Keywords cervical corpectomy - expandable cage - anterior cervical plate - radiological outcomes
Introduction
Anterior cervical corpectomy and interbody fusion was introduced for anterior decompression
of the spinal cord. As anterior cervical discectomies became well accepted, nowadays
its extended approaches led to cervical corpectomies.[1 ] Cervical corpectomy is a ventral cervical spine procedure for safe and effective
neural decompression, deformity correction, mechanical stabilization, and single-step
neck kyphosis correction. The ultimate goal is neurologic improvement and bony fusion
after corpectomy. For that after cervical corpectomy, it is essential to develop the
stable vertebral restoration construct. Nowadays, we have various options for anterior
column reconstruction, including autologous bone graft taken from fibula or iliac
crest, allograft bone and a variety of cages such as expandable cage, mesh cage, and
hybrid cage. Because of graft donor site-related complications, we now preferred cage
to restore corpectomy defect.[2 ] However, the choice of type of the implant device for interbody fusion following
cervical corpectomy remains a debatable topic with different studies giving divergent
results. Moreover, the selection of the implant also depends on the surgeon preference
and the type of pathology. Vertebral body reconstruction using various cages are not
completely devoid of complications and they also carries a risk of complications such
as nonunion, graft displacement, migration, subsidence and adjacent segment degeneration.[3 ] One of the important goals of interbody fusion is to achieve the appropriate cervical
alignment because it allows tolerating the axial load of the head, optimizes forward
gaze and supports head and neck movement. Application of anterior cervical plate along
with cage also supports the construct.[4 ] Expandable titanium cages are the latest construct for vertebral body replacement
after a cervical corpectomy. Expandable cages have been used successfully to reconstruct
the anterior spinal column in the treatment of traumatic cervical spine injury, neoplastic,
infectious causes such as Pott's spine, degenerative spine disease and ossification
of the posterior longitudinal ligament (OPLL).[5 ]
[6 ]
[7 ]
[8 ]
[9 ] Optimal graft placement and sizing are especially important in the reconstruction
following multilevel corpectomy and fusion. Although titanium mesh cage has its own
advantages but one technical problem often faced is the preparation of exact size
of the implant matching into the corpectomy defect. Size adjustment made by cutting
the cage while placement can cause implant mal-alignment predisposing to construct
failure. In addition, repeated cage removal in an attempt to correct mal-alignment
usually damages the vertebral endplate. To overcome the technical disadvantages of
nonexpandable cages, variety of expandable cages have been introduced. Overall, cage
placement is much easier with expandable cages and results in less end plate damage
from intraoperative placement.[10 ] Expandable cages allow vertebral height adjustment in situ and deformity correction
at same time with property of easy distraction.[4 ] The sizing of expandable cage is easier compared with a mesh cage. A disadvantage
is their smaller caliber for packing bone versus other cage, yet studies indicate
high fusion rate.[11 ] An internal fixation device, usually an anterior cervical plating system, is often
used to further secure the construct and whether to use posterior supplemental fixation
is also an important consideration.[12 ] Newer expandable cages come with an integrated plate that obviates the need for
any additional anterior plating, and it prevents graft migration. In this study, the
outcomes were compared in terms of deformity correction, implant fusion rate, subsidence
rate, displacement rate, and re-operation rate.
Materials and Methods
This study was conducted on 100 patients admitted in the Department of Neurosurgery,
SMS Hospital, Jaipur, India, from January 2019 to December 2021 and all patients were
undergone anterior cervical corpectomy and fusion and divided in two groups. In Group
A, 60 patients using expandable cage alone and in Group B, 40 patients using expandable
cage with anterior cervical plate. In this study, we compared the procedure-related
complications and long-term neurological benefits and radiological outcomes in both
groups. Inclusion and exclusion criteria were used in this study as mentioned below:
Inclusion criteria: (1) Indications—traumatic spine injury, neoplastic, degenerative
spine disease, infectious disease, metabolic conditions (i.e., OPLL), (2) C3-C7 vertebral
levels, (3) level of corpectomy—1 or 2 or more vertebral body levels, and (4) expandable
cage used alone and used with anterior cervical plate. Exclusioncriteria: (1) Radiologic
signs of severe osteoporosis, (2) neck deformity excluding kyphosis, (3) previous
history of neck radiation, and (4) mesh cage or hybrid cage. Patient data including
indications for procedure, ASA, modified Frankle's classification, Nurick's grading,
diabetes mellitus, smoking status, preoperative osteoporosis, corpectomy levels (one/two/three
vertebral body level), additional procedures such as anterior cervical plating or
posterior instrumentation, type of cage used, and preoperative and postoperative radiographic
imaging were collected. Fusion was determined by CT scan or flexion/extension X-rays
of cervical spine at 6 months. Postoperative complications were divided in two groups
(intraoperative and postoperative complications) and compared in both group A and
group B. All patients were followed postoperatively for 6 months and data were collected
on the 15th day and 6th month. In both groups, among all patients, neurological, clinical,
and long-term radiological outcomes undergoing cervical corpectomy were compared.
Surgical Technique
All patients had anterior cervical corpectomy and decompression performed using a
standard transcervical supraclavicular approach. Microsurgical technique was performed
during decompression in all cases. Adjacent vertebral endplates and osteophytes were
removed using a high-speed drill. Endplates were meticulously prepared after corpectomy.
The appropriate implant size was determined by using a calliper to measure the height
and width of the corpectomy defect. Autograft bone from the corpectomy and iliac crest
was used to fill the expandable cage ([Fig. 1A,B ] and [Fig. 2C ]). Expansion of the cage can be done by either an expansion instrument or an expansion
wrench. First, cage was expanded up to the length of dead space and the bone filling
was done and then distracted and bone filled cage was inserted into the grafting site
and final distraction was performed. As expansion of the cage occurs, increasing stiffness
of endplate purchase can be felt and visualized. In this respect, a tight fit of the
cage into the corpectomy defect can easily be achieved and deformity correction is
possible. Once expansion of the cage was completed to satisfaction, the end piece
can be secured to the central core using a locking set screw thereby preventing further
collapse of the expansion. In 60 patients, we used expandable cage only without anterior
cervical plate support and in 40 patients, we used anterior cervical plating with
variable angle screws to additional fixation ([Fig. 1C ], [2C ]). If posterior column integrity is compromised, an additional posterior stabilization
was also performed.
Fig. 1 (A ) Expandable cage with multiple sharp teeth on both ends, these sharp teeth anchored
in adjacent vertebral end plates. (B ) Expandable cage with blunt end (without sharp teeth). (C ) Cervical plate with screws.
Fig. 2 (A ) Preoperative evaluation of cervical lordosis and kyphotic deformity by measurement
of the C2-C7 Cobb's angle. (B ) Postoperative evaluation of correction of cervical lordosis and kyphotic deformity
by measurement of the C2-C7 Cobb's angle. (C ) Multiple level corpectomy with anterior cervical plate; well-placed expandable cage
and plate showing fusion; 1-anterior cervical plate with variable angle screws, 2-expandable
cage. (D ) expandable cage subsidence at lower end plate (white arrow ).
Radiographic Evaluation
Expandable cage-related complications were monitored using radiography: cage migration,
dislodgement, progressive instability, and plate and screw dislodgement. Serial postoperative
imaging was obtained on the 15th day and 6 months, postoperatively. Dynamic flexion–extension
cervical spine radiographs were obtained after 6 months to evaluate stability, which
will be defined as less than 3 mm of translatory movement and a less than 5 degree
change in angulation between flexion and extension. On plain radiograph fusion was
defined as less than 1 mm of interspinous process motion on a more than 150% magnified
image with more than 4 mm of motion at an adjacent, unoperated level. Fusion was considered
to be achieved by the absence of lucency at the cage end caps and vertebral endplates,
or extra cage bridging bone formation or the absence of instability on dynamic X-rays.
Reduction of kyphosis (change in C2–C7 Cobb's angle) was determined between preoperative
and postoperative radiographs ([Fig. 2A,B ]). Sagittal alignment was measured before surgery, immediately after surgery and
at a final follow-up. The sagittal alignment was derived by the Cobb method of measurement.
The lines of measurement were taken from the superior endplate of the cephalad vertebra
fused and the inferior endplate of the caudal vertebra fused. The subsidence or settling
of the cage was observed from the radiographic studies in a sequential fashion. The
subsidence of the bone graft was diagnosed by a loss of graft height of 2 mm or more
detected on radiographs ([Fig. 2D ]). The subsidence (mm) was a combined measurement of the distance of the cage intrusion
into the upper and lower end plates.
Results
In this study, 100 patients were included and all patients underwent corpectomy followed
by the insertion of expandable cage only in 60 patients (Group A) and expandable cage
with anterior cervical plate in 40 patients (Group B). In this study, 76 patients
were male and 24 patients were female and the mean age of patients were included in
study was 51.78 ± 16.74 years in group A and 41.68 ± 15.60 years in group B. Eighty
four (Group A 53 and Group B 31) patients were under ASA grade 1 or 2. Fourteen patients
had history of smoking and 16 patients had history of DM. Various indications for
the reconstruction of anterior column in both groups by expandable cage with or without
anterior cervical plate were included in as 53 patients of traumatic cervical spine
disease, 34 patients of cervical degenerative spine disease, 6 patients of cervical
Pott's spine, 6 patients of ossified posterior longitudinal ligament, and 1 patient
of multiple myeloma. Corpectomy was done in 83 patients at single level, in 15 patients
at two vertebral body levels and in two patients at three vertebral body levels for
above mentioned indications. Patients were classified according to Modified Frankel's
classification as grade A (38%), B (20%), C (6%), D (24%), and E (12%) ([Table 1 ]). Variable parameters such as change in C2–C7 Cobb's angle and Nurick's scale scores
were compared in all patients, preoperatively and postoperatively, in both groups.
There were significant changes in cervical lordosis, reduction of kyphosis and sagittal
balance were evaluated by calculating C2–C7 Cobb's angle by radiological or X-ray
cervical spine pre- and postoperatively. In our study, preoperatively mean C2–C7 Cobb's
angle was 17.96 ± 6.54 degree in Group A and 18.33 ± 7.90 degree in group B and postoperatively
mean C2–C7 Cobb's angle was 21.48 ± 6.2 degree in group A and 22.68 ± 5.10 degree
in group B. There was an improvement in C2–C7 Cobb's angle in group B was significantly
higher than group A (p < 0.05). Nurick's scale was calculated by clinical neurological examination of patient
preoperatively and compared with improvement in Nurick's scale grading after cervical
spinal cord decompression by anterior cervical corpectomy with interbody fusion using
expandable cage with or without plate for various cervical pathological conditions.
As per the evaluation and observations, decrease in Nurick's scale in group B was
significantly higher than group A (p < 0.05); ([Table 2 ]). In our study, all patients were evaluated for implant fusion, cage subsidence,
procedure-related complications and implant-related complications. Great vessels injury,
trachea-esophageal injury and pneumothorax during surgery were not reported and five
patients (group A [3.33%], group B [7.5%]) had iatrogenic dural tear during surgery
and only one in group B (2.5%) patient had thyroid retraction injury along with recurrent
laryngeal nerve injury with postoperative hoarseness of voice, which was managed conservatively.
In this study, dysphagia was noted in 11 patients (group A [5%], group B [20%]) in
immediate postoperative period which was later recovered and the incidence of dysphagia
was more in postoperative period in group B as compare with group A (p < 0.043). There was no case reported for large local wound hematoma in immediate
postoperative period for life threatening tracheal compression or shortness of breath
although three cases of small hematoma were reported (3%). Total five (group A [3.33%],
group B [7.5%]) patients had soft tissue swelling, which was later confirmed as CSF
collection at wound site presented as soft tissue swelling, they were managed by medical
management and insertion of lumbar drain for CSF diversion and later on wound was
healed and lumbar drain was removed. Wound infection was reported in six patients
(group A [5%], group B [7.5%]) and five patients were recovered by higher antibiotics
and regular dressing and one patient had undergone for implant removal (2.5%) in group
B. On radiological evaluation after 6 months by dynamic flexion-extension cervical
spine X-ray or CT cervical spine, demonstrated by bridging bone between the vertebral
bodies or by the absence of motion on dynamic radiographs, good fusion of expandable
cage alone in 78.3% of patients and there was significantly better fusion of expandable
cage with anterior cervical plate in 95% of patients (p < 0.045). Cage subsidence was reported in 15 cases (group A [21.67%], group B [5%])
and subsidence was more in group A as compare with group B (p < 0.045), there was a cage settling into adjacent vertebral end plate (Fig. 4), which
was evaluated by radiological comparison of cage settled into adjacent lower or upper
endplate of vertebrae. In our study, 14 patients (group A [16.67%], group B [10%])
were undergone revision surgery, in group A, 10 patients had revision because of structural
failure and cage migration. One patient re-explored for fusion failure due to high
mobility of cage with cord compression in group A. In group B, three patients were
undergone revision surgery for cage migration, implant structural failure and malpositioned
screws which were used for plate fixation. There was no case reported for adjacent
segmental disease, tracheo-esophageal fistula, implant explantation, cage over distraction
or further neck deformity in long term follow up period in group B but in group A,
cage over-distraction and persistent neck deformity in two patients and adjacent segmental
deformity in one patient was noted ([Table 3 ]).
Table 1
Comparative study of epidemiological parameters
Variable
Group A (n = 60) Expandable cage only
Group B (n = 40) Expandable cage with anterior cervical plate
Total
(n = 100)
Number
Percentage
Number
Percentage
Sex
Male
45
75
31
77.5
76
Female
15
25
9
22.5
24
DM
Yes
8
13.33
8
20
16
No
52
86.66
32
80
84
Smoking
Yes
10
16.33
4
10
14
No
50
83.33
36
90
86
Diagnosis
Traumatic cervical injury
32
53.33
21
52.5
53
Degenerative spine disease with or without OPLL
22
36.66
12
40
34
Ossified Posterior longitudinal ligament only (OPLL)
2
3.33
4
10
6
Multiple Myeloma
0
0
1
2.5
1
Cervical Pott's spine
4
6.66
2
5
6
Level of corpectomy
Single
50
83.33
33
82.5
83
Multiple (≥ 2 levels)
9 (2 level)
15
6 (2 level)
15
15
1 (3 level)
1.66
1 (3 level)
2.5
2
ASA grade
1
35
58.33
16
40
51
2
18
30
15
37.5
33
3
3
5
5
12.5
8
4
4
6.66
4
10
8
Modified Frankel's classification
A
24
40
14
35
38
B
14
23.33
6
15
20
C
4
6.66
2
5
6
D
13
21.66
11
27.5
24
E
5
8.33
7
17.5
12
Mean age (y)
51.78 ± 16.74
41.68 ± 15.60
Table 2
Comparative study of change in C2-C7 Cobb's angle and Nurick's scale score
Variables
Group A (n = 60)
Expandable cage only
Group B (n = 40)
Expandable cage with anterior cervical plate
Pre-operative
Post-operative
p -Value
Pre-operative
Post-operative
p -Value
Cobb's angle (degree)
17.96 ± 6.54
21.48 ± 6.2
t = 3.03, df = 59
p
< 0.05
18.33 ± 7.90
22.68 ± 5.10
t = 7.9, df = 39
p
< 0.001
Change in C2-C7 Cobb's angle (degree)
3.52
4.35
Nurick's scale score
2.68 ± 1.16
2.26 ± 1.02
t = 2.11, df = 59
p
< 0.05
2.55 ± 1.87
1.90 ± 1.98
t = 3.9, df = 39
p
< 0.001
Table 3
Comparative study of various complications occurs in both groups
Complications
Group A (n = 60) Expandable cage only
Group B (n = 40) Expandable cage with anterior cervical plate
p -Value
Total
(n = 100)
Number
Percentage
Number
Percentage
Intraoperative complications
Bleeding/great vessel injury
No case reported
No case reported
–
Tracheal injury
–
Esophageal perforation
–
Pneumothorax
–
Nerve injury (Vagus/RLN)
1
2.5
–
1
Iatrogenic Dural tear
2
3.33
3
7.5
0.64
5
Thyroid injury
No case reported
1
2.5
–
1
Early post-operative complications
Dysphagia
3
5
8
20
0.043
11
RLN palsy/Hoarseness of voice
1
1.67
1
2.5
0.662
2
Hematoma
2
3.33
1
2.5
0.72
3
Soft tissue swelling
4
6.67
2
5
0.932
6
CSF Leak from wound
2
3.33
3
7.5
0.64
5
Surgical site infection
3
5
3
7.5
0.932
6
Late post-operative complications
Tracheo-esophageal fistula
No case reported
No case reported
–
–
Implant structural failure
10
16.67
3
7.5
0.302
13
Persistent neck deformity
2
3.33
No case reported
–
2
Implant subsidence
13
21.67
2
5
0.045
15
Cage over-distraction
2
3.33
No case reported
–
Fusion failure
13
21.67
2
5
0.045
15
Implant or cage migration
4
6.67
2
5
0.932
6
Revision surgery
10
16.67
4
10
0.518
14
Adjacent segmental disease
1
1.67
No case reported
–
1
Discussion
Anterior cervical single or multilevel (≥ 2 levels) corpectomy was done for cervical
pathological conditions. Recently, there has been a rapid increase in the commercial
availability and the clinical use of expandable cages or non-expandable cages with
additional anterior cervical plating for VB replacement in the cervical spine after
corpectomy because of donor site related complications and poor structural reconstruct.
Expandable cage can be used alone or also it can be used with additional anterior
cervical plate system. Anterior cervical plating system can give multiple technical
benefits to structural reconstruct. Therefore, the purpose of this study was to compare,
the biomechanical properties of expandable cages with or without anterior cervical
plating used for better neurological and radiological outcomes, correction of cervical
spine lordosis, change in segmental angle, correction of kyphotic deformities, subsidence,
and fusion rate.
In our study, fusion rate in both study group was 85% (expandable cage alone—78.33%
and with anterior cervical plate—95%), which is almost similar to the study done by
Pojskic et al, Brenke et al, Art et al, Hassan Allouch et al, Cappelletto et al, Byvaltsev
et al, and Tohamy et al.[13 ]
[14 ]
[15 ]
[16 ]
[17 ]
[18 ]
[19 ] The placement of expandable cage is very smooth and avoids any major damage to the
vertebral endplates. It is an instinctive thought that subsidence should be lower
in the cervical spine because of less axial loading in contrast to the dorsal and
lumbar spine. Biomechanical studies reported that the cervical spine is in fact more
susceptible to subsidence than any other region. Subsidence depends on several factors:
(i) surgical preparation of the vertebral bodies, (ii) bone density, (iii) modulus
of elasticity of the material in implant (closer the modulus is to that of bone, lesser
is the probability of subsidence), (iv) type of footprints and diameter of the implant
(lower is the chance of subsidence when greater is the contact area), (v) application
of anterior cervical plate with cage, and (vi) proportion of distraction on the adjacent
vertebrae.[10 ] Subsidence occurs minimally with expandable cages because of its greater diameter
and dull edged footplates. Hence, the preference should be to use implant with the
largest diameter possible. In addition, the end-plates integrity may further prevent
the chance of future subsidence of the cage.[9 ]
[20 ] Additional anterior cervical plating with expandable cage also beneficial to decrease
rate of cage subsidence with load diversion by plate. One of the subsidence prevention
features of expandable cage is limited footprint surface area which leads to less
fusion due to inadequate graft–host bone contact and in turn increases the risk of
implant failure as compare with other nonexpendable cage so anterior cervical plating
is useful.[21 ] Cage subsidence in our study was 15% (expandable cage alone—21.67% and with anterior
cervical plate—5%), similar findings were also reported by Brenke et al (14%) and
Tohamy et al (5.68–14.71%), while in a study done by Pojskic et al and Art et al cage
subsidence was relatively higher (24.4% and 42.7%, respectively).[13 ]
[14 ]
[15 ]
[16 ]
[17 ]
[18 ]
[19 ] Previous studies have reported that expandable cages allow for improvement in cervical
lordosis but no large comparative studies done evaluating the effect on cervical lordosis.[3 ] In our study, change in C2-C7 Cobb's angle ranges from 3.52° to 4.35° similar to
the study done by Brenke et al (5°), Tohamy et al (4°), and Byvaltsev et al (5.8°),
and more change as compared with studies done by Cappelletto et al (1.3°), and Pojskic
et al (1.8°), and these changes are may be as it allows the expansion of the cage
in-situ and optimal fitting into the corpectomy defect, leading to the correction
of kyphosis/lordosis or change in C2-C7 Cobb's angle, restoration of vertebral height,
and sagittal alignment in single stage. They have wide footprints that disseminates
axial load evenly.[3 ]
[9 ] The change in segmental angle was calculated as a difference between the segmental
angle prior to surgery and the segmental angle post-surgery at the last follow-up
visit. This greater mean difference suggests that the expandable cage with anterior
cervical plating is better than the expandable cage alone in terms of correcting the
deformity, restoring the cervical lordosis and maintenance of cervical lordosis. Failure
in restoring cervical lordosis can lead to uneven distribution of axial load over
adjacent vertebral end plates and strain over neck paraspinal muscles. As per the
comparison of correction of cervical lordosis by measuring segmental angle in cervical
spine, it is likely in favour of good correction with the application of anterior
cervical plating with expandable cage as compared with cage alone ([Table 4 ]). As per the study done by Liu et al, postoperative wound or epidural hematoma is
reported as a rare and fatal early complication after anterior cervical spine surgery.
Many case reports and larger studies investigating overall complication rates have
demonstrated the incidence of postoperative hematoma to be 0.1% to 9.9%. However,
the incidence of hematoma after anterior cervical spine surgery remains controversial.[22 ] In this study, hematoma was seen in 3% of cases, which is similar to the results
reported by Pojskic et al, Brenke et al, and Byvaltsev et al ([Table 5 ]).
Table 4
Comparative analysis of postoperative outcomes with previous studies
Pojskic, 2020
Brenke, 2015
Art, 2008
Allouch, 2020
Cappelletto, 2020
Byvaltsev, 2021
Tohamy, 2022
Current study
Total numbers of patients
86
50
60
(Cervical cases: 41)
69
39
78
31
100
1) Expandable cage only
58
34
1
16
10
78
31
60
2) Expandable cage with anterior cervical plating
28
16
40
53
0
0
0
40
Mean age (y)
61.3
61
54
61.9
55
58
66.5
47.74
Favorable neurological outcomes
91.6%
66%
89%
90%
90%
93.5%
–
94%
Fusion rate
86%
88%
93%
94.1%
90%
92.3%
100%
(a) Group A – 78.33%
(b) Group B – 95%
Cage subsidence
24.4%
14%
42.7%
–
low
low
5.68–14.71%
(a) Group A – 21.67%
(b) Group B – 5%
Correction of lordosis or khyphosis/C2–C7 Cobb's angle change
1.8°
5°
3.3 ± 13.9°
–
1.3°
5.8°
4°
(a) Group A – 3.52°
(b) Group B – 4.35°
Table 5
Comparative analysis of complications with previous studies
Variables
Pojskic, 2020
Brenke, 2015
Cappelletto, 2020
Byvaltsev, 2021
Tohamy, 2022
Current study
Total numbers of patients
86
50
39
78
31
100
Implant migration
9 (10.5%)
–
1 (2.6%)
1 (1.3%)
–
6 (6%)
Revision surgery
13 (15.1%)
12 (24%)
1 (2.6%)
–
–
14 (14%)
RLN injury
3 (3.5%)
–
–
–
–
1 (1%)
Hematoma
4 (4.7%)
3 (6%)
–
3 (3.8%)
–
3 (3%)
Adjacent segmental disease
9 (10.5%)
–
–
2 (2.6%)
–
1 (1%)
Esophageal injury
0
1 (2%)
–
–
–
–
Surgical site infection
–
–
–
1 (1.3%)
–
6 (6%)
Dysphagia
–
–
–
–
19 (61.4%)
11 (11%)
In present study, implant migration or displacement was seen in 6% of cases, which
is almost similar to the results reported by Pojskic et al (10.5%), Cappelletto et
al (2.6%), and Byvaltsev et al (1.3%) ([Table 5 ]). Implant displacement is one of the most dreaded complications of multilevel (≥
2 levels) of cervical corpectomy. The risk of displacement is proportional to the
level of the corpectomy. The displacement of graft is low with one level and up to
some extent in two level corpectomy with or without plating. Graft displacement is
significantly higher in three or more levels of corpectomy. Theoretically, it is assumed
that the rate of graft displacement can be decreased by placing a plate over graft.[23 ] Plate fixation increases the stability of the graft by reducing the range of motion
and also decreases the probability of pseudo-arthrosis.[24 ] Another study done by Brenke et al suggested that expandable cage can be used for
cervical spine vertebral body replacement and that the complication rate significantly
increases when implemented for a multilevel corpectomy (≥ 2 levels); however, in this
study there was a significant difference in cage displacement following multilevel
(≥ 2 levels) of corpectomy, followed by vertebral body reconstruction using expandable
cage alone as compare with additional anterior cervical plate, however more number
of studies were required to appropriate evaluation of rate of complication after multilevel
(≥ 2 levels) corpectomy. In this recent study, authors considered expandable cage
not to be an ideal implant for multilevel (≥ 2 levels) corpectomy if used alone so
it should be additionally support with anterior cervical plating.[14 ] One feasible reason mentioned was the limited cage and bone interface when the expandable
cage is placed over long segments.[25 ] Insertion of expandable cage requires a precise adjustment of implant height in
situ according to the size of corpectomy with firm contact between footplates and
vertebral endplates, to prevent cage migration. To achieve this firm and secure fit
into the defect, some over-distraction is required. So, inadequate distraction in
view of misjudgment of cage height can result in weak compressive forces over endplates
and may lead to cage migration.[24 ] As compare with dull edges of footprints of expandable cage, sharp footprints of
mesh cage usually subside into the vertebral end plate at the time of fixation providing
a more firm placement than expandable cages. For the above-mentioned reason, we should
prefer the additional anterior cervical plate to prevent cage migration during neck
motion while using expandable cage alone. In both groups, implant-related factors
(displacement or migration and subsidence) led to the majority number of revision
surgery. Other less common causes were epidural hematoma, pseudoarthrosis, infection,
and delayed union or fusion failure. In this study, revision surgery was required
in 14% of cases, similarly revision surgery was required in 15% of cases in a study
done by Pojskic et al while in a study done by Brenke et al around one-fourth (24%)
of cases required revision surgery and only 2.6% of cases required revision surgery
in a study done by Capelletto et al[13 ]
[14 ]
[17 ] ([Table 5 ]). Spivak et al also emphasized that combined plating should be considered in the
severely unstable cervical spine and application of anterior plate also improves the
fusion rate of expandable cage, but it can cause stiffness of neck movement in extension.
Sometimes plate application can lead to reverse the graft load or excessive load to
cage leads to failure of multilevel (≥ 2 levels) reconstruct.[26 ]
In this study of 100 patients, postoperative dysphagia was in 11 patients (11%). It
was more common in group B (20%) as compare with group A, which was later recovered.
Tohamy et al suggested that newer stand-alone cages without an anterior plate may
avoid some of the complications seen with conventional methods, especially dysphagia.
Dysphagia can range from mild discomfort to inability of control of the muscles used
for swallowing. Persistent dysphagia can result in serious medical complications,
potential significant morbidity and possible mortality. Although the exact cause of
postoperative dysphagia is unknown, it has been speculated that the profile of the
plate, adhesions, and scar tissue have an impact on the esophagus. The outcomes after
plate application to support the construct were good in multilevel (≥ 2 levels) corpectomy
except postoperative dysphagia.[19 ] ([Table 5 ])
A recent study done by Hassan et al suggested that patients with and without plates
had no outcome differences but due concerns regarding postoperative stability, loss
of lordosis, and subsidence or migration of the implant cages, they are commonly used
with supplemental fixation such as pedicle screw systems or anterior plates. Anterior
plates are commonly used to stabilize corpectomy constructs in single or multiple
(≥ 2 level) implant migration or displacement. Sometimes, post-laminectomy kyphosis,
osteoporosis, oncologic reconstructions, and severe deformity also may be indications
for ventral cervical plating after corpectomy.[16 ] Grubb et al also used a C5 corpectomy model in human and porcine cervical spines
to determine the stabilizing effect of different anterior plate systems.[27 ] Kandziora et al demonstrated that all stand-alone implants were not able to restore
normal stability of the motion segment in extension. Therefore, anterior stabilization
performed using stand-alone nonexpandable or expandable cages is not suitable for
VB replacement in the cervical spine.[28 ] Punjabi et al suggested the cages plus anterior stabilization and cages plus anteroposterior
instrumentation significantly increased stiffness in all test modes compared with
the intact motion segment. Therefore, the cage plus anterior or combined anteroposterior
stabilization provide sufficient stiffness for vertebral body replacement and should
be preferred over a stand-alone implant. In comparison with the stand-alone implants,
additional anterior plating demonstrated a further increase in stiffness of up to
254%, especially in extension. This was due to the position of the anterior plate,
mimicking the stabilizing effect of the anterior longitudinal ligament. Although additional
anterior plating significantly increased positive biomechanical results, additional
posterior stabilization increased rotational stiffness up to 102%. Therefore, additional
posterior instrumentation should be considered in severe rotational instability of
the cervical spine.[29 ]
The limitations of this study include its small sample size. Small sample size is
not enough to evaluate the different outcomes and early or late complications. Further
studies with long-term follow-up are required to assess the effect of such cages and
anterior cervical plate. We can take the decision of additional plating or dorsal
stabilization tailored to individual patient characteristics such as overall stability,
bone quality and underlying pathology.
Conclusion
We conclude the limitations of expandable cage alone in terms of cage migration, fusion
rate, adjacent segmental disease, failure of multilevel (≥ 2 levels) construct, subsidence
as compare with expandable cage used with additional anterior cervical plate. The
application of anterior cervical plate in construct support with expandable cage and
long-term benefits such as good structural support to multilevel (≥ 2 levels) reconstruct,
improved fusion rate, to restore normal stability while motion in extension of cervical
spine, less chance of cage subsidence, prevention of the adjacent segmental disease
and prevention of the migration of expandable cage but application of plate can leads
to various postoperative complications which were mentioned earlier such as dysphagia,
neck stiffness and reversal of graft load leads to failure of multilevel (≥ 2 levels)
construct. The limitations of this study include its small sample size and it is not
enough to evaluate the percentage of the postoperative complications in such a population.
Further studies with long-term follow-up are required to assess the effect of such
cages with plate on the adjacent level.
