Distractor Removal Research Articles

Distractive Force Relative to Initial Graft Compression in an In Vivo Anterior Cervical Discectomy and Fusion Model

An in vivo biomechanical anterior cervical discectomy and instrumented fusion (ACDFI) model employing a calibrated distractor and a subminiature load cell used to intraoperatively measure distractive force across the discectomy site and subsequent compressive force across the interbody load cell following distractor removal. To determine the relationship between the distractive force and resultant initial graft compression in an in vivo ACDFI model. The relationship between the distractive force and subsequent graft compression following distractor removal has not been studied in an in vivo ACDFI model. The consequences of over or under distraction and its subsequent effect on graft compression with regards to axial neck pain, endplate failure with graft subsidence, and fusion rates is an area of clinical significance for ACDFI. Intraoperative measurements were obtained from 17 discectomy sites in 12 patients undergoing one and two level ACDFI. Informed consent was obtained from all subjects before surgery. A calibrated Caspar distractor was used to measure the distraction across the discectomy site and a subminiature interbody load cell was placed into the discectomy site and used to measure the resultant initial compressive force following distractor removal. The statistical significance and correlation between the distractive force across the discectomy site and the subsequent compressive force across the load cell were investigated with the Pearson correlation coefficient. The average distractive force across the discectomy site was 33.5 +/- 11.6 lbs and the subsequent compressive force across the interbody load cell was 16.9 +/- 5.9 lbs following distractor removal. The Pearson correlation coefficient was r = 0.912 (P < 0.0005). The data showed a statistically significant linear correlation between the distractive force and the subsequent compressive force across the range of distraction investigated. This study demonstrated a statistically significant linear correlation between the distractive force applied across the discectomy site and the subsequent compressive force across a load cell placed in the interbody space following distractor removal in an in vivo ACDFI model.

Evaluation of distracted mandibular bone using computed tomography scan and ultrasonography: technical note

Distraction osteogenesis is considered an important reconstruction armamentarium in the management of mandibular deformities and deficiency disorders. The duration of the consolidation period is still a debatable issue among the clinicians. Evaluation of the newly formed bone is the cornerstone for terminating the consolidation period safely. The aim of this study is to find a more conservative protocol for the evaluation of callus distraction by monitoring bone healing using two different examination tools: ultrasonography and dental CT. Four adult patients (three women and one man) underwent mandibular distraction (using two intraoral and two extraoral devices). The latency period was 5-7 days and the distraction was at a rate of 2 mm per day, with 12-14 weeks of consolidation. All patients were evaluated during activation, 3 months, 6 months and 1 year post-distraction. Evaluation included clinical examination, plain radiographs, CT and ultrasonography examinations. Ultrasonographic examination of the healing callus revealed four different phases of maturation. These phases were similar to the degree of tissue calcification as measured by CT. Tissue density across the distraction wound at the time of distractor removal (12-14 weeks) was equal to or less than one-third of normal bone density. Clinical monitoring of mandibular distraction wounds can be successfully achieved through frequent use of ultrasonographic examinations. Standardization of ultrasonography based on CT findings will expand the reliability of ultrasound in monitoring callus maturation. An algorithm for evaluation of distraction wound healing is suggested.

Evaluation of cephalometric points in midface bone lengthening with the use of a rigid external device in syndromic craniosynostosis patients

Distraction osteogenesis has been extensively used to correct severe midface hypoplasia in syndromic craniosynostosis patients. However few studies have reported midface distraction outcomes through cephalometric evaluation. AIM: The purpose of the present study was to evaluate outcomes with midface distraction rigid external device (RED) in patients with syndromic craniosynostosis, in terms of quantity of bone lengthening, skeletal stability and facial growth. MATERIALS AND METHODS: Eleven patients were retrospectively evaluated in this study. Cephalometrics was carried out through three teleradiographies from each patient (T1 -before surgery; T2- immediate postop, rigth after distractor removal; T3 - late postop, obtained with a minimal interval of 12 months after surgery). RESULTS: Significant midface advancement was achieved with the procedure. The rate of horizontal relapse was minimal. We noticed a clear vertical facial growth, contrary to what was seen in the horizontal aspect, when there was a mild posterior relapse and no growth evidence. CONCLUSION: Cephalometric evaluation showed adequate results in midface bone lengthening with rigid external distractor.

Evaluation of cephalometric points in midface bone lengthening with the use of a rigid external device in syndromic craniosynostosis patients

SummaryDistraction osteogenesis has been extensively used to correct severe midface hypoplasia in syndromic craniosynostosis patients. However few studies have reported midface distraction outcomes through cephalometric evaluation.AimThe purpose of the present study was to evaluate outcomes with midface distraction rigid external device (RED) in patients with syndromic craniosynostosis, in terms of quantity of bone lengthening, skeletal stability and facial growth.Materials and methodsEleven patients were retrospectively evaluated in this study. Cephalometrics was carried out through three teleradiographies from each patient (T1 -before surgery; T2- immediate postop, rigth after distractor removal; T3 - late postop, obtained with a minimal interval of 12 months after surgery).ResultsSignificant midface advancement was achieved with the procedure. The rate of horizontal relapse was minimal. We noticed a clear vertical facial growth, contrary to what was seen in the horizontal aspect, when there was a mild posterior relapse and no growth evidence.ConclusionCephalometric evaluation showed adequate results in midface bone lengthening with rigid external distractor.

Long-Term Skeletal Stability After Maxillary Advancement With Distraction Osteogenesis in Nongrowing Patients

We assessed the long-term skeletal stability of the repositioned maxilla, midface in patients who underwent maxillary advancement using distraction osteogenesis (DO). The study included 19 nongrowing patients with maxillary hypoplasia with a Class III relationship, a normally developed mandible, and follow-up after DO exceeding 2 years. Eleven men and 8 women participated, with a mean age at treatment of 20.7 years (range 15.4-33.4 years). Twelve patients had midfacial hypoplasia associated with a cleft lip and palate (CLP), and 7 patients had developed noncleft-related hypoplasia. The surgical treatment included our modified Le Fort I osteotomy in combination with intraoral (5 cases) or extraoral (14 cases) distraction devices. Distraction was started after a latency period of 5 to 7 days and continued until the proper convexity was obtained. After active distraction, a 3- to 4-week period of retention was allowed, followed by rigid internal fixation (IF) with or without distractor removal. Lateral cephalometric films before midfacial distraction (T0), after IF with or without distractor removal (T1), 6 months after T1 (T2), and 2 or more years (mean 2.8 years) after T1 (T3) were analyzed. The maxillary A-point in the Frankfort horizontal reference plane was used to assess the skeletal changes in the maxillary position (x, y) at each time point (T1-T3). In addition, we analyzed the differences in the devices and techniques. Midfacial DO was successful in all cases, resulting in a mean change obtained at point A of 10.3 mm (8.4 mm horizontally, 4.7 mm inferiorly). Point A underwent a moderate amount of skeletal relapse at T2 [0.4 mm (5%) horizontally and 0.6 mm (13%) superiorly], with a mean of 8% (0.6 mm) horizontally and 19% (1.0 mm) superiorly over the mean 2.8-year (2.0-4.8 years) follow-up. After long-term follow-up, the maxillary advancement with DO was stable in both CLP and non-CLP patients with maxillary hypoplasia. In addition, our original technique using a rigid external device provided the most reliable results in terms of skeletal stability. This retrospective study showed that DO of the maxilla gives a very stable midface, offering a promising treatment alternative for patients with maxillary hypoplasia.

The perceptual consequences of the attentional bias: evidence for distractor removal

A fundamental question of attentional research concerns the perceptual consequences of attention. Spatial attention can enhance stimuli within the focus of attention relative to stimuli outside; or attention can remove the influence of distracting stimuli and other forms of external noise inside the focus of attention. It is known that both strategies apply depending on how attention is cued to a location in space. Here we asked which strategy applies in an uncued situation in which people show a spontaneous bias of attention to the left side. To measure bias, we used a gratingscales task with stimuli corrupted by pixel noise. If biased attention resulted in biased stimulus enhancement its effect should be largest when there is little noise or few distractors within the attended region, and bias should decline with increasing noise. If, however, bias caused distractors to be removed asymmetrically, larger bias should show up with noisy stimuli. We found that bias rose exponentially as noise increased, in agreement with the external noise removal model, and we found evidence that noise modified interhemispheric competition between attentional systems. Our data offer new insights into the neural mechanisms of the right-hemisphere dominance in spatial and attentional tasks.

Gray-scale ultrasonography in the evaluation of bone callus in distraction osteogenesis of the mandible: initial findings

The accuracy of panoramic radiography (RX) and ultrasound (US) in the evaluation of both the length of the osteotomic gap and the quality of new bone formation in patients undergoing mandibular distraction osteogenesis (DO) was assessed, verifying the results against intraoperative and histologic findings. In 31 patients, three RX and three US examinations were performed after DO. RX and US findings were each independently compared, at the time of distractor removal, to the direct intraoperative measurement of the osteotomic gap and to the histologic evaluation of the maturity of a resected specimen. No significant differences (P>0.1) resulted at any step between RX (average length: 18.19 mm) and US (18.29 mm) measurement of the osteotomic gap. In the assessment of the callus maturity the difference between RX and US (P<0.001) was statistically significant: at the final control the maturity score averaged 0.612 at RX, 3 at US and 3 at histology. RX and US are equally reliable in the measurement of the osteotomic gap, while US is much more accurate than RX in the evaluation of the callus maturity. US-based follow-up might allow a safe shortening of the fixation period.

Rapid Maxillary Distraction Protocol Utilizing the Halo Distraction System and Rigid Internal Fixation

To shorten head frame wear time associated with external halo distraction (HD), we have adapted a protocol for maxillary distraction with the halo system that integrates plate fixation. All patients had a history of cleft lip and/or palate and maxillary retrusion > or = 8 mm. Five patients treated with this protocol and followed for at least 1 year were included in this study. The protocol included a 3-day latency period, variable maxillary distraction, and removal of the halo device with simultaneous rigid internal fixation. Two patients had a variable period of maxillomandibular fixation (MMF), which maintained the maxillary advancement and idealized intercuspal position while permitting further callus maturation. Cephalographs were obtained preoperatively, immediately following distractor removal, and 1 year after rigid internal fixation. The mean age at time of surgery was 18.7 years. The maxillary deficiency ranged from 8 to 15 mm (mean = 10.6 mm). All five patients demonstrated excellent occlusion. Cephalometric analysis 1-year post rigid internal fixation revealed minimal (<1 mm) skeletal relapse. Rapid maxillary distraction followed by MMF to maintain maxillary advancement may reduce halo device wear to 1 to 2 weeks. MMF optimizes occlusion by forcing the maxillary teeth into maximal intercuspal position. Rigid fixation is not only associated with less long-term relapse compared to nonrigid forms of fixation, but also minimizes the incidence of nonunion. This treatment protocol provides the advancement possible with distraction osteogenesis and the accuracy of orthognathic surgery, thereby minimizing external head frame wear.

Quantitative Study of New Bone Formation in Distraction Osteogenesis of Craniofacial Bones by Bone Scintigraphy

Although distraction osteogenesis is widely accepted as a technique to augment the craniofacial skeleton, timing to start distraction after an osteotomy or to remove distractors is basically based on studies on long bones. Because bone scintigraphy is well known to be the gold standard for quantitative measurement of bone formation, we conducted this pilot study to evaluate its feasibility as a tool for assessing new bone formation by distraction osteogenesis. Five patients with midface hypoplasia and four with mandibular hypoplasia were studied. Each patient had five bone scans: before surgery, 3 and 30 days after stopping distraction, and 3 days before and 3 months after distractor removal. Radiotracer uptake values at distraction sites were measured at 1 and 3 hours. Each uptake value was compared with preoperative study as uptake ratio. A typical pattern of radiotracer uptake ratio was observed in all cases with successful distraction. Uptake rose to the maximum during the consolidation period and remained at or above the preoperative level until the study end point. In one patient who had mandibular distraction and nonunion of the right ramus, there was no uptake peak during early consolidation as seen in the successfully distracted body and in the other cases. Bone scintigraphy was found to be a useful investigation in craniofacial distraction. It showed the dynamic of new bone formation by demonstrating the osteoblastic activity, which is important objective information for determining distraction rate and consolidation duration in each case. It may also be a tool that can predict the outcome of distraction osteogenesis.

Reduction of Morbidity of the Frontofacial Monobloc Advancement in Children by the Use of Internal Distraction

Surgical treatment of faciocraniosynostosis is a complex problem that includes both function and aesthetics. Treatment goals are to prevent further neurologic disorders and to correct the morphologic impairment. Thirty-six patients with faciocraniosynostosis (mean age, 5.2 years) were evaluated prospectively after frontofacial monobloc advancement and quadruple internal distraction. Four distractors were used in combination with a frontofacial monobloc advancement osteotomy. Complications and advancement were evaluated clinically and radiographically. Respiratory status was evaluated by polysomnography. Relapse was evaluated by comparing results at the time of distractor removal to 6-month values. The mean follow-up was 30 months. Distraction was completed in 35 patients. Twenty-eight patients (80 percent) completed their distraction uneventfully in the initial period. In seven patients, a problem related to the distraction devices required revision surgery, and subsequently six of them completed the distraction. One patient died the day after surgery from acute brain tonsillar herniation before distraction was begun. The exorbitism was corrected clinically in all patients in whom distraction was completed (n = 34). A class I occlusal relationship was obtained in 28 of 35 patients (80 percent). When respiratory impairment was present, it was corrected in all but two cases (14 of 16). A septic frontal osteonecrosis occurred in one patient 2 months after distraction was completed (frontal bone loss in one of 35 patients). Reossification at time of distractor removal was limited. Relapse has been observed predominantly at the occlusal level (six of 35) and more frequently in Pfeiffer syndrome. Internal distraction allows for early correction of respiratory impairment and exorbitism of faciocraniosynostosis, and limits the major risks of frontofacial monobloc advancement. Previous operations performed before the frontofacial monobloc advancement increased its morbidity.

Manipulating the Mandibular Distraction Site at Different Stages of Consolidation

The purpose of this study was to define optimal timing and conditions for correcting an open bite side effect by manipulating the distraction site with orthodontic springs after mandibular distraction. At 0, 1, 2, 3, and 8 weeks postdistraction, interarch springs were attached for 2 weeks to close distraction-produced open bites in 45 rabbits. Distractors were removed in half of the animals receiving spring treatment. Segment position was recorded by weekly direct measurements and radiographs. Tissue samples were collected at the end of spring application for microcomputerized tomography analysis and measurements of lateral symmetry. Orthodontic springs closed the open bite with or without distractors in place immediately after distraction and partially corrected the bite at later stages of bone consolidation. Distractor removal produced more rapid bite closure but also introduced lateral buckling of the distraction site during early consolidation. The lateral buckling was not observed if springs were applied after 2 weeks of consolidation. The amount of bite correction with orthodontic springs correlated with mineralization of the distraction site. During the consolidation period, a distraction site can be callus manipulated with orthodontic springs to correct an open bite. The amount of correction depended on when springs were placed and whether distractors were removed at the time of spring application.

Alveolar Distraction Osteogenesis for Bone Augmentation of Severely Atrophic Ridges in 10 Consecutive Cases: A Histologic and Histomorphometric Study

This study analyzed bone healing in surgically osteodistracted maxillary and mandibular ridges histologically and histomorphometrically at two different times to determine the best time to insert dental implants. Ten consecutive patients with severe maxillary (two patients) or mandibular (eight patients) atrophy underwent surgical osteodistraction with an extraosseous distractor. Seven days after the surgery, the distractor was activated at a rate of 1 mm/day until achieving the planned bone lengthening. The distractor was removed after a consolidation period of 70 days. Bone biopsies were obtained at implant insertion: 70 days after the end of distraction on the day of distractor removal in six patients (group A) or 180 days afterwards in four patients (group B). The biopsies were evaluated histologically and histomorphometrically to measure the osteocyte lacunar area (OLA). The histologic and histomorphometrical analysis of the distracted bone 70 days after the end of distraction showed well-organized lamellar bone. At 180 days, the bone was more compact and mature; the mineralization of the matrix was greater; and an increased, but small, amount of marrow space was evident (35% versus 45%). The mean OLA was 80.11 +/- 27.59 microm2 in group A and 70.4 +/- 33.58 microm2 in group B. The difference between the two biopsy groups was not significant (P = 0.315). The results of this study showed that there was definitely similar bone formation in the distracted area for both healing periods, and placing implants clinically worked in both of these time periods in the limited number of cases observed.

Pediatric Feeding Disorder and Growth Decline following Mandibular Distraction Osteogenesis

Mandibular distraction osteogenesis has proven to be an effective treatment for upper airway obstruction related to micrognathia. Changes in the aerodigestive space can help facilitate tracheostomy removal in children and prevent tracheostomy in newborns. However, this may also precipitate changes in the ability to orally feed. There are few data on early postoperative feeding and growth rate following mandibular lengthening. The authors found evidence of growth rate decline and feeding difficulty in pediatric patients following mandibular distraction osteogenesis. Ten pediatric patients underwent mandibular distraction osteogenesis for treatment of upper airway obstruction. Outcomes in resolution of upper airway obstruction, oral feeding success, and growth rate were analyzed. Follow-up ranged from 12 to 28 months. All 10 patients had complete resolution of upper airway obstruction. The length of distraction ranged from 10 to 17 mm. Three patients demonstrated a feeding disorder after mandibular distraction osteogenesis, defined as requiring a long-term (>1 month) alternate feeding method (gastric tube in two patients and gastric gavage in one). Seven of 10 patients exhibited an early decline in growth rate following distraction. Data used to determine growth rate changes were weight measurements at the time of distraction, at the time of distractor removal (6 to 8 weeks after distraction), and at 6 and 12 months after the date of distraction initiation. These results suggest that infants and children undergoing mandibular lengthening by distraction osteogenesis should be carefully monitored for postdistraction feeding disorder and growth rate disturbance.

TREATMENT OF PATIENTS WITH GRADE III–IV THORACOLUMBAR SCOLIOSIS AFTER PRIOR SURGERY BY HARRINGTON METHOD

Objective. To analyze the results of idiopathic scoliosis correction with instrumentation developed by the authors in patients previously operated by the Harrington method. Material and Methods. Ten patients of 14–31 years of age with grade III–IV scoliotic deformity previously operated by the Harrington method were reoperated with universal endocorrector. The reasons for repeat surgery included a fracture of Harrington rod, insufficient correction of scoliotic deformity, perforation of the vertebral arch by distractor hook, and the trunk imbalance. All patients underwent simultaneous two-stage surgery involving distractor removal and scoliosis correction with universal endocorrector. The follow-up period was 6–24 months. Results. Mean correction in rod fracture group was 61.08 % without complications, in undercorrection group (mean correction 27.24 %) it achieved 63.39 %. In the group of patients with vertebra arch penetration and pain syndrome the mean correction by universal endocorrector was 34.29 % with 100 % reduction of pain. During the 6–24 months follow- up there were no correction loss or neurologic and septic complications in operated patients. Conclusions. The new instrumentation provides greater correction (1.8 times) of scoliotic deformity than Harrington rod instrumentation. It is successfully used in repeat surgery and equally effective both in adolescent and in adult scoliosis.

Intracranial Migration of a Halo Pin During Distraction Osteogenesis for Maxillary Hypoplasia: Case Report and Literature Review

Halo devices are most frequently used by orthopedic and neurosurgeons. The first reported use was by Perry and Nickel in 1959, who used a halo to immobilize the cervical spine of a poliomyelitis patient after complete fusion of the cervical spine. One of the relatively newer uses is as part of an external distraction device for stabilization and providing predictable forces to the craniofacial skeleton for distraction osteogenesis after osteotomies are performed. This is now widely used for treating maxillary hypoplasia, after being reported by Polley and Figueroa in 1997. Many of the patients that require this treatment have craniofacial abnormalities because of craniosynostosis syndromes such as Crouzon, Pfeiffer, and Apert. The common characteristic shared by these syndromes is midface recession with shallow orbits resulting in proptosis and a class III malocclusion. The procedure includes performing a Le Fort I or III osteotomy. The head frame is then secured to the skull with percutaneous pins and attached to the midface with wires. Because the device is often left in position for periods of up to 3 months, changes in the position of the pins and the device are possible. We report the case of a 19-year-old man with Crouzon’s syndrome who underwent a Le Fort III osteotomy for distraction osteogenesis, and at the time of distractor removal was found to have intracranial migration of 1 of the halo pins with dural penetration.

Analysis of complications following alveolar distraction osteogenesis and implant placement in the partially edentulous mandible

The purpose of this retrospective study was to evaluate complications before, during, and after vertical alveolar distraction osteogenesis and to assess the survival rate of dental implants placed in distracted bone. In a consecutive series, 37 patients with 45 alveolar ridge deficiencies of the partially edentulous mandible were treated with 14 intraosseous and 31 subperiosteal distraction devices. Seventy-two dental implants could be placed at the time of distractor removal and 21 implants at a second stage. Complications associated with the distraction procedure affected 75.7% of patients. The majority of complications were of minor nature with the exception of fractures of basal bone (n = 3), fracture of transport segment (n = 1), breakage of distractor (n = 1), and severe mechanical problems (n = 3). Eleven secondary grafting procedures were necessary to allow the placement of dental implants. Implant survival was 95.7% (mean postloading follow-up: 35.7 months). Vertical alveolar distraction osteogenesis is not an uncomplicated procedure; however, long-term survival of dental implants inserted into distracted areas is satisfactory.

Corrélation entre les données échographiques et radiographiques dans l’évaluation de la maturation du cal osseux symphysaire après distraction

To search for means of reducing ionizing radiation during treatment planning for transmandibular osteodistraction. Eleven patients (6 female, 5 male) underwent combined bimaxillary osteodistraction at a mean age of 18 Years. The following investigations were performed to determine symphyseal callus maturation: occlusal radiographs (O-RX) preoperatively, after the active phase of distraction (mean 27 days); ultrasound investigations (US) after the active and consolidation phase. US showed calcification foci at the end of the active phase, when O-RX failed to do so. Both US and O-RX detected callus immaturity after 2 Months of consolidation in 1 patient. Both detected bridging ossification one Month later. US can replace radiography in the diagnosis of callus maturation related to distractor removal.

Mandibular distraction in neonates: a strategy to avoid tracheostomy.

Over the past 5 years, the authors developed an application of mandibular distraction osteogenesis to eliminate existing tracheostomy. That experience led the authors to attempt mandibular distraction osteogenesis in neonates as an alternative before tracheostomy. Success with this approach using supporting objective airway measurements has been reported previously. This report includes six neonates diagnosed with Pierre Robin sequence. Of the six, five neonates ranging in age from 6 to 26 days (mean, 14.5 days) were treated by the authors with mandibular distraction over a 22-month period. The sixth neonate was treated with tracheostomy, because of other airway abnormalities. Findings included retrognathia, glossoptosis, incomplete cleft palate, and airway obstruction in each patient. Birth weights ranged from 2.8 to 3.2 kg. All patients were unable to control their airway during feeding, as evidenced by repeated episodes of choking and obstruction. Resting oxygen saturations were in the 70 to 80 percent range in all patients, with further deterioration during attempted feeding. Bronchoscopy was performed in all patients under anesthesia before distraction. Recurrent near-complete and intermittent complete airway obstruction were present in all patients at the level of the tongue base. There was a consensus by a pediatric intensivist, a pediatric anesthesiologist, and a pediatric otolaryngologist in all cases. Each patient met all criteria requiring ventilation for life support. Tracheostomy would be required if mandibular distraction osteogenesis was not performed, or if it failed. Patients with other airway abnormalities were not considered for treatment. Maxillomandibular disharmony measured at the midline ranged from 8 to 15 mm (mean, 11.2 mm). Active distraction was performed at the rate of 1 to 2 mm a day, with a consolidation period of 4 weeks. Total time of treatment was less than 6 weeks in all cases. All patients were extubated by the completion of active distraction. Distraction distance ranged from 8 to 15 mm (mean, 12.4 mm). All patients were discharged to home on apnea monitors, the use of which was discontinued after 90 days with no further apneic events. Weight gains met or exceeded the average 500 g a month after distraction. Bronchoscopy at the time of distractor removal showed correction of airway obstruction at the tongue base. Radiographs showed bilateral ossification of the distraction sites. Tracheostomy was avoided in all cases selected for treatment by distraction. Patient follow-up range was 9 to 22 months. In selected Pierre Robin sequence patients with tongue base airway obstruction, mandibular distraction osteogenesis can successfully avoid the need for and the associated mortality and morbidity of indwelling tracheostomy.

CT-assisted volumetry and densitometry of distraction osteogenesis lengthened mandibular areas

Gradual callus distraction in the correction of hypoplastic areas in the viscerocranial skeleton is an established method due to its efficacy. Whereas functional and esthetical improvements can be seen easily, it is impossible to get the increase of the bony mass right using the distractor scale or by clinical investigation. Only in animal studies can volumetric and densitometric measurements be done directly. By permission of the local ethics commission, in a clinical study, CT data of 24 children (12 unilateral and bilateral hypoplasias each) taken before and after mandibular distraction osteogenesis were used to get information on the amount of created bone and the grade of ossification of the callus at the time of the distractor removal. The CT data were prepared for computer evaluation using software which had been especially developed for this investigation. The quality of the investigation was influenced by disturbed data acquisition (insufficient sedation, Gantry deviation, different axial cuts). Therefore, the estimation of the real increase of bone was not possible, but all in all an increase of the volume could be seen. Using a grey scale analysis, the grade of new bone ossification was over 90% at the time of distractor removal. In our opinion, these results argue against the use of CT scans for the validation of a mandibular distraction. The estimation of the volume is very imprecise, the grade of ossification of the new bone very constant.

Palatal distraction in a canine cleft palate model.

The purpose of this study was to determine whether the canine hard palate can be lengthened by distraction osteogenesis in a cleft palate model using a mostly submucosal distractor. Five mongrel dogs were used. After raising mucoperiosteal flaps, a midline strip of bone was removed from the hard palate of each dog to simulate the bony defect seen in a cleft palate. A transverse osteotomy was then made to separate the posterior segment of the hard palate from the anterior segment. Posterior osteotomies were also made laterally parallel to the teeth so that the 2 posterior segments (one on either side of the bony cleft) were mobile. An intraoral distractor that was mostly submucosal was attached to the anterior hard palate and both segments of the mobilized posterior hard palate. Radiopaque bone markers were placed, and x-rays were obtained. After a 10-day latency period, the distractor was expanded 0.675 mm per day until it had been lengthened 10.125 mm. Distractors were left in place for an additional 8 weeks. After distractor removal, animals were observed for an additional 8 weeks before euthanization. Follow-up x-rays and histologic examinations were performed. New bone formation was found at the site of distraction in all dogs at the time of death. This new bone was seen on the follow-up x-rays and on histologic examination of the hard palates using both hematoxylin and eosin staining and Masson's trichrome stain. Distraction osteogenesis using a mostly submucosal device is an effective technique for lengthening the hard palate in a canine cleft palate model. The technique may eventually provide an alternative treatment for velopharyngeal incompetence in humans that is more precise and involves less morbidity than existing treatments.