Vascularized Periosteal Flaps Accelerate Osteointegration and Revascularization of Allografts in Rats

Cascaded controlled delivering growth factors to build vascularized and osteogenic microenvironment for bone regeneration

The process of bone regeneration is intricately regulated by various cytokines at distinct stages. The establishment of early and efficient vascularization, along with the maintenance of a sustained osteoinductive microenvironment, plays a crucial role in the successful utilization of bone repair materials. This study aimed to develop a composite hydrogel that would facilitate the creation of an osteogenic microenvironment for bone repair. This was achieved by incorporating an early rapid release of VEGF and a sustained slow release of BMP-2. Herein, the Schiff base was formed between VEGF and the composite hydrogel, and VEGF could be rapidly released to promote vascularization in response to the early acidic bone injury microenvironment. Furthermore, the encapsulation of BMP-2 within mesoporous silica nanoparticles enabled a controlled and sustained release, thereby facilitating the process of bone repair. Our developed composite hydrogel released more than 80% of VEGF and BMP-2 in the acidic medium, which was significantly higher than that in the neutral medium (about 60%). Moreover, the composite hydrogel demonstrated a significant improvement in the migratory capacity and tube formation ability of human umbilical vein endothelial cells (HUVECs). Furthermore, the composite hydrogel exhibited an augmented ability for osteogenesis, as confirmed by the utilization of ALP staining, alizarin red staining, and the upregulation of osteogenesis-related genes. Notably, the composite hydrogel displayed substantial osteoinductive properties, compared with other groups, the skull defect in the composite hydrogels combined with BMP-2 and VEGF was full of new bone, basically completely repaired, and the BV/TV value was greater than 80%. The outcomes of animal experiments demonstrated that the composite hydrogel effectively promoted bone regeneration in cranial defects of rats by leveraging the synergistic effect of an early rapid release of VEGF and a sustained slow release of BMP-2, thereby facilitating vascularized bone regeneration. In conclusion, our composite hydrogel has demonstrated promising potential for vascularized bone repair through the enhancement of angiogenesis and osteogenic microenvironment.

Current Management of Acute and Posttraumatic Critical Bone Defects

SUMMARY

Limb reconstruction in patients with critical-sized bone defects remains a challenge due to the availability of various technically demanding treatment options and a lack of standardized decision algorithms. Although no consensus exists, it is apparent from the literature that the combination of patient, surgeon, and institutional collaborations is effective in providing the most efficient care pathway for these patients. Success relies on choosing a particular surgical approach that manages infection, soft tissue defects, stability, and alignment. Recent systematic reviews demonstrate high success rates with the following management options: Ilizarov bone transport, Masquelet (induced membrane) technique, cancellous bone grafting, and vascularized bone grafts.

Research progress of vascularization strategies of tissue-engineered bone

The bone defect caused by fracture, bone tumor, infection, and other causes is not only a problematic point in clinical treatment but also one of the hot issues in current research. The development of bone tissue engineering provides a new way to repair bone defects. Many animal experimental and rising clinical application studies have shown their excellent application prospects. The construction of rapid vascularization of tissue-engineered bone is the main bottleneck and critical factor in repairing bone defects. The rapid establishment of vascular networks early after biomaterial implantation can provide sufficient nutrients and transport metabolites. If the slow formation of the local vascular network results in a lack of blood supply, the osteogenesis process will be delayed or even unable to form new bone. The researchers modified the scaffold material by changing the physical and chemical properties of the scaffold material, loading the growth factor sustained release system, and combining it with trace elements so that it can promote early angiogenesis in the process of induced bone regeneration, which is beneficial to the whole process of bone regeneration. This article reviews the local vascular microenvironment in the process of bone defect repair and the current methods of improving scaffold materials and promoting vascularization.

Non-vascularised corticocancellous (tricortical) iliac bone graft longer than 3 cm for non-union after failed surgical treatment

PURPOSE

We hypothesised that traditional iliac tricortical bone grafts (no vascularised) still have a reasonable role in promoting satisfactory bony healing in non-union defects of certain sizes. Here, we report the clinical/radiological outcomes through a retrospective case series.

METHODS

We screened 74 patients with definitive non-union in the long bones of the upper extremities who visited the outpatient department from 2008 to 2018. Among these patients, 25 who met our inclusion/exclusion criteria were investigated.

RESULTS

The mean age was 51.92 years, and there were 12, 9, 1, and 3 lesions of the radius, ulna, clavicle, and humerus, respectively. The tools for primary fixations were plate and intramedullary nails in 24 and 1 patients, respectively. Six patients presented with atrophic non-union. The mean period from a previous surgery was 6.84 months. The mean defective bone sizes were 1.81 and 3.50 cm pre-debridement and post-debridement, respectively. All devices had locking plates longer than the previous plate, and the graft was concurrently fixed by screws in three patients. At a mean of 15.92 weeks after the revision surgery, all patients experienced union. At the final follow-up, the clinical outcomes were satisfactory. No significant differences in clinical outcomes were found according to the lesion, type of non-union, period from the previous surgery, or harvest length of the iliac bone.

CONCLUSIONS

If the proper indications and some technical aspects are considered, a non-vascularised iliac bone graft longer than 3 cm could still be a reasonable option for treating diaphyseal non-union of the upper extremities.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Combined Free Flaps for Optimal Orthoplastic Lower Limb Reconstruction: A Retrospective Series

Background and Objectives: Open fracture of the lower limb can lead to substantial bone and soft tissue damage, resulting in a challenging reconstructive scenarios, especially in presence of bone or periosteal loss, with a relevant risk of non-union. This work analyzes outcomes of using a double approach for orthoplastic reconstruction, adopting the free medial condyle flap to solve the bone defects, associated to a second free flap for specific soft tissue coverage. Indications, outcomes and reconstructive rationales are discussed. Materials and Methods: A retrospective investigation was performed on patients who underwent complex two-flap microsurgical reconstruction from January 2018 to January 2022. Inclusion criteria in this study were the use of a free femoral condyle periostal/bone flap together with a second skin-only flap. Only distal third lower limb reconstructions were included in order to help equalize our findings. Out of the total number of patients, only patients with complete pre- and post-operative follow-up (minimum 6 months) data were included in the study. Results: Seven patients were included in the study, with a total of 14 free flaps. The average age was 49. Among comorbidities, four patients were smokers and none suffered from diabetes. Etiology of the defect was acute trauma in four cases and septic non-union in three cases. No major complications occurred, and all flaps healed uneventfully with complete bone union. Conclusions: Combining a bone periosteal FMC to a second skin free flap for tailored defect coverage allowed achievement of bone union in all patients, despite the lack of initial bone vascularization or chronic infection. FMC is confirmed to be a versatile flap for small-to-medium bone defects, especially considering its use as a periosteal-only flap, with minimal donor site morbidity. Choosing a second flap for coverage allows for a higher inset freedom and tailored reconstruction, finally enhancing orthoplastic success.

Advances in In Vitro and In Vivo Bioreactor-Based Bone Generation for Craniofacial Tissue Engineering

Craniofacial reconstruction requires robust bone of specified geometry for the repair to be both functional and aesthetic. While native bone from elsewhere in the body can be harvested, shaped, and implanted within a defect, using either an in vitro or in vivo bioreactors eliminates donor site morbidity while increasing the customizability of the generated tissue. In vitro bioreactors utilize cells harvested from the patient, a scaffold, and a device to increase mass transfer of nutrients, oxygen, and waste, allowing for generation of larger viable tissues. In vivo bioreactors utilize the patient's own body as a source of cells and of nutrient transfer and involve the implantation of a scaffold with or without growth factors adjacent to vasculature, followed by the eventual transfer of vascularized, mineralized tissue to the defect site. Several different models of in vitro bioreactors exist, and several different implantation sites have been successfully utilized for in vivo tissue generation and defect repair in humans. In this review, we discuss the specifics of each bioreactor strategy, as well as the advantages and disadvantages of each and the future directions for the engineering of bony tissues for craniofacial defect repair.

Mechanical strain induces ex vivo expansion of periosteum

Segmental bone defects present complex clinical challenges. Nonunion, malunion, and infection are common sequalae of autogenous bone grafts, allografts, and synthetic bone implants due to poor incorporation with the patient's bone. The current project explores the osteogenic properties of periosteum to facilitate graft incorporation. As tissue area is a natural limitation of autografting, mechanical strain was implemented to expand the periosteum. Freshly harvested, porcine periosteum was strained at 5 and 10% per day for 10 days with non-strained and free-floating samples serving as controls. Total tissue size, viability and histologic examination revealed that strain increased area to a maximum of 1.6-fold in the 10% daily strain. No change in tissue anatomy or viability via MTT or Ki67 staining and quantification was observed among groups. The osteogenic potential of the mechanical expanded periosteum was then examined in vivo. Human cancellous allografts were wrapped with 10% per day strained, fresh, free-floating, or no porcine periosteum and implanted subcutaneously into female, athymic mice. Tissue was collected at 8- and 16-weeks. Gene expression analysis revealed a significant increase in alkaline phosphatase and osteocalcin in the fresh periosteum group at 8-weeks post implantation compared to all other groups. Values among all groups were similar at week 16. Additionally, histological assessment with H&E and Masson-Goldner Trichrome staining showed that all periosteal groups outperformed the non-periosteal allograft, with fresh periosteum demonstrating the highest levels of new tissue mineralization at the periosteum-bone interface. Overall, mechanical expansion of the periosteum can provide increased area for segmental healing via autograft strategies, though further studies are needed to explore culture methodology to optimize osteogenic potential.

Preparation of Collagen/Hydroxyapatite Composites Using the Alternate Immersion Method and Evaluation of the Cranial Bone-Forming Capability of Composites Complexed with Acidic Gelatin and b-FGF

Bone-substitute materials are essential in dental implantology. We prepared collagen (Col)/hydroxyapatite (Hap)/acidic gelatin (AG)/basic fibroblast growth factor (b-FGF) constructs with enhanced bone-forming capability. The Col/Hap apatite composites were prepared by immersing Col sponges alternately in calcium and phosphate ion solutions five times, for 20 and 60 min, respectively. Then, the sponges were heated to 56 °C for 48 h. Scanning electron microscopy/energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses showed that the Col/Hap composites contained poorly crystalline Hap precipitates on the Col matrix. Col/Hap composite granules were infiltrated by AG, freeze-dried, and immersed in b-FGF solution. The wet quaternary constructs were implanted in rat cranial bone defects for 8 weeks, followed by soft X-ray measurements and histological analysis. Animal studies have shown that the constructs moderately increase bone formation in cranial bone defects. We found that an alternate immersion time of 20 min led to the greatest bone formation (p < 0.05). Constructs placed inside defects slightly extend the preexisting bone from the defect edges and lead to the formation of small island-like bones inside the defect, followed by disappearance of the constructs. The combined use of Col, Hap, AG, and b-FGF might bring about novel bone-forming biomaterials.

Surgical Classification for Preclinical Rat Femoral Bone Defect Model: Standardization Based on Systematic Review, Anatomical Analysis and Virtual Surgery

Though surgical techniques profoundly influence in vivo experiments, significant heterogeneity exists in current surgeries for inducing rat femoral bone defects. Such variations reduce the reproducibility and comparability of preclinical studies, and are detrimental to clinical translation. The purposes of this study were: (1) to conduct a systematic review of rat femoral defect models, summarizing and analyzing the surgical techniques; (2) to analyze surgical design and potential pitfalls via 3D anatomy and virtual surgeries for fostering future precision research; and (3) to establish a surgical classification system, for improving the reproducibility and comparability among studies, avoiding unnecessary repetitive experiments. The online database PubMed was searched to identify studies from January 2000 to June 2022 using keywords, including rat, femur, bone defect. Eligible publications were included for a review of surgical methods. Anatomical analysis and virtual surgeries were conducted based on micro-CT reconstruction of the rat femur for further investigation and establishment of a classification system. A total of 545 publications were included, revealing marked heterogeneity in surgical methods. Four major surgical designs were reported for inducing defects from the proximal to distal femur: bone tunnel, cortical window, segmental defect, and wedge-shaped defect. Anatomical analysis revealed potential pitfalls hindering efficient clinical translation. A classification system was established according to the anatomical region, surgical design, and fixation devices. This systematic review in combination with 3D analysis and virtual surgery provides a general overview of current surgical approaches to inducing femoral defects in rats, and establishes a surgical classification facilitating preclinical research of quality and translational value.

Utilization of a Chimeric Medial Femoral Condyle Free Flap for Mandibular Osteoradionecrosis

BACKGROUND

Primary options for oromandibular reconstruction with osteocutaneous free flaps are the vascularized fibula and iliac crest. Complications of mandible reconstruction are not uncommon and include osteomyelitis, malunion, and osteoradionecrosis (ORN) after radiation therapy. The medial femoral condyle (MFC) free flap is an established salvage option for carpal reconstruction in hand surgery, frequently used for scaphoid nonunion and avascular necrosis. We hypothesize that the MFC flap can be utilized to restore blood supply and reverse the negative effects of radiotherapy in patients who require mandibular reconstruction due to ORN.

METHODS

A retrospective chart review was conducted at Beaumont Health System, Royal Oak, for patients who underwent MFC free flap reconstruction for mandibular ORN between the years 2012 and 2018. Demographic data, operative details, complications, medical comorbidities, and patient outcomes were retrospectively gathered.

RESULTS

A total of four patients were isolated. Four patients developed ORN after resection of squamous cell carcinoma and adjuvant radiotherapy. No patients experienced donor site deficits. Revisions after MFC reconstruction were dependent on individual aesthetics and involvement of neighboring tissue. All four patients continue to be followed with no current issues to the osseous component of the MFC flap.

CONCLUSION

Utilization of the MFC periosteal flap is a viable option in selected patients to salvage nonunion/resorption of mandible reconstruction and ORN of the mandible. Our experience found that the MFC is able to provide pain resolution and healing of intraoral soft tissue defects, and may halt the progression of ORN of the mandible.

Vascularized Medial Femoral Condyle Periosteal Flaps With Allograft Bone for Distal Radius Giant Cell Tumors: A Case Report

CASE

Distal radius reconstruction after giant cell tumor (GCT) resection is typically performed with free fibular flaps when a vascularized bone is needed. However, vascularized fibular flaps are contraindicated in patients with peroneal artery variants. We present 2 patients with GCTs of the radius and bilateral peronea arteria magna who underwent resection with wrist fusion using an allograft bone and vascularized free medial femoral condyle periosteal flaps. Both patients had excellent outcomes with minimal postoperative morbidity.

CONCLUSION

Allograft bone with vascularized medial femoral condyle periosteal flaps is an effective option for reconstructing distal radius defects after GCT resection when conventional methods fail.

Corticoperiosteal Pedicle Flap of Greater Trochanter for Salvage of Old Femoral Neck Fracture in Children: Outcomes After a Minimum 5 Years Follow-up

BACKGROUND

Old femoral neck fracture (OFNF) generally refers to fractures for more than 3 weeks. Corticoperiosteal pedicle flap of greater trochanter (CPPF-GT) was designed to restore blood supply and donor bone for OFNF. This study aimed to assess the efficacy and radiographic results of CPPF-GT for treatment of OFNF in children after a minimum 5 years follow-up.

METHODS

Twenty-three patients with OFNFs, age from 8 to 16 years old, who underwent open reductions, fracture fixations, and transpositions of CPPF-GTs were retrospectively reviewed. Clinical and radiological outcomes, including union, nonunion, avascular necrosis of femoral head, limb shortening, coxa vara, premature epiphyseal closure and Ratliff's assessment, were investigated in the postoperative follow-up. The results were compared with previously published joint-salvage study of OFNFs.

RESULTS

All patients were followed for an average of 5.9 years (range: 5 to 10 years). All cases (100%) achieved hip unions at an average duration of 3.5 months (range: 2.5 to 5 months). No nonunion hip was observed. Three hips (13.0%) progressed to avascular necrosis of femoral head after 1.5 to 3 years of operation, respectively, and the revision surgeries to hip replacements were conducted. Premature epiphyseal closures were observed in 3 hips. Three hips visibly presented an average 2 cm shortening of the femoral neck. Coxa vara deformities were observed in 2 hips. According to the Ratliff's criteria, there were 20 cases (87.0%) with satisfactory union, good results were achieved in 17 cases, fair results in 3 cases, and poor result in 3 cases.

CONCLUSIONS

Corticoperiosteal pedicle flap of greater trochanter is an effective and desirable option for treating old femoral neck fractures in children with a low rate of avascular necrosis and without nonunion.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Periosteal Skeletal Stem Cells and Their Response to Bone Injury

Bone exhibits remarkable self-repair ability without fibrous scars. It is believed that the robust regenerative capacity comes from tissue-resident stem cells, such as skeletal stem cells (SSCs). Roughly, SSC has two niches: bone marrow (BM) and periosteum. BM-SSCs have been extensively studied for years. In contrast, our knowledge about periosteal SSCs (P-SSCs) is quite limited. There is abundant clinical evidence for the presence of stem cell populations within the periosteum. Researchers have even successfully cultured “stem-like” cells from the periosteum in vitro. However, due to the lack of effective markers, it is difficult to evaluate the stemness of real P-SSCs in vivo. Recently, several research teams have developed strategies for the successful identification of P-SSCs. For the first time, we can assess the stemness of P-SSCs from visual evidence. BM-SSCs and P-SSCs not only have much in common but also share distinct properties. Here, we provide an updated review of P-SSCs and their particular responses to bone injury.

Vascularized ulnar periosteal pedicled flap for forearm nonunion in children

We report our experience with the use of a vascularized ulnar periosteal pedicled flap to treat forearm nonunion in children. Seven children underwent surgical treatment of radial diaphysis nonunion with this technique. The mean duration of nonunion prior to the flap was 9 months. Significant postoperative improvements were observed in pain severity (mean visual analogue scale score of 0.6), Quick Disabilities of the Arm, Shoulder, and Hand (mean score of 7.1) and grip strength (89% higher than preoperative status). Union was achieved in all patients, with a mean time to union of 3 months. One patient developed distal radioulnar synostosis as a postoperative complication. A vascularized ulnar periosteal pedicled flap is a reliable and versatile technique for treating forearm nonunion in children, associated with both good outcomes and low donor morbidity.Level of evidence: IV.

Role of Slit/Robo Signaling pathway in Bone Metabolism

Slit/Robo signals were initially found to play an essential role in nerve development as axonal guidance molecules. In recent years, with in-depth study, the role of Slit/Robo in other life activities, such as tumor development, angiogenesis, cell migration, and bone homeostasis, has gradually been revealed. Bone is an organ with an active metabolism. Bone resorption and bone formation are closely related through precise spatiotemporal coordination. There is much evidence that slit, as a new bone coupling factor, can regulate bone formation and resorption. For example, Slit3 can promote bone formation and inhibit bone resorption through Robo receptors, which has excellent therapeutic potential in metabolic bone diseases. Although the conclusions of some studies are contradictory, they all affirm the vital role of Slit/Robo signaling in regulating bone metabolism. This paper reviews the research progress of Slit/Robo signaling in bone metabolism, briefly discusses the contradictions in the existing research, and puts forward the research direction of Slit/Robo in the field of bone metabolism in the future.

Vascularized Ulnar Periosteal Pedicled Flap for Upper Extremity Reconstruction in Adults: A Prospective Case Series of 11 Patients

PURPOSE

We hypothesized that a vascularized ulnar periosteal pedicled flap (VUPPF) is a versatile graft applicable in adult patients that yields good outcomes and is a reliable alternative to other vascularized bone grafts to reduce both the technical demands and donor site morbidity of other options.

METHODS

We reviewed 11 adult patients who underwent surgical treatment of forearm atrophic nonunion with a VUPPF. Patients' demographics, outcomes (measured by pain on the visual analog scale; Quick Disabilities of the Arm, Shoulder, and Hand score; range of motion; and grip strength), and associated complications were reported.

RESULTS

Of the 11 patients, 5 had previous surgery in an attempt to treat the nonunion with an autologous cancellous bone graft from the iliac crest or olecranon. The average time from nonunion until the VUPPF was 9 months (SD, ±3 months; range, 6-14 months). The mean visual analog scale score improved considerably after surgery (8.7 vs 0.6), and considerable improvement was also noted in the Quick Disabilities of the Arm, Shoulder, and Hand score (50 vs 6). A notable improvement was seen in grip strength after surgery. Pronation/supination also improved considerably between the preoperative assessment and the final postoperative follow-up.

CONCLUSIONS

A vascularized ulnar periosteal pedicled flap seems to be a useful and versatile option for a variety of bone union failures of the upper extremity in adults, either at initial presentation or as a salvage technique.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Periosteal medial femoral condyle free flap for metacarpal nonunion

Background

Metacarpal nonunion is a rare condition. The osteogenic capacity of periosteal free flap was investigated in five patients with metacarpal nonunion and impaired bone vascularization.

Patients and methods

Surgery was performed between 64 and 499 days after the initial bone osteosynthesis. The average age was 27.6 (range 16–32) years. Nonunion was caused by excessive periosteal removal in two patients, extensive open trauma in three. Four nonunions were diaphyseal, one metaphyseal. A periosteal medial femoral condyle free flap was raised on the descending genicular artery for four patients, the superomedial genicular artery for one. After osteosynthesis with a plate, the flap was wrapped around the metacarpal, overlapping the bone proximally and distally. The recipient vessel were the dorsal branch of the radial artery and a vena comitans in the anatomical snuffbox in four patients, at the base of the first webspace in one.

Results

The flap size ranged from 5 × 3.5 cm to 8 × 4 cm. No postoperative complication occurred. Radiological bone union was achieved 3 to 8 months after surgery. One patient had a full range of motion, one a slight extension lag of the proximal interphalangeal joint, two moderate joint stiffness of the proximal interphalangeal or metacarpophalangeal joint (one requiring plate removal and extensor tenolysis), one severe stiffness that allowed using a hook grip which was the aim of the surgery.

Conclusion

In case of metacarpal nonunion with impaired bone vascularization, the periosteal medial femoral condyle free flap provides an effective and biomimetic approach to bone healing.

Free vascularized iliac periosteal graft for bilateral forearm nonunion reconstruction in a child with bilateral transfemoral amputation

Vascularized periosteal flaps have been reported as very effective for treating biologically complex bone nonunion in pediatric patients, owing to their high angiogenic and osteogenic potentials. The purpose of this article is to report a case of a 6-year-old patient with nonunion involving both forearms and a very limited bone flap donor site in the context of prior bilateral transfemoral amputation due to meningococcal sepsis. Two free vascularized iliac periosteal flaps (VIPF), supplied by the deep circumflex iliac vessels, were used in two stages to reconstruct the forearms. In the first stage, the left forearm, which had a diaphyseal bone defect of 5 cm diameter in the ulna and 4 cm in the radius, was combined with an iliac-crest bone allograft, fixed with two longitudinal 1.8 mm Kirschner wires and surrounded with a free VIPF of 24 cm² . Consolidation was achieved 3 months after left forearm surgery, while complete allograft revascularization and remodeling was observed at 12 months. In the second stage, the right forearm, which had a diaphyseal bone defect of 3 cm diameter in the ulna and 1 cm in the radius, was fixed the radius with a 2.7 mm plate and surrounded with a free VIPF of 24 cm² . The radius nonunion healed 6 weeks after surgery. There were no postoperative complications. Two years postoperatively, the patient had again resumed his arm gait painlessly and without a splint. VIPF may be considered a valuable and reliable surgical option for nonunion reconstruction in complex clinical scenarios in children.

[Research progress of in vivo bioreactor for bone tissue engineering]

Objective

To review the research progress of in vivo bioreactor (IVB) for bone tissue engineering in order to provide reference for its future research direction.

Methods

The literature related to IVB used in bone tissue engineering in recent years was reviewed, and the principles of IVB construction, tissue types, sites, and methods of IVB construction, as well as the advantages of IVB used in bone tissue engineering were summarized.

Results

IVB takes advantage of the body's ability to regenerate itself, using the body as a bioreactor to regenerate new tissues or organs at injured sites or at ectopic sites that can support the regeneration of new tissues. IVB can be constructed by tissue flap (subcutaneous pocket, muscle flap/pocket, fascia flap, periosteum flap, omentum flap/abdominal cavity) and axial vascular pedicle (axial vascular bundle, arteriovenous loop) alone or jointly. IVB is used to prefabricate vascularized tissue engineered bone that matched the shape and size of the defect. The prefabricated vascularized tissue engineered bone can be used as bone graft, pedicled bone flap, or free bone flap to repair bone defect. IVB solves the problem of insufficient vascularization in traditional bone tissue engineering to a certain extent.

Conclusion

IVB is a promising method for vascularized tissue engineered bone prefabrication and subsequent bone defect reconstruction, with unique advantages in the repair of large complex bone defects. However, the complexity of IVB construction and surgical complications hinder the clinical application of IVB. Researchers should aim to develop a simple, safe, and efficient IVB.

Postconditioning With Red-Blue Light Therapy Improves Survival of Random Skin Flaps in a Rat Model

BACKGROUND

Random skin flap ischemic necrosis is a serious challenge in reconstructive surgery. Photobiomodulation is a noninvasive effective technique to improve microcirculation and neovascularization. Photobiomodulation with red or blue light has been separately proven to partially prevent skin flap necrosis, but the synergistic effect of red and blue light not been elucidated. Our experiment evaluated the impact of postconditioning with red-blue light therapy on the viability of random flaps.

METHODS

Thirty Sprague-Dawley male rats (male, 12 weeks) with a cranially based random pattern skin flap (3 × 8 cm) were divided into 3 groups: control group, red light group, and red-blue light group. On postoperative day 7, flap survival was observed and recorded using transparent graph paper, flaps were obtained and stained with hematoxylin and eosin, and microvessel density was measured. Micro-computed tomography was used to measure vascular volume and vascular length. On days 0, 3, and 7 after surgery, blood flow was measured by laser Doppler. To investigate the underlying mechanisms, the amount of nitric oxide (NO) metabolites in the flap tissue was assessed on days 3, 5, and 7 after surgery.

RESULTS

The mean percentage of skin flap survival was 59 ± 10% for the control group, 69 ± 7% for the red light group, and 79 ± 9% for the red-blue light group (P < 0.01). The microvessel density was 12.3 ± 1.2/mm2 for the control group, 31.3 ± 1.3/mm2 for the red light group, and 36.5 ± 1.4/mm2 for the red-blue light group (P < 0.01). Both vascular volume and total length in the red-blue light group showed significantly increased compared with the red light and control group (P < 0.01). Blood flow in the red-blue light treated flap showed significantly increased at postsurgery days 3 and 7 compared with the red light and control group (P < 0.01). The level of the NO metabolites was significantly increased in flap tissues belonging to the red-blue light group compared with the other 2 groups (P < 0.01).

CONCLUSIONS

This study showed that postconditioning with red-blue light therapy can enhance the survival of random skin flap by improving angiogenesis and NO releasing.

Experimental study on repair of large segmental bone defects of goat femur by nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer membrane tubes

OBJECTIVE

The purpose of this study was to observe feasibility of nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer (n-CDHA-MAC) membrane tubes in repairing goat femurs' large defects.

METHODS

Twelve goats were divided into two groups, whose femurs were created 30 mm segmental bone defects and then implants were performed. In experimental group, the bone defect of right femur was reconstructed by n-CDHA-MAC membrane tube, while left side was reconstructed by allogenic bone tube in control group. Every three goats were sacrificed at 4, 8, 16, 24 weeks after operation respectively. General observation, X-ray analysis, histology, Scanning electron microscope (SEM) examination and protein level comparison of BMP-2 were conducted to evaluate the effects of repairing segmental bone defects.

RESULTS

All goats recovered well from anesthesia and surgical interventions. The radiographic evaluations showed that periosteal reaction outside of the membrane tubes and allogenic bone tubes were observed 4 weeks after surgery. At 16 weeks, callus was continuously increased in experimental group, which was more obvious than control group. At 24 weeks, callus outside of the membrane tubes connected together. Histologic evaluation showed fibro-cartilage callus was evolved into bony callus in experimental group, which was more obvious than control group at 8 and 16 weeks. The protein expression level of BMP-2 increased at 4, 8 weeks and peaked at 16 weeks in experimental groups. There were statistical differences at 8 and 16 weeks (P < 0.05). At each time point in 8, 16, 24 weeks after surgery, the bending stiffness, torsional stiffness and compressive strength of the two groups were similar, and there was no significant difference (P > 0.05).

CONCLUSIONS

This novel surface degradation n-CDHA-MAC membrane tube has good ability to maintain enough membrane space, which can provide long-term and stable biomechanical support for large bone defects and integrate well with the surrounding bone.

Lateral pterygoid muscle enthesis reconstruction in total temporomandibular joint replacement: An animal experiment with radiological correlation

A novel total temporomandibular joint replacement (TMJR) was developed with CADskills BV (Ghent, Belgium), aiming to achieve reinsertion of the (LPM) onto a scaffold in the implant. In order to investigate the possibility of reinsertion of the LPM, an animal experiment was conducted. An in vivo sheep experiment was conducted, which involved implanting sheep with a TMJR. Clinical parameters were recorded regularly and computed tomography (CT) scan images of two randomly selected sheep per scan were made at 1, 3, and 6 months. After 9.5 months, the sheep were euthanized, and CT scans of all animals were performed in order to evaluate the LPM's enthesis. A total of 13 sheep were implanted with a TMJR. One sheep was used as a sham. Radiographs revealed four outcome types of enthesis reconstruction. In four sheep, there was no reconstruction between the implant and the LPM. In three sheep, there was a purely soft tissue connection of 0.5-0.9 mm (average 0.7 mm) between the ostectomized bony LPM insertion and the implant's lattice structure. A combination of partial bony and partial soft tissue enthesis attachment (0.3-0.5 mm, average 0.4 mm) was found in three sheep. A bony ingrowth of the enthesis into the scaffold occurred in two sheep. A secondary bony connection between the mandible and the insertion of the LPM was found in 10 of 13 sheep. Four fossa components were found to be displaced, yet TMJ function remained in these ewes. The heterotopic ossification that was seen may be a confounding factor in these results. This in vivo experiment showed promising results for improving the current approach to TMJR with the possibility of restoring the laterotrusive function. The fossa displacement was considered to be due to insufficient fixation and predominant laterotrusive force not allowing for proper osseointegration. Further optimization of the reattachment technique, scaffold position and surface area should be done, as well as trials in humans to evaluate the effect of proper revalidation.

Effect of vascularized periosteum on revitalization of massive bone isografts: An experimental study in a rabbit model

INTRODUCTION

In the last years, limb salvage has become the gold standard treatment over amputation. Today, 90% of extremity osteogenic sarcomas can be treated with limb salvage surgery. However, these reconstructions are not exempt from complications. Massive allografts have been associated to high risk of nonunion (12-57%), fracture (7-30%) and infection (5-21%). Association of vascularized periosteum flap to a massive bone allograft (MBA) has shown to halve the average time of allograft union in clinical series, even compared to vascularized fibular flap. Creeping substitution process has been reported in massive allograft when periosteum flap was associated. However, we have little data about whether it results into allograft revitalization. We hypothesize that the association of a periosteum flap to a bone isograft promotes isograft revitalization, defined as the colonization of the devitalized bone by new-form vessels and viable osteocytes, turning it vital.

MATERIALS AND METHODS

Forty-four New Zealand white male rabbits underwent a 10 mm segmental radial bone defect. In 24 rabbits the bone excision included the periosteum (controls); in 20 rabbits (periosteum group) bone excision was performed carefully detaching periosteum in order to preserve it. Cryopreserved bone isograft from another rabbit was trimmed and placed to the defect gap and was fixed with a retrograde intramedullar 0.6 mm Kirschner wire. Rabbits were randomized and distributed in 3 subgroups depending on the follow-up (control group: 5 rabbits in 5-week follow up group, 8 rabbits in 10-week follow-up group, 7 rabbits in 20-week follow-up group; periosteum group: 5 rabbits in 5-week follow up group, 7 rabbits in 10-week follow-up group, 7 rabbits in 20-week follow-up group). Fluoroscopic images of rabbit forelimb were taken after sacrifice to address union. Each specimen was blindly evaluated in optical microscope (magnification, ×4) after hematoxylin and eosin staining to qualitative record: presence of new vessels and osteocytes in bone graft lacunae (yes/no) to address revitalization, presence of callus (yes/no) and woven bone and cartilage tissue area (mm2 ) to address remodeling (osteoclast resorption of old bone and substitution by osteoblastic new bone formation).

RESULTS

No isograft revitalization occurred in any group, but it was observed bone graft resorption and substitution by new-formed bone in periosteum group. This phenomenon was accelerated in 5-week periosteum group (control group: 49.5 ± 9.6 mm2 vs. periosteum group: 34.9 ± 10.4 mm2 ; p = .07). Remodeled lamellar bone was observed in both 20-week groups (control group: 6.1 ± 6.3 mm2 vs. periosteum group: 5.8 ± 3.0 mm2 , p = .67). Periosteum group showed complete integration and graft substitution, whereas devitalized osteons were still observed in 20-week controls. All periosteum group samples showed radiographic union through a bone callus, whereas controls showed nonunion in eight specimens (Union rate: control group 60% vs. periosteum group 100%, p = .003).

CONCLUSIONS

Association of vascularized periosteum to a massive bone isograft has shown to accelerate bone graft substitution into a newly formed bone, thus, no bone graft revitalization occurs.

[Microvascular reconstruction of foot defects using a free femoral periostal flap]

BACKGROUND

The reconstruction of defects in the foot region is a challenge due to the anatomical peculiarities of the soft tissue covering.

OBJECTIVE

This article presents the results of the reconstruction of postoperative foot defects using the free femoral periosteal flap (FFPF).

MATERIAL AND METHODS

In a patient collective (n = 10) with postoperative wound healing disorders of the foot, the defect zone was covered using a vascularized FFPF from the distal femoral region. The wound healing process was retrospectively analyzed.

RESULTS

The mean follow-up time was 20.2 ± 8.22 months (7-35 months). All patients had a soft tissue defect in the foot region with a mean area of 17.9 ± 3.72 cm² (12-24 cm²). On average, a wound healing disorder occurred 2 weeks after the primary surgery. In the group of patients followed up the vascularized FFPF enabled a stable, definitive and aesthetically pleasing reconstruction and contributed to the bony consolidation. The duration of inpatient care after defect closure was 8-10 days and was significantly less than the duration of wound management prior to transplantation of the FFPF.

CONCLUSION

The FFPF is an effective and elegant method for the regenerative reconstruction of defects with accompanying osseous components in the foot region. The FFPF has the advantage of instant thin and pliable tissue coverage in contrast to many other reconstructive methods. The FFPF can promote wound consolidation through the regenerative properties of a vascularized periosteal sheath in the context of a one-step and permanent infection control.

Free vascularised medial femoral condyle periosteal flaps in recalcitrant long bone non-union: a systematic review

INTRODUCTION

In adults, treatment of recalcitrant long bone non-union is extremely challenging, with poorly vascularised and atrophic defects unresponsive to standard non-vascularised bone graft treatment. Recent studies have documented the use of free vascularised periosteal flaps to achieve union in refractory long bone fracture non-union, yet its use is not well established. This systematic review aims to assess the evidence for free vascularised periosteal flaps in recalcitrant long bone non-union.

MATERIALS AND METHODS

The MEDLINE®/PubMed^® and Embase databases were searched for the Medical Subject Heading (MeSH) terms periosteal flap/vascularised flap/long bone/non-union/non united fracture in accordance with the PRISMA guidelines. Bibliographies were scrutinised for additional articles.

RESULTS

Pooled data from 14 studies met the inclusions criteria, comprising 137 cases of non-union, with 117 relating to long bone non-union. Pooled data indicated an overall 99% (116/117) successful union rate. All studies were of mid- to low-level evidence (Level III, IV and V). Only one study directly compared vascularised periosteal flaps to non-vascularised bone grafts, showing union rates of 100% versus 80% and faster time to union (2 versus 5.5 months).

CONCLUSIONS

Free vascularised periosteal flaps are promising with pooled data showing a 99% success rate in achieving union in refractory long bone non-union. This compares favourably with standard orthopaedic care consisting of revision fixation and non-vascularised bone graft union rates of approximately 80%. However, study design flaws should be addressed by validated outcome measures plus adequate blinding, and further comparative studies with greater patient numbers are required.

Are Vascularized Periosteal Flaps Useful for the Treatment of Difficult Scaphoid Nonunion in Adults? A Prospective Cohort Study of 32 Patients

PURPOSE

To evaluate clinical and radiological outcomes after surgical treatment of difficult scaphoid nonunion in adults with a vascularized thumb metacarpal periosteal pedicled flap (VTMPF).

MATERIALS AND METHODS

Thirty-two patients at least 18 years old, with scaphoid nonunion and characteristics associated with a poor prognosis, who underwent a VTMPF procedure, were included in this retrospective cohort study with a mean follow-up of 17 months. Factors associated with a poor prognosis were a delay in presentation of over 5 years, the presence of avascular necrosis, and previous nonunion surgery. All patients had at least 1 poor prognostic factor and 25% had 2 or more.

RESULTS

In 30 men and 2 women, the mean age was 36 years (range, 19-56 years). There were 11 type D3 nonunions (Herbert classification) and 15 type D4. Five patients had delayed presentation of over 5 years. Fourteen patients had previously undergone an unsuccessful surgical attempt to treat their nonunion. The patients experienced no postoperative complications. Overall union rate was 97% (31 of 32 patients), with 72% cross-sectional trabecular percentage bridging at 12 weeks. Pain subsided after surgery and patients experienced improvements in both their Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) and Modified Mayo Wrist Score (MMWS). Overall 41% and 42% gains in strength and wrist motion, relative to the contralateral normal side, were observed. At final follow-up, there were no differences between the treated and the untreated (healthy) hands, in terms of wrist range of motion, grip, or pinch strength.

CONCLUSIONS

In this study, the use of VTMPF for difficult scaphoid nonunion in adults was associated with good general outcomes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Motivating role of type H vessels in bone regeneration

Coupling between angiogenesis and osteogenesis has an important role in both normal bone injury repair and successful application of tissue‐engineered bone for bone defect repair. Type H blood vessels are specialized microvascular components that are closely related to the speed of bone healing. Interactions between type H endothelial cells and osteoblasts, and high expression of CD31 and EMCN render the environment surrounding these blood vessels rich in factors conducive to osteogenesis and promote the coupling of angiogenesis and osteogenesis. Type H vessels are mainly distributed in the metaphysis of bone and densely surrounded by Runx2⁺ and Osterix⁺ osteoprogenitors. Several other factors, including hypoxia‐inducible factor‐1α, Notch, platelet‐derived growth factor type BB, and slit guidance ligand 3 are involved in the coupling of type H vessel formation and osteogenesis. In this review, we summarize the identification and distribution of type H vessels and describe the mechanism for type H vessel‐mediated modulation of osteogenesis. Type H vessels provide new insights for detection of the molecular and cellular mechanisms that underlie the crosstalk between angiogenesis and osteogenesis. As a result, more feasible therapeutic approaches for treatment of bone defects by targeting type H vessels may be applied in the future.