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Discocerv cervical prosthesis for TDR replacement

Monday, 03 Dec 2007 00:00
Discovery (Cervidisc Evolution) cervical prosthesis
Discovery (Cervidisc Evolution) cervical prosthesis
Discocerv (Cervidisc Evolution) total cervical disc prosthesis manufactured by Scient'X (France) was implanted in over 1000 patients in more than 20 countries all over the world and encountered a great success, mostly due to its unique biomechanical features allowing to restore mobility at the affected level and to preserve the adjacent levels from degeneration.

The first Cervidisc cervical mobile prosthesis was implanted in Geneva on June 11, 1999. At seven years follow-up, a persisting mobility was found in 96% of cased in 52 implanted devices, despite a high rate of subsidence of the lower component. This very encouraging result led to redesign this ceramic on ceramic prosthesis to a new generation called Discocerv, Cervidisc Evolution.

The first Discocerv prosthesis was implanted on April 4, 2006 and since then more than 1,000 cases were reported in over 20 countries around the world.

"I have experienced a follow-up period of seven years in this moving field of cervical mobility since the first generation of Cervidisc was born. During these years I learned a lot from my mistakes and this new knowledge led me to develop a new generation of this implant that we called Discocerv Cervidisc Evolution.

"As I always said during the last years, the only real justification of a mobile prosthesis at the cervical spine is, until otherwise proven, the presence and evidence of an adjacent segment disease to a fused level. This is just to remind everyone that we must be honest and very cautious with each step done in the evolution and technical modifications of any prosthesis", says the designer of Discocerv, Dr Aymen Ramadan, Geneva, Switzerland.

The Discocerv Cervidisc Evolution is a semi-constraint prosthesis composed of two parts, allowing a spherical motion by 'head-cup' coupling. The cervical prosthesis includes a spherical upper convex head formed on the first insert while another spherical concave cup is formed on the lower second insert. These two inserts are made of ceramic material. The use of ceramic materials (Zirconia and Alumina) provides optimal wear properties. The shape of the device, convex upward in sagittal plane and downward in frontal plane, is designed to fit exactly the disc space.

As part of a collaborative effort of several centres in France and Switzerland, an ongoing multi-centre systematic evaluation study revealed that Discocerv palliates all drawbacks associated with its former version. The preliminary clinical and biomechanical outcomes show that Discocerv fully addresses the requirements of total disc replacement and achieves the original goals for which it was designed. Functions include:
  • Restoring the mobility at the treated segment and improves patient's function

  • Avoiding post operative morbidity related to instrumentation, pseudarthrosis, exposure, bone graft, and post-operative immobilisation, formerly associated with fusion procedures

  • Preventing from adjacent disc disease thanks to its biomechanical behaviour

  • Security and efficacy
    The purpose of the ongoing prospective study was to evaluate the security of use and the efficiency of cervical disc arthroplasty with Discocerv in relieving pain, recovering function and restoring a close-to-physiological mobility.

    The data collected since April 2006 were analysed in a blind fashion by an independent observer in order to accurately assess the outcomes of patients operated with Discocerv in seven centres in France and Switzerland (Professor A Ramadan, Geneva; Professor O Gille, Bordeaux; Dr G Roualdes; Poitiers; Professor J Auque, Nancy; Dr Jacquet, Besançon; Professor Ch Mazel, Paris; Dr L Nogues, St Pierre La Réunion).

    From April 2006 to June 2007, 77 patients (mean age 46 years) have been enrolled in an ongoing non comparative multi-centre prospective study which is expected to involve over 100 patients for a follow-up of five years. All patients signed the informed consent form prior to surgery and underwent total cervical disc replacement with Discocerv for degenerative disc disease (DDD) and disc herniation, with neck and radicular pain, after failure of conservative treatments.

    As reported by most of the users and confirmed by the relatively short operative time (mean operative 60 minutes), the surgical procedure is rather easy to perform, making Discocerv one of the preferred prosthesis on the market.

    "The choice of the implant size is critical. Indeed, if the prosthesis is too small it may migrate and if it is too big, it may interfere with mobility. Besides, particular attention must be paid not to overdistract the intervertebral space that my cause secondary displacement or dislocation. The prosthesis must be placed at the frontal midline of the cervical spine to allow symmetry of lateral bending motion. To do so, we thought that radiographic control during surgery was mandatory, but this could be argued. During the 2nd Discocerv training meeting in Paris (December 14, 2006), some surgeons from Bordeaux reported no better midline placement on post-operative CAT [computerised axial tomography] scan when per operative C-arm was used. Last but not least, the posterior edge of the device must be aligned with the posterior wall of the cervical spine in order to get the center of rotation at the right place," explained Ramadan.

    The results of the preliminary study are rather relevant in terms of clinical and functional improvement as well as from a biomechanical point of view. In the 77 patients' series, there was only one case with post-operative complications. At minimum six months follow-up visual analog scale (VAS)-reported arm and neck pain decreased significantly (70% decrease) and function measured by means of the Neck Disability Index was fully recovered in most of the patients. The radiographic analysis demonstrated that mobility was restored in all cases but one, with a mean flexion-extension range of movement of 6° (max 12°) and local spinal balance was also preserved in most cases, with values of cervical lordosis within physiological ranges. Besides, the mobility at the adjacent levels remained normal, ie., within physiological values reported in literature.

    The overall outcome was rated excellent in 85% of cases and good in 15% according to the ODOM criteria and patients declared to be satisfied with the results of the surgery and most of them resumed their previous activity within three months after the surgery.

    The results obtained with the device are due to the facility of use of the device and its specific design features, as well as to the particular biomechanical behavior of Discocerv, as pointed out by Ramadan:

    "The orientation of the spherical joint is important because it defines the location of the mean center of rotation (MCR) of the upper vertebra versus the lower one. Beyond restoring the range of motion, respecting the nature of the physiological motion is critical. Indeed, surrounding tissues must be loaded in a natural way in order to reproduce adequate motion pattern. A non-physiological motion can lead to an overloading of the surrounding structures, and mechanical conflicts with the implant. The MCR at each level of the cervical spine is known to be located downward and corresponds with the upper part of the inferior vertebra. The Discocerv is a 'ball and socket' prosthesis with a center of rotation located upward. This concept brings new and important considerations related to the biomechanics of the spine: the Discocerv has a more natural motion in the frontal plane, thus allowing optimal preservation of the uncii during lateral bending unlike traditional designs. A second advantage is the facet release/distraction during flexion in the sagittal plane. Of course maximum attention must be paid not to over distract the facet joints with the risk of impairing or reducing mobility and thus creating pain. The biomechanical behavior of Discocerv Cervidisc Evolution will make the object of a dedicated paper. However, these final considerations may prove useful to understand the performance of the presented device, based on a new biomechanical concept."

    Pre-operative X-rays: neutral AP and lateral + dynamic flexion/extension
    Forty-five year old man, working in tapestry and decoration, came for consultation in October 2005, complaining of severe left cervico-brachial neuralgia.

    In January 2006, the clinical examination revealed a cervical syndrome with pain in the left upper limb and the neurological examination showed bicipital paresis on the left side and no tricipital reflex.

    Pre-operative MRI (November 2005 and April 2006) and oblique X-rays
    The initial MRI (November 2005) showed a C5-C6 left foraminal stenosis due to osteophyte formation. The oblique X-rays confirmed the C5-C6 left side foraminal stenosis.

    A second MRI (April 4, 2006) confirmed the initial diagnosis.

    On May 26, 2006 the patient underwent surgery for C5-C6 discectomy by anterior approach (Cloward technique) and left side postero-lateral bony decompression, followed by disc arthroplasty with Dicocerv - Cervidisc evolution prosthesis. Per-operative radiological control of the prosthesis location was performed (AP and lateral X-rays views). Neither per-operative nor immediate post-operative complications were reported.

    Post-operative X-rays (three month follow-up) : neutral lateral + lateral bending + flexion/extension
    Post-operative three months follow-up: Dynamic functional X-rays show the restoration of mobility both in lateral bending and in flexion- extension. All neurological symptoms were fully relieved. The patient experiences mild fatigue-related discomfort at the end of the day but is fully satisfied with the result of the surgery. He resumed his previous job and all daily life activities.

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