Kensaku Masuhara

Ectopic bone induction on and in porous hydroxyapatite combined with collagen and bone morphogenetic protein.

Porous hydroxyapatite (HA-P) discs (5 mm in diameter; 1.5 mm thick; porosity, 80%; mean pore size, 200 micron) were impregnated with purified bovine skin collagen (1 mg/disc) and a small amount of semipurified bone morphogenetic protein (BMP) of sarcoma origin (100 micrograms/disc) and implanted into dorsal muscles of ddY mice. Within one week new ectopic cartilagenous tissue was consistently formed on the surface of the discs adjacent to the host tissue. The cartilage was resorbed and replaced by normal bone containing hematopoietic bone marrow four weeks after implantation and the discs became encased in the newly formed bone. HA-P discs impregnated with only collagen (HA-P/collagen) or only BMP (100 micrograms/disc; HA-P/BMP) did not evoke formation of new cartilage or bone. These results indicate that collagen is effective as a carrier of BMP for expression of the biologic activity of the latter in vivo and that it may be of practical use as a carrier of BMP with synthetic biomaterials.

Longitudinal evaluation of time related bone remodeling after cementless total hip arthroplasty.

Bone remodeling after cementless total hip arthroplasty was evaluated by dual energy xray absorptiometry in a longitudinal study of 32 hips. After insertion of a fully porous surface anatomic stem made of cobalt chromium, bone mineral density was analyzed until at least 2 years postoperatively. Bone remodeling was evaluated in terms of regional bone density changes in the seven adjacent periprosthetic zones as well as the global change in bone density distribution over the entire periprosthetic area. At 12 months after the operation, the averaged regional bone mineral density in all seven zones showed a rapid decrease, ranging from 9% to 24% of the bone mineral density present at 2 weeks postoperatively. Thereafter, the bone density change appeared to be stabilized. The global change in the bone density distribution was expressed as two summarizing statistical indexes derived from principal component analysis: the first index represents the change of average bone mineral density over the entire periprosthetic area, and the second represents the severity of bone mineral density decrease in the proximal area versus the distal area. The second index proved that more bone density reduction occurred in the proximal area, but this was variable among patients and correlated significantly with the stem size and the initial bone mineral density in the distal part of the periprosthetic area. This longitudinal dual energy xray absorptiometry study suggests that a large part of the bone remodeling after cementless hip arthroplasty ceases within 1 year postoperatively, and stem size and the initial bone density around the distal portion are important considerations for predicting the proximal bone density decrease during the early rapid remodeling period.

Prognostication of osteonecrosis of the femoral head in patients with systemic lupus erythematosus by magnetic resonance imaging.

To detect and prognosticate osteonecrosis of the femoral head in the preradiographic stage, 60 patients with systemic lupus erythematosus who had normal hip radiology were followed prospectively for a mean period of 5 years (range, 3–7 years) using magnetic resonance imaging (MRI). The first MRI scans showed a low intensity band in the femoral head of normal fat intensity on Tl weighted images in 16 hips of 9 patients. The MRI findings were used to classify the lesions into three categories. Type A (six hips): the lesions occupied the medial one third or less of the weight bearing portion. Type B (two hips): the lesions occupied the medial two thirds or less of the weight bearing portion. Type C (eight hips): the lesions occupied more than the medial two thirds of the weight bearing portion. At the final followup, all of the Type A and one of the Type B hips were classified as being in Stage 1, and one Type B and two Type C hips had progressed to Stage 2. The MRI appearance of six Type C hips had changed from a band to an inhomogeneous pattern with the femoral head progressing to collapse on radiographs 2–5 years after the diagnosis of systemic lupus erythematosus. The remaining hips, which had been classified as normal at the first MRI, maintained a normal appearance, except for one hip that developed a Type A lesion. The presence of a low intensity band on Tl weighted images was an early specific finding of osteonecrosis of the femoral head, and extensive lesions demarcated by band images signified a poorer prognosis in systemic lupus erythematosus patients. If no MRI abnormalities appeared after 1 year of the startup treatment for systemic lupus erythematosus, there was little risk of femoral head collapse based on the subsequent clinical course of the patients followed in the current study.

Interleukin-1β enhance and tumor necrosis factor-α inhibits bone morphogenetic protein-2-induced alkaline phosphatase activity in MC3T3-E1 osteoblastic cells

The modulatory effects of interleukin (IL)-1β and tumor necrosis factor (TNF)-α on bone morphogenetic protein (BMP)-2- and -4-induced alkaline phosphatase (ALP) activity were examined in cultures of mouse MC3T3-E1 osteoblastic cells. Both BMP-2 and -4 significantly induced ALP in these cells. IL-1β alone had no effect on ALP activity, but it significantly enhanced BMP-2- and -4-induced ALP activity. TNF-α suppressed the induction of ALP by BMP-2 or -4. The results suggest that the action of BMP on osteogenic differentiation may be regulated by such immuno/inflammatory cytokines as IL-1β and TNF-α.

Immunolocalization of alkaline phosphatase in osteoblasts and matrix vesicles of human fetal bone

A monoclonal antibody raised against alkaline phosphatase (ALP) of human osteosarcoma was used to localize this enzyme in human fetal bone tissue. For light microscopy, the presence of alkaline phosphatase in osteoblasts and osteocytes was demonstrated by use of an avidin-biotin immunoperoxidase procedure. Electron microscopic immunolocalization was accomplished with an indirect immunoperoxidase method which revealed a concentration of the enzyme on matrix vesicle and osteoblast plasma membranes. In addition, many vesicular protrusions arising from areas of plasma membrane on the lateral surfaces of adjacent osteoblasts were strongly immunolabeled. Immunostaining for ALP was absent in vesicles which contained fine crystallites. Alkaline-phosphatase-rich matrix vesicles may play a significant role in the mineralization of the extracellular matrix.

Tranexamic Acid Reduces Postoperative Blood Loss in Cementless Total Hip Arthroplasty

BACKGROUND Tranexamic acid, an inhibitor of fibrinolysis that blocks the lysine-binding site of plasminogen to fibrin, has been reported to reduce intraoperative and postoperative blood loss in patients undergoing total hip arthroplasty with cement. However, there have been few reports describing the effects of tranexamic acid on blood loss during and following total hip arthroplasty without cement. METHODS We investigated the effects of tranexamic acid in twenty-one patients who underwent staged bilateral total hip arthroplasty without cement for the treatment of osteoarthritis of the hip. The average interval between the two procedures was 16 +/- 16 months. On one side, 1000 mg of tranexamic acid was administered intravenously five minutes before the skin incision. On the other side, tranexamic acid was not administered. Baseline hemoglobin and hematocrit values were obtained three weeks before each arthroplasty. The volume of postoperative blood loss was recorded at two-hour intervals for the first twelve hours and then again at twenty-four hours, and the values were compared between the two groups. RESULTS The total intraoperative blood loss in the tranexamic acid group (607 +/- 298 mL) was similar to that in the control group (633 +/- 220 mL). The postoperative blood loss in the tranexamic acid group was significantly lower than that in the control group at all time-points during the first twenty-four hours (p < 0.001 for all comparisons). The greatest reduction in blood loss was observed during the first four hours after surgery in the tranexamic acid group (p < 0.01). CONCLUSIONS In patients undergoing total hip arthroplasty without cement, preoperative administration of tranexamic acid is associated with decreased postoperative blood loss during the first twenty-four hours, especially during the first four hours after surgery.

MRI OF EARLY OSTEONECROSIS OF THE FEMORAL HEAD AFTER TRANSCERVICAL FRACTURE

We have carried out a prospective study of 17 patients (14 women, 3 men) of mean age 48 years (21 to 76) with transcervical fractures of the femur using MRI to detect early evidence of avascular necrosis of the head. Two fractures were Garden stage I, 12 stage II, and three stage III. We performed internal fixation under radiological control at a mean of five days (2 to 15) after injury using a titanium cannulated cancellous screw or a titanium compression hip screw. MRI was performed at one, six and 12 months and then yearly after operation. T1- and T2-weighted images were obtained by a spin-echo technique. The duration of follow-up of patients who did not subsequently require replacement of the head of the femur was from 2 to 5 years (mean 3.2). One month after operation eight of the 17 hips showed a band of low signal intensity on T1-weighted images and high signal intensity on T2-weighted images indicating lesions in the femoral head away from the fracture line. These were of three types: type I was a small infarct at the superolateral region of the femoral head and was seen in three hips; type II was a shallow lesion from the superolateral region to the fovea of the femoral head (three hips); and type III was a large lesion occupying most of the femoral head (two hips). No further changes were seen in the MRI after six months from operation. Collapse of the femoral head did not occur in the three hips with type-I lesions, but two of the three type-II hips and both type-III hips subsequently collapsed. At the final follow-up the three hips with a type-I lesion and one with a type-II were still asymptomatic but radiography showed sclerosis in the femoral head corresponding to the MRI lesions. The nine hips which showed no changes on MRI at one month had no abnormal findings on physical examination, radiography or MRI at final follow-up.

Evaluation of periprosthetic bone-remodeling after cementless total hip arthroplasty. The influence of the extent of porous coating.

Background: Total hip arthroplasty changes the levels of stress within the proximal part of the femur, and the femur remodels adjacent to the prosthesis. The stem size and the initial bone-mineral density around the distal portion of the stem affect postoperative bone-remodeling after the insertion of a fully porous-coated metal-cancellous prosthesis. The purpose of this study was to evaluate the influence of the extent of porous coating of this prosthesis on femoral bone-remodeling. Methods: A longitudinal examination of sixty-one hips in fifty-four patients was performed. Thirty-one hips in twenty-seven patients with a fully porous-coated stem (Group A) and thirty hips in twenty-seven patients with a proximally porous-coated stem (Group B) were followed for twenty-four to thirty months. Periprosthetic bone-mineral density was measured with dual-energy x-ray absorptiometry at specific intervals after the operation. Results: In both groups, the greatest loss of bone-mineral density, compared with the initial (three-week) value, was approximately 20 percent in zone 7 at twelve to eighteen months. In other zones, bone-remodeling appeared to cease by twelve months. At the last follow-up evaluation, the loss of bone-mineral density in the distal and middle regions in Group A was significantly greater than that in Group B (p < 0.01 for zone 3 and p < 0.05 for zone 6). In contrast, with the numbers available, there were no significant differences in loss of bone-mineral density in the proximal regions (zones 1 and 7) between the two groups at any follow-up period. Conclusions: The extent of porous coating affects bone-remodeling in the distal periprosthetic region rather than in the proximal region. The results in the present report are specific to the particular implants that were studied.

ARTICULAR CARTILAGE EVALUATION IN OSTEOARTHRITIS OF THE HIP WITH MR IMAGING UNDER CONTINUOUS LEG TRACTION

We conducted MR evaluations of acetabular and femoral cartilages in 27 hips of patients with osteoarthritis and 10 hips of normal volunteers by a fat-suppressed three-dimensional (3D) pulse sequence using a continuous leg traction method, and correlated the results with radiographic assessment. Normal condition of the acetabular and femoral cartilages was clearly demonstrated in the normal volunteers. Grading of abnormalities was possible for each cartilage in the patients with osteoarthritis. In early osteoarthritis graded by radiography, a high prevalence of abnormalities was detected in the acetabular cartilage as compared with the femoral cartilage. Despite the structural difficulty in evaluation of the hip joint cartilage, our MR imaging technique can provide information concerning a wide spectrum of cartilage abnormalities even in the identical radiographic stage, which will lead to improvement in the evaluation of disease progression and in surgical planning.

Prognostication of nontraumatic avascular necrosis of the femoral head. Significance of location and size of the necrotic lesion.

After reviewing the radiographs of 149 hips with nontraumatic avascular necrosis of the femoral head (ANFH), a method for evaluating the prognosis in patients with ANFH in its early stages was devised. The evaluation was made primarily by classifying the radiographic features of each involved femoral head according to the location and size of its necrotic lesion. In a group of 120 hips, massive collapse occurred without exception in cases where both of the following criteria were true. First, in a standing position, the necrotic lesion involved more than the medial one third of the weight-bearing surface from the anteroposterior view. Second, from the lateral view, the lesion occupied more than 43% of the total area of the femoral head. However, in 29 hips, the extent and size of necrosis was less than the above, and no massive collapse occurred during the follow-up period of three to 15 years (average, 5.2 years). In these 29 hips, function was preserved. These data suggest that hips with a high risk for collapse can be reliably selected during the early stages of ANFH.