Cement thickness of at least 2 mm is generally associated with more favorable results for the femoral component in cemented hip arthroplasty. However, French-designed stems have shown favorable outcomes even with thin cement mantle. The biomechanical behaviors of a French stem, Charnley-Marcel-Kerboull (CMK) and cement were researched in this study. Six polished CMK stems were implanted into a composite femur, and one million times dynamic loading tests were performed. Stem subsidence and the compressive force at the bone-cement interface were measured. Tantalum ball (ball) migration in the cement was analyzed by micro CTObjective
Methods
Favourable results for collarless polished tapered stems have been reported, and cement creep due to taper slip may be a contributing factor. However, the ideal cement thickness around polished stems remains unknown. We investigated the influence of cement thickness on stem subsidence and cement creep. We cemented six collarless polished tapered (CPT) stems (two stems each of small, medium and large sizes) into composite femurs that had been reamed with a large CPT rasp to achieve various thicknesses of the cement mantle. Two or three tantalum balls were implanted in the proximal cement in each femur. A cyclic loading test was then performed for each stem. The migration of the balls was measured three-dimensionally, using a micro-computed tomography (CT) scanner, before and after loading. A digital displacement gauge was positioned at the stem shoulder, and stem subsidence was measured continuously by the gauge. Final stem subsidence was measured at the balls at the end of each stem.Objectives
Methods
The French paradox regarding cemented femoral components has not been resolved, so we compared the mechanical behavior of a French stem, the CMK stem (Biomet, Warsaw, IN, USA), with a collarless, polished, tapered stem (CPT, Zimmer, Warsaw, IN, USA) using an original biomechanical instrument. Two size-3 CPT stems and two size-302 CMK stems stems were fixed with bone cement into a composite femur soaked in vegetable oil to simulate wet condition. The composite femur was attached to a biomechanical testing instrument after stem implantation, and a 1-Hz dynamic sine wave load (3000 N) was applied to the stems for a total of 1 million cycles. An 8-hour unload period was set after every 16 hours of load. Femur temperature was maintained at 37°C during testing. The femoral canal was prepared for the CPT stems by standard rasping; for the CMK stems, however, the French method was used, in which cancellous bone was removed with a reamer. One CMK stem (CMK-1) was inserted into a femur without collar contact (>2 mm above the calcar), and the other (CMK-2) was inserted into a femur with collar contact. Stem subsidence was measured at the stem shoulder. Compressive force and horizontal cement movement were measured via rods set at the cement–bone interface on the medial, lateral, anterior, and posterior sides of the proximal and distal portions of the composite femurs.Introduction
Materials and Methods
In cemented total hip arthroplasty (THA), proper cement mantle thickness in the femoral canal is still controversial subject. It is widely accepted that the cement mantle around a femoral stem should be at least 2 mm in thickness. But articles from France reported good long-term result with thin cement mantle. It is so called “The French paradox”. We have already reported that the greater compressive force at the cement-bone interface was seen in collarless polished tapered (CPT, Zimmer, USA) stem with thick cement mantle than that with thin cement mantle. However, the stem with thick cement mantle subsided more than with thin mantle. It may have a possibility to cause an early mechanical failure of cemented THA. We compared to stem and cement subsidence in various cement mantles using tantalum ball into cement in this study. A cemented stem model was used for this study with a CPT stem into composite femur. Three sizes of CPT stems (No. 1, No. 2 and No. 3) and one size composite femur were prepared for this study. We inserted two stems for each size, for a total of six stems. Composite femurs were reamed with a No. 3 rasp, and various size of stem was fixed with cement in each composite femur to make a various thicknesses of cement mantle. Two to three tantalum marker balls were injected into the cement in each femur before cement was hardened. 1-Hz dynamic load applied to the stems for half a-million cycles. Each 16 hours of loading was followed by 8 hours without loading. We used micro-CT before and after loading to measure the movement of the tantalum balls in three dimensions. And we analyzed occupation ratio of stem in the femoral canal by computed reconstructed three dimensional model of bone cement and stem.Introduction
Methods
To prevent excessive tension on the posterior cruciate ligament (PCL) in cruciate-retaining total knee arthroplasty (CR-TKA), some knee prosthesis-systems offer the option of creating a posterior slope for the tibial polyethylene insert. Vanguard® Complete Knee System offers two different types of tibial bearing for CR -TKA. CR Lipped Bearing (LB) has a slightly raised posterior lip, whereas CR Standard Bearing (SB) is recessed downward at the posterior margin and has 3° posterior slope. The objective of this study was to investigate the effect of the tibial bearing slope on PCL load using the original devise in vivo conditions. Twenty osteoarthritic varus knees were included in this study. After implantation of the trial components, PCL stiffness was measured using the original tension analyzer intra-operatively. Elastic modulus of PCL was calculated at 90 and 120 degrees knee flexion on two types of bearing surface.Background
Material and Methods
The rotational acetabular osteotomy (RAO), that was developed in Japan, has been used successfully in patients with developmental dysplasia of the hip (DDH) (Figure 1). However there are some patients who are forced to have a total hip arthroplasty (THA) due to the progression of osteoarthritis. It is unknown if a RAO poses technical difficulties or increases the chances of complications if a THA must be performed afterwards becausethere is not much data on patients who underwent a THA after a previous RAO. The purpose of this study was to investigate the mid-term results of a THA after a RAO.Background
Objectives
The objective of this study was to identify fat emboli in the arterioles of the femoral bone marrow by Scanning Electron Microscopy (SEM) after glucocorticoid administration. Female adult rabbits weighing 3.5 to 4.0 kg received a single injection of prednisolone at a dose of 4 mg/kg body weight. The day after injection was designated as day 1. Control rabbits were injected with only physiological saline and euthanized on day 14. The femoral bone marrow was obtained on days 5, 8, and 14, and processed for SEM. Aortic blood serum was passed through a filter, and the filter was processed for SEM. Some SEM specimens were embedded in a plastic resin and sectioned for correspondence of SEM-photomicroscopy or SEM-TEM.Introduction
Methods
The mechanism for development of corticosteroid-induced osteonecrosis of the femoral head remains to be understood. Elucidation of the mechanism and the establishment of preventive methods have been critical issues. To establish a clinical method for prevention of corticosteroid-induced osteonecrosis, we have examined the suppressive effect of reduced glutathione (GSH) in a corticosteroid-induced rabbit model. Female Japanese white rabbits were separated into five groups: Group S4, a single intramuscular 4 mg/kg methyl prednisolone acetate (MPSL) administration in the gluteus; Group G4, administration of a 5 mg/kg regular dose GSH for 5 consecutive days starting on the day of a single 4 mg/kg MPSL administration; Group S20, a single intramuscular administration of 20 mg/kg MPSL in the gluteus; Group G20, administrations of 5 mg/kg GSH for 5 consecutive days starting on the day of a single 20 mg/kg MPSL administration; and Group N, control group with no treatment. All rabbits were sacrificed 14 days after MPSL administration. Histopathological analyses were performed by hematoxylin-eosin staining. Immunohistological analyses were performed using anti-lectinlike oxidized LDL reseptor-1 antibody (anti-LOX-1 antibody).Introduction
Methods
Recently, oxidative stress has been implicated in the development of osteonecrosis. Here we focused on vitamins with marked antioxidant potency to see whether their use might prevent the development of osteonecrosis associated with corticosteroid administration. Fifteen male Japanese white rabbits weighing about 3.5 kg were injected once into the right gluteal muscle with methylprednisolone (MPSL) 40 mg/kg (S Group). Ten other rabbits, in addition, received consecutive daily intravenous injections of vitamin E 50 mg/kg starting from the day of MPSL administration (E Group), and 10 other animals similarly received consecutive daily intravenous injections of vitamin C 30 mg/kg (C Group). All animals were euthanized 2 weeks after MPSL administration, and femurs were extracted, and stained with hematoxylin-eosin. Blood levels of glutathione (GSH) were also measured.Introduction
Methods
In this study, bone ingrowth was investigated in three-different cementless acetabular cups, titanium fiber mesh cup (non-HA), hydroxyapatite tricalcium phosphate sprayed cup (HA/TCP), alkali- and heat-treated titanium porous cup (AH). “Gap filling” was evaluated as the finding of the bone ingrowth on X-ray. The phenomenon is that slight gap between acetabulum and the cup observed after total hip arthroplasty (THA) disappear gradually. One hundred and thirty-seven consecutive primary THAs using cementless cups were evaluated for the rate of bone ingrowth. Patients were divided into three groups based on the different types of cups, 51 non-HA cups, 51 HA/TCP cups and 35 AH cups. The groups were similar with regards to age, sex, body mass index, original diagnosis, surgical technique and post operative rehabilitation. Average follow up period was35months, 33 month and 32 months respectively. Initial gap between acetabulum and the cup after operation was observed in 44 hips of non HA group, 39 hips of HA/TCP group and 33 hips of AH group. Rate of the gap filling at the last follow up was 2 hips (4.5%) in non-HA, 31 hips (79.5%) in HA/TCP and 33 hips (100%) in AH. Early gap filling that occurred for less than three months was 17.9% (7 of 39) in HA/TCP and 72.7% (24 of 33) in AH. The HA/TCP coated cup and the alkali- and heat-treated cup had the high frequency which gap filling occurred compared with the cup of only titanium fiber mesh processing. Additionally, in the AH cup more gap filling for less than three months had occurred compared with the HA/TCP cup, so AH cup is the most effective implant to obtain the bone ingrowth at an early stage and it is expected to acquire the better results.
Studies have reported stem subsidence without loosening in cemented polished tapered stems. And also, the initial radiolucency seen immediately after surgery at the bone-cement interface has decreased in some cases with polished tapered stem as time passed. The etiologies of these phenomena are not still elucidated. We made a comparative study on the relation between stem subsidence and the initial radiolucency in polished and rough surface stems. Subjects were 42 hips of 38 cases and 36 hips of 31 cases received primary THA using a Collarless Polished Tapered (CPT) stem and a polymethylmethacrylate pre-coated (VerSys Cemented Plus) stem respectively. Three x-ray films taken within 2 months, at 6 months and a year after surgery were reviewed. Stem subsidence was seen in 34 hips of 31 cases (81.0%) in the CPT group and averaged 0.72mm (range, 0–2.52mm) at a year after surgery. Decrease in the initial radiolucency was seen in 15 hips (35.7%) in the CPTgroup. Stem subsidence averaged 1.12mm (range, 0.46–2.52mm) and 0.48 mm(range, 0.00–1.91mm) in the cases with decrease in the initial radiolucency and in those without any change respectively. Stem subsidence was significantly greater in the cases with decrease in the initial radiolucency(P<
0.005). In the VerSys group, no stem subsidence was seen except in 1 case of mechanical failure with 0.65mm of subsidence. No decrease in the initial radiolucency was seen, either. It has been reported that the decrease in the radiolucency as we showed was thought a dense appearance of cancellous bone by load transfer in other polished tapered stem. In this study, stem subsidence may have caused decrease in the initial radiolucency. It has a possibility that not only a dense appearance of cancellous bone but also cement creep caused decrease in the initial radiolucency.
