SPINE Volume 39, Number 10, pp E607-E614 ©2014, Lippincott Williams & Wilkins
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Characterization and Surgical Outcomes of Proximal Junctional Failure in Surgically Treated Patients With Adult Spinal Deformity Mitsuru Yagi, MD, PhD,* Mark Rahm, MD,† Robert Gaines, MD,‡ Ali Maziad, MD,§ Tom Ross, RN,§ Han Jo Kim, MD,§ Khaled Kebaish, MD,¶ and Oheneba Boachie-Adjei, MD,§ Complex Spine Study Group
Study Design. Retrospective case series of surgically treated patients with adult spine deformity (ASD). Objective. To report the incidence of proximal junctional failure (PJF), characterize PJF and evaluate the outcome of revision surgery for PJF. A modified classification is also proposed. Summary of Background Data. Although recent reports have shown the catastrophic results of PJF, few reports have shown the incidence, characteristics, and clinical outcomes of PJF in ASD. Methods. This retrospective analysis reviewed data entered prospectively into a multicenter database. Surgically treated patients with ASD with a minimum 2-year follow-up were included. PJF was defined as any type of symptomatic proximal junctional kyphosis (PJK) requiring surgery. On the basis of our previous classification, the following modified PJK classification was established: grade A, proximal junctional increase of 10° to 19°; grade B, 20° to 29°; and grade C, 30° or more. Three types of PJK were also defined: ligamentous failure (type 1), bone failure (type 2), and implant/ bone interface failure (type 3). An additional criterion was added for the presence or absence of spondylolisthesis above the upper instrumentation vertebra (UIV). Results. PJF developed in 23 of the 1668 patients with ASD. The incidence of PJF was 1.4%. The mean age was 62.3 ± 7.9 years, and the mean follow-up was 4.0 ± 2.3 years. Seventeen patients had undergone prior surgical procedures. Six patients had UIV
From the *National Hospital Organization Murayama Medical Center, Tokyo; †Scott and White Clinic, Temple, TX; ‡Columbia Spine Center and Orthopaedic Group, Columbia, MO; §Hospital for Special Surgery, New York, NY; ¶Johns Hopkins University, Baltimore, MD; and Complex Spine Study Group, Leesburg VA, US. Acknowledgment date: October 7, 2013. First revision date: January 16, 2014. Second revision date: January 22, 2014. Acceptance date: January 25, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: grant, payment for lectures, support for travel, consultancy, royalties, grants/grants pending, stock/stock options, travel/accommodations/meeting expenses, patents, and research support. Address correspondence and reprint requests to Mitsuru Yagi, MD, PhD, 2-37-1 Gakuen, Musashi-Murayama, Tokyo, Japan; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000266 Spine
above T8, and 17 had UIV below T9. Six patients had associated spondylolisthesis above the UIV (PJF-S), whereas 17 patients did not (PJF-N). The radiographical data show a significant difference in the preoperative sagittal vertical axis between the PJF-S and PJF-N groups, whereas no significant difference was observed in the preoperative sagittal parameters (5.2 ± 3.9 cm vs. 11.4 ± 6.0 cm, P = 0.04). The most common type of PJF was type 2N. The PJF symptoms consisted of intolerable pain (n = 17), neurological deficits (n = 6), and progressive trunk deformity (n = 1). Eleven patients had additional PJK/PJF and 9 required additional revision surgical procedures. Conclusion. The incidence of PJF among surgically treated patients with ASD was 1.4%. The most common type of PJF was 2N. Preoperative large sagittal vertical axis change and large amount of correction was a causative factor for spondylolisthesis above the UIV. After the revision surgery, further PJF was a commonly occurred event. Key words: PJK, PJF, adult spine deformity, complication. Level of Evidence: 3 Spine 2014;39:E607–E614
T
he essential goals of corrective surgery are maintaining both coronal and sagittal balance in addition to achieving an optimal curve correction and solid arthrodesis.1–10 Proximal junctional kyphosis (PJK) is a well-recognized postoperative phenomenon in adults and adolescents after scoliosis surgery.11–18 A uniform and consistent phenomenon is the increased junctional stress concentration that causes softtissue and ligamentous failure, bone failure, and bone implant interface failure.19–22 Recent reviews have shown a high prevalence of PJK in posterior spinal fusion, providing additional information on this complication and pathology.19,20,23–27 Glattes et al23 reported a 26% prevalence of PJK in adults with spinal deformity undergoing long posterior spinal fusion at a minimum of 2 years postsurgery. We have identified a 22% incidence of PJK among surgically treated patient with adult spine deformity (ASD). Although the overall clinical outcome of the patient developing PJK was equal to those who did not show PJK, some patients with PJK did have symptoms.27 In a previous study, we identified the incidence of symptomatic PJK to be approximately 4%.27 The most devastating form of symptomatic PJK is PJK with neurological deficit.21,27 www.spinejournal.com
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DEFORMITY Considering the severity of this complication, it is essential to understand the pathology of PJK with a neurological deficit in patients with ASD, although the incidence of symptomatic PJK is relatively low. Despite recent reports, the prevalence, surgical outcomes, and risk factors of symptomatic PJK development are still controversial. The aims of this study are to assess the incidence, characterization, and surgical outcomes of symptomatic PJK after long-instrumented spinal fusion for ASD. A modified PJK/proximal junctional failure (PJF) classification is also proposed.
MATERIALS AND METHODS This study was approved by the institutional review boards of the participating hospitals. A retrospective review of a multicenter, prospectively collected database of adults (older than 50 yr) who underwent posterior spinal fusion and instrumentation as part of their spinal deformity correction for scoliosis/ kyphosis was conducted. A retrospective review of the medical records and radiographs included 1668 consecutive patients with ASD who were treated with long-instrumented (>5 levels) spine fusion. The indication of the index surgery was the patients who have disabling back and/or leg pain and spinal imbalance and failed all reasonable conservative (nonoperative) treatment for at least more than 3 months. The cause of the patients consisted of adult idiopathic scoliosis, degenerative spine scoliosis and fixed sagittal imbalance. On the basis of the patient history, the other pathological condition was excluded. Surgeons performed the operations at centers between 1996 and 2010. All patients had a minimum 2-year follow-up (mean, 4.3 yr; range, 2–12 yr). The inclusion criteria consisted of being older than 50 years at the time of the surgery and having an ASD that was treated with instrumented spinal fusion at a minimum of 5-motion segments and complete radiographical follow-ups. We identified PJF as a symptomatic PJK requiring any type of surgery. The complete radiographical review required adequate preoperative, immediate postoperative (8–12 wk postsurgery), and the most recent follow-up anteroposterior and lateral standing 36-inch long cassette radiographs. Patients were asked to stand naturally with their shoulders flexed forward at approximately 30° to ensure that their upper thoracic vertebral bodies could be visualized on the lateral radiograph. The endplates at the proximal junction had to be clearly visible for study inclusion. Degenerative scoliosis and other nonidiopathic patients with spine deformity were excluded from this study. Clinical examinations and investigations were performed to rule out other causes of scoliosis.27 The preoperative and postoperative radiographical measurements, age, sex, weight, height, body mass index (BMI, weight [kg]/height2 [m2]), bone mineral density (BMD), upper instrumentation vertebra (UIV) instrumentation type, surgery type, fusion to sacrum, bone fusion, complications, and clinical outcomes were investigated. The density of the femoral neck was determined using dual-energy x-ray absorptiometry. Osteoporosis and osteopenia were defined using the World Health Organization criteria (i.e., the patients with T scores ≤2.5 were considered osteoporotic and those between ≤1 and −2.5 were considered E608
Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
osteopenic). Data collection was performed retrospectively by an independent senior spine surgeon who was not involved in the surgical treatment of the study patients.
Radiographical Measurements On the lateral radiographs, the sagittal vertical axis (SVA) was measured as the distance from the C7 plumb line to the perpendicular line drawn from the superior posterior endplate of the S1 vertebral body. If the C7 plumb line fell behind the SVA, then the global sagittal balance was negative. If the C7 plumb line fell in front of the SVA, then the sagittal balance was positive. If the C7 plumb line fell on the SVA, then the sagittal balance was 0. Thoracic kyphosis was measured from the upper endplate of T5 to the lower endplate of T12, and lumbar lordosis (LL) was measured from the lower endplate of T12 to the upper endplate of S1. The pelvic incidence (PI) was measured from the angle subtended by a perpendicular line from the cephalad endplate of S1 and a line connecting the center of the femoral head to the center of the cephalad endplate of S1.28,29 We defined the normal global spine alignment as thoracic kyphosis + LL + PI < 45°.27,30 The proximal junction was defined as the caudal endplate of the UIV to the cephalad endplate of 2 proximal vertebrae. An abnormal PJK was defined by a proximal junctional angle more than 10° and at least 10° greater than the corresponding preoperative measurement. The presence of both criteria was necessary to be considered abnormal.27,30 On the basis of our previous classification, a modified PJK classification was established: grade A, a proximal junctional increase of 10° to 19°; grade B, a proximal junctional increase of 20° to 29°; and grade C, a proximal junctional increase 30° or more. Three types of PJK were also defined: PJK from disc and ligamentous failure (type 1), from bone failure (type 2), and from implant/bone interface failure (type 3). An additional criterion was added for PJF with the presence or absence of spondylolisthesis above the UIV. An S modifier was added in the presence of spondylolisthesis above the UIV, and an N modifier was added in the absence of spondylolisthesis above the UIV (Table 1; Figures 1–3).
Statistical Analysis P values are based on the Student t test for continuous variables. χ2 tests were used on ordinal and nominal data when more than 5 observations were expected in each category, and Fisher exact tests were used on ordinal and nominal data when fewer than 5 observations were expected in each category. An analysis of variance was used to assess the difference of continuous measures across the groups. A P < 0.05 with a confidence interval of 95% was considered significant. All analyses were performed with the Statistical Package for the Social Sciences (SPSS, Chicago, IL).
RESULTS Incidence, Characteristics, and Classification of PJF in Surgically Treated Patients With ASD Among 1668 patients with ASD, 23 patients (1.4%) developed PJF (6 males and 17 females). The demographic data of the
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DEFORMITY TABLE 1. Classification of PJK/PJF Type 1
Disc and ligamentous failure
2
Bone failure
3
Implant/bone interface failure
Grade A
Proximal junctional increase 10°–19°
B
Proximal junctional increase 20°–29°
C
Proximal junctional increase 30°
Spondylolisthesis PJF-N
No obvious spondylolisthesis above UIV
PJF-S
Spondylolisthesis above UIV
PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure; UIV, upper instrumentation vertebra.
patients are shown in Table 1. Seventeen of these 23 patients (74%) underwent prior spine surgical procedures, and all patients underwent multilevel fusions from the thoracic spine to L5 or to the sacropelvis for their ASD. The instrumentation consisted of posterior pedicle screw constructs in all patients. Ten patients were osteopenic; 9 patients had normal bone mineral densities, and no patients were osteoporotic. Four patients were considered obese (BMI > 30 kg/m2), and no patients were underweight (BMI < 18.5 kg/m2). The PJF symptoms consisted of intolerable pain (n = 16), neurological deficits (n = 6), and head ptosis (n = 1) (Figure 1). The mean PJ angle was 26.8 ± 8.8° at the time PJF was identified. The mean time to PJF from the surgery was 10.5 ± 9.3 months (range, 1–33 mo). Twenty patients (87%) showed PJF within 2 years postsurgery (Table 2). Seven patients were PJF grade A (proximal junctional angle < 20°); 8 patients were grade B (proximal junctional increase 20° to 29°), and 8 patients were grade C (proximal junctional increase 30°) (Table 3). Eight patients were defined as type 1, 13 were type 2, and 2 were type 3.
Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
Seventeen patients were PJF-N (no obvious spondylolisthesis above the UIV), whereas 6 patients were PJF-S (spondylolisthesis above the UIV). The most common type of PJF seen in this study was type 2N. The most devastating form of PJF (with a neurological deficit) was most commonly observed in type 2S. A significantly high incidence of neurological deficits developed in PJF-S (P = 0.02, 2/19 patients in PJF-N and 4/6 patients in PJF-S; Table 4). Revision extension spinal fusion to a more proximal thoracic level was performed to treat PJF in all 23 patients. No differences were observed for age, sex, BMI, BMD, and pre- and postoperative thoracic kyphosis, lumbar lordosis, PI, PI-LL between the PJF-S and PJF-N groups, whereas the PJF-S group demonstrated a significantly larger SVA preoperatively (5.2 ± 3.9 cm vs. 10.5 ± 6.0 cm; P = 0.04; Table 5). On the contrary, postoperative radiographical data showed no difference between these 2 groups. There was a trend in the SVA change in the S modifier PJF group, but this trend was not significant (3.5 ± 1.2 cm vs. 11.0 ± 5.0 cm; P = 0.08; Table 6).
Surgical Outcome All patients underwent revisions with fusion extensions to a more proximal thoracic level. Twelve patients developed major complications. Eleven of these patients (48%) had additional PJK/PJF at the new UIV, and 9 patients required additional revision surgical procedures. Among these 9 patients, 2 patients had further PJF at the new UIV and had revision extension surgery again during follow-up (Figures 4, 5). One patient had a deep wound infection requiring incision and debridement, and 1 patient developed pseudoarthrosis at the new UIV and required revision PSF. The patients with PJF with associated neurological deficits consisted of 5 in Frankel C and 1 in Frankel B, preoperatively. The neurological status improved in all patients after surgery, 1 in Frankel C, 4 in Frankel D, and 1 in Frankel E at the final follow-up.
DISCUSSION PJK has been recently identified in patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis and
Figure 1. Radiographical example of type 1 ligamentous failure PJF. A, Type 1AN PJK 2 level (16°). B, Type 1CN PJK 2 level (66°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure. Spine
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
TABLE 2. Demographics of the Patients With
ASD With PJF
Total No. of patients
23/1668 (1.4)
Age (yr)
62.3 ± 7.9
F/U (yr)
4.3 ± 2.3 (2–12)
Sex, F:M
17:6
Cause
Figure 2. Radiographical example of type 2 bone failure PJF with or without spondylolisthesis. A, Type 2CN PJK 2 level (16°). B, Type 2BS PJK 2 level (23°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
Scheuermann kyphosis. Lonner et al31 have reported a 30% incidence of PJK in surgically treated patients with Scheuermann kyphosis. However, to the best of our knowledge, there is a paucity of information regarding the incidence and clinical outcome of symptomatic PJK in a long-term follow-up study. We have previously reported the prevalence and the clinical outcome of PJF in surgically treated adults with idiopathic scoliosis. In that study, we reported a prevalence of 3.8% (6/157 patients) for symptomatic PJK, 2.5% prevalence (4/157 patients) of PJF at 3.3 yr, and significantly lower clinical outcomes for those patients with PJF. Hart et al32 recently reported the incidence and characteristics of developing acute PJF. They reported that the prevalence of acute PJF was 5.6% in the surgically treated patients with ASD. In this study, we identified a PJF incidence of 1.4% (23/1668) in the surgically treated patients with ASD. The difference in the incidence of PJF in this study and their study might be due to the differences in the
Degenerative scoliosis
14
Idiopathic scoliosis
5
Flat back syndrome
4
BMI (kg/m )
27.6 ± 3.7
BMD (T score)
−1.1 ± 0.9
Time to PJF (mo)
10.5 ± 9.3
2
No. of neurological deficit
6 (26.1)
UIV Above T8
7 (30.4)
Below T9
16 (69.6)
No. of revision surgery
17 (73.9)
Values denote mean and standard deviations. Percentage in parenthesis. ASD indicates adult spine deformity; PJF, proximal junctional failure; F/U, follow-up; BMI, body mass index; BMD, bone mineral density; UIV, upper instrumentation vertebra.
diagnostic criteria for PJF. In this study, we have defined PJF as symptomatic PJK requiring any type of surgery, whereas Hostin et al32 included the patients with an increased proximal junctional angle greater than 15° and symptomatic PJK. Although the incidence of PJF among surgically treated patients with ASD is relatively low, the impact of PJF on clinical outcomes of those patients strongly suggests that surgeons should not overlook this devastating complication.
TABLE 3. Classification of PJF in Surgically
Treated Patients With ASD
Figure 3. Radiographical example of type 2 bone/interface failure PJF. A, B: Type 3CN PJK 2 level (49°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
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Type 1
Type 2
Type 3
Total
Grade A
3
4
0
7
Grade B
4
3
1
8
Grade C
1
6
1
7
Total
8
13
2
23
PJF-N
7
8
2
17
PJF-S
1
5
0
6
Total
8
13
2
23
ASD indicates adult spine deformity; PJF, proximal junctional failure.
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
TABLE 4. Characteristic Comparison Between PJF-N Group and PJF-S Group P
Total
PJF-N
PJF-S
23 (100)
17 (73.9)
6 (26.1)
62.3 ± 7.9
62 ± 7.9
65 ± 0.5
0.53
17:6
14:3
4:2
0.74
Degenerative scoliosis
14
10
4
0.64
Flat back syndrome
4
3
1
0.71
Idiopathic scoliosis
5
4
1
0.69
BMI (kg/m2)
27.6 ± 3.7
27.4 ± 3.9
27.3 ± 3.2
0.81
BMD (T score)
−1.1 ± 0.9
−1.1 ± 0.7
−1.1 ± 0.5
0.94
Time to PJF (mo)
10.5 ± 9.3
11.7 ± 10
8.4 ± 6.8
0.45
6 (26.1)
2 (11.8)
4 (66.7)
0.02*
Above T8
7 (30.4)
5 (29.4)
2 (33.3)
0.82
Below T9
16 (69.6)
12 (70.6)
4 (66.7)
0.81
17 (73.9)
12 (70.6)
5 (83.3)
0.59
No. of patients Age (y) F/U (yr) Sex, F:M Cause
No. of neurological deficit UIV
No. of revision surgery
Values denote mean ± standard deviations. Percentage in parenthesis. *Statistically significant. ASD indicates adult spine deformity; PJF, proximal junctional failure; F/U, follow-up; BMI, body mass index; BMD, bone mineral density; UIV, upper instrumentation vertebra.
In this series, the most common type of PJF was type 2N. The most common form of PJF in this study was different from those observed in PJK in our previous studies.27,30,33 We have previously reported that the most common type of PJK was type 1 (ligamentous failure) at 2 postoperative years, whereas the most common type of PJF observed in this study was type 2 bone failure.27,30,33 We have previously
reported that the mean PJ angle of patients who had PJK at 3.3 years postsurgery was 17.6°, and PJFs are most commonly seen in grade C PJK in our single-center study.27 This study confirmed this result. The mean PJ angle of patients who developed PJF in this study was 26.8°. Compared with the mean PJ angle of those patients with PJK, the large magnitude in the PJ angle seen in those who developed PJF
TABLE 5. Radiographical Comparison Between PJF-N Group and PJF-S Group at Preoperation Total
PJF-N
PJF -S
P
PJ angle (°)
26.7 ± 8.4
26.2 ± 8.2
28.3 ± 9.5
0.63
TK (°)
35.1 ± 12.9
35.5 ± 13.9
33.5 ± 9.9
0.74
LL (°)
−40.7 ± 15.6
−41.9 ± 15.0
−36.6 ± 19.4
0.63
PI (°)
54.7 ± 7.2
55.4 ± 7.5
52.4 ± 6.1
0.45
SVA (cm)
6.6 ± 5.5
5.2 ± 3.9
11.4 ± 6.0
0.04*
PI-LL (°)
16.9 ± 10.4
17.3 ± 8.3
15.8 ± 10.6
0.91
TK + LL + PI (°)
50.4 ± 13.6
50.8 ± 5.6
49.3 ± 16.9
0.89
Values denote mean ± standard deviations. *Statistically significant. TK indicates thoracic kyphosis; PI, pelvic incidence; LL, lumbar lordosis; SVA, sagittal vertical axis; PJF, proximal junctional failure.
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
TABLE 6. Radiographical Comparison Between PJF-N Group and PJF-S Group Postoperatively Total
PJF-N
PJF-S
P
TK (°)
36.9 ± 8.8
35.7 ± 9.5
40.6 ± 4.9
0.21
LL (°)
−51.3 ± 11.7
−51.1 ± 11.9
−52.1 ± 12.6
0.9
SVA (cm)
1.5 ± 3.7
1.7 ± 0.5
0.6 ± 4.7
0.22
PI-LL (°)
3.4 ± 10.8
4.2 ± 4.4
0.4 ± 9.3
0.52
TK + LL + PI (°)
40.4 ± 13.7
39.9 ± 5.1
40.9 ± 12.3
0.92
SVA change (cm)
5.6 ± 5.1
3.5 ± 1.2
11.0 ± 5.0
0.08
Values denote mean ± standard deviations. TK indicates thoracic kyphosis; PI, pelvic incidence; LL, lumbar lordosis; SVA, sagittal vertical axis; PJF, proximal junctional failure.
strongly suggested that progression of the PJ angle might be the reason for the PJF. We have previously studied the natural course of PJK for a mean of 8.1 years of follow-up and found a continuous progression of the PJ angle in those who developed PJK, whereas no progression of the PJ angle was observed in those who did not have PJK.30 In this study, the most devastating form of PJK had an associated neurological injury and was not uncommon; most patients with neurological deficits had PJF type 2S. Four of the 6 (67%) patients with PJF-S (PJF with associated spondylolisthesis) developed a neurological deficit, and 70% (16/23) of the patients with PJF had UIVs below T9; 74% (17/23) of the patients with PJF had prior surgical procedures. We have previously reported that an abnormal global spine alignment (thoracic kyphosis + LL + PI > 45°), large SVA change (>5 cm), and low BMD are risk factors for developing PJK.27,30,33 Results of our present report are consistent with those of our previous report. Forty-eight percent (11/23) of the patients who developed PJF had postoperative abnormal global spine alignment, 52% (12/23) of the patients had a large SVA change, and 61% (14/23) of the patients had a low BMD. Taken together, the results show that the patients who underwent revision surgical procedures to treat ASD (with a significantly large preoperative positive SVA requiring large SVA correction and a UIV stop below T9) were at significant
risk of developing PJF with associated spondylolisthesis and subsequent neurological deficit. Our findings suggest uncertainty in the cause of PJF. Various studies have proposed that the development of PJK is related to a combination of patient and surgery-related factors. Of these factors, the integrity of the soft-tissue tension band, stress concentration, bone quality, instrumentation type, UIV below sagittal apex, and amount of sagittal plane correction are all implicated in PJK development.11–16,23,27,30,33,34 The same can be said for the cause of PJF. The fact that multiple revision extension surgical procedures were required to treat the patients with PJF strongly suggested that PJF results from not only iatrogenic causes but also patient-related causes. The results of this comprehensive review allowed better definition and a classification of PJK/PJF based on severity and type. The results will also guide spine surgeons in their preoperative planning and surgical management of ASD to eliminate or minimize the occurrence of PJF as a devastating form of PJK.
CONCLUSION In this series, the incidence of PJF among surgically treated patients with ASD was 1.4%. The most common type of PJF was 2N. The most devastating form, with associated neurological injury, was not uncommon, and most of the patients
Figure 4. A 55-year-old female with adult idiopathic scoliosis treated with combined anteroposteriorinstrumented fusion to T3 pelvis. Because of neck pain, she had revision extension PSF and developed further PJF at the new UIV level. A, Preoperative PJK 2 level (6°). B, Immediate postoperative PJK 2 level (21°). C, Two-year postoperative PJK 2 level (49°). D, Postrevision extension PSF to C7 PJK 2 level (15°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure; UIV, upper instrumentation vertebra.
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DEFORMITY
Figure 5. A 69-year-old female with adult idiopathic scoliosis treated with combined anteroposterior-instrumented fusion to T1-pelvis and had type 2CN PJF. Because of head ptosis, she had revision extension PSF. A, Three-month postoperative PJK 2 level (66°). B, Postrevision extension PSF to C6 PJK 2 level (−4°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
with neurological deficits had type 2S. Preoperative large SVA change and large amount of correction was a causative factor for spondylolisthesis above the UIV. After revision surgery, further PJF commonly occurred.
➢ Key Points The incidence of PJF among surgically treated patients with ASD was 1.4%. Older age, previous surgery, and UIV at the thoracolumbar junction were identified as PJF risk factors. Further PJF was a commonly occurred event after the revision surgery.
References
1. Anand N, Baron EM, Thaiyananthan G, et al. Minimally invasive multilevel percutaneous correction and fusion for adult lumbar degenerative scoliosis: a technique and feasibility study. J Spinal Disord Tech 2008;21:459–67. 2. Boachie-Adjei O, Ferguson JA, Pigeon RG, et al. Transpedicular lumbar wedge resection osteotomy for fixed sagittal imbalance: surgical technique and early results. Spine (Phila Pa 1976) 2006;31:485–92. 3. Cho KJ, Lenke LG, Bridwell KH, et al. Selection of the optimal distal fusion level in posterior instrumentation and fusion for thoracic hyperkyphosis: the sagittal stable vertebra concept. Spine (Phila Pa 1976) 2009;34:765–70.
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
4. Crandall DG, Revella J. Transforaminal lumbar interbody fusion versus anterior lumbar interbody fusion as an adjunct to posteriorinstrumented correction of degenerative lumbar scoliosis: three year clinical and radiographic outcomes. Spine (Phila Pa 1976) 2009;34:2126–33. 5. Heary RF, Kumar S, Bono CM. Decision making in adult deformity. Neurosurgery 2008;63:69–77. (Phila Pa 1976) 2008;33:1675–81. 6. Hosman AJ, Langeloo DD, de Kleuver M, et al. Analysis of the sagittal plane after surgical management for Scheuermann disease: a view on overcorrection and the use of an anterior release. Spine (Phila Pa 1976) 2002;27:167–75. 7. Kim YJ, Bridwell KH, Lenke LG, et al. Results of lumbar pedicle subtraction osteotomies for fixed sagittal imbalance: a minimum 5-year follow-up study. Spine (Phila Pa 1976) 2007;32: 2189–97. 8. Kim YJ, Lenke LG, Bridwell KH, et al. Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases. Spine (Phila Pa 1976) 2007;32: 2731–8. 9. Lee GA, Betz RR, Clements DH, III, et al. Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis. Spine (Phila Pa 1976) 1999;24:795–9. 10. Bridwell KH, Glassman S, Horton W, et al. Does treatment (nonoperative and operative) improve the two-year quality of life in patients with adult symptomatic lumbar scoliosis: a prospective multicenter evidence-based medicine study. Spine (Phila Pa 1976) 2009;34:2171–8. 11. Denis F, Sun EC, Winter RB. Incidence and risk factors for proximal and distal junctional kyphosis following surgical treatment for Scheuermann kyphosis: minimum five-year follow-up. Spine (Phila Pa 1976) 2009;34:E729–34. 12. DeWald CJ, Stanley T. Instrumentation-related complications of multilevel fusions for adult spinal deformity patients over age 65: surgical considerations and treatment options in patients with poor bone quality. Spine (Phila Pa 1976) 2006;31:S144–51. 13. Hart RA, Prendergast MA, Roberts WG, et al. Proximal junctional acute collapse cranial to multi-level lumbar fusion: a cost analysis of prophylactic vertebral augmentation. Spine J 2008;8:875–81. 14. Lafage V, Schwab F, Patel A, et al. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976) 2009;34:E599–606. 15. Kim YJ, Bridwell KH, Lenke LG, et al. Proximal junctional kyphosis in adult spinal deformity after segmental posterior spinal instrumentation and fusion: minimum five-year follow-up. Spine (Phila Pa 1976) 2008;33:2179–84. 16. Kim YJ, Bridwell KH, Lenke LG, et al. Proximal junctional kyphosis in adolescent idiopathic scoliosis following segmental posterior spinal instrumentation and fusion: minimum 5-year follow-up. Spine (Phila Pa 1976) 2005;30:2045–50. 17. Yang SH, Chen PQ. Proximal kyphosis after short posterior fusion for thoracolumbar scoliosis. Clin Orthop Relat Res 2003:152–8. 18. Helgeson MD, Shah SA, Newton PO, et al. Evaluation of proximal junctional kyphosis in adolescent idiopathic scoliosis following pedicle screw, hook, or hybrid instrumentation. Spine (Phila Pa 1976) 2010;35:177–81. 19. Hollenbeck SM, Glattes RC, Asher MA, et al. The prevalence of increased proximal junctional flexion following posterior instrumentation and arthrodesis for adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 2008;33:1675–81. 20. Lowe TG, Kasten MD. An analysis of sagittal curves and balance after Cotrel-Dubousset instrumentation for kyphosis secondary to Scheuermann disease. A review of 32 patients. Spine (Phila Pa 1976) 1994;19:1680–5. 21. Bomback DA, Charles G, Widmann R, et al. Video-assisted thoracoscopic surgery compared with thoracotomy: early and late follow-up of radiographical and functional outcome. Spine J 2007;7:399–405. 22. Watanabe K, Lenke LG, Bridwell KH, et al. Proximal junctional vertebral fracture in adults after spinal deformity surgery using pedicle screw constructs: analysis of morphological features. Spine (Phila Pa 1976) 2010;35:138–45. www.spinejournal.com
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DEFORMITY 23. Glattes RC, Bridwell KH, Lenke LG, et al. Proximal junctional kyphosis in adult spinal deformity following long-instrumented posterior spinal fusion: incidence, outcomes, and risk factor analysis. Spine (Phila Pa 1976) 2005;30:1643–9. 24. Good CR, Lenke LG, Bridwell KH, et al. Can posterior-only surgery provide similar radiographic and clinical results as combined anterior (thoracotomy/thoracoabdominal)/posterior approaches for adult scoliosis? Spine (Phila Pa 1976) 2010;35:210–8. 25. Rose PS, Lenke LG, Bridwell KH, et al. Pedicle screw instrumentation for adult idiopathic scoliosis: an improvement over hook/ hybrid fixation. Spine (Phila Pa 1976) 2009;34:852–7; discussion 8. 26. Suk SI, Lee SM, Chung ER, et al. Selective thoracic fusion with segmental pedicle screw fixation in the treatment of thoracic idiopathic scoliosis: more than 5-year follow-up. Spine (Phila Pa 1976) 2005;30:1602–9. 27. Yagi M, King A, Boachie-Adjei O. Incidence, risk factors and classification of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Spine (Phila Pa 1976) 2011;36: E60–8. 28. Bridwell KH, Lewis SJ, Rinella A, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance. Surgical technique. J Bone Joint Surg Am 2004;86-A(suppl 1):44–50.
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29. Ploumis A, Liu H, Mehbod AA, et al. A correlation of radiographic and functional measurements in adult degenerative scoliosis. Spine (Phila Pa 1976) 2009;34:1581–4. 30. Yagi M, King AB, Boachie-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) 2012;37:1479–89. 31. Lonner BS, Newton P, Betz R, et al. Operative management of Scheuermann kyphosis in 78 patients: radiographic outcomes, complications, and technique. Spine (Phila Pa 1976) 2007;32:2644–52. 32. Hart R, McCarthy I, O’brien M, et al. Identification of decision criteria for revision surgery among patients with proximal junctional failure following surgical treatment for spinal deformity. Spine (Phila Pa 1976) 2013. 33. Kim HJ, Yagi M, Nyugen J, et al. Combined anterior-posterior surgery is the most important risk factor for developing proximal junctional kyphosis in idiopathic scoliosis. Clin Orthop Relat Res 2012;470:1633–9. 34. Kim YJ, Bridwell KH, Lenke LG, et al. Is the T9, T11, or L1 the more reliable proximal level after adult lumbar or lumbosacralinstrumented fusion to L5 or S1? Spine (Phila Pa 1976) 2007;32: 2653–61.
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Characterization and Surgical Outcomes of Proximal Junctional Failure in Surgically Treated Patients With Adult Spinal Deformity Mitsuru Yagi, MD, PhD,* Mark Rahm, MD,† Robert Gaines, MD,‡ Ali Maziad, MD,§ Tom Ross, RN,§ Han Jo Kim, MD,§ Khaled Kebaish, MD,¶ and Oheneba Boachie-Adjei, MD,§ Complex Spine Study Group
Study Design. Retrospective case series of surgically treated patients with adult spine deformity (ASD). Objective. To report the incidence of proximal junctional failure (PJF), characterize PJF and evaluate the outcome of revision surgery for PJF. A modified classification is also proposed. Summary of Background Data. Although recent reports have shown the catastrophic results of PJF, few reports have shown the incidence, characteristics, and clinical outcomes of PJF in ASD. Methods. This retrospective analysis reviewed data entered prospectively into a multicenter database. Surgically treated patients with ASD with a minimum 2-year follow-up were included. PJF was defined as any type of symptomatic proximal junctional kyphosis (PJK) requiring surgery. On the basis of our previous classification, the following modified PJK classification was established: grade A, proximal junctional increase of 10° to 19°; grade B, 20° to 29°; and grade C, 30° or more. Three types of PJK were also defined: ligamentous failure (type 1), bone failure (type 2), and implant/ bone interface failure (type 3). An additional criterion was added for the presence or absence of spondylolisthesis above the upper instrumentation vertebra (UIV). Results. PJF developed in 23 of the 1668 patients with ASD. The incidence of PJF was 1.4%. The mean age was 62.3 ± 7.9 years, and the mean follow-up was 4.0 ± 2.3 years. Seventeen patients had undergone prior surgical procedures. Six patients had UIV
From the *National Hospital Organization Murayama Medical Center, Tokyo; †Scott and White Clinic, Temple, TX; ‡Columbia Spine Center and Orthopaedic Group, Columbia, MO; §Hospital for Special Surgery, New York, NY; ¶Johns Hopkins University, Baltimore, MD; and Complex Spine Study Group, Leesburg VA, US. Acknowledgment date: October 7, 2013. First revision date: January 16, 2014. Second revision date: January 22, 2014. Acceptance date: January 25, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: grant, payment for lectures, support for travel, consultancy, royalties, grants/grants pending, stock/stock options, travel/accommodations/meeting expenses, patents, and research support. Address correspondence and reprint requests to Mitsuru Yagi, MD, PhD, 2-37-1 Gakuen, Musashi-Murayama, Tokyo, Japan; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000266 Spine
above T8, and 17 had UIV below T9. Six patients had associated spondylolisthesis above the UIV (PJF-S), whereas 17 patients did not (PJF-N). The radiographical data show a significant difference in the preoperative sagittal vertical axis between the PJF-S and PJF-N groups, whereas no significant difference was observed in the preoperative sagittal parameters (5.2 ± 3.9 cm vs. 11.4 ± 6.0 cm, P = 0.04). The most common type of PJF was type 2N. The PJF symptoms consisted of intolerable pain (n = 17), neurological deficits (n = 6), and progressive trunk deformity (n = 1). Eleven patients had additional PJK/PJF and 9 required additional revision surgical procedures. Conclusion. The incidence of PJF among surgically treated patients with ASD was 1.4%. The most common type of PJF was 2N. Preoperative large sagittal vertical axis change and large amount of correction was a causative factor for spondylolisthesis above the UIV. After the revision surgery, further PJF was a commonly occurred event. Key words: PJK, PJF, adult spine deformity, complication. Level of Evidence: 3 Spine 2014;39:E607–E614
T
he essential goals of corrective surgery are maintaining both coronal and sagittal balance in addition to achieving an optimal curve correction and solid arthrodesis.1–10 Proximal junctional kyphosis (PJK) is a well-recognized postoperative phenomenon in adults and adolescents after scoliosis surgery.11–18 A uniform and consistent phenomenon is the increased junctional stress concentration that causes softtissue and ligamentous failure, bone failure, and bone implant interface failure.19–22 Recent reviews have shown a high prevalence of PJK in posterior spinal fusion, providing additional information on this complication and pathology.19,20,23–27 Glattes et al23 reported a 26% prevalence of PJK in adults with spinal deformity undergoing long posterior spinal fusion at a minimum of 2 years postsurgery. We have identified a 22% incidence of PJK among surgically treated patient with adult spine deformity (ASD). Although the overall clinical outcome of the patient developing PJK was equal to those who did not show PJK, some patients with PJK did have symptoms.27 In a previous study, we identified the incidence of symptomatic PJK to be approximately 4%.27 The most devastating form of symptomatic PJK is PJK with neurological deficit.21,27 www.spinejournal.com
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DEFORMITY Considering the severity of this complication, it is essential to understand the pathology of PJK with a neurological deficit in patients with ASD, although the incidence of symptomatic PJK is relatively low. Despite recent reports, the prevalence, surgical outcomes, and risk factors of symptomatic PJK development are still controversial. The aims of this study are to assess the incidence, characterization, and surgical outcomes of symptomatic PJK after long-instrumented spinal fusion for ASD. A modified PJK/proximal junctional failure (PJF) classification is also proposed.
MATERIALS AND METHODS This study was approved by the institutional review boards of the participating hospitals. A retrospective review of a multicenter, prospectively collected database of adults (older than 50 yr) who underwent posterior spinal fusion and instrumentation as part of their spinal deformity correction for scoliosis/ kyphosis was conducted. A retrospective review of the medical records and radiographs included 1668 consecutive patients with ASD who were treated with long-instrumented (>5 levels) spine fusion. The indication of the index surgery was the patients who have disabling back and/or leg pain and spinal imbalance and failed all reasonable conservative (nonoperative) treatment for at least more than 3 months. The cause of the patients consisted of adult idiopathic scoliosis, degenerative spine scoliosis and fixed sagittal imbalance. On the basis of the patient history, the other pathological condition was excluded. Surgeons performed the operations at centers between 1996 and 2010. All patients had a minimum 2-year follow-up (mean, 4.3 yr; range, 2–12 yr). The inclusion criteria consisted of being older than 50 years at the time of the surgery and having an ASD that was treated with instrumented spinal fusion at a minimum of 5-motion segments and complete radiographical follow-ups. We identified PJF as a symptomatic PJK requiring any type of surgery. The complete radiographical review required adequate preoperative, immediate postoperative (8–12 wk postsurgery), and the most recent follow-up anteroposterior and lateral standing 36-inch long cassette radiographs. Patients were asked to stand naturally with their shoulders flexed forward at approximately 30° to ensure that their upper thoracic vertebral bodies could be visualized on the lateral radiograph. The endplates at the proximal junction had to be clearly visible for study inclusion. Degenerative scoliosis and other nonidiopathic patients with spine deformity were excluded from this study. Clinical examinations and investigations were performed to rule out other causes of scoliosis.27 The preoperative and postoperative radiographical measurements, age, sex, weight, height, body mass index (BMI, weight [kg]/height2 [m2]), bone mineral density (BMD), upper instrumentation vertebra (UIV) instrumentation type, surgery type, fusion to sacrum, bone fusion, complications, and clinical outcomes were investigated. The density of the femoral neck was determined using dual-energy x-ray absorptiometry. Osteoporosis and osteopenia were defined using the World Health Organization criteria (i.e., the patients with T scores ≤2.5 were considered osteoporotic and those between ≤1 and −2.5 were considered E608
Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
osteopenic). Data collection was performed retrospectively by an independent senior spine surgeon who was not involved in the surgical treatment of the study patients.
Radiographical Measurements On the lateral radiographs, the sagittal vertical axis (SVA) was measured as the distance from the C7 plumb line to the perpendicular line drawn from the superior posterior endplate of the S1 vertebral body. If the C7 plumb line fell behind the SVA, then the global sagittal balance was negative. If the C7 plumb line fell in front of the SVA, then the sagittal balance was positive. If the C7 plumb line fell on the SVA, then the sagittal balance was 0. Thoracic kyphosis was measured from the upper endplate of T5 to the lower endplate of T12, and lumbar lordosis (LL) was measured from the lower endplate of T12 to the upper endplate of S1. The pelvic incidence (PI) was measured from the angle subtended by a perpendicular line from the cephalad endplate of S1 and a line connecting the center of the femoral head to the center of the cephalad endplate of S1.28,29 We defined the normal global spine alignment as thoracic kyphosis + LL + PI < 45°.27,30 The proximal junction was defined as the caudal endplate of the UIV to the cephalad endplate of 2 proximal vertebrae. An abnormal PJK was defined by a proximal junctional angle more than 10° and at least 10° greater than the corresponding preoperative measurement. The presence of both criteria was necessary to be considered abnormal.27,30 On the basis of our previous classification, a modified PJK classification was established: grade A, a proximal junctional increase of 10° to 19°; grade B, a proximal junctional increase of 20° to 29°; and grade C, a proximal junctional increase 30° or more. Three types of PJK were also defined: PJK from disc and ligamentous failure (type 1), from bone failure (type 2), and from implant/bone interface failure (type 3). An additional criterion was added for PJF with the presence or absence of spondylolisthesis above the UIV. An S modifier was added in the presence of spondylolisthesis above the UIV, and an N modifier was added in the absence of spondylolisthesis above the UIV (Table 1; Figures 1–3).
Statistical Analysis P values are based on the Student t test for continuous variables. χ2 tests were used on ordinal and nominal data when more than 5 observations were expected in each category, and Fisher exact tests were used on ordinal and nominal data when fewer than 5 observations were expected in each category. An analysis of variance was used to assess the difference of continuous measures across the groups. A P < 0.05 with a confidence interval of 95% was considered significant. All analyses were performed with the Statistical Package for the Social Sciences (SPSS, Chicago, IL).
RESULTS Incidence, Characteristics, and Classification of PJF in Surgically Treated Patients With ASD Among 1668 patients with ASD, 23 patients (1.4%) developed PJF (6 males and 17 females). The demographic data of the
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DEFORMITY TABLE 1. Classification of PJK/PJF Type 1
Disc and ligamentous failure
2
Bone failure
3
Implant/bone interface failure
Grade A
Proximal junctional increase 10°–19°
B
Proximal junctional increase 20°–29°
C
Proximal junctional increase 30°
Spondylolisthesis PJF-N
No obvious spondylolisthesis above UIV
PJF-S
Spondylolisthesis above UIV
PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure; UIV, upper instrumentation vertebra.
patients are shown in Table 1. Seventeen of these 23 patients (74%) underwent prior spine surgical procedures, and all patients underwent multilevel fusions from the thoracic spine to L5 or to the sacropelvis for their ASD. The instrumentation consisted of posterior pedicle screw constructs in all patients. Ten patients were osteopenic; 9 patients had normal bone mineral densities, and no patients were osteoporotic. Four patients were considered obese (BMI > 30 kg/m2), and no patients were underweight (BMI < 18.5 kg/m2). The PJF symptoms consisted of intolerable pain (n = 16), neurological deficits (n = 6), and head ptosis (n = 1) (Figure 1). The mean PJ angle was 26.8 ± 8.8° at the time PJF was identified. The mean time to PJF from the surgery was 10.5 ± 9.3 months (range, 1–33 mo). Twenty patients (87%) showed PJF within 2 years postsurgery (Table 2). Seven patients were PJF grade A (proximal junctional angle < 20°); 8 patients were grade B (proximal junctional increase 20° to 29°), and 8 patients were grade C (proximal junctional increase 30°) (Table 3). Eight patients were defined as type 1, 13 were type 2, and 2 were type 3.
Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
Seventeen patients were PJF-N (no obvious spondylolisthesis above the UIV), whereas 6 patients were PJF-S (spondylolisthesis above the UIV). The most common type of PJF seen in this study was type 2N. The most devastating form of PJF (with a neurological deficit) was most commonly observed in type 2S. A significantly high incidence of neurological deficits developed in PJF-S (P = 0.02, 2/19 patients in PJF-N and 4/6 patients in PJF-S; Table 4). Revision extension spinal fusion to a more proximal thoracic level was performed to treat PJF in all 23 patients. No differences were observed for age, sex, BMI, BMD, and pre- and postoperative thoracic kyphosis, lumbar lordosis, PI, PI-LL between the PJF-S and PJF-N groups, whereas the PJF-S group demonstrated a significantly larger SVA preoperatively (5.2 ± 3.9 cm vs. 10.5 ± 6.0 cm; P = 0.04; Table 5). On the contrary, postoperative radiographical data showed no difference between these 2 groups. There was a trend in the SVA change in the S modifier PJF group, but this trend was not significant (3.5 ± 1.2 cm vs. 11.0 ± 5.0 cm; P = 0.08; Table 6).
Surgical Outcome All patients underwent revisions with fusion extensions to a more proximal thoracic level. Twelve patients developed major complications. Eleven of these patients (48%) had additional PJK/PJF at the new UIV, and 9 patients required additional revision surgical procedures. Among these 9 patients, 2 patients had further PJF at the new UIV and had revision extension surgery again during follow-up (Figures 4, 5). One patient had a deep wound infection requiring incision and debridement, and 1 patient developed pseudoarthrosis at the new UIV and required revision PSF. The patients with PJF with associated neurological deficits consisted of 5 in Frankel C and 1 in Frankel B, preoperatively. The neurological status improved in all patients after surgery, 1 in Frankel C, 4 in Frankel D, and 1 in Frankel E at the final follow-up.
DISCUSSION PJK has been recently identified in patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis and
Figure 1. Radiographical example of type 1 ligamentous failure PJF. A, Type 1AN PJK 2 level (16°). B, Type 1CN PJK 2 level (66°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure. Spine
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TABLE 2. Demographics of the Patients With
ASD With PJF
Total No. of patients
23/1668 (1.4)
Age (yr)
62.3 ± 7.9
F/U (yr)
4.3 ± 2.3 (2–12)
Sex, F:M
17:6
Cause
Figure 2. Radiographical example of type 2 bone failure PJF with or without spondylolisthesis. A, Type 2CN PJK 2 level (16°). B, Type 2BS PJK 2 level (23°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
Scheuermann kyphosis. Lonner et al31 have reported a 30% incidence of PJK in surgically treated patients with Scheuermann kyphosis. However, to the best of our knowledge, there is a paucity of information regarding the incidence and clinical outcome of symptomatic PJK in a long-term follow-up study. We have previously reported the prevalence and the clinical outcome of PJF in surgically treated adults with idiopathic scoliosis. In that study, we reported a prevalence of 3.8% (6/157 patients) for symptomatic PJK, 2.5% prevalence (4/157 patients) of PJF at 3.3 yr, and significantly lower clinical outcomes for those patients with PJF. Hart et al32 recently reported the incidence and characteristics of developing acute PJF. They reported that the prevalence of acute PJF was 5.6% in the surgically treated patients with ASD. In this study, we identified a PJF incidence of 1.4% (23/1668) in the surgically treated patients with ASD. The difference in the incidence of PJF in this study and their study might be due to the differences in the
Degenerative scoliosis
14
Idiopathic scoliosis
5
Flat back syndrome
4
BMI (kg/m )
27.6 ± 3.7
BMD (T score)
−1.1 ± 0.9
Time to PJF (mo)
10.5 ± 9.3
2
No. of neurological deficit
6 (26.1)
UIV Above T8
7 (30.4)
Below T9
16 (69.6)
No. of revision surgery
17 (73.9)
Values denote mean and standard deviations. Percentage in parenthesis. ASD indicates adult spine deformity; PJF, proximal junctional failure; F/U, follow-up; BMI, body mass index; BMD, bone mineral density; UIV, upper instrumentation vertebra.
diagnostic criteria for PJF. In this study, we have defined PJF as symptomatic PJK requiring any type of surgery, whereas Hostin et al32 included the patients with an increased proximal junctional angle greater than 15° and symptomatic PJK. Although the incidence of PJF among surgically treated patients with ASD is relatively low, the impact of PJF on clinical outcomes of those patients strongly suggests that surgeons should not overlook this devastating complication.
TABLE 3. Classification of PJF in Surgically
Treated Patients With ASD
Figure 3. Radiographical example of type 2 bone/interface failure PJF. A, B: Type 3CN PJK 2 level (49°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
E610
Type 1
Type 2
Type 3
Total
Grade A
3
4
0
7
Grade B
4
3
1
8
Grade C
1
6
1
7
Total
8
13
2
23
PJF-N
7
8
2
17
PJF-S
1
5
0
6
Total
8
13
2
23
ASD indicates adult spine deformity; PJF, proximal junctional failure.
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
TABLE 4. Characteristic Comparison Between PJF-N Group and PJF-S Group P
Total
PJF-N
PJF-S
23 (100)
17 (73.9)
6 (26.1)
62.3 ± 7.9
62 ± 7.9
65 ± 0.5
0.53
17:6
14:3
4:2
0.74
Degenerative scoliosis
14
10
4
0.64
Flat back syndrome
4
3
1
0.71
Idiopathic scoliosis
5
4
1
0.69
BMI (kg/m2)
27.6 ± 3.7
27.4 ± 3.9
27.3 ± 3.2
0.81
BMD (T score)
−1.1 ± 0.9
−1.1 ± 0.7
−1.1 ± 0.5
0.94
Time to PJF (mo)
10.5 ± 9.3
11.7 ± 10
8.4 ± 6.8
0.45
6 (26.1)
2 (11.8)
4 (66.7)
0.02*
Above T8
7 (30.4)
5 (29.4)
2 (33.3)
0.82
Below T9
16 (69.6)
12 (70.6)
4 (66.7)
0.81
17 (73.9)
12 (70.6)
5 (83.3)
0.59
No. of patients Age (y) F/U (yr) Sex, F:M Cause
No. of neurological deficit UIV
No. of revision surgery
Values denote mean ± standard deviations. Percentage in parenthesis. *Statistically significant. ASD indicates adult spine deformity; PJF, proximal junctional failure; F/U, follow-up; BMI, body mass index; BMD, bone mineral density; UIV, upper instrumentation vertebra.
In this series, the most common type of PJF was type 2N. The most common form of PJF in this study was different from those observed in PJK in our previous studies.27,30,33 We have previously reported that the most common type of PJK was type 1 (ligamentous failure) at 2 postoperative years, whereas the most common type of PJF observed in this study was type 2 bone failure.27,30,33 We have previously
reported that the mean PJ angle of patients who had PJK at 3.3 years postsurgery was 17.6°, and PJFs are most commonly seen in grade C PJK in our single-center study.27 This study confirmed this result. The mean PJ angle of patients who developed PJF in this study was 26.8°. Compared with the mean PJ angle of those patients with PJK, the large magnitude in the PJ angle seen in those who developed PJF
TABLE 5. Radiographical Comparison Between PJF-N Group and PJF-S Group at Preoperation Total
PJF-N
PJF -S
P
PJ angle (°)
26.7 ± 8.4
26.2 ± 8.2
28.3 ± 9.5
0.63
TK (°)
35.1 ± 12.9
35.5 ± 13.9
33.5 ± 9.9
0.74
LL (°)
−40.7 ± 15.6
−41.9 ± 15.0
−36.6 ± 19.4
0.63
PI (°)
54.7 ± 7.2
55.4 ± 7.5
52.4 ± 6.1
0.45
SVA (cm)
6.6 ± 5.5
5.2 ± 3.9
11.4 ± 6.0
0.04*
PI-LL (°)
16.9 ± 10.4
17.3 ± 8.3
15.8 ± 10.6
0.91
TK + LL + PI (°)
50.4 ± 13.6
50.8 ± 5.6
49.3 ± 16.9
0.89
Values denote mean ± standard deviations. *Statistically significant. TK indicates thoracic kyphosis; PI, pelvic incidence; LL, lumbar lordosis; SVA, sagittal vertical axis; PJF, proximal junctional failure.
Spine
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Characterization of PJF in Surgically Treated Patients With ASD • Yagi et al
TABLE 6. Radiographical Comparison Between PJF-N Group and PJF-S Group Postoperatively Total
PJF-N
PJF-S
P
TK (°)
36.9 ± 8.8
35.7 ± 9.5
40.6 ± 4.9
0.21
LL (°)
−51.3 ± 11.7
−51.1 ± 11.9
−52.1 ± 12.6
0.9
SVA (cm)
1.5 ± 3.7
1.7 ± 0.5
0.6 ± 4.7
0.22
PI-LL (°)
3.4 ± 10.8
4.2 ± 4.4
0.4 ± 9.3
0.52
TK + LL + PI (°)
40.4 ± 13.7
39.9 ± 5.1
40.9 ± 12.3
0.92
SVA change (cm)
5.6 ± 5.1
3.5 ± 1.2
11.0 ± 5.0
0.08
Values denote mean ± standard deviations. TK indicates thoracic kyphosis; PI, pelvic incidence; LL, lumbar lordosis; SVA, sagittal vertical axis; PJF, proximal junctional failure.
strongly suggested that progression of the PJ angle might be the reason for the PJF. We have previously studied the natural course of PJK for a mean of 8.1 years of follow-up and found a continuous progression of the PJ angle in those who developed PJK, whereas no progression of the PJ angle was observed in those who did not have PJK.30 In this study, the most devastating form of PJK had an associated neurological injury and was not uncommon; most patients with neurological deficits had PJF type 2S. Four of the 6 (67%) patients with PJF-S (PJF with associated spondylolisthesis) developed a neurological deficit, and 70% (16/23) of the patients with PJF had UIVs below T9; 74% (17/23) of the patients with PJF had prior surgical procedures. We have previously reported that an abnormal global spine alignment (thoracic kyphosis + LL + PI > 45°), large SVA change (>5 cm), and low BMD are risk factors for developing PJK.27,30,33 Results of our present report are consistent with those of our previous report. Forty-eight percent (11/23) of the patients who developed PJF had postoperative abnormal global spine alignment, 52% (12/23) of the patients had a large SVA change, and 61% (14/23) of the patients had a low BMD. Taken together, the results show that the patients who underwent revision surgical procedures to treat ASD (with a significantly large preoperative positive SVA requiring large SVA correction and a UIV stop below T9) were at significant
risk of developing PJF with associated spondylolisthesis and subsequent neurological deficit. Our findings suggest uncertainty in the cause of PJF. Various studies have proposed that the development of PJK is related to a combination of patient and surgery-related factors. Of these factors, the integrity of the soft-tissue tension band, stress concentration, bone quality, instrumentation type, UIV below sagittal apex, and amount of sagittal plane correction are all implicated in PJK development.11–16,23,27,30,33,34 The same can be said for the cause of PJF. The fact that multiple revision extension surgical procedures were required to treat the patients with PJF strongly suggested that PJF results from not only iatrogenic causes but also patient-related causes. The results of this comprehensive review allowed better definition and a classification of PJK/PJF based on severity and type. The results will also guide spine surgeons in their preoperative planning and surgical management of ASD to eliminate or minimize the occurrence of PJF as a devastating form of PJK.
CONCLUSION In this series, the incidence of PJF among surgically treated patients with ASD was 1.4%. The most common type of PJF was 2N. The most devastating form, with associated neurological injury, was not uncommon, and most of the patients
Figure 4. A 55-year-old female with adult idiopathic scoliosis treated with combined anteroposteriorinstrumented fusion to T3 pelvis. Because of neck pain, she had revision extension PSF and developed further PJF at the new UIV level. A, Preoperative PJK 2 level (6°). B, Immediate postoperative PJK 2 level (21°). C, Two-year postoperative PJK 2 level (49°). D, Postrevision extension PSF to C7 PJK 2 level (15°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure; UIV, upper instrumentation vertebra.
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DEFORMITY
Figure 5. A 69-year-old female with adult idiopathic scoliosis treated with combined anteroposterior-instrumented fusion to T1-pelvis and had type 2CN PJF. Because of head ptosis, she had revision extension PSF. A, Three-month postoperative PJK 2 level (66°). B, Postrevision extension PSF to C6 PJK 2 level (−4°). PJK indicates proximal junctional kyphosis; PJF, proximal junctional failure.
with neurological deficits had type 2S. Preoperative large SVA change and large amount of correction was a causative factor for spondylolisthesis above the UIV. After revision surgery, further PJF commonly occurred.
➢ Key Points The incidence of PJF among surgically treated patients with ASD was 1.4%. Older age, previous surgery, and UIV at the thoracolumbar junction were identified as PJF risk factors. Further PJF was a commonly occurred event after the revision surgery.
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