**7. Reconstruction of the temporomandibular joint (TMJ) in children**

Reconstruction of the TMJ is of great challenge to maxillofacial surgeons because of difficulties of intubation in ankyloses and cases with hemifacial microsomia or first arch dysplasia syndrome and hypoplasia of the condyle.

There are two successful techniques for reconstruction of the TMJ:

### **1.** *Costochondral graft*

**4. Orbital floor reconstruction**

**6. Reconstruction of the chin**

and bone graft is through submental incision [5].

syndrome and hypoplasia of the condyle.

**frontal bone**

Blowout injuries are quiet common with road traffic accident where the orbital floor content is displaced down to the sinus with herniation of orbital fat and incarceration of inferior oblique and inferior rectus muscles featuring enophthalmos and diplopia. The orbital floor defect measured if small can be successfully reconstructed by silicone rubber material sialastic (rubber silicone material) which is a biologically inert material, but once the defect is large, bone graft is harvested from the outer cortical plate of the iliac crest to simulate the floor, but our observation on bone graft of the floor might show some degree of resorptions in that case. An additional layer of silastic of 2 mm thickness is required to correct the case. It was noticed that

Severe craniofacial injuries may end with head injuries, with severe damage to the frontal bone, roof of the orbit, nose, and anterior cranial fossa. After the recovery of the patient from head injuries, the anterior cranial fossa is approached through bicoronal flap with craniotomy. The brain and dura are retracted backward, and the dura is repaired by the galea or temporalis muscle. The dura should be closed as watertight closure, the roof of the orbit and anterior cranial fossa was reconstructed by bone graft from the iliac crest with silastic, and the frontal bone was reconstructed by bone graft. The author successfully reported few cases with severe

craniofacial trauma treated by this technique with collaboration with neurosurgeons.

**7. Reconstruction of the temporomandibular joint (TMJ) in children**

Reconstruction of the TMJ is of great challenge to maxillofacial surgeons because of difficulties of intubation in ankyloses and cases with hemifacial microsomia or first arch dysplasia

Hypoplasia of the chin or receded chin usually required bone grafting by sandwich technique by doing transverse osteotomy of the lower anterior border of the lower jaw. Bone graft was harvested from the iliac crest as horse shows cortical-cancellous bone graft inserted in between the two bones and fixed by rigid fixation with soft stainless steel wire of 0.25 mm or by plate, but some of these bone graft may show some degree of resorption. We prefer kidneyshaped silastic implant in three sizes, small, medium, and large, and the access for the silastic

membranous bone graft from skull vault is less liable for resorptions.

6 Bone Grafting - Recent Advances with Special References to Cranio-Maxillofacial Surgery

**5. Reconstruction of anterior cranial fossa, orbital roof, and** 

#### **2.** *Kummoona chondro-osseous graft*

Many other techniques have been used like sternoclavicular graft. This technique is only reported once or twice. This graft failed to restore growth of the condyle of TMJ but was used as gap arthroplasty, and this showed technical difficulties with a large head of sternoclavicular graft to fit small glenoid fossa [7].

The costochondral graft for reconstruction of the TMJ has been used since 1973 by Kennett [8] and experimental studies by Poswillo [9] on Macaca iris monkey to prove the viability of the graft and the cellular changes to simulate the condyle for restoration of growth and function of the TMJ. The objection about costochondral graft is that the junction between osteoid element and cartilaginous part is very fragile and easy to dislodge. Possibilities of pleural perforation and long duration of intermaxillary fixation (IMF) for 6 weeks end after the release of IMF. A spasm of muscles of mastication developed besides overgrowth of the graft was reported [10].

Kummoona chondro-osseous graft advocated in 1986 [11, 12] is the most popular graft nowadays because its junction between osseous element and cartilaginous cap is very stable but rigid fixation of the graft to ascending ramus with no IMF, and the child is advised to chew within the next few days to restore function and growth of the graft and the TMJ. This statement is based on Moss theory (1962) [4], the theory of functional demand of the periosteal matrix of facial skeleton.

Experimental research and study were done on a rabbit to demonstrate the viability of the chondro-osseous graft [12] and to demonstrate that the condyle is a growth center. At the end of the experiment, we did postmortem studies and observed an excellent union between the graft and ramus of the rabbit mandible.

Histological examination of the graft showed four zones. The first layer showed a thick articular layer of dense fibrocartilage due to the demand of hard masticatory process of rabbit food, the second layer showed several zones of active layers of round mesenchymal stem cells which represent the proliferative layer, and the third layer showed a series of hypertrophic chondrocyte passing through a series of changes. This layer represents the differentiation of mesenchymal stem cells to chondrocyte and osteocyte. These cellular changes represent the growth potential of the graft, and the fourth layer was an osteoid bone with bony trabecula and bone marrow spaces in between.

In the previous research on the bone and cartilage, they did find a G-protein-coupled receptor (CXCR4) predominately expressed in hypertrophic chondrocyte, while its ligand chemokine stromal cell-derived factor (SDF-1) is expressed in the bone marrow adjacent to hypertrophic chondrocyte. These findings explained the endogenous growth potential of the graft to continue to grow, repair, and remodel the condyle and restore growth of the mandible and midface in children for correction of facial deformity in the affected side.
