Low-intensity pulsed ultrasound is frequently used to treat fractures after osteosynthesis in elderly patients: A study using open data from the national database of health insurance claims of Japan.

BACKGROUND: The national database of health insurance claims of Japan (NDB) includes almost all health insurance claims in Japan. Currently, we have many cases of geriatric fracture in Japan, probably due to an increase of the elderly population. The increase of geriatric fractures may influence the use of low-intensity pulsed ultrasound (LIPUS), which is used to accelerate the fracture repair process. The present state of LIPUS treatments was analyzed using the large dataset of the NDB. METHODS: The open data from the NDB that were used included receipts from April 2015 to March 2016. The total numbers of fracture treatments were counted as the sum of the claim items that were involved in fracture treatments. Two types of the insurance claim items for LIPUS treatments were counted separately: those used for delayed or non-union fractures; and those used for fractures within two weeks after osteosynthesis. Additionally, the ratio of the LIPUS treatments per the fracture treatments was calculated. RESULTS: In female patients, the number of LIPUS treatments for fractures early after osteosynthesis showed a large peak in the senile generation. Additionally, the ratio of LIPUS treatments early after osteosynthesis to all osteosynthesis treatments tended to increase with age in both males and females, while the ratio of the LIPUS treatments for delayed or non-union fractures to all fracture treatments decreased with age. CONCLUSIONS: LIPUS treatments were frequently used to treat fractures early after osteosynthesis in elderly patients, probably due to the large number of fractures in the elderly population. Additionally, the ratio of LIPUS treatments early after osteosynthesis was high in both elderly female and elderly male patients, suggesting that there is a demand for early fracture repair.

Factors associated with diagnostic stage of hip osteoarthritis due to acetabular dysplasia among Japanese female patients: a cross-sectional study.

BACKGROUND: In Japan, the majority of hip osteoarthritis (OA) was caused by acetabular dysplasia, and about 90 % of patients were female. The present study focused on Japanese female patients with hip OA due to acetabular dysplasia, and examined the associated factors with OA staging at diagnosis, in special reference to body weight. METHODS: Study subjects were 336 Japanese women who were newly diagnosed with hip OA caused by acetabular dysplasia at 15 hospitals in 2008. The self-administered questionnaire elicited patients' body weight at age 20 and at OA diagnosis. Four ranked OA staging according to radiographic findings of the hip joint (pre-OA, initial stage, advanced stage or terminal stage) was regarded as the outcome index. Proportional odds models in logistic regression were used to calculate odds ratios (ORs) and 95 % confidence intervals (CIs) for severer stage of OA. RESULTS: At diagnosis, 45 % of patients suffered from terminal stage of OA, whereas 13 % and 14 % were categorized into pre-OA and initial stage, respectively. After adjustment for potential confounders, weight gain since age 20 revealed the increased ORs for severer OA stage at diagnosis (OR 2.02; 95 % CI, 1.07-3.80). Other significant characteristics were age (67+ vs. 20-49 years, OR 12.4), lower education (junior high school vs. junior college or higher, OR 4.00), parity (OR 2.19), lower acetabular head index (<60.0 vs. 71.1+, OR 2.36), and longer duration since symptom onset (6.0+ vs. <1.0 year, OR 2.94). CONCLUSIONS: Weight gain since age 20 might be involved in mechanisms of OA development, which is independent of age or severity of acetabular dysplasia.

Relationship of acetabular dysplasia in females with osteoarthritis of the hip to the distance between both anterior superior iliac spines.

BACKGROUND: Acetabular dysplasia (AD) is the main cause of hip osteoarthritis in Japan. A simple method to evaluate acetabular dysplasia would be helpful for early treatment or prevention of hip osteoarthritis. Acetabular dysplasia is reported to be associated with pathological transverse growth of the pelvis, indicating that the distance between the 2 anterior superior iliac spines might be useful for screening and detection of acetabular dysplasia. The purpose of this study was to determine if the acetabular dysplasia radiographic parameters are related to the distance between the 2 anterior superior iliac spines in patients with hip osteoarthritis. MATERIAL AND METHODS: In this study, data obtained in a previous multi-institutional examination of patients with hip osteoarthritis in Japan were evaluated. The anterior superior iliac spine distances of 176 female patients (mean age, 54 years; range, 18-85 years) were measured by physical examination. The relationship between the anterior superior iliac spine distance and acetabular dysplasia was analyzed, and the anterior superior iliac spine distances of the patients with acetabular dysplasia who were at relatively high risk for hip osteoarthritis were compared with that of the patients at lower risk. RESULTS: A statistically significant relationship between the anterior superior iliac spine distance and all of the acetabular dysplasia parameters was observed. The anterior superior iliac spine distances of the acetabular dysplasia patients with a relatively high risk for radiographic acetabular dysplasia parameters were significantly smaller than those of patients at lower risk. Even after adjustment for age, height, and weight, significantly increased relative risk for having high risk AD was found in patients with an ASIS distance of less than 24.5 cm. CONCLUSIONS: There was a significant relationship between the anterior superior iliac spine distance and the degree of acetabular dysplasia.

Osteoarthritis hip joints in Japan: involvement of acetabular dysplasia.

BACKGROUND: We conducted a nationwide epidemiologic study regarding hip osteoarthritis (OA) in Japan, and a previous report found these patients to be unique in comparison to Caucasians. This report focused on the data regarding each hip joint, and the involvement of acetabular dysplasia with hip OA was analyzed. METHODS: Seven hundred twenty OA hips were examined. Sixty-five joints with osteonecrosis of the femoral head and 215 non-OA contralateral joints of the unilateral patients were examined as controls. The revised system of stage classification for hip OA of the Japanese Orthopedic Association (JOA) was used according to the reproducibility in order to ensure reliable data from the multiple institutions. The acetabular dysplasia indexes were also chosen according to the reproducibility and measured in the radiograph of bilateral hip joints. The clinical score was assessed using the JOA scoring system. The relative risk of the grade of acetabular dysplasia indexes for hip OA was calculated as the odds ratio and the 95% confidence interval. RESULTS: The stage of the OA joints deteriorated with increasing age. The clinical scores also decreased. The grade of the acetabular dysplasia indexes of the OA joints was significantly higher than that of the control joints. Each index of acetabular dysplasia demonstrated significantly increased odds ratios for hip OA. Among the OA joints, the deterioration of the OA stage was found to be significantly associated with an increasing grade of acetabular dysplasia. The odds ratio for OA deterioration in the acetabular dysplasia index was also obtained. The joints of females tended to have a higher grade and prevalence of acetabular dysplasia than those of males. CONCLUSIONS: These findings confirmed a high prevalence of acetabular dysplasia in hip OA joints in Japan. Acetabular dysplasia was one of the most important factors associated with hip OA.

Atypical periprosthetic femoral fractures after arthroplasty for fracture are at high risk of complications.

It is difficult to investigate clinical features in a single-center study because atypical periprosthetic femoral fracture (APFF) is rare. This study aims to perform a nationwide survey of APFF to investigate the characteristics of this fracture and compare the clinical outcome with that of typical periprosthetic femoral fracture (typical PFF). A nationwide survey was performed asking for cooperation from 183 councilors of the Japanese Society for Fracture Repair. The subjects were patients with APFF injured between 2008 and 2017. The control group was comprised of patients with typical PFF of our facility injured in the same period. A total of 43 patients met the APFF definition. The control group was comprised of 75 patients with typical PFF. The rate of bisphosphonate use was significantly higher in the APFFs group than in the typical PFF group (62.8% and 32%, p < 0.02). The rate of cemented stem was significantly higher in the APFFs group than in the typical PFF group (30.2% and 6.7%, p < 0.001). In the patients with arthroplasty for hip fracture, multivariable logistic regression analyses showed that APFF was an independent risk factor of complications following the initial management (Odds ratio 11.1, 95% confidence interval 1.05-117.2, p = 0.045). However, no significant association between PFF and APFF was observed in the patients with arthroplasty for other hip diseases. The risk of complications was higher in the APFF group than in the typical PFF group in the patients with arthroplasty for fracture. When AFPP after arthroplasty for the fracture is suspected, it may be necessary to add not only internal fixation with a normal plate but also some additional treatment.

Subchondral insufficiency fracture of the femoral head may be associated with hip dysplasia: a pilot study.

BACKGROUND: Subchondral insufficiency fracture of the femoral head occurs mainly in elderly patients with osteoporosis. Spontaneous resolution is observed after nonoperative treatment in some patients whereas other show progressive joint destruction requiring THA. Several studies report the occurrence of subchondral insufficiency fracture of the femoral head in dysplastic hips. QUESTIONS/PURPOSES: We asked whether the extent of hip dysplasia or osteoporosis was greater in patients with subchondral insufficiency fracture of the femoral head than in normal control subjects. PATIENTS AND METHODS: We compared the clinical and imaging findings of 13 patients with subchondral insufficiency fractures of the femoral head and 12 patients scheduled for TKA with asymptomatic hips. Age, gender, and body mass index were comparable in the two groups. RESULTS: Higher mean Sharp angles, lower acetabular head indices, lower center-edge angles, and higher acetabular roof angles in patients with subchondral insufficiency fracture of the femoral head than in those with asymptomatic hips suggested a greater degree of hip dysplasia. Bone mineral density and serum levels of Type I collagen cross-linked N-telopeptide and bone alkaline phosphatase were similar in the two groups. CONCLUSIONS: We speculate an excessive amount of stress on the acetabular edge from dysplasia may be associated with the occurrence of subchondral insufficiency fracture of the femoral head.

Analysis of interobserver reliability for radiographic staging of coxarthrosis and indexes of acetabular dysplasia: a preliminary study.

BACKGROUND: We are planning a multicenter survey on coxarthrosis and acetabular dysplasia in Japan. To collect reliable data, we performed a preliminary study to elucidate the observer agreement on assessment items. METHODS: We collected radiographs of hip joints in eight patients with various findings of coxarthrosis. Twelve registered orthopedic specialists evaluated them regarding the roentgenographic stage of coxarthrosis and five indexes of acetabular dysplasia (acetabular angle, center-edge angle, acetabular roof obliquity, acetabular head quotient, approximate acetabular quotient). To assess observer agreement, we calculated the value of the kappa statistic for stages and the coefficient of variation for the indexes. The same 12 specialists then assessed the coxarthritis stage on the same radiographs 1 month after the first evaluation based on our own descriptions of the roentgenographic stages. RESULTS: For the first evaluation of the roentgenographic stage, the value of the kappa statistic was 0.448; and for the second evaluation it was 0.600. The results of the coefficient of variation for the indexes of acetabular dysplasia, ranked in ascending order, were as follows: acetabular angle, acetabular head quotient, acetabular roof obliquity, center-edge angle, approximate acetabular quotient. CONCLUSIONS: For the upcoming multicenter survey, clear descriptions of the stages of coxarthrosis and selection of appropriate indexes can be helpful for collecting dependable results.

Intraarticular findings in symptomatic developmental dysplasia of the hip.

BACKGROUND: The purpose of this study was to examine intraarticular pathology in patients younger than 20 years with symptomatic developmental dysplasia of the hip. METHODS: We performed hip arthroscopy during corrective osteotomy in 23 hips in 22 patients. All patients were female, and the average age at operation was 16.4 years. Eighteen hips were in a prearthritic stage, and 5 hips were in an early stage. The presence and location of cartilage degeneration and labral tears were evaluated. Second-look arthroscopy was performed in 13 hips in 12 patients. RESULTS: Fourteen hips (77.8%) in the prearthritic stage had cartilage degeneration. Cartilage lesions were more frequent in the acetabulum than in the femoral head (72.2% vs 16.7%). Sixty-one percent of acetabular lesions were located at the anterosuperior area. Labral tears were observed in 77.8% of hips in prearthritic stages located at the anterosuperior (72.2%) and superior (44.4%) areas. The degree of cartilage and labral lesions in the early stage was more severe than in the prearthritic stage. On second-look arthroscopy, there were no changes in the state of the cartilage and labrum in the majority (84.6%) of hips. CONCLUSIONS: The incidence of intraarticular lesions in developmental dysplasia of the hip was high, even in the prearthritic stage. These lesions tended to originate in the anterosuperior area of the acetabulum and were generally progressive.

Effects of the femoral offset and the head size on the safe range of motion in total hip arthroplasty.

The purpose of this study was to quantify the effects of femoral offset and head size on range of motion (ROM) after total hip arthroplasty. Modular prostheses were implanted into 11 cadaveric hips using a posterolateral approach and tested for ROM with 3 different offsets and 5 different femoral head sizes. Increasing the femoral offset to 4 and 8 mm resulted in 21.1 degrees and 26.7 degrees of improved flexion, and 13.7 degrees and 21.2 degrees of improved internal rotation, respectively. The ROM improved in a head size-dependent manner primarily because of increasing the jumping distance of the femoral head rather than delaying any impingement. In contrast, the effectiveness of femoral offset was driven by delayed osseous impingement.

Transposition osteotomy of the acetabulum for advanced-stage osteoarthritis of the hips.

BACKGROUND: Transposition osteotomy of the acetabulum (TOA) was the first periacetabular osteotomy in which the acetabulum was transposed with articular cartilage. TOA improves coverage of the femoral head and joint congruity. The purpose of this study was to investigate whether TOA is an appropriate option for treating osteoarthritis of the hips at the advanced stage by comparing it with matched control hips at the early stage. METHODS: Between 1998 and 2001, TOA was performed in 104 hips of 98 patients. Altogether, 16 of 17 hips (94%) with osteoarthritis at the advanced stage were examined and compared with 37 matched control hips at the early stage. The mean age at the operation was 48 years (38-56 years), and the mean follow-up period was 88 months (65-107 months). RESULTS: TOA corrected the acetabular dysplasia and significantly improved containment of the femoral head. Clinical scores were also significantly improved in both groups. In the advanced osteoarthritis cases, there was a tendency for abduction congruity before transposition osteotomy of the acetabulum to reflect the clinical outcome. CONCLUSIONS: TOA is a promising treatment option for advanced osteoarthritis of the hips as well as for patients at an early stage when preoperative radiographs show good congruity or containment of the joint.

[Bone fracture and the healing mechanisms. Fracture treatment by low-intensity pulsed ultrasound].

The principles of fracture treatment are the reduction and fixation of the fracture site, while the subsequent biological healing process is expected. Currently, some treatment options that actively stimulate the repair reaction at the fracture site are either available, or they are soon going to become available for clinical use. Low-intensity pulsed ultrasound (LIPUS) or local growth factors are examples of these modalities. They are non-invasive or less invasive than the previous stimulating options such as bone grafting at the fracture site. These treatment modalities are not only used to heal delayed union or non-union but they also have the potential to shorten the repair period until union is achieved while also reducing complications, including deformity or non-union.

Effects of tacrolimus (FK506) on the development of osteonecrosis in a rabbit model.

The present study examined the effects of tacrolimus (FK506) on the development of osteonecrosis in rabbits. In Experiment A, rabbits were given FK506, and also given a single dose of steroid. Control rabbits were given the same dose of steroid only. In Experiment B, rabbits were given FK506 and a reduced dose of steroid. The results showed that addition of FK506 did not change the number of rabbits with osteonecrosis when an identical steroid dose was given. When the steroid dose was reduced, the osteonecrosis incidence significantly decreased (p < 0.01). These results suggest that the clinically reported decrease in the osteonecrosis incidence following the introduction of FK506 is most likely attributable to the lower doses of steroids.

Local application of recombinant human fibroblast growth factor-2 on bone repair: a dose-escalation prospective trial on patients with osteotomy.

Based on preclinical evidence in animal models, the present study examined the clinical efficacy and safety of recombinant human fibroblast growth factor-2 (rhFGF-2) to accelerate bone repair in a dose-escalation prospective trial. One of three dosages (200, 400 or 800 microg) of rhFGF-2 in a biodegradable gelatin hydrogel was injected during surgery into the osteotomy site of 59 knee osteoarthritis patients undergoing high tibial osteotomy, and 57 of them were monitored for 16 weeks. The rhFGF-2 dose dependently increased the percentage of patients with radiographic bone union, and decreased the average time needed for such union. The percentages of patients with an absence of pain and full-weight bearing were also greater in the higher dosage groups than in the low dosage group, especially in the clinically critical periods 6, 8, and 10 weeks. Neither blood chemistries nor clinical adverse events were associated with the rhFGF-2 dosages. We therefore conclude that the rhFGF-2 in gelatin hydrogel dose dependently accelerated radiographic bone union of a surgical osteotomy with a safety profile at least at the dosages used, suggesting the clinical efficacy of this agent for bone repair.

The accuracy of socket orientation using a pelvic fixation device for total hip arthroplasty with the patient in the lateral decubitus position in comparison to the vacuum bag fixation method.

BACKGROUND: In our department, a vacuum bag with two lateral boards used to be utilized in order to maintain patients in the lateral decubitus position during THA. However, we recently changed this modality to a three-point fixation device for the pelvis in order to accurately control the position of the acetabular socket. The purpose of this study was to retrospectively compare the orientation of the acetabular socket when THA was carried out using two different positioning methods. METHODS: Group 1 consisted of 66 hips that underwent THA in 1997 using a vacuum bag, which became rigid with suction. Group 2 consisted of 42 hips that were treated in 2000 using a three-point fixation device for the pelvis. This device was designed to able to rigidly fix the bilateral anterior superior iliac spines and the sacrum. Before fixation with the device, the angle between the line aligning the anterior-superior iliac spines and the vertical plane in the lateral decubitus position was measured as the lateral pelvic tilt. The orientation of the fixed acetabular socket was evaluated based on postoperative radiographs. RESULTS: The average absolute value from 45 degrees in the abduction angle was significantly lower in group 2 than that in group 1 (p < 0.01). In 18% of the cases in group 1, the anteversion angle was over 30 degrees. In contrast, no such cases were observed in group 2. Postoperative dislocation occurred in six cases (9%) in group 1. In contrast, it only occurred in one case (2%) in group 2. CONCLUSIONS: The positioning method using the pelvic fixation device enabled surgeons to more accurately control the position of the sockets during THA comparison to using the vacuum bag. The positioning of the patient is therefore suggested to be an important first step in successfully performing THA procedures.

Factors associated with functional limitations in the daily living activities of Japanese hip osteoarthritis patients.

AIM: As society ages, there is a vast number of elderly people with locomotive syndrome. In this study, the factors associated with functional limitations in daily living activities evaluated by female hip osteoarthritis (OA) patients were investigated. METHODS: This study was a cross-sectional study. The subjects were 353 female patients who were newly diagnosed with hip OA at an orthopedic clinic with no history of hip joint surgery. Outcome indices were functional limitations in two daily living activities obtained from a questionnaire completed by the patients: (i) standing up (standing from a crouched position) and (ii) stair-climbing (climbing and/or descending stairs). The odds ratios (ORs) and 95% confidence intervals (CIs) were computed for explanatory variables using the proportional odds model in logistic regression to evaluate their associations with functional limitations. RESULTS: Functional limitations in standing up were associated with heavy weight (third tertile vs. first tertile: 1.91, 1.11-3.27), participation in sports at school (0.62, 0.40-0.98), parity (vs. nullipara: 1.96, 1.08-3.56), old age and OA stage. Associations with functional limitations in stair-climbing were seen with short height (< 151.0 cm vs. ≥ 156.0 cm: 2.05, 1.02-4.12), bilateral involvement (vs. unilateral: 1.71, 1.01-2.88), old age and OA stage. CONCLUSION: Old age, OA stage, heavy weight, parity, shorter height and bilateral OA were associated with functional limitations in standing up and/or stair-climbing, whereas participation in sports such as club activities in school maintained standing up.

Repetitive tensile stress to rat caudal vertebrae inducing cartilage formation in the spinal ligaments: a possible role of mechanical stress in the development of ossification of the spinal ligaments.

OBJECT: Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed. METHODS: The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically. After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein-2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans. CONCLUSIONS: The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.

Intramuscular bone induction by the simultaneous administration of recombinant human bone morphogenetic protein 2 and bisphosphonate for autobone graft.

An ideal substitute for bone graft is autobone tissue, of which there is an ample supply of the required form and with vascularity. Our strategy is to generate intramuscular autogenous bone by administering recombinant human bone morphogenetic protein 2 (rhBMP-2) with beta-tricalcium phosphate (beta-TCP) as a carrier, and to transplant this bone as a muscle-pedicled autograft. However, in a previous study (Jingushi et al., J. Orthop. Sci. 7, 490, 2002), bone resorption occurred early after bone induction. This study was conducted to determine whether rhBMP-2-induced bone tissue could be maintained by simultaneous administration of bisphosphonate, and to investigate whether the induced bone could be used for bone grafting. In this study, we first applied rhBMP-2 alone to a beta-TCP disk and inoculated it into rat quadriceps muscle. Bone area and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the induced bone disk peaked at 2 weeks, and induced bone resorption occurred later. Bisphosphonate and rhBMP-2 were then simultaneously applied to a beta-TCP disk and inoculated as in the first experiment. The addition of bisphosphonate decreased the number of TRAP-positive cells and increased the bone area and compression strength at 4 weeks. In the last experiment, a rhBMP-2 applied beta-TCP disk treated with or without bisphosphonate was free-grafted to parietal bone 4 weeks after inoculation. Both bone disks united similarly. We concluded that the concurrent use of bisphosphonate prevented bone absorption attributed to osteoclast activity after bone induction by rhBMP-2. The bisphosphonate application did not disturb the union of induced bone to host bone.

Expression of parathyroid hormone-related peptide and insulin-like growth factor I during rat fracture healing.

Parathyroid hormone-related peptide (PTHrP) and insulin-like growth factor I (IGF-I) are both involved in the regulation of bone and cartilage metabolisms and their interaction has been reported in osteoblasts. To investigate the interaction of PTHrP and IGF-I during fracture healing, the expression of mRNA for PTHrP and IGF-I, and receptors for PTH/PTHrP and IGF were examined during rat femoral fracture healing using an in situ hybridization method and an immunohistochemistry method, respectively. During intramembranous ossification, PTHrP mRNA, IGF-I mRNA and IGF receptors were detected in preosteoblasts, differentiated osteoblasts and osteocytes in the newly formed trabecular bone. PTH/PTHrP receptors were markedly detected in osteoblasts and osteocytes, but only barely so in preosteoblasts. During cartilaginous callus formation, PTHrP mRNA was expressed by mesenchymal cells and proliferating chondrocytes. PTH/PTHrP receptors were detected in proliferating chondrocytes and early hypertrophic chondrocytes. IGF-I mRNA and IGF receptor were co-expressed by mesenchymal cells, proliferating chondrocytes, and early hypertrophic chondrocytes. At the endochondral ossification front, osteoblasts were positive for PTHrP and IGF-I mRNA as well as their receptors. These results suggest that IGF-I is involved in cell proliferation or differentiation in mesenchymal cells, periosteal cells, osteoblasts and chondrocytes in an autocrine and/or paracrine fashion. Furthermore, PTHrP may be involved in primary callus formation presumably co-operating with IGF-I in osteoblasts and osteocytes, and by regulating chondrocyte differentiation in endochondral ossification.

Evaluation of the clinical performance of ultrahigh molecular weight polyethylene fiber cable using a dog osteosynthesis model.

The purpose of this study was to assess the removability and biological reactivity of an ultrahigh molecular weight polyethylene (UHMWPE) fiber cable as a new biomaterial for osteosynthesis. We used a pull-out test and an implantation test to analyze the performance of the UHMWPE fiber cable using a dog model, and compared its characteristics with those of a wire cable and a soft wire. In the pull-out test, the UHMWPE fiber cable was as easy to remove as the soft wire, and both the UHMWPE fiber cable and the soft wire were significantly easier to remove than the wire cable. The fixation capability and the biological reactivity of the UHMWPE fiber cable were examined in an osteosynthesis model of the dog greater trochanter, and were compared with those of the soft wire. The bone union rate, assessed radiographically, was very similar when using the UHMWPE fiber cable and the soft wire. However, in the soft wire group, both the surface of the greater trochanter under the fixation material and the penetration area around the fixation material showed an increased tendency toward a biological reaction, including inflammation and granulation tissue formation, as compared to the UHMWPE fiber cable group. The UHMWPE fiber cable was as easily removed from the bone tissue as the soft wire, and was easier to remove than the wire cable. Additionally, the UHMWPE fiber cable caused reduced biological reactivity with the surrounding tissue, as compared with the soft wire. In conclusion, the UHMWPE fiber cable appeared to be a suitable fixation material for osteosynthesis.