Nobuhiro Kaku

Manipulation of anabolic and catabolic responses with bone morphogenetic protein and zoledronic acid in a rat spinal fusion model.

Bone fusion involves a complex set of regulated signaling pathways that control the formation of new bone matrix and the resorption of damaged bone matrix at the surgical site. It has been reported that systemically administering a single dose of zoledronic acid (ZA) at the optimal time increases the strength of the bone morphogenetic protein (BMP)-mediated callus. In the present study, we aimed to investigate the effect of BMP-2 and ZA in a rat spinal model. Sixty-seven rats were divided into 6 groups: group I (n=11) animals were implanted with a carrier alone, group II (n=12) animals were implanted with a carrier and a subcutaneous injection of ZA was administered 2weeks after surgery, group III (n=12) animals were implanted with a carrier containing 1μg of rhBMP-2, group IV (n=12) animals were implanted with a carrier containing 1μg of rhBMP-2 and a subcutaneous injection of ZA was administered 2weeks after surgery, group V (n=10) animals were implanted with a carrier containing 3μg of rhBMP-2, and group VI (n=10) animals were implanted with a carrier containing 3μg of rhBMP-2 and a subcutaneous injection of ZA was administered 2weeks after surgery. The rats were euthanized after 6weeks, and their spines were explanted and assessed by manual palpation, radiography, high-resolution micro-computerized tomography (micro-CT), and histologic analysis. The fusion rates in group VI (60%) were considerably higher than those in the groups I (0%), II (0%), III (12.5%), IV (20.8%), and V (35%), (P<0.05). Additionally, the radiographic scores of group VI were higher than those in the other groups, (P<0.05). In micro-CT analysis, the tissue and bone volumes of the callus were significantly higher in group VI than those in the other groups, (P<0.05). The trabecular number was significantly higher and the trabecular spacing was significantly lower in group VI than those in the other groups, (P<0.05). The combination of rhBMP-2 and ZA administered systemically as a single dose at the optimal time was efficacious in our rat spinal fusion model. Our results suggest that this combination facilitates spinal fusion and has potential clinical application.

Analysis of wear and oxidation on retrieved bipolar polyethylene liner

BackgroundFor bipolar prostheses, most of the previous studies attributed the occurrence of osteolysis to wear debris generated from the bearing surface. We looked closely into the wear debris and reported on our findings with respect to the oxidation index and the rate of wear in ultra-high molecular weight polyethylene (UHMWPE) inserts retrieved from bipolar prostheses after various spans of time in vivo.MethodThe inserts were retrieved from the heads of three types of bipolar prosthesis (UH1, UPF1, UPF2). We retrieved 24 bipolar prostheses from 23 patients whose mean implantation period was 10.0 years (2.7–15.4 years).ResultsAll the retrieved polyethylene had a burnished bearing surface. In all, 92% (22/24) of these inserts had indentation and roughness at the rim and flange, suggesting neck-cup impingement; periprosthetic fracture occurred in the other two inserts. The mean linear wear rate was 0.035 mm per year. The average maximum oxidation index for the inserts with osteolysis was 3.34, and it was was 3.49 for the inserts without osteolysis. We, therefore, could not detect any significant difference between the aforesaid groups of inserts.ConclusionsThe results strongly suggest that most of the polyethylene wear debris was not generated from the bearing surface. Moreover, the wear debris generated from neck-cup impingement may well be the cause of an inflammatory reaction, which in turn has a strong potential to become the primary cause of osteolysis.

Subchondral cyst of the tibia secondary to Wilson disease

We present the case of a 40-year-old male patient who had been suffering from Wilson disease for over 20 years, whose knee was diagnosed as osteoarthritis combined with subchondral cyst of the tibia. Preoperative examinations (X-ray, CT and MRI) confirmed the diagnosis. The microscopic examination detected thickening of the synovial membrane, and histopathological findings revealed that lymphoid cells and plasma cells were infiltrated at the synovial membrane. On copper-specific staining, no copper pigmentation was identified. However, the energy-dispersive X-ray (EDX) microanalysis revealed copper pigmentation in high concentration. These findings may contribute to our better comprehension of the development process of the arthropathy in patients with Wilson disease. The combination of subchondral cyst with Wilson disease is extremely rare, as only about 16 such cases have been reported in the English literature.

Influence of the volume of bone defect, bone grafting methods, and hook fixation on stress on the Kerboull-type plate and screw in total hip arthroplasty: three-dimensional finite element analysis.

For total hip arthroplasty or revision surgery using acetabular reinforcement cross-plates, choosing between bulk and morselized bone grafts for filling acetabular defects is challenging. We used finite element model (FEM) analysis to clarify various stresses on the cross-plate based on bone defect size, bone graft type, and presence or absence of hook fixation to the bone. We constructed 12-pattern FEMs and calculated the maximum stress generated on the Kerboull-type (KT) plate and screw. Bone defects were classified into four patterns according to the volume. Regarding the bone graft type, bulk bone grafts were considered as cortical bone, and morselized bone grafts were considered to consist of cancellous bone. Models were compared based on whether hook fixation was used and whether a gap was present behind the plate. The upper surface of the host bone was fixed, and a 1,000-N load was imposed on the horizontal axis at 71°. Larger bone defects increased the stress on the KT plate and screws. This stress increased when no bone was grafted; it was lower when bulk cortical bone grafts were used for filling than when morselized cancellous bone grafts were used. For cortical bone grafts, the increased stress on the KT plate and screws was lowered with hook removal. Attaching the hook to the bone and filling the gap behind the KT plate with an adequate bone graft reduced the stress on the KT plate and screws, particularly for large bone defects filled by bulk bone grafting.

Does the self-centering mechanism of bipolar hip endoprosthesis really work in vivo?

Purposes. To examine radiographically the component motion in a bipolar prosthesis and to determine whether the self-centering mechanism really works in vivo. Methods. 38 patients with 41 bipolar hip endoprostheses (30 for coxarthrosis and 11 for osteonecrosis of femoral head) were included in this study. Two radiographs of each case were taken to evaluate the self-centering mechanism. The first anteroposterior radiograph of both hip joints was taken at the maximum abduction while the patient standing on the endoprosthetic leg. The second radiograph was taken after the patient returned to neutral position while standing on 2 legs. In the present study, the order in which the radiographs were taken differed from previously reported studies. The radiographs were analysed using the method similar to that of Drinker and Murray. The adductive motion from abduction to a neutral position is within the range of inner bearing oscillation. Results. The outer head alignment changed from 23 degrees to 12 degrees in the patients with osteonecrosis. However, the valgus position of the outer head (36 degrees) remained unchanged in the patients with coxarthrosis standing on 2 legs in the neutral position. Conclusion. The self-centering mechanism of the bipolar endoprosthesis functioned in the patients with osteonecrosis, but did not work in the coxarthrosis group.

Enhancement of the Effects of Exfoliated Carbon Nanofibers by Bone Morphogenetic Protein in a Rat Femoral Fracture Model

Exfoliated carbon nanofibers (ExCNFs) are expected to serve as excellent scaffolds for promoting and guiding bone‐tissue regeneration. We aimed to enhance the effects of ExCNFs with bone morphogenetic proteins (BMPs) and examine their feasibility and safety in clinical applications using a rat femoral fracture model. Group I (n = 16) animals were implanted with control MedGEL. Group II (n = 17) animals were implanted with MedGEL containing ExCNFs. Group III (n = 15) animals were implanted with MedGEL containing 1 μg rhBMP‐2. Group IV (n = 15) animals were implanted with MedGEL containing 1 μg rhBMP‐2 and ExCNFs. The rats were euthanized after 6 weeks, and their fractured femurs were explanted and assessed by manual palpation, radiographs, and high‐resolution microcomputerized tomography (micro‐CT); the femurs were also subjected to biomechanical and histological analysis. The fusion rates in Group IV (73.3%) were considerably higher than those in Groups I (25.0%), II (52.9%), and III (46.7%). The results demonstrated the enhancement of the bone repair effects of ExCNFs by BMP in a rat femoral fracture model. Our results suggest that the enhancement of the effects of ExCNFs by BMP makes the combination a possible attractive therapy for various orthopedic surgeries.

Symptomatic Spinal Cord Kinking Due to Focal Adhesive Arachnoiditis, With Ossification of the Ligamentum Flavum: A Case Report

Study Design. A case report. Objective. To describe a rare case of symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with ossification of the ligamentum flavum (OLF). Summary of Background Data. Spinal cord kinking without spinal surgery is rare, and symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is even rarer. Methods. A 66-year-old female presented with numbness of the lower extremities and subsequently experienced gait disturbance due to motor weakness. Magnetic resonance imaging of the thoracic spine showed anterior displacement and kinking of the spinal cord from T11 to T12. Laminectomy and OLF resection were performed. The arachnoid membrane at the affected part was markedly thick and seemed cloudy. Adhesiolysis for arachnoid adhesion and release of spinal kinking were performed. Results. She could walk with a cane 6 months postoperatively. One year postoperatively, thoracic computed tomography–myelography showed that the cord was repositioned in the dural sac, and that release of the spinal cord kink was maintained. Conclusion. Symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is a rare clinical condition. It was difficult to diagnose the precise pathology of the spinal cord before surgery. Microsurgical arachnoidolysis resolved the spinal cord kinking, and no recurrence was noted within the follow-up period. Level of Evidence: N/A

Qualitative analysis of polyethylene wear in a bipolar femoral prosthesis: A case report.

We researched the qualitative changes in the polyethylene of a bipolar head retrieved at revision occurring in vivo using optical microscopy and Fourier transform infrared spectroscopy. The bearing surface of the outer head was smooth with no definable scratches delamination. However, the evidence of delamination of the beveled throat region and cracking at the base of the leaf was noticed. The degree of oxidation was different in each area of the polyethylene in the bearing component and that of the rim was shown to be higher than that of the bearing surface. Comparing the rate of ketone and ester, ketone binding was frequently found around the prosthetic rim rather that at the bearing surface. However, the ratio of ester at the surface was higher than that at the deep area of the same rim. We considered these results showed local environmental effects in vivo play a significant role in dictating the response.

Prevalence and distribution of thoracic and lumbar compressive lesions in cervical spondylotic myelopathy.

Study Design Retrospective cross-sectional study. Purpose This study analyzed the prevalence and distribution of horacic and lumbar compressive lesions in cervical spondylotic myelopathy as well as their relationships with cervical developmental spinal canal stenosis (DCS) by using whole-spine postmyelographic computed tomography. Overview of Literature There are few studies on missed compressive lesions of the spinal cord or cauda equina at the thoracolumbar level in cervical spondylotic myelopathy. Furthermore, the relationships between DCS, and the prevalence and distribution of thoracic and lumbar compressive lesions are unknown. Methods Eighty patients with symptomatic cervical spondylotic myelopathy were evaluated. Preoperative image data were obtained. Patients were classified as DCS or non-DCS (n=40 each) if their spinal canal longitudinal diameter was <12 mm at any level or ≥12 mm at all levels, respectively. Compressive lesions in the anterior and anteroposterior parts, ligamentum flavum ossification, posterior longitudinal ligament ossification, and spinal cord tumors at the thoracolumbar levels were analyzed. Results Compressive lesions in the anterior and anteroposterior parts were observed in 13 (16.3%) and 45 (56.3%) patients, respectively. Ligamentum flavum and posterior longitudinal ligament ossification were observed in 19 (23.8%) and 3 (3.8%) patients, respectively. No spinal cord tumors were observed. Thoracic and lumbar compressive lesions of various causes tended to be more common in DCS patients than non-DCS patients, although the difference was statistically insignificant. Conclusions Surveying compressive lesions and considering the thoracic and lumbar level in cervical spondylotic myelopathy in DCS patients are important for preventing unexpected neurological deterioration and predicting accurate neurological condition after cervical surgery.

Bilateral Greater Trochanteric Avulsion Fractures after Bilateral Simultaneous Total Hip Arthroplasty

We report a case of bilateral spontaneous greater trochanteric fracture after bilateral simultaneous total hip arthroplasty (THA) performed via the posterolateral approach during the early postoperative phase. A 75-year-old woman underwent bilateral simultaneous THA (BS-THA) for severe osteoarthritis with developmental dysplasia of the hip; she also presented a limited range of adduction. BS-THA was successful without any intraoperative complications. Rehabilitation with full weight-bearing exercises was initiated the day after the surgery. On the 14th postoperative day, she experienced a spontaneous left greater trochanteric fracture during a walking exercise without any trauma. Osteosynthesis was performed for the fracture on the 18th postoperative day. On the 20th postoperative day, a right spontaneous greater trochanteric avulsion fracture occurred during a transfer exercise without any trauma; this was treated on the 27th postoperative day. In the 18th postoperative month, although the right fragment showed slight upper migration, the patient had no complaints of coxalgia and both hip joints showed an excellent range of motion.