Simultaneous standard total joint prosthesis reconstruction with SSRO and Le Fort I osteotomy in the treatment of unilateral temporomandibular joint ankylosis with jaw deformity: a case cohort study

Temporomandibular joint ankylosis (TMJA) is a severe joint disease that is mainly caused by trauma or infection. It can affect masticatory function, digestion, speech, as well as oral hygiene [1‐5]. When it occurs in childhood, dentofacial deformities and obstructive sleep apnea syndrome (OSAS) may develop [6‐11]. Surgery is the only treatment for TMJA. According to our previous classification [3], patients who had no joint structures or insufficient functional residual condyles require joint reconstruction. Total joint prosthesis (TJP) has gradually replaced autogenous bone graft for TMJ reconstruction with the advantages of no resorption and low relapse rates [12, 13].

For patients with jaw deformities, joint reconstruction is combined with orthognathic surgery simultaneously or secondarily [5]. We have reported using standard TJP with Le Fort I osteotomy to correct bilateral TMJA with severe mandibular deficiency [12‐14]. However, for patients with unilateral TMJA with jaw deformity (UTMJAJD), the method of joint reconstruction and stability of the contralateral healthy joint with orthognathic surgery has not been reported.

The aim of this study was to introduce a surgical method for UTMJAJD under the guide of computer-assisted surgery (CAS) and to evaluate its stability by three-dimensional measurement.

Seven patients were included in the study. They were all females with an average age of 28.4 ± 15.5 years (ranging from 19 to 53 years). Their mean duration of ankylosis was 21.0 ± 11.4 years (ranging from 11 to 45 years). One patient had ankylosis due to infection, while the other six were caused by trauma. Five patients were on the right sides and two on the left. Their preoperative MIO was 11.4 ± 9.3 mm (ranging from 0 to 25 mm, shown in Table 2).

Three-dimensional measurements showed that before operation, the mean chin deviation was 9.5 ± 4.2 mm (ranging from 6.0 to 15.3 mm), and retrusion was 29.1 ± 9.1 mm (ranging from 17.9 to 42.6 mm). The maxillary cant was 2.4 ± 1.2 mm on the canines (ranging from 1.3 to 4.5 mm) and 4.5 ± 2.9 mm on the first molars (ranging from 1.8 to 9.3 mm), with a cant angle of 5.1 ± 3.0° (ranging from 2.1 to 9.7°) (Table 3).

After operation, the ramus height on the affected side increased by 9.2 ± 11.7 mm, the chin deviation was corrected 7.6 ± 4.1 mm (p = 0.015), and advanced 5.9 ± 2.5 mm (p = 0.006) significantly. Maxillary cant was corrected 1.7 ± 1.0 mm at the canines (p = 0.02) and 3.5 ± 2.4 mm at the first molars (p = 0.03). The maxillary cant angle was corrected 4.0 ± 2.4° (p = 0.02) (Table 3).

After an average of 29.0 ± 20.1 months follow-up (ranging from 7 to 62 months), no recurrence of ankylosis occurred. MIO was significantly improved to 35.7 ± 2.6 mm (ranging from 32 to 40 mm, p = 0.000 < 0.05). No patient reported joint pain or occlusion changes. There were no significant position changes of both the maxilla and the mandible (p > 0.05, Table 3). The contralateral healthy condyle had 4.6 ± 5.2° of yaw rotation, but the difference was not statistically significant (p = 0.122 > 0.05, Table 3). There was no obvious condylar surface bone resorption at the last follow-up (Fig. 5).

There are two types of TMJA according to our previous classification for treatment method selection: with and without residual condyle [3]. For the residual condyle which is larger than one-half of the healthy side, lateral gap arthroplasty (LAP) is selected, while for the small or no residual condyle, autogenous bone graft or TJP is recommended for joint reconstruction. Compared with commonly used autogenous bone graft for joint reconstruction such as costochondral graft (CCG), coronoid process graft (CPG), and distraction osteogenesis (DO), which had excellent histocompatibility and reasonable cost [5], TJP is more and more used because of stability and predictability, especially for patients who need large mandibular advancement to correct jaw deformity [19]. We have reported using standard TJP and Le Fort I osteotomy simultaneously for bilateral TMJA with severe mandibular deficiency [14]. Their mean chin advancement was 10.19 mm with significantly improved SNB and ramus heights. After a mean follow-up period of 22 months, the results were stable.

However, for UTMJAJD patients, the outcome of joint reconstruction with orthognathic surgery to the contralateral healthy condyle is unknown. It was reported that about 30% of patients who received TJP treatment experienced symptoms on the contralateral temporomandibular joint [20]. In patients with jaw asymmetry, the articular disc experiences an overload of force, which could lead to disc displacement [21]. After BSSO, the forces on the condyles may become balanced due to the correction of facial asymmetry. But in UTMJAJD patients, there are currently no reports on the influence of TJP implantation with simultaneous SSRO and Le Fort I osteotomy on the contralateral healthy condyle. Results of our study showed an average mandibular ramus elongation of 9.2 ± 11.7 mm, with chin deviation correction of 7.6 ± 4.1 mm, and chin advancement of 5.9 ± 2.5 mm. However, these significant changes did not lead to condylar resorption on the contralateral sides, and no positional or rotational changes were found in follow-ups. The possible reason for this may be that SSRO reduces the force accumulation on the healthy side condyle.

For patients with TMJA and mild-to-moderate deformities, a one-stage surgical procedure can be a suitable option, with the advantages of immediate satisfaction and low cost. However, in those cases with severe dentofacial deformities, staged treatment is necessary for optimal results [5]. In this study, unilateral TJP reconstruction with simultaneous SSRO and Le Fort I osteotomy had a stable outcome in UTMJAJD patients, which can be attributed to the application of CAS technique. First, 3D cephalometry was performed to thoroughly evaluate facial asymmetry, which led to a more accurate treatment plan. There were differences in surgical planning and operation procedures for these patients. In virtual surgery, the level of the occlusal plane was the first step. Then, the ankylotic bone release, TJP implantation, and SSRO were designed. However, during the actual operation, the ankylosis release was the first step, in order to remove the bony mass and to gain mobility of the mandible, so a mandible-first procedure was necessary. After removing the ankylosed bony mass, SSRO was performed on the contralateral side. The intermediate occlusal splint determined by initial maxillary position and final mandibular position was then inserted prior to SSRO fixation and implantation of TJP. Additionally, the installation of the prosthesis and Le Fort I osteotomy were guided by custom-made templates, which improved the surgical accuracy.

We used the method as we previously reported to assess jaw stability after simultaneous TMJ and orthognathic surgery, which includes jaw position, rotation, contralateral healthy condyle position, and surface bone remodeling [18]. The results showed that at the last follow-up, jaw and condylar position were stable, and no obvious bone resorption happened on the condylar bone surface (Fig. 6). There were no patients that developed recurrent ankylosis. The occlusion was stable. However, being a preliminary study, the sample size and follow-up period were limited. It is well known that TMJ prostheses work over a few years but often not for 10 and more years due to several factors [22]. Infection is the main cause of prosthesis failure within the first 6 months after surgery. HO formation, wear or fracture of the prosthesis, foreign body reaction, and allergy to the prosthesis are the common reasons for prosthesis revision [23]. The patients should be informed and understand the necessary of revision surgery to extend the implantation periods [22]. In this study, the results provide encouragement for the future extension of this simultaneous TJR and orthognathic treatment method to a larger number of patients.

In conclusion, the combination of TJP, SSRO, and Le Fort I osteotomy for the simultaneous treatment of UTMJAJD is reliable and effective.