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Proximal Junctional Kyphosis After Vertical Expandable Prosthetic Titanium Rib Insertion
Spine Deformity 1 (2013) 425e433 www.spine-deformity.org
Case Series
Proximal Junctional Kyphosis After Vertical Expandable Prosthetic Titanium Rib Insertion Ying Li, MDa,*, Meryl Gold, BAb, Lawrence Karlin, MDb a
Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241, USA b Department of Orthopaedic Surgery, Children’s Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, USA Received 6 May 2012; revised 25 July 2013; accepted 27 July 2013
Abstract Study Design: Retrospective review of patients who had undergone vertical expandable prosthetic titanium rib (VEPTR) treatment at a single institution. Objectives: To evaluate whether clinically significant proximal junctional kyphosis (PJK) occurs after VEPTR insertion. Summary of Background Data: PJK is a potential problem after posterior spinal instrumentation and fusion. PJK after VEPTR insertion has not been well-described. Methods: A total of 68 patients underwent VEPTR treatment between 1999 and 2009. Diagnosis, age at time of VEPTR insertion, location of VEPTR anchors, preoperative and postoperative scoliosis, T2eT12 kyphosis and PJK, time from VEPTR insertion to development of PJK, revision procedure for significant PJK, change in PJK after the revision procedure, and PJK at final follow-up were recorded. Results: Four patients developed PJK (6%). One patient had congenital scoliosis with rib fusions, 1 had scoliosis associated with a syndrome, and 2 had neuromuscular scoliosis. Mean follow-up was 5.7 years. Average T2eT12 kyphosis and PJK before VEPTR insertion were 77 and 14 , respectively. Mean T2eT12 kyphosis and PJK after VEPTR insertion were 63 and 33 , respectively. Average T2eT12 kyphosis and PJK before the recommended revision procedure for treatment of PJK were 89 and 53 , respectively. All patients developed PJK within the first year after VEPTR insertion. Two patients underwent revision to growing rods. One of these patients had preoperative halo-gravity traction. Mean PJK in these 2 patients improved from 39 to 18 after revision and remained stable at 19 at an average follow-up of 2.9 years. Conclusions: PJK after VEPTR insertion can occur. Patients with preoperative thoracic hyperkyphosis may be at higher risk. PJK can develop within the first year of VEPTR treatment, and can become progressive and severe enough to require complex interventions. In this small case series, patients were revised to growing rods. Ó 2013 Scoliosis Research Society. Keywords: Vertical expandable prosthetic titanium rib; Complications; Kyphosis; Proximal junctional kyphosis
Introduction Proximal junctional kyphosis (PJK) is a nonphysiologic, acute sagittal plane angulation that occurs cephalad to an instrumented spine. Numerous studies have described the development of PJK after posterior instrumentation and fusion for the treatment of spinal deformity [1-8]. Although the incidence of PJK after posterior spinal instrumentation and fusion has been reported to be as high Author disclosures: YL (none); MG (none); LK (none). *Corresponding author. Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241, USA. Tel.: (734) 936-5715; fax: (734) 647-3291. E-mail address: [email protected] (Y. Li). 2212-134X/$ - see front matter Ó 2013 Scoliosis Research Society. http://dx.doi.org/10.1016/j.jspd.2013.07.013
as 46% [1], PJK was found to have little clinical significance in most studies [1-8]. Both mechanical and anatomic causes have been theorized to be risk factors for PJK [1-6,8-10]. Growing rods and the vertical expandable prosthetic titanium rib (VEPTR; Synthes Inc., Paoli, PA) are currently the most popular options for the surgical management of early-onset scoliosis. Both techniques have a high rate of complications. Implant- and wound-related complications have been well-documented [11-22]. PJK has been noted in patients after growing rod and VEPTR insertion, but the severity of the deformity and treatment have not been specifically studied [12,17,19,20,22].
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Table 1 Diagnoses for entire study population. Diagnosis
No proximal junctional kyphosis
Congenital scoliosis without rib fusions Congenital scoliosis with rib fusions Scoliosis associated with syndrome Neuromuscular scoliosis Infantile idiopathic scoliosis Chest wall deformity Total
11 37 8 1 2 5 64
* y
Developed proximal junctional kyphosis 1 (3%)* 1 (11%)* 2 (67%)*
and PJK at final follow-up. PJK was measured between the inferior end plate of the vertebra 1 level caudad to the instrumented rib and the superior end plate of the vertebra 2 levels cephalad to the instrumented rib. PJK was defined as a sagittal Cobb angle > 25 , or a Cobb angle 10 greater than the summed normal segmental sagittal angulation over 4 spinal levels, as reported by Bernhardt and Bridwell [23].
Results 4 (6%)y
Percentage of patients with the same diagnosis. Percentage of the entire study population.
There is no contact between the proximal end of a VEPTR construct and the spine. Accordingly, many factors thought to contribute to PJK are not present. The assumption could be made that PJK is less problematic in the VEPTR population. This study was designed to determine whether clinically significant PJK occurs after VEPTR insertion, and if so, to evaluate its treatment. Materials and Methods A search of the authors’ institutional database identified 68 patients who had undergone VEPTR treatment between 1999 and 2009 with a minimum follow-up of 2 years. Institutional review board approval was obtained before data collection and analysis. A retrospective review of patient records and radiographs was performed. Diagnosis, age at the time of VEPTR insertion, location of proximal and distal VEPTR anchors, and time from VEPTR insertion to development of PJK were recorded. Patients who developed PJK significant enough to require surgical intervention were identified, and the revision procedures were studied. All radiographs were obtained in the upright position. The recorded measurements were: preoperative and postoperative scoliosis, preoperative and postoperative T2eT12 kyphosis, preoperative and postoperative L1eS1 lordosis, preoperative kyphosis of the segments later included in PJK (preoperative PJK) and postoperative PJK, change in T2eT12 kyphosis, L1eS1 lordosis and PJK after the revision procedure, and T2eT12 kyphosis, L1eS1 lordosis,
Table 1 lists the diagnoses for the entire study population. Four patients had PJK (6%) (Table 2). One patient had congenital scoliosis with rib fusions, 1 had scoliosis associated with a syndrome (arthrogryposis), and 2 had neuromuscular scoliosis (core myopathy and spinal cord tumor). Average age at the time of VEPTR insertion was 3.9 years (range, 2.4e6.7 years) for patients with PJK and 5.1 years (range, .8e14.6 years) for those without PJK. In the PJK group, 3 patients had bilateral rib-to-pelvis constructs and 1 had unilateral rib-to-spine and rib-to-rib constructs. In the non-PJK group, 11 patients had bilateral rib-to-rib constructs, 2 had bilateral rib-to-spine constructs, 10 had bilateral rib-to-pelvis constructs, 2 had bilateral rib-to-spine and rib-to-rib constructs, 13 had unilateral rib-to-rib constructs, 8 had unilateral rib-to-spine constructs, 2 had unilateral rib-to-pelvis constructs, 18 had unilateral rib-to-spine and rib-to-rib constructs, and 2 had unilateral rib-to-pelvis and rib-to-rib constructs. Average follow-up for the 4 patients with PJK was 5.7 years (range, 3.9e9.4 years). Table 3 lists radiographic data for the patients with PJK. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK before VEPTR insertion were 77 (range, 61 to 88 ), 56 (range, 44 to 67 ), and 14 (range, 4 to 41 ), respectively. Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK after VEPTR insertion were 63 (range, 35 to 79 ), 46 (range, 42 to 49 ), and 33 (range, 4 to 49 ), respectively. All patients with PJK developed this deformity within the first year after VEPTR insertion. One patient (Patient 48) experienced failure of the right proximal anchor at 3 months postoperatively and had a new anchor placed 1 rib lower. Revision surgery to treat the PJK was recommended to all of these patients. Indications for revision
Table 2 Demographic data for patients with proximal junctional kyphosis. Patient
22 30 48 59
Diagnosis
Core myopathy Arthrogryposis Spinal cord tumor Congenital scoliosis with rib fusions
Age at time of VEPTR insertion, years 2.6 3.7 6.7 4.3
VEPTR, vertical expandable prosthetic titanium rib.
Type of VEPTR construct VEPTR 2
VEPTR 1 Ribs Ribs Ribs Ribs
3/4 3/5 3/4 4/5
to to to to
pelvis pelvis pelvis L1
Ribs 3/4 Ribs 4/6 Ribs 3/4 Rib 4 to
to pelvis to pelvis to pelvis rib 10
Total follow-up, years 9.4 3.9 5.3 4.1
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Table 3 Radiographic data for patients with proximal junctional kyphosis (PJK). Patient
22 30 48 59
Before VEPTR insertion
After VEPTR insertion
Scoliosis
T2eT12 kyphosis
L1eS1 lordosis
PJK
Scoliosis
T2eT12 kyphosis
L1eS1 lordosis
PJK
55/60 36/84 90 49/106
88 86 73 61
44 65 49 67
4 41 6 6
43/55 48/58 46 59/51
71 79 35 66
45 46 49 42
49 47 4 30
VEPTR, vertical expandable prosthetic titanium rib. Data shown are degrees.
surgery were a deformity sufficiently severe to endanger the neural elements, or the concern that a further increase in the deformity would necessitate a far more difficult and dangerous revision technique. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK before the recommended revision procedure for treatment of PJK were 89 (range, 77 to 97 ), 51 (range, 41 to 61 ), and 53 (range, 32 to 70 ), respectively (Table 4). Two patients underwent revision to growing rods for management of PJK (Figs. 1, 2). Average follow-up after revision to growing rods was 2.9 years. One of these patients had preoperative halogravity traction (Fig. 2). Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK before revision to growing rods were 84 , 51 , and 39 , respectively. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK after revision to growing rods were 60 , 46 , and 18 , respectively. Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK at final follow-up were 63 , 55 , and 19 , respectively. Patient 30 had a history of arthrogryposis, restrictive lung disease, and tracheostomy, and she developed pneumonia after halo placement. Her pulmonary status never returned to baseline and she died before revision to growing rods. Her T2eT12 kyphosis and PJK at final follow-up were 90 and 70 , respectively (Fig. 3). Patient 22 was advised to undergo halo-gravity traction and posterior spinal fusion, but the family chose to continue with VEPTR treatment
despite severe and progressive PJK. His T2eT12 kyphosis and PJK at the most recent follow-up were 128 and 78 , respectively (Fig. 4). Discussion PJK is a non-physiologic, acute sagittal angulation between the upper instrumented vertebra in a construct and a cephalad vertebra. There is no standard method to measure PJK. The levels to be included in the measurement and the magnitude of sagittal angulation that defines PJK are inconsistent in the literature [1-5]. The etiology of PJK is also not clearly understood. Reported risk factors for PJK after spinal fusion for Scheuermann kyphosis are contradictory and include larger preoperative thoracic kyphosis [5], failure to include the proximal end vertebra in the fusion [2,10], disruption of the junctional ligamentum flavum [2], O 50% correction of kyphosis [10], insufficient kyphosis correction, and larger kyphosis at final follow-up [5]. Risk factors for PJK after posterior spinal fusion for adolescent idiopathic scoliosis include preoperative T5eT12 kyphosis O 40 [4], O 5 decrease in T5eT12 kyphosis immediately after surgery [4], and O 5 of preoperative junctional kyphosis above the proposed upper instrumented vertebra [1]. A recent biomechanical analysis showed that sagittal balance and disruption of the posterior
Table 4 Treatment of patients with proximal junctional kyphosis (PJK). Patient Revision procedure
22
30 48 59
Family chose to continue VEPTR treatment Died after halo placement Revision to growing rods (T2eL3) Halo-gravity traction plus revision to growing rods (T1eL3)
Before recommended revision procedure
After revision procedure
Follow-up after revision, Scoliosis T2eT12 L1eS1 PJK Scoliosis T2eT12 L1eS1 PJK Scoliosis T2eT12 L1eS1 PJK years kyphosis lordosis kyphosis lordosis kyphosis lordosis 50/24
97
43
65
n/a
n/a
n/a
n/a
66/15
128
29
78
n/a
86/69
90
60
70
n/a
n/a
n/a
n/a
86/69
90
60
70
n/a
81
90
41
46
46
70
37
20
48
76
55
21
3.5
58/65
77
61
32
22/12
49
54
16
22/12
49
54
16
2.3
n/a, not applicable; VEPTR, vertical expandable prosthetic titanium rib. Data shown are degrees.
At most recent follow-up
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Fig. 1. (A) Initial anteroposterior and lateral radiographs of Patient 48 demonstrate thoracic hyperkyphosis of 73 and proximal junctional kyphosis (PJK) of 6 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion reveal improvement of thoracic kyphosis to 35 . PJK is stable at 4 . (C) Anteroposterior and lateral radiographs obtained 1.6 years after VEPTR insertion demonstrate progression of thoracic hyperkyphosis to 90 and PJK to 46 . There is loss of fixation of the left upper rib cradle. This patient underwent 2 unplanned surgeries to revise the VEPTR construct because of loss of fixation and loosening of the implants, likely related to the progressive thoracic hyperkyphosis and PJK. (D) Anteroposterior and lateral radiographs obtained after revision to growing rods show improvement of the thoracic kyphosis to 70 and PJK to 20 . (E) At 2.5 years after revision to growing rods, thoracic kyphosis is 76 and PJK is maintained at 21 .
ligaments and joint capsules may be associated with the development of PJK [9]. Although PJK has been identified as a potential complication after posterior spinal instrumentation and
fusion, the deformity appears to have little clinical significance. Lonner et al. [5] reported PJK in 25 patients (32.1%), but this was problematic in only 2 patients. One patient underwent proximal extension of the fusion by 1
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Fig. 2. (A) Initial anteroposterior and lateral radiographs of Patient 59 show thoracic hyperkyphosis of 61 and proximal junctional kyphosis (PJK) of 6 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion demonstrate slight worsening of thoracic hyperkyphosis to 66 and a more significant increase in PJK to 30 . (C) Anteroposterior and lateral radiographs obtained 6 months after VEPTR insertion reveal further progression of thoracic hyperkyphosis to 77 . PJK is stable at 32 . (D) Anteroposterior and lateral radiographs obtained after halogravity traction and revision to growing rods show improvement in thoracic kyphosis to 49 and PJK to 16 . (E) At 2.3 years after revision to growing rods, thoracic kyphosis and PJK are maintained at 49 and 16 , respectively.
level. The second patient had a clinically evident deformity but did not require revision surgery. Twenty patients (30%) in the series by Denis et al. [2] developed PJK. Four of those patients underwent minor revision surgery to remove prominent proximal instrumentation resulting from PJK. Kim et al. [4] described PJK in 111 patients
(27%). There was no difference in the Scoliosis Research Society Patient Questionnairee24 outcome scores between those with and without PJK, and no patients required additional surgery. PJK has been found to be a complication of growing rods, but it is unclear whether this presents a clinical
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Fig. 3. (A) Initial anteroposterior and lateral radiographs of Patient 30 demonstrate thoracic hyperkyphosis of 86 and proximal junctional kyphosis (PJK) of 41 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion show slight improvement in thoracic kyphosis to 79 and PJK of 47 . (C) Anteroposterior and lateral radiographs obtained 3.8 years after VEPTR insertion reveal progression of thoracic hyperkyphosis to 90 and PJK to 70 . (D) Sagittal computed tomography scan further demonstrates the significant PJK.
problem. Akbarnia et al. [19] described 1 patient (4%) with junctional kyphosis in their series of 23 patients treated with dual growing rods. This patient required extension of the growing rod construct. Bess et al. [12] reviewed 140 patients treated with single and dual growing rods, and found that 3 patients (2%) developed junctional kyphosis. One patient had a single growing rod and 2 had dual growing rods. The authors did not report whether an intervention was necessary to treat the junctional kyphosis. Farooq et al. [20] reported the development of PJK in 2 of 88 patients (2%) treated with a single growing rod. Both patients necessitated early fusion. To avoid PJK with growing rods, Akbarnia and Emans [11] suggested contouring the proximal aspect of the rods into kyphosis, keeping the interspinous ligaments intact, and placing the proximal anchor sites at T2 or occasionally even higher, especially in non-idiopathic scoliosis. In patients with thoracic hyperkyphosis, excessive correction should be avoided. There are few reports of PJK after VEPTR insertion. Theoretically, this complication should be less likely to develop with the VEPTR, because the upper end of the
construct does not attach to the spine. Thompson et al. [17] described 6 patients (38%) who developed junctional kyphosis above a VEPTR construct. Most of those patients had preoperative thoracic hyperkyphosis. The authors did not define or quantitate the junctional kyphosis and did not state whether an intervention was necessary. Hasler et al. [22] reported a high thoracic junctional kyphosis in 5 patients (22%) treated with VEPTR. Four patients had preoperative thoracic hyperkyphosis. Three patients were treated with extension of the VEPTR construct to the pelvis. The authors did not define or quantify the junctional kyphosis, or establish the reason for surgical intervention. They also did not report whether the junctional kyphosis improved after revision of the construct. Again, it is unclear whether the PJK in those 2 series was clinically significant. This study is the first to specifically evaluate the occurrence and treatment of clinically significant PJK after VEPTR insertion. Of 68 patients in this series, 4 (6%) developed PJK that was felt to be severe enough to require intervention. Indications for revision surgery were an acute deformity severe enough to be concerning for neurologic complications with further progression, or in 1 case, the
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Fig. 4. (A) Initial anteroposterior and lateral radiographs of Patient 22 show thoracic hyperkyphosis of 88 and proximal junctional kyphosis (PJK) of 4 . (B) Anteroposterior and lateral radiographs obtained 5 months after vertical expandable prosthetic titanium rib (VEPTR) insertion reveal improvement of thoracic kyphosis to 71 and PJK of 49 . (C) At 9.4 years after VEPTR insertion, the patient developed severe and progressive thoracic hyperkyphosis of 128 and PJK of 78 . (D) The significant PJK can be further appreciated on sagittal computed tomography scan.
development of significant PJK so early in the treatment course that continued progression was assumed. All of these patients developed PJK within the first year after VEPTR insertion and the angulation progressed. The population studied was heterogeneous and the number of patients who developed severe PJK was small. Accordingly, statistically significant causes cannot be determined. However, there are some characteristics worth noting. All of the patients in this series who developed PJK had thoracic hyperkyphosis, a risk factor noted in previous studies. Most patients who developed PJK in both the series of Thompson et al. [17] and of Hasler et al. [22] also had preoperative thoracic hyperkyphosis. A neuromuscular etiology may also be a risk factor. Of the 3 patients with neuromuscular scoliosis in this series, 2 developed PJK. One patient had core myopathy and 1 had weakness after spinal cord tumor resection. A reasonable assumption is that weak paraspinal muscular support contributed to the deformity in these cases. Three patients in the current series who developed PJK had rib-to-pelvis constructs. Although Hasler et al. [22]
described treating 3 of their patients who developed a high thoracic junctional kyphosis with extension of the VEPTR to the pelvis, they did not report whether the junctional kyphosis improved after revision of the construct. The current study shows that rib-to-pelvis constructs do not necessarily prevent the development of PJK. The PJK deformities in this series were dramatic. It was the clinical judgment of the treating surgeon that based on the severity of the radiographic deformity, the patients were at risk of impending neurologic injury and additional surgical intervention was required. The revision procedures were difficult because of the severity of the kyphosis. Two patients underwent revision to growing rods. One patient had preoperative halo-gravity traction. His thoracic kyphosis improved to within physiologic limits. The other patient’s thoracic kyphosis after revision was 70 . Caubet and Emans [24] found that halo-gravity traction is more effective than spinal release or no spinal release for correction of kyphosis before growing rod or VEPTR insertion in early-onset spinal deformity. McClendon et al.
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[25] also described a 2-stage procedure involving cervical traction and multilevel osteotomies for correction of PJK in adults. Akbarnia and Emans recently reported that severe upper thoracic kyphosis may be difficult to treat successfully with VEPTR and may be better managed with growing rods. Growing rods are currently used off-label and are not approved by the Food and Drug Administration. Distraction-based systems, such as growing rods and VEPTR, may be unable to control upper thoracic kyphosis because repetitive distraction below or at the apex of an existing upper thoracic kyphosis may significantly worsen the deformity above. The VEPTR cannot extend above the second rib for proximal fixation and is likely ineffective at controlling severe upper thoracic kyphosis. However, growing rod instrumentation can extend into the upper cervical spine above the kyphosis [11]. Patients with thoracic hyperkyphosis may also be difficult to treat successfully with VEPTR. Reinker et al. [26] reviewed 14 patients who had undergone VEPTR treatment for early-onset kyphoscoliosis. Eleven patients (79%) had progression of their kyphosis, with an average increase in T2eT12 kyphosis from 68 to 91 . The authors found that upper cradle placement below the third rib, distal anchor placement at too proximal a level, and recurrent erosion and loss of fixation on the proximal ribs contributed to progression of thoracic kyphosis. They recommended placing the upper cradle at the second rib, distal extension of the construct to the pelvis, and using bilateral implants. The current results demonstrate that bilateral rib-to-pelvis constructs do not necessarily prevent progression of thoracic hyperkyphosis. None of the patients in this series began VEPTR treatment with upper cradle placement at the second rib. Perhaps the authors would not have seen progression of thoracic hyperkyphosis if all patients had fixation on the second rib at the time of VEPTR insertion. However, it seems likely that development of PJK would still have occurred if the VEPTR had been unable to prevent the spine from deforming independently from the ribs into kyphosis. One limitation of this study is the small number of patients. The conditions that lead to VEPTR treatment are rare. The authors also began using more growing rods for treatment of early-onset kyphoscoliosis after they started to note PJK in some patients. Second, the study had a short follow-up. No patients who developed PJK had reached skeletal maturity. There is a possibility that PJK will progress despite revision to growing rods. Third, accurate measurement of kyphosis with coexisting scoliosis can be difficult because of tilting of the vertebral end plates out of plane of the radiograph. In addition, the vertebrae in the upper thoracic spine are sometimes difficult to visualize, especially with overlying implants, so there was minor variability in the levels used for the measurements. Other authors have reported similar problems [2,26]. The
measurement difficulties preclude the assessment of minor PJK, but the dramatic deformities identified here are evident. Although VEPTR has no contact with the spine, the procedure does not protect against the development of PJK. This study does not support a statistically significant determination for the etiology of PJK. Patients who developed severe PJK had preoperative thoracic hyperkyphosis, a finding noted in other studies. In this study, PJK developed within the first year of VEPTR treatment, and was progressive and severe enough to require complex interventions. In this small case series, patients were revised to growing rods. References [1] Lee GA, Betz RR, Clements III DH, et al. Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis. Spine 1999;24:795e9. [2] 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 2009;34:E729e34. [3] 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 2010;35: 177e81. [4] 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 2007;32:2731e8. [5] Lonner BS, Newton P, Betz R, et al. Operative management of Scheuermann’s kyphosis in 78 patients: radiographic outcomes, complications, and technique. Spine 2007;32:2644e52. [6] 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 2008;33: 2179e84. [7] 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 2005;30:1643e9. [8] Yagi M, King AB, Boachie-Adjei O. Incidence, risk factors, and natural course of proximal junctional kyphosis. Spine 2012;37: 1479e89. [9] Cammarata M, Wang X, Mac-Thiong JM, et al. Biomechanical analysis of proximal junctional kyphosis: preliminary results. Stud Health Technol Inform 2012;176:299e302. [10] Lowe TG, Kasten MD. An analysis of sagittal curves and balance after Cotrel-Dubousset instrumentation for kyphosis secondary to Scheuermann’s disease: a review of 32 patients. Spine 1994;19: 1680e5. [11] Akbarnia BA, Emans JB. Complications of growth-sparing surgery in early onset scoliosis. Spine 2010;35:2193e204. [12] Bess S, Akbarnia BA, Thompson GH, et al. Complications of growing-rod treatment for early-onset scoliosis: analysis of one hundred and forty patients. J Bone Joint Surg Am 2010;92:2533e43. [13] Klemme WR, Denis F, Winter RB, et al. Spinal instrumentation without fusion for progressive scoliosis in young children. J Pediatr Orthop 1997;17:734e42. [14] Mineiro J, Weinstein SL. Subcutaneous rodding for progressive spinal curvatures: early results. J Pediatr Orthop 2002;22:290e5. [15] Sankar WN, Acevedo DC, Skaggs DL. Comparison of complications among growing spinal implants. Spine 2010;35:2091e6.
Y. Li et al. / Spine Deformity 1 (2013) 425e433 [16] Blakemore LC, Scoles PV, Poe-Kochert C, et al. Submuscular Isola rod with or without limited apical fusion in the management of severe spinal deformities in young children: preliminary report. Spine 2001;26:2044e8. [17] Thompson GH, Akbarnia BA, Campbell Jr RM. Growing rod techniques in early-onset scoliosis. J Pediatr Orthop 2007;27:354e61. [18] Samdani AF, Ranade A, Dolch HJ, et al. Bilateral use of the vertical expandable prosthetic titanium rib attached to the pelvis: a novel treatment for scoliosis in the growing spine. J Neurosurg Spine 2009;10:287e92. [19] Akbarnia BA, Marks DS, Boachie-Adjei O, et al. Dual growing rod technique for the treatment of progressive early-onset scoliosis: a multicenter study. Spine 2005;30:S46e57. [20] Farooq N, Garrido E, Altaf F, et al. Minimizing complications with single submuscular growing rods: a review of technique and results on 88 patients with minimum two-year follow-up. Spine 2010;35: 2252e8. [21] Ramirez N, Flynn JM, Serrano JA, et al. The Vertical Expandable Prosthetic Titanium Rib in the treatment of spinal deformity due to
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progressive early onset scoliosis. J Pediatr Orthop B 2009;18: 197e203. Hasler CC, Mehrkens A, Hefti F. Efficacy and safety of VEPTR instrumentation for progressive spine deformities in young children without rib fusions. Eur Spine J 2010;19:400e8. Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine 1989;14:717e21. Caubet JF, Emans JB. Halo-gravity traction versus surgical release before implantation of expandable spinal devices: a comparison of results and complications in early-onset spinal deformity. J Spinal Disord Tech 2011;24:99e104. McClendon Jr J, O’Shaughnessy BA, Sugrue PA, et al. Techniques for operative correction of proximal junctional kyphosis of the upper thoracic spine. Spine 2012;37:292e303. Reinker K, Simmons JW, Patil V, et al. Can VEPTR control progression of early-onset kyphoscoliosis? A cohort study of VEPTR patients with severe kyphoscoliosis. Clin Orthop Relat Res 2011;469:1342e8.
Case Series
Proximal Junctional Kyphosis After Vertical Expandable Prosthetic Titanium Rib Insertion Ying Li, MDa,*, Meryl Gold, BAb, Lawrence Karlin, MDb a
Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241, USA b Department of Orthopaedic Surgery, Children’s Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, USA Received 6 May 2012; revised 25 July 2013; accepted 27 July 2013
Abstract Study Design: Retrospective review of patients who had undergone vertical expandable prosthetic titanium rib (VEPTR) treatment at a single institution. Objectives: To evaluate whether clinically significant proximal junctional kyphosis (PJK) occurs after VEPTR insertion. Summary of Background Data: PJK is a potential problem after posterior spinal instrumentation and fusion. PJK after VEPTR insertion has not been well-described. Methods: A total of 68 patients underwent VEPTR treatment between 1999 and 2009. Diagnosis, age at time of VEPTR insertion, location of VEPTR anchors, preoperative and postoperative scoliosis, T2eT12 kyphosis and PJK, time from VEPTR insertion to development of PJK, revision procedure for significant PJK, change in PJK after the revision procedure, and PJK at final follow-up were recorded. Results: Four patients developed PJK (6%). One patient had congenital scoliosis with rib fusions, 1 had scoliosis associated with a syndrome, and 2 had neuromuscular scoliosis. Mean follow-up was 5.7 years. Average T2eT12 kyphosis and PJK before VEPTR insertion were 77 and 14 , respectively. Mean T2eT12 kyphosis and PJK after VEPTR insertion were 63 and 33 , respectively. Average T2eT12 kyphosis and PJK before the recommended revision procedure for treatment of PJK were 89 and 53 , respectively. All patients developed PJK within the first year after VEPTR insertion. Two patients underwent revision to growing rods. One of these patients had preoperative halo-gravity traction. Mean PJK in these 2 patients improved from 39 to 18 after revision and remained stable at 19 at an average follow-up of 2.9 years. Conclusions: PJK after VEPTR insertion can occur. Patients with preoperative thoracic hyperkyphosis may be at higher risk. PJK can develop within the first year of VEPTR treatment, and can become progressive and severe enough to require complex interventions. In this small case series, patients were revised to growing rods. Ó 2013 Scoliosis Research Society. Keywords: Vertical expandable prosthetic titanium rib; Complications; Kyphosis; Proximal junctional kyphosis
Introduction Proximal junctional kyphosis (PJK) is a nonphysiologic, acute sagittal plane angulation that occurs cephalad to an instrumented spine. Numerous studies have described the development of PJK after posterior instrumentation and fusion for the treatment of spinal deformity [1-8]. Although the incidence of PJK after posterior spinal instrumentation and fusion has been reported to be as high Author disclosures: YL (none); MG (none); LK (none). *Corresponding author. Department of Orthopaedic Surgery, C.S. Mott Children’s Hospital, 1540 E. Hospital Drive, SPC 4241, Ann Arbor, MI 48109-4241, USA. Tel.: (734) 936-5715; fax: (734) 647-3291. E-mail address: [email protected] (Y. Li). 2212-134X/$ - see front matter Ó 2013 Scoliosis Research Society. http://dx.doi.org/10.1016/j.jspd.2013.07.013
as 46% [1], PJK was found to have little clinical significance in most studies [1-8]. Both mechanical and anatomic causes have been theorized to be risk factors for PJK [1-6,8-10]. Growing rods and the vertical expandable prosthetic titanium rib (VEPTR; Synthes Inc., Paoli, PA) are currently the most popular options for the surgical management of early-onset scoliosis. Both techniques have a high rate of complications. Implant- and wound-related complications have been well-documented [11-22]. PJK has been noted in patients after growing rod and VEPTR insertion, but the severity of the deformity and treatment have not been specifically studied [12,17,19,20,22].
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Table 1 Diagnoses for entire study population. Diagnosis
No proximal junctional kyphosis
Congenital scoliosis without rib fusions Congenital scoliosis with rib fusions Scoliosis associated with syndrome Neuromuscular scoliosis Infantile idiopathic scoliosis Chest wall deformity Total
11 37 8 1 2 5 64
* y
Developed proximal junctional kyphosis 1 (3%)* 1 (11%)* 2 (67%)*
and PJK at final follow-up. PJK was measured between the inferior end plate of the vertebra 1 level caudad to the instrumented rib and the superior end plate of the vertebra 2 levels cephalad to the instrumented rib. PJK was defined as a sagittal Cobb angle > 25 , or a Cobb angle 10 greater than the summed normal segmental sagittal angulation over 4 spinal levels, as reported by Bernhardt and Bridwell [23].
Results 4 (6%)y
Percentage of patients with the same diagnosis. Percentage of the entire study population.
There is no contact between the proximal end of a VEPTR construct and the spine. Accordingly, many factors thought to contribute to PJK are not present. The assumption could be made that PJK is less problematic in the VEPTR population. This study was designed to determine whether clinically significant PJK occurs after VEPTR insertion, and if so, to evaluate its treatment. Materials and Methods A search of the authors’ institutional database identified 68 patients who had undergone VEPTR treatment between 1999 and 2009 with a minimum follow-up of 2 years. Institutional review board approval was obtained before data collection and analysis. A retrospective review of patient records and radiographs was performed. Diagnosis, age at the time of VEPTR insertion, location of proximal and distal VEPTR anchors, and time from VEPTR insertion to development of PJK were recorded. Patients who developed PJK significant enough to require surgical intervention were identified, and the revision procedures were studied. All radiographs were obtained in the upright position. The recorded measurements were: preoperative and postoperative scoliosis, preoperative and postoperative T2eT12 kyphosis, preoperative and postoperative L1eS1 lordosis, preoperative kyphosis of the segments later included in PJK (preoperative PJK) and postoperative PJK, change in T2eT12 kyphosis, L1eS1 lordosis and PJK after the revision procedure, and T2eT12 kyphosis, L1eS1 lordosis,
Table 1 lists the diagnoses for the entire study population. Four patients had PJK (6%) (Table 2). One patient had congenital scoliosis with rib fusions, 1 had scoliosis associated with a syndrome (arthrogryposis), and 2 had neuromuscular scoliosis (core myopathy and spinal cord tumor). Average age at the time of VEPTR insertion was 3.9 years (range, 2.4e6.7 years) for patients with PJK and 5.1 years (range, .8e14.6 years) for those without PJK. In the PJK group, 3 patients had bilateral rib-to-pelvis constructs and 1 had unilateral rib-to-spine and rib-to-rib constructs. In the non-PJK group, 11 patients had bilateral rib-to-rib constructs, 2 had bilateral rib-to-spine constructs, 10 had bilateral rib-to-pelvis constructs, 2 had bilateral rib-to-spine and rib-to-rib constructs, 13 had unilateral rib-to-rib constructs, 8 had unilateral rib-to-spine constructs, 2 had unilateral rib-to-pelvis constructs, 18 had unilateral rib-to-spine and rib-to-rib constructs, and 2 had unilateral rib-to-pelvis and rib-to-rib constructs. Average follow-up for the 4 patients with PJK was 5.7 years (range, 3.9e9.4 years). Table 3 lists radiographic data for the patients with PJK. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK before VEPTR insertion were 77 (range, 61 to 88 ), 56 (range, 44 to 67 ), and 14 (range, 4 to 41 ), respectively. Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK after VEPTR insertion were 63 (range, 35 to 79 ), 46 (range, 42 to 49 ), and 33 (range, 4 to 49 ), respectively. All patients with PJK developed this deformity within the first year after VEPTR insertion. One patient (Patient 48) experienced failure of the right proximal anchor at 3 months postoperatively and had a new anchor placed 1 rib lower. Revision surgery to treat the PJK was recommended to all of these patients. Indications for revision
Table 2 Demographic data for patients with proximal junctional kyphosis. Patient
22 30 48 59
Diagnosis
Core myopathy Arthrogryposis Spinal cord tumor Congenital scoliosis with rib fusions
Age at time of VEPTR insertion, years 2.6 3.7 6.7 4.3
VEPTR, vertical expandable prosthetic titanium rib.
Type of VEPTR construct VEPTR 2
VEPTR 1 Ribs Ribs Ribs Ribs
3/4 3/5 3/4 4/5
to to to to
pelvis pelvis pelvis L1
Ribs 3/4 Ribs 4/6 Ribs 3/4 Rib 4 to
to pelvis to pelvis to pelvis rib 10
Total follow-up, years 9.4 3.9 5.3 4.1
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Table 3 Radiographic data for patients with proximal junctional kyphosis (PJK). Patient
22 30 48 59
Before VEPTR insertion
After VEPTR insertion
Scoliosis
T2eT12 kyphosis
L1eS1 lordosis
PJK
Scoliosis
T2eT12 kyphosis
L1eS1 lordosis
PJK
55/60 36/84 90 49/106
88 86 73 61
44 65 49 67
4 41 6 6
43/55 48/58 46 59/51
71 79 35 66
45 46 49 42
49 47 4 30
VEPTR, vertical expandable prosthetic titanium rib. Data shown are degrees.
surgery were a deformity sufficiently severe to endanger the neural elements, or the concern that a further increase in the deformity would necessitate a far more difficult and dangerous revision technique. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK before the recommended revision procedure for treatment of PJK were 89 (range, 77 to 97 ), 51 (range, 41 to 61 ), and 53 (range, 32 to 70 ), respectively (Table 4). Two patients underwent revision to growing rods for management of PJK (Figs. 1, 2). Average follow-up after revision to growing rods was 2.9 years. One of these patients had preoperative halogravity traction (Fig. 2). Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK before revision to growing rods were 84 , 51 , and 39 , respectively. Average T2eT12 kyphosis, L1eS1 lordosis, and PJK after revision to growing rods were 60 , 46 , and 18 , respectively. Mean T2eT12 kyphosis, L1eS1 lordosis, and PJK at final follow-up were 63 , 55 , and 19 , respectively. Patient 30 had a history of arthrogryposis, restrictive lung disease, and tracheostomy, and she developed pneumonia after halo placement. Her pulmonary status never returned to baseline and she died before revision to growing rods. Her T2eT12 kyphosis and PJK at final follow-up were 90 and 70 , respectively (Fig. 3). Patient 22 was advised to undergo halo-gravity traction and posterior spinal fusion, but the family chose to continue with VEPTR treatment
despite severe and progressive PJK. His T2eT12 kyphosis and PJK at the most recent follow-up were 128 and 78 , respectively (Fig. 4). Discussion PJK is a non-physiologic, acute sagittal angulation between the upper instrumented vertebra in a construct and a cephalad vertebra. There is no standard method to measure PJK. The levels to be included in the measurement and the magnitude of sagittal angulation that defines PJK are inconsistent in the literature [1-5]. The etiology of PJK is also not clearly understood. Reported risk factors for PJK after spinal fusion for Scheuermann kyphosis are contradictory and include larger preoperative thoracic kyphosis [5], failure to include the proximal end vertebra in the fusion [2,10], disruption of the junctional ligamentum flavum [2], O 50% correction of kyphosis [10], insufficient kyphosis correction, and larger kyphosis at final follow-up [5]. Risk factors for PJK after posterior spinal fusion for adolescent idiopathic scoliosis include preoperative T5eT12 kyphosis O 40 [4], O 5 decrease in T5eT12 kyphosis immediately after surgery [4], and O 5 of preoperative junctional kyphosis above the proposed upper instrumented vertebra [1]. A recent biomechanical analysis showed that sagittal balance and disruption of the posterior
Table 4 Treatment of patients with proximal junctional kyphosis (PJK). Patient Revision procedure
22
30 48 59
Family chose to continue VEPTR treatment Died after halo placement Revision to growing rods (T2eL3) Halo-gravity traction plus revision to growing rods (T1eL3)
Before recommended revision procedure
After revision procedure
Follow-up after revision, Scoliosis T2eT12 L1eS1 PJK Scoliosis T2eT12 L1eS1 PJK Scoliosis T2eT12 L1eS1 PJK years kyphosis lordosis kyphosis lordosis kyphosis lordosis 50/24
97
43
65
n/a
n/a
n/a
n/a
66/15
128
29
78
n/a
86/69
90
60
70
n/a
n/a
n/a
n/a
86/69
90
60
70
n/a
81
90
41
46
46
70
37
20
48
76
55
21
3.5
58/65
77
61
32
22/12
49
54
16
22/12
49
54
16
2.3
n/a, not applicable; VEPTR, vertical expandable prosthetic titanium rib. Data shown are degrees.
At most recent follow-up
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Fig. 1. (A) Initial anteroposterior and lateral radiographs of Patient 48 demonstrate thoracic hyperkyphosis of 73 and proximal junctional kyphosis (PJK) of 6 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion reveal improvement of thoracic kyphosis to 35 . PJK is stable at 4 . (C) Anteroposterior and lateral radiographs obtained 1.6 years after VEPTR insertion demonstrate progression of thoracic hyperkyphosis to 90 and PJK to 46 . There is loss of fixation of the left upper rib cradle. This patient underwent 2 unplanned surgeries to revise the VEPTR construct because of loss of fixation and loosening of the implants, likely related to the progressive thoracic hyperkyphosis and PJK. (D) Anteroposterior and lateral radiographs obtained after revision to growing rods show improvement of the thoracic kyphosis to 70 and PJK to 20 . (E) At 2.5 years after revision to growing rods, thoracic kyphosis is 76 and PJK is maintained at 21 .
ligaments and joint capsules may be associated with the development of PJK [9]. Although PJK has been identified as a potential complication after posterior spinal instrumentation and
fusion, the deformity appears to have little clinical significance. Lonner et al. [5] reported PJK in 25 patients (32.1%), but this was problematic in only 2 patients. One patient underwent proximal extension of the fusion by 1
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Fig. 2. (A) Initial anteroposterior and lateral radiographs of Patient 59 show thoracic hyperkyphosis of 61 and proximal junctional kyphosis (PJK) of 6 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion demonstrate slight worsening of thoracic hyperkyphosis to 66 and a more significant increase in PJK to 30 . (C) Anteroposterior and lateral radiographs obtained 6 months after VEPTR insertion reveal further progression of thoracic hyperkyphosis to 77 . PJK is stable at 32 . (D) Anteroposterior and lateral radiographs obtained after halogravity traction and revision to growing rods show improvement in thoracic kyphosis to 49 and PJK to 16 . (E) At 2.3 years after revision to growing rods, thoracic kyphosis and PJK are maintained at 49 and 16 , respectively.
level. The second patient had a clinically evident deformity but did not require revision surgery. Twenty patients (30%) in the series by Denis et al. [2] developed PJK. Four of those patients underwent minor revision surgery to remove prominent proximal instrumentation resulting from PJK. Kim et al. [4] described PJK in 111 patients
(27%). There was no difference in the Scoliosis Research Society Patient Questionnairee24 outcome scores between those with and without PJK, and no patients required additional surgery. PJK has been found to be a complication of growing rods, but it is unclear whether this presents a clinical
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Fig. 3. (A) Initial anteroposterior and lateral radiographs of Patient 30 demonstrate thoracic hyperkyphosis of 86 and proximal junctional kyphosis (PJK) of 41 . (B) Anteroposterior and lateral radiographs obtained 1 month after vertical expandable prosthetic titanium rib (VEPTR) insertion show slight improvement in thoracic kyphosis to 79 and PJK of 47 . (C) Anteroposterior and lateral radiographs obtained 3.8 years after VEPTR insertion reveal progression of thoracic hyperkyphosis to 90 and PJK to 70 . (D) Sagittal computed tomography scan further demonstrates the significant PJK.
problem. Akbarnia et al. [19] described 1 patient (4%) with junctional kyphosis in their series of 23 patients treated with dual growing rods. This patient required extension of the growing rod construct. Bess et al. [12] reviewed 140 patients treated with single and dual growing rods, and found that 3 patients (2%) developed junctional kyphosis. One patient had a single growing rod and 2 had dual growing rods. The authors did not report whether an intervention was necessary to treat the junctional kyphosis. Farooq et al. [20] reported the development of PJK in 2 of 88 patients (2%) treated with a single growing rod. Both patients necessitated early fusion. To avoid PJK with growing rods, Akbarnia and Emans [11] suggested contouring the proximal aspect of the rods into kyphosis, keeping the interspinous ligaments intact, and placing the proximal anchor sites at T2 or occasionally even higher, especially in non-idiopathic scoliosis. In patients with thoracic hyperkyphosis, excessive correction should be avoided. There are few reports of PJK after VEPTR insertion. Theoretically, this complication should be less likely to develop with the VEPTR, because the upper end of the
construct does not attach to the spine. Thompson et al. [17] described 6 patients (38%) who developed junctional kyphosis above a VEPTR construct. Most of those patients had preoperative thoracic hyperkyphosis. The authors did not define or quantitate the junctional kyphosis and did not state whether an intervention was necessary. Hasler et al. [22] reported a high thoracic junctional kyphosis in 5 patients (22%) treated with VEPTR. Four patients had preoperative thoracic hyperkyphosis. Three patients were treated with extension of the VEPTR construct to the pelvis. The authors did not define or quantify the junctional kyphosis, or establish the reason for surgical intervention. They also did not report whether the junctional kyphosis improved after revision of the construct. Again, it is unclear whether the PJK in those 2 series was clinically significant. This study is the first to specifically evaluate the occurrence and treatment of clinically significant PJK after VEPTR insertion. Of 68 patients in this series, 4 (6%) developed PJK that was felt to be severe enough to require intervention. Indications for revision surgery were an acute deformity severe enough to be concerning for neurologic complications with further progression, or in 1 case, the
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Fig. 4. (A) Initial anteroposterior and lateral radiographs of Patient 22 show thoracic hyperkyphosis of 88 and proximal junctional kyphosis (PJK) of 4 . (B) Anteroposterior and lateral radiographs obtained 5 months after vertical expandable prosthetic titanium rib (VEPTR) insertion reveal improvement of thoracic kyphosis to 71 and PJK of 49 . (C) At 9.4 years after VEPTR insertion, the patient developed severe and progressive thoracic hyperkyphosis of 128 and PJK of 78 . (D) The significant PJK can be further appreciated on sagittal computed tomography scan.
development of significant PJK so early in the treatment course that continued progression was assumed. All of these patients developed PJK within the first year after VEPTR insertion and the angulation progressed. The population studied was heterogeneous and the number of patients who developed severe PJK was small. Accordingly, statistically significant causes cannot be determined. However, there are some characteristics worth noting. All of the patients in this series who developed PJK had thoracic hyperkyphosis, a risk factor noted in previous studies. Most patients who developed PJK in both the series of Thompson et al. [17] and of Hasler et al. [22] also had preoperative thoracic hyperkyphosis. A neuromuscular etiology may also be a risk factor. Of the 3 patients with neuromuscular scoliosis in this series, 2 developed PJK. One patient had core myopathy and 1 had weakness after spinal cord tumor resection. A reasonable assumption is that weak paraspinal muscular support contributed to the deformity in these cases. Three patients in the current series who developed PJK had rib-to-pelvis constructs. Although Hasler et al. [22]
described treating 3 of their patients who developed a high thoracic junctional kyphosis with extension of the VEPTR to the pelvis, they did not report whether the junctional kyphosis improved after revision of the construct. The current study shows that rib-to-pelvis constructs do not necessarily prevent the development of PJK. The PJK deformities in this series were dramatic. It was the clinical judgment of the treating surgeon that based on the severity of the radiographic deformity, the patients were at risk of impending neurologic injury and additional surgical intervention was required. The revision procedures were difficult because of the severity of the kyphosis. Two patients underwent revision to growing rods. One patient had preoperative halo-gravity traction. His thoracic kyphosis improved to within physiologic limits. The other patient’s thoracic kyphosis after revision was 70 . Caubet and Emans [24] found that halo-gravity traction is more effective than spinal release or no spinal release for correction of kyphosis before growing rod or VEPTR insertion in early-onset spinal deformity. McClendon et al.
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[25] also described a 2-stage procedure involving cervical traction and multilevel osteotomies for correction of PJK in adults. Akbarnia and Emans recently reported that severe upper thoracic kyphosis may be difficult to treat successfully with VEPTR and may be better managed with growing rods. Growing rods are currently used off-label and are not approved by the Food and Drug Administration. Distraction-based systems, such as growing rods and VEPTR, may be unable to control upper thoracic kyphosis because repetitive distraction below or at the apex of an existing upper thoracic kyphosis may significantly worsen the deformity above. The VEPTR cannot extend above the second rib for proximal fixation and is likely ineffective at controlling severe upper thoracic kyphosis. However, growing rod instrumentation can extend into the upper cervical spine above the kyphosis [11]. Patients with thoracic hyperkyphosis may also be difficult to treat successfully with VEPTR. Reinker et al. [26] reviewed 14 patients who had undergone VEPTR treatment for early-onset kyphoscoliosis. Eleven patients (79%) had progression of their kyphosis, with an average increase in T2eT12 kyphosis from 68 to 91 . The authors found that upper cradle placement below the third rib, distal anchor placement at too proximal a level, and recurrent erosion and loss of fixation on the proximal ribs contributed to progression of thoracic kyphosis. They recommended placing the upper cradle at the second rib, distal extension of the construct to the pelvis, and using bilateral implants. The current results demonstrate that bilateral rib-to-pelvis constructs do not necessarily prevent progression of thoracic hyperkyphosis. None of the patients in this series began VEPTR treatment with upper cradle placement at the second rib. Perhaps the authors would not have seen progression of thoracic hyperkyphosis if all patients had fixation on the second rib at the time of VEPTR insertion. However, it seems likely that development of PJK would still have occurred if the VEPTR had been unable to prevent the spine from deforming independently from the ribs into kyphosis. One limitation of this study is the small number of patients. The conditions that lead to VEPTR treatment are rare. The authors also began using more growing rods for treatment of early-onset kyphoscoliosis after they started to note PJK in some patients. Second, the study had a short follow-up. No patients who developed PJK had reached skeletal maturity. There is a possibility that PJK will progress despite revision to growing rods. Third, accurate measurement of kyphosis with coexisting scoliosis can be difficult because of tilting of the vertebral end plates out of plane of the radiograph. In addition, the vertebrae in the upper thoracic spine are sometimes difficult to visualize, especially with overlying implants, so there was minor variability in the levels used for the measurements. Other authors have reported similar problems [2,26]. The
measurement difficulties preclude the assessment of minor PJK, but the dramatic deformities identified here are evident. Although VEPTR has no contact with the spine, the procedure does not protect against the development of PJK. This study does not support a statistically significant determination for the etiology of PJK. Patients who developed severe PJK had preoperative thoracic hyperkyphosis, a finding noted in other studies. In this study, PJK developed within the first year of VEPTR treatment, and was progressive and severe enough to require complex interventions. In this small case series, patients were revised to growing rods. References [1] Lee GA, Betz RR, Clements III DH, et al. Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis. Spine 1999;24:795e9. [2] 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 2009;34:E729e34. [3] 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 2010;35: 177e81. [4] 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 2007;32:2731e8. [5] Lonner BS, Newton P, Betz R, et al. Operative management of Scheuermann’s kyphosis in 78 patients: radiographic outcomes, complications, and technique. Spine 2007;32:2644e52. [6] 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 2008;33: 2179e84. [7] 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 2005;30:1643e9. [8] Yagi M, King AB, Boachie-Adjei O. Incidence, risk factors, and natural course of proximal junctional kyphosis. Spine 2012;37: 1479e89. [9] Cammarata M, Wang X, Mac-Thiong JM, et al. Biomechanical analysis of proximal junctional kyphosis: preliminary results. Stud Health Technol Inform 2012;176:299e302. [10] Lowe TG, Kasten MD. An analysis of sagittal curves and balance after Cotrel-Dubousset instrumentation for kyphosis secondary to Scheuermann’s disease: a review of 32 patients. Spine 1994;19: 1680e5. [11] Akbarnia BA, Emans JB. Complications of growth-sparing surgery in early onset scoliosis. Spine 2010;35:2193e204. [12] Bess S, Akbarnia BA, Thompson GH, et al. Complications of growing-rod treatment for early-onset scoliosis: analysis of one hundred and forty patients. J Bone Joint Surg Am 2010;92:2533e43. [13] Klemme WR, Denis F, Winter RB, et al. Spinal instrumentation without fusion for progressive scoliosis in young children. J Pediatr Orthop 1997;17:734e42. [14] Mineiro J, Weinstein SL. Subcutaneous rodding for progressive spinal curvatures: early results. J Pediatr Orthop 2002;22:290e5. [15] Sankar WN, Acevedo DC, Skaggs DL. Comparison of complications among growing spinal implants. Spine 2010;35:2091e6.
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