A Prospective Study on Relapse Following Bilateral Sagittal Split Osteotomy in Mandibular Set Back Approach

ABSTRACT

Introduction:

Orthognathic surgical correction of the mandible by Bilateral sagittal split osteotomy (BSSO) rectifies dental deformities. Despite its advances, skeletal relapse remains a common complication.

Aim:

The study aimed to assess skeletal stability following BSSO with mandibular setback stabilized by rigid internal fixation with one four-hole titanium miniplate bilaterally.

Materials and Method:

A total of nine patients with skeletal class III malocclusions who required BSSO and setback were included. Following the procedure, rigid internal fixation with one four-hole titanium miniplate bilaterally was performed. Evaluation for relapse during the first week, third month, and sixth month postoperatively was performed.

Result:

Posterior and anterior facial height increased mildly in three patients, respectively. Pogonion was stable in all patients, with no significant relapse.

Conclusion:

This study provides insight into low skeletal relapse following BSSO with mandibular setback.

INTRODUCTION

The correction of dentofacial deformities focuses on attaining facial aesthetics. The most common dentofacial deformity encountered in the south Asian population is mandibular prognathism. Orthodontic and surgical interventions jointly improve the functioning of the oral cavity,[1,2] facial aesthetics, psychological state,[3,4] and self-esteem.[5]

The most performed orthognathic surgical procedure is bilateral sagittal split osteotomy (BSSO) of the mandible.[6] BSSO was described in German literature by Schudardt, described in English by Obwegesser and Trauner,[7] modified by Dalpont, Hunsuck, and Epker[8] and remains the mainstay in the correction of mandibular prognathism. The drawback of this procedure is skeletal relapse.[9] It occurs due to slippage of the segment because of inadequate stabilization and fixation.[4] Thus, therapeutically, Spiessis enumerated rigid internal fixation. This accomplished better stabilization, usage of associated muscles and joints with minimal injury to the masticatory system.[10] Furthermore, it provides patient satisfaction with minimal surgical correction.[11]

Realignment and stabilization of the osseous segment are attained by fixation systems, including miniplates and screws.[12] Therefore, we aim to assess the skeletal stability following BSSO and mandibular setback procedure stabilized by rigid internal fixation with one four-hole titanium miniplate bilaterally.

MATERIALS AND METHODS

A prospective study design was employed in Oral and Maxillofacial Surgery, Govt. Dental College, Calicut during 2021 to 2022. Nine healthy individuals aged 18 years and above, having mandibular prognathism and required mandibular setback, were included. Exclusion criteria include individuals with asymmetrical mandibular prognathism and patients requiring bi-jaw surgery or other osteotomies.

Clinical, radiological examination, Model analysis, and Lateral cephalogram in centric occlusion were taken and analyzed using COGS and Steiner’s analysis.

Under pre-surgical orthodontics, a lateral cephalogram was taken 2 days prior, post-operatively, at the third and sixth month after the surgery to correct rotation, remove dental compensation, and establish arch width compatibility. Prediction tracing was performed, and the set-back procedure was evaluated.

The patient’s bite was recorded. Using a face bow, the models were articulated in a Hanau articulator. “Mock surgery” was performed, and an intermediate occlusal splint was prepared after adequate mandibular setback. Routine blood investigations were assessed.

Surgical Procedure

General anesthesia was induced by endotracheal intubation. 2% lignocaine containing 1:80,000 adrenaline was injected over the anterior border of the ramus and along the medial aspect of the ramus. BSSO technique was performed as elucidated by Obwegesser, along with the Dalpont, Hunsuck, and Epker modification.[7,8]

Following osteotomy on either side, the condyle was seated in the glenoid fossa. The prefabricated occlusal wafer splint was fixed. For all patients, one four-hole titanium mini-plate fixation technique was employed on either side. Following irrigation, the site was sutured. The maxillomandibular fixation was released, and the wafer splint was removed. A pressure dressing with Elastoplast was applied. Cephalometric analysis was studied for relapse [Plate 1]. Review ranged over eight to 10 months.

Plate 1.

Radiographic images showing postoperative setback

RESULTS

An immediate post-surgical setback of Pogonion [Table 1, Plate 1] by an average of 6.3 mm was noted. The average surgical relapse of Pogonion, as quantified from the sixth month post-operative cephalogram, was 1.3 mm. The Go-Po distance showed a decrease of 15 mm post-surgically with a relapse of 5 mm. Pogonion moved superiorly and downward in two three cases, respectively. The average post-operative AFH increase was 3.0 mm, with 1.1 mm lost before 6 month post-operative. The PFH and AFH increased mildly in three and four patients, respectively. Pogonion relapse was stable in all patients.

Table 1.

Case 1

Time of measurement	Vertical measurement (mm)		Horizontal measurement (mm)
	AFH	PFH	N Pog	Go-Pog
Pre surgical	136.5	91	+15.5	82.5
1st Post Op	134	88.5	5	80.5
Three-month Post Op	136	90	6.5	79
Six-month post Op	136	90	6.5	79

DISCUSSION

Orthognathic surgical repositioning of the condylar segment in anatomic position prior to fixation avoids relapse and postoperative TMJ disturbances. The occurrence of relapse is due to improper condyle positioning. Ellis reported that the use of manual methods was superior. Our cases were reflected prior to fixation to ensure the accuracy of condylar positioning in the glenoid fossa.

The principal inciting factors of relapse after setback surgery is intersegmentary instability and collapse of the ascending ramus.[3] Muscle tissue tends to get stretched, and their failure to adapt to the current site often results in relapse. The critical period of relapse is during the early retention period.[4,5,6,7] Studies[8] reports relapse during 6–8 postoperative weeks and it is directly proportional to the magnitude of correction.[9] Relapse occurs due to intersegmentary instability, the magnitude of setback, paramandibular connective tissue, muscle action, method and duration of intermaxillary fixation, stable occlusion and maximum intercuspation after surgery, condylar sag/torquing, and inadequate bone contact between proximal and distal segments. Though 20%–30% relapse occurs irrespective of the fixation methods used,[7,12] most authors consider a significant relapse of 2 mm or more. Relapse after BSSO and setback can be classified into two groups.

1. Early postoperative relapse, which occur due to destruction of the condyle or due to migration of osteotomized segments.[13]

2. Late postoperative relapse, which occurs due to condylar resorption.

Rigid internal fixation[14] helps in firm positioning of osteotomized segments during early postoperative stages. Soft tissue stripping and detachment of muscles tend to compromise the blood supply to the proximal segment and thus delay union between the segments. Full strength across the osteotomy is attains over 25 weeks postoperatively.[15] Miniplate fixation provides intersegmentary stability, bridges gaps between segments, prevents condylar torquing of biocritical screws, inferior alveolar nerve compression, and condylar resorption.

CONCLUSION

Our study suggests a lack of relapse following BSSO with mandibular setback stabilized by rigid internal fixation with one four-hole titanium miniplate bilaterally.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.