Role of cellular allograft containing mesenchymal stem cells in high-risk foot and ankle reconstructions

Comparing Rates of Fusion and Time to Fusion in Viable Cellular Allograft and Autograft

BACKGROUND

Autograft or allograft frequently are used to enhance bone union in foot and ankle surgery. Viable cellular bone allograft uses viable cells and bone scaffolding in a gel base, but uncertainty remains around allograft's greater efficacy than autograft regarding rates of fusion (ROF) and time to fusion (TTF).

METHODS

Autograft, viable cellular allograft, and viable cellular allograft with autograft were compared in 199 forefoot, midfoot, and hindfoot arthrodeses performed over a 6-year period. Data collected from electronic medical records and radiographs were analyzed to determine ROF and TTF as well as rates of revision surgery for delayed or nonunion and compared among groups.

RESULTS

Eighty-seven patients comprised the autograft group, 81 the allograft group, and 31 the combined group. No significant differences were noted in patient demographics among the groups. No statistically significant differences in ROF were noted among the 3 groups, with 86% (75 of 87) fusion in the autograft group, 93% (75 of 81) in the allograft group, and 84% (26 of 31) in the combined group (P = .20). After conducting a multivariate analysis, we found no statistically significant difference for allograft or combined graft on TTF (P = .1379 and .2311, respectively). No significant difference was found in rate of revision surgery for nonunion, which was 1.2% (1 of 81) in the allograft group, 3.4% (3 of 87) in the autograft group, and 6.5% (2 of 31) in the combined group (P = .3).

CONCLUSION

No significant difference was found in ROF, TTF, or rate of revision surgery when comparing viable cellular allograft to autograft or combined allograft-autograft. Viable cellular allograft may be a reasonable alternative to the gold standard of autograft and should be considered an option in patients undergoing arthrodesis in foot and ankle surgery.

LEVEL OF EVIDENCE

Level III, therapeutic.

A Retrospective Analysis of Outcomes From Foot and Ankle Arthrodesis and Open Reduction and Internal Fixation Using Cellular Bone Allograft Augmentation

BACKGROUND

ViviGen is an allogeneic cellular bone matrix product containing lineage-committed bone cells, and can be used as an alternative to autograft bone or other augments to aid in arthrodesis or to enhance bony healing in open reduction and internal fixation (ORIF) procedures.

METHODS

This study included 153 consecutive patients undergoing ankle, midfoot, or hindfoot arthrodesis or ORIF procedures from January 2017 to October 2018, in which an allogeneic cellular bone matrix product was used to aid in bony healing. Retrospective chart review identified patient demographic factors and medical comorbidities and evaluated clinical and radiographic data to determine fusion/union rate and complications.

RESULTS

The overall fusion rate for the arthrodesis cohort was 97/113 (85.8%). The overall complication rate in this cohort was 22/113 (19.5%). Smokers had significantly lower rates of fusion compared with nonsmokers (P = .01). The observed bony healing rate for the ORIF cohort was 19/22 (86.4%), with a complication rate of 3/22 (13.6%).

CONCLUSION

With satisfactory fusion rates and relatively few complications, our findings suggest that ViviGen is a safe and efficacious alternative to other forms of bone graft augmentation for fusion and ORIF procedures about the foot and ankle. Further study is needed to compare the efficacy of ViviGen with autograft bone and other augments.

LEVELS OF EVIDENCE

Level IV: Case series.

Nonoperative and Operative Soft-Tissue and Cartilage Regeneration and Orthopaedic Biologics of the Foot and Ankle: An Orthoregeneration Network Foundation Review

Orthoregeneration is defined as a solution for orthopaedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electromagnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the foot and ankle (including acute traumatic injuries and fractures, tumor, infection, osteochondral lesions, arthritis, and tendinopathy) and procedures, including osteotomy or fusion. Promising and established treatment modalities include 1) bone-based therapies (such as cancellous or cortical autograft from the iliac crest, proximal tibia, and/or calcaneus, fresh-frozen or freeze-dried cortical or cancellous allograft, including demineralized bone matrix putty or powder combined with growth factors, and synthetic bone graft substitutes, such as calcium sulfate, calcium phosphate, tricalcium phosphate, bioactive glasses (often in combination with bone marrow aspirate), and polymers; proteins such as bone morphogenic proteins; and platelet-derived growth factors; 2) cartilage-based therapies such as debridement, bone marrow stimulation (such as microfracture or drilling), scaffold-based techniques (such as autologous chondrocyte implantation [ACI] and matrix-induced ACI, autologous matrix-induced chondrogenesis, matrix-associated stem cell transplantation, particulated juvenile cartilage allograft transplantation, and minced local cartilage cells mixed with fibrin and platelet rich plasma [PRP]); and 3) blood, cell-based, and injectable therapies such as PRP, platelet-poor plasma biomatrix loaded with mesenchymal stromal cells, concentrated bone marrow aspirate, hyaluronic acid, and stem or stromal cell therapy, including mesenchymal stem cell allografts, and adipose tissue-derived stem cells, and micronized adipose tissue injections. LEVEL OF EVIDENCE: Level V, expert opinion.

Orthobiologics

Use of orthobiologics in sports medicine and musculoskeletal surgery has gained significant interest. However, many of the commercially available and advertised products are lacking in clinical evidence. Widespread use of products before fully understanding their true indications may result in unknown adverse outcomes and may also lead to increased health care costs. As more products become available, it is important to remain judicial in use and to practice evidence-based medicine. Likewise, it is important to continue advances in research in hopes to improve surgical outcomes. This article reviews clinical evidence behind common orthobiologics in the treatment of foot and ankle pathology.

Triple Arthrodesis for Adult-Acquired Flatfoot Deformity

Originally described as a means to address fixed deformities or uncontrolled movement of the hindfoot observed in paralytic foot deformities, triple arthrodesis has evolved into a powerful procedure for the correction of a variety of foot deformities. Over the past decade, multiple advances have been made with respect to diagnostic imaging, fixation options, bone graft substitutes, and postoperative regimens. While this operation requires experience and skill to execute, when properly performed, it allows for correction of deformity and a plantigrade and ideally pain-free foot for ambulation. The purpose of this review is to highlight advances in the procedure and its application to the rigid planovalgus foot.

Level of Evidence:

Level V, review.

Stem and progenitor cell microenvironment for bone regeneration and repair

Stem cells reside in their native microenvironment, which provides dynamic physical and chemical cues essential to their survival, proliferation and function. A typical cell-based therapeutic approach requires the mesenchymal stem cells (MSC) to depart their native microenvironment, transplant to in-vivo environment, differentiate toward multiple lineages and participate in bone formation. The long-term survival, function and fate of MSC are dependent on the microenvironment in which they are transplanted. Transplantation of morselized autologous bone, which contains both stem cells and their native microenvironment, results in a good clinical outcome. However, implantation of bone graft substitutes does not provide the complete and dynamic microenvironment for MSC. Current bone graft therapeutics may need to be improved further to provide an optimal engineered MSC microenvironment.

[Stimulation of fracture healing by growth factors and cell-based technologies]

Bone has the special capability to completely regenerate after trauma and to re-establish its original geometry and biomechanical stability corresponding to the pretrauma conditions. Nevertheless, in daily clinical practice impaired fracture healing and nonunions are regular complications as a result of inadequate mechanical stability and/or insufficient biological processes around the fracture region. Since the beginning of the millennium, intensive research on the physiological processes in bone healing as well as the production and clinical administration of growth factors have enabled the possibility to improve the local biological processes during fracture healing by osteoinduction. Although the initial clinical results, particularly of bone morphogenetic proteins, in fracture healing were promising, growth factors did not become established for unrestricted use in the clinical application. Currently, additional growth factors are being investigated with respect to the potential supportive and osteoinductive characteristics for enhancement of fracture healing and possible clinical applications. Furthermore, the development of cell-based technologies is another promising approach to positively stimulate fracture healing. In addition to the gold standard of autologous bone grafting, harvesting of mesenchymal stroma cells by aspiration has gained in importance in recent years. Allogeneic bone cell transplantation procedures and in particular gene therapy are promising new strategies for the treatment of disorders of fracture healing. This review gives an overview of present and future possibilities for modulation of fracture healing by growth factors and cell-based technologies.

Comparison and Use of Allograft Bone Morphogenetic Protein Versus Other Materials in Ankle and Hindfoot Fusions

Bone grafting is a common procedure in foot and ankle surgery. Because autogenous graft use results in comorbidity to the patient, the search has been ongoing for the ideal substitute. A novel processing technique for allograft using bone marrow, which retains many of the growth factors, has shown promise in the spinal data and early reports of foot and ankle surgery. We performed a retrospective, comparative study of patients undergoing hindfoot and ankle arthrodesis, with a total of 68 patients included. Of the 68 patients, 29 (42.65%) received a bone morphogenetic protein allograft and 39 (57.35%) did not. The patient demographics and social and medical history were similar between the 2 groups and both groups had a similar time to union (p = .581). Of the 29 patients in the bone morphogenetic protein allograft group, 3 (10.3%) experienced nonunion and 4 (13.8%) developed a complication. Of the 39 patients undergoing other treatment, 7 (17.9%) experienced nonunion and 14 (35.9%) developed a complication. The difference for nonunion was not statistically significant (p = .5). However, the difference in the overall complication rate was statistically significant (p = .04). We found that this novel bone graft substitute is safe and can be used for foot and ankle arthrodesis.

Living Cryopreserved Bone Allograft as an Adjunct for Hindfoot Arthrodesis

Hindfoot arthrodesis is a frequently performed procedure by foot and ankle surgeons. The relatively high nonunion rate associated with these procedures has led surgeons to use adjunctive bone graft to help augment osseous union. Cellular bone allografts are a specific type of graft that incorporates osteoconductive, osteoinductive, and osteogenic properties while also eliminating the common disadvantages of autografts and traditional allografts. This article discusses the role of cellular bone allografts in hindfoot arthrodesis procedures, a review of current literature, and a comparison of available products.

Principles of Nonunion Management: State of the Art

A substantial proportion of fractures can present with nonunion, and the management of nonunion continues to present a challenge for orthopaedic surgeons. A variety of biological, mechanical, patient, and injury factors can contribute to the occurrence of nonunion, and often the cause of nonunion may be multifactorial. Successful management often requires assessment and treatment of more than one of these factors. This article reviews common factors that may contribute to nonunion including infection, impaired biology, and metabolic disorders. In addition, new and evolving strategies for diagnosing the cause and effectively treating nonunion including the diagnosis of infection, metabolic workup, bone grafting, cell-based therapies, and biological adjuvants are reviewed and discussed.

Commercial Products for Osteochondral Tissue Repair and Regeneration

The osteochondral tissue represents a complex structure composed of four interconnected structures, namely hyaline cartilage, a thin layer of calcified cartilage, subchondral bone, and cancellous bone. Due to the several difficulties associated with its repair and regeneration, researchers have developed several studies aiming to restore the native tissue, some of which had led to tissue-engineered commercial products. In this sense, this chapter discusses the good manufacturing practices, regulatory medical conditions and challenges on clinical translations that should be fulfilled regarding the safety and efficacy of the new commercialized products. Furthermore, we review the current osteochondral products that are currently being marketed and applied in the clinical setting, emphasizing the advantages and difficulties of each one.

Osseous Healing in Foot and Ankle Surgery with Autograft, Allograft, and Other Orthobiologics

In the surgical treatment of foot and ankle abnormality, many problems require bone grafting for successful osseous union. Nonunion, reconstruction, and arthrodesis procedures pose specific challenges due to bony defects secondary to trauma, malunions, or previous surgery. Nonunion in foot and ankle arthrodesis is a significant risk and is well documented in recent literature. This article is a review of the recent literature regarding the use of bone graft and orthobiologics in foot and ankle surgery.

Bone repair with skeletal stem cells: rationale, progress to date and clinical application

Bone marrow (BM) contains stem cells for both hematopoietic and nonhematopoietic lineages. Hematopoietic stem cells enable hematopoiesis to occur in a controlled manner in order to accurately compensate for the loss of short- as well as long-lived mature blood cells. The physiological role of nonhematopoietic BM stem cells, often referred to as multipotential stromal cells or skeletal stem cells (SSCs), is less understood. According to an authoritative current opinion, the main function of SSCs is to give rise to cartilage, bone, marrow fat and hematopoiesis-supportive stroma, in a specific sequence during embryonic and postnatal development. This review outlines recent advances in the understanding of origins and homeostatic functions of SSCs in vivo and highlights current and future SSC-based treatments for skeletal and joint disorders.

Prospective, Multicenter Evaluation of Allogeneic Bone Matrix Containing Viable Osteogenic Cells in Foot and/or Ankle Arthrodesis

BACKGROUND

Cellular bone allograft (CBA) possesses osteogenic, osteoinductive, and osteoconductive elements essential for bone healing. The purpose of this study was to assess the safety and effectiveness of CBA in foot and/or ankle arthrodeses.

METHODS

A prospective, multicenter, open-label clinical trial using CBA was performed. At 6 weeks and at 3, 6, and 12 months, imaging was performed and the subject's pain, function, and quality of life (QOL) status (Visual Analog Scale, American Orthopaedic Foot & Ankle Society Hindfoot Scale, and the Short Form 36) were recorded. The per protocol population consisted of 92 patients at 6 months and 76 patients at 12 months, with 153 and 129 total arthrodeses, respectively.

RESULTS

At 6 months, fusion rates were 68.5% for all patients and 81.1% for all joints; at 12 months, rates were 71.1% and 86.8%, respectively. Certain high-risk subjects (eg, with diabetes or obesity) had fusion rates comparable to those of normal patients. Statistically significant improvements in pain, function, and QOL were observed, and fusion correlated with both function and QOL outcomes at 6 and 12 months. There were no adverse events attributable to CBA.

CONCLUSION

Fusion rates using CBA were higher than or comparable to fusion rates with autograft that have been reported in the recent literature, and CBA fusion rates were not adversely affected by several high-risk patient factors. CBA was a safe and effective graft material to achieve fusion in patients with compromised bone healing and may provide an effective autograft replacement for foot and/or ankle arthrodeses.

LEVEL OF EVIDENCE

Level II, prospective study.

Effect of Osteogenic Progenitor Cell Concentration on the Incidence of Foot and Ankle Fusion

The use of biologics, namely demineralized bone matrix, bone marrow aspirate (BMA), and other growth factors, has gained popularity in foot and ankle surgery for use in compromised hosts or high-risk situations. Our research has shown the concentration of these pluripotent cells was greatest in the iliac crest. A medical record and radiographic review was performed to compare the effect of BMA harvest site osteogenic progenitor cells on the incidence of fusion. Radiographs were reviewed for radiographic evidence of trabecular bridging in 2 or more views. If fusion occurred, the number of osteogenic progenitor cells found in the combined BMA at surgery was recorded. A total of 33 patients were included in the present study. Of the 33 patients, 32 (97.0%) had radiographic fusion at a mean of 13 ± 6 (range 8 to 30) weeks, and 1 (3.0%) experienced nonunion and required revision. The patient procedures were as follows: 18 (54.5%) hindfoot arthrodeses, 8 (24.2%) forefoot arthrodeses, 4 (12.1%) fractures, and 3 (9.1%) isolated ankle fusions. The mean colony-forming units for the patients with fusion was 20.3 ± 23.5 (range 0.0 to 107.0). In the patient with nonunion, it was 0.20 colony-forming unit. Our comparison of the incidence of fusion with the use of osteogenic progenitor cells from 3 anatomic sites showed a low incidence of complications and a high incidence of fusion. No association was found between the BMA concentration and the incidence of fusion, suggesting a minimum concentration and biologic potential of pluripotent cells is necessary to achieve the clinical effect of fusion.

Osteocel Plus cellular allograft in anterior cervical discectomy and fusion: evaluation of clinical and radiographic outcomes from a prospective multicenter study

STUDY DESIGN

Prospective, multicenter, nonrandomized, institutional review board-approved clinical and radiographic study.

OBJECTIVE

To evaluate and summarize the 2-year outcomes of patients treated with Osteocel Plus cellular allograft as part of an anterior cervical discectomy and fusion procedure.

SUMMARY OF BACKGROUND DATA

Osteocel Plus is an allograft cellular bone matrix containing native mesenchymal stem cells and osteoprogenitor cells that is intended to mimic the performance of iliac crest autograft without the morbidity associated with its harvest.

METHODS

A total of 182 patients were treated with anterior cervical discectomy and fusion using Osteocel Plus in a polyetheretherketone cage and anterior plating at 1 or 2 consecutive levels. Clinical outcomes included visual analogue scale for neck and arm pain, neck disability index, and SF-12 physical and mental component scores. Computed tomography and plain film radiographic measures included assessment of bridging bone, disc height, disc angle, and segmental range of motion.

RESULTS

A total of 249 levels were treated in 182 patients. Mean procedure time was 100 minutes, blood loss was less than 50 mL in 93% of patients, and hospital stay was 1 day or less in 84% of patients. Significant (P<0.05) average improvements in clinical outcomes from preoperatively to 24 months included the following: neck disability index: 21.5%; visual analogue scale neck: 34 mm; visual analogue scale arm: 35 mm; SF-12 physical component score: 11.2; SF-12 mental component score: 6.8. At 24 months, 93% of patients were satisfied with their outcome. In patients treated at a single level with a minimum of 24-month follow-up, 92% (79/86) of levels achieved solid bridging and 95% of levels demonstrated range of motion of less than 3°. In combined single- and 2-level procedures, 87% (157/180) of levels achieved solid bridging and 92% (148/161) had range of motion of less than 3° at 24 months. No patient required revision for pseudarthrosis.

CONCLUSION

Improvements in clinical results at 2 years, high patient satisfaction, and high radiographic and clinical fusion rates provide confidence in Osteocel Plus as an effective alternative to structural allograft or autograft in anterior cervical discectomy and fusion procedures.

LEVEL OF EVIDENCE

4.

Stem cells: innovations in clinical applications

The use of mesenchymal stem cells (MSCs) as clinical therapeutics is a relatively new avenue of study for treatment of a variety of diseases. The therapeutic impact of the MSCs is based upon their multiplicities of function and interaction with host tissues. MSCs can be anti-inflammatory, antifibrotic, antimicrobial, and regenerative, all which may improve outcomes in scenarios of damaged tissues and inflammation. Although most studies focus on utilizing MSCs to direct clinical efficacy, it is the ability to orchestrate host response in surrounding tissue that is especially unique and versatile. This orchestration of host response can be applied to a variety of clinical scenarios not only through cell-cell interactions but also through production of bioactive secreted factors. These bioactive factors include small proteins, chemokines, cytokines, and other cellular regulators. These factors have the capacity to induce angiogenesis or blood vessel development, be chemotactic, and induce cellular recruitment. MSCs also have the capacity to differentiate with the implicated environment to regenerate tissue or accommodate host tissue in a cell specific manner. The differentiation cannot only be done in vivo but also can be optimized in vitro prior to in vivo administration, potentiating the versatility of the MSCs and opening avenues for corrective therapy and cell delivery of genes. The differentiation process depends on the environment with which the MSCs are put and results in active communication between the newly administered cells host tissue. Since these properties have been identified, there are a variety of clinical trials and studies being conducted on MSCs ability to treat human disease. This review outlines the potential use of MSCs, the types of tissue, and the innovative applications of MSCs for the treatment of diseases.

Multipotential stromal cell abundance in cellular bone allograft: comparison with fresh age-matched iliac crest bone and bone marrow aspirate

AIM

To enumerate and characterize multipotential stromal cells (MSCs) in a cellular bone allograft and compare with fresh age-matched iliac crest bone and bone marrow (BM) aspirate.

MATERIALS & METHODS

MSC characterization used functional assays, confocal/scanning electron microscopy and whole-genome microarrays. Resident MSCs were enumerated by flow cytometry following enzymatic extraction.

RESULTS

Allograft material contained live osteocytes and proliferative bone-lining cells defined as MSCs by phenotypic and functional capacities. Without cultivation/expansion, the allograft displayed an 'osteoinductive' molecular signature and the presence of CD45(-)CD271(+)CD73(+)CD90(+)CD105(+) MSCs; with a purity over 100-fold that of iliac crest bone. In comparison with BM, MSC numbers enzymatically released from 1 g of cellular allograft were equivalent to approximately 45 ml of BM aspirate.

CONCLUSION

Cellular allograft bone represents a unique nonimmune material rich in MSCs and osteocytes. This osteoinductive graft represents an attractive alternative to autograft bone or composite/synthetic grafts in orthopedics and broader regenerative medicine settings.