Biomechanics of Internal Fixation Modalities for Middle Phalangeal Base Fracture Dislocation

Area of Science:

• Orthopedic surgery
• Biomechanics
• Hand surgery

Background:

• Unstable middle phalangeal volar lip fracture-dislocations often require internal fixation.
• Current fixation options include interfragmentary screw and volar buttress plating.

Purpose of the Study:

• To compare the mechanical properties of three internal fixation methods for middle phalangeal volar lip fractures.
• Investigate yield strength, ultimate tensile strength, and stiffness of different fixation constructs.

Main Methods:

• Fifteen cadaveric digits underwent simulated oblique osteotomies of the proximal interphalangeal joint.
• Fixation was achieved using interfragmentary screw (IS), simple buttress plating (BP), or buttress plating with subchondral screw (BP+S).
• Specimens were subjected to mechanical loading to failure to assess fixation stability.

Main Results:

• Buttress plating with subchondral screw (BP+S) demonstrated significantly higher yield strength (33.5 N), ultimate tensile strength (49.1 N), and stiffness (4.77 N/mm).
• Interfragmentary screw (IS) fixation showed intermediate mechanical properties.
• Simple buttress plating (BP) exhibited the lowest mechanical strength and stiffness.

Conclusions:

• A buttress plate and subchondral screw construct provides superior biomechanical stability compared to interfragmentary screw or buttress plate alone.
• This enhanced stability may translate to improved outcomes for treating these specific phalangeal fractures.