The Metacarpal Locked Intramedullary Nail: Comparative Biomechanical Evaluation of New Implant Design for Metacarpal Fractures
Chinnakart Boonyasirikool MD*, Sakkarin Tanakeatsakul MD**, Sunyarn Niempoog MD*
Affiliation : * Department of Orthopedics, Faculty of Medicine, Thammasat University, Pathumthani, Thailand ** Department of Orthopedics, Buddhachinnaraj Hospital, Phitsanulok, Thailand
Background : The optimal fixation of metacarpal fracture should provide sufficient stability to permit early function for all
types of fracture. However, it must preserve surrounding soft tissue during application and not require secondary removal
due to its prominence. The prototype of metacarpal locked intramedullary nail (MCLN) was designed by our institute aiming
to achieve those all features.
Objective : To biomechanically test our newly designed, locked metacarpal nail and compare with common current available
fixation methods.
Material and Method: Thirty chicken humeri were devided into 3 groups (n = 10 per group) according to fixation techniques:
MCLN, 1.5 mm miniplate (Synthes), and Kirschner wire. After complete fixation, all specimens were osteotomized at mid-
shaft creating transverse fractures. Five specimens from each group were tested by load of failure under axial compression,
and another five under bending force.
Results : In axial compression model, the loads to failure in MCLN group was greatest (460+17 N), which was significant
higher than the Kirschner wire group. The MCLN group also showed the highest load to failure in bending test (341+10 N).
This value reaches statistical significance when compared with plate and Kirschner wire groups.
Conclusion : The MCLN construct provided higher stability than miniplate and Kirschner wire fixation both in axial and
bending mode. Together with the minimally invasive and soft tissue-friendly design concept, this study suggests that MCLN is
promising fixation option for metacarpal fracture.
Keywords : Metacarpal, Metacarpal fracture, Locked intramedullary nail, Minimal invasive fixation
