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The aim of our paper was to provide comprehensive data on the prevalence of absence of palmaris longus muscle (PLM) and its anatomical characteristics and conduct two separate meta-analyses comparing cadaveric and functional studies while identifying variation among different ethnic groups. An extensive search was conducted through the major electronic databases to identify eligible articles. Data extracted included prevalence of absence of PLM among subjects, ethnicity, laterality, side, and gender. Our main findings revealed that the absence of PLM is more frequently reported in functional studies. Moreover, functional tests likely overestimated the absence of PLM and recommend future studies to assess the validity of functional tests and use an imaging assessment prior to excluding the use of a palmaris longus tendon graft in patients in whom a function test identified the absence of PLM.

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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.

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Absence of the palmaris longus muscle has been well documented in several populations at a prevalence rate ranging between 2.2 and 63.9% which varies according to race, sex, and side of the body. There is little documentation of the prevalence of absence of this muscle from populations in the Arabian Gulf region. We examined 1,043 subjects, 3-85 years old, from the Kingdom of Bahrain for the presence or absence of the palmaris longus muscle using the conventional test for the presence of this muscle. Statistical analyses investigated the association of muscle absence with sex, hand dominance, and laterality. The palmaris longus muscle was absent in 36.8% of subjects. Bilateral absence (19%) was more common than unilateral absence (17.9%) with preponderance in female subjects. The muscle was absent more often on the left side than the right (P = 0.003). In the right upper limbs the muscle was absent in female subjects more than male subjects (P = 0.031). This study reaffirms that there is population variation in the frequency of absence of the palmaris longus muscle. The tendon of the palmaris longus bifurcated at the wrist in 7.1% of subjects, with male subjects showing this feature more frequently than female subjects in the right hand (P = 0.037) and the left hand (P = 0.030). This has not been reported before. The clinical significance of our findings is discussed.

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The palmaris longus (PL) is a weak flexor of the wrist that may be harvested as a tendon graft and used in surgical procedures for reconstructive purposes. The PL is congenitally absent in 15% of the worldwide population. However, the frequency of absence varies considerably among different population groups, being as high as 63.9% in the Turkish population and as low as 3% in the black population in the Republic of Congo. In this study, South African persons of mixed race (n = 201) were assessed by two anatomists for the presence of the PL tendon using three clinical tests, namely the Traditional Test, Mishra's Test II, and the Gangata Test. The most reliable of the three tests used was determined using Kendall's coefficient of concordance. Of the total number of subjects used, 11.5% had absence (either bilaterally or unilaterally) of the PL tendon. There was a 5.5% bilateral absence of the PL. The study revealed that the PL tendon may present in six different patterns according to the clinical assessment tests applied, the presence or absence of the PL alongside the flexor capi radialis, and the degree of prominence of PL, if present. Using the Kendall's coefficient of concordance, the Mishra's Test II, and the Gangata Test, both involving abduction of the thumb, were found to be most effective in revealing the PL. The frequency of absence of the PL in South Africans of mixed race has been determined.

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INTRODUCTION: It is well known that there is a wide variation in the reported prevalence of the palmaris longus (PL) absence in different ethnic groups. This prospective study was conducted to determine the prevalence of absence of PL and correlate it with gender and body side in Turkish population. METHOD: In total, 1,350 randomly selected adult patients (675 men and 675 women) who admitted to our outpatient clinic were examined for the absence of PL using Schaeffer's test and Mishra's second test. The absence of PL on both sides, results of the first and second examination tests, age, gender and dexterity were recorded and analyzed statistically. RESULTS: The overall prevalence of absence of PL (unilateral or bilateral) was 26.6% in Turkish population. The absence of PL in women was statistically more common than men. Bilateral absence of PL was statistically frequent than unilateral absence. The prevalence of absence of PL was statistically similar between the body sides. CONCLUSION: Mishra's second test which involves resisted abduction of the thumb, may be better in demonstration of the PL where the muscle was feebly developed, particularly in women.

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A lot has been reported about variation of palmaris longus muscle in journals and conventional textbooks. The incidence of palmaris longus muscle absence among people of the six geo-political zones of Nigeria was evaluated using 600 subjects. 31.25 percent (187 subjects) lack palmaris longus muscleon either of the forearms. 12.5 percent (75 subjects) shows unilateral absence and 18.75 percent (112 subjects) shows bilateral absence. 25 percent (150) of subjects lacks palmaris longus muscleon their right forearms while 25 percent also lacks it on their left forearms. 6 percent (37) shows double tendons of palmaris longus muscleon both forearms. Highest incidence of absence was recorded among people of South-West zone.

Mucho se ha informado acerca de la variación del músculo palmar largo en revistas y libros de texto convencionales. La incidencia de ausencia del músculo palmar largo entre las personas de las seis zonas geo-políticas de Nigeria se evaluó usando 600 sujetos. 31,25 por ciento (187 sujetos) no tenían músculo palmar largo en cualquiera de los antebrazos, 12,5 por ciento (75 sujetos) mostró ausencia unilateral y 18,75 por ciento (112 sujetos) mostró ausencia bilateral. 25 por ciento (150) de los sujetos carece de músculo palmar largo en su antebrazo derecho, mientras que el 25 por ciento carece de él también en su antebrazo izquierdo. 6 por ciento (37) muestra dobles tendones de músculo palmar largo en ambos antebrazos. Mayor incidencia de ausencia se registró entre las personas de la zona Sur-Oeste.

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The aim of this work was to test whether postaxial hexadactyly had different clinical and epidemiological characteristics depending on hand or foot involvement. In the period 1967-1993, the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) enrolled 1,582,289 births, and 2,271 cases with isolated (nonsyndromal) postaxial polydactyly (5th-digit hexadactyly). The prevalence was 14.3/10,000 births. Postaxial polydactyly (PP) of the hand (HPP) was the most frequent type (N:1,733; 76.3%; prevalence: 11.0/10,000), followed by foot PP (FPP=N:351; 15.5%; prevalence: 2.2), and hand and foot PP (BPP=N:187; 8.2%; prevalence: 1.2). Unlike HPP (55.0% bilateral; 77.2% left), FPP was less frequently bilateral (19.4%), with lower preference for the left side (55.5%). As expected, HPP was associated with African Black ethnicity, male sex, twinning, low maternal education, parental consanguinity, and there was frequent recurrence in 1st-degree relatives. Conversely, FPP was associated with Amerindian racial background, parental subfertility, and bleeding in the 1st trimester of pregnancy. BPP displayed the highest frequency of associated congenital defects (23.4%, vs HPP:6.6%, FPP: 15.4%). In its isolated form, BPP resembled HPP more than FPP with respect to left preference (90.9%), familial recurrence (11.0% of 1st degree relatives), and low maternal education. Although male sex preference and high frequency of twinning was observed in the 3 PP subtypes, statistical significance was present only in HPP. None of the 3 PP subtypes showed abnormal values for perinatal mortality, birth weight, length of gestation, parental ages, or parity. A logistic regression analysis showed Black race only to be associated with HPP, parental subfertility with FPP, parental consanguinity with BPP, and non-Black race with both FPP and BPP. The data presented here are the first indication that HPP and FPP are 2 different entities, with a larger genetic component in HPP than in FPP.

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