Abnormal type III fusion between lunate and triquetrum: A case report

•Knowledge of type III complete fusion is essential to the proper diagnosis and management of this variation.•Imaging modalities can easily diagnose in type III complete lunotriquetral coalition without pathological evidence.•The lunotriquetral coalition provides an enhanced understanding of unexplained carpal wrist pain or trauma. Surgical treatment of fusion has revealed pain relief, restored mobility, and acceptable postoperative wrist motion effects.•Comprehensive postoperative rehabilitation is required to ensure optimal improvement. The lunotriquetral coalition is the fusion of the lunate and triquetral bones of the wrist and is the most frequent carpal coalition type. It is frequently asymptomatic and discovered as an incidental due to chronic wrist pain, trauma, or fracture. This case aims to present an unusual unilateral lunotriquetral coalition and clinical significance for diagnosis and treatment. In this case, we presented a 37-year-old male who exhibited with right-sided trauma and wrist pain. He was diagnosed to had a type III complete osseous lunotriquetral coalition on the right side and detected by plain radiography and CT without lytic, destructive, and sclerotic lesions. An avulsion fracture was recognized in the distal end of the right radius. A fragmented fracture was identified in the scaphoid bone, and an internal fixator extending from scaphoid bone to lunate bone. The internal fixators were observed among the lunate, capitate, and distal end of the radius bones. The plain anteroposterior, lateral radiograph and CT of the right wrist exhibited a right-sided unilateral type III osseous coalition between the lunate and triquetrum bones. Knowledge of type III complete fusion is essential to the proper diagnosis and management of this variation when a subject exhibits unexplained wrist pain, trauma, or fracture. It should be noted that plain radiographs and CT can provide an accurate diagnosis in type III complete lunotriquetral coalition without pathological evidence.