Growth potential in onlay bone grafts: a comparison of vascularized and free calvarial bone and suture bone grafts

Vascularized bone grafts are characterized by a viable cell population with osteogenic potential. These features suggest that continued growth can be anticipated following vascularized membranous bone transfer in a growing craniofacial skeleton. The present paper compares the potential for appositional bone growth in vascularized and free calvarial onlay bone grafts. In seven 8-week-old beagles, growth was assessed by direct caliper measurements of graft dimensions intraoperatively and 16 weeks postoperatively. Vascularized grafts demonstrated a 50 to 60 percent increase in size in all dimensions compared to 10 to 20 percent growth in free grafts (p less than 0.01). Microradiography revealed preservation of calvarial bony architecture and minimal resorption in vascularized grafts, while triple-fluorochrome labeling confirmed subperiosteal appositional bone formation. Free grafts were characterized by significant resorption and a delay in subperiosteal bone formation.     

Secondary correction of the unilateral cleft lip nose using a conchal composite graft

The secondary deformity of the unilateral cleft lip nose has many components. One is the dorsal dislocation of the lateral crus of the alar cartilage. We used a conchal composite graft positioned between the piriform aperture and the lateral crus and the upper lateral cartilage to correct this dislocation in nine patients. We believe that this graft is effective because it elevates the lateral crus of the alar cartilage off the depressed piriform aperture. This technique is very simple to perform, and it is easy to achieve nasal symmetry. Our results have been quite satisfactory, with no recurrence of dorsal dislocation. The donor site was covered by a subcutaneous pedicled flap from the cephaloauricular sulcus, leaving an inconspicuous deformity.     

Cell fate specification during calvarial bone and suture development

In this study we have addressed the fundamental question of what cellular mechanisms control the growth of the calvarial bones and conversely, what is the fate of the sutural mesenchymal cells when calvarial bones approximate to form a suture. There is evidence that the size of the osteoprogenitor cell population determines the rate of calvarial bone growth. In calvarial cultures we reduced osteoprogenitor cell proliferation; however, we did not observe a reduction in the growth of parietal bone to the same degree. This discrepancy prompted us to study whether suture mesenchymal cells participate in the growth of the parietal bones. We found that mesenchymal cells adjacent to the osteogenic fronts of the parietal bones could differentiate towards the osteoblastic lineage and could become incorporated into the growing bone. Conversely, mid-suture mesenchymal cells did not become incorporated into the bone and remained undifferentiated. Thus mesenchymal cells have different fate depending on their position within the suture. In this study we show that continued proliferation of osteoprogenitors in the osteogenic fronts is the main mechanism for calvarial bone growth, but importantly, we show that suture mesenchyme cells can contribute to calvarial bone growth. These findings help us understand the mechanisms of intramembranous ossification in general, which occurs not only during cranial and facial bone development but also in the surface periosteum of most bones during modeling and remodeling.     

Integration of FGF and TWIST in calvarial bone and suture development

Mutations in the FGFR1-FGFR3 and TWIST genes are known to cause craniosynostosis, the former by constitutive activation and the latter by haploinsufficiency. Although clinically achieving the same end result, the premature fusion of the calvarial bones, it is not known whether these genes lie in the same or independent pathways during calvarial bone development and later in suture closure. We have previously shown that Fgfr2c is expressed at the osteogenic fronts of the developing calvarial bones and that, when FGF is applied via beads to the osteogenic fronts, suture closure is accelerated (Kim, H.-J., Rice, D. P. C., Kettunen, P. J. and Thesleff, I. (1998) Development 125, 1241-1251). In order to investigate further the role of FGF signalling during mouse calvarial bone and suture development, we have performed detailed expression analysis of the splicing variants of Fgfr1-Fgfr3 and Fgfr4, as well as their potential ligand Fgf2. The IIIc splice variants of Fgfr1-Fgfr3 as well as the IIIb variant of Fgfr2 being expressed by differentiating osteoblasts at the osteogenic fronts (E15). In comparison to Fgf9, Fgf2 showed a more restricted expression pattern being primarily expressed in the sutural mesenchyme between the osteogenic fronts. We also carried out a detailed expression analysis of the helix-loop-helix factors (HLH) Twist and Id1 during calvaria and suture development (E10-P6). Twist and Id1 were expressed by early preosteoblasts, in patterns that overlapped those of the FGF ligands, but as these cells differentiated their expression dramatically decreased. Signalling pathways were further studied in vitro, in E15 mouse calvarial explants. Beads soaked in FGF2 induced Twist and inhibited Bsp, a marker of functioning osteoblasts. Meanwhile, BMP2 upregulated Id1. Id1 is a dominant negative HLH thought to inhibit basic HLH such as Twist. In Drosophila, the FGF receptor FR1 is known to be downstream of Twist. We demonstrated that in Twist(+/)(-) mice, FGFR2 protein expression was altered. We propose a model of osteoblast differentiation integrating Twist and FGF in the same pathway, in which FGF acts both at early and late stages. Disruption of this pathway may lead to craniosynostosis.     

Fixation effects on membranous and endochondral onlay bone graft revascularization and bone deposition.

This paper investigates the relationship between bone resorption, the process of bone revascularization, and graft fixation. Vital staining techniques and microangiography were used to study the extent of graft revascularization of fixed and nonfixed endochondral (rib) and membranous (skull) onlay bone grafts in 20 adult sheep mandibles bilaterally. This assessment was carried out at 2 and 20 weeks postoperatively. Sequential fluorochrome staining was performed to examine the pattern of new bone deposition. Fixation was achieved using the lagscrew technique. At 2 weeks, membranous bone demonstrated a greater area of graft revascularization if fixed than if the graft was not fixed. The opposite result was seen for endochondral grafts, where nonfixed grafts showed a greater area of revascularization than fixed grafts. At 20 weeks, all bone that was present was fully vascularized. The inconsistencies in the results on the relationship between fixation and revascularization for membranous and endochondral grafts in the early stages of healing (2 weeks) suggest that although revascularization is a necessary precondition for bone resorption and deposition, biomechanical and structural factors may be a more satisfactory explanation for the differences observed in the maintenance of bony volume.     

The free tongue graft for correction of secondary deformities of the vermilion in patients with cleft lip

From January of 1985 to January of 1990, 31 patients with repaired cleft lip and secondary vermilion defects underwent 45 revisional procedures. A free tongue graft was utilized seven times in six patients (19 percent). Indications for its use were a V-shaped vermilion deficit or a "whistling" deformity associated with a sagittal vermilion deficiency and normal or insufficient lateral vermilion bulk. Of the seven free tongue grafts, none was lost. Three patients have required revisions, including repeat free tongue graft in one. Proper positioning of the graft along the free vermilion border has made color and texture match satisfactory. The free tongue graft is a simple and reliable means of transferring both vermilion bulk and surface mucosa. Introduction of the free tongue graft has eliminated the need for more cumbersome procedures, such as the Abbé flap or the tongue flap, in properly selected patients.     

Growth potential in suture bone inlay grafts: a comparison of vascularized and free calvarial bone grafts

The present study investigates transsutural growth in vascularized and free calvarial bone grafts and notes the effects of such growth on craniofacial development. The temporalis myoosseous flap served as a model of vascularized graft. In ten 8-week-old dogs, a standardized skeletal defect, including a segment of the zygomatico-maxillary suture, was created. The defect was reconstructed with a vascularized graft in half the animals and a corresponding free graft in the remaining animals. Growth was assessed by means of serial cephalometric radiography and direct osteometry. Vascularized bone grafts demonstrated persistent transsutural growth following transplantation. Growth at the recipient site was preserved, resulting in less restriction of vertical maxillary development.     

Primary repair of the unilateral cleft lip nose in the Oriental: a 20-year follow-up

The unilateral cleft lip nasal deformity is corrected as a primary procedure with the lip repair. The abnormal attachment of the alar base is first released by an incision along the superior buccal sulcus and piriform margin. There is no intercartilaginous incision. Basically, we use the Brown-McDowell technique with the addition of an alar rim incision. Undermining of the ala between the two incisions is carefully and adequately done, splitting it into two layers. The first is a skin and the second, a chondrocutaneous (vestibular skin) layer, which is handled as a single unit, thus enhancing its vascularity. This second layer is a bipedicle flap with a broad medial pedicle and a narrow lateral pedicle at the alar base. When the alar base is rolled into its normal position, the chondrocutaneous unit hinging on its two pedicles counterrotates, correcting the subluxation of the ala, a major component of the cleft lip nasal deformity. We depend on the normal position of the alar base, the postoperative scar tissue, and the inherently thick nostril wall in the Oriental to keep the alar dome up. No transfixion sutures are used. Ten consecutive patients are shown 20 years after surgery. All had one operation only. None showed any disturbance of nasal growth.     

Cleft lip with and without cleft palate in blacks: an analysis of 81 patients

The clinical records of 81 black patients with cleft lip with or without cleft palate were reviewed. Four had midline clefts. Of the remaining 77, 45 were unilateral (left 28, right 17), with 11 of these involving only the primary palate. Bilateral clefts were seen in 32, with only 2 involving just the primary palate. Males and females were approximately equal in number. Two were associated with EEC syndrome. Other congenital anomalies were seen in 9 patients. The family history was positive for clefts in 5 of 65 patients (7.7 percent). A review of 255 white patients with cleft lip with or without cleft palate revealed a positive family history in 94 (37 percent). The difference was statistically significant.     

Lengthening of the postoperative short nose: combined use of a gull-wing concha composite graft and a rib costochondral dorsal onlay graft

Several causes of short nose are known: congenital anomaly, developmental problem, trauma, and various types of rhinoplasty-the postoperative short nose being one of the most difficult problems to correct in plastic surgery. Contracted skin envelope, tissue deficiency of cartilage and mucosal lining, and poor circulation make postoperative short nose difficult to lengthen and susceptible to recurrence. Thus, for effective lengthening and long-term maintenance of it, specific grafts should be used to supplement the missing lining and cartilage and a mechanical support also is needed to withstand the skin contraction. The nose consists of three structural layers: the outer skin envelope, middle osteocartilaginous framework, and inner mucosal lining. Many methods have been proposed to correct short nose deformity. Those procedures lengthen the nose slightly, but none of them take into account the unique characteristics of postoperative causes and the structural concept of the nose. The procedures have resulted in only limited success. On the basis of the above clinical findings and the structural concept, we developed a surgical technique to correct postoperative short nose according to the structural layers. Our method consists of three main surgical maneuvers: (1) a gull-wing concha chondrocutaneous composite graft to supplement the deficient middle and inner layers, (2) a rib costochondral onlay graft on the dorsum to reinforce the framework, and (3) wide dissection of the outer skin envelope to cover the lengthened framework without tension. We prefer a closed surgical approach rather than an open approach to avoid too much tension on the columellar incision site and to allay patients' fear of an additional scar. From 1988 to 1998, we performed our lengthening technique on six female patients. All six patients demonstrated a significant lengthening and improved appearance postoperatively. After the lengthening procedure, the average nasolabial angle improved from 116 degrees to 104 degrees. The mean follow-up period was 8.7 months, with a range of 3 to 17 months. Sometimes, epidermal sloughing in the vertical strut of the gull-wing     

Reconstruction of the maxilla with a double musculoperiosteal flap in connection with a composite calvarial bone graft

A new technique is shown for a one-stage reconstruction of the mucosa of the floors of the nose and maxillary sinus, the bone structures of the maxilla and the hard palate, as well as the mucosal layers of the hard and soft palates and vestibulum. To accomplish this coverage, a vascularized calvarial bone graft with temporal muscle from one side is combined with a vascularized temporal muscle flap from the other side to achieve a three-layer "sandwich" plasty. The advantage of this procedure is reconstruction of the complete maxillary defect with the possibility of denture rehabilitation and the avoidance of oronasal fenestration. Besides the possible complication of insufficient vascularization of the bone and muscle grafts, the donor defect in the calvarial bone and the missing muscle for mastication are to be considered.