Calvarial vault reconstruction in craniosynostosis surgery : overcoming commonly seen challenges

Research output: ThesisDoctoral Thesis


Craniosynostosis is the premature fusion of a suture between cranial bones and is the second most common congenital dysmorphology in the craniofacial region (Boulet et al., 2008; Kweldam et al., 2011). Brain growth is rapid after birth and sutures are sites that allow the calvarium to accomodate the growing brain (Flaherty et al., 2016). Accordingly, growth restriction occurs at the site of the fused suture. Compensatory growth occurs perpendicularly with respect to the closed suture, causing deformation of the calvarium. Craniosynostosis leads to mechanical compression of the brain and possibly to reduced intracranial volume and occasionally raised intracranial pressure (Eckelt et al., 2007; Rogers and Stephen, 2013; Shim et al., 2016). Neurodevelopmental deficits are also related to craniosynostosis (Chummun et al., 2016; Rogers and Stephen, 2013). Craniosynostosis is treated surgically by reconstruction of the calvarium. The ultimate reconstruction goal is to expand the intracranial volume to allow the brain to grow normally and release raised intracranial pressure. The second goal is to provide a biomechanically stable calvarium with aesthetically satisfying contour. Challenges such as unossifiated calvarial defects, operation invasiveness and establishment of stable reconstruction are related to traditional open calvarial vault reconstruction (CVR). In the past two decades, several new techniques, materials and devices have been introduced to overcome open CVR-related problems. However, long-term results of the new treatment modalities are mostly still missing and treatment protocols are highly variable between centres. The new applications include bone substitutes to address open CVR-related calvarial defects, calvarial distraction osteogesis (DO) to reduce invasiveness of treatment and resorbable fixation systems to overcome titanium fixation-related problems. There is a need to better understand the new treatment modalities such that surgical results can be improved and treatment protocols standardised. Patients and methods In study I, we retrospectively compared the ossification of calvarial defects covered with demineralised bone (DBM) plate or DBM plate and bone dust to uncovered calvarial defects on the calvariums of the same patients from open-CVR patients. The measurement method was developed for the study to define The fusion degree (dF) of the calvarial defects from one-week to one-year postoperative 3-D CT reconstructed images. DBM-related complications were retrieved from medical records. In study II, we developed a non-invasive method to measure resisting force in calvarial DO. A further aim of the study was to understand the biomechanical environment in calvarial DO. Distraction force was measured for four posterior calvarial vault DO (PCVDO) patients. In studies III and IV, we tested in a laboratory setting the mechanical properties of resorbable CVR fixation systems. Mechanical load was conducted via a universal testing machine to pins or screws fixed to bone until the fixation broke. In study III, conventional resorbable screws (CRS) and ultrasound-activated pins (UAP) were used. In study IV, we tested the suitability of three resorbable fixation systems, namely CRS, heat-activated pin (HAP) and UAP for cranial distractor fixation. Results The mean dF of the DBM and control defects were 74% (SD 30) and 54% (SD 43) (p2.3 years). DBM appears to be more effective when used with bone dust. The developed force measurement method can be used during calvarial DO with sufficient accuracy and without additional harm to the patient. We propose that dividing the distraction protocol to more frequent sessions with shorter distraction distance could reduce distraction resistance that in turn could reduce force-related complications. There is no clinically significant difference of the fixation strength between UAPs and CRSs. Careful sonotrode handling is required to establish stable fixation with UAPs. Cranial distractors can be fixed with four CRSs or six HAPs per footplate in PCVDO and Monoblock DO. Distraction fixation with resorbable materials can reduce PCVDO complications.
Original languageEnglish
  • Leikola, Junnu, Supervisor
  • Tukiainen, Erkki, Supervisor
Place of PublicationHelsinki
Print ISBNs978-951-51-4109-5
Electronic ISBNs978-951-51-4116-3
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Bibliographical note

M1 - 81 s. + liitteet

Fields of Science

  • Osteogenesis, Distraction
  • Intracranial Pressure
  • Calcium Phosphates
  • Ceramics
  • Sutures
  • Internal Fixators
  • Craniosynostoses
  • +surgery
  • Brain
  • +physiopathology
  • Glass
  • Titanium
  • Tomography
  • Treatment Outcome
  • Biocompatible Materials
  • 3126 Surgery, anesthesiology, intensive care, radiology

Cite this