Extra-articular deformity in distal radial fractures treated by external fixation.

OBJECTIVE: To determine the radiographic outcome in fractures of the distal radius treated with closed reduction and external fixation. DESIGN: A retrospective study. SETTING: The orthopedic department of National Taiwan University Hospital. PATIENTS: Eighty-five consecutive patients (36 female, 49 male), average age 48 years, with fractures of the distal radius seen between March 1995 and June 1998. INTERVENTIONS: Closed reduction and external fixation of fractures, followed up by good-quality posteroanterior and lateral radiographs to evaluate healing. MAIN OUTCOME MEASURES: Radial height, radial inclination and volar tilt were measured on radiographs obtained initially, immediately postoperatively and at the time of removal of external fixation. Data were analyzed by the t-test. RESULTS: Immediately after reduction and fixation, there was a significant improvement in the measurements of radial height and radial inclination. This improvement was gradually lost and height and inclination were significantly decreased at the time the external fixation device was removed. External fixation did not improve the volar tilt. CONCLUSION: External fixation is a popular method to improve the reduction of osseous deformity but cannot effectively protect comminuted distal radial fractures from loss of reduction, which may be associated with shortening and redisplacement.

Staged reimplantation of total knee arthroplasty after Candida infection.

Prosthetic joint infection with Candida is uncommon. Only 28 cases have been reported in the English literature. Successful reimplantation after eradication of Candida infection has been reported in 3 hip joints and only 1 knee. We present the case of a 68-year-old woman with chronic Candida parapsilosis infection of a prosthetic knee joint. Removal of the prosthesis, thorough débridement, and antifungal therapy treated the infection successfully. Antifungal therapy included 6 weeks of parenteral administration of fluconazole followed by 4 weeks of oral fluconazole. The involved knee joint was reimplanted 3 months after initial treatment. The prosthetic joint was pain free and functioned satisfactorily during the ensuing 4 years. No recurrence of infection was noted. The principle in treating Candida prosthetic infection generally has been the same as that of bacterial prosthetic infection. In chronic cases, removal of implants, thorough débridement, and effective antifungal therapy are mandatory for the eradication of infection. Reimplantation of the prosthesis can be performed successfully in a staged surgical procedure with the interval between the 2 stages shortened to 3 months.

Treatment of humeral shaft delayed unions and nonunions with humeral locked nails.

OBJECTIVE: To report experience with use of humeral locked nails in treating humeral delayed unions and nonunions. The following techniques yielded encouragingly good results: static locking, short-to-long segment nailing, bone grafting, fracture compression, and minimal surgical trauma. DESIGN AND METHODS: A total of 41 consecutive patients with 13 delayed unions and 28 nonunions were treated with humeral locked nails. Delay from trauma to surgery averaged 4.2 months for delayed union and 15.5 months for nonunion. The average age of patients was 50.2 years; average follow-up time was 23.2 months. There were 7 proximal-third fractures, 21 middle-third fractures, and 13 distal-third fractures. The antegrade approach was used for 13 fractures and retrograde for 28. Open nailing was performed in 39 fractures and closed nailing in 2. If the fracture motion was still present after nail insertion, axial compression of the fracture site was specially applied. Bone grafting was performed in the fractures with open nailing. Thirty-four fractures were nailed with 8-mm nails, and 7 fractures were nailed with 7-mm nails. RESULTS: With a single operation, all but two patients achieved osseous union in, on average, 5.6 months. One of these two patients eventually gained union after another surgery with fracture compression along the original nail and concurrent bone grafting. The second patient, undergoing hemodialysis for chronic renal failure, had persistent nonunion. At follow-up, for patients with antegrade nailing, all but four patients had less than 20 degrees limitation of shoulder abduction. For patients with retrograde nailing, all but two had less than 10 degrees limitation of elbow motion. Only the patient with persistent nonunion had continual pain and significant impairment of arm function. CONCLUSIONS: Humeral locked nailing seems to be effective for humeral delayed unions or nonunions. It may be an acceptable alternative for fractures unsuited for plate fixation, such as those with comminution, osteoporosis, or a severely adhered radial nerve.

In vivo kinematic study of normal wrist motion: an ultrafast computed tomographic study.

OBJECTIVE: To quantify in vivo carpal kinematics of a normal wrist in a dynamic continuous model. DESIGN: The instantaneous changes in the radiocarpal and midcarpal joints during normal wrist motion were analyzed using ultrafast computed tomography (CT). BACKGROUND: Wrist injuries account for a considerable and growing proportion of work-related disorders and disability. However, little is known about normal wrist kinematics. METHODS: Ten uninjured subjects were studied using ultrafast CT to measure the continuous motion of the wrist from full flexion to full extension. Sagittal plane scanning was performed mediolaterally at six different locations as the wrists were moved slowly and repeatedly from full flexion to full extension. The data were printed to X-ray film and transferred to an independent work station with a video camera. The motion of the radiocarpal, midcarpal and wrist joints was determined by an image analyzing system. RESULTS: Wrist motion was expressed as a ratio of capitate-lunate (C-L) (midcarpal) motion and radio-lunate (R-L) (radiocarpal) motion. In the volar flexion of normal wrists, the contribution of the radiocarpal joint and midcarpal joint were approximately equal; while dorsal flexion of the normal wrist occurred mainly at the midcarpal joint. CONCLUSIONS: In normal wrists, the radiocarpal joint and midcarpal joint contribute equally to volar flexion, while the midcarpal joint is more important in dorsal flexion. RELEVANCE: In this study, we demonstrated the suitability of using two-dimensional computed tomographic images in a quantitative study of flexion/extension kinematics of the normal wrist.

Factor of risk for hip fracture in normal Chinese men and women in Taiwan.

We have investigated the age-related change in factor of risk (Phi) for the proximal femoral load during free fall in 548 females and 240 males aged 21-79 years. These individuals were divided into either young (age <50 years) or old group (age >/=50 years). Another 26 females with hip fractures were included for comparison. The bone mineral density (BMD) of proximal femoral neck was measured by a Norland XR-26 dual-energy X-ray absorptiometer (DXA). The estimated fracture load (L) of femoral neck was calculated from the BMD with the regression equation derived by Courtney et al. [2,3] and estimated fall force (F) by body weight and height according to the regression equation derived by Nakamura et al. [6] respectively. Phi was defined as the quotient of F/L. The results showed an age-related decrease of BMD (P < 0.001) in both genders corrected for weight and height. By multiple linear regression analysis, the F decreased significantly with aging corrected for BMD in old males (partial r = -0.255, P < 0.01) and increased with aging in all females (young, partial r=0.287, p < 0.001; old, partial r = 0.252, P < 0.001). L decreased significantly with aging corrected for height and weight in males (young, partial r = -0.401, P < 0.01; old, partial r = -0.178, P < 0.05) and females (young, partial r = -0. 168, P < 0.05; old, partial r = -0.459, P < 0.001). However Phi decreased with aging in young males (P < 0.01) and females (young: P < 0.001, old: P < 0.001). Phi increased in old women but not in old men, and was higher in old women compared with old men. The 26 patients with hip fractures had a significantly higher Phi value than 85 age-matched women. In conclusion, Phi may provide a comprehensive comparison of the risk of hip fracture in the elderly population.

Anatomic considerations of locked humeral nailing.

To investigate the risk of axillary nerve injury by the proximal locking screws in antegrade nailing of humeral fractures, the anatomy of the axillary nerve was examined in 20 fresh anatomic specimen humeri, which subsequently were nailed antegrade with specially designed humeral locked nails. The axillary nerve was found to be on average 45.6 mm below the tip of the greater tuberosity; it was jeopardized by insertion of the lower proximal locking screw in one of the 20 specimens. Short humeri, humeri with small heads, or too deeply inserted nails may increase the risk of nerve injury; likewise, a lower location and more horizontal direction of the locking screws and a greater curvature of the nail can heighten the risk. In addition to the examination of the axillary nerve, a geometric study of these anatomic specimen was performed and was aimed at improving retrograde nailing technique and thus treatment results. The humeral geometry indicated that for the best linearity in the sagittal plane, an entry portal incorporating the superior margin of the olecranon fossa would be recommended for the 14 humeri with a distal humeral offset less than 4 mm, whereas a supracondylar entry portal would be recommended for the six humeri with an offset larger than 4 mm. For best linearity in the coronal plane, the entry portal and nailing direction should be more lateral in humeri with a smaller humeral elbow angle.

Antioxidant status following acute ischemic limb injury: a rabbit model.

Although ischemic injury to skeletal muscle is a matter of great clinical importance, relatively little is known about the mechanisms which determine systemic responses. One purpose of this study is to elucidate the systemic antioxidant status following an episode of acute ischemic limb injury and subsequent reperfusion. Twelve New Zealand white rabbits were used in this study. After the animals were anesthetized, an ischemic insult was created in the right hind limb for twelve hours, followed by four hours of reperfusion. Several series of blood samples were obtained. At the end of the experiment, the animals were killed and necropsies undertaken in order to evaluate the antioxidant status of various visceral organs. The results link ischemia and reperfusion injury to a significant decline in antioxidative activity in various tissues. The weakening in antioxidant status after ischemic limb injury was most pronounced in the heart tissue, followed in descending order by the spleen, skeletal muscle, lung, liver, and kidney tissue. The levels of specific antioxidants and reactive oxygen species in various organs changed significantly, and the changes were tissue specific. Endogenous radical scavenging systems were not entirely overwhelmed in most of the tissues studied. But higher levels of malondialdehyde (MDA) found in cardiac tissue suggest that the production of oxygen free radicals is accelerated by an ischemic injury. Based on the study, we believe that the cardiac tissue is particularly susceptible to the effects of ischemia and reperfusion injury. Damage to cardiac tissue is probably the major cause of mortality following acute ischemic injury in a limb.

Scavenging effect of benzophenones on the oxidative stress of skeletal muscle cells.

Benzophenone is an ultraviolet (UV)-absorbing agent that has been used in industry and medicine for more than 30 years. Consumers of cosmetics and sunscreens containing UV-absorbers are exposed to benzophenones on a daily basis, owing to the widespread use of these compounds. However, the efficacy of these compounds as scavengers of oxidative stress is still not well established. In the present study, we investigate the antioxidative capacity of six sunscreen benzophenone compounds. A primary myoblast culture was mixed in vitro with 100 microM menadione. The cytotoxic effect by menadione-induced oxidative stress was monitored by the lucigenin- or luminol-amplified chemiluminescence, methylthiotetrazole (MTT) assay, and the antioxidative effects of various benzophenone compounds were evaluated. The results showed that the addition of menadione can induce oxidative stress on myoblasts by superoxide and hydrogen peroxide production, which can be eradicated by superoxide dismutase (SOD) and catalase, respectively, in a dose-dependent mode. The catalase has a protective effect on the cytotoxicity induced by menadione as measured by the MTT assay, while the SOD does not. The selected benzophenones also have a significant scavenging effect on the menadione-induced cell death on the myoblasts. The ortho-dihydroxyl structure and other hydroxy groups in the same ring have a stronger scavenging effect on the superoxide anion on myoblasts; thus, a stable penoxy radical may be formed. The mechanism of this effect remains to be clarified.

The effect of sintered beta-dicalcium pyrophosphate particle size on newborn Wistar rat osteoblasts.

During recent years, sintered dicalcium phosphate (SDCP) has been shown to be an effective artificial bone filler for repairing bone defects. The goal of this study was to elucidate the effect of SDCP particle size on osteoblasts. Osteoblasts were mixed and cultured with various sized SDCP particles (0.5-3.0, 37-63, 177-250, and 420-841 microns) for 1 h, 3 h, 1 day, 3 days, and 7 days and then analyzed. The results show that the adding of smaller sized SDCP particles (0.5-3.0 and 37-63 microns) into osteoblast culture can significantly affect the cell counts of osteoblasts. The secretion of transforming growth factor-beta 1, alkaline phosphatase, and prostaglandin E2 in culture medium increased significantly. The changes were most significant and persisted longer in smaller particle groups. Small sintered dicalcium phosphate particles can inhibit the proliferation of the osteoblasts. The inhibitory effects of the smaller sized SDCP particles on the osteoblasts were mediated by the promotion of osteoblast differentiation and the increased synthesis of prostaglandin E2.

Locked nailing for displaced surgical neck fractures of the humerus.

OBJECTIVE: To report experience with a newly devised humeral locked nail for treating surgical neck fractures of the humerus. This device has the advantages of a small diameter for minimal tissue trauma and transfixing locking screws for reliable fixation. METHODS: From 1993 to 1996, 21 consecutive severely displaced surgical neck fractures of the humerus were antegrade nailed with humeral locked nails; 2 fractures were associated with dislocation and 1 fracture was a comminuted metaphyseal fracture with a failed plating. The average age of patients was 65.8 years; average follow-up time was 19.2 months. The proximal screws were applied upward in 5 patients and downward in 16 patients. Static locking was performed in 8 patients, dynamic locking in 13 others. RESULTS: The average operation time was 55 minutes. No patients needed blood transfusion. All fractures eventually achieved union with an average time to union of 14.8 weeks. On the basis of Neer criteria for outcome analysis, excellent or satisfactory results were obtained for 86% of the patients (18 of 21 patients). No patients had deep infection, implant failure, malunion, osteonecrosis, or nail migration that interfered with joint motion. Due to technique errors, one patient had shoulder joint impingement caused by protrusion of the proximal nail tip. CONCLUSION: The operative method reported here has the advantages of minimal tissue trauma, minimal hardware application, sufficient fixation, and easy operative technique, and it can be a worthy alternative for the treatment of severely displaced surgical neck fractures of the humerus.

An ultra-weak chemiluminescence study on oxidative stress in rabbits following acute thermal injury.

It is not easy to detect oxygen free radicals directly because of their very short half-life. In the present study, a sensitive ultra-weak chemiluminescence detector was used to detect the generation of oxygen free radicals following thermal injury. Twelve New Zealand white rabbits were used in this study. After anesthesia, the bilateral hind-limbs were exposed to 100 degrees C water for 30 s. Six control animals were exposed to 22 degrees C water to act as a control. The chemiluminescence of whole blood and visceral organs were measured with both luminol-amplified t-butyl hydroperoxide-initiated and lucigenin-initiated methods. The results showed that chemiluminescence of blood was affected significantly by acute thermal injury. The chemiluminescence of blood increased significantly at 1 h following acute thermal injury, reached a peak at 2 h, then decreased but still remained above the control level at 4 h following thermal injury. The results for TBHP-initiated chemiluminescence from visceral organs following acute thermal injury were much higher than that of the control rabbits. The effects of lucigenin-initiated tissue chemiluminescence following acute thermal injury were not statistically significant. It is suggested that the decreased vascular antioxidant activity following local thermal injury is partially contributed by the superoxide pathway; while, the remote pathophysiologic events are mediated by the defective scavenging defenses.

Biomechanical comparison of antegrade and retrograde nailing of humeral shaft fracture.

A pair-controlled study was conducted to compare biomechanical properties of antegrade and retrograde nailing of humeral fractures. First, six paired fresh anatomic specimen humeri were used to compare the properties of humeri fractured at the middle to distal diaphyses junction that were nailed from the retrograde approach with the Humeral Locked nail with those of contralateral intact humeri. An 18 additional pairs were divided into three equal groups by distal, proximal, or mid-diaphysis location of a standardized 5-mm bone defect to simulate unstable fractures. The retrograde and antegrade nailings were performed in each pair in a random manner. Nail and bone constructs were tested for bending stiffness by nondestructive three-point bending and for torsional stiffness by destructive torsional tests. Compared with intact humeri, fractured humeri fixed with nails had 28.6% posteroanterior and 31.4% mediolateral bending stiffness, 22.5% torsional stiffness, and 43.3% failure torque. For distal fractures, retrograde nailing showed significantly more initial stability and higher bending and torsional stiffness; for proximal fractures, antegrade nailing showed similar properties. For middle to distal diaphyses junction fractures, retrograde and antegrade nailing were indistinguishable. The defect created as an entry portal for retrograde nailing reduced the bone strength only 11.1%. These results suggest that retrograde nailing, which is less detrimental to shoulder function than is antegrade nailing, is an acceptable alternative treatment for humeral shaft fractures. In addition, nailing from the short to the long bone segments can improve mechanical properties of the fixation construct because of better nail and bone interface purchase.

Biochemical and histopathological changes in the mortality caused by acute ischemic limb injury: a rabbits' model.

Restoration of blood flow to an acute ischemic extremity may deteriorate the ischemic injury, lead to multiple organ dysfunction or even death. This paradox of continuing injury during reperfusion is not completely understood. The role of multi-organ damage in the mortality caused by ischemic limb injury is also still not clarified. The purpose of this study is to determine the biochemical and histopathological changes in the mortality caused by ischemic limb injury. After anesthesia, the hindlimbs of 14 New Zealand white rabbits were made ischemic and set into 8 hours or 12 hours of ischemia. Blood samples were obtained then the creatine kinase (CK) levels were determined and CK isoenzymes analyzed. All rabbits with 8 hours' ischemia survived well, and 5 of the 7 rabbits with 12 hours' ischemia expired within 8 hours after reperfusion. CK elevation was correlated most strongly with the time of the ischemic insults. The percentage of CK-MB isoenzyme remained unchanged after 8 hours' ischemia-reperfusion insult, while increased significantly after 12 hours' ischemia-reperfusion insult. Histologic examinations showed that the major systemic manifestation was massive destruction of the liver and kidney. The injuries are more obvious in areas with the greatest blood flow during reperfusion. We concluded that the ratio of CK-MB isoenzyme is most useful for distinguishing the risk of mortality caused by acute ischemic limb injury, and the cause of systemic complications are attributed to the multi-organ failure.

In vitro and in vivo mechanical evaluations of plasma-sprayed hydroxyapatite coatings on titanium implants: the effect of coating characteristics.

This study was undertaken to evaluate the effect of coating characteristics on the mechanical strengths of the plasma-sprayed HA-coated Ti-6Al-4V implant system both in vitro and in vivo. Two types of HA coatings (HACs) with quite different microstructures, concentrations of impurity-phases, and indices-of-crystallinity were used. In vitro testings were done by measuring the bonding-strength at the Ti-6Al-4V-HAC interface, with HACs that had and had not been immersed in a pH-buffered, serum-added simulated body fluid (SBF). The shear-strength at the HAC-bone interface was investigated in a canine transcortical femoral model after 12 and 24 weeks of implantation. The results showed a bonding degradation of approximately 32% or higher of the original strength after 4 weeks of immersion in SBF, and this predominantly depended on the constructed microstructure of the HACs. After the push-out measurements, it was demonstrated that the HACs with higher bonding-strength in vitro would correspondingly result in significantly higher shear-strength at each implant period in vivo. Nevertheless, there were no substantial histological variations between the two types of HACs evaluated. The most important point elucidated in this study was that, among coating characteristics, the microstructure was the key factor in influencing the mechanical stability of the HACs both in vitro and in vivo. As a consequence, a denser HAC was needed to ensure mechanical stability at both interfaces.

The effects of calcium phosphate particles on the growth of osteoblasts.

With advances in ceramics technology, calcium phosphate bioceramics have been applied as bone substitutes for several decades. The focus of this work is to elucidate the biocompatibility of the particulates of various calcium phosphate cytotoxicities. Four different kinds of calcium phosphate powders, including beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), beta-dicalcium pyrophosphate (beta-DCP), and sintered beta-dicalcium pyrophosphate (SDCP), were tested by osteoblast cell culture. The results were analyzed by cell count, concentration of transforming growth factor-beta 1 (TGF-beta 1), alkaline phosphatase (ALP), and prostaglandin E2 (PGE2) in culture media. The changes were most significant when osteoblasts were cultured with beta-TCP and HA bioceramics. The changes in cell population of the beta-TCP and HA were quite low in the first 3 days, then increased gradually toward the seventh day. The changes in TGF-beta 1 concentration in culture medium inversely related to the changes in cell population. The ALP titer in the culture media of the beta-TCP and HA were quite high in the first 3 days, then decreased rapidly between the third and seventh days. The concentrations of PGE2 in the culture media tested were quite high on the first day, decreased rapidly to the third day, and then gradually until the seventh day. The changes in the beta-DCP and SDCP were quite similar to those of HA and beta-TCP but much less significant. We conclude that HA and beta-TCP have an inhibitory effect on the growth of osteoblasts. The inhibitins effects of the HA and beta-TCP powders on the osteoblast cell cultures possibly are mediated by the increased synthesis of PGE2.

Treatment of humeral shaft fractures by retrograde locked nailing.

From 1992 to 1994, 29 middle and 19 distal humeral shaft fractures (39 acute fractures, six nonunions, and three pathologic fractures) in 48 patients were treated by retrograde locked nailing. The first eight acute fractures were treated with Seidel nails, the other 40 fractures with specially designed humeral locked nails. Nails were inserted from the supracondylar (6) or the olecranon fossa (42) entry portal. With a single operation, all acute fractures and nonunions achieved osseous union without serious complications. The average time to union was 8.2 weeks for acute fractures and 14.2 weeks for nonunions. Recovery of shoulder function was complete. Elbow motion was excellent in all but one nonunion that resulted from a Type IIIB open fracture. Two patients with supracondylar entry had apex to posterior angular malunion. One patient with a distal comminuted fracture had varus malunion. Three patients had an iatrogenic bony split, but healing was unaffected. Patients with pathologic fractures maintained satisfactory arm function postoperatively. Given the few complications and good functional recovery seen in this study, retrograde locked nailing appears to be a good alternative treatment in middle and distal humeral shaft fractures. The olecranon fossa approach, with more linearity to the humerus, is preferred. In the authors' experience, humeral locked nails are inserted more easily and are associated with fewer complications than are Seidel nails.

Effects of calcium phosphate bioceramics on skeletal muscle cells.

With advances in ceramics technology, calcium phosphate bioceramics have been applied as bone substitutes. The effects of implants on bony tissue have been investigated. The effects upon adjacent skeletal muscles have not been determined. The focus of this work is to elucidate the biological effects of various calcium phosphate bioceramics on skeletal muscles. Four different kinds of powder of calcium phosphate biomaterials including beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), beta-dicalcium pyrophosphate (beta-DCP) and sintered beta-dicalcium pyrophosphate (SDCP), were tested by myoblast cell cultures. The results were analyzed by cell count, cell morphology and concentration of transforming growth factor beta 1 (TGF-beta 1) in culture medium. The cell population and TGF-beta 1 concentration of the control sample increased persistently as the time of culture increased. The changes in cell population and TGF-beta 1 concentration in culture medium of the beta-TCP and HA were quite low in the first 3 days of culture, then increased gradually toward the seventh day. The changes in cell population and TGF-beta 1 concentration in culture medium of the silica, beta-DCP, and SDCP were quite similar. They were lower during the first day of culture but increased and reached that of the control medium after 7 days' culture. Most cells on B-TCP and HA diminished in size with radially spread, long pseudopods. We conclude that HA and beta-TCP are thought to have an inhibitory effect on growth of the myoblasts. The HA and beta-TCP may interfere with the repair and regeneration of injured skeletal muscle after orthopedic surgery.

In vitro cell behavior of osteoblasts on Pyrost bone substitute.

BACKGROUND: Pyrost bone substitute has been shown to be a promising orthopedic biomaterial. However, little is known about mechanisms that are responsible for the genesis and development of the bond between bone and the Pyrost bone substitute. The purpose of this study is to elucidate the in vitro cell behavior of osteoblasts on Pyrost bone substitute. METHODS: By using primary culture of rat osteoblasts, the changes in cell morphology during adhesion and flattening onto the surface of Pyrost bone substitute were studied in vitro. At 1 hour, at 3 hours, and at days 1, 3, and 7 after layering, the cell behavior was observed with scanning electron microscope. RESULTS: The processes of trypsinized osteoblast adhesion and spreading on Pyrost bone substitute consisted of 1) contact of rounded osteoblasts with the Pyrost substrate; 2) attachment of osteoblasts at point of contact; 3) centrifugal growth of filopodia; 4) flattening and spreading of the osteoblasts on the Pyrost substrate; 5) division and growth of osteoblasts; and 6) suspension of the osteoblasts across the pores by their processes. CONCLUSIONS: These results demonstrated that Pyrost can form a physico-chemical bond with osteoblasts. The Pyrost bone substitute not only supports osteoblasts attachment but also allows proliferation of the osteoblasts.

Biocompatibility and osteoconductivity of the pyrost bone substitutes.

The purpose of this study was to re-evaluate the bone regeneration power and the in vitro biocompatibility of the Pyrost bone substitute. Twenty-four adult New Zealand White rabbits were used. Bony defect over both iliac crest and mid-diaphyseal portion of the ulna bone were created. Appropriate sized-block of Pyrost bone substitute were implanted. Four of the animals were killed at each postoperative month to evaluate its bone regeneration power by histologic study. The Pyrost bones were co-cultured with osteoblasts to evaluate its biocompatibility. The results showed that Pyrost bone substitute was quite stable and incorporated well with active bone regeneration. The Pyrost heal better at the iliac crest than at the ulnar defect. The Pyrost was compatible to the osteoblasts. Osteoblasts had successfully seeded and mitotically expanded on the porous surface of the Pyrost bone graft. The result showed that Pyrost bone obviously exerts an intense stimulus on osteo-regeneration in the presence of osteoblasts. We consider Pyrost to be an alternate to the conventional preserved allografts that is occasionally necessary.

Menadione-induced cytotoxicity to rat osteoblasts.

Oxygen-derived free radical injury has been associated with several cytopathic conditions. Oxygen radicals produced by chondrocytes is an important mechanism by which chondrocytes induce matrix degradation. In the present study, we extend these observations by studying oxidative processes against osteoblasts. Osteoblasts were mixed in in vitro culture with 200 microM menadione. The cytotoxic effect of menadione-induced oxidative stress was monitored by lucigenin- or luminol-amplified chemiluminescence, tetrazolium assay and immunocytochemical study. Results showed that adding menadione induces an oxidative stress on osteoblasts, via superoxide and hydrogen peroxide production, that can be eradicated by superoxide dismutase (SOD) and catalase in a dose-dependent manner. Catalase and the appropriate concentration of dimethyl sulfoxide have a protective effect on cytotoxicity induced by menadione, whereas SOD does not. Menadione-treated osteoblasts have a strong affinity for annexin V, and the nuclei are strongly stained by TUNEL (TdT-mediated dUTP nick-end labelling). The results suggest that menadione-triggered production of reactive oxygen species leads to apoptosis of osteoblasts.