Displacement of the mandible in a child with congenital unilateral temporomandibular joint ankylosis treated with two-stage condylar replacement: a long-term study with the aid of roentgen stereometric analysis.

OBJECTIVE: To monitor mandibular displacement in three dimensions with a high degree of accuracy before, during, and after treatment.

DESIGN: Prospective roentgen stereometric analysis from age 3 years 7 months to age 13 years 8 months.

SETTING: Center for Craniofacial Anomalies and Department of Maxillofacial Surgery, Malmö University Hospital, Malmö, Sweden.

PATIENT: Girl with unilateral congenital temporomandibular joint (TMJ) ankylosis and marked facial asymmetry.

INTERVENTIONS: Epipharyngeal inspection at age 2 years 6 months and insertion of implants under general anesthesia. Resection of the affected right condyle at age 5 years 4 months, replacement of the ramus-condyle complex with a custom made titanium prosthesis at age 5 years 5 months, and replacement of the artificial condyle by a costochondral graft at age 9 years 7 months. Roentgen examinations were performed at intervals from age 3 years 7 months to age 13 years 8 months. Body length was measured annually.

MAIN OUTCOME MEASURES: Stereo roentgenograms were digitized by the Department of Orthopedic Surgery, Malmö University Hospital.

RESULTS: Unexpected lowering of the mandible occurred before treatment. Each procedure had a distinct effect on the direction of mandibular displacement. There was little or no pathological involvement of the functional matrix. Growth of the costochondral graft exceeded growth of the unaffected TMJ. Anterior displacement as well as rotation and tilting of the mandible to the unaffected side accelerated after the age of body peak height velocity.

CONCLUSIONS: Accurate monitoring of mandibular displacement may contribute to a rationale for clinicians' decision on treatment protocol and reveal compensatory differential growth.