Purpose of the study. In a recent study, O'Leary et al. [2005] reported their observations on the patterns of Charité disc prosthesis motion under physiologic loads. The purpose of this study was to investigate whether the motion patterns observed in the in vitro model are replicated in clinical practice. Methods. 55 patients with implanted SB Charité 111 artificial lumbar discs were subjected to flexion extension x-rays. Two consultant spinal surgeons and a neuro-radiological consultant were asked to classify the pattern of motion in the clinical subjects based on the patterns observed in the in vitro model. The results were recorded independently then collated. Following this first round of observations an algorithm was devised and the method of measurement was standardised. Summary of findings: There was modest correlation amongst the three observers in distinguishing motion from nonmotion (Kappa 5.6). There was less agreement on what type of motion was present. On both counts using the algorithm there was no correlation. The clinical study based on patients' flexion-extension radiographs identified the following patterns of prosthesis motion:. angular motion between both the upper and lower endplates and core, with visual evidence of core motion;. angular motion predominantly between the upper endplate and core, with little visual evidence of core motion;. lift-off of upper prosthesis endplate from core or of core from lower endplate;. core entrapment and deformation; and. no motion. There are difficulties associated with the interprtation of these using only flexion extension views. Conclusions. In devising artificial discs the requirement would be to replicate spinal motion as closely as possible. O'Leary et al have found non-physiological motions in in vitro models. These have been found in this clinical study but interobserver correlations were far from conclusive. Demonstrating non physiological patterns may have important implications for outcome

Introduction

The viscoelastic cervical disk prosthesis ESP is an innovative one-piece deformable but cohesive interbody spacer. It is an evolution of the LP ESP lumbar disk implanted since 2006. CP ESP provides 6 full degrees of freedom about the 3 axes including shock absorption. The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion (figure 1)

It thus differs substantially from current prostheses. This study reports the results of a prospective series of 49 patients who are representative of the current use of the ESP implant since 2012.

Introduction

The ESP prosthesis is a one-piece deformable but cohesive interbody spacer. it provides 6 full degrees of freedom about the 3 axes including shock absorption (fig1). The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion in this “silentblock” implant. It thus differs substantially from current prostheses.

Introduction

The viscoelastic lumbar disk prosthesis ESP is an innovative one-piece deformable but cohesive interbody spacer; it provides 6 full degrees of freedom about the 3 axes including shock absorption. The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion. It thus differs substantially from current prostheses. This study reports the results of a prospective series of 120 patients who are representative of the current use of the ESP implant since 2006.

Background. There have been limited published reports on the clinical results of cervical artificial disc replacement. Goffin et al reported a 90% rate of good to excellent results at 1 to 2 yrs after Bryan disc replacement. Wigfield et al reported a 46% improvement in pain and 31% improvement in disability 2 yrs after Prestige cervical disc replacement. Objectives. The study was designed to determine whether new functional cervical disc prosthesis can provide improvement in the ability to perform activities of daily living, decrease pain and segmental motion. Methods. All patients who had Prestige cervical disc replacement over last 2yrs 3 months were identified. Oswestry disability index score and SF36 Quality of life instrument were administered to each patient. Site specific pain scores were obtained using visual analogue scale. Clinical and operative details were reviewed and correlated. Results. 35 Patients underwent 48 Prestige cervical disc replacement during study period. There was 48%, 54% and 70% improvement in Oswestry disability index at 6 weeks, 6 months and 19 months follow-ups respectively. There was significant improvements in both neck and arm pain during immediate post op period and during further follow-ups. There was one neck wound haematoma and one left sided Horner's syndrome as complications. Conclusion. Anterior cervical disc replacement is a viable surgical alternative to fusion for cervical disc degenerative disease and herniation with preservation of motion and alignment without compromising clinical outcomes. At least 5yrs follow-up will be needed to assess the long term functionality of the prosthesis and protective influence on the adjacent levels