INTRODUCTION

 

Anterior cervical discectomy and fusion (ACDF) has been considered the common treatment of cervical degenerative disc disease (DDD).¹ After failure of the Initial Conservative treatment to improve pain and neurological symptoms, Surgical management is considered.² ACDF offers decompression of spinal canal and eliminates motion at the fused segment but it causes degeneration in the adjacent segment through altering the normal biomechanics of the spine.^3,4 Disc prosthesis is an emerging treatment for patients with disc degeneration. Artificial cervical disc arthroplasty (ACDA) can be considered an alternative to cervical fusion in selected patients with cervical degenerative disc disease (DDD). The theoretical advantages of cervical disc arthroplasty include maintenance of range of motion to avoid adjacent segment degeneration. They also include restoring the intervertebral disc and foraminal height to prevent recurrence of nerve root compression.^{5, 6} First implantation of a cervical arthroplasty device in a human was described by Fernström in 1966 with poor results. The first two generations of SB Charité

 

prosthesis was first implanted in 1984. Third generation became commercially available in 1987 and was the most widely implanted artificial cervical disc. In 1989, Cummins designed a stainless steel metal-on-metal cervical artificial disc in Bristol, UK but with unfavorable outcomes. It was redesigned and reintroduced as the Frenchay cervical disc which had better clinical results and was later renamed the Prestige Disc. The ProDisc, emerged in 1990, is a metal-on-metal design and has yielded favorable long-term outcomes. Bryan disc emerged in the late 1990s as a metal-on-plastic disc. In 2009, The Porous Coated Motion Disc Prosthesis, or PCM device was designed. Development of arthroplasty devices is continuing and will appear in the coming years such as the Maverick disc, Medtronic Sofamor Danek, Memphis and others.^{7, 8}

 

The Aim of This Study

Is to evaluate the clinical outcome and efficacy of artificial cervical disc replacement in treatment of cases of DDD.

 

SUBJECTS AND METHODS

 

Eleven patients with cervical degenerative disc disease were studied prospectively in the period from 2009 to 2012. Patients included in this study suffered from soft cervical disc disease (without facet joint arthrosis) as shown in figure 1. All patients in this study were subjected to history taking, complete general and neurological examination. They were treated by artificial cervical disc arthroplasty in Neurosurgery Department, National Defense hospitals. They all did not respond to conservative treatment. Nine were males (75%) and two were females (25%). The age varied from 26 to 58 years with mean age of 39.4 years. No patients suffering from posterior cord compression or instability were included in this study. Ten patients had been operated upon by anterior cervical discectomy with artificial cervical disc replacement in one level. The eleventh case was operated upon by double level. Disc prosthesis used in this series is the ProDisc. Clinical preoperative data of the patients is mentioned in Table (1).

Clinical follow-up was evaluated by visual analogue scale (VAS). VAS has a range from 0-10. It measures the degree of neck pain, brachialgia as shown in the following categories: 0: No pain, 1-3: Uncomfortable or mild pain, 4-7: Dreadful or moderate pain and 8-10: Horrible or severe pain.

An anterior cervical complete discectomy was carried out through a classic Smith–Robinson approach, posterior longitudinal ligament was removed for accessing any herniated disc passed through the ligament and the osteophytes were removed to avoid the postoperative radiculopathy. Inferior endplate of upper vertebra and superior endplate of the lower one were sharpened for a better holding of the implant. The prosthesis was placed and centered in the frontal plane under fluoroscopy guidance for an optimal positioning (Figure 2).

 

 

 

 

Figure 1. Preoperative T2-weighted MRI sagittal showing soft C5-6 disc prolapse.

 

Table 1. Preoperative Data of the patients.

 

Data                                                          Value

Age (y)                                                 39.4 (26-58)

Sex

Male : female                                 9 male : 2 female

Symptoms and signs (No.) Neck pain                                              11

Brachialgia       Right                                                 4       Left                                                   6       Bilateral                                            1                      Motor affection                                      -

 

 

 

Figure 2. Postoperative plain x-ray of the cervical spine anteroposterior (AP) view showing C5-6 disc prosthesis

 

 

RESULTS

 

All patients received anterior cervical discectomy followed by artificial cervical disc arthroplasty. Only one patient received double level arthroplasty. Clinical outcome and motion at the treated as well as the adjacent level were prospectively reviewed. Cervical levels treated by disc arthroplasty are showed in table 2. Visual analogue scale (VAS) was used to assess the clinical outcome. Patients’ clinical presentation preoperatively and outcome postoperatively are showed in Table (3).

Motion preservation was followed radiologically. Plain x-ray was done immediate post operatively and dynamic views were added on the 3, 6, 12 and 18 months follow up. Motion was maintained at the treated level in all eleven cases with no change in sagittal plane motion. (Figure 3)

The commonest postoperative complications in this study were dysphagia and hoarseness of voice which spontaneously disappeared within 1-2 weeks. No device subsidence, breakage or --major complications was reported. 

 

 

Table 2. Distribution of cervical levels arthroplasty.

 

Cervical level	No.	%
C 3-4	2	18.2
C 4-5	3	27.2
C 5-6	4	36.4
C 6-7	1	9.1
C4-5, C5-6	1	9.1

 

Table 3. Clinical results of patients (measured by VAS score).

 

Results (VAS)	Preoperatively						Postoperatively						p (df=1)
	0 – 3		4 – 7		8 – 10		0 – 3		4 - 7		8 – 10
	No.	%	No.	%	No.	%	No.	%	No.	%	No.	%
Neck pain	5	45.5	6	54.5	-	-	8	72.8	3	27.2	-	-	0.193
Brachialgia	-	-	7	63.6	4	36.4	11	100	-	-	-	-	0.000

 

Figure 3. Postoperative plain X-rays cervical spine flexion and extension views

showing C5-6 disc prosthesis with preserved motion in the segment

 

 

DISCUSSION

 

Cervical degenerative disc diseases are routinely managed by anterior cervical discectomy and fusion. It provides high fusion rates (reaches 90% fusion after 6 months and 100% fusion after 12 months postoperatively) and clinical success with little morbidity. ACDF helps in restoring disc height and increasing the area of the foramen.⁹ Disadvantage of ACDF is that it accelerates adjacent segment degeneration. Gore and Sepics’ cohort included 121 patients who had undergone an ACDF .Patients follow-up for an average period of 5 years revealed that 25% had developed spondylosis and another 25% had progression of preexisting spondylosis.¹⁰

The goal of using cervical arthroplasty is to maintain motion in a functional cervical motion unit after anterior decompression. This reduces the rates of adjacent level disease.¹¹ In this study, this was proved by dynamic plain x-rays at 3, 6, 12, 18 months which showed maintained motion at the level with no change in sagittal plane motion. They also showed preservation normal motion at the adjacent levels.

Rudolf Bertagnolis’ performed a prospective study evaluating cervical arthroplasty. The patient follow-up showed that arthroplasty restored functional motion and reduced incidence of adjacent-level disease.¹² Also he mentioned that Degenerative changes occurring above and/or below a fused segment may simply be due to increased intradiscal pressures at levels adjacent to intervertebral fusions.

Newly published studies, analyzing cervical arthroplasty, described that the motion compensation was distributed among the unfused segments. Significant compensation at the segment adjacent to the fusion leaded to increased motion at the adjacent level above or below the fusion.^8,13 No increase in adjacent-level motion was seen in patients who underwent anterior cervical discectomy followed by insertion of an artificial joint. There was no significant change in sagittal rotation after surgery in the patients.¹⁴ Radiographic evidence of severe adjacent segment degeneration was significantly lower in the cases received cervical arthroplasty.¹⁵ Cervical disc arthroplasty (CDA) allowed maintaining disc height, preserving motion at operated level and normal motion at adjacent levels. This establishes the idea that CDA reduced kinematic strain on both above or below levels.¹⁶   

Fusion altered spinal biomechanics. Anterior cervical arthrodesis increased the mechanical demand on the adjacent unfused spinal units. Subsequently, it accelerated the rate of disc degeneration or mechanical instability. This increased the adjacent-level motion resulting in upper or lower level failure. On the contrary adjacent-level motion was not seen in patients who underwent anterior cervical discectomy followed by insertion of an artificial joint with a very low incidence of adjacent-segment failure.²

Rates of re-surgery for adjacent segment degeneration have been documented in patients who underwent ACDF. 25.6 % of them will require surgery for recurrent symptoms within 10 years of the index fusion .¹⁷ Goffin et al.¹⁸ reported on 181 patients treated by anterior cervical interbody fusion with an average follow-up of greater than 8 years. Moderate to severe radiologic deterioration at adjacent levels was seen in 43% of cases.

Results achieved in this study proved improvement of the functional outcome after cervical disc arthroplasty .Neck pain improved postoperatively (p=0.193) and significantly improvement of the brachialgia (p< 0.001). Garrido et al.¹⁹ and Coric et al.²⁰ assessed Primary outcome after 48 months in their cohort by VAS for neck and arm pain. It showed improvement of overall clinical success in cervical arthroplasty. Heller et al.¹⁰ reported in his prospective and randomized Study that neck and arm pain improved significantly in patient treated with artificial cervical disc replacement. Lali H. Sekhon et al. ²¹ reported in 11 patients’ study with cervical spinal cord compression managed via an anterior approach with artificial disc prosthesis. Among 2 years follow, clinical outcome of the patients was about 90% good or excellent.

In this study, there were no significant complications of cervical arthroplasty apart from dysphagia and hoarseness of voice which spontaneously disappeared within 1-2 weeks. Another series reported other adverse effects of cervical arthroplasty as heterotrophic ossification which may result from faulty design or implantation Techniques, neurological deterioration or prosthesis subsidence.²²

In the period of follow up of the study, cervical arthroplasty showed maintained same range of movement at operated levels, less rate of adjacent segment degeneration than fusion proved by serial dynamic plain x-rays. Also CDA achieved restored foraminal height and improved functional outcome.

Longer follow-up periods will be necessary to support the evidence of that preservation of segmental mobility with disc arthroplasty provides better long-term outcome than fusion by limiting the adjacent-level degeneration.

 

Conclusion

In treatment of DDD, anterior cervical discectomy followed by cervical disc arthroplasty provide improved functional outcome and preserves motion at operated level and normal motion at adjacent levels.

 

[Disclosure: Author reports no conflict of interest]

 

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