• Proceedings of the KSME Conference
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• 2000.04a
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• pp.387-392
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• 2000

In cementless total hip replacement(THR), an initial stability of the femoral component is important to long term fixation of femoral stem. The initial stability has close relationship with the relative displacement of prosthesis and spongy bone at the proximal of femur. After implantation of the prosthesis. the surrounding bone is partially shielded from load carrying and starts to resort. Stress shielding is the cause of the loss of proximal bone. Assessing stress distribution of femur is important to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and a stair climbing. Three types of stems were studied by the finite element method to analyze the biomechanical effects of distal filling of cementless femoral stems, Three types of stems employed are a distal filling stem, a distal flexible stem, and a distal tapered stem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2777-2785
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• 2000

In cementless total hip replacement(THR), an initial stability of the femoral component is important to long term fixation of femoral stem. The intial stability has close relationship with the relative displacement of prosthessis and sponge bone at the proximal of femur. After implantation of the proshesis, the surrounding bone is partially shielded from load carrying and starts to resorb. Stress shielding is the cause of the loss of proximal bone. Assessing stress distribution of femur is important to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and a stair climbing. Three types of stems were studied by the finite element method to analyze the biomechanical effects of distal filling of cementless femoral stems. Three types of stems empolyed are a distal filling stem, a distal flexible stem, and a distal tapered stem.

• Hip & pelvis
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• v.30 no.4
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• pp.241-253
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• 2018

Purpose: This study was conducted to compare cemented and cementless bipolar hemiarthroplasty in elderly patients with unstable intertrochanteric fractures via meta-analysis and systematic review of relevant studies. Materials and Methods: Systematic review and meta-analysis were performed on 31 available clinical studies; 19 of these studies used cemented stems, 12 used cementless stems, one used both types of stems, and two studies involved a comparative analysis of both stem types. Results: There were statistically significant differences in rates of leg length discrepancy (LLD) greater than 1 cm between the cemented (event rate, 0.089) and cementless groups (event rate, 0.015 and 0.047; P=0.03). Conclusion: Cemented bipolar hemiarthroplasty and cementless bipolar hemiarthroplasty performed on elderly patients with unstable intertrochanteric fracture revealed similar mortality and complication rates; however, the rate of LLD greater than 1 cm was significantly higher in the cemented group compared with the cementless group.

• Hip & pelvis
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• v.30 no.4
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• pp.210-218
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• 2018

Purpose: This is a report on the outcomes associated with a consecutive series of 1,000 cementless hip arthroplasties utilizing the $Bencox^{(R)}$ hip stem-the first Korean-developed hip prosthesis. Materials and Methods: A consecutive series of 1,000 hip arthroplasties using the $Bencox^{(R)}$ hip stem were analyzed, starting from its initial release (September 2006) until June 2014. Patients in this consecutive series underwent surgery for fractures (n=552), arthritis (n=155), avascular necrosis (n=209), and revisions (n=84). Of these 1,000 cases, patients with a minimum follow-up of at least 1 year (n=616) were retrospectively analyzed for radiographic and clinical outcomes (i.e., Harris hip score). The stability of the prosthesis was evaluated by examining subsidence. Results: During the follow-up period (mean follow-up period of 54.8 months), there were 2 cases requiring revision of the femoral stem-both were caused by periprosthetic fractures and neither involved stem loosening. The mean Harris hip score during follow-up was 95.5. Bone ongrowth occurred in 95% of patients; no cases of subsidence or aseptic loosening of the stem were detected, and no cases of postoperative complications such as ceramic breakage were observed. Conclusion: Clinical and radiographic evaluations of hip arthroplasty using the $Bencox^{(R)}$ hip stem revealed excellent outcomes with an average of 54.8 month follow-up in a consecutive series of 1,000 cases.

• Advances in biomechanics and applications
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• v.1 no.3
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• pp.187-210
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• 2014

With the goal of increasing the survivorship of the prosthesis and anticipating primary stability problems of new prosthetic implants, finite element evaluation of the micromotion, at an early stage of the development, is mandatory. This allows assessing and optimizing different designs without manufacturing prostheses. This study aimed at investigating, using finite element analysis (FEA), the difference in the prediction of the primary stability of cementless hip prostheses implanted into a $Sawbones^{(R)}$ 4th generation, using the manufacturer's mechanical properties and using mechanical properties close to that of human bone provided by the literature (39 papers). FEA was carried out on the composite $Sawbones^{(R)}$ implanted with a straight taper femoral stem subjected to a loading condition simulating normal walking. Our results show that micromotion increases with a reduction of the bone material properties and decreases with the augmentation of the bone material properties at the stem-bone interface. Indeed, a decrease of the cancellous Young modulus from 155MPa to 50MPa increased the average micromotion from $29{\mu}m$ up to $41{\mu}m$ (+42%), whereas an increase of the cancellous Young modulus from 155MPa to 1000MPa decreased the average micromotion from $29{\mu}m$ to $5{\mu}m$ (-83%). A decrease of cortical Young modulus from 16.7GPa to 9GPa increase the average global micromotion from $29{\mu}m$ to $35{\mu}m$ (+33%), whereas an increase of the cortical Young modulus from 16.7GPa to 21GPa decreased the average global micromotion from $29{\mu}m$ to $27{\mu}m$ (-7%). It can also be seen that the material properties of the cancellous structure had a greater influence on the micromotion than the material properties of the cortical structure. The present study shows that micromotion predicted at the stem-bone interface with material properties of the $Sawbones^{(R)}$ 4th generation is close to that predicted with mechanical properties of human femur.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.12
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• pp.71-74
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• 1994

In cementless total hip arthroplasty(THA), an initial stability of the femoral component is mandatory to achieve bony ingrowth and secondary long term fixation. Bone ingrowth depends strongly on relative micromotion and stress distributions at the interface. Primary stability of the femoral component can be obtained by minimizing the magnitude of relative micromotions at bone-prosthesis interface, Hence an accurate evaluation of interface behavior and stress/strain fields in the bone implant system may be relevant for better understanding of clinical situations and improving THA design. However, complete evaluation of load transfer in the bone remains difficult to assess experimentally, Hence, recently finite element method (FEM) was introduced in orthopaedic research field to fill the gap due to its unique capacity to evaluate stress in structure of complex shape, loading and material behavior. The authors developed the 3-dimensional numerical finite element model which is composed of totally 1179 elements off and 8 node blick. We also analyzed the micromotions at the bone-stem interface and mechanical behavior of existing bone prosthesis for a loading condition simulating the single leg stance. The result indicates that the values of relative motion for this well fit Multilock stem were $150{\mu}m$ in maximum, $82{\mu}m$ in minimum, and the largest relative motion developed in medial region of proximal femur with anterior-posterior direction. The proximal region of the bone was much larger in motion than the distal region and the stress pattern shows high stress concentration on the cortex near the tip of the stem. These findings indicates that the loading in the proximal femoral bone in the early postoperative situation can produce micromotions on the interface and clinically cementless TEA patient should not be allowed weight bearing strictly early in the postoperative period.

• Hip & pelvis
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• v.35 no.2
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• pp.88-98
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• 2023

Purpose: The objectives of this study were to examine the prevalence and risk factors for development of periprosthetic occult femoral fractures during primary cementless total hip arthroplasty (THA) and to assess the clinical consequences of these fractures. Materials and Methods: A total of 199 hips were examined. Periprosthetic occult femoral fractures were defined as fractures not detected intraoperatively and on postoperative radiographs, but only observed on postoperative computed tomography (CT). Clinical, surgical, and radiographic analysis of variables was performed for identification of risk factors for periprosthetic occult femoral fractures. A comparison of stem subsidence, stem alignment, and thigh pain between the occult fracture group and the non-fracture group was also performed. Results: Periprosthetic occult femoral fractures were detected during the operation in 21 (10.6%) of 199 hips. Of eight hips with periprosthetic occult femoral fractures that were detected around the lesser trochanter, concurrent periprosthetic occult femoral fractures located at different levels were detected in six hips (75.0%). Only the female sex showed significant association with an increased risk of periprosthetic occult femoral fractures (odds ratio for males, 0.38; 95% confidence interval, 0.15-1.01; P=0.04). A significant difference in the incidence of thigh pain was observed between the occult fracture group and the non-fracture group (P<0.05). Conclusion: Occurrence of periprosthetic occult femoral fractures is relatively common during primary THA using tapered wedge stems. We recommend CT referral for female patients who report unexplained early postoperative thigh pain or developed periprosthetic intraoperative femoral fractures around the lesser trochanter during primary THA using tapered wedge stems.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.263-266
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• 1997

Three dimensional numerical model based on the finite element method(FEM) were developed to predict the mechanical behavior of hip implants. The purpose of this study is to investigate the stress distribution of two types of cementless total hip replacement femoral component -a straight stem and a curved stem, and to compare their effect on the stress shielding between two types by three dimensional finite element method. The authors analyzed von Mises stress in the cortex & stem and compared the stress between the straight and the curved stem. In comparison of stresses between two different design of femoral stem, there was 25% more decrease of stress in straight stem than curved stem in the medial cortex at proximal region. The straight stem had consistently much lower stresses than the curved stem throughout the whole medial cortex with maximum 70% reduction of stress. However, there was little change in stress between nature and 2 implanted femur throughout the lateral cortex. Stress of femoral stem was much higher in the straight stem than the curved stem up to 60%. The straight stem had more chance of stress shielding and a risk of fatigue fracture of the stem compared with the curved stem in noncement hip arthroplasty. In design of femoral stem still we have to consider to develop design to distribute more even stress on the proximal medial cortex.

• Journal of Veterinary Clinics
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• v.36 no.1
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• pp.53-61
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• 2019

Total hip arthroplasty (THA) is a successful surgical treatment for both patients with chronical lameness and dogs who are nonresponsive to medical treatments, providing excellent joint function for returning dogs to the normal gait in 80% to 98% of hip dysplasia (HD) patients. The THA surgical implant system manufactured by BioMedtrix and Kyon are today widely accepted. When comparing the BioMedtrix biological fixation (BFX) system to the BioMedtrix cemented fixation (CFX) system, the many advantages of BFX, which include longer potential implant life, decreased risk of postoperative or later infection, and better implant stability, become evident. However, BFX implies a greater risk of femoral fracture during reaming and requires a more precise surgical technique to achieve good implant fit, given the press-fit nature of cementless THA. The purposes of this study are to both describe the mistakes and complications during stem implantation for beginner surgeons with both the BFX and the CFX systems and to document the initial result of 12 implantations in canine cadavers. Given the detailed evaluations of 3 specialists, who are Diplomate American College of Veterinary Surgeons (DACVS), only 3 of 11 stems were appropriately sized. Specifically, 6 stems were anteverted rather than being retroverted; further, although 7 stems were coaxial with the femoral long axis in the frontal plane, the other stems were in the varus at the frontal plane, with the proximal medial stem adjacent to the medial femoral cortex. Moderate angulation from the cranial to the caudal directions was found in 4 cases in the sagittal plane. Additionally, 1 case of femoral fissure and 1 case of perforated femoral cortex were reported. It is not easy for surgeons performing cementless THA for the first time to achieve a good result, even though they completed an educational course about it and given that catastrophic complications often occurred during early surgical clinical cases. Therefore, ex-vivo studies are sincerely required to get an expertise by rehearsing the preparation of the femoral envelop in isolated bones. Further studies should be conducted to achieve both highly accurate implant size and correct orientation during the preoperative planning. Additionally, surgeons' learning curve should be examined in future investigations.

• Hip & pelvis
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• v.35 no.2
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• pp.99-107
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• 2023

Purpose: Bipolar hemiarthroplasty has recently been acknowledged as an effective option for treatment of unstable intertrochanteric fracture. Trochanteric fragment nonunion can cause postoperative weakness of the abductor muscle and dislocation; therefore, reduction and fixation of the fragment is essential. The purpose of this study was to perform an evaluation and analysis of the outcomes of bipolar hemiarthroplasty using a useful wiring technique for management of unstable intertrochanteric fractures. Materials and Methods: A total of 217 patients who underwent bipolar hemiarthroplasty using a cementless stem and a wiring technique for management of unstable intertrochanteric femoral fractures (AO/OTA classification 31-A2) at our hospital from January 2017 to December 2020 were included in this study. Evaluation of clinical outcomes was performed using the Harris hip score (HHS) and the ambulatory capacity reported by patients was classified according to Koval stage at six months postoperatively. Evaluation of radiologic outcomes for subsidence, breakage of wiring, and loosening was also performed using plain radiographs at six months postoperatively. Results: Among 217 patients, five patients died during the follow-up period as a result of problems unrelated to the operation. The mean HHS was 75±12 and the mean Koval category before the injury was 2.5±1.8. A broken wire was detected around the greater trochanter and lesser trochanter in 25 patients (11.5%). The mean distance of stem subsidence was 2.2±1.7 mm. Conclusion: Our wiring fixation technique can be regarded as an effective additional surgical option for fixation of trochanteric fracture fragments during performance of bipolar hemiarthroplasty.