Yasutaka Matsuda

Development of bioactive bone cement and its clinical applications

This paper is a summary of already published papers on the bioactive bone cement (BA cement) which consists of CaO-SiO2-P2O5-MgO-CaF2 (AW glass-ceramic) powder and bisphenol-a-glycidyl methacrylate (Bis-GMA) resin. Two types of BA cement, dough and injection type, were prepared by changing their chemical compositions slightly. They harden in a few minutes exhibiting much lower curing temperature than PMMA cement. They have significantly higher compressive, bending, and tensile strengths than PMMA cement and have a character of bonding directly with bone in 4-8 weeks in vivo. Intercalary prosthetic replacement of the femur and total prosthetic replacement of the hip were performed in dogs using either PMMA cement or BA cement. Mechanical tests demonstrated that fixation strengths of these prostheses with BA cement increased with time and were significantly greater than those with PMMA cement tested at any time. Results of histological examinations showed direct bonding between BA cement and bone, and that the bone trabeculae around BA cement mantle grew with time, while with PMMA cement an intervening soft tissue layer was always observed at the cement-bone interface. BA cement was used in a few aged patients to install a hip prosthesis either in cases of revision or femoral neck fracture. The longest follow-up period of the patient is 4 yrs. The patients have been doing well with no adverse effect of the cement to date.

Cementless total hip replacement. Bio-active glass ceramic coating studied in dogs.

We studied 2 types of a cementless total hip prosthesis in dogs. Both were coated with titanium plasma-spray. In both components, the pores in the deep layer of 1 group were further coated with apatite and wollastonite containing glass-ceramic (AW glass-ceramic). 50 dogs underwent unilateral total hip replacements, and were killed at 1, 3, or 6 months postoperatively. We evaluated the femoral and the acetabular components mechanically and histologically. At 1 month, the detaching load and bone ingrowth of the AW glass-ceramic-coated femoral and acetabular components were higher than those of the control implants. At 3 and 6 months there were no differences between the 2 types of components. Thus, AW glass-ceramic enhanced the early phase of cementless implant fixation.

Considerations for surgical treatment of patients with upper lumbar disc herniations

Nine patients treated by surgery for upper lumbar disc herniations were reviewed. Of nine patients with upper lumbar disc herniations at the L1-L2 or L2-L3 level, five were treated by anterior procedures, whereas four underwent posterior procedures. Four of the five patients on whom anterior procedures were performed underwent additional spinal instrumentation using the Kaneda device and Z-plate system. Clinical symptoms improved in all nine patients. Confirmation of the type and level of disc herniation and increased thoracolumbar kyphosis must be taken into consideration when the optimal surgical procedure and spinal instrumentation method are selected.

Femoral component made of Ti-15Mo-5Zr-3Al alloy in total hip arthroplasty

We have developed a femoral component made of Ti-15Mo-5Zr-3Al alloy for total hip prostheses. In vitro mechanical experiments showed that this alloy had better mechanical properties than Ti-6Al-4V alloy with respect to yield strength, tensile strength, elongation, and reduction of area. The elastic modulus of the Ti-15Mo-5Zr-3Al alloy was lower than and its fatigue properties were superior to those of the Ti-6Al-4V alloy. Intraosseous implantation experiments in vivo revealed favorable bone formation around the implants made of Ti-15Mo-5Zr-3Al in rat tibia and no inflammatory responses to the implant. Ti-15Mo-5Zr-3Al alloy appears to be a suitable material for the femoral components of total hip prostheses.

Severe metallosis due to abnormal abrasion of the femoral head in a dual-bearing hip prosthesis : a case report

The authors report on a patient with a case of severe metallosis due to an abnormal abrasion of the femoral head. A primary arthroplasty was performed using a dual bearing hip prosthesis with acetabular bone grafting by ceramic screws. At the time of the revision surgery the synovia was black, and an analysis using a scanning electron microscope and scanning electron microscope-electron probe micro-analyzer revealed numerous small particles of small alumina ceramic on the inner surface of the bearing insert of high-density polyethylene. These particles, which came from the broken ceramic screws due to proximal migration of the prosthesis, scraped the femoral head away. A line and area analysis of the black synovia revealed that the synovia contained metal particles of a cobalt-chromium alloy as well as a cobalt ion. The patients serum showed elevated concentrations of cobalt, chromium, and molybdenum that dramatically reduced 2 months after the revision surgery.

A New Model of Bone-Conserving Cementless Hip Prosthesis Made of High-Tech Materials: Kobelco H-5

A new model of bone-conserving cementless hip prosthesis was developed aiming at reducing the wear rate of the ultrahigh-molecular-weight polyethylene (UHMWPE) socket, minimizing the stress-shielding effect on the femur, accelerating the initial bonding between the bone and prosthesis components, and preventing third body wear. The stem and the socket back are made of vanadium-free titanium alloy (Ti-6A1-2Nb-lTa); a zirconia femoral head with a diameter of 22 mm is articulated against a UHMWPE socket, and the titanium plasma spray coating in combination with a bottom coating of apatite-wollastonite containing glass-ceramic (AW-GC) is applied over the whole surface of the socket back and a small area of the proximal part of the stem. Animal experiments using canine hip joints revealed that the AW-GC bottom-coated socket and stem developed significantly earlier bone-bonding than those with titanium plasma spray coating alone. Ninety-six osteoarthritic hip joints of 76 female and 12 male patients aged between 37 and 79 years underwent total hip replacement by the use of this cementless hip prosthesis during the period between 1992 and 1995. There were 4 cases of early postoperative dislocation and 1 case of thigh pain, but no cases of loosening of the prosthesis. Radiologically, bone ingrowth into the bottom-coated surface was satisfactory in 95% of cases at the latest follow-up at an average of 4 years postoperatively.

Computer Simulation for the Planning of Total Hip Replacement: Improvement of the Simulation System

We have already developed a system using computerized tomography (CT) and computer simulation for estimating the optimal size and position of the socket in total hip replacement [1]. We have now improved the system, in that CT images are input not by a digitizer but by a TV camera. It takes only 10–15 min to complete the simulation in the new system. Another benefit is that the socket images are overlapped not on the contours of the acetabulum but on its real CT images. Therefore, we can easily distinguish whether sclerotic subchondral bone or soft cancellous bone contacts the socket after reaming. The new system is time-saving and provides us with more accurate preoperative information; it can easily be used routinely, supporting the surgeon’s intraoperative visual assessments.

Preclinical and Clinical Application of Bioactive Bone Cement

ABSTRACT A new bioactive bone cement, consisting of CaO-SiO 2 -P 2 O 5 -CaF 2 glass powder and disphenol-a-glycidyl methacrylate (Bis-GMA) resin, forms direct bonding with living bone tissue within a few weeks after implantation. Its compressive strength after hardening is 180MPa. The bioactive bone cement has been used to fix a hip prosthesis in 12 dogs, and the results of histological and mechanical examinations performed 4 to 25 weeks after implantation were compared with those obtained in another 12 dogs with PMMA bone cement. Femurs containing the prosthesis stem were transectioned into 5mm thick segments, and failure loads obtained in each group by push out test of the stem for each segment were compared to each other. The failure load with bioactive bone cement was 1.2 and 1.7 times greater than that with PMMA cement one month and three months after implantation respectively. The former further increased significantly as time goes thereafter, while the latter remained unchanged. The bioactive bone cement was used in a few aged patients with loosened hip prostheses for the purpose to substitute for a large bone defect and to fix a new prosthesis at revision operation. The longest follow up period is still 10 months, but the patients have been doing well with no adverse effect to date.

The application of titanium alloy wires for the reattachment of the greater trochanter in total hip arthroplasty

We developed a new fixing method using titanium alloy wires in order to facilitate the attachment of the greater trochanter in total hip arthroplasty. This wire is composed of Ti-3Al-2.5V by weight. According to the fatigue test in vitro, the titanium alloy wire had better fatigue properties than Ortron 90 wire of the same diameter. In experiments in vivo, both titanium alloy wires and SUS-316L wires were used for the reattachment of the greater trochanter of dogs, and the titanium alloy wires showed better biocompatibility than the latter. Thus, titanium alloy wires seem applicable for the reattachment of the greater trochanter in human total hip arthroplasty.

Glass ceramic augmentation of the acetabulum: Total hip arthroplasties in 24 dogs

Implants made of glass-ceramic containing apatite and wollastonite were used for reconstruction of large bone defects of the weight-bearing acetabulum in canine total hip arthroplasties. 24 dogs underwent replacements and were killed after 3, 6, and 12 months. The interface between the prosthesis and bone was examined radiographically, histologically, and mechanically. Bone bonding with the prosthesis occurred in all the implants. Glass ceramic containing apatite and wollastonite implants seem promising for use in total hip arthroplasty as filling materials for large defects in weight-bearing bone.