Clavicular fractures are common, accounting for 2.6%-10% of all adult fractures. Approximately 80% of the fractures were located in the middle shaft of the clavicle, among which 48% were associated with displacement, and 19% were associated with comminution. Generally, clavicular fractures are treated conservatively, but for displaced or severely comminuted fractures, surgery should be considered. The traditional surgical treatment method is mainly plate fixation, and locking plate is widely used with good functional result. However, postoperative internal fixation failure includes loosening, deformation, fracture, etc., and the postoperative revision rate reached 6.9%-16.7%, especially for wedge or comminution fractures that directly affects the stability of internal fixation. Currently, intramedullary nail has been gradually recognized in the treatment of clavicle fracture, with the advantages such as small incision and good blood supply protection. However, some studies have reported related complications, in which the incidences of fracture, deformation or displacement of intramedullary nailing reached 5%-10%. As far as we know, there are no specific studies on the mechanism and biomechanical causes of such complications, as well as relevant theories to guide the selection of internal fixator type and length.

To investigate and analyze the causes of internal fixation failure after clavicular fractures by lever reconstruction balance theory.

This study conducted a manual search on MEDLINE, EMBASE, PubMed, PQDT, Wanfangdata, CNKI, QCVIP and other databases, and the research objects were domestic and foreign case reports, publications and reviews of complications after internal fixation of clavicular fracture published from January 2001 to January 2021, and those who met the inclusive and exclusive criteria were selected. The end points were plate fracture, deformity, loosening or perforation after internal fixation of clavicle fractures. The observation indicators were recorded according to the text description or pictures provided by the literatures.

A total of 17 literatures were included in this study, among which 65 cases met the inclusive criteria, with 43 cases fixed with plates and 22 cases fixed with elastic intramedullary nails. There were 25 patients of internal fixation loosening (38.5%) , 11 patients of internal fixation penetration (16.9%) , and 33 patients of internal fixation deformation or fracture (50.8%) . At the end point, 31 cases (47.7%) had fracture redisplacement, 26 cases (40%) had nonunion, and 2 cases (3%) had pseudo-articulation.

A new lever system was reconstructed after internal fixation of clavicular fracture, and the selection of internal fixation length should be determined according to the position of fracture line. The internal fixation length at both ends of fulcrum should be the same with equal power arm and resistance arm, so as to achieve a three-point balance of distal clavicle, fulcrum and proximal clavicle. In the meanwhile, early rehabilitation exercise should be avoided as far as possible to prevent the occurrence of complications. This theory can guide the principle of clavicular fracture treatment, the selection and development of internal fixators, and rehabilitation programs, and effectively reduce clinical complications, providing a new idea and direction for the treatment of clavicle fracture and even other parts of the body fractures in the future.