Trapezoid is a very well protected carpal bone. Its dislocation and fractures are documented in the literature but are very rare. We present a case of bipartite trapezoid, where there was a diagnostic dilemma on the basis of clinical and radiological findings.
A 17 year old boy presented to Casualty with pain in the base of right thumb. He had a recent history of minor fall in outstretched hand. On examination, there was mild tenderness at the base of the right thumb. Neurovascular status was intact. A plain X-ray of the right wrist showed a suspected undisplaced fracture of the right trapezoid. In suspicion of a fracture, a plaster cast was applied. On review at the fracture clinic, 3 days later, we found that the wrist was almost pain-free. The plaster was removed. On examination, there was no external injury, bruising or swelling. There was mild tenderness at the base of the right thumb in the anatomical snuffbox. Movements of the wrist did not elicit any discomfort or pain. X-ray showed that there was a clear, smooth line along the radial 1/3rd of the right trapezoid passing through the entire length of the bone. There was no other fracture or 'fat pad sign' that excluded bony or soft tissue injury. As the boy was in his late teen-age, the epiphyseal fusion was yet not complete. The distal end of the radius clearly showed the epiphyseal line. Axial CT scan in coronal plane showed that the trapezoid bone was in 2 parts and the margins were corticated, indicating either established non-union or a bipartition of trapezoid, which is considered as a normal but rare variant. As he was asymptomatic with almost normal clinical picture a diagnosis of bipartite trapezoid was made.
Bipartite trapezoid is a natural but rare variant. As far as we have found from the literature search such a case was not reported. However, a few cases of fracture of the trapezoid reported 2, 3,4,5. The main concerns about our patient were the age (17 years) and the nature of the presentation, which raised the suspicion of a fracture. Trapezoid is situated in the radial side of the distal row of carpal bones surrounded by trapezium, 2nd metacarpal, scaphoid and capitate. Because of its anatomy, its wedge shape, with the dorsal part being twice as broad as the volar part, and its tight ligamentous connections to the other carpal bones, the trapezoid is extremely well protected 1. The carpal bones develop from secondary centres of ossification. The fusion of different parts of such bones occurs after teen-age. The x-rays and the CT scan clearly demonstrated that the line between the two parts of the trapezoid is full length, highly suggestive of a bipartite trapezoid. . Finally, the pain that was there after the fall might be due to soft tissue injury like sprain of ligaments. The boy became symptom-free with conservative treatment and was discharged from the clinic.
Bipartite right trapezoid
Based on the provided X-ray and CT images, an abnormal radiological structure is observed on the radial side of the distal wrist, located at the normal position of the carpal bone (the trapezoid bone, also known as the lesser multangular bone). Specific characteristics include:
Based on the above radiological findings and the patient’s medical history, the following diagnoses are considered:
Given the patient’s lack of previous wrist problems, the relatively mild trauma mechanism, and the radiological appearance, the fracture risk is relatively low. However, further clinical correlation is still needed to rule it out definitively.
Taking into account the patient’s age (17 years old), the radiological findings, and the resolution of symptoms after conservative observation, the most likely diagnosis is:
Congenital Bipartite Trapezoid
This diagnosis is considered because the separation line seen on the images is regular in shape, extends through the entire bone, and shows smooth cortical margins. Additionally, there are no obvious signs of traumatic fracture, which aligns with the typical features of a congenital anomaly.
No special surgical intervention is required for congenital bipartite trapezoid itself. The main treatment goals are:
Treatment Strategies:
Rehabilitation/Exercise Prescription:
During the rehabilitation process, if the wrist becomes swollen again, develops severe pain, or shows restricted mobility, discontinue the current training and seek timely follow-up to rule out new injuries or complications.
Disclaimer: This report is based on limited information provided and is for reference only. It does not replace an in-person consultation or professional medical diagnosis and treatment. If you have any concerns, please consult a professional medical institution or specialist.
Bipartite right trapezoid
