Anterior cervical diskectomy and fusion (ACDF) is a safe and effective treatment for cervical spondylosis refractory to nonoperative management. Despite excellent results, concern remains about the decreased neck range of motion and the possibility for accelerated development of adjacent segment disease (ASDz) as a consequence of this procedure. Kinematic, radiologic, and retrospective clinical studies have been performed that have lent plausibility to the idea that cervical fusion may increase the risk for ASDz. 1 Kinematic studies have demonstrated that levels adjacent to cervical fusion experience hypermobility and increased intradiscal pressures as a consequence of lost mobility from fusion. 1 Although it is well known that the natural history of degenerative cervical spondylosis produces many of the findings that occur in ASDz both radiographically and clinically, a significant body of literature suggests that fusion accelerates this process. Ueda et al suggest that there is likely an iatrogenic role to ASDz, but the exact relationship between ACDF and accelerated adjacent level degeneration remains to be understood. Conversely, there is a notable body of literature that challenges the stance that arthrodesis plays a causative role in symptomatic ASDz . One study cites a lower incidence of ASDz in patients who underwent multilevel ACDF compared with single-level ACDF. 2 It was initially hypothesized in this study that more hypermobility would occur in adjacent segments with a longer moment arm following fusion, thereby incurring a higher rate of adjacent segment disease. Surprisingly, patients with longer fusions tended to have a lower incidence of ASDz. This finding lends support to the argument that ASDz may be due to the natural history of cervical spondylosis, with some joints at higher risk for degeneration than others and not completely due to increased stresses caused by fusion. In any case, these two arguments are at the crux of whether or not cervical disk arthroplasty (CDA) offers superior outcomes with regard to lowering the incidence of morbidity from ASDz. A number of studies suggest a lower rate of complications and fewer secondary surgical procedures after CDA compared with ACDF. CDA has been shown to be safe and effective compared with ACDF, 3 but more studies of higher quality and with longer follow-up are needed to understand all the possible long-term benefits and pitfalls of CDA. Recent randomized clinical trials have suggested improved outcomes in CDA patients compared with ACDF patients with respect to rate of reoperation and neck disability index score. 4 Some have raised concerns that many of the trials conducted so far have been industry sponsored. A recent meta-analysis found that studies with reported conflicts of interest were significantly more likely to report lower rates of ASDz, as well as heterotopic ossification in patients who underwent CDA. 5 Radiculopathy related to single-level degenerative disk disease from C3–4 to C6–7, with or without neck pain, which has been refractory to nonoperative management Myelopathy with the aforementioned criteria Symptomatic multilevel disease that would require multiple-level CDA Adjacent level disease (degenerative disease adjacent to a previous cervical fusion) Infection that is systemic or active at the site of implantation Osteoporosis Allergy to implant materials Severe spondylosis with > 50% disk height loss, bridging osteophytes or absence of motion on flexion–extension views at the symptomatic site Severe facet joint arthropathy; ankylosing spondylitis Rheumatoid arthritis Anatomical deformity secondary to previous fracture Ossification of the posterior longitudinal ligament Malignancy Severe cervical spine deformity of any kind As the approach in CDA is almost identical to that of ACDF, many of the complications of CDA are the same as those of ACDF. Heterotopic ossification (HO) of the implant is a unique complication of CDA that results in lost range of motion at the affected level. 6 Persistent posterior neck pain Dysphagia Reoperation Recurrent laryngeal nerve injury Recurrence of neurologic symptoms Symptomatic postoperative hematoma Infection Spinal cord injury Dural tear Implant migration Appropriate preoperative imaging is imperative to achieve a successful surgical result. A computed tomographic scan or magnetic resonance image of the cervical spine with axial slices parallel to the vertebral end plates should be obtained. From these axial images, the smaller of the two end plates at the target disk space is used to determine the size of the artificial disk to be implanted. Do not include in this measurement any bone spurs or ridges that will be removed during decompression. The final selection of implant size will be based on the surgeon’s clinical judgment, the disk space preparation, and trialing. Various CDA implants are on the market, and although the exposure, decompression, and end plate preparation are essentially the same, implantation varies with each device The patient positioning and surgical exposure are essentially identical to those used in anterior cervical diskectomy. With the patient supine on the operating table, an inflatable pillow is placed beneath the shoulders to maintain cervical lordosis. The head and neck should be in a neutral position while avoiding overextending the neck, which can result in using an implant that is too large. If necessary, the shoulders can be pulled caudally to improve radiographic visualization. Preoperative fluoroscopy is used to identify the target level and confirm patient positioning. A 2.5 to 3.0 cm transverse skin incision is planned (ideally along an existing skin crease) at the target level and centered over the anterior margin of the sternocleidomastoid muscle. A right- or left-sided approach is chosen based on the surgeon’s preference or any specific patient-related factors such as previous neck surgeries. The standard anterior cervical soft tissue dissection is developed (along the avascular plane between the trachea and esophagus medially and the carotid sheath laterally) to expose the ventral cervical spine. The correct target disk space level is confirmed radiographically. The longus colli muscles are elevated widely bilaterally using electrocautery, and a self-retaining retractor is placed for soft tissue retraction. A complete diskectomy is performed using pituitary and angled rongeurs, curets, and the drill. Vertebral body distraction pins may also be used for disk space distraction. A bilateral uncinate resection and spondylotic ridge removal should be performed even if symptoms are unilateral as motion is maintained. After cartilaginous end plate removal using curets, the rostral and caudal bony end plates may be prepared using a round or cylindrical high-speed drill ( ▶ Fig. 12.1). The goal is to make the end plates flat and parallel to better accommodate the implant, but care must be taken to preserve as much end plate cortical bone as possible to minimize the risk of implant subsidence. A rasp device can also be used to prepare the cortical end plate, using an in-and-out motion with slight medial–lateral rocking ( ▶ Fig. 12.2). The ventral vertebral surfaces (in particular, the anterior lip of the superior vertebral body) should also be “gardened” with a rongeur or drill to make them flat. Fig. 12.1 Drilling to make the rostral and caudal bony end plates parallel. As much of the bony end plate should be spared as possible to minimize the risk of subsidence. (a) Close-up view. (b) Lateral view. (c) Ventral view.
12.2 Patient Selection
12.2.1 Indications
12.2.2 Contraindications
12.2.3 Adverse Events
Common adverse events
Rare complications
12.3 Preoperative Preperation
12.4 Operative Procedure
12.4.1 Exposure
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
