Use Of Periosteum Research Articles

Ex Vivo Preservation of Ovine Periosteum Using a Perfusion Bioreactor System.

Periosteum is a highly vascularized membrane lining the surface of bones. It plays essential roles in bone repair following injury and reconstruction following invasive surgeries. To broaden the use of periosteum, including for augmenting in vitro bone engineering and/or in vivo bone repair, we have developed an ex vivo perfusion bioreactor system to maintain the cellular viability and metabolism of surgically resected periosteal flaps. Each specimen was placed in a 3D printed bioreactor connected to a peristaltic pump designed for the optimal flow rates of tissue perfusate. Nutrients and oxygen were perfused via the periosteal arteries to mimic physiological conditions. Biochemical assays and histological staining indicate component cell viability after perfusion for almost 4 weeks. Our work provides the proof-of-concept of ex vivo periosteum perfusion for long-term tissue preservation, paving the way for innovative bone engineering approaches that use autotransplanted periosteum to enhance in vivo bone repair.

Trend of Bioactive Molecules and Biomaterial Coating in Promoting Tendon—Bone Healing

The tendon-bone junction (TBJ) is a graded structure consisting of tendons, nonmineralised, and mineralised fibrocartilage and bone. Given the complex gradient of the TBJ structure, TBJ healing is particularly challenging. Injuries to the TBJ such as anterior cruciate ligament (ACL) tears and rotator cuff injuries are common and serious sports injuries, affecting more than 250,000 patients annually in the United States, particularly people older than 50 years. ACL reconstruction and rotator cuff repair are the commonly performed TBJ repair surgeries. However, the re-tear rate is high post-operation. In recent years, studies on improving TBJ healing have focused on promoting tendon-bone integration at tendon sites. This process includes the use of periosteum, hydrogels, scaffolds, growth factors, stem cells or other reconstruction materials that promote bone growth or ligament attachment. In this study, we will highlight the utilisation of the unique properties of biomaterial coating in promoting tendon-bone healing and discuss recent advances in understanding their role in TBJ healing. Furthermore, we aim to provide a systematic and comprehensive review of approaches to promoting TBJ healing.

Periosteum-induced ossification effect in skull defect through interleukin-8 and NF-κB pathway: An experimental study with Oryctolagus cuniculus rabbits.

Background: The purpose of this study was to analyze the response of inflammatory cytokines interleukin-8 (IL-8) and NF-κB to the closure of skull defect with periosteum as a scaffolding material in bone healing used after surgery.Methods: Thirty Oryctolagus cuniculus rabbits underwent a craniotomy to create a 20 mm diameter round defect in the parietal bones. The parietal bones were returned to its place and stabilized by an internal plate fixation. The defects were either left empty or implanted with periosteum. At 6 weeks, the specimens were euthanized and examined.Results: Histological examination showed a more well-developed formation of woven bone in the periosteum group. Immunohistochemical examinations showed that the use of periosteum in the closure of skull defects reduced the NF-κB and IL-8 response which affected the ossification process.Conclusion: The experiment showed that the use of periosteum was linked with IL-8 and NF-κB downregulation toward ossification effects at any point throughout the trial. Periosteum usage might be beneficial as a scaffolding material in bone healing for autograft cranioplasty in animal model and could be applied to clinical practice.

Advantage of the regenerative potentials of the periosteum especially in children, Oghara experience: A case series

The periosteum is a composite tissue comprising an outer protective fibrovascular layer and an inner cambium regenerative pluripotent layer. The regenerative function of periosteum has been put to clinical use by dental surgeons to manage alveolar ridge reduction and by tissue engineers to produce autologous micrograft and collagen used to manage complex wounds and scars. The essence of this study is to add to the body of knowledge on clinical use of periosteum to treat bone defects from the orthopaedic perspective. We highlight a case series to demonstrate the use of periosteum in managing bone defects caused by benign bone tumour, chronic osteomyelitis, tibial hemimelia and traumatic bone loss of the distal tibia in Delta State University Teaching Hospital, Oghara. Treatment of bone defects by this means is cost effective and the outcome is very satisfactory.
 Key words: Periosteum, mesenchymal stem cells, bone defects, distraction histiogenesis.

Long-term Outcomes of Autologous Chondrocyte Implantation in Adolescent Patients

Background: Treating symptomatic articular cartilage lesions is challenging, especially in adolescent patients, because of longer life expectancies and higher levels of functional activity. For this population, long-term outcomes after autologous chondrocyte implantation (ACI) remain to be determined. Purpose: To evaluate long-term outcomes in adolescents after ACI using survival analyses, validated outcome questionnaires, and standard radiographs. Study Design: Case series; Level of evidence, 4. Methods: We performed a review of prospectively collected data from patients who underwent ACI between 1996 and 2013. We evaluated 27 patients aged <18 years old (29 knees; mean age, 15.9 years) who were treated by a single surgeon for symptomatic, full-thickness articular cartilage lesions over a mean 9.6-year follow-up (median, 13 years; range, 2-19 years). A mean of 1.5 lesions per knee were treated over a mean total surface area of 6.2 cm2 (range, 2.0-23.4 cm2) per knee. Survival analysis was performed using the Kaplan-Meier method, with graft failure as the end point. The modified Cincinnati Knee Rating Scale, Western Ontario and McMaster Universities Osteoarthritis Index, visual analog scale, and Short Form 36 scores were used to evaluate clinical outcomes. Patients also self-reported knee function and satisfaction. Standard radiographs were evaluated using Kellgren-Lawrence grades. Results: Both 5- and 10-year survival rates were 89%. All clinical scores improved significantly postoperatively. A total of 96% of patients rated knee function as better after surgery, and all patients indicated that they would undergo the same surgery again. Approximately 90% rated knee-specific outcomes as good or excellent and were satisfied with the procedure. At last follow-up, 12 of 26 successful knees were radiographically assessed (mean, 5.6 years postoperatively), with no significant osteoarthritis progression. Three knees were considered failures, which were managed by autologous bone grafting or osteochondral autologous transplantation. Twenty knees required subsequent surgical procedures. These were primarily associated with periosteum and were arthroscopically performed. Conclusion: ACI resulted in satisfactory survival rates and significant improvements in function, pain, and mental health for adolescent patients over a long-term follow-up. ACI was associated with very high satisfaction postoperatively, despite the subsequent procedure rate being relatively high primarily because of the use of periosteum. If periosteum is used, this rate should be a consideration when discussing ACI with patients and their parents.

Translating Periosteum's Regenerative Power: Insights From Quantitative Analysis of Tissue Genesis With a Periosteum Substitute Implant.

In the past 2 centuries, the periosteum, a niche for stem cells and super-smart biological material, has been used empirically in surgery to repair tissues as diverse as trachea and bone. In the past 25 years, the number of articles indexed in PubMed for the keywords "periosteum and tissue engineering" and "periosteum and regenerative medicine" has burgeoned. Yet the biggest limitation to the prescriptive use of periosteum is lack of easy access, giving impetus to the development of periosteum substitutes. Recent studies have opened up the possibility to bank periosteal tissues (e.g., from the femoral neck during routine resection for implantation of hip replacements). This study used an interdisciplinary, quantitative approach to assess tissue genesis in modular periosteum substitute implants, with the aim to provide translational strategies for regenerative medicine and tissue engineering.

The character of gene expression of human periosteum used to form new tissue in allograft bone

Of more than 2 million segmental bone defects repaired annually with bone autografts and allografts, 15–40% fail. Improving healing rates may be approached with tissue engineering and use of periosteum overlying an allograft. The present study documents gene expression in human periosteum–allograft constructs compared to allografts alone. Strips of human cadaveric periosteum (26 years, f, distal femur) were sutured about sterilized human femoral cortical strut bone allograft (54 years, m) segments. After construct incubation (M199 supplemented medium) for 8 d, constructs and allografts alone were implanted in nude mice. At 10 and 20 weeks, constructs (N = 4, each group) and allografts (N = 2, each group) were retrieved and placed in RNAlater for quantitative PCR to determine expression of human- and murine-specific genes relevant to remodeling. Specimens were frozen-ground to powders and RNA was extracted, purified, reverse-transcribed, and amplified. Ribosomal protein (P0) was used to normalize sample quantities. Fold change plots were generated following statistical analyses comparing 20- to 10-week gene expression data. Allografts alone yielded no human-specific gene expression. Notable fold changes of human-specific alkaline phosphatase, bone sialoprotein, type I collagen, decorin, RANKL, RANK, cathepsin K, and osteocalcin in 20-week compared to 10-week specimens were found. Murine-specific expression of genes indicative of host mouse vascularization (RANK, type I collagen) was detected in both allograft alone and periosteum–allograft samples. Gene data confirm viable periosteum in constructs after 20 weeks. Relatively higher fold-change values of RANK, RANKL and cathepsin K indicate activities of osteoclast precursors, osteoclasts and osteoblasts involved in allograft remodeling during implantation. All additional genes of interest indicate osteoblast activity in new bone matrix formation. Gene data are directly correlated with previous and present histology work. The results of this study suggest that further investigations could help to establish whether autologous periosteum–allograft constructs could be used for the repair of bone defects.

Periosteum derived stem cells for regenerative medicine proposals: Boosting current knowledge.

Periosteum is a thin fibrous layer that covers most bones. It resides in a dynamic mechanically loaded environment and provides a niche for pluripotent cells and a source for molecular factors that modulate cell behaviour. Elucidating periosteum regenerative potential has become a hot topic in orthopaedics. This review discusses the state of the art of osteochondral tissue engineering rested on periosteum derived progenitor cells (PDPCs) and suggests upcoming research directions. Periosteal cells isolation, characterization and migration in the site of injury, as well as their differentiation, are analysed. Moreover, the role of cell mechanosensing and its contribution to matrix organization, bone microarchitecture and bone stenght is examined. In this regard the role of periostin and its upregulation under mechanical stress in order to preserve PDPC survival and bone tissue integrity is contemplated. The review also summarized the role of the periosteum in the field of dentistry and maxillofacial reconstruction. The involvement of microRNAs in osteoblast differentiation and in endogenous tissue repair is explored as well. Finally the novel concept of a guided bone regeneration based on the use of periosteum itself as a smart material and the realization of constructs able to mimic the extracellular matrix features is talked out. Additionally, since periosteum can differentiate into insulin producing cells it could be a suitable source in allogenic transplantations. That innovative applications would take advantage from investigations aimed to assess PDPC immune privilege.

Periosteal thickness and cellularity in mid‐diaphyseal cross‐sections from human femora and tibiae of aged donors

Due to lack of access in healthy patients, the structural properties underlying the inherent regenerative power and advanced material properties of the human periosteum are not well understood. Periosteum comprises a cellular cambium layer directly apposing the outer surface of bone and an outer fibrous layer encompassed by the surrounding soft tissues. As a first step to elucidating the structural and cellular characteristics of periosteum in human bone, the current study aims to measure cambium and fibrous layer thickness as well as cambium cellularity in human femora and tibiae of aged donors. The major and minor centroidal axes (CA) serve as automated reference points in cross-sections of cadaveric mid-diaphyseal femora and tibiae. Based on the results of this study, within a given individual, the cambium layer of the major CA of the tibia is significantly thicker and more cellular than the respective layer of the femur. These significant intraindividual differences do not translate to significant interindividual differences. Further, mid-diaphyseal periosteal measures including cambium and fibrous layer thickness and cellularity do not correlate significantly with age or body mass. Finally, qualitative observations of periosteum in amputated and contralateral or proximal long bones of the lower extremity show stark changes in layer organization, thickness, and cellularity. In a translational context, these novel data, though inherently limited by availability and accessibility of human mid-diaphyseal periosteum tissue, provide important reference values for the use of periosteum in the context of facilitated healing and regeneration of tissue.

Cost-Effectiveness Analysis of Autologous Chondrocyte Implantation

Background: Autologous chondrocyte implantation (ACI) involves the use of a periosteal patch (ACI-P) as a cover for transplanted chondrocytes. Theoretically, this periosteal patch provides mesenchymal stem cells and growth factors that encourage chondrocyte development/differentiation. However, there is a significant rate of graft hypertrophy with the use of periosteum compared with using a type I/III collagen patch (ACI-C). This type I/III collagen patch, although not approved by the United States Food and Drug Administration for ACI, has been used extensively in Europe and in an “off-label” nature in the United States as a cover during ACI. Purpose: To examine the cost effectiveness of ACI and determine whether ACI-C is more cost effective than ACI-P. Study Design: Economic and decision analysis; Level of evidence, 2. Methods: Outcome data and complication rates from patients undergoing ACI (ACI-P and ACI-C) were derived from the best evidence in the literature. Costs were determined by examining the typical patient charges undergoing ACI at a local orthopaedic hospital. The costs, results, and complication rates were used to develop a decision analysis model comparing ACI-P to ACI-C. Results: The cost of ACI-P was $66,752 and for ACI-C was $66,939.50 ($187.50 difference). The cost per quality-adjusted life year (QALY) for ACI-P was $9466 compared with $9243 for ACI-C. Sensitivity analysis was performed regarding the additional cost of the type I/III collagen patch ($780) in ACI-C as well as the rate of graft hypertrophy after ACI-P (25%). This analysis revealed that the cost of the type I/III collagen patch would have to reach $1721, or the rate of graft hypertrophy after ACI-P reduced to almost 11%, before ACI-P became more cost effective than ACI-C. Conclusion: This cost-effectiveness analysis reveals that, while both ACI-P and ACI-C are cost effective, ACI-C is slightly more cost effective than ACI-P. This is likely secondary to the significant rate of patch-related complications associated with ACI-P, which is significantly reduced with ACI-C. Although the model is very sensitive to differences in outcomes between ACI-P and ACI-C, there is no high-quality evidence to suggest that there is a significant difference between the two. Thus, ACI-P becomes more cost effective if the cost of the type I/III collagen membrane is significantly increased or if the rate of graft hypertrophy after ACI-P were to be markedly reduced.

Comparison of periosteal pedicle graft and subepithelial connective tissue graft for the treatment of gingival recession defects

The use of periosteum as a pedicle graft in the treatment of gingival recession defects is a recent advancement. The subepithelial connective tissue graft (SCTG) is considered the gold standard for the treatment of gingival recession defects. The present randomized controlled trial was done to compare periosteal pedicle graft (PPG) with SCTG for the treatment of gingival recession defects. 10 males and 10 females between the ages of 16 and 40 years (mean age 25.2 years) with Miller's Class I and II recessions ≥3 mm participated in this one-year clinical study. They were assigned randomly to test group (PPG) and control group (SCTG). Results were evaluated based on parameters measuring patient satisfaction and clinical outcomes associated with two treatment procedures. Significance was set at p < 0.05. At the end of the study, the defect coverage was 3.1 ± 0.13 mm or 92.6% in the test group compared to the control group in which the defect coverage was 2.70 ± 0.11 mm or 88.5%. The difference between the two groups was statistically significant (p < 0.0001). The average residual defect was comparable between the two groups, i.e. 0.3 ± 0.67 and 0.5 ± 0.84 in the PPG and SCTG group respectively. The test group was rated higher in terms of overall patient satisfaction (p < 0.02) and comfort during and after the procedure (p < 0.001). PPG and SCTG have comparable clinical effectiveness, but PPG is superior to SCTG in terms of patient-centred outcomes, reflecting improved patient comfort and overall patient satisfaction.

Periosteum: A Highly Underrated Tool in Dentistry

The ultimate goal of any dental treatment is the regeneration of lost tissues and alveolar bone. Under the appropriate culture conditions, periosteal cells secrete extracellular matrix and form a membranous structure. The periosteum can be easily harvested from the patient's own oral cavity, where the resulting donor site wound is invisible. Owing to the above reasons, the periosteum offers a rich cell source for bone tissue engineering; hence, the regenerative potential of periosteum is immense. Although the use of periosteum as a regenerative tool has been extensive in general medical field, the regenerative potential of periosteum is highly underestimated in dentistry; therefore, the present paper reviews the current literature related to the regenerative potential of periosteum and gives an insight to the future use of periosteum in dentistry.

Cartilage Tissue Engineering; Lessons Learned From Periosteum

Cartilage, due to its unique physiology (lack of vasculature), can be potentially repaired using tissue engineered in the laboratory, by combining cells and with a supporting scaffold. This requires a marriage between material science, cell biology, and translational medicine, a concept well established as Tissue Engineering. Over the years the in vivo and in vitro chondrogenic potential of periosteum has been recognised by many researchers and as such periosteum is explored both to repair cartilage defects directly by transplanting periosteum into the cartilage defect or by using periosteum as a cell source for cartilage engineering purposes. The initial example hereof is the first generation of Autologous Chondrocyte Transplantation. Graft hypertrophy and ossification remain the primary drawbacks of cartilage repair strategies using engineered cartilage. These drawbacks may (partially) be due to the endochondral ossification process that can take over when cartilage is repaired. In this process chondrogenesis of progenitor cells is followed by hypertrophy of these cells and subsequent ossification. Periosteal progenitor cells go through this process in order to heal bone fractures. This review provides an overview of the role of periosteum in cartilage repair and cartilage tissue engineering and illustrates how periosteum can be used as a model to study the endochondral process. Such studies may provide clues to further optimize cartilage tissue engineering by identifying important factors which are capable of maintaining cells in their chondrogenic phenotype. Finally, the use of periosteum to engineer cartilage in vivo at an extra-articular site is described.

Malalignment and cartilage lesions in the patellofemoral joint treated with autologous chondrocyte implantation

The aim of our current study is to present the 12.6years' follow-up results in patients with cartilage lesions of the patellofemoral joint, treated with autologous chondrocyte implantation (ACI) with the use of periosteum. Ninety-two patients having patella or trochlea lesion participated in this study. Lysholm and Tegner questionnaires were completed 12.6years (SD 2.3years) after the surgery. The patients were asked whether they feel better, worse or had not experienced any difference compared to previous years and whether they would undergo the operation again. Complications or subsequent surgeries were also assessed. Median Tegner score was three, improved by one level compared with preoperative values (P=0.02). Median Lysholm score was 70, improved by nine points (n.s.). Seventy-two percent of the patients were better or unchanged while 93% would undergo the operation again. Patients with no kissing lesions appeared to have a better prognosis. Patients with malalignment or instability that had undergone a realignment procedure had comparable outcomes to the patients that did not need any additional surgery. Realignment procedures increased the incidence of serious complications but they were associated with decreased incidence of periosteal hypertrophy. No association was found between the age of the patients at the time of the ACI or the size per lesion and any of the clinical outcomes. ACI provides a satisfactory outcome for the treatment of cartilage lesions of the patellofemoral joint, even for the cases with concomitant patellar instability. It seems that correcting the coexisting background factors with realignment, stabilizing or unloading procedures, along with the treatment of cartilage lesions, is improving the clinical outcomes over time and decreases the incidence of periosteal hypertrophies although increasing the incidence of serious complications. Our study reveals the good results and the high level of patients' activities (as shown by Tegner score), were preserved 12.6years after the implantation, in both isolated trochlea and patella lesions and also in multiple and in kissing lesions where an intervention could be considered as a salvage procedure.

Graft healing in anterior cruciate ligament reconstruction

Successful anterior cruciate ligament reconstruction with a tendon graft necessitates solid healing of the tendon graft in the bone tunnel. Improvement of graft healing to bone is crucial for facilitating an early and aggressive rehabilitation and ensuring rapid return to pre-injury levels activity. Tendon graft healing in a bone tunnel requires bone ingrowth into the tendon. Indirect Sharpey fiber formation and direct fibrocartilage fixation confer different anchorage strength and interface properties at the tendon-bone interface. For enhancing tendon graft-to-bone healing, we introduce a strategy that includes the use of periosteum, hydrogel supplemented with periosteal progenitor cells and bone morphogenetic protein-2, and a periosteal progenitor cell sheet. Future studies include the use of cytokines, gene therapy, stem cells, platelet-rich plasma, and mechanical stress for tendon-to-bone healing. These strategies are currently under investigation, and will be applied in the clinical setting in the near future.

Evaluation of Osteogenic Potential of Cultured Periosteum Derived Cells

Periosteum is a source of osteoprogenitor cells and some investigators advocated the effective use of periosteum as a grafting material for the repair of bone and joint defects. In the present study, we showed bone formation induced from cultured periosteum-derived cells (CPDC) in the rat calvarial defect model. Periosteum taken from a rat tibia was immediately placed in culture medium with 10% fetal bovine serum. After confluence, periosteal cells were re-cultured three dimensionally on a collagen sponge for 7 days. Periosteal cell/collagen complex was grafted in calvarial defect of rats. At 30 and 60 days post grafting, grafted tissue was extracted and compared histologically and radiographically with control groups. In the experimental group at 30 days after implantation, new bone formation was seen. Radiographically, mineralized new bone formation was revealed in the defect at 60 days post grafting. New bone formation in periosteal cell/ collagen complex was greater than the other groups. Our results suggest that CPDC may have an important role in bone formation in the calvarial defect in rats.

Biodegradable Elastomeric Polyurethane Membranes as Chondrocyte Carriers for Cartilage Repair

Autologous chondrocyte implantation in combination with an autologous periosteal patch has become a clinically accepted procedure for the treatment of articular cartilage defects. The use of periosteum has, however, several drawbacks. We have been able to fabricate thin elastomeric biodegradable polyurethane (PU) membranes that may possibly have an application as a tissue-engineered substitute for the periosteal patch. Three types of membranes varying in pore size and surface texture were used as substrates for bovine chondrocytes in culture. The membranes, marked as P-I, P-II, and P-R, had average pore sizes of 10 to 20 microm, 40 to 60 microm, and less than 5 microm, respectively. A poly(L/DL-lactide) 80/ 20% micro-porous membrane (PLA) with an average pore size in the range of 10 to 70 microm was used as a control. There was no difference in the cell proliferation profile among the 4 membranes. In terms of proteoglycan and collagen production, P-I, P-R, and PLA performed similarly to one another. The rate of matrix production appears to be greater in the PU membranes than in the PLA membrane in the first 10 days, although by day 30, the PLA membrane had caught up. In all comparisons, the performance of P-II lagged behind those of the other materials. In conclusion, this preliminary study supports the potential use of this novel group of PUs as a periosteal flap substitute or perhaps as a chondrocyte carrier for matrix-assisted chondrocyte implantation and related techniques. Further studies will be necessary to better define their role in clinical applications for cartilage repair.

FGF-2 enhances TGF-β1-induced periosteal chondrogenesis

The use of periosteum as a cell source for the in vitro engineering of grafts for articular cartilage repair requires the development of methods to obtain high viable cell numbers in the early stages of culture. In this study, we demonstrate that the addition of a mitogen, fibroblast growth factor-2 (FGF-2), during the early stage of the in vitro culture of periosteum in the presence of transforming growth factor-β1 (TGF-β1), significantly enhances cell proliferation, which results in increased neo-cartilage formation at later stages. Periosteal explants were cultured in vitro within alginate or agarose based gels in the presence of either FGF-2 for the first week, TGF-β1 for the first 2 weeks, FGF-2 and TGF-β1 for the first week and first 2 weeks respectively, or no added factors. Consistent with previous studies, periosteum derived neo-chondrogenesis occurred only in the presence of TGF-β1. The neo-cartilage was found to contain cartilage specific proteoglycans and Type-II collagen as determined by safranin-O and immunohistochemical staining respectively. Further medium supplementation with FGF-2 stimulated early cell proliferation (>3 fold higher total DNA content per explant at day 10). This resulted in a marked increase in the size of the cultured explants and in the total area of the explant staining positive for safranin-O (from around 50% to 85%, ( p<0.05)) after 6 weeks culture. The ability to generate significant quantities of neo-cartilage within a biocompatible and biodegradable matrix such as alginate, which lacks the immunogenicity of agarose, could open new pathways to utilizing such constructs in articular cartilage tissue engineering applications.

Periosteal flaps and grafts in primary cleft repair: a follow-up study.

A long-term follow-up study of maxillary clefts operated on primarily with the maxillary periosteal flap (67 patients) and the free tibial periosteal graft (23 patients) showed a definite bone bridge in 64 versus 85 percent of the patients. Still, secondary bone grafting was indicated in both in over 70 percent. Lateral crossbite was observed in all and anterior crossbite (mostly dental) was seen in over 80 percent of both groups. There were no statistically significant differences in the cephalometric angular measurements between the groups. Inside the maxillary periosteal flap group the maxillary growth was more retarded in unilateral and especially bilateral complete clefts than in alveolar clefts only. The maxillary growth seemed to be on average better than in primarily bone-grafted materials. The primary use of periosteum had been abandoned in our unit already in 1974, because it did not fulfill the expectations of prevention of maxillary collapse, lesser need for secondary bone grafting, and better midfacial growth.

The use of periosteum and Surgicel for bone restoration in congenital clefts of the maxilla. A clinical report and experimental investigation.

New principles are introduced for the primary repair of the maxilla in congenital cleft deformities, founded on the assumption that periosteum and bone bordering the cleft possesses normal growth potential. By periosteum to periosteum apposition all around the cleft new bone was formed. In complete clefts continuity between the segments was achieved, the premaxilla became firmly consolidated into the arch, maxillary collapse was prevented, and there was a favourable approximation within the alveolar region. Over denuded bone complete periosteal regeneration took place and appositional growth of the lateral segment was promoted.To obtain a larger volume of bone by periostealplasty it proved necessary to keep the flaps suitably separated. In maintaining the periosteal membranes in the desired position Surgicel® provided a useful scaffolding. Animal experiments demonstrated that this hemostatic material can be safely used for subperiosteal implantation. This procedure will lead to the formation of cancellous...