Selection of the appropriate surgical approach for the treatment of the most prevalent craniosynostosis

Summary

Sagittal synostosis is the most common type of isolated craniosynostosis, resulting in an abnormal skull shape that requires surgical correction. Various surgical techniques have gradually evolved based on historical and medical advancements. The aim of our work is to present the principles, benefits, and limitations of the most commonly used surgical techniques worldwide. Currently, there is no universally applicable surgical technique suitable for all age groups and all types of scaphocephaly. Aesthetic and functional outcomes vary within surgical techniques and among different centers. Some open and minimally invasive techniques yield comparable aesthetic results. The choice of surgical technique should be made individually for each patient.

Keywords:

endoscopy – surgical procedures – craniosynostosis – scaphocephaly

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

 

Introduction

Sagittal synostosis is defined by the premature demise of the arrow suture. The skull is narrow and elongated due to compensatory growth in the preserved sutures. This results in a dolichocephalic shape of the lbi on the basis of sagittal synostosis, so-called scaphocephaly. The incidence of this congenital developmental defect is around 1:5,000 and thus represents the most common type of isolated craniosynostosis [1]. The disease predominantly affects boys in a ratio of 4:1. The cause of sagittal synostosis is still not clarified. A genetic background is detected in a small proportion of patients [2].

 

Historical development

The first scaphocephaly operation was performed by Lannelong in Paris in 1890 [3]. The operation consisted of creating two bony defects in the parietal bones parallel to the fused sagittal suture. On the other hand, Lane of San Francisco introduced the technique of displacing the fused sagittal suture, the so-called strip craniectomy [4]. At that time, the mortality rate of these operations was high, up to 45% [5]. As a result, the surgery was abandoned for several decades. It was not until the 1940s that strip craniectomy was rediscovered by Town and Faber. The mortality rate was already low. Emphasis was placed on timing the operation to 3 months of age, because it was in older patients that the results were not favorable [6]. With advances in anaesthesiology and especially the possibility of transfusion, open invasive techniques began to develop in the 1960s. Their main advantages were better aesthetic results even in elderly patients and a lower risk of recurrence of scaphocephaly. At the turn of the millennium, Jimenez et al. returned to strip craniectomy, however, now under the heading of minimally invasive endoscopically assisted surgery supplemented by postoperative cranial bracing [7]. The same technique was introduced in the Czech-Slovak area by neurosurgeons from the University Hospital Ostrava in 2008 [8]. Currently, scaphocephaly correction using various techniques is performed at the Czech neurosurgical departments of the Motol University Hospital in Prague, the University Hospitals in Brno, Ostrava, Olomouc, Plzeň and Hradec Králové [8,9].

 

Pathogenesis

Premature suture closure leads to restriction of growth perpendicular to the suture, as already described by Virchow in 1851 [10]. According to the site of premature adhesion and compensatory growth of the skull, scaphocephaly is divided into several types. In posterior scaphocephaly present in 35% of cases, the dorsal part of the sagittal suture disappears first in front of the posterior fontanelle, this leads to the characteristic occipital bowing. The anterior part of the sagittal suture disappears in 24% of cases, leading to an arched forehead. The complete form of scaphocephaly is present in 29% of patients and represents the most severe form leading to a combination of arched forehead and occipital arching and narrowing of the labium. The central type present in 13% of cases leads to a mild morphological variant [11]. At the time of diagnosis, the adhesion tends to be complete in 73% and partial in 27% of cases [12]. In partial adhesion, only the adherent portion of the suture can be considered for dislocation, preserving the functional area [13].

 

Diagnostics

The sagittal suture can be identified by palpation in the expressed cases as an edge at the site of suspected synostosis. Verification by an experienced anthropologist is usually necessary to establish the diagnosis. Using imaging methods, the finding can be objectively confirmed by ultrasonography, but this requires an experienced ultrasonographer [14]. In a study of 102 neurosurgeons from four continents by Doumit et al. CT scanning was still the most commonly used method [15]. Seven percent of respondents use CT when multiple sutural pathologies are suspected and 71% always use CT, even with clear clinical findings. The radiation dose from a single brain CT scan in patients under one year of age increases the lifetime risk for cancer by 0.07% [16]. For CT scans with the aim of diagnosing craniosynostosis, imaging of pure bone tissue is sufficient and therefore low-dose protocols should be used, reducing the radiation dose to one to two mSv. In CT scans of the abdomen of infants, doses reach 20 mSv and are therefore 10-20× higher [17]. The latest CT scanners in the low-dose protocol achieve doses comparable to two to four skull X-rays, depending on the number of detectors in the machine. Another advantage of CT scanning is the assessment of the severity of compensatory skull growth and planning of surgical intervention; moreover, multiple sutural pathologies can be detected in 3-6% of patients [18,19]. CT examination has been included in the routine diagnostic process at our institution since 2021. Of the 91 patients examined, we detected a patent sagittal suture in three patients with hyperdolichocephalic shape and concomitant suspected scaphocephaly. This entity is referred to as a sticky sagittal suture, surgery is not indicated and a cranial remodeling brace is sufficient [20]. With the use of special sequences, MRI scans can also be used in the diagnosis [21]. Single photon emission computed tomography (SPECT) examination provides additional information about cerebral perfusion and at the same time a CT scan shows the atrophied suture. In severe forms of scaphocephaly or complex craniosynostoses, SPECT detects areas of cerebral hypoperfusion. Thus, the examination can help both in the indication for surgery and in the postoperative follow-up, when, according to the authors, normalization occurs after 3 months [22-24]. Some institutions use SPECT examination in routine diagnosis.

 

Indications

Indications for scaphocephaly surgery include improvement of the resulting head shape and prophylaxis of elevation of intracranial pressure and learning disabilities. Precisely to prevent functional impairment, surgery should be planned preferably before 6 months of age [25-28], but no later than 1 year of age [29]. Late diagnosed patients may develop intracranial hypertension, Chiari malformation, swelling of the papillary optic nerves and even blindness [6,30,31]. Renier et al. described increased intracranial pressure in 14% of patients with synostosis of one cranial suture [32]. Another argument for surgery is the prevention of psychosocial disadvantage in the pediatric population during adolescence [33].

 

Timing of surgery and selection of the best technique, preoperative recommendations, prevention of transfusion

In terms of psychomotor development, surgery should be performed early after diagnosis [25-29]. From an aesthetic point of view, different surgical techniques have better results at precise age intervals (Table 1) [19,31,34-45].

The type of surgical technique should be chosen based on the severity of the compensatory mechanisms, not on the localization of the adhesive suture [46]. Another factor in the success of surgery may be positioning the patient in the supine position or the use of a preoperative cranial brace to improve the preoperative cephalic index (CI). According to studies, up to three units of CI can be obtained by positioning [47] and eight units by cranial bracing [48].

The administration of blood transfusion is a comparative study parameter and a factor of mini-invasiveness. At the time of surgery, fetal hemoglobin (Hb) is gradually converted to adult-type Hb and anemia is detected in the blood count. Many protocols have been published to prevent the administration of blood transfusions. For example, subcutaneous administration of erythropoietin at a dose of 600 μm/kg/week in combination with oral iron replacement [49]. Neurosurgeons from the University Hospital Brno have also addressed this issue. They developed a preoperative protocol in 2007. After blood draws, they recommend substitution with actiferrin, pyridoxine, ascorbic acid, folic acid and possibly erythropoietin according to the results [9].

Surgical techniques

The approach to the management of scaphocephaly varies considerably between sites. In a survey study, Doumit et al. asked surgeons from 14 countries and four continents what surgical technique they would choose for a patient with scaphocephaly within 4 months of life. Of those surveyed, 31% would choose an open surgical technique, 24% would plan open surgery at 6 months of life, 19% would prefer endoscopically assisted extended craniectomy with adjunctive incisions, 16% would prefer endoscopically assisted strip craniectomy, and 10% would prefer the spring technique [15].

 

Open surgical techniques

Open surgical techniques are increasingly preferred over minimally invasive techniques worldwide. A total of 55% and 81% of surgeons surveyed use open techniques [15,50]. Open techniques require a large skin incision, most often bicoronal, invasive anesthesia, increased need for blood products, longer hospital stay and postoperative subcutaneous drainage [51,52]. Most studies focusing on psychomotor development and intracranial pressure demonstrating a protective effect have been described for open techniques, and some surgeons use this argument to justify open techniques. However, there are now studies supporting a protective effect for minimally invasive procedures as well [53].

 

Open strip craniectomy

Lane's open strip craniectomy [4] represents the first corrective technique for scaphocephaly. In the 1940s and 1950s, it became a safe and most widely used technique due to advances in transfusion therapy. The operation itself consists of a large skin incision over the sagittal synostosis and displacement of the bone including the adhesive suture with a variable width of 1-4 cm (Figure 1). Strip craniectomy before 8 weeks of life leads to more frequent resynostoses with recurrence of dolichocephaly; therefore, it is recommended to postpone surgery until 3 months of age [54,55].

A variation of strip craniectomy is the removal of a narrow strip of bone and insertion of polyethylene plates with fixation to the parietal bone margins to prevent resynostosis [56].

 

Renier H technique

The Renier H technique was described by Marchac and Renier in Paris in the 1980s. It soon gained popularity due to its simplicity and excellent aesthetic results in up to 85% of cases [57]. The technique consists of a bicoronal skin incision and displacement of the bone above the sagittal suture, together with a striated displacement of the parietal bone behind the coronal and in front of the lambda suture into the resulting H-shape (Figure 2). The bone plate from the sagittal craniectomy is shaped, shortened and then fixed with sutures to the dura. The authors report a protective effect on the patient's neurological development. Reoperation is necessary in only 1% of patients [30,45].

 

Pi technique

The Pi technique was described in 1978 [58]. It starts again with a bicoronal skin incision and displacement of the bone plate in both parietal bones throughout the course behind the coronal suture. The rest of the sagittal suture is preserved. Conversely, two strips of bone parallel to the fused sagittal suture are dissected out to form the resulting Greek letter π (Fig. 3). The preserved sagittal suture can be pulled with a suture to the frontal bone plate, and thus the skull can be shortened anteroposteriorly. Depending on the active shortening, Jane et al. termed the technique as the squeeze technique [59]. This maneuver will secondarily expand the biparietal dimension. Because of the concern of cerebral compression, studies have been performed with perioperative monitoring of intraventricular pressure. Shortening the anteroposterior length of the lbi to one centimeter has been shown to be safe [60]. The results are excellent in 53%, good in 43% and poor in 4% of cases. Poor results are more common in patients younger than 8 weeks. The ideal operative time has been determined to be between 3-6 months [61,62].

 

Our modified combination of Pi and H techniques

It was first introduced in 2015 in response to the numerous postoperative bone defects of the previous technique. After bicoronal skin incision, skin flap retraction and exposure of the calva including periosteum, we mark the craniotomy with a gentian violet (Figure 4). Similar to the Renier H technique, we create incisions behind the coronal and anterior to the lambda suture. From the Pi technique, we leave the synostotic sagittal suture and use active shortening of the anteroposterior dimension. In addition, we add ray craniotomies in the frontal and occipital bones. We model the bone plates using Tessier forceps. The advantage of our technique is the reduced risk of bone defects. The individual bony prominences have preserved vascular supply to the bone from at least one side and this promotes ossification of the defects. The technique is suitable for patients from 6 months to 4 years of age. Patients older than 1 year require bone fixation with absorbable plates. The disadvantages are the low possibility of affecting the arched forehead and the invasiveness of the procedure. The average operation time is 167 min. In our cohort, we measured a mean CI before surgery of 68.8 and 79.5 after surgery. At the last follow-up, 3.7 years after surgery, the mean CI was 77.1. None of the 68 patients required reoperation.

 

Clamshell technique

The operation begins with bicoronal incision, contraction of the frontal and occipital skin flap with exposure of the skull. First, a bifrontal craniotomy is performed with anterior remodeling of the frontal bones as in complex cranial remodeling. Subsequently, craniotomy over the sagittal synostosis by leaving part of the sagittal crest alternately on the right or left parietal bone. This produces a pattern of an expanding shell. After detachment from the dura mater, the bony discs open laterally on the hinge of the squamosal suture (Figure 5). Fixation with sutures or absorbable plates is essential to prevent the parietal discs from returning to their original state. The technique is suitable for late diagnosed cases of scaphocephaly where the bones are not as pliable. Authors using the clamshell technique have reported mean ages at surgery of 1.8 years [31], 4.2 years [37] and 4.9 years [36]. The relative difficulty of bone remodeling corresponds to an operation time of 2.4-5.4 h [31,36,37]. 3.7-5.7 cranial units can be obtained by surgery [31,37]. Rottgers et al. reported a positive effect on intracranial pressure in five out of six patients [31].

Total cranial remodelling

Total cranial remodelling is the most invasive surgical method. The technique consists of complete exposure of the calva, creation of multiple craniectomies and bone plate transfers. In contrast to the H and Pi techniques, it is more targeted to shape deformities caused by compensatory growth mechanisms and, due to the smaller postoperative bone defects, it is also suitable for patients older than one year. The surgery can be single or double operation. An example of a single-joint procedure is the Melbourne method published by Greensmith et al. in 2008. Multiple craniectomies are performed after exposure of the calva. The frontal bone plate with an intact coronal suture is modified outside the patient's body with osteotomies and sculpted to reduce the arching of the forehead. A 3-4 cm strip of bone is cut behind the coronal suture and then moved caudally under the detached occipital bone plate. The parietal bone plates are rotated 180° and moved to the opposite side. All bone discs are fixed together with resorbable plates and bone sutures (Fig. 6). The average duration of surgery is 4.75 h. The average CI gain is 12.9 units [38].

 

Minimally invasive techniques - introduction

From the history mentioned above, it is the minimally invasive methods that try to overcome the historically rooted open techniques. The primary advantage is less surgical burden on the patient. Surgical times are shorter, blood loss is lower. Length of hospital stay and healthcare costs decrease [52]. For the family, an earlier solution is an advantage, and conversely, the age limit for performing the mini-vascular technique is usually around 6 months of age of the child. This is due to the malleability factor of the cranial bones and taking advantage of the dynamic period of skull growth. The disadvantage of some techniques is a longer dependence on a postoperative helmet or the need for a second operation in order to extract the instrumentation.

 

Endoscopically assisted craniectomy with postoperative cranial brace

Jimenez and Barone first described the method on four patients in 1998 [7]. They subsequently developed the technique further. In 2004, the published cohort already included 139 patients with a mean age of 3.6 months. The results were excellent in 87% of patients, good in 9% and poor in only 4% [19,63]. The method then gained popularity worldwide. In our country, the method was first used in Ostrava [8]. The method is intended for patients up to 6 months of age, or up to 9 months of age in the absence of severe compensatory manifestations [63]. The surgical technique consists in two skin incisions of 2 cm length. The first localized behind the bregma and the second in front of the lambda. Preparation is subgaleal with retractions in the parietal bones and release of the diaper under endoscopic control. Osteotomy of the parietal bones is performed with special so-called bone scissors. A striated sagittal craniectomy with an average width of 5.4 cm is created [7,19]. Further V-shaped auxiliary incisions are made perpendicular to the sagittal craniectomy in the parietal bones anteriorly and posteriorly (Fig. 7). Bleeding from the bone margins is stopped by the authors with instrumentation with integrated monopolar coagulation under endoscopic control. Blood loss averaged 27 mL and only 7% of patients required blood transfusion during hospitalization [63]. The mean duration of surgery was 57 min [63]. The resulting head shape is conditioned by the cranial remodeling orthosis. The duration of wearing the cranial brace ranges from 3 to 12 months [7]. During this time, the patient needs 2-4 new braces due to rapid head growth in infants [63,64]. Helmeting can be divided into three phases. During the first phase lasting 1-2 months, CI is normalized. The second phase lasting 1-3 months is for the purpose of recorrection. The last phase is maintenance [19].

Other minimally invasive techniques based on strip craniectomy

Other authors have modified the minimally invasive technique by adding skin incisions, extending the scope of osteotomies, or even eliminating endoscopic assistance [40,41,57,65]. More will be mentioned in the discussion.

Spring technology

The spring technique was first described by Lauritzen from Sweden in 1998 [66]. The technique consists of a narrow sagittal synostectomy from an incision over the vertex. One to three springs are placed in the indentations in the parietal bones (Fig. 8). Lateral expansion of the calva takes 2 weeks in 90% [47,67]. The technique requires a certain bone width in terms of pliability, effective CI changes, and prevention of spring dislocation. Therefore, surgery is planned for a period of 3-6 months of age. In the preoperative period, positioning or a preoperative cranial brace significantly improves CI [47,67]. On average, the resulting CIs reach almost the lower limit of normocephaly (73.7-74.4) [67,68], but the index gradually decreases by one or two units over a long-term trend of 3 years [42], and most patients end up in the dolichocephaly range. Among the advantages of the spring technique, we can pick up just the use of expansive forces, when the brain is not subject to any restriction or contraction. Complications of springs may include dural fistulas, sagittal tears, spring dislocation (in 3%), and decubitus over the spring (in 2%) [69,70]. Finally, the overall risk of complications is around 5% [70]. Springs are removed in 4.2-7 months [70,71]. The duration of surgery is within 1 h in 79% [42]. Laurizen et al. published difficult spring extraction in up to 7% [70]. The method does not affect existing deformities such as arched forehead or occipital vaulting [42]. In a comparative study by Skolnick, the spring method achieved significantly poorer postoperative CI results of 74.3 vs. 77.0 compared to endoscopically assisted strip craniectomy [72]. The inferior aesthetic results, low spring distribution, and the need for secondary surgery are likely the reasons for the low popularity of the spring technique.

 

Distraction techniques

The first mention of the use of distractors in patients with craniosynostosis was found in a 1998 publication by Sugawara et al. He used distractors in two patients with Crouzon syndrome and also in one patient with scaphocephaly. The operation consists of a large skin incision over the vertex, a gentle craniotomy without detaching the dura, screwing the distractors to the bone and bringing them out through the skin (Figure 9). Subsequent distraction of 1 mm per day to the desired final head shape begins several days after the procedure [73]. Other authors have described the combined use of lateral distraction and anteroposterior compression in more severe forms of scaphocephaly [74,75]. Removal of the distractors usually takes place 2-3 months after insertion. Documented cranial index gains with this method range from 68 units to the normocephaly range with 78 units with significant improvement in psychomotor development [75]. Sakamoto et al. even demonstrated comparable aesthetic results when compared with total cranial remodeling [43]. As with springs, a second surgery is needed to remove the distractors. At the same time, absorbable plates can be implanted during extraction to prevent collapse of the achieved head shape [76]. Transcutaneous distractors pose a risk for the spread of infection ranging up to between 9% and 22%. Similar to spring systems, dural tears and distractor loosening are potential risks, especially with insufficient bone thickness [77-79].

Discussion

The development and popularity of each technique was and is shaped by historical background. First, advances in perioperative care allowed the development of invasive surgical techniques with more predictable and better aesthetic outcomes [80]. Open strip craniectomy has gradually been abandoned. When compared with total cranial remodeling, it achieves significantly poorer aesthetic results with a difference of 3.4 cephalic units [80]. Similar results are also confirmed by Brichtová et al. from the Brno neurosurgery [9]. Already in the 1990s, strip craniectomy was not recommended in patients older than 18 months [33]. Nowadays, it has receded into the background, however, in the Di Rocca survey study, still 27.5% of surgeons used strip craniectomy or its modification as the main technique [50,81].

Surgical disciplines generally tend to be minimally invasive, which should result in a lower surgical burden on the patient. Thus, after the mastery of invasive techniques and the rise of technology, the inclination towards minimal invasiveness prevailed at the turn of the millennium with the development of more technically demanding procedures. The wider involvement and development of endoscopes and instrumentation, the discovery of distractors and springs, the development of materials such as absorbable plates, individually fabricated cranial orthoses, all opened up new possibilities. Especially endoscopically assisted surgeries have become widespread across the world [7,82].

John A. Jane already in the 1970s emphasized the importance of correcting compensatory growths of the skull. It is necessary to work with the fact that there are multiple forms of scaphocephaly and there is no one-size-fits-all operation that will resolve all variants [83]. In most cases, arched forehead or arching and narrowing of the lbi parieto-occipitally, or a combination, predominates. According to the dominant deformity, the frontal or occipital bone plate can be targeted and the operative technique adapted accordingly. The variety of findings has led to modifications of the different techniques [84]. Examples include the aforementioned reverse Pi technique for posterior scaphocephaly or the modification with parieto-occipital osteotomies correcting the posterior cranium published by us [41]. Endoscopically assisted strip craniectomy followed by cranial bracing can significantly affect compensatory skull growth. A properly fabricated and functional cranial orthosis can affect all compensatory deformities, mainly due to the young age of the child, the pliable bone plate, and the rapid growth of the skull. In contrast, the spring technique does not completely affect compensatory growth [42].

The age of the child has a significant influence on the choice of surgical technique. Minimally invasive techniques are suitable for patients up to 6-9 months of age. Later, the results are no longer aesthetically satisfactory due to maturation of the diploe and slowing of skull growth [63]. The age minimum is not clearly given. In endoscopically assisted strip craniectomy, even 2-week-old newborns can be operated [7]. For spring and distraction techniques, a higher age is recommended because of the need to attach the instrumentation to the bone plate. Thin bone could lead to loosening of the instrumentarium. In spring techniques, loosening is published in 3% of cases despite adherence to the age interval [69].

Open surgical techniques are better performed at an older age due to higher blood loss and manipulation of bone plates. Most often 6 months of age and a weight of around 6 kg is preferred. In our department the techniques are not perceived as competing but clearly complementary. Since the introduction of minimally invasive endoscopically assisted surgery in 2017 at our institution, there has been a dramatic shift in indication approaches and minimally invasive surgery has become predominant. On the other hand, there are still patients with scaphocephaly who were diagnosed late, and the method of choice for them is open remodelling. Due to advances in operative techniques, technical facilities, neuroanesthesia and perioperative care, open surgery is as close as possible to a minimally invasive technique, with the added advantage of immediate remodeling of the lbi. Parents can therefore be offered a positive perspective even with relatively late detection of scaphocephaly. A special category is cases of patients over 1, 2 or even 4 years of age, sometimes referred to as late scaphocephaly. In these cases, the patient benefits from invasive surgical techniques such as the clamshell technique or total cranial remodeling [31, 36-38]. In these late seizures, the situation is complicated by an unyielding bone plate, retarded skull growth, and reduced regeneration of bone defects. The standard approach to prevent postoperative defects is to divide the bone in the diploe over two bone plates with overlapping defect, incorporate bone dust and shavings into the defect site, or use hydroxyapatite substitutes [31,85].

Minimally invasive methods are based on iatrogenic creation of bone defects. Too large defects may not ossify with possible need for reoperation. On the other hand, narrow osteotomies may lead to resynostosis and recurrence of dolichocephaly. There is no unanimous opinion on the issue. Some authors create defects with an average width of 5.4 cm and length of 10 cm and do not mention persistent defects. Because of concerns about defect healing, some authors cut a narrower strip of bone two centimeters wide [51,86]. Other authors excise defects 4 cm wide but return a centimeter strip of bone above the sagittal raft [87]. Pulsation of the dura preventing ossification has been reported as a cause of defects in craniectomies [85].

Another interesting topic is the ancillary lateral osteotomies in the parietal bone in the Jimenez method. In the case of such partial incisions, a number of authors have failed to demonstrate an effect; moreover, they lead to prolongation of the operation [86,88,89]. On the contrary, other studies have advocated adjunctive incisions and reported a gain of 5 CI [18]. A study using 3D modeling to determine the importance of the extent of lateral incisions is currently underway at our institution.

Other authors focused on the duration of wearing the cranial brace. Iyer et al. point out the ineffectiveness of helmeting for 8.4 months [90]. Nguyen et al. recommend 8 months [91], Ridgway et al. 7.5 months, or helmet deferral in patients who reach 80 CI units [86]. Some authors point out the interesting fact that the aesthetic outcome is more dependent on the experience of the orthotist than on the experience of the surgeon [91,92]. Jimenez et al. agree with this and point to improperly fabricated helmets, low compliance in wearing a cranial brace (up to 17.1% of patients), and narrow sagittal synostectomy as the main causes of poor outcomes [19,93].

Reducing the length of helmet wearing can be achieved by extended techniques. Our published article documented a reduction in the need for a cranial brace to 1.5 months (P25: 1, P75: 2 months) with parietal lengthening and the addition of two occipital incisions [41]. Some authors omit the postoperative cranial brace altogether. In fact, the extension of endoscopic strip craniectomy brings us closer to open remodeling techniques from small skin incisions. Mutchnick et al. added 3-4 parietal incisions leading up to the squamous suture from three short skin incisions to strip craniectomy. In the case of occipital vaulting, they added two more incisions in the occipital bone parallel to the sagittal flap. They report a gain from 69 to 79 cephalic units [40]. Massimi et al. use up to six small skin incisions. The technique is similar to the open Renier H method. They cut the sagittal strip 3-4 cm wide and the lateral craniectomy 1-2 cm wide. Craniectomies are always bordered on one side by a coronal or lambda suture. In case of occipital arching, they add posterior incisions [39].

In recent years, studies on postoperative secondary synostosis have been emerging. The reason for the disappearance of the preoperative functional suture is unknown. Seruya et al. published a risk of secondary synostosis in patients after total cranial remodeling of 42.6%, 38.3%, and 74.5% for right coronal, left coronal, right lambda, and left lambda sutures, respectively [94]. Arnaud et al. determined the incidence of secondary coronal synostosis in 10% of patients operated with the Renier H technique, of which 1% required further surgical management [95]. The cause of secondary synostosis could be due to loss of vascular supply caused by suture detachment during surgery; this explains the higher incidence in invasive surgical techniques. On the other hand, in the special technique where the authors remove functional coronal and lambda sutures, coronal and lambda sutures are present in 56% and 86%, respectively, on follow-up CT scan [96]. Furthermore, the placement of the suture in the dead space in the Melbourne technique would explain the higher risk of lambda suture disappearance. Rottgers et al. described a case report of secondary synostosis even in an unoperated patient. This points to a genetic background as one of the factors [31].

The other side of the issue is the formation of a new suture after the adhesive suture has been removed. Agrawal et al. formed defects at the site of sagittal synostosis of 1.5-2.5 cm in open strip craniectomies and detected a new suture in 16.7% of cases on follow-up radiographs one to two years apart; the remaining patients had the defect completely overgrown [97]. The neogenesis of the suture has not been clarified. Sauerhammer et al. observed complete formation of a new suture in 17.6% of cases in patients after coronal synostosis surgery. Furthermore, in 70.6% it was a partial formation in combination with minor bony defects. In the remaining patients, resynostosis occurred. This was associated with poorer aesthetic results of surgery [98]. In some cases, a new suture is even created outside the original site of placement [99]. The influence of mechanical forces, dura pulsation or genetic background have been offered as explanations for suture neogenesis [85]. However, further studies are needed to clarify this phenomenon.

A number of studies have been devoted to the results of the different techniques and their comparison. When comparing open cranial remodeling with open strip craniectomy, cranial remodeling has shown better aesthetic results [55,100,101], up to twice as much [102], better cognitive outcomes in patients younger than 6 months of age [25], and a lower risk of increased intracranial pressure after surgery [103]. The only advantage of open strip craniectomy is the shorter operative time [101].

Endoscopic-assisted strip craniectomy offers the advantages of a less invasive surgical technique compared with open cranial remodeling, such as less blood loss and need for blood transfusions, shorter hospital stay, and shorter operative times [52]. Cosmetic outcomes are less clear-cut [52,104]. Most authors report comparable cosmetic outcomes [105,106]. Complications occur comparably or less with endoscopically assisted surgery [52].

In general, in craniosynostosis surgery, the administration of blood derivatives should not be too restrictive, as hemorrhagic shock is the most common cause of perioperative mortality [55,107]. The threshold for transfusion administration varies by institution and ranges from an Hb value of 60 to 80 g/L. A total of 44% of respondents administer transfusions in 90% of patients [50].

Conclusion

The surgical options for the correction of scaphocephaly are varied and still debated among specialists. Currently, there is no universal surgical technique. The choice depends on several factors such as the age of the child, the presence and severity of compensatory skull deformities, and the experience and equipment of the clinic. The aesthetic and functional results vary within the surgical techniques, but also within the different departments. The different techniques are not competitive but complementary and the choice should be made individually for each patient.

 

Conflict of interest

The authors declare that they have no conflict of interest in relation to the topic of the paper.

 

Financial support

The research was supported by the Grant Agency of Charles University (project no. 32122).

 

 

Tables

Table 1: Comparison of different techniques in terms of incision size, optimal timing of surgery, impact on forehead and head, change in CI, need for special instrumentation and postoperative care, and risk of resynostosis.