[Distraction osteogenesis in the treatment of facial and mandibular deformities]

<Zakljucak> Prikazani protokoli lecenja i kriterijumi uspesnosti svakako ce zahtevati dalje izmene i dopune, ali se mogu koristiti u buducim klinickim studijama u cilju obezbedjivanja objektivnih podataka. Buduci pravci razvoja kraniofacijalne OD ukljucuju: uticaj faktora rasta na OD, uticaj OD na kraniofacijalni skelet u procesu rasta, usavrsavanje tehnike osteotomije putem endoskopije, razvoj minijaturnih multidirekcionih distrakcionih uredjaja koji omogucavaju interceptivnu OD i modifikaciju i usavrsavanje protokola lecenja putem kraniofacijalne OD.

Bite force and occlusal contact area changes following mandibular widening using distraction osteogenesis

OBJECTIVE

To examine changes in bite force and occlusal contact area after mandibular widening by distraction osteogenesis using pressure-sensitive sheet (Dental-Prescale; Fuji Photo Film, Tokyo, Japan).

STUDY DESIGN

Fifteen patients with transverse mandibular deficiency (6 to 9 mm, mean distraction interval: 8 mm) were examined. They were measured just before the operation and at 1 week, 1 month, 3 months, 6 months, and 1 year after the operation. Ten control subjects with normal occlusion were also measured.

RESULTS

Both bite force and occlusal contact area were lowest at 1 month postoperatively. The values of bite force and occlusal contact area steadily increased thereafter. The bite force and occlusal contact area reached to the preoperative levels at 6 months after operation and slightly above the preoperative level at 12 months after operation. There were no statistically significant differences between 12 months and the control values for bite force measurements (P > .05).

CONCLUSION

Although statistically not significant, this study suggests that mandibular symphyseal distraction osteogenesis increases the bite force and occlusal contact area in patients with transverse mandibular deficiency.

Low-intensity pulsed ultrasound for bone healing: an overview

Low-intensity ultrasound is a biophysical form of intervention in the fracture-repair process, which through several mechanisms accelerates healing of fresh fractures and enhances callus formation in delayed unions and nonunions. The goal of this review is to present the current knowledge obtained from basic science and animal studies, as well as existing evidence from clinical trials and case series with the different applications of ultrasound in the management of fractures, delayed unions, nonunions and distraction osteogenesis. Low-intensity pulsed ultrasound is currently applied transcutaneously, although recent experimental studies have proven the efficacy of a trans-osseous application for both enhancement and monitoring of the bone healing process with modern smart implant technologies.

Distraction Osteogenesis in Irradiated Rabbit Mandibles With Adjunctive Hyperbaric Oxygen Therapy

PURPOSE

The purpose of this study was to evaluate the effect of hyperbaric oxygen therapy on bone regeneration during distraction of irradiated rabbit mandibles.

MATERIALS AND METHODS

Twenty New Zealand white rabbits were randomly sub-divided into 4 groups. Group 1 served as control, group 2 received preoperative radiation therapy, group 3 received pre- and postoperative hyperbaric oxygen (HBO) therapy, and group 4 received preoperative radiation therapy and pre- and postoperative HBO therapy. All rabbits underwent a corticotomy of the left body of the mandible after placement of a distraction device. Distraction, at a rate of 1 mm/day and a rhythm of 1 turn/day, began after a 3-day latency period for 14 days. Thirty days after completion of the distraction protocol, the animals were euthanized, and histomorphometric and radiographic data of the distraction segments were obtained.

RESULTS

Histomorphometric analysis of new bone fill was greatest in the non-irradiated groups compared to groups receiving radiation therapy, regardless of HBO therapy (P = .03). Pre-corticotomy bone density measurements showed a significant increase in bone density over time (P = .0007). This resulted in a significant relationship between HBO therapy, radiation therapy, and time (P = .0050).

CONCLUSIONS

The results of the study support the use of HBO therapy during distraction osteogenesis. Any additional therapeutic benefit of HBO therapy in irradiated bone would require additional investigation.

Axial shortening during distraction osteogenesis leads to enhanced bone formation in a rabbit model through the HIF-1alpha/vascular endothelial growth factor system

Axial micromotion of bone fragments enhances callus formation during fracture repair or limb lengthening. To examine this, we used an axial-shortening model of the tibial callus in rabbits and performed histological analyses. After 10-mm lengthening of the left tibia with an external fixator, we shortened the callus by 2 mm. Radiographs and quantitative evaluation of corrected bone mineral density showed a significant increase in mineralization in the shortened callus (57.3 vs. 36.2%, p = 0.001). Histologically, greater osteoblast proliferation and more vigorous trabecular bone formation were noted in the shortened calluses than in the controls. Around the front of membranous bone formation in the shortened callus, there was a significant decrease in mean percentage area of vascular lumens (1.8 vs. 4.5%, p = 0.009), which seemed attributable to compressive force, and a significantly increased production of vascular endothelial growth factor (VEGF; 422.5 vs. 142.7 pg/mg protein, p = 0.007) and its receptors. There were also increased numbers of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and proliferating cell nuclear antigen (PCNA)-positive cells. A marked increase of hypoxia inducible factor-1alpha (HIF-1alpha) expression in osteoblasts was also observed in this area. Thus, enhancement of membranous bone formation by static compression or axial dynamization may be at least partly attributable to HIF-1alpha-mediated VEGF induction following the local hypoxia caused by collapse of vascular lumens.

[Effects of mesenchymal stem cells transplantation on cranial suture distraction osteogenesis in growing goats]

OBJECTIVE

To observe the effects of mesenchymal stem cells (MSCs)on cranial suture under mechanical strain in growing goats.

METHODS

10 growing goats were used in this study. A customized distractor was used for distraction of the coronal suture at a rate of 0.4 mm/day for 8 days. The experimental group(5 goats) was injected with autologous MSCs into the distracted region, whereas the control group (5 goats) with injection of physiological saline. All animals were killed at 4 weeks after the end of distraction. Scanning electron microscopy and histological analysis were taken to observe the samples.

RESULTS

4 weeks after the end of distraction, the cranial sutures in all animals were separated successfully. The new bone formation at the edge of suture in the experimental group was superior to that in the control group.

CONCLUSION

Autologous MSCs transplantation may promote the cranial suture distraction osteogenesis in the growing goats.

Relief of Upper Airway Obstruction With Mandibular Distraction Surgery

OBJECTIVE

To evaluate the long-term benefits of mandibular distraction on sleep-related upper airway obstruction in young children with mandibular hypoplasia.

DESIGN

Cross-sectional study. Subjects were examined for sleep-disordered breathing using medical history, physical examination results, and a written questionnaire. Subjects underwent standard overnight polysomnography, during which measures of sleep-disordered breathing were collected.

SETTING

Tertiary care hospital.

PATIENTS

Five children with upper airway obstruction from craniofacial anomalies treated with mandibular distraction, with a minimum follow-up of 12 months.

MAIN OUTCOME MEASURES

Apnea-hypopnea index, oxygen saturation nadir, and peak end-tidal carbon dioxide value.

RESULTS

Of the 5 children, 3 were cured of upper airway obstruction as documented by polysomnography, with an apnea-hypopnea index of less than 1.5 and no snoring. The fourth child had primary snoring without apnea. The fifth child had severe obstructive sleep apnea, with an apnea-hypopnea index of 20.2.

CONCLUSIONS

Most children who undergo mandibular distraction for upper airway obstruction associated with mandibular hypoplasia demonstrate significant clinical improvement of obstructive sleep apnea. However, those children who continue to have symptoms of sleep-disordered breathing after surgery should undergo polysomnography for evaluation of persistent obstructive sleep apnea.

Effects of calcitonin and alendronate on distraction osteogenesis

In this experimental animal study the effects of calcitonin and alendronate on distraction osteogenesis are investigated. Forty-five mature female New Zealand type rabbits were used. Rabbits were randomized into three groups, each consisting of 15 animals. Under optimal operating conditions a pre-reconstructed circular external fixator was applied to the right tibia of rabbits, and osteotomy was performed with a Gigli saw just below the tibial tuberosity. During the ten days of distraction, a placebo was administered for group I (control group), group II received 10 U of calcitonin, and group III was treated with alendronate (0.5 mg/kg/day) gavages. Rabbits were examined histologically (at the third and eighth weeks, according to Huddlestone et al.), radiologically (at the third, sixth, and eighth weeks, according to Lane and Sandhu), and mechanically (at the eighth week, as torsional loading). During the first three weeks, the groups did not differ much with regard to radiological parameters. However, in the calcitonin and alendronate groups improved histological scores were detected compared with the control group. Radiological images obtained at the end of six weeks demonstrated improved consolidation in the calcitonin and alendronate groups compared with the control group. At the end of eight weeks postoperatively, radiological and histological parameters did not differ among the groups, while torsional failure load was found to be much improved in the calcitonin group (p=0.006). During the distraction osteogenesis period, calcitonin and alendronate affected the quality of regenerate favourably. This effect is sustained until the end of the consolidation period. However, this finding needs to be supported by experimental and human studies.

Distraction Osteogenesis in a Patient with Juvenile Arthritis

We present a 26-year-old patient with juvenile-onset arthritis, Alagille's syndrome, micrognathia, and progressive sleep apnea. Despite the presence of significant temporomandibular joint pathology, mandibular distraction was indicated to correct life-threatening sleep apnea. Before distraction, the patient had only 10 mm of maximal interincisal opening and bilateral temporomandibular joint symptomatology. After distraction, the patient's sleep apnea resolved. There was slight improvement in her maximal incisal opening (12 mm) with neither exacerbation nor improvement of her temporomandibular joint symptomatology.

Long term results of mandibular distraction

Mandibular distraction osteogenesis has become a popular surgical modality due to its many advantages over conventional orthognathic surgical procedures. However, in spite of the technique having been used for over 15 years, no concrete long term results are available regarding the stability of results. We discuss the various studies which have reported either in favour or against the stablility of results after distraction. We report a series of 6 cases (3 unilateral and 3 bilateral distraction) where distraction was carried out before puberty and followed them up to seven years after removal of distractors. This case series shows that results achieved by distraction osteogenesis are unstable or best unpredictable with respect to producing a permanent size increase in the mandible. The role of the distraction osteogenesis in overcoming the pterygomassetric sling is questionable. We suggest a multicenter study with adequate patient numbers treated with a similar protocol and documented after growth cessation to have meaningful conclusions on the debate of distraction osteogenesis versus orthognathic surgery.

Distraction osteogenesis versus autogenous onlay grafting. Part II: biology of regenerate and onlay bone

PURPOSE

Few studies have directly compared the quality of bone generated by distraction osteogenesis with that generated by autogenous onlay grafting. The purpose of this study was to compare rates of bone turnover at 5 months in bone produced by distraction osteogenesis and onlay grafting.

MATERIALS AND METHODS

Alveolar defects created in jaws of American foxhounds were augmented with distraction osteogenesis or onlay grafting and allowed to heal for 5 months. The animals were then sacrificed and the jaws were resected and prepared for decalcified and undecalcified histologic examination.

RESULTS

Both procedures produced bone containing a mixture of haversian systems and trabecular bone. A significantly greater ratio of osteoblast-covered bone surface to total trabecular bone surface (mean +/- SEM) was noted in distraction bone (0.124 +/- 0.049) compared to onlay bone (0.081 +/- 0.048) or control host bone (0.085 +/- 0.042 microm) (P < .05). In addition, significantly (P <.05) greater numbers of osteoclasts per microm of bone surface were noted in distraction bone (0.939 +/- 0.07) compared to onlay bone (0.605 +/- 0.06) or control host bone (0.725 +/- 0.08). No differences in rates of mineralization were noted between the groups.

DISCUSSION

While bone from both experimental groups appeared adequate for implant placement, distraction bone appeared to be remodeling at a higher rate than either onlay or control bone.

CONCLUSION

Given that the state of healing of the bone in each of these comparative groups was examined at a static point in time, it is premature to draw conclusions about the efficacy of one procedure over the other.

Posttraumatic thumb reconstruction

LEARNING OBJECTIVES

After reading this article, the reader should be able to: 1. Discuss the critical anatomic features of the thumb as they affect on reconstructive decision making. 2. Define the goals of reconstruction. 3. Discuss an algorithm for thumb reconstruction according to the level of amputation. 4. Understand the role of prosthetics in thumb reconstruction.

BACKGROUND

The function of the thumb is critical to overall hand function. Uniquely endowed with anatomic features that allow circumduction and opposition, the thumb enables activities of pinch, grasp, and fine manipulation that are essential in daily life. Destruction of the thumb secondary to trauma represents a much more significant loss than would result from loss of any other digit. Therefore, significant effort has been focused on thumb reconstruction. Numerous techniques have been described, ranging from simple osteoplastic techniques to complex microsurgical procedures. With an appreciation of the unique anatomic properties of the thumb, the hand surgeon is better able to understand the goals of thumb reconstruction and to develop an algorithm for thumb reconstruction. With such an understanding, an individualized reconstructive plan can be developed for each patient.

METHODS

A great many options are available for posttraumatic thumb reconstruction. Optimal results are obtained by pursuing an organized and logical approach to reconstruction based upon the level of tissue loss. Reconstruction methods depend on the location of the amputation and range from homodigital and heterodigital flaps to partial-toe transfer or a great-toe wrap-around flap to first-web-space deepening using Z-plasties, a dorsal rotation flap, or a distant flap, to distraction osteogenesis, lengthening of the thumb ray, spare parts from another injured digit in the acute setting for pollicization or heterotopic replantation, and microvascular toe transfer.

RESULTS

Amputations in the distal third of the thumb are generally well-tolerated. The primary reconstructive issues are the restoration of a padded and sensate soft-tissue cover, as well as aesthetic considerations. First-web-space deepening will generally provide excellent results for amputations at the distal half of the middle third. In the proximal half of the middle third, lengthening of the thumb ray is generally required. Distraction lengthening of the first metacarpal is a useful and reliable technique that provides up to 3 cm of length without requiring complex microsurgical methods. Spare parts from another injured digit may be used in the acute setting for pollicization or heterotopic replantation. Microvascular toe transfer is an excellent option for elective reconstruction. However, other options also are available and may be more appropriate in some cases. Less ideal options include the various types of osteoplastic reconstruction.

CONCLUSIONS

The reconstruction of posttraumatic thumb defects is a challenging and rewarding surgical endeavor. The value of a functioning thumb is immense, and its reconstruction is worthy of considerable effort. Despite the elegant reconstructive options available, the best results are obtained with replantation or revascularization whenever possible. Finally, the treatment plan always must be derived from a careful assessment of each patient's posttraumatic function and specific reconstructive needs.

Low intensity pulsed ultrasound accelerated bone remodeling during consolidation stage of distraction osteogenesis

Bone regeneration in distraction osteogenesis occurs under tensile stress with axial rhythmic distraction after osteotomy. In this study, we evaluated if the low intensity pulsed ultrasound (LIPUS) was also effective on enhancement of bone remodeling during consolidation stage of distraction osteogenesis. Open osteotomy of seventeen 18-week-old female New Zealand rabbit tibiae were performed. The distraction was applied with the rate of 1 mm per day. LIPUS (30 mW/cm(2), 1.5 MHz) was delivered for 20 min per day during 4-week consolidation stage (n=10). The animals without treatment served as sham group (n=7). Plain X-ray, peripheral quantitative computational tomography (pQCT), and torsional test were performed. Results showed that smaller radiolucent interzone of LIPUS treatment group was gradually occupied by calcified tissue in plain X-ray at week 2. The bone mineral density (BMD) measured on radiographs increased by 9.18% in the LIPUS group. Bone mineral content (BMC), hard callus volume, and bone strength index (BSI) measured by pQCT were 83%, 116%, and 94%, respectively, in LIPUS group that were significantly greater than those of the controls. At the 4th week, LIPUS-treated callus showed the development of neocorticalization in the proximal and distal region. The BMC, hard callus volume, and BSI of LIPUS group decreased and was not significantly different from control. This was also confirmed by the maximum torque of LIPUS-treated callus (1424.2+/-457.3 N . mm) obtained at week 4, which did not differ from that of the sham group (1968.8+/-895.1 N . mm). In conclusion, the effective period of LIPUS treatment was at the initial stage of consolidation, with accelerated bone formation and remodeling.

[Distraction osteogenesis for treatment of unilateral temporomandibular joint ankylosis and secondary OSAHS in children: report of 4 cases]

PURPOSE

To evaluate the efficiency of distraction osteogenensis for treatment of unilateral temporomandibular joint ankylosis and secondary OSAHS in children.

METHODS

4 children with temporomandibular joint ankylosis and secondary OSAHS were retrospectively reviewed for their treatment. There were 2 males and 2 females, ranging from 5 to 13 years in age with the median of 6.5 years. Based on the history of the disease, the clinical manifestations, CT scan and PSG findings, the diagnosis was confirmed to be unilateral temporomandibular joint ankylosis and secondary OSAHS. All the patients were treated by gap arthroplasty to restore mouth opening, combined with mandibular body distraction osteogenesis for treatment of OSAHS. One-stage operation was performed on 3 patients, and two-stage operation on 1 patient. Unilateral and bilateral mandibular distraction osteogenesis was undergone on 2 patients individually. At the end of consolidation period of 3 months, the PSG examination was performed again and the distractor was removed.

RESULTS

OSAHS was cured, the average AHI was lowered from 42.7 to 4.9, the average lowest saturation of blood oxygen rose from 74.3% to 89.8%, the average incisor distance reached 25.5mm compared to 6.5mm before surgery and facial deformity was corrected satisfactorily. Following up 38.1 months (13-58 months), no relapse appeared.

CONCLUSION

Mandibular body distraction osteogenesis, combined with gap arthroplasty, could be the potential treatment modality for children with unilateral temporomandibular joint ankylosis, secondary OSAHS and facial asymmetry; it is recommended that both procedures be performed at the same time.

Prognosis of airway obstruction and feeding difficulty in the Robin sequence

OBJECTIVE

To evaluate the course and prognosis of airway obstruction and feeding difficulty in the Pierre Robin sequence (PRS).

METHODS

Retrospective review of 60 patients with PRS between 1993 and 2002 at the University of California, Davis Medical Center. Patients were placed into diagnostic subgroups: (1) Isolated PRS; (2) Syndromic PRS (known syndrome with PRS); (3) Unique PRS (unique anomalies with PRS). Data regarding severity, duration, and management of airway obstruction and feeding difficulty were collected.

RESULTS

Airway obstruction requiring intervention beyond positional therapy was seen in 28% isolated, 42% syndromic, and 58% unique PRS. One-third of patients who failed positional therapy were temporarily stabilized with a nasopharyngeal airway or endotracheal intubation. The remaining two-thirds of patients, who failed positional therapy required a surgical airway procedure. Four patients underwent mandibular distraction osteogenesis, resulting in successful decannulation or avoidance of tracheostomy. Thirteen patients underwent tracheostomy; mean duration of tracheostomy-dependence was 17.0 months in Isolated PRS and 31.7 months in Unique PRS (p < 0.01). Successful decannulation by age of 3 years was confirmed in 85% of patients who underwent tracheostomy. Tube feeding was required in 53% Isolated, 67% Syndromic, and 83% Unique PRS. Forty-two percent of PRS patients with a successful positional airway still demonstrated feeding difficulty. Short-term (0-3 months) and intermediate (4-18 months) tube feeding was more commonly required in Isolated and Syndromic PRS, while long-term (beyond 18 months) gastrostomy tube feeding was more commonly required in Unique PRS (p < 0.01). By 3 years of age, a successful oral diet was seen in 91% Isolated, 92% Syndromic, and 78% Unique PRS.

CONCLUSIONS

Diagnostic subgroups based on the presence of additional anomalies help families and physicians in understanding the severity and duration of feeding and airway difficulty in PRS. Two-thirds of PRS patients who fail positional therapy may ultimately require a surgical airway procedure. Feeding difficulty can be present in the absence of clinically significant airway obstruction. Families and physicians should be encouraged that by 3 years of age, most patients were successfully taking an oral diet without airway obstruction.

[Development of a novel in-vitro culture device simulating distraction osteogenesis and expression of osteoblast cytoskeleton]

OBJECTIVE

To establish a novel in-vitro culture device simulating distraction osteogenesis, and to understand the the changes of cytoskeleton of osteoblasts under different magnitudes of mechanical distraction.

METHODS

A novel in-vitro culture device simulating distraction osteogenesis was developed with titanium and silicon membrane. The expressions of F-actin cytoskeleton subjected to different magnitudes of distraction were observed in situ under a confocal laser scanning microscope, and protein levels of actin and tubulin alpha were analyzed by electrophoresis of Western blot.

RESULTS

The mode of culture device simulating distraction osteogenesis was similar to that of distraction osteogenesis used in clinic. After 24 h mechanical distraction with physiological magnitude, F-actin of osteoblasts was organized and paralleled to the direction of distraction forces. After 24 h mechanical distraction with hyperphysiological magnitude, however, F-actin of osteoblasts became reorganized and disrupted, and protein levels of actin and tubulin alpha decreased.

CONCLUSIONS

The novel in vitro culture device simulating distraction osteogenesis is suitable for the study of distraction osteogenesis in vitro. Physiological mechanical distraction causes organization and rearrangement of actin cytoskeleton. However, hyperphysiological mechanical distraction results in reorganization and disruption of actin cytoskeleton.

Rational Treatment for Multiple Digit Congenital Absence

A case is discussed in which a young male was born with symbrachydactyly of multiple digits in whom nonvascularized proximal toe phalanges were transferred to the aphalangic digits when he was an infant. This initial surgical procedure was later followed by webspace deepening and ultimately by distraction lengthening of the digits. At 8 years of age, he has a very functional hand with mobile metacarpophalangeal joints in all reconstructed fingers. In fact, he uses this reconstructed right hand as his dominant extremity. The case is discussed in context of phalangeal growth potential, specific indications for this type of reconstruction, and final long-term outcome. This case also helps to recommend rational treatment protocols for similar congenital hand anomalies.

Favorable Morphologic Change of Preosteoblasts in a Three-Dimensional Matrix with In Vitro Microdistraction

BACKGROUND

Distraction osteogenesis has been used to correct hypoplastic and asymmetric bony deformities in the growing patient, yet its underlying cellular mechanisms are poorly understood. Using a new in vitro model, the microdistractor, morphologic properties of preosteoblasts under mechanical strain were studied.

METHODS

Mouse calvarial MC3T3 cells were suspended in a polymerized three-dimensional collagen gel and stressed for 14 days as one of three groups (n = 30): (1) distraction (0.5 mm/day); (2) oscillation (1 mm/day for 2 days alternated with 1 mm/day for 2 days); and (3) control (no force). A computer modeling system, KS-300, was used to record cell shape (aspect ratio) and orientation (deviance from axis of stress).

RESULTS

In part I of the study, morphologic cellular changes were found to be even throughout different regions of the gel (central versus peripheral, versus different vertical layers), suggesting the force was evenly applied to all cells in the gel. In addition, when linear distraction forces were applied, morphologic change occurred over time, suggesting a morphologic response to the applied stress. In part II of the study, with different forces applied, morphologic changes occurred over time such that linear distraction forces caused cells to elongate and align in a parallel direction to the force, whereas oscillation caused cells to switch from parallel (with distraction) to perpendicular (with compression) orientation relative to the force applied.

CONCLUSION

The authors' data suggest that the microdistractor device is an effective in vitro model for studying the cellular response to distraction stresses. It may be used in future studies to optimize clinical methods of distraction.

Effect of recombinant human tissue inhibitor of matrix metalloproteinase-1 in mandibular distraction osteogenesis in rabbits: A computed tomographic study

Matrix metalloproteinases (MMPs), together with their tissue inhibitors (TIMPs), are responsible for the controlled degradation of collagen in bone. We studied the long-term stability of the regenerated bone formed by distraction osteogenesis, and the effect of recombinant human TIMP-1 on the remodelling of bone formed by mandibular distraction osteogenesis in rabbits. Nine rabbits were subjected to distraction osteogenesis of the mandible and divided into three groups: a control group with no collagen implanted; a sham-control group with a collagen sheet implanted; and an experimental group with a collagen sheet impregnated with rhTIMP-1 implanted. Computed tomograms were taken at weeks 4, 12, and 24 after distraction, and micro-computed tomograms and histological examinations were made at week 24. There was no significant resorption of regenerated bone at the site of distraction in any group after 6 months of consolidation, suggesting that the regenerated bone formed by distraction osteogenesis is stable. We found no obvious influence of rhTIMP-1 in the collagen sheet on the bony regenerate after 6 months of consolidation.

The effect of chitosan bead encapsulating calcium sulfate as an injectable bone substitute on consolidation in the mandibular distraction osteogenesis of a dog model

PURPOSE

The purpose of this project was to study the effect of chitosan bead encapsulating calcium sulfate, which provides a sustained release of chitosan and calcium sulfate after implantation, on early bony consolidation in distraction osteogenesis of a dog model.

MATERIALS AND METHODS

Forty-five dogs were used for this study. An external distraction device was applied to the mandibular body after a vertical osteotomy and mandibular distraction was initiated 5 days after the operation at a rate of 1 mm/day up to a 10-mm distraction. The experimental group was divided into a control group (I), hyaluronic acid group (II), chitosan group (III), calcium sulfate group (IV), and chitosan bead encapsulating calcium sulfate group (V). Normal saline was injected in group I. In group II, 1 mL of hyaluronic acid solution was injected into the distracted region. In group III, 1 mL of injectable solution of chitosan mixed with hyaluronic acid was implanted. In group IV, 1 mL of injectable solution of calcium sulfate mixed with hyaluronic acid was implanted. In group V, an injectable form of powdered chitosan bead encapsulating calcium sulfate mixed with 1 mL volume of hyaluronic acid was implanted.

RESULTS

Bone mineral density was 12% of the contralateral normal mandible at 3 weeks, 23.4% at 6 weeks in group I, 15% at 3 weeks, 29.1% at 6 weeks in group II, 16% at 3 weeks and 32% at 6 weeks in group III, 30.4% at 3 weeks and 52.8% at 6 weeks in group IV, and 33.6% at 3 weeks and 55% at 6 weeks in group V with statistical significance (P < .005). The mean 3-point failure load was compared with the intact contralateral mandible and noted to be 12% in the control group, 16% in group II, 18% in group III, 34.3% in group IV, and 31.7% in group V. Difference of mean percentages between one group and another was statistically significant (P < .005). In the histologic findings, new bone was generated in all groups. In groups IV and V, the formation of active woven bone was observed throughout the distracted region at 6 weeks. The amount of new bone formation in the distracted zone was in the order of group IV and V, III and II, and the control group.

CONCLUSIONS

These findings suggest that chitosan bead encapsulating calcium sulfate appears to facilitate early bony consolidation in distraction osteogenesis.

Comparison of various types of stiffness as predictors of the load-bearing capacity of callus tissue

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis. Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.

Immunohistochemical Localization of Bone Morphogenetic Protein-signaling Smads during Long-bone Distraction Osteogenesis

In this study we investigated the expression of bone morphogenetic protein (BMP)-signaling Smads in distraction osteogenesis (DO). Osteotomy of the right tibia was performed in 14 skeletally mature white New Zealand male rabbits. Lengthening was started 1 week later at a rate of 0.5 mm/12 hr and was maintained for 3 weeks. Expression of Smad proteins 1, 4, 5, 6, 7, and 8 and Smad ubiquitin regulatory factors (Smurfs) 1 and 2 was evaluated in the distracted zone using immunohistochemistry. Expression of receptor-regulated Smads (R-Smads) 1, 5, and 8 showed a significant increase during the distraction phase, followed by a gradual decrease during the consolidation phase. Smad 4 showed significant expression during both distraction and the beginning of the consolidation phase. Smad 6 and Smad 7 were highly expressed during the consolidation phase. Staining for both Smurfs 1 and 2 was maximal at the end of the distraction period. Staining for all proteins was most intense in chondrocyte and fibroblast-like cells. Expression pattern of R-Smads correlated with our previously reported expression pattern of BMPs 2, 4, and 7 and their receptors. These results therefore suggest a role for the whole BMP signaling pathway including the Smad proteins in DO.

Mandibular distraction osteogenesis in hemifacial microsomia: long-term follow-up

AIM

Prospective, longitudinal, clinical long-term follow-up study of a homogeneous sample of children affected by hemifacial microsomia and treated by mandibular distraction osteogenesis.

MATERIAL

Eight patients affected by types I and II hemifacial microsomia were operated on at an average age of 5.6 years with an average follow-up of 5.8 years.

METHODS

Vertical changes were measured on postero-anterior cephalometric and panoramic radiographs taken sequentially.

RESULTS

Angular changes of the infraorbital and nasal floor planes were not significant, showing that distraction osteogenesis starting after 5 years of age did not influence the maxillary skeletal base. Occlusal (plane) cant was reduced by 7 degrees on average following distraction osteogenesis, showing good dentoalveolar plasticity. Mandibular vertical changes showed a gradual return of the asymmetry, with growth in all patients (the ratio between affected and non-affected rami returned by 77% of the correction obtained by means of distraction 5 years postoperatively).

CONCLUSION

Although aesthetic and psychological advantages of distraction osteogenesis are well accepted it should only be applied after careful patient selection and honest explanation of the long-term recurrence by genetically determined craniofacial growth patterns.