Recently, the combination of press-fit acetabular cup with ceramic articulation is a widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, these methods may lead to elevating stresses, changing in the bearing geometries, and increasing wear due to deformation of the cup and insert. In addition, there is a potential for failure of ceramic inserts when a large ball head was used because it should be assembled with shallow thickness of the acetabular cup. For risk reduction of it, we applied direct metal tooling (DMT) based on 3D printing for porous coating on the cup. Due to its capability of mechanical strength, DMT coated cup could be feasible to provide better stability than conventional coating. Therefore, we constructed laboratory models for deformation test simulating an press-fit situation with large ceramic ball head to evaluate stability of the DMT coated cup compared with conventional coated cup. The deformation test was performed according to the test setup described by Z. M. Jin et al. The under reaming of the cavity in a two-point pinching cavity models of polyurethane (PU) foam block (SAWBONES, Pacific Research Laboratories, USA) with a grade 30 were constructed. Titanium plasma spray (TPS) and direct metal tooling (DMT) coated acetabular cups (BENCOX Mirabo and Z Mirabo Cup, Corentec Co. Ltd., KOREA) with a 52 mm size (n=3, respectively) were used for the test. These cups were implanted into the PU foam blocks, and followed by impaction of the inserts (BIOLOX delta, Ceramtec, GE) with a 36/44 size (n=6) into the acetabupar cups as shown in Fig. 1. Roundness and inner diameter of the acetabular cups and inserts were measured using a coordinate measuring machine (BHN 305, Mitutoyo Neuss, GE) in three levels; E2, E3, and E4 (3, 5, and 7 mm below the front face, respectively). Also, these parameters of the acetabular cup were measured in two level; E1 and E5 (5 and 11 mm below the front face) as shown in Fig. 2. Changes in roundness and inner diameter of the cup and insert were measured to evaluate deformation in relation to porous coating on the acetabular cups.Introduction
Materials and Methods
Although thigh pain is an annoying problem after total hip arthroplasty (THA), little information has been known about its natural course. To determine the frequency, time of onset, and duration of thigh pain after cementless THA, we evaluated 240 patients (240 hips) who underwent primary THA because of femoral head osteonecrosis with the use of a single tapered stem.Background
Methods
The acetabular cup should be properly oriented to prevent dislocation and to reduce wear and leg length discrepancy. Despite advances in surgical techniques and instrumentation, achieving proper cup placement in total hip arthroplasty (THA) is challenging with potentially large variations of cup position and limited accuracy. We evaluated whether cup placement on anatomical location ensured original center of rotation (COR) and surgeon's experiences of THA reduced variations in acetabular component positioning. We retrospectively reviewed 145 patients (145 hips) of unilateral THAs with normal contralateral structures of acetabulum and femoral head. All surgeries were performed using the modified posterolateral approach that preserves short external rotator muscles. All of the 145 THAs were performed by two surgeons, who were in the same teaching hospital, but had differences in surgical experience and expertise for THA. The patients were divided into two groups based upon surgical experience: (1) the highly experienced surgeon's group: who had previously performed over 1000 THAs (YSK, 101 hips), and (2) the less experienced novice's group: who had performed fewer than 30 THAs (YWL, 44 hips). Real vertical distances, from the COR to the inter-tear drop line, and the real horizontal distances, from the COR to the lateral wall of the tear drop, were measured preoperatively using picture archiving communication system (PACS) based precise method. Postoperative ones were measured and equalized by use of a magnification marker placed on preoperative plain radiographs. And cup inclination was measured directly on the AP radiographs and anteversion was calculated by trigonometric functions. The patient's mean age was 52.1 years (range, 20–86).Introduction
Methods
Cementless arthroplasty has been widely used for younger patients with osteoarthritis and other joint pathology. Cementless arthroplasty will be required to porous surface which is to similar to the trabecular bone for bone ingrowth. Titanium Plasma Spray (TPS) has been worldwide used for the porous coating method on arthroplasty. However, TPS coating is limited that would not to establish optimal porosity for bone ingrowth due to arbitary position of melted powder by plasma gas on substrate. Therefore, it is reported coating detached from its substrate (i.e. arthroplasty) is induced implant loosening. Thus, a novel Laser-aided Direct Metal Tooling (DMT) based on Additive Manufacturing (AM) was developed to overcome these limitations. In this study, we were done to assess stereological analysis, static tensile, shear, abrasion test, and physical analysis for evaluation of the efficacy of DMT which was newly-developed coating technology. Then, mechanical characteristics of DMT coating were compared to commercial TPS coating's. First, porosity of the DMT coating was evaluated using Microphotography and Scanning Electron Microscopy (SEM), as described in Figure 1. Static tensile and shear test for assessment of mechanical characteristic in relation to the DMT and TPS coating specimens were conducted on the basis of ASTM F1147 and F1044 using universal testing machine (Endolab®, Servohydraulic Test Frame, DE). Maximum tensile strength and maximum shear strength were evaluated for each specimen (n=5). Abrasion test was performed based on ASTM F1978 using Taber® Rotary Platform Abraser Model 5135 (TABER®Industries, USA). Abrasion losses for each specimen (n=6) were measured at 2, 5, 10, and 100 cycles, respectively.Introduction
Materials and Methods
3-D Printing with direct metal tooling (DMT) technology was innovatively introduced in the field of surface treatment of prosthesis to improve, moreover to overcome the problems of plasma spray, hopefully resulting in opening the possibility of another page of coating technology. We presumed such modification on the surface of Co-Cr alloy by DMT would improve the ability of Co-Cr alloys to osseointegrate. We compared the in vitro and in vivo ability of cells to adhere to DMT coated Co-Cr alloy to that of two different types of surface modifications: machined and plasma spray(TPS). We performed energy-dispersive x-ray spectroscopy and scanned electron microscopy investigations to assess the structure and morphology of the surfaces. Biologic and morphologic responses to osteoblast cell lines of human were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase activity), and avb3 integrin. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the MAO group increased in comparison to those in the machined and grit-blasted groups.Introduction
Method
The osseointegration of implants is related to the early interactions between osteoblastic cells and titanium surfaces. The behavior of osteoblast cells was compared on four different titanium surfaces in vitro and in vivo: machined, blasted, plasma spray and micro-arc oxidation. X-ray diffraction and scanning electron microscope investigations were performed in order to assess the structure and morphology. Biologic and morphologic responses to the osteoblast cell lines (Saos-2) were then examined, using Promega proliferation assay, alkaline phosphatase activity, vβ3 integrin expression and cytoskeleton staining (Rhodamine-Phallodine). The analysis of gene expression for osteocalcin and collagen I was done through RT-PCR. In addition, differential histologic evaluation and interfacial strength at the bone-implant interfaces were then evaluated in the distal femur of four beagle dogs. In conclusion, micro-arc oxidation of titanium appears to exhibit more favorable osteoblast adhesion and stronger interfacial strength than the compared groups in vitro and in vivo as well.
Spinal fusion has been used as the gold standard to treat some spinal disorders such as degenerative disc or disc herniation of the cervical spine. However, some clinical complications have been reported caused by high stiffness of spinal fusion. Recently, total disc arthroplasty using motion preservation devices such as artificial discs (ADs) have been proposed as an alternative treatment technique. In current study, we analysed biomechanical influences including inter-segmental motion, facet joint forces, and ligament stresses of two different clinical available ADs and compared with those of intact cervical spine in various loading conditions using finite element analysis. A three dimensional finite element model was developed for C2-C7 spinal motion segment based on CT images and previous anatomical literatures. The finite element models for two different types of ADs, semi-constraint (Prodisc-C®, Synthes, U.S.A) and un-constraint (Mobi-C®, LDR Spine, U.S.A), were developed. Each AD was inserted at C6–C7 segments. Superior and inferior plates of ADs were fixed on inferior plane of C6 and superior plane of C7 vertebrae, respectively. Based on the conventional surgical techniques, anterior longitudinal ligaments and some parts of intervertebral disc in C6–C7 motion segment were removed to insert ADs. Inferior plane of C7 vertebra was constrained in all directions and 1Nm of flexion, extension, lateral bending and torsion were applied on superior plane of C2 vertebra with 50N of compressive load along follower load direction. Rotation angle in flexion of C5–C6 segment in cases of semi-constraint and un-constraint AD was 3.3° and 3.7°, respectively. Both values were greater than that in case of the intact cervical spine by 18% and 32%, respectively. Rotation angle in extension, lateral bending and torsion were greater than intact model by 45%, 26% and 43% for the case of semi-constraint AD and 55%, 35%, 100% for the case of un-constraint one, respectively. In extension, facet joint forces were about two times higher than intact model in cases of semi-constraint and un-constraint AD. Also in flexion, on average, ligament stresses in cases of semi-constraint and un-constraint AD were higher than intact model by 66% and 116%, respectively. The results of this study showed that ADs were useful to generate inter-segmental motion at surgical level. And the un-constraint type of AD had higher mobility than semi-constraint one. However, high mobility of ADs would lead not only higher facet joint forces but also ligament stresses than intact cervical spine. Therefore, more careful care must be taken to choose surgical method of total disc arthroplasty.
Biocompatibility of Co-Cr alloy was significantly improved by forming rough TiO2 layer on the surface. The TiO2 layer was formed by coating the Co-Cr alloy with Ti through electron beam deposition followed by micro-arc oxidation (MAO) of the Ti. Biocompatibility of Co-Cr alloy was enhanced by coating with titanium, and it was improved further by micro-arc oxidation treatment. MAO process was dependent on the thickness of coated titanium layer and applied voltage. There were close relationships between the phase, morphology and thickness of TiO2 layer and the applied voltage. Biocompatibility of the specimens coated with Ti and MAO treated after Ti coating were evaluated by in vitro ALP activity tests.
Modified posterior approach preserving short external rotators would be able to contribute greatly to prevent dislocation after total hip arthroplasty. We modified the posterior approach to the hip by preserving the external rotator muscles in order to enhance joint stability after total hip arthroplasty in patients with osteonecrosis of the femoral head. The aim of the this study was to determine the influence of external rotator preserving posterior approach in primary total hip replacement on early dislocation and clinical outcome. Three hundred sixty-four primary total hip replacements were divided into two groups based on how the external rotators were treated at surgery. External rotator preservation (Group 1, 165 hips) group was compared with reattachment (Group 2, 199 hips) group by evaluating the clinical and radiographic outcome at one year postoperative. Anteversion was significantly less in Group 1 as compared to Group 2 (P <
0.001). There was no significant difference in inclination between the groups (P >
0.05 in all comparisons). No dislocations were found in 165 hips with external rotator preservation whereas dislocations was noted in 11 (3.9%) in Groups 2, respectively. Group 1 had the higher mean Harris hip score (97.2±2.9 points) as compared with Group 2(94.9±3.4). The results of this study showed that external rotators could play an important role in preserving joint stability after total hip arthroplasty in patients with osteonecrosis of the femoral head. It can be implied that this modified posterior approach would be able to contribute greatly to prevention of dislocation, and improve clinical outcome after total hip arthroplasty.
Modular femoral stem provides significant flexibility in total hip revision arthroplasty. There have been few clinical studies that have dealt with modular stem. We have evaluated the clinical and radiographic performance of 59 patients with distal fix modular Link MP stem. The average follow-up period was 6.4 years. The average Harris hip score was improved from 47 to 87.6. Of 19 patients with trochanteric osteotomy, greater trochanter was displaced in four patients. Re-revision was done to five patients. Three were for subsidence, one of them showed dissociation of the coupling part and the other two were for a nonunion of osteotomy site. There was no statistical relation (p=0.40) between stem subsidence and bone deficiency; the subsidence may have been too small for the canal. As a result of last follow-up, survival rate was 91.5 %(CI 95%, 89–101), but there was no case of recurrent dislocation or femoral stem fracture.
