YIJOM-4335; No of Pages 9

Clinical Paper

Orthognathic Surgery

Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxxhttps://doi.org/10.1016/j.ijom.2019.12.001, available online at https://www.sciencedirect.com

Relevance of 3D virtualplanning in predicting bonyinterferences between distaland proximal fragments aftersagittal split osteotomyA. Valls-Ontanon, R. D. J. Ascencio-Padilla, A. Vela-Lasagabaster, A. Sada-Malumbres, O. L. Haas-Junior, J. Masia-Gridilla, F. Hernandez-Alfaro: Relevance of3D virtual planning in predicting bony interferences between distal and proximalfragments after sagittal split osteotomy. Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx. ã 2019 International Association of Oral and Maxillofacial Surgeons. Publishedby Elsevier Ltd. All rights reserved.

Abstract. After sagittal split osteotomy, the mandibular distal and proximal fragmentsdo not always align themselves passively to one another, resulting in bonyinterferences and subsequent anomalous settlement of the condyles. Predicting theseinterferences could be an important ancillary procedure for avoiding intra- andpostoperative surgical complications, rendering orthognathic surgery more effectiveand safer. This study evaluated the relevance of virtual surgical planning in assessingthe displacement of the proximal segments after virtual distal segment repositioning,for predicting bony interferences between the segments and thus avoiding relatedintra- and postoperative surgical complications. The presence of interferencesbetween the distal and proximal segments was compared between virtually predicted(computer-assisted simulation surgery, Dolphin software) and real cases in 100consecutive patients diagnosed with dentofacial deformities who underwentorthognathic surgery with mandibular repositioning (using a short lingual osteotomy(SLO)). The results indicated that clockwise rotation of the mandible was themandibular movement most prone to segment interference. Furthermore, virtualplanning was sensitive (100%) but had low specificity (51.6%) in predicting proximaland distal segment interferences. This low specificity was due to the software-basedautomated design of the mandibular osteotomy, where the length of the distal segmentwas longer than the real SLO, and the mandibular ramus sagittal split was located justbehind Spix’s spine. Thus, more precise simulated osteotomies are needed to furthervalidate the accuracy of virtual planning for this purpose.

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distal and proximal fragments after sagittal split osteotomy, Int J Oral Maxillofac

0901-5027/000001+09 ã 2019 International Association of Oral and Maxillofacial Surge

A. Valls-Ontanon1,2,R. D. J. Ascencio-Padilla1,A. Vela-Lasagabaster1,A. Sada-Malumbres1,O. L. Haas-Junior1,J. Masia-Gridilla1,2,F. Hernandez-Alfaro1,2

1Institute of Maxillofacial Surgery, TeknonMedical Centre Barcelona, Barcelona, Spain;2Department of Oral and MaxillofacialSurgery, Universitat Internacional deCatalunya, Sant Cugat del Valles, Barcelona,Spain

Key words: orthognathic surgery; interfer-ences; distal segment; proximal segment; con-dylar settlement; accuracy; three dimensions;virtual planning; CBCT.

Accepted for publication

in predicting bony interferences between

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ons. Published by Elsevier Ltd. All rights reserved.

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Fig. 1. Marking the sagittal split in virtual planning with Dolphin software.

The bilateral sagittal split ramus osteot-omy (BSSRO) is a technique used wide-ly in orthognathic surgery for thecorrection of mandibular deformities.It has advantages compared to othermandibular osteotomies due to the wideoverlapping cutting surface, whichenables a variable range of three-dimen-sional (3D) movements of the distal seg-ment (DS), ensuring broad enoughsurface contact for osteosynthesis andbone healing1.Unfortunately, the distal and proximal

fragments do not always align themselvespassively to one another, resulting ininterferences between them: (1) forwardor backward movement of the DS of themandible may lead to external rotation ofthe proximal segments (PS) in the pitchand roll axes; (2) lateral shifting of themidline causes one DS to rotate laterallywhile the other is rotated medially in theroll and yaw axes; (3) occlusal cant mod-ifications can produce a gap at the lowermargin on one side and at the uppermargin on the other, in the vertical andtransverse axes; and (4) occlusal planechanges may require pitch adaptation ofthe PS2.Thus, inadequate accommodation of the

PS may result in anomalous positioning ofthe condyles. If left uncorrected, this couldcause temporomandibular joint (TMJ) dis-orders, impaired bone healing, inferioralveolar nerve (IAN) overextension, anda tendency to relapse, as well as unaes-thetic outcomes3.Nowadays, 3D virtual surgical plan-

ning (VSP) has become an increasinglyused tool, allowing more precise orthog-nathic surgery and final outcomesthat come as close as possible to theintended outcomes. An improved virtualanatomical study is possible usingthis technique, with better symmetryaxes and the anticipation of surgicalcomplications such as the osteotomizedbone segment interferences mentionedabove4. Predicting these interferencescould be an important ancillary proce-dure for avoiding intra- and postopera-tive surgical complications, renderingorthognathic surgery more effectiveand safer5–7. Few studies have addressedthis issue in the literature to date.The aim of the present study wastherefore to evaluate the relevance of3D VSP in assessing displacement ofthe PS after virtual BSSRO, predictingbony interferences between thesegments and thus avoiding related in-traoperative and postoperative surgicalcomplications.

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distal and proximal fragments after sagi

Materials and methods

Sample selection

This prospective study included 100 con-secutive patients diagnosed with a dento-facial deformity and subjected toorthognathic surgery with BSSRO atTeknon Medical Centre Barcelona be-tween February 2017 and January 2018.All surgeries were virtually planned andperformed by the same surgeon (FHA).The patients were selected on the basis

of the following inclusion criteria: age>18 years, dentofacial deformity in needof mandibular correction, and signed in-formed consent. Patients who underwentan isolated maxillary Le Fort I osteotomywere excluded, as were those presentingany craniofacial syndrome or pathologicalbackground that could compromise bonehealing, and patients failing to sign theinformed consent.The study was approved by the Ethics

Committee of Teknon Medical Centre(Barcelona, Spain; Ref. LO-OS) and wasconducted in accordance with the ethicalstandards laid down in the 1964 Declara-tion of Helsinki and its later amendments.

Data acquisition

All patients followed the standard work-flow for orthognathic surgery planningand surgical splint fabrication of the de-partment, as described elsewhere1. Theprotocol is based on a single cone beamcomputed tomography (CBCT) scan(iCAT; Imaging Sciences International,Hatfield, PA, USA) of the head of thepatient, with surface intraoral scanningof the dental arches using the Lava ScanST scanner (3 M ESPE, Ann Arbor, MI,USA) for subsequent fusion of the twodatasets. In addition, facial photographicrecords were obtained to complete thepreoperative study protocol.

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ttal split osteotomy, Int J Oral Maxillofac

Virtual planning work-up

Computer-assisted simulation surgery wasconducted using specific software (Dolphin3D Orthognathic Surgery Planning Softwareversion 11.8; Dolphin Imaging & Manage-ment Solutions, Chatsworth, U.S.A.)1,2. TheBSSRO design was generated according tothe standardized Dolphin protocol, wherethe clinician only needs to mark the follow-ing landmarks (Fig. 1): (1) in the lingualview, two landmarks are placed parallel tothe occlusal plane, located slightly aboveSpix’s spine, on the front and back; (2) inthe topview, four landmarksare usedto tracethe osteotomy line between the most mediallandmark in the lingual view and a landmarkbetween the first and the second molars justbelow the molar gingival line; (3) in thebuccal view, five landmarks are placedslightly above the caudad edge of the bodyof the mandible: the most medial point isplaced following a perpendicular line acrossthe occlusal plane between the first andsecond molars, and the most distal point islocated following an imaginary line parallelto the mandibular ramus through the poste-rior-most landmark of the lingual view.Once the mandibular and maxillary

osteotomies had been designed (Fig. 2),surgical repositioning of the maxilloman-dibular complex was virtually simulatedfollowing the upper incisor to soft tissueplane (UI-STP) protocol (Fig. 3), validat-ed previously and described in detail else-where3. The new mandibular DS positionin turn determined 3D settlement of themandibular PS, in order to avoid mis-matches between them (Fig. 4).Finally, any observed interferences be-

tween the distal and proximal segmentswere noted in the surgical plan for furtherconsideration as possible intraoperativeinterferences requiring an additional sur-gical approach, as described later in thisarticle (Fig. 2).

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Fig. 2. Sagittal split according to the Dolphin software design. The red dotted lines represent theHunsuck–Dal Pont–Obwegeser or so-called short lingual osteotomy (SLO). The black dottedline represents the lingual osteotomy (LO) (For interpretation of the references to colour in thisfigure legend, the reader is referred to the web version of this article).

Fig. 3. Virtual planning: distal segment repositioning according to the UI-STP protocol, andsubsequent interference between the distal segment and left proximal segment.

Surgical procedure

The patients were operated upon undergeneral anaesthesia. In all cases, the man-dible was operated on first, and the sagittal

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distal and proximal fragments after sagi

Fig. 4. Three-dimensional settlement of the mandshown in virtual orthognathic surgery planning.

split was performed using the Hunsuck–Dal Pont–Obwegeser technique or so-called short lingual osteotomy (SLO)4,8.Next, interferences between the distal andproximal bony segments precluding gentle

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ttal split osteotomy, Int J Oral Maxillofac

ibular proximal segments in order to avoid misma

settlement of the PS were checked subjec-tively by the main surgeon (Fig. 5). In theevent of any such interference, a green-stick osteotomy of the lingual corticallayer of the DS was performed, withoutstripping the soft tissues on the lingualsurface in order to avoid IAN damage, andthe osteotomized bone fragment was leftin place (Figs 2, 6, and 7). This technique,referred to as a lingual osteotomy (LO),was first described by Ellis in 20079 – theonly difference being that we performedthe osteotomy with a piezoelectric sawdevice (Implant Center 2; Satelec-ActeonGroup, Tuttlingen, Germany).This technique should enable smooth

transition between the segments and prop-er 3D repositioning of the DS with passiveaccommodation of the condyle at the gle-noid fossa, while increasing the contactsurface between the two fragments. As aroutine measure, proper seating of thecondyles into the uppermost-anterior partof the fossa was ensured with a bidirec-tional manoeuvre. Then, rigid internal fix-ation with a hybrid technique (a miniplatefixed with four monocortical screws and aretromolar bicortical screw) was per-formed10, followed by removal of theintermaxillary fixation. Before removingthe intermediate splint, proper condylarpositioning and intermediate occlusionwere checked again. Lastly, if necessary,the upper maxilla was repositionedaccording to the final splint.

Postoperative management

All patients wore a closed-circuit coldmask (17 �C) during hospital admissionand were discharged 24 hours after sur-gery. Standard antibiotic and anti-inflam-matory medications for orthognathicsurgery were prescribed. Functional train-ing with light guiding elastics was fol-lowed for 1 month, with the observationof a soft diet for the same period of time.

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distal and proximal fragments after sagittal split osteotomy, Int J Oral Maxillofac

Fig. 5. Intraoperative view showing interference between the distal segment and left proximalsegment.

Fig. 6. Intraoperative lingual osteotomy.

Evaluation

Inorder toevaluate the relevanceof3DVSPin assessing 3D displacements of the PSafter mandibular distal fragment reposition-ing in orthognathic surgery, the following3D surgical movements were registered ineach virtually planned case: (1) B-pointmovements (which are to be DS move-ments) in all three axes: sagittal, vertical,and transverse. (2) Mandibular occlusalplane changes (which are to be DS move-ments) on the right and left sides. (3) PSangular movements while maintaining thecondyles in place (right and left sides) foradaptation to the DS movement in all threeaxes: pitch, roll, and yaw (Fig. 4).Then, interferences between the distal

and proximal segments were comparedbetween the virtually predicted casesand the real cases (those that required aLO) in order to examine the true capacityof 3D VSP to predict bony interferences.Moreover, the LO technique described

above was subjectively tested by the mainsurgeon (FHA) in terms of fragment inter-ference and subsequent 3D gentle settlementof the PS after performing the osteotomy.Finally, inassessing the safety of surgery,

the following conditions were consideredpotential complications of the procedure:IAN or lingual nerve damage, bone seques-tration, intra- or postoperative malocclu-sion secondary to condylar sag11,12, andTMJ symptoms at 1 year of follow-up.

Statistical analysis

A descriptive analysis was made of thestudy variables, with calculation of themean, standard deviation, minimum andmaximum values, and median for contin-uous variables. Absolute and relative fre-quencies (percentages) were used forqualitative variables.A one-sample t-test was used to deter-

mine whether the change in a certain ceph-alometric parameter was relevant, and thekappaconcordance indexwas used toassessagreement between planning and executionof the osteotomy procedure. In addition,simple binary logistic regression modelswere used to evaluate the impact of cepha-lometric changes upon the probability ofperforming an osteotomy. The level of sig-nificance was set at 5% (a = 0.05).

Results

Sample characterization

One hundred and twenty-seven patientswere scheduled for orthognathic surgeryduring the study period; a total 100 wereenrolled based on the inclusion and exclu-

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Fig. 7. Smooth transition between the left proximal and distal segments after lingual osteotomy.Note that the osteotomized bone fragment is left in place.

sion criteria. Five patients were excludedbecause of insufficient data, 15 becausethey had undergone isolated Le Fort Imaxillary surgery, six because they wereunder-aged, and one patient because sur-gery was in the context of a craniofacialsyndrome.The study sample comprised 61 women

(61%) and 39 men (39%), with a mean ageof 27.6 years (range 18–56 years).

Virtual surgical planning

The magnitudes of the planned surgicalmandibular movements are reported in

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distal and proximal fragments after sagi

Table 1. Planned surgical movements are reporte95% confidence interval, and single-sample t-te

Mean �Right occlusal plane �7.50 �Left occlusal plane �7.36 �Sagittal B-point 8.67 � 6Axial B-point 0.44 � 2Coronal B-point �0.28 �Axial right proximal segment 4.16 � 4Axial left proximal segment �4.88 �Sagittal right proximal segment 0.08 � 2Sagittal left proximal segment 0.23 � 2Coronal right proximal segment 0.00 � 0Coronal left proximal segment 0.03 � 0

SD, standard deviation; CI, confidence interval.

Table 1. Although movements of the DSwere performed in all planes, only occlu-sal plane in pitch changes on both sidesand sagittal B-point movements provedstatistically significant (P < 0.001) whencomparing the pre- and postoperative VSP(Figs 8 and 9).In terms of PS accommodation dis-

placement, substantial results wereachieved for roll movements of both PS(P < 0.001), being positive on the rightside (+4.16�) and negative on the left side(�4.88�) (Fig. 10). Insignificant changeswere reported for the pitch and yaw axes(Fig. 10).

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d (in millimetres): mean � standard deviation,st result.

SD 95% CI P-value

4.09 �8.31; �6.70 <0.001*** 4.23 �8.20; �6.52 <0.001***.41 7.40; 9.94 <0.001***.53 �0.06; 0.94 0.086 3.64 �1.01; 0.44 0.439.68 3.23; 5.10 <0.001*** 4.83 �5.84; �3.92 <0.001***.57 �0.43; 0.59 0.745.68 �0.30; 0.76 0.395.36 �0.07; 0.07 0.951.31 �0.03; 0.09 0.302

*P < 0.05; ** P < 0.01; *** P < 0.001.

After DS repositioning and PS adapta-tion to it, the VSP predicted interferencesbetween the proximal and distal segmentsin 51% of the patients (specifically accord-ing to side: right side 23%, left side 16%,and right and left side 12%).

Surgical procedure

All patients underwent bimaxillaryorthognathic surgery, except for one pa-tient who only underwent mandibular sur-gery. Four setback surgeries wererecorded versus 96 mandibular advance-ment surgeries. Of the total, five (5%)underwent LO (specifically according toside: right side 3% and left side 2%) – allof them in the context of forward mandib-ular movement. In addition, 26 (26%)genioplasties and 30 (30.3%) segmenta-tions of the upper maxilla were reported.Surgeon satisfaction with the procedure

was high, since all true interferences wereaddressed with the LO technique.There were no complications related to

the LO procedure during the perioperativeperiod, such as IAN or lingual nerve dam-age, bone sequestration, or intra- or post-operative malocclusion secondary tocondylar sag. Furthermore, no patientsreported postoperative TMJ symptoms at1 year of follow-up.

Statistical agreement between virtual

surgical planning and actual surgery

regarding the need for lingual osteotomy

Only five of the 51 virtually predictedinterferences ended with the applicationof the LO technique. Thus, 46% of thepreviously predicted cases did not requirethe application of this technique (Fig. 11).Overall, there was agreement between

VSP and actual surgery in 54% of thepatients. It follows that virtual planningis very sensitive (100%) but not specific(51.6%), because it predicts bony interfer-ences that finally do not take place.Regarding the relationship between DS

surgical movement and the need for LO, acorrelation was found with the magnitudeof movement of B-point in the verticalaxis (P = 0.081): for each additional unitincrease in this parameter (mandible downin the context of clockwise rotation), therisk of osteotomy increased by 26% (oddsratio (OR) = 1.26) (Fig. 12).

Discussion

The bilateral sagittal split ramus osteot-omy (BSSRO) is the preferred mandibularosteotomy, due to its adaptability for treat-ing a broad spectrum of mandibular de-

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distal and proximal fragments after sagittal split osteotomy, Int J Oral Maxillofac

Fig. 10. Box plot showing that the roll dimension of the proximal segment underwent asignificant change (P < 0.001) to adapt to the movement of the jaw: positive (+4.16�) on theright side and negative (�4.88�) on the left side. The pitch and yaw dimensions remainedconstant with surgery.

Fig. 8. Box plot illustrating that approximately 75% of the sample achieved an occlusal planechange of over �5� on both sides.

Fig. 9. Box plot showing the significant advancement of B-point (P < 0.001), a strong tendencytowards the left in the transverse axis (P = 0.086), and invariability in the vertical axis(P = 0.439).

formities: prognathism, retrognathism,and asymmetries. Despite its popularity,one of the major drawbacks of BSSRO isthe eventual short- and long-term postsur-gical relapse rate, which has been relatedto the following contributing factors: themethod of fixation used; the amount anddirection of DS movement; proper seatingof the condyles into the fossa; 3D dis-placement of the PS; idiopathic condylarresorption; and interaction of the sur-rounding para-mandibular tissues12–15.Although the exact mechanism of relapseis multifactorial in nature, one of the mostcritical points is postsurgical instabilitydue to displacement of the PS from itsseated position in 3D space (sagittal, ver-tical, and transverse) when the distal andproximal segments are not passively posi-tioned to one another during the applica-tion of fixation devices16–19.Modifications of the conventional BSSROtechnique, rigid internal fixation (RIF)methods, and condylar positioning tech-niques have been suggested in order toresolve this problem.On the one hand, several conventional

BSSRO modifications have been pro-posed: from the internal vertical ramusosteotomy (IVRO)20, which can only beused in cases of mandibular prognathismbecause of the lack of area of bony con-tact, to other procedures that reduce thelong length of the DS at the ascendingramus, such as the technique used in ourstudy, i.e., SLO (traditionally known asthe Hunsuck–Dal Pont–Obwegeser tech-nique)4,8. In this context, it has been dem-onstrated that SLO is more favourablethan conventional BSSRO or IVRO inreducing flaring of the PS21. Subsequently,additional methods have been described tofurther reduce interferences between theDS and PS, such as the abovementionedLO9, the distal cutting technique22, and thelingual short split technique14. In thisstudy, the LO technique was used becausewe consider it easy to perform, complica-tion-free, and safe.Regarding the relationship between the

DS surgical movement and the need forLO, a correlation was observed with theamount of movement of B-point in thevertical axis (P = 0.081) (Fig. 12), mean-ing that clockwise rotation of the occlusalplane is more prone to lingual interfer-ences (26%, OR 1.26) than counterclock-wise rotation. This can be explained by theorientation of the sagittal osteotomy, be-cause if the DS is rotated in a downposition, the thick lingual bone segmentwill be near to the PS, with a greaterchance of contact. Likewise, B-pointbackward movement in the sagittal plane

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Fig. 12. The magnitude of variation at B-point in the vertical axis showed a tendency to beassociated with the need for lingual osteotomy.

Fig. 11. Agreement between the virtual planning and real surgery regarding the need for lingualosteotomy.

should give rise to interferences. Howev-er, no interferences were reported in any ofthe patients who received a backwardmovement (a mean of 2 mm in a total offour patients). No conclusions can bedrawn from this finding, since apart fromthe small sample involved, this could berelated to the minimum amounts of set-back movement that the authors imple-ment in order to avoid airway narrowingand a double-chin appearance5.On the other hand, there has been con-

siderable discussion as to which RIF meth-od produces the least condylar torque. Inthis regard, some methodologies requiringno fixation have been described in order tosecure physiological positioning of the PSwhile avoiding condylar displacement,such as IVRO or SLO without fixation23.However, the maxillomandibular fixationperiod is lengthened when these techni-ques are used. Similarly, several studieshave appeared to indicate that the use ofRIF after BSSRO results in greater trans-

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distal and proximal fragments after sagi

verse condylar displacement than the useof wire fixation. However, the latter failsto provide enough stability between thefragments, and a longer maxillomandibu-lar fixation period is also required. Withregard to RIF procedures, it is agreed thatminiplates with monocortical screws orposition screws are to be preferred overcompression or lag screws, because force-ful closure of a gap between the segmentswill cause the condyle to be displacedmedially or laterally, depending on wherethe gap is located1.Lastly, condylar positioning techniques

such as navigation systems or positioningdevices are rarely used because they aretoo time-consuming, are difficult to use,and moreover cannot reproduce the origi-nal condylar position intraoperatively be-cause of the supine position of the patient,who is under general anaesthesia and mus-cle relaxants24,25.Despite the various methods seeking to

maintain the condyle in its natural posi-

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tion, some flaring of the PS due to move-ment of the DS must be assumed, but thisshould be minimal in order not to increasethe TMJ dysfunction rates.With regard to imaging techniques for

PS positioning, sagittal and vertical dis-placement of the condyle has been widelystudied using cephalometric and frontalradiographs, respectively18,19. However,it was not until the 3D virtual era whenassessment of the changes in condylarposition in the six degrees of freedom(sagittal, vertical, transverse, pitch, roll,and yaw) became feasible26.The benefit of VSP in orthognathic

surgery has been extensively documentedover the last decades, because it allowsmore precise outcomes and reduces thesurgery time and complications. For diag-nostic purposes it is especially relevant forthe correction of facial asymmetries.Moreover, as seen in the present study,predicting interferences between proximaland distal segments may be helpful forplanning specific DS and PS mandibularmovements, and keeping in mind an even-tual additional LO in order to solve suchproblems. The results suggest that VSP isvery sensitive (100%). This means that inall cases subjected to LO, bony interfer-ence had been predicted previously. Thus,if VSP shows no bone contact, the surgeoncan go into the operating room being surethat LO will not be needed. In contrast,specificity was low, because far moreinterferences than those that actually oc-curred were predicted, finally implying aneasier surgical procedure than expected.This low specificity is due to the software-based automated design of the osteotomy,where the length of the DS is longer thanthe real SLO, and the mandibular ramus issplit sagittally just behind Spix’s spine(Fig. 2).Similarly, regarding the relevance of

virtual planning in assessing the 3D dis-placement of the PS after DS positioning,substantial results were achieved regard-ing the roll movements of both PS(P < 0.001), and insignificant changeswere reported for the pitch and yaw axes(Fig. 10). These results cannot be trans-ferred to actual surgery for the same rea-son as mentioned above (differencesbetween software-designed and surgicallyperformed mandibular osteotomies). Moreprecise simulated osteotomies are there-fore needed to further validate the accura-cy of virtual planning for PS settlementand the prediction of interferences be-tween mandibular segments.A manual osteotomy design together

with cutting guides could be a potentialsolution for transferring virtual planning

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to the operating room, but neither manualdesign nor cutting guides are sufficientlyprecise8,27. Furthermore, surgical guidesare bulky, require invasive soft tissue de-tachment, and while they are useful formarking the osteotomy superficially, thecutting direction is not totally transferredto the basal-most area of the mandible,which is precisely where most bony inter-ferences arise.Thus, so far, VSP cannot replace the

need for constant intraoperative monitor-ing of jaw movements and real-time com-parisons between the planned and actualoutcomes. It is therefore imperative tocheck proper condylar positioning andocclusion before RIF as well as aftermaxillomandibular fixation, in order torule out condylar sag, asymmetries, andmalocclusions2.In conclusion, the reported results sug-

gest that clockwise rotation of the mandi-ble is the mandibular movement mostprone to segment interferences. In dailypractice, VSP may alert us to eventualinterferences between mandibular frag-ments with a sensitivity of 100%, althoughintraoperatively most cases will not showreal interferences. When these ariseintraoperatively, LO is a safe and compli-cation-free technique that enables passiveaccommodation of the DS.VSP is an essential tool in the planning

of orthognathic surgery, but is currentlyunable to reproduce either the settlementof the PS according to DS positioning orinterferences between mandibular seg-ments, mainly because of the differencesbetween software-designed and surgicallyperformed mandibular osteotomies. Thus,more precise simulated osteotomies areneeded to further validate the accuracyof VSP for this purpose.

Funding

None.

Competing interests

None.

Ethical approval

The study was approved by the EthicsCommittee at Teknon Medical Centre un-der number 3DIDPS.

Patient consent

Not required.

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distal and proximal fragments after sagi

Acknowledgements. The authors wouldlike to thank all of the staff members atthe Institute of Maxillofacial Surgery,Teknon Medical Centre (Barcelona), fortheir administrative and clinical support.

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Address:Adaia Valls-OntanonMaxillofacial InstituteTeknon Medical CentreCarrer de Vilana12 (desp 185)08022 BarcelonaSpainTel: +34 93 393 31 85E-mail: avalls@institutomaxilofacial.com

in predicting bony interferences between

Surg (2020), https://doi.org/10.1016/j.