11.6)5.4 (3.0–9.1)0.2004.7 (1.8–6.6)<0.001
PI (°)55.4 (49.8–61.6)53.6 (49.9–60.5)0.61754.8 (49.4–60.2)0.109
PT (°)28.7 (20.4–32.6)16.6 (12.3–24.9)<0.00117.1 (10.8–25.2)<0.001
SS (°)28.2 (21.3–35.0)37.7 (30.1–41.0)<0.00137.1 (30.8–40.9)<0.001
PI-LL mismatch (°)24.7 (11.2–31.2)7.0 (0.3–18.7)<0.0017.7 (−1.2 to 19.5)<0.001
PJ Cobb angle (°)4.2 (1.9–7.4)7.2 (4.4–11.8)0.0018.0 (5.8–10.3)0.002
UIV sagittal slope (°)0.0 (−9.0 to 13.2)1.6 (−7.6 to 16.1)
FU = follow-up.The p values are based on Wilcoxon signed-rank tests comparing either immediate or final follow-up to preoperative radiographic values.

Furthermore, while the T1 slope did not significantly increase in the immediate postoperative period, PJ Cobb angles did (preoperatively: 4.2°, IQR 1.9°–7.4°; immediate postoperative: 7.2°, IQR 4.4°–11.8°; p = 0.001). In the period between the immediate postoperative and final follow-up radiographs, both T1 slope (27.8°, IQR 20.2°–32.1° vs 25.7°, IQR 20.9°–30.4°, respectively; p = 1.00) and PJ Cobb angle (7.2°, IQR 4.4°–11.8° vs 8.0°, IQR 5.8°–10.3°; p = 0.324) values remained stable. The UIV sagittal slope—an independent risk factor for PJK development36—was stable over the immediate and final follow-up time points (0.0°, IQR −9.0° to 13.2° vs 1.6°, IQR −7.6° to 16.1°, respectively).

The index instrumented arthrodesis levels for the patients are detailed in Table 6. Upper thoracic (T-3 to T-5) instrumentation was performed in 14 cases and lower thoracic instrumented (T-9 to T-11) was performed in 26 cases. All instrumented constructs were extended down to the L-5 to iliac levels (L-5, 1 case; S-1, 10 cases; and ilium, 29 cases). Cobalt-chrome rods were used in all upper thoracic surgeries and in 12/26 lower thoracic surgeries (the remaining 14 patients were instrumented with titanium rods). The change in PJ Cobb angles with respect to the preoperative value was measured individually for each patient at both the immediate (ΔPJ Cobb1) and final follow-up (ΔPJ Cobb2) time points. Three patients (7.5%; cases 23, 27, and 31) developed radiological PJK during the follow-up period (mean ΔPJ Cobb2 15.5°). The average age and BMD for these 3 patients on presentation were 64.7 years and −1.36 g/cm2, respectively. The mean preoperative TK Cobb angle was 40.8° and the mean ΔSVA was −7.8 cm. Two patients (cases 27 and 31), both treated with cobalt-chrome rods, met the criteria for PJK starting at the immediate postoperative time point. Two constructs were taken to the lower thoracic spine (cases 23 and 27), while 1 patient had the construct taken to the upper thoracic spine (case 31; Fig. 4).

TABLE 6.

Patient-specific changes in PJ Cobb angles

Case No.Arthrodesis LevelsΔPJ Cobb1 (°)ΔPJ Cobb2 (°)Rod
1T9–S10.62.8CC
2T3–S1−0.86.3CC
3T11–ilium6.10.7CC
4T3–ilium−0.74.6CC
5T10–ilium−13.4−13.4T
6T11–ilium11.25T
7T11–ilium4.75.3CC
8T10–S13.57.3CC
9T10–ilium3.76.1CC
10T11–S13.20.0T
11T11–S13.76.6T
12T10–ilium3.910T
13T10–ilium0.6−2.4T
14T10–L5−5.20.2T
15T3–ilium9.19.2CC
16T10–S1−0.84.8T
17T3–ilium4.03.8CC
18T3–ilium1.92.0CC
19T5–ilium−2.3−6.1CC
20T10–S12.6−0.9T
21T4–ilium8.86.8CC
22T10–S10.4−4CC
23*T10–S17.014.1T
24T11–S1−2.3−7.3T
25T3–ilium8.13.8CC
26T10–ilium−3.4−1.7T
27*T10–ilium17.712.5CC
28T10–ilium2.40.9CC
29T10–ilium8.08.9T
30T10–ilium0.55.9CC
31*T4–ilium12.820.0CC
32T10–ilium5.73.4T
33T10–ilium1.02.0CC
34T3–ilium2.34.4CC
35T11–ilium7.17.1CC
36T4–ilium2.2−1.5CC
37T4–ilium1.43.7CC
38T10–ilium−9.9−9.5CC
39T3–ilium0.84.5CC
40T4–ilium5.14.0CC
CC = cobalt-chrome rod; ΔPJ Cobb1 = change in PJ Cobb angle between immediate postoperative and preoperative radiographs; ΔPJ Cobb2 = change in PJ Cobb angle between last follow-up and preoperative radiographs; T = titanium rod.

Indicates development of PJK (3 patients).

FIG. 4.
FIG. 4.

Case 31. A: Preoperative standing 36-inch whole-spine anteroposterior and lateral radiographs. A sagittal plane deformity with an SVA of +28.6 cm was noted. B: Postoperative standing 36-inch whole-spine anteroposterior and lateral radiographs showing T-4 to ilium arthrodesis and deformity correction (SVA +6.1 cm). Radiological PJK is noted with PJ Cobb2 and ΔPJ Cobb2 of 21.9° and 20.0°, respectively.

Discussion

Surgery for ASD

Surgical management of ASD is complex and associated with frequent complications.5,42,48,50 Patient age (60 years or older),10 preexisting comorbidities,5,48 high BMI,48 revision surgery,50 anterior or combined anteroposterior surgical approaches,39 and osteotomies9 have all been associated with higher complication rates. A recent prospective multicenter trial of ASD patients who were managed surgically49 revealed that 71.5% of the patients experienced at least 1 complication at a minimum 2-year follow-up, although significant improvements in all health-related quality of life indices (including ODI, SF-36, SRS-22, and pain scores) and relevant radiological parameters (SVA, PT, and PI-LL) were noted.

Incidence and Prevention of PJK

Proximal junctional kyphosis was initially purported to be a radiological observation of doubtful clinical relevance.17,33,35 Subsequent studies have confirmed PJK progression to PJF in a subset of patients, which typically occurred in the first 3 months after surgery.30,34,59 Proximal junctional failure is characterized by clinically significant PJK deformity and associated symptomatology.22,57 The incidence of this phenomenon has reportedly increased along with the evolution of ASD surgeries, which often involve multilevel osteotomies and long-segment pedicle screw fixation for sagittal balance restoration.22,32,39 Considering the negative impact and costs of repeat surgery,53 the importance of developing strategies to reduce the incidence of PJK cannot be understated.

Proximal junctional kyphosis pathogenesis is broadly linked to ligamentous deficiency, vertebral compression fracture, and/or instrumentation failure or pullout.3,7,8,22,28,31,44 One theory posits that a biomechanical disadvantage occurs as a result of the abrupt change in spinal column rigidity between the nonmobile fused and the relatively mobile noninstrumented vertebrae.3,7,8,15 In addition to the strict avoidance of posterior tension band violation (including ligaments and facet capsules) at the proximal levels, various surgical strategies have been proposed to facilitate a smoother transition across the proximal junction. These include using a less rigid proximal “hybrid” implant system with hooks, less rigid rods or tapered rods, cement augmentation of adjacent vertebral bodies, rib fixation at UIV+1, and enhancement of the posterior tension band elements with either Mersilene tape attached to the spinous processes or polyester sublaminar tethers.3,7,8,21,24,25,37,40,42,52,60

Prophylactic UIV and UIV+1 vertebroplasty has recently been assessed in a cohort of patients undergoing surgery for ASD.36,46 Despite the anterior column supplementation and likely transition zone widening, this technique did not directly mitigate the persistently elevated stresses across the PJ posterior elements. Thus, while the incidence of PJF remained stable at 5.1% in that series, the development of PJK was primarily delayed beyond the usual early (< 3 months) time period as the reported 2-year and 5-year rates were 8% and 28.2%, respectively.38,46

The posterior ligamentous complex acts as a primary constraint against pathological flexion stresses. Biomechanical studies have demonstrated that forward angulation is significantly increased when this restraint is lost.3,58 Thus, posterior tension band reinforcement has been proposed for PJK prevention and has formed the basis for using Mersilene tape as a spinous process augmentation technique.60 The insertion of posterior polyester tethers and sublaminar bands as tension band–enhancing modalities has also been suggested as a novel PJK prevention method.3,43 The rationale behind the use of PJ sublaminar bands includes widening of the transition zone at the proximal end of constructs by incorporating an additional anchor between the fused and nonfused segments and thus facilitating a smoother transition (rigid—semirigid—nonrigid). In addition, UIV+1 sublaminar bands provide a stronger proximal anchor based on the relatively cortical laminar bone and thereby mitigating the strain at the immediate adjacent level. Apart from enhancing the transition zone, the posteriorly directed vector force created by UIV+1 sublaminar band placement may also optimally supplement the posterior ligamentous complex and thus further limit the kyphotic forces that lead to PJK development. Despite these potential benefits, PJ sublaminar band placement unfortunately remains associated with the theoretical possibility of a paradoxical increase in PJK because of the required additional muscle dissection, laminotomies, and posterior ligamentous disruption.16,55 Reassuringly, Ghailane and colleagues did not identify an increased postoperative incidence of PJK in their cohort of AIS patients treated with hybrid constructs that included proximal lamino-laminar claws and sublaminar bands.16

Current Study

Patient Characteristics

This study was performed in the first ASD patient cohort treated with long-segment thoracolumbar arthrodesis supplemented by a novel technique of sublaminar band placement at the UIV+1 (Fig. 1). We prospectively evaluated a consecutive series of 40 patients (with no loss to follow-up to date) to assess this technique’s feasibility, safety, and potential effect on the occurrence of PJK and PJF. Although we have reported outcomes at early time points (median of 12 months), our follow-up intervals did encompass the period over which PJK and PJF can occur.30,34,59 In support of this concept, 2 of the 3 sublaminar band patients who developed PJK met the criteria starting at the immediate follow-up time point.

Over half (70.0%) of the patients in our cohort underwent revision surgeries, whereas 57.5% of the patients had a BMI ≥ 30 kg/m2 and 35.0% had osteopenia or osteoporosis. A majority of our cohort had significant sagittal imbalance (80.0% with SVA ≥ 4 cm) and 25.0% had severe associated coronal deformities. Osteotomies were performed in 97.5% of patients; all of these patients underwent multilevel SPOs and 3 (7.5%) also underwent a PSO. The comparatively more rigid cobalt-chrome rods have been linked to a greater risk of PJK development than titanium rods,18 but the former were used in most of the patients in this study (26 patients overall and 2 of the 3 who developed PJK) given their recognized ability to more optimally maintain deformity correction.

Complications

Nearly two-thirds of our cohort experienced at least 1 complication with an overall total of 39 prospectively identified complications, including 16 graded as mild, 20 as moderate, and 3 as severe. The overall and system-specific complication rates appear to be generally consistent with rates reported in the literature.48 Specifically, we noted 3 procedure-related complications, all of which occurred in the early phase of the study. These included 2 dural tears, which required no further intervention beyond the initial patching and thus were graded as mild in severity, and 1 transient neurological deficit, graded as moderate in severity. One patient (case 22) sustained a dural tear and the neurological deficit, which we believe was related to a disc prolapse at the level of band insertion, compromising the space available in the canal (Fig. 3). We noted a unilateral decrease in MEPs immediately following ipsilateral sublaminar band insertion. As a result of this experience, we recommend careful preoperative review of MRI studies at the level of band insertion for all patients to assess the canal dimension. In cases of significant canal compromise, one might consider choosing a different level for band insertion to minimize the risk of neurological complications. Overall, we believe these data support the notion that UIV+1 sublaminar band placement in ASD patients can be safely performed without a significant increase in overall complications.

Clinical Outcomes

Despite our relatively small number of patients, we observed significant improvements in VAS (back), ODI, and RAND SF-36 scores at various follow-up time points. We also observed a significant improvement in radiological parameters such as TK, TLK, LL, SVA, PT, SS, and PI-LL mismatch by the final follow-up. Given the above, we believe that our UIV+1 sublaminar band cohort is representative of the wider population of ASD patients managed surgically.

Radiological Outcomes

At this early stage of follow-up, our PJK incidence of 7.5% and absence of PJF represent low rates as compared with those in the literature (Table 7). While direct comparisons are not possible given the disparate follow-up periods, we believe it is reasonable to conclude that UIV+1 sublaminar band placement is not associated with increased PJK or PJF rates. Of note, neither hybrid fixation using proximal hooks2 nor minimally invasive stabilization41 has proven to significantly reduce the incidence of PJK. Enhanced PJ anterior column support with UIV/UIV+1 vertebroplasty is another intriguing option but recently was shown not to convincingly reduce PJK or PJF rates at 5 years postoperatively; instead, the increased anterior column support appears to delay the occurrence of PJK beyond the usual early period.38,46

TABLE 7.

Comparative PJK and PJF values in the present study and reported in the literature

StudyPJKPJF
Current study (no./total [%])3/40 (7.5%)0 (0%)
Literature studies
 Posterior pedicle screw–only instrumentation (Hostin et al., 2013; Liu et al., 2016)22,3718.7%–52.6%5.6%–21%
 Hybrid fixation w/ UIV hooks (Bess et al., 2007)221.1%–34.1%
 Minimally invasive instrumentation (Mummaneni et al., 2016)4131.3%–48.1%
 Supplemental vertebroplasty (Raman et al., 2017)4628.2%5.1%

Despite the low incidence of PJK in our sublaminar band cohort, we observed that mean PJ Cobb angles significantly increased at the immediate postoperative time point as compared with preoperative values; however, the angles subsequently stabilized with no significant difference between the final follow-up and the immediate postoperative values. In contrast, PJ Cobb angles have been shown to successively increase over time in patients who develop PJK with pedicle screw–only constructs.54

Study Limitations

Study limitations include an absence of randomization and comparisons that are limited to findings in the previously published literature, which can introduce confounding effects related to patient characteristics and surgical techniques (for example, the proportion of patients implanted with stiffer cobalt-chrome rods). As with the recent experience with prophylactic vertebroplasty,46 it remains to be seen whether our early results at the 1-year median follow-up (3 patients with a 3-month follow-up, 11 patients with a 6-month follow-up, and 26 patients with a 1-year follow-up) will be maintained over the long term. Finally, our analysis does not exclude the possibility of added PJK prevention related to perioperative teriparatide treatment, which was administered in 6 patients.

Conclusions

These observations are based on our initial experience with sublaminar band placement at the UIV+1 of long-segment thoracolumbar fusion constructs. According to data in this prospective analysis, sublaminar band placement is a relatively safe technique without an associated increase in PJK and no cases of PJF in a well-defined cohort of patients with ASD. Larger-scale and longer-term follow-up analysis with contemporary matched control patients will be required to better define the potential benefit of UIV+1 sublaminar bands in mitigating the incidence of PJK and PJF following adult deformity correction.

Disclosures

Research support was provided by Implanet America Inc. for the development of the web-based REDCap database. Implanet had no role in data gathering, analysis, interpretation, or manuscript preparation.

Author Contributions

Conception and design: Farhadi, Minnema. Acquisition of data: all authors. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Farhadi. Statistical analysis: all authors. Administrative/technical/material support: Farhadi, Minnema. Study supervision: Farhadi, Minnema.

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    • Search Google Scholar
    • Export Citation
  • 49

    Smith JSLafage VShaffrey CISchwab FLafage RHostin R: Outcomes of operative and nonoperative treatment for adult spinal deformity: a prospective, multicenter, propensity-matched cohort assessment with minimum 2-year follow-up. Neurosurgery 78:8518612016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 50

    Smith JSSansur CADonaldson WF IIIPerra JHMudiyam RChoma TJ: Short-term morbidity and mortality associated with correction of thoracolumbar fixed sagittal plane deformity: a report from the Scoliosis Research Society Morbidity and Mortality Committee. Spine (Phila Pa 1976) 36:9589642011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 51

    Smith MWAnnis PLawrence BDDaubs MDBrodke DS: Acute proximal junctional failure in patients with preoperative sagittal imbalance. Spine J 15:214221482015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 52

    Thawrani DPGlos DLCoombs MTBylski-Austrow DISturm PF: Transverse process hooks at upper instrumented vertebra provide more gradual motion transition than pedicle screws. Spine (Phila Pa 1976) 39:E826E8322014

    • Search Google Scholar
    • Export Citation
  • 53

    Theologis AAMiller LCallahan MLau DZygourakis CScheer JK: Economic impact of revision surgery for proximal junctional failure after adult spinal deformity surgery: a cost analysis of 57 operations in a 10-year experience at a major deformity center. Spine (Phila Pa 1976) 41:E964E9722016

    • Search Google Scholar
    • Export Citation
  • 54

    Wang HMa LYang DWang TYang SWang Y: Incidence and risk factors for the progression of proximal junctional kyphosis in degenerative lumbar scoliosis following long instrumented posterior spinal fusion. Medicine (Baltimore) 95:e44432016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 55

    Wang JZhao YShen BWang CLi M: Risk factor analysis of proximal junctional kyphosis after posterior fusion in patients with idiopathic scoliosis. Injury 41:4154202010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 56

    Ware JE JrSherbourne CD: The MOS 36-Item Short-Form Health Survey (SF-36). I. Conceptual framework and item selection. Med Care 30:4734831992

  • 57

    Watanabe KLenke LGBridwell KHKim YJKoester LHensley M: Proximal junctional vertebral fracture in adults after spinal deformity surgery using pedicle screw constructs: analysis of morphological features. Spine (Phila Pa 1976) 35:1381452010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 58

    Yagi MAkilah KBBoachie-Adjei O: Incidence, risk factors and classification of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Spine (Phila Pa 1976) 36:E60E682011

    • Search Google Scholar
    • Export Citation
  • 59

    Yagi MKing ABBoachie-Adjei O: Incidence, risk factors, and natural course of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Minimum 5 years of follow-up. Spine (Phila Pa 1976) 37:147914892012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 60

    Zaghloul KMMatoian BJDenardin NBPatel VV: Preventing proximal adjacent level kyphosis with strap stabilization. Orthopedics 39:e794e7992016

    • Search Google Scholar
    • Export Citation

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Article Information

Contributor Notes

Correspondence H. Francis Farhadi: The Ohio State University Wexner Medical Center, Columbus, OH. francis.farhadi@osumc.edu.INCLUDE WHEN CITING Published online February 9, 2018; DOI: 10.3171/2017.8.SPINE17672.Disclosures Research support was provided by Implanet America Inc. for the development of the web-based REDCap database. Implanet had no role in data gathering, analysis, interpretation, or manuscript preparation.
Headings
Figures
  • View in gallery

    Drawings of the steps involved in the insertion of the sublaminar bands at the UIV+1. A: Hemilaminotomy and widening of the interlaminar space at the superior aspect of the UIV lamina. B: Hemilaminotomy and widening of the interlaminar space at the superior aspect of the UIV+1 laminas. C: Insertion of the band from the inferior hemilaminotomy window. D: Careful retrieval of the band through the superior hemilaminotomy window. E: Posterior, lateral, and axial views of the vertebra showing sublaminar band placement prior to rod attachment. F: Posterior and lateral views of the vertebrae showing the sublaminar bands anchored to the pedicle screw-rod construct. Copyright H. Francis Farhadi. Published with permission.

  • View in gallery

    A: Preoperative 36-inch whole-spine lateral standing radiograph. Line 1, sagittal C-7 plumb line (vertical line dropped from the center of the C-7 vertebral body); line 2, SVA, distance between the sagittal C-7 plumb line and the posterosuperior margin of the S-1 vertebra; TK, angle between superior endplate of T-3 vertebra to inferior endplate of T-12 vertebra; TLK, angle between superior endplate of T-10 vertebra to inferior endplate of L-2 vertebra; LL, angle between superior endplate of L-1 vertebra to superior endplate of S-1 vertebra; SS, angle between superior endplate of S-1 and the horizontal; PT, angle between the line joining the midpoint of the superior endplate of S-1 and the center of the femoral head and the vertical; PI, angle between the line perpendicular to the superior endplate of S-1 and bisecting it and the line joining the midpoint of superior sacral endplate and the center of the femoral heads. B: Lateral postoperative thoracolumbar radiograph showing instrumentation between T-10 and T-12 levels. Proximal junctional (PJ) Cobb angle, angle between inferior endplate of UIV (T-10) and superior endplate of UIV+2 vertebra (T-8); UIV sagittal tilt, angle between the inferior endplate of UIV and the horizontal.

  • View in gallery

    Case 22. Pre-ASD surgery T2-weighted MR images. A: Midsagittal section showing severe multilevel degeneration and postoperative laminectomy changes at the L2–5 levels. There is a herniated disc at the T9–10 level causing narrowing of the central spinal canal. B: Axial section at the corresponding T9–10 level showing the central herniated disc, slightly eccentric to the left, and associated canal compromise.

  • View in gallery

    Case 31. A: Preoperative standing 36-inch whole-spine anteroposterior and lateral radiographs. A sagittal plane deformity with an SVA of +28.6 cm was noted. B: Postoperative standing 36-inch whole-spine anteroposterior and lateral radiographs showing T-4 to ilium arthrodesis and deformity correction (SVA +6.1 cm). Radiological PJK is noted with PJ Cobb2 and ΔPJ Cobb2 of 21.9° and 20.0°, respectively.

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    Smith JSLafage VShaffrey CISchwab FLafage RHostin R: Outcomes of operative and nonoperative treatment for adult spinal deformity: a prospective, multicenter, propensity-matched cohort assessment with minimum 2-year follow-up. Neurosurgery 78:8518612016

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    • PubMed
    • Search Google Scholar
    • Export Citation
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    Smith JSSansur CADonaldson WF IIIPerra JHMudiyam RChoma TJ: Short-term morbidity and mortality associated with correction of thoracolumbar fixed sagittal plane deformity: a report from the Scoliosis Research Society Morbidity and Mortality Committee. Spine (Phila Pa 1976) 36:9589642011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 51

    Smith MWAnnis PLawrence BDDaubs MDBrodke DS: Acute proximal junctional failure in patients with preoperative sagittal imbalance. Spine J 15:214221482015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 52

    Thawrani DPGlos DLCoombs MTBylski-Austrow DISturm PF: Transverse process hooks at upper instrumented vertebra provide more gradual motion transition than pedicle screws. Spine (Phila Pa 1976) 39:E826E8322014

    • Search Google Scholar
    • Export Citation
  • 53

    Theologis AAMiller LCallahan MLau DZygourakis CScheer JK: Economic impact of revision surgery for proximal junctional failure after adult spinal deformity surgery: a cost analysis of 57 operations in a 10-year experience at a major deformity center. Spine (Phila Pa 1976) 41:E964E9722016

    • Search Google Scholar
    • Export Citation
  • 54

    Wang HMa LYang DWang TYang SWang Y: Incidence and risk factors for the progression of proximal junctional kyphosis in degenerative lumbar scoliosis following long instrumented posterior spinal fusion. Medicine (Baltimore) 95:e44432016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 55

    Wang JZhao YShen BWang CLi M: Risk factor analysis of proximal junctional kyphosis after posterior fusion in patients with idiopathic scoliosis. Injury 41:4154202010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 56

    Ware JE JrSherbourne CD: The MOS 36-Item Short-Form Health Survey (SF-36). I. Conceptual framework and item selection. Med Care 30:4734831992

  • 57

    Watanabe KLenke LGBridwell KHKim YJKoester LHensley M: Proximal junctional vertebral fracture in adults after spinal deformity surgery using pedicle screw constructs: analysis of morphological features. Spine (Phila Pa 1976) 35:1381452010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 58

    Yagi MAkilah KBBoachie-Adjei O: Incidence, risk factors and classification of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Spine (Phila Pa 1976) 36:E60E682011

    • Search Google Scholar
    • Export Citation
  • 59

    Yagi MKing ABBoachie-Adjei O: Incidence, risk factors, and natural course of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Minimum 5 years of follow-up. Spine (Phila Pa 1976) 37:147914892012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 60

    Zaghloul KMMatoian BJDenardin NBPatel VV: Preventing proximal adjacent level kyphosis with strap stabilization. Orthopedics 39:e794e7992016

    • Search Google Scholar
    • Export Citation
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