Technology overview | Mobi-C for cervical disc replacement | Advice

About the technology

CE marking

CE marks (class III implants; Medical Device Directive 93/42/EEC amended 2007/47/EC) were awarded to LDR Medical in October 2004 for Mobi‑C and in November 2007 for Mobi‑C Plug and Fit, which includes the 'Plug and Fit' implantation system. The CE marks were renewed in September 2015.

Description

Mobi‑C is a prosthetic device for cervical intervertebral disc replacement (C3/C4, C4/C5, C5/C6, C6/C7) intended to restore disc height and retain movement in the cervical spine. It can be used for either the replacement of 1 (1‑level) or 2 (2‑level) cervical discs; 2‑level replacement requires 2 Mobi‑C devices. The prosthesis consists of a superior spinal plate, an inferior spinal plate and a mobile insert. The plates are made of chromium cobalt molybdenum alloy with a pure titanium and hydroxyapatite coating, and the insert is made from polyethylene. Mobi‑C is delivered pre‑assembled on a disposable PEEK cartridge, with jaws keeping the 2 plates and the insert together. This aims to make inserting the prosthesis easier and replaces the previous version of the device. The cartridge allows the prosthesis to be viewed under X‑ray for optimal positioning. The device has an accompanying instrument kit that contains all equipment needed to complete procedures with Mobi‑C.

The prostheses come in various sizes, which are detailed on the product website. Before surgery, an X‑ray is taken to check that the affected disc size is at least 14 mm from front to back and that disc height is adequate for disc replacement. During surgery, the correct prosthesis is selected under fluoroscopy ensuring it does not exceed the height of healthy adjacent discs. The depth of the disc is verified during surgery by direct measurement with a depth gauge, supplied by the manufacturer in the instrument kit. All measurements must take into consideration any osteophytes (bony projections) that will be removed at the beginning of the procedure.

The surgical approach for implanting Mobi‑C is similar to that of an anterior cervical discectomy and fusion (ACDF), involving a number of steps:

partial discectomy
width gauge and positioning of a centring pin (with fluoroscopy to confirm correct positioning)
distraction of the disc space
complete discectomy
parallel distraction
depth measurement
insertion of trial prostheses (screwed onto a holder) to assess the final prosthesis size
loading the prosthesis
millimetre adjustment of the stop setting
prosthesis insertion
position checking
removal of the prosthesis holder and clamps
anchorage optimisation.

As well as the potential adverse events arising from any surgery, some adverse events are specific to the anterior approach to the cervical spine (such as recurrent laryngeal nerve palsy or nerve root injury leading to arm weakness or numbness), or to cervical disc replacement itself (for example, the prosthesis becoming displaced or components failing, allergy to materials or degeneration in adjacent discs).

People who have discs replaced with Mobi‑C should be advised that they can return to normal activities 3 to 6 months after surgery in most circumstances, but that any excessive loading or movement of the neck (for example, gymnastics or rugby) should be avoided.

Contraindications include:

known or suspected sensitivity to the materials
degenerative arthrosis of the facet joint
neck pain without radiculopathy
systemic spinal or local infection
fever
any local condition that could compromise the stability of the prosthesis (such as a tumour or osteoporosis)
significant cervical anatomical deformity (for example ankylosing spondylitis or rheumatoid arthritis).

Setting and intended use

Mobi‑C is designed to be used to replace cervical spine discs in adults who need cervical disc replacement because of radiculopathy or myelopathy. For people with myelopathy, the presence of at least 1 of the following conditions should be confirmed by radiographic imaging before the procedure: spondylosis, herniated nucleus pulposus or visible loss of disc height compared with adjacent levels. Cervical discs C3 to C7 can be replaced using Mobi‑C, and 1 or 2 discs may be replaced during the procedure. For 2‑level procedures, 2 Mobi‑C devices are needed. People may be suitable for surgery if their cervical disc degeneration has not responded to at least 6 weeks of conservative management, or if they have shown progressive signs or symptoms despite non‑operative treatment.

The surgical procedure for cervical disc replacement with Mobi‑C is technically demanding, with a risk of serious injury to the person having the procedure comparable to ACDF. Because of this, the prosthesis should only be implanted by experienced spinal surgeons who are trained in using Mobi‑C and who understand the mechanical limitations of the cervical disc prosthesis.

Current NHS options

NICE interventional procedure guidance on prosthetic intervertebral disc replacement in the cervical spine notes that conservative treatment options include rest, analgesic medication, physical therapy and local corticosteroid injections. If these conservative options fail, or if a person is at risk of permanent neurological damage, surgery may be offered. The guidance recommends that the procedure may be used with normal arrangements for clinical governance, consent and audit. It also encourages further research including long‑term outcomes on the preservation of mobility, occurrence of adjacent segment disease and the avoidance of revision surgery.

A number of surgical treatment options are available. ACDF is a well‑accepted treatment option to relieve symptoms caused by spinal cord or spinal nerve compression (that is, myelopathy or radiculopathy). During the procedure, cervical disc material that is compressing the spinal cord or nerve is removed. The space is then generally filled with a bone graft taken from a separate site in the body, or with a synthetic 'cage' to encourage bone fusion. ACDF has a high success rate, but can be complicated by recurrent neck pain and adjacent segment disease (Delamarter and Zigler 2013).

Prosthetic intervertebral discs may be used as an alternative to ACDF. NICE interventional procedure guidance on prosthetic intervertebral disc replacement in the cervical spine notes that the aim of prosthetic disc surgery is to preserve mobility in the affected area of the spine, reducing the risk of long‑term adjacent segment degeneration. More than 1 disc can be replaced during the same procedure and various devices may be used. The guidance states that cervical disc replacement procedures should only be done in specialist units where cervical spine surgery is common.

NICE is aware of the following CE‑marked devices that appear to fulfil a similar function to Mobi‑C:

BRYAN Cervical Disc (Medtronic)
PCM Cervical Disc (NuVasive)
PRESTIGE LP Cervical Disc (Medtronic)
ProDisc‑C Total Disc Replacement (DePuy Synthes).

Costs and use of the technology

The cost of a single Mobi‑C prosthesis, including the jaws and screw needed for the procedure, is £1,750 (so £3,500 for a 2‑level procedure; excluding VAT). Cervical disc replacements with Mobi‑C also require the accompanying instrument kit that the manufacturer provides at no extra cost. The instruments can be reused following sterilisation. Intraoperative fluoroscopy will also be needed throughout the procedure to ensure accurate instrument and prosthesis positioning.

The manufacturer provides onsite training, staff and technical support in the operating room, and user meetings at no extra cost.

In practice, hospitals that use Mobi‑C are reimbursed through the NHS National Tariff Payment for cervical disc replacement (table 1). The total difference between disc replacement and fusion procedures, at usual NHS prices, is expected to be £1,622 for 1‑level replacement and £3,511 for 2‑level replacement (British Association of Spine Surgeons 2011, NHS England 2016). This is similar to the cost of the Mobi‑C device (£1,750 for 1‑level and £3,500 for 2‑level replacement).

Table 1 Tariff payments: cervical disc replacement and ACDF

Intervention	HRG code		PbR tariff value
Intervention	1 level	More than 1 level	1 level	More than 1 level
Cervical disc replacement	HC02C	HC01Z	£7,607	£11,118
Anterior cervical discectomy and fusion	HC03C	HC02C	£5,985	£7,607
Difference			£1,622	£3,511
Tariff payments for spinal surgery are currently adjusted to account for specialised services commissioning, which increases the tariff by 32%. The adjusted prices are shown.

Likely place in therapy

The Mobi‑C prosthesis would be used as an alternative to ACDF and other prosthetic discs.

Specialist commentator comments

One commentator stated that Mobi‑C may have advantages over other prostheses because it is only semi‑constrained, which means it provides excellent mobility when inserted optimally, and is perhaps more forgiving than other devices if the placement is not perfect. They added that constrained devices offer only limited height variation, whereas Mobi‑C prostheses are available in a range of heights. For example, Mobi‑C can even replace a disc of 4 mm to 5 mm in height, making it suitable for people with smaller discs.

One commentator stated that ACDF is the gold-standard procedure for people with cervical myelopathy or radiculopathy, but that it has the disadvantage of adjacent segment disease and the possibility of further surgery. They noted that cervical disc replacement procedures aim to address these disadvantages. A second commentator considered that Mobi‑C should be used instead of ACDF for certain indications, specifically in people who have had previous fusion surgery and develop adjacent disc disease; people with symptomatic multi‑level disc disease; and young adults with a soft disc prolapse causing compression who also have a degenerate disc not causing compression. They added that Mobi‑C results are likely to be more favourable in people with 2‑level procedures when compared with ACDF. This is because 2‑level fusion procedures have a more detrimental effect on cervical movement and biomechanics than 1‑level ACDF. A third commentator noted that Mobi‑C should be used for the same indications as other prosthetic replacement devices.

One commentator remarked that all procedures with Mobi‑C should be done by surgeons competent in anterior cervical disc replacement, and that because of this the procedure is likely to be restricted to neurosurgical units or spinal surgery centres with orthopaedic surgeons who do anterior neck surgery. They added that the procedure with Mobi‑C should not be more technically demanding than fusion procedures, and in both types of surgery the main risk arises from the decompression process. They estimated the risk of serious injury with both procedures to be approximately 1 in 400 to 1 in 800, which they deemed to be low. The commentator was of the opinion that revision procedures were no more risky than initial placement. A second commentator considered that revision procedures are likely to be more risky and that there are limited long-term data regarding failure rates with cervical disc replacement. They added that cervical disc replacement can be associated with major complications such as paralysis, and these complications can have a significant effect on the cost‑effectiveness of the procedure. A third commentator stated that it is particularly important to explain the expected outcomes to people considering both options so that they can make an informed decision about treatment. One commentator stated that cervical disc replacement procedures require spinal joints to be in a relatively good condition (for example, low levels of osteoarthritis and disc height of at least 50%), and this often limits the procedure to younger people.

One commentator noted that heterotopic calcification is an important consideration with the Mobi‑C procedure because most people will develop evidence of anterior osteophytes over time after surgery. Depending on their severity, osteophytes can limit movement, and when osteophytes fuse together this can stop movement altogether. However, even if patients experience fused osteophytes at 10 years after surgery, the commentator considered that retention of movement up until that point would still deliver significant benefits. The commentator also noted that the rate of calcification is likely to be comparable across different prostheses and is not unique to Mobi‑C. A second commentator remarked that there have been reports of spontaneous fusion with cervical disc replacement procedures. This usually occurs anteriorly or due to heterotopic ossification, and will restrict movement leading to similar outcomes to ACDF procedures.

One commentator noted that people are more regularly requesting cervical disc replacement over fusion procedures based on research they have done themselves, with 1 person also specifically requesting disc replacement with Mobi‑C.

One commentator stated that people with cervical disc degeneration are commonly given neuropathic medication, or even no treatment.

Equality considerations

NICE is committed to promoting equality, eliminating unlawful discrimination and fostering good relations between people with particular protected characteristics and others. In producing guidance, NICE aims to comply fully with all legal obligations to:

promote race and disability equality and equality of opportunity between men and women.
eliminate unlawful discrimination on grounds of race, disability, age, sex, gender reassignment, marriage and civil partnership, pregnancy and maternity (including women post‑delivery), sexual orientation, and religion or belief (these are protected characteristics under the Equality Act 2010).

People with cervical degeneration may be considered to have a disability if their symptoms have an adverse and long‑term effect on their ability to carry out daily activities, for example as a result of pain and reduced mobility. Mobi‑C may enable people with cervical disc degeneration to become more mobile and, therefore, partake in more everyday activities. Cervical disc degeneration becomes more common with age, so the device may be used more regularly in older people. Age and disability are protected characteristics under the Equality Act (2010).