Bilateral carpal second row duplication – a case report

Introduction The number of carpal bones may be increased due to anatomical variants or true congenital anomalies. Numerical increment arises from additional bones or from split bones. Over twenty different accessory carpal ossicles have been described. However, no case of bilateral total second carpal row duplication has ever been reported, associated or not with other general conditions. Case report A 75-years-old woman first presented with pain in the left wrist, located at the base of the fifth metacarpal. The pain was mechanical, slowly progressive over a few months, of low intensity, with no traumatism or inflammation. The wrist mobility was subnormal, no hyper-laxity was noted. In her medical history, she reported a diagnosis of both Marfan and Ehlers-Danlos syndromes in childhood, with no clear medical evidence, no further investigation or follow-up since 1953. A standard X ray first revealed an abnormal number of carpal bones, respecting the global shape of the wrist anatomy. The CT-scan showed a total second row duplication - in each wrist, the trapezium and the trapezoid are each divided in four regular fragments with symmetry in both frontal and sagittal plans. The capitate and the hamatum are each divided in three regular fragments, with a sagittal alignment. No anatomical anomalies were noted regarding the first row. The total count of carpal bones in each wrist was 18. The CT-scan also showed bilateral chondrocalcinosis, with scapho-lunate dislocation on the left side, compatible with a SCAC wrist. The base of the left fifth metacarpal, the only initial clinical complaint of the patient, was articulated with all three hamatum fragments and presented degenerative arthritic changes. Further questioning revealed several ancient articular pains. Old X rays showed an early-onset, severe osteoarthritis of knees and hips with irregular epiphysis. Further imaging investigation showed irregular epiphysis of the elbows, with chronicle left radial head luxation, and bilateral tarsal duplication - each foot has six cuneiform bones, with an axial symmetry, as in the carpus. These clinical and radiological features are compatible with the diagnosis of Multiple Epiphyseal Dysplasia. Conclusion The wrists anomalies we observed in this patient, especially the CT-scan findings, present all the characteristics of bipartite bones, caused by a lack of fusion of the initial ossification centers, or, in this case, quadripartite or tripartite bones. Some syndromes are known to provide carpal malformations, but none were reported causing second row carpal duplication.