Etsuo Chosa

Analysis of the effect of lumbar spine fusion on the superior adjacent intervertebral disk in the presence of disk degeneration, using the three-dimensional finite element method

The purpose of this study was to analyze the effect of lumbar spine fusion on the superior adjacent intervertebral disk in the context of disk degeneration, using a nonlinear three-dimensional finite element method. Detailed L3–L5 motion segment models of normal and degenerated intervertebral disks were developed. In fusion models, L4–L5 was fixed by either posterolateral fusion or posterior lumbar interbody fusion (PLIF). Various loading conditions such as compression loading, compression loading plus flexion moment loading, or compression loading plus extension moment loading were applied to study the corresponding stress. Tresca stress on the posterolateral part of intervertebral annulus fiber and von Mises stress on the vertebral endplate (the superior and inferior sides of L3 and L4) were reduced in all degenerated disk models compared with the normal disk models. The PLIF model showed an increase in the percentage change of stress on the vertebral endplate and on the intervertebral annulus fibrosus when flexion and extension moment loadings were applied. This finding suggests that surgeons should consider the risk of exacerbating degeneration of intervertebral disks by undertaking lumbar spine fusion, when degeneration is found in intervertebral disks adjacent to vertebrae requiring fusion.

A biomechanical study of lumbar spondylolysis based on a three-dimensional finite element method

Biomechanical analyses under compression only, and for a combination of flexion, extension, rotation, and lateral bending were performed to evaluate the stress of the interarticular portion of the lumbar vertebra using a nonlinear three‐dimensional finite element method. A detailed three‐dimensional L4–L5 motion segment model was developed that took into consideration the material nonlinearities of ligaments and annular fibers and the contact nonlinearities of facet joints. For a more accurate examination, the separation of cortical bone and cancellous bone for both posterior and anterior elements were also considered. The stress in the pars interarticularis was weakest under compression alone, but stronger under compression with lateral bending loading, with flexion, with rotation, and with extension. Under each loading condition, the region of the stress concentration was consistent with the separated region of the spondylolysis observed in clinical situations. Since the stress in the pars interarticularis was high under extension and rotation in particular, those loadings were suggested to be relatively high risk factors leading to spondylolysis.

Bone Apposition of the Acetabular Rim in Deep Hips: A Distinct Finding of Global Pincer Impingement

BACKGROUND Hips with coxa profunda can develop a pincer-type impingement with linear impact between the proximal part of the femur and the acetabulum, leading to bone apposition on the acetabular rim. METHODS Twenty hips with radiographic features of rim ossification were isolated from a pilot cohort of 220 patients for histologic assessment of the acetabular rim and the labrum. In the second part of the study, the prevalence of radiographic signs of bone apposition in a cohort of 148 hips treated for femoroacetabular impingement was assessed. RESULTS Histologic analysis confirmed that the labrum may become displaced and replaced by the appositional bone formation. The double-line sign and the recess sign are suggestive of an ongoing process of this bone formation, and the described phenotypes of bone apposition indicate the site of the impingement problem. Morphological anomalies of the proximal part of the femur, such as a low neck-shaft angle or a short femoral neck, may further contribute to the mechanism of pincer impingement. CONCLUSIONS In later stages, this bone formation cannot be distinguished from the native bone and the labrum may appear to be nearly absent on imaging studies. While the bone apposition on the rim is first reactive to chronic impingement, the impingement then increases and may lead to further bone apposition.

Effect of periacetabular osteotomy for acetabular dysplasia clarified by three-dimensional finite element analysis.

BackgroundFinite element analysis (FEA) has been applied for the biomechanical analysis of acetabular dysplasia, but not for biomechanical studies of periacetabular osteotomy (PAO) or those performing analysis taking into consideration the severity of acetabular dysplasia. This study aimed to perform biomechanical evaluation of changes in stress distribution following PAO and to determine the effect of the severity of developmental dysplasia of the hip (DDH) using three-dimensional FEA.MethodsA normal model was designed with a 25° center-edge (CE) angle and a 25° vertical-center-anterior margin (VCA) angle. DDH models were designed with CE and VCA angles each of 10, 0, or −10°. Post-PAO models were created by separating each DDH model and rotating the acetabular bone fragment in the anterolateral direction so that the femoral head was covered by the acetabular bone fragment, with CE and VCA angles each at 25°.ResultsCompared to the normal hip joint model, the DDH models showed stress concentration in the acetabular edge and contacting femoral head, and higher stress values; stress increased with decreasing CE and VCA angles. Compared to the DDH models, the post-PAO models showed near-normal patterns of stress distribution in the acetabulum and femoral head, with stress concentration areas shifted from the lateral to medial sides. Stress dispersion was especially apparent in the severe acetabular dysplasia models. PAO provided greater decreases in the maximum values of von Mises stress in the load-bearing area of the acetabulum and femoral head when applied to the DDH models of higher degrees of severity, although the values increased with increasing severity of DDH.ConclusionsPAO is expected to provide biomechanical improvement of the hip joint and to be particularly effective in patients with severe preoperative DDH, although the results also suggested a limitation in the applicability of PAO for these patients.

Bone marrow stimulation at the footprint of arthroscopic surface-holding repair advances cuff repair integrity

BACKGROUND Bone marrow stimulation (BMS) at the footprint of arthroscopic rotator cuff repair has not been fully evaluated according to the preoperative tear size and surgical technique. In this study, we investigated the effect of BMS on cuff repair integrity after an arthroscopic surface-holding (ASH) repair. MATERIALS AND METHODS A total of 111 patients (mean age, 64.5 years) with chronic rotator cuff tears who underwent treatment by the ASH method with BMS by drilling of multiple holes at the footprint (67 shoulders) or without BMS (44 shoulders) were studied, and all patients were observed prospectively. Sugayas classification was used to evaluate cuff integrity by postoperative magnetic resonance imaging, with types IV and V classified as rotator cuff retears. RESULTS The mean scores for cuff integrity were 2.2 ± 0.2 and 1.7 ± 0.2 in the non-BMS and BMS groups, respectively. The mean scores were similar between the 2 groups for medium tears; however, scores for large-massive tears were significantly lower in the BMS group. The overall retear rate was 23.9% in the non-BMS group and 9.1% in the BMS group, and the distribution of repair types differed significantly. For large-massive tears, the retear rate was much higher in the non-BMS group (28.6%) than in the BMS group (4.5%), although the rates for medium tears were comparable between the 2 groups. CONCLUSIONS These findings demonstrate that applying BMS to the footprint during ASH repair results in improved cuff repair integrity, particularly in large-massive tears, and suggest the importance of biologic treatment for rotator cuff healing after arthroscopic rotator cuff repair.

Anterior acetabular head index of the hip on false-profile views: NEW INDEX OF ANTERIOR ACETABULAR COVER

The vertical-centre-anterior margin (VCA) angle quantifies the anterior cover of the femoral head. However, when the femoral head is deformed it may be difficult to identify its centre. We have therefore created a new index, the anterior acetabular head index (AAHI) which is measured on the false-profile radiograph. We measured the VCA and AAHI angles in 312 hips in which the centre-edge angle was >25 degrees. There were 250 patients, 86 men and 164 women, whose ages ranged from 20 to 65 years. The mean AAHI was 84.1% (81.7% in women and 88.5% in men). There was a correlation between the AAHI and VCA angles. Our data suggest that the AAHI is useful in the evaluation of anterior acetabular cover and that it is higher in men than in women.

Regulation of ER molecular chaperone prevents bone loss in a murine model for osteoporosis

Endoplasmic reticulum (ER) stress response is important for protein maturation in the ER. Some murine models for bone diseases have provided significant insight into the possibility that pathogenesis of osteoporosis is related to ER stress response of osteoblasts. We examined a possible correlation between osteoporosis and ER stress response. Bone specimens from 8 osteoporosis patients and 8 disease-controls were used for immunohistochemical analysis. We found that ER molecular chaperones, such as BiP (immunoglobulin heavy-chain binding protein) and PDI (protein-disulfide isomerase) are down-regulated in osteoblasts from osteoporosis patients. Based on this result, we hypothesized that up-regulation of ER molecular chaperones in osteoblasts could restore decreased bone formation in osteoporosis. Therefore, we investigated whether treatment of murine model for osteoporosis with BIX (BiP inducer X), selective inducer BiP, could prevent bone loss. We found that oral administration of BIX effectively improves decline in bone formation through the activation of folding and secretion of bone matrix proteins. Considering these results together, BIX may be a potential therapeutic agent for the prevention of bone loss in osteoporosis patients.

Evaluation of acetabular coverage of the femoral head with anteroposterior and false profile radiographs of hip joint

To assess the three-dimensional acetabular coverage of the femoral head, we focused on Wibergs center-edge (CE) angle on anteroposterior radiographs and Lequesnes vertical-center-anterior margin (VCA) angle on false profile radiographs of the hip joint. The study analyzed 566 hip joints of 283 subjects with coxarthrosis (mean age, 34 years). We examined three-dimensional coverage using a calculation program for determining acetabular coverage from anteroposterior radiographs of the hip. There was a significant correlation between acetabular coverage, the CE angle, and the VCA angle (P<0.001). The relationship between the VCA angle (X1), the CE angle (X2), and the acetabular coverage (Y) on multiple regression analysis was:Y=47.8+0.06 X1+1.03 X2 (r=0.97;P<0.001)We investigated patients showing normal CE and Sharp angles, despite having clinical symptoms, but abnormal VCA angles. This was the finding for 11 joints (10.9%). Therefore, to assess acetabular coverage, it is important to examine not only the CE angle but also the VCA angle. The VCA angle reflects both anterior coverage and pelvic tilt in the standing position. This technique makes it possible to estimate acetabular coverage without special facilities and may be useful for the mass screening of hip joints for detecting acetabular dysplasia.

Therapeutic efficacy of intra-articular adrenomedullin injection in antigen-induced arthritis in rabbits

IntroductionAdrenomedullin is a potent vasodilatory and hypotensive peptide as well as an endogenous immunomodulatory factor with predominantly anti-inflammatory effects. The purpose of the present study was to evaluate the therapeutic effects of adrenomedullin in rabbits with antigen-induced arthritis, an experimental model of rheumatoid arthritis.MethodsFollowing the induction of arthritis in both knee joints by ovalbumin injection into the joint spaces of pre-immunized rabbits, increasing daily doses of adrenomedullin were injected into the knee joint spaces or saline was injected into the contralateral knee joint spaces as the control. For time-course experiments, adrenomedullin and saline were injected into the knee joint spaces daily for 7 days and 20 days. The degree of joint swelling and the histological change in the knee joints injected with adrenomedullin were compared with the control knee joints. Histological evaluation of the infrapatellar fat pads and synovial tissue was performed. TNFα, IL-6, vascular endothelial growth factor and transforming growth factor-beta mRNA levels in the synovial tissue were measured using real-time quantitative PCR.ResultsDaily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis decreased joint swelling. Histological examination revealed that adrenomedullin reduced edematous changes and the infiltration of inflammatory cells in the synovial tissues. Analysis of mRNA levels showed that adrenomedullin significantly reduced TNFα mRNA expression by 21% to 49% in a dose-dependent manner, and dose-dependently increased IL-6 mRNA expression by 45% to 121%.ConclusionsThese results suggest that daily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis ameliorated the inflammatory response in arthritic joints. Adrenomedullin may thus be useful as a treatment for rheumatoid arthritis; however, the effect of adrenomedullin on IL-6 production in the synovial tissue may be an undesirable adverse effect in rheumatoid arthritis therapy.

In-vitro biomechanical evaluation of stress shielding and initial stability of a low-modulus hip stem made of β type Ti-33.6Nb-4Sn alloy

Stress shielding-related proximal femoral bone loss after total hip arthroplasty occurs because of the different stiffness of metallic alloy stems and host bone. To overcome this, we fabricated a low-modulus cementless hip stem from β-type Ti-33.6Nb-4Sn alloy (TNS). Then we evaluated its stiffness, stress shielding, and initial stability compared with a similar Ti-6Al-4V alloy stem. Stiffness was determined by axial compression and cantilever-bending tests. Thirteen triaxial strain gages measured cortical strain. Stress shielding was defined as the percentage of intact strain after stem insertion. To evaluate initial stability, displacement transducers measured axial relative displacement and rotation. Intact and implanted femurs underwent single-leg-stance loading. Axial stiffness was 56% lower in the TNS stem than in the Ti-6Al-4V stem, and bending stiffness of the TNS stem decreased gradually from the proximal region to the distal region, being ≤ 53% that of the Ti-6Al-4V stem, indicating gradation of Youngs modulus. The TNS stem decreased stress shielding in the proximal calcar region (A1: 83%, B1: 85% relative to intact cortical strain) without affecting the proximal lateral region (B3: 53%). The initial stabilities of the stems were comparable. These findings indicate that the TNS stem with gradation of Youngs modulus minimizes proximal femoral bone loss and biological fixation, improving long-term stability.