Highly crosslinked, ultra-high molecular weight polyethylene (HXLPE) acetabular liners inherently have a risk of fatigue failure associated with femoral neck impingement. One of the potential reasons for liner failure was reported as crosslinking formulations of polyethylene, increasing the brittleness and structural rigidity. In addition, the acetabular component designs greatly affect the mechanical loading scenario, such as the offset (lateralized) liners with protruded rim above the metal shells, which commonly induce a weak resistance to rim impingement. The purpose of the present study was to compare the influence of the liner offset length on the impingement resistance in the annealed (first generation) and vitamin E-blended (second-generation) HXLPE liners with a commercial design. The materials tested were the 95-kGy irradiated annealed GUR1020, and the 300-kGy irradiated vitamin E-blended GUR1050 HXLPE offset liners, which were referred to as “20_95” and “50E_300”, respectively. These liners had 2, 3, 4-mm rim offset, 2.45-mm rim thickness, and 36-mm internal diameter. Their rims were protruded above the metal rim at 2, 3, 4mm. Rim impingement testing was performed using an electrodynamic axial-torsional machine. The cyclic impingement load of 25–250N was applied on the rims through the necks of the femoral stems at 1Hz. The rotational torque was simultaneously generated by swinging the stem necks on the rims at 1Hz and its rotational angle was set at the range of 0–10˚. The percent crystallinity was analyzed on the as-received (intact) and impinged HXLPE acetabular rims by confocal Raman microspectroscopy.Introduction
Materials and Methods
Factors determining improvement of the long-term outcome of total knee arthroplasty include accurate reproduction of lower limb alignment. To acquire appropriate lower limb alignment, tibial component rotation is an important element for outcomes. We usually determine the tibial component rotation using the anatomical rotaional landmark of the proximal tibia and range of motion technique. In addition we followed by confirmation of overall lower limb alignment referring to the distal tibial index. When the tibia have a rotational mismatch between its proximal and distal AP axis, a larger error of the distal tibial index than those of other rotational landmark is of concern. The purpose of this study is to evaluate the reliability of the distal tibial AP axis as a reference axis of tibial compornent rotation in the intraoperative setting. The 86 patients (104 knees) with osteoarthritis of the knee who underwent primary TKA were evaluated with use of computerized tomography scans. A 3D images of the proximal tibial and ankle joint surfaces and foot were prepared, and the reference axis was set. In measurement, the images and reference axes were projected on the same plane. We measured the angle caluculated by the proximal and distal tibial AP axes (torsion angle) in preoperative 3D CT images. As a proximal tibial AP reference axis, AP-1 is a line connecting the medial margin of the tibial tubercle and Middle of the PCL attachment site and AP-2 is a line connecting the 1/3 medial site of the tibial tubercle and center of the PCL attachment site. As a distal tibial AP reference axis, D3 is a line connecting the anteroposterior middle point of the talus, D4 is a perpendicular line of transmalleoler axes, and D5 is the second metatarsal bone axis.[Background]
[Subjects and Methods]
In most cases of revision acetabular total hip arthoplasty (THA), some degree of bone loss will be accompanied. If the bone loss is massive, the management of bone defect is more challenging problem. We consider that using cementless accetabular cup for revision acetabular reconstruction is good indication when stable interface fit between the acetabular cup and bone is achieved. The purpose of this study is to review the result of revision hip arthroplasty using cementless acetabular cup with and without bone graft. Between 1998 and 2012, 65 revisions using cementless acetabular cup (Mallory-Head 4 Finned component) were performed in 64 patients, whose mean age was 64.9 years. The cases of revision are aseptic loosening (53 joints), and infection (12 joints). All patients were followed up for a minimum period of 24.0 months (mean, 84 months) and were divided into two groups as follows: in group A, revisions without bone graft (28 joints); in group B, revisions with bone graft (37 joints). We compared clinical and radiographical results of group A with group B.Introduction
Materials and methods
Bipolar hemiarthroplasty (following BHA) have historically had poor results in patients with idiopathic osteonecrosis of femoral head (OFNH). However, most recent report have shown excellent results with new generation BHA designs that incorporate advances in bearing technology. These optimal outcomes with bipolar hemiarthroplasty will be more attractive procedure for young patients who need bone stock for future total arthroplasty. The purpose of the current study was to evaluate the clinical and radiographic finding of this procedure for the treatment of OFNH at our institution after 7-to 21years follow-up. We retrospectively reviewed a consecutive series of 29 patients (40 hips) who underwent primary bipolar hemiarthroplasty for ION (36 hips with stage III and 4 hips with stage IV) with a cementless femoral component between 1992 and 2006. Osteonecrosis was associated with corticosteroid use (23 patients), alcohol (16 patients), idiopathic (one patients). The mean follow-up duration was approximately 12 (range 7 to 21) years. Patients were evaluated according to the Japan Orthopaedic Association (JOA) hip score. We evaluate osteolysis and bone response of acetabulum or femur, and migration distance of outer head were calculated at the latest follow-up. Kaplan-Meier survivorship rate was investigated to examine implant failure rate.[Background]
[Subjects and Methods]
Bi-Metric® cementless primary stem is tapered, rounded conical shaped and coated with plasma spray porous to one-third from the proximal. Fixation is achieved by a press-fit insertion in the Metaphyseal-diaphyseal junction. From 1986 until now, nearly 700 Bi-Metric® stems have been implanted at our hospital. The purpose of this study was to present the clinical and radiological findings including a survival analysis of a consecutive Bi-Metric® stems series followed for over 10 years. 112 primary cementless THAs in 96 patients using the Bi-Metric® femoral tapered stem were available for clinical and radiological evaluation with a minimum follow-up of ten years. Malloy-Head 4-fined acetabular cup was used in all hips. Follow-up was at a mean of 13 years. We applied THA in 84 patients for osteoarthritis, in 6 avascular necrosis for the femoral head and in 6 for rheumatoid arthritis. The mean age of the patients was 59.5 years. Clinically, pain ROM walking and ADL were evaluated according to the Japanese association hip (JOA) score, and complications and survivorship were investigated. Radiographic results were described according to the 7 femoral Gruen zones. Stem fixation in accordance with the method of Engh at al, cancellous condensation, reactive line, osteolysis, stem subsidence, and bone atrophy with stress shielding were examined. Wear was measured according to the method described by Livermore et al., and the effect of the wear on osteolysis was investigated.Introduction
Materials and methods
The objective of this study was to compare the wear mode of 100 Mrad PE cups run in a hip simulator to retrieved 100 Mrad PE cups, and to evaluate the efficacy of the PE wear model. 15 In-vitro PE cups: 3 each 0,2.5.50,100 and 150 Mrad (9 channel hip simulator, 6.2 million cycle duration, physiological load profile by Paul, 2000N maximum load at 1Hz using 30% bovine serum). 5 Retrieved PE cups: three SOM cups (Mizuho Medical Instrument Co., COP alloy 28 mm head)-0 Mrad after 8 years of clinical use, two 100 Mrad cups after 15 years of clinical use, two T28 PE 2.5 Mrad cups (Zimmer): 18 years and 13 years of clinical use. The cups were examined using a SEM (Philip XL30 FEG) for wear scar locations and PE wear-topography. Original machine marks were observed in the weight-bearing areas of the highly cross-linked in-vitro PE. No machine marks were observed for the 0 and 2.5 Mrad in-vitro cups and none were seen in any of the retrieved cups. The formation of more nodules and fibrils in the 0Mrad cups compared to the extensivley cross-linked cups (in-vitro and retrieved) was striking. The frequency of occurrence and length of the fibrils and nodules was dependent on the dose of gamma irradiation. More ripples were formed in the 2.5 Mrad and higher cups compared to the non-irradiated cups (in-vitro and retrieved). The in-vitro cups formed more ripples than the retrieved cups. In general, the SEM features for in-vitro Mrad cups appeared similar to those of the retrieved Mrad cups. The in-vitro Mrad cups accurately reflected the conditions of the artificial joint in living body. Therefore, comparisons of retrieved PE cups with simulator PE cups appeared to be a very powerful research tool. (2) SEM observation demonstrated far less wear damage in the extensively cross-linked cups than in the non-extensively cross-linked PE. Thus the extensive cross-linked PE cups appeared to be a significant improvement over conventional PE cups in terms of wear resistance.
