• Journal of the Korean Orthopaedic Association
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• v.56 no.3
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• pp.253-260
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• 2021

Purpose: The least constrained prosthesis is generally recommended in primary total knee arthroplasty (TKA). Nevertheless, a varus/valgus constrained (VVC) prosthesis should be implanted when a semi-constrained prosthesis is not good for adequate stability, especially in the coronal plane. In domestic situations, however, the VVC prosthesis could not always be prepared for every primary TKA case. Therefore, it is sometimes impractical to use a VVC prosthesis for unsual unstable situations. This study provides information for preparing VVC prostheses in the preoperative planning of primary TKA through an analysis of primary VVC TKA cases. Materials and Methods: This study reviewed 1,797 primary TKAs, performed between May 2003 and February 2016. The reasons for requiring VVC prosthesis and the preoperative conditions in 29 TKAs that underwent primary TKA with a VVC prosthesis were analyzed retrospectively. Results: In primary TKA, 29 cases (1.6%) in 27 patients (6 male and 21 female) used VVC prosthesis. Two patients underwent a VVC prosthesis on both knees. The mean age of the patients was 63.4 years old (34-79 years). The mean flexion contracture was 16.2° (-20°-90°), and the mean angle of great flexion was 111.7° (35°-145°). The situations requiring a VVC prosthesis were severe valgus deformity in 10 knees, knee stiffness requiring extensive soft tissue release in 10 knees, previously injured collateral ligaments in five knees, and distal femoral bone defect due to avascular necrosis in four knees. The mean tibiofemoral angle was 25.7° (21°-43°) in 10 cases with a valgus deformity. The mean flexion contracture was 37.5° (20°-90°), and the mean range of motion was 48.5° (10°-70°) in 10 cases with knee stiffness. Conclusion: The preparation of VVC prosthesis is recommended, even for primary TKA in cases of severe valgus deformity (tibiofemoral angle>20°), stiff knee (the range of motion: less than 70° with more than 20° flexion contracture), and the cases with a previous collateral ligament injury. This information will help in the preparation of adequate TKA prostheses for unusual unstable situations.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2002.10a
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• pp.177-179
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• 2002

Total elbow prostheses which are now available in clinical use can generally be classified into two major categories ; one bing linked prostheses, another being unlinked prostheses. Of those two categories I am dealing here only with the problems of the unlinked type prosthesis, particularly with those of non-constrained, surface-replacement prostheses. Furthermore, my presentations this time may have to be narrowed down only to the topics regrading the particular features and some of the technical problems with Kudo Elbow Prosthesis, due to the time limit assigned for this presentation.

• Clinics in Shoulder and Elbow
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• v.14 no.1
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• pp.105-110
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• 2011

Purpose: The purpose of this article is to identify and understand the complications of RTSA and to review the current methods of preventing and treating this malady. Materials and Methods: Previous constrained prostheses (ball-and-socket or reverse ball-and-socket designs) have failed because their center of rotation remained lateral to the scapula, which has limited of the motion of the prostheses and produced excessive torque on the glenoid component, and this leads to early loosening. The Grammont reverse prosthesis imposes a new biomechanical environment for the deltoid muscle to act, thus allowing it to compensate for the deficient rotator cuff muscles. Results: The clinical experience does live up to the lofty biomechanical concept and expectations: the reverse prosthesis restores active elevation above $90^{\circ}$ in patients with a cuff-deficient shoulder. However, external rotation often remains limited and particularly in patients with an absent or fat-infiltrated teres minor. Internal rotation is also rarely restored after a reverse prosthesis. Failure to restore sufficient tension in the deltoid may result in prosthetic instability. Conclusion: Finally, surgeons must be aware that the results are less predictable and the complication/revision rates are higher in revision surgery than that in the first surgery. A standardized monitoring tool that has clear definitions and assessment instructions is surely needed to document and then prevent complications after revision surgery.

• Biomaterials and Biomechanics in Bioengineering
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• v.5 no.1
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• pp.37-50
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• 2020

Development of lightweight implant plates are important to reduce the stress shielding effect for a prosthesis of femur bone fractures. Stainless steel (SS-316L) is a widely used material for making implants. Stress shielding effect and other issues arise due to the difference in mechanical properties of stainless steel when compared with bone. To overcome these issues, composite materials seem to be a better alternative solution. The comparison is made between two biocompatible composite materials, namely Ti-hydroxyapatite and Ti-polypropylene. "Titanium (Ti)" is fiber material while "hydroxyapatite" and "polypropylene" are matrix materials. These two composites have Young's modulus closer to the bone than stainless steel. Besides the variety of bones, present paper constrained to femur bone analysis only. Being heaviest and longest, the femur is the most likely to fail among all bone failures in human. Modelling of the femur bone, screws, implant and assembly was carried out using CATIA and static analysis was carried out using ANSYS. The femur bone assembly was analyzed for forces during daily activities. Ti-hydroxyapatite and Ti-polypropylene composite implants induced more stress in composite implant plate, results less stress induced in bone leading to a reduction in shielding effect than stainless steel implant plate thus ensuring safety and quick healing for the patient.

• Journal of Korean Neurosurgical Society
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• v.45 no.3
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• pp.169-175
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• 2009

Objective : The goal of this study was to evaluate the biomechanical features of human cadaveric spines implanted with the Activ L prosthesis. Methods : Five cadaveric human lumbosacral spines (L2-S2) were tested for different motion modes, i.e. extension and flexion, right and left lateral bending and rotation. Baseline measurements of the range of motion (ROM), disc pressure (DP), and facet strain (FS) were performed in six modes of motion by applying loads up to 8 Nm, with a loading rate of 0.3 Nm/second. A constant 400 N axial follower preload was applied throughout the loading. After the Activ L was implanted at the L4-L5 disc space, measurements were repeated in the same manner. Results : The Activ L arthroplasty showed statistically significant decrease of ROM during rotation, increase of ROM during flexion and lateral bending at the operative segment and increase of ROM at the inferior segment during flexion. The DP of the superior disc of the operative site was comparable to those of intact spine and the DP of the inferior disc decreased in all motion modes, but these were not statistically significant. For FS, statistically significant decrease was detected at the operative facet during flexion and at the inferior facet during rotation. Conclusion : In vitro physiologic preload setting, the Activ L arthroplasty showed less restoration of ROM at the operative and adjacent levels as compared with intact spine. However, results of this study revealed that there are several possible theoretical useful results to reduce the incidence of adjacent segment disease.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.117-117
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• 2016

Total ankle replacement (TAR) is a visible option in the surgical treatment of degenerative or inflammatory diseases of ankle joint. it is attributed to the current TAR which has improvements in surgical technique, uncemented implant fixation and minimally constrained articulation. In the clinical result, they can show promised surgical result when compared to earlier attempts in TAR. However, TAR is still not as successful as total knee replacement (TKR) or total hip replacement (THR), it needs to be note that there are limitations in concerning of long term performance of TAR, the high failure rate still associated with wear of the PE (polyethylene) component that has related with their material property and surface roughness. The aim of this study was to introduce the tribology characteristics of total ankle joint prosthesis with one of TDR model which was fabricated to try multi-axis wear test as a region of motion in ankle joint. The wear specimen of TDR was prepared with Ti-6Al-4V alloy and UHMWPE (ultra-high molecular weight polyethylene) for tibia-talus and bearing component, respectively. A wear test was carried out using a Force 5 (AMTI, Massachusetts, US) wear simulator which can be allowed to move in three axis to flexion-extension ($+3^{\circ}{\sim}-6^{\circ}$), internal-external axial rotation (${\pm}5^{\circ}$), as well as sinusoidal compressive load (1.6 kN, R=10). All tests were performed following standard ISO 14243, wear rate was calculated with weight loss of UHMWPE bearing while the specimen has tested at certain cycles. As based on the preliminary results, wear rate of UHMWPE bearing was $7.9{\times}10^{-6}mg/cycles$ ($R^2=0.86$), calculated loss weight until $10^7cycles$ was 79 mg, respectively.

• Journal of the Korean Orthopaedic Association
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• v.54 no.2
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• pp.110-119
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• 2019

Proximal humerus fracture can be defined as a fracture that occurs in the surgical neck or proximal part of the humerus. Despite the appropriate treatment, however, various complications and sequelae can occur, and the treatment is quite difficult often requiring surgical treatment, such as a shoulder replacement. The classification of sequelae after a proximal humerus fracture is most commonly used by Boileau and can be divided into two categories and four types. Category I is an intracapsular impacted fracture that is not accompanied by important distortions between the tuberosities and humeral head. An anatomic prosthesis can be used without greater tuberosity osteotomy. In category I, there are type 1 with cephalic collapse or necrosis with minimal tuberosity malunion and type 2 related to locked dislocation or fracture-dislocation. Category II is an extracapsular dis-impacted fracture with gross distortion between the tuberosities and the humeral head. To perform an anatomic prosthesis, a tuberosity osteotomy should be performed. In category II, there are type 3 with nonunion of the surgical neck and type 4 with severe tuberosity malunion. In type 1, non-constrained arthroplasty (NCA) without a tuberosity osteotomy should be considered as a treatment. On the other hand, reverse shoulder arthroplasty (RSA) should be considered if types 1C or 1D accompanied by valgus or varus deformity or severe fatty degeneration of the rotator cuff. In general, the results are satisfactory when NCA is performed in type 2 sequelae. On the other hand, RSA can be considered as an option when there is no bony defect of the glenoid and a defect of the rotator cuff is accompanied. In type 3, it would be effective to perform internal fixation with a bone wedge graft rather than shoulder replacement arthroplasty. Recent reports on the results of RSA are also increasing. On the other hand, recent reports suggest that good results are obtained with RSA in type 3. In type 4, RSA should be considered as a first option.