Comparison of the vascularity of fasciocutaneous tissue and muscle for coverage of open tibial fractures

3D-Printed Flat-Bone-Mimetic Bioceramic Scaffolds for Cranial Restoration

The limitations of autologous bone grafts necessitate the development of advanced biomimetic biomaterials for efficient cranial defect restoration. The cranial bones are typical flat bones with sandwich structures, consisting of a diploe in the middle region and 2 outer compact tables. In this study, we originally developed 2 types of flat-bone-mimetic β-tricalcium phosphate bioceramic scaffolds (Gyr-Comp and Gyr-Tub) by high-precision vat-photopolymerization-based 3-dimensional printing. Both scaffolds had 2 outer layers and an inner layer with gyroid pores mimicking the diploe structure. The outer layers of Gyr-Comp scaffolds simulated the low porosity of outer tables, while those of Gyr-Tub scaffolds mimicked the tubular pore structure in the tables of flat bones. The Gyr-Comp and Gyr-Tub scaffolds possessed higher compressive strength and noticeably promoted in vitro cell proliferation, osteogenic differentiation, and angiogenic activities compared with conventional scaffolds with cross-hatch structures. After implantation into rabbit cranial defects for 12 weeks, Gyr-Tub achieved the best repairing effects by accelerating the generation of bone tissues and blood vessels. This work provides an advanced strategy to prepare biomimetic biomaterials that fit the structural and functional needs of efficacious bone regeneration.

The Effect of Free versus Local Flaps on Time to Union in Open Tibia Fractures

BACKGROUND

Early soft-tissue reconstruction of open fractures has been shown to decrease infection rates and improve rates of bony union. The purpose of this study was to compare the rates and time to union of open tibia fractures that underwent soft-tissue coverage.

METHODS

A retrospective chart review of 118 patients with open tibia fractures requiring soft-tissue reconstruction treated at a single level 1 trauma center was performed. Demographic data as well as flap type were collected. Union status was determined using modified Radiographic Union Scale in Tibia Fractures score greater than 11.

RESULTS

Limb salvage was achieved in 90% of patients. The overall rate of nonunion was 33%. Flap type significantly affected time to union, with local fasciocutaneous and keystone flaps having significantly longer time to union [202 days (SD 120.3)] than all other flap groups ( P = 0.01). Free flaps had significantly shorter time to union than local flaps [115 days (SD 49.6) versus 149 days (SD 75.4); P = 0.02]. Muscle flaps had significantly shorter time to union than fasciocutaneous flaps [123 days (SD 52.4) versus 165 days (SD 104.1); P = 0.04]. This remained true after controlling for fracture location, patient age, need for second flap, and fixation method ( P = 0.037). Patients who underwent an initial soft-tissue reconstruction with a local muscle flap were more likely to require a second flap to achieve wound closure (OR, 3.7; P = 0.008) and needing a second flap significantly increased time to union [162 days (SD 95.9) versus 122 days (SD 51.9); P = 0.03].

CONCLUSION

Flap type affects time to union but not nonunion rate in open tibia fractures.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Outcome comparison between muscle and fasciocutaneous flaps after secondary orthopedic procedures

Lower extremity wounds associated with fractures and bony defects often require secondary orthopedic procedures after flap coverage has been performed. In this study, we compare complications between muscle and fasciocutaneous flaps after secondary orthopedic procedures. A retrospective chart review study of all lower extremity soft tissue reconstructions by a single surgeon over seven years yielded a subgroup of patients who underwent secondary orthopedic procedures, including hardware removal, hardware revision, and bone grafting after flap reconstruction. Of 355 lower extremity, soft tissue reconstructions for orthopedic coverage performed in the time period studied, 102 patients underwent secondary orthopedic procedures after flap reconstruction. Of these, 54 received muscle flaps (52.94%), and 48 received fasciocutaneous flaps (47.06%). Using this subgroup of 102 patients, we compared muscle and fasciocutaneous flaps using three categories of wound complications following these secondary procedures: There were no superficial wounds requiring local wound care only in the muscle flap group (0%, n = 0) versus 4.17% (n = 2; p = 0.130) in the fasciocutaneous flap group. There were 2 lost flaps requiring surgical debridement and additional skin grafting in the muscle flaps group (3.70%) versus 2 (4.17%; p = 0.904) in the fasciocutaneous flap group. In the third category, flap loss requiring additional soft tissue reconstruction was 18.52% (n = 10) in the muscle group versus 2.08% (n = 1; p = 0.008) in the fasciocutaneous flap group. Our data support the existing literature indicating that fasciocutaneous flaps can tolerate secondary procedures better than muscle flaps and should initially be considered in patients with higher probability of needing additional orthopedic procedures after reconstruction.

Muscle/musculocutaneous versus fasciocutaneous free flap reconstruction in the lower extremity: A systematic review and meta-analysis

BACKGROUND

Free flaps for soft tissue coverage of the lower extremity can be broadly divided into muscle/musculocutaneous and fasciocutaneous flaps. The purpose of this systematic review and meta-analysis was to assess their different post-operative outcomes.

METHODS

A systematic search was performed in PubMed, Scopus, and the Web of Science from their inception to February 2022. Non-randomized comparative studies, which describe any post-operative outcome of muscle/musculocutaneous and fasciocutaneous free flaps reconstruction in the lower extremity were included. Articles with duplicate titles, editorials, review articles, case series, case reports, and publications lacking an abstract, those reporting pediatric patients, those describing only muscle/musculocutaneous or fasciocutaneous free flaps, those with incomplete or incomparable post-operative outcomes, and studies involving <10 muscle/musculocutaneous or fasciocutaneous free flaps were excluded. A comparative meta-analysis was conducted on muscle/musculocutaneous and fasciocutaneous free flaps outcomes, comprising vascular thrombosis, partial or complete flap necrosis, infection, donor-site complications, non-union, and primary or recurrent osteomyelitis. The fixed-effects meta-analysis model was used when low heterogeneity (I²  < 50%) was identified.

RESULTS

Twenty-two articles with a total of 2711 flaps (1584 muscle/musculocutaneous flaps and 1127 fasciocutaneous flaps) were included in the qualitative and quantitative assessment. The rates of any flap necrosis (12.0% vs. 7.4%; p = 0.007) and donor-site complications (16.7% vs. 6.7%; p < 0.0001) were significantly higher for muscle/musculocutaneous flaps than for fasciocutaneous flaps. There were no significant differences in the rates of vascular thrombosis (10.5% vs. 10.7%; p = 0.98), complete flap necrosis (6.2% vs. 4.7%; p = 0.30), infection (19.4% vs. 14.7%; p = 0.18), non-union (18.9% vs. 14.8%; p = 0.33), and primary or recurrent osteomyelitis (14.7% vs. 12.4%; p = 0.69).

CONCLUSION

This meta-analysis revealed no significant difference in long-term post-operative outcomes, but suggested that fasciocutaneous flaps should be preferred to avoid flap necrosis and donor-site complications.

Effects of Muscles on Bone Metabolism—with a Focus on Myokines

Skeletal muscles and bones, the largest tissues in the body of a non-obese person, comprise the musculoskeletal system, which allows mobility and protects internal organs. Although muscles and bones are closely related throughout life, observations during development and aging and in human and animal disuse models have revealed the synchronization of tissue mass such that muscle phenotype changes precede alterations in bone mineral density and strength. This review discussed that mechanical forces, which have been the traditional research focus, are not the only mechanism by which muscle-derived signals may affect bone metabolism and emphasized the significance of skeletal muscles as an endocrine organ that secretes bone-regulatory factors. Consequently, both mechanical and biochemical aspects should be considered to fully understand muscle–bone crosstalk. This review also suggested that specific myokines could be ideal therapeutic targets for osteoporosis to both increase bone formation and reduce bone resorption; moreover, these myokines could also be potential circulating biomarkers to predict musculoskeletal health.

Correlation between microRNA-320 and postoperative delirium in patients undergoing tibial fracture internal fixation surgery

Background

Although the incidence of postoperative delirium (POD) in the elderly after surgery are rising as individuals are living longer, the pathogenesis of POD remains poorly understood. It has been suggested that miRNA-320 may play a role in POD based on animal study and human study.

Methods

We first carried out an animal study, and designed and conducted a human study based on the result of animal study. The aged rats were randomly assigned to five groups: the control (C), anesthesia and surgery (AS), saline (NS), agomir-320 (AG), and antagomir-320 (AT) groups. Postoperative spatial learning and memory in rats were analyzed by the Morris water maze and the open field tests. The plasma levels of insulin-like growth factor-1 (IGF-1), amyloid precursor protein (APP) proteins, miRNA320 and IGF-1mRNA were measured by ELISA and qRT-PCR, respectively. A total of 240 Chinese Han patients over 65 years who underwent tibial fracture internal fixation were included in the PNDABLE study. POD cases and non-POD controls (1:1 matched) were selected by an anesthesiologist using Confusion Assessment Method.

Results

For Group AS, the escape latency was significantly longer and the ratio of time spent in the target quadrant was significantly reduced, APP and miR-320 were upregulated and IGF-1mRNA was downregulated compared with Group C. For Group AG, the escape latency was significantly longer and the ratio of time spent in the target quadrant was significantly reduced, APP and miR-320 were upregulated and IGF-1mRNA was downregulated compared with Group AS. For Group AT, the escape latency was significantly reduced and the ratio of time spent in the target quadrant was significantly longer, APP and miR-320 were downregulated and IGF-1mRNAwas upregulated compared with Group AS. Compared with NPOD patients, the expressions of plasma miR-320 and APP protein were increased and the expression of plasma IGF-1 mRNA was decreased in POD patients after surgery.

Conclusions

MiRNA-320 might play a role in up-regulating the levels of IGF-1mRNA and APP protein, which offered a new target for POD treatment.

Trial registration

Correlation of perioperative neurocognitive disorders with lifestyle and biomarkers. ChiCTR2000033439. Registered 1 June 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01612-w.

Muscle vs. Fasciocutaneous Microvascular Free Flaps for Lower Limb Reconstruction: A Meta-Analysis of Comparative Studies

(1) Background: Lower extremity microvascular reconstruction aims at restoring function and preventing infection while ensuring optimal cosmetic outcomes. Muscle (M) or fasciocutaneous (FC) free flaps are alternatively used to treat similar conditions. However, it is unclear whether one option might be considered superior in terms of clinical outcomes. We performed a meta-analysis of studies comparing M and FC flaps to evaluate this issue. (2) Methods: The PRISMA guidelines were followed to perform a systematic search of the English literature. We included all articles comparing M and FC flap reconstructions for lower limb soft tissue defects following trauma, infection, or tumor resection. We considered flap loss, postoperative infection, and donor site morbidity as primary outcomes. Secondary outcomes included minor recipient site complications and the need for revision surgery. (3) Results: A total of 10 articles involving 1340 patients receiving 1346 flaps were retrieved, corresponding to 782 M flaps and 564 FC flaps. The sizes of the studies ranged from 39 to 518 patients. We observed statistically significant differences (p < 0.05) in terms of donor site morbidity and total flap loss with better outcomes for FC free flaps. Moreover, the majority of authors preferred FC flaps because of the greater aesthetic satisfaction and lesser rates of postoperative infection. (4) Conclusion: Our data suggest that both M and FC free flaps are safe and effective options for lower limb reconstruction following trauma, infection, or tumor resection, although FC flaps tend to provide stronger clinical benefits. Further research should include larger randomized studies to confirm these data.

Enhancing health span: muscle stem cells and hormesis

Sarcopenia is a significant public health and medical concern confronting the elderly. Considerable research is being directed to identify ways in which the onset and severity of sarcopenia may be delayed/minimized. This paper provides a detailed identification and assessment of hormetic dose responses in animal model muscle stem cells, with particular emphasis on cell proliferation, differentiation, and enhancing resilience to inflammatory stresses and how this information may be useful in preventing sarcopenia. Hormetic dose responses were observed following administration of a broad range of agents, including dietary supplements (e.g., resveratrol), pharmaceuticals (e.g., dexamethasone), endogenous ligands (e.g., tumor necrosis factor α), environmental contaminants (e.g., cadmium) and physical agents (e.g., low level laser). The paper assesses both putative mechanisms of hormetic responses in muscle stem cells, and potential therapeutic implications and application(s) of hormetic frameworks for slowing muscle loss and reduced functionality during the aging process.

Pedicled sural flaps versus free anterolateral thigh flaps in reconstruction of dorsal foot and ankle defects in children: a systematic review

BACKGROUND

This systematic review compared free anterolateral thigh (ALT) flaps versus pedicled distally based sural artery (DBSA) flaps for reconstruction of soft tissue defects of dorsal foot and ankle in children.

METHODS

A systematic literature search was performed to identify cases where an ALT or DBSA was used to reconstruct the dorsal foot in children. A total of 19 articles were included in the systematic review.

RESULTS

Eighty-three patients underwent an ALT reconstruction and 138 patients underwent a DBSA reconstruction. Patients who had a DBSA were more likely to require grafting of the donor site (P<0.001). The size of ALT flaps was significantly larger than DBSA flaps (P=0.002). Subsequent flap thinning was required in 30% of patients after ALT and 12% of patients after DBSA reconstruction (P<0.001). Complications occurred in 11.6% of DBSA and 8.4% of ALT flaps (8.4%).

CONCLUSIONS

Both flaps are valid options in reconstructing pediatric foot and ankle defects. Each flap has advantages and disadvantages as discussed in this review article. In general for larger defects, an ALT flap was used. Flap choice should be based on the size of the defect.

Lower extremity reconstruction for limb salvage and functional restoration - The Combat experience

Evolution in extremity injury treatment often occurs during major conflicts, with lessons learned applied and translated among military and civilian settings. In recent periods of war, improvements in protective equipment, in-theater damage control resuscitation/surgery, delivery of antibiotics locally/systemically, and rapid evacuation to higher levels of medical care capabilities have greatly improved combat casualty survivability rates. Additionally, widespread application of lower extremity tourniquets also has prevented casualties from exsanguination, thus reducing hemorrhagic-related deaths. Secondary to these, a high number of combat casualties suffering lower extremity traumatic injuries have presented for functional limb reconstruction and restoration as well as residual limb care.

Gait biomechanics: A clinically relevant outcome measure for preclinical research of musculoskeletal trauma

Traumatic injuries to the musculoskeletal system are the most prevalent of those suffered by United States Military Service members and accounts for two-thirds of initial hospital costs to the Department of Defense. These combat-related wounds often leave survivors with life-long disability and represent a significant impediment to the readiness of the fighting force. There are immense opportunities for the field of tissue engineering and regenerative medicine (TE/RM) to address these musculoskeletal injuries through regeneration of damaged tissues as a means to restore limb functionality and improve quality of life for affected individuals. Indeed, investigators have made promising advancements in the treatment for these injuries by utilizing small and large preclinical animal models to validate therapeutic efficacy of next-generation TE/RM-based technologies. Importantly, utilization of a comprehensive suite of functional outcome measures, particularly those designed to mimic data collected within the clinical setting, is critical for successful translation and implementation of these therapeutics. To that end, the objective of this review is to emphasize the clinical relevance and application of gait biomechanics as a functional outcome measure for preclinical research studies evaluating the efficacy of TE/RM therapies to treat traumatic musculoskeletal injuries. Specifically, common musculoskeletal injuries sustained by service members-including volumetric muscle loss, post-traumatic osteoarthritis, and composite tissue injuries-are examined as case examples to highlight the use of gait biomechanics as an outcome measure using small and large preclinical animal models.

A Retrospective Comparative Functional and Aesthetic Outcome Study of Muscle versus Cutaneous Free Flaps for Distal Upper Extremity Reconstruction

BACKGROUND

 Function and cosmesis are crucial in upper extremity reconstruction. Yet, there persists a lack of outcome evaluations, particularly regarding differences between free flap types.

METHODS

 In a single-center retrospective analysis, outcomes were compared between patients with cutaneous or muscle free flaps for distal upper extremity reconstruction between 2008 and 2018. The Disabilities of Arm, Shoulder and Hand -Score, Michigan-Hand (MHQ), and Short Form 36 Health Survey (SF-36) Questionnaires were assessed, motor function was quantified, and self-reported measures of cosmesis were compared, including the Vancouver Scar-Scale (VSS), MHQ aesthetics-subscale (MAS), and Moscona's cosmetic validation-score (CVS).

RESULTS

 One-hundred forty-one cases were identified, with a shift toward cutaneous flaps over the study period. Muscle flaps were used for larger defects (251 vs. 142 cm², p = 0.008). Losses, thromboses, and donor-site complications were equally distributed. Partial necroses were more frequent in muscle flaps (11 vs. 1%, p = 0.015). Seventy patients with 53 cutaneous versus 17 muscle flaps were reexamined. There was no difference in the timing of flap coverage (after 16 vs. 15 days, p = 0.79), number of preceding (2 vs. 1.7, p = 0.95), or subsequent operations (19/53 vs. 5/17, p = 0.77). Patients with cutaneous flaps showed higher grip strength (25 vs. 17 kg, p = 0.046) and reported better hand function (MHQ: 58 vs. 47, p = 0.044) and general health (SF-36: 70 vs. 61, p = 0.040), as well as more favorable appearance (MAS: 71 vs. 57, p = 0.044, CVS: 77 vs. 72, p = 0.048), and scar burden (VSS: 0 vs. 3, p < 0.001).

CONCLUSION

 Cutaneous flaps yielded better motor function, self-perceived cosmesis, patient satisfaction, and quality of life in our cohort of distal upper extremity reconstructions.

Proximal Trauma Increases Risk of Venous Thrombosis in Soft Tissue Reconstruction of Open Lower Limb Fractures

Lower limb salvage after major trauma is a complex undertaking. For patients who have suffered multi-level trauma to their lower limb we postulated that pelvic injury or ipsilateral lower limb injury proximal to the site of a free flap may increase the rate of post-operative complications. All patients who underwent lower limb free flap reconstruction as a result of acute trauma between January 2010 and December 2017 were included. The patients were divided into the study group (50 patients), who sustained a lower limb or pelvic injury proximal to the free flap site, and control group (91 patients) who did not sustain proximal lower limb or pelvic trauma. Complication rates were compared between the two groups. Overall, the proximal trauma group anastomotic thrombosis rate of 18.0% was significantly higher than the control group thrombosis rate of 2.2%. There was no statically significant difference in rates of hematoma, swelling or infection. Flap loss rate in the proximal trauma group was 4.0%, compared to the control group at 2.2%. All patients with a failed flap went onto have a successful reconstruction with a subsequent flap in the acute admission and there were no amputations. In the proximal injury study group despite the significantly increased rate of microvascular thrombosis requiring revision, the ultimate primary free flap survival rate was still 96%. Overall, severe coexisting proximal trauma predicted a higher venous microvascular complication rate but was not a contraindication to limb salvage.

Muscle-Derived Lumican Stimulates Bone Formation via Integrin α2β1 and the Downstream ERK Signal

Skeletal muscle and bone are highly interrelated, and previous proteomic analyses suggest that lumican is one of muscle-derived factors. To further understand the role of lumican as a myokine affecting adjacent bone metabolism, we investigated the effects of lumican on osteoblast biology. Lumican expression was significantly higher in the cell lysates and conditioned media (CM) of myotubes than those of undifferentiated myoblasts, and the known anabolic effects of myotube CM on osteoblasts were reduced by excluding lumican from the CM. Lumican stimulated preosteoblast viability and differentiation, resulting in increased calvaria bone formation. The expression of osteoblast differentiation markers was consistently increased by lumican. Lumican increased the phosphorylation of ERK, whereas ERK inhibitors completely reversed lumican-mediated stimulation of Runx2 and ALP activities in osteoblasts. Results of a binding ELISA experiment in osteoblasts show that transmembrane integrin α2β1 directly interacted with lumican, and an integrin α2β1 inhibitor attenuated the stimulation of ERK and ALP activities by lumican. Taken together, the results indicate that muscle-derived lumican stimulates bone formation via integrin α2β1 and the downstream ERK signal, indicating that this is a potential therapeutic target for metabolic bone diseases.

Free Tissue Transfer with Distraction Osteogenesis and Masquelet Technique Is Effective for Limb Salvage in Patients with Gustilo Type IIIB Open Fractures

Osteocutaneous reconstruction can be challenging because of concomitant injuries and limited donor sites. There is a paucity of data on limb salvage outcomes following combined soft-tissue reconstruction and bone transport or Masquelet procedures. The authors reviewed a consecutive series of open tibia fracture patients undergoing soft-tissue reconstruction with either distraction osteogenesis or Masquelet technique. Endpoints were perioperative flap complications and bone union. Fourteen patients with Gustilo type IIIB open tibia fractures were included. Half of the group received muscle flaps and the remaining half received fasciocutaneous flaps. Ten patients (71.4 percent) underwent distraction osteogenesis and the remaining patients underwent Masquelet technique. Average bone gap length was 65.7 ± 31.3 mm (range, 20 to 120 mm). In the bone transport group, the average external fixation duration was 245 days (range, 47 to 686 days). In the Masquelet group, the average duration of the first stage of this two-stage procedure (i.e., time from cement spacer placement to bone grafting) was 95 days (range, 42 to 181 days). Bone union rate, as determined by radiographic evidence, was 85.7 percent. There was one complete flap failure (7.1 percent). One patient underwent below-knee amputation after failing bone transport and developing chronic osteomyelitis and subsequent infected nonunion. Our case series demonstrates that nonosteocutaneous flap methods of limb reconstruction are a viable option in patients with segmental long bone defects, with a bone union rate of 85 percent and a limb salvage rate over 90 percent in patients with Gustilo type IIIB fractures. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, IV.

Convergence of Scaffold-Guided Bone Reconstruction and Surgical Vascularization Strategies-A Quest for Regenerative Matching Axial Vascularization

The prevalent challenge facing tissue engineering today is the lack of adequate vascularization to support the growth, function, and viability of tissue engineered constructs (TECs) that require blood vessel supply. The research and clinical community rely on the increasing knowledge of angiogenic and vasculogenic processes to stimulate a clinically-relevant vascular network formation within TECs. The regenerative matching axial vascularization approach presented in this manuscript incorporates the advantages of flap-based techniques for neo-vascularization yet also harnesses the in vivo bioreactor principle in a more directed "like for like" approach to further assist regeneration of the specific tissue type that is lost, such as a corticoperiosteal flap in critical sized bone defect reconstruction.

The Adipo-Fascial ALT Flap in Lower Extremities Reconstruction Gustillo IIIC-B Fractures. An Osteogenic Inducer?

RESULTS

Mean time from injury to flap coverage was 72 hours. The mean size of bone defects was 4-7,6 cm. All flaps were Antero Lateral Tight flaps, and the fracture sites did not have any evidence of infection. None of the patients was a smoker. A solid bone union was reached, and full wearing was in a mean of 11 (4-20) weeks after the injury. The lower limb was saved in 100% of the cases.

CONCLUSION

Despite the goods results, further studies applied on a large number of patients are needed to confirm authors theory, however, we can consider the fascial ALT flap as a valid help for bone healing in 3B-C open tibial fractures.

The effects of myokines on osteoclasts and osteoblasts

Recently, muscle has received much attention as an endocrine organ regulating other biological targets, including the pancreas, liver, and adipose tissue. Although there is a possibility that muscle-secreting factors biochemically affect bone metabolism in a paracrine manner, the net effects of myokines on the biology of osteoclasts and osteoblasts, particularly on bone mass in vivo, have not yet been thoroughly investigated. Therefore, we performed in vitro as well as animal experiments using conditioned media (CM) collected from C2C12 myoblast and myotube cultures to better understand the interactions between muscle and bone. Compared with non-CM (i.e., control) and myoblast CM, myotube CM markedly inhibited in vitro bone resorption through the suppression of osteoclast differentiation and resorptive activity of individual osteoclasts. Consistently, the expressions of osteoclast differentiation markers, such as tartrate-resistant acid phosphatase (Trap) and calcitonin receptor (Ctr), decreased with myotube CM. Myotube CM significantly stimulated preosteoblast viability and migration and reduced apoptosis, thereby resulting in an increase in calvaria bone formation. Importantly, systemic treatment with myotube CM for 4 weeks increased bone per tissue volume by 30.7% and 19.6% compared with control and myoblast CM, respectively. These results support the hypothesis that muscle plays beneficial roles in bone health via secretion of anabolic factors, in addition to mechanical stimuli, and importantly indicate that muscle-derived factors can be potential therapeutic targets against metabolic bone diseases.

Comparing Radiographic Progression of Bone Healing in Gustilo IIIB Open Tibia Fractures Treated With Muscle Versus Fasciocutaneous Flaps

OBJECTIVES

To investigate how muscle and fasciocutaneous flaps influence the progression of bone healing in acute Gustilo IIIB tibia fractures.

DESIGN

Retrospective Chart Review.

SETTING

Urban Academic Level I Trauma Center.

PATIENTS/PARTICIPANTS

Between 2006 and 2016, 39 patients from a database of operatively treated long bone fractures met the inclusion criteria, which consisted of adults with acute Gustilo IIIB tibia shaft fracture requiring flap coverage and having at least 6 months of radiographic follow-up.

INTERVENTION

Soft tissue coverage for patients with Gustilo IIIB open tibia fractures was performed with either a muscle flap or fasciocutaneous flap.

MAIN OUTCOME MEASUREMENTS

A radiographic union score for tibia (RUST) fractures, used to evaluate fracture healing, was assigned to patients' radiographs postoperatively, at 3, 6, and 12 months from the initial fracture date. Mean RUST scores at these time points were compared between those of patients with muscle flaps and fasciocutaneous flaps. Union was defined as a RUST score of 10 or higher.

RESULTS

There was a significant difference (P = 0.026) in the mean RUST score at 6 months between the muscle group (8.54 ± 1.81) and the fasciocutaneous group (6.92 ± 2.46). There was no significant difference in the mean RUST score at 3 months (P = 0.056) and at 12 months (P = 0.947) between the 2 groups. There was also significance in the number of fractures reaching union, favoring muscle flaps, at 6 months (P = 0.020).

CONCLUSIONS

Patients with acute Gustilo IIIB tibia fractures who received muscle flaps have significantly faster radiographic progression of bone healing in the first 6 months than do patients who received fasciocutaneous flaps. Furthermore, according to radiographic evaluation, more Gustilo IIIB tibia fractures receiving muscle flaps reach union by 6 months than those flapped with fasciocutaneous tissue.

LEVEL OF EVIDENCE

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

Diagnosis and Management of Polytraumatized Patients With Severe Extremity Trauma

Multiply injured patients with severe extremity trauma are at risk of acute systemic complications and are at high risk of developing longer term orthopaedic complications including soft-tissue infection, osteomyelitis, posttraumatic osteoarthritis, and nonunion. It is becoming increasingly recognized that injury magnitude and response to injury have major jurisdiction pertaining to patient outcomes and complications. The complexities of injury and injury response that affect outcomes present opportunities to apply precision approaches to understand and quantify injury magnitude and injury response on a patient-specific basis. Here, we present novel approaches to measure injury magnitude by adopting methods that quantify both mechanical and ischemic tissue injury specific to each patient. We also present evolving computational approaches that have provided new insight into the complexities of inflammation and immunologic response to injury specific to each patient. These precision approaches are on the forefront of understanding how to stratify individualized injury and injury response in an effort to optimize titrated orthopaedic surgical interventions, which invariably involve most of the multiply injured patients. Finally, we present novel methods directed at mangled limbs with severe soft-tissue injury that comprise severely injured patients. Specifically, methods being developed to treat mangled limbs with volumetric muscle loss have the potential to improve limb outcomes and also mitigate uncompensated inflammation that occurs in these patients.

An ABC Technical Algorithm to Treat the Mangled Upper Extremity: Systematic Surgical Approach

Mangled upper extremity, as a result of trauma, is a life-altering event requiring a multidisciplinary approach for a successful outcome. All attempts are made to salvage the extremity and preserve function, which may require multiple complex procedures. This paper discusses the importance of a systematic reconstructive sequence and provides a review of commonly utilized techniques, supported with illustrative cases.

Autologous minced muscle grafts improve endogenous fracture healing and muscle strength after musculoskeletal trauma

The deleterious impact of concomitant muscle injury on fracture healing and limb function is commonly considered part of the natural sequela of orthopedic trauma. Recent reports suggest that heightened inflammation in the surrounding traumatized musculature is a primary determinant of fracture healing. Relatedly, there are emerging potential therapeutic approaches for severe muscle trauma (e.g., volumetric muscle loss [VML] injury), such as autologous minced muscle grafts (1 mm3 pieces of muscle; GRAFT), that can partially prevent chronic functional deficits and appear to have an immunomodulatory effect within VML injured muscle. The primary goal of this study was to determine if repair of VML injury with GRAFT rescues impaired fracture healing and improves the strength of the traumatized muscle in a male Lewis rat model of tibia open fracture. The most salient findings of the study were: (1) tibialis anterior (TA) muscle repair with GRAFT improved endogenous healing of fractured tibia and improved the functional outcome of muscle regeneration; (2) GRAFT repair attenuated the monocyte/macrophage (CD45+CDllb+) and T lymphocyte (CD3+) response to VML injury; (3) TA muscle protein concentrations of MCP1, IL-10, and IGF-1 were augmented in a proregenerative manner by GRAFT repair; (4) VML injury concomitant with osteotomy induced a heightened systemic presence of alarmins (e.g., soluble RAGE) and leukocytes (e.g., monocytes), and depressed IGF-1 concentration, which GRAFT repair ameliorated. Collectively, these data indicate that repair of VML injury with a regenerative therapy can modulate the inflammatory and regenerative phenotype of the treated muscle and in association improve musculoskeletal healing.

Decellularized extracellular matrix repair of volumetric muscle loss injury impairs adjacent bone healing in a rat model of complex musculoskeletal trauma

BACKGROUND

Traumatic muscle loss (i.e., volumetric muscle loss [VML] injury) impairs adjacent fracture healing but is often left untreated. A promising therapy for this application is a decellularized extracellular matrix (ECM) because of their capacity to regenerate a vascularized tissue bed. This study tested the hypothesis that repair of VML concomitant to fracture with a small intestine submucosa (SIS)-ECM improves musculoskeletal healing.

METHODS

In male Lewis rats (~375 g), a 3-mm segmental bone defect (SBD) was created in concomitance with a 6-mm, full-thickness VML injury to the adjacent tibialis anterior (TA) muscle. For all rats (n = 10), the SBD was treated with internal plate fixation and delivery of recombinant human bone morphogenetic protein 2 (1 μg) on a collagen sponge. The VML either had no repair or SIS-ECM repair (n = 5/group). Bone regeneration within the SBD (BV/TV [bone volume as a fraction of total volume]) was assessed via in vivo micro-computed tomography at 2, 4, and 6 weeks and histology at 6 weeks after injury. Tibialis anterior muscle in vivo strength and histologic assessments were performed at 6 weeks after injury.

RESULTS

Compared with no repair, SIS-ECM presented -21% (p = 0.09) and -27% (p = 0.004) BV/TV at 4 and 6 weeks after injury, respectively. At 6 weeks, the SBD gap length was shorter for the no repair than that for the SIS-ECM (2.64 ± 0.30 and 3.67 ± 0.41 mm, respectively; p = 0.09), whereas the distances from the end of each cortical segment to the center of the first stabilization screw were longer (1.86 ± 0.25 and 0.85 ± 0.30 mm, respectively; p = 0.035), indicating enhanced resorption in the SIS-ECM group. Both groups presented similar magnitude TA muscle strength deficits compared with their contralateral limbs (10-150 Hz: no repair, -58% to 67%; SIS-ECM, -51% to 74%). The TA muscle of the SIS-ECM group was remarkable for its presentation of fibrosis, edema, and immune cell presence.

CONCLUSIONS

Small intestine submucosa-ECM VML repair impaired open fracture healing and failed to improve skeletal muscle strength.

Systematic Review and Comparative Meta-Analysis of Outcomes Following Pedicled Muscle versus Fasciocutaneous Flap Coverage for Complex Periprosthetic Wounds in Patients with Total Knee Arthroplasty

Background

In cases of total knee arthroplasty (TKA) threatened by potential hardware exposure, flap-based reconstruction is indicated to provide durable coverage. Historically, muscle flaps were favored as they provide vascular tissue to an infected wound bed. However, data comparing the performance of muscle versus fasciocutaneous flaps are limited and reflect a lack of consensus regarding the optimal management of these wounds. The aim of this study was to compare the outcomes of muscle versus fasciocutaneous flaps following the salvage of compromised TKA.

Methods

A systematic search and meta-analysis were performed to identify patients with TKA who underwent either pedicled muscle or fasciocutaneous flap coverage of periprosthetic knee defects. Studies evaluating implant/limb salvage rates, ambulatory function, complications, and donor-site morbidity were included in the comparative analysis.

Results

A total of 18 articles, corresponding to 172 flaps (119 muscle flaps and 53 fasciocutaneous flaps) were reviewed. Rates of implant salvage (88.8% vs. 90.1%, P=0.05) and limb salvage (89.8% vs. 100%, P=0.14) were comparable in each cohort. While overall complication rates were similar (47.3% vs. 44%, P=0.78), the rates of persistent infection (16.4% vs. 0%, P=0.14) and recurrent infection (9.1% vs. 4%, P=0.94) tended to be higher in the muscle flap cohort. Notably, functional outcomes and ambulation rates were sparingly reported.

Conclusions

Rates of limb and prosthetic salvage were comparable following muscle or fasciocutaneous flap coverage of compromised TKA. The functional morbidity associated with muscle flap harvest, however, may support the use of fasciocutaneous flaps for coverage of these defects, particularly in young patients and/or high-performance athletes.

Comparing Muscle and Fasciocutaneous Free Flaps in Lower Extremity Reconstruction--Does It Matter?

INTRODUCTION

Plastic surgeons are often asked to assist with the reconstruction of lower extremity wounds. These patients many times require free tissue transfer for coverage given paucity of soft tissue. Anecdotally, many orthopedic surgeons prefer muscle coverage--particularly in the setting of potentially infected bone. Today's surgeons now easily harvest and transfer fasciocutaneous flaps--a versatile option with less donor-site morbidity. We hypothesized that there would be no difference in outcomes between these 2 types of reconstruction.

METHODS

We performed a single-institution retrospective review of lower extremity free flap reconstructions in the last 10 years. Demographics, preoperative and postoperative course, and the documented time to weight-bearing and bony union were collected. Major cohorts compared were muscle free flaps and fasciocutaneous free flaps, further divided into subgroups including acute trauma, tumor resection, osteomyelitis, and nonunion. Data comparisons were made using paired t test and Fischer exact tests.

RESULTS

There were 121 patients who met inclusion criteria--86 in the muscle flap group, and 35 in the fasciocutaneous group and demographics were equal. Total complication rates were higher in smokers than nonsmokers (P < 0.03). There was no significant difference in major or minor complication rates between muscle and fasciocutaneous flaps in any subgroup. In both the acute fracture group and the infected nonunion group, there was a significantly faster return to weight bearing in the fasciocutaneous group (P < 0.03) although there was no difference in documented time to bony union. Patients who underwent fasciocutaneous reconstruction were more likely to require revisionary surgery for improved aesthetics (P < 0.001).

CONCLUSIONS

Our data suggest that in essentially all clinical parameters, there is no difference between free flap type used for soft tissue coverage of the lower extremity. Patients undergoing reconstruction with a fasciocutaneous flap may return to weight bearing earlier--although they are more likely to require elective flap revisions. These results imply essentially equivalent outcomes regardless of flap type or operative indication, in contrast with some of the biases in the orthopedic community. The particular flap chosen for any reconstruction should remain solely at the discretion of the plastic surgeon.

Plastic Surgery Challenges in War Wounded I: Flap-Based Extremity Reconstruction

Scope and Significance: Reconstruction of traumatic injuries requiring tissue transfer begins with aggressive resuscitation and stabilization. Systematic advances in acute casualty care at the point of injury have improved survival and allowed for increasingly complex treatment before definitive reconstruction at tertiary medical facilities outside the combat zone. As a result, the complexity of the limb salvage algorithm has increased over 14 years of combat activities in Iraq and Afghanistan. Problem: Severe poly-extremity trauma in combat casualties has led to a large number of extremity salvage cases. Advanced reconstructive techniques coupled with regenerative medicine applications have played a critical role in the restoration, recovery, and rehabilitation of functional limb salvage. Translational Relevance: The past 14 years of war trauma have increased our understanding of tissue transfer for extremity reconstruction in the treatment of combat casualties. Injury patterns, flap choice, and reconstruction timing are critical variables to consider for optimal outcomes. Clinical Relevance: Subacute reconstruction with specifically chosen flap tissue and donor site location based on individual injuries result in successful tissue transfer, even in critically injured patients. These considerations can be combined with regenerative therapies to optimize massive wound coverage and limb salvage form and function in previously active patients. Summary: Traditional soft tissue reconstruction is integral in the treatment of war extremity trauma. Pedicle and free flaps are a critically important part of the reconstructive ladder for salvaging extreme extremity injuries that are seen as a result of the current practice of war.

Microvascular free tissue transfer in acute and secondary burn reconstruction

INTRODUCTION

The mainstay of operative treatment in burns is split skin grafting with free tissue transfer being indicated in a minority of cases. However, free tissue transfer faces a number of challenges in the burns patient. These include; overall cardiovascular and respiratory stability of the patient, availability of suitable vessels for anastomosis, sufficient debridement of devitalised tissue and a potentially increased risk of infection. We carried out a retrospective study in order to determine the indications, timing, principles of flap selection, complications, outcomes and methods of promoting flap survival when free tissue transfer was utilised for burn reconstruction in our unit.

MATERIALS AND METHODS

All patients who underwent soft tissue reconstruction for burn injuries with microvascular free tissue transfer between May 2002 and September 2014 were identified from our burns database. The records of these patients were then retrospectively reviewed. Data extracted included, age, gender, type of injury, total body surface area involved, indications for free tissue transfer, anatomical location, timing of reconstruction, complications and flap survival.

RESULTS

Out of a total of 8776 patients admitted for operative treatment over a 12-year period, 23 patients required 26 free flaps for reconstruction. Out of 26 free flaps, 23 were utilised for acute burn reconstruction while only 3 free flaps were utilised for secondary burn reconstruction. All 26 free flaps survived regardless of timing or burn injury mechanism. Complications included haematomas in 2 flaps and tip necrosis in 4 flaps. Two flaps required debridement and drainage of pus, 1 flap required redo of the venous anastomosis while 1 required redo of the arterial anastomosis with a vein graft.

CONCLUSIONS

Free tissue transfer has a small but definite role within acute and secondary burn reconstruction surgery. Despite the complexity of the burn defects involved, free flaps appear to have a high success rate within this cohort of patients. This appears to be the case as long as the appropriate patient and flap is selected, care is taken to debride all devitalised tissue and due diligence paid to the vascular anastomosis by performing it away from the zone of injury.

Is delayed reconstruction using the latissimus dorsi free flap a worthy option in the management of open IIIB tibial fractures?

Early reconstruction of severe open fractures, performed within 7 days of the injury, has a better outcome than closure after 7 days. However, the uncertain demarcation of damaged tissue often results in delayed reconstruction. In this article, we report our surgical outcomes of delayed reconstruction using latissimus dorsi free flap with internal fixation. Twenty-three patients with Gustilo type IIIB open tibial fractures Between March 2009 and May 2012 were included in this study. There were 16 cases of distal 1/3 fracture of the tibia, 4 of midshaft fracture, 1 of proximal 1/3 fracture, and 2 of segmental fracture. Serial debridement with application of negative pressure wound therapy (NPWT) was performed before the final operation. All patients underwent internal fixation of the bone and reconstruction of soft tissue defect using latissimus dorsi free flap. The number of serial debridements, excluding those performed during emergency and finial operation, ranged from 1 to 5 (mean 2.69) times. Mean time from injury to final operation was 10.65 (range, 7-22) days. All flaps survived without complications. Three cases (13%) were infected, and three cases required further bone graft surgery to facilitate bone union (13%). Bone union was achieved after a mean 6.3 (range, 3-12) months. Mean follow-up period was 16.34 (range, 12-26) months. During follow-up, all patients were able to ambulate without use of an aid. In cases of severe open fracture, treatment should emphasize soft tissue coverage rather than rushing to achieve definitive fixation in the setting of poor surrounding tissues. When delayed reconstruction is inevitable, radical debridement is performed first, then NPWT is used as bridging therapy, and free flap could be considered for definite soft tissues coverage. © 2015 Wiley Periodicals, Inc. Microsurgery 36:453-459, 2016.

Muscle and bone, two interconnected tissues

As bones are levers for skeletal muscle to exert forces, both are complementary and essential for locomotion and individual autonomy. In the past decades, the idea of a bone-muscle unit has emerged. Numerous studies have confirmed this hypothesis from in utero to aging works. Space flight, bed rest as well as osteoporosis and sarcopenia experimentations have allowed to accumulate considerable evidence. Mechanical loading is a key mechanism linking both tissues with a central promoting role of physical activity. Moreover, the skeletal muscle secretome accounts various molecules that affect bone including insulin-like growth factor-1 (IGF-1), basic fibroblast growth factor (FGF-2), interleukin-6 (IL-6), IL-15, myostatin, osteoglycin (OGN), FAM5C, Tmem119 and osteoactivin. Even though studies on the potential effects of bone on muscle metabolism are sparse, few osteokines have been identified. Prostaglandin E2 (PGE2) and Wnt3a, which are secreted by osteocytes, osteocalcin (OCN) and IGF-1, which are produced by osteoblasts and sclerostin which is secreted by both cell types, might impact skeletal muscle cells. Cartilage and adipose tissue are also likely to participate to this control loop and should not be set aside. Indeed, chondrocytes are known to secrete Dickkopf-1 (DKK-1) and Indian hedgehog (Ihh) and adipocytes produce leptin, adiponectin and IL-6, which potentially modulate bone and muscle metabolisms. The understanding of this system will enable to define new levers to prevent/treat sarcopenia and osteoporosis at the same time. These strategies might include nutritional interventions and physical exercise.

Medial triceps brachii free flap in reconstructive surgery: a prospective study in eight patients

INTRODUCTION

In this study, we present a prospective series of medial triceps free flaps for ankle and foot complex defects coverage and discuss its numerous advantages.

MATERIALS AND METHODS

Between January 2011 and December 2012, eight patients, two women and six men underwent medial triceps brachii (MTB) free flap procedure to cover defects localized at the ankle and foot in our department. Patient mean age was 37.3 ± 15.2 years at the time of surgery (range of 13-53 years). Mean defect size to be covered was 21.8 ± 9.9 cm(2). The bone was exposed at the level of the calcaneum in six cases, at the level of the forefoot in one case, and at the level of the lateral malleolus in one case. Special attention was accorded to intra-operative findings. Flap survival and complications on both the donor and recipient site were prospectively evaluated.

RESULTS

Mean MTB flap raising time was 51.3 ± 6.0 min. All the flaps survived and there was no partial flap necrosis. A skin graft was performed after a mean time of 11.8 ± 2.1 days post-operative. The mean follow-up was 18.1 ± 3.8 months. Complications at the donor site level included one hematoma and a case of hypertrophic scar. Complete healing of both the donor and recipient sites was achieved in all cases.

CONCLUSIONS

MTB free flap appears to be a useful option for covering small to medium defects in lower limb extremities. Due to the constant anatomy of the MTB nerve, we suggest that the flap could also be used as an innervated free flap for small or medium muscular reanimation such as sequelae of forearm and hand muscle impairment, or facial palsy.

Size does matter: an integrative in vivo-in silico approach for the treatment of critical size bone defects

Although bone has a unique restorative capacity, i.e., it has the potential to heal scarlessly, the conditions for spontaneous bone healing are not always present, leading to a delayed union or a non-union. In this work, we use an integrative in vivo - in silico approach to investigate the occurrence of non-unions, as well as to design possible treatment strategies thereof. The gap size of the domain geometry of a previously published mathematical model was enlarged in order to study the complex interplay of blood vessel formation, oxygen supply, growth factors and cell proliferation on the final healing outcome in large bone defects. The multiscale oxygen model was not only able to capture the essential aspects of in vivo non-unions, it also assisted in understanding the underlying mechanisms of action, i.e., the delayed vascularization of the central callus region resulted in harsh hypoxic conditions, cell death and finally disrupted bone healing. Inspired by the importance of a timely vascularization, as well as by the limited biological potential of the fracture hematoma, the influence of the host environment on the bone healing process in critical size defects was explored further. Moreover, dependent on the host environment, several treatment strategies were designed and tested for effectiveness. A qualitative correspondence between the predicted outcomes of certain treatment strategies and experimental observations was obtained, clearly illustrating the model's potential. In conclusion, the results of this study demonstrate that due to the complex non-linear dynamics of blood vessel formation, oxygen supply, growth factor production and cell proliferation and the interactions thereof with the host environment, an integrative in silico-in vivo approach is a crucial tool to further unravel the occurrence and treatments of challenging critical sized bone defects.

In 5–10% of fracture patients, the bone fractures do not heal in the normal healing period (delayed healing) or do not heal at all (non-union). In order to investigate the causes of impaired healing and design potential treatment strategies, we have used a combined experimental and computational approach. More specifically, large bone defects were analyzed in mouse models and simulated by a previously published computational model. After showing that the predictions of the computational model match the observations of the experimental model, we have used the computational model to investigate the underlying mechanisms of action. In particular, the results indicated that the new blood vessels do not reach the central fracture zone in time due to the large defect size, which leads to insufficient oxygen delivery, increased cell death and disrupted bone healing. The healing, however, could be rescued by adequate blood vessel ingrowth from the overlying soft tissues. Moreover, potential treatment strategies were designed based on the influence of these soft tissues. In conclusion, this study demonstrates the potential of a combined experimental and computational approach to contribute to the understanding of pathological processes like the impaired bone regeneration in large bone defects and design future treatments thereof.

The ortho-plastic approach to soft tissue management in trauma

Fractures with associated soft tissue injuries, or those termed 'open,' are not uncommon. There has been much discussion regarding there management, with the guidance from the combined British Orthopaedic Association and British Association and Aesthetic Surgeons teams widely accepted as the gold level of therapy. We aim to discuss the current evidence about the initial management of this group of injuries, taking a journey from arrival in the accident and emergency department through to the point of definitive closure. Other modes of therapy are also reviewed.

Revisiting the scapular flap: applications in extremity coverage for our U.S. combat casualties

BACKGROUND

Combat injuries commonly result in massive bony and soft-tissue destruction within the extremities. These extremity wounds often require large free tissue transfers and/or composite flaps for definitive reconstruction. In U.S. military war trauma experience, the authors' practice has found the scapular flap increasingly useful for reconstruction of complex extremity injuries. The purpose of this study is to report the authors' experience using the scapular flap in extremity reconstruction and evaluate the indications for use in the authors' patient population.

METHODS

All consecutive limb salvage cases requiring free flaps from 2009 to 2012 at Walter Reed National Military Medical Center were reviewed retrospectively. Scapular flap cases were identified. Data collected included Injury Severity Score, flap characteristics, and complications.

RESULTS

Twelve scapular free flaps were performed for extremity reconstruction for combat-related trauma, representing 16.2 percent of all microsurgical reconstructions during that period. Cases included eight traditional scapular flaps, two osteocutaneous scapular flaps, one chimeric latissimus/scapular flap, and one chimeric parascapular/scapular/scapula bone flap. The complication rate was 17 percent, consisting of one flap hematoma and one donor-site dehiscence. Complication rates were similar between scapular flaps, other fasciocutaneous flaps, and muscle flaps.

CONCLUSIONS

In a decade of war trauma, the authors' practice has found the scapular flap useful for reconstruction of complex extremity injuries. This flap is uniquely suited to the authors' patients, given the severity of their injuries and rehabilitation needs. The scapular flap continues to have various indications in injuries seen within the authors' military population that may be applicable to the authors' civilian patient counterparts.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Attenuated human bone morphogenetic protein-2-mediated bone regeneration in a rat model of composite bone and muscle injury

Extremity injuries involving large bone defects with concomitant severe muscle damage are a significant clinical challenge often requiring multiple treatment procedures and possible amputation. Even if limb salvage is achieved, patients are typically left with severe short- and long-term disabilities. Current preclinical animal models do not adequately mimic the severity, complexity, and loss of limb function characteristic of these composite injuries. The objectives of this study were to establish a composite injury model that combines a critically sized segmental bone defect with an adjacent volumetric muscle loss injury, and then use this model to quantitatively assess human bone morphogenetic protein-2 (rhBMP-2)-mediated tissue regeneration and restoration of limb function. Surgeries were performed on rats in three experimental groups: muscle injury (8-mm-diameter full-thickness defect in the quadriceps), bone injury (8-mm nonhealing defect in the femur), or composite injury combining the bone and muscle defects. Bone defects were treated with 2 μg of rhBMP-2 delivered in the pregelled alginate injected into a cylindrical perforated nanofiber mesh. Bone regeneration was quantitatively assessed using microcomputed tomography, and limb function was assessed using gait analysis and muscle strength measurements. At 12 weeks postsurgery, treated bone defects without volumetric muscle loss were consistently bridged. In contrast, the volume and mechanical strength of regenerated bone were attenuated by 45% and 58%, respectively, in the identically treated composite injury group. At the same time point, normalized muscle strength was reduced by 51% in the composite injury group compared to either single injury group. At 2 weeks, the gait function was impaired in all injury groups compared to baseline with the composite injury group displaying the greatest functional deficit. We conclude that sustained delivery of rhBMP-2 at a dose sufficient to induce bridging of large segmental bone defects failed to promote regeneration when challenged with concomitant muscle injury. This model provides a platform with which to assess bone and muscle interactions during repair and to rigorously test the efficacy of tissue engineering approaches to promote healing in multiple tissues. Such interventions may minimize complications and the number of surgical procedures in limb salvage operations, ultimately improving the clinical outcome.

Biomaterial delivery of morphogens to mimic the natural healing cascade in bone

Complications in treatment of large bone defects using bone grafting still remain. Our understanding of the endogenous bone regeneration cascade has inspired the exploration of a wide variety of growth factors (GFs) in an effort to mimic the natural signaling that controls bone healing. Biomaterial-based delivery of single exogenous GFs has shown therapeutic efficacy, and this likely relates to its ability to recruit and promote replication of cells involved in tissue development and the healing process. However, as the natural bone healing cascade involves the action of multiple factors, each acting in a specific spatiotemporal pattern, strategies aiming to mimic the critical aspects of this process will likely benefit from the usage of multiple therapeutic agents. This article reviews the current status of approaches to deliver single GFs, as well as ongoing efforts to develop sophisticated delivery platforms to deliver multiple lineage-directing morphogens (multiple GFs) during bone healing.

Soft-tissue reconstruction of open fractures of the lower limb: muscle versus fasciocutaneous flaps

Early vascularized soft-tissue closure has long been recognized to be essential in achieving eventual infection-free union. The question of whether muscle or fasciocutaneous tissue is superior in terms of promoting fracture healing remains unresolved. In this article, the authors review the experimental and clinical evidence for the different tissue types and advocate that the biological role of flaps should be included as a key consideration during flap selection.

The skeletal muscle secretome: an emerging player in muscle-bone crosstalk

In vitro and in vivo studies provide evidence that a variety of growth factors and cytokines are actively secreted by muscle tissue. Muscle can therefore function as an endocrine and paracrine organ. These peptides characterize the muscle secretome, and many muscle-derived factors such as insulin-like growth factor-1, basic fibroblast growth factor, interleukin-15, myostatin and secreted protein acidic and rich in cysteine (osteonectin) are also known to have significant effects on bone metabolism. The factors secreted by muscle may vary according to muscle activity, in that muscle contraction, muscle atrophy or traumatic muscle injury can alter the type and relative abundance of particular factors released from muscle cells. The molecular and cellular pathways by which muscle-derived factors affect different types of bone cells (for example, osteoblasts, osteoclasts and osteocytes) are, however, poorly understood. Nevertheless, these findings further underscore the complex nature of muscle-bone interactions, and highlight the importance of integrating muscle biology and physiology into our understanding of bone growth, development and aging.

Myogenic progenitors contribute to open but not closed fracture repair

BACKGROUND

Bone repair is dependent on the presence of osteocompetent progenitors that are able to differentiate and generate new bone. Muscle is found in close association with orthopaedic injury, however its capacity to make a cellular contribution to bone repair remains ambiguous. We hypothesized that myogenic cells of the MyoD-lineage are able to contribute to bone repair.

METHODS

We employed a MyoD-Cre+:Z/AP+ conditional reporter mouse in which all cells of the MyoD-lineage are permanently labeled with a human alkaline phosphatase (hAP) reporter. We tracked the contribution of MyoD-lineage cells in mouse models of tibial bone healing.

RESULTS

In the absence of musculoskeletal trauma, MyoD-expressing cells are limited to skeletal muscle and the presence of reporter-positive cells in non-muscle tissues is negligible. In a closed tibial fracture model, there was no significant contribution of hAP+ cells to the healing callus. In contrast, open tibial fractures featuring periosteal stripping and muscle fenestration had up to 50% of hAP+ cells detected in the open fracture callus. At early stages of repair, many hAP+ cells exhibited a chondrocyte morphology, with lesser numbers of osteoblast-like hAP+ cells present at the later stages. Serial sections stained for hAP and type II and type I collagen showed that MyoD-lineage cells were surrounded by cartilaginous or bony matrix, suggestive of a functional role in the repair process. To exclude the prospect that osteoprogenitors spontaneously express MyoD during bone repair, we created a metaphyseal drill hole defect in the tibia. No hAP+ staining was observed in this model suggesting that the expression of MyoD is not a normal event for endogenous osteoprogenitors.

CONCLUSIONS

These data document for the first time that muscle cells can play a significant secondary role in bone repair and this knowledge may lead to important translational applications in orthopaedic surgery. Please see related article: http://www.biomedcentral.com/1741-7015/9/136.