Adjacent Segment Disease after Anterior Cervical Inter body Fusion using Conventional Plate versus Zero-Profile Implant - A Preliminary Report
Jae-Sung Ahn , Ho-Jin Lee*, Eugene J Park and Ho-Seok Lee
Department of Orthopaedic Surgery, Chungnam National University School of Medicine, Daejeon, Republic of Korea
Submission: September 12, 2016;; Published: September 28, 2016
*Corresponding author: Ho-Jin Lee, Department of Orthopaedic Surgery, Chungnam National University Hospital 282 Munhwa-ro, Jung-gu, Daejeon, 301-721, Republic of Korea,Tel: 820129799849; Email: email@example.com
How to cite this article: Jae-Sung A , Ho-Jin L Eugene J P, Ho-Seok L. Adjacent Segment Disease after Anterior Cervical Inter body Fusion using Conventional Plate versus Zero-Profile Implant - A Preliminary Report. Ortho & Rheum Open Access J. 2016; 3(1): 555603. DOI: DOI: 10.19080/OROAJ.2016.03.555603
Background: Anterior cervical discectomy and interbody fusion is a common surgical method used for treatment of single or 2 level cervical lesion. Recently, zero-profile implant, which lessened irritation of adjacent structures by preventing the contact with them, was design for anterior cervical fusion, and was assumed that it would reduce the occurrence of adjacent segment disease. Thus, authors compared the occurrence of adjacent segment disease after using conventional plate or zero-profile for anterior cervical interbody fusion.
Methods: 48 consecutive cases that underwent single-level anterior cervical discectomy and fusion for lesions of cervical spine that did not respond to nonsurgical treatment and were able to follow up for at least 1 year were included in this study. Clinical and radiologic features of 25 cases (group A) that used conventional plate from April 2007 to January 2011 and 23 cases (group B) that used zero-profile plate from March 2011 to February 2014 were retrospectively compared.
Results: Adjacent segment degeneration was present in 10 cases in group A and 6 cases in group B. The occurrence of the degeneration was statistically insignificant. In aspect of grade of ossification, group A consisted of 6 cases of grade 1, 2 cases of grade 2, and 1 case of grade 3 while group B consisted of 5 cases of grade 1, 1 case of grade 2, and no case of grade 3.
Conclusion: It is considered rather than the insult to adjacent structures by implants, natural degeneration or increased loading to the adjacent segment after interbody fusion are more important factors for occurrence of adjacent segment degeneration.
Keywords: Adjacent segment disease; Anterior cervical inter body fusion; Zero-profile implant
Anterior cervical discectomy and fusion is a widely used technique for cervical spine disease and trauma such as herniation of intervertebral disc, cervical spondylotic radiculopathy, cervical fracture, and etc . The technique requires relatively short operation time, has less blood loss and complication, shows immediate symptom relief, and high union rate of over 90% compared to lumbar spine . Though the technique has become popular due to such merits, there are a few possible complications at risk, for example, dysphagia and adjacent segment disease. Adjacent segment disease refers to a radiologic degeneration on the segment adjacent to previous arthrodesis with accompanied symptom due to such degeneration and adjacent segment degeneration refers to only radiologic degeneration. However, the correlation between the degree of degeneration and occurrence of symptom due to degeneration is not well established [3,4]. According to Hilibrand
et al, the annual occurrence of adjacent segment disease after anterior cervical discectomy and interbody fusion is about 2.5% . In the other hand, some clinical and mechanical studies reveal that there are no increased motion or pressure of adjacent level after interbody fusion [5,6].
Another study showed that cases with postoperative kyphotic angulation are more likely to have adjacent segment disease [7,8]. As indicative above, numerous studies reported that various factors influence the occurrence of adjacent segment disease and results whether it is brought about due to trauma by surgery or natural history is inconsistent. Based on studies that concluded that adjacent segment degeneration was more frequently occurred and accelerated by insult of tissue due to surgery [9-11], authors investigated the occurrence of adjacent segment disease after anterior cervical discectomy and fusion using zero-profile plate and conventional plate hypothesizing that group using zero-profile plate will show lower occurrence.
The study was conducted after the approval of the
institutional review board (IRB file no. 2015-08-015). All patients
signed consent that they will be enrolled in clinical study. Medical
records and radiologic evaluation of 48 consecutive cases that
underwent a single level anterior cervical discectomy and fusion
due to degenerative change from April 2007 to February 2014
were retrospectively analyzed. All cases had been followed up
for at least 12 months clinically and radiologically. Surgery
was performed for cases refractory to adequate nonsurgical
treatment of at least 6 weeks with a diagnosis of single level
cervical radiculopathy or myeloradiculopathy with subtle
myelopathy symptoms such as mild numbness on the hand.
Patients’ symptoms were well correlated with the conventional
radiograph and magnetic resonance images with evident
stenosis (Figure 1). The senior author (JS Ahn) performed every
surgery and Smith-Robinson technique was used for surgical
approach for all patients.
Before the introduction of zero-profile plate on February
2011, a conventional plate (Vectra-T plate, Synthes, Switzerland)
was used and ever since, zero-profile plate (Zero-P plate, Synthes,
Switzerland) was used for degeneration cases (Figure 2). For postoperative care, soft cervical collar (Philadelphia brace) was
applied for 1 day and then all neck motion was allowed without
brace. Conventional radiograph was performed on the final
follow up for each case (Figure 3). To eliminate the difference
of loading due to difference numbers of fused segment, multi
segment fusion cases were excluded from the study. In addition,
since compromised soft tissues such as anterior longitudinal
ligament and bony structures could accelerate degeneration of
the adjacent segment, trauma or tumor cases were also excluded
[11,12]. Also, cases without radiological follow up at least 12
months after surgery were not included.
Clinical factors such as sex, age, alcohol, smoking, and index
level of every patient were checked. The preoperative and
postoperative curvature of the index level was measured using
simple radiograph. Diagnosis of adjacent segment degeneration
and classification of ossification was made according to Katsuura
et al. and Nassr et al. [8,9]. Patient was diagnosed as adjacent
segment degeneration if at least 1 of the following findings was
Evident intervertebral disc space narrowing
Newly developed instability on flexion-extension
Vertebral anterior or posterior spur formation.
Cases were also were classified by the degree of ossification
Grade 0: no ossification
Grade 1: extending across less than 50% of adjacent
Grade 2: extending across more than 50% of adjacent
Grade 3: complete bridging of adjacent disc space .
For evaluate the clinical judgment after surgery, Odom’s
criteria along with symptom and sign of each patient were
investigated. Odom’s criteria are as follows:
Excellent: all preoperative symptoms relieved;
abnormal findings improved
Good: minimal persistence of preoperative symptoms;
abnormal findings unchanged or improved
Fair: definite relief of some preoperative symptoms;
other symptoms unchanged or slightly improved
Poor: symptoms and signs unchanged or exacerbated.
1 for Excellent,
2 for Good,
3 for Fair, and
4 for Poor
As a result, group A showed 1.96±0.73 points while group B
showed 1.65±0.88 points which showed no significant difference
between 2 groups (p=0.092). Authors emphasized to keep
For the comparison of diverse clinical factors between two
groups, the Mann-Whitney U and chi-squared tests were used.
Various pre and postoperative findings were analyzed using the
Mann-Whitney U-test, Chi-square test, and Fisher’s exact test.
All statistical analysis was performed using the SPSS analytical
software version 18.0 (SPSS Inc., Chicago, Ill., USA). In all analyses
differences were considered significant at a level of p < 0.05.
Total of 48 cases were included in the study. 25 cases used
conventional plate with cage insertion (group A) and 23 cases
used zero-profile plate (group B) for cervical interbody fusion.
The demographic data of both groups are descripted on (Table 1).
All factors mentioned above showed no statistically significant
difference between the 2 groups. Cases’ clinical improvements
were graded according to Odom’s criteria:
lordosis of the index level, and as a result, postoperatively, sagittal
angle was maintained as a lordotic curve (group A: 5.19±6.00,
group B: 5.38±4.96) (+; lordosis, -; kyphosis). Adjacent segment
degeneration was present in 10 cases in group A and 6 cases in
group B. Specifically, spur formation, disc space narrowing, and
instability was found in 9 cases, 2 cases, and 1 case in group A
and 6 cases, 0 case, and 2 cases in group B.
The occurrence of the degeneration was statistically
insignificant. (p=0.307) In aspect of grade of ossification, group
A consisted of 6 cases of grade 1, 2 cases of grade 2, and 1 case
of grade 3 while group B consisted of 5 cases of grade 1, 1 case
of grade 2, and no case of grade 3. There were 1 cases of each
group that had new radiculopathic symptom (tingling sensation)
apart from preoperative symptoms, however, both cases were
able to be managed non-surgically (Tables 2 & 3). Each clinical
and radiological factor (age, sex, smoking, alcohol drinking,
index level, and preoperative and postoperative sagittal angle
of the index level) were statistically analyzed for influence
to the adjacent segment degeneration. As a result, cases that
have smoked and regular alcohol drinker showed a statistically
significantly higher occurrence rate of adjacent segment
Anterior cervical discectomy and fusion is a common
procedure for single or two level cervical spondylotic changes
or disc disease. Rarely, however, complications of the technique
such as postoperative dysphagia, hematoma, recurrent laryngeal
nerve, and adjacent segment disease could occur. Specifically,
58.4% of the patients that underwent anterior cervical
discectomy and fusion suffered from symptoms related to
swallowing difficulty immediately after surgery  and among
them, 6.6% had the symptom continued until 2 years follow
up, [14,15] and adjacent segment disease is reported that the
annual occurrence is about 3% . It is assumed that anterior
cervical plating bring about dysphagia and adjacent segment
However, even with such evidence, most of the anterior
cervical discectomy cases are augmented with plating rather than
using cage alone since plate augmentation shows higher union
rate and preservation of intervertebral disc height [6,17,18].
Thus, to minimize complications while maintain firm fixation
with plate, recently a zero-profile plate has been developed and
promising results, especially in aspect of dysphagia, are being
reported [19-22]. Though the causes of adjacent segment disease
is multivariate, however, the issue is that whether it is a result of
natural course of degeneration or due to insult after interbody
fusion of the cervical spine. Some reports are conflicting with
the theory of accelerated adjacent segment degeneration after
Biomechanical studies by Reitman et al.  reported no
increased motion of cephalad segment after anterior cervical
interbody fusion, and Fuller et al.  found that sagittal
rotation of the immediately adjacent segment of arthrodesis was
not statistically significantly increased. However, there are other studies show contrary results with accelerated degeneration and
motion of the adjacent segment after fusion, for example, Eck et
al.  reported significantly higher intervertebral pressure and
motion of the segments adjacent to arthrodesis. Since Park et
al.  reported that adjacent segment degeneration is prone
to occur when the distance of plate end and adjacent disc is less
than 5mm and Mahrling  reported accelerated degenerative
change after wider resection of anterior longitudinal ligament,
zero-profile plate was considered to minimize such problems
which in order will decrease the occurrence of adjacent segment
However, against to our expectation, according to the result
of our study, the difference of occurrence rate between cases
using conventional plate and zero-profile plate was statistically
insignificant. In view of such result, it is considered that rather
than insult to the adjacent segment caused by plating, increased
loading to the adjacent segment due to interbody fusion is the
major factor for degeneration. In addition, since there are some
reports of accelerated degeneration after postoperative kyphotic
sagittal alignment [8,26], postoperative sagittal balance should
be carefully considered.
There are some limitations of this study, which are small
numbers of cases and the results are obtained after a shortterm
follow up. Since there is chance of development of adjacent
segment problems in longer follow up, which is necessary to
make a final conclusion of our study? In addition, as Cherubino
et al.  described, the degree of degeneration and clinical
symptom showed no correlation thus, factors influencing clinical
symptoms of adjacent segment was not established. Further
evaluation to investigate the factors that cause symptoms due
to adjacent segment degeneration is necessary. However, the
strength of our study is that, to the best of our knowledge, this is the first study comparing the zero-profile plate with
conventional plate in aspect of adjacent segment disease.
Contrary to our expectation, surgery using both implants
showed similar results in aspect of adjacent segment
degeneration. It is considered rather than the insult to
adjacent structures by implants, other factors such as natural
degeneration or increased loading to the adjacent segment after
interbody fusion might be more important factors for occurrence
of adjacent segment degeneration. In short-term after surgery,
adjacent segment disease is not a frequently complication,
however, longer term follow up is necessary since degeneration
of adjacent segment is accelerated.