Ossa Sesamoidea - prevalence of sesamoid bones in human hands.

BACKGROUND: This study describes the morphology of sesamoid bones in the human hand. Ultrasound imaging was used to record the presence and measurements of sesamoids in 120 hands of 60 healthy, young adults of Caucasian ethnicity. MATERIALS AND METHODS: The mean number of sesamoid bones was 4.16 in the left hand and 4.03 in the right hand. 21.6% of cases showed asymmetry between the right hand and the left. There was a significant difference in the prevalence of sesamoid bones between right and left hand in males in this study. Females show a higher incidence of sesamoid bones overall, but do not demonstrate a significant difference between the sides. RESULTS: Prevalence findings: Two in the 1st Metacarpophalangeal joint (MCPJ) in 99.2% of cases, with one case of a single bone. One in the 2nd MCPJ in 43.3% of cases. One in the 5th MCPJ in 84.2% of cases. One in the 1st Interphalangeal joint (IPJ) in 83.4%of cases. Aside from that there was one case of sesamoid in the 3rd MCPJ and separate case of sesamoid in the 3rd proximal IPJ. CONCLUSIONS: Moreover, this study discusses discrepancies of opinion regarding sesamoid bones in morphological research.

Musculus Palmaris Longus: Influence on Playing Capability of Keyboard Musicians - Preliminary Report.

Musculus Palmaris Longus (PL) is one of the most variable anatomical structures in the human body. Despite being biomechanically active, it is vastly considered to have no impact on the functionality of the upper extremity in the general population. The aim of this study is to examine the relation between playing capability of young musicians and morphology of Musculus PL and to compare it with the relation between manual capability of non-musicians and morphology of their Musculus PL. 42 forearms of 21 healthy individuals (11 musicians and 10 non-musicians) were subjected to Shaeffer's test and ultrasound imaging and tested by dynamometer for hand grip strength and the first and fifth finger opposition before and after exertion. No difference in morphology pattern was observed between the groups. In the musicians, a substantial loss of a hand grip strength of the left hand compared to the right hand after exertion, regardless of lateralization, was observed. A disproportion in exhaustion of the musician's hands with unilateral absence of PL was observed - the difference in grip strength between the dominant and non-dominant hand before and after exertion increased over eight times more than in the musicians with bilateral presence. There is no difference in PL morphology between either the musicians or non-musicians. Regardless of lateralization, the musician's left hand in musicians seems weaker and therefore more prone to misuse related injuries. PL may play a role in musicians in balancing muscular exhaustion.