Sesamoid displacement: a rare cause of 'clicking thumb'

The prevalence of the sesamoid bones of the hand: a systematic review and meta-analysis

The literature contains various estimates of the prevalence and distribution of the sesamoid bones in the hands. The aims of this systematic review are to provide a better estimate of the frequency of hand sesamoids and its association with variables such as ancestry, gender, and side. Nineteen studies met the inclusion criteria. The pooled rates of the sensitive meta-analyses from large-sample studies in adults showed: (a) true overall rates of 99.9% for the metacarpophalangeal (MCP) joint of the thumb (MCP-I), 53% for the interphalangeal joint (IP-I), 43.4% for the MCP of the index (MCP-II), 1.47% for the MCP of the medius finger (MCP-III), 0.6% for the MCP of the ring finger (MCP-IV), and 67.7% for the MCP of the auricular finger (MCP-V); (b) true radiological rates of 99.9% for the radial thumb sesamoid, 99.6% for the ulnar thumb sesamoid, 47.8% for IP-I, 40% for MCP-II, 1.3% for MCP-III, 0.8% for MCP-VI, and 62.8% for MCP-V. Black, Middle Eastern, and European ancestries conferred significantly higher sesamoid frequencies at IP-I, MCP-II, and MCP-V, respectively. There was a significant association with female gender at MCP-II, MCP-IV, and MCP-V, with ORs of 1.53, 4, and 1.3, respectively, and a nonsignificant "female" trend for the other locations. There was no significant association with hand side. The pooled rates of hand sesamoids in children aged 10-17 years were 92.7, 42.2, 33.8, 0.5, 0.3, and 36.5% for MCP-I, IP-I, MCP-II, MCP-III, MCP-IV, and MCP-V, respectively. The findings of this evidence-based anatomical review provide quantitative evidence that the incidence of sesamoid bones in human hands depends on genetic rather than functional factors.

Sesamoid and accessory bones of the hand--an epidemiologic survey in a Mediterranean population

The prevalence and distribution of sesamoid and accessory bones in the hands is quite variable between different populations and ethnic groups. However, there are no published data on their distribution in Mediterranean populations. Studies on the validity of radiographic assessment for the presence of these bones are also lacking. A retrospective review of 442 radiographs of adult patients was performed in order to assess the incidence of sesamoid and accessory bones in the hands of a Mediterranean population. Additionally, two independent observers reviewed 174 radiographs and used the Kappa parameter in order to assess the validity of radiographic interpretation of radiographs for the presence of those bones. There was an incidence of 99.5% sesamoid bones (n = 440) in the 1st metacarpophalangeal (MCP) joint, 42.3% in the 2nd MCP joint (n = 187), and 41.1% (n = 182) in the 5th MCP joint. The incidence in the 1st interphalangeal joints was 26.2% (n = 116). The incidence of sesamoid bones in the 1st, 2nd, and 5th metacarpophalangeal joints in a Mediterranean population was found to be similar to that of Arab and Caucasian populations, whereas their prevalence in the 1st interphalageal joint coincided more with Arab populations. Interobserver reliability of the interpretation of radiographs for the presence of sesamoid bones in the hand was good (Kappa > 0.68) in all locations, except for the 1st MCP joint. Further research is warranted to further elucidate the genetic and/or environmental reasons for the differences between those populations.

Rotary subluxation of the metacarpophalangeal thumb joint: a case report

Irreducible rotary subluxation of the metacarpophalangeal joint (MCPJ) of the thumb is a rare entity. Open reduction is indicated when signs of irreducibility are seen on the radiographs. We present one such case caused by displacement of the sesamoid bone into the intercondylar notch of the first metacarpal bone. A 35-year-old woman sustained a twisting injury to her right thumb by pronating and hyperextending it while attempting to retrieve things that she had dropped into a basin conduit. True lateral radiographs showed rotary subluxation of the thumb MCPJ, a sesamoid bone overlapping with the metacarpal head, and loss of the subsesamoid joint space and an incongruent MCPJ on full flexion. A high level of clinical suspicion is needed to diagnose this rare entity.

Incidence and ossification of sesamoid bones in the hands and feet: a radiographic study in an Arab population

The incidence and ossification of sesamoid bones in the hands and feet were studied in 922 radiographs (400 hands and 522 feet) in an Arab population from Bahrain, 5-83 years of age and consisting of 549 adults (393 men and 156 women) and 373 children (286 boys and 97 girls). All radiographs of the hand and foot in the adult population showed two sesamoid bones in the thumb metacarpophalangeal (MCP) joint and in the hallucal metatarsophalangeal (MTP) joint, respectively. Only 2.3% and 1.5% of hands showed sesamoids at the MCP joints of the middle and ring fingers respectively compared to a reported incidence of 7.1% for each digit in Caucasians. The incidence of sesamoids in the MTP joints of third and fourth toes (0.6% each) and inferior to the hallucal interphalangeal joint (3.1%) is probably the lowest reported so far in the literature. In the hands, ossification commenced first in the thumb sesamoids, at the age of 10 years in females and 11 years in males and was completed by the age of 13 and 14 years, respectively. In the feet, ossification began first in the hallucal sesamoids at the age of 8 years in females and 9 years in males and was completed by the age of 10 years in both sexes. The incidence and ossification of sesamoids in the hands and feet in the Arab population from Bahrain seem to differ considerably from reports in other populations. The clinical significance of our findings is discussed.