LeFort III Versus Monobloc Frontofacial Advancement: A Comparative Analysis of Soft Tissue Changes.

INTRODUCTION: The LeFort III and monobloc are commonly used midface advancement procedures for patients with syndromic craniosynostosis with well characterized postoperative skeletal changes. However, the differential effects of these procedures on facial soft tissues are less understood. The purpose of this study was to critically analyze and compare the effects of these 2 procedures on the overlying soft tissues of the face. METHODS: Frontal and lateral preoperative and postoperative photographs of patients undergoing monobloc or LeFort III were retrospectively analyzed using ImageJ to measure soft tissue landmarks. Measurements included height of facial thirds, nasal length and width, intercanthal distance, and palpebral fissure height and width. Facial convexity was quantified by calculating the angle between sellion (radix), subnasale, and pogonion on lateral photographs. RESULTS: Twenty-five patients with an average age of 6.7 years (range 4.8-14.5) undergoing monobloc (n=12) and LeFort III (n=13) were identified retrospectively and analyzed preoperatively and 6.4±3.6 months postoperatively. Patients undergoing LeFort III had a greater average postoperative increase in facial convexity angle acuity (28.2°) than patients undergoing monobloc (17.8°, P =0.021). Patients in both groups experience postoperative increases in nasal width ( P <0.001) and decreases in palpebral fissure height ( P <0.001). CONCLUSIONS: Both subcranial LeFort III advancements and monobloc frontofacial advancements resulted in significant changes in the soft tissues. Patients undergoing LeFort III procedures achieved greater acuity of the facial convexity angle, likely because the nasion is not advanced with the LeFort III segment.

Frontofacial Monobloc Advancement With Internal Distraction: Surgical Technique and Osteotomy Guide.

BACKGROUND: Craniosynostosis are cranial deformities resulting from the early closure of 1 or more sutures. Concomitant facial changes are complex and usually result from the involvement of multiple sutures, which may lead to restriction of cranial growth and brain expansion, ocular compression, and breathing difficulties. Surgical techniques to correct syndromic craniosynostosis have improved over time, considerably reducing the rate of complications of this procedure. OBJECTIVE: To describe in detail (step-by-step) and with pertinent anatomic considerations the technique of monobloc frontofacial advancement using internal distractors. METHODS: We describe the monobloc frontofacial advancement technique with the use of internal distractors, which we use in patients with primary syndromic craniosynostosis (Apert, Crouzon, and Pfeiffer) who have major facial hypoplasia and secondary respiratory repercussions. To illustrate this technique, the procedure was performed in 2 cranial models: an adult artificial acrylic skull of normal morphology for better evidence of anatomic repairs and a 3-dimensional printed infant skull from a tomography file obtained from a child diagnosed with Apert syndrome. RESULTS: The benefits of osteogenic distraction and better surgical timing for each procedure are presented. We presented the changes and details of osteotomies performed during the procedure, as well as anatomic details and care regarding the pterygomaxillary dysjunction. CONCLUSION: Monobloc frontofacial distraction is a procedure with widely demonstrated aesthetic and functional results, and this detailed step-by-step description may improve familiarity with the anatomic landmarks of the procedure and provide a better dynamic understanding of the distraction process.

Syndrome-related outcomes following posterior vault distraction osteogenesis.

PURPOSE: The most commonly occurring syndromic craniosynostoses are Apert syndrome, Crouzon syndrome, Pfeiffer syndrome, and Saethre-Chotzen syndrome. There is insufficient data regarding postoperative syndrome-related outcomes following the posterior vault distraction osteogenesis (PVDO) procedure, as well as data addressing whether or not additional procedures will be subsequently necessary to comprehensively treat children who undergo PVDO. Thus, the objective of this study is to describe and compare syndrome-related potential complications and outcomes associated with the PVDO procedure. METHODS: An observational retrospective study was performed on consecutive patients (n=24) with Apert syndrome, Crouzon syndrome, Pfeiffer syndrome, or Saethre-Chotzen syndrome, respectively, who underwent PVDO between 2012 and 2019. Demographic data (patient gender and age when the PVDO procedure was performed), diagnosis, surgery-related data, and outcome data (perioperative and midterm complications and need for additional surgery) were verified. RESULTS: Total relative blood transfusion volumes per kilogram for the patients were as follows: 22.75 ± 9.30 ml for Apert syndrome, 10.73 ± 2.28 ml for Crouzon syndrome (Apert versus Crouzon, p<0.05), 18.53 ± 8.08 ml for Pfeiffer syndrome, and 19.74 ± 9.12 ml for Saethre-Chotzen syndrome. None of the patients required a secondary procedure to alleviate intracranial pressure except for a Saethre-Chotzen patient. CONCLUSION: PVDO is an effective technique to address elevated intracranial pressure in SC patients that alleviates the need for secondary procedures at midterm follow-up. Apert syndrome patients presented relatively higher total blood transfusion rates than Crouzon syndrome patients who were operated on at a later age and weighed more.

Midface Morphology and Growth in Syndromic Craniosynostosis Patients Following Frontofacial Monobloc Distraction.

BACKGROUND: Facial advancement represents the essence of the surgical treatment of syndromic craniosynostosis. Frontofacial monobloc distraction is an effective surgical approach to correct midface retrusion although someone consider it very hazardous procedure. The authors evaluated a group of patients who underwent frontofacial monobloc distraction with the aim to identify the advancement results performed in immature skeletal regarding the midface morphologic characteristics and its effects on growth. METHODS: Sixteen patients who underwent frontofacial monobloc distraction with pre- and postsurgical computed tomography (CT) scans were evaluated and compared to a control group of 9 nonsyndromic children with CT scans at 1-year intervals during craniofacial growth. Three-dimensional measurements and superimposition of the CT scans were used to evaluate midface morphologic features and longitudinal changes during the craniofacial growth and following the advancement. Presurgical growth was evaluated in 4 patients and postsurgical growth was evaluated in 9 patients. RESULTS: Syndromic maxillary width and length were reduced and the most obtuse facial angles showed a lack in forward projection of the central portion in these patients. Three-dimensional distances and images superimposition demonstrated the age did not influence the course of abnormal midface growth. CONCLUSION: The syndromic midface is hypoplastic and the sagittal deficiency is associated to axial facial concavity. The advancement performed in mixed dentition stages allowed the normalization of facial position comparable to nonsyndromic group. However, the procedure was not able to change the abnormal midface architecture and craniofacial growth.

Midface distraction osteogenesis using a modified external device and 3D virtual simulation: technical note.

INTRODUCTION/BACKGROUND: Distraction osteogenesis (DO) with an external distraction device such as the rigid external distraction frame has become an established method for treating midface hypoplasia in faciocraniosynostosis. It allows for greater advancement of the midface in comparison with traditional Le Fort III osteotomies, associated or not with fronto-orbital osteotomies (Le Fort IV). However, the forward movement of the bone segments may not always be performed obeying an ideal distraction vector, resulting in asymmetries, anterior open bite, and loosening of screws. In addition, the cost of the distraction devices is significant and may preclude their routine use in developing countries. METHOD: We present an alternative device and method for craniofacial advancement in a clinical case of Crouzon's syndrome. RESULTS: A 3D virtual simulation of the distraction vector and a modified external device were used in the current case. CONCLUSION: The alternative external device in this case proved to be safe, effective, and reliable.

Custom-Made Titanium Miniplates Associated With Ultrahigh-Molecular-Weight Polyethylene Graft in Orthognathic Surgery: An Adjunct to Maxillary Advancement.

Patients with considerable maxillomandibular anteroposterior discrepancies and maxillary hypoplasia require corrective treatment through orthognathic surgery. However, in the treatment of severe maxillary retrognathism, it is necessary to reconstruct areas of bone deficiency through grafting techniques in addition to maxillary advancement using only the Le Fort I osteotomy. Treatment in these patients is more challenging and requires high surgical predictability. Alloplastic materials often have been used for the reconstruction of poor bone contours. Ultrahigh-molecular-weight polyethylene (UHMWPE) is currently an excellent filler material for poor bone regions and is a good substitute for autografts and other alloplastic materials for its unique properties, including high biocompatibility. Insertion of this material in the fixation system customized for virtually planned orthognathic surgeries is an innovative technique. This report describes the insertion of UHMWPE into custom-made titanium miniplates manufactured by computer-aided design and computer-aided manufacturing technology for orthognathic surgery consisting of maxillary advancement and mandibular retrusion to treat a patient with Crouzon syndrome, Class III malocclusion, and severe maxillary retrognathism.

Internal Distraction Resulted in Improved Patient-Reported Outcomes for Midface Hypoplasia.

BACKGROUND: Both internal and external distraction devices have been used successfully in correcting midface hypoplasia. Although the indication for surgery and the osteotomy techniques may be similar, deciding when to use internal versus external devices has not been studied. The authors studied patient-reported outcomes with FACE-Q and functional surveys for internal and external devices for midface distraction patients. METHODS: Patients who underwent distraction advancement after Le Fort I and Le Fort III were surveyed using the FACE-Q survey and a functional survey. Equal groups of internal and external device patients were compared (n = 64). Data recorded included: sex, age, follow-up, diagnosis, operating room time, expected blood loss, length of stay, distraction length, consolidation time, and complications. RESULTS: Internal and external device groups were similar with regards to patient diagnosis, operative time, expected blood loss, distraction length but consolidation times differed (internal = 3.6 versus external = 1.1 months). For FACE-Q appearance appraisal, there were similarities in domain and scale. For the functional survey (airway/breathing, ocular/vision, occlusion/eating, speech/articulation), there was also similar scoring. However, internal device patients had superior FACE-Q scores for Quality of Life: Social Function (80.9 versus 68.9), Early Life Impact (92.9 versus 62.4), Dental Anxiety (70.2 versus 48.3), Psychological Well-being (87.8 versus 68.6); and Decision Satisfaction (81.2 versus 56.9) and Outcome Satisfaction (91.0 versus 84.7). CONCLUSIONS: Internal and external midface distraction patients had similar patient-reported outcomes for appearance and functional improvement; however, internal device patients were more satisfied with their quality of life and their decision to undergo the procedure.

Use positional screws for Le Fort I osteotomy fixation: technical note.

In recent years, several studies related to fixation systems have been published, but few suggest any variations of the Le Fort I osteotomy technique, and the use of plates and screws placed along the canine and zygomatic pillar are common. The 20-year-old patient with Crouzon syndrome presented with severe hypoplasia of the maxillary, mandibular prognathism, and class III facial pattern. The patient underwent orthognathic surgery and high Le Fort I osteotomy with the fixation of eight positional screws. The aim of this paper is to describe a different technique for the fixation in high maxillary osteotomies, which can be used in specific cases.

Family of Crouzon Syndrome Represents the Evolution of the Frontofacial Monobloc Advancement Technique: From Immediate Movement to Monobloc Distraction to Monobloc Bipartition Distraction.

Crouzon syndrome (CS) is an autosomal dominant disorder characterized by premature fusion of cranial sutures, midface and supraorbital ridge retrusion, exorbitism, and in some clinical scenarios strabismus, parrot-beaked nose, short upper lip and hypertelorbitism. Treatment of CS is overlapped with the beginning of craniofacial surgery and is grounded on morphologic and functional objectives. The authors reported on the outcomes and complications of family members (mother and 2 siblings) with CS, who were operated on by different techniques of frontofacial advancement and have attained skeletal maturity. Operations were performed in different moments throughout the last 3 decades of craniofacial surgery history. A 10-year-old Crouzon progenitor underwent a monobloc osteotomy with acute advancement, using rigid fixation and bone grafting in the osteotomy sites. An 8-year-old Crouzon daughter underwent gradual lengthening of a monobloc segment, using an external, institutionally made distracter device. In addition, a 10-year-old Crouzon son underwent gradual lengthening of a monobloc segment associated to facial bipartition, using an internal distracter device. After 30 years, the mother presented a mild relapse on the orbit level, but her children had satisfactory stable outcomes. The family members with CS have undergone different modifications of the monobloc approach based on different chronological momentum, from acute monobloc advancement, to monobloc distraction, to monobloc facial bipartition distraction.

Assessment of orbital volume in frontofacial advancements.

OBJECTIVES: The objective of this study was to evaluate the variation of the orbital volume and the correlation with the magnitude of craniofacial advances as well as demonstrate its effectiveness through comparisons with normal levels of orbital volumes. INTRODUCTION: Syndromic craniofacial synostosis is characterized by cranial morphological alterations and hypoplasia of the midface that may result in obstructive sleep apnea and exorbitism; these effects are indications of surgical treatment. The gradual advancement of tissues is the surgical treatment to correct accentuated exorbitisms and jaw retrusions. METHODS: This was a retrospective study by review of medical records and tomographic examinations of 20 patients submitted to distraction osteogenesis between 2001 and 2012, who were divided into 2 groups: groups MB and LF with 11 and 9 patients, who underwent frontofacial or Le Fort III osteotomy. The orbit volume was measured with the InVesalius and Magics software, and facial advancements with Rhinoceros software. Statistical analyses were conducted using Student t test and analysis of variance. RESULTS: Patients' ages ranged from 6 to 29 years. Group MB showed an increase of 8.94 and 9.84 mm(3) in the right and left orbit volume variation, whereas group LF presented 5.70 and 5.77 mm(3). The average advancements in the right and left orbits were 11.36 ± 3.80 and 11.11 ± 3.45 mm in group LF, respectively, and 14.22 ± 4.12 and 14.48 ± 4.49 mm in group MB. CONCLUSIONS: Exorbitism was satisfactorily treated. The correlation was proportional in group LF and group MB. There was normalization of orbital volume compared with normal levels of orbital volumes.

A subcranial Le Fort III advancement with distraction osteogenesis as a clinical strategy to approach pycnodysostosis with midface retrusion and exorbitism.

Pycnodysostosis is a rare autosomal recessive skeletal disorder involving a constellation of craniofacial manifestations including midface retrusion. We report the case of a 13-year-old girl with pycnodysostosis who presented with exorbitism, midface retrusion, malocclusion, and obstructive sleep apnea. Here, we describe the successful use of subcranial Le Fort III advancement using distraction osteogenesis with internal Kawamoto distracters. After a latency of 5 days, distraction for 10 days, and consolidation for 12 weeks, her midface was advanced by 10 mm with slight overcorrection at the occlusion level. At 2 years postoperatively, the patient had complete remission of her sleep apnea, resolution of her exorbitism, and amelioration of her class III malocclusion to class I. To the best of our knowledge, this is the first report of a successful subcranial Le Fort III midface advancement with distraction osteogenesis for craniofacial reconstruction of a pycnodysostosis. Our report highlights the surgical options that have been described for this craniofacial deformity and presents a novel and expedient approach for patients with pycnodysostosis presenting with exorbitism, midface retrusion, and/or sleep apnea.

Transmaxillary osteogenic distraction with intraoral tooth-borne distractors.

Midfacial retrusion and class III malocclusion in maxillary hypoplasia are frequent sequelae in patients with cleft lip and palate. Similar deformities are seen in craniofacial dysostosis surgically treated in infancy. Recurrences after orthognathic surgery are unpredictable even using rigid fixations. Distraction osteogenesis, using Le Fort I osteotomies with external distractors, is uncomfortable for the patient, and internal distractors require a second procedure for removing the retractor. A new model of distraction osteogenesis is presented. Transmaxillary osteogenic distraction, using tooth-borne devices, is a simple method and allows ambulatory retraction of distractors. Osteogenesis between molars and premolars at the alveolar level is stable and allows orthodontic mobilization and dental implants. Anchorage in molars and maxillary tuberosities avoids velopharyngeal incompetence. Transmaxillary osteogenic distraction techniques are described, as well as results after 7 years of experience in 45 patients with maxillary hypoplasia. Results are satisfactory and stable, surgery is simple, and custom-made intraoral devices are easy to handle with minimal discomfort for the patients.

Spring-mediated skull expansion: overall effects in sutural and parasutural areas. An experimental study in rabbits / Expansão craniana com molas: efeitos globais nas áreas suturais e parassuturais. Estudo experimental em coelhos

Purpose: The use of springs in cranial expansion has proven to be effective in the treatment of craniosynostosis. Spring-mediated expansion has been studied both in the sagittal and in parasagittal regions, especially in scaphocephaly. A rabbit model was used in the present study to analyze the effects of springs on the cranial vault and sutures. Methods: Thirteen 4-week-old New Zealand rabbits were divided into 4 groups: in group I, only amalgam markers were used as control; in group II, amalgam markers were used and sagittal suturectomy was performed; in group III, amalgam markers were used, a sagittal suturectomy was performed and an expansible spring was fitted in the interparietal region and in group IV, markers were used and linear parasagittal craniectomy was carried out with springs. Animals were sacrificed after 2, 4, 8 and 12 weeks. Radiological control and histological analysis were performed in the area of spring implantation. RESULTS: In the groups using springs distraction of the craniectomy borders was greater than in those that did not use springs. New bone formation was observed in all groups, and was faster in group II. Bone growth started from the borders and depth. Bone regeneration presented a similar histological pattern in the groups with spring in the sagittal and parasagittal region. Conclusion: The rabbit model proved to be adequate for the analysis proposed by the study. The use of springs in the groups with sagittal and parasagittal osteotomy led to a similar distraction of amalgam markers and both groups had similar ossification histological pattern.(AU)

Objetivo: O uso de molas na expansão craniana tem provado ser efetivo no tratamento da craniossinostoses. A expansão com molas tem sido estudada nas regiões sagital e parassagital, especialmente nas escafocefalias. Um modelo com coelho foi usado no presente estudo para analizar os efeitos das molas sobre a calota craniana e suturas. Métodos: Treze coelhos Nova Zelândia, com quarto semanas de vida, foram divididos em quatro grupos: no grupo I, somente marcadores de amálgama foram implantados como controle; no grupo II, marcadores de amálgama foram implantados e foi retirada a sutura sagital; no grupo III, marcadores de amálgama foram implantados, foi retirada a sutura sagital e foi colocada uma mola expansora na região interparietal e no grupo IV, marcadores de amálgamas foram implantados, uma craniectomia linear parassagital foi realizada e foi colocada uma mola expansora. Os animais foram sacrificados com 2, 4, 8 e 12 semanas. Foi realizado controle radiológico e histológico nas áreas de implantação das molas. RESULTADOS: Nos grupos que utilizaram molas a distração das margens ósseas de craniectomia foi maior do que nos grupos que não utilizaram molas. Neoformação óssea foi observada em todos os grupos, tendo sido mais rápida no grupo II. O crescimento ósseo teve início a partir das margens e da profundidade. A regeneração óssea apresentou padrões histológicos similares nos grupos com o uso de molas na região sagital e parassagital. Conclusões: O modelo experimental com coelho provou ser adequado para a análise proposta pelo estudo. O uso das molas nos grupos com osteotomia sagital e parassagital promoveu uma distração similar dos marcadores de amálgamas e ambos os grupos tiveram padrão histológico de ossificação similar.(AU)

Palpebral fissure changes after monobloc frontofacial advancement in faciocraniosynostosis.

There is virtually no literature on the effect of correction of syndromal faciocraniosynostosis with monobloc advancement on the palpebral fissure shape. Using image processing software, we measured the effect of monobloc advancement on the position of the upper and lower eyelids as well as the palpebral fissure slant in a series of 18 patients with syndromal faciocraniosynostosis who had undergone surgery for correction of orbital and midface hypoplasia. For both eyes of each patient, 3 variables were measured on the pre- and postoperative photographs: the linear distances between the upper and lower eyelid margins, the pupil center and the angle between the inner and outer canthi. The globe protrusion was also measured on axial computed tomography scans before and after surgery. The results indicate that the exorbitism reduction induced by monobloc advancement is accompanied by a diminution of the distance between both eyelids and the pupil center. However, the downward slant of the palpebral fissure is increased after surgery. The data suggest that the lower and upper eyelid retraction seen preoperatively in the majority of patients with faciocraniosynostosis tend to be corrected when the frontofacial region is advanced by the monobloc. On the other hand, the surgery tends to lower the outer canthus, increasing the negative slant of the fissure. The postoperative changes induced by the frontofacial monobloc advancement need to be taken into account when the surgery is going to be performed.

Hiperteleorbitismo: uma proposta de tratamento / Orbital hypertelorism: a treatment proposal

Nos casos de hiperteleorbitismo em que não existia meningoencefalocele transetmoidal, os ossos próprios do nariz e a glabela estejam presentes e a arcada superior esteja colapsada, indica-se uma osteotomia que combina duas técnicas: a bipartição facial de Van der Meulen por via extracraniana e a mobilização orbital com manutenção das estruturas centrais, de Psilakis. Realiza-se uma disjunção craniofacial (por via extracraniana) e as hemifaces são medializadas em direção ao dorso nasal fixo. A diminuição da distância interorbital se dá por ressecção de faixas ósseas paramedianas, como se a osteotomia em V central da bipartição margeasse a linha média do dorso nasal sem atingi-la. Sem a necessidade da enxertia óssea no dorso nasal e ostectomia em área de lâmina crivosa, a cirurgia se torna rápida, de baixa morbidade e esteticamente eficaz. A linha média fixa confere adequada projeção do dorso nasal, proporcionando excelente referência espacial para a rotação centrípeta das hemifaces.

[Crouzon syndrome: factors related to the neuropsychological development and to the quality of life]. / Síndrome de crouzon: fatores envolvidos no desenvolvimento neuropsicologico e na qualidade de vida.

Crouzon syndrome is characterized by cranial and facial abnormalities and exophtalmos. Mental retardation is sometimes observed. The objective of this study was to correlate brain malformations, timing for surgery and also social classification of families and parents education to the neuropsychological evaluation and to the quality of life of these families. Eleven patients with Crouzon syndrome were studied, whose ages were between 16 and 132 months. The multidisciplinary evaluation included : social evaluation, cognitive evaluation, brain studies by magnetic resonance imaging and quality of life evaluation. The intelligence quotient values observed were between 46 and 102 (m=84.2) and was correlated (inverted correlation) to the factor IV of the short-form of the Questionnaire on Resources and Stress. Mental development was not correlated to brain malformation, neither to the age at time of operation or to the level of family environment and parents education.

Síndrome de crouzon: fatores envolvidos no desenvolvimento neuropsicologico e na qualidade de vida / Crouzon syndrome: factors related to the neuropsychological development and to the quality of life

A síndrome de Crouzon é caracterizada por deformidade craniana, alterações faciais e exoftalmia. O retardo no desenvolvimento neuropsicomotor é observado em alguns casos. Este estudo tem como objetivo analisar a influência do momento da cirurgia, da classe sócio-econômica associada ao nível educacional dos pais e da ocorrência de malformações do sistema nervoso central no desenvolvimento cognitivo destes pacientes correlacionando estes achados à qualidade de vida deles e de suas famílias. Foram estudados 11 pacientes com diagnóstico de síndrome de Crouzon com idade entre um ano e quatro meses e treze anos. A avaliação multidisciplinar dos pacientes incluiu, avaliação social, avaliação cognitiva, estudo do encéfalo por ressonância magnética e avaliação da qualidade de vida. O quociente de inteligência variou de 46 a 102 (m=84,2) e foi correlacionado de forma inversa com o Fator 4 do Questionário de Recursos e Estresse Simplificado (incapacidade da criança); não se correlacionou com as alterações encefálicas, com a condição sócio-econômica dos pais e nem com o momento do tratamento neurocirúrgico.

Crouzon syndrome is characterized by cranial and facial abnormalities and exophtalmos. Mental retardation is sometimes observed. The objective of this study was to correlate brain malformations, timing for surgery and also social classification of families and parents education to the neuropsychological evaluation and to the quality of life of these families. Eleven patients with Crouzon syndrome were studied, whose ages were between 16 and 132 months. The multidisciplinary evaluation included : social evaluation, cognitive evaluation, brain studies by magnetic ressonance imaging and quality of life evaluation. The intelligence quotient values observed were between 46 and 102 (m=84.2) and was correlated (inverted correlation) to the factor IV of the short-form of the Questionnaire on Resources and Stress. Mental development was not correlated to brain malformation, neither to the age at time of operation or to the level of family environment and parents education.

Craniofacial distraction osteogenesis en bloc.

Bone distraction of the superior and medial thirds of the craniofacial skeleton en bloc, avoiding a frontal craniectomy is presented. We applied this procedure in eight patients who were more than 5 years old with different types of craniofacial synostosis and who had not received previous treatment, and with a normal frontal shape. During monobloc advancement, major complications were encountered in older patients, especially the impossibility of the brain to expand rapidly to fill the retrofrontal dead space. Distraction osteogenesis of the craniofacial skeleton en bloc (without craniectomy) is feasible. Miniplates and screws are avoided as well as the possibility of frontal relapse or fractures of the frontozygomatic region. The patients did not need skull vault remodeling, except for a small cranioplasty at the bregma zone. The results obtained were satisfactory and stable at the time. This procedure avoids any kind of osteosynthesis, there is no extradural dead space, the operative time is brief, and blood loss is minimal. The inconvenience is the necessity of a second operation to remove the distractor.