There are numerous sesamoid bones in the hand, small ossified nodes embedded in tendons; the exact number varies between people: whereas a pair of sesamoid bones are found at virtually all thumb metacarpophalangeal joints, sesamoid bones are also common at the interphalangeal joint of the thumb (72.9%) and at the metacarpophalangeal joints of the little finger (82.5%) and the index finger (48%). In rare cases, sesamoid bones have been found in all the metacarpophalangeal joints and all distal interphalangeal joints except that of the long finger. The articulations are:

interphalangeal articulations of hand (the hinge joints between the bones of the digits)
metacarpophalangeal joints (where the digits meet the palm)
intercarpal articulations (where the palm meets the wrist)
wrist (may also be viewed as belonging to the forearm). Arches
The fixed and mobile parts of the hand adapt to various everyday tasks by forming bony arches: longitudinal arches (the rays formed by the finger bones and their associated metacarpal bones), transverse arches (formed by the carpal bones and distal ends of the metacarpal bones), and oblique arches (between the thumb and four fingers):
Of the longitudinal arches or rays of the hand, that of the thumb is the most mobile (and the least longitudinal). While the ray formed by the little finger and its associated metacarpal bone still offers some mobility, the remaining rays are firmly rigid.
The exudate is then sent for microbiological analysis for identification of the pathogen and determination of its antibiotic sensitivity profile, which may in turn give an indication for changing the antibiotics. At follow-up, a mammography is performed if the condition has resolved; otherwise the ultrasound-guided fine-needle aspiration with lavage and microbiological analysis is repeated. If three to five aspirations still do not resolve the condition, percutaneous drainage in combination with placement of an indwelling catheter is indicated, and only if several attempts at ultrasound-guided drainage fail, surgical resection of the inflamed lactiferous ducts (preferably performed after the acute episode is over). It is noted, however, that even the excision of the affected ducts does not necessarily prevent recurrence.Nonpuerperal breast abscesses have a higher rate of recurrence compared to puerperal breast abscesses. There is a high statistical correlation of nonpuerperal breast abscess with diabetes mellitus (DM). On this basis, it has recently been suggested that diabetes screening should be performed on patients with such abscess.Although there are a number of recommendations regarding the treatment of breast abscesses, a 2015 review found insufficient evidence of whether needle aspiration is comparable to incision and drainage, or whether antibiotics should generally be given to women undergoing incision and drainage. Prognosis
Temperature and severity of symptoms at presentation do not predict outcome; women with sore or damaged nipples may need special attention. Epidemiology
Mastitis is quite common among breastfeeding women. The WHO estimates that although incidences vary between 2.6% and 33%, the prevalence globally is approximately 10% of breastfeeding women.