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Postoperative skeletal stability at the one-year follow-up after splintless Le Fort I osteotomy using patient-specific osteosynthesis versus conventional osteosynthesis: a randomized controlled trial

  • H. van der Wel
    Correspondence
    Correspondence to: Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, PO Box 30.001, NL-9700 RB Groningen, the Netherlands.
    Affiliations
    Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands
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  • J. Kraeima
    Affiliations
    Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands
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  • F.K.L. Spijkervet
    Affiliations
    Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands
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  • R.H. Schepers
    Affiliations
    Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands

    Department of Oral and Maxillofacial Surgery, Martini Hospital Groningen, Groningen, the Netherlands
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  • J. Jansma
    Affiliations
    Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands

    Department of Oral and Maxillofacial Surgery, Martini Hospital Groningen, Groningen, the Netherlands
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Open AccessPublished:October 03, 2022DOI:https://doi.org/10.1016/j.ijom.2022.09.005

      Abstract

      The purpose of this study was to assess the 1-year skeletal stability of the osteotomized maxilla after Le Fort I surgery, comparing conventional osteosynthesis with patient-specific osteosynthesis. Patients were assigned to a conventional or patient-specific osteosynthesis group using prospective randomization. The primary outcome was the three-dimensional change in postoperative skeletal position of the maxilla between the 2-week and 1-year follow-up cone beam computed tomography scans. Fifty-eight patients completed the protocol for the 2-week postoperative analysis, and 27 patients completed the 1-year follow-up study protocol. Of the 27 patients completing the entire protocol, 13 were in the conventional group and 14 in the patient-specific osteosynthesis group. The three-dimensional translation analysis showed that the use of the patient-specific osteosynthesis resulted in a skeletally stable result, comparable to that of conventional miniplate fixation. For both the patient-specific osteosynthesis and conventional miniplate fixation groups, median translations of less than 1 mm and median rotations of less than 1° were observed, indicating that both methods of fixation resulted in a stable result for the 27 patients examined. For the Le Fort I osteotomy, the choice between patient-specific osteosynthesis and conventional osteosynthesis did not affect the postoperative skeletal stability after 1 year of follow-up.

      Keywords

      Preoperative virtual surgical planning (VSP) has become an important tool in orthognathic surgery. High-resolution cone beam computed tomography (CBCT) and dental scans obtained during the work-up allow improved accuracy of planning and simulation of the result. In the search for accurate translation of the VSP to the surgical result, a splintless procedure using patient-specific osteosynthesis (PSO) for Le Fort I osteotomies has recently been introduced at the authors’ centre.
      • Suojanen J.
      • Leikola J.
      • Stoor P.
      The use of patient-specific implants in orthognathic surgery: a series of 32 maxillary osteotomy patients.
      • Heufelder M.
      • Wilde F.
      • Pietzka S.
      • Mascha F.
      • Winter K.
      • Schramm A.
      • Rana M.
      Clinical accuracy of waferless maxillary positioning using customized surgical guides and patient specific osteosynthesis in bimaxillary orthognathic surgery.
      • Kraeima J.
      • Schepers R.H.
      • Spijkervet F.K.L.
      • Maal T.J.J.
      • Baan F.
      • Witjes M.J.H.
      • Jansma J.
      Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.
      PSO has proven to be valuable in terms of improving the accuracy of maxillary placement during surgery, especially for larger (>3.7 mm) translations.
      • Kraeima J.
      • Schepers R.H.
      • Spijkervet F.K.L.
      • Maal T.J.J.
      • Baan F.
      • Witjes M.J.H.
      • Jansma J.
      Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.
      In addition to the initial surgical accuracy, the postoperative stability of the result should be considered when evaluating the accuracy of orthognathic surgery. For the Le Fort I osteotomy, relapse rates are considerably high, with a clinically significant (>2 mm) amount of horizontal relapse reported to occur in 14% of patients.
      • Dowling P.A.
      • Espeland L.
      • Sandvik L.
      • Mobarak K.A.
      • Hogevold H.E.
      LeFort I maxillary advancement: 3-year stability and risk factors for relapse.
      Since the introduction of Le Fort I surgery, developments aimed at improving the stability by improving the fixation method have been reported.
      • Van Sickels J.E.
      • Richardson D.A.
      Stability of orthognathic surgery: a review of rigid fixation.
      • Egbert M.
      • Hepworth B.
      • Myall R.
      • West R.
      Stability of Le Fort I osteotomy with maxillary advancement. A comparison of combined wire fixation and rigid fixation.
      • Ragaey M.
      • Van Sickels J.E.
      Stability of large maxillary advancements using a combination of prebent and conventional plates for fixation.
      • Susarla S.M.
      • Ettinger R.
      • Preston K.
      • Kapadia H.
      • Egbert M.A.
      Two-point nasomaxillary fixation of the Le Fort I osteotomy: assessment of stability at one year postoperative.
      Patient-specific osteosynthesis (PSO) plates are designed to follow the anatomical contour of the maxilla without the need for intraoperative bending, ideally resulting in a passive and tension-free fitting.
      • Kotaniemi K.V.M.
      • Heliövaara A.
      • Kotaniemi M.
      • Stoor P.
      • Leikola J.
      • Palotie T.
      • Suojanen J.
      Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy, using patient-specific implant versus mini-plate fixation.
      In contrast, the miniplates that are conventionally used have to be bendable during surgery to achieve a proper, passive and tension-free fitting. The rigidity of the PSO plates might influence the postoperative stability, as has been indicated in two previous studies, where it was shown that PSO provided enough stability for application at the nasomaxillary buttresses only without posterior fixation,
      • Susarla S.M.
      • Ettinger R.
      • Preston K.
      • Kapadia H.
      • Egbert M.A.
      Two-point nasomaxillary fixation of the Le Fort I osteotomy: assessment of stability at one year postoperative.
      or using only wire fixation for posterior fixation.
      • Carneiro Júnior J.T.
      • Voss de Oliveira D.
      • Goodday R.
      Maxillary stability following Le Fort I osteotomy using prebent plates and wire fixation in patients undergoing surgery for OSAS.
      Besides the publications mentioned above, there have only been a few other studies on skeletal stability after the application of PSO. One study that directly compared the stability after PSO and conventional osteosynthesis was found, which concluded that the two methods resulted in equally stable results.
      • Kotaniemi K.V.M.
      • Heliövaara A.
      • Kotaniemi M.
      • Stoor P.
      • Leikola J.
      • Palotie T.
      • Suojanen J.
      Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy, using patient-specific implant versus mini-plate fixation.
      Overall, the current literature seems to indicate that PSO results in a stable fixation, comparable to that of conventional miniplate osteosynthesis, albeit with scarce evidence. Studies lack objective analysis on accuracy and the amount of relapse measured in three dimensions. As recommended by previous authors, research using a three-dimensional (3D) image fusion analysis instead of two-dimensional (2D) radiography tracings is necessary.
      • Kotaniemi K.V.M.
      • Heliövaara A.
      • Kotaniemi M.
      • Stoor P.
      • Leikola J.
      • Palotie T.
      • Suojanen J.
      Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy, using patient-specific implant versus mini-plate fixation.
      The aim of this study was to compare the skeletal stability of the maxilla at 1 year after Le Fort I osteotomy performed using either PSO or conventional osteosynthesis, based on 3D image fusion analysis, in a randomized controlled trial (RCT).

      Materials and methods

      Study population

      The population of this multicentre RCT consisted of patients treated at the University Medical Centre Groningen and Martini Hospital Groningen between August 2015 and October 2018. The trial was approved by the local medical ethics board (Medical Ethics Review Committee, University Medical Centre Groningen; File Number METc 2015/084). The short-term results (maxillary placement accuracy at 2 weeks postoperative) have been reported previously by Kraeima et al.
      • Kraeima J.
      • Schepers R.H.
      • Spijkervet F.K.L.
      • Maal T.J.J.
      • Baan F.
      • Witjes M.J.H.
      • Jansma J.
      Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.
      The study was performed according to the CONSORT guidelines (http://www.consort-statement.org/).
      Inclusion criteria for this study were (1) patient due to receive a Le Fort I osteotomy, with or without simultaneous mandibular osteotomy, (2) patient able to complete the routine 3D VSP work-up, and (3) patient age at least 18 years. Patient exclusion criteria were (1) patient did not agree to participate in the trial, (2) patient was unable to undergo the 3D virtual planning procedure for any reason, (3) pregnancy, and (4) patient had a known allergy to titanium.
      The included patients were divided into two groups by means of block randomization: (1) a conventional osteosynthesis group of patients (control group), in whom a 3D computer-aided design and manufacturing (CAD/CAM) surgical splint and miniplate fixation were used; and (2) a patient-specific osteosynthesis group of patients (PSO group), in whom 3D-printed drilling/osteotomy guides were used to indicate the osteotomy line and drilling location, and fixation was performed using four 3D milled titanium PSO plates, as described by Kraeima et al.
      • Kraeima J.
      • Jansma J.
      • Schepers R.H.
      Splintless surgery: does patient-specific CAD–CAM osteosynthesis improve accuracy of Le Fort I osteotomy?.

      3D planning and intervention

      Prior to surgery, a 3D VSP was made for every patient using Maxilim v2.3 (Medicim, Mechelen, Belgium) according to the triple scan protocol described by Swennen et al.
      • Swennen G.R.
      • Mollemans W.
      • De Clercq C.
      • Abeloos J.
      • Lamoral P.
      • Lippens F.
      • Neyt N.
      • Casselman J.
      • Schutyser F.
      A cone-beam computed tomography triple scan procedure to obtain a three-dimensional augmented virtual skull model appropriate for orthognathic surgery planning.
      The design of the PSO, drilling/osteotomy guides, and surgical splints was based on this 3D VSP. For the conventional group, the LevelOne Orthognathics 1.5 miniplate system by KLS Martin (KLS Martin Group, Tuttlingen, Germany) was used. For the PSO group, 3D milled medical grade titanium osteosynthesis designed and fabricated by Createch Medical (Createch Medical SL, Mendaro, Spain) was used. In both cases, the same type and length of screws were used (LevelOne 1.5 system, KLS Martin Group).
      For all patients, the surgery included a conventional Le Fort I approach with an upper vestibular incision exposing the maxillary bone. The maxilla was mobilized and guided to the new position using either the surgical splint (conventional group) or the PSO (PSO group). A schematic overview of the procedure used to position the maxilla in the PSO group is provided in Fig. 1, including the 3D VSP (Fig. 1A, B), the guide placement and drilling (Fig. 1C), and the PSO placement (Fig. 1D). For bimaxillary osteotomies, the mandible was repositioned using a conventional bilateral sagittal split osteotomy (BSSO) and guidance with the final 3D surgical splint. The maxilla-first sequence was used for all bimaxillary cases.
      Fig. 1
      Fig. 1Schematic overview of the 3D VSP PSO workflow. (A) 3D VSP for maxillary translation/rotation. (B) Screw position planning (screws shown in red). (C) Drilling and indication of the osteotomy line using surgical drill guides. (D) Positioning and fixation of the maxillary segment using the PSO. (3D, three-dimensional; VSP, virtual surgical planning; PSO, patient-specific osteosynthesis.).

      Analysis of postoperative skeletal stability

      The patients underwent two postoperative CBCT scans as part of the routine follow-up protocol: one at the first postoperative follow-up consultation (range 9–16 days) and the other at 1 year (range 10–15 months) after surgery. 3D virtual head models were made for both scans and registered to the 3D VSP in Maxilim using voxel-based matching.
      • Maes F.
      • Collignon A.
      • Vandermeulen D.
      • Marchal G.
      • Suetens P.
      Multimodality image registration by maximization of quantitative–qualitative measure of mutual information.
      The anterior cranial base was used as the region of interest for the matching. After the bone-based matching, three landmarks on the dentition were used to quantify the movement of the maxilla: the most mesial point of the incisor edge of the right upper central incisor (UI) and the most inferior points of the mesial cusps of the crown of the right first upper molar (#16) and left first upper molar (#26).
      • Baan F.
      • Liebregts J.
      • Xi T.
      • Schreurs R.
      • de Koning M.
      • Bergé S.
      • Maal T.
      A new 3D tool for assessing the accuracy of bimaxillary surgery: the OrthoGnathicanAlyser.
      The landmarks chosen are on the dentition, but the registration process only includes the maxilla and not the dentition. Because the points are simply moved along in a rigid manner without considering the changes in dental position, postoperative orthodontics or other changes in dental position do not influence the measurement. Fig. 2 presents an overview of the alignment of the 2-week and 1-year postoperative data.
      Fig. 2
      Fig. 2Quantification of maxilla movement: (1) alignment of the 2-week and 1-year postoperative CBCT scans with the planning, based on the anterior skull region of interest; (2) alignment of the osteotomized maxilla with the 2-week and 1-year postoperative CBCT.
      The virtually osteotomized maxilla was translated from its preoperative position to the 2-week and 1-year postoperative positions using voxel-based matching, rigidly moving the three landmarks along. For the preoperative VSP, 2-week postoperative, and 1-year postoperative 3D head models, the coordinates of the three maxilla landmarks were exported to compare the 2-week and 1-year postoperative positions (see Fig. 3). Translations and rotations were assessed in relation to the Frankfort horizontal plane, the CBCT coronal plane, and the CBCT sagittal plane. Using the UI landmark, the translations in anterior/posterior, cranial/caudal, and left/right directions between the scans were calculated. By examining the rotation of the triangle formed by the #16, UI, and #26 landmarks, the rotation (roll, pitch, and yaw) of the osteotomized maxilla around the UI point was calculated.
      Fig. 3
      Fig. 3Detailed view of the method used to quantify the maxilla movement. After registration of the osteotomized maxilla, the position of the triangle formed by three landmarks was exported from the 2-week position (A) and 1-year position (B), in order to calculate the translation and rotation between them (C).

      Statistical analysis

      The Mann–Whitney U-test was performed to test for significant differences, using IBM SPSS Statistics version 23 (IBM Corp., Armonk, NY, USA). Values of P < 0.05 were considered statistically significant. The inter-observer variation was determined for a randomly selected sample group (n = 6) analysed by a second observer (J.K.), for both the 2-week and 1-year postoperative measurements.

      Results

      Inclusion

      A total of 64 patients provided informed consent to participate in the RCT. Fifty-eight patients completed the protocol for the 2-week postoperative analysis, but unfortunately only 27 patients completed the 1-year follow-up study protocol. Reasons for drop-out between the 2-week and 1-year protocol were as follows: no CBCT dataset available due to ‘no-show’ of the patient (n = 25) or CBCT scan was performed outside the follow-up period (n = 6).
      Of the 27 patients who completed the follow-up protocol, 13 were treated with conventional osteosynthesis (control group) and 14 patients with PSO (PSO group). Except for two patients in the PSO group, all patients underwent a bimaxillary procedure, combining the Le Fort I procedure with a BSSO. The demographics and 2-week postoperative 3D results of the included patients are presented in Table 1. There was no significant difference in the 2-week postoperative 3D results between the two groups.
      Table 1Patient characteristics. The Mann–Whitney U-test was performed, and it was determined that there was no significant difference in the 2-week 3D results between the two groups.
      Patient characteristics
      CharacteristicsControlPSO
      Number of patients1314
      Sex, n
       Female95
       Male49
      Age (years), mean± SD26.8 ± 6.928.6 ± 9.7
      Number of bimaxillary1312
      Planned translation of UI2-week results (mm)
      DirectionControl, n patientsPSO, n patientsControl

      Median (IQR)
      PSO

      Median (IQR)
       Cranial740.9 (0.2, 5.4)2.1 (0.6, 6.5)
       Caudal6102.0 (1.0, 3.0)2.1 (1.2, 3.2)
       Anterior13142.8 (1.2, 4.5)3.8 (2.3, 4.3)
       Left681.2 (0.9, 1.6)0.5 (0.2, 1.7)
       Right760.9 (0.9, 1.3)0.9 (0.3, 1.8)
      Planned rotation of maxilla2-week results (°)
       DirectionControl, n patientsPSO, n patientsControlPSO
       Pitch CW771.8 (0.0, 3.6)2.6 (1.7, 3.3)
       Pitch CCW671.9 (0.2, 7.3)2.9 (0.5, 5.7)
       Roll CW381.6 (0.9, 1.6)1.2 (0.2, 2.6)
       Roll CCW1060.6 (0.2, 1.9)0.7 (0.4, 2.0)
       Yaw CW670.9 (0.3, 1.2)0.2 (0.2, 0.6)
       Yaw CCW770.6 (0.0, 1.3)0.2 (0.0, 1.8)
      3D, three-dimensional; CCW, counterclockwise; CW, clockwise; IQR, interquartile range (Q1, Q3); PSO, patient-specific osteosynthesis; SD, standard deviation; UI, upper central incisor.

      Inter-observer variability

      Regarding the 2-week postoperative measurements, the intra-class correlation coefficient (ICC) for all measurements of the randomly selected six cases was 0.98, with a median error of 0.20 mm (interquartile range (IQR) 0.09–0.80 mm). Regarding the 1-year postoperative measurements, the ICC for all measurements was 0.97, with a median error of 0.23 mm (IQR 0.11–0.71 mm).

      -year skeletal stability results

      The 1-year skeletal stability results are presented in Table 2, Table 3. No significant difference in relapse at 1 year was found between the control group and PSO group for translation in any direction when the results in each group were compared to the 2-week postoperative 3D position of the maxilla. The median relapse observed was below 1 mm in both the control group and PSO group. Considering the rotational stability, a significant difference was found for the absolute rotational stability around the yaw axis, where relapse was smaller in the control group than in the PSO group (P < 0.01).
      Table 2Absolute movement between 2 weeks and 1 year, and median directional movement between 2 weeks and 1 year; the median and interquartile range (Q1, Q3) are reported.
      Translation of UI (mm)Absolute difference 1-yearDirectional difference
      DirectionControlPSOControlDirectionPSODirectionSig.
      Cranial0.4 (0.3, 0.8)0.2 (0.0, 0.4)0.3 (−0.4, 0.6)Cranial0.2 (0.0, 0.4)Caudal> 0.05
      Caudal0.2 (0.0, 0.5)0.7 (0.2, 1.3)0.0 (−0.2, 0.4)0.7 (0.1, 1.3)Cranial> 0.05
      Anterior0.2 (0.2, 0.4)0.5 (0.2, 0.8)0.1 (−0.2, 0.3)Posterior0.1 (−0.2, 0.6)Posterior> 0.05
      Left0.2 (0.1, 0.4)0.3 (0.2, 0.4)0.0 (−0.2, 0.3)0.1 (−0.3, 0.3)Left> 0.05
      Right0.2 (0.1, 0.2)0.5 (0.2, 1.3)0.2 (0.1, 0.2)Left0.4 (−0.3, 1.3)Left> 0.05
      Rotation of maxilla (°)Absolute difference 1-yearDirectional difference
      DirectionControlPSOControlDirectionPSODirectionSig.
      Pitch CW0.0 (0.0, 0.1)0.1 (0.0, 0.3)0.0 (0.0, 0.1)CW0.0 (−0.1, 0.2)CCW> 0.05
      Pitch CCW0.0 (0.0, 0.7)0.1 (0.0, 1.0)0.0 (−0.2, 0.2)0.0 (−0.7, 0.1)> 0.05
      Roll CW0.2 (0.1, 0.2)0.7 (0.2, 1.5)0.2 (0.1, 0.2)CCW0.3 (−0.5, 1.5)CCW> 0.05
      Roll CCW0.2 (0.0, 0.6)0.2 (0.1, 0.9)0.1 (0.0, 0.6)CCW0.1 (−0.2, 0.5)CCW> 0.05
      Yaw CW0.1 (0.0, 0.2)0.2 (0.2, 0.8)0.0 (−0.1, 0.1)0.2 (−0.2, 0.8)CW> 0.05
      Yaw CCW0.0 (0.0, 0.1)0.1 (0.1, 0.6)0.0 (0.0, 0.1)0.1 (−0.1, 0.6)CW> 0.05
      CCW, counterclockwise; CW, clockwise; PSO, patient-specific osteosynthesis; UI, upper central incisor.
      Table 3Translations and rotations in the two study groups, along the cranial/caudal, anterior/posterior, left/right axis directions, and pitch, roll, and yaw dimensions; the median and interquartile range (Q1, Q3) are reported. A significant difference in absolute yaw was found between the control and PSO groups.
      Translation of UI (mm)2-week resultAbsolute difference at 1 year
      DirectionControlPSOControlPSOControlPSOSig.
      Cranial/caudal13141.5 (0.6, 4.5)2.1 (0.9, 3.5)0.3 (0.2, 0.7)0.3 (0.1, 1.3)> 0.05
      Anterior/posterior13142.8 (1.2, 4.5)3.8 (2.3, 4.3)0.2 (0.2, 0.4)0.5 (0.2, 0.8)> 0.05
      Left/right13141.2 (0.9, 1.4)0.5 (0.3, 1.7)0.2 (0.1, 0.3)0.3 (0.2, 0.6)> 0.05
      Rotation of maxilla (°)2-week resultAbsolute difference at 1 year
      DirectionControlPSOControlPSOControlPSOSig.
      Pitch13141.8 (0.2, 4.0)2.6 (0.7, 4.7)0.0 (0.0, 0.3)0.1 (0.0, 0.4)> 0.05
      Roll13140.9 (0.2, 2.4)0.7 (0.3, 2.3)0.2 (0.0, 0.6)0.5 (0.1, 1.1)> 0.05
      Yaw13140.6 (0.3, 1.2)0.2 (0.2, 0.9)0.0 (0.0, 0.1)0.2 (0.1, 0.6)< 0.01 *
      PSO, patient-specific osteosynthesis; UI, upper central incisor. *Significant, P < 0.05.

      Discussion

      In this prospective multicentre RCT, the 1-year follow-up skeletal stability of the maxilla after Le Fort I osteotomy was compared between PSO and conventional miniplate fixation groups. The 3D translation analysis showed that the use of PSO did not result in a significant difference in 1-year skeletal stability compared to the conventional miniplate osteosynthesis approach. 3D rotation analysis showed that the rotational stability was comparable in the PSO and conventional osteosynthesis groups, with the exception of rotation around the yaw axis, where the PSO fixation seemed less stable. For both the PSO and conventional miniplate fixation groups, median relapse translations were less than 1 mm and median rotations were less than 1°, indicating that both methods of fixation gave stable results for the 27 patients examined.
      Assessing the stability along the three primary axes without subdivision in direction of movement, the translations in all directions were comparably stable in the two groups. These results confirm the conclusions of Kotaniemi et al.,
      • Kotaniemi K.V.M.
      • Heliövaara A.
      • Kotaniemi M.
      • Stoor P.
      • Leikola J.
      • Palotie T.
      • Suojanen J.
      Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy, using patient-specific implant versus mini-plate fixation.
      who previously compared PSO fixation with conventional osteosynthesis. A 3D fusion analysis method was used in the current study, in contrast to the 2D methods used by Kotaniemi et al. and in other previous PSO relapse studies.
      • Susarla S.M.
      • Ettinger R.
      • Preston K.
      • Kapadia H.
      • Egbert M.A.
      Two-point nasomaxillary fixation of the Le Fort I osteotomy: assessment of stability at one year postoperative.
      • Kotaniemi K.V.M.
      • Heliövaara A.
      • Kotaniemi M.
      • Stoor P.
      • Leikola J.
      • Palotie T.
      • Suojanen J.
      Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy, using patient-specific implant versus mini-plate fixation.
      • Carneiro Júnior J.T.
      • Voss de Oliveira D.
      • Goodday R.
      Maxillary stability following Le Fort I osteotomy using prebent plates and wire fixation in patients undergoing surgery for OSAS.
      Comparison of the current results with those in the previous literature is therefore only indicative of the fact that the results are in the same range.
      The rotational stability in this study was found to be comparable for pitch and roll, but significantly higher for the conventional osteosynthesis group for rotations around the yaw axis. Sub-grouping the initial correction of the rotation into either clockwise or counterclockwise groups did not give a significant difference in either group. Although significant, the higher stability for rotation along the yaw axis in the conventional group, in absolute values, is only slightly more stable (0.0° vs 0.2°). Considering a value of relapse larger than 1° as the cut-off point for a stable result, both the PSO and conventional osteosynthesis resulted in very stable results at the 1-year follow-up.
      In the literature, larger advancement of the maxilla has been found to be more unstable in a number of studies.
      • Ragaey M.
      • Van Sickels J.E.
      Stability of large maxillary advancements using a combination of prebent and conventional plates for fixation.
      • Bailey L.T.J.
      • Cevidanes L.H.S.
      • Proffit W.R.
      Stability and predictability of orthognathic surgery.
      • Fahradyan A.
      • Wolfswinkel E.M.
      • Clarke N.
      • Park S.
      • Tsuha M.
      • Urata M.M.
      • Hammoudeh J.A.
      • Yamashita D.R.
      Impact of the distance of maxillary advancement on horizontal relapse after orthognathic surgery.
      • Lee C.C.
      • Xhori O.
      • Tannyhill R.J.
      • Kaban L.B.
      • Peacock Z.S.
      Variables associated with stability after Le Fort I osteotomy for skeletal Class III malocclusion.
      • Proffit W.R.
      • Turvey T.A.
      • Phillips C.
      The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension.
      • Louis P.J.
      • Waite P.D.
      • Austin R.B.
      Long-term skeletal stability after rigid fixation of Le Fort I osteotomies with advancements.
      In the current study, the PSO group had a larger median advancement of 3.8 mm in comparison to the control group advancement of only 2.8 mm; however the difference was not significant. Regardless of the larger advancement in the PSO group, the two groups had comparable postoperative stability in the anterior/posterior direction.
      Of note, the statistical comparison between the directional and rotational sub-groups suffered from the skewedness in group sizes. Considering the prevalence of relapse, the skewedness in group sizes might have influenced the results of the statistical comparison. Generally, the results of this study are limited by a relatively small sample size due to the large number of patients lost during follow-up.
      The accuracy of PSO is significantly favourable in a maxillary advancement of more than 3.7 mm.
      • Kraeima J.
      • Schepers R.H.
      • Spijkervet F.K.L.
      • Maal T.J.J.
      • Baan F.
      • Witjes M.J.H.
      • Jansma J.
      Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.
      The current results suggest that PSO provides a stable result for a median anterior translation of 3.8 mm. The choice between conventional osteosynthesis and PSO should possibly also be based on the patient’s specific surgery plan, considering not only the immediate postoperative accuracy but also the expected stability after 1 year of follow-up.
      A previous study reported in the literature on relapse when using conventional four-miniplate fixation for larger maxillary advancements, indicated that maxillary advancements of 0–6 mm, 7–9 mm, and> 10 mm resulted in increasing instability of 0.0 ± 0.6 mm, 0.7 ± 1.5 mm, and 1.9 ± 1.8 mm relapse, respectively.
      • Louis P.J.
      • Waite P.D.
      • Austin R.B.
      Long-term skeletal stability after rigid fixation of Le Fort I osteotomies with advancements.
      Given the indication for the use of PSO for larger maxillary advancements, and the suggestion from the current results that PSO might result in a comparable or possibly better postoperative stability than conventional osteosynthesis for larger maxillary advancements, a separate study to compare the stability of larger (>3.5 mm) maxillary advancements might be useful.
      The 1-year follow-up data presented suggest that the choice between patient-specific and conventional osteosynthesis does not affect the postoperative skeletal stability. Although a statistically significant difference was found when considering rotation around the yaw axis, the difference was too small to be of clinical significance. Considering the clinical relevance, the postoperative stability when using PSO appears to be non-inferior to the postoperative stability when using conventional osteosynthesis.

      Ethics approval and consent to participate

      Approved by the Medical Ethics Review Committee, University Medical Centre Groningen (File Number METc 2015/084).

      Funding

      This collaboration project is co-financed by the Dutch Ministry of Economic Affairs and Climate Policy by means of the Public–Private Partnership allowance made available by Top Sector Life Sciences & Health to stimulate public–private partnerships.

      Competing interests

      None.

      Patient consent

      Written patient consent was obtained.

      Trial registration

      The trial was registered in the Netherlands Trial Registry (number NTR5324).

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