Three-dimensional dento-skeletal effects of mandibular midline distraction and surgically assisted rapid maxillary expansion: A retrospective study.

It was the aim of the study to provide a three-dimensional evaluation of dento-skeletal effects following bone-borne vs tooth-borne mandibular midline distraction (MMD) and tooth-borne surgically assisted rapid maxillary expansion (SARME). A retrospective observational study was conducted. Cone beam computed tomography (CBCT) records were taken pre-operatively (T1), immediately post-distraction (T2) and 1 year post-operatively (T3). All included 30 patients had undergone MMD (20 bone-borne MMD; 10 tooth-borne MMD). A total of 20 bone-borne MMD and 8 tooth-borne MMD patients had simultaneously undergone tooth-borne SARME. At T1 vs T3, canine (p = 0.007; 26.0 ± 2.09 vs 29.2 ± 2.02) and first premolar (p = 0.005; 33.8 ± 2.70 vs 37.0 ± 2.43) showed significant expansion on the tip level for tooth-borne MMD. This was no significant on the apex level, indicating tipping. Bone-borne MMD showed a parallel distraction gap, whereas tooth-borne MMD showed a V-shape. There was a significant (p = 0.017; 138 ± 17.8 vs 141 ± 18.2) inter-condylar axes increase for bone-borne MMD. In conclusion, bone-borne vs tooth-borne MMD and tooth-borne SARME showed stable dento-skeletal effects at 1 year post-operatively. Bone-borne and tooth-borne MMD seemed not to be superior to each other. The choice of distractor type therefore depends more on anatomical and comfort factors.

Correlation between head shape and volumetric changes following spring-assisted posterior vault expansion.

The aim of the study was to investigate whether different head shapes show different volumetric changes following spring-assisted posterior vault expansion (SA-PVE) and to investigate the influence of surgical and morphological parameters on SA-PVE. Preoperative three-dimensional skull models from patients who underwent SA-PVE were extracted from computed tomography scans. Patient head shape was described using statistical shape modelling (SSM) and principal component analysis (PCA). Preoperative and postoperative intracranial volume (ICV) and cranial index (CI) were calculated. Surgical and morphological parameters included skull bone thickness, number of springs, duration of spring insertion and type of osteotomy. In the analysis, 31 patients were included. SA-PVE resulted in a significant ICV increase (284.1 ± 171.6 cm3, p < 0.001) and a significant CI decrease (-2.9 ± 4.3%, p < 0.001). The first principal component was significantly correlated with change in ICV (Spearman ρ = 0.68, p < 0.001). Change in ICV was significantly correlated with skull bone thickness (ρ = -0.60, p < 0.001) and age at time of surgery (ρ = -0.60, p < 0.001). No correlations were found between the change in ICV and number of springs, duration of spring insertion and type of osteotomy. SA-PVE is effective for increasing the ICV and resolving raised intracranial pressure. Younger, brachycephalic patients benefit more from surgery in terms of ICV increase. Skull bone thickness seems to be a crucial factor and should be assessed to achieve optimal ICV increase. In contrast, insertion of more than two springs, duration of spring insertion or performing a fully cut through osteotomy do not seem to impact the ICV increase. When interpreting ICV increases, normal calvarial growth should be taken into account.

Correlation of Intracranial Volume With Head Surface Volume in Patients With Multisutural Craniosynostosis.

Intracranial volume (ICV) is an important parameter for monitoring patients with multisutural craniosynostosis. Intracranial volume measurements are routinely derived from computed tomography (CT) head scans, which involves ionizing radiation. Estimation of ICV from head surface volumes could prove useful as 3D surface scanners could be used to indirectly acquire ICV information, using a non-invasive, non-ionizing method.Pre- and postoperative 3D CT scans from spring-assisted posterior vault expansion (sPVE) patients operated between 2008 and 2018 in a single center were collected. Patients were treated for multisutural craniosynostosis, both syndromic and non-syndromic. For each patient, ICV was calculated from the CT scans as carried out in clinical practice. Additionally, the 3D soft tissue surface volume (STV) was extracted by 3D reconstruction of the CT image soft tissue of each case, further elaborated by computer-aided design (CAD) software. Correlations were analyzed before surgery, after surgery, combined for all patients and in syndrome subgroups.Soft tissue surface volume was highly correlated to ICV for all analyses: r = 0.946 preoperatively, r = 0.959 postoperatively, and r = 0.960 all cases combined. Subgroup analyses for Apert, Crouzon-Pfeiffer and complex craniosynostosis were highly significant as well (P < 0.001).In conclusion, 3D surface model volumes correlated strongly to ICV, measured from the same scan, and linear equations for this correlation are provided. Estimation of ICV with just a 3D surface model could thus be realized using a simple method, which does not require radiations and therefore would allow closer monitoring in patients through multiple acquisitions over time.