Mouse Model of Fracture Pain

Background: The aim of this study was to validate a model of postfracture pain in mice, which was evaluated in the presence and the absence of morphine and ketoprofen.

Methods: The study was divided into two parts: protocol A, the effects of closed fracture; and protocol B, the effects of morphine and ketoprofen on fracture pain. In protocol A, mice were assigned to three groups: group 1, sham incision; group 2, sham pinning; or group 3, fracture. In protocol B, mice were randomly assigned to four groups to receive morphine (3 or 10 mg/kg body weight), ketoprofen (50 mg/kg body weight), or placebo (vehicle). Three tests were used to assess pain behavior: von Frey filament application, hot plate test, and a subjective pain scale.

Results: In protocol A, thermal nociception, mechanical nociception, and subjective pain were significantly modified in group 3 (fractured) compared with control groups 1 and 2 (sham groups). In protocol B, when tests were repeated for 240 min in morphine-treated animals and in ketoprofen-treated animals, reduction of mechanical nociception, thermal nociception, and subjective pain scale score were observed. Morphine and ketoprofen administration provided the same effect on behavioral testing on postoperative days 1 and 2.     

Congenital Coxa Vara and Perthes' Disease

Mechanical properties of fractured and intact femora have been studied in young and adult, male rats. A standardized, closed, mid-diaphyseal fracture was produced in the left femur, the right femur serving as control. The fracture was left to heal without immobilization. At various intervals, both fractured and intact femora were loaded in torsion until failure.

The fractured femora regained the mechanical properties of the contralateral, intact bones after about 4 weeks in young and after about 12 weeks in adult rats. For intact bones, both the ultimate torsional moment (strength) and the torsional stiffness increased with age of the animals, whereas the ultimate torsional angle remained unchanged. For bone as a material, however, the ultimate torsional stress (strength) and the modulus of rigidity (stiffness) increased with age only in young rats, being almost constant in the adult animals.

The various biomechanical parameters of the healing fractures did not reach those of the contralateral, intact bones simultaneously. The torsional moment required to twist a healing femoral fracture 20 degrees (0.35 radians), a deformation close to what an intact femur can resist, proved to be a functional and simple measure of the degree of fracture repair in rats.     

Role of dual energy X-ray absorptiometry in monitoring fracture healing in a rat femoral fracture model

Earlymobilizationandweightbearingplayimportantrolesinminimizingtheamountofbonelosstoachievegoodhealingafterbonefracture.1Areliableandnoninvasivemethodforevaluatingfracturehealingcannotonlyhelpdecidewhentostarweightbearing, butalsohelpdetecttheimpairedboneunionearlytopreventdelayedunionsornonunions.However, objectivequantitativemethodsforearlyevaluationoffracturehealinghavenotbeendevelopedyet. DualenergyX rayabsorptiometry(DEXA)isoneofthemostaccuratemethodsformeasuringbonemassinvivo. Itismain…     

Influence of Age on Mechanical Properties of Healing Fractures and Intact Bones in Rats

Mechanical properties of fractured and intact femora have been studied in young and adult, male rats. A standardized, closed, mid-diaphyseal fracture was produced in the left femur, the right femur serving as control. The fracture was left to heal without immobilization. At various intervals, both fractured and intact femora were loaded in torsion until failure.

The fractured femora regained the mechanical properties of the contralateral, intact bones after about 4 weeks in young and after about 12 weeks in adult rats. For intact bones, both the ultimate torsional moment (strength) and the torsional stiffness increased with age of the animals, whereas the ultimate torsional angle remained unchanged. For bone as a material, however, the ultimate torsional stress (strength) and the modulus of rigidity (stiffness) increased with age only in young rats, being almost constant in the adult animals.

The various biomechanical parameters of the healing fractures did not reach those of the contralateral, intact bones simultaneously. The torsional moment required to twist a healing femoral fracture 20 degrees (0.35 radians), a deformation close to what an intact femur can resist, proved to be a functional and simple measure of the degree of fracture repair in rats.     

Effects of a monoclonal antibody raised against nerve growth factor on skeletal pain and bone healing after fracture of the C57BL/6J mouse femur.

A closed femur fracture pain model was developed in the C57BL/6J mouse. One day after fracture, a monoclonal antibody raised against nerve growth factor (anti-NGF) was delivered intraperitoneally and resulted in a reduction in fracture pain-related behaviors of approximately 50%. Anti-NGF therapy did not interfere with bone healing as assessed by mechanical testing and histomorphometric analysis. INTRODUCTION: Current therapies to treat skeletal fracture pain are limited. This is because of the side effect profile of available analgesics and the scarcity of animal models that can be used to understand the mechanisms that drive this pain. Whereas previous studies have shown that mineralized bone, marrow, and periosteum are innervated by sensory and sympathetic fibers, it is not understood how skeletal pain is generated and maintained even in common conditions such as osteoarthritis, low back pain, or fracture. MATERIALS AND METHODS: In this study, we characterized the pain-related behaviors after a closed femur fracture in the C57BL/6J mouse. Additionally, we assessed the effect of a monoclonal antibody that binds to and sequesters nerve growth factor (anti-NGF) on pain-related behaviors and bone healing (mechanical properties and histomorphometric analysis) after fracture. RESULTS: Administration of anti-NGF therapy (10 mg/kg, days 1, 6, and 11 after fracture) resulted in a reduction of fracture pain-related behaviors of approximately 50%. Attenuation of fracture pain was evident as early as 24 h after the initial dosing and remained efficacious throughout the course of fracture pain. Anti-NGF therapy did not modify biomechanical properties of the femur or histomorphometric indices of bone healing. CONCLUSIONS: These findings suggest that therapies that target NGF or its cognate receptor(s) may be effective in attenuating nonmalignant fracture pain without interfering with bone healing.     

Effect of Systemic and Intrathecal Morphine in a Rat Model of Postoperative Pain

Background: To learn more about persistent pain after an incision, a rat model for postoperative pain has been developed. To further evaluate this model, the authors examined the effect of intrathecal (IT) and subcutaneous (SC) morphine, effective for postoperative pain relief in patients, on pain behaviors immediately after surgery and 1 day after surgery.

Methods: Rats were anesthetized with halothane, and a 1-cm incision was made in the plantar aspect of the foot and closed. After recovery, the rats were placed on an elevated plastic mesh floor, and withdrawal threshold was determined using calibrated von Frey filaments (15-522 mN) applied from beneath the test cage to an area adjacent to the wound at the heel. Pain behaviors also were assessed using the response frequency to a nonpunctate mechanical stimulus and a cumulative pain score.

Results: Mechanical hyperalgesia and nonevoked pain behaviors were present on the day of surgery and 1 day after surgery. Administration of either SC (0.3-3.0 mg/kg) or IT (0.16-5.0 micro gram) morphine reversibly increased the withdrawal threshold. The response frequency to the nonpunctate stimulus and the nonevoked pain scores also were decreased by 3 mg/kg of SC or 5 micro gram of IT morphine. Naloxone (1 mg/kg) reversed morphine-produced hypoalgesia.     

骨质疏松性骨折实验模型的设计与建立

目的：建立较理想的骨质疏松性骨折实验模型，方法：SD大鼠60只，8月龄，雌性，手术方法：切除双侧卵巢；术后3个月，手术造成股骨中段骨折，进行骨圆针髓腔内固定。模型建立前后双能X线骨密度仪（DEXA），组织学、放射学等动态观察。结果：卵巢切除3个月后DEXA检测结果与术前比较：全身骨密度明显降低（P＜0．02）；子宫内膜组织萎缩变薄，内膜内腺体消失或萎缩，变性呈空泡状；软骨内成骨与膜内成骨共同参与了骨质疏松性骨折的修复，且以软骨内成骨为主，与一般骨折愈合方式相似，模型动物骨折愈合过程中，软骨内成骨延缓，骨性骨痂改建（骨吸收＞骨形成）加速，骨痂内胶原纤维疏松，排列紊乱，与主应力方向不一致，放射学观察模型动物骨折位置，类型统一，内固定后骨折断端稳定。结论：本实验建立的骨质疏松性骨折动物模型模型其方法，易于复制，可应用于骨质疏松林骨折的相关研究。     

Fracture healing in rats inhibited by locally administered indomethacin.

We studied the inhibitory effect of indomethacin on fracture healing in 135 young, male rats after oral administration compared with local application into the fracture. A closed mid-diaphyseal fracture of the left femur was performed in all the rats. The fractures were not immobilized. In one experiment, half of the animals received indomethacin via a stomach tube (2 mg/kg/day) for 10 days; the controls received only the vehicle. In another experiment, 0.5 mg of indomethacin, contained in a bioerodible polyorthoester gel, was injected into the fracture area in half the rats; in the controls, only the gel was injected. In both experiments, random animals were killed on Days 0, 5, 10, and 20. As assessed by radiographs and manual testing, the same inhibition of fracture healing was found regardless of whether indomethacin was given orally or locally. However, the amount of indomethacin that was applied locally was only one fourth of the total dose given orally; no indomethacin was detected in the serum.     

Age and ovariectomy impair both the normalization of mechanical properties and the accretion of mineral by the fracture callus in rats.

The impact of age and ovariectomy on the healing of femoral fractures was studied in three groups of female rats at 8, 32 and 50 weeks of age at fracture. In the two older groups, the rats had been subjected to ovariectomy or sham surgery at random at 26 weeks of age. At fracture, all rats received unilateral intramedullary pinning of one femur and a middiaphyseal fracture. Rigidity and breaking load of the femora were evaluated at varying times up to 24 weeks after fracture induction by three-point bending to failure. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. In the youngest group, 8-week-old female rats regained normal femoral rigidity and breaking load by 4 weeks after fracture. They exceeded normal contralateral values by 8 weeks after fracture. In the middle group, at 32 weeks of age, fractures were induced, and the femora were harvested at 6 and 12 weeks after fracture. At 6 weeks after fracture there was partial restoration of rigidity and breaking load. At 12 weeks after fracture, only the sham-operated rats had regained normal biomechanical values in their fractured femora, while the fractured femora of the ovariectomized rats remained significantly lower in both rigidity and breaking load. In contrast, for the oldest group of rats, 50 weeks old at fracture, neither sham-operated nor ovariectomized rats regained normal rigidity or breaking load in their fractured femora within the 24 weeks in which they were studied. In all fractured bones, there was a significant increase in BMD over the contralateral intact femora due to the increased bone tissue and bone mineral in the fracture callus. Ovariectomy significantly reduced the BMD of the intact femora and also reduced the gain in BMD by the fractured femora. In conclusion, age and ovariectomy significantly impair the process of fracture healing in female rats as judged by measurements of rigidity and breaking load in three-point bending and by accretion of mineral into the fracture callus.     

Strain and Sex Influence on Pain Sensitivity after Plantar Incision in the Mouse

Background: A small surgical incision in mouse glabrous hind-paw skin induces short-lasting guarding behavior and mechanical and heat hyperalgesia-like behaviors, which imitate human postoperative pain. The increasing popularity of this animal model in drug discovery necessitates the understanding of genetic and sex influence on this animal model.

Methods: The authors examined pain behaviors on DBA2, C57Bl/6, and 129X1/SvJ mice and male and female DBA2 mice before and after plantar incision.

Results: The baseline nociceptive responses of these strains were similar, with a few exceptions. Heat responses were different between DBA2 and C57Bl/6 mice, and responses to one filament, 14.0 mN, were intermittently different. Sex did not greatly influence baseline responses. After plantar incision, these three strains of mice were not different in the development of guarding behaviors. Heat responses were only different on postincision day 3 (129X1/SvJ vs. C57Bl/6 mice); otherwise, they were the same. The responses to the series of von Frey filaments were the same after incision in the three strains. Sex did not influence incision-induced pain behaviors in DBA2 mice.     

OP-1 Augments Glucocorticoid-inhibited Fracture Healing in a Rat Fracture Model

Glucocorticoids inhibit bone remodeling and fracture healing. We sought to determine whether osteogenic protein 1 (OP-1) can overcome this inhibition in a closed fracture model in the rat. Time-released prednisolone or placebo pellets were implanted subcutaneously; closed femoral fractures were created 2 weeks later in rats. Fractures received sham, OP-1 and collagen, or collagen-only implants. Femurs were harvested at 3, 10, 21, 28, and 42 days postfracture. Fractures were examined radiographically for amount of hard callus; mechanically for torque and stiffness (also expressed as a percentage of the contralateral intact femur); and histomorphometrically for amount of cartilaginous and noncartilaginous soft callus, hard callus, and total callus. Glucocorticoid administration inhibited fracture healing. The application of a devitalized Type I collagen matrix mitigated the inhibitory effects of prednisolone on fracture healing However, further increases in indices of fracture healing were observed when OP-1 was added to the collagen matrix compared with collagen alone. OP-1 and collagen was more effective than collagen alone.     

雌激素对去势SD雌性大鼠骨折愈合早期骨痂形成影响的实验研究

目的：初步探讨雌激素在雌性ＳＤ大鼠骨折愈合早期的作用及其机制。方法：将ＳＤ大鼠分为Ａ、Ｂ、Ｃ３组,后２组摘除卵巢,２１ｄ后定支点折骨造成动物左胫腓骨闭合骨折,Ｃ组应用雌激素,分别于骨折后１、２、３、５周采取骨痂标本行ＡＫＰ测定,Ｘ线及组织学检查。结果：骨痂形成早期Ｂ组软骨骨痂较另两组稍多,但各组骨痂成熟程度无明显差异,骨痂形成后期Ｂ组骨痂结构疏松,而Ｃ组小梁致密,有编织、板层化趋势。结论：雌激素在ＳＤ大鼠骨痂形成早期轻度抑制软骨骨痂形成,骨痂形成后期有利于小梁骨形成、堆积及向编织骨的转化。     

Mechanical Pain Hypersensitivity after Incisional Surgery Is Enhanced in Rats Subjected to Neonatal Peripheral Inflammation: Effects of N-Methyl-d-aspartate Receptor Antagonists

Background: Neonatal pain and inflammation may lead to a long-term effect on nociceptive processing in adults. The current study examined the characteristics of postoperative incisional pain behaviors in adult rats that were subjected to neonatal peripheral inflammation.

Methods: Rat pups received a subcutaneous injection of saline or carrageenan into the plantar surface of the left hind paw at postnatal day 1. Naive pups were used as the control. Paw withdrawal thresholds to punctuate mechanical stimuli were examined at postnatal days 35, 42, and 49. After rats received a plantar incision on the left or right hind paw at postnatal day 50, paw withdrawal thresholds were measured at 4 h, 1 day, 2 days, 3 days, 5 days, and 7 days after incision. In addition, spinal cord Fos expression was detected at 2 h after incision. Finally, the effects of intrathecal N-methyl-d-aspartate receptor antagonists dl-2-amino-5-phosphonovaleric acid and dizocilpine and the nitric oxide synthase inhibitor l-NG-nitro-arginine methylester on incisional pain were examined at 4 h after incision.

Results: Although the rats subjected to neonatal peripheral carrageenan injection developed mechanical hypoalgesia in bilateral hind paws at baseline, they displayed increased spinal cord Fos expression at 2 h and exaggerated mechanical pain hypersensitivity at 4 h (but not at other time points) after plantar incision. Intrathecal dl-2-amino-5-phosphonovaleric acid, dizocilpine, and l-NG-nitro-arginine methylester significantly attenuated incision-induced mechanical pain hypersensitivity at 4 h after incision in the neonatally carrageenan-treated rats, but not in the naive or neonatally saline-treated rats.     

Mechanical Properties of Fractured and Intact Rat Femora Evaluated by Bending, Torsional and Tensile Tests

Mechanical properties of healing fractures and growing, intact bones were studied in male rats aged 8 weeks at the beginning of the study period. A standardized, closed fracture was produced in the middle of the left femur. The fracture was not immobilized. At various intervals after the fracture, the healing fractured femora and the contralateral, intact femora were subjected to bending, torsional and tensile tests.

The fractured femora regained the strength and the ultimate deformation of the contralateral, intact femora after about 8 weeks when tested in bending, and after about 13 weeks when tested in torsion. In the first phases of fracture repair, the healing fractures could resist more torsional than bending load, whereas the opposite was found for solidly consolidated fractures and intact bones.

For intact bones, the ultimate bending and torsional moments increased with increase in age and weight of the animals, whereas the ultimate angular deformation remained constant. The ultimate bending and torsional stresses (bone material strength) increased to reach a plateau when the rats were about 14 weeks old. No significant differences were observed between the bending, torsional and tensile test methods. For the evaluation of fracture repair, each test has its particular application.     

Subtrochanteric osteoid osteoma: A misdiagnosed case complicated by a hipfracture

A 34-year-old man with a subtrochanteric osteoid osteoma localized to the lateral cortex of the left femur is reported. The patient presented with mild spontaneous pain of the lateral thigh and knee. He refused a radiographic examination and was treated as a greater trochanteric pain syndrome for 9 months. He was then admitted with a transcervical fracture of the neck of the left femur after a fall from standing height. The fracture was fixed with 3 cannulated screws and healed uneventfully. His symptoms worsened after the first postoperative year. Eighteen months postoperatively the pain was dull, worsening at night, and relieved only with anti-inflammatory drugs, and he had a limp. New radiographs and tomograms were indicative of a lateral subtrochanteric osteoid osteoma with a subperiosteal localization. The lesion was treated successfully with surgical excision of a piece of reactive bone including the nidus.     

麝香乌龙丸对卵巢切除大鼠股骨骨折愈合的实验研究

目的研究麝香乌龙丸对卵巢切除大鼠股骨干骨折愈合的作用。方法将30只雌性、12周龄Sprague-Dawley大鼠分成3组假手术组(Sham F V)、卵巢切除 骨折 生理盐水对照组(OVX F V)、卵巢切除 骨折 麝香乌龙丸给药组(OVX F M),每组10只大鼠。所有需制造骨折的大鼠均采用右股骨中段横行骨折,髓内针固定;麝香乌龙丸给药组采用大鼠灌胃给药(1.2g.kg-1.d-1),于术后4周杀死,取大鼠右侧股骨标本;分别进行CR摄片、组织形态学染色,并应用双能X线骨密度仪(DEXA)测量右股骨整体骨密度(tBMD)、远段骨密度(dBMD)和中段骨密度(mBMD)以及BMP-2免疫组化观察,并应用病理图像分析仪对BMP-2免疫组化进行光密度测定。结果麝香乌龙丸给药组与OVX F V比较,前者骨痂mBMD和BMP-2的表达显著增高,骨小梁增宽、排列较整齐,板层骨形成,软骨组织可见。结论麝香乌龙丸对OVX大鼠股骨骨折有明显促进骨折愈合的作用,并加快编织骨向板层骨的演变过程,这与BMP-2的表达有明显相关性。     

髋部骨折426例分布调查

通过对426例髋部骨折的流行病学调查发现:(1)髋部骨折多分布于老年人,男性分布高峰在70～80岁,女性在60～80岁。儿童少见。(2)50岁以上年龄组男女髋部骨折分布比为1:1.33;50岁以下为1:0.36。(3)粗隆间骨折与股骨颈骨折分布比为1:1.51。(4)摔、跌、扭等轻度损伤是髋部骨折的常见致伤原因,占68.5％。(5)四季发病分布比为1:0.65:0.70:1.35。(6)左、右侧别分布比为1.45:1。     

Fascia Iliaca Compartment Blockade for Acute Pain Control in Hip Fracture Patients: A Randomized, Placebo-controlled Trial

Background: Hip fracture patients are in severe pain upon arrival at the emergency department. Pain treatment is traditionally based on systemic opioids. No study has examined the effect of fascia iliaca compartment blockade (FICB) in acute hip fracture pain management within a double-blind, randomized setup.

Methods: Forty-eight patients with suspected hip fracture were included immediately after arrival in the emergency department, before x-ray confirmation of their fracture. Included patients were randomly assigned to two groups of 24. In the FICB group, the patients received an FICB with 1.0% mepivacaine and a placebo intramuscular injection of isotonic saline. In the morphine group, the patients received a placebo FICB with 0.9% saline and an intramuscular injection of 0.1 mg/kg morphine. Patients received intravenous rescue morphine when necessary.

Results: Maximum pain relief was superior in the FICB group both at rest (P < 0.01) and on movement (P = 0.02). The median total morphine consumption was 0 mg (interquartile range, 0-0 mg) in the FICB group and 6 mg (interquartile range, 5-7 mg) in the morphine group (P < 0.01). More patients (P = 0.05) were sedated in the morphine group at 180 min after block placement as compared with the FICB group.     

Development of a fracture osteomyelitis model in the rat femur

Osteomyelitis contributes significantly to fracture morbidity. Our objective was to develop a model of induced implant‐associated osteomyelitis following fracture repair by modifying an existing rat femur fracture model. Thirty male Sprague–Dawley rats were divided into three groups (Control, Staphylococcus aureus, S. aureus + ceftriaxone). The closed femur fracture model (right femur), stabilized with an intramedullary pin, was combined with inoculation of 10⁴ colony‐forming units (CFU) of S. aureus. Radiographs were obtained immediately after surgery and at weeks 1, 2, and 3 and were evaluated by individuals blinded to treatment group. At necropsy the CFU of S. aureus per femur and pin were determined and synovial tissue and blood were cultured. The fractured femur from two rats in each group was evaluated histologically. A statistically significant difference in the CFU/femur and CFU/pin was found across treatment groups, with the highest CFU in the S. aureus group and the lowest in the Control group. Cultures of synovial tissue were positive in 11/19 of inoculated limbs. Osteomyelitis was present both radiographically and histopathologically in both S. aureus groups but not in the controls. No rats were systemically ill or had positive blood cultures at the study endpoint. This model will be useful for the evaluation of treatments or prophylactics designed for use in implant‐associated osteomyelitis. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:131–137, 2011     

Calcitonin Producing Tumour: Effects on Fracture Repair and Normal Bone in Rats

The mechanical properties and the collagen metabolism of healing fractures and intact bones have been studied in rats with a transplanted, calcitonin (CT) secreting, medullary thyroid carcinoma (MCT). Sham operated animals served as controls. the MCT was transplanted beneath the kidney capsule. Seven months later, when the rats with MCT had increased circulating levels of CT, a standardized femoral fracture was produced in all the animals.

The serum levels of CT were 3-40 times higher in tumour bearing rats than in controls in the period following the fracture. the fracture strength of rats with MCT was reduced by about 60 per cent compared to controls at 16 weeks after the fracture. the strength of intact femora (ultimate torsional moment) seemed to be progressively impaired by increasing levels of circulating CT. Also the strength of bone as a material (ultimate torsional stress) was reduced in the rats with MCT. the collagen synthesis was reduced in MCT rats, but the amounts of collagen in fractured or intact bones were not changed compared to controls.

We conclude that chronic hypercalcitoninaemia due to MCT seems to have a negative influence both on fracture healing and on bone metabolism.