Costochondral Reconstruction for Absent Temporomandibular Joint
Patrick A. Gerety
Scott P. Bartlett
DEFINITION
Costochondral graft is a rib graft harvested with osseous and cartilaginous portions.
Hemifacial microsomia (HFM) is a congenital condition in the distribution of the 1st and 2nd branchial arch embryology affecting the mandible, ear, orbit, facial soft tissue, and facial nerve function.
Pruzansky-Kaban modified classification system1 is a fourpoint scale (I, IIA, IIB, III) used to rate mandibular hypoplasia in patients with HFM.
ANATOMY
Mandibular anatomy (FIG 1A)
Ramus: vertical, posterior height often deficient in HFM patients; often shifted medially in HFM; site of costochondral reconstruction
Coronoid process: insertion of temporalis muscle; affected by ramus hypoplasia
Condyle: may be hypoplastic or absent in HFM
Body
Symphysis/parasymphysis
Alveolar process
Temporomandibular joint (TMJ; FIG 1B)
Synovial articular joint of the mandible
FIG 1 • A. Mandible. B. Temporomandibular joint.
Complex multicomponent structure that includes the condyle, glenoid fossa, capsule, articular disk, lateral pterygoid muscle, and ligaments
Joint allows rotation and anterior translocation.
Glenoid fossa
Site of mandibular articulation on the temporal bone just anterior to the external auditory meatus/canal
In severe HFM, this structure is absent/hypoplastic.
Rib osteocartilaginous junction (FIG 1C) is located at approximately the midclavicular line. This location will allow a portion of rib that has a long osseous and shorter cartilaginous portion for mandible reconstruction.
PATHOGENESIS
Disorder of 1st and 2nd branchial arch development causing facial hypoplasia
Theories:
Stapedial artery disruption/hematoma
Neural crest cell migration error
NATURAL HISTORY
The hypoplastic mandible does grow but does not attain catch-up growth and is outpaced by the normal side.2
Facial asymmetry may worsen with growth in more severe cases.
 FIG 1 (Continued) • C. Rib harvest. An incision is designed in the inframammary crease to harvest an osseocartilaginous rib graft. |
 FIG 2 • A. Hypoplastic mandible. Features include an occlusal cant, vertically short ramus with loss of facial height, effacement of the gonial angle, and medialization of the ramus-condyle. B. Pruzansky type III mandible deformity. The ramus, coronoid process, and condyle are absent. |
PATIENT HISTORY AND PHYSICAL FINDINGS
OMENS+ classification describes abnormalities in HFM patients.3
Stands for orbit, mandible, ear, facial nerve, and soft tissue
Extracraniofacial manifestations—requires medical workup
Mandibular hypoplasia can be variable in morphology and degree (FIG 2A).
Vertically shortened ramus—loss of posterior facial height and blunted gonial angle
Occlusal cant up toward the affected side
Loss of posterior facial width with a medially shifted mandible
Displaced dental midline
Severity of mandibular hypoplasia
Pruzansky-Kaban classification
Type I: small mandible with normal morphology
Type IIA: mandible with a ramus that is abnormal in size and shape, but with a TMJ that is normally situated
Type IIB: abnormal ramus and a TMJ that is medially displaced
Type III: absent ramus, condyle, and TMJ (FIG 2B)
This classification system has been shown to have low inter-rater reliability, which is largely related to the highly variable morphology of the hypoplastic mandible in HFM. There is no system in use that has better inter-rater reliability.Related posts:
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