Condylar Hyperplasia (CH) Type 1
CH Type 1 patients may have a Class I occlusion at the beginning of puberty and develop into a Class III or begin as a Class III but develop a worse Class III relationship with accelerated mandibular growth that can continue into the mid 20’s, although it is eventually self-limiting. Bilateral symmetrical active CH Type 1A causes progressive worsening prognathism and occlusion, but usually asymptomatic TMJs. Unilateral CH Type 1B or bilateral CH Type 1A with asymmetric rate of condylar growth can cause progressive deviated prognathism, facial asymmetry, TMJ disc dislocations, TMJ pain, headaches, masticatory dysfunction, etc. Not all prognathic mandibles are caused by CH; only those demonstrating accelerated, excessive mandibular growth continuing beyond the normal growth years. MRI may show thin discs that sometimes are difficult to identify, vertically long but otherwise normally shaped condyles, long condylar necks, and disc displacements more commonly seen in asymmetric growth with deviated prognathism. Posterior disc displacements will occasionally occur.22, 23 In the coronal view, the condylar head is commonly more rounded than a normal condyle.
Our treatment protocol (Figure 30) for active CH Type 1A and B patients includes: 1) High condylectomy to arrest the mandibular growth; 2) TMJ disc repositioning over top of the condyle with Mitek anchor technique; 3) Bilateral mandibular ramus osteotomies; 4) Maxillary osteotomies if indicated, and 5) Adjunctive procedures if indicated. Our studies22,23 demonstrate that this protocol stops mandibular growth and provides highly predictable and stable skeletal and occlusal outcomes with normal jaw function and good facial esthetics. Treating active CH Type 1 with orthodontics and/or orthognathic surgery only, without including the high condylectomy will result in a high relapse rate with redevelopment of a Class III skeletal and malocclusal relationship.
Figure 30: A) The high condylectomy removing 4 to 5 mm of the condyle. B) Repositioning and stabilizing the disc with a Mitek (M) anchor.
Figure 32, CASE 1: A) Presurgery cephalometric evaluation. B) Surgical treatment objective.