Toshihiko Hara

Hydroxyapatite‐coating on titanium arc sprayed titanium implants

We developed a new titanium spray technique using an inert gas shielded arc spray (titanium arc spray). Hydroxyapatite (HA)-coating can be applied to the implant without any surface pore obstruction after the rough surface is made by this technique. Scanning electron microscopy (SEM) of various porous implant surfaces after HA-coating revealed that the bead and fiber metal-coated implants had either a pore obstruction or an uneven HA-coating. On the other hand, the titanium arc sprayed implant demonstrated an even HA-coating all the way to the bottom of the surface pore. In the first set of animal experiments (Exp. 1), the interfacial shear strength to bone of four kinds of cylindrical Ti-6A1-4V (Ti) implants were compared using a canine transcortical push-out model 4 and 12 weeks after implantation. The implant surfaces were roughened by titanium arc spray (group A-C) and sand blasting (group D) to four different degrees (roughness average, Ra = group A: 56.1, B: 44.9, C: 28.3, D: 3.7 microns). The interfacial shear strength increased in a surface roughness-dependent manner at both time periods. However, the roughest implants (group A) showed some failed regions in the sprayed layers after pushout test. In the second set of animal experiments (Exp. 2), four kinds of Ti implants; HA-coated smooth Ti (sHA) with Ra of 3.4 microns, bead-coated Ti (Beads), titanium arc sprayed Ti (Ti-spray) with Ra of 38.1 microns and HA-coated Ti-spray (HA + Ti-spray) with Ra of 28.3 microns were compared using the same model as that in Exp. 1. The interfacial shear strength of HA + Ti-spray was significantly greater than that of sHA and Beads at both time periods, and that of Ti-spray at 4 weeks. Although a histological examination revealed that HA-coating enhanced bone ingrowth, sHA showed the lowest shear strength at both time periods. SEM after pushout test showed that sHA consistently demonstrated some regional failure at the HA-implant substrate interface. HA + Ti-spray had many failed regions either at the HA-bone interface or within the bone tissue rather than at the HA-implant substrate interface. These results suggested that the HA-coated smooth surfaced implants had a mechanical weakness at the HA-substrate interface. Therefore, HA should be coated on the rough surfaced implants to avoid a detachment of the HA-coating layer from the substrate and thus obtain a mechanical anchoring strength to bone. HA-coating on this new type of surface morphology may thus lead to a solution to the problems of conventional HA-coated and porous-coated implants.

Contrast-enhanced MR imaging of subchondral insufficiency fracture of the femoral head: a preliminary comparison with that of osteonecrosis of the femoral head

IntroductionSubchondral insufficiency fracture of the femoral head (SIF) may be confused with osteonecrosis of the femoral head (ON) due to clinical and imaging similarities.Materials and methodsContrast-enhanced MR images in patients with SIF (ten hips in ten patients) were retrospectively reviewed and compared with those from patients with ON (ten hips in six patients).ResultsLow-signal intensity bands on T1-weighted images were present within the femoral head in all hips examined. The segment proximal to the band was contrast-enhanced following IV gadolinium administration in nine of ten hips (90%) with SIF and in none of the 10 hips with ON.ConclusionThese results suggest that the presence of contrast enhancement in the segment proximal to the low-signal intensity band in the femoral head may serve as a supplemental diagnostic measure for the differentiation of SIF from ON.

Deficiency of a parathyroid hormone fragment containing the midportion and 1,25-dihydroxyvitamin D in serum of patients with slipped capital femoral epiphysis.

The endocrine abnormality that causes slipped capital femoral epiphysis (SCFE) has not been revealed. Recent studies have shown that parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1,25-(OH)2D] are involved in growth-plate chondrogenesis and matrix mineralization. Thus we examined in 13 patients with SCFE the serum levels of three immunoreactive forms of PTH (iPTH): the whole peptide [(1-84)PTH], the fragment containing the COOH-terminal portion (C-PTH), and the midportion (M-PTH). Additionally, serum levels of 25-hydroxyvitamin D [25-(OH)D] and 1,25-(OH)2D were measured. We found that the levels of M-PTH were significantly lower than those of controls, whereas levels of C-PTH and (1-84)PTH were not significantly different from those of controls. Similarly, levels of 1,25-(OH)2D were also significantly lower than control levels. In patients with initially low levels of M-PTH and 1,25-(OH)2D in whom the levels were monitored over a period, all levels returned to normal within a year after the onset of disease. The deficiency of M-PTH or 1,25-(OH)2D during the growth spurt could result in SCFE, although in this study, we cannot deny the possibility that the slippage may cause the deficiency.

Co-occurrence of subchondral insufficiency fracture of the femoral head and contralateral femoral neck fracture in a rheumatic patient receiving steroid treatment

We describe a 79-year-old woman with rheumatoid arthritis who suffered from subchondral insufficiency fracture of the femoral head (SIF) and contralateral femoral neck fracture. Radiographs obtained two months after the onset of thigh pain showed collapse of the right femoral head and contralateral femoral neck fracture. MRI revealed a subchondral serpiginous low-intensity band in the right femoral head on the T2-weighted image. This case report suggests that SIF should be considered in the differential diagnoses of rheumatic patients who suffer from thigh pain without antecedent trauma.

Minimum Lateral Bone Coverage Required for Securing Fixation of Cementless Acetabular Components in Hip Dysplasia

Objectives. To determine the minimum lateral bone coverage required for securing stable fixation of the porous-coated acetabular components (cups) in hip dysplasia. Methods. In total, 215 primary total hip arthroplasties in 199 patients were reviewed. The average follow-up period was 49 months (range: 24–77 months). The lateral bone coverage of the cups was assessed by determining the cup center-edge (cup-CE) angle and the bone coverage index (BCI) from anteroposterior pelvic radiographs. Further, cup fixation was determined using the modified DeLee and Charnley classification system. Results. All cups were judged to show stable fixation by bone ingrowth. The cup-CE angle was less than 0° in 7 hips (3.3%) and the minimum cup-CE angle was −9.2° (BCI: 48.8%). Thin radiolucent lines were observed in 5 hips (2.3%), which were not associated with decreased lateral bone coverage. Loosening, osteolysis, dislocation, or revision was not observed in any of the cases during the follow-up period. Conclusion. A cup-CE angle greater than −10° (BCI > 50%) was acceptable for stable bony fixation of the cup. Considering possible errors in manual implantation, we recommend that the cup position be planned such that the cup-CE angle is greater than 0° (BCI > 60%).

Stimulatory Effects of Ceramic Particles on the Production of Bone Resorbing Mediators

ABSTRACT We investigated the effects of size and dose of various ceramic particles on the release of bone-resorbing mediators from macrophages. Mouse macrophage cell line, J-774 was co-cultured with either alumina or hydroxyapatite particles. Uniform suspensions of alumina or hydroxyapatite particles, ranging in 1–1000 μm were prepared, and amount of 0.002 and 0.02gram of the particles were used in each group. After forty-eight hours of exposure, each medium was harvested and tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1 α (IL-1α) levels were assayed by enzyme-linked immunosorbent assay kit. The release of TNF-α from macrophages was increased by smaller size of both particles in a dose-dependent fashion. IL-1α and IL-6 production were enhanced in a similar manner. Hydroxyapatite particles, especially in small size (1 μm), caused greater release of mediators than alumina particles. These results suggested that the particles small enough, even if it was biocompatible, had ability to stimulate bone resorption by increasing the production of bone-resorbing mediators.

Acetabular reconstruction with Chiari pelvic osteotomy: report of 2 cases.

We performed cementless total hip arthroplasty combined with acetabular reconstruction with Chiari pelvic osteotomy on 3 hips in 2 patients. This procedure increased the osseous coverage of the shell and decreased the load around the hip by medialization of the hip center. Osteosynthesis of the proximal and distal bone fragment was performed using a shell with screws. Nonunion between the proximal and distal fragments was not noticed to include the case with small contact area. Postoperative dislocation had not occurred in these cases as of 1 year after surgery. This method may be an effective solution for severe dysplasia and revision surgery.