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[Osteomyelitic pseudarthrosis of the tibia with loss of substance treated with a graft of the opposite fibula].

Dragan Dj./Re. No. 2755/76, 5,5-year-old boy, referred to this hospital with signs of bipolar osteomyelitis, destruction and fistulisation of the left tibia and talocrural arthritis. Staphylococcus albus and streptococcus haemoliticus were isolated from the fistula. Osteomyelitis was treated with an adequate therapy including long usage of Lincocin. In Feb. and Oct. of 1977 a sequestrotomy of the mid portion of the tibia and transmedular fixation using Ratschmann's nail were performed. The process resulted in pseudarthrosis of the mid portion of the tibia with loss of bone substance in the length of 2.5 cm and talocrural arthrosis and deformed foot. The boy walking support. In July 1980, in the stage of "ripe" pseudarthrosis a complete resection of pseudoarthrosis with sclerotic portions of tibia to healthy bone was performed. The mid part of the right tibia was resected subperiostally and was grafted centromedularlly into the upper and lower medular channel of the left tibia. Two Kirschner's needles were implanted centromedularlly so as to strengthen the bone osteosynthesis. Complete union of the grafted fibula with treppassage of the medular channel occurred with its tibilisation and growth in length and width. In July 1982, the concave foot was corrected using Bertrand's method. The present difference in the length between the two legs is 4.5 cm which is corrected by the use of padded shoes. Lengthening of the leg is planned to be performed before he reaches the age of 14.

Child↗

Successful limb salvage of pathological fracture of the distal tibia caused by cancer metastasis.

Pathological fractures of the distal tibia as a result of cancer metastases are rare. In particular, the management of intraarticular fractures of the distal tibia has not been established. In this article, we present a case of pathological intraarticular fracture with an extensive bone defect of the distal tibia that was successfully treated by limb salvage with a locked intramedullary nail and pirarubicin-impregnated methylmethacrylate. A 52-year-old patient with duodenal cancer presented with a painful swelling in the left crus. The condition was diagnosed as an impending pathological fracture of the tibia because of cancer metastasis. During radiation therapy, an actual pathological fracture of the distal tibia occurred due to an accident. Limb-salvage surgery was performed by removing the metastatic lesion, followed by using a locked intramedullary nail. Three distal and seven proximal locking screws were inserted into the tarsal bones and the remaining tibia. About 10 cm of bone defect was reconstructed by pirarubicin-impregnated methylmethacrylate. Consequently, good stability was achieved. One month later the patient could walk without any aid. Postoperative functional score was 77% according to the Musculoskeletal Tumor Society criteria. There was no recurrence; however, the patient died of lung metastases 4 months after the limb-salvage surgery.

Bone Nails↗

Insufficiency fractures of the tibia and fibula.

OBJECTIVE: Insufficiency fractures (IF) occur when normal or physiological muscular activity stresses a bone that is deficient in mineral or elastic resistance. IF of the tibia and fibula are probably less common than IF of the ribs, vertebrae, hip, pelvis, and distal ulna, and therefore they are frequently underrecognized and mistaken for other conditions. Our aim was to analyze the main features and outcome of IF of the tibia and fibula in patients attending our Rheumatology Service. METHODS: IF was considered when occurring spontaneously or with minimal trauma. Between January 1984 and July 1997, 25 patients were diagnosed as having IF of the tibia and fibula. The main predisposing factors, clinical features, therapy, and outcome were retrospectively reviewed. RESULTS: All the patients except four were women (mean age, 66+/-12 years). Three cases were diagnosed between 1984 and 1990 (0.42 cases/year) and 22 between 1991 and 1997 (three cases/year). Eighteen patients had an underlying condition: rheumatoid arthritis (RA, 13 cases), psoriatic arthritis (2), systemic lupus erythematosus (SLE) (1), kidney transplant (1), and Crohn's disease (1). Eleven patients had osteoporotic fractures in other locations. Risk factors for osteoporosis were corticosteroids (13 cases), prolonged immobilization (10), early menopause (2), and methotrexate therapy (10). All patients had pain on weight bearing and marked functional impairment, 16 had local inflammatory signs, and 10 had deformity. In only five patients the diagnosis of IF was considered at the first examination. The diagnostic delay was 76+/-117 days (median, 21). The initial radiograph was diagnostic in 20 patients, and in the remaining the diagnosis was made by computed tomography (CT) scan (three cases), magnetic resonance imaging (MRI) (1), and bone scan (1). IF were located as follows: tibia (10 cases), fibula (seven), tibia and fibula (eight). Nineteen patients were treated with conservative management, four received no specific treatment, and two required surgery. Sixteen patients were hospitalized for a mean period of 12+/-8 days. Most patients had complete recovery. The high frequency of IF seen in RA patients is probably due to the severe disease in patients treated by our Service and that such patients have a higher risk for osteoporosis and its complications. CONCLUSIONS: IF of the tibia and fibula are probably more common than previously thought. They usually occur in patients with underlying rheumatic diseases, mainly RA, and are frequently mistaken for other joint and bone conditions. Despite a frequent delay in diagnosis, they have a good prognosis with conservative management. Nonetheless, a higher index of suspicion may avoid unnecessary investigations and treatments.

Absorptiometry, Photon↗

No biological advantage with a low temperature curing versus a conventional bone cement: an experimental, mechanical and histomorphometrical study in the rabbit tibia.

Both tibial marrow cavities of 12 rabbits were evacuated and filled with curing bone cement. In one of the tibias conventional curing bone cement (Simplex P) was injected, while the other tibia of the same animal was filled with a low temperature curing bone cement (Boneloc). Three titanium implants were inserted along the proximal metaphysis of each tibia. Eight weeks after insertion the most distal implant in each tibia was removed while recording the removal torque. The implant was then once again screwed home into its bone bed. The animals were sacrificed 16 weeks after implant insertion. The previously removed implant and another implant in each tibia were then both removed while recording the removal torque. The third implant in each tibia was cut out en bloc with surrounding tissue and processed for ground section. We found no statistical differences in the mechanical or the histomorphometric evaluation of implant integration between the two cements, indicating that the low temperature curing bone cement does not result in a significantly different bone response from that of a conventional acrylic cement.

Journal Article↗

Resonant frequency analysis of the tibia as a measure of fracture healing.

The Resonant Frequency (RF) of the tibia is proportional to its stiffness. As a fractured tibia heals, its RF should increase. The RF was serially determined in 74 fractured tibias (205 examinations). These were subdivided by fracture location and fixation. Fast Fourier transform software generates the RF from data obtained with an instrumented impactor and accelerometer. The RF was normalized by expressing it as a ratio of the intact tibia. This ratio is called the tibial stiffness index (TSI). A 20 point tibial fracture score (TFS) quantitated the clinical and radiographic signs of healing. For each group the paired TSI and TFS were compared by regression analysis. Except for those fractures limited to the proximal fourth of the tibia, the TSI was found to correlate significantly (p = 0.0001) with the TFS. Fractures without fixation and those with unlocked, unreamed tibial nails showed very significant correlation of TSI with TFS (p = 0.0001). RF analysis was not useful in fractures with locked or reamed tibial nails. Examination of tibia with external fixation showed significant correlation (p = 0.02) of the TSI with the TFS.

Biophysical Phenomena↗

Assessment of fracture healing in the tibia using the impulse response method.

The resonant frequency of a long bone as measured using the impulse response method (IRM) can reflect the bending rigidity of the bone. A study was performed using IRM to quantitatively assess fracture healing in 67 tibial fractures. A temporary decrease in resonant frequency early in the treatment course was found in 55.6% of tibias, most frequently in the cases treated by external fixation (83.3%) and the AO plate (80%). The resonant frequency also decreased temporarily following the removal of the fixation devices in 76% of the tibias where they were removed. The resonant frequency of the fractured tibia at the final follow-up exceeded that of the contralateral side in 18% of tibias, approached within 20 Hz in 11.5%, and did not reach within 20 Hz in 70.5%. A questionnaire on the effectiveness of the IRM examination in the treatment of the tibia fractures was completed by the treating orthopaedic surgeons. The IRM examinations were found to be very useful in 58.2% of cases, useful in 31.3%, and useless in 10.4%. Thus, IRM examinations are most helpful when they are able to detect the change in bending rigidity early in the treatment of tibia fractures.

Acceleration↗

Trabecular bone strain changes associated with subchondral comminution of the distal tibia.

OBJECTIVE: To measure trabecular bone strain changes resulting from three increasing subchondral bone defects in the distal tibia. DESIGN: Cadaveric biomechanical model. SETTING: Contact radiographs were made from sagittal sections of human cadaveric distal tibia under no load and loaded to 400 N. Digital images, made from contact radiographs of unloaded specimens, were compared to corresponding digital images of loaded specimens using custom software that measures trabecular deformation and calculates trabecular bone strain. INTERVENTION: Twelve specimens were initially loaded intact in compression. Testing was repeated after creating three increasing circular subchondral bone defects in the center of a sagittal cross-section of the distal tibia. Defects were 10%, 20%, and 30% of the sagittal diameter of the distal tibia. MAIN OUTCOME MEASURES: Maximum shear strain, maximum principal strain, and minimum principal strain were measured in six discrete regions in the trabecular bone in the distal tibia. RESULTS: Small defects (10%) caused minimal strain elevations. Significant increases in trabecular bone strain were measured with medium (20%) and large (30%) defects. Compressive strain increases as high as 1400 microstrain (10 strain) were measured adjacent to and proximal to the defects with medium and large defects. CONCLUSIONS: Subchondral defects cause size-dependent elevations in trabecular bone strain in the distal tibia. Medium and large defects caused rapidly increasing trabecular bone deformation under load.

Adult↗

Does fibular plating improve alignment after intramedullary nailing of distal metaphyseal tibia fractures?

OBJECTIVE: Evaluate whether supplementary fibular fixation helped maintain axial alignment in distal metaphyseal tibia-fibula fractures treated by locked intramedullary nailing. DESIGN: Retrospective chart and radiographic review. SETTING: Three, level 1, trauma centers. PATIENTS: Distal metaphyseal tibia-fibula fractures were separated into 2 groups based on the presence of adjunctive fibular plating. Group 1 consisted of fractures treated with small fragment plate fixation of the fibula and intramedullary (IM) nailing of the tibia, whereas group 2 consisted of fractures treated with IM nailing of the tibia without fibular fixation. OUTCOME MEASURES: Malalignment of the tibial shaft was defined as 1) >5 degrees of varus/valgus angulation, or 2) >10 degrees anterior/posterior angulation. Measures of angulation were obtained from radiographs taken immediately after the surgery, a second time 3 months later, and at 6-month follow-up. Leg length and rotational deformity were not examined. RESULTS: Seventy-two fractures were studied. In 25 cases, the associated fibula fracture was stabilized, and in 47 cases the associated fibula fracture was not stabilized. Cases were more likely to have the associated fibula fracture stabilized where the tibia fracture was very distal. In multivariate adjusted analysis, plating of the fibula fracture was significantly associated with maintenance of reduction 12 weeks or later after surgery (odds ratio = 0.03; P = 0.036). The use of 2 medial-lateral distal locking bolts also was protective against loss of reduction; however, this association was not statistically significant (odds ratio = 0.29; P = 0.275). CONCLUSIONS: In this study, the proportion of fractures that lost alignment was smaller among those receiving stabilization of the fibula in conjunction with IM nailing compared with those receiving IM nailing alone. Adjunctive fibular stabilization was associated significantly with the ability to maintain fracture reduction beyond 12 weeks. At the present time, the authors recommend fibular plating whenever IM nailing is contemplated in the unstable distal tibia-fibular fracture.

Adolescent↗

Comparison of soccer shin guards in preventing tibia fracture.

The goal of this study was to evaluate the effectiveness of a number of shin guards in protecting against tibia fracture in soccer players. A secondary purpose was to determine the relationship between the material and structural differences in shin guard design and the protection provided. Twenty-three commercially available shin guards were tested on a model leg containing a synthetic tibia that had been calibrated against human cadaver specimens. Each guard was categorized into one of four material types: plastic (N = 9), fiberglass (N = 6), compressed air (N = 4), and Kevlar (N = 4). The maximum combined force at the ends of the tibia, the principal strain on the posterior side of the tibia, and the contact time of the impact were measured using a drop track impact simulation. Shin guards provided significant protection from tibia fracture at all drop heights. The average guard reduced force by 11% to 17% and strain by 45% to 51% compared with the unguarded leg. At the higher drop heights, material composition and structural characteristics of the shin guards showed significant differences in protective abilities. These findings indicate that all shin guards provide some measure of protection against tibia fracture, although the level of protection may vary significantly among the different guards.

Adult↗

Correction of tibia vara with six-axis deformity analysis and the Taylor Spatial Frame.

Operative correction for infantile and adolescent tibia vara has been described using both external and internal fixation. Gradual correction using a circular fixator offers the advantage of accurate coronal, sagittal, and axial plane correction without significant soft tissue dissection. This study evaluated the use of six-axis deformity analysis and the Taylor Spatial Frame (TSF) for the correction of tibia vara. Nineteen patients (22 tibias), 6 with infantile and 13 with adolescent tibia vara, underwent correction with TSF. On the basis of mechanical axis correction, 21 of 22 tibias were corrected within 3 degrees of normal. Using Schoenecker's criteria, all patients achieved good results (no pain, <5 degrees difference in tibial-femoral angle from the normal side). Complications included one intractable pin-site infection, two superficial pin-site infections, and one delayed union. Six-axis deformity analysis and TSF provide accurate and safe correction of infantile and adolescent tibia vara.

Adolescent↗

[Segmental tibia fractures: a critical retrospective analysis of 49 cases].

PURPOSE OF THE STUDY: Segmental tibia fracture is defined by the presence of two distinct fracture lines separating the cortical and completely isolating an intermediary segment of the tibia. Little work has been published on this clinical entity. We report a retrospective analysis of 49 patients treated in one center for segmental tibia fracture in order to determine more precisely the indications for three surgical techniques: locked intramedullary nailing with or without reaming, and external fixation. MATERIAL AND METHODS: The series included 34 men and 15 women, mean age 40.8 years. All patients had traffic accident: 25 had multiple fractures, 17 had multiple organ injury, and 9 had floating knees. There were 30 open fractures; 2 patients developed compartment syndrome. The segments were: distal-proximal metaphyso-metaphyseal (n=1), proximal diaphyso-metaphyseal (n=17), diaphyso-diaphyseal (n=27), and distal diaphyso-metaphyseal (n=4). The mean length of the intermediary segment was 14.1 cm. The emergency procedure involved intramedullary nailing with reaming (Grosse-Kempf nail) in 32 patients, intramedullary nailing without reaming in 7 patients (Collin nail in 5 and UTN in 2) and external fixation with non-transfixing pins in 10 patients (Orthofix). External fixation was converted early to intramedullary nailing in three patients (Grosse-Kempf nail in 2 and Collin nail in 1). RESULTS: Three patients were excluded: 2 underwent amputation after failure of vessel repair and 1 developed septic necrosis of a free latissimus dorsi flap; 1 patient died from multiple organ failure. Outcome at at least 18 months was known for 42 patients (4 patients lost to follow-up). There were 4 cases of post-nailing compartment syndrome; one case of deep infection on a Grosse-Kempf nail was treated by external fixation. Among the 27 patients with segment tibia fractures finally stabilized with a Grosse-Kempf nail, nonunion developed in 8; mean time to bone healing was 10 +/- 4.8 months (with dynamization in 13 patients). For the 7 external fixations, nonunion developed in 2; mean time to bone healing was 9.2 +/- 2.9 months. For the 8 nailings without reaming, nonunion developed in 2; mean time to bone healing was 9.5 +/- 2.5 months. Bone healing was not simultaneous in the two foci in more than half of patients. Two patients developed clinical sequelae of their compartment syndrome with deficient knee flexion in two. The 12 cases of aseptic nonunion were successfully treated by nailing with reaming and early weight bearing. DISCUSSION: Comparing our results with the therapeutic modalities used in published reports on segmentary tibia fractures showed that time to bone healing and the rate of nonunion were generally greater than in our series. A critical analysis of these results allows us to propose a more interventionalistic attitude before the development of late healing. We also propose a classification of segmental tibia fractures and a decisional tree for choosing between the three techniques based on the presence of soft tissue damage, the presence of compartment syndrome (nailing without reaming), and the presence of proximal or distal metaphyseal fractures (distal locked nail). Nailing with moderate reaming remains the preferred method.

Adolescent↗

Does right leg require extra protection? Five-year review of type 3 open fractures of the tibia.

INTRODUCTION: Open fracture of the tibia is very common among motorcyclists. The morbidity associated with this injury is well-documented as treatment of severe open fractures is very difficult. There is currently no study done in the literature to see the relationship between fracture severity and the side of the injury. METHODS: We reviewed 239 patients with open fractures of the tibia admitted to our institution from 1998 to 2002. RESULTS: From 241 tibias studied, 150 (62.2 percent) involved the right side and 91 (37.8 percent) involved the left side. Statistical analysis showed that there was a significant difference in the severity of open fracture between the sides of fracture. Less severe injury (grades 1 and 2 fractures) was associated with injury of the left tibia and severe injury (grades 3A, B and C fractures combined) was associated with right tibia fracture. CONCLUSION: Since the right leg was more exposed to the injury, it is imperative to protect the limb. This may reduce the overall incidence and severity of tibia fractures.

Accidents, Traffic↗

Effect of weight-bearing on healing of cortical defects in the canine tibia.

UNLABELLED: It has been generally accepted that mechanical stimulation is an important factor in the promotion of formation of bone. Fracture-healing consists of periosteal bridging of the fracture, which achieves stability, and proliferation of endosteal bone to fill the defects between the ends of the bone. To evaluate the effect of weight-bearing on bone-healing, an operatively created defect in the tibial cortex was chosen as an experimental model. In one set of dogs (Group 1), a bilateral defect in the tibial cortex was created and weight-bearing was permitted on one tibia but not on the opposite one. In Group 2, a bilateral defect in the tibial cortex was made and weight-bearing was allowed on both tibiae. A third group of dogs of similar age (Group 3) had no tibial defects. Quantitative histomorphometry was used to measure formation and porosity of bone. Weight-bearing was measured with both static and dynamic techniques. Significantly less woven bone formed in the defects in the non-weight-bearing tibiae than in the weight-bearing tibiae. This appeared to be due to a disuse response in the underloaded tibiae, in which less bone formed, rather than to the formation of more bone in the weight-bearing tibiae. The data suggest that weight-bearing is a permissive factor, not a stimulus, for formation of woven bone in a tibial defect. CLINICAL RELEVANCE: This animal model supports the concept that lack of weight-bearing decreases the amount of woven bone that is formed in a healing tibial defect. The results of this study indicate that weight-bearing increases the formation of bone in fracture-healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Secondary intramedullary nailing osteosynthesis in primarily conservative treatment of fractures of tibia and fibula shafts (author's transl)].

In a retrospective trial 235 patients with fractures of the tibia and/or fibula shafts were followed up. In 16 cases non-union of the fracture occurred after closed reduction and plaster cast treatment. In 16 of these patients closed nailing of the tibia was performed 8--14 weeks after the accident. The healing of the fracture was uncomplicated and occurred in 10--14 weeks p. op. The results in primary nailing cases 8--14 days after the accident were much better than in cases treated with plaster casts, with regard to joint mobility, venous insufficiency and duration of treatment; however two serious complications occurred. In two patients, osteitis occurred after primary nailing of the tibia. Localisation of the fractures (distal part of the tibia) and type of the fracture (short torsion fracture) correlated more frequently with formation of non-union than the rare changes in blood chemistry observed in our study. We regard intramedullary nailing of the tibia as the best available method in treating non-union or pseudarthrosis of the tibia.

Adult↗

The infected nonunion of the tibia.

Ununited fracture of the tibia complicated by infection is not only a complex surgical problem but also a chronic and at times debilitating condition. The principle methods used to diagnose and stage posttraumatic tibial osteomyelitis are described. Infected nonunions of the tibia are characterized by the extent of bony loss and the presence of a functional ipsilateral fibula. Using this tibial staging criteria, a series of 37 infected nonunions of the tibia are reviewed. Twenty patients were male and 16 were female, with an average age of 33 years. The distal third of the tibia was involved in 19 patients, the middle third in 11, and proximal third in 7. Twenty three of the tibia were infected with > 1 organism. Thirty were Type 3 (tibial defect of 6 cm or less with a long and usable fibula), 4 Type 4 (tibial defect > 6 cm without usable fibula), and 3 Type 5 (tibial defect > 6 cm without usable fibula). The patients were evaluated at an average of 61 months after treatment. Union and eradication of infection were achieved in 35 of 37 patients. The results of the Health Impact Analysis suggest that the infected nonunion of the tibia represented a chronic and debilitating disorder with a lasting impact.

Adolescent↗

[Treatment concepts and results in non-infected post-traumatic pseudarthroses of the femur and tibia].

AIM OF INVESTIGATION: Different methods of internal and external fixation are used to treat aseptic posttraumatic nonunion of the femur and tibia. The advantages and disadvantages of the different methods will be demonstrated by analysing the clinical course and the outcome of our patients. Utilizing these data, a therapeutic concept tailored to the individual situation is recommended. METHODS: Depending on the form of reaction we distinguish between vital and non-vital nonunions. The classification is made according to the clinical course, x-ray-findings and in special cases the results of scintigraphy. Due to anatomic differences in vascularisation and soft tissue coverage nonunion of the femur and the tibia are discussed separately. Stabilisation is achieved by intramedullary nail, plate or external fixator. As new methods the internal plate fixator was used for the femur and the Ilizarov ring fixator for the tibia. If there has been a mistake in the choice of the method of the primary stabilisation a change of method is done. If the indication for the initial method of stabilisation was correct, the therapy of nonunions is limited to the correction of technical mistakes. Additionally, a biologic stimulation is required for the therapy of non-vital nonunion. RESULTS: The clinical data of 77 patients treated from 1985-1993 were analysed retrospectively. Vital nonunions of the femur (11) healed after 9.5 months on the average, those of the tibia (49) after 10 months. The duration of treatment of non-vital nonunions was much longer and required 20 and 16 months, respectively. The treatment of two non-vital nonunions of the tibia could not be completed. For the femur only intramedullary nail (4) and plate (8) were used, for the tibia mainly the fixator (43), of these in 18 cases the Ilizarov-apparatus. Differences in the duration of treatment due to the choice of implant could not be recognized. Complications were pin problems (14) and one lesion of the peroneal nerve in the fixator group and superficial wound infection (2), nerve irritation (1) and fracture (1) in the group treated with intramedullary nailing. CONCLUSIONS: Due to the good soft tissue coverage and vascularisation internal fixation is favored for the treatment of femoral nonunions. The fixator should only be used if distraction osteogenesis is necessary because of a bony defect. Due to the problematic soft tissue situation and poorer vascularisation on the external fixator is preferred in the treatment of tibial nonunions if a change of method is indicated. For this purpose, we currently use predominantly the Ilizarov-apparatus because of its biomechanical properties and the convincing results. Initial problems with its use could markedly be reduced with growing experience.

Adolescent↗

The economics of treating tibia fractures. The cost of delayed unions.

The tibia, being the most commonly fractured long bone, is associated with a high incidence of delayed union and non-union. A previously published prospective, randomized, double-blind and placebo-controlled tibia study demonstrated that pulsed, low-intensity ultrasound shortened the time to a healed fracture and significantly reduced the incidence of delayed union. The economics of treating tibia fractures has never been calculated. We have reviewed the literature pertaining to the tibia, the results of the above published tibia study, and stratified the data from that study for those patient and fracture co-morbidity factors that can influence healing of tibia fractures. Three economic models are presented with the total costs of treating a pool of 1,000 patients with tibial shaft fractures divided into two treatment paths--operative and conservative. These costs include surgery and recovery, outpatient costs, and Workers' Compensation costs for both the primary and secondary procedures, and emergency room and disability costs. The first model does not use low-intensity ultrasound and provides a summary of the costs associated with fracture treatment for each treatment path. The second model uses low-intensity ultrasound adjunctively with the conservatively treated group while the third model uses ultrasound adjunctively in both the operative and conservative groups. When comparing the conservative treatment path of Model 2 to Model 1 a cost savings of over $15,000 per case (40%) is realized by dramatically lowering secondary procedures and Workers' Compensation costs when pulsed low-intensity ultrasound is used adjunctively with conservative treatment. A similar savings of over $13,000 per case results from the use of ultrasound in the operative treatment path of Model 3 when compared with the standard operative care of Model 1. The total savings realized is over $14.6 million when adjunctively using low-intensity ultrasound in both the conservative and operative treatment paths. These analyses demonstrate that reduced healing time could yield substantial cost savings for third party payors, employers, and government agencies by lessening the need for secondary procedures and reducing the amount of Workers' Compensation payments.

Adult↗

Bone response to alternate-day mechanical loading of the rat tibia.

Mechanical loading of the living skeleton influences bone formation, mass, and strength. The primary purpose of the present study was to examine the influence of different loading schedules (days/week) on the bone response to external loading using an in vivo rat tibia four-point bending model. Three studies were conducted to (1) characterize the loaded region, (2) examine the variation of the response within the loaded region, and (3) test the response to different loading schedules. In all studies adult female retired breeder Sprague-Dawley rats were used (6 months, 285 g). First, the location of the loaded region during four-point bending was determined by radiogrammetry of 7 rats. Second, 5 rats were externally loaded for 8 of 10 days at 31 N, 36 cycles, and 2 Hz (1349 +/- 244 mu epsilon). The extent of labeled (forming) periosteal and endocortical surface in the loaded region was compared both among four serial sections from the same tibia and between the loaded and the contralateral tibiae. Finally, 50 rats were randomized into five groups: two nonloaded, control and sham, and three loaded, alternate day, Monday, Wednesday, and Friday, and daily. The rats were externally loaded for 3 weeks at 35 N, 36 cycles, and 2 Hz (1533 +/- 308 mu epsilon). The tibia and fibula were studied for labeled surfaces and mineral apposition rate. For adult female rats with tibial length 39 mm, the loaded region was located 3.5-14 (+/- 0.7) mm proximal to the tibia-fibula junction (TFJ).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗