Clinical evaluation of new bone formation during limb lengthening in children using ultrasound combined with superb microvascular imaging.

Aims: Given the possible radiation damage and inaccuracy of radiological investigations, particularly in children, ultrasound and superb microvascular imaging (SMI) may offer alternative methods of evaluating new bone formation when limb lengthening is undertaken in paediatric patients. The aim of this study was to assess the use of ultrasound combined with SMI in monitoring new bone formation during limb lengthening in children. Methods: In this retrospective cohort study, ultrasound and radiograph examinations were performed every two weeks in 30 paediatric patients undergoing limb lengthening. Ultrasound was used to monitor new bone formation. The number of vertical vessels and the blood flow resistance index were compared with those from plain radiographs. Results: We categorized the new bone formation into three stages: stage I (early lengthening), in which there was no obvious callus formation on radiographs and ultrasound; stage II (lengthening), in which radiographs showed low-density callus formation with uneven distribution and three sub-stages could be identified on ultrasound: in Ia punctate callus was visible; in IIb there was linear callus formation which was not yet connected and in IIc there was continuous linear callus. In stage III (healing), the bone ends had united, the periosteum was intact, and the callus had disappeared, as confirmed on radiographs, indicating healed bone. A progressive increase in the number of vertical vessels was noted in the early stages, peaking during stages IIb and IIc, followed by a gradual decline (p < 0.001). Delayed healing involved patients with a prolonged stage IIa or those who regressed to stage IIa from stages IIb or IIc during lengthening. Conclusion: We found that the formation of new bone in paediatric patients undergoing limb lengthening could be reliably evaluated using ultrasound when combined with the radiological findings. This combination enabled an improved assessment of the prognosis, and adjustments to the lengthening protocol. While SMI offered additional insights into angiogenesis within the new bone, its role primarily contributed to the understanding of the microvascular environment rather than directly informing adjustments of treatment.

Mass Spectrometry Reveals Molecular Effects of Citrulline Supplementation during Bone Fracture Healing in a Rat Model.

Bone fracture healing is a complex process in which specific molecular knowledge is still lacking. The citrulline-arginine-nitric oxide metabolism is one of the involved pathways, and its enrichment via citrulline supplementation can enhance fracture healing. This study investigated the molecular effects of citrulline supplementation during the different fracture healing phases in a rat model. Microcomputed tomography (µCT) was applied for the analysis of the fracture callus formation. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and liquid-chromatography tandem mass spectrometry (LC-MS/MS) were used for lipid and protein analyses, respectively. µCT analysis showed no significant differences in the fracture callus volume and volume fraction between the citrulline supplementation and control group. The observed lipid profiles for the citrulline supplementation and control group were distinct for the different fracture healing stages. The main contributing lipid classes were phosphatidylcholines (PCs) and lysophosphatidylcholines (LPCs). The changing effect of citrulline supplementation throughout fracture healing was indicated by changes in the differentially expressed proteins between the groups. Pathway analysis showed an enhancement of fracture healing in the citrulline supplementation group in comparison to the control group via improved angiogenesis and earlier formation of the soft and hard callus. This study showed the molecular effects on lipids, proteins, and pathways associated with citrulline supplementation during bone fracture healing, even though no effect was visible with µCT.

Titanium versus stainless steel alloy bridge plates for distal femur fractures: Does callus form earlier with titanium?

INTRODUCTION: Distal femur fractures account for 3-6% of all femur fractures. Internal fixation of most distal femur fractures with an anatomic lateral locking plate should permit some motion at the metaphyseal portion of the fracture when secondary bone healing is planned by the operating surgeon. While several studies have been performed evaluating union rates for distal femur fractures with stainless steel and titanium plates, the timing of callus formation between stainless steel and titanium implants used as bridge plates for distal femur fractures (AO/OTA 33-A and -C) has been investigated to a lesser extent. We hypothesize that callus will be visualized earlier with post-operative radiographs with titanium versus stainless steel bridge plates. METHODS: We retrospectively reviewed a consecutive cohort of patients over 18 years of age with acute AO/OTA 33-A and 33-C fracture patterns treated with an isolated stainless steel or titanium lateral bridge plate within 4 weeks of injury by a single fellowship-trained orthopedic trauma surgeon from 2011 to 2020 at one academic Level 1 trauma center. An independent, fellowship-trained orthopedic trauma attending surgeon reviewed anterior-posterior (AP) and lateral radiographs from every available post-operative clinic visit and graded them using the Modified Radiographic Score for Tibia (mRUST). RESULTS: Twenty-five subjects were included in the study with 10 with stainless steel and 15 with titanium plates. There were no significant differences in demographics between both groups, including age, sex, BMI, injury classification, open versus closed, mechanism, and laterality. Statistically significant increased mRUST scores, indicating increased callus formation, were seen on 12-week radiographs (8.4 vs. 11.9, p = 0.02) when titanium bridge plates were used. There were no statistically significant differences in mRUST scores at 6 or 24-weeks, but scores in the titanium group were higher in at every timepoint. DISCUSSION: In conclusion, we observed greater callus formation at 12 weeks after internal fixation of 33-A and 33-C distal femur fractures treated with titanium locked lateral distal femoral bridge plates compared to stainless steel plates. Our data suggest that titanium metallurgy may have quicker callus formation compared to stainless steel if an isolated, lateral locked bridge plate is chosen for distal femur fracture fixation.

Moderate static magnetic field promotes fracture healing and regulates iron metabolism in mice.

BACKGROUND: Fractures are the most common orthopedic diseases. It is known that static magnetic fields (SMFs) can contribute to the maintenance of bone health. However, the effect and mechanism of SMFs on fracture is still unclear. This study is aim to investigate the effect of moderate static magnetic fields (MMFs) on bone structure and metabolism during fracture healing. METHODS: Eight-week-old male C57BL/6J mice were subjected to a unilateral open transverse tibial fracture, and following treatment under geomagnetic field (GMF) or MMF. The micro-computed tomography (Micro-CT) and three-point bending were employed to evaluate the microarchitecture and mechanical properties. Endochondral ossification and bone remodeling were evaluated by bone histomorphometric and serum biochemical assay. In addition, the atomic absorption spectroscopy and ELISA were utilized to examine the influence of MMF exposure on iron metabolism in mice. RESULTS: MMF exposure increased bone mineral density (BMD), bone volume per tissue volume (BV/TV), mechanical properties, and proportion of mineralized bone matrix of the callus during fracture healing. MMF exposure reduced the proportion of cartilage in the callus area during fracture healing. Meanwhile, MMF exposure increased the number of osteoblasts in callus on the 14th day, and reduced the number of osteoclasts on the 28th day of fracture healing. Furthermore, MMF exposure increased PINP and OCN levels, and reduced the TRAP-5b and ß-CTX levels in serum. It was also observed that MMF exposure reduced the iron content in the liver and callus, as well as serum ferritin levels while elevating the serum hepcidin concentration. CONCLUSIONS: MMF exposure could accelerate fracture healing via promote the endochondral ossification and bone formation while regulating systemic iron metabolism during fracture healing. This study suggests that MMF may have the potential to become a form of physical therapy for fractures.

Estrogen deficiency impedes fracture healing despite eliminating the excessive absorption of the posterior callus in a semi-fixed distal tibial fracture mouse model.

BACKGROUND: Treatment of distal tibial fractures is a challenge due to their specific anatomical location. However, there is no appropriate mouse model to simulate a clinical distal tibial fracture for basic research. The aim of this investigation was to evaluate the feasibility of simulating a clinical fracture of the distal tibia of mice and to investigate the effect of ovariectomy (OVX)-induced osteoporosis on fracture healing in this model. METHODS: Sixty female 8-week-old C57BL/6 mice were randomly divided into two groups, either sham or OVX. A semi-fixation distal tibia fracture was established in the right tibia after 8 weeks of OVX. The right tibias were collected at 7, 14, 21, and 28 days post fracture. RESULTS: In the semi-fixation distal tibia fracture model, the posterior callus in the sham group showed excessive bone resorption and lower bone mass phenotype compared with the anterior site; a similar trend was not found in the OVX group. At 28 days post fracture, the posterior callus was more mineralized than the anterior callus in the OVX group. Although the fracture healing of the sham group showed a special phenotype in this mode, the progress and quality of fracture healing were still better than those of the OVX group. CONCLUSION: A semi-fixed distal tibial closed fracture mouse model was successfully established. In this model, excess bone resorption of the posterior callus impaired normal fracture healing, but not in OVX-induced osteoporotic bone. Although the stress shielding effect was not observed in the OVX group, impaired bone healing caused by OVX was still present. Our results suggest that this fracture model may have potential for studies on distal tibial fractures and stress shielding.

Higher-intensity ultrasound accelerates fracture healing via mechanosensitive ion channel Piezo1.

Osteoporosis-related fractures are a major public health problem. Mechanobiological stimulation utilizing low-intensity pulsed ultrasound (LIPUS) is the most widely accepted modality for accelerating fracture healing. However, recent evidence has demonstrated the ineffectiveness of LIPUS, and the biophysical mechanisms of ultrasound-induced bone formation also remain elusive. Here, we demonstrate that ultrasound at a higher intensity than LIPUS effectively accelerates fracture healing in a mouse osteoporotic fracture model. Higher-intensity ultrasound promoted chondrogenesis and hypertrophic differentiation of chondrocytes in the fracture callus. Higher-intensity ultrasound also increased osteoblasts and newly formed bone in the callus, resulting in accelerated endochondral ossification during fracture healing. In addition, we found that accelerated fracture healing by ultrasound exposure was attenuated when the mechanosensitive ion channel Piezo1 was inhibited by GsMTx4. Ultrasound-induced new bone formation in the callus was attenuated in fractured mice treated with GsMTx4. Similar results were also confirmed in a 3D osteocyte-osteoblast co-culture system, where osteocytic Piezo1 knockdown attenuated the expression of osteoblastic genes after ultrasound exposure. Together these results demonstrate that higher-intensity ultrasound than clinically used LIPUS can accelerate endochondral ossification after fractures. Furthermore, our results suggest that mechanotransduction via Piezo1 mediates ultrasound-stimulated fracture healing and bone formation.

Combined electric and magnetic field therapy for bone repair and regeneration: an investigation in a 3-mm and an augmented 17-mm tibia osteotomy model in sheep.

BACKGROUND: Therapies using electromagnetic field technology show evidence of enhanced bone regeneration at the fracture site, potentially preventing delayed or nonunions. METHODS: Combined electric and magnetic field (CEMF) treatment was evaluated in two standardized sheep tibia osteotomy models: a 3-mm non-critical size gap model and a 17-mm critical size defect model augmented with autologous bone grafts, both stabilized with locking compression plates. CEMF treatment was delivered across the fracture gap twice daily for 90 min, starting 4 days postoperatively (post-OP) until sacrifice (9 or 12 weeks post-OP, respectively). Control groups received no CEMF treatment. Bone healing was evaluated radiographically, morphometrically (micro-CT), biomechanically and histologically. RESULTS: In the 3-mm gap model, the CEMF group (n = 6) exhibited higher callus mineral density compared to the Control group (n = 6), two-fold higher biomechanical torsional rigidity and a histologically more advanced callus maturity (no statistically significant differences). In the 17-mm graft model, differences between the Control (n = 6) and CEMF group (n = 6) were more pronounced. The CEMF group showed a radiologically more advanced callus, a higher callus volume (p = 0.003) and a 2.6 × higher biomechanical torsional rigidity (p = 0.024), combined with a histologically more advanced callus maturity and healing. CONCLUSIONS: This study showed that CEMF therapy notably enhanced bone healing resulting in better new bone structure, callus morphology and superior biomechanical properties. This technology could transform a standard inert orthopedic implant into an active device stimulating bone tissue for accelerated healing and regeneration.

Closed reduction with percutaneous Kirschner wire drill-and-pry for pediatric supracondylar humeral fractures with bony callus formation and delayed presentation.

BACKGROUND: Supracondylar humeral fractures are the most common type of pediatric elbow fractures, and are primarily treated using closed reduction and percutaneous pinning. For patients who are treated ≥14 days after the injury, after callus formation has occurred, closed reduction is usually not possible. The purpose of this study is to report the clinical outcomes of closed reduction with percutaneous Kirschner wire (K-wire) drill-and-pry for the delayed treatment of pediatric supracondylar humeral fractures with bony callus formation. METHODS: We retrospectively reviewed the data of 16 patients who underwent percutaneous K-wire drill-and-pry between November 2019 and August 2021 for the treatment of supracondylar humeral fractures with bony callus formation ≥14 days after the injury. Clinical outcomes were assessed using the Flynn criteria. The postoperative Baumann angle and pin configuration were evaluated using x-ray examinations. RESULTS: All patients were followed up for 8-28 months (average, 16.63 months). The fractures healed in 4-6 weeks (average, 4.38 weeks). The operative time ranged from 10 to 124 min (average, 35.12 min). No iatrogenic vascular or nerve injury occurred. No patient developed cubitus varus. According to the Flynn criteria, 12 patients had excellent outcomes, 2 patients had good outcomes, 1 patient had a fair outcome and 1 patient had a poor outcome. CONCLUSION: Closed reduction with percutaneous K-wire drill-and-pry is a mini invasive technique for supracondylar humeral fractures with bony callus formation in children. Most patients had a good clinical and cosmetic outcomes without scarring.

A new method for segmentation and analysis of bone callus in rodent fracture models using micro-CT.

Fracture burden has created a need to better understand bone repair processes under different pathophysiological states. Evaluation of structural and material properties of the mineralized callus, which is integral to restoring biomechanical stability is, therefore, vital. Microcomputed tomography (micro-CT) can facilitate noninvasive imaging of fracture repair, however, current methods for callus segmentation are only semiautomated, restricted to defined regions, time/labor intensive, and prone to user variation. Herein, we share a new automatic method for segmenting callus in micro-CT tomograms that will allow for objective, quantitative analysis of the bone fracture microarchitecture. Fractured and nonfractured mouse femurs were scanned and processed by both manual and automated segmentation of fracture callus from cortical bone after which microarchitectural parameters were analyzed. All segmentation and analysis steps were performed using CTAn (Bruker) with automatic segmentation performed using the software's image-processing plugins. Results showed automatic segmentation reliably and consistently segmented callus from cortical bone, demonstrating good agreement with manual methods with low bias: tissue volume (TV): -0.320 mm3 , bone volume (BV): 0.0358 mm3 , and bone volume/tissue volume (BV/TV): -3.52%, and was faster and eliminated user-bias and variation. Method scalability and translatability across rodent models were verified in scans of fractured rat femora showing good agreement with manual methods with low bias: TV: -3.654 mm3 , BV: 0.830 mm3 , and BV/TV: 7.81%. Together, these data validate a new automated method for segmentation of callus and cortical bone in micro-CT tomograms that we share as a fast, reliable, and less user-dependent tool for application to study bone callus in fracture, and potentially elsewhere.

Assessment of Bone Fracture Healing Using Micro-Computed Tomography.

Micro-computed tomography (µCT) is the most common imaging modality to characterize the three-dimensional (3D) morphology of bone and newly formed bone during fracture healing in translational science investigations. Studies of long bone fracture healing in rodents typically involve secondary healing and the formation of a mineralized callus. The shape of the callus formed and the density of the newly formed bone may vary substantially between timepoints and treatments. Whereas standard methodologies for quantifying parameters of intact cortical and trabecular bone are widely used and embedded in commercially available software, there is a lack of consensus on procedures for analyzing the healing callus. The purpose of this work is to describe a standardized protocol that quantitates bone volume fraction and callus mineral density in the healing callus. The protocol describes different parameters that should be considered during imaging and analysis, including sample alignment during imaging, the size of the volume of interest, and the number of slices that are contoured to define the callus.

Wireless Measurements Using Electrical Impedance Spectroscopy to Monitor Fracture Healing.

There is an unmet need for improved, clinically relevant methods to longitudinally quantify bone healing during fracture care. Here we develop a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy (EIS) to provide real-time data on tissue composition within the fracture callus. To validate our technology, we created a 1-mm rabbit tibial defect and fixed the bone with a standard veterinary plate modified with a custom-designed housing that included two impedance sensors capable of wireless transmission. Impedance magnitude and phase measurements were transmitted every 48 h for up to 10 weeks. Bone healing was assessed by X-ray, µCT, and histology. Our results indicated the sensors successfully incorporated into the fracture callus and did not impede repair. Electrical impedance, resistance, and reactance increased steadily from weeks 3 to 7-corresponding to the transition from hematoma to cartilage to bone within the fracture gap-then plateaued as the bone began to consolidate. These three electrical readings significantly correlated with traditional measurements of bone healing and successfully distinguished between union and not-healed fractures, with the strongest relationship found with impedance magnitude. These results suggest that our EIS smart bone plate can provide continuous and highly sensitive quantitative tissue measurements throughout the course of fracture healing to better guide personalized clinical care.

Time-Dependent Collagen Fibered Structure in the Early Distraction Callus: Imaging Characterization and Mathematical Modeling.

Collagen is a ubiquitous protein present in regenerating bone tissues that experiences multiple biological phenomena during distraction osteogenesis until the deposition of phosphate crystals. This work combines fluorescence techniques and mathematical modeling to shed light on the mechano-structural processes behind the maturation and accommodation-to-mineralization of the callus tissue. Ovine metatarsal bone calluses were analyzed through confocal images at different stages of the early distraction osteogenesis process, quantifying the fiber orientation distribution and mean intensity as fiber density measure. Likewise, a mathematical model based on the experimental data was defined to micromechanically characterize the apparent stiffening of the tissue within the distracted callus. A reorganization of the fibers around the distraction axis and increased fiber density were found as the bone fragments were gradually separated. Given the degree of significance between the mathematical model and previous in vivo data, reorganization, densification, and bundle maturation phenomena seem to explain the apparent mechanical maturation observed in the tissue theoretically.

The progress in quantitative evaluation of callus during distraction osteogenesis.

The manual monitoring of callus with digital radiography (X-ray) is the primary bone healing evaluation, assessing the number of bridged callus formations. However, this method is subjective and nonquantitative. Recently, several quantitative monitoring methods, which could assess the recovery of the structure and biomechanical properties of the callus at different stages and the process of bone healing, have been extensively investigated. These methods could reflect the bone mineral content (BMC), bone mineral density (BMD), stiffness, callus and bone metabolism at the site of bone lengthening. In this review, we comprehensively summarized the latest techniques for evaluating bone healing during distraction osteogenesis (DO): 1) digital radiography; 2) dual-energy X-ray scanning; 3) ultrasound; 4) quantitative computed tomography; 5) biomechanical evaluation; and 6) biochemical markers. This evidence will provide novel and significant information for evaluating bone healing during DO in the future.

Effects of different intensities of intermittent pneumatic soft-tissue compression on bone defect repair.

BACKGROUND: To estimate the effects of different intensities of intermittent pneumatic soft-tissue compression on bone defect repair in an animal model. METHODS: Five mm radial bone defect in length was made in 64 mature New Zealand rabbits and all animals randomly assigned into four groups: Group A (control group without compression), Group B (5-7 kPa intensity), Group C (8-10 kPa intensity) and Group D (11-13 kPa intensity). On the fourth day after surgery, their legs were intermittently pneumatic compressed for 4 weeks. The stimulation lasted 30 min every day and the frequency of compression was 15 Hz. New bone formation in 4 groups was evaluated by gross observation, X-ray, Micro-CT, and histological staining at 2 and 4 weeks after surgery. RESULT: There was more new bony callus in the bone defect in group C than in other groups by gross observation and X-ray radiography at 2 and 4 weeks. The Micro-CT results showed more new bony callus, bone trabecula and higher bone mineral density in group C. Fluorescent labeling results showed the speed of new bone formation in Group C was faster than that in other groups, among which the control group had the slowest speed of new bone formation. The result of histology had shown that the trabeculae in bone callus in group C had a regular form, the trabeculae were wide and had a more become osteoblast around them. CONCLUSION: The intermittent pneumatic soft-tissue compression can accelerate new bone formation of bone defects and the optimal intensity is 8-10 kPa for repairing the rabbit radial bone defect.

Tetracalcium phosphate treatment on experimental fracture model in rats.

OBJECTIVES: This study aims to investigate the efficacy of tetracalcium phosphate (TTCP) on fracture healing in rat femurs. MATERIALS AND METHODS: Forty-two female Wistar Albino rats were randomized into two groups (Group 1 and Group 2, n=21 for each). The left femur of all animals was fractured by osteotomy after deep anesthesia with ketamine. Additional procedure was not applied to the rats in Group 1. Rats in Group 2, following osteotomy, were applied to the fracture line approximately 2 mL TTCP. The animals were sacrificed at Weeks 1, 2, and 3 after surgery (seven animals were sacrificed from each group each week) and the broken femurs were removed. The femurs were examined first radiographically and second histopathologically. RESULTS: Radiologically, callus maturity and bone union increased with time in both groups. However, no significant differences were found regarding callus maturity and bone union in weekly comparisons (anteroposterior plain: p=0.53, p=0.37, p=0.42, lateral plain: p=0.26, p=0.42, p=0.87). Histopathologically, the fractures healed normally as the weeks progressed in both groups. The histological scores of Group 2 were higher at Weeks 1, 2, and 3. In the evaluation, no significant difference was found between the groups in terms of histological scores except for the first week (p=0.024, p=104, p=462, respectively). CONCLUSION: Although there was no statistically significant difference in the histological evaluation of both groups, except for the first week, the histological scores of Group 2, which underwent TTCP in all weeks, were higher. According to the results of this study, we believe that TTCP may be beneficial, particularly in the early stages of fracture healing.

Optimal timing for intermittent administration of parathyroid hormone (1-34) for distraction osteogenesis in rabbits.

BACKGROUND: To date, the usefulness of parathyroid hormone [PTH (1-34)] in distraction osteogenesis has been reported in several studies. We aimed to determine the optimal timing of PTH (1-34) administration in a rabbit distraction osteogenesis model. METHODS: The lower hind leg of a Japanese white rabbit was externally fixed, and tibial osteotomy was performed. One week after the osteotomy, bone lengthening was carried out at 0.375 mm/12 h for 2 weeks. After 5 weeks, the lower leg bone was collected. Bone mineral density (BMD), peripheral quantitative computed tomography (pQCT), micro-computed tomography (micro-CT), and mechanical tests were performed on the distracted callus. The rabbits were divided into three groups according to the timing of PTH (1-34) administration: 4 weeks during the distraction and consolidation phases (group D + C), 2 weeks of the distraction phase (group D), and the first 2 weeks of the consolidation phase (group C). A control group (group N) was administered saline for 4 weeks during the distraction and consolidation phases. Furthermore, to obtain histological findings, lower leg bones were collected from each rabbit at 2, 3, and 4 weeks after osteotomy, and tissue sections of the distracted callus were examined histologically. RESULTS: The BMD was highest in group C and was significantly higher than group D. In pQCT, the total cross-sectional area was significantly higher in groups D + C, D, and C than group N, and the cortical bone area was highest in group C and was significantly higher than group D. In micro-CT, group C had the highest bone mass and number of trabeculae. Regarding the mechanical test, group C had the highest callus failure strength, and this value was significantly higher compared to group N. There was no significant difference between groups D and N. The histological findings revealed that the distracted callus mainly consisted of endochondral ossification in the distraction phase. In the consolidation phase, the chondrocytes were almost absent, and intramembranous ossification was the main type of ossification. CONCLUSION: We found that the optimal timing of PTH (1-34) administration is during the consolidation phase, which is mainly characterized by intramembranous ossification.

Image-based radiodensity profilometry measures early remodeling at the bone-callus interface in sheep.

Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling.

Repeated mild traumatic brain injury impairs fracture healing in male mice.

OBJECTIVES: The goal of this study was to evaluate the long-term impact of repeated (r) mild traumatic brain injury (mTBI) on the healing of fractures in a mouse model. Ten week-old male mice were subjected to r-mTBI once per day for 4 days followed by closed femoral fracture using a three-point bending technique, 1 week post impact and fracture healing phenotype evaluated at 20 weeks of age. RESULTS: Micro-CT analysis of the fracture callus region at nine weeks post fracture revealed reduced bone volume (30%, p < 0.05) in the r-mTBI fracture group compared to the control-fracture group. The connectivity density of the fracture callus bone was reduced by 40% (p < 0.01) in the r-mTBI fracture group. Finite element analysis of the fracture callus region showed reduced failure load (p = 0.08) in the r-mTBI group compared to control group. There was no residual cartilage in the fracture callus region of either the r-mTBI or control fracture group. The reduced fracture callus bone volume and mechanical strength of fracture callus in r-mTBI mice 9 weeks post fracture are consistent with negative effects of r-mTBI on fracture healing over a long-term resulting in decreased mechanical strength of the fracture callus.

Comparison of accordion maneuver with compression technique alone for the treatment of atrophic fracture nonunion: A rabbit model.

OBJECTIVE: The aim of this study was to compare the histological results of Accordion Maneuver (AM) with Compression Technique Alone (CA) in the treatment of atrophic fracture nonunion in a rabbit model. METHODS: The study was performed on 91 male New Zealand rabbits aged six months, weighing 3.1 to 3.6 kg. The standardized models of atrophic nonunion with a 3-mm fracture were created in the tibias of rats. For the histomorphological study, 22 rabbits were randomly selected and sacrificed. The remaining 69 rabbits were divided into two groups based on the treatment technique: Group AM (n = 36) and Group CA (n = 33). The group AM was further randomly divided into four subgroups based on the amplitude and interval parameters: subgroup A1B1 (0 day, 4 mm; n = 9), subgroup A1B2 (0 day, 8 mm; n = 7), subgroup A2B1 (6 days, 4 mm; n = 10), and subgroup A2B2 (6 days, 8 mm; n = 10). A monolateral external fixator was employed in each group. Animals were sacrificed 6 weeks after the treatment, and bony healing was assessed both radiologically and histologically. The efficiency of bony healing was assessed using the bone content index, bone mineral density, and bone volume fraction indexes. RESULTS: In X-ray and micro-computed tomography assessments, periosteal reaction was detected at the fracture site in all specimens. In group CA, sclerosis was observed at the ends of the fragments. Bony absorption, nonunion, and a little amount of island-like high density were also observed at the nonunion site. Among AM subgroups, sparse callus-like bone formation in A1B1 subgroup and a high density of callus connecting most parts of the gap and large amount of periosteal callus formation in A1B1 subgroup were observed. In A2B2 subgroup, the cortex was initially connected. No gap was observed, and the medullary cavity was recanalized. In histological analyses, the intermission of 0 day at rate of 8 mm was of the highest level of bony regeneration, and the intermission of 6 days at the rate of 4 mm was of the lowest level of bony regeneration (P < 0.05). CONCLUSION: Based on the radiological and histological results obtained from the present study, AM seems to be more effective than CA in treating atrophic nonunion. AM can shorten the period of treatment. The interval of 0 day and an amplitude of 8 mm may be more proper for AM.