The assessment of the short‐ and long‐term changes in the condylar position following sagittal split ramus osteotomy (SSRO) with rigid fixation

Summary The purpose of this study was to compare the short‐ and long‐term changes in condylar position related to the glenoid fossa, and skeletal and occlusal stability after orthognathic surgery. All of the study patients were assessed by cone‐beam computed tomography images for condylar rotational changes and anteroposterior position in the pre‐surgery, post‐surgery and post‐retention period. The condylar positions were evaluated on three planes: axial, coronal and sagittal. In the skeletal and occlusal measurements, there was no significant difference between the post‐surgery group and the post‐retention group. After sagittal split ramus osteotomy (SSRO), the condyle on the axial plane rotated inward (P < 0·05) and maintained during the post‐retention period. In the anteroposterior condylar position related to the glenoid fossa, the condyles had changed from the anterior position in the pre‐surgery group to a concentric position in the post‐surgery group and then returned to the anterior position in the post‐retention groups. These results suggested that the changed anteroposterior condylar position in the glenoid fossa after SSRO with rigid fixation had moved from a concentric to anterior position for post‐retention period.     

功能板影响错伴特发性髁突吸收正颌术后稳定性的初步研究

目的:探讨特发性髁突吸收（idiopathic condylar resorption, ICR）患者在关节功能板治疗结合正颌-正畸联合治疗后下颌骨及髁突位置的改变,为后期研究提供依据。方法:回顾分析2008—2012年收治的13例特发性髁突吸收患者的临床数据,所有患者均在正颌手术前接受关节功能板治疗7.5±1.5个月。对患者正颌术前(T0)、正颌术后即刻(T1)、正颌术后至少12个月(T2)的咬合、头颅侧位片、MRI检查结果进行测量,采用SPSS 22.0软件包对数据进行统计学分析,评价正颌术后髁突和下颌骨的位置变化。结果:正颌手术(T1)纠正了所有患者的骨性Ⅱ类错畸形,建立了正常的咬合关系、前伸运动及侧方斜导运动。正颌手术平均下颌骨前移量(Y Axis-B, T1-T0)为（5.05±3.54）mm。与T1相比,T2时颞下颌关节间隙参数无显著改变。下颌骨位置参数中, 仅Y轴到B点的距离（Y轴-B）在T2与T1间存在统计学差异,其改变量平均值为（-1.64±2.48）mm,其余参数均无显著差异。13例患者中,11例患者Y轴-B 改变值<2 mm（84.6%）,仅 2例患者出现>2 mm的后退（15.4%）。结论:关节功能板治疗可增加ICR患者正颌手术的稳定性,可能是关节功能板保守治疗能够稳定ICR患者髁突在关节窝内的位置。     

Regeneration of mandibular condyle following unilateral condylectomy in canines.

PURPOSE: The purpose of this experimental study was to investigate regeneration of the mandibular condyle after unilateral condylectomy in canines. MATERIAL AND METHODS: Five 2-year-old beagle dogs underwent unilateral mandibular condylectomy and were sacrificed either immediately postoperatively (n=1) or 3 months later (n=4). Temporomandibular joints were examined radiologically and histologically, and sides were compared. RESULTS: All joints showed postoperative regeneration of the condylar head. Maximum regeneration of the condyle occurred medially, where most bone of the glenoid fossa was present, rather than laterally. From an anteroposterior perspective, regeneration of the condylar head was more favourable anteriorly, facing the inferior slope of the glenoid fossa. Regenerated articular cartilage was irregular. Articular discs displayed central thickening compared with unoperated joints. The bone of the glenoid fossa was normal. CONCLUSION: Unilateral mandibular condylectomy in canines resulted in a certain degree of condylar regeneration during a 3-month postoperative period, with some irregular articular cartilage formation.     

Condyle fossa relationship associated with functional posterior crossbite,before and after rapid maxillary expansion

Objective:To investigate condylar symmetry and condyle fossa relationships in subjects with functional posterior crossbite comparing findings before and after rapid maxillary expansion (RME) treatment through low-dose computed tomography (CT).Materials and Methods:Twenty-six patients (14 girls and 12 boys, mean age 9.6 ± 1.4 years) with functional posterior crossbite (FPXB) diagnosis underwent rapid palatal expansion with a Hyrax appliance. Patients'' temporomandibular joints (TMJ) underwent multislice CT scans before rapid palatal expansion (T0) and after (T1). Joint spaces were compared with those of a control sample of 13 subjects (7 girls and 5 boys, mean age 11 ± 0.6 years).Results:Anterior space (AS), superior space (SS), and posterior space (PS) joint space measurements at T0 between the FPXB side and contralateral side demonstrated no statistically significant differences. After RME treatment (T1), all three joint spaces increased on both the FPXB side and the non-crossbite side. However, differences were statistically significant only for the SS when comparing the two sides at T1. SS increased more than AS and PS in the non-crossbite condyle (0.28 mm) and FPXB condyle (0.37 mm), and PS increased only on the FPXB side (0.34 mm).Conclusions:There were no statistically significant differences in condyle position within the glenoid fossa between the FPXB and non-crossbite side before treatment. Increases in joint spaces were observed after treatment with RME on both sides. These changes were, however, of small amounts.     

Amount and direction of temporomandibular joint growth changes in Herbst treatment: a cephalometric long-term investigation

The amount and direction of condylar growth, glenoid fossa displacement, and "effective" temporomandibular joint (TMJ) changes (a summation of condylar growth, glenoid fossa displacement, and condylar position changes within the fossa) were analyzed in 35 Class II, Division 1 malocclusions (23 boys and 12 girls) treated with the Herbst appliance. Lateral head films in habitual occlusion and with the mouth wide open from before (T1) and after 7.5 months of Herbst treatment (T2) as well as 7.5 months (T3) and three years (T4) after treatment were evaluated. As a control group, a sample of 12 untreated male Class II Division I malocclusions was used during a 7.5-month time period corresponding to the treatment period (T2-T1) of the Herbst cases. The results revealed that during the treatment period (T2-T1) condylar growth was directed posteriorly about twice the amount as in the control subjects, and the fossa was displaced in an anterior inferior direction. The effective TMJ changes showed a pattern similar to condylar growth but were more pronounced. During the first posttreatment period (T3-T2), all TMJ changes reverted. The glenoid fossa was displaced backward; the amount of condylar growth and effective TMJ changes was reduced, and the changes were more superiorly directed. During the second posttreatment period (T4-T3), all TMJ changes were considered physiological. Conclusion: During Herbst treatment, the amount and direction of TMJ changes (condylar growth, fossa displacement, and effective TMJ changes) were only temporarily affected favorably by Herbst treatment.     

Radiographic evaluation of condylar positioning in patients undergoing orthognathic surgery

Objective

The aim of this study was to evaluate alterations in condylar positioning through submentovertex projection (Hirtz Radiographic Technique) in patients who underwent orthognathic surgery for maxillary advancement and mandibular setback with stable internal fixation.

Methods

A prospective longitudinal clinical study of 40 surgical patients presenting dentofacial deformity admitted in the Oral and Maxillofacial Surgery Department of Federal University of Paraná (UFPR) in the period between March 2013 and December 2015. We performed two submentovertex digital radiographs, one 7 days before surgery and the other one 30 days after the procedure. Cephalometric tracings were made using Radiocef® Studio 2 Software and measured the intercondylar and condylar angles (right and left).

Results

There was a decrease in the intercondylar angle (p < 0.001) and an increase in condylar angles both the right and the left side (p < 0.001) when compared with the pre and postoperative period. There was a larger increase in condylar angle on the right side in males (p = 0.007).

Conclusion

There is a tendency of decreasing of the intercondylar angle after orthognathic surgery, regardless of the alteration in the condylar angles, creating a new position of the condyle in the glenoid fossa. Patients with asymmetry may present greater alterations in the positioning of the opposite condylar to the deviation of the mandibular midline.

     

Evaluation of treatment with unilateral mandibular sagittal split ramus osteotomy and maxillary osteotomy in patients with condylar osteochondroma and mandibular asymmetry: A retrospective case series

The aim of the study was to describe an approach where condylar resection with condylar neck preservation was combined with Le Fort I osteotomy and unilateral mandibular sagittal split ramus osteotomy (SSRO).Patients with a unilateral condylar osteochondroma combined with dentofacial deformity and facial asymmetry who underwent surgery between January 2020 and December 2020 were enrolled. The operation included condylar resection, Le Fort I osteotomy and contralateral mandibular sagittal split ramus osteotomy (SSRO). Simplant Pro 11.04 software was used to reconstruct and measure the preoperative and postoperative craniomaxillofacial CT images. The deviation and rotation of the mandible, change in the occlusal plane, position of the “new condyle” and facial symmetry were compared and evaluated during follow-up. Three patients were included in the present study. The patients were followed up for 9.6 months on average (range, 8–12). Immediate postoperative CT images showed that the mandible deviation and rotation and occlusion plane canting decreased significantly postoperatively; facial symmetry was improved but still compromised. During the follow-up, the mandible gradually rotated to the affected side, the position of the “new condyle” moved further inside toward the fossa, and both the mandible rotation and facial symmetry were more significantly improved.Within the limitations of the study it seems that for some patients a combination of condylectomy with condylar neck preservation and unilateral mandibular SSRO can be effective in achieving facial symmetry.     

髁突在关节窝中的位置及其在临床诊断治疗中的意义

临床治疗中,特别是髁突外伤骨折、正颌手术、修复咬合重建、正畸治疗以及在颞下颌关节紊乱病的诊断和治疗中,要考虑髁突在关节窝中的位置变化。本文通过文献回顾,结合我们的研究成果,讨论髁突在关节窝中的正常生理位置及其在颞下颌关节紊乱病特别是关节盘移位的诊断和治疗中的意义。目前多项研究认为,健康成年人髁突平均位置为基本中性,但存在较大变异;髁突后移可能是关节盘前移位的危险因素,关节盘前移位也可导致髁突后移;在关节盘移位的牙合垫治疗中,髁突在牙合垫戴入后显著向前、下移位,可有效改善盘突关系;稳定牙合垫使髁突前下移位不明显,改善盘突关系的效果有限。此外,再定位牙合垫使髁突前下移位还可促进髁突骨质的改建。     

Tomographic assessment of alterations of the temporomandibular joint after orthognathic surgery.

The aims of the study were: (1) to identify absolute condylar displacements and glenoid fossa changes; (2) to assess alterations in the condyle-fossa relationships following orthognathic surgery, by means of linear temporomandibular joint tomography. The sample consisted of 44 adults who received pre- and post-operative orthodontic therapy and management of their dentofacial deformities with various osteotomies (maxillary: 10; mandibular: 24; combined: 10). The material consisted of the tomograms of the right temporomandibular joints taken within 1 week pre-operatively, immediately post-surgery, and 6 months postoperatively. The X-rays were taken with the mouth closed. Tracing, superimposition, and interpretation of the tomograms were made according to a new method. The findings of the study regarding the groups which received mandibular or combined osteotomies indicated that immediately post-operatively there was a tendency for the condyle to be distracted downward and anteriorly from its original position in the fossa. However, in the 6 months follow-up the condyle showed a tendency to re-establish its initial position. Large variation in posterior space was observed among the patients of the mandibular osteotomy group who were also examined individually. In the maxillary osteotomy group no significant post-operative changes were observed on the average. Remodelling was noticed in both condylar and fossa surfaces of all groups.     

����-����������ƹ��԰��Ϣ�������϶�����ؽ�Ӱ���ٴ��о�

目的 研究成人骨性安氏Ⅲ类错(殆)正畸-正颌联合治疗前后颞下颌关节(TMJ)变化.方法 选择2002-2010年在中国医科大学口腔医院正畸科就诊的成人骨性安氏Ⅲ类错(殆)患者30例,采用正畸治疗加双侧下颌升支矢状劈开后退术(BSSRO)的正畸-正颌联合治疗方案,分别在BSSRO术前、术后1个月、矫治结束时拍摄标准薛氏位片,采用Cohlmia测量法对关节片进行关节间隙及关节窝形态测量,观察髁突位置及关节形态的变化.结果 (1)关节间隙变化:与术前比较,术后1个月双侧关节各间隙均明显变大(P＜0.05);矫治结束后关节间隙测量值与术前比较,差异无统计学意义(P＞0.05).(2)髁突位置和关节窝形态变化:术后1个月髁突位置与术前比较,矢状向髁突位置后移,垂直向髁突位置下移.矫治结束后与术前比较,髁突位置各项指标差异无统计学意义(P＞005).反映关节窝形态的指标在术前、术后1个月和矫治结束后三者间比较差异均无统计学意义(P＞0.05).(3)30例患者中治疗前9例有关节弹响,治疗后5例弹响消失,术前无关节弹响者术后均未出现弹响,所有患者治疗前后均未出现关节疼痛及开口受限.结论 (1)BSSRO术后1个月关节间隙增大,髁突位置稍偏后,矫治结束后恢复正常.正畸-正颌联合治疗未引起关节窝形态的改变.(2)所有患者均未引起颞下颌关节紊乱病(TMD),且部分患者治疗后关节弹响消失,提示正畸-正颌联合治疗可能对TMD有一定的治疗作用.     

Changes in the position of the condyle after bilateral sagittal split ramus osteotomy in patients with mandibular retrusion and protrusion: a new condyle: fossa matching concept

The purpose of this study was to compare the condylar positional changes after bilateral sagittal split ramus osteotomy (BSSRO) in patients with mandibular retrusion and those with mandibular prognathism. We also studied the correlation between the degree of matching of the condyle and fossa, and condylar displacement. Thirty patients with mandibular retrusion (n = 11) or mandibular prognathism (n = 19) who underwent BSSRO were included. The condylar position was assessed from spiral computed tomographic (CT) scans taken preoperatively, during the first postoperative week, and at least 6 months postoperatively. All data were measured by MIMICS 17.0 and analyzed by Student’s t test and Pearson’s correlation analysis. The size of the condyles of patients with mandibular retrusion was significantly less than those of patients with mandibular prognathism (491.5 (172.8) compared with 823.2 (212.0) mm³). The size of the glenoid fossa in those with mandibular retrusion (599.6 (110.4) mm³) and those with prognathism (597.6 (151.6) mm³) did not seem to differ. Postoperatively the condyles moved outwards, backwards, and downwards in both groups of patients. Correlation analysis between the condyle:fossa volume ratio and the condylar positional changes showed that a large condyle:fossa volume ratio correlated with the smaller positional changes in the condyle. The condylar position changed immediately after mandibular advancement and setback, and persisted in the long term. Larger condyles tended to have fewer positional changes.     

��ͻ�ڹؽ����е�λ�ü������ٴ���������е�����

??Abstract??The condylar position should be taken into account in the diagnosis and treatment of condyle fracture??orthognathic surgery??occlusal reconstruction and temporomandibular disorders. The normal condylar position in the glenoid fossa and its clinical significance in the diagnosis and treatment of temporomandibular disorders??for example the disc displacement??will be discussed here through the literature review and the combination of our research findings. Many research data suggested a centric position of condyle in a normal joint??with individually variances. A posterior condylar position might be a risk factor of disc displacement??and on the other hand??the disc displacement might induce condyle to move posteriorly. With the use of anterior repositioning splint for treating anterior disc displacement with reduction??the condyle moved anteriorly and inferiorly??the condyle-disc relationship could be improved immediately. Besides??splint therapy may facilitate regenerative remodeling of condyles.     

Morphological differences in the temporomandibular joints in asymmetrical prognathism patients

OBJECTIVE: To investigate the morphology of the temporomandibular joints (TMJ) in skeletal asymmetry with prognathism. DESIGN: Three-group observational clinical study. SETTING AND SAMPLE POPULATION: University setting. Thirty-five patients undergoing orthognathic surgery without signs and symptoms of TMJ disorder were assigned to three groups (right deviation, n = 11; left deviation, n = 14; and non-deviation; n = 10) based on anteroposterior cephalometric analysis. OUTCOME MEASURE: Positional and morphological differences of the TMJs were evaluated using a total of 70 bilateral sagittal TMJ magnetic resonance images. RESULTS: In both the right and left deviation groups, the TMJ on the deviated side showed a significantly steeper eminence than that on the non-deviated side (p < 0.05). The anterior joint space was narrower on the deviated side than on the non-deviated side whereas the posterior joint space did not differ markedly, indicating an anterior position of the condyle in the glenoid fossa of the TMJ on the deviated side. Disk displacement comparisons revealed no significant differences between left and right sides in the symmetry or asymmetry group. CONCLUSION: Asymmetrical prognathism patients exhibit significant morphological differences between the right and left TMJs concerning the slope of the articular eminence, which correspond to facial asymmetry.     

Short-term condylar and glenoid fossa changes in infants with Pierre Robin sequence undergoing mandibular distraction osteogenesis

The purpose was to evaluate short-term changes in condylar and glenoid fossa morphology in infants with Pierre Robin sequence (PRS) undergoing early (age <4 months) mandibular distraction osteogenesis (MDO) for the management of severe airway obstruction. Computed tomography data from infants with PRS who had MDO were compared to those of age-matched control infants without facial skeletal dysmorphology. Surface/volume, linear, and angular measurements of the condyle and glenoid fossa were obtained and compared between infants with PRS and controls. Eleven infants with PRS met the inclusion criteria. There were five female and six male subjects with a mean age at the time of MDO of 41 ± 32 days. Prior to MDO, PRS mandibles had a smaller condylar articulating surface area and volume than age-matched control mandibles, with a more laterally positioned condylar axis (P ≤ 0.05). Following MDO, there were significant increases in condylar articulating surface area and volume, approaching those of normal controls, with further lateral translation of the condylar axis (P ≤ 0.05). Condyle and glenoid fossa morphology is largely normalized following early MDO in infants with PRS. The condylar axis translates laterally as a result of MDO; this change is not observed with mandibular growth in infants without PRS.     

One-stage treatment of acquired facial deformity caused by severe unilateral condylar hyperplasia

Condylar hyperplasia (CH) is a rare and self-limiting process manifesting between the first and third decades of life. It causes facial asymmetry and derangement of occlusion. The management involves resection of the condylar head and orthognathic surgery followed by orthodontic treatment. We present a 33-year-old man with spontaneous onset of CH during a span of 10 years. This was managed with resection of the condyle alone, which dramatically improved facial asymmetry in addition to restoration of the occlusion within a few months of follow-up. Therefore, orthognathic surgery or orthodontic treatment was not needed.     

The relationship between the changes in three-dimensional facial morphology and mandibular movement after orthognathic surgery

PurposeThe purpose of this study was to investigate the relationship between changes in three-dimensional (3D) facial morphology and mandibular movement after orthognathic surgery. We hypothesized that facial morphology changes after orthognathic surgery exert effects on 3D mandibular movement.Materials and methodsWe conducted a prospective follow-up study of patients who had undergone orthognathic surgical procedures. Three-dimensional facial morphological values were measured from facial CT images before and three months after orthognathic surgery. Three-dimensional maximum mandibular opening (MMO) values of four points (bilateral condylions, infradentale, and pogonion) were also measured using a mandibular movement tracking and simulation system. The predictor variables were changes in morphological parameters divided into two groups (deviated side (DS) or contralateral side (CS) groups), and the outcome variables were changes in the MMO at four points.ResultsWe evaluated 21 subjects who had undergone orthognathic surgical procedures. Alterations in the TFH (total facial height), LFH (lower facial height), CS MBL (mandibular body length), and DS RL (ramus length) were negatively correlated with changes in bilateral condylar movement. The UFH, DS MBL and CS ML (mandibular length) showed correlations with infradentale movement. The CS ML, DS ML, MBL, UFH, and SNB were correlated with pogonion movement.ConclusionThe height of the face is most likely to affect post-operative mandibular movement, and is negatively correlated with movement changes in the condyles, infradentale and pogonion. The changes in CS morphological parameters are more correlated with mandibular movement changes than the DS. The changes in CS MBL and bilateral RL were negatively correlated with condylar movement changes, while the bilateral MBL and CS ML were positively correlated with changes in infradentale and pogonion.     

Surgical induction of TMJ bony ankylosis in growing sheep and the role of injury severity of the glenoid fossa on the development of bony ankylosis

ObjectiveThe purpose of this paper is to summarize our experiences in creating an animal model of TMJ bony ankylosis based on 2 sequential experiments.MethodsTwo sequential experiments were performed with the aim of creating a model of TMJ bony ankylosis. Seven growing sheep were used in the first experiment, in which 1 was served as a control animal. Condylar fracture with disc preservation was performed on the control side. On the contralateral side, condylar fracture, excision of the lateral 2/3 disc and injury to the glenoid fossa were performed to induce bony ankylosis. Three animals were sacrificed respectively at 3 and 6 months after surgery. In the second experiment, 7 growing sheep were used. The only difference of modeling between the 2 experiments was that more serious injury to the glenoid fossa was made in the ankylosis-induced side in experiment 2. Three, 2, and 2 animals were sacrificed respectively at 1, 3, and 6 months postoperatively. The TMJ complexes were examined by computed tomography (CT) and histological evaluation.ResultsIn experiment 1, only fibrous ankylosis was observed in the ankylosis-induced side both at 3 and 6 months postoperatively. In experiment 2, CT and histological evaluation showed that the outcomes of the ankylosis-induced side were fibrous-bony ankylosis, fibrous-bony ankylosis, and bony ankylosis respectively at 1, 3, and 6 months after surgery.ConclusionThrough summarizing the differences of the modeling and the different outcomes in the 2 experiments, we concluded that severe damage to the glenoid fossa played an important role in the development of TMJ bony ankylosis.     

骨性Ⅲ类偏颌患者髁突与(牙合)平面特征的CBCT研究

目的 利用锥形束CT(CBCT)测量分析骨性Ⅲ类偏颌患者髁突及(牙合)平面特征。方法 选取符合纳入标准的骨性Ⅲ类成年患者40例,所有个体按照颏下点偏离正中矢状面距离进行分组,分别测量各组左右两侧(牙合)平面角、髁突位置及形态,并对数据进行统计学分析。结果 骨性Ⅲ类偏颌患者的偏侧与对侧相比,(牙合)平面角、关节前间隙、关节上间隙、关节外间隙及髁突内外径差异有统计学意义(P<0.05),偏侧关节后位所占比例较大,下颌骨偏移量与偏侧髁突前间隙及对侧(牙合)平面角均呈正相关(P<0.01)。骨性Ⅲ类非偏颌患者的左右两侧(牙合)平面角、髁突位置及形态指标之间差异均无统计学意义(P>0.05),关节以前位、中位为主。结论 骨性Ⅲ类偏颌患者左右两侧(牙合)平面角、髁突位置及形态不对称,偏侧(牙合)平面角及髁突内外径较小,髁突向后下内方移位,且偏颌程度与(牙合)平面角及髁突位置之间存在相关性。     

What we really see in a TMJ radiograph

1. 1. The zygomatic arch has been ruled out as forming the image of the glenoid fossa on TMJ radiographs.

2. 2. The three-dimensional head position that is required for a TMJ radiograph accommodates for condylar asymmetry and aligns that condyle almost perpendicular to the film.

3. 3. Due to the 75 degree x-ray angulation that is required, the lateral third of the condyle is outlined on the radiograph almost in profile, or as a cross-sectional view, and not in a “composite” view as commonly thought.

4. 4. The central and medial portions of the condyle are projected inferiorly on the radiograph and are obliterated by the profile view of the lateral third of the condyle.

5. 5. The corresponding central and medial portions of the fossa are projected inferiorly on the radiograph and not usually observable.

6. 6. The TMJ space varies in relative width from the lateral to the medial portions. It is generally widest laterally, which may be associated with providing space for condylar rotation in lateral mandibular movements.

7. 7. Although the joint space is not constant in various sagittal locations, the relative anterior and posterior joint spaces remain proportional so that the classification of the condyle position in the fossa (i.e., retruded, concentric, or protruded) remains the same.

8. 8. Variations in head position, in all three planes of space, do not effectively alter the resultant TMJ radiograph.

9. 9. Variations in x-ray angulation and position do not effectively permit the recording of the midline or medial portions of the fossa and condyle.

10. 10. The floor of the midcranial fossa in the TMJ area is not seen in cross section on the TMJ radiograph.

11. 11. Variations in the anatomy of the fossa (bony protruberances) may be seen as projections into the joint space on the radiograph. Corresponding alterations in condylar anatomy (which maintain a relatively proportional joint space) are projected inferiorly on the radiograph and are hidden by the profile or cross-sectional image of the lateral third of the condyle.

12. 12. The definite radiopaque outline of the fossa on the radiograph represents the true shape of the fossa at the lateral third. All superimpositions into the joint space are bony projections of the fossa that are more medial to the lateral third area.

13. 13. Most TMJ radiographs are profile or cross-sectional images of the lateral third of the fossa and condyle, and it is extremely difficult to record the image of any other portion.

     

3D vector analysis of mandibular condyle stability in mandibular setback surgery with bicortical bioabsorbable screw fixation

IntroductionBioabsorbable screws became widely used for stable fixation in orthognathic surgery as biomechanical technology advanced. Recently, 3D image analyses begin to be used to evaluate surgical changes. The purpose of this study was to evaluate, using 3D vector analysis, the stability of bicortical bioabsorbable screw fixation in mandibular setback using a sagittal split ramus osteotomy.Spatial change of the mandibular condyle was determined by 3D coordinates containing directional information.Materials and methodsBicortical screw fixation was performed using either a bioabsorbable screw (25 patients) or a titanium screw (5 patients) in orthognathic surgery. Pre- and post-operative CT images (6 months after surgery) were superimposed digitally. A 3D coordinate (X, Y, Z) and vectors were employed to quantify spatial changes of the condyle and analysed statistically.ResultsMeasuring on 3D image showed stable error about 0.16 mm. There were no significant differences in the total spatial changes of the condyle between titanium and bioabsorbable screws with the exception of the lateral–medial direction of the condylar centre (P = 0.042). The directional vector components were stable, regardless of mandibular setback.ConclusionIn 3D vector analysis, bioabsorbable screw fixation in SSRO with distal segment osteotomy shows clinically acceptable postoperative condylar position stability.