A single-stage computer-guided gap arthroplasty with simultaneous patient-specific total joint replacement with a novel flat fossa design: A case report

•Custom made TMJ total joint replacements are now considered a reliable treatment method.•Computer guided approach to TMJ reconstruction guarantees the predictability and reliability of the whole surgery.•Dislocation of the artificial condylar head from the artificial fossa was reported in some cases when the normal concave anatomical fossa design was employed.•A flattened articular surface of a customized artificial TMJ fossa was employed in this case report.•The whole computer guided approach allowed for a simultaneous treatment of a recurrent TMJ ankylosis and facial asymmetry through a sagittal split ramus osteotomy of the contralateral side of the mandible. The computer-guided approach for the patient-specific TMJ replacement is considered an ultimate reliable option in advanced cases. However, dislocation of the condylar head could happen with the concave fossa design. A flat design was described and used in this case. A 15 years old male patient with mandibular asymmetry and class IV recurrent ankylosis of the right TMJ received a patient-specific artificial joint with computer-guided gap arthroplasty and orthognathic corrective mandibular surgery for the left side. The fossa component was made entirely flat, and the patient was followed up over the next year. Customized TMJ prosthetic solutions are reliable in advanced cases, especially when facial corrections are indicated; however, the commonly used concave design showed reported dislocations requiring some design modifications as proposed in the presented case. The flat fossa design of the artificial TMJ secures the same results as the anatomical fossa design without the incidence of dislocation.