Stress fractures in 51 runners

A prospective study was initiated in 1976 to investigate runners who are at risk for incurring stress fractures and how these fractures can be prevented. Fifty-one runners incurred 57 stress fractures. Tibial fractures were most common (25), followed by fibula (12) and metatarsal (8). Seven runners had previously sustained stress fractures, and six developed two stress fractures simultaneously. Five women over 30 years old had pelvic stress fractures. Stress fracture development was positively correlated with the presence of pes planus, weekly training distances greater than 20 miles, hard training surfaces, and training regimen modifications. The incidence did not correlate with generalized musculoskeletal laxity or tightness. Forty-four of 51 patients had initially positive roentgenograms. Five of five bone scans were positive. The average duration of rest before running was resumed was 7.4 weeks.     

兔骨折延迟愈合动物模型的建立

目的为骨折延迟愈合的实验研究建立一种客观的动物实验模型。方法选取纯种新西兰大白兔,在后肢胫骨中下段截断,切除远近端各1 cm内外骨膜及黄骨髓,保留断端约1 mm间隙,并且钢板固定。术后4、8、12周后经大体标本、病理组织学及X线检查确定骨折愈合情况。结果大体标本肉眼观察、放射学检查及病理组织学检查均显示术后8周仍未见骨性连接,术后12周才达骨性愈合。结论本实验所建立的动物模型,具有骨折延迟愈合的表现,又未出现骨不连,符合骨折延迟愈合的要求,可以认为是一种可靠而实用的实验性骨折延迟愈合动物模型。     

Bone adaptation to a mechanical loading program significantly increases skeletal fatigue resistance.

Using a mechanical loading program to induce bone adaptation, we found that small (<2-fold) changes in the structural properties of the rat ulna increased its fatigue resistance >100-fold. This indicates that a moderate exercise program may be an effective preventative strategy for stress fractures. INTRODUCTION: There are currently limited preventative strategies for stress fractures. Because stress fracture risk is directly influenced by skeletal properties, it has been hypothesized that modification of these properties using a mechanical loading program may positively influence risk. The aim of this study was to investigate whether the bone changes associated with a mechanical loading program can enhance skeletal fatigue resistance. MATERIALS AND METHODS: Site-specific mechanical loading was performed on one forearm of adult female Sprague-Dawley rats using the axial compression loading model. Loading was performed 3 days/week for 5 consecutive weeks to induce adaptation. The loaded and nonloaded ulnas in each animal were removed after the loading program, and their material and structural properties were determined. The ulna pairs were subsequently loaded until fatigue failure at the same constant peak axial load. RESULTS: Mechanical loading induced consistent and predictable changes in the structural properties of loaded ulnas, with the largest change being a nearly 2-fold increase in midshaft minimum second moment of area (I(MIN)). The mechanical-loading induced bone changes resulted in a >100-fold increase in fatigue resistance in loaded ulnas, with resistance being exponentially related to the structural properties of the ulna. CONCLUSIONS: This study found that by enhancing the structural properties of a bone through a mechanical loading program, its fatigue resistance could be significantly improved. This indicates that an exercise program aimed at modifying bone structure may be used as a possible prevention strategy for stress fractures.     

The effect of prophylactic treatment with risedronate on stress fracture incidence among infantry recruits

When subjected to strains or strain rates higher than usual, the bone remodels to repair microdamage and to strengthen itself. During the initial resorption phase of remodeling, the bone is transitorily weakened and microdamage can accumulate leading to stress fracture. To determine whether short-term suppression of bone turnover using bisphosphonates can prevent the initial loss of bone during the remodeling response to high bone strain and strain rates and potentially prevent stress fracture, we conducted a randomized, double-blind, placebo-controlled trial of 324 new infantry recruits known to be at high risk for stress fracture. Recruits were given a loading dose of 30 mg of risedronate or placebo daily for 10 doses during the first 2 weeks of basic training and then a once a week maintenance dose for the following 12 weeks. Recruits were monitored by biweekly orthopedic examinations during 15 weeks of basic training for stress fractures. Bone scans for suspected tibial and femoral stress fractures and radiographs for suspected metatarsal stress fractures were used to verify stress fracture occurrence. By the intention-to-treat analysis and per-protocol analysis, there was no statistically significant difference in the tibial, femoral, metatarsal, or total stress fracture incidence between the treatment group and the placebo. We conclude that prophylactic treatment with risedronate in a training population at high risk for stress fracture using a maintenance dosage for the treatment of osteoporosis does not lower stress fracture risk.     

Biomechanical evaluation of early fracture healing in normal and diabetic rats.

Diabetes mellitus has been shown to alter the properties of bone and impair fracture healing in both humans and animals. The objective of this study was to document changes in the structural and material properties of intact bone and bone with healed fractures in diabetic rats compared with nondiabetic controls after 3 and 4 weeks of healing. Rods were inserted in the right femurs of control rats and rats with streptozotocin-induced diabetes, and the femurs were fractured in a standardized procedure and then allowed to heal for 3 and 4 weeks. After death, all femurs were mechanically tested to failure in torsion. The degree of healing was quantified for each animal by normalizing mechanical parameters for the femur with a healed fracture with those for the intact contralateral femur. At both time points of healing, diabetic rats exhibited inferior healing compared with that of control animals in terms of failure torque, failure stress, structural stiffness, and material stiffness of the femur with the healed fracture relative to the intact contralateral femur (p < 0.05). Our results demonstrate that the recovery of structural and material strength in femurs with healed fractures in diabetic rats is delayed by at least 1 week compared with that in controls.     

Insufficiency stress fractures of the femoral neck in children

Stress fractures can be subdivided into fatigue fractures caused when normal bone is exposed to abnormal stress and insufficiency fractures where normal stress is applied to abnormal bone. Stress fractures of the femoral neck, although uncommon, have a high complication rate if the diagnosis is missed or the patient is improperly treated. Femoral neck stress fracture in children is a rare event. Eight children with 10 insufficiency fractures of femoral neck were treated successfully. There were 2 boys and 6 girls with the average age 11 years. The right hip affected in 4 children and the left hip in 2 and 2 children with bilateral hip affection. Four fractures were incomplete, and 6 were complete. The average follow-up period was 5 years. The time for radiological union ranged between 6 and 12 weeks (average 8 weeks). The time for full weight bearing ranged between 4 and 8 weeks (average 6 weeks). Most of the children became asymptomatic from the fracture at the average of 7 weeks. Stress insufficiency fracture of the femoral neck in children considered as high-risk fracture and should be treated aggressively with attention to lower the risk of additional fractures and preserve quality of life in these children. So, intervention should be targeted toward limiting further bone loss and decrease the risk of falls.     

Bisphosphonate treatment delays stress fracture remodeling in the rat ulna

Because bisphosphonates (BPs) are potent inhibitors of bone resorption, we hypothesized that they would retard direct remodeling of stress fractures. The aim of this study was to determine the effect of risedronate on direct remodeling and woven bone callus formation following stress fracture formation in the rat ulna. In 135 adult female Wistar rats, cyclic loading of the ulna created stress fractures. Rats were treated daily with oral saline, or risedronate at 0.1 or 1.0 mg/kg. From each bone, histomorphometry was performed on sections stained with toluidine blue at a standard level along the fracture. The high dose of risedronate caused a significant decrease in the percentage of repaired stress fracture and bone resorption along the stress fracture line at 6 and 10 weeks after loading (p < 0.05). At this dose, intracortical resorption was significantly reduced at 10 weeks after loading and intracortical new bone area was significantly reduced at 6 and 10 weeks. Woven bone formation and consolidation phases of stress fracture repair were not affected by low or high doses of risedronate. In conclusion, high dose bisphosphonate treatment impaired healing of a large stress fracture line by reducing the volume of bone resorbed and replaced during remodeling. We also confirmed that periosteal callus formation was not adversely affected by risedronate treatment. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1827–1833, 2011     

Knöcherne Stressreaktionen des Fußes im Sport

Stress reactions and stress fractures are defined as structural damage to bone caused by repetitive stress or stereotypical loading. The balance between loading and unloading of bone is disrupted in stress reactions and stress fractures through the sport-specific demands and by the exogenous or endogenous risk factors present. In sports orthopedics the localization of stress reactions and stress fractures are subdivided into high risk fractures and low risk fractures. Conventional diagnostic radiology can initially be inconclusive. With symptoms persisting over 2 weeks further diagnostics using magnetic resonance imaging (MRI) should be performed. In the area of the foot stress reactions and stress fractures can often occur bilaterally or multifocally and most commonly affect the second metatarsals followed by the third metatarsals. Fractures of the fifth metatarsal, second metatarsal base, medial malleolus as well as navicular and sesamoid fractures are high risk fractures requiring special clinical and radiological monitoring. Basically, conservative treatment using the 2-phase model is the treatment of choice. In delayed union or severe pain surgical treatment is indicated.     

可吸收棒加骨水泥髓内固定的实验性研究

目的 研究自增强型可吸收棒（PDLLA）联合磷酸钙骨水泥（CPC）髓内固定管状骨骨折的可行性，为用于手部掌、指骨骨折提供实验室依据。方法 将自增强型可吸收棒植入兔股骨干（横形骨折）髓腔内，两端用磷酸钙骨水泥粘合固定（实验组），克氏针髓内固定（对照组）。术后比较两组周围组织的反应，X线片变化及力学强度。结果 术后4周实验组和对照组的股骨干横向截骨均未见明显畸形，X线片示实验组的骨痂量多于对照组；测定股骨三点弯曲最大破坏载荷实验，结果两组无明显差异。术后8周剪切力较术后4周无下降。术后8周两组的骨折均愈合，未出现局部反应性肿胀、积液、感染及全身毒性反应。结论 自增强型可吸收棒与磷酸钙骨水泥在骨内具有良好的组织相容性，两者联合应用行管状骨骨折髓内固定，效能与克氏针固定相当。     

Development of an atrophic nonunion model and comparison to a closed healing fracture in rat femur.

Although most fractures heal, some fail to heal and become nonunions. Many animal models have been developed to study problems of fracture healing. The majority of nonunion models have involved segmental bone defects, but this may not adequately represent the biologic condition in which nonunions clinically develop. The objective of the present study is to develop a nonunion model that better simulates the clinical situation in which there is soft tissue damage including periosteal disruption and to compare this model to a standard closed fracture model utilizing identical fracture stabilization, providing a similar mechanical environment. A total of 96 three month old Long Evans rats were utilized. A 1.25 mm diameter K-wire was inserted into the femur in a retrograde fashion, and a mid-diaphyseal closed transverse fracture was created using a standard three-point bending device. To create a nonunion, 48 of the rats received additional surgery to the fractured femur. The fracture site was exposed and 2 mm of the periosteum was cauterized on each side of the fracture. Fracture healing was evaluated with serial radiographs every two weeks. Animals were maintained for intervals of two, four, six or eight weeks after surgery. Specimens from each time interval were subjected to biomechanical and histological evaluation. None of the cauterized fractures healed throughout the eight weeks experimental duration. The radiographical appearance of nonunion models was atrophic. This investigation showed pronounced differences between the experimental nonunions and standard closed fractures both histologically and biomechanically. In conclusion, we have developed a reproducible atrophic nonunion model in the rat femur that simulates the clinical condition in which there is periosteal disruption but no bone defect.     

A pneumatic leg brace for the treatment of tibial stress fractures

Forty-two competitive athletes with posterior medial pain in the lower one-half of the tibia were evaluated by plain roentgenograms and bone scans. Twenty stress fractures were diagnosed in 17 patients by plain roentgenograms or bone scans or both. The remaining 25 patients were diagnosed as having shin splints. All 42 patients subsequently had a pneumatic leg brace applied to the affected limb or limbs. The 17 patients with stress fractures were able to ambulate without pain and were allowed to resume light training in an average of one week. Their injuries were nontender to palpation. The patients were allowed to resume intensive training at an average of 3.7 weeks postinjury. Patients returned to competition at the preinjury level in an average of 5.3 weeks after application of the brace. The pneumatic leg brace allowed the athletes with tibial stress fractures to begin pain-free ambulation and rehabilitation, thus facilitating the maintenance of their cardiovascular fitness and permitting an early return to competition.     

Mechanical strength of fracture callus in osteopenic bone at different phases of healing

OBJECTIVES: To quantify and compare peak bending force and stiffness of fractured femurs during healing of ovariectomized (OVX) and sham-operated (SHAM) rats. DESIGN: Temporal biomechanical animal study. SETTING: Rat femurs were fractured and surgically fixed by a qualified surgeon. The inherent instability of the fixation system employed produced delayed union of the fracture. All biomechanical assessments were performed with servohydraulic test machines (Instron Inc., Canton, MA, U.S.A.; and MTS Corp., Eden Prairie, MN, U.S.A.). INTERVENTION: OVX was performed sixteen weeks before femur fracture, and the effect of OVX on healing fractures was determined. MAIN OUTCOMES: Peak bending force and stiffness of the healing femurs at four, six, and eight weeks after fracture. RESULTS: Peak bending loads of the healing fractured femurs in the OVX and SHAM animals were not significantly different. Peak bending loads for the OVX animals at four and six weeks were significantly lower than the peak load at eight weeks (p < 0.05), whereas no difference was found in the peak load with respect to time for the SHAM animals. Both SHAM and OVX animals had greater bending stiffness of the healing fractured femur after eight weeks of healing than at four weeks (p < 0.05). CONCLUSIONS: OVX is known to reduce cancellous bone mass and strength, but the effect of OVX on healing of fractures in cortical bone is controversial. This study, using a delayed-union model, found no significant differences between OVX and SHAM animals in the breaking strength of healing fractures.     

Less Invasive Surgery With Autologous Bone Grafting for Proximal Fifth Metatarsal Diaphyseal Stress Fractures

Surgery with autologous bone grafting for proximal fifth metatarsal diaphyseal stress fracture has a potential to decrease nonunion, but it is not performed widely as the primary surgery because of donor-site morbidity. We have devised and performed a less invasive surgical procedure with autologous bone grafting and aimed to investigate the clinical and radiologic outcomes of this procedure. The data for 73 patients who underwent primary intramedullary screw fixation with autologous bone grafting from the fifth metatarsal base for proximal fifth metatarsal diaphyseal stress fractures were investigated retrospectively. The clinical and radiologic outcomes were evaluated. The mean time to bone union, starting running, and return to play was 11.8, 6.3, and 13.4 weeks, respectively. Bone union was achieved in 76 of the 78 cases. Intramedullary screw fixation with autologous bone grafting from the fifth metatarsal base showed good outcomes. It may be a useful surgical option for patients with proximal fifth metatarsal diaphyseal stress fractures.     

A Controlled Study of the Effects of Alendronate in a Growing Mouse Model of Osteogenesis Imperfecta

Recent studies have reported that bisphosphonates reduce fracture incidence and improve bone density in children with osteogenesis imperfecta (OI). However, questions still persist concerning the effect of these drugs on bone properties such as ultrastructure and quality, particularly in the growing patient. To address these issues, the third-generation bisphosphonate alendronate was evaluated in the growing oim/oim mouse, an animal model of moderate-to-severe OI. Alendronate was administered to 6-week-old mice during a period of active growth at a dosage of 73 microg alendronate/kg/day for the first 4 weeks and 26 microg alendronate/kg/day for the next 4 weeks. Positive treatment effects included a reduction in the number of fractures sustained by the alendronate-treated oim/oim mice compared with untreated oim/oim mice (2.1+/-2.0 vs 3.2+/-1.6 fractures per mouse), increased femoral metaphyseal density (0.111+/-0.02 vs 0.034+/-0.04 g/cm2), a tendency towards reduced tibial bowing (4.0+/-3.7 vs 6.1+/-5.8 degrees), and towards increased femoral diameter (1.22+/-0.12 vs 1.15+/-0.11 mm). Potential negative effects included a persistence of calcified cartilage in the treated oim/oim metaphyses compared with treated wildtype (+/+) (33.8+/-11.1 vs 22.1+/-10.2%), and significantly shorter femora compared with nontreated oim/oim mice (14.8+/-0.67 vs 15.3+/-0.37 mm). This preclinical study demonstrates that alendronate is effective in reducing fractures in a growing mouse model of OI, and is also an important indicator of potential positive and negative outcomes of third-generation bisphosphonate therapy in children with OI.     

Measurement of blood flow in tibial fracture patients using positron emission tomography.

The quantification of local bone blood flow in man has not previously been possible, despite its importance in the study of normal and pathological bone. We report the use of positron emission tomography, using 15O-labelled water, to measure bone blood flow in patients with closed unilateral fractures of the tibia. We compared fractured and unfractured limbs; alterations in blood flow paralleled those found in animal models. There was increased tibial blood flow at the fracture site as early as 24 hours after fracture, reaching up to 14 times that in the normal limb at two weeks. Blood flow increase was less in displaced than in undisplaced fractures. The muscle to bone ratios of blood flow were similar to those in previous animal work using other techniques. Positron emission tomography will allow study of human bone blood flow in vivo in a wide variety of pathological conditions.     

Repetition of an unusual stress fracture in an anorexic man: a case report

Stress fractures of the fibula commonly occur distally in runners, whereas stress fractures of the proximal fibula are uncommon and typically occur in jumpers. Furthermore, it is rare for a stress fracture to be repeated in the same bone. We report a case of a repeated stress fracture of the proximal fibula in a male runner with abnormal gait that primarily involved excessive pronation. Unusual risk factors in this case were anorexia nervosa and use of an inhaled corticosteroid. The patient was treated conservatively, and healing of the fracture was completed at 12 weeks.     

Reamed nailing of Gustilo grade-IIIB tibial fractures

Reamed intramedullary nailing was carried out on R57 Gustilo grade-IIIB tibial fractures in 55 patients. After debridement, there was substantial bone loss in 28 fractures (49%). The mean time to union was 43 weeks (14 to 94). When there was no bone loss, the mean time to union was 32 weeks; it was 45 weeks if there was bone loss. Fractures complicated by infection took a mean of 53 weeks to heal. Revision nailing was necessary in 13 fractures (23%) and bone grafting in 15 (26%). In ten fractures (17.5%) infection developed, in four within six weeks of injury and in six more than four months later. Of these, nine were treated successfully, but one patient required an amputation because of osteomyelitis. Our results indicate that reamed intramedullary nailing is a satisfactory treatment for Gustilo grade-III tibial fractures.     

Unusual distribution and onset of stress fractures in soldiers

Ninety-four stress fractures were detected in 64 soldiers by scintigraphy during the first 11 weeks of basic training. Unlike past military studies that showed large numbers of stress fractures of the feet, only 2% were in the metatarsals and none were in the calcaneus. Most fractures were in the tibia (71%) and femoral shaft (25%). Contrary to previous reports in the literature, the fractures occurred later in training, with 67% occurring during the fifth to eighth weeks of basic training and 12 percent during the ninth to eleventh weeks. This unusual distribution and onset has possible explanations in (1) new training concepts to fit modern warfare, with more emphasis on runs and marches; (2) new apparel and equipment carried by the soldiers; (3) changes in prearmy lifestyle; and (4) the extensive use of bone scan for diagnosis.     

Histomorphometric analysis of diabetic osteopenia in streptozotocin-induced diabetic mice: a possible role of oxidative stress

Diabetic osteopenia causes an increase in bone fracture and a delay in healing of fractures, and affects the quality of life. However, the mechanisms responsible for the disease have not been clearly identified. Oxidative stress may be a potential candidate for the pathogenesis, since it is increased under diabetic conditions and is known to induce cellular dysfunction in a wide variety of cell types. Although in vitro studies have shown that oxidative stress inhibits osteoblastic differentiation and induces osteoblast insults and apoptosis, the relationship between diabetic osteopenia and oxidative stress remains unclear. To explore these issues, analysis of a mouse model that represents the diabetic osteopenia as seen in patients with diabetes is necessary. However, there are few reports of such a model. Therefore, we focused on the streptozotocin (STZ)-induced diabetic mouse, one of the most common animal models of type 1 diabetes. Eight-week-old male C57BL/6 mice were randomly assigned to the following three groups: 1) control group, 2) diabetic group, and 3) insulin-treated diabetic group. After 12 weeks of STZ treatment, the physical properties of the femora, and the static and dynamic parameters of bone histomorphometry of the tibiae from STZ-induced diabetic mice (STZ-mice) were assessed, and oxidative stress in the whole body and bone of the mice was evaluated. Renal function was comparable in all three groups at the end of the experimental period. In addition, no significant difference in serum PTH, Ca, and P was found among the three groups. In contrast, radiological analysis demonstrated a significant decrease in trabecular bone volume, and histomorphometric analyses confirmed that parameters for both bone formation (OV/BV, OS/BS, and BFR/BS) and bone resorption (ES/BS and Oc.S/BS) were also significantly lower in STZ-mice. In addition, urinary excretion of 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage, was elevated in STZ-mice. Further immunohistological studies showed intensified immunostaining of an oxidative stress marker in bone tissue including the osteoblasts of diabetic mice. Here, we demonstrated that STZ-mice exhibit low-turnover osteopenia associated with increased oxidative stress.     

Stress fractures of the femoral neck following strenuous activity

Stress fractures of the femoral neck following sustained strenuous physical activity are uncommon. In 194 military recruits in elite basic training who had sustained 257 stress fractures, most of them in long bone diaphyses, nine such fractures were located in the femoral neck. Seven of these fractures were transverse and undisplaced, and were treated successfully by bed rest and non-weight bearing for 6-8 weeks. The other two fractures displaced into a varus position. One of them was treated successfully by manipulation and plaster of paris spica immobilization. Solid union of the fracture followed within 3 months. The second displaced fracture was treated by two successive procedures of internal fixation because it did not unite after the first intervention and slipped again into varus position. It is therefore suggested that unstable stress fractures of the femoral neck should be initially operated on and stabilized by rigid internal fixation, in order to avoid displacement and severe disability.