Comparison between zero-profile spacer and plate with cage in the treatment of single level cervical spondylosis

Abstract

BACKGROUND:

Retrospective study of 68 patients of symptomatic cervical spondylosis who were treated by anterior cervical discectomy and fusion (ACDF).

OBJECTIVE:

The purpose of this study was to compare the clinical and radiological outcomes of patients with single level cervical spondylosis using either zero-profile spacer (group A) or anterior cervical plate and cage (group B).

METHODS:

Clinical and radiological data of 68 patients undergoing ACDF from C3-C7 were collected retrospectively. There were 35 patients with a mean age of 54.05 years who received treatment by zero-profile implant. A total of 33 patients with a mean age of 52.09 years underwent fusion by traditional plate with cage. Group A and group B were followed up for an average of 23.68 months and 24.39 months, respectively. Age, blood loss, and operation time were assessed. The clinical outcomes were evaluated by JOA and VAS score before and after surgery. In addition, incidence of dysphagia was recorded. The Cobb angle (from C2 to C7) change was measured on the lateral cervical spine radiographs.

RESULTS:

There was no significant difference in terms of operation time and blood loss between two groups. The postoperative JOA significantly increased and the VAS decreased correspondently in both groups. The postoperative Cobb angle increased and showed statistical difference compared with preoperative Cobb angle in both groups. There was no significant difference between group A and group B in achieving clinical symptoms and radiograph improvement according to postoperative JOA, VAS and Cobb angle comparison. The incidence of postoperative dysphagia was lower in the group A than group B.

CONCLUSIONS:

Our study suggests that the application of zero-p spacer can achieve similar clinical and radiological improvement compared with traditional plate and cage. Meanwhile, zero-p is superior to plate and cage with a lower incidence of postoperative dysphagia.

Keywords

Cervical spine ACDF zero-p spacer plate and cage

1. Introduction

Neck pain, radiating pain and limb numbness are the most common clinical manifestation of cervical spondylosis [1]. Since the theory of anterior cervical surgical approach proposed by Smith and Robinson in the 1950s [2], anterior cervical discectomy and fusion (ACDF) has become the gold-standard procedure for the treatment of cervical degenerative diseases. Commonly, surgeons will place an anterior plate to maintain the stability of cage. Meanwhile, the application of anterior plate can improve the cervical sagittal alignment [3], prevent interbody graft dislocation [4] and increase intervertebral fusion rate [3, 4, 5, 6, 7]. However, different studies have reported that the application of anterior plate is associated with many complications including postoperative dysphagia [8, 9, 10], trachea-esophageal injury [11, 12], plate shift [13, 14] and adjacent level degeneration [15, 16].

Zero-profile spacer (Zero-p; Synthes GmbH, Switzerland) is a newly invented interbody fusion device. It consists of a stand-alone cage and a plant with 4 locking screws, with the aim to avoid the potential complications and maintain the benefits of plate with cage.

The purpose of this study was to compare the clinical and radiological outcomes as well as complications of patients after application of the zero-p device and the conventional cage-plate device for single level ACDF.

2. Materials and methods

A total of 68 patients (39 males and 29 females) who underwent single level ACDF from January 2013 to May 2015 were enrolled retrospectively. All patients went to hospital with typical radiculopathy and/or myelopathy and conservative treatment was ineffective. The inclusion criteria were; (1) signs and symptoms of cervical radiculopathy or cervical spondylotic myelopathy which was unresponsive to the conservative treatment for at least six weeks; (2) one level spinal cord or root compression visible on recent magnetic resonance imaging (MRI). Exclusion criteria were: (1) previous cervical spine surgery, (2) others cervical diseases, including infection, tumor, instability or ossification of posterior longitudinal ligament. A total of 35 patients with a mean age of 54.05 years who received treatment by zero-profile implant (group A). Another 33 patients with a mean age of 52.09 years underwent fusion by traditional plate and intervertebral cage (group B). Intraoperative blood loss and operation time were recorded to investigate the surgery safety. Japanese Orthopaedic Association (JOA) score and Visual Analogue Scale (VAS) score of neck were used to evaluate clinical outcomes. The incidence of dysphagia was recorded using the Bazaz [9] system during the follow-up visits (Table 3). The lateral plain radiographs of cervical spine were used to measure the Cobb angle that is defined as the acute angle between the cranial endplate of C2 and the caudal endplate of C7. All patients were required to take cervical X-ray on admission, 3 days after surgery and follow up at 1, 3, 6 month and last visit. The average follow-up duration of group A and group B were 23.68 months and 24.39 months, respectively. Fusion criteria was evaluated by X-ray and CT scan simultaneously. Fusion criteria included: 1. No transparent belt between fusion cage and the interfaces of upper and lower endplate; 2. Bone trabecula passes through fusion cage and the interface of endplate; 3. CT scan shows that continuous bone trabecula passes through the gap between interbody fusion cage and adjacent endplate. General information was summarized in Table 1.

Table 1
General data of group A and group B

	Group A	Group B	P
	(Zero-p)	(Plate-cage)
Patient no.	35	33
Sex (male/female)	19/16	20/13
Age (year)	54.05 $\pm$ 10.11	52.09 $\pm$ 10.46
Operative levels
C3/4	8	7
C4/5	10	12
C5/6	13	11
C6/7	4	3
Blood loss (ml)	93.40 $\pm$ 9.04	97.94 $\pm$ 10.76	$>$ 0.05
Operation time (min)	101.57 $\pm$ 14.36	107.88 $\pm$ 14.35	$>$ 0.05
Follow-up time (month)	23.68 $\pm$ 1.93	24.39 $\pm$ 2.00	$>$ 0.05

All surgeries were performed by an experienced spinal surgeon of our department. Patients underwent routine surgery in a supine position with anterior left-sided approach. Casper vertebral distracter was used to expose target intervertebral space. Anterior longitudinal ligament, disc, osteophyte and posterior longitudinal ligament were removed for anterior decompression. In group A, a corresponding zero-p spacer was inserted into the intervertebral space and the zero-p was fixed by 4 screws cranially and caudally. In group B, an anterior plate and cage filled with autograft bone was used to reconstruct vertebral stability. All patients wore a Philadelphia collar for one month postoperatively.

Statistical analyses were performed using SPSS (version 17.0). Quantitative data were presented as the mean $\pm$ standard deviation (SD). T test and the Pearson’s X ${}^{2}$ test were used to analyze differences between the two groups. $P<$ 0.05 was considered statistically significant.

Table 2

JOA, VAS, and Cobb angle comparison between the zero-p and cage with plate

	Group A			Group B
Time	JOA	VAS	Cobb angle	JOA	VAS	Cobb angle
Pre-	9.63 (1.48)	7.23 (1.00)	16.25 (7.16)	9.21 (1.36)	7.21 (1.14)	16.48 (7.05)
1 m	13.09 (1.31)	1.86 (0.91)	23.51 (6.50)	12.55 (1.44)	1.94 (0.97)	23.03 (6.98)
3 m	14.14 (1.12)	1.46 (0.61)	22.60 (7.12)	14.27 (1.07)	1.55 (0.67)	22.09 (7.03)
6 m	14.46 (1.17)	1.23 (0.55)	21.69 (6.87)	14.70 (1.02)	1.24 (0.61)	21.42 (6.84)
Last-	14.86 (1.24)	1.11 (0.53)	21.20 (6.94)	15.03 (1.21)	1.15 (0.57)	21.03 (6.72)

3. Results

The mean operation time was 101.57 $\pm$ 14.36 minutes with an average blood loss of 93.40 $\pm$ 9.04 ml in group A. Group B had an average operation time of 107.88 $\pm$ 14.35 minutes with an average blood loss of 97.94 $\pm$ 10.76 ml. There was no statistical significance between group A and group B in terms of operation time and intraoperative blood loss. All patients achieved clinical recovery after surgery and there was a significant improvement in the mean JOA and VAS scores in both groups from Table 2. Compared with preoperative measurement, the JOA scores increased significantly and the VAS scores decreased correspondently at 1, 3, 6 month and last visit. In addition, there was no significant difference between both groups in terms of JOA and VAS scores at any time.

Table 3
Dysplasia score

Severity	Liquid	Solid
	Symptoms
None	None	None
Mild	None	Rare
Moderate	None or rare	Occasionally (only with specific food)
Severe	None or rare	Frequent (majority of solids)

Table 4

Incidence of dysplasia

	Operation day	1 month	3 months	6 months	12 months
Group A	9/2/0	4/0/0	2/0/0	0/0/0	0/0/0
Group B	9/4/0	9/2/0	7/1/0	5/0/0	2/0/0
P value	0.613	0.041	0.042	0.023	0.232

After surgery, all patients achieved target segment fusion and no implant displacement was observed. The Cobb angle was calculated as the angle formed by lines along the superior endplate of C2 to the inferior endplate of C7 on the lateral X-ray (Fig. 1C). The mean Cobb angle improved from 16.25 $\pm$ 7.16 points before surgery to 21.20 $\pm$ 6.94 points at the final follow up in group A and from 16.48 $\pm$ 7.05 point to 21.03 $\pm$ 6.72 in group B (Table 2). The cervical Cobb angle had an evident correction right after the surgery while it decreased slowly during the rest follow-up duration.

Figure 1.

Images of a 56-year-old female with C5/6 cervical spondylosis. (A) sagittal and (B) axial views of this MRI show the spinal cord compressed by degenerative disk herniation at C5/6. (C) postoperative sagittal and (D) axial cervical X-ray with zero-p spacer. The cobb angle was recorded as $\alpha$ in figure C.

In group A, 11 patients complained dysphagia on the day of operation, 4 patients had dysphagia after 1 month and only 2 patients had dysphagia at the 3-month follow-up. By 6 months postoperatively, dysphagia resolved completely in group A. In group B, 13 patients complained dysphagia on the day of operation, 11 patients suffered from dysphagia at the 1-month follow up, and 8 patients and 5 patients had dysphagia at the 3 and 6 month visit respectively. By 12 months postoperatively, 2 patients still had mild dysphagia (Table 4). There were significant differences in terms of dysphagia incidence between both groups at the 1, 3 and 6-month follow-up.

4. Discussion

Cervical spondylosis is a common cause of adult spinal dysfunction. Most patients come to hospital because of neck pain, radiculopathy or myelopathy. When conservative treatment fails, surgery should be taken into consideration. Anterior cervical discectomy and fusion (ACDF) has become the most popular procedure for treating cervical degenerative conditions since the introduction by Smith and Robinson in 1958 [2]. Compared with stand-alone cage and iliac bone graft, application of anterior plate can provide immediate cervical stability [17] and prevent interbody graft dislocation [4]. Moreover, multiple studies have reported that anterior plate can improve intervertebral fusion rate [3, 4, 5, 6, 7]. However, plate associated complications such as postoperative dysphagia [8, 9, 10], screws or plate dislodgement [13, 14] and soft tissue injury have been reported in different studies.

To lessen potential complications while maintaining benefits of conventional cage and plate, zero-profile anchored spacer was invented. This device is made up of a radiolucent PEEK polymer cage and a small radio-opaque titanium plate which is incorporated into intervertebral space. In addition, it has four screws for internal fixation with one step locking mechanism. Studies conducted by Scholz et al. [18] and Dvm et al. [19] revealed that the anchored spacer provided a similar biomechanical stability to that of the established anterior fusion technique using an anterior plate plus cage.

Our study compared the clinical and radiological outcomes of single level ACDF with zero-p spacer and with anterior plate with cage. This study showed that there was no statistical difference in terms of blood loss and operation time in both groups. Both groups achieved similar and satisfactory clinical improvement. Patients recovered soon from neck pain, radiculopathy and/or myelopathy after surgery in group A and group B. We compared the pre- and postoperative cobb angle and found that a significant improvement of cervical lordosis was achieved in both groups. Moreover, the cervical lordosis was well maintained in our final visit. Meanwhile, postoperative radiological study showed that all patients had solid osseous fusion and there was no internal fixation failure in both groups. Nowadays, many different studies have demonstrated the application of zero-p spacer was safe and efficient in treating cervical diseases. A report by Wang et al. [20] showed that both the Zero-P implant and traditional titanium plate with cage are effective treatments for single level cervical spondylotic myelopathy. Another retrospective study conducted by Doo Kyung et al. [21] also demonstrated that the zero-p spacer showed the same or favorable clinical and radiological outcomes compared with the plate with cage for treating single level cervical spondylosis. However, this study revealed that there was more blood loss in plate with cage surgery which was different from studies conducted by Wang and us. Additionally, Studies of two or more levels involved also showed that the zero-p spacer can provide favorable clinical outcomes as plate with cage but it remains controversial in terms of blood loss and operation time [22, 23, 24]. This might be a big limitation of our study because all patients enrolled in this study was single level. The reasons for the difference of blood loss maybe due to the extensive preparation of the anterior vertebral surface for the plate fixation. Because during this process, osteophytes should be removed and soft tissue and small blood vessels maybe damaged. Also, surgeon’s experience should be taken into consideration.

Postoperative dysphagia is one of the most common complication of anterior cervical discectomy and fusion, with the early incidence (within 3-month) varying from 2% to 67% [9, 25, 26, 27, 28] and the chronic dysphagia incidence ranging from 3% to 21% [8, 25, 29] according to previous reports. To date, the exact pathophysiological mechanism remains unknown. Many studies have showed that application of anterior plate is associated with higher incidence of dysphagia. Postoperative soft tissue swelling, hematoma, esophageal injury and adhesion formation around anterior plate are the underlying causes of dysphagia [9, 25]. Additionally, direct contact of plate with the esophagus may cause postoperative dysphagia. Fogel and McDonnell [30] reported that removal of plate and adhesion can significantly improve postoperative dysphagia. On the contrary, zero-p device is smaller in size which needs small incision and less exposure. Furthermore, zero-p is completely contained in the decompressed intervertebral space that avoids mechanical stimulus to esophagus. A research conducted by Lee et al. [31] has proved that the use of a smaller and smoother profile plate reduced the incidence of dysphagia as compared with a slightly larger and less smooth plate. Jagannathan et al. [32] reported that only 3% of patients who underwent ACDF without plate complained of dysphagia at the 3-month follow-up. Chen et al. measured the postoperative prevertebral soft tissue thickness and found that there was a positive relationship between the incidence of dysphagia and prevertebral tissue swelling within 6 months. However, with the improvement of soft tissue edema, mechanical irritation plays a more important role in chronic dysphagia [22]. In our study, 11 patients (31.4%) complained of mild ( $n=$ 9) or moderate ( $n=$ 2) dysphagia in zero-p group while 13 patients (39.4%) suffered from mild ( $n=$ 9) or moderate ( $n=$ 4) dysphagia in plate with cage group on the day of surgery ( $p=$ 0.613). The plate and cage group have a higher rate of dysphagia and there is a statistical difference between both groups at 1, 3, and 6-month follow-up. Meanwhile, none of zero-p group patients complained dysphagia after 6-month postoperatively, whereas 5 and 2 patients still suffered from mild dysphagia at 6- and 12-month follow-up respectively. So we conclude that prevertebral soft tissue swelling and mechanical irritation lead to dysphagia at the early stage and mechanical stimulus may be the more important factor of chronic dysphagia.

5. Conclusion

Our study suggests that the clinical and radiological outcomes of zero-p are satisfactory for treating single level ACDF. Zero-p is an optimal alternative to traditional anterior plate with a lower dysphagia rate. However, there are several limitations of this study. Firstly, two or more surgical levels are needed to overall evaluate the safety and efficacy of zero-p implant. Secondary, more patients and longer follow up are required for further assessment of our findings.

Footnotes

Conflict of interest

None to report.

References

Morio

Teshima

Nagashima

, et al. Correlation between operative outcomes of cervical compression myelopathy and mri of the spinal cord. Spine 2001; 26: 1238-45.

Smith

Robinson

. The treatment of certain cervical-spine disorders by anterior removal of the intervertebral disc and interbody fusion. Journal of Bone & Joint Surgery American Volume 1958; 40-A: 607.

Kim

Limson

Kim

, et al. Comparison of radiographic changes after ACDF versus Bryan disc arthroplasty in single and bi-level cases. European Spine Journal 2009; 18: 218-31.

Pitzen

Chrobok

Stulik

, et al. Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study. Spine 2009; 34: 641-6.

Schneeberger

Boos

Schwarzenbach

, et al. Anterior cervical interbody fusion with plate fixation for chronic spondylotic radiculopathy: a 2- to 8-year follow-up. J Spinal Disord 1999; 12: 215-20.

Fraser

Härtl

. Anterior approaches to fusion of the cervical spine: a metaanalysis of fusion rates. Journal of Neurosurgery Spine 2007; 6: 298.

Mobbs

Rao

Chandran

. Anterior cervical discectomy and fusion: analysis of surgical outcome with and without plating. Journal of Clinical Neuroscience 2007; 14: 639-42.

Skolasky

Albert

, et al. Dysphagia after anterior cervical decompression and fusion: prevalence and risk factors from a longitudinal cohort study. Spine 2005; 30: 2564-9.

Bazaz

Lee

Yoo

. Incidence of dysphagia after anterior cervical spine surgery: a prospective study. Spine 2002; 27: 2453-8.

10.

Hwang

Lin

Lieu

, et al. Three-level and four-level anterior cervical discectomies and titanium cage-augmented fusion with and without plate fixation. Journal of Neurosurgery Spine 2004; 1: 160.

11.

Sahjpaul

. Esophageal perforation from anterior cervical screw migration. Surgical Neurology 2007; 68: 209-10.

12.

Orlando

Caroli

Ferrante

. Management of the cervical esophagus and hypofarinx perforations complicating anterior cervical spine surgery.

13.

Fujibayashi

Shikata

Kamiya

, et al. Missing anterior cervical plate and screws: a case report. Spine 2000; 25: 2258-61.

14.

Lowery

McDonough

. The significance of hardware failure in anterior cervical plate fixation. Patients with 2- to 7-year follow-up. Spine 1998; 23: 181.

15.

Yang

Song

Lee

, et al. Adjacent level ossification development after anterior cervical fusion without plate fixation. Spine 2009; 34: 30.

16.

Park

Cho

Riew

. Development of adjacent-level ossification in patients with an anterior cervical plate. Journal of Bone & Joint Surgery American Volume 2005; 87: 558.

17.

Song

Taghavi

Lee

, et al. The efficacy of plate construct augmentation versus cage alone in anterior cervical fusion. Spine 2009; 34: 2886-92.

18.

Scholz

Reyes

Schleicher

, et al. A new stand-alone cervical anterior interbody fusion device: biomechanical comparison with established anterior cervical fixation devices. Spine 2009; 34: 156-60.

19.

Dvm

Bürki

Ecvdi

CSD

, et al. Comparison of the biomechanical properties of a ventral cervical intervertebral anchored fusion device with locking plate fixation applied to cadaveric canine cervical spines. Veterinary Surgery 2013; 42: 825.

20.

Wang

Zhu

Yang

, et al. The application of a zero-profile implant in anterior cervical discectomy and fusion. Journal of Clinical Neuroscience 2014; 21: 462-6.

21.

Doo Kyung

Wuk

Ho Sang

, et al. Comparative study of clinical and radiological outcomes of a zero-profile device concerning reduced postoperative Dysphagia after single level anterior cervical discectomy and fusion. Journal of Korean Neurosurgical Society 2014; 56: 103-7.

22.

Chen

Cao

, et al. Anterior cervical interbody fusion with the Zero-P spacer: mid-term results of two-level fusion. European Spine Journal: Official Publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2015; 24: 1666-72.

23.

Wang

Jiang

, et al. The application of zero-profile anchored spacer in anterior cervical discectomy and fusion. European Spine Journal 2015; 24: 148-54.

24.

Yang

Liang

, et al. Stand-alone anchored spacer versus anterior plate for multilevel anterior cervical diskectomy and fusion. Orthopedics 2012; 35: e1503.

25.

Fountas

Kapsalaki

Nikolakakos

, et al. Anterior cervical discectomy and fusion associated complications. Spine Journal 2006; 6: 2310-7.

26.

Tortolani

Cunningham

Vigna

, et al. A comparison of retraction pressure during anterior cervical plate surgery and cervical disc replacement: a cadaveric study. Journal of Spinal Disorders & Techniques 2006; 19: 312-7.

27.

Frempong-Boadu

Houten

Osborn

, et al. Swallowing and speech dysfunction in patients undergoing anterior cervical discectomy and fusion: a prospective, objective preoperative and postoperative assessment. Journal of Spinal Disorders & Techniques 2002; 15: 362-8.

28.

Smith-Hammond

New

Pietrobon

, et al. Prospective analysis of incidence and risk factors of dysphagia in spine surgery patients: comparison of anterior cervical, posterior cervical, and lumbar procedures. Spine 2004; 29: 1441-6.

29.

Kasimatis

Panagiotopoulos

Gliatis

, et al. Complications of anterior surgery in cervical spine trauma: an overview. Clinical Neurology & Neurosurgery 2009; 111: 18-27.

30.

Fogel

McDonnell

. Surgical treatment of dysphagia after anterior cervical interbody fusion. Spine Journal 2005; 5: 140-4.

31.

Lee

Bazaz

Furey

, et al. Influence of anterior cervical plate design on Dysphagia: a 2-year prospective longitudinal follow-up study. Journal of Spinal Disorders & Techniques 2005; 18: 406-9.

32.

Jagannathan

Shaffrey

Oskouian

, et al. Radiographic and clinical outcomes following single-level anterior cervical discectomy and allograft fusion without plate placement or cervical collar. Journal of Neurosurgeryspine Spine 2008; 8: 420-8.

Comparison between zero-profile spacer and plate with cage in the treatment of single level cervical spondylosis

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Materials and methods

Table 1 General data of group A and group B

Table 3 Dysplasia score

5. Conclusion

Footnotes

Conflict of interest

References

Table 1
General data of group A and group B

Table 3
Dysplasia score