Al-Azhar Assiut Medical Journal

: 2018  |  Volume : 16  |  Issue : 4  |  Page : 377--385

Comparative study between cervical polyetheretherketone cages and dynamic cervical implant postanterior cervical discectomy

Mostafa G Eldin, Mohammed S Mohammed 
 Department of Neurosurgery, Al-Azhar Faculty of Medicine for Girls, Cairo, Egypt

Correspondence Address:
Mohammed S Mohammed
Al Zahraa University Hospital, Abbassia, Cairo


Objective This is a prospective comparative study between polyetheretherketone (PEEK) cages and dynamic cervical implants (DCI) to evaluate the safety, the effectiveness, and the clinical outcome with radiological outcome for patients with single-level degenerated cervical disc disease treated by anterior cervical discectomy. Patients and methods We studied 30 patients with single-level cervical disc disease. Preoperative evaluation included plain cervical radiography including dynamic views. MRI was carried out to confirm the clinical diagnosis. Results Our study showed that the procedures of two groups were safe and easy without major complications and do not show significant differences between DCI and anterior cervical discectomy and fusion (ACDF) with PEEK cages in terms of improvement in clinical symptoms, blood loss, or operation time; however, DCI was associated with better postoperative neck disability index scores and also resulted in better overall cervical range of motion and segmental range of motion at the treated level than ACDF with PEEK cage. ACDF with PEEK cage is still the gold standard technique for treatment of cervical degenerative disc disease. It improves patient activity and provides a stable segment. However, it fails to restore normal cervical biomechanics and does not prevent adjacent segment disease. Conclusion DCI is considered as a new strategy and an intermediate stage between ACDF and total disc replacement.

How to cite this article:
Eldin MG, Mohammed MS. Comparative study between cervical polyetheretherketone cages and dynamic cervical implant postanterior cervical discectomy.Al-Azhar Assiut Med J 2018;16:377-385

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Eldin MG, Mohammed MS. Comparative study between cervical polyetheretherketone cages and dynamic cervical implant postanterior cervical discectomy. Al-Azhar Assiut Med J [serial online] 2018 [cited 2020 Jul 5 ];16:377-385
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During the past decades, anterior cervical discectomy and fusion (ACDF) has been an effective and safe procedure for the surgical treatment of patients with radiculopathy and myelopathy [1],[2],[3],[4],[5]. The goals of ACDF are to decompress the neural elements, provide permanent segmental stabilization, maintain the physiological lordosis, and preserve the anatomical disc-space height. Various types of cages [e.g. titanium, carbon, polyetheretherketone (PEEK), and hydroxyapatite coated] are currently widely used for the treatment of degenerative cervical disc disease [6],[7],[8],[9]. Therefore, PEEK (a semicrystal polyaromatic linear polymer) appears to be an adequate biomaterial for ACF cages and is becoming popular because of better elasticity and radiolucency [3],[4],[5]. However, increased motion and increased intradiscal pressure have been reported in the untreated levels adjacent to fused levels. Some investigators have postulated that these changes may lead to an increased risk of adjacent segment disease [23]. ACDF has a high rate of clinical success for the treatment of cervical degenerative disc disease (DDD), but the rigid fixation may result in adjacent segment disease [12],[13],[14],[15],[16]. Dynamic cervical implant (DCI) is a new type of implant that stabilizes the cervical spine while providing controlled motion in flexion-extension, which is the main motion in subaxial cervical spine. Shock absorption, a main advantage compared with most existing prostheses, prevents adjacent accelerated degeneration [5],[7],[8],[9]. Thus, the DCI aims at combining the advantages of the gold standard ‘fusion’ with a motion-preservation philosophy. The DCI is a titanium implant, originally developed in 2002 by Matgé [17], Luxembourg. It was introduced in clinical use, by him, in 2004. The DCI is used in this study with a unique design. The omega shape was designed to fit to the lateral anatomical view of the disc and the adjacent endplates. It is a one-piece anatomical-shaped, self-fixing dynamic spacer made of titanium, which is easy to implant like a cage ([Figure 1]). The DCI as a new design with a rectangular shape and sharper teeth optimized the primary stability of the implant [18]. DCI arthroplasty has the following theoretical advantages: (a) the U-shaped structure absorbs vibrations; (b) it restricts excessive flexion, extension, and rotation, thereby protecting the small cervical joints; and (c) as there is no grinding of metal, polyethylene, or ceramic, there is no local or systemic reaction to debris [17],[18].{Figure 1}

 Patients and methods

Patient choice

This is a prospective and retrospective comparative study trial to evaluate the results of treatment of patients with degenerative cervical disc disease by PEEK cage and DCI to treat single-level cervical disc disease, respectively, from October 2012 to October 2015. The same inclusion and exclusion criteria were adopted for both groups. Conset for cervical implant: a) procedure: surgery through the front of the neck to remove the degenerated disc and bone spurs, and to place an artificial disc. b) alternatives: nonsurgical management, surgical fusion (from the front or the back of the neck). c) complications: swallowing difficulties are common but usually resolve, hoarseness of the voice (<4% chance of it being permanent), injury to: food pipe (esophagus), wind pipe (trachea), arteries to the brain (carotid) with stroke, spinal cord with paralysis, nerve root with paralysis. The disc may eventually wear out and further surgery may be needed. Conset for PEEk Cages: a) procedure: surgery through the front of the neck to remove the degenerated disc and bone spurs, and to place a graft where the disc was, and possibly place a metal plate on the front of the spine. Some surgeons take bone from the hip to replace the removed disc. b) alternatives: nonsurgical management, surgery from the back of the neck, artificial disc (in some cases). c) complications: swallowing di culties are common but usually resolve, hoarseness of the voice (<4% chance of it being permanent), injury to: foodpipe (esophagus), windpipe (trachea), arteries to the brain (carotid), spinal cord with paralysis, nerve root with paralysis, possible seizures with MEPs.

Inclusion principles

The following were the inclusion criteria: (a) DDD within levels between C3 and C7 causing neck and/or arm pain with functional/neurological deficit, (b) radiographically determined degenerated disc disease diagnosed either by plain radiography or MRI or both of them, (c) age younger than 60 years, (d) patients’ refractory to conservative treatment for at least 3 months, and (e) patients able to comply with protocol and follow-up instructions.

Exclusion principles

The following were the exclusion criteria: (a) marked cervical instability, i.e., translation more than 3 mm and/or more than 11° angulation difference; (b) severe facet arthrosis at the affected level; (c) cervical myelopathy; (d) severe spondylosis at the affected level (bridging osteophyte, >50% loss of disc height and absence of motion <2°); (e) prior fusion at one adjacent level; (f) history of prior cervical laminectomy and posterior compressive disease not amenable to decompression through anterior approach; (g) rheumatoid arthritis, ankylosing spondylitis, or other autoimmune disease; (H) malignancy; (I) active infection; and (J) poor bone quality [osteoporosis (DEXA T-score <2.5) or osteomalacia].

The study included 30 patients having single cervical disc herniation with variable degrees of other spondylodegenerative changes at the levels from C3/C4 to C6/C7, diagnosed mainly by routine cervical spine MRI. All patients had anterior cervical discectomy, with 15 cases treated with PEEK cage and 15 cases with DCI. All patients had axial neck pain, radicular arm pain (cervical brachialgia), myelopathy, and/or radiculomyelopathy. Mean preoperative duration of complaint was 1.5 year (6 month to 5 years).

Surgical technique

Patient positioning and surgical approach are standard as in microsurgical ACDF using CASPAR vertebral distractors. Microdiscectomy was performed, leaving a clean disc space. End-plate cleaning must be careful to respect cartilage and avoid bony bleeding. It is recommended not to remove anterior osteophytes preventing heterotopic ossification. Internal foraminotomy is an important step in radiculopathy cases together with posterior longitudinal ligament resection for optimal decompression in myelopathy cases. As no bone graft was required, with three trial/PEEK cages or implant sizes, there is a selection of to define: means to define (choose) the appropriate cage size or implant size to be used after taking atrial. Exact size selection is most important to avoid migration. The most common DCI prosthesis used in this study was the 6M size with a width of 12 mm, a depth of 12 mm, and a height of 9 mm. Hospital stay was minimal, ranging from 1 to 3 days with an average of 1.5 days [4],[11],[18],[19],[20].

Follow-up evaluation

All operative and postoperative data (operative time, blood loss, hospital stay, and the complications) were recorded. Patients can normally be mobilized the next day, avoiding excessive cervical motion, under neck collar protection. Follow-up plain radiography was performed on the first postoperative day. Periodic dynamic radiography was done on an outpatient basis at 1, 3, 6, 12, and 24 months after surgery.


Patient population

The study enrolled 30 patients: 15 patients treated by PEEK cage (group 1) with minimum age of 35 years and maximum age of 58 years, and with mean age of 49±5.25 years, and 15 patients were treated by DCI (group 2), with minimum age of 40 years and maximum age of 58 years and with mean age of 47.13±8.03 years ([Figure 2]).{Figure 2}

All the patients in the study had single-level affection. The most common level affected was C6/C7, which accounts for 40.00%, whereas the least affected was C4/C5, which accounts (6.70%). Operative time ranged from 70 to 110 min in single level in group 1 and 75 to 105 min in group 2. Intraoperative bleeding ranged from 80 to 120 ml in both groups. Postoperative follow-up ranged from 18 to 24 months in both groups, with a mean follow-up of 23.2±2.11 months in group 1 and 22±2.93 months in group 2.

Clinical result (neurological deficit, visual analog scale neck, visual analog scale arm, and neck disability index)

The patients complained of neck and arm pain in both groups. Cases having neurological deficit represented 80% in group 1 and 86.6% in group 2. Improvement was more in sensory deficit postoperatively in both groups ([Figure 3]).{Figure 3}

Radiological result

Postoperative dynamic plain cervical radiography (lateral views) in flexion and extension positions was performed and shows preserved disc heights with no PEEK cages or implant dropping into the adjacent endplates or vertebral bodies. According to range of motion and global range of motion, there is significant improvement in the range of flexion and extension from preoperative to postoperative in both groups with no evidence of significant instability which is crucial in postoperative assessment. The used prostheses in both groups in the current study are fully compatible with MRI, and this will allow safe evaluation of the cervical cord and thecal sac as well as the paravertebral areas including the muscular framework; however, the resultant unavoidable metallic artifacts will not hinder the evaluation of these different structures ([Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8],[Figure 9]).{Figure 4}{Figure 5}{Figure 6}{Figure 7}{Figure 8}{Figure 9}


ACDF with PEEK cage has good curative effects on single-level cervical DDD [14],[15],[16]. DCI implantation, as a new nonfusion approach, is easy and simple to operate with short learning curve. It is an interbody fixed device between ACDF and cervical disc replacement surgery, being able to partially keep the motion function of cervical surgical segments and a new alternative of treating cervical DDD [17]. Generally, improvements of arm pain (radiculopathy) and neurologic deficit are directly related to adequacy of decompression [12]. In our study, improvements in arm pain (radiculopathy) and in neurologic deficit are similar in both groups (85% in group 1 and 90% in group 2), but improvement of the motor outcome was more rapid than the sensory outcome. Postoperatively, in group 1, the mean visual analog scale (VAS) for neck pain has decreased dramatically from 7.56 to 1.37 (P<0.01) and for arm pain decreased dramatically from 6.57 to 1 (P<0.01) and also in group 2, the mean visual analog scale for neck pain has decreased dramatically from 7.67 to 1.74 (P<0.01) and for arm pain decreased dramatically from 6.89 to 0.87, with a mean difference between preoperative and postoperative values of 6.02 (P<0.01). Our results are comparable with other studies in next [Table 1],[Table 2],[Table 3],[Table 4],[Table 5],[Table 6] [15],[19],[21],[22].{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}{Table 6}

According to global range of motion, in our result, there is significant difference between preoperative and postoperative in both groups (decreased in group 1, P<0.05, and increased in group 2, P>0.05).

According to segmental range of motion, there is significant difference from preoperative to postoperative in both groups (in group 1, P<0.05, and in group 2, P>0.05).

This study and other studies are comparable regarding range of motion at operated level and global range of motion ([Table 7]).{Table 7}

No remarkable complication in our study is shown except two cases of persistent neck pain, but Eldin [19] reported that one patient had transient postoperative swallowing difficulty and another with mild hoarseness of voice. Another patient developed remote spondylodiscitis (C6–C7) three levels below the operative site (C3–C4) 2.5 months postoperatively. This patient was treated conservatively and had resolution of symptoms in 3 months. In Li et al. [21], the reported anterior migration of the prosthesis by 2 mm was detected in one patient in the DCI group at the 12-month follow-up, and cage subsidence of more than 1 mm was observed in two patients in the ACDF group at the final follow-up. Zhu and colleagues reported three cases with postoperative dysphagia in 1 week, which recovered in 2 months in PEEK cage group. Rollinghof et al. [15] noticed subsidence is significantly more often in the cage group (6/23 or 26.1%). Kahraman and colleagues reported in one patient, a minimal collapse fracture was observed owing to bone resorption in the superior corpus. Conservative treatment was preferred, and the patient recovered without additional surgery. However, Elsawaf et al. [13] found one patient who showed a slight pseudoarthrosis after 13 months of follow-up without effect on the clinical outcome. Faldini et al. [6] reported no complications.


We did not find any major differences between DCI arthroplasty and ACDF with PEEK cage for cervical DDD in terms of improvement in clinical symptoms, blood loss, operation time, and radiological outcome, but DCI arthroplasty was associated with better postoperative neck disability index scores than ACDF with PEEK cage. DCI arthroplasty also resulted in better overall cervical range of motion and segmental range of motion at the treated level than ACDF with PEEK cage. Generally, the results show that DCI arthroplasty is an effective, reliable, and safe procedure for the treatment of cervical DDD. However, there is no definitive evidence that DCI arthroplasty has better intermediate-term outcomes than ACDF with PEEK cage.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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