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 plasma spray(TPS) has come to be accepted as one of the more reliable methods of porous coating of prosthesis, it is not without some technical limitations, especially with regard to precise modulation of pore size, porosity, and roughness. However, the plasma spray(TPS) not often but seriously faces problems such as bead detachment related poor osteointegration, weakness of metal strength and high manufacturing costs in addition to its various technical limitations. Currently, there has been much research into developing a more economical and effective method for porous coating of the prosthesis. In light of such demand, 3D Printing with DMT Technology has been introduced into the field of surface treatment of prosthesis with promising expectations. DMT technology -an additive fabrication process that uses high-power laser and various metal powders in order to produce fully dense and geometrically complex metal components, molds, and dies directly from digital CAD model data of 3D subjects aims to help overcome many of the problems associated with plasma spray and thereby open a new chapter of endless possibilities for coating technology. In this study, the porous coating specimen using 3-D DMT metal printing was characterized morphologically as well as biomechanically, in terms of 1) pore size 2) porosity 3) tensile strength 4) shear strength 5) roughness respectively. The biological cyto-compatibility was evaluated by culturing human osteoblast-like cells(Saos-2: ATCC HTB85) on the surface of round discs with porous coating to demonstrate the biological influence on the porosity of the specimens with different surface treatment for comparative analysis. The evaluation was accompanied by assessment of cell proliferation and morphology with arrangement of actin filament and expression of adhesion molecule with αvβ3 integrin. While 3-D DMT coating specimen showed relatively regular porosity in the range of 150–500µm with the increase of porosity about 83%, the mechanical behavior remarkably improved, compared to TPS: shear strength 13%, fatigue failure 30%, roughness 16%, respectively. Also worth noting, the tensile strength was unable to be measured because the glue for test had fallen off. (Fig. 1) There is no transitional zone underneath the porous coating layer.(Fig. 2) From the aspect of biocompatibility, 3-D coating showed better cell attachment, spreading of cytoskeleton, cell proliferation, and expression of osteogenic markers than TPS, even if not significantly.(Fig. 3) Additionally, cell migration assay was performed with double chamber study, and gene expression was evaluated by measuring alkaline phosphatase(ALP) levels and analyzing mRNA expression for ostepontin(OPG) and osteocalcin(OC). In conclusion, the study reinforces the popular stance that the implementation of 3-D DMT could open up new possibilities for coating technology and form a new chapter in the history of prosthesis development.
