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Case Report

Polyetheretherketone (PEEK) cages for cervicalinterbody replacement

P.K. Sahoo*

Prof., Chief Consultant e Neuro & Spine Surgery, Apollo Hospitals, Plot No 251, Old Sainik School Road, Unit-15,

Bhubaneswar 751005, India

a r t i c l e i n f o

Article history:

Received 2 August 2013

Accepted 7 August 2013

Available online 4 September 2013

Keywords:

Cervical surgery

Interbody implant

PEEK cage

* Fax: þ91 0674 2303888.E-mail addresses: prafullksahoo@hotmai

0976-0016/$ e see front matter Copyright ªhttp://dx.doi.org/10.1016/j.apme.2013.08.009

a b s t r a c t

Objective: This study evaluates the efficiency of interbody polyetheretherketone (PEEK) cage

implantation in 52 consecutive cases related for discogenic cervical disorders with radi-

culopathy or myelopathy.

Material and methods: Between the years 2010 and 2012, 52 patients were treated with cer-

vical interbody fusion using a PEEK cage. There were 27 male and 25 female patients and

the mean age was 46 years (range, 21e82 years). PEEK cages were packed with bone grafts

from anterior Superior vertebral body. Additional plating was used in some cases. The

median duration of follow-up was 12 months (range, 6e36months). Cervical X-rays were

routinely used in the follow-up to assess the fusion, pseudoarthrosis, kyphosis, cage

migration, subsidence or breakage.

Results: No implant insufficiency was observed in any case.

Conclusion: Efficient interbody replacement is still an ongoing problem in cervical surgery.

Different techniques and materials have been developed to overcome this problem. The

use of a cervical PEEK cage seems to be a good alternative in that it does not require bone

graft harvesting from iliac crest for achieving cervical interbody replacement.

Copyright ª 2013, Indraprastha Medical Corporation Ltd. All rights reserved.

1. Introduction sectional area of the neural foramina and helped to correct

Surgery for cervical disc disease is one of the most common

procedures in daily neurosurgical practice. Since conventional

cervical fusion surgeries using autologous bone graft have

some complications such as graft collapse, expulsion, pseu-

doarthrosis, denovo neural, compression and graft site

morbidity, cervical cage implantation has been introduced

during the last decade. Spinal cage instrumentation to

enhance spinal fusion and stability in cervical spine surgery

has ensured an adequate increase in the height and the cross-

l.com, drpksahoo52@gma2013, Indraprastha Medic

cervical kyphosis.1,2

Different cage types have been introduced to neurosurgical

practice. Although the early results with the Titanium cages

were satisfactory, problems such as migration, subsidence

and structural failure of the cage with some difficulties in post

operativemagnetic resonance imaging were observed.3,4 PEEK

cages have recently been used in cervical surgery.

PEEK is polyetheretherketone, a semi-crystal polyaromatic

linear polymer. The use of a PEEK cage is becoming popular

because of better elasticity and radiolucency.5,6 In this study,

il.com.al Corporation Ltd. All rights reserved.

a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 2 3 3e2 3 6234

we evaluated the efficiency of cervical PEEK cage replacement

in 52 patients with cervical discogenic disorders.

2. Patients and methods

During a 3-year interval, 52 patients with cervical Disc Her-

niation or degenerative disease underwent Surgery and cer-

vical PEEK cage replacement was done.

There were 27 male and 25 female patients and the mean

age was 46 years (range, 21e82 years). Clinical features were

cervical radiculopathy in 30 patients, myelopathy in 12 pa-

tients and myelo-radiculopathy in 10 patients. Anterior cer-

vical approaches were performed at one level in 42 patients

and at two levels in 10 patients. Ten of the patients with two

levels were operated on at neighboring vertebra levels.

The clinical data of the operated patients are summarized

in Table 1.

The operative procedure was performed by an anterior

approach and disc material was resected microscopically.

Spinal cord and nerve roots were decompressed in routine

fashion. Following decompression, a PEEK (Corner Stone;

Medtronic sofardanek) cage with suitable height and width

was packed with bone grafts from ant superior vertebral body

of the affected disc and the cage was introduced into the

intervertebral space with the help of intervertebral body dis-

tractor. Different commercial sizes of the cages are available.

The available heights for the cage are 5e6e7 mm and the

widths are 12e14 mm.

Additional plating was used in some cases. In the post

operative period, cervical orthoses were used for 2weeks post

operatively.

3. Results

The mean operative time was 90 min (range, 80e100 min) in

single-level surgery. The mean blood loss during surgery was

40 cc (range, 20e70 cc). The mean hospital stay was 4 days

ranging between 3 and 5 days. Patients’ follow-up ranged be-

tween 6 months and 3 years (mean, 12 months). All of the

patients were followed with cervical X-rays to evaluate cage

Table 1 e Demographic data of the patients operated onusing PEEK cages.

Men/women 27/25

Radiculopathy 30

Myelopathy 12

Myelo-radioculopathy 10

One level 42

C3e4 2

C4e5 9

C5e6 18

C6e7 13

Two levels 10

C3e4,4e5 1

C4e5,5e6 5

C5e6,6e7 4

migration, subsidence or breakage, cervical lordosis, pseu-

doarthrosis and fusion.

In one patient, a minimal collapse fracture was observed

due to bone resorption in the superior Vertebral body. Con-

servative treatment was preferred and the patient recovered

without additional surgery. Cervical interbody replacement

with PEEK cage was uneventful in all patients, continuing to

the present (Figs.1e3). Cervical X-rays were used to assess the

cages for fusion. A strong Bony bridge was observed between

the two corpuses with no mobility and no radiolucency

around the Cage in all patients. In rare instances, 3 DCT-scan

reconstructions were used to confirm bone fusion.

There were no patients with pseudo arthritis or wound

infection. We did not observe any problems such as cage

migration, subsidence or breakage. Fusion rates of PEEK cages

were 100% in cases with two years follow-up. The fusion rate

and duration were not related to the number of operated

levels.

4. Discussion

The PEEK cage is a polyetheretherketone, which provides

strength and stiffness in the intervertebral space. Biome-

chanical studies on PEEK cages demonstrate satisfactory

physiological values. The Resistance to pressure is 4170 N

(Newton) under a static position and 2160 N under a dynamic

position. The elastic character of the cage is similar to

bone.2,5,7 The PEEK cage induces cell attachment and Fibro-

blast proliferation and increases the protein content of the

osteoblasts.5,8 Following neural decompression, interbody

Fig. 1 e PEEK cage AT C5eC6.

Fig. 2 e PEEK cage AT C5eC6, C6eC7.

a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 2 3 3e2 3 6 235

replacement and bone fusion are the main goal of cervical

spine surgery.9 With autologous bone graft fusion, arthrodesis

was reported to be 97% by Brown et al.10 Savolainen et al. re-

ported a 98% fusion rate with autologous bone grafts but there

was a 16% rate of donor site complication.11 Reviews with ti-

tanium cages reveal bone fusion in 98%.12 When compared

with these data, the fusion rate with the PEEK cage presented

in this study seems to be superior to the autologous bone graft

Fig. 3 e Preoperative and post operative images of the case. Foll

C5eC6 level. Image shows corrected cervical lordosis and bone

pins.

and titanium cage applications. In different studies, fusion

with PEEK cage showed excellent resistance to crushing.12 The

force values applied during these biomechanical experiments

were higher than the forces applied to the cervical spine under

normal circumstances.12,7 In our cases, we did not observe any

problem such as cage migration, subsidence or breakage. We

used additional plating, to keep the PEEK cage in the disc space

and do not lead to cage migration.

Increasing the height and cross-sectional area of foramina

serves for nerve root decompression after cervical spine sur-

gery. However, extensive distraction for cage placement may

end up causing Radicular pain due to stretching of the nosi-

ceptive fiber in the joint capsule.1,4 Cages with 5e6e7 mm

thickness were inserted to maintain adequate foraminal

space. In our series, there was no case with post operative

radicular pain, indicating adequate foraminal height and

decompression.

Autologous bone from anterior superior body of the

involved disc was used for packing the PEEK cages to avoid the

necessity of autologous bone harvesting from iliac crest Cho

et al. Reported 40 patients who were operated on using PEEK

cages and autologous bone graft. They reported no donor site

complications. However, other series reported a 10e18% rate

of donor site complications.5

In our series, autologous bone from anterior superior

vertebral body of the involved disc demonstrated effective

bone fusion without any complication and with short hospital

stay.

Another advantage of the PEEK cage is its radio trans-

parency. It is compatible with magnetic resonance and

computed tomography imaging. This feature provides good

post operative spinal cord and Nerve root imaging without

implant artifact. Bone fusion can be easily evaluatedwith post

operative X-rays. The upper and bottom pins of the PEEK cage

also let us identify the actual cage position. The bio compati-

bility of the cage was excellent. There was no foreign body

reaction in our series. The time of implantationwas shortwith

limited blood loss.

ow-up image of the patient with one-level PEEK cage at the

fusion while the cage location is easily recognized by the

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5. Conclusion

In our clinical study, usage of PEEK cage in cervical spine

surgery has a low complication rate, and is physiological,

strong and bio compatible, providing a good alternative for

interbody replacement.

Conflicts of interest

The author has none to declare.

r e f e r e n c e s

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2. Krammer M, Dietl R, Lumenta CB, et al. Resistance of thelumbar spine against axial compression forces afterimplantation of three different posterior lumbar inter bodycages. Acta Neurochir (Wien). 2001;143(12):1217e1222.

3. Brantigan JW, Steffee AD. A carbon fiber implant to aidinterbody lumbar fusion. Two year clinical results in the first26 patients. Spine. 1993;18(14):2106e2107.

4. Matge G. Cervical cage fusion with 5 different implants: 250cases. Acta Neurochir (Wien). 2002;144(6):539e550.

5. Cho DY, Liau WR, Lee WY, Liu JT, Chiu CL, Sheu PC.Preliminary experience using a polyetheretherketone (PEEK)cage in the treatment of cervical disc disease. Neurosurgery.2002;51(6):1343e1350.

6. Malone Q, Lynn J, Lunn J. Surgical out come for anteriorcervical discectomy and fusion using the Signus RabeaPEEK cage. Proc NASS 18th Annual Meeting/Spine J. 2003;3:129Se130S.

7. Wilke HJ, Kettler A, Claes L. Stabilizing effect andsintering tendency of 3 different cages and bone cement forfusion of cervical vertebrae segments. Orthopade. 2002;31(5):472e480.

8. Petillo O, Peluso G, Ambrosio L, Nicolais L, Kao WJ,Anderson JM. Invivo induction of macrophage Ia antigen(MHC class II) expression by biomedical polymers in the cageimplant system. J Biomed Mater Res. 1994;28(5):635e646.

9. Casey ATH. Bone grafts and anterior cervical discectomy-lackof evidence, but no lack of opinion. Br J Neurosurg.1999;13(5):445e448.

10. Brown MD, Malinin TI, Davis PB. A roentgenographicevaluation of frozen allografts versus autografts in anteriorcervical spine fusions. Clin Orthop. 1976;119:231e236.

11. Savolainen S, Usenius JP, Hernesniemi J. Iliac crest versusartificial bonegrafts in 250 cervical fusions. Acta Neurochir(Wien). 1994;129(1e2):54e57.

12. Siddiqui AA, J ackowski A. Cage versus tricortical graft forcervical interbody fusion. J Bone Joint Surg (Br). 2003;85-B(7):1019e1025.

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