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Background: To date there are yet no available approved therapies for Geographic Atrophy (GA) secondary to age-related macular degeneration (AMD). Methods: Single site, non-randomized safety and efficacy study presenting the preliminary results in a cohort of five late stage AMD (GA) patients successfully implanted with the Argus II Retinal Prosthesis System (Second Sight Medical Products Inc., Sylmar, CA, USA). Extensive fundus imaging including retinal photographs from which the GA area was measured. A combination of custom and traditional tests designed for very low vision subjects assessed visual function in study subjects. A Functional Low-Vision Observer Rated Assessment was carried out to evaluate the impact of the system on the subject’s daily life. In addition, a study to evaluate structural characteristics of the visual cortex of the brain was performed in one subject using magnetic resonance imaging. Results: Seven device-related adverse events were reported, four of which were classed as serious adverse events. Retinal detachment was reported in three patients and was successfully treated within 12 months of onset. Testing showed an improvement in visual function in three of five patients with the system turned on. Magnetic resonance imaging assessed in one patient after implantation indicates a selective increase in cortical myelin and thickness in visual brain regions 1 year post implantation. Conclusions: Epiretinal prostheses can successfully be implanted in those affected by GA secondary to late-stage AMD and can elicit visual percepts by electrical stimulation of residual neuroretinal elements and improve basic visual function in those affected.

Purpose To analyze and provide an overview of the incidence, management, and prevention of conjunctival erosion in Argus II clinical trial subjects and postapproval patients. Methods This retrospective analysis followed the results of 274 patients treated with the Argus II Retinal Prosthesis System between June 2007 and November 2017, including 30 subjects from the US and European clinical trials, and 244 patients in the postapproval phase. Results were gathered for incidence of a serious adverse event, incidence of conjunctival erosion, occurrence sites, rates of erosion, and erosion timing. Results Overall, 60% of subjects in the clinical trial subjects versus 83% of patients in the postapproval phase did not experience device- or surgery-related serious adverse events. In the postapproval phase, conjunctival erosion had an incidence rate of 6.2% over 5 years and 11 months. In 55% of conjunctival erosion cases, erosion occurred in the inferotemporal quadrant, 25% in the superotemporal quadrant, and 20% in both. Sixty percent of the erosion events occurred in the first 15 months after implantation, and 85% within the first 2.5 years. Conclusion Reducing occurrence of conjunctival erosion in patients with the Argus II Retinal Prosthesis requires identification and minimization of risk factors before and during implantation. Implementing inverted sutures at the implant tabs, use of graft material at these locations as well as Mersilene rather than nylon sutures, and accurate Tenon's and conjunctiva closure are recommended for consideration in all patients.

The Argus II retinal prosthesis (Second Sight Medical Products, Sylmar, CA, USA) is an electronic epiretinal implant designed for use in patients with end-stage retinitis pigmentosa, as well as for other outer retinal degenerative conditions, such as choroideremia, Leber’s congenital amaurosis, Bardet-Biedl syndrome, Usher syndrome and rod–cone disease.1 This device was tested in a clinical trial of 30 subjects in the USA and in Europe to measure the rate of serious adverse events (SAEs) and to assess its effects on functional vision and visual acuity.2–4 Subjects performed better on visual tasks with the device turned on and retained these improvements at 5 years postsurgery.4 Additionally, an acceptable safety profile enabled approval of the device for consumer use by the European regulatory authorities in 2011 (Conformite Europeenne (CE) mark) and by the US Food and Drug Administration (FDA) in 2013 (FDA approval). The implant is composed of an extraocular component, namely, an electronics case and implant coil, as well as an intraocular component involving a 60-electrode array that is tacked over the macula (figure 1). The extraocular and intraocular components are connected by a trans-scleral silicone-coated polyamide electrode cable, and the implantation procedure involves a 5.2 mm pars plana sclerotomy incision to insert the electrode array and the electrode cable into the eye. The sclerotomy is then sutured around the cable and covered by an allograft or autograft material.5 Figure 1 The Argus II retinal prosthesis. Labelled image of the Argus II implant (adapted from Humayun et al 2). As with any system having both intraocular and extraocular components, the trans-scleral electrode cable that traverses the sclerotomy permanently is a high-risk feature of the device, as leakage through the pars plana incision can result in chronic hypotony. The percentages of clinical trial subjects who experienced hypotony were 10.0% at …

Background Retinal prosthesis systems (RPS) are a novel treatment for profound vision loss in outer retinal dystrophies. Ideal prostheses would offer stable, long-term retinal stimulation and reproducible spatial resolution in a portable form appropriate for daily life. Methods We report a prospective, internally controlled, multicentre trial of the Argus II system. Twenty-eight subjects with light perception vision received a retinal implant. Controlled, closed-group, forced-choice letter identification, and, open-choice two-, three- and four-letter word identification tests were carried out. Results The mean±SD percentage correct letter identification for 21 subjects tested were: letters L, T, E, J, F, H, I, U, 72.3±24.6% system on and 17.7±12.9% system off; letters A, Z, Q, V, N, W, O, C, D, M, 55.0±27.4% system on and 11.8%±10.7% system off, and letters K, R, G, X, B, Y, S, P, 51.7±28.9% system on and 15.3±7.4% system off. (p

Hypothesis: We hypothesized that the malpositioning of the humeral component can preclude the long-term success of anatomical total shoulder arthroplasty. The goal of this study was to evaluate the mechanical consequences of superior and inferior malpositioning of the humeral head. Materials and methods: A numerical musculoskeletal model of the shoulder joint allowing natural humeral head translation was used to simulate a loaded abduction movement controlled by muscular activation. An inferior and superior malpositioning of 5 mm were compared to an optimal positioning. Impingements, articular contact pattern, and cement stress were evaluated. Results: Inferior malpositioning of the humeral head induced impingement and limited the abduction level, while superior malpositioning increased the subluxation risk. Both inferior and superior malpositioning increased the stress level within the cement mantle. Discussion: This numerical study highlights the importance of an anatomical reconstruction of the glenohumeral surfaces for the success rate of anatomical total shoulder arthroplasty.

Reversed shoulder prostheses are increasingly being used for the treatment of glenohumeral arthropathy associated with a deficient rotator cuff. These non-anatomical implants attempt to balance the joint forces by means of a semi-constrained articular surface and a medialised centre of rotation. A finite element model was used to compare a reversed prosthesis with an anatomical implant. Active abduction was simulated from 0° to 150° of elevation. With the anatomical prosthesis, the joint force almost reached the equivalence of body weight. The joint force was half this for the reversed prosthesis. The direction of force was much more vertically aligned for the reverse prosthesis, in the first 90° of abduction. With the reversed prosthesis, abduction was possible without rotator cuff muscles and required 20% less deltoid force to achieve it. This force analysis confirms the potential mechanical advantage of reversed prostheses when rotator cuff muscles are deficient.

Reference LBO-PRESENTATION-2008-036View record in Web of Science Record created on 2008-05-26, modified on 2017-05-10

INTRODUCTION Glenohumeral osteoarthritis is frequently associated with some amount of degenerative changes in the rotator cuff tendons, especially in the supraspinatus. Consequently, a partial dysfunction of the cuff may be observed after prosthetic shoulder replacement. This situation could preclude the survival of the implant. The aim of this study was therefore to analyze the biomechanical consequences of the supraspinatus deficiency after an anatomic shoulder arthroplasty.

Anatomic total shoulder arthroplasty is an accepted treatment for degenerative pathologies of the glenohumeral joint. However, when degenerative changes in the supraspinatus tendon are expected, it has been proposed to tilt downward the glenoid implant to avoid excessive upward humerus migration and eccentric loading of the glenoid. The advantage of glenoid tilting on joint stability has been measured on cadavers [Konrad, 2006] and bone substitutes [Oosterom, 2004], but its effect on glenoid stress is unknown. The goal of this study was evaluate the effect of a downward tilting of the glenoid when the supraspinatus muscle is deficient.

Wear of polyethylene is associated with aseptic loosening of orthopaedic implants and has been observed in hip and knee prostheses and anatomical implants for the shoulder. The reversed shoulder prostheses have not been assessed as yet. We investigated the volumetric polyethylene wear of the reversed and anatomical Aequalis shoulder prostheses using a mathematical musculoskeletal model. Movement and joint stability were achieved by EMG-controlled activation of the muscles. A non-constant wear factor was considered. Simulated activities of daily living were estimated from in vivo recorded data. After one year of use, the volumetric wear was 8.4 mm3 for the anatomical prosthesis, but 44.6 mm3 for the reversed version. For the anatomical prosthesis the predictions for contact pressure and wear were consistent with biomechanical and clinical data. The abrasive wear of the polyethylene in reversed prostheses should not be underestimated, and further analysis, both experimental and clinical, is required.

A combined experimental/numerical study was performed to calculate the 3D octahedral shear strain map in a mouse tibia loaded axially. This study is motivated by the fact that the bone remodelling analysis, in this in vivo mouse model should be performed at the zone of highest mechanical stimulus to maximise the measured effects. Accordingly, it is proposed that quantification of bone remodelling should be performed at the tibial crest and at the distal diaphysis. The numerical model could also be used to furnish a more subtle analysis as a precise correlation between local strain and local biological response can be obtained with the experimentally validated numerical model.

Hypothesis: Supraspinatus deficiency associated with total shoulder arthroplasty (TSA) provokes eccentric loading and may induce loosening of the glenoid component. A downward inclination of the glenoid component has been proposed to balance supraspinatus deficiency. Methods: This hypothesis was assessed by a numeric musculoskeletal model of the glenohumeral joint during active abduction. Three cases were compared: TSA with normal muscular function, TSA with supraspinatus deficiency, and TSA with supraspinatus deficiency and downward inclination of the glenoid. Results: Supraspinatus deficiency increased humeral migration and eccentric loading. A downward inclination of the glenoid partly balanced the loss of stability, but this potential advantage was counterbalanced by an important stress increase within the glenoid cement. The additional subchondral bone reaming required to incline the glenoid component indeed reduced the bone support, increasing cement deformation and stress. Conclusion: Glenoid inclination should not be obtained at the expense of subchondral bone support. Level of evidence: Basic science study

Background. Reversed shoulder arthroplasty is an accepted treatment for glenohumeral arthritis associated to rotator cuff deficiency. For most reversed shoulder prostheses, the baseplate of the glenoid component is uncemented and its primary stability is provided by a central peg and peripheral screws. Because of the importance of the primary stability for a good osteo-integration of the baseplate, the optimal fixation of the screws is crucial. In particular, the amplitude of the tightening force of the non-locking screws is clearly associated to this stability. Since this force is unknown, it is currently not accounted for in experimental or numerical analyses. Thus, the primary goal of this work is to measure this tightening force experimentally. In addition, the tightening torque was also measured, to estimate an optimal surgical value. Methods. An experimental setup with an instrumented baseplate was developed to measure simultaneously the tightening force, tightening torque and screwing angle, of the nonlocking screws of the Aquealis reversed prosthesis. In addition, the amount of bone volume around each screw was measured with a micro-CT. Measurements were performed on 6 human cadaveric scapulae. Findings. A statistically correlated relationship (p < 0.05, R = 0.83) was obtained between the maximal tightening force and the bone volume. The relationship between the tightening torque and the bone volume was not statistically significant. Interpretation. The experimental relationship presented in this paper can be used in numerical analyses to improve the baseplate fixation in the glenoid bone.