Condylar position with rigid fixation versus wire osteosynthesis of a sagittal split advancement

J Oral Maxibfac Surg 57:3 l-34, 1999

Condylar Position with Rigid Fixation Versus wire Osteosynthesis of a Sagittal Split Advancement Joseph E. Van Sickels, DDS, * B.D. Tiner, DDS, MD, f Stephen D. Keeling, DDS, DS,f Gary M. Clark, PbD,,f’ Robert Bays, DDS, I I and John Rug& PhDY In this randomized clinical study, two groups of patients who underwent Purpose: split osteotomy and either wire osteosynthesis or rigid fixation were compared.

a bilateral sagittal

Patients and Methods: Cephalometric radiographs obtained before surgery, immediately after surgery, and at 8 weeks, 6 months, and 1 and 2 years after surgery were available for 125 of these patients, 63 with wire fixation and 62 with rigid fixation. All were traced by an independent examiner, and vertical and horizontal changes in condylar position were recorded for each period.

Condylar movement was slightly different with the two fixation techniques beyond 8 weeks Results: postsurgery, but the ultimate position of the condyle was not different. The condyles in both groups moved posterior and superior. There initially was a correlation between the amount of advancement and the amount the condyle moved inferior in both groups, but this diminished with time. In addition, there was a weak but significant positive relationship between forward rotation of the proximal segment and superior condylar position immediately after surgery, which did not exist at later periods. Whether wire osteosynthesis or rigid fixation was used, the ultimate condylar position Conclusions: was posterior and superior after a bilateral sagittal split osteotomy to advance the mandible. No single factor could be identified to account for this change. It is suggested that change in mechanical load may have resulted in remodeling and adaptation of the condyles. Condylar position after orthognathic surgery has been studied by numerous authors.1-6 After advancement of the mandible with a bilateral sagittal split osteotomy (BSSO) fixed with wire osteosynthesis, Will et al6

observed that both condyles moved superiorly, with one condyle exhibiting posterior movement. Several authors have suggested that the type of fixation can influence condylar position. 1,2,5Stroster and PangrazioKulbershs noted greater condylar displacement after a bilateral sagittal split osteotomy fixed with rigid fixation than with wire osteosynthesis. Kundert and Hadjianghelou’ likewise believed there was greater displacement of the condyles when rigid fixation was used. Ellis and Hinton’ studied two groups of animals undergoing a bilateral sagittal split osteotomy and advancement of the mandible and found that those animals that had a BSSO and maxillomandibular tixation (MMF) showed a tendency for anterior movement of the condyles; animals who underwent a BSSO with rigid fixation showed a tendency for posterior condylar position. Previous clinical studies on this subject have not been randomized nor done in a prospective fashion. The purpose of this multicenter trial was to compare condylar position in two groups of patients involved in a randomized clinical study who had a BSSO with either wire osteosynthesis or rigid fixation.

*Professor and Senior Surgeon, Department of Oral and Maxillofacial Surgery, University of Texas, HSCSA, San Antonio, TX. tilssociate Department

Professor

and Director

of Oral and Maxillofacial

of Postgraduate

Education,

Surgery, University

of Texas,

HSCSA, San Antonio, TX. iAssociate Professor, Department cial Orthopedics,

of Orthodontics

and Dentofa-

University of Florida, Gainsville, FL; Deceased.

BProfessor, Department of Medicine, University of Texas, HSCSA, San Antonio, TX. 11Professor and Chief, Division of Oral and Maxillofacial

Surgery,

Department of Medicine, Emory University, Atlanta, GA. BProfessor and Director

of Research, Department

of Orthodon-

tics, University of Texas, HSCSA, San Antonio, TX. Supported by NIH/NIDR DE Grant No. 09630. Address correspondence

and reprint requests to Dr Van Sickels:

Professor and Senior Surgeon, Department of Oral and Maxillofacial Surgery, University

of Texas, HSCSA, 7703 Floyd Curl Dr, San

Patients

Antonio, TX 782847908. 0 1999 American Association of Oral and Maxillofacial

and Methods

Patients were enrolled prospectively in this randomized clinical trial at three sites (University of Texas at

Surgeons

0278.2391/99/5701-0006$3,00/O

31

32 San Antonio, Emory University, and the University of Florida). Subjects were stratified on the basis of the following prognostic factors: overjet greater than or less than 7 mm, neuroticism score on the Eysenck Personality Inventory, and study site. Groups were balanced across prognostic factors. The schedule was generated by a computer algorithm that was kept by the study statistician. All patients were informed of the nature of the study and gave informed consent. Assignment was not concealed from the participants or surgeons because this was not possible. Patients were 13 years or older at the time of surgery, with a Class II facial deformity that, in the opinion of the referring orthodontist and the oral and maxillofacial surgeon, was suitable for mandibular advancement using a bilateral sagittal split ramus osteotomy. Exclusion criteria were 1) previous maxillofacial surgery within 6 months, 2) previous TMJ arthrotomy (arthrocentesis or arthroscopy was acceptable), 3) medical, physical, or mental conditions that would impair the patient’s ability to follow instructions, 4) patients with fewer than 20 teeth total, fewer than 10 teeth in an arch, or patients with severe periodontal disease, 5) identifiable craniofacial deformity, 6) possible change in residence that would preclude a 2-year follow-up, 7) simultaneous maxillary surgery, 8) previous mandibular advancement procedures, and 9) pregnancy. Eligibility of subjects was determined by the trial coordinator at each site. The randomized treatment assignment was generated by the study statistician. The generator and keeper of the randomization sequence were not involved with determining eligibility, administering treatment, nor assessing outcome. Intervention assignment was communicated in writing from the statistician to the site coordinator. TREATMENT Soft tissue dissection and splitting of the mandible were done in a standardized fashion as described by Bell et al8 The wire osteosynthesis used was inferior border wires as described by Booth,9 and Smith, Moloney, and West. lo Patients receiving rigid fixation had three bicortical position screws placed as described by Jeter et al. l1 All patients had skeletal suspension wires applied. A 24-gauge wire was placed circumferentially around the mandible between the second premolars and the first molar bilaterally and in the symphyseal region. In the maxilla, a per-alveolar wire was placed between the canine and first premolar and in the midline between the centrals. The group with inferior wires was kept in MMF for 6 weeks. At 7 weeks, the suspension wires were removed. The splint was removed at 8 weeks before obtaining a lateral cephalogram. The group with position screws was not placed in MMF. Instead, elastics were placed between the skeletal wires at the

CONDYLAR POSITION RIGID VS WIRE time of surgery that would limit but not eliminate opening after surgery. Suspension wires were removed at 2 weeks after surgery, and the occlusal splint was removed at 3 weeks after surgery. CEPHALOMETRICRADIOGRAPHS Cephalometric radiographs were obtained before surgery (T2), immediately after surgery (T3), at 8 weeks (T4), 6 months (T5), 1 year (TG), and 2 years (T7). All were traced by an independent examiner and digitized on a Hipad TM 1200 Digitizer (TM, Houston Instruments) interfaced with an IBM PC XT computer (lBM, Research Triangle Park, NC) using “CephMaster” (Trilobyte Software, Ann Arbor, Ml) software. Patients were randomized to either rigid fixation and no MMF, (three screws per side) or wire osteosynthesis and 6 weeks of MMF (inferior border wires). An X,Y coordinate system was established on the preoperative cephalogram by drawing a line parallel to Frankfort horizontal at sella for the X coordinate. A perpendicular line was then drawn intersecting this line at sella. This X,Y coordinate was transcribed to each successive radiograph by superimposition on a best fit of cranial base landmarks. Vertical and horizontal changes in condylar position were recorded perpendicular to the X,Y lines. Condylar position was traced on a preoperative radiograph and transferred from one radiograph to another by superimposing on a template of the ramus. Data were analyzed by twosample t-tests and Spearman correlation coefficients. Data analysis was postponed until all participants had received surgery.

Results Two hundred fifteen patients were eligible for the study; 75 patients chose not to be randomized for a number of reasons. Thus, 140 patients participated in the randomized clinical trial. At the time of analysis, cephalometric radiographs were available for 125 of these patients, 63 with wire fixation and 62 with rigid fixation (Table 1). Extenuating circumstances at the time of surgery rarely dictated a change in fixation technique; patients were followed in the group to which they were randomized under an intent-to-treat philosophy. The mean age of the total group was 30 years (range, 14 to 57 years); 75% of the patients were female. Immediately after surgery (T3), inferior condylar movement was significantly different between the two fixation procedures (0.64 I 1.3 mm for rigid fixation compared with 1.27 + 1.4 mm for wire fixation, P = .02; Table 1, Fig 1). There was a weak, but significant, positive relationship between the amount of advancement and the amount the condyle moved inferiorly in the wire group at T3 (Spearman

33

VAN SICKELS ET AL

No. of patients Age Gender (% females) Condyle movement Immediate postsurgery (T3) (mm)

8 Weeks postsurgery (T4) (mm) 6 Months postsurgery (T5) (mm)

1 Year postsurgery (T6) (mm)

2 Years postsurgery (T7) (mm)

Rigid Fixation

Wire Fixation

P

62 29 2 9.9 (15-48) 74.2%

63 30.4 i- 10.4 (14-57) 76.2%

.44 .80

0.04 t 1.5 Posterior 0.64 ? 1.3 Inferior (n = 62) 0.35 * 1.5 Posterior 0.17 2 1.2 Superior (n = 61) 0.44 -C 1.4 Posterior 0.26 ? 1.4 Superior (n = 60) 0.67 + 1.2 Posterior 0.50 + 1.3 Superior (n = 58) 0.56 i- 1.6 Posterior 0.44 ? 1.4 Superior (n=57)

0.04 1. 1.3 Anterior 1.27 ? 1.4 Inferior

.73 .02

correlation coefficient = .27; P = .03). This continued through time T4 (Spearman correlation coefficient = .41; P = .0009), but no further. Likewise, there was a strong positive relationship between the amount of advancement and the amount the condyle moved inferiorly in the rigid group at T3 (Spearman correlation coefficient = 0.55, P = .OOOl>. This relationship continued to a lesser extent through time periods T4 and T5 (T4 Spearman correlation coefficient = 0.39, P = .OOlS, T5 Spearman correlation coefficient = .25, P = .05). Condylar movement was slightly different with the two fixation techniques beyond 8 weeks postsurgery, but the ultimate position of the condyle was not

1.0

(n = 63) 0.59 -t 1.0 Posterior 0.18 -C 1.3 Superior

.31 .94

(n = 63) 0.99 0.18 (n 0.88 0.46 (n 0.66 0.39 (n

+- 1.1 Posterior i 1.2 Superior = 62) i: 1.1 Posterior -C 1.3 Superior = 58) -C 1.2 Posterior ? 1.3 Superior = 56)

.02 .72 .34 .85 .69 .85

different. In the rigid group, the average condylar movement was 0.35 mm posteriorly and 0.17 mm superiorly at T4; 0.44 mm posteriorly and 0.26 mm superiorly at T5; 0.67 mm posteriorly and 0.50 mm superiorly at T6; and 0.56 mm posteriorly and 0.44 mm superiorly at T7. In the wire group, the condyle on average moved 0.59 mm posteriorly and 0.18 mm superiorly at T4; 0.99 mm posteriorly and 0.18 mm superiorly at T5; 0.88 mm posteriorly and 0.46 mm superiorly at T6; and 0.66 mm posteriorly and 0.39 mm superiorly at T7. The position of the condyle in both groups was significantly different at T7 than at T2 in both the x and y axis (wire: x, P = .OOOl; y, P = .02; rigid: x, P = .009; y, P = .02).

Superior 1

FIGURE 1.

Graph comparing movement between the two groups. Ellipsoids around each point represent one standard error in both the x and y axis [Approximately 68% confidence regions around the mean x-y coordinate at each perlod).

g 9 z fi

0.0

- 0.5

z 5

-1.0 Anterior

34 There was a weak but significant relationship between proximal segment movement and condylar position at T3 for both the wire osteosynthesis and rigid fixation groups. As the proximal segment was rotated forward, the condyle tended to go superiorly (wire: Spearman correlation coefficient = .27, P = .03; rigid, 0.25, P = 0.048). This relationship did not exist at any other times.

Discussion This study assessed condylar position indirectly by tracing the proximal segment. The method was similar to that used in a study done with wire osteosynthesis by Will et al.6 The period in that study was limited to the first 6 weeks after surgery. They noted that during the time of MMF both condyles exhibited a significant superior movement. The left condyle also moved posteriorly. In our study, the condyles in both the wire and rigid fixation groups moved superiorly and posteriorly during the first 8 weeks. In the subsequent periods, the condyle moved slightly more posteriorly and superiorly. The ultimate position of the condyles in both groups was very similar. Proximal segment movement associated with the initial surgery also was similar in both groups and was not correlated with the ultimate joint position. Interestingly, there was minimal correlation between the position of the condyle and the amount of initial movement. There was a difference between the two groups in the initial period, with the wire group having more inferior condylar movement. This movement may account for differences in stability seen between the two groups.12 Examination of condylar position after a BSSO from a submental position shows that the position of the condylar and proximal segment is altered in a highly variable manner regardless of the magnitude of the move.3,4 Several investigators also have shown that there is a great deal of variability from one side to the other.*,5 Despite these findings, our results suggest that the differences between rigid fixation and wire osteosynthesis in the anteroposterior projection are minimal.

CONDYLAR

POSITION

RIGID

VS WIRE

Our results also showed that the ultimate position of the condyles after a BSSO, whether wire osteosynthesis or rigid fixation was used to fix the segments, was in a more posterior and superior position. This position was significantly different from the presurgical position in both the x and y axes. No single factor could be identified to account for these changes. Although speculative, these findings suggest that this change in position may be secondary to change in the mechanical lever arm of the mandible and remodeling and adaptation of the condyles.

References 1. Kundert M, Hadjianghelou 0: Condylar displacement after sagittal splitting of the mandibular rami. J Maxillofac Surg 8:278, 1980 2. Tuinzing DB, Swartz JGN: Lageveranderungen des caput mandlbulae bei verwendung von zugschrauben nach sagittaler osteotomie des unterkiefers. Dtsch 2 Mund Kiefer Gesichtschir 2:94, 1978 3. Hackney FL, Van Sickels JE, Nummikoski PR: Condylar displacement and temporomandibular joint dysfunction following bilateral sagittal split osteotomy and rigid fixation. J Oral Maxillofac Surg 47:223, 1989 4. Magalhaes AEO, Stella JP, Tahasuri TH: Changes in condylar position following bilateral sagittal split ramus osteotomy with setback. Int J Adult Orthod Orthognath Surg 10:137, 1995 5. Stroster TG, Pangrazio-Kulbersh V: Assessment of condylar position following bilateral sagittal split ramus osteotomy with wire fixation or rigid fixation. lnt J Adult Orthod Orthognath Surg 9:55, 1994 6. Will LA, Joondeph DR, Hohl TH, et al: Condylar position following mandibular advancement: Its relationship to relapse. J Oral Maxillofac Surg 41:578, 1984 7. Ellis E, Hinton RJ: Histologic examination of the temporomandibular joint after mandibular advancement with and without rigid fixation: An experimental investigation in adult Macacu mulatta. J Oral Maxillofac Surg 49:1316, 1991 8. Bell WH, Proffit WR, Chase DL, et al Mandibular deficiency, in Bell WH, Proflit WR, White RP (eds): Surgical Correction of Dentofacial Deformities. Philadelphia, PA, Saunders, 1980, pp 685-843 9. Booth DF: Control of the proximal fragment by lower border wiring in the sagittal split osteotomy. J Maxillofac Surg 9:126, 1981 10. Smith GC, Moloney FB, West RA: Mandibular advancement surgery: A study of the lower border wiring technique for osteosynthesis. Oral Surg Oral Med Oral Path01 60:467, 1985 11. Jeter TS, Van Sickels JE, Dolwick MF: Modified techniques for internal ftxation of sagittal ramus osteotomies. J Oral Maxillofac Surg 42:270, 1984 12. Van Sickels JE, Keeling S, Tiner BD, et al: Stability of rigid versus wire osteosynthesis for a BSSO advancement. J Oral Maxillofac Surg 54:106, 1996 (suppl)