SEMI-SAGITTAL SPLITOSTEOTOMY OF ANKYLOSINGBONY MASS FOR RELEASE OF LONG STANDINGAND RECURRENT TEMPOROMANDIBULAR JOINT BONY ANKYLOSIS

Mohammad Dehis 1 and Abeer Kamal 2 . 1. Prof. of Oral and Maxillofacial Surgery, Faculty of Dentistry, Cairo University, Cairo, Egypt. 2. Associate Prof. of Oral and Maxillofacial Surgery, College of Oral & Dental Surgery, Misr University for Science & technology, Giza, Egypt. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 20 October 2018 Final Accepted: 22 November 2018 Published: December 2018


ISSN: 2320-5407
Int. J. Adv. Res. 6(12), 1373-1381 1374 posterior border of the ascending ramus. The segment of bone between these two lines is removed to create the gap,it should be as wide as possible to prevent the recurrence. The created gap, should be established at the most superior part of the ramus to maintain maximum ramal height, minimize the possibility of occurrence of anterior open bite and increase the chance of normality of postoperative mandibular functions. (6)(7)(8) The advantages of gap arthroplasty are its simplicity, low coast and short operative time. The disadvantages include: creation of psudoarticulation and short ramus, failure to remove all bony pathology, increased risk of reankylosis, extending post-operative follow up and increased possibility of anterior open bite in bilateral cases (9)(10)(11)(12)(13) . Occlusal derangement is one of the major disadvantages of gap arthroplasty. It is usually take the form of anterior open bite. The muscle action pulls the proximal portion of the mandible upwards. In unilateral cases premature contact of the affected sideand an open bite on the contralateral side were reported.Complications develop as profuse bleeding occurred during surgery whichmay indicate ligation ofexternal carotid artery. Weakening of the facial nerve was reported in upper branch and this attributed tosurgical trauma. In young children, the removal of large section of bone presents surgical and postoperative difficulties as a large percentage of ascending ramus is destroyed.Complications of gap arthroplasty also included infection, otologic complications, parotid gland injury, cranial fossa perforation, reankylosis,and suboptimal postoperative range of movement. (9,(14)(15)(16) The aim of the present study was to introduceand evaluate the semi-sagittal split osteotomy of ankylosing bony massin thetreatment ofin cases of recurrent and long standingTMJ bony ankylosis. The obtained results may contribute to minimize the disadvantages of conventional technique of gap arthroplasty and improve its results.

Patients and methods:-
Twelvepatients suffering from TMJ bony ankylosis were included in the present study. They were selected from those attending outpatient clinics, Oral and Maxillofacial Surgery Department of Faculty of Dentistry, Cairo University, Egypt. A detailed history and systematic clinical examination were carried out after taking consent from patients.Inclusion criteriainvolved the recurrent or long standing TMJ bony ankylosis, and bulbous ankylosing bony mass more than the conventional condyle mediolateral and anteroposterior as indicated by CT scan.Exclusion criteria included: young children, medically compromised patients, all types of fibrous ankylosis, patients with short duration of ankylosis and recent recurrent cases. Computerized tomographic scan (CT) were performed for each patients with axial, coronal, sagittal and 3D reformatted images preoperatively for diagnosis of ankylosis, determination of the size of ankylosing bony mass and the site and angulation of cut. Another CT were performed three months postoperatively. Lateral cephalometry were ordered preoperatively and three months postoperatively for calculation of possibledownward mandibular translation.

Analysis of patient's data:-
The sample comprised8females and 4males with mean of age equal 19.9 years. The group included 8 cases suffering from bilateralTMJ bony ankylosis and 4 cases unilateral ankylosis only. They were complaining of long standing restricted mouth openingwith mean of durationof ankylosis equal to 13 years. The mean of the maximum inter incisal openingpreoperatively was 3 mm. Diagnosisof TMJ bony ankylosis was established on the basis of thorough clinical examinationand CT scan.Preoperative routine blood investigations for general anesthesiawere performed.

Surgical technique:-
Hospital admission was carried out aday before surgery. Patients were operated under general anesthesia with fiberoptic nasotracheal intubation. They were draped and disinfected as routine program.Local anesthetic (Mepivacaine HCl 2%, Levonordefrin HCl 1:200000 1.8 ml. Alexandria Co. For Pharmaceuticals & Chemical Industries. Egypt) was injected subcutaneously in the preauricular area for hemostasis.Gain access was carried out via modified preauricular incision. It was made vertically approximately for4 cm length just anterior to the helix of the auricle in the preauricular skin fold. The incision was carried out through the skin and subcutaneous tissue blunt dissection was carried out in close contact following the direction of perichondrium and periosteum of the external auditory meatus. Dissection was carried out in this relatively avascular plane and directed downward, inward and forward below and behind the glenoid lobuleof the parotid gland, the condylar mass was approached from the posterior aspect at the level of the root of zygomatic arch.At this point the periosteum was incised and elevated, so the dissection at this plane was carried out at the subperiosteal level. Further elevation was extended anteriorly to expose the sigmoid notch,also caudal dissection started from the lower border of the zygomatic arch so that the joint region could be exposed. (Figure 1a&b The osteotomy cut was performed by drilling multiple horizontal holes using round surgical bur then connected by fissure surgical bur in the outer cortex at most superior point of ankylosing bony mass laterally. The cutthrough the deeper spongy bone was completed by the use of bone osteotome (bibeveled chisel). The angle of inclination of the osteotome was guided by aid ofblade of accessory unibeveled chisel. It was engineered preoperatively with degree of angulation about 130-150 O ,this reading wasobtained from interpretation of the CTon coronal cutso it was used only as a guide( Figure 2& 3). Delicate knocking by mallet on the cutting osteotome was continued.The cut was gliding by the guide of the unibeveled chisel and directed downwards and mediallytowards the most inferior point of the most constricted part just below the ankylosing bony mass and above the mandibular foramen.The separation was completed finally at the inner cortex by leverage and torque actions using osteotome to induce crack separation of inner cortex of bone. ( Figure 4&5).  The cut of ankylosing bony mass in this study were obtained at three steps, the outer horizontal cut of the mass by the use of surgical burs, the inner spongy bony is cut by incrementally increased osteotome thickness guided with special pre-determined inclination,and finally the inner cortex was splitted by leverage and torque action of the osteotome at the depth of the previous cut. ( Figure 4&5) After releasing of ankylosis, the free mobility of the mandible was gained by the use of mouth gag and maximum interincisal opening was recorded at this moment. Pterygomasseteric sling release was performed to achieve free intraoperative satisfactory inter incisal opening (about 35 mm). Coronoidotomywere performed if indicated.The semi-sagittal split osteotomy and pterygomasseteric sling release were performed in the other side in bilateral cases ( Figure 6-b).
The surgical field was debrided and the remaining bony chips were removed. Copious irrigation with normal saline solution was performed. Vacuum suction drain was inserted subcutaneously via posterior auricular puncture. Closure of the wound were done in layers and finally pressure dressing was applied ( Figure 6). Postoperative care:-It was implemented until discharge of the patients on the second postoperative day. Delayed postoperative care and muscle rehabilitation program were carried out at outpatient clinic to prevent recurrence. The muscle rehabilitation program included negative mouth opening at the first day postoperatively. Forced mouth opening started on the second postoperative day using mouth gag and increasing numbers of intermaxillary wooden tongue blades.Computerized tomograms were performed 3 months postoperativelyfor follow up.
The following quantitative and qualitative calipers were used to assess the technique:-Intraoperative difficulties:-1. Hemorrhage.

2.
Fragmentation at the osteotomy cut.
Developing of anterior open bite. 2.

Results:-
The postoperative course was uneventful. The patients discharged on the second postoperative day with their normal activity and started muscle rehabilitation programin outpatient clinic as following: Fragmentation at the osteotomy cut:-It was seen in only one case (8.3%).

Need for coronoidotomy:-
It was carried out in four cases (33%) to obtain satisfactory intraoperative interincisal opening.

Discussion:-
The present study has presenteda new modality for TMJ arthroplasty.It was used to release long standing and recurrent bony ankylosis with extensive bony mass. It designed semi-sagittal osteotomy of the ankylosing bony mass to prevent shortening of ascending ramus, limiting the frequency ofdeveloping open bite and backward and upward position of the mandible. The present techniquewas planned also to avoid injury to the important vital structures located medial to the ankylosing bony mass. Creation of the conventional gap may endanger the common carotid artery at its entrance in the petrous part of temporal bone and the internal maxillary artery may also be jeopardized (17)(18)(19)(20) .
The advantage of semi-sagittal splitting of the ankylosing bony mass is intended to transfer the false joint inferiorly to keep the posterior vertical height. The outer cut at the root of zygomatic arch isdirected medially and downward to emerge just above the mandibular foramen. Excessive functional rehabilitation movement tend to change the 1379 spongy interface of large area of bony cuts into cartilage producing false joint (Figure 8) with minimum compromise of the posterior vertical dimension. Bodily translation of the ramus downward by gravitation and release of pterygomasseteric sling will widen the osteotomy line and change it into semi-vertical gap. Creation of the gap on the expense of ankylosing bony mass may induce shortening of ramus with subsequentdecrease in posterior vertical heightand creation of postoperative anterior open bite.This opinion was supported by many authors. (21)(22)(23)(24)(25) For this reason the current technique was introduced. The semi-sagittal split osteotomy is intended to preserve the ankylosing bony mass instead of its removal as stated by others. The present technique is designed to avoid cutting of bone medially ( Figure 5& 8) and desist entering of areas of disorderly bone deposition at the base of skull in close proximity to the carotid canal and middle meningeal artery ( Figure 9). In order to prevent injury to vital structures medial to ankylosing bony mass the cutting was done with three methods; first the outer cortex was cut using surgical bur, the wide slot was created in cancellous bone by using gentle tapping on the different thickness of 6 mm widthosteotome,finally the medial cortex was splitted by the useof leverage by simple hand rotation of the inserted osteotome. The proposed technique is intended to keep away the sharp edge of the osteotome and blind rotating cutting surgical burs not to reach the medial cortex and the leverage usually induce tension at the medial cortex. Treatment of recurrent or long standing TMJ ankylosis with massive bony massby conventional gap arthroplasty poses a significant challenge because of technical difficulties, a high incidence of recurrence, and development of open bite. A variety of techniques for treatment have been described in the literature. However, no single method has achieved uniformly successful results. Previous study reported that the factors affecting the incidence of reankylosis are: disregard of post-operative physiotherapy, technique of surgery and inadequate intraoperative maximum interincisal opening (less than 35 mm) (8, 9, 16.21, 26. 27) . In the present research three items are going to help translation of the ramus and released mandible inferiorly hence the semi-sagittal split osteotomy will be transformed into gap,these three items are: gravity, release of pterygomasseteric sling and muscle rehabilitation program.
The complications encountered in the present study as numbness of lower lip16.7%; it represent only two cases;this is due to occupancy of the mandibular foramen a higher position in ankylosis patients than normal subjects as reported by Dehis et al (28) . The existence of weakening of the zygomatic and frontal branches of facial nerve (25%) is attributed to heavy soft tissue retraction during surgery. The developed open bite was also so minimal(8.3%) and this is because the case was long standing TMJ ankylosis in an old age female with subsequent deficiency in ramus height. The muscle was severely fibrosed with the resultant affection of neuromuscular transmission. Excessive consolidation of the cortical bone was the cause of fragmentation that seen in the osteotomy cut (8.3%). Tendency for recurrence of TMJ ankylosis (8.3%) was due to delinquency of the physiotherapy by the patients and disappearance during the critical first five weeks of follow up.
The present study concluded that, the semi-sagittal osteotomy is indicated in cases with excessive bulbous ankylosing bony mass that extend medially along the petrous temporal bone, this technique is recommended in order to preserve the major vital structures at the base of the skull and avoid further shortening of the ramus by bone loss due to creation of the horizontal gap in already deficient ramus height. Recommendations:computer guided surgery for creation of template to guide this semi-sagittal osteotomy is recommended and represent the future field in the developing countries.