Expression of Bone-related Genes in Bone Marrow MSCs after Cyclic Mechanical Strain: Implications for Distraction Osteogenesis

Aim Understanding the response of mesenchymal stem cells （MSCs） to mechanical strain and their consequent gene expression patterns will broaden our knowledge of the mechanobiology of distraction osteogenesis. Methodology In this study, a single period of cyclic mechanical stretch （0.5 Hz, 2,000 με） was performed on rat bone marrow MSCs. Cellular proliferation and alkaline phosphatase （ALP） activity was examined. The mRNA expression of six bone-related genes （Ets-1, bFGF, IGF-Ⅱ, TGF-β, Cbfal and ALP） was detected using real-time quantitative RT-PCR. Results The results showed that mechanical strain can promote MSCs proliferation, increase ALP activity, and up-regulate the expression of these genes. A significant increase in Ets-1 expression was detected immediately after mechanical stimulation, but Cbfal expression became elevated later. The temporal expression pattem of ALP coincided perfectly with Cbfal. Conclusion The results of this study suggest that mechanical strain may act as a stimulator to induce differentiation of MSCs into osteoblasts, and that these bone-related genes may play different roles in the response of MSCs to mechanical stimulation.

Mandibular Distraction Osteogenesis for the Treatment of an Obstructive Sleep Apnea Patient with Orthognathic Anomaly:A Case Report and Literature Review

Objective: skeletal advancement in order to improve the airway dimensions is known as one of the most effective surgical theraphy for treating obstructive sleep apnea (OSA). Distraction osteogenesis (DO) can be a better treatment alternative in some selected cases similar to our patient. Using custom made distractors can make this technique more safe and successful. Study Design: Surgically assisted rapid palatal expansion (SARPE), bilateral intraoral mandibular distraction osteogenesis (MDO) and orthodontic treatment were tried to a 20-year-old OSA patient with orthognathic anomaly. For mandibular distraction, custom made distractors were used. Results: The initial AHI of the patient was 23.3. At the end of the treatment it decreased to 8.7. Conclusions: Distraction osteogenesis could be a better alternative than the conventional orthognathic surgery in this kind of selected patients. Customization of the distraction devices can contribute to making this procedure safer and more successful.

Histological changes following surgically-assisted rapid tooth movement through resistance reduction and distraction osteogenesis in dogs

Objective To investigate the histological changes of rapid tooth movement in dogs treated by resistance reduction and distraction osteogenesis,aiming to establish an animal model and further to reveal the remodeling mechanism of rapid tooth movement. Methods A total of 8 local hybrid dogs were selected as subjects for this study. The second pre-molar was extracted on both sides. The experimental side underwent alvelor surgery for resistance reduction and a home-made tooth-borne intraoral distraction device was installed for rapid tooth movement,while for the other side (control side) only tooth-borne intraoral distraction device was used for rapid tooth movement. The longest active force-delivery span was 2 weeks,followed by 6-week retention. The distance between the moved tooth and anchor unit was recorded weekly,and radiography was performed for each side before and after distraction. The surrounding tissues including periodontal ligament and alveolar bone were sectioned for histological analysis. Results The average distance of tooth movement was 3.55mm on the experimental side and 1.11mm on the control side. The rate of tooth movement was notably higher (P<0.01) and no significant apical root resorption was detected by X-ray on the experimental side. The active alvelor bone remodeling was found on the tension and pressure sides. However,there was no significant difference between the experimental side and the control side after the retention period. Conclusion The rate of orthodontic tooth movement can be accelerated through resistance reduction and periodontal distraction without any unfavorable effects but at minimal anchorage loss.

Distraction osteogenesis for correction of post ankylosis mandibular deformities

Temporomandibular joint ankylosis, a debilitating disease mainly affecting children, is characterized by progres- sive restriction of mouth opening and maxilla-mandibular developmental deformities. Craniofacial distraction osteo- genesis has been developed as a standard surgical strategy for rectification of craniofacial deformities. The purpose of this study was to assess mono-planar distraction devices for the correction of various mandibular asymmetries in patients with unilateral temporomandibular joint ankylosis who developed restricted mouth opening and mandibular retrognathia. All patients were treated using one-stage distraction osteogenesis followed by temporalis fascia inter- positional arthroplasty under general anesthesia. A significant increase in mandibular ramus and base length was observed. Although an increase in anterior lower facial height was observed, it was not significant statistically. A decrease in posterior lower facial height and corpus was observed. Oblique distraction with angular osteotomy allowed lengthening of both the ramus and corpus, yielding satisfactory results and hence eliminating the need of secondary surgery. In conclusion, univector internal distractors are effective for correction of multi-planar mandib-ular deficiencies by optimizing its placement through meticulous planning.

Application of a pre-filled tissue expander for preventing soft tissue incarceration during tibial distraction osteogenesis

BACKGROUND Bone transport and distraction osteogenesis has been widely used to treat bone defects after traumatic surgery,but,skin and soft tissue incarceration can be as high as 27.6%.AIM To investigate the efficacy of inserting a tissue expander to prevent soft tissue incarceration.METHODS Between January 2016 and December 2018,12 patients underwent implantation of a tissue expander in the subcutaneous layer in the vicinity of a tibial defect to maintain the soft tissue in position.A certain amount of normal saline was injected into the tissue expander during surgery and was then gradually extracted to shrink the expander during the course of transport distraction osteogenesis.The tissue expander was removed when the two ends of the tibial defect were close enough.RESULTS In all 12 patients,the expanders remained intact in the subcutaneous layer of the bone defect area during the course of transport distraction osteogenesis.When bone transport was adequate,the expander was removed and the bone transport process was completed.During the whole process,there was no incarceration of skin and soft tissue in the bone defect area.Complications occurred in one patient,who experienced poor wound healing.CONCLUSION The pre-filled expander technique can effectively avoid soft tissue incarceration.The authors’primary success with this method indicates that it may be a valuable tool in the management of incarcerated soft tissue.

Management of Mandibular Hypoplasia Using Distraction Osteogenesis Technique

By using distraction osteogenesis technique, 3 cases of mandibular hypoplasia were treat ed by home made and German made jaw distractors: including one patient suffered from bilateral ankylosis of temporo mandibular joint and 2 patients from deficiency of mandible. The duration of distraction osteogenesis was one month. The bone distractor was removed 3 months after operation. Satisfactory results were obtained in all 3 cases. Distraction osteogenesis can successfully be used in mandibular functional reconstruction and has much more advantages than traditional technique.

Upper Airway Changes after Maxillary Distraction Osteogenesis in Cleft Lip and Palate Patients

Purpose: To measure the upper airway changes associated with maxillary distraction osteogenesis in cleft lip and palate patients in the immediate post operative period and 12 months later. Materials and Methods: Seven patients with repaired cleft lip and palate (CLP) presented with severe maxillary hypoplasia. They were examined initially at T1 predistraction phase. Records taken included radiographs (orthopantograms OPG, lateral cephalometric, posteroanterior). Cephalometric analysis was done to evaluate the upper airway. Mean age is 17 years and the reverse overjet > 6 mm. They underwent maxillary Le Fort I distraction using external rigid distracters (RED). Cephalometric analysis to evaluate the upper airway was repeated at the end of the consolidation phase T2 and twelve months after distractor removal T3. Results: The range of maxillary advancement was between 8 - 15 mm (mean 9 mm). The anteroposterior distance of the superior velopharynx (PPS) and middle velopharynx (SPPS) increased at T2. A small amount of reduction in these values was recorded at T3. The inferior velopharynx (MPS) and the oropharynx (IPS, EPS) showed minimum increase in anteroposterior distance in only two patients at T2 and no change at T3. Conclusion: All seven patients showed clinical improvement in the upper airway and an increase in the upper airway values on lateral cephalometric radiographs.

Rapid tooth movement through distraction osteogenesis of the periodontal ligament in dogs

Background Animal models are needed for the study of rapid tooth movement into the extraction socket through distraction osteogenesis of the periodontal ligament. Methods Modified distraction devices were placed on eight dogs between the first and third mandibular premolars on the left sides; similar placement of traditional straight wise appliances on the right sides served as the control. The experimental distractors were activated （0.25 mm/d） twice a day and the control devices were activated （100 g） for two weeks with consolidation periods at weeks two, three, six, and ten. Two dogs were sacrificed at each consolidation time point; rates and patterns of tooth movement, loss of anchorage, and periapical films were evaluated, and the affected premolars and surrounding periodontal tissues were decalcified and examined histologically. General observations, X-ray periapical filming and histology examination were performed. Results Distal movement （（3.66±0.14） mm） measured two weeks after modified distraction exceeded that achieved using the traditional device （（1.15±0.21） mm; P 〈0.05）. Loss of anchorage was minimally averaged （0.34±0.06） mm and （0.32±0.07） mm in the experimental and control sides, respectively. By radiography, apical and lateral surface root resorptions on both sides were minimal. Alveolar bone lesions were never evident. Fibroblasts were enriched in periodontal ligaments and bone spicules formed actively along directions of distraction. Conclusions The canine model is suitable for the study of rapid tooth movement through distraction osteogenesis of the periodontal ligament. The technique accelerates tooth movement, periodontal remodeling, alveolar bone absorption, and may induce fibroblast formation, as compared to the traditional orthodontic method, without adversely affecting root absorption, bone loss, tooth mobility and anchorage loss.

Advancement of maxillary anterior segment by distraction osteogenesis for severe maxillary retrusion in cleft lip and palate

Background Maxillary anterior segmental distraction osteogenesis （MASDO） is a recently used method for correction of severe maxillary retrusion in cleft lip and palate （CLP） patients.In this article,we evaluated the feasibility of MASDO using rigid external distraction （RED） and rapid orthodontic tooth movement to correct severe maxillary retrusion in CLP patients.Methods Fourteen male and five female complete CLP patients between the ages of 18 and 22 years （mean age 19.7 years） at the time of distraction,with severe maxillary retrusion,were treated with the rigid external distraction （RED） device after maxillary anterior osteotomy.Rapid orthodontic tooth movement was started one week after the MASDO.Standard profile photographic,cephalometric films were obtained preoperatively and after therapy.Sella-nasion-point A （SNA） and Sella-nasion-point B （SNB） angles were measured to reflect changes in maxillary and mandibular position,and the distance between anterior nasal spine and posterior nasal spine （ANS-PNS） was measured to represent the maxillary dental arch length.Results The SNA angle increased from an average of 74.6° （range 73.0°-78.0°）,preoperatively,to 83.4° （range 78.6°-88.0°） after the RED was removed （P ＜0.01）.All cases of severe maxillary retrusion were improved.Nine patients＇ profiles became harmonious after therapy.One patient had a bimaxillary protrusion deformity and needed further surgery.The regenerate alveolar crest and edentulous space on both segments was almost completely eliminated after rapid orthodontic tooth movement.Conclusion MASDO with the RED system and rapid orthodontic tooth movement is a successful way of correcting severe maxillary retrusion in CLP patients.

Mechanical regulation of bone regeneration during distraction osteogenesis

Distraction osteogenesis(DO)is a mechanobiological process of regenerating bone tissue by tension stress.DO is used clinically to lengthen bones or to treat critical size bone defects.Although DO provides satisfactory results in many cases,the prolonged period of treatment remains a major challenge that needs to be overcome.Various attempts have been devoted to accelerating bone regeneration during DO.One common approach is manipulation of the applied mechanical loading by altering distraction strategies.In this article,we reviewed relevant in vivo animal studies exploring the effects of changing mechanical environments,by varying distraction parameters(e.g.,rate and frequency)or adding compression loading,on bone regeneration in DO.We further presented how the mechanically-regulated bone regeneration process during DO could be simulated by in silico models incorporating mechano-regulatory tissue differentiation rules.A comprehensive review of those in vivo and in silico studies may not solely provide important references for development of improved DO protocols in clinic,but also promote a deeper understanding of the mechanobiological mechanism of bone regeneration.

Relationship of distraction rate with inferior alveolar nerve degeneration-regeneration shift

Distraction osteogenesis is an important technique for the treatment of maxillofacial abnormities and defects. However, distraction osteo- genesis may cause the injury of the inferior alveolar nerve. The relationship between distraction rate and nerve degeneration-regeneration shift remains poorly understood. In this study, 24 rabbits were randomly divided into four groups. To establish the rabbit mandibular distraction osteogenesis model, the mandibles of rabbits in distraction osteogenesis groups were subjected to continuous osteogenesis dis- traction at a rate of 1.0, 1.5 and 2.0 mm/d, respectively, by controlling rounds of screwing each day in the distractors. In the sham group, mandible osteotomy was performed without distraction, Pin-prick test with a 10 g blunt pin on the labium, histological and histomorpho- metric analyses with methylene blue staining, Bodian＇s silver staining, transmission electron microscopy and myelinated fiber density of inferior alveolar nerve cross-sections were performed to assess inferior alveolar nerve conditions. At 28 days after model establishment, in the pin-prick test, the inferior alveolar nerve showed no response in the labium to a pin pricks in the 2 mm/d group, indicating a severe dysfunction. Histological and histomorphometric analyses indicated that the inferior alveolar nerve suffered more degeneration and in- juries at a high distraction rate （2 mm/d）. Importantly, the nerve regeneration, indicated by newborn Schwann cells and axons, was more abundant in 1.0 and 1.5 mm/d groups than in 2.0 mm/d group. We concluded that the distraction rate was strongly associated with the inferior alveolar nerve function, and the distraction rates of !.0 and 1.5 mm/d had regenerative effects on the inferior alveolar nerve. This study provides an experimental basis for the relationship between distraction rate and nerve degeneration-regeneration shift during dis- traction osteogenesis, and may facilitate reducing nerve complications during distraction osteogenesis.

A two-stage but time-saving reconstructive scheme to treat severe lower limb length discrepancy:Two case reports

Limb length discrepancy(LLD)is a common orthopedic condition that can result in significant functional impairment,pain,and cosmetic deformities.Current reconstructive techniques for severe LLD are primarily based on callus distraction,which is a time-consuming process that can lead to complications,such as significant infection,joint stiffness,and stress fractures.To reduce the therapeutic time and minimize the risk of complications,we investigated the use of vascularized bone flaps as a technical supplement to callus distraction in the reconstruction of short limbs.We present two cases of severe LLD in the upper and lower legs,in which a twostage reconstruction approach was used.In the first stage,external fixation was applied to the affected limb to correct the soft tissue length and convert the short deformity into a bone defect.In the second stage,the bone defect was reconstructed using bilateral(patient A)or unilateral(patient B)free vascularized fibula bone grafts.Both patients had complete survival of the fibular grafts without stress fractures,and bone consolidation took 8 months(patient A)and 4 months(patient B).Compared to the traditional callus distraction,the two-stage approach was found to be more time-saving and reliable.The entire reconstructive scheme required 18 and 4 months for patients A and B,respectively,whereas the traditional callus distraction required 41 and 17 months,respectively.These findings suggest that the use of vascularized bone flaps as a technical supplement for callus distraction may provide an effective and efficient alternative for the treatment of severe LLD.Further studies are needed to validate these results and assess the long-term outcomes of this approach.

Role of the Ilizarov non-free bone plasty in the management of long bone defects and nonunion: Problems solved and unsolved

BACKGROUND Ilizarov non-free bone plasty is a method of distraction osteogenesis using the Ilizarov apparatus for external fixation which originated in Russia and was disseminated across the world. It has been used in long bone defect and nonunion management along with free vascularized grafting and induced membrane technique. However, the shortcomings and problems of these methods still remain the issues which restrict their overall use.AIM To study the recent available literature on the role of Ilizarov non-free bone plasty in long bone defect and nonunion management, its problems and the solutions to these problems in order to achieve better treatment outcomes.METHODS Three databases(Pub Med, Scopus, and Web of Science) were searched for literature sources on distraction osteogenesis, free vascularized grafting and induced membrane technique used in long bone defect and nonunion treatment within a five-year period(2015-2019). Full-text clinical articles in the English language were selected for analysis only if they contained treatment results,complications and described large patient samples(not less than ten cases for congenital, post-tumor resection cases or rare conditions, and more than 20 cases for the rest). Case reports were excluded.RESULTS Fifty full-text articles and reviews on distraction osteogenesis were chosen.Thirty-five clinical studies containing large series of patients treated with this method and problems with its outcome were analyzed. It was found that distraction osteogenesis techniques provide treatment for segmental bone defects and nonunion of the lower extremity in many clinical situations, especially in complex problems. The Ilizarov techniques treat the triad of problems simultaneously(bone loss, soft-tissue loss and infection). Management of tibial defects mostly utilizes the Ilizarov circular fixator. Monolateral fixators are preferable in the femur. The use of a ring fixator is recommended in patients with an infected tibial bone gap of more than 6 cm. High rates of successful treatment were reported by the authors that ranged from 77% to 100% and depended on the pathology and the type of Ilizarov technique used. Hybrid fixation and autogenous grafting are the most applicable solutions to avoid after-frame regenerate fracture or deformity and docking site nonunion.CONCLUSION The role of Ilizarov non-free bone plasty has not lost its significance in the treatment of segmental bone defects despite the shortcomings and treatment problems encountered.

International recognition of the Ilizarov bone reconstruction techniques: Current practice and research (dedicated to 100th birthday of G. A. Ilizarov)

The Ilizarov method is one of the current methods used in bone reconstruction.It originated in the middle of the past century and comprises a number of bone reconstruction techniques executed with a ring external fixator developed by Ilizarov GA.Its main merits are viable new bone formation through distraction osteogenesis,high union rates and functional use of the limb throughout the course of treatment.The study of the phenomenon of distraction osteogenesis induced by tension stress with the Ilizarov apparatus was the impetus for advancement in bone reconstruction surgery.Since then,the original method has been used along with a number of its modifications developed due to emergence of new fixation devices and techniques of their application such as hexapod external fixators and motorized intramedullary lengthening nails.They gave rise to a relatively new orthopedic subspecialty termed“limb lengthening and reconstruction surgery”.Based on a comprehensive literature search,we summarized the recent clinical practice and research in bone reconstruction by the Ilizarov method with a special focus on its modification and recognition by the world orthopedic community.The international influence of the Ilizarov method was reviewed in regard to the origin country of the authors and journal’s rating.The Ilizarov method and other techniques based on distraction osteogenesis have been used in many countries and on all populated continents.It proves its international significance and confirms the greatest contribution of Ilizarov GA to bone reconstruction surgery.

Ilizarov bone transport combined with the Masquelet technique for bone defects of various etiologies (preliminary results)

BACKGROUND The Ilizarov bone transport(IBT)and the Masquelet induced membrane technique(IMT)have specific merits and shortcomings,but numerous studies have shown their efficacy in the management of extensive long-bone defects of various etiologies,including congenital deficiencies.Combining their strong benefits seems a promising strategy to enhance bone regeneration and reduce the risk of refractures in the management of post-traumatic and congenital defects and nonunion that failed to respond to other treatments.AIM To combine IBT and IMT for the management of severe tibial defects and pseudarthrosis,and present preliminary results of this technological solution.METHODS Seven adults with post-traumatic tibial defects(subgroup A)and nine children(subgroup B)with congenital pseudarthrosis of the tibia(CPT)were treated with the combination of IMT and IBT after the failure of previous treatments.The mean number of previous surgeries was 2.0±0.2 in subgroup A and 3.3±0.7 in subgroup B.Step 1 included Ilizarov frame placement and spacer introduction into the defect to generate the induced membrane which remained in the interfragmental gap after spacer removal.Step 2 was an osteotomy and bone transport of the fragment through the tunnel in the induced membrane,its compression and docking for consolidation without grafting.The outcomes were retrospectively studied after a mean follow-up of 20.8±2.7 mo in subgroup A and 25.3±2.3 mo in subgroup B.RESULTS The“true defect”after resection was 13.3±1.7%in subgroup A and 31.0±3.0%in subgroup B relative to the contralateral limb.Upon completion of treatment,defects were filled by 75.4±10.6%and 34.6±4.2%,respectively.Total duration of external fixation was 397±9.2 and 270.1±16.3 d,including spacer retention time of 42.4±4.5 and 55.8±6.6 d,in subgroups A and B,respectively.Bone infection was not observed.Postoperative complications were several cases of pin-tract infection and regenerate deformity in both subgroups.Ischemic regeneration was observed in two cases of subgroup B.Complications were corrected during the course of treatment.Bone union was achieved in all patients of subgroup A and in seven patients of subgroup B.One non-united CPT case was further treated with the Ilizarov compression method only and achieved union.After a follow-up period of two to three years,refractures occurred in four cases of united CPT.CONCLUSION The combination of IMT and IBT provides good outcomes in post-traumatic tibial defects after previous treatment failure but external fixation is longer due to spacer retention.Refractures may occur in severe CPT.

Reducing relapse and accelerating osteogenesis in rapid maxillary expansion using an injectable mesoporous bioactive glass/fibrin glue composite hydrogel

Rapid maxillary expansion(RME),as a common treatment for craniomaxillofacial deformity,faces the challenge of high relapse rates and unsatisfactory therapeutic effects.In this study,a standardized Sprague-Dawley(SD)rat RME model was first established with a modified expander as well as retainer design and optimized anterior maxillary expanding force of 100 g which exerted the most synchronized mobility of mid-palatal suture and incisors.Via the standardized model,the high relapse rate was proven to be attributed to insufficient osteogenesis in expanded suture,requiring long-term retainer wearing in clinical situations.To reduce the relapse rate,mesoporous bioactive glass/fibrin glue(MBG/FG)composite hydrogels were developed for an in situ minimal invasive injection that enhance osteogenesis in the expanded palate.The component of 1 wt%MBG was adopted for enhanced mechanical strength,matched degradation rate and ion dissolution,excellent in vitro biocompatibility and osteoinductivity.Effects of 1%MBG/FG composite hydrogel on osteogenesis in expanded mid-palatal sutures with/without retention were evaluated in the standardized model.The results demonstrated that injection of 1%MBG/FG composite hydrogel significantly promoted bone formation within the expanded mid-palatal suture,inhibited osteoclastogenesis and benefited the balance of bone remodeling towards osteogenesis.Combination of retainer and injectable biomaterial was demonstrated as a promising treatment to reduce relapse rate and enhance osteogenesis after RME.The model establishment and the composite hydrogel development in this article might provide new insight to other craniomaxillofacial deformity treatment and design of bone-repairing biomaterials with higher regenerative efficiency.

Nanotechnology applications in osteodistraction

Most current strategies for bone regeneration have relatively satisfactory results.However,there are drawbacks and limitations associated with their use and availability,and even controversial reports about their efficacy and cost-effectiveness.The induction of new bone formation through distraction osteogenesis(DO)is widespread clinical application in the treatment of bone defects,limb deformities,and fracture nonunions.However,a lengthy period of external fixation is usually needed to allow the new bone to consolidate,and complications such as refracture at the distraction gap often occur.Although various biomaterials have been used as injectable delivery systems in DO models,little has been reported on the use of nanobiomaterials as carrier materials for the sustained release of growth factors in bone regeneration.One area of focus in nanotechnology is the delivery of osteogenic factors in an attempt to modulate the formation of bone.This review article seeks to demonstrate the potential of nanobiomaterials to improve biological applications pertinent to osteodistraction.