Carbon fibre cage vs. autograft for anterior cervical ...

Clinical Study

474

Carbon fibre cage vs. autograft for anterior cervical discectomy and interbody fusion: Graft morbidity and clinical outcome Mahmoud Taha, Laura MacNally, Anreas Kemeny, Matthias Radatz, Abstract: We performed a study to evaluate and compare the clinical outcome following anterior cervical discectomy and interbody fusion (ACDF) with either carbon fibre cage (CFC) implant or iliac crest autograft for cervical spondylotic patients. A retrospective review of 66 consecutive patients (30 in the autograft group and 36 in the CFC group) who underwent ACDF for cervical spondylotic radiculopathy, myelopathy, or both at one or two levels over a 4 year period from 1999 2002. We evaluated clinical outcome including symptomatic relief, operative morbidity and length of stay in each group. Postal questionnaires were sent to all patients to assess their clinical outcome (one year minimum follow-up) Neck Disability Index (NDI) was slightly better in the CFC group (mean: 16.42, SD: 10.24) compared to autograft group (mean: 19.9, SD: 14), the difference was statistically insignificant (p > 0.2). Patient’s self-rating of overall functions in the CFC group were better in 73% of patients, same in 21% and worse in 6% compared to better in 55%, same in 27%, and worse in 18% in the autograft group (p > 0.2). Arm pain rating were better in 70%, same in 24%, and worse in 6% (CFC group) compared to better in 59%, same in 27%, and worse in 14% (autograft group) (p > 0.2). There was a significant rate of long-term donor site pain in the autograft group (mild to moderate pain at the time of answering in 54.5% of patients). There was one graft-related complication in each group. In the radiculopathic patients (19 autograft, 20 CFC) the difference in length of stay was significant (autograft; mean 4.1, median 4 vs. CFC; mean 3.75 median 3) (p = 0.050). Autograft and CFC implants for anterior cervical disectomy and interbody fusion are both safe and effective. No significant differences were found in the long-term clinical outcomes. The use of CFC implant however, can avoid donor site pain and achieve a shorter hospital stay. Key words: Anterior cervical discectomy, anterior cervical fusion, carbon fibre cage and autograft

Introduction Degenerative cervical spine disease can result in osteophyte formation with consequent foraminal narrowing, thickening and buckling of the ligamentum flavum and alteration of normal intervertebral disc anatomy. All these changes can lead to neck pain, radicular and/or myelopathic symptoms.

Department of Neurosurgery Royal Hallamshire Hospital Sheffield United Kingdom Correspondence: Dr. Mahmoud Taha Department of Neurosurgery Hull and East Yorkshire Hospitals NHS Trust Hull, HU3 2JZ United Kingdom Tel: (44 148) 260 5338 Fax: (44 148) 260 7892 Email: [email protected]

1

It is a commonly encountered pathology in neurosurgical practice, often requiring operative correction with anterior cervical discectomy with or without interbody fusion. Despite almost 60 years of managing this condition, controversy remains as to which operative method produces the best outcome with the least operative morbidity and complication rate. Cloward, and Smith and Robinson initially described the anterior approach to cervical discectomy in 1958.3,12 Both recommended interbody fusion. The need for fusion has subsequently been questioned and four randomised controlled trials have deemed it to be unnecessary.4,8,10,13 However, other retrospective studies have refuted this finding.16 Despite the evidence against grafting, in 1998 only 4% of surgeons in UK were found to perform simple discectomy for all of their cases.6 The use of grafts was felt to be necessary to relieve neck pain, promote stability by preventing early postoperative collapse of the empty disc space and maintain the normal cervical

PAN ARAB JOURNAL OF NEUROSURGERY

CARBON FIBRE CAGE VS. AUTOGRAFT • Taha, et al

lordosis. The initial method of fusion via tricortical iliac crest autograft described by Cloward, Smith and Robinson has been the gold standard but this may be associated with complications with the donor and implantation site.14 In an effort to overcome this potential morbidity, numerous alternatives such as bone bank allografts, methymethacralate, hydroxyapetite, titanium cage and more recently CFC have been used. Experimental work with CFC coupled with preliminary clinical experience of this device has suggested it to be an ideal prosthesis that may provide good clinical results.2,7,9 In a review of the relevant literature, we found only two small studies comparing CFC with other grafts.5,11

posterior to the anterior margins of the vertebral body. The CFC is a composite of long carbon fibres and a polymer matrix (polyetheretherketone). It has a C shape (Fig. 1). The inner part of the cage is empty and can be filled with hydroxyapetites granules to improve bony conduction and fusion. The upper and the lower surfaces of the graft have struts to prevent any cage displacement. Table 1 - Summary of clinical data of the 66 patients No. of cases Variables No. of patients

CFC group

Autograft group

36

30

Age (years)

This study was undertaken as a service evaluation to compare the efficiency and safety of CFC with tricortical autograft for ACDF patients.

Method Patient population Sixty-six patients treated with ACDF for cervical myelopathy, radiculopathy or myeloradiculopathy at one or two levels over the period from 1999 - 2002. Between 1999 and 2000, 31 patients had ACDF with autograft, 19 had radiculopathy, 8 had myelopathy and 3 had myeloradiculopathy. Twenty-two had one level fused, 8 had two levels fused, giving a total of 38 separate grafts. Fourteen of the patients in this group were male and 16 were female. Ages of the patients in this arm of the study ranged from 29 - 72 with a mean of 47 years. In the second period (2001 - 2002) 36 patients underwent ACDF using CFC. Of these, 20 had radiculopathy, 11 had myelopathy and 5 had myeloradiculopathy. Twenty-six had one level fused, 10 had two levels fused (total of 46 grafts). Twentythree of the patients in this group were male and 13 were female. The range of ages in the CFC group was 29 - 84 with a mean of 52 years (Table 1). Operative technique All operations were performed in a similar way. Following general anaesthesia, and supine position, a standard anterolateral approach of the neck is performed. The level of discectomy is confirmed by using intraoperative x-ray. Caspar distractor is always used before performing the microscopical discectomy. High speed drill was used to remove the posterior osteophyte and expose the posterior longitudinal ligament. The ligament was always incised to achieve complete freedom of the dura. Central decompression of the spinal canal was used for myelopathic patients while, lateral decompression was used for radiculopathic patients. In the cage group, an empty CFC (Cornertstone SR, Medtronic) was inserted with its anterior edge 1 - 2 mm

VOLUME , NO. ,

Mean

51.42

47

Range

(29 - 80)

(29 - 72)

Male

23

14

Female

13

16

Radiculopathy

20

19

Myelopathy

11

8

Both

5

3

One

26

22

Two

10

8

46

38

Sex

Clinical presentation

No. of levels operated

Total No. of grafts/ cages

Figure 1 - Carbon fibre cage

In autograft group, a tricortical graft was taken from the right anterior iliac crest. The shape of the graft was fashioned by a high speed drill. Small suction drain was always used before wound closure. Patients in both groups were mobilised on the 1st day, and lateral check up x-ray used to rule out any graft displacement and to confirm the level. No collars are used for postoperative patients, as patients will be reviewed by

2


physiotherapists for neck exercises before discharge. Finally, a routine 6-8 weeks follow-up in out-patient clinic with another check up x-ray to check for early fusion.

Outcome measures Postal questionnaires were sent to all identified patients to assess their clinical outcome. The mean follow-up was 38 months (range 12 - 48 months). We assessed in the questionnaires the patients’ general function, arm pain, neck disability and donor site morbidity (for the autograft group). General function, arm pain and donor site pain were measured on the basis of patients’ self rating, as has been done in previous studies looking at clinical postoperative outcome.5,7 Patients were asked to rate their overall function and arm pain as either ‘better, same or worse’ than preoperatively and were asked to rate donor site pain as either ‘none, mild to moderate or severe’. Neck pain was measured using the Neck Disability Index (NDI), which has been validated for use in patients with neck related disability. Outcome in terms of graft-related complications and length of stay were extracted from the clinical notes.

Table 2 - Summary of the clinical outcome Outcome measure

CFC group

Autograft group

Improved

24(73%)

12 (55%)

Same

7 (21%)

6 (27%)

Worse

2 (6%)

4 (18%)

Improved

23(70%)

13 (59%)

Same

8 (24%)

6 (27%)

Worse

2 (6%)

3 (14%)

General function

Arm pain

Neck Disability Index (mean) Length of stay (mean)

16.42 (SD:10.24)

19.9 (SD:14)

4.47 (SD:2.92)

4.83 (SD:2.18)

plain film x-ray showed a fracture line in C6 vertebral body which could be caused by over-sized grafts in the disc levels. He was treated with a hard collar for 6 weeks. His symptoms improved but 6 months later his myelopathic symptoms recurred and further MRI scan showed C5/6 stenosis (Fig. 3).

Statistical analysis Statistical analysis was accomplished using the Student ttest for continuous data and Chi-square or Fisher’s exact tests or categorical data

Results Clinical results Altogether, 55 out of the 66 patients responded; 33 out of 36 (92%) in the CFC group and 22 out of 30 (73 %) in the autograft group. Of those patients who had ACDF with the CFC, overall function was rated as ‘better’ in 24 patients (73%), ‘same’ in 7 (21%) and ‘worse’ in 2 (6%), compared with ‘better’ in 12 patients (55%), ‘same’ in 6 (27%) and ‘worse’ in 4 (18%) of those who had ACDF with autograft. Arm pain was rated by the CFC group as ‘better’ in 23 (70%), ‘same’ in 8 (24%) and ‘worse’ in 2 (6%) compared to ‘better’ in 13 (59%), ‘same’ in 6 (27%) and ‘worse’ in 3 (14%) of the autograft group. The average (mean) NDI score for the CFC group was 16.4 (SD: 10.24) compared with 19.9 (SD: 14) for autograft group. (Table 2)

Figure 2 - C6 fracture following 2 level ACDF with CFC

All the differences in outcome measures were statistically insignificant (p > 0.2). Graft-related morbidity Two complications were elicited, one in the CFC group and one in the autograft group. In the CFC group the complication consisted of a bony fracture of C6 vertebral body (Fig. 2), the patient who is a 36 male had C5/6 and C6/7 ACDF for radiculomyelopathy, he had increased postoperative neck pain with no neurological changes. The

3

Figure 3 - Magnetic resonance imaging for the same patient in Fig. 2 six months postoperatively showing the C5/6 canal stenosis

PAN ARAB JOURNAL OF NEUROSURGERY


He underwent C5/6 decompressive laminectomy. In the autograft group there was one case of graft collapse in a 46year-old male with progressive myelopathy. The patient had C5/6 and C6/7 ACDF, his 1st day x-ray was fine however his symptoms recurred 2 months later, and x-rays showed collapsed grafts with canal stenosis (Fig. 4). His ACDF was revised by using allograft.

and patients self-rating of his postoperative arm pain and general function. The radiological outcomes were not validated in this study as several studies have shown little correlation between the radiological and the clinical outcomes, and the difficulty in defining fusion on plain x-rays.7,15 Both grafts were safe and reliable. Based on the results we found no significant difference in long-term clinical outcomes. This finding indicates that clinical outcome is probably related more to the surgical technique rather than the type of graft used for fusion. Graft-related morbidity was similar in both groups; one graft collapse in the autograft group and vertebral body fracture in the CFC group. In the two cases, 2 level ACDF were performed and both required further surgery. We believe that over-size grafts especially in multiple level ACDF could be one of the reasons for the autograft collapse.

Figure 4 - Computed tomography scan showing graft collapse in 2 level ACDF with autograft

Donor site pain at the time of answering the questionnaire was rated as ‘none’ by 10 patients (45.5%) and ‘mildmoderate’ by 12 (54.5%). Length of stay Length of hospital stay was almost similar with 4.83 for CFC group and 4.47 for autograft group (not significant: p > 0.1). In the radiculopathic patients (19 autograft, 20 CFC). The difference in length of stay was significant (autograft; mean 4.1, median 4 vs. CFC; mean 3.75 median 3) (p = 0.05).

Discussion Microsurgical ACD is a standard treatment for degenerative cervical disc disease. The debate whether to perform fusion remains ongoing and is beyond the scope of our paper. The goals of fusion are to maintain the disc height, prevent kyphosis and achieve rapid segmental stability. Prolonged operative time, graft-related morbidity and adjacent level degeneration are the disadvantages of grafting.

The same thing can happen in CFC cage except that CFC is an extremely hard implant and the consequence of oversized graft can be bony injury, especially when excessive force is used to insert the cage. No previous bony injury following CFC implant has been reported in the literature. Chronic donor site pain in autograft patients is real and significant; our study has shown that 54.5% of patients had mild to moderate pain at the donor site. No patient had severe chronic pain at the donor site. The incidence of chronic donor varies in the literature; Silber reported chronic pain in 26.1% of patients, and 11.2% use regular analgesia.14 Savolainen however, reported 7% of patients having severe prolonged donor site pain.13 The donor site pain in the immediate postoperative recovery might explain the longer length of stay in the autograft group especially in the radiculopathic group (median 4 days vs. 3 in CFC group).

Two types of grafts have been studied in this paper. The goal is to establish whether the newly developed, and costly CFC graft is superior to the old fashioned and free autograft.

Our results were similar to the Vavuruch, et al study in which anterior cervical discectomy with CFC was compared with Cloward procedure.17 In Vavurruch study the clinical outcomes were similar between the two groups but when assessing the radiological findings there was a correlation between the segmental kyphosis and clinical outcome. The incidence of psuedoarthrosis was slightly higher in the CFC group.

The long-term clinical outcome (minimum of one year) has been studied by using Oswestry Disability Index scores to assess the patient’s disability as regards to his neck pain,

Our study indicates that both grafts are equal in terms of long-term clinical outcomes and morbidity. However, the absence of donor site pain and significantly shorter length

VOLUME , NO. ,

4


of stay makes the CFC more advantageous. The limitations of our study are the small number of patients, its retrospective nature and the absence of radiographic evaluation.

7.

8.

Conclusion Autograft and CFC implants for anterior cervical disectomy and interbody fusion are both safe and effective. Both methods achieved similar long-term clinical outcome and graft-related morbidity. The use of CFC implant however, can avoid donor site pain and achieve a shorter hospital stay.

9.

10.

11.

Disclaimer None of the authors has received any financial support from any company mentioned in this study, and none of the authors has any financial or other interest in the company involved in this study.

References 1.

2.

3. 4. 5.

6.

Agrillo U, Mastronardi L, Puzzilli F: Anterior cervical fusion with carbon fibre cage containing coralline hydroxyapatite: Preliminary observations in 45 consecutive cases of soft-disc herniation. J Neurosurg 2002, 96(Spine 3): 273-276 Brooke NSR, Rorke AW, King AT, Gullan RW: Preliminary experience of carbon fibre cage prostheses for treatment of cervical spine disorder. Br J Neurosurg 1997, 11(3): 221-227 Cloward RB: The anterior approach for removal of ruptured cervical discs. J Neurosurg 1958, 15: 602-617 Dowd GC, Wirth FP: Anterior cervical discectomy: is fusion necessary? J Neurosurg 1999, 90(Suppl 1): 8-12 Frederic S, Benedict R, Payer M: Implantation of an empty carbon fiber cage or a tricortical iliac crest autograft after cervical discectomy for single-level disc herniation: a prospective comparative study. J Neurosurg: Spine 2006, 4(4): 292-299 Harland SP, Laing RJ: A survey of the perioperative

12.

13.

14.

15.

16.

17.

management of patients undergoing anterior cervical discectomy in the UK and Eire. Br J Neurosurg 1998, 12(2): 113117 Laing RJ, Seeley HM, Hutchinson PJ: Prospective study of clinical and radiological outcome after anterior cervical disectomy. Br J Neurosurg 2001, 15(4): 319-323 Martins AN: Anterior cervical discectomy with and without interbody bone graft. J Neurosurg 1976, 44: 290-295 Payer M, May D, Reverdin A, Tessitore E: Implantation of an empty carbon fibre composite frame cage after single-level anterior cervical discectomy in the treatment of cervical disc herniation: Preliminary results. J Neurosurg 2003, 98( 2 Suppl): 143-148 Rosenorn J, Hansen EB, Rosenorn MA: Anterior cervical discectomy with and without fusion: A prospective study. J Neurosurg 1983, 59: 252-255 Ryu SI, Mitchell M, Kim DH: A prospective randomized study comparing a cervical carbon fibre cage to the Smith-Robinson technique with allograft and plating: up to 24 months follow-up. Eur Spine J 2006, 15(2): 157-164 Savolainen S, Rinne J, Hernesniemi J: A prospective randomized study of anterior single-level cervical disc operations with long-term follow-up: Surgical fusion is unnecessary. Neurosurg 1998, 43(1): 51-55 Silber JS, Anderson DG, Daffner SD, Brislin BT, Leland JM, Hilibrand AS, et al: Donor site morbidity after anterior iliac crest bone harvest for single level anterior cervical discectomy and fusion. Spine 2003, 28(2): 134-139 Smith G, Robinson R: The treatment of certain cervical spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone J Surg 1958, 40A: 607-624 Sudhakar N, Laing RJ, Redfern RM: Assessment of fusion after anterior cervical discectomy. Br J Neurosurg 2003, 17(1): 54-59 Thorell W, Cooper J, Hellbusch L, Leibrock L: The long-term clinical outcome of patients undergoing anterior cervical discectomy with and without intervertebral bone graft placement. Neurosurg 1998, 43(2): 268-272 Vavruch L, Hedlund R, Javid D, Leszniewski W, Shalabi A: A prospective randomized comparison between the Cloward procedure and a carbon fiber cage in the cervical spine: A clinical and radiological study. Spine 2002, 27(16): 1694-1701

PAN ARAB JOURNAL OF NEUROSURGERY 8