Abstract
OBJECTIVE:
To analyze the clinical results of a partial vertebrectomy with titanium mesh implantation and pedicle screw fixation using a posterior approach to reconstruct the spine in the treatment of thoracolumbar burst fractures.
METHOD:
From January 2006 to August 2008, 20 patients with severe thoracolumbar fractures were treated.For vertebral bodies associated with one injured intervertebral disk, subtotal vertebrectomy surgery and single-segment fusion were performed. For vertebral bodies with two injured adjacent intervertebral disks, partial vertebrectomy surgery and two-segment fusion were performed.
RESULTS:
All 20 patients were followed up for 12 to 24 months (average of 18 months). There were no complications such as wound infections, hemopneumothorax or abdominal infections in any of the patients. The neurological status of all of the patients was improved by at least one American Spinal Injury Association grade by the last follow-up. The anterior vertebral body height was an average of 50.77% before surgery, 88.51% after surgery and 87.86% at the last follow up; the sagittal Cobb angle was improved, on average, from 26.15° to 5.39° and was 5.90° at the last follow up. The percentage of spinal stenosis was improved, on average, from 26.07% to 4.93%° and was 6.15% at the last follow up. There were significant differences in the anterior vertebral body height pre- and post-surgery and in the sagittal Cobb angle and the percentage of spinal stenosis (p<0) in all patients.
CONCLUSIONS:
This surgical procedure is simple and can accomplish decompression, reduction, fixation and fusion of the spine in one stage. This approach could be widely used in orthopedics.
Thoracolumbar Burst Fracture; Partial Vertebrectomy; Posterior Approach
INTRODUCTION
In clinical settings, thoracolumbar three-column fractures are typically treated using an anterior-posterior combined approach. The reduction and fixation of thoracolumbar fractures is achieved through the posterior approach, whereas the decompression and fusion of the spine are completed using the anterior approach. However, the main drawbacks of the anterior-posterior combined approach include the major trauma associated with these procedures, longer operation time, increased blood loss and a high incidence of complications. Thus, we used a one-stage surgery that included partial vertebrectomy, titanium mesh implantation and pedicle screw fixation using the posterior approach; this approach produced good clinical results.
MATERIALS AND METHODS
Study population
After obtaining institutional ethics committee approval (Third Hospital of Hebei Medical University, Shijiazhuang, China) and written informed consent from the patients, twenty patients with serious thoracolumbar burst fractures that were treated using the one-stage posterior approach in a prospective study. There were 13 males and 7 females, and the average age was 38 years, ranging from 20 years to 56 years. There were 5 cases caused by car accident injuries, 9 cases caused by falling from a height and 6 cases caused by other mechanisms. The spinal level distribution of the cases was as follows: T3 vertebra, 1 case; T4 vertebra, 4 cases; T5 vertebra, 3 cases; T7 vertebra, 1 case; T11 vertebra, 6 cases; T12 vertebra, 1 case; L1 vertebra, 1 case; and L2 vertebra, 2 cases. All of the thoracic vertebrae injuries were associated with pulmonary contusions and pleural effusions, 2 cases of which were associated with calcaneus fractures, 1 case was associated with scapula fracture and 1 case was associated with an odontoid fracture. Only 1 of the 3 lumbar vertebrae cases was associated with a pelvic fracture. According to the American Spinal Injury Association (ASIA) neurological function classification, there were 4 A grade cases, 9 B grade cases, 5 C grade cases and 2 D grade cases. The average time from the day of the injury to the day of the operation was 13 days (range 3-23 days). Computed tomography (CT) examination of each patient showed that all three columns were injured and the corresponding MRI examination showed abnormal signals in the spinal cord.
Surgical procedure
The patient was placed in a prone position on the operating table. After successful anesthesia, routine surgical antiseptic techniques were performed and sterile towels were placed. Then, the incision markers for the injured vertebra were made using C-Arm fluoroscopy. A mid-line incision was made to expose the vertebral lamina, the articular process and the base of the transverse process of the injured vertebra. The exposure was expanded to the vertebral lamina, the articular process and the base of the transverse process of adjacent vertebra in cases associated with fracture and dislocation. Four pedicle screws were placed for single fractures and fracture-dislocation injuries required 8 pedicle screws. A total laminectomy was then performed, retaining the least-injured facet. If both of the adjacent intervertebral disks were injured, the facets of the upper and lower parts of the injured vertebra were removed. Each fracture was reduced and fixed temporarily using a pedicle screw system. The decompression was performed through the side that sustained serious damage; the medial wall of the pedicle was removed to expose the dura mater and venous plexus bleeding was stopped with bipolar coagulation. Subsequently, the dura mater and nerve roots were gently and slowly pulled to the opposite side; it was important not to pull too tightly on the nerve structures. Light activity of the nerve roots was kept intact and the range was not more than 1 mm; the stretching of the dura mater was performed more carefully above the L1 level. Parts of the injured vertebra were removed using ring drilling (1.0 cm) along the medial wall of the pedicle at a 30° angle; vertebral cancellous bone was further removed using a curettage curette to expose the upper and lower discs. Thereafter, fragments of broken discs and the bone that had fallen into the spinal column were completely removed using a cutter knife. Nerve root canal decompression in the region adjacent to the injured vertebra increases the activity of the nerve root, which can facilitate the implantation of the titanium mesh. Titanium mesh of a suitable diameter was selected after measurement with a caliper, filled with cancellous bone from the injured vertebra and implanted into the middle of the two adjacent vertebral bodies from a posterolateral direction under distraction while the spinal cord and the nerve roots were retracted using a nerve dissector. The distance from the titanium mesh to the posterior margin of the vertebral bodies was greater than 0.5 cm. Then, the pedicle screws were connected with the rod and fixed permanently by applying axial pressure after satisfactory positioning of the titanium mesh was confirmed using C-arm fluoroscopy. Bone grafting was performed on the posterior lateral aspect of the injured vertebra. Lastly, a drainage tube was placed and the wound was carefully closed with sutures (Figures 1, 2).
Typical case one: a) and b) the preoperative X-ray shows an L1 fracture and dislocation; c) and d) preoperative CT scan of the L1 vertebral body; e) and f) the postoperative X-ray of L1 vertebral body shows that the fracture achieved good reduction; g) and h) postoperative CT scan of the L1 vertebral body.
Typical case two: a) and b) the preoperative X-ray shows the L1 fractures; c) and d) preoperative CT scan of the L1 vertebral body; e) the preoperative MRI examination shows spinal cord compression; f) and g) the postoperative X-ray of the L1 body shows that the fracture achieved good reduction; h) postoperative CT scan of the L1 vertebral body.
Postoperative management
The drainage tube was removed after 48 hours and routine postoperative antibiotics were administered for 72 hours. Low back muscle activity was restricted for 2 weeks after the surgery under the guidance of the doctors and activities away from the bed while wearing a thoracolumbar brace were allowed 3 weeks later.
Follow-up and assessment methods
The recovery of neurological function was assessed using ASIA score standards.
The quality of reduction was assessed by postoperative x-ray and the measurement
of Cobb angle and the anterior vertebral body height. The degree of spinal canal
decompression was assessed by evaluating the percentage of spinal stenosis,
which was estimated as previously described (11. Gertzbein SD, Court-Brown CM, Marks P, Martin C, Fazl M, Schwartz
M, et al. The neurological outcome following surgery for spinal fractures. Spine
(Phila Pa 1976). 1988;13(6):641-44,
http://dx.doi.org/10.1097/00007632-198813060-00007.
http://dx.doi.org/10.1097/00007632-19881...
). Briefly, “The least sagittal diameter of the spinal canal
at the level of injury (referred to as, a, below) was measured on the CT scan.
The normal diameter of the spinal canal was estimated by calculating the average
of the respective measurements at the adjacent unaffected levels above and below
the injury (referred to as, b, below). The percentage of spinal canal stenosis
was calculated by using the formula (a/b×100)”. Bone graft fusion
was assessed based on postoperative three-dimensional CT. The data were analyzed
using SPSS 13.0 for Windows (SPSS Inc., Chicago, IL, USA). The one-sample
Kolmogorov-Smirnov test was applied to analyze the continuous variables. For
normally distributed data, probability values were calculated based on the
analysis of variance. The Friedman test was applied to compare the anterior
vertebral body height, sagittal Cobb angle and percentage of spinal stenosis. A
p-value <0.05 was considered statistically
significant.
RESULTS
The surgery time for the 20 patients ranged from 120 to 270 minutes (averaged 195 minutes) and the total blood loss ranged from 1200 to 4000 ml (averaged 2800 ml). Postoperative cerebrospinal fluid leakage occurred in only one patient who recovered after symptomatic treatment. The vertebral structure was returned to normal according to the following parameters: the anterior vertebral body height was, on average, 50.77% before surgery and 88.51% after surgery and it was 87.86% at the last follow up; the sagittal Cobb angle was improved, on average, from 26.15° to 5.39° and it was 5.90° at the last follow up; the percentage of spinal stenosis was improved, on average, from 26.07% to 4.93% and it was 6.15% at the last follow up. There was a significant difference between the pre- and post-surgery values of the anterior vertebral body height, sagittal Cobb angle and the percentage of spinal stenosis in all patients (p<0) (Table 1). There were no large vessel injury complications or increased neurological symptoms in any of the 20 patients. There was also no loosening or breaking of the internal fixation on X-ray at the last follow-up. There was no obvious recovery of neurological function in the 4 cases with ASIA grade A. The ASIA score in 13 cases improved, including 7 cases that improved from B to C, 4 cases that improved from C to D and 2 cases that improved from D to E (Table 2).
DISCUSSION
The concept of thoracolumbar burst fracture was originally proposed by Holdsworth (22. Holdworth F. Fractures dislocations. and fracture. dislocation of the spine. J Bone Joint Surg Am. 1970;52(8):1534-51.) in 1970. The main features of this fracture are a wedge-shaped compression of the anterior column, middle column fractures and bone fragments of the posterior margin extruded into the spinal canal. These fractures are unstable and are often associated with neurological dysfunction.
The goal of surgical treatment is to decompress the neural elements, restore the
vertebral height, correct the angular deformity and stabilize the spinal column
(33. Hitchon PW, Torner J, Eichholz KM, Beeler SN. Comparison of
anterolateral and posterior approaches in the management of thoracolumbar burst
fractures. J Neurosurg Spine. 2006;5(2):117-25,
http://dx.doi.org/10.3171/spi.2006.5.2.117.
http://dx.doi.org/10.3171/spi.2006.5.2.1...
). In recent years, several
developments, such as the establishment of Denis' spinal three-column theory
(44. Denis F. The three column spine and its significance in the
classification of acute thoracolumbar spinal injuries. Spine (Phila Pa
1976).1983;8(8):817-31,
http://dx.doi.org/10.1097/00007632-198311000-00003.
http://dx.doi.org/10.1097/00007632-19831...
), the popularity of CT
three-dimensional reconstruction and magnetic resonance imaging (MRI) examinations
and the development of spinal fixation devices, have led to the extensive
implementation of various surgical methods for thoracolumbar burst fractures.
However, there has been no definitive evidence to help surgeons determine the
optimal surgical treatment (55. Vaccaro AR, Lim MR, Hurlbert RJ, Lehman RA Jr, Harrop J, Fisher
DC, et al. Surgical decision making unstable thoracolumbar spine injuries:
result of a consensus panel review by the spine trauma study group.
J Spinal Disord Tech. 2006;19(1):1-10,
http://dx.doi.org/10.1097/01.bsd.0000180080.59559.45.
http://dx.doi.org/10.1097/01.bsd.0000180...
,66. Dai LY, Jiang LS, Jiang SD. Anterior-only stabilization using
plating with bone structural autograft versus titanium mesh cages for two- or
three-column thoracolumbar burst fractures: a prospective randomized study.
Spine (Phila Pa 1976). 2009;34(14):1429-35,
http://dx.doi.org/10.1097/BRS.0b013e3181a4e667.
http://dx.doi.org/10.1097/BRS.0b013e3181...
). Currently, there are three main commonly
used surgical approaches: the posterior approach, the anterior approach and the
posterior-anterior combined approach. The posterior approach of open reduction and
internal fixation is used to restore vertebral body height and to partially reduce
bone fragments through the stretching and distraction of the posterior longitudinal
ligament and the posterior annulus fibrosus, which can also produce indirect
decompression. However, this approach is associated with several disadvantages. 1)
The indirect reduction is inaccurate and cannot ensure the anatomical reduction of
the bone fragments that entered the spinal canal, resulting in an incomplete
decompression of the spinal cord. 2) Although laminectomy helps in decompression, it
may also further increase the instability of the spine. 3) Posterior pedicle screw
fixation alone does not effectively maintain vertebral height, which could be
responsible for the high failure rate of internal fixation that is observed even in
cases without laminectomy. Additionally, the loss of vertebral height can result in
the subsequent development of kyphosis. 4) The effect of posterolateral bone
grafting fusion is inaccurate. 5) For old fractures (more than 2 weeks), posterior
vertebral body reduction is very difficult (77. McLain RF, Sparling E, Benson DR. Early failure of short segment
pedicle instrumentation for thoracolumbar fracture. A preliminary
report. J Bone Joint Surg Am. 1993;75(2):162-7.,88. Payer M. Unstable burst fractures of the thoracolumbar junction:
treatment by posterior bisegmental correction/fixation and staged anterior
corpectomy and titanium cage implantation. Acta Neurochir(Wien).
2006;148(3):299-06,
http://dx.doi.org/10.1007/s00701-005-0681-5.
http://dx.doi.org/10.1007/s00701-005-068...
). Moreover, even if the
serious collapse of thoracolumbar fractures is associated with satisfactory
reduction through the posterior approach, the “shell vertebral body”
phenomenon (99. Pappou IP, Papadopoulos EC, Swanson AN, Cammisa FP Jr, Girardi
FP. Osteoporotic vertebral fractures and collapse with intravertebral vacuum
sign (Kümmel's disease).Orthopedics. 2008;31(1):61-6.) can still occur and cause
secondary vertebral kyphosis. Secondary vertebral kyphosis usually requires the
anterior approach correction, which significantly increases the physical and
economic burden for patients (1010. Weidenbaux M, Farcy JPC. Surgical management of thoracic and
lumbar burst fractures A. In: Bridwell KH, Dewald RL, eds. The textbook of
spinal surgery. 2nd ed. Philadelphia(NY):Lippinoott-Raven Publishers,
1997;1839-80.,1111. McDonough PW, Davis R, Tribus C, Zdeblick TA. The management of
acute thoracolumbar burst fractures with anterior corpectomy and Z-plate
fixation. Spine (Phila Pa 1976). 2004;29(17):1901-8,
http://dx.doi.org/10.1097/01.brs.0000137059.03557.1d.
http://dx.doi.org/10.1097/01.brs.0000137...
).
Through the anterior approach alone, compression can be implemented under direct
vision to achieve complete decompression of the spinal canal, which produces little
disturbance for the already injured or edematous spinal cord and cauda equina.
However, this approach cannot solve such problems, such as, a severely damaged
vertebral posterior column structure, facet twisting, severe vertebral collapse,
dural tears and epidural hematomas. Some doctors have adopted the combined anterior
and posterior approach to increase the success rate; however, this increases the
trauma and consequent surgical morbidity (44. Denis F. The three column spine and its significance in the
classification of acute thoracolumbar spinal injuries. Spine (Phila Pa
1976).1983;8(8):817-31,
http://dx.doi.org/10.1097/00007632-198311000-00003.
http://dx.doi.org/10.1097/00007632-19831...
,1212. Sasso RC, Renkens K, Hanson D, Reilly T, McGuire RA Jr, Best NM.
Unstable thoracolumbar burst fractures: anterior only versus short-segment
posterior fixation. J Spinal Disord Tech. 2006;19(4):242-8,
http://dx.doi.org/10.1097/01.bsd.0000211298.59884.24.
http://dx.doi.org/10.1097/01.bsd.0000211...
). Thus, we used single-stage
posterior corpectomy, interbody fusion with titanium mesh and transpedicle screw
fixation for this type of injury. This approach combines the advantages of the
anterior only approach and the posterior only approach and reduces the trauma and
complications that may arise with the combined approach (1313. Tofuku K, Koga H, Ijiri K, Ishidou Y, Yamamoto T, Zenmyo M, et
al. Combined posterior and delayed staged mini-open anterior short-segment
fusion for thoracolumbar burst fractures. J Spinal Disord Tech.
2012;25(1):38-46,
http://dx.doi.org/10.1097/BSD.0b013e31820bb20f.
http://dx.doi.org/10.1097/BSD.0b013e3182...
,1414. Sasani M, Ozer AF. Single-stage posterior corpectomy and
expandable cage placement for treatment of thoracic or lumbar burst fractures.
Spine (Phila Pa 1976). 2009;34(1):E33-40,
http://dx.doi.org/10.1097/BRS.0b013e318189fcfd.
http://dx.doi.org/10.1097/BRS.0b013e3181...
); however, this
approach is not suitable for patients with severe osteoporosis or those in poor
physical condition. Nonetheless, this method allows for the completion of
decompression, reduction, fusion and fixation in one stage and has the following
advantages: less trauma, shorter operative time, less blood loss and total
decompression. It is especially suited for patients with poor lung function who
cannot tolerate a thoracotomy.
During the operation, the spine must be temporarily stabilized before decompression to avoid secondary spinal cord injury caused by instability. The decompression is generally started from the seriously injured side of the injury. In addition, the decompression of the vertebra associated with laminar fractures should be performed carefully, as cauda equina herniation can result from a fractured lamina.
Although there is controversy regarding the fusion of segments (1515. Sapkas G, Kateros K, Papadakis SA, Brilakis E, Macheras G,
Katonis P. Treatment of unstable thoracolumbar burst fractures by indirect
reduction and posterior stabilization: short-segment versus long-segment
stabilization. Open Orthop J. 2010;4(11):7-13,
http://dx.doi.org/10.2174/1874325001004010007.
http://dx.doi.org/10.2174/18743250010040...
16. Oken F, Yildirim O, Oken O. Short or long fusion after
thoracolumbar burst fractures does not alter selected gait parameters: a
preliminary study. J Orthop Res. 2011;29(6):915-8,
http://dx.doi.org/10.1002/jor.21329.
http://dx.doi.org/10.1002/jor.21329...
-1717. Yang H, Shi JH, Ebraheim M. Outcome of thoracolumbar burst
fractures treated with indirect reduction and fixation without fusion. Eur
Spine J. 2011;20(3):380-6,
http://dx.doi.org/10.1007/s00586-010-1542-3.
http://dx.doi.org/10.1007/s00586-010-154...
), we suggest the
following: for patients with a single disk injury and small portions of vertebral
body resection, a single-level fusion should be performed for the maximum
restoration of the activities of the adjacent segments; for patients with an injury
to two adjacent discs, corpectomy and double-segment fusion may be more
effective.
In conclusion, the present study allows us to propose that posterior corpectomy and stability reconstruction with titanic mesh autografting and pedicle screw fixation in one stage is an effective technique for unstable thoracolumbar burst fractures. However, it is important to consider some key limitations of this study, such as the small number of patients and the lack of a control group.
REFERENCES
-
1Gertzbein SD, Court-Brown CM, Marks P, Martin C, Fazl M, Schwartz M, et al. The neurological outcome following surgery for spinal fractures. Spine (Phila Pa 1976). 1988;13(6):641-44, http://dx.doi.org/10.1097/00007632-198813060-00007.
» http://dx.doi.org/10.1097/00007632-198813060-00007 -
2Holdworth F. Fractures dislocations. and fracture. dislocation of the spine. J Bone Joint Surg Am. 1970;52(8):1534-51.
-
3Hitchon PW, Torner J, Eichholz KM, Beeler SN. Comparison of anterolateral and posterior approaches in the management of thoracolumbar burst fractures. J Neurosurg Spine. 2006;5(2):117-25, http://dx.doi.org/10.3171/spi.2006.5.2.117.
» http://dx.doi.org/10.3171/spi.2006.5.2.117 -
4Denis F. The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine (Phila Pa 1976).1983;8(8):817-31, http://dx.doi.org/10.1097/00007632-198311000-00003.
» http://dx.doi.org/10.1097/00007632-198311000-00003 -
5Vaccaro AR, Lim MR, Hurlbert RJ, Lehman RA Jr, Harrop J, Fisher DC, et al. Surgical decision making unstable thoracolumbar spine injuries: result of a consensus panel review by the spine trauma study group. J Spinal Disord Tech. 2006;19(1):1-10, http://dx.doi.org/10.1097/01.bsd.0000180080.59559.45.
» http://dx.doi.org/10.1097/01.bsd.0000180080.59559.45 -
6Dai LY, Jiang LS, Jiang SD. Anterior-only stabilization using plating with bone structural autograft versus titanium mesh cages for two- or three-column thoracolumbar burst fractures: a prospective randomized study. Spine (Phila Pa 1976). 2009;34(14):1429-35, http://dx.doi.org/10.1097/BRS.0b013e3181a4e667.
» http://dx.doi.org/10.1097/BRS.0b013e3181a4e667 -
7McLain RF, Sparling E, Benson DR. Early failure of short segment pedicle instrumentation for thoracolumbar fracture. A preliminary report. J Bone Joint Surg Am. 1993;75(2):162-7.
-
8Payer M. Unstable burst fractures of the thoracolumbar junction: treatment by posterior bisegmental correction/fixation and staged anterior corpectomy and titanium cage implantation. Acta Neurochir(Wien). 2006;148(3):299-06, http://dx.doi.org/10.1007/s00701-005-0681-5.
» http://dx.doi.org/10.1007/s00701-005-0681-5 -
9Pappou IP, Papadopoulos EC, Swanson AN, Cammisa FP Jr, Girardi FP. Osteoporotic vertebral fractures and collapse with intravertebral vacuum sign (Kümmel's disease).Orthopedics. 2008;31(1):61-6.
-
10Weidenbaux M, Farcy JPC. Surgical management of thoracic and lumbar burst fractures A. In: Bridwell KH, Dewald RL, eds. The textbook of spinal surgery. 2nd ed. Philadelphia(NY):Lippinoott-Raven Publishers, 1997;1839-80.
-
11McDonough PW, Davis R, Tribus C, Zdeblick TA. The management of acute thoracolumbar burst fractures with anterior corpectomy and Z-plate fixation. Spine (Phila Pa 1976). 2004;29(17):1901-8, http://dx.doi.org/10.1097/01.brs.0000137059.03557.1d.
» http://dx.doi.org/10.1097/01.brs.0000137059.03557.1d -
12Sasso RC, Renkens K, Hanson D, Reilly T, McGuire RA Jr, Best NM. Unstable thoracolumbar burst fractures: anterior only versus short-segment posterior fixation. J Spinal Disord Tech. 2006;19(4):242-8, http://dx.doi.org/10.1097/01.bsd.0000211298.59884.24.
» http://dx.doi.org/10.1097/01.bsd.0000211298.59884.24 -
13Tofuku K, Koga H, Ijiri K, Ishidou Y, Yamamoto T, Zenmyo M, et al. Combined posterior and delayed staged mini-open anterior short-segment fusion for thoracolumbar burst fractures. J Spinal Disord Tech. 2012;25(1):38-46, http://dx.doi.org/10.1097/BSD.0b013e31820bb20f.
» http://dx.doi.org/10.1097/BSD.0b013e31820bb20f -
14Sasani M, Ozer AF. Single-stage posterior corpectomy and expandable cage placement for treatment of thoracic or lumbar burst fractures. Spine (Phila Pa 1976). 2009;34(1):E33-40, http://dx.doi.org/10.1097/BRS.0b013e318189fcfd.
» http://dx.doi.org/10.1097/BRS.0b013e318189fcfd -
15Sapkas G, Kateros K, Papadakis SA, Brilakis E, Macheras G, Katonis P. Treatment of unstable thoracolumbar burst fractures by indirect reduction and posterior stabilization: short-segment versus long-segment stabilization. Open Orthop J. 2010;4(11):7-13, http://dx.doi.org/10.2174/1874325001004010007.
» http://dx.doi.org/10.2174/1874325001004010007 -
16Oken F, Yildirim O, Oken O. Short or long fusion after thoracolumbar burst fractures does not alter selected gait parameters: a preliminary study. J Orthop Res. 2011;29(6):915-8, http://dx.doi.org/10.1002/jor.21329.
» http://dx.doi.org/10.1002/jor.21329 -
17Yang H, Shi JH, Ebraheim M. Outcome of thoracolumbar burst fractures treated with indirect reduction and fixation without fusion. Eur Spine J. 2011;20(3):380-6, http://dx.doi.org/10.1007/s00586-010-1542-3.
» http://dx.doi.org/10.1007/s00586-010-1542-3
-
No potential conflict of interest was reported.
Publication Dates
-
Publication in this collection
2014
History
-
Received
27 Mar 2014 -
Reviewed
2 June 2014 -
Accepted
10 Sept 2014