Mandibular growth after distraction in patients under 48 months of age

Non-progressive mandibular changes in children with Type I and II craniofacial microsomia

OBJECTIVE

To describe the mandibular growth of craniofacial microsomia (CFM) patients during early childhood to adolescence with attention to symmetry.

MATERIALS AND METHODS

Altogether 61 CFM patients were studied at the Cleft Palate and Craniofacial Center, Helsinki University Hospital between 1986 and 2006. In this cohort study, we measured and analysed 293 radiographs (posteroanterior, panoramic and lateral); 165 radiographs of 40 patients met the final inclusion criteria. The vertical height of the ramus in anteroposterior and panoramic radiographs, the length of the mandible in anteroposterior radiographs and the maxillary protrusion and mandibular retrognathia in lateral cephalograms were measured in four different age groups.

RESULTS

A statistical difference existed between the groups in the vertical height of the ramus and in the mandibular length. The vertical height of the ramus measured from the panoramic radiograph grew on both sides, and the ratios remained unchanged. In the sagittal dimension, the maxilla and mandible grew forward, but no significant differences emerged between the groups.

CONCLUSIONS

Results suggest that mild-type CFM is not progressive in nature. During growth, mandibular asymmetry measured in the horizontal, vertical and sagittal planes did not increase.

Balancing Distraction Forces in the Mandible: Newton's Third Law of Distraction

Vertical mandibular distraction results in translation of both proximal and distal segments. The force exerted on the condylar segment not only places unwanted force on the joint but also rotates the coronoid process into the cranial base. To prevent these sequelae, we investigate the use of a "check plate" on the condylar segment in an attempt to decrease force at the Temporomandibular joint (TMJ) and prevent unwanted rotation of the coronoid. Patients with hemifacial microsomia, seen at our Children's Hospital from 2012 to 2016 having undergone unilateral vertical mandibular distraction with placement of check plate were compared with a sample of those similarly having undergone distraction without use of the plate. Preoperative and postoperative cephalometric measures and 3-dimensional computed tomography imaging were analyzed. Three subjects were identified in each group. Age and Pruzansky-Kaban classification did not differ between groups. Vertical distance from the coronoid process perpendicular to the Frankfort Horizontal did not differ between groups (P < 0.07); however, postoperative distance significantly differed with the coronoid process rotating upward into the cranial base in subjects without a check plate (P < 0.005). Preoperative angle of the coronoid process based on the Frankfort Horizontal did not differ (P < 0.06); however, postoperative angle significantly changed, confirming upward rotation into the cranial base (P < 0.01). Total regenerate did not differ (P < 0.08). Vertical mandibular distraction results in undesirable upward rotation of the proximal segment into the cranial base and superior displacement of regenerate. This can be prevented with the use of a check plate.

Management of Cleft Maxillary Hypoplasia with Anterior Maxillary Distraction: Our Experience

Maxillary hypoplasia is a common developmental problem in cleft lip and palate deformities. Since 1970s these deformities have traditionally been corrected by means of orthognathic surgery. Management of skeletal deformities in the maxillofacial region has been an important challenge for maxillofacial surgeons and orthodontists. Distraction osteogenesis is a surgical technique that uses body's own repairing mechanisms for optimal reconstruction of the tissues. We present four cases of anterior maxillary distraction osteogenesis with tooth borne distraction device-Hyrax, which were analyzed retrospectively for the efficacy of the tooth borne device-Hyrax and skeletal stability of distracted anterior maxillary segment.

True hemifacial microsomia and hemimandibular hypoplasia with condylar-coronoid collapse: diagnostic and prognostic differences

INTRODUCTION

Long-term results after orthopedic or surgical treatment of hemifacial microsomia (HFM) have shown a tendency toward recurrence of the facial asymmetry. However, the literature contains a number of successful case reports that show surprising changes in the morphology of the condyles. In addition, patients with similar mandibular asymmetries, treated early with surgery, have excellent long-term follow-ups, especially those who have little or no soft-tissue involvement, but only severe mandibular ramal deformities. The phenotypes of these cases are unexpectedly similar, with a consistent collapse of the condyle against the coronoid and a deep sigmoid notch. The objectives of this article were to help distinguish true HFM from this peculiar type of hemimandibular asymmetry morphologically and to quantify their differences before treatement and in the long term.

METHODS

Panoramic radiographs taken at pretreatment and the long-term follow-up of 9 patients with hemimandibular hypoplasia, characterized by the collapse of the condyle against the coronoid, were compared with those of 8 patients with severe type I and type II HFM; these records were collected before and at least 10 years after distraction osteogenesis.

RESULTS

Ratios and angular measurements before and after treatment differed significantly between the 2 groups.

CONCLUSIONS

Perhaps these patients were misdiagnosed and actually had secondary injuries of the condyle, which have a normal functional matrix. Therefore, with growth and functional stimulation, they would tend to grow toward the original symmetry. To make a differential diagnosis between true HFM and this peculiar type of hemimandibular hypoplasia, the collaboration between not only orthodontists and surgeons, but also geneticists and dysmorphologists, is of great importance because of the different prognoses.

Comparison of mandibular vertical growth in hemifacial microsomia patients treated with early distraction or not treated: follow up till the completion of growth

AIM

Comparison of the long-term follow-up until the completion of growth of two homogeneous samples of children affected by hemifacial microsomia (HFM), one treated by mandibular distraction osteogenesis (DO) in the deciduous or early mixed dentition, the other not subjected to any treatment until adulthood.

MATERIAL

Fourteen patients affected by vertically severe type I or II HFM were operated at an average age of 5.9 years with an average follow-up of 11.2 years. They were compared to a sample of eight patients who were never treated until the completion of growth.

METHODS

Mandibular vertical changes were measured on panoramic radiographs taken at different time points. Ratios between affected and non affected ramal heights were calculated and compared.

RESULTS

In the DO sample, after correction, mandibular vertical changes showed a gradual return of the asymmetry with growth in all patients. The ratio in the non treated sample was unchanged between the initial and the long term panoramic x-rays.

CONCLUSION

The facial proportions of HFM patients are maintained, when not treated, throughout growth. The same proportions return to their original asymmetry after DO. Even though short term aesthetic and psychological advantages of distraction osteogenesis are well accepted, early surgery should only be applied after careful patient selection and honest clarification of the long term recurrence by genetically guided craniofacial growth pattern.

Analysis of the biomechanical properties of the mandible after unilateral distraction osteogenesis

BACKGROUND

The purpose of this study was to establish biomechanical outcomes measures to evaluate how mandibular distraction osteogenesis affects the overall quality of bone healing. Strength and functional integrity of the regenerate were determined quantitatively after unilateral mandibular distraction osteogenesis in comparison with the contralateral mandible and a partially reduced fracture. The authors hypothesized that the breaking load, yield, and stiffness of mandibular distraction osteogenesis would be significantly reduced in comparison with both the contralateral mandible and a partially reduced fracture.

METHODS

Sprague-Dawley rats underwent mandibular distraction osteogenesis (n = 8) or a partially reduced fracture (n = 6). Distraction was performed using 4 days' latency and then 0.3 mm every 12 hours for 8 days (5.1 mm). Partially reduced fractures had gaps fixed postoperatively at 2.1 mm. Both groups underwent 4 weeks of consolidation. The contralateral mandibles were used as controls (n = 14). Mandibles were tension tested at 0.5 mm/second to failure, and then breaking load, yield, and stiffness were determined.

RESULTS

Mandibular distraction osteogenesis had significantly lower breaking load, yield, and stiffness than contralateral mandible, by 40, 30, and 60 percent, respectively. Breaking load was reduced in partially reduced mandibular fractures by 40 percent when compared with distraction osteogenesis.

CONCLUSIONS

Using a standard Ilizarov protocol, the biomechanical properties of breaking load, yield, and stiffness in mandibular distraction osteogenesis were significantly lower than those in contralateral mandibles. Surprisingly, the breaking load of mandibular distraction osteogenesis was significantly greater than that of partially reduced mandibular fracture. These verifiable metrics of regenerate integrity can be used to discern optimal outcomes of mandibular distraction osteogenesis, potentially enhancing the clinical applications of this powerful technique.

The importance of a differential diagnosis between true hemifacial microsomia and pseudo-hemifacial microsomia in the post-surgical long-term prognosis

Long-term results after surgical treatment of the mandibular asymmetry in growing children with hemifacial microsomia (HFM), whether with osteotomies or distraction osteogenesis, have mostly shown a tendency towards the recurrence of the asymmetry. In contrast, in the literature we find sporadic case reports where the long-term post-surgical follow-up of patients diagnosed as HFM, are surprisingly stable. All these reports refer to patients who have substantially no soft tissue involvement, but only severe mandibular ramus and condyle deformities. The phenotypes of these cases are unexpectedly similar. The authors suggest, that it is possible that all of these cases might be isolated hemimandibular hypoplasias, misdiagnosed as HFM, which present a normal functional matrix and, therefore, tend to grow towards the original symmetry. Differential diagnosis between true HFM and this HFM-like isolated hemimandibular hypoplasia (pseudo-HFM) is of great importance given the very different prognosis and it is possible through the collaboration between not only surgeons and orthodontists, but also of geneticists and dysmorphologists.

Cephalometric evaluation of the craniofacial complex in patients treated with an intraoral distraction osteogenesis device: a long-term study

INTRODUCTION

Distraction osteogenesis has gained popularity because of the hypothesized concurrent soft-tissue expansion, which is believed to reduce postoperative relapse. Although many articles describe the immediate success of mandibular distraction, little research has been done on its long-term stability. Our goal was to examine the long-term craniofacial changes after distraction.

METHODS

Four hemifacial microsomic patients treated with unilateral mandibular distraction were recalled. Changes in maxillary width and height, occlusal height, ramus height, mandibular length, and chin position were quantified by using the posteroanterior and 45 degrees lateral oblique cephalographs. Predistraction and postdistraction measurements were taken over a 5-year period. The data were analyzed by using paired t tests and ANOVA.

RESULTS

Maxillary height, ramus height, mandibular length, and chin point deviation all experienced moderate improvement after distraction. Although the growth patterns between the control side and the treated side were comparable until 2 years after removal of the device, the normal side outgrew the affected side thereafter until 5 years after distraction.

CONCLUSIONS

Because of the greater inherent growth potential of the unaffected side, more overcorrection than originally believed is needed to offset the persistent asymmetry in growing hemifacial microsomia patients who undergo unilateral distraction osteogenesis.

Long-term stability after craniofacial distraction osteogenesis

PURPOSE

This study was conducted to systematically review long-term skeletal stability after craniofacial distraction osteogenesis.

MATERIALS AND METHODS

Several electronic databases (Old Medline, Medline, Medline In-Process and Other Non-Indexed Citations, Pubmed, Embase, Web of Science, and all EBM reviews [Cochrane Database of Systematic Reviews, ACP Journal Club, DARE, and CCTR]) were searched. Key words used in the search were "distraction," "osteogenesis," "craniofacial," "maxillofacial," "stability," "relapse," and "recurrence." MeSH terms and truncations of these terms were selected with the help of a health science librarian. Abstracts that appeared to contain at least 3 years of postsurgical data were selected. The original articles were then retrieved and evaluated to ensure that they actually had 3 years of data after craniofacial distraction osteogenesis. The references were also hand-searched for possible missing articles that were not indexed in the searched databases.

RESULTS

A total of 118 abstracts were found in the electronic searches. After the first set of selection criteria was applied on these abstracts, 22 articles were retrieved. After the final selection criteria were applied on these 22 articles, only 6 articles were finally selected. These 6 articles reported long-term stability after craniofacial distraction osteogenesis. Sample sizes were small, and the methodological quality of the studies was poor.

CONCLUSIONS

Although, based on the selected studies, craniofacial bone distraction osteogenesis appeared to show long-term stability; limitations of the studies merit caution in interpreting these findings. Some early relapse occurred in the first 3 years postdistraction, but stability was maintained thereafter. Some methodologically sounder studies are needed to confirm the present findings.

Does functional appliance treatment truly improve stability of mandibular vertical distraction osteogenesis in hemifacial microsomia?

AIM

After mandibular unilateral distraction osteogenesis (DO) a gradual reappearance of the vertical asymmetry during growth is observed. A pre- and post-surgical functional-orthodontic treatment was added to our distraction protocol in the attempt to increase long-term stability. In order to evaluate the actual efficacy of such a combined treatment, two samples of children affected by hemifacial microsomia were compared long-term.

MATERIAL

Ten children were treated by a combined orthodontic-distraction treatment, seven by distraction only.

METHOD

Only the vertical changes in the mandible and maxilla in the panoramic and postero-anterior cephalometric X-rays were measured.

RESULTS

All of the patients showed a gradual return of the asymmetry with growth. Occlusal plane correction and, to a much lesser extent, mandibular vertical ramus height correction were better maintained over 5 years post-DO in the orthopaedic group.

CONCLUSION

Although orthopaedic treatment allows for a more stable occlusal plane and for a slower return of the mandibular vertical asymmetry, it has mainly a dento-alveolar effect. Therefore, the decision of applying an orthopaedic treatment associated with distraction, should be taken by surgeon and orthodontist together, considering both the advantages and the disadvantages of this treatment.

Bi-directional distraction in the treatment of micro-orbitism: A case report

INTRODUCTION

Correction of micro-orbitism, resulting from clinical or congenital anophthalmia, has traditionally been performed by multiple segmentation of the orbital rim, orbital expanders and orbital conformers. Although distraction osteogenesis is a widely employed surgical approach in the treatment of patients with bony malformations, it has not been employed to enlarge micro-orbits.

MATERIAL AND METHODS

The present article describes the development of a new bi-directional orbital distractor to treat a 17-year-old patient affected by micro-orbitism, caused by clinical anophthalmia. The deformity required an internal device to expand and to pull the orbit laterally. Surgical planning and device design were performed by means of patient-specific finite element analysis and a stereolithography model. The surgery consisted of a uni-lateral orbito-malar osteotomy performed via coronal and intraoral access. A 7-day-latency period was observed. The consolidation phase was chosen as six months.

RESULTS

At the end of the distraction process, symmetry of the malar bones and orbital roofs was achieved. During removal of the device, newly formed bone was found at the original osteotomy and distraction gaps.

CONCLUSION

The reported clinical case suggests that distraction osteogenesis can be a useful procedure for enlargement of micro-orbits. Despite this, a number of questions need to be addressed by long-term follow-up and careful study of future cases.

Distraction osteogenesis versus bilateral sagittal split osteotomy for advancement of the retrognathic mandible: a review of the literature

Bilateral sagittal split osteotomy (BSSO) and distraction osteogenesis (DO) are the most common techniques currently applied to surgically correct mandibular retrognathia. It is the responsibility of the maxillofacial surgeon to determine the optimal treatment option in each individual case. The aim of this study was to review the literature on BSSO and mandibular DO with emphasis on the influence of age and post-surgical growth, damage to the inferior alveolar nerve, and post-surgical stability and relapse. Although randomized clinical trials are lacking, some support was found in the literature for DO having advantages over BSSO in the surgical treatment of low and normal mandibular plane angle patients needing greater advancement (>7 mm). In all other mandibular retrognathia patients the treatment outcomes of DO and BSSO seemed to be comparable. DO is accompanied by greater patient discomfort than BSSO during and shortly after treatment, but it is unclear whether this has any consequences in the long term. There is a need for randomized clinical trials comparing the two techniques in all types of mandibular retrognathia, in order to provide evidence-based guidelines for selecting which retrognathia cases are preferably treated by BSSO or DO, both from the surgeon's and the patient's perspective.

Long-term maxillomandibular skeletal and dental changes in children with cleft lip and palate after maxillary distraction

Long-term skeletal and dental changes were examined in 8 children with cleft lip and palate who underwent maxillary distraction to allow the maxilla to catch up to their mandibular growth at the treatment point. Changes in the overjet (OJ), overbite (OB), and positions of the anterior nasal spine (ANS), upper incisors (U1), pogonion (Pog), and lower incisors (L1) were measured on preoperative to 36 months postoperative lateral-cephalograms. In most of the children, the long-term changes after the maxillary distraction resulted in an inferior growth of the maxilla and anteroinferior growth of the mandible. This seems to suggest that maxillary distraction performed during childhood needs considerable overcorrection. However, if the maxilla is distracted to an adult position during childhood, the masticatory functions of the children will markedly deteriorate until their jaws grow. Therefore, we believe that one goal of maxillary distraction during childhood can be to allow the maxilla to catch up to the mandibular growth of the children at the treatment point.

Mandibular mechanics after osteotomy and distraction appliance placement I: Postoperative mobility of the osteotomy site

PURPOSE

Fixation at the osteotomy site for mandibular distraction osteogenesis (DO) is probably not rigid, especially during mastication. Micromotion may affect the course of DO. This study aimed to measure the mobility of the fresh distractor-fixed osteotomy site in response to mastication and masticatory muscle stimulation.

MATERIALS AND METHODS

Twenty-eight domestic pigs, 6 to 8 weeks old, underwent osteotomy of the right mandible and placement of a distractor appliance. Immediately after surgery, displacement at 3 different locations (superior-lateral, inferior-lateral, and inferior-medial) of the osteotomy site was assessed using ultrasound piezoelectric crystals or differential variable reluctance transducers (DVRTs). The amount of lengthening or shortening at each location was measured during mastication and muscle stimulation. Displacement was also measured for bilateral osteotomy during muscle stimulation from a subgroup of 12 pigs.

RESULTS

The osteotomy site demonstrated significant mobility during power strokes of mastication with an average magnitude of 0.3 to 0.4 mm. Distinct patterns of displacement were associated with different locations, and the patterns varied between chewing sides. The most common pattern was lengthening at the superior-lateral and shortening at both inferior sites. Similar amounts of displacement were observed during the stimulation of jaw-closers (masseter and medial pterygoid), but the patterns produced by these muscles did not completely explain the masticatory pattern. Opening the osteotomy to 1.5 mm did not alter the displacements observed during muscle stimulation. Bilateral osteotomy tended to decrease displacement.

CONCLUSIONS

The study demonstrates that during mastication and masticatory muscle stimulation, an acute mandibular osteotomy site is mobile despite fixation by a distractor appliance.

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.

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.

Relapse in Alveolar Distraction Osteogenesis: An Indication for Overcorrection

PURPOSE

The aim of this study was to indicate the necessity of overcorrection regarding the occurrence of bone height relapse at the end of consolidation period in distracted alveolar bone.

MATERIALS AND METHODS

Eleven patients with a total of 17 distractions performed and 43 implants placed were included in this study. Bone height was evaluated on computed tomography before the procedure and on orthopantomographic radiographs following distraction and consolidation. Measurement was performed on the aproximal surfaces of implants and on identical points before and after distraction.

RESULTS

The mean of distraction performed was 6.08 +/- 1.82 mm at mesial points and 6.18 +/- 1.90 mm at distal points of measurement. The mean of bone relapse following consolidation period was 1.57 +/- 1.82 mm at the mesial and 1.79 +/- 1.68 mm at the distal aspects of implants. Statistical evaluation revealed that alveolar bone distraction should include 20% of overcorrection for both mesial and distal points of measurements plus 0.34 mm for mesial and 0.52 mm for distal points of measurement.

CONCLUSIONS

Occurrence of relapse found in this study indicates that overcorrection should be included when performing alveolar distraction osteogenesis.

Patients' responses to distraction osteogenesis: a multi-centre study

This investigation aimed to compare and contrast practical difficulties experienced by 54 children from three different centres (Mexico City, New York, Paris) treated with either extra-oral or intra-oral distraction devices. The possible effect of distraction osteogenesis on pain/sleeping difficulty, speech and eating problems and disturbance of recreational activities and alteration in sensation were investigated. It was expected that intra-oral devices would reduce the difficulties associated with the distraction process and their psychological effect on the child. Some benefits resulting from the use of intra-oral devices were identified, these included fewer sleeping problems (P = 0.006) and less disturbance of recreational activities (P = 0.002). However, eating and maintaining oral hygiene were more problematic with intra-oral devices the differences between the intra-oral and extra-oral groups was approaching significance at P = 0.07. A major disadvantage of the extra oral device was scarring. In both groups the alteration of lip sensation was temporary, pain was limited to the time of activation of the distraction device. A high level of patients' cooperation was mandatory for successful completion of the treatment.

The bone regenerative effect of chitosan microsphere-encapsulated growth hormone on bony consolidation in mandibular distraction osteogenesis in a dog model

The purpose of this project was to study the effect of chitosan microsphere-encapsulated human growth hormone, which causes sustained release of chitosan and human growth hormone after implantation on early bony consolidation in distraction osteogenesis of a canine model. Forty-eight dogs were used for this study. An external distraction device was applied to the mandibular body after a vertical osteotomy, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was divided into a control group (I), hyaluronic acid group (II), chitosan microsphere group (III), and chitosan microsphere-encapsulated human growth hormone group (IV). Normal saline was injected in group I. In group II, a 1-ml volume of hyaluronic acid solution was injected into the distracted area. In the group III, powder of chitosan microspheres and hGH were mixed with a 1-ml volume of hyaluronic acid to make an injectable form, and it was implanted into the distracted area. In group IV, powder of chitosan microsphere-encapsulated hGH was mixed with a 1-ml volume of hyaluronic acid. A total of 1-ml volume of the solution mix was implanted into the distracted area. Five dogs in each group (total of 20 dogs) were killed 3 weeks after completion of distraction. Twenty-eight dogs were killed at 6 weeks. Bone mineral density was 13.1% of the contralateral normal mandible at 3 weeks and 29.6% at 6 weeks in group I, 16.4% at 3 weeks and 40.4% at 6 weeks in group II, 16.6% at 3 weeks and 45.95% at 6 weeks in group III, and 29.6% at 3 weeks and 66.7% at 6 weeks in group IV. The mean three-point failure load was 16.1% in the control group, 34.7% in group II, 41.5% in group III, and 52.1% in group IV compared with the intact contralateral mandible, with statistical significance. In the histological findings, new bone was generated in all groups. In group IV, the formation of active woven bone was observed throughout the distracted area at 6 weeks. The amount of new bone formation in the distracted zone was in the order of group IV, group III, group II, and the control group. In conclusion, these findings suggest that chitosan microsphere-encapsulated hGH seems to be quite effective in early bone consolidation in distraction osteogenesis.

Occlusal Difficulties After Simultaneous Mandibular and Maxillary Distraction in an Adult Case of Hemifacial Microsomia

A 23-year-old woman with hemifacial microsomia type IIB was treated by simultaneous mandibular and maxillary distraction. During the course of the distraction, cephalometric analysis showed that the maxilla was not moving downward and that the upper edge of the mandibular condyle was moving upward into the space between the condyle and the glenoid fossa. This phenomenon could lead to early consolidation of the osteotomized maxilla, resulting in malposition and occlusal difficulties. This is thought to be a problem unique to bimaxillary distraction of hemifacial microsomia type IIB with severe hypoplasia of the mandibular ramus and space between the condyle and the glenoid fossa. Surgeons should be alerted to this risk and prepared to address it when performing this procedure.

Stability after distraction osteogenesis to lengthen the mandible: results in 50 patients

PURPOSE

The purpose of this study was to investigate mandibular stability after lengthening the mandible by means of distraction.

MATERIALS AND METHODS

Fifty patients (mean age, 14.7 years; range, 11.2 to 37.3 years) with Angle Class II mandibular hypoplasia were treated by bilateral distraction osteogenesis to lengthen the mandible. Patients were divided into a high-angle group, with a high mandibular angle (sella/nasion-mandibular plane [SN-MP] >38 degrees), and a normal-to-low mandibular angle group (SN-MP <or=38 degrees). Clinical measurements and standardized cephalometric radiographs were taken just before operation; postdistraction at time of removal of the distraction devices, and 6 months and 1 year postoperatively. Analysis was performed by means of angle measurements: sella/nasion-maxilla point A (SNA), sella/nasion-mandibular point B (SNB), and SN-MP.

RESULTS

Eight of 14 high-angle patients showed a degree of relapse (57%), and only 3 of 36 patients showed relapse in the low/normal-angle group (8.3%).

CONCLUSION

It can be concluded that high-angle patients are still at risk of relapsing and that distraction osteogenesis cannot prevent relapse in cases with a high mandibular plane angle. For low-angle patients, however, distraction is a safe and predictable procedure.

Amniotic Band Sequence: The Use of Bone Grafting and Distraction Osteogenesis

Distraction has proven to be a useful technique in cases of severe bone deficiency in the craniofacial skeleton. This is a report of its use in the treatment of a child affected by amniotic band sequence. This 5 year old Hispanic female presented with transverse deficiences of one lower extremity and both upper extremities. Additionally, she was missing the mandible and overlying soft tissue from ramus to ramus. Although free fibula transfer was a possibility, due to the presence of only one lower extremity, it was elected to utilize the technique of distraction. After preliminary bone grafting to unite these two hemimanibles, the bone graft was distracted bilaterally to create a neomandible. Following consolidation and removal of the distraction devices, the child was markedly improved despite what appeared to be a pathologic fracture in the region of the mandibular angle. Repeat distraction was planned.

Alterations of morphology and microdensity in the condyle after mandibular osteodistraction in the rat

PURPOSE

In this study, we examined the effects of mandibular distraction osteogenesis on the morphology and the microdensity of the rat condyle.

MATERIALS AND METHODS

One hundred twenty-nine rats were allocated to 4 experimental groups (n = 32 or 33). Each received unilateral mandibular ramus osteotomy and distraction device placement. After a 3-day latency, these were distracted once a day for 5 days. The slow distraction group was distracted a total of 1 mm (0.2 mm/d); the moderate group, 2 mm (0.4 mm/d); the rapid group, 3 mm (0.6 mm/d); and the sham group, no distraction (0.0 mm/d). Eight to 9 rats in each group were sacrificed at each of 4 time points after device placement (6, 10, 24, and 38 days). Baseline data were obtained 3 days after osteotomy and device placement without distraction from an additional 10 rats. Radiographs of the hemimandibles were scanned and measured to evaluate changes in condylar size (height, width, and area), angulation, and bone microdensity converted to equivalent bone thickness using a stepwedge. The wet weights of masseter muscle were measured at the time of harvest.

RESULTS

1) Muscle weight gains over time were significantly lower in the treated than the untreated sides throughout the consolidation period (P <.001). 2) Condylar size and angulation on the untreated side increased postoperatively, whereas there was a significant reduction of these parameters (P <.01 to.001) on the treated side at 24 and/or 38 days. 3) Condylar microdensity significantly increased on the untreated side at 24 and 38 days (P <.05 to.01) but not on the treated side. 4) Faster or larger distraction caused more severe size reduction and more upright condylar angulation, prevented an increase in bone microdensity on the treated side, especially during the consolidation periods (P <.05 to.01), and retarded increase in muscle weight, whereas a slower distraction rate showed few negative, and even some positive effects. 5) Correlations in size, angulation, and microdensity between right and left condyles became less significant over time. 6) There were positive correlations between muscle weight and condylar size, angulation, and microdensity.

CONCLUSION

An increased rate of mandibular distraction has significant negative effects on condylar morphology and microdensity.

The bone regenerative effect of growth hormone on consolidation in mandibular distraction osteogenesis of a dog model

The purpose of this project was to study the effect of growth hormone on early bony consolidation in distraction osteogenesis of a dog model. Sixteen dogs were used for this study. The vertical osteotomy on the mandibular body was extended downward. An external distraction device was applied to the mandibular body and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was divided into a control group and growth hormone group. Dogs in the growth hormone group received a daily subcutaneous injection of 100 microg (1 IU) of recombinant human growth hormone per kilogram of body weight. The daily administration of growth hormone was performed from the day of the osteotomy through the whole distraction period to the sacrifice. Normal saline was injected in the control group. Eight dogs were allocated to each group. Two dogs in each group, a total of four dogs, were killed at 2 weeks after completion of distraction, four dogs were killed at 4 weeks, and the other eight dogs were killed at 6 weeks. The level of serum IGF-I in the growth hormone group was elevated and peaked between 8 days and 12 days after systemic administration of growth hormone. Bone mineral density was higher in the growth hormone group and lower in the control group for the whole period. Bone mechanical strength was 300% higher in the growth hormone group than in the control group. However, results were more suggestive than conclusive. On histological examination, the formation of a substantial amount of active woven bone was observed throughout the distracted zone at six weeks in the growth hormone group. In the control group, new bone was generated from the edge to the center of the distracted zone. In addition, most of the central area of the distracted zone was filled with fibrous tissue at six weeks. In conclusion, these findings suggest that growth hormone appears to be effective in early bony consolidation in distraction osteogenesis.

The role of hyaluronic acid, chitosan, and calcium sulfate and their combined effect on early bony consolidation in distraction osteogenesis of a canine model

The purpose of this project was to study the effect of hyaluronic acid, calcium sulfate, and chitosan on early bony consolidation in distraction osteogenesis of a canine model. Sixteen dogs were used for this study. The lateral surface of the mandibular body was exposed in the subperiosteal plane, and the vertical osteotomy on the mandibular body was extended downward. An external distraction device was applied to the mandibular body, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was then divided into a control group, chitosan group, hyaluronic acid group, calcium sulfate combined with hyaluronic acid group, and calcium sulfate combined with chitosan group, depending on the type of implantation material in the distracted area. After completing the distraction, implantation material was injected into the distracted area, although no material was implanted into the distracted area of the control group. After implanting the materials, the distraction device was left in place for 6 weeks to allow for bony consolidation. Four dogs were allocated to each group. Two dogs in each group (total of 8 dogs) were killed 3 weeks after implantation of the material, and the other 8 dogs were killed after 6 weeks. New bone was generated in the distracted zone of all groups. In the calcium sulfate combined with chitosan group and calcium sulfate combined with hyaluronic acid group, the formation of active woven bone was observed throughout the distracted zone. Moreover, the new bone seemed to be nearly normal cortical bone at 6 weeks after implantation. In the chitosan group and hyaluronic acid group, the development of new bone was observed in the distracted zone at 6 weeks. The amount was less than that in the calcium sulfate combined with hyaluronic acid group and calcium sulfate combined with chitosan group. These findings suggest that calcium sulfate and its combined materials seem to be quite effective in early bony consolidation in distraction osteogenesis.

Is early osteodistraction a solution for the ascending ramus compartment in hemifacial microsomia? A literature study

AIM

In hemifacial microsomia, osteodistraction before skeletal maturation claims to induce both bone- and soft-tissue generation in such a way that conventional bone grafting and soft-tissue grafts are not necessary. Early osteodistraction in facial microsomia would have a positive effect on the 'functional matrix', and allow symmetrical vertical and sagittal expansion of the midface and mandible. The aim of this literature survey was to find evidence for this hypothesis by analysing long-term follow-up reports on distraction histiogenesis in the ascending ramus.

MATERIAL

Only eight published studies were found, of which only two had more than ten patients, two were case reports, and three were from the same institution.

RESULT

Invariably, the results pointed towards over-correction, repeated osteodistraction procedures, soft-tissue stretching (but no lateral augmentation), and to soft-tissue complications. The studies did not allow a conclusion to be made as whether increased vertical gain in the ascending ramus was unstable because of decreased growth on the affected side, inborn or iatrogenic, or due to resorption of the bone generated by distraction. To date, there is no evidence that osteodistraction produces better results and has lower morbidity than conventional growth centre transplantation and separate soft-tissue augmentation.

CONCLUSION

Recommendations for prospective studies are: sharp differentiation between the four Pruzansky-Kaban mandibular types, multi-centre study of a surgical protocol to increase the sample number using a standard three-dimensional evaluation protocol, and differentiation between decreased growth and collapse of the newly generated bone.

Clinical application of injectable calcium sulfate on early bony consolidation in distraction osteogenesis for the treatment of craniofacial microsomia

The purpose of this project was to study the effect of calcium sulfate on early bony consolidation in distraction osteogenesis. A total of eight patients with craniofacial microsomia were treated between April 2000 and February 2001. The age of the patients ranged from 2 to 40 years, and all were male. The follow-up period was 1 to 15 months. The operative procedure in adults was based on Ortiz Monasterio's simultaneous mandibular and maxillary distraction technique. In children, osteotomy of the mandible was performed for distraction. On the fifth day after the operation, distraction was performed at a rate of 1 mm/d in three adults. In children, distraction was performed at a rate of 1 mm/d in one patient and 2 mm/d in four patients without a latent period. On the day of completion of distraction, calcium sulfate was implanted into the distracted zone. Radiographs showed bony consolidation at 4 weeks in one child at a rate of 1 mm/d, at 5 to 7 weeks in four children at a rate of 2 mm/d, and at 5 weeks in three adults after implantation of the calcium sulfate. In conclusion, these findings suggest that calcium sulfate is effective for early bony consolidation in distraction osteogenesis and that it would shorten the whole treatment period.

Craniofacial distraction osteogenesis: a review of 3278 cases

The nascent field of craniofacial distraction osteogenesis has not yet been subjected to a rigorous evaluation of techniques and outcomes. Consequently, many of the standard approaches to distraction have been borrowed from the experience with long bones in orthopedic surgery. The ideal "latency period" of neutral fixation, rate and rhythm of distraction, and consolidation period have not yet been determined for the human facial skeleton. In addition, because the individual craniofacial surgeon's experience with distraction has generally been small, outcomes and meaningful complication rates have not yet been published. In this study, a four-page questionnaire was sent to 2476 craniofacial and oral/maxillofacial surgeons throughout the world, asking about their experiences with distraction osteogenesis. Information about the types of cases, indications for surgery, surgical techniques, postoperative management, outcomes, and complications were tabulated. Of 274 respondents (response rate, 11.4 percent), 148 indicated that they used distraction in their surgical practice. One hundred forty-five completed surveys were entered into a database that provided information about 3278 craniofacial distraction cases. Statistical analyses were performed comparing the rates of premature consolidation, fibrous nonunion, and nerve injury, on the basis of the use of a latency period and different rates and rhythms of distraction. In addition, the rates of all complications were determined and compared on the basis of the number of distraction cases performed per surgeon. The results of the study clearly show a wide variation in the surgical practice of craniofacial distraction osteogenesis. Although the cumulative complication rate was found to be 35.6 percent, there is a pronounced learning curve, with far fewer complications occurring among more experienced surgeons (p < 0.001). The presence of inferior alveolar nerve injury as a result of mandibular distraction was much lower for respondents whose distraction regimens consisted of no more than 1 mm of distraction per day (19.5 percent versus 2.4 percent; p < 0.001). No evidence was found to support the use of a latency period or to divide the daily distraction regimen into more than one session per day. Conclusions could not be drawn from this study regarding the length of the consolidation period. Overall, the surgeon-reported outcomes are comparable with those published for other craniofacial procedures, despite the higher incidence of complications. Although conclusions made on the basis of a subjective questionnaire need to be interpreted cautiously, this study has strength in the large numbers of cases reviewed. Because of the anonymity of responses, it has been assumed that surgeons who responded to the survey reported accurate numbers of complications and successful outcomes. Finally, additional clinical and animal studies that will be of benefit in advancing the field of craniofacial distraction osteogenesis are outlined.

Imaging the neonatal mandible for accurate distraction osteogenesis

The position of mandibular teeth is difficult to document in the neonatal patient. Panorex images are difficult to obtain in an uncooperative pediatric patient. The new technique presented by the authors uses computed tomographic data to create a curved, reformatted image of the mandible, and generates an image similar to a panorex image. This curved, reformatted mandibular image provides accurate visualization of the mandible and mandibular teeth. This technique allows for precise pin placement and osteotomy in distraction osteogenesis.