Haruo Kawamura

Zinc-releasing calcium phosphate for stimulating bone formation ☆

Zinc-containing tricalcium phosphate (ZnTCP) is biocompatible and bioactive, and functions as an effective zinc carrier. ZnTCP contains a maximum of 12 mol% of zinc. ZnTCP ceramics and composite ceramics of ZnTCP and hydroxyapatite (ZnTCP/HAP) with a (Ca+Zn)/P molar ratio of 1.60 were prepared by sintering at 1100 °C. ZnTCP/HAP continued to release zinc for more than 50 days in 0.9 wt.% sodium chloride solution. ZnTCP/HAP with a zinc content of 1.2 wt.% significantly increased osteoblastic MC3T3-E1 cell proliferation and alkaline phosphatase activity of rat stromal cells in vitro. ZnTCP/HAP with a zinc content of 0.316 wt.% increased bone formation by 51% (n=6; p=0.0509) 4 weeks after implantation in rabbit compared to the control without zinc. A zinc concentration within a noncytotoxic level of a solution does not completely block the crystal growth of apatite in the solution. When ZnTCP is added to calcium phosphate cement, the ZnTCP showed neither inhibitory nor promoting effect on the setting ability of the cement. All these findings suggest that the zinc-containing tricalcium phosphate is a biomaterial that has a pharmaceutical effect of promoting bone formation.

Stimulatory effect of zinc-releasing calcium phosphate implant on bone formation in rabbit femora

Although hydroxyapatite (HAP) and tricalcium phosphate (TCP) are currently used as bone graft substitutes or coatings on metallic prostheses because of their excellent biocompatibility and osteoconductivity, they do not stimulate bone formation or inhibit bone resorption. Zinc, an essential trace element in many animals, has a direct specific proliferative effect on osteoblastic cells and has a potent and selective inhibitory effect on osteoclastic bone resorption in vitro. Therefore, zinc-containing beta-tricalcium phosphate (ZnTCP) ceramics and composite ceramics of ZnTCP and HAP (ZnTCP/HAP) were implanted in the femora of New Zealand White rabbits for 4 weeks to promote bone formation. The implants were sintered ceramics with zinc contents of 0 (control), 0.063, 0.316 and 0.633 wt %. Histological and histomorphometrical investigation of the undecalcified sections revealed an increase by 51% (p =.0509) in the area of newly formed bone around the ZnTCP/HAP implants of 0. 316 Zn wt % compared with the control. Plasma zinc concentration was unchanged. An increased bone resorption on the endosteal surface was observed when ZnTCP and ZnTCP/HAP of 0.633 Zn wt % were implanted. To promote bone formation, the optimum zinc content of the calcium phosphate ceramics was therefore 0.316 wt %.

Midterm results of the Synergy cementless tapered stem : stress shielding and bone quality

BackgroundTapered femoral stems have been shown to produce less thigh pain and stress shielding than other cement-less stem designs. The purpose of this study was to examine the performance of this type of femoral stem in Japanese patients.MethodsA series of 40 total hip arthroplasties with a Synergy tapered femoral component were performed in 33 patients between March 1999 and February 2001 at our institution. Three hips (in three patients) were lost to follow-up, so 37 hips in 30 patients were followed for an average of 70 months. The patients’ average age at the time of surgery was 59 years (range 43–80 years). Clinical evaluation included the Japanese Orthopaedic Association (JOA) Hip Score and the incidence of thigh pain. Preoperative radiographic examination included the cortical index and Dorr’s bone type. Postoperative radiographic examination included evaluation of biological fixation, spot welds, cortical hypertrophy, and stress shielding.ResultsThe average JOA Hip Score improved significantly from 35 preoperatively to 91 postoperatively. No patient suffered thigh pain. All femoral components were classified as bony stable. Spot welds and cortical hypertrophy were commonly found in the middle to the distal portion of the component. Severe (third and fourth degree) stress shielding was observed in 24.3% of the cases. A low cortical index, a Dorr type C femur, and a large stem size were associated with severe stress shielding.ConclusionsThe midterm clinical results with the Synergy femoral component were satisfactory for Japanese patients. Although severe stress shielding was frequently observed in patients with poor bone quality, stem stability was not affected. Extent of grit blasting and stem length may be factors causing severe stress shielding in Japanese patients with poor bone quality. In conclusion, poor bone quality is a less favorable indication for the cementless tapered stem.

Follow-Up Results of 10–12 Years After Total Hip Arthroplasty Using Cementless Tapered Stem — Frequency of Severe Stress Shielding With Synergy Stem in Japanese Patients

Synergy stems are tapered stems featuring a proximal porous coating, grid blasting below the proximal third to the distal end. This study included 41 patients (50 hips) who underwent total hip arthroplasty with follow-ups for 10 years or more. No stem reimplantations were performed. Spot welds were observed in the distal stem in Gruen zones 3 and 5 in 35 and 32 hips, respectively. First-degree stress shielding occurred in 8 hips; 2nd-degree, 20 hips; 3rd-degree, 13 hips; and 4th-degree, 9 hips. Because of bone fixation to the distal grit-blasted section of the stem, severe stress shielding was observed in nearly half of the cases. Multiple regression analysis of stress shielding determinants revealed a correlation between stem size and short patient height, showing the cause of stress shielding to be a mismatch in size between the stem and the femoral bone.

Osseointegration of porous titanium implants with and without electrochemically deposited DCPD coating in an ovine model

BackgroundUncemented fixation of components in joint arthroplasty is achieved primarily through de novo bone formation at the bone-implant interface and establishment of a biological and mechanical interlock. In order to enhance bone-implant integration osteoconductive coatings and the methods of application thereof are continuously being developed and applied to highly porous and roughened implant substrates. In this study the effects of an electrochemically-deposited dicalcium phosphate dihydrate (DCPD) coating of a porous substrate on implant osseointegration was assessed using a standard uncemented implant fixation model in sheep.MethodsPlasma sprayed titanium implants with and without a DCPD coating were inserted into defects drilled into the cancellous and cortical sites of the femur and tibia. Cancellous implants were inserted in a press-fit scenario whilst cortical implants were inserted in a line-to-line fit. Specimens were retrieved at 1, 2, 4, 8 and 12 weeks postoperatively. Interfacial shear-strength of the cortical sites was assessed using a push-out test, whilst bone ingrowth, ongrowth and remodelling were investigated using histologic and histomorphometric endpoints.ResultsDCPD coating significantly improved cancellous bone ingrowth at 4 weeks but had no significant effect on mechanical stability in cortical bone up to 12 weeks postoperatively. Whilst a significant reduction in cancellous bone ongrowth was observed from 4 to 12 weeks for the DCPD coating, no other statistically significant differences in ongrowth or ingrowth in either the cancellous or cortical sites were observed between TiPS and DCPD groups.ConclusionThe application of a DCPD coating to porous titanium substrates may improve the extent of cancellous bone ingrowth in the early postoperative phase following uncemented arthroplasty.

The 21- to 27-year results of the Harris-Galante cementless total hip arthroplasty

BACKGROUND The Harris-Galante total hip arthroplasty (THA) is a first-generation cementless THA with a porous coating for biological fixation of the implant. Many studies report excellent long-term results for the acetabular cup, but few long-term studies exist for the femoral stem because of relatively poor short-term and midterm results. Here we present the 21- to 27-year results of the cup and the stem of the Harris-Galante THA. METHODS From 1985 to 1991, 102 Harris-Galante THAs were inserted in 82 patients. At the time of the THA, the mean patient age was 54 years (range, 20-78 years). The primary diagnosis was secondary osteoarthritis due to developmental hip dysplasia (69 [68%] hips). The Japanese Orthopaedic Association (JOA) hip score and thigh pain were measures of clinical outcome. Radiographic review was performed retrospectively. Implant survival was evaluated by Kaplan-Meier analysis. RESULTS Of 102 hips, 35 hips were from 31 deceased patients, 5 patients (6 hips) were lost to follow-up, 12 hips were revised, and 49 hips were from patients living at the latest follow-up. Among the living patients, 36 hips had a clinical evaluation and 42 hips had a radiograph obtained more than 21 years. The JOA hip score improved from 42 points preoperatively to 83.5 points at the latest follow-up. Thigh pain was reported in 13 hips. One cup and four stems were loose at the latest radiographic review. Most cup revisions were related to acetabular osteolysis. Fifteen hips showed severe stress shielding. Kaplan-Meier analysis of survivorship with any revision, acetabular reoperation, stem revision, and stem loosening as the end point was 87.0%, 90.3%, 95.7% and 86.4%, respectively, at 24.6 years. CONCLUSIONS Long-term implant survival and clinical results of the Harris-Galante THA were good. Acetabular osteolysis-related cup loosening was a problem of the cup. Loosening, thigh pain, and stress shielding were problems of the stem.

Nontraumatic central fracture dislocation of the hip in a patient with chronic kidney disease and post gastrectomy.

Objective: Patients with secondary hyperparathyroidism caused by chronic kidney disease (CKD) develop secondary osteoporosis, which increases fracture risk. We report a case of insufficiency fractures complicated by secondary osteoporosis caused by chronic renal failure and gastrectomy. Patient: A 78-year-old man with a medical history of nephrotic syndrome and gastric cancer experienced an occult intertrochanteric fracture of his left femur after falling. Results: Ten days after the first fracture, the patient was treated with hemodialysis for acute uremic symptoms. Eight weeks after this fracture, he sustained a right insufficiency acetabular fracture and was treated with total hip arthroplasty (THA). Conclusion: For patients with CKD, effective fracture prevention is difficult. THA with reconstruction of the acetabulum was an effective therapy in a patient with nontraumatic central fracture dislocation of the hip.