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Background: Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles' absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles. Materials: Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted. Results: The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified. Conclusion: The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations. [ABSTRACT FROM AUTHOR]

Background: Although hand and upper limb malformations are quite frequent, up to now very few reports have been published on epidemiology. The aim of this study is to evaluate the number of infants who presented with hand and upper limb malformations from 2010 to 2015 in Italy. Methods: A retrospective analysis of a pediatric population presenting with hand and upper extremity malformations was carried out, gathering reports achieved from eight Italian Centers of pediatric hand surgery. Other factors such as gender, date and region of birth, family distribution of malformations and associated syndromes, were analysed. Results: Out of 3,100,421 live births, 765 children presented with hand and upper limb malformations. The incidence was 2,5/10,000 live births with a predominance of males and the right side. Radial polydactyly was the anomaly with the highest percentage, closely followed by simple syndactyly, simbrachidactyly and complex syndactyly. Less common conditions were the triphalangic thumb, thumb in palm, proximal radioulnar synostosis and Sprengel deformity. Inheritance of and familial predisposition to those malformations was recorded in 25 cases, while 84 children presented with syndromes related to hand anomalies. Conclusions: In conclusion the incidence of hand and upper extremity malformations in Italy is lower than that registered in other countries. The retrospective nature of the study combined with the fact that some defects frequently evade pediatric hand surgeon consultations are some possible limitations of the study. However, our data confirmed that, in spite of the decrease in the birth rate in Italy, the trend of congenital hand disorders maintained a stable trend. We aim to integrate this study with a prospective analysis and to involve the institutional health authorities in other countries so as to register the correct incidence of hand and upper extremity defects.