Primary stability is achieved by the press fit technique, where an oversized component is inserted into an undersized reamed cavity. The major geometric design of an acetabular shell is hemispherical type. On the other one, there are the hemielliptical type acetabular shells for enhanced peripheral contact. In the case of developmental dysplasia of the hip (DDH), the aseptic loosening may be induced by instability due to decreased in the contact area between the acetabular shell and host bone. The aim of this study was to assess the effect of reaming size on the primary stability of two different outer geometry shells in DDH models. The authors evaluated hemispherical (Continuum Acetabular Shell, Zimmer Biomet G.K.) and hemielliptical (Trabecular Metal Modular Acetabular Shell, Zimmer Biomet G.K.) acetabular shells. Both shells had a 50 mm outer diameter and same tantalum 3D highly porous surface. An acetabular bone model was prepared using a solid rigid polyurethane foam block with 20 pcf density (Sawbones, Pacific Research Laboratories Inc.) as a synthetic bone substrate. Press fit conditions were every 1 mm from 4 mm under reaming to 2 mm over reaming. To simulate the acetabular dysplasia the synthetic bone substrate was cut diagonally at 40°. Where, the acetabular inclination and cup-CE angle were assumed to 40° and 10°, respectively. Acetabular components were installed with 5 kN by a uniaxial universal testing machine (Autograph AGS-X, Shimadzu Corporation). Primary stability was evaluated by lever-out test. The lever-out test was performed in 4 mm undersized to 2 mm oversized reaming conditions. Lever out moment was calculated from the multiplication of the maximum load and the moment arm for primary stability of the shell. The sample size was 6 for each shell type.Introduction
Materials and methods
The preparation of antibiotic-containing polymethyl methacrylate (PMMA), as spacers generates a high polymerization heat, which may affect their antibiotic activity; it is desirable to use bone cement with a low polymerization heat. Calcium phosphate cement (CPC) does not generate heat on polymerization, and comparative elution testings are reported that vancomycin (VCM)-containing CPC (VCM-CPC) exceeded the antibiotic elution volume and period of PMMA (VCM-PMMA). Although CPC alone is a weak of mechanical property spacer, the double-layered, PMMA-covered CPC spacer has been created and clinically used in our hospital. In this study, we prepared the double-layered spacers: CPC covered with PMMA and we evaluated its elution concentration, antimicrobial activity and antibacterial capability. We prepared spherical, double-layered, PMMA-coated (CPC+PMMA; 24 g CPC coated with 16 g PMMA and 2 g VCM) and PMMA alone (40 g PMMA with 2 g VCM) spacers (5 each). In order to facilitate VCM elution from the central CPC, we drilled multiple holes into the CPC from the spacer surface. Each spacer was immersed in phosphate buffer (1.5 mL/g of the spacer), and the solvent was changed daily. VCM concentrations were measured on days 1, 3, 7, 14, 28, 56, and 84. Antimicrobial activity against MRSA and MSSA was evaluated by the broth microdilution method. After measuring all the concentration, the spacers were compressed at 5 mm/min and the maximum compressive load up to destruction was measured.Aim
Method
Although the wear of conventional polyethylene liner becomes a serious problem in a long term follow up after total knee arthroplasty, there are few reports of measuring the polyethylene wear. Is it possible to measure the linear wear rates in the non-cross-linked polyethylene liner used in the Press Fit Condylar (PFC) Sigma total knee system? Does the polyethylene wear influence on the clinical results?Background
Questions/purposes
We reported a case of the acetabular depression fracture in conjunction with a central fracture dislocation of the hip that was treated with a unique surgical technique. A 76-year-old man suffered a left acetabular fracture with severe left hip joint pain and walking disability. Acetabular fracture was not apparent on the initial radiographs including anteroposterior and oblique views of the pelvis. However, computed tomography (CT) scanning showed displaced acetabular depression fracture (a third fracture fragment) in the center of the weight-bearing area with fracture of the ilium and spontaneous reposition of central dislocation of the hip (Fig. 1, 2). It seemed that this fracture fragment created incongruity of the acetabular articular surface and the potential for hip joint instability. Therefore, the patient was treated with open reduction and internal fixation. To perform the procedure, the patient was placed in the lateral decubitus position. A direct lateral approach to the hip was used for exposure. The vastus lateralis was released 1 cm distal from its origin, trochanteric osteotomy was done by the Gigli saw. To observe the hip articular surface and to identify the fracture fragment, the femoral head was posterior dislocated with excision of teres ligamentum after T-shaped capsulotomy. The depressed fragment in the acetabulum was identified under direct vision but could not be reduced. Therefore, the outer cortex of the ilium was fenestrated in a size of 2 × 2 cm so that a 1-cm-wide levator was inserted to the depressed fragment at 2 cm proximal from the hip articular surface through the fenestrated window (Fig. 3). Subsequently, the displaced bone fragment was pushed down by using the levator to the adequate articular joint level. The fragment was stabilized with packed cancellous bone graft harvested from the osteotomized greater trochanter. The removed outer cortex of the ilium from fenestrated site was repositioned and fixed by a reconstruction plate and screws. The osteotomized greater trochanter was reattached and fixed with two cannulated cancellous hip screws.CASE REPORT:
SURGICAL TECHNIQUE:
