Modified Osteotomy for TMJ Ankylosis in Paediatric Patients with Deficient Interpositional Temporalis Muscle Mass and Buccal Fat Pad – A case Series and Literature Review

Abstract

Ankylosis of the temporomandibular joint (TMJ) is a bony or fibrous fusion of the articular surfaces of the mandibular condyle and the glenoid fossa. Gap arthroplasty, Interpositional arthroplasty, Condyle reconstruction with autogenic or alloplastic grafts and total joint replacement are some common modalities of management. In this article, we discuss a series of three cases of unilateral TMJ ankylosis in paediatric patients, managed by gap arthroplasty using a modified osteotomy cut. The modification was adapted due to inadequate interpositionable temporalis muscle or buccal fat on the affected side and chances of adaptive remodelling of the CCG (Costochondral graft), if placed were rendered negative.

Introduction

Ankylosis of the temporomandibular joint (TMJ) is a bony or fibrous fusion of the articular surfaces of the mandibular condyle and the glenoid fossa. This fusion substantially limits jaw movements and growth, especially if it occurs during the patient’s growth stage. Apart from facial abnormalities, speech impairment, mastication problems, and a restriction in airway space, it also causes psychological suffering to the patient [1]. Treatment for this condition is challenging and focuses on restoring function and appearance while taking necessary precautions to avoid reankylosis. Inter-positional gap arthroplasty followed by intensive jaw physiotherapy is the most successful and cost effective treatment among the reported treatment options [2]. The surgical excision of the ankylosed mass to create a space between the glenoid fossa and the ramus stump is known as gap arthroplasty. This is accomplished by placing two horizontal osteotomies in the TMJ region with a spacing of 10–15 mm between the bony surfaces [3, 4]. An autogenous or alloplastic graft material is subsequently used to reconstruct the condylar component.

Making a correct osteotomy design, providing an adequate gap and employing interpositional graft material to prevent contact between the two bone surfaces is essential to reduce the chances of reankylosis. Temporalis muscle or buccal fat pad serve ideal choice for interpositioning material in TMJ ankylosis cases. In this series of cases, with inadequate thickness of temporalis muscle due to atrophy, the osteotomy cuts were planned and modified such that the contact between bony surfaces on maximal mouth opening is avoided in order to reduce reankylosis from occurring.

Technique

The ankylosed joint, zygomatic arch, coronoid process, and ramus stump were exposed through pre-auricular incision and layer-wise dissection. Pre-operative evaluation revealed markedly thinned out and inadequate temporalis muscle mass (bulk and length for rotation) for interpositioning. Intra-operatively while dissection, atrophic muscle mass and buccal fat pad was confirmed (Fig. 1A). With the intraoperative finding of unusually atrophic muscle and negligible amount of buccal fat pad for interpositioning, the gap between the osteotomy cuts were increased (Fig. 2). Hence, the inferior cut was executed as per plan to align at a level below the sigmoid notch there by involving the ipsilateral coronoidectomy in the same osteotomy (Fig. 3). A superior osteotomy cut was made conventionally by referring to the surrounding recognisable structures and therefore separating the ramus stump from the skull base while taking proper care of the structures medial and superior to the joint. Average maximal mouth opening (MMO) of 33 mm was achieved intra-operatively (Fig. 1B). A jaw stretcher was used to examine the proximity of the bone cuts at MMO during the surgery. After complete ankylosis release, a space of 5 mm was maintained between the bony surfaces (at MMO) with this modified osteotomy. The surgical site was then sutured in layers. On 2 years follow-up, there are no significant weakness on the operated site with MMO maintained at an average of 31 mm for all three patients (Table 1).

Fig. 1.

1A Shows thinned out temporalis muscle inadequate for interpositioning. 1B. Maximal Mouth Opening after modified Osteotomy cut

Fig. 2.

Modified osteotomy cuts, Solid lines show conventional osteotomy cuts with a gap of 1-1.5 cm between bony segments. Dotted line shows the modified inferior osteotomy cut involving coronoidectomy, with an increased inter-segmental gap. 2A. Coronal view. 2B. Sagittal view

Fig. 3.

Specimen photograph showing (A) Condyle along Mediolateral width. (B) Coronoid process, Note the dotted line showing inferior osteotomy limit extending below the sigmoid notch

Table 1.

Demographic and clinical features of the patients.

Sl. No.	Patient Age (years)	Gender	Aetiology of Ankylosis	Time lapse between history of trauma and Surgery (years)	Primary or Revision Surgery	Follow-up period (months)	Intra-operative MMO (mm)	MMO at 2 years follow-up (mm)
1.	8	Male	Post-Traumatic	5	Primary	38	31	30
2.	13	Male	Post-Traumatic	8	Primary	35	35	32
3.	12	Female	Post-Traumatic	8	Primary	29	33	31

Discussion

The aetiology of ankylosis of the TMJ can be classified broadly into injuries, infection, and systemic diseases, in addition to previous TMJ operations [3–7]. The higher prevalence of TM joint ankylosis in rural areas are contributed to the unavailability of access to specialist and unawareness of the patients about the consequences following a trauma or infection in and around the joint region. Hence, the prevalence is basically due to misdiagnosis, non-diagnosis of condylar fractures, or neglect of proper follow-up [7]. The treatment of ankylosis of the TMJ is a major challenge for surgeons. There is no published consensus on a standard protocol to treat TMJ ankylosis, but three are in common use: gap arthroplasty; interpositional arthroplasty; and articular reconstruction [7, 8]. There are contradicting opinions on how and where to use the available treatment options. Costochondral graft (CCG) for reconstruction of ramus condyle unit (RCU) was one of the options for management of these cases of paediatric TMJ ankylosis, but there are studies reporting the incredibly unpredictable growth pattern of CCGs, as it can take the form of either no growth at all or rapid growth [9, 10]. Overgrowth of the mandible on the grafted site actually can be more problematic than the absence of growth [11]. There have been many theories put forth regarding the graft’s natural capacity for development, but none have been wholly accepted. Therefore, it appears that it is more probable for hyperplasia to develop in the condylar head when active growth occurs instead of adaptive remodelling [12, 13]. As the post-surgical adaptive remodelling of CCG was anticipated to be non-satisfactory and also to avoid the donor site morbidity, the authors preferred to modify the conventional gap arthroplasty. Various modifications have been done in gap arthroplasty osteotomy design (Table 2). The origin of these modified techniques were carried out to match the given clinical scenario to bring out the best possible outcomes and to create ease in the operative method. Selvaraj [8] in 2020 reported a case of unilateral TMJ ankylosis with elongated coronoid process, managed by aggressive resection of ankylotic mass followed by fixation of resected coronoid process to the ascending ramus. They reported that the partial stripping of attachments of coronoid process (lateral and inferior) and preservation of temporalis attachment to the mandibular coronoid process helped avoidings the occurrence of open bite which is an unforeseen complication in complete coronoidectomy. In 2019, in a study involving 37 patients, Andrade NN [14] gave a modified osteotomy cut following removal of ankylotic mass in which the posterior part of the inferior osteotomy in the ramus was angulated postero-inferiorly. This modified osteotomy helped increase the gap between the bone segments posteriorly on maximal mouth opening without compromising the vertical ramal height thereby reducing the chances of contact in one of the most common sites of recurrence. In 2016, in a selected age group study including 15 joints, Telmerek AT [7] reported a technique called as the conservative gap arthroplasty. In this conservative gap arthroplasty, a gap of 7–9 mm was created between the bone segments in selected cases in which the ankylotic mass was not involving the sigmoid notch region. Their study showed that there was satisfactory maximal mouth opening with no reported recurrence for a follow-up period of four years using this less aggressive gap arthroplasty. In a study in 2014 [15], type 3 ankylosis with evidence of gap present between the superior surface of the joint and the medially displaced condylar stump, was managed by lateral arthroplasty in which the osteotomy was limited only to the laterally fused ankylotic mass thereby preserving the medially displaced condyle for future functional purpose following remodelling of the joint space. Yonglong in a retrospective clinical study [16], reported usage of resected coronoid process as autogenous coronoid grafts to reshape the condyle following resection of ankylotic mass. The facial aesthetics and function were restored with a simultaneous sagittal split osteotomy of the mandible thereby allowing the rotation of the distal teeth bearing segment to be fixed in position to give satisfactory occlusion. Also there are reports showing utilisation of the temporalis fascia with or without adjacent galea aponeuratica for interpositional arthroplasty in cases of atrophic temporalis muscle [17]. The cases discussed in this article presented with a history of several years (Average- 7 years) between trauma to the lower jaw region and patient seeking for treatment. Therefore the mouth opening and jaw movements were severely affected with almost nil palpable movement on the ipsilateral side. In a case report, Elsayed N [18] documented a case of disuse atrophy of masticatory muscles following a surgery for resection of intracranial trigeminal schwannoma. Hence, as an opinion, authors suggest that the massive atrophy of soft tissue structures associated with TM joint seen in these paediatric cases could potentially be related either due to the trauma itself or to the remodelling due to limited usage following the trauma. Further detailed studies and radiographic analysis are needed to conclude such a cause for the atrophic changes.

Table 2.

Various recent studies with modifications in osteotomy design for TMJ Ankylosis

Study name	No. of cases	Design/ Modification	Study outcomes
Selvaraj DS (2020)	Case report	Coronoidoplasty for unilateral TMJ ankylosis	Improved MMO, Preservation action of temporalis muscle action
Andrade NN (2019)	37	Divergent lower cut in posterior one‑third directed inferiorly away from the superior osteotomy cut	More space on posterior aspects of the osteotomized surfaces during maximal mouth opening. No effect on decreasing the vertical ramus height.
Temerel AT (2016)	13( 15 Joints)	Conservative gap arthroplasty(7-9 mm) in cases not involving Sigmoid notch,with no interpositioning	Improvement in MMO, No recurrence in Ankylosis for four years.
Singh V et al. (2014)	15 patients (17 joints)	Lateral arthroplasty, preserving medial condylar stump	Preservation of joint function and ramal height with adequate MMO, Technique sensitive.
Yonglong (2002)	6	Sagittal split ramus osteotomy, coronoid process, and fibular graft	Improved MMO, facial profile, graft acceptance in all cases

This modification of inferior osteotomy cut presented in this article, can be incorporated in similar clinical situations with no significant effect on lowering the vertical ramus height and patients with issues to afford an alloplastic graft or TM joint PSIs. The usage of this technique might be limited to unilateral cases, as there can be significant reduction in ramal height if done bilaterally. As per some studies [5, 6], patients undergoing bilateral coronoidectomies may suffer from the pronounced loss of temporalis action resulting in post-operative open bite and need for physiotherapy and training for mouth closure.

Conclusion

This inferiorly repositioned osteotomy cut, increases the gap between the bony surfaces to a maximum even on active stretching of the lower jaw thereby reducing the chances of reankylosis. This modification allowed the surgeons (i) to adapt the clinical situation which presented as inadequate amount of local interpositionable material, (ii) to forecome the shortcoming of gap arthroplasty (higher reported recurrence due to inadequate and uneven gap created medio-laterally) [3], (iii) to reduce secondary donor site morbidity (dermal fat graft), (iv) reduced duration of surgery. This change allowed more liberty to the lower jaw in the post-op recovery period for physiotherapy. Authors report that with the given situation of deficient inter-positional material and unaffordability of patients to alloplastic total joint reconstruction, best possible outcomes were achieved using this modified aggressive osteotomy design.

Funding

No funding was received for this study.

Declarations

Conflict of Interest

The authors declare no conflict of interest.

Informed Consent

Informed and written consent was obtained for treatment and publishing of photographs.