• Progress in Medical Physics
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• v.19 no.3
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• pp.157-163
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• 2008

Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa or age-related macular degeneration. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we investigated differences of the retinal waveforms in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). $8{\times}8$ grid layout MEA (electrode diameter: $30{\mu}m$, electrode spacing: $200{\mu}m$, and impedance: 50 $k{\Omega}$ at 1 kHz) was used to record in-vitro retinal ganglion cell activity. In normal mice (C57BL/6J strain) of postnatal day 28, only short duration (<2 ms) retinal spikes were recorded. In rd/rd mice (C3H/HeJ strain), besides normal spikes, waveform with longer duration (~100 ms), the slow wave component was recorded. We attempted to understand the mechanism of this slow wave component in degenerate retina using various synaptic blockers. We suggest that stronger glutamatergic input from bipolar cell to the ganglion cell in rd/rd mouse than normal mouse contributes the most to this slow wave component. Out of many degenerative changes, we favor elimination of the inhibitory horizontal input to bipolar cells as a main contributor for a relatively stronger input from bipolar cell to ganglion cell in rd/rd mouse.

• Clinics in Shoulder and Elbow
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• v.14 no.1
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• pp.140-145
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• 2011

Purpose: Installing a radial head prosthesis has developed into a reliable procedure to replace the native radial head for treating unreconstructible radial head fracture when this is associated with an unstable elbow or forearm. A variety of implants have been developed and these are now commercially available. This article reviews the literature related to the indications, the available implants and the surgical techniques of radial head replacement arthroplasty. Materials and Methods: The main indication for a metallic radial head prosthesis is a comminuted fracture that is not amenable to reconstruction, and particularly if it is associated with complex elbow injuries. Excision of the radial head should be avoided in the presence of combined injured ligaments or interosseous membrane injury. Three different implants are available in Korea, including the bipolar, press fit monopolar and loose fit monopolar radial head prostheses. A primary technical goal of radial head arthroplasty is the insertion of an implant that closely replicates the native radial head. The major pitfall when using a metallic radial head prosthesis is the insertion of a longer implant, which results in overstuffing of the radiocapitellar joint. Results and Conclusion: Satisfactory clinical results can be anticipated when a radial head prosthesis is used for the correct indications and when a systemic approach is undertaken to ensure proper sizing. For the future studies, we need data regarding the long term outcomes and comparison of the various types of prostheses.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2002.10a
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• pp.11-19
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• 2002

This prospective clinical study evaluates the 5-10 year results of the BiPolar shoulder Arthroplasty in patients with end-stage RotatorCuff Arthropathy. The study group consisted of 48 patients (59 shoulders). Average age was 72 years and average FU time was 73 months. Results showed that the average UCLA score went from 7.9 Pre-op to 23.3 Post-op. Final Constant score averaged $52\% (unadjusted). Pain relief using the VAS was 1.2(were 0=no pain. 15 = excruciating pain). ROM improved by an average of $20^\circ$. There were 2 reoperations because of periprosthetic fractures. Despite rather poor functional results, these patients were satisfied with their pain relief and the functional gains accompanying pain relief would be an added benefit.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2002.10a
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• pp.125-134
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• 2002

This is a prospective study in which we evaluate the 5-10 year results of BiPolar shoulder arthroplasty in 64 patients (71 shoulders) with primary glenohumeral osteoarthritis. Fifty two patients (56 shoulders) were followed for greater than 60 months (average 79months)1 and no patients were lost to follow Lip. The average age of the patient at operation was 72.5 years. The UCLA score increased from 10.8 preoperatively to 25,7 postoperatively. The final Constant score in this elderly subset of patients averaged $65\%$ (unadjusted). Eighty seven percent of patients were satisfied with their final result. Excellent pain relief was achieved with a VAS of 2.5 (0=no pain, 15=excruciating pain). Active anterior forward flexion improved from $45^{\circ}$ to $104^{\circ}$. Seventy five percent of patients reveal persisting head-shell motion at an average of 7 years. There were two reoperations because of humeral stem loosening; both stems should have been cemented at the initial arthroplasty. It is demonstrated that BiPolar shoulder arthroplasty is durable over time, with clinical results equivalent to that in the literature when compared with hemiarthroplasty and total shoulder replacement.