In the current study, biomechanical stability of various fixation methods for diaphyseal metacarpal fractures were compared. In transverse fractures, intramedullary headless compression screw was compared to dorsal plating. The former was found to be superior in both stiffness and peak load to failure. In the oblique fractures, intramedullary headless compression screw, dorsal plating, and two lag screws were compared. While the intramedullary compression screw had significantly higher peak to load failure compared to the other two methods, there was no significant difference in stiffness.
Cannulated headless compression screws have been widely used in hand surgery since Herbert and Fisher  introduced its utility in scaphoid fractures. However, its use as an intramedullary device for metacarpal fractures is relatively new [6, 14, 15].
The intramedullary compression screw has several advantages over conventional fixation methods. It avoids the risk of pin tract infection or need for removal associated with percutaneous K-wire fixation. Unlike dorsal plating which requires a more extensive dissection, the intramedullary screw can be inserted through a small dorsal incision. Furthermore, with the compression screw, the entire hardware is buried inside the metacarpal and thus unlikely to cause irritation of surrounding soft tissue or tendon ruptures. Finally, the compression screw allows for early active motion exercises to minimize stiffness when compared to K-wires [7, 8, 16]. These advantages make intramedullary compression screw an attractive option for fixation of metacarpal fractures. Some downsides of intramedullary screw fixation have to be mentioned on the other hand as extensor tendon disruption and difficult explantation in case of infection or refracture is possible [10, 17].
The results from the current study support that compression screw fixation provides excellent biomechanical stability that is comparable to dorsal plating or lag screws. Analogous to plate fixation, it may provide an option for rapid return to sport  with a lower risk of adverse effects. All construct exceeded by far the invivo forces generated by the flexor tendons of 30 N and therefore can be considered possible options  from a biomechanically point of view.
In comparison to existing biomechanical data by Oh et al. we could demonstrate higher peak loads for all tested devices . This may be due to the effect of a more stable plate and larger diameter intramedullary compression screws with a different design. Especially the size of the intramedullary compression screw has to fit perfectly in order to generate optimize fixation strength. Oftentimes the available screw size may not be large enough to archive endosteal purchase .
Reported clinical results for compression screw fixation have been good. Del Pinal et al.  reported a series of 48 metacarpal fractures, all of which healed with total active motion (sum of distal phalangeal joint, proximal phalangeal joint, and metacarpophalangeal joint motion) averaging 249 degrees. Ruchelsman et al.  first reports a series of 20 metacarpal fractures in which all fractures healed with full flexion and grip strength measuring 105% (range 58 to 230%) compared to the contralateral side. In their second series of now 91 patients they could continue to show favorable results without the disadvantages of open reduction and fixation .
There are several limitations of the study. Failure of the constructs was tested only in one dimension and without cyclic loads demonstrating a possible loosening during the early postoperative phase. We chose to load the construct with an apex-dorsal force based on previous biomechanical studies [5, 10, 11]. Axial, rotational, or cyclical loading may reveal clinically important differences. Also, only 3-point bending instead of cantilever bending was used that may not reflect individual anatomy and physiology of the hand and metacarpal loading.
Particularly with plate fixation, other methods or construct configurations are possible and are not accounted for, such as locking plate constructs, which could demonstrate different results. Additionally, the current study was performed on cadavers and does not account for any differences in biological healing the different constructs induce. However, differences in bone mineral density between cadaver specimens was tested and found to be insignificant.
It should also be noted that the retrograde placement of intramedullary screw requires an arthrotomy of MCP joint as it is inserted through the articular surface of the metacarpal head which may put the joint at an increased risk for future arthritis . Furthermore perfect anatomic reduction may be more difficult percutaneously than in open techniques, but clinical results remain good [6, 7, 14].