Anterior Cervical Discectomy – An Overview of Technique and Developments for the Future

Cervical anterior discectomy (CAD) was introduced by Smith and Robinson, and Cloward, in 1958.^1,2 They described the anterior approach to the cervical disc. After removal of the disc and herniated part an autograft taken from the iliac crest was introduced in the intervertebral space to promote fusion between the two adjacent vertebral bodies. The introduction of a microscope facilitated the procedure enormously. At this time the main reason for performing a CAD is still degeneration of the disc with signs and symptoms due to compression of the nerve root and/or spinal cord by a herniated disc or spondolytic spurs.
Nowadays, various kinds of CAD are distinguished depending upon the implant that is used to fill the intervertebral space. A discectomy can be performed solely without introducing any implant in the intervertebral space (CAD). If an implant is used with the intent of fusing the adjacent vertebral bodies it is called in literature a cervical anterior discetomy with fusion (CADF). Recently, prostheses have been used in order to maintain mobility at the operated segment.
A standard abbreviation has not been used yet, but for this review we will use CADP. The advantages and disadvantages of each of the procedures will be addressed below.
CAD was described by Hirsch in 1960.³ Through an anterior approach the cervical disc was removed as were the compressing factors on the nerve root or spinal cord, such as herniated disc or accompanying spondylotic spurs. Since the intervertebral space will collapse after removal of the disc an adequate decompression of the
exiting nerve roots should be achieved.
In the case of CADF an implant is used. Various implants can be used, ranging from autograft – most frequently obtained from the iliac crest – allograft, cages filled with bone (auto- or allograft) or biomaterials, or polymethylmethacrylate (PMMA) bone cement. PMMA is used as a spacer without the intention of promoting fusion, but eventually fusion occurs around the PMMA. After performing a thorough discectomy the implant is introduced. The disc space is slightly overdistracted. This manoeuvre will increase the height of the neuroforamina.^4,5
The use of a plate as an adjunct to CADF is still subject of discussion. It has been proven that for one- or two-level CADF, a plate does not have any advantage and is considered not to be useful.^6–8 Recently, arthroplasty has been introduced. The theoretical advantages of CADP are, in the first instance, providing at least as good clinical results as CADF. Furthermore, prostheses maintain mobility and could prevent the occurrence of degeneration of the adjacent segment (adjacent disc degeneration [ADD]). There is no benefit relating to the clinical result.⁹
The existence of ADD is subject to debate. The proponents of arthroplasty frequently cite the article by Hilibrand,¹⁰ in which he reported an annual rate of ADD after fusion of 2.9 % after 10 years of follow-up. However, correction for the patients lost to follow-up and pre-existing degeneration of the adjacent segment decreased the annual rate to 0.4 %.¹¹ Furthermore, recent studies in asymptomatic volunteers disclosed that degeneration of initially normal discs and progression of existing degeneration is a natural phenomenon.^12–14
Therefore, it can be questioned whether ADD is really induced by fusion of a segment or is a natural phenomenon. Finally, it is remarkable that ADD was not a subject in many of the recently published results of randomised clinical trials (RCTs) comparing arthroplasty with CADF.¹⁵

From the available studies a benefit for athroplasty in relation to the prevention of ADD has not been proven.¹⁵ The results for each procedure relating to relief of arm and/or neck pain are within the same range. Over 75 % of patients have a good-to-excellent result regarding arm pain; the results for concomitant neck pain are slightly worse.6,16 For one- or two-level degenerative disc disease a difference in clinical outcome has not been established comparing CAD or CADF.⁶ Any clinical benefit of the use of a prosthesis compared with CADF has also not been proven.⁹
The major theoretical advantage of CADF is maintenance of the disc height and lordotic shape of the cervical spine. However, a correlation with a clinical effect has never been established.¹⁷
The most common complications of CAD are hoarseness and dysphagia. A lesion of the recurrent laryngeal nerve can lead to dysfunction. Since the approach to the disc and the discectomy is the same for all kinds of CAD, they are referred to as approach-related complications; in most instances they are asymptomatic. Of the direct post-operative symptomatic patients, a large number become asymptomatic after several months.
In different studies the prevalence of persistent hoarseness varied between 0 % and 5.0 %.18–20 The prevalence of dysphagia varied from 50 % within one month post-operatively to 21 % after one year.^21–24 Other (rare) approach-related complications are Horner’s syndrome, lesion of the dura, worsening of neurologic symptoms, perforation of the oesophagus, lesion of the vertebral artery, infection of the wound and post-operative haemorrhage.¹⁸
Complications related to implants also occur. The most frequent complication of an autograft taken from the iliac crest is pain at the donor site. Usually this pain diminishes, but can remain persistent.^25,26 This complication and others related to obtaining a bone graft, like neurovascular lesions, can be prevented by using cages. However, as well as subsidence, pseudoarthrosis can occur.
The main question remains as to whether this is clinically significant. In observational studies, these were not correlated to clinical failure.^27–30
A specific complication related to cervical disc prostheses is periprosthetic ossification.^31–36 Bone is formed around the prosthesis and can restrict movement. It is remarkable that this occurrence does not alter clinical outcome. More recently, problems due to design have been reported. Metal-on-metal total disc prostheses induced a lymphocytic reaction with signs and symptoms after initial clinical success. They underwent surgery again with removal of the system and fusion. Although three of the four reported cases had lumbar disc prosthesis, surgeons should be aware of possible failure in the future due to the design of the prosthesis.
In conclusion, CAD is a safe procedure with a good-to-excellent result in most cases. The debate whether to fuse or not and, if fusion is the goal, which implant should be applied is still not closed. Before developing fancy new implants, a definitive answer to the question of CAD with or without fusion should be provided. A large RCT on this subject with the participation of several centres in Europe would probably solve this question. The available literature is at this time certainly not in favour of cervical arthroplasty. I doubt whether based on recent investigations this will change, since a thorough review by independent epidemiologists will certainly reveal many biases and flaws.