Principles of fracture remodeling in children

In treating fractures in children, the surgeon must have a good knowledge of the three phases of bone healing, ie, inflammatory, reparative, and remodeling and understand how they contribute to the final recovery of the fracture healing process. By and large, the ability to remodel depends on the bone involved, the patient's age, the proximity to the joint, and its orientation to the joint axis. In the typical long bone, 75% of the remodeling occurs by reorientation of the physis while appositional remodeling of the diaphysis can only be expected to contribute 25% to the remodeling process. The various values of acceptable alignment for each of the major fracture patterns are outlined. These serve only as guidelines. The patient's functional capacity and the surgeon's experience should also be factors in determining whether to depend on the remodeling capacity of the specific fracture or to consider performing a more aggressive, invasive technique to achieve a satisfactory result. There are two advantages in treating children's fractures. First, the healing process is very rapid. Nonunion is a rare event in the pediatric age group. The second perk is that there is a very good remodeling capacity should there be less than anatomical alignment of the affected bone once the fracture has healed. Any individual treating fractures in the pediatric age group should fully understand how pediatric fractures heal and how the remodeling process occurs.     

Special aspects of renal osteodystrophy in children

Renal osteodystrophy represents a spectrum of skeletal lesions that range from high-turnover to low-turnover bone disease. Similar factors are involved in the pathogenesis of renal osteodystrophy in adult and pediatric patients with chronic kidney disease (CKD). However, growth retardation and the development of bone deformities are specific complications that occurred in pediatric patients with CKD. Metabolic acidosis, renal osteodystrophy, malnutrition, and disturbances in the insulin growth factor (IGF)/growth hormone (GH) are among the main factors involved and they are discussed briefly in this article. In addition to disturbances in bone remodeling, longitudinal bone growth occurs at the growth plate cartilage by endochondral ossification. Although young rats with experimental CKD have growth retardation, the characteristics of the growth plate are markedly different between animals with severe secondary hyperparathyroidism and those with calcium-induced adynamic osteodystrophy. These disturbances may suggest potential molecular mechanisms by which endochondral bone formation may be altered in renal failure, consequently leading to growth retardation.     

Vertebroplasty in a 10-year-old boy with Gorham–Stout syndrome

Purpose

To describe our experience using balloon vertebroplasty with polymethylmethacrylate filler in a 10-year-old boy with Gorham–Stout syndrome.

Summary of background data

Gorham–Stout syndrome is a rare disorder of unknown etiology characterized by intraosseous proliferation of fibrovascular or lymphatic tissue that results in progressive osteolysis and bone destruction. It can affect any part of the skeleton and lead to pathological fractures and muscular weakness or atrophy. The literature contains few reports on the surgical management of vertebral osteolysis with risk of fracture in children. Spinal fusion is the treatment of choice.

Methods

The patient was asymptomatic until age 10 years, when he began to experience back pain. Annual magnetic resonance scans did not show progression of bone disease. Medical treatment was unsuccessful, and the visual analog scale (VAS) for lumbar back pain was 8–10. Balloon vertebroplasty with polymethylmethacrylate filler was performed at L3 and L4, the vertebrae with an increased risk of pathological fracture.

Results

The postoperative course was uneventful. One month after surgery the VAS was 2–3. Four years later, the patient remains free of procedure-related complications, his clinical situation is stable, and no further low back pain has been reported.

Conclusions

We report the only application to date of vertebroplasty to treat vertebral osteolysis in a pediatric patient. The outcome and possible complications of this technique remain unknown in children. The patient in the present report underwent vertebroplasty at two levels, and his progress remains satisfactory 4 years after surgery. He has not developed technical complications or changes in spinal growth. Therefore, we propose vertebroplasty for the treatment of vertebral osteolysis in pediatric patients at risk of pathological fracture.

     

Bone healing in children

Just as pediatric fractures and bones are basically similar to adult fractures and bones, pediatric bone healing is basically similar to adult bone healing. They both go through the three same phases of inflammation, reparation, and remodeling. It is those differences between pediatric and adult bone, however, that affect the differences in the healing of pediatric bone. Because pediatric bone can fail in compression, less initial stability and less callus formation is required to achieve a clinically stable or healed fracture. The greater subperiosteal hematoma and the stronger periosteum all contribute to a more rapid formation of callous strong enough to render the fracture healed more rapidly than the adult. Genes and hormones that are necessary for the initial formation of the skeleton are the same as, or at least similar in most instances, to those necessary for the healing of fractures. This osteogenic environment of the pediatric bone means that these fracture healing processes are already ongoing in the child at the time of the fracture. In the adult, these factors must be reawakened, leading to the slower healing time in the adult. Once the fracture is healed, the still-growing pediatric bone can correct any "sins" of fracture alignment or angulation leaving the bone with no signs of having ever been broken. The final result is bone that is, in the child's words, "as good as new."     

Mechanical Effects on the Skeleton: Are There Clinical Implications?

The basic morphology of the skeleton is determined genetically, but its final mass and architecture are modulated by adaptive mechanisms sensitive to mechanical factors. When subjected to loading, the ability of bones to resist fracture depends on their mass, material properties, geometry and tissue quality. The contribution of altered bone geometry to fracture risk is unappreciated by clinical assessment using absorptiometry because it fails to distinguish geometry and density. For example, for the same bone area and density, small increases in the diaphyseal radius effect a disproportionate influence on torsional strength of bone. Mechanical factors are clinically relevant because of their ability to influence growth, modeling and remodeling activities that can maximize, or maintain, the determinants of fracture resistance. Mechanical loads, greater than those habitually encountered by the skeleton, effect adaptations in cortical and cancellous bone, reduce the rate of bone turnover, and activate new bone formation on cortical and trabecular surfaces. In doing so, they increase bone strength by beneficial adaptations in the geometric dimensions and material properties of the tissue. There is no direct evidence to demonstrate anti-fracture efficacy for mechanical loading, but the geometric alterations engendered undoubtedly increase the structural properties of bone as an organ, increasing the resistance to fracture. Like all interventions, issues of safety also arise. Physical activities involving high strain rates, heavy lifting or impact loading may be detrimental to the joints, leading to osteoarthritis; may stimulate fatigue damage leading to stress fractures; or may interact with some pharmaceutical interventions to increase the rate of microdamage within cortical or trabecular bone. Received: 16 March 2000 / Accepted: 21 June 2000     

Proximal Humeral Fractures: Nailing

Abstract Treating proximal humeral fractures surgically has always been a challenge for the orthopaedic trauma surgeon. The challenge was and is due to numerous factors such as the specific anatomy of the proximal humerus, problems of an adequate approach and exposure of the fracture and different fracture fragments, possible iatrogenic injuries to the rotator cuff on approach and the detrimental effects of the former on the latter’s gliding and contracting ability after surgery. Furthermore, the very different fracture patterns that can occur at the proximal humerus, the shear number of fragments which can be of extremely bad bone quality, the necessity for anatomic reduction of these fragments with an implant that will allow for a stable osteosynthesis and at the meantime will not impinge in the subacromial area and lastly, the intention of the physician-in-charge to commence with physical therapy as soon as possible post OP. All of these added to the fact that not one fixation technique with one certain implant could be recommended as a treatment or implant of choice in dealing with these difficult fractures. Most of the supposedly applicable surgical techniques and implants had major setbacks such as being limited to only very expert hands, necessitating a long-standing postoperative immobilisation, resulting in secondary loosening of implants, secondary loosening of reduction or impaired bone healing and, despite all efforts, finally led to poor function at the shoulder. With the advent of angular stable implants such as angular stable, anatomically contoured plates designed for proximal humeral fractures only and special angular stable nails for the same or similar indications the treatment options and the quality of treatment in this area was much improved. Our experience with angular stable nails of two different manufacturers in now more than 320 implantations reveals that indications for the surgical treatment of such fractures can be extended constantly, that the number of complications will simultaneously decline, the necessity for primary joint arthroplasty even in multiple fragment fractures is minimal and that long-term results are, comparing the published results in the literature with those of our institution, equal if not superior to other treatment options.     

Current concepts in plate and screw fixation of osteoporotic proximal humerus fractures

Most surgeons feel that angular stable implants have improve the ability to obtain reliable fixation of an osteoporotic fracture of the proximal humerus fracture, but complications such as varus fracture collapse and screw penetration of the articular surface remain problematic. The use of limited drilling, blunt tipped locking bolts and routine incorporation of the rotator cuff into the internal fixation construct may help limit these complications. It may be of benefit to replace the concept of standard screw fixation of the osteoporotic proximal humerus with a concept of an angular stable scaffold support of the subchondral bone combined with fixation that does not rely on bone quality and utilizes the more predictable fixation of sutures through the rotator cuff attachments.     

Pediatric skeletal trauma: a review and historical perspective

Pediatric fractures are commonly classified into five types: plastic deformation, buckle fracture, greenstick fracture, complete fracture, and physeal injuries. The most important anatomic characteristic in the pediatric skeleton is the presence of growth plates and the thick periosteum. It is important to emphasize that just as adult intra-articular fractures require anatomic reduction, so do pediatric articular injuries. The periosteum in children contributes immensely to rapid fracture healing and helps in the reduction and in the maintenance of reduction. In this study, I review some basic principles for the treatment of fractures in children, the main complications of pediatric fractures, and the outcomes assessment in children. The main complications of fractures in children are malalignment, physeal arrest, and refracture cause by fast fracture healing. Nearly all fractures in children can be treated in a cast without worry about stiff joints or need for physical therapy to mobilize injured joints.     

Incorporation of sodium fluoride into cortical bone does not impair the mechanical properties of the appendicular skeleton in rats

Summary Clinical studies on the use of sodium fluoride (NaF) in osteoporotic patients have demonstrated increased spinal bone mass without a reduction in vertebral fracture incidence, and a trend towards reduced appendicular bone mass with an increase in peripheral fracture incidence. As previous reports have suggested that NaF becomes incorporated into bone's crystal structure, possibly affecting bone strength, we sought to examine the relationship among bone fluoride content, bone mass, and skeletal fragility. Twenty-one-day-old female Sprague-Dawley rats were treated with four different doses of NaF. The tibiae were subjected to histomorphometric and biochemical analyses, and the femora were tested in torsion for the properties of strength, stiffness, energy storage capacity, and angular deformation. The results showed that over 50% of the skeleton in these rats was turned over in the presence of NaF. The four different doses resulted in a linear increase in bone F concentration and suggested excellent absorption and incorporation of this drug. No changes in histomorphometric indices of bone formation or turnover were found. Despite the large fraction of bone formed during NaF treatment, and the linear increase in bone fluoride content in relation to dose, there were no changes observed in any of the mechanical properties. These results suggest that, even extensive incorporation of fluoride into bone, in the absence of an effect on bone mass or remodeling, does not significantly alter its capacity to withstand mechanical loads.     

Use of a biphasic cement bone substitute in the management of metaphyseal fractures

ObjectivesIn recent years, the increase in utilisation of bone substitutes in the reconstruction of bone defects has been fuelled by donor site complications associated with autologous bone harvesting. However the ability of bone substitute to stimulate bone union while maintaining fracture reduction has been a topic of debate. Cerament Bone Void Filler (CBVF) is a novel biphasic and injectable ceramic bone substitute that has high compressive strength and the ability to promote cancellous bone healing.Materials and MethodThis is a retrospective study to evaluate the surgical outcome of utilising CBVF in the treatment of depressed metaphyseal bone fractures over a two year period. The patients were followed up for at least six months after surgery and clinical parameters such as wound site complications were collated. Radiographic imaging was evaluated to determine loss of fracture reduction and rate of cement resorption.ResultsThirteen patients with depressed metaphyseal fractures were enrolled, which included: (i) one proximal humerus fracture; (ii) three tibial plateau fractures; and (iii) nine calcaneal fractures. None of the patients showed significant collapse in fracture reduction after six months of follow up. Cement resorption was noted in one patient as early as three weeks after surgery. There were no cases of cement leak or wound site complications.ConclusionCerament Bone Void Filler (CBVF) is a promising bone graft substitute in the management of depressed metaphyseal bone fractures, with the ability to maintain fracture reduction despite cement resorption.     

Neuropeptide Y innervation during fracture healing and remodeling

Background and purpose Autonomic neuropeptide Y (NPY) is involved in local bone remodeling via the central nervous system. However, the role of peripheral neuronal NPY in fracture healing is not known. We investigated the relationship between bone healing and side-specific occurrence of NPY in angular and straight fractures.

Methods Tibial fractures in Sprague-Dawley rats were fixed with intramedullary pins in straight alignment and anterior angulation. The samples were analyzed by radiography, histology, and immunohistochemistry (IHC) between 3 and 56 days postfracture.

Results In the angular fractures, radiography and histology showed a 3.5-fold increase in callus thickness on the concave side compared to the convex side at day 21, whereas a 0.2-fold reduction in callus thickness was seen on the convex side between days 21 and 56. IHC showed regenerating NPY fibers in the callus and woven bone in both fractures at day 7. In angular fractures, a 5-fold increase in NPY fibers was observed on the concave side compared to the convex side at 7 days, whereas a 6-fold increase in NPY fibers was seen on the convex side between 21 and 56 days; only a 0.1-fold increase in NPY fibers was seen on the concave side during the same time period. In straight fractures, similar bony and neuronal changes were observed on both sides.

Interpretation The increase in NPY innervation on the convex side appears to correlate with the loss of callus thickness on the same side in angular fractures. Our results highlight the probable function of the peripheral NPY system in local bone remodeling.     

大鼠不同部位骨骼对外源性甲状腺激素反应性的研究

目的：用左旋甲状腺素（L－T4）制备实验性甲状腺功能亢进（甲亢）大鼠模型，以探讨甲亢大鼠的胫骨和椎骨对外源性甲状腺激素的反应性，为临床监测长期L-T4治疗提供依据。方法：9周龄雄性Sprague-Dawley(SD)大鼠18只，随机分为甲亢组11只、对照组7只。甲 亢组予L－T4腹腔内注射，对照组予生理盐水注射，连续注射3周后取大鼠的胫骨近端、第四腰椎用非脱钙骨组织形态学计量法进行同期观察和研究。结果：在胫骨甲亢组的骨小梁数量降低，骨形成表面、吸收表面均增加，但骨吸收表面增加更明显，骨小梁平均宽度、骨纵向生长率降低，而骨矿化率增加。椎骨未观察到此变化。结论：L－T4引起继发性胫骨骨量减少，骨转换增加，椎骨无反应，表明不同部位的骨骼对甲状腺激素的反应存在异质性。     

Rapidly growing Brtl/+ mouse model of osteogenesis imperfecta improves bone mass and strength with sclerostin antibody treatment

Osteogenesis imperfecta (OI) is a heritable collagen-related bone dysplasia, characterized by brittle bones with increased fracture risk that presents most severely in children. Anti-resorptive bisphosphonates are frequently used to treat pediatric OI and controlled clinical trials have shown that bisphosphonate therapy improves vertebral outcomes but has little benefit on long bone fracture rate. New treatments which increase bone mass throughout the pediatric OI skeleton would be beneficial. Sclerostin antibody (Scl-Ab) is a potential candidate anabolic therapy for pediatric OI and functions by stimulating osteoblastic bone formation via the canonical Wnt signaling pathway. To explore the effect of Scl-Ab on the rapidly growing OI skeleton, we treated rapidly growing 3 week old Brtl/+ mice, harboring a typical heterozygous OI-causing Gly → Cys substitution on col1a1, for 5 weeks with Scl-Ab. Scl-Ab had anabolic effects in Brtl/+ and led to new cortical bone formation and increased cortical bone mass. This anabolic action resulted in improved mechanical strength to WT Veh levels without altering the underlying brittle nature of the material. While Scl-Ab was anabolic in trabecular bone of the distal femur in both genotypes, the effect was less strong in these rapidly growing Brtl/+ mice compared to WT. In conclusion, Scl-Ab was able to stimulate bone formation in a rapidly growing Brtl/+ murine model of OI, and represents a potential new therapy to improve bone mass and reduce fracture risk in pediatric OI.     

Spontaneous correction of angular fracture deformity in the rat

Background The different parts of long bone are known to participate in the spontaneous correction of fracture deformity. However, the relative contribution of growth plate, epiphysis and diaphysis of bone during the correction process is not clear.

Animals and methods We used a rat model of tibial fracture fixed with a semi-rigid intramedullary pin in anterior angulation, and evaluated the magnitude, temporal course and pertinent sites of spontaneous deformity correction by means of radiography and bone mineral uptake.

Results Over a 12-week period, the mean angular deformity was corrected from 27° to 11°. The major portion of the correction (14° of 16°) occurred within 3 weeks, concomitantly with fracture healing. The angle of the proximal growth plate changed 8° over the study period. The first 3 weeks were characterized by intense bone formation on the concave side of the fracture. From weeks 3–8, signs of resorption predominated on the corresponding convex side. On the concave side, the front of new bone formation in the proximal diaphysis moved in the opposite direction to that at the fracture level, so that both sites contributed to deformity correction.

Interpretation We found that different sites of a diaphyseal bone fractured in angulation respond quite differently, but still in an orchestrated way to promote correction by modeling. Notably, most of the spontaneous correction occurred during the reparative phase, the major contributor being the diaphysis, not the growth plate. Compared to other reports on angulated fracture using rigid fixation and limb immobilization, our data suggest that semi-rigid fixation and early weight bearing is more efficient in enhancing not only healing, but also deformity correction.     

Evaluation of mandibular fracture healing in rats under zoledronate therapy: A histologic study

IntroductionTo evaluate fracture healing in mandible of rats under zoledronate therapy.MethodsA total of 135 Wistar rats were randomly allocated into 3 groups. Group L received two intravenous infusion of 0.06 mg/kg zoledronate 6 weeks apart. Group H received the same dose of zoledronate as group L once a week for 6 weeks and group C were treated with normal saline. Seven days after the last infusion, rats underwent unilateral mandibular osteotomy to replicate a fracture. Fifteen rats from each group were sacrificed 2, 4, and 6 weeks after surgery. Fracture calluses were examined and scored using a histological grading system (1 to 10).ResultsAfter 2 weeks, substantial woven bone and some lamellar bone were seen in control and L groups. In group H, healing was delayed and consisted of fibrous and cartilaginous tissue and some woven bone. After 4 weeks, most of woven bone in control group was replaced with lamellar bone but in group L, comparatively less bone remodeling occurred. In group H, healing process was nearly the same as that at 2 weeks. After 6 weeks, complete bone remodeling was seen in control group. In group L, bone remodeling was under way and in group H, histological findings were nearly the same as those at 2 and 4 weeks. Except for L and control groups at 2 weeks, healing score was significantly different between all corresponding groups.ConclusionZoledronate therapy delayed healing process of mandibular fracture in rats in a dose-dependent manner.     

Clavicular fractures in pediatric traumatology

Clavicle fractures are most common in children. Due to the thick periosteum that provides appositional bone proliferation on the one hand and a high potential of the medial physis for longitudinal growth on the other hand the fractures have an enormous healing potential. Both factors are also responsible for good fracture remodeling. In adolescents, the periosteal tube gets thinner and fracture types correspond to fractures in adults. Most fractures heal with good results after conservative treatment. In this article clavicle fractures in children and adolescents and options for therapy including the rare surgical treatment depending on different fracture localizations and morphologies are discussed.     

Effects of age and rate of twist on torsional fracture patterns in infant porcine femora

ObjectiveLong bone fractures are a common injury in the pediatric population. Differentiation between abusive, or non-accidental trauma, and accidental trauma in children remains challenging for forensic practitioners. A recent clinical-based study was able to separate pediatric abusive from accidental trauma based on femoral fracture pattern using the ratio of fracture length over bone diameter (fracture ratio), as determined from radiographic analysis of this fractured bone. The forensic literature indicates more cases of abuse in younger pediatric victims than accidental cases. While this was the case in the clinical study, the effect was not shown to be statistically significant. Furthermore, while speed of trauma was not considered in the clinical study, a laboratory study with an immature bovine model indicates rotational speed influences fracture pattern, but specimen age was not varied in that study. Therefore, the objective of the current study was to use immature porcine femora to investigate the effects of age and rate of twist on a modified version of this fracture ratio parameter.MethodsFifteen pairs of porcine femora with various ages were twisted until observable failure using a custom-built torsional fixture. The left femur of each pair was twisted to failure at a rate of 3 deg/s, while the right femur was twisted at a rate of 90 deg/s. The torque and angle of rotation were recorded at a sampling rate of 10,000 Hz. Fracture ratio was defined as total fracture length divided by bone diameter.ResultsFracture ratio increased with specimen age, with specimens under the low rate of twist yielding a consistently lower fracture ratio than those from specimens under the high rate of twist. The results showed that both specimen age and rate of twist were significant factors influencing fracture ratio.ConclusionThe determination of abusive from accidental trauma in criminal cases, based on the pattern of long bone fracture alone, may need to include additional data on the specific age of the pediatric victim and the potential speed of the traumatic event.     

Hand and wrist injuries in young athletes

Successful treatments of musculoskeletal injuries in the pediatric population demand a thorough understanding of the basic anatomy and its biomechanics, and the physiology of growth and development of the immature skeleton. In addition, good treatment outcomes rely on the treating physician being an effective teacher to the young athlete and the patient's parents, coaches, and trainers. At the same time, the physician must be a good student in learning the nature of the patient's sports and each patient's athletic ability and aspirations. Most pediatric hand and wrist injuries can be treated nonoperatively with proper immobilization techniques and activity modification, but cases requiring surgical intervention must be recognized promptly to avoid long-term complications.     

Mechanical Competence and Bone Quality Develop During Skeletal Growth

Bone fracture risk is influenced by bone quality, which encompasses bone's composition as well as its multiscale organization and architecture. Aging and disease deteriorate bone quality, leading to reduced mechanical properties and higher fracture incidence. Largely unexplored is how bone quality and mechanical competence progress during longitudinal bone growth. Human femoral cortical bone was acquired from fetal (n = 1), infantile (n = 3), and 2- to 14-year-old cases (n = 4) at the mid-diaphysis. Bone quality was assessed in terms of bone structure, osteocyte characteristics, mineralization, and collagen orientation. The mechanical properties were investigated by measuring tensile deformation at multiple length scales via synchrotron X-ray diffraction. We find dramatic differences in mechanical resistance with age. Specifically, cortical bone in 2- to 14-year-old cases exhibits a 160% greater stiffness and 83% higher strength than fetal/infantile cases. The higher mechanical resistance of the 2- to 14-year-old cases is associated with advantageous bone quality, specifically higher bone volume fraction, better micronscale organization (woven versus lamellar), and higher mean mineralization compared with fetal/infantile cases. Our study reveals that bone quality is superior after remodeling/modeling processes convert the primary woven bone structure to lamellar bone. In this cohort of female children, the microstructural differences at the femoral diaphysis were apparent between the 1- to 2-year-old cases. Indeed, the lamellar bone in 2- to 14-year-old cases had a superior structural organization (collagen and osteocyte characteristics) and composition for resisting deformation and fracture than fetal/infantile bone. Mechanistically, the changes in bone quality during longitudinal bone growth lead to higher fracture resistance because collagen fibrils are better aligned to resist tensile forces, while elevated mean mineralization reinforces the collagen scaffold. Thus, our results reveal inherent weaknesses of the fetal/infantile skeleton signifying its inferior bone quality. These results have implications for pediatric fracture risk, as bone produced at ossification centers during children's longitudinal bone growth could display similarly weak points. © 2019 American Society for Bone and Mineral Research.     

Fracture of the astragalus in pediatric patients,an unusual entity

Introduction and importanceThe fracture of the astragalus is an unusual bone fracture (Ladero and Concejero, 2004) and is even more unusual in pediatric patients. The astragalus is a bone surrounded by cartilage and other structures making it difficult to appreciate on an X-ray which can lead to misdiagnosis (Ladero and Concejero, 2004; Inal and Inal, 2014) and could lead to not applying the right treatment and risk avascular necrosis or other sequelae.Case presentation3-year-old male with foot pain and edema+++, unable to walk or stand up since a fall 2 days before, had a doubtful diagnosis after an x-ray showed no apparent bone injury. A CT scan confirmed astragulus fracture; it was then treated adequately, thus avoiding complications that could have occurred had the fracture not been diagnosed and treated correctly.Clinical findings and interventions and outcomeThe limb was immobilized with a suropodalic cast for 5 weeks. No surgery was performed because of the patient's age and because the fracture was not displaced (Hawkins type 1) (Jasqui-Remba and Rodriguez-Corlay, 2016; Urrutia et al., 1999).Relevance and impactThere is a risk of misdiagnosis in these cases since the astragulus fracture might not show up in an X-ray, as in the case presented. A CT scan can detect the fracture and thus help consolidate the bone correctly. The correct differential diagnosis also reduces the risk of avascular necrosis, which increases due to poor blood supply to the astragalus.