Journal of Postgraduate Medicine, Vol. 47, Issue 3, 2001 pp. 208-209
Bilateral Congenital Capitate-Hamate Fusion
Hosalkar HS, Shaw BA, Carrie LC, Read H
Division of Paediatric Orthopaedics, The Valley Childrens Hospital, Fresno, UCSF, USA.
Code Number: jp01060
A 14-year-old Hispanic boy, a high-end soccer player, presented to us following injury to the knee. There was an epiphyseal injury (type III Salter-Harris) to the lower femoral epiphysis on the right side. It was surgically treated and the leg was placed in a cast. During the course of management of the femoral fracture, wrist and hand x-rays were taken for determination of bone age to help predict any possible development of limb-length discrepancy/deformity with remaining skeletal growth. Bilateral capitate-hamate coalition was incidentally detected (figure 1). There were no symptoms in both wrists and physical exam findings were normal. In view of full function and asymptomatic nature of the condition no intervention was done for the carpal coalition although the patient was made aware of the findings and the possible implications.
Carpal fusions are relatively common, usually asymptomatic abnormalities that occur as normal variations in about 0.1% of the population. These fusions can occur as isolated abnormalities or as a part of generalised syndromic manifestation. It is important to note that isolated fusions usually present involvement of the same carpal row, while syndrome related fusions affect bones in different rows.(1) Although previously considered as a rule, exceptions have been reported.
Capitate-hamate coalitions although reported are extremely rare. Trapezium-trapezoid and pisiform-hamate fusions are also rare.(2) Triquetro-lunate fusions are the most common and occur in 0.1 to 1.6 % of the general population, more frequently in males, and in blacks.
Isolated coalitions have been described in almost all-possible combinations, including those affecting more than two bones.(1,3)
Massive carpal fusions, fusion between bones of the proximal and distal carpal rows, or between the carpal bones and radius or ulna are generally associated with additional malformations. These include tarsal coalitions or one of the congenital syndromes such as acrocephalosyndactyly syndrome, arthrogryposis, diastrophic dwarphism, Ellis-van Creveld syndrome, hand-foot-uterus syndrome, Holt-Oram syndrome, otopalatodigital syndrome, Turners syndrome, or symphalangism.(3) Capitate-hamate fusion has been noted to be a finding in Kabuki make-up syndrome.(4) Acquired carpal fusion is most commonly seen in juvenile rheumatoid arthritis. Carpal coalition is also sometimes associated with ray anomalies in the hand.
Carpal coalitions are implied to develop from failure of segmentation of the primitive cartilaginous canals and absence of joint formation.(1,5) Bilateral and unilateral capitate-hamate fusions have been noted as a part of foetal-alcohol syndrome. In fact Jaffer et al emphasize consideration of diagnosis of foetal-alcohol syndrome in patients presenting with such carpal fusions or with radio-ulnar synostosis.(6) McCredie (5) noted carpal fusions along with other congenital fusion of bones as a recurrent feature in thalidomide embryopathy. He suggested that congenital bony fusions were a disorder of organisation of mesenchyme in the fifth week of life, and that the organising tissue was possibly the sensory nerve. Heridity was also possibly implicated. None of these risk factors were noted in our case.
The osseous centers of the involved bones coalesce at variable ages usually between six and 15 years of age. Most cases of isolated carpal coalition are asymptomatic although pain has been observed in some cases. Partial coalitions and cystic changes have more incidence of pain. Fused carpal bones also carry a definite risk of fracture. Patients with congenital lunato-triquetral coalition may poorly tolerate stress loading or trauma, resulting in a symptomatic state similar to degenerative arthritis or pseudoarthrosis, which is demonstrated by enhanced MR imaging.(7) Cases of carpal coalition with ulnar neuropathy have been described. Kienbocks disease may also present in association with carpal coalition. Increased demand on the joint especially in high activity levels like sportsmen may lead to progressive stress loading and early degenerative arthritis or pseudoarthrosis. There is also a risk of fracture or progressive neuropathy. Sporting activities involving high demand on the wrist movements (like tennis unlike lower limb sports in our case) thus may lead to early presentation.
Interestingly, iatrogenic or surgically induced capitate-hamate fusion is commonly used as a treatment modality for Kienbocks disease.(8) Biomechanical analysis of the surgically induced fusions reveal an increased radioscaphoid mean pressure, decreased radiolunate mean pressure, and, little effect on radiocarpal mean pressure. Surgically induced capitate-hamate fusion has also been noted to increase the grip strength in patients with Kienbocks disease. In view of partial or incomplete nature of the coalition in some cases, it may be necessary to take multiple projections (including oblique views), for proper definition of the coalition. Radiographically, continuous trabeculae traced from one carpus to the next signify a fusion. Intraosseous cysts adjacent to the area of coalition are sometimes seen, which can usually be differentiated from acquired ankylosis (infection, trauma, surgery and arthritis).(1)
Treatment is rarely required for the asymptomatic cases of capitate-hamate coalition. Intervention if at all is restricted to the cases with secondary sequelae including arthritis, neuropathy or fracture. Modalities would include immobilization for fractures, decompression for neuropathy and carpus (isolated or row) excision for severe arthritis.
Clinicians should recognize that capitate-hamate coalitions (or carpal coalitions in general) could be a part of syndromic manifestations. Isolated capitate-hamate coalition although generally asymptomatic, may present with sequelae of neuropathy or arthritis. Multiple radiographs may be required for proper definition. Treatment is usually symptom based.
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