Carpal Coalitions

Carpal coalition refers to failure of segmentation of the carpal bones. Isolated coalitions tend to occur between two bones in the same carpal row (e.g., luontriquetral and scapholunate), while syndromic coalitions tend to cross carpal rows and involve more than two bones.

Various syndromes and congenital abnormalities have been associated with carpal coalitions.

• Arthrogryposis: The clinical finding of multiple congenital contractures that affect two or more different areas of the body. Seen as part of more than 300 different disorders. Carpal coalitions more common than tarsal coalitions.
• Ellis-van Creveld syndrome: Also called chondroectodermal dysplasia. Usually coalition is between the capitate and hamate.
• Hand-foot-genital syndrome: Limb malformations and urogenital defects. The most common malformation is mild bilateral shortening of the thumbs and great toes, predominantly of the distal phalanges and/or the first metacarpal or metatarsal. Urogenital abnormalities include abnormalities of the ureters and urethra, incomplete Müllerian fusion (females), and hypospadias (males). The most common coalition is between the scaphoid and trapezium.
• Symphalangism: Partial or total absence of interphalangeal joints sometimes with tarsal and carpal coalition. The most common coalition is between the triquetrum and the hamate.

The case shown here is lunotriquetral coalition, which is the most common of the carpal coalitions and is twice as common in females. Because patients with lunotriquetral coalition tend have widened scapholunate intervals without injury to the scapholunate ligament, this finding should be considered a normal variant in patients with lunotriquetral coalition.

References

• Bamshad M, Van Heest AE, Pleasure D. Arthrogryposis: a review and update. J Bone Joint Surg Am. 2009 Jul;91 Suppl 4:40-6.
• Innis JW. Hand-Foot-Genital Syndrome . In: Pagon RA, Bird TC, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2006.
• Metz VM, Schimmerl SM, Gilula LA, Viegas SF, Saffar P. Wide scapholunate joint space in lunotriquetral coalition: a normal variant? Radiology. 1993 Aug;188(2):557-9.
• Poznanski AK, Holt JF. The carpals in congenital malformation syndromes. Am J Roentgenol Radium Ther Nucl Med. 1971 Jul;112(3):443-59.