Yusuke Kubo

The role of sclerotic changes in the starting mechanisms of collapse: A histomorphometric and FEM study on the femoral head of osteonecrosis

PURPOSE To assess the distributions of stress, strain, and fractured areas using a finite element model (FEM), and examine the osteoclastic activity histopathologically in osteonecrosis of the femoral head. METHODS Three femoral heads were obtained during hip arthroplasty for femoral head osteonecrosis. One sample with a normal area, two samples with a non-sclerotic boundary without collapse (Type 1), two samples with a non-collapsed sclerotic boundary (Type 2), and two samples with a collapsed sclerotic boundary (Type 3) were collected from each femoral head for the FEM and histopathological analyses. FEM was performed using CT data, and the distributions of von Mises equivalent stress, octahedral shear stress, octahedral shear strain, and simulated fractured area were evaluated. Furthermore, the osteoclast count at the boundary was compared for each type. RESULTS In normal and Type 1 samples, the distributions of von Mises equivalent stress, octahedral shear stress, octahedral shear strain, and the fractured area were equally concentrated along the whole analytical range; however, in the Type 2 and 3 samples, they were concentrated along the thickened bone trabeculae at the boundary, which corresponded to the fractured area. Histopathologically, a significantly increased osteoclast number was observed only at the collapsed sclerotic boundary. CONCLUSION These results demonstrated that both shear stress and shear strain tend to be concentrated on thickened bone trabeculae at the boundary. Fracture analyses revealed that the boundary of sclerotic changes, which results from the repair process, may be the starting point of the fracture. Additionally, the osteoclastic activity increases after collapse.

Common site of subchondral insufficiency fractures of the femoral head based on three-dimensional magnetic resonance imaging

ObjectivesThe objective of this study was to investigate the common sites of subchondral insufficiency fractures of the femoral head (SIF) based on three-dimensional (3-D) reconstruction of MR images.Materials and methodsIn 33 hips of 31 consecutive patients diagnosed with SIF, 3-D reconstruction of the bone, fracture, and acetabular edge was performed using MR images. These 3-D images were used to measure the fractured areas and clarify the positional relationship between the fracture and degree of acetabular coverage.ResultsThe fractured area in the anterior portion was significantly larger than in the posterior area. In 11 cases, the fractures contacted the acetabular edge and were distributed on the lateral portion. The indices of acetabular coverage (center-edge angle and acetabular head index) in these cases were less than the normal range. In the remaining 22 cases, the fractures were apart from the acetabular edge and distributed on the mediolateral centerline of the femoral head. The majority of these cases had normal acetabular coverage.ConclusionsThe common site of SIF is the anterior portion. In addition, two types of SIF are proposed: (1) Lateral type: the contact stress between the acetabular edge and lateral portion of the femoral head causes SIF based on the insufficient acetabular coverage, and (2) Central type: the contact stress between the acetabular surface and the mediolateral center of the femoral head causes SIF independent from the insufficiency of acetabular coverage. These findings may be useful for considering the treatment and prevention of SIF.

Thermoelectric properties of delafossite-related layered metal oxides

Thermoelectric properties of layered metal oxides Na/sub x/CoO/sub 2/ in a delafossite (CuFeO/sub 2/)-related crystal structure are investigated, and a possible mechanism of p-type metallic conduction leading to outstanding thermoelectric performance as an oxide is discussed in terms of crystal chemistry. Sintered samples of Na/sub x/CoO/sub 2/ (x/spl ap/0.5) were prepared from Na/sub 2/CO/sub 3/ and Co/sub 3/O/sub 4/ through the conventional solid state reaction by firing in air. Probably due to losses of Na during firing, electrical properties of the oxides are revealed to be sensitive to the heating atmosphere. The oxides show almost temperature-independent electrical conductivities of >10/sup 2/ S cm/sup -1/ up to 1000 K, being accompanied by the positive Seebeck coefficients of 100-200 /spl mu/V K/sup -1/ which increase linearly with temperature. Although a poor sinterability of our samples at the present state limits the conductivity to the values lower than those previously reported, the oxide shows a power factor value of >6/spl times/10/sup -4/ W m/sup -1/ K/sup -2/ at 1000 K. Since the thermal conductivity of the oxides was measured as 1.5-2.5 W m/sup -1/ K/sup -1/ at room temperature, and is usually expected to become lower at higher temperatures, the maximum figure of merit is anticipated to reach >0.4/spl times/10/sup -3/ K/sup -1/. The oxide is thereby confirmed to be the most promising p-type oxide candidate so far investigated.

Computed tomography findings of subchondral insufficiency fractures of the femoral head

Objectives The objective of this study was to describe the appearance of Subchondral insufficiency fracture (SIF) by computed tomography (CT). Methods Images of 52 consecutive patients diagnosed with SIF were retrospectively reviewed. CT was available for five patients (7 cases). Results Corresponding to a low-intensity band on MR images, a radiolucent or sclerotic band was observed on CT images. Conclusion The present study is the first to report CT findings of SIF. A radiolucent or sclerotic band was observed on CT images. The results of the present study provide useful information for diagnosis of SIF.

Effects of sclerotic changes on stress concentration in early-stage osteonecrosis: A patient-specific, 3D finite element analysis: FINITE ELEMENT ANALYSIS IN OSTEONECROSIS

Stress distribution remains unclear in early‐stage osteonecrosis of the femoral head (ONFH). To clarify this issue, we generated patient‐specific finite element models (FEMs) from 51 patients with ONFH. Patients’ hips were classified into three groups: ONFH without a sclerotic boundary (Stage 1, n = 6), ONFH with a sclerotic boundary (Stage 2, n = 10), and ONFH with both a sclerotic boundary and <2 mm collapse (Stage 3, n = 35). Four hips without ONFH were used as controls. Stress distribution in each FEM was compared with magnetic resonance imaging (MRI) and computed tomography (CT) results. Fifteen wholly resected femoral heads in Stage 3 hips were assessed by micro‐CT. Furthermore, we histologically examined three Stage 2 femoral heads that subsequently developed subchondral fractures after FEM analyses. In all FEMs of both control and Stage 1 hip, stress was equally distributed on the femoral head surface. However, in all FEMs of both Stages 2 and 3 hips, stress was concentrated at the lateral boundary of the femoral head surface, corresponding to both a low‐intensity band on T1‐weighted MRI images and sclerotic changes on CT. On micro‐CT, subchondral fractures consistently began at the lateral boundary with sclerotic changes, in which bone volume fraction was increased. Histology showed breakage of subchondral plates at the junction between necrotic and reparative zones. In early‐stage ONFH, sclerotic changes caused stress concentration, which can trigger subchondral fractures at the lateral boundary. Clinical Significance: Our results will clarify the pathogenic mechanism of collapse in ONFH.

Osteoclast-related markers in the hip joint fluid with subchondral insufficiency fracture of the femoral head: OSTEOCLAST-RELATED MARKERS IN SIF

Similar to the radiological findings in rapidly destructive arthrosis of the hip joint (RDA), subchondral insufficiency fracture of the femoral head (SIF) can result in progressive femoral head collapse of unknown etiology. We thus examined the osteoclast activity of hip joint fluid in SIF with progressive collapse in comparison with that in RDA. Twenty‐nine hip joint fluid samples were obtained intraoperatively with whole femoral heads from 12 SIF patients and 17 RDA patients. SIF cases were classified into subgroups based on the presence of ≥2 mm collapse on preoperative radiographs: SIF with progressive collapse (n = 5) and SIF without progressive collapse (n = 7). The levels of tartrate‐resistant acid phosphatase (TRACP)‐5b, interleukin‐8, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)‐9 were measured. The number of multinuclear giant cells at the subchondral region was histopathologically assessed using mid‐coronal slice of each femoral head specimen. The median levels of all markers and the median number of multinuclear giant cells in SIF with progressive collapse were significantly higher than those in SIF without progressive collapse, while there were no significant differences in SIF with progressive collapse versus RDA. Regression analysis showed that the number of multinuclear giant cells was positively correlated with the level of TRACP‐5b in joint fluid. The present study demonstrated the possible association of increased osteoclast activity with the existing condition of progressive collapse in SIF, which was quite similar to the findings in RDA, indicating that increased osteoclast activity may reflect the condition of progressive collapse in SIF as well as RDA.

Effects of intertrochanteric osteotomy plane and preoperative femoral anteversion on the postoperative morphology of the proximal femur in transtrochanteric anterior rotational osteotomy: 3D CT-based simulation study

BACKGROUND Transtrochanteric anterior rotational osteotomy (ARO) is joint-preserving surgery for patients with osteonecrosis of the femoral head (ONFH). During ARO, femoral neck-shaft varus angulation by changing intertrochanteric osteotomy plane is often designed to obtain a sufficient postoperative intact ratio. However, the effect of intertrochanteric osteotomy plane on postoperative femoral anteversion has not been well examined. Therefore, we performed a simulation study of ARO to determine how intertrochanteric osteotomy plane and preoperative femoral anteversion affect both femoral neck-shaft varus angle and postoperative femoral anteversion. HYPOTHESIS Both femoral neck-shaft varus angle and postoperative femoral anteversion are predicted by intertrochanteric osteotomy plane and preoperative femoral anteversion in ARO. MATERIALS AND METHODS Using CT-data obtained from 10 hips in 10 patients with ONFH, ARO was simulated. On anteroposterior view, basic intertrochanteric osteotomy line (AP-view line) was defined as the perpendicular line to the femoral neck axis. On lateral view, basic intertrochanteric osteotomy line (lateral-view line) made through the cut surface of greater trochanter was defined as the perpendicular line to the lateral axis of the femur. By changing either AP-view or lateral-view line, 49 ARO models/hip were produced, in which femoral neck-shaft varus angle and postoperative femoral anteversion were assessed. RESULTS With increase in the vertically-inclined degree of AP-view line, both neck-shaft varus angle and postoperative femoral anteversion increased. With increase in the posteriorly-tilted degree of lateral-view line, neck-shaft varus angle increased, whereas postoperative femoral anteversion decreased. The approximation equations based on the multiple regression analyses were as follows: neck-shaft varus angle≈vertically-inclined degree of AP-view line×0.9+posteriorly-tilted degree of lateral-view line×0.8+preoperative femoral anteversion×0.7; postoperative femoral anteversion≈vertically-inclined degree of AP-view line×1.1-posteriorly-tilted degree of lateral-view line×0.8. DISCUSSION The postoperative morphology of proximal femur was nearly defined by intertrochanteric osteotomy plane with preoperative femoral anteversion, which is useful for preoperative planning in terms of both achieving a sufficient postoperative intact ratio and maintaining femoral anteversion. LEVEL OF EVIDENCE Level IV case series without control group.

Use of a long distally fixed intramedullary stem to treat a periprosthetic femoral fracture following total hip arthroplasty using a thrust plate hip prosthesis: A case report

Highlights • We report a periprosthetic fracture following the use of a discontinued prosthesis.• Marked bone ongrowth on the thrust plate made it difficult to remove.• A long distally fixed intramedullary stem was selected for revision.• Sufficient implant preparation based on precise preoperative planning is necessary.

Transient epiphyseal lesion of the femoral head after traumatic hip dislocation: A case report

Highlights • We report a transient epiphyseal lesion of femoral head after hip dislocation.• On MRI performed two days after dislocation, no bony injuries were observed.• Hip pain and a transient epiphyseal lesion appeared four months after dislocation.• Hip pain and a transient lesion disappeared after two-month conservative therapy.• Prolonged rest after the injury may contribute to an insufficiency fracture.

The choice of locking plate in the treatment of peri-implant femoral fracture eight years after trans-trochanteric rotational osteotomy: A case report ☆

Highlights • We report a peri-implant fracture after transtrochanteric rotational osteotomy.• Preservation of the nutrient artery of the femoral head is important.• The entry point of an anterograde nail would have been very close to the artery.• A locking plate is preferable to ante-grade nailing to avoid damaging the artery.• The operation resulted in satisfactory results without any complications.